Artigos de revistas: "Glycan derivatives"

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Park, Sungjin, Jung-Won Sung e Injae Shin. "Fluorescent Glycan Derivatives: Their Use for Natural Glycan Microarrays". ACS Chemical Biology 4, n.º 9 (18 de setembro de 2009): 699–701. http://dx.doi.org/10.1021/cb9002078.

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Zhang, Yao Y., Ahmed M. Senan, Ting Wang, Li Liu e Josef Voglmeir. "1-(2-Aminoethyl)-3-methyl-1H-imidazol-3-ium tetrafluoroborate: synthesis and application in carbohydrate analysis". Pure and Applied Chemistry 91, n.º 9 (25 de setembro de 2019): 1441–50. http://dx.doi.org/10.1515/pac-2019-0117.

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AbstractReductive alkylation of the carbonyl group of carbohydrates with fluorescence or ionizing labels is a prerequisite for the sensitive analysis of carbohydrates by chromatographic and mass spectrometric techniques. Herein, 1-(2-aminoethyl)-3-methyl-1H-imidazol-3-ium tetrafluoroborate ([MIEA][BF4]) was successfully synthesized usingtert-butylN-(2-bromoethyl)carbamate andN-methylimidazole as starting materials. MIEA+was then investigated as a multifunctional oligosaccharide label for glycan profiling and identification using LC-ESI-ToF and by MALDI-ToF mass spectrometry. The reductive amination of this diazole with carbohydrates was exemplified by labelingN-glycans from the model glycoproteins horseradish peroxidase, RNase B, and bovine lactoferrin. The produced MIEA+glycan profiles were comparable to the corresponding 2AB labeled glycan derivatives and showed improved ESI-MS ionization efficiency over the respective 2AB derivatives, with detection sensitivity in the low picomol to the high femtomol range.

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Hung, Wei-Ting, Yi-Ting Chen, Chung-Hsuan Chen, Yuan Chuan Lee, Jim-Min Fang e Wen-Bin Yang. "Flow Chemistry System for Carbohydrate Analysis by Rapid Labeling of Saccharides after Glycan Hydrolysis". SLAS TECHNOLOGY: Translating Life Sciences Innovation 25, n.º 4 (19 de junho de 2020): 356–66. http://dx.doi.org/10.1177/2472630320924620.

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This study demonstrates the utilization of a flow chemistry system for continuous glycan hydrolysis and saccharide labeling to assist with the existing methods in glycan structural analysis. Acidic hydrolysis of glycans could be accelerated in a flow system. Aldoses and α-ketoacid-type saccharides were effectively labeled with naphthalene-2,3-diamine (NADA) at 60 °C for 10 min to form the fluorescent naphthimidazole (NAIM) and quinoxalinone (QXO) derivatives, respectively. The NADA-labeled derivatives improved the structural determination and composition analysis for their parent saccharides by using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), liquid chromatography mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR). Furthermore, this protocol was applied to determine the SA–Gal–Glc sequence of GM3-sugar out of six possible permutations.

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Tang, Jo Sing Julia, Sophia Rosencrantz, Lucas Tepper, Sany Chea, Stefanie Klöpzig, Anne Krüger-Genge, Joachim Storsberg e Ruben R. Rosencrantz. "Functional Glyco-Nanogels for Multivalent Interaction with Lectins". Molecules 24, n.º 10 (15 de maio de 2019): 1865. http://dx.doi.org/10.3390/molecules24101865.

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Interactions between glycans and proteins have tremendous impact in biomolecular interactions. They are important for cell–cell interactions, proliferation and much more. Here, we emphasize the glycan-mediated interactions between pathogens and host cells. Pseudomonas aeruginosa, responsible for a huge number of nosocomial infections, is especially the focus when it comes to glycan-derivatives as pathoblockers. We present a microwave assisted protecting group free synthesis of glycomonomers based on lactose, melibiose and fucose. The monomers were polymerized in a precipitation polymerization in the presence of NiPAm to form crosslinked glyco-nanogels. The influence of reaction parameters like crosslinker type or stabilizer amount was investigated. The gels were characterized in lectin binding studies using model lectins and showed size and composition-dependent inhibition of lectin binding. Due to multivalent presentation of glycans in the gel, the inhibition was clearly stronger than with unmodified saccharides, which was compared after determination of the glycan loading. First studies with Pseudomonas aeruginosa revealed a surprising influence on the secretion of virulence factors. Functional glycogels may be in the future potent alternatives or adjuvants for antibiotic treatment of infections based on glycan interactions between host and pathogen.

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Fujikawa, Kohki. "Glycan Derivatives That Possess Chaperone-Like Activity". Trends in Glycoscience and Glycotechnology 30, n.º 177 (25 de novembro de 2018): E241—E243. http://dx.doi.org/10.4052/tigg.1831.6e.

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Fujikawa, Kohki. "Glycan Derivatives That Possess Chaperone-Like Activity". Trends in Glycoscience and Glycotechnology 30, n.º 177 (25 de novembro de 2018): J201—J202. http://dx.doi.org/10.4052/tigg.1831.6j.

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Brockhausen, Inka, Gabriele Möller, Annette Pollex-Krüger, Volker Rutz, Hans Paulsen e Khushi L. Matta. "Control of O-glycan synthesis: specificity and inhibition of O-glycan core 1 UDP-galactose:N-acetylgalactosamine-α-R β3-galactosyltransferase from rat liver". Biochemistry and Cell Biology 70, n.º 2 (1 de fevereiro de 1992): 99–108. http://dx.doi.org/10.1139/o92-015.

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The specificity of glycosyltransferases is a major control factor in the biosynthesis of O-glycans. The enzyme that synthesizes O-glycan core 1, i.e., UDP-galactose:N-acetylgalactosamine-α-R β3-galactosyltransferase (β3-Gal-T; EC 2.4.1.122), was partially purified from rat liver. The enzyme preparation, free of pyrophosphatases, β4-galactosyltransferase, β-galactosidase, and N-acetylglucosaminyltransferase I, was used to study the specificity and inhibition of the β3-Gal-T. β3-Gal-T activity is sensitive to changes in the R-group of the GalNAcα-R acceptor substrate and is stimulated when the R-group is a peptide or an aromatic group. Derivatives of GalNAcα-benzyl were synthesized and tested as potential substrates and inhibitors. Removal or substitution of the 3-hydroxyl or removal of the 4-hydroxyl of GalNAc abolished β3-Gal-T activity. Compounds with modifications of the 3- or 4-hydroxyl of GalNAcα-benzyl did not show significant inhibition. Removal or substitution of the 6-hydroxyl of GalNAc reduced activity slightly and these derivatives acted as competitive substrates. Derivatives with epoxide groups attached to the 6-position of GalNAc acted as substrates and not as inhibitors, with the exception of the photosensitive 6-O-(4,4-azo)pentyl-GalNAcα-benzyl, which inhibited Gal incorporation into GalNAcα-benzyl. The results indicate that the enzyme does not require the 6-hydroxyl of GalNAc, but needs the 3- and the axial 4-hydroxyl as essential requirements for binding and activity. In the usual biochemical O-glycan pathway, core 2 (GlcNAcβ6[Galβ3]GalNAcα-) is formed from core 1 (Galβ3GalNAc-R). We have now demonstrated an alternate pathway that may be of importance in human tissues.Key words: β3-Gal-transferase, mucin synthesis, O-glycan core 1, enzyme specificity, enzyme inhibition.

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Yamada, Keita, Jun Hirabayashi e Kazuaki Kakehi. "Analysis of O-Glycans as 9-Fluorenylmethyl Derivatives and Its Application to the Studies on Glycan Array". Analytical Chemistry 85, n.º 6 (março de 2013): 3325–33. http://dx.doi.org/10.1021/ac303771q.

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Pikora, Cheryl, Christine Wittish e Ronald C. Desrosiers. "Identification of Two N-Linked Glycosylation Sites within the Core of the Simian Immunodeficiency Virus Glycoprotein Whose Removal Enhances Sensitivity to Soluble CD4". Journal of Virology 79, n.º 19 (1 de outubro de 2005): 12575–83. http://dx.doi.org/10.1128/jvi.79.19.12575-12583.2005.

