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Journal articles on the topic 'Base pyrimidique'

Author: Grafiati

Published: 4 June 2021

Last updated: 6 February 2022

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1

Montemayor, Eric J., Johanna M. Virta, Lauren D. Hagler, Steven C. Zimmerman, and Samuel E. Butcher. "Structure of an RNA helix with pyrimidine mismatches and cross-strand stacking." Acta Crystallographica Section F Structural Biology Communications 75, no. 10 (September 24, 2019): 652–56. http://dx.doi.org/10.1107/s2053230x19012172.

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The structure of a 22-base-pair RNA helix with mismatched pyrimidine base pairs is reported. The helix contains two symmetry-related CUG sequences: a triplet-repeat motif implicated in myotonic dystrophy type 1. The CUG repeat contains a U–U mismatch sandwiched between Watson–Crick pairs. Additionally, the center of the helix contains a dimerized UUCG motif with tandem pyrimidine (U–C/C–U) mismatches flanked by U–G wobble pairs. This region of the structure is significantly different from previously observed structures that share the same sequence and neighboring base pairs. The tandem pyrimidine mismatches are unusual and display sheared, cross-strand stacking geometries that locally constrict the helical width, a type of stacking previously associated with purines in internal loops. Thus, pyrimidine-rich regions of RNA have a high degree of structural diversity.

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2

Fairlamb, Max S., Amy M. Whitaker, and Bret D. Freudenthal. "Apurinic/apyrimidinic (AP) endonuclease 1 processing of AP sites with 5′ mismatches." Acta Crystallographica Section D Structural Biology 74, no. 8 (July 24, 2018): 760–68. http://dx.doi.org/10.1107/s2059798318003340.

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Despite the DNA duplex being central to biological functions, many intricacies of this molecule, including the dynamic nature of mismatched base pairing, are still unknown. The unique conformations adopted by DNA mismatches can provide insight into the forces at play between nucleotides. Moreover, DNA-binding proteins apply their own individualized steric and electrochemical influences on the nucleotides that they interact with, further altering base-pairing conformations. Here, seven X-ray crystallographic structures of the human nuclease apurinic/apyrimidinic (AP) endonuclease 1 (APE1) in complex with its substrate target flanked by a 5′ mismatch are reported. The structures reveal how APE1 influences the conformations of a variety of different mismatched base pairs. Purine–purine mismatches containing a guanine are stabilized by a rotation of the guanine residue about the N-glycosidic bond to utilize the Hoogsteen edge for hydrogen bonding. Interestingly, no rotation of adenine, the other purine, is observed. Mismatches involving both purine and pyrimidine bases adopt wobble conformations to accommodate the mismatch. Pyrimidine–pyrimidine mismatches also wobble; however, the smaller profile of a pyrimidine base results in a gap between the Watson–Crick faces that is reduced by a C1′–C1′ compression. These results advance our understanding of mismatched base pairing and the influence of a bound protein.

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3

Stasevych, Maryna, Svitlana Sabat, Rostyslav Musyanovych, and Volodymyr Novikov. "Synthesis of condensed S-, N- containing heterocyclic systems on the base of 2-amino-4,9-dioxo-4,9-dihydronaphto[2,3-b]thiophene-3-ethylcarboxilate." Chemistry & Chemical Technology 2, no. 3 (September 15, 2008): 157–62. http://dx.doi.org/10.23939/chcht02.03.157.

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Synthesis of a new 2-aryl-4Н-naphtho[2’,3’,4,5]thieno[2,3-d][1,3]oxazine-4,5,10-triones, 2-arylnaphtho[2’,3’,4,5]thieno[2,3-d][1,3]pyrimidine-4,5,10(3Н)-triones, 3-phenyl naphtho[2’,3’,4,5]thieno[2,3-d][1,3]pyrimidine-2,4,5,10(1Н, 3Н)-tetraone and 2-thioxo-2,3-dyhydronaphth[2’,3’,4,5]thieno[2,3-d]pyrimidine-4,5,10(1Н)-trione was carried out. The mechanism of 2-aryl-4Н-naphtho[2’,3’,4,5]thieno[2,3-d][1,3]oxazine-4,5,10-triones formation was suggested.

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4

Kadioglu, Ela, Semra Sardas, Meltem Ergun, Selahattin Unal, and Ali Esat Karakaya. "The role of oxidative DNA damage, DNA repair, GSTM1, SOD2 and OGG1 polymorphisms in individual susceptibility to Barrett’s esophagus." Toxicology and Industrial Health 26, no. 2 (January 7, 2010): 67–79. http://dx.doi.org/10.1177/0748233709359278.

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Determination of the genetic alterations, which play a role in the etiology of Barrett’s esophagus (BE), could help identify high-risk individuals for esophageal adenocarcinoma (EA). The aim of the present study was to investigate the role of oxidative DNA damage, glutathione (GSH) concentration as oxidative stress parameters and DNA repair capacity, GSTM1, SOD1 Ala16Val and OGG1 Ser326Cys genetic polymorphisms as individual susceptibility parameters in the etiology of BE. The study groups comprised BE patients who were clinically diagnosed (n = 40) and a healthy control group (n = 40). Basal DNA damage, pyrimidine and purine base damage after H2O2 induction, H 2O2 sensitivity, DNA repair capacity, oxidized pyrimidine and purine base damage repair were evaluated in peripheral blood lymphocytes with a modified comet assay using specific endonucleases (Endo III and Fpg). Polymerase chain reaction—restriction length polymorphism (PCR-RFLP)-based assays were used for genotyping. The patient group showed elevated levels of basal DNA damage, pyrimidine base damage and H2O2 sensitivity as compared to controls (p < .05). DNA repair capacity, oxidized pyrimidine and purine base damage repair capacity, were not statistically different between patients and controls. GSH concentration was found to be significantly lower in smoking patients than in the controls (p < .05). None of the genetic variations changed the risk of having BE disease. However, patients carrying the variant OGG1 Cys allele showed elevated levels of pyrimidine base damage as compared to patients carrying the wild-type OGG1 Ser (p < .05). The results of this study point to a role of oxidative DNA damage in BE. However, DNA repair capacity, GSTM1, SOD1 Ala16Val and OGG1 Ser326Cys genetic polymorphisms appeared to play no role in the individual susceptibility to this disease.

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5

Kouchakdjian, Michael, Benjamin F. L. Li, Peter F. Swann, and Dinshaw J. Patel. "Pyrimidine · pyrimidine base-pair mismatches in DNA." Journal of Molecular Biology 202, no. 1 (July 1988): 139–55. http://dx.doi.org/10.1016/0022-2836(88)90526-8.

