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Journal articles on the topic 'Chemical kinetics. Nuclear magnetic resonance'

Author: Grafiati

Published: 4 June 2021

Last updated: 11 February 2022

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1

Grzesiek, S., M. Allan, F. Cordier, et al. "Nuclear magnetic resonance as a quantitative tool to study interactions in biomacromolecules." Pure and Applied Chemistry 77, no. 8 (2005): 1409–24. http://dx.doi.org/10.1351/pac200577081409.

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High-resolution nuclear magnetic resonance (NMR) has emerged as one of the most versatile tools for the quantitative study of structure, kinetics, and thermodynamics of biomolecules and their interactions at atomic resolution. Traditionally, nuclear Overhauser enhancements (NOEs) and chemical shift perturbation methods are used to determine molecular geometries and to identify contact surfaces, but more recently, weak anisotropic orientation, anisotropic diffusion, and scalar couplings across hydrogen bonds provide additional information.Examples of such technologies are shown as applied to th

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2

Pagès, Guilhem, and Philip W. Kuchel. "Mathematical Modeling and Data Analysis of Nmr Experiments Using Hyperpolarized 13C Metabolites." Magnetic Resonance Insights 6 (January 2013): MRI.S11084. http://dx.doi.org/10.4137/mri.s11084.

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Rapid-dissolution dynamic nuclear polarization (DNP) has made significant impact in the characterization and understanding of metabolism that occurs on the sub-minute timescale in several diseases. While significant efforts have been made in developing applications, and in designing rapid-imaging radiofrequency (RF) and magnetic field gradient pulse sequences, very few groups have worked on implementing realistic mathematical/kinetic/relaxation models to fit the emergent data. The critical aspects to consider when modeling DNP experiments depend on both nuclear magnetic resonance (NMR) and (bi

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3

Van Den Thillart, G., and A. Van Waarde. "Nuclear magnetic resonance spectroscopy of living systems: applications in comparative physiology." Physiological Reviews 76, no. 3 (1996): 799–837. http://dx.doi.org/10.1152/physrev.1996.76.3.799.

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The most attractive feature of nuclear magnetic resonance spectroscopy (MRS) is the noninvasive and nondestructive measurement of chemical compounds in intact tissues. MRS already has many applications in comparative physiology, usually based on observation of 31P, since levels of phosphorus compounds indicate tissue energy status and are changed during exercise, fatigue, recovery, hypometabolism, anesthesia, hypoxia, hypercapnia, and osmotic and acid stress. Nuclei other than 31P may also be monitored, such as 1H, 13C, 15N, 19F, or 23Na, and applied in biological research. Particularly, 13C-M

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4

Whittier, Sean K., Alvan C. Hengge, and J. Patrick