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ABSTRACT Using PCR mutagenesis to disrupt the NXT/S N-linked glycosylation motif of the Env protein, we created 27 mutants lacking 1 to 5 of 14 N-linked glycosylation sites within regions of gp120 lying outside of variable loops 1 to 4 within simian immunodeficiency virus strain 239 (SIV239). Of 18 mutants missing N-linked glycosylation sites predicted to lie within 10 Å of CD4 contact sites, the infectivity of 12 was sufficient to measure sensitivity to neutralization by soluble CD4 (sCD4), pooled immune sera from SIV239-infected rhesus macaques, and monoclonal antibodies known to neutralize certain derivatives of SIV239. Three of these 12 mutants (g3, lacking the 3rd glycan at position 79; g11, lacking the 11th glycan at position 212; and g3,11, lacking both the 3rd and 11th glycans) were approximately five times more sensitive to neutralization by sCD4 than wild-type (WT) SIV239. However, these same mutants were no more sensitive to neutralization than WT by pooled immune sera. The other 9 of 12 replication-competent mutants in this group were no more sensitive to neutralization than the WT by any of the neutralizing reagents. Six of the nine mutants that did not replicate appreciably had three or more glycosylation sites eliminated; the other three replication-deficient strains involved mutation of site 15. Our results suggest that elimination of glycan attachment sites 3 and 11 enhanced the exposure of contact residues for CD4. Thus, glycans at positions 3 and 11 of SIV239 gp120 may be particularly important for shielding the CD4-binding site from antibody recognition.

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Soriano del Amo, David, Wei Wang, Christen Besanceney, Tianqing Zheng, Yizheng He, Brian Gerwe, Ronald D. Seidel e Peng Wu. "Chemoenzymatic synthesis of the sialyl Lewis X glycan and its derivatives". Carbohydrate Research 345, n.º 9 (junho de 2010): 1107–13. http://dx.doi.org/10.1016/j.carres.2010.03.032.

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Zhao, Xuesen, Fang Guo, Mary Ann Comunale, Anand Mehta, Mohit Sehgal, Pooja Jain, Andrea Cuconati et al. "Inhibition of Endoplasmic Reticulum-Resident Glucosidases Impairs Severe Acute Respiratory Syndrome Coronavirus and Human Coronavirus NL63 Spike Protein-Mediated Entry by Altering the Glycan Processing of Angiotensin I-Converting Enzyme 2". Antimicrobial Agents and Chemotherapy 59, n.º 1 (27 de outubro de 2014): 206–16. http://dx.doi.org/10.1128/aac.03999-14.

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ABSTRACTEndoplasmic reticulum (ER)-resident glucosidases I and II sequentially trim the three terminal glucose moieties on the N-linked glycans attached to nascent glycoproteins. These reactions are the first steps of N-linked glycan processing and are essential for proper folding and function of many glycoproteins. Because most of the viral envelope glycoproteins contain N-linked glycans, inhibition of ER glucosidases with derivatives of 1-deoxynojirimycin, i.e., iminosugars, efficiently disrupts the morphogenesis of a broad spectrum of enveloped viruses. However, like viral envelope proteins, the cellular receptors of many viruses are also glycoproteins. It is therefore possible that inhibition of ER glucosidases not only compromises virion production but also disrupts expression and function of viral receptors and thus inhibits virus entry into host cells. Indeed, we demonstrate here that iminosugar treatment altered the N-linked glycan structure of angiotensin I-converting enzyme 2 (ACE2), which did not affect its expression on the cell surface or its binding of the severe acute respiratory syndrome coronavirus (SARS-CoV) spike glycoprotein. However, alteration of N-linked glycans of ACE2 impaired its ability to support the transduction of SARS-CoV and human coronavirus NL63 (HCoV-NL63) spike glycoprotein-pseudotyped lentiviral particles by disruption of the viral envelope protein-triggered membrane fusion. Hence, in addition to reducing the production of infectious virions, inhibition of ER glucosidases also impairs the entry of selected viruses via a post-receptor-binding mechanism.

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Le Guennec, Loic, Zoé Virion, Haniaa Bouzinba-Ségard, Catherine Robbe-Masselot, Renaud Léonard, Xavier Nassif, Sandrine Bourdoulous e Mathieu Coureuil. "Receptor recognition by meningococcal type IV pili relies on a specific complex N-glycan". Proceedings of the National Academy of Sciences 117, n.º 5 (21 de janeiro de 2020): 2606–12. http://dx.doi.org/10.1073/pnas.1919567117.

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Bacterial infections are frequently based on the binding of lectin-like adhesins to specific glycan determinants exposed on host cell receptors. These interactions confer species-specific recognition and tropism for particular host tissues and represent attractive antibacterial targets. However, the wide structural diversity of carbohydrates hampers the characterization of specific glycan determinants. Here, we characterized the receptor recognition of type IV pili (Tfp), a key adhesive factor present in numerous bacterial pathogens, using Neisseria meningitidis as a model organism. We found that meningococcal Tfp specifically recognize a triantennary sialylated poly-N-acetyllactosamine–containing N-glycan exposed on the human receptor CD147/Basigin, while fucosylated derivatives of this N-glycan impaired bacterial adhesion. Corroborating the inhibitory role of fucosylation on receptor recognition, adhesion of the meningococcus on nonhuman cells expressing human CD147 required prior defucosylation. These findings reveal the molecular basis of the selective receptor recognition by meningococcal Tfp and thereby, identify a potential antibacterial target.

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Cruz, Esteban, Vicki Sifniotis, Zeynep Sumer-Bayraktar, Mouhamad Reslan, Lorna Wilkinson-White, Stuart Cordwell e Veysel Kayser. "Glycan Profile Analysis of Engineered Trastuzumab with Rationally Added Glycosylation Sequons Presents Significantly Increased Glycan Complexity". Pharmaceutics 13, n.º 11 (20 de outubro de 2021): 1747. http://dx.doi.org/10.3390/pharmaceutics13111747.

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Protein aggregation constitutes a recurring complication in the manufacture and clinical use of therapeutic monoclonal antibodies (mAb) and mAb derivatives. Antibody aggregates can reduce production yield, cause immunogenic reactions, decrease the shelf-life of the pharmaceutical product and impair the capacity of the antibody monomer to bind to its cognate antigen. A common strategy to tackle protein aggregation involves the identification of surface-exposed aggregation-prone regions (APR) for replacement through protein engineering. It was shown that the insertion of N-glycosylation sequons on amino acids proximal to an aggregation-prone region can increase the physical stability of the protein by shielding the APR, thus preventing self-association of antibody monomers. We recently implemented this approach in the Fab region of full-size adalimumab and demonstrated that the thermodynamic stability of the Fab domain increases upon N-glycosite addition. Previous experimental data reported for this technique have lacked appropriate confirmation of glycan occupancy and structural characterization of the ensuing glycan profile. Herein, we mutated previously identified candidate positions on the Fab domain of Trastuzumab and employed tandem mass spectrometry to confirm attachment and obtain a detailed N-glycosylation profile of the mutants. The Trastuzumab glycomutants displayed a glycan profile with significantly higher structural heterogeneity compared to the HEK Trastuzumab antibody, which contains a single N-glycosylation site per heavy chain located in the CH2 domain of the Fc region. These findings suggest that Fab N-glycosites have higher accessibility to enzymes responsible for glycan maturation. Further, we have studied effects on additional glycosylation on protein stability via accelerated studies by following protein folding and aggregation propensities and observed that additional glycosylation indeed enhances physical stability and prevent protein aggregation. Our findings shed light into mAb glycobiology and potential implications in the application of this technique for the development of “biobetter” antibodies.

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Hitchen, Paul, Joanna Brzostek, Maria Panico, Jonathan A. Butler, Howard R. Morris, Anne Dell e Dennis Linton. "Modification of the Campylobacter jejuni flagellin glycan by the product of the Cj1295 homopolymeric-tract-containing gene". Microbiology 156, n.º 7 (1 de julho de 2010): 1953–62. http://dx.doi.org/10.1099/mic.0.038091-0.