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6

Inde, Takeshi, Yoshiaki Masaki, Atsuya Maruyama, Yu Ito, Naoaki Makio, Yuya Miyatake, Takahito Tomori, Mitsuo Sekine, and Kohji Seio. "Synthesis of oligonucleotides containing 2-N-heteroarylguanine residues and their effect on duplex/triplex stability." Organic & Biomolecular Chemistry 15, no. 39 (2017): 8371–83. http://dx.doi.org/10.1039/c7ob01875d.

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7

Shekouhy, Mohsen, and Ali Khalafi-Nezhad. "Polyethylene glycol-bonded 1,8-diazabicyclo[5.4.0]undec-7-ene (PEG–DBU) as a surfactant-combined base catalyst for the application of nucleosides as reagents in multi-component syntheses of 8-substituted pyrido[2,3-d]pyrimidine-6-carbonitriles in water." Green Chemistry 17, no. 10 (2015): 4815–29. http://dx.doi.org/10.1039/c5gc01448d.

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8

Lu, Nan, Yuxiang Bu, and Huatian Wang. "Intensified effects of multi-Cu modification on the electronic properties of the modified base pairs containing hetero-ring-expanded pyrimidine bases." Physical Chemistry Chemical Physics 18, no. 4 (2016): 2913–23. http://dx.doi.org/10.1039/c5cp06133d.

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9

Yamamoto, Seigi, Soyoung Park, and Hiroshi Sugiyama. "Development of a visible nanothermometer with a highly emissive 2′-O-methylated guanosine analogue." RSC Advances 5, no. 126 (2015): 104601–5. http://dx.doi.org/10.1039/c5ra24756j.

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10

Henley, Robert Y., Ana G. Vazquez-Pagan, Michael Johnson, Anastassia Kanavarioti, and Meni Wanunu. "Osmium-Based Pyrimidine Contrast Tags for Enhanced Nanopore-Based DNA Base Discrimination." PLOS ONE 10, no. 12 (December 11, 2015): e0142155. http://dx.doi.org/10.1371/journal.pone.0142155.

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11

Urata, Hidehito, Eriko Yamaguchi, Yasunari Nakamura, and Shun-ichi Wada. "Pyrimidine–pyrimidine base pairs stabilized by silver(i) ions." Chem. Commun. 47, no. 3 (2011): 941–43. http://dx.doi.org/10.1039/c0cc04091f.

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12

Prasad, Pratibha, Anirudhdha G. Kalola, and Manish P. Patel. "Microwave assisted one-pot synthetic route to imidazo[1,2-a]pyrimidine derivatives of imidazo/triazole clubbed pyrazole and their pharmacological screening." New Journal of Chemistry 42, no. 15 (2018): 12666–76. http://dx.doi.org/10.1039/c8nj00670a.

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An efficient synthetic microwave-assisted, one-pot three-component condensation route for imidazo[1,2-a]pyrimidine derivatives of imidazole 4/triazole 5 clubbed pyrazole catalysed by ecofriendly base KOH.

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13

Gallagher, P. E., and N. J. Duker. "Detection of UV purine photoproducts in a defined sequence of human DNA." Molecular and Cellular Biology 6, no. 2 (February 1986): 707–9. http://dx.doi.org/10.1128/mcb.6.2.707.

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The UV-irradiated, 3'-end-labeled, 92-base-pair terminus of the human alphoid sequence was incubated with purified endonuclease v. Previously unreported photoproducts were incised at purine loci. These were not pyrimidine photodimers, 6-4'-(pyrimidin-2'-one)-pyrimidines, base loss sites, or ring-opened purines. Therefore, purine-containing photoproducts, possibly dimers, were incised by the enzyme preparation.

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14

Gallagher, P. E., and N. J. Duker. "Detection of UV purine photoproducts in a defined sequence of human DNA." Molecular and Cellular Biology 6, no. 2 (February 1986): 707–9. http://dx.doi.org/10.1128/mcb.6.2.707-709.1986.

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The UV-irradiated, 3'-end-labeled, 92-base-pair terminus of the human alphoid sequence was incubated with purified endonuclease v. Previously unreported photoproducts were incised at purine loci. These were not pyrimidine photodimers, 6-4'-(pyrimidin-2'-one)-pyrimidines, base loss sites, or ring-opened purines. Therefore, purine-containing photoproducts, possibly dimers, were incised by the enzyme preparation.

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15

Behera, Manoranjan, M. Sambaiah, Poosa Mallesham, K. Shiva Kumar, Yamini Bobde, Prasanta Hota, Satyanarayana Yennam, and Balaram Ghosh. "Tandem Schiff-Base Formation/Heterocyclization: An Approach to the Synthesis of Fused Pyrazolo–Pyrimidine/Isoxazolo-Pyrimidine Hybrids." Synlett 30, no. 05 (February 5, 2019): 586–92. http://dx.doi.org/10.1055/s-0037-1612081.

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A new synthesis of pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines is described. Key steps in the synthesis involve Stille coupling of 4,6-dichloro-2-phenyl-pyrimidine with tributyl(1-ethoxyvinyl)stannane and tandem Schiff-base formation/heterocyclization of 2,6-di-aryl-5-fluoro-4-acetylpyrimidine with hydrazines or hydroxylamine to give pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines, respectively. The position of the fluoro group in the pyrimidine ring is important for the success of heterocylization reaction.

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16

Kalaf gabar, Kaleda. "Schiff Base Complexes: Synthesis, Characterization and Study of Bioactive Such As Antibacterial and Antifungal." Ibn AL- Haitham Journal For Pure and Applied Science 31, no. 2 (September 12, 2018): 115. http://dx.doi.org/10.30526/31.2.1962.

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The complexes of Schiff base (6-[Hydroxy - benzylidene)-amino]-pyrimidine-2,4-diol ) (L) with Mn(II), Fe(II), Co(II) and Ni(II) were prepared. The Schiff base and complexes have been characterized by FT-IR, 1H-NMR, UV-Vis, LC-mass spectra, magnetic moment, elemental microanalyses (C.H.N.), chloride containing, atomic absorption and molar conductance. The Schiff base, metal salts and complexes were also screened for their bioactivity such as antibacterial and antifungal.

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17

Pinheiro, Alessandra C., Thaís C. M. Nogueira, Cristiane França da Costa, Cristina Lourenço, John N. Low, James L. Wardell, Solange M. S. V. Wardell, and Marcus V. N. de Souza. "A study of antituberculosis activities and crystal structures of (E)-2-[2-(arylidene)hydrazinyl]pyrimidine and (E)-N1-(arylidene)pyrimidine-2-carbohydrazide derivatives." Zeitschrift für Naturforschung B 75, no. 12 (December 16, 2020): 1011–28. http://dx.doi.org/10.1515/znb-2020-0108.

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AbstractA study of the anti-tuberculosis activity against Mycobacterium tuberculosis ATTC 27294 and an X-ray structural determination of (E)-2-[2-(arylidene)hydrazinyl]pyrimidine, 1, and (E)-N1-(arylidene)pyrimidine-2-carbohydazide, 2, derivatives are presented. The effect of the substituents in the aryl moiety on the antituberculosis (anti-TB) activities of 1 and 2 is compared with that of other heteroaryl hydrazonyl and acylhydrazonyl derivatives. The biological activities of 1 do not depend on the coordinating ability of the substituted aryl group: in 2, the most effective aryl group is 5-nitrofuranyl. The structure determinations of (E)-2-((2-(pyrimidin-2-yl)hydrazono)methyl)-phenol, (E)-N′-(2,5-dihydroxybenzylidene)pyrimidine-2-carbohydrazide and of the hydrate of (E)-N′-(2-hydroxy-4-methylbenzylidene)pyrimidine-2-carbohydrazide, and a literature search of related structures in the CCDC data base, allowed an examination of the more important interactions, including the occurrence of X–Y⋯π interactions.

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18

Wal, Helmut Jansen in de, and Manfred Lissel. "Notizen: Reaktionen mit Dimethylcarbonat, 5 Methylierung der Pyrimidin-Basen der Nucleinsäuren / Reactions with Dimethyl Carbonate, 5 Methylation of the Pyrimidine Bases of Nucleic Acids." Zeitschrift für Naturforschung B 44, no. 7 (July 1, 1989): 863–65. http://dx.doi.org/10.1515/znb-1989-0724.

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The methylation of the pyrimidine bases of nucleic acids by dimethyl carbonate is described compared to dimethyl sulphate. The reaction needs higher temperature, a base and the help of 18-crown-6 and DMF as cosolvent.

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19

Wang, Tao, Jun Xiong, Wenjuan Wang, Rou Li, Xiaoli Tang, and Fei Xiong. "Tunable regioselective synthesis of pyrazolo[3,4-d]pyrimidine derivatives via aza-Wittig cyclization and dimroth-type rearrangement." RSC Advances 5, no. 26 (2015): 19830–37. http://dx.doi.org/10.1039/c4ra15777j.

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A novel tunable regioselective synthesis of pyrazolo[3,4-d]pyrimidine derivatives via aza-Wittig/Ag(i) or base-promoted tandem reaction has been developed. This approach provides a concise way to construct this derivatives under mild condition.

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20

Yousaf, Muhammad, Nathan J. Yutronkie, Raúl Castañeda, Jacob A. Klein, and Jaclyn Brusso. "Boratriazines: inducing luminescence through boron incorporation into a terpy-type framework." New J. Chem. 41, no. 20 (2017): 12218–24. http://dx.doi.org/10.1039/c7nj02462b.

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The synthesis and physicochemical properties of pyridyl and pyrimidyl functionalized 1,3,5,2-triazaborinines are reported, along with the Lewis acid–base adduct pyrimidine-2-carboximidamide trifluoroborane, which forms as a side product in the reaction with the pyrimidyl substituents.

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21

Karunakaran, Indumathi, Abiram Angamuthu, and Praveena Gopalan. "Impact of N-(2-aminoethyl) Glycine Unit on Watson-Crick Base Pairs." Zeitschrift für Physikalische Chemie 233, no. 3 (March 26, 2019): 449–69. http://dx.doi.org/10.1515/zpch-2017-1095.

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Abstract We aim to understand the structure and stability of the backbone tailored Watson-Crick base pairs, Guanine-Cytosine (GC), Adenine-Thymine (AT) and Adenine-Uracil (AU) by incorporating N-(2-aminoethyl) glycine units (linked by amide bonds) at the purine and pyrimidine sites of the nucleobases. Density functional theory (DFT) is employed in which B3LYP/6-311++G∗∗ level of theory has been used to optimize all the structures. The peptide attached base pairs are compared with the natural deoxyribose nucleic acid (DNA)/ribonucleic acid (RNA) base pairs and the calculations are carried out in both the gas and solution phases. The structural propensities of the optimized base pairs are analyzed using base pair geometries, hydrogen bond distances and stabilization energies and, compared with the standard reference data. The structural parameters were found to correlate well with the available data. The addition of peptide chain at the back bone of the DNA/RNA base pairs results only with a minimal distortion and hence does not alter the structural configuration of the base pairs. Also enhanced stability of the base pairs is spotted while adding peptidic chain at the purine site rather than the pyrimidine site of the nucleobases. The stability of the complexes is further interpreted by considering the hydrogen bonded N–H stretching frequencies of the respective base pairs. The discrimination in the interaction energies observed in both gas and solution phases are resulted due to the existence of distinct lowest unoccupied molecular orbitals (LUMO) in the solution phase. The reactivity of the base pairs is also analyzed through the in-depth examinations on the highest occupied molecular orbital (HOMO)-LUMO orbitals.

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22

STARIKOV, E. B. "IMPORTANCE OF CHARGE TRANSFER EXCITATIONS IN DNA ELECTRON SPECTRUM: A ZINDO SEMIEMPIRICAL QUANTUM-CHEMICAL STUDY." Modern Physics Letters B 18, no. 16 (July 10, 2004): 825–31. http://dx.doi.org/10.1142/s0217984904007360.

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Electron spectra of DNA model compounds, adenosine-thymidine and guanosine-cytidine nucleoside base pairs, as well as the relevant homogeneous stacked base pair steps in A-DNA and B-DNA conformations, were investigated using ZINDO semiempirical quantum-chemical method. This work confirms that, in DNA with intact Watson–Crick hydrogen bonding and base stacking, the highest occupied molecular orbitals (HOMO) are residing on purine base residues, whereas the lowest unoccupied molecular orbitals (LUMO) — on pyrimidine base residues. In general, the present results are satisfactorily comparable with the available experimental data. The role of charge transfer excitations in the polymer DNA 260 nm spectral band is discussed.

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23

Tebiev, Dmitry T., Diana D. Guz’, Victor V. Dotsenko, Nicolai A. Aksenov, and Inna V. Aksenova. "A New Approach to 7-Amino-4-oxo-4,5-dihydro-3H-pyrano[2,3-d]pyrimidine-6-carbonitriles." Chemistry Proceedings 3, no. 1 (November 13, 2020): 50. http://dx.doi.org/10.3390/ecsoc-24-08105.

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S-alkyl derivatives of thiobarbituric acid easily react with arylmethylene malononitriles in the presence of base to give new 7-amino-4-oxo-4,5-dihydro-3H-pyrano[2,3-d]pyrimidine-6-carbonitriles. The structure of products and the mechanism of formation are discussed.

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24

Hocek, Michal, Hana Dvořáková, and Ivana Císařová. "Covalent Analogues of DNA Base-Pairs and Triplets V. Synthesis of Purine-Purine and Purine-Pyrimidine Conjugates Connected by Diverse Types of Acyclic Carbon Linkages." Collection of Czechoslovak Chemical Communications 67, no. 10 (2002): 1560–78. http://dx.doi.org/10.1135/cccc20021560.