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The Campylobacter jejuni flagellin protein is O-glycosylated with structural analogues of the nine-carbon sugar pseudaminic acid. The most common modifications in the C. jejuni 81-176 strain are the 5,7-di-N-acetylated derivative (Pse5Ac7Ac) and an acetamidino-substituted version (Pse5Am7Ac). Other structures detected include O-acetylated and N-acetylglutamine-substituted derivatives (Pse5Am7Ac8OAc and Pse5Am7Ac8GlnNAc, respectively). Recently, a derivative of pseudaminic acid modified with a di-O-methylglyceroyl group was detected in C. jejuni NCTC 11168 strain. The gene products required for Pse5Ac7Ac biosynthesis have been characterized, but those genes involved in generating other structures have not. We have demonstrated that the mobility of the NCTC 11168 flagellin protein in SDS-PAGE gels can vary spontaneously and we investigated the role of single nucleotide repeats or homopolymeric-tract-containing genes from the flagellin glycosylation locus in this process. One such gene, Cj1295, was shown to be responsible for structural changes in the flagellin glycoprotein. Mass spectrometry demonstrated that the Cj1295 gene is required for glycosylation with the di-O-methylglyceroyl-modified version of pseudaminic acid.

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Farese, R. V., D. R. Cooper, T. S. Konda, G. Nair, M. L. Standaert e R. J. Pollet. "Insulin provokes co-ordinated increases in the synthesis of phosphatidylinositol, phosphatidylinositol phosphates and the phosphatidylinositol–glycan in BC3H-1 myocytes". Biochemical Journal 256, n.º 1 (15 de novembro de 1988): 185–88. http://dx.doi.org/10.1042/bj2560185.

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BC3H-1 myocytes were cultured in the presence of [3H]inositol or [3H]glucosamine during their entire growth cycle to ensure that all lipids containing inositol and glucosamine were labelled to isotopic equilibrium or maximal specific radioactivity. After such labelling, a lipid (or group of lipids), which was labelled with both inositol and glucosamine, was observed to migrate between phosphatidylinositol 4-phosphate and phosphatidylinositol (PI) in two different t.l.c. systems. Insulin provoked rapid, sizeable, increases in the inositol-labelling of this lipid (presumably a PI-glycan), and these increases were similar to those observed in PI and PI phosphates. Our results indicate that insulin provokes co-ordinated increases in the net synthesis de novo of PI and its derivatives, PI phosphates and the PI-glycan, in BC3H-1 myocytes. This increase in synthesis of PI may serve as the mechanism for replenishing the PI-glycan during stimulation of its hydrolysis by insulin. Moreover, increases in the content of the PI-glycan may contribute to increases in the generation of head-group ‘mediators’ during insulin action.

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Wang, W., T. Hu, P. A. Frantom, T. Zheng, B. Gerwe, D. S. del Amo, S. Garret, R. D. Seidel e P. Wu. "Chemoenzymatic synthesis of GDP-L-fucose and the Lewis X glycan derivatives". Proceedings of the National Academy of Sciences 106, n.º 38 (4 de setembro de 2009): 16096–101. http://dx.doi.org/10.1073/pnas.0908248106.

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Shao, M. C., C. C. Chin, R. M. Caprioli e F. Wold. "The regulation of glycan processing in glycoproteins. The effect of avidin on individual steps in the processing of biotinylated glycan derivatives." Journal of Biological Chemistry 262, n.º 7 (março de 1987): 2973–79. http://dx.doi.org/10.1016/s0021-9258(18)61455-3.

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Tang, Jo Sing Julia, Kristin Schade, Lucas Tepper, Sany Chea, Gregor Ziegler e Ruben R. Rosencrantz. "Optimization of the Microwave Assisted Glycosylamines Synthesis Based on a Statistical Design of Experiments Approach". Molecules 25, n.º 21 (4 de novembro de 2020): 5121. http://dx.doi.org/10.3390/molecules25215121.

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Glycans carry a vast range of functions in nature. Utilizing their properties and functions in form of polymers, coatings or glycan derivatives for various applications makes the synthesis of modified glycans crucial. Since amines are easy to modify for subsequent reactions, we investigated regioselective amination conditions of different saccharides. Amination reactions were performed according to Kochetkov and Likhoshertov and accelerated by microwave irradiation. We optimized the synthesis of glycosylamines for N-acetyl-d-galactosamine, d-lactose, d-glucuronic acid and l-(−)-fucose using the design of experiments (DoE) approach. DoE enables efficient optimization with limited number of experimental data. A DoE software generated a set of experiments where reaction temperature, concentration of carbohydrate, nature of aminating agent and solvent were investigated. We found that the synthesis of glycosylamines significantly depends on the nature of the carbohydrate and on the reaction temperature. There is strong indication that high temperatures are favored for the amination reaction.

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Mohammed, Soran, e Natalie Ferry. "Characterization of Sialic Acid Affinity of the Binding Domain of Mistletoe Lectin Isoform One". International Journal of Molecular Sciences 22, n.º 15 (31 de julho de 2021): 8284. http://dx.doi.org/10.3390/ijms22158284.

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Sialic acid (Sia) is considered as one of the most important biomolecules of life since its derivatives and terminal orientations on cell membranes and macromolecules play a major role in many biological and pathological processes. To date, there is only a limited number of active molecules that can selectively bind to Sia and this limitation has made the study of this glycan challenging. The lectin superfamily is a well-known family of glycan binding proteins, which encompasses many strong glycan binding peptides with diverse glycan affinities. Mistletoe lectin (ML) is considered one of the most active members of lectin family which was initially classified in early studies as a galactose binding lectin; more recent studies have suggested that the peptide can also actively bind to Sia. However, the details with respect to Sia binding of ML and the domain responsible for this binding are left unanswered because no comprehensive studies have been instigated. In this study, we sought to identify the binding domain responsible for the sialic acid affinity of mistletoe lectin isoform I (MLI) in comparison to the binding activity of elderberry lectin isoform I (SNA), which has long been identified as a potent Sia binding lectin. In order to execute this, we performed computational carbohydrate-protein docking for MLB and SNA with Neu5Ac and β-Galactose. We further analyzed the coding sequence of both lectins and identified their glycan binding domains, which were later cloned upstream and downstream to green fluorescent protein (GFP) and expressed in Escherichia coli (E. coli). Finally, the glycan affinity of the expressed fusion proteins was assessed by using different biochemical and cell-based assays and the Sia binding domains were identified.

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Virág, Dávid, Tibor Kremmer, Kende Lőrincz, Norbert Kiss, Antal Jobbágy, Szabolcs Bozsányi, Lili Gulyás et al. "Altered Glycosylation of Human Alpha-1-Acid Glycoprotein as a Biomarker for Malignant Melanoma". Molecules 26, n.º 19 (3 de outubro de 2021): 6003. http://dx.doi.org/10.3390/molecules26196003.

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A high-resolution HILIC-MS/MS method was developed to analyze anthranilic acid derivatives of N-glycans released from human serum alpha-1-acid glycoprotein (AGP). The method was applied to samples obtained from 18 patients suffering from high-risk malignant melanoma as well as 19 healthy individuals. It enabled the identification of 102 glycan isomers separating isomers that differ only in sialic acid linkage (α-2,3, α-2,6) or in fucose positions (core, antenna). Comparative assessment of the samples revealed that upregulation of certain fucosylated glycans and downregulation of their nonfucosylated counterparts occurred in cancer patients. An increased ratio of isomers with more α-2,6-linked sialic acids was also observed. Linear discriminant analysis (LDA) combining 10 variables with the highest discriminatory power was employed to categorize the samples based on their glycosylation pattern. The performance of the method was tested by cross-validation, resulting in an overall classification success rate of 96.7%. The approach presented here is significantly superior to serological marker S100B protein in terms of sensitivity and negative predictive power in the population studied. Therefore, it may effectively support the diagnosis of malignant melanoma as a biomarker.

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Stelzl, Tamara, Kerstin E. Geillinger-Kästle, Jürgen Stolz e Hannelore Daniel. "Glycans in the intestinal peptide transporter PEPT1 contribute to function and protect from proteolysis". American Journal of Physiology-Gastrointestinal and Liver Physiology 312, n.º 6 (1 de junho de 2017): G580—G591. http://dx.doi.org/10.1152/ajpgi.00343.2016.

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Despite the fact that many membrane proteins carry extracellular glycans, little is known about whether the glycan chains also affect protein function. We recently demonstrated that the proton-coupled oligopeptide transporter 1 (PEPT1) in the intestine is glycosylated at six asparagine residues (N50, N406, N439, N510, N515, and N532). Mutagenesis-induced disruption of the individual N-glycosylation site N50, which is highly conserved among mammals, was detected to significantly enhance the PEPT1-mediated inward transport of peptides. Here, we show that for the murine protein the inhibition of glycosylation at sequon N50 by substituting N50 with glutamine, lysine, or cysteine or by replacing S52 with alanine equally altered PEPT1 transport kinetics in oocytes. Furthermore, we provide evidence that the uptake of [14C]glycyl-sarcosine in immortalized murine small intestinal (MODE-K) or colonic epithelial (PTK-6) cells stably expressing the PEPT1 transporter N50Q is also significantly increased relative to the wild-type protein. By using electrophysiological recordings and tracer flux studies, we further demonstrate that the rise in transport velocity observed for PEPT1 N50Q is bidirectional. In line with these findings, we show that attachment of biotin derivatives, comparable in weight with two to four monosaccharides, to the PEPT1 N50C transporter slows down the transport velocity. In addition, our experiments provide strong evidence that glycosylation of PEPT1 confers resistance against proteolytic cleavage by proteinase K, whereas a remarkable intrinsic stability against trypsin, even in the absence of N-linked glycans, was detected. NEW & NOTEWORTHY This study highlights the role of N50-linked glycans in modulating the bidirectional transport activity of the murine peptide transporter PEPT1. Electrophysiological and tracer flux measurements in Xenopus oocytes have shown that removal of the N50 glycans increases the maximal peptide transport rate in the inward and outward directions. This effect could be largely reversed by replacement of N50 glycans with structurally dissimilar biotin derivatives. In addition, N-glycans were detected to stabilize PEPT1 against proteolytic cleavage.

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Lafont, Dominique, Paul Boullanger, Joseph Banoub e Gerard Descotes. "Synthesis of glycan fragments of glycoproteins using peracetylated N-allyloxycarbonyl-β-D-glucosamine and 1,6-anhydro-β-D-mannopyranose derivatives". Canadian Journal of Chemistry 68, n.º 6 (1 de junho de 1990): 828–35. http://dx.doi.org/10.1139/v90-131.

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The disaccharides β-D-GlcNAOC-(1 → 2)-D-Man, β-D-GlcNAOC-(1→ 4)-D-Man, the trisaccharide β-D-GlcNAOC-(1 → 2)-[β-D-GlcNAOC-(1→ 4)]-D-Man, and the tetrasaccharide β-D-GlcNAOC-(1 → 2)-[β-D-GlcNAOC-(1→ 3)]-[β-D-GlcNAOC-(1 → 4)]-D-Man have been synthesized in their peracetylated form, using the Lewis acid catalyzed condensations of 1,3,4,6-tetra-O-acetyl-2-N-allyloxycarbonylamino-2-deoxy-β-D-glucopyranose 1 with properly substituted 1,6-anhydro-β-D-mannopyranose derivatives. The anhydro glycosylation products obtained were then easily transformed into the 4C1 peracetylated derivatives by acetolysis. The N-allyloxycarbonyl groups could be converted into N-acetyl groups in the presence of Pd(0) complexes, followed by reacetylation of the free amino function in high yields. Keywords: N-allyloxycarbonyl, glycosylation, glucosamine, glycan fragments.

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Ohkawa, Yuki, Yoichiro Harada e Naoyuki Taniguchi. "Keratan sulfate-based glycomimetics using Langerin as a target for COPD: lessons from studies on Fut8 and core fucose". Biochemical Society Transactions 49, n.º 1 (22 de fevereiro de 2021): 441–53. http://dx.doi.org/10.1042/bst20200780.

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Glycosylation represents one of the most abundant posttranslational modification of proteins. Glycosylation products are diverse and are regulated by the cooperative action of various glycosyltransferases, glycosidases, substrates thereof: nucleoside sugars and their transporters, and chaperons. In this article, we focus on a glycosyltransferase, α1,6-fucosyltransferase (Fut8) and its product, the core fucose structure on N-glycans, and summarize the potential protective functions of this structure against emphysema and chronic obstructive pulmonary disease (COPD). Studies of FUT8 and its enzymatic product, core fucose, are becoming an emerging area of interest in various fields of research including inflammation, cancer and therapeutics. This article discusses what we can learn from studies of Fut8 and core fucose by using knockout mice or in vitro studies that were conducted by our group as well as other groups. We also include a discussion of the potential protective functions of the keratan sulfate (KS) disaccharide, namely L4, against emphysema and COPD as a glycomimetic. Glycomimetics using glycan analogs is one of the more promising therapeutics that compensate for the usual therapeutic strategy that involves targeting the genome and the proteome. These typical glycans using KS derivatives as glycomimetics, will likely become a clue to the development of novel and effective therapeutic strategies.

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Shamsi Kazem Abadi, Saeideh, Matthew C. Deen, Jacqueline N. Watson, Fahimeh S. Shidmoossavee e Andrew J. Bennet. "Directed evolution of a remarkably efficient Kdnase from a bacterial neuraminidase". Glycobiology 30, n.º 5 (4 de dezembro de 2019): 325–33. http://dx.doi.org/10.1093/glycob/cwz099.

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Abstract N-acetylneuraminic acid (5-acetamido-3,5-dideoxy-d-glycero-d-galacto-non-2-ulosonic acid), which is the principal sialic acid family member of the non-2-ulosonic acids and their various derivatives, is often found at the terminal position on the glycan chains that adorn all vertebrate cells. This terminal position combined with subtle variations in structure and linkage to the underlying glycan chains between humans and other mammals points to the importance of this diverse group of nine-carbon sugars as indicators of the unique aspects of human evolution and is relevant to understanding an array of human conditions. Enzymes that catalyze the removal N-acetylneuraminic acid from glycoconjugates are called neuraminidases. However, despite their documented role in numerous diseases, due to the promiscuous activity of many neuraminidases, our knowledge of the functions and metabolism of many sialic acids and the effect of the attachment to cellular glycans is limited. To this end, through a concerted effort of generation of random and site-directed mutagenesis libraries, subsequent screens and positive and negative evolutionary selection protocols, we succeeded in identifying three enzyme variants of the neuraminidase from the soil bacterium Micromonospora viridifaciens with markedly altered specificity for the hydrolysis of natural Kdn (3-deoxy-d-glycero-d-galacto-non-2-ulosonic acid) glycosidic linkages compared to those of N-acetylneuraminic acid. These variants catalyze the hydrolysis of Kdn-containing disaccharides with catalytic efficiencies (second-order rate constants: kcat/Km) of greater than 105 M−1 s−1; the best variant displayed an efficiency of >106 M−1 s−1 at its optimal pH.

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Yang, Wen-Bin, Wei-Ting Hung, Yi-Ting Chen, Shwu-Huey Wang e Yin-Chen Liu. "A new method for aldo-sugar analysis in beverages and dietary foods". Functional Foods in Health and Disease 6, n.º 4 (27 de abril de 2016): 234. http://dx.doi.org/10.31989/ffhd.v6i4.251.