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The title 1,2-bis(purin-6-yl)acetylenes, -diacetylenes, -ethylenes and -ethanes were prepared as covalent base-pair analogues starting from 6-ethynylpurines and 6-iodopurines by the Sonogashira cross-coupling or oxidative alkyne-dimerization reactions followed by hydrogenations. 6-[(1,3-Dimethyluracil-5-yl)ethynyl]purine (11) was prepared analogously and hydrogenated to the corresponding purine-pyrimidine conjugates linked via vinylene and ethylene linkers. Unlike the cytostatic bis(purin-6-yl)acetylenes and -diacetylenes, the purine-pyrimidine conjugates were inactive. Crystal structures of bis(purin-6-yl)acetylene 6a, -diacetylene 8a and -ethane 5a were determined by single-crystal X-ray diffraction.

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25

Kook, Insun, and Joseph M. Ziegelbauer. "Monocyte chemoattractant protein-induced protein 1 directly degrades viral miRNAs with a specific motif and inhibits KSHV infection." Nucleic Acids Research 49, no. 8 (April 6, 2021): 4456–71. http://dx.doi.org/10.1093/nar/gkab215.

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Abstract Kaposi's sarcoma-associated herpesvirus (KSHV) expresses miRNAs during latency. However, regulation of viral miRNAs remains largely unknown. Our prior studies demonstrated that MCPIP1 regulates KSHV miRNA biogenesis by degrading most KSHV pre-miRNAs through its RNase activity. Some viral pre-miRNAs are partially resistant to degradation by MCPIP1. Here, we further characterized MCPIP1 substrate specificity and its antiviral potential against KSHV infection. In vitro cleavage assays and binding assays showed that MCPIP1 cleavage efficiency is related to binding affinity. Motif-based sequence analysis identified that KSHV pre-miRNAs that are well degraded by MCPIP1 have a 5-base motif (M5 base motif) within their terminal loops and this motif region consists of multiple pyrimidine-purine-pyrimidine (YRY) motifs. We further demonstrated that mutation of this M5 base motif within terminal loop of pre-miRNAs inhibited MCPIP1-mediated RNA degradation. We also revealed that MCPIP1 has an antiviral effect against KSHV infection. MCPIP1 can reduce the expression of Dicer, which in turn restricts KSHV infection. Conclusively, our findings demonstrated that MCPIP1 inhibited KSHV infection and suppressed viral miRNA biogenesis by directly degrading KSHV pre-miRNAs and altering the expression of miRNA biogenesis factors.

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26

Fiorito, Serena, Salvatore Genovese, and Francesco Epifano. "An Easy Way to Pyrimidine Based Nucleoterpenes." Natural Product Communications 9, no. 6 (June 2014): 1934578X1400900. http://dx.doi.org/10.1177/1934578x1400900604.

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The direct synthesis of N3 substituted pyrimidine nucleoterpenes from uridine, thymidine, and inosine with C5, C10, and C15 side chains and using DBU as the base is described. In all cases the reaction proceeded smoothly in very good yields (85–99%) affording selectively N3 substituted adducts.

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27

Chen, X., K. Bastow, B. Goz, L. Kucera, S. L. Morris-Natschke, and K. S. Ishaq. "Boronic Acid Derivatives Targeting HIV-1." Antiviral Chemistry and Chemotherapy 7, no. 2 (April 1996): 108–14. http://dx.doi.org/10.1177/095632029600700208.

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A series of novel boronic acid derivatives containing either a pyrimidine or purine base was synthesized. The preparation involved the condensation of 4-bromobutyl boronic acid with the appropriate base. These acyclic nucleosides were designed as potential antiviral agents especially targeting the human immunodeficiency virus. Two analogues, 6-chloro-9-(4-dihydroxyborylbutyl)purine and 2,6-dichloro-9-(4-dihydroxyborylbutyl)purine, exhibited EC50 values of 7.7 μM and 0.99 μM, respectively, in an HIV-1 syncytial plaque reduction assay.

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28

Kiliç, Hasan, and Er Birol. "Potentiometric investigation of acid-base equilibria of two new pyrimidine derivatives in various methanol-water media." Journal of the Serbian Chemical Society 71, no. 1 (2006): 43–54. http://dx.doi.org/10.2298/jsc0601043k.

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The acid-base properties of 1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-one (L1) and 1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-thione (L2) were investigated potentiometrically at an ionic strength of 0.10M(LiCl) in 19.8, 33.6 and 55.9 % (v/v) methanol-water mixtures at 25.0 ? 0.1 ?C. The apparent dissociation constants (psKa) were calculated for the di-protonated form (L1H2+2 and L2H2+2) of pyrimidine bases, using a software package TITFIT, which were then extrapolated to pure water to derive the dissociation constants in aqueous solution (pKa). The aqueous pKa constants were found to be: L1, pKa1 = 3.76 and pKa2 = 6.95; L2, pKa1 = 3.57 and pKa1 = 6.90. At pH <- 2.00, the dominant species in solution were the protonated form of the amino group substituted at the 1-position, while at a pH around 5.00, they were the protonated form of the pyrimidine ring nitrogen at the 3-position. An effect of intramolecular hydrogen bonding on the psKa values was observed with L1 but not L2. The effects of molecular structure and solvent medium on the psKa values are also discussed.

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29

Nassar, Ibrahim F., Wael A. El-Sayed, Tamer I. M. Ragab, Al Shimaa Gamal Shalaby, and Ahmed B. M. Mehany. "Design, Synthesis of New Pyridine and Pyrimidine Sugar Compounds as Antagonists Targeting the ERα via Structure-Based Virtual Screening." Mini-Reviews in Medicinal Chemistry 19, no. 5 (February 21, 2019): 395–409. http://dx.doi.org/10.2174/1389557518666180820125210.

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Background: New aryl substituted cyclohepta[b]pyridine and cyclohepta[d]pyrimidine derivatives were synthesized. The sugar hydrazones of the synthesized pyridine and pyrimidine compounds were also prepared. </P><P> Method: In addition, the 1,3,4-oxadiazolyl acyclic C-nucleoside analogs of the pyridine system were prepared. The hemolytic, prebiotic, anticancer and antimicrobial activities of some of the synthesized compounds were also studied. Compounds 10 and 12 showed high activity against MCF-7, HEPG-2 and HCT-116 cell lines with IC50 at range 3.56-8.55 µg/mL. In addition, the synthesized condensed thiopyrimidine derivative 10 exhibited more potent bactericidal activity while compound 7 demonstrated potent antifungal activity against Aspergillus niger. Furthermore, the synthetic compounds of the pyrimidine base promoted the growth of lactic acid bacteria. </P><P> Results: The predicted binding patterns of three of the prepared derivatives as possible antagonists against ERα were investigated which showed good binding patterns.