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Background: Carbohydrates are found in most of our everyday diet; however, sugar analysis is difficult and inconvenient in food materials such as beverages, fruits and vegetables. Here, we report a new method for labeling the sugar ingredients in beverages and plant foods. The mentioned method provides a high sensitive and efficient tool for sugar compositional analysis by labeling the aldoses in beverages and foods with 2,3-naphthalenediamine via an iodine-promoted oxidative condensation reaction to form highly fluorescent aldo-naphthylimidazole (NAIM) derivatives. We have also separated the natural glycosides from dietary foods, for instance, solanines from tomato and potato. The various types of solanines with different sugar moieties were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). The glycan is released by acidic hydrolysis, and the sugar components are subjected to NAIM labeling. These aldo-NAIM derivatives not only show enhanced mass signaling, but also provide fluorescent moiety at the reducing end of sugar to assist the detection in HPLC analysis.Objective: To develop a rapid and sensitive sugar detection method for research and commercial use, as well as to understand the sugar composition in dietary beverages and functional foods.Results: Five beverages in Taiwan were examined for the composition of six common sugars. Two Solanaceae samples extracted from the potato and tomato plants were measured by MALDI MS and ESI-MS/MS. The structures of solanines were elucidated and the glycan moieties were converted to the fluorescent NAIM derivatives to confirm their composition.Conclusions: The results suggest that the aldo-NAIM method is efficient and rapid for evaluation of sugar composition and concentration in beverages and foods.Key words: beverages, foods, potato, tomato, aldose, sugar analysis, fluorescence, NAIM kit

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Pongracz, Tamas, Aswin Verhoeven, Manfred Wuhrer e Noortje de Haan. "The structure and role of lactone intermediates in linkage-specific sialic acid derivatization reactions". Glycoconjugate Journal 38, n.º 2 (18 de janeiro de 2021): 157–66. http://dx.doi.org/10.1007/s10719-020-09971-7.

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AbstractSialic acids occur ubiquitously throughout vertebrate glycomes and often endcap glycans in either α2,3- or α2,6-linkage with diverse biological roles. Linkage-specific sialic acid characterization is increasingly performed by mass spectrometry, aided by differential sialic acid derivatization to discriminate between linkage isomers. Typically, during the first step of such derivatization reactions, in the presence of a carboxyl group activator and a catalyst, α2,3-linked sialic acids condense with the subterminal monosaccharides to form lactones, while α2,6-linked sialic acids form amide or ester derivatives. In a second step, the lactones are converted into amide derivatives. Notably, the structure and role of the lactone intermediates in the reported reactions remained ambiguous, leaving it unclear to which extent the amidation of α2,3-linked sialic acids depended on direct aminolysis of the lactone, rather than lactone hydrolysis and subsequent amidation. In this report, we used mass spectrometry to unravel the role of the lactone intermediate in the amidation of α2,3-linked sialic acids by applying controlled reaction conditions on simple and complex glycan standards. The results unambiguously show that in common sialic acid derivatization protocols prior lactone formation is a prerequisite for the efficient, linkage-specific amidation of α2,3-linked sialic acids, which proceeds predominantly via direct aminolysis. Furthermore, nuclear magnetic resonance spectroscopy confirmed that exclusively the C2 lactone intermediate is formed on a sialyllactose standard. These insights allow a more rationalized method development for linkage-specific sialic derivatization in the future.

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Faltinek, Lukáš, Eva Fujdiarová, Filip Melicher, Josef Houser, Martina Kašáková, Nikolay Kondakov, Leonid Kononov, Kamil Parkan, Sébastien Vidal e Michaela Wimmerová. "Lectin PLL3, a Novel Monomeric Member of the Seven-Bladed β-Propeller Lectin Family". Molecules 24, n.º 24 (11 de dezembro de 2019): 4540. http://dx.doi.org/10.3390/molecules24244540.

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The Photorhabdus species is a Gram-negative bacteria of the family Morganellaceae that is known for its mutualistic relationship with Heterorhabditis nematodes and pathogenicity toward insects. This study is focused on the characterization of the recombinant lectin PLL3 with an origin in P. laumondii subsp. laumondii. PLL3 belongs to the PLL family of lectins with a seven-bladed β-propeller fold. The binding properties of PLL3 were tested by hemagglutination assay, glycan array, isothermal titration calorimetry, and surface plasmon resonance, and its structure was determined by X-ray crystallography. Obtained data revealed that PLL3 binds similar carbohydrates to those that the other PLL family members bind, with some differences in the binding properties. PLL3 exhibited the highest affinity toward l-fucose and its derivatives but was also able to interact with O-methylated glycans and other ligands. Unlike the other members of this family, PLL3 was discovered to be a monomer, which might correspond to a weaker avidity effect compared to homologous lectins. Based on the similarity to the related lectins and their proposed biological function, PLL3 might accompany them during the interaction of P. laumondii with both the nematode partner and the insect host.

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Collot, Mayeul, Julie Savreux e Jean-Maurice Mallet. "New thioglycoside derivatives for use in odourless synthesis of MUXF3 N-glycan fragments related to food allergens". Tetrahedron 64, n.º 7 (fevereiro de 2008): 1523–35. http://dx.doi.org/10.1016/j.tet.2007.11.002.

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Adamiak, Kathrin, Thorsten Anders, Manja Henze, Helmut Keul, Martin Möller e Lothar Elling. "Chemo-enzymatic synthesis of functionalized oligomers of N-acetyllactosamine glycan derivatives and their immobilization on biomaterial surfaces". Journal of Molecular Catalysis B: Enzymatic 84 (dezembro de 2012): 108–14. http://dx.doi.org/10.1016/j.molcatb.2012.02.002.

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Liu, Mingqi, Xiang Luo, Qiujun Qiu, Le Kang, Tang Li, Junqiang Ding, Yan Xiong et al. "Redox- and pH-Sensitive Glycan (Polysialic Acid) Derivatives and F127 Mixed Micelles for Tumor-Targeted Drug Delivery". Molecular Pharmaceutics 15, n.º 12 (3 de novembro de 2018): 5534–45. http://dx.doi.org/10.1021/acs.molpharmaceut.8b00687.

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Kiso, Makoto, Masayuki Kitagawa, Hideharu Ishida e Akira Hasegawa. "Studies on Glycan Processing Inhibitors: Synthesis of N-Acetylhexosamine Analogs and Cyclic Carbamate Derivatives of 1-Deoxynojirimycin". Journal of Carbohydrate Chemistry 10, n.º 1 (janeiro de 1991): 25–45. http://dx.doi.org/10.1080/07328309108543888.

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Hoagland, Luke F. M., Michael J. Campa, Elizabeth B. Gottlin, James E. Herndon e Edward F. Patz. "Haptoglobin and posttranslational glycan-modified derivatives as serum biomarkers for the diagnosis of nonsmall cell lung cancer". Cancer 110, n.º 10 (2007): 2260–68. http://dx.doi.org/10.1002/cncr.23049.

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Qu, Xiaowang, Xiaoben Pan, Jessica Weidner, Wenquan Yu, Dominic Alonzi, Xiaodong Xu, Terry Butters, Timothy Block, Ju-Tao Guo e Jinhong Chang. "Inhibitors of Endoplasmic Reticulum α-Glucosidases Potently Suppress Hepatitis C Virus Virion Assembly and Release". Antimicrobial Agents and Chemotherapy 55, n.º 3 (20 de dezembro de 2010): 1036–44. http://dx.doi.org/10.1128/aac.01319-10.

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ABSTRACTα-Glucosidases I and II are endoplasmic reticulum-resident enzymes that are essential for N-linked glycan processing and subsequent proper folding of glycoproteins. In this report, we first demonstrate that downregulation of the expression of α-glucosidase I, II, or both in Huh7.5 cells by small hairpin RNA technology inhibited the production of hepatitis C virus (HCV). In agreement with the essential role of α-glucosidases in HCV envelope glycoprotein processing and folding, treatment of HCV-infected cells with a panel of imino sugar derivatives, which are competitive inhibitors of α-glucosidases, did not affect intracellular HCV RNA replication and nonstructural protein expression but resulted in the inhibition of glycan processing and subsequent degradation of HCV E2 glycoprotein. As a consequence, HCV virion assembly and secretion were inhibited. In searching for imino sugars with better antiviral activity, we found that a novel imino sugar, PBDNJ0804, had a superior ability to inhibit HCV virion assembly and secretion. In summary, we demonstrated that glucosidases are important host factor-based antiviral targets for HCV infection. The low likelihood of drug-resistant virus emergence and potent antiviral efficacy of the novel glucosidase inhibitor hold promise for its development as a therapeutic agent for the treatment of chronic hepatitis C.