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30

Abele, Edgars, and Ramona Abele. "Oximes of Nucleosides and Related Compounds: Synthesis, Reactions and Biological Activity." Current Organic Synthesis 15, no. 5 (July 5, 2018): 650–65. http://dx.doi.org/10.2174/1570179415666180524112811.

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Background: Literature data on the synthesis and structure of oximes of nucleosides and related nitrogenous bases from pyrimidine and purine were reviewed. Synthesis of novel heterocyclic systems from nucleoside oximes related pyrimidine oximes was described. The biological activity of derivatives of nucleoside and nitrogenous base oximes was also reviewed. <p> Objective: The review focuses on the recent progress in the area of nucleoside oxime synthesis, reactions and biological activity. Conclusion: In summary, literature data on the synthesis and structure of oximes of nucleosides and related nitrogenous bases derived from pyrimidine, which play an important role in the biological processes, were reviewed. Synthesis of novel heterocyclic systems from nucleoside oximes related pyrimidine oximes was described. The biological activity of derivatives of nucleoside and nucleotide oximes was also reviewed. The studied class of compounds show a wide range of imino-amino and imino-nitroso tautomerism, which was investigated in the presented literature by 1H, 13C and 15N NMR spectroscopy methods. Also, according to the authors point of view, due to imino-amino and/or imino-nitroso tautomerism the nucleoside oximes show interesting activity. Most of the compounds exhibit biological activity characteristic of not only oxime derivatives, but also activity of hydroxylamines or nitroso compounds.

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31

Gu, Xiaorong, Rita Tohme, Mendel Goldfinger, Benjamin K. Tomlinson, Nneha Sakre, Shannon Hanmer, Babal K. Jha, Jaroslaw P. Maciejewski, Amit Verma, and Yogenthiran Saunthararajah. "Venetoclax Inhibition of Pyrimidine Synthesis Guides Methods for Integration with Decitabine or 5-Azacytidine That Are Non-Myelosuppressive." Blood 136, Supplement 1 (November 5, 2020): 26–27. http://dx.doi.org/10.1182/blood-2020-143200.

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Venetoclax (Ven) administered daily with pulse-cycled parenteral decitabine (Dec) or 5-azacytidine (5Aza) is standard therapy for acute myeloid leukemia (AML) in the elderly. In practice, toxicity/myelosuppression is frequent, and prompts Ven dose reductions, but by guess-work, because the mechanism downstream of BCL2-inhibition by which Ven augments Dec/5Aza activity is unclear. For the first time, we show that Ven inhibits de novo pyrimidine synthesis, an effect that can guide its integration with Dec/5Aza in a way that enhances anti-AML activity without suppressing normal myelopoiesis. Dec and 5Aza are pro-drugs processed by pyrimidine metabolism into a deoxycytidine analog that depletes the key epigenetic regulator DNA methyltranseferase 1 (DNMT1), a pharmacodynamic effect that terminates malignant but not normal self-replication. We recently demonstrated that Dec- and 5Aza-resistance emerges automatically from adaptive responses of the pyrimidine metabolism network to Dec/5Aza-induced nucleotide perturbations, such that Dec/5Aza processing into DNMT1-depleting nucleotide is forestalled (Leukemia - https://rdcu.be/b58pS). A key element in this auto-resistance is upregulated de novo pyrimidine synthesis, that out-competes salvaged Dec/5Aza. De novo pyrimidine synthesis has an electron-transport dependent mitochondrial step executed by dihydroorotate dehydrogenase (DHODH): BCL2-inhibition by Ven depolarizes mitochondrial membranes - we examined for the first time Ven impact on DHODH/pyrimidine synthesis (others have focused on apoptosis and other metabolic consequences of mitochondrial depolarization). Consistent with Ven inhibiting DHODH/pyrimidine synthesis, both Ven and the direct DHODH inhibitor teriflunomide, at non-apoptotic concentrations, significantly decreased cytidine- and deoxycytidine triphosphate (CTP, dCTP) in AML cells (Fig1A). To see if this effect of Ven can counter Dec/5Aza resistance, we selected for THP1 AML cells double-resistant to Dec 0.5 μM and 5Aza 5 μM - these cells upregulated expression of de novo pyrimidine synthesis enzymes and contained uridine, cytidine and deoxycytidine at levels up to 7-fold higher than parental cells. The double-resistant AML cells were significantly cytoreduced by Ven at a clinically relevant concentration of 1 μM, even though parental THP1 AML cells were minimally sensitive (Fig1B). Consistent with inhibition of de novo pyrimidine synthesis as the mechanism, this action was significantly abrogated by cytidine supplementation (Fig1B). We previously showed that timed alternation of Dec with 5Aza, and incorporation of the cytidine deaminase inhibitor tetrahydrouridine (THU), counters metabolic Dec or 5Aza-resistance to extend non-cytotoxic DNMT1-depletion and survival in vivo (https://rdcu.be/b58pS). However, AML still eventually progresses, via upregulated de novo pyrimidine synthesis. In considering use of Ven to counter this mode of resistance, we reasoned that concurrent administration risks antagonism, because Ven can cause transient cytostasis, and DNMT1-depletion by Dec/5Aza is S-phase dependent. Prior Ven administration, however, creates effect-time sufficient to deplete endogenous nucleotides from AML cells and hence upregulate pyrimidine salvage (that uptakes Dec/5Aza) (Fig1A), as well as resumed cell cycle. Therefore, in vivo in a patient-derived xenotransplant model (PDX) of AML, we introduced Ven (at human equivalent dose), parsimoniously 2X/week, the day before each Dec or 5Aza administration, and at the time of overt AML progression on the base THU-Dec/5Aza regimen. This minimalist Ven application significantly extended survival (time-to-distress) even though it was initiated at progression (Fig1C). As expected, use of this regimen upfront in a PDX of Dec/5Aza-resistant AML produced even greater (several-fold) survival extension (treatment ongoing) vs the base regimen (Fig1D). A non-cytotoxic/non-myelosuppressive mechanism-of-action was confirmed by serial blood counts on-therapy. In practice, Ven dose in combination with Dec or 5Aza to treat AML is frequently empirically reduced because of toxicity/myelosuppression. Instead, Ven inhibition of de novo pyrimidine synthesis can guide mechanism-based, intermittent administration that avoids toxicity/myelosuppression yet enhances Dec/5Aza anti-AML activity. Disclosures Maciejewski: Novartis, Roche: Consultancy, Honoraria; Alexion, BMS: Speakers Bureau. Saunthararajah:EpiDestiny: Consultancy, Current equity holder in private company, Patents & Royalties: University of Illinois at Chicago.

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32

Hardin, Ellington, Nguyen, Rheingold, Tschumper, Watkins, and Hammer. "A Raman Spectroscopic and Computational Study of New Aromatic Pyrimidine-Based Halogen Bond Acceptors." Inorganics 7, no. 10 (October 2, 2019): 119. http://dx.doi.org/10.3390/inorganics7100119.

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Two new aromatic pyrimidine-based derivatives designed specifically for halogen bond directed self-assembly are investigated through a combination of high-resolution Raman spectroscopy, X-ray crystallography, and computational quantum chemistry. The vibrational frequencies of these new molecular building blocks, pyrimidine capped with furan (PrmF) and thiophene (PrmT), are compared to those previously assigned for pyrimidine (Prm). The modifications affect only a select few of the normal modes of Prm, most noticeably its signature ring breathing mode, ν1. Structural analyses afforded by X-ray crystallography, and computed interaction energies from density functional theory computations indicate that, although weak hydrogen bonding (C–H···O or C–H···N interactions) is present in these pyrimidine-based solid-state co-crystals, halogen bonding and π-stacking interactions play more dominant roles in driving their molecular-assembly.

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33

Toma, Štefan, Martin Putala, and Marta Sališová. "Ultrasound-accelerated synthesis of ferrocene-containing pyrimidine derivatives." Collection of Czechoslovak Chemical Communications 52, no. 2 (1987): 395–98. http://dx.doi.org/10.1135/cccc19870395.

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The base-catalysed addition of thiourea to ferrocene analogues of chalcones is faster and more selective when the reaction mixture is sonicated than when merely heated. 4-Aryl-6-ferrocenyl- and 6-aryl-4-ferrocenyl-3,4-dihydropyrimidine-2(1H)-tyhiones were isolated in 58-79% yields.

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34

Wang, Haiwei, Xinrui Wang, Liangpu Xu, Ji Zhang, and Hua Cao. "High expression levels of pyrimidine metabolic rate–limiting enzymes are adverse prognostic factors in lung adenocarcinoma: a study based on The Cancer Genome Atlas and Gene Expression Omnibus datasets." Purinergic Signalling 16, no. 3 (July 8, 2020): 347–66. http://dx.doi.org/10.1007/s11302-020-09711-4.

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Abstract Reprogramming of metabolism is described in many types of cancer and is associated with the clinical outcomes. However, the prognostic significance of pyrimidine metabolism signaling pathway in lung adenocarcinoma (LUAD) is unclear. Using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets, we found that the pyrimidine metabolism signaling pathway was significantly enriched in LUAD. Compared with normal lung tissues, the pyrimidine metabolic rate–limiting enzymes were highly expressed in lung tumor tissues. The high expression levels of pyrimidine metabolic–rate limiting enzymes were associated with unfavorable prognosis. However, purinergic receptors P2RX1, P2RX7, P2RY12, P2RY13, and P2RY14 were relatively downregulated in lung cancer tissues and were associated with favorable prognosis. Moreover, we found that hypo-DNA methylation, DNA amplification, and TP53 mutation were contributing to the high expression levels of pyrimidine metabolic rate–limiting enzymes in lung cancer cells. Furthermore, combined pyrimidine metabolic rate–limiting enzymes had significant prognostic effects in LUAD. Comprehensively, the pyrimidine metabolic rate–limiting enzymes were highly expressed in bladder cancer, breast cancer, colon cancer, liver cancer, and stomach cancer. And the high expression levels of pyrimidine metabolic rate–limiting enzymes were associated with unfavorable prognosis in liver cancer. Overall, our results suggested the mRNA levels of pyrimidine metabolic rate–limiting enzymes CAD, DTYMK, RRM1, RRM2, TK1, TYMS, UCK2, NR5C2, and TK2 were predictive of lung cancer as well as other cancers.

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35

Ying, C., A. Holý, D. Hocková, Z. Havlas, E. De Clercq, and J. Neyts. "Novel Acyclic Nucleoside Phosphonate Analogues with Potent Anti-Hepatitis B Virus Activities." Antimicrobial Agents and Chemotherapy 49, no. 3 (March 2005): 1177–80. http://dx.doi.org/10.1128/aac.49.3.1177-1180.2005.

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ABSTRACT Novel acyclic nucleoside phosphonates with a pyrimidine base preferentially containing an amino group at C-2 and C-4 and a 2-(phosphonomethoxy)ethoxy or (R)-2-(phosphonomethoxy)propoxy group at C-6 selectively inhibit the replication of wild-type and lamivudine-resistant hepatitis B viruses. The activity of the most potent compounds was comparable to that of adefovir.

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36

Sánchez-Viesca, Francisco and Gómez, Reina. "The chemistry of the Kossel’s test for purine bases." Magna Scientia Advanced Research and Reviews 1, no. 2 (February 28, 2021): 018–23. http://dx.doi.org/10.30574/msarr.2021.1.2.0001.

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Albrecht Kossel discovered the purine adenine and the pyrimidine thymine. He extended the murexide test for uric acid to adenine, guanine, hypoxanthine and xanthine. Since the structural differences in these compounds alter the pathways in these tests, we disclosed the reaction course in these assays. We provide the reaction sequence from the bi-annular base to the final product, the colored sodium purpurate.

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37

Balzarini, J., C. Pannecouque, E. De Clercq, S. Aquaro, C. F. Perno, H. Egberink, and A. Holý. "Antiretrovirus Activity of a Novel Class of Acyclic Pyrimidine Nucleoside Phosphonates." Antimicrobial Agents and Chemotherapy 46, no. 7 (July 2002): 2185–93. http://dx.doi.org/10.1128/aac.46.7.2185-2193.2002.

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ABSTRACT A novel class of acyclic nucleoside phosphonates has been discovered in which the base consists of a pyrimidine preferably containing an amino group at C-2 and C-4 and a 2-(phosphonomethoxy)ethoxy (PMEO) or a 2-(phosphonomethoxy)propoxy (PMPO) group at C-6. The 6-PMEO 2,4-diaminopyrimidine (compound 1) and 6-PMPO 2,4-diaminopyrimidine (compound 11) derivatives showed potent activity against human immunodeficiency virus (HIV) in the laboratory (i.e., CEM and MT-4 cells) and in primary (i.e., peripheral blood lymphocyte and monocyte/macrophage) cell cultures and pronounced activity against Moloney murine sarcoma virus in newborn NMRI mice. Their in vitro and in vivo antiretroviral activity was comparable to that of reference compounds 9-[(2-phosphonomethoxy)ethyl]adenine (adefovir) and (R)-9-[(2-phosphonomethoxy)-propyl]adenine (tenofovir), and the enantiospecificity of (R)- and (S)-PMPO pyrimidine derivatives as regards their antiretroviral activity was identical to that of the classical (R)- and (S)-9-(2-phosphonomethoxy)propyl purine derivatives. The prototype PMEO and PMPO pyrimidine analogues were relatively nontoxic in cell culture and did not markedly interfere with host cell macromolecular (i.e., DNA, RNA, or protein) synthesis. Compounds 1 and 11 should be considered attractive novel pyrimidine nucleotide phosphonate analogues to be further pursued for their potential as antiretroviral agents in the clinical setting.