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Reihill, Mark, Lorenzo Guazzelli, Han Remaut e Stefan Oscarson. "Synthesis of Fucose Derivatives with Thiol Motifs towards Suicide Inhibition of Helicobacter pylori". Molecules 25, n.º 18 (18 de setembro de 2020): 4281. http://dx.doi.org/10.3390/molecules25184281.

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The syntheses of six thiol-exhibiting monosaccharides towards suicide inhibition of Helicobacter pylori are reported. Blood group Antigen Binding Adhesin (BabA), a bacterial membrane-bound lectin, binds to human ABO and Lewis b blood group structures displayed on the surface of host epithelial cells. Crystal structures of the carbohydrate-recognition domain revealed a conserved disulfide bonded loop that anchors a critical fucose residue in these blood group structures. Disruption of this loop by N-acetylcysteine results in reduced BabA-mediated adherence to human gastric tissue sections and attenuated virulence in Lewis b-expressing transgenic mice. With a view of creating specific inhibitors of the lectin, we designed and successfully synthesised six fucose-derived compounds with thiol motifs to engage in a thiol-disulfide exchange with this disulfide bond of BabA and form a glycan-lectin disulfide linkage. Branching and extending the fucose backbone with 2- and 3-carbon thiol motifs delivered a range of candidates to be tested for biological activity against BabA.

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Tanaka, Katsunori, e Koichi Fukase. "Development of Azaelectrocyclization-Based Labeling and Application to Noninvasive Imaging and Targeting Using N-Glycan Derivatives—In Pursuit of N-Glycan Functions on Proteins, Dendrimers, and Living Cells—". Trends in Glycoscience and Glycotechnology 24, n.º 136 (2012): 47–64. http://dx.doi.org/10.4052/tigg.24.47.

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Nakano, M., D. Higo, E. Arai, T. Nakagawa, K. Kakehi, N. Taniguchi e A. Kondo. "Capillary electrophoresis-electrospray ionization mass spectrometry for rapid and sensitive N-glycan analysis of glycoproteins as 9-fluorenylmethyl derivatives". Glycobiology 19, n.º 2 (24 de outubro de 2008): 135–43. http://dx.doi.org/10.1093/glycob/cwn115.

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KISO, M., M. KITAGAWA, H. ISHIDA e A. HASEGAWA. "ChemInform Abstract: Studies on Glycan Processing Inhibitors: Synthesis of N- Acetylhexosamine Analogs and Cyclic Carbamate Derivatives of 1- Deoxynojirimycin." ChemInform 23, n.º 3 (22 de agosto de 2010): no. http://dx.doi.org/10.1002/chin.199203310.

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WU, Albert M., June H. WU, Anthony HERP e Jia-Hau LIU. "Effect of polyvalencies of glycotopes on the binding of a lectin from the edible mushroom, Agaricus bisporus". Biochemical Journal 371, n.º 2 (15 de abril de 2003): 311–20. http://dx.doi.org/10.1042/bj20021361.

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Agaricus bisporus agglutinin (ABA) isolated from edible mushroom has a potent anti-proliferative effect on malignant colon cells with considerable therapeutic potential as an anti-neoplastic agent. Since previous studies on the structural requirement for binding were limited to molecular or submolecular levels of Galβ1-3GalNAc (T; Thomsen–Friedenreich disaccharide glycotope; where Gal represents d-galactopyranose and GalNAc represents 2-acetamido-2-deoxy-d-galactopyranose) and its derivatives, the binding properties of ABA were further investigated using our collection of glycans by enzyme-linked lectinosorbent assay and lectin–glycan inhibition assay. The results indicate that polyvalent Galβ1-related glycotopes, GalNAcα1-Ser/Thr (Tn), and their cryptoforms, are the most potent factor for ABA binding. They were up to 5.5×105 and 4.7×106 times more active than monomeric T and GalNAc respectively. The affinity of ABA for ligands can be ranked as: multivalent Tα (Galβ1-3GalNAcα1-), Tn and I/II (Galβ1-3GlcNac/Galβ1-4GlcNAc, where GlcNAc represents 2-acetamido-2-deoxy-d-glucopyranose)>>>>monomeric Tα and Tn>I>>GalNAc>>>II, L (Galβ1-4Glc, where Glc represents d-glucopyranose) and Gal (inactive). These specific binding features of ABA establish the importance of affinity enhancement by high-density polyvalent (versus multiantennary I/II) glycotopes and facilitate our understanding of the lectin receptor recognition events relevant to its biological activities.

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Tkachuk, Zenoviy, Nataliia Melnichuk, Roman O. Nikolaiev, Kosma Szutkowski e Igor Zhukov. "The Natural Oligoribonucleotides Functionalized by D-Mannitol Affected Interactions of Hemagglutinin with Glycan Receptor Indicating Anti-Influenza Activity". Membranes 11, n.º 10 (30 de setembro de 2021): 757. http://dx.doi.org/10.3390/membranes11100757.

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Hemagglutinin (HA), the class I influenza A virus protein is responsible for the attachment of virus particles to the cell by binding to glycan receptors, subsequent virion internalization, and cell entry. Consequently, the importance of HA makes it a primary target for the development of anti-influenza drugs. The natural oligoribonucleotides (ORNs) as well as their derivatives functionalized with D-mannitol (ORNs-D-M) possess anti-influenza properties in vitro and in vivo due to interaction with HA receptor sites. This activity suppresses the viral infection in host cells. In the present work, the complexes of ORNs and ORNs-D-M with HA protein were studied by agglutination assay, fluorescence spectroscopy, as well as molecular docking simulations. Acquired experimental data exhibited a decrease in HA titer by 32 times after incubation with the ORNs-D-M for 0.5–24 h. Quenching fluorescence intensity of the HA suggests that titration by ORNs and ORNs-D-M probably leads to changes in the HA structure. Detailed structural data were obtained with the molecular docking simulations performed for ORNs and ORNs-D-M ligands containing three and six oligoribonucleotides. The results reveal that a majority of the ORNs and ORNs-D-M bind in a non-specific way to the receptor-binding domain of the HA protein. The ligand’s affinity to the hemagglutinin was estimated at the micromolar level. Presented experimental data confirmed that both natural ORNs and functionalized ORNs-D-M inhibit the interactions between HA and glycan receptors and demonstrate anti-influenza activity.

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Horník, Štěpán, Lucie Červenková Šťastná, Petra Cuřínová, Jan Sýkora, Kateřina Káňová, Roman Hrstka, Ivana Císařová, Martin Dračínský e Jindřich Karban. "Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine". Beilstein Journal of Organic Chemistry 12 (20 de abril de 2016): 750–59. http://dx.doi.org/10.3762/bjoc.12.75.

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Background: Derivatives of D-glucosamine and D-galactosamine represent an important family of the cell surface glycan components and their fluorinated analogs found use as metabolic inhibitors of complex glycan biosynthesis, or as probes for the study of protein–carbohydrate interactions. This work is focused on the synthesis of acetylated 3-deoxy-3-fluoro, 4-deoxy-4-fluoro and 3,4-dideoxy-3,4-difluoro analogs of D-glucosamine and D-galactosamine via 1,6-anhydrohexopyranose chemistry. Moreover, the cytotoxicity of the target compounds towards selected cancer cells is determined. Results: Introduction of fluorine at C-3 was achieved by the reaction of 1,6-anhydro-2-azido-2-deoxy-4-O-benzyl-β-D-glucopyranose or its 4-fluoro analog with DAST. The retention of configuration in this reaction is discussed. Fluorine at C-4 was installed by the reaction of 1,6:2,3-dianhydro-β-D-talopyranose with DAST, or by fluoridolysis of 1,6:3,4-dianhydro-2-azido-β-D-galactopyranose with KHF2. The amino group was introduced and masked as an azide in the synthesis. The 1-O-deacetylated 3-fluoro and 4-fluoro analogs of acetylated D-galactosamine inhibited proliferation of the human prostate cancer cell line PC-3 more than cisplatin and 5-fluorouracil (IC50 28 ± 3 μM and 54 ± 5 μM, respectively). Conclusion: A complete series of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine is now accessible by 1,6-anhydrohexopyranose chemistry. Intermediate fluorinated 1,6-anhydro-2-azido-hexopyranoses have potential as synthons in oligosaccharide assembly.

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Johnson, Welkin E., Hannah Sanford, Linda Schwall, Dennis R. Burton, Paul W. H. I. Parren, James E. Robinson e Ronald C. Desrosiers. "Assorted Mutations in the Envelope Gene of Simian Immunodeficiency Virus Lead to Loss of Neutralization Resistance against Antibodies Representing a Broad Spectrum of Specificities". Journal of Virology 77, n.º 18 (15 de setembro de 2003): 9993–10003. http://dx.doi.org/10.1128/jvi.77.18.9993-10003.2003.

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ABSTRACT Simian immunodeficiency virus (SIV) of macaques isolate SIVmac239 is highly resistant to neutralization by polyclonal antisera or monoclonal antibodies, a property that it shares with most primary isolates of human immunodeficiency virus type 1 (HIV-1). This resistance is important for the ability of the virus to persist at high levels in vivo. To explore the physical features of the viral envelope complex that contribute to the neutralization-resistant phenotype, we examined a panel of SIVmac239 derivatives for sensitivity to neutralization by a large collection of monoclonal antibodies (MAbs). These MAbs recognize both linear and conformational epitopes throughout the viral envelope proteins. The variant viruses included three derivatives of SIVmac239 with substitutions in specific N-linked glycosylation sites of gp120 and a fourth variant that lacked the100 amino acids that encompass the V1 and V2 loops. Also included in this study was SIVmac316, a variant of SIVmac239 with distributed mutations in env that confer significantly increased replicative capacity in tissue macrophages. These viruses were chosen to represent a broad range of neutralization sensitivities based on susceptibility to pooled, SIV-positive plasma. All three of these very different kinds of mutations (amino acid substitutions, elimination of N-glycan attachment sites, and a 100-amino-acid deletion spanning variable loops V1 and V2) dramatically increased sensitivity to neutralization by MAbs from multiple competition groups. Thus, the mutations did not simply expose localized epitopes but rather conferred global increases in neutralization sensitivity. The removal of specific N-glycan attachment sites from V1 and V2 led to increased sensitivity to neutralization by antibodies recognizing epitopes from both within and outside of the V1-V2 sequence. Surprisingly, while most of the mutations that gave rise to increased sensitivity were located in the N-terminal half of gp120 (surface subunit [SU]), the greatest increases in sensitivity were to MAbs recognizing the C-terminal half of gp120 or the ectodomain of gp41 (transmembrane subunit [TM]). This reagent set and information should now be useful for defining the physical, structural, thermodynamic, and kinetic factors that influence relative sensitivity to antibody-mediated neutralization.

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PARODI, Armando J. "Role of N-oligosaccharide endoplasmic reticulum processing reactions in glycoprotein folding and degradation". Biochemical Journal 348, n.º 1 (9 de maio de 2000): 1–13. http://dx.doi.org/10.1042/bj3480001.

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The endoplasmic reticulum (ER) is the subcellular site where proteins following the secretory pathway acquire their proper tertiary and, in certain cases, quaternary structures. Species that are not yet properly folded are prevented from exit to the Golgi apparatus and, if permanently misfolded, are transported to the cytosol, where they are degraded in the proteasomes. This review deals with a mechanism, applicable to proteins that are N-glycosylated in the ER, by which the quality control of folding is performed. Protein-linked monoglucosylated glycans, formed by glucosidase I- and glucosidase II-dependent partial deglucosylation of the oligosaccharides transferred from dolichol diphosphate derivatives in N-glycosylation (Glc3Man9GlcNAc2), mediate glycoprotein recognition by two ER-resident lectins, membrane-bound calnexin (CNX) and its soluble homologue, calreticulin (CRT). A still not yet fully confirmed interaction between the lectins and the protein moieties of folding glycoproteins may occur after lectin recognition of monoglucosylated structures. Further deglucosylation of glycans by glucosidase II, and perhaps also by a change in CNX/CRT and/or in the substrate glycoprotein conformation, liberates the glycoproteins from their CNX/CRT anchors. Glycans may be then reglucosylated by the UDP-Glc:glycoprotein glucosyltransferase (GT), and thus be recognized again by CNX/CRT, but only when linked to not yet properly folded protein moieties, as this enzyme behaves as a sensor of glycoprotein conformation. Deglucosylation/reglucosylation cycles catalysed by the opposing activities of glucosidase II and GT only stop when proper folding is achieved. The interaction between CNX/CRT and a monoglucosylated glycan is one of the alternative mechanisms by which cells retain not yet properly folded glycoproteins in the ER; in addition, it enhances folding efficiency by preventing protein aggregation and thus allowing intervention of classical chaperones and other folding-assisting proteins. There is evidence suggesting that both glycoprotein glucosylation and mannose removal, respectively mediated by GT and ER mannosidase I, might be involved in cell recognition of permanently misfolded glycoproteins bound for proteasome degradation.

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Deng, Lingquan, Xin Wang, Suji Uppalapati, Oscar Norberg, Hai Dong, Adrien Joliton, Mingdi Yan e Olof Ramström. "Stereocontrolled 1-S-glycosylation and comparative binding studies of photoprobe-thiosaccharide conjugates with their O-linked analogs". Pure and Applied Chemistry 85, n.º 9 (1 de setembro de 2013): 1789–801. http://dx.doi.org/10.1351/pac-con-12-08-13.

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The use of thioglycosides and other glycan derivatives with anomeric sulfur linkages is gaining increasing interest, both in synthesis and in various biological contexts. Herein, we demonstrate the occurrence and circumvention of anomerization during 1-S-glycosylation reactions, and present highly efficient and stereocontrolled syntheses of a series of photoprobe-thiosaccharide conjugates. Mutarotation of glycosyl thiols proved to be the origin of the anomeric mixtures formed, and kinetic effects could be used to circumvent anomerization. The synthesized carbohydrate conjugates were then evaluated by both solution- and solid-phase-based techniques. Both binding results showed that the S-linked glycosides interact with their cognate lectins comparably to the corresponding O-analogs in the present cases, thus demonstrating the reliability of the solid-support platform built upon our photo-initiated carbohydrate immobilization method for probing protein bindings, and showing the potential of combining these two means for studying carbohydrate–protein interactions.

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Hattori, Kazuyuki, e Takashi Yoshida. "Synthesis of a new 2-amino-glycan, poly-(1→6)-α-D -mannosamine, by ring-opening polymerization of 1,6-anhydro-mannosamine derivatives". Journal of Polymer Science Part A: Polymer Chemistry 50, n.º 21 (3 de agosto de 2012): 4524–31. http://dx.doi.org/10.1002/pola.26262.

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Astronomo, Rena D., Hing-Ken Lee, Christopher N. Scanlan, Ralph Pantophlet, Cheng-Yuan Huang, Ian A. Wilson, Ola Blixt, Raymond A. Dwek, Chi-Huey Wong e Dennis R. Burton. "A Glycoconjugate Antigen Based on the Recognition Motif of a Broadly Neutralizing Human Immunodeficiency Virus Antibody, 2G12, Is Immunogenic but Elicits Antibodies Unable To Bind to the Self Glycans of gp120". Journal of Virology 82, n.º 13 (23 de abril de 2008): 6359–68. http://dx.doi.org/10.1128/jvi.00293-08.