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38

Loakes, D., D. M. Brown, N. Mahmood, J. Balzarini, and E. De Clercq. "Antiviral Activity of Bicyclic Pyrimidine Nucleosides." Antiviral Chemistry and Chemotherapy 6, no. 6 (December 1995): 371–78. http://dx.doi.org/10.1177/095632029500600604.

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A number of pyrimidine nucleosides, which may show two hydrogen bonding modes, have been prepared and tested for antiviral activity against a series of viruses. Whilst none of the compounds described showed significant activity against human immunodeficiency virus (HIV), the bicyclic 2′-deoxynucleoside, [2], derived from the base 6H,8H-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one, was shown to inhibit herpes simplex virus type 1 (HSV-1) at similar concentrations as BVDU1 and ACV. Compounds 13, 6-(2-deoxyribofuranosyl)-6H,8H-2-methyl-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one, and 14, N4-hydroxy-5-(2-chloroethyl)-2′-deoxyuridine, were as active as ACV against varicella-zoster virus (VZV).

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39

Subashini, Annamalai, Packianathan Thomas Muthiah, Gabriele Bocelli, and Andrea Cantoni. "2,6-Diamino-5-(2,4-diamino-6-oxo-1,6-dihydropyrimidin-5-ylmethyl)-4-oxopyrimidin-1-ium 3,5-dinitrobenzoate." Acta Crystallographica Section E Structure Reports Online 63, no. 11 (October 26, 2007): o4408—o4409. http://dx.doi.org/10.1107/s1600536807051276.

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In the title compound, C9H13N8O2 +·C7H3N2O6 −, the aminopyrimidine molecule is protonated at one of the pyrimidine N atoms. The carboxylate group of the 3,5-dinitrobenzoate anion interacts with the protonated N atom and the 2-amino group in a nearly linear fashion through a pair of N—H...O hydrogen bonds, generating the typical R 2 2(8) motif. Two inversion-related pyrimidine units are connected through a pair of N—H...N hydrogen bonds, forming a cyclic hydrogen-bonded R 2 2(8) motif. In addition to the base pairing, one of the carboxylate O atoms bridges the 4′-amino and 6′-amino groups on both side of the pairing, forming a DADA array. The molecular conformation of the cation is stabilized by two intramolecular N—H...O hydrogen bonds.

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40

Helland, D. E., P. W. Doetsch, and W. A. Haseltine. "Substrate specificity of a mammalian DNA repair endonuclease that recognizes oxidative base damage." Molecular and Cellular Biology 6, no. 6 (June 1986): 1983–90. http://dx.doi.org/10.1128/mcb.6.6.1983.

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The substrate specificity of a calf thymus endonuclease on DNA damaged by UV ligh, ionizing radiation, and oxidizing agents was investigated. End-labeled DNA fragments of defined sequence were used as substrates, and the enzyme-generated scission products were analyzed by using DNA sequencing methodologies. The enzyme was shown to incise damaged DNA at pyrimidine sites. The enzyme incised DNA damaged with UV light, ionizing radiation, osmium tetroxide, potassium permanganate, and hydrogen peroxide at cytosine and thymine sites. The substrate specificity of the calf thymus endonuclease was compared to that of Escherichia coli endonuclease III. Similar pyrimidine base damage specificities were found for both enzymes. These results define a highly conserved class of enzymes present in both procaryotes and eucaryotes that may mediate an important role in the repair of oxidative DNA damage.

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41

Fox, Keith R., and Tom Brown. "Formation of stable DNA triplexes." Biochemical Society Transactions 39, no. 2 (March 22, 2011): 629–34. http://dx.doi.org/10.1042/bst0390629.

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Triple-helical nucleic acids are formed by binding an oligonucleotide within the major groove of duplex DNA. These complexes offer the possibility of designing oligonucleotides which bind to duplex DNA with considerable sequence specificity. However, triple-helix formation with natural nucleotides is limited by (i) the requirement for low pH, (ii) the requirement for homopurine target sequences, and (iii) their relatively low affinity. We have prepared modified oligonucleotides to overcome these limitations, including the addition of positive charges to the sugar and/or base, the inclusion of cytosine analogues, the development of nucleosides for recognition of pyrimidine interruptions and the attachment of one or more cross-linking groups. By these means we are able to generate triplexes which have high affinities at physiological pH at sequences that contain pyrimidine interruptions.

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42

Helland, D. E., P. W. Doetsch, and W. A. Haseltine. "Substrate specificity of a mammalian DNA repair endonuclease that recognizes oxidative base damage." Molecular and Cellular Biology 6, no. 6 (June 1986): 1983–90. http://dx.doi.org/10.1128/mcb.6.6.1983-1990.1986.

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The substrate specificity of a calf thymus endonuclease on DNA damaged by UV ligh, ionizing radiation, and oxidizing agents was investigated. End-labeled DNA fragments of defined sequence were used as substrates, and the enzyme-generated scission products were analyzed by using DNA sequencing methodologies. The enzyme was shown to incise damaged DNA at pyrimidine sites. The enzyme incised DNA damaged with UV light, ionizing radiation, osmium tetroxide, potassium permanganate, and hydrogen peroxide at cytosine and thymine sites. The substrate specificity of the calf thymus endonuclease was compared to that of Escherichia coli endonuclease III. Similar pyrimidine base damage specificities were found for both enzymes. These results define a highly conserved class of enzymes present in both procaryotes and eucaryotes that may mediate an important role in the repair of oxidative DNA damage.

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43

Lloyd, R. Stephen. "Base excision repair of cyclobutane pyrimidine dimers." Mutation Research/DNA Repair 408, no. 3 (September 1998): 159–70. http://dx.doi.org/10.1016/s0921-8777(98)00032-9.

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44

West, Thomas P., and Chien-Peng Chu. "Pyrimidine base and nucleoside metabolism inPseudomonas cepacia." Journal of Basic Microbiology 27, no. 5 (1987): 283–86. http://dx.doi.org/10.1002/jobm.3620270514.

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45

Mavunkel, Babu, Yong-jin Xu, Bindu Goyal, Don Lim, Qing Lu, Zheng Chen, Dan-Xiong Wang, et al. "Pyrimidine-based inhibitors of CaMKIIδ." Bioorganic & Medicinal Chemistry Letters 18, no. 7 (April 2008): 2404–8. http://dx.doi.org/10.1016/j.bmcl.2008.02.056.