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ABSTRACT The glycan shield of human immunodeficiency virus type 1 (HIV-1) gp120 contributes to viral evasion from humoral immune responses. However, the shield is recognized by the HIV-1 broadly neutralizing antibody (Ab), 2G12, at a relatively conserved cluster of oligomannose glycans. The discovery of 2G12 raises the possibility that a carbohydrate immunogen may be developed that could elicit 2G12-like neutralizing Abs and contribute to an AIDS vaccine. We have previously dissected the fine specificity of 2G12 and reported that the synthetic tetramannoside (Man4) that corresponds to the D1 arm of Man9GlcNAc2 inhibits 2G12 binding to gp120 as efficiently as Man9GlcNAc2 itself, indicating the potential use of Man4 as a building block for creating immunogens. Here, we describe the development of neoglycoconjugates displaying variable copy numbers of Man4 on bovine serum albumin (BSA) molecules by conjugation to Lys residues. The increased valency enhances the apparent affinity of 2G12 for Man4 up to a limit which is achieved at ∼10 copies per BSA molecule, beyond which no further enhancement is observed. Immunization of rabbits with BSA-(Man4)14 elicits significant serum Ab titers to Man4. However, these Abs are unable to bind gp120. Further analysis reveals that the elicited Abs bind a variety of unbranched and, to a lesser extent, branched Man9 derivatives but not natural N-linked oligomannose containing the chitobiose core. These results suggest that Abs can be readily elicited against the D1 arm; however, potential differences in the presentation of Man4 on neoglycoconjugates, compared to glycoproteins, poses challenges for eliciting anti-mannose Abs capable of cross-reacting with gp120 and HIV-1.

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Easton, CJ, e SC Peters. "Reactions of α-Substituted Glycine Derivatives With Stannanes in the Presence of Disulfides". Australian Journal of Chemistry 47, n.º 5 (1994): 859. http://dx.doi.org/10.1071/ch9940859.

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Reactions of α- bromo -, α- benzoyloxy - and α- methoxy -substituted glycine derivatives with stannanes afforded the corresponding α- centred glycinyl radical, which reacted with di -t-butyl disulfide and diphenyl disulfide by homolytic substitution to give the corresponding α-t- butylthio- and α-phenylthio -substituted glycine derivatives, respectively. The glycinyl radical reacted with dibenzyl disulfide by displacement of benzyl radical to give a mixed disulfide, which was subsequently reduced to the corresponding α- benzylthio-substituted glycine derivative. In related reactions of a cystine derivative the corresponding S-glycinylcysteine derivative was produced, indicating that, while the chemical integrity of disulfide bonds in cystine derivatives is likely to be affected in radical reactions of peptides, the reactions are suitable for exploitation in the synthesis of cross-linked amino acid derivatives.

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Jankowska, Ewa, e John Cipollo. "Platform for analysis of anthranilic acidN-glycan derivatives utilizing multipolarity mode LC–MS with hydrophilic interaction chromatography separation and ion trap MS/MS". Bioanalysis 3, n.º 21 (novembro de 2011): 2401–17. http://dx.doi.org/10.4155/bio.11.247.

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Cao, Benjamin, Jonathan M. White e Spencer J. Williams. "Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan". Beilstein Journal of Organic Chemistry 7 (28 de março de 2011): 369–77. http://dx.doi.org/10.3762/bjoc.7.47.

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Mycobacterium tuberculosis, the causitive agent of tuberculosis (TB), possesses a complex cell wall containing mannose-rich glycophospholids termed phosphatidylinositol mannosides (PIMs), lipomannan (LM), and lipoarabinomannan (LAM). These glycophospholipids play important roles in cell wall function and host–pathogen interactions. Synthetic PIM/LM/LAM substructures are useful biochemical tools to delineate and dissect the fine details of mannose glycophospholipid biosynthesis and their interactions with host cells. We report the efficient synthesis of a series of azidooctyl di- and trimannosides possessing the following glycan structures: α-Man-1,6-α-Man, α-Man-1,6-α-Man-1,6-α-Man, α-Man-1,2-α-Man-1,6-α-Man and 2,6-di-(α-Man)-α-Man. The synthesis includes the use of non-benzyl protecting groups compatible with the azido group and preparation of the branched trisaccharide structure 2,6-di-(α-Man)-α-Man through a double glycosylation of a 3,4-butanediacetal-protected mannoside. The azidooctyl groups of these synthetic mannans were elaborated to fluorescent glycoconjugates and squaric ester derivatives useful for further conjugation studies.

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Mistry, Rakesh N., e K. R. Desai. "Studies on Synthesis of Some Novel Heterocyclic Azlactone Derivatives and Imidazolinone Derivatives and their Antimicrobial Activity". E-Journal of Chemistry 2, n.º 1 (2005): 42–51. http://dx.doi.org/10.1155/2005/542938.

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p- Methyl benzoic acid on reaction with phosphorus pentachloride gives p - methyl benzoyl chloride derivative which on condensation with glycine gives p - methyl benzoyl glycine derivative. Now, this p - methyl benzoyl glycine derivative on condensation with various substituted aldehydes gives corresponding substituted 4 - [aryl methylidine] - 2 - [p - methyl phenyl] - oxazole - 5 - one derivatives [1(a-j)]. Further, these derivatives [1(a-j)] on condensation with 4 , 4’ - diamino diphenyl sulphone gives corresponding substituted imidazolinone - dibenzsulphone derivatives [2(a-j)], on condensation with 4 , 4’ - diamino diphenyl methane gives corresponding substituted imidazolinone - dibenzmethane derivatives [3(a-j)], on condensation with 4,4’- diamino benzanilide gives corresponding substituted imidazolinone - benzanilide derivatives [4(a-j)] and on condensation with 2 - amino pyridine gives corresponding substituted imidazolinone - pyridine derivatives [5(a-j)] respectively. Structure elucidation of synthesised compounds has been made on the basis of elemental analysis, I.R. spectral studies and1H N.M.R. spectral studies. The antimicrobial activity of the synthesised compounds has been studied against the cultures “Staphylococcus aureus”, “Escherichia coli” and “Candela albicans”.

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Pföstl, Andreas, Sonja Zayni, Andreas Hofinger, Paul Kosma, Christina Schäffer e Paul Messner. "Biosynthesis of dTDP-3-acetamido-3,6-dideoxy-α-D-glucose". Biochemical Journal 410, n.º 1 (29 de janeiro de 2008): 187–94. http://dx.doi.org/10.1042/bj20071044.

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Derivatives of 3-amino-3,6-dideoxyhexoses are widespread in Nature. They are part of the repeating units of lipopolysaccharide O-antigens, of the glycan moiety of S-layer (bacterial cell surface layer) glycoproteins and also of many antibiotics. In the present study, we focused on the elucidation of the biosynthesis pathway of dTDP-α-D-Quip3NAc (dTDP-3-acetamido-3,6-dideoxy-α-D-glucose) from the Gram-positive, anaerobic, thermophilic organism Thermoanaerobacterium thermosaccharolyticum E207-71, which carries Quip3NAc in its S-layer glycan. The biosynthesis of dTDP-α-D-Quip3NAc involves five enzymes, namely a transferase, a dehydratase, an isomerase, a transaminase and a transacetylase, and follows a pathway similar to that of dTDP-α-D-Fucp3NAc (dTDP-3-acetamido-3,6-dideoxy-α-D-galactose) biosynthesis in Aneurinibacillus thermoaerophilus L420-91T. The ORFs (open reading frames) of interest were cloned, overexpressed in Escherichia coli and purified. To elucidate the enzymatic cascade, the different products were purified by HPLC and characterized by NMR spectroscopy. The initiating reactions catalysed by the glucose-1-phosphate thymidylyltransferase RmlA and the dTDP-D-glucose-4,6-dehydratase RmlB are well established. The subsequent isomerase was shown to be capable of forming a dTDP-3-oxo-6-deoxy-D-glucose intermediate from the RmlB product dTDP-4-oxo-6-deoxy-D-glucose, whereas the isomerase involved in the dTDP-α-D-Fucp3NAc pathway synthesizes dTDP-3-oxo-6-deoxy-D-galactose. The subsequent reaction steps of either pathway involve a transaminase and a transacetylase, leading to the specific production of nucleotide-activated 3-acetamido-3,6-dideoxy-α-D-glucose and 3-acetamido-3,6-dideoxy-α-D-galactose respectively. Sequence comparison of the ORFs responsible for the biosynthesis of dTDP-α-D-Quip3NAc revealed homologues in Gram-negative as well as in antibiotic-producing Gram-positive bacteria. There is strong evidence that the elucidated biosynthesis pathway may also be valid for LPS (lipopolysaccharide) O-antigen structures and antibiotic precursors.

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