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46

Lambert, B., B. K. Jones, B. P. Roques, J. B. Le Pecq, and A. T. Yeung. "The noncovalent complex between DNA and the bifunctional intercalator ditercalinium is a substrate for the UvrABC endonuclease of Escherichia coli." Proceedings of the National Academy of Sciences 86, no. 17 (September 1989): 6557–61. http://dx.doi.org/10.1073/pnas.86.17.6557.

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We have demonstrated that the noncovalent complex formed between DNA and an antitumor bifunctional intercalator, ditercalinium, is recognized in vitro as bulky covalent DNA lesions by the purified Escherichia coli UvrABC endonuclease. It was established that no covalent drug-DNA adduct was formed during the incubation of the drug with DNA or during subsequent incubation with the UvrAB proteins. The nucleoprotein-ditercalinium complexes appear different from those generated by repair of pyrimidine dimers. The UvrA protein is able to form a stable complex with ditercalinium-intercalated DNA in the presence of ATP, whereas both UvrA and UvrB proteins are required to form a stable complex with pyrimidine dimer-containing DNA. The apparent half-life of the UvrA- and UvrAB-ditercalinium-DNA complexes following removal of free ditercalinium is 5 min. However, if the free ditercalinium concentration is maintained to allow the intercalation of one molecule of ditercalinium per 3000 base pairs, the half-life of the UvrA- or UvrAB-ditercalinium-DNA complex is 50 min, comparable to that of the complex of UvrAB proteins formed with pyrimidine dimer-containing DNA. UvrABC endonuclease incises ditercalinium-intercalated DNA as efficiently as pyrimidine dimer-containing DNA. However, unlike repair of pyrimidine dimers, the incision reaction is strongly favored by the supercoiling of the DNA substrate. Because UvrA- or UvrAB-ditercalinium-DNA complexes can be formed with relaxed DNA without leading to a subsequent incision reaction, these apparently dead-end nucleoprotein complexes may become lesions in themselves resulting in the cytotoxicity of ditercalinium. Our results show that binding of excision repair proteins to a noncovalent DNA-ligand complex may lead to cell toxicity.

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47

Tsunoda, Masaru, Takeshi Sakaue, Satoko Naito, Tomoko Sunami, Naoko Abe, Yoshihito Ueno, Akira Matsuda, and Akio Takénaka. "Insights into the Structures of DNA Damaged by Hydroxyl Radical: Crystal Structures of DNA Duplexes Containing 5-Formyluracil." Journal of Nucleic Acids 2010 (2010): 1–10. http://dx.doi.org/10.4061/2010/107289.

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Hydroxyl radicals are potent mutagens that attack DNA to form various base and ribose derivatives. One of the major damaged thymine derivatives is 5-formyluracil (fU), which induces pyrimidine transition during replication. In order to establish the structural basis for such mutagenesis, the crystal structures of two kinds of DNA d(CGCGRATfUCGCG) with R = A/G have been determined by X-ray crystallography. The fU residues form a Watson-Crick-type pair with A and two types of pairs (wobble and reversed wobble) with G, the latter being a new type of base pair between ionized thymine base and guanine base.In silicostructural modeling suggests that the DNA polymerase can accept the reversed wobble pair with G, as well as the Watson-Crick pair with A.

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48

Han, Xiaosi, and Charles L. Turnbough. "Regulation of carAB Expression inEscherichia coli Occurs in Part through UTP-Sensitive Reiterative Transcription." Journal of Bacteriology 180, no. 3 (February 1, 1998): 705–13. http://dx.doi.org/10.1128/jb.180.3.705-713.1998.

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ABSTRACT In Escherichia coli, expression of thecarAB operon is subject to cumulative repression, which occurs by ArgR-mediated repression at a downstream promoter, P2, and by pyrimidine-mediated regulation at an upstream promoter, P1. In this study, we show that pyrimidine-mediated regulation occurs in part through a mechanism involving UTP-sensitive reiterative transcription (i.e., repetitive addition of U residues to the 3′ end of a nascent transcript due to transcript-template slippage). In this case, reiterative transcription occurs at the end of a run of three T · A base pairs in the initially transcribed region of thecarAB P1 promoter. The sequence of this region is 5′-GTTTGC (nontemplate strand). In the proposed regulatory mechanism, increased intracellular levels of UTP promote reiterative transcription, which results in the synthesis of transcripts with the sequence GUUUU n (where n = 1 to >30). These transcripts are not extended downstream to include structural gene sequences. In contrast, lower levels of UTP enhance normal template-directed addition of a G residue at position 5 of the nascent transcript. This addition precludes reiterative transcription and permits normal transcript elongation capable of producing translatable carAB transcripts. Thus, carABexpression, which is necessary for pyrimidine nucleotide (and arginine) biosynthesis, increases in proportion to the cellular need for UTP. The proposed mechanism appears to function independently of a second pyrimidine-mediated control mechanism that involves the regulatory proteins CarP and integration host factor.

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49

Bonati, Flavio, Alfredo Burini, and Bianca Rosa Pietroni. "Mono- and Binuclear Gold(I) Compounds Containing Deprotonated Purines and Pyrimidines." Zeitschrift für Naturforschung B 40, no. 12 (December 1, 1985): 1749–52. http://dx.doi.org/10.1515/znb-1985-1226.

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Abstract In the presence of alkali and LAuCl one or two -NH - groups of a purine or pyrimidine base can be transformed into - N(AuL)- groups giving stable and soluble compounds containing one or two two-coordinated gold(I) nuclei; mononuclear LAu - Q' or binuclear LAu - Q - AuL with a monodentate Q'- or an exobidentate O-- ligand, resp. (Q'H = adenine, guanine, theobromine, theophylline, azaguanine or cytosine; QH2 - thymine or uracyl; L = triphenylphosphine)

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50

Milokhov, Demyd S., Vasyl Y. Hys, Olesya B. Volovenko, Irina S. Konovalova, Svitlana V. Shishkina, and Yulian M. Volovenko. "Synthetic Approach to Fused Azasultams with 1,2,4-Thiadiazepine Framework." Synthesis 52, no. 19 (June 16, 2020): 2857–69. http://dx.doi.org/10.1055/s-0040-1707405.

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Synthetic approach to fused azasultams with 1,2,4-thiadiazepine framework via base promoted protocols has been developed. 1H-Azole-2-carboxylates and N-(chloromethyl)-N-methylmethanesulfonamide were used as ambiphilic building blocks in the one-pot and two-step reaction sequences. Chemical behavior of the obtained azasultams in reactions with amines, hydrazine, DMFDMA, and NaBH4 was investigated. An enamino ketone derived from an azasultam was exploited in the synthesis of new pyrazole and pyrimidine heterocycles.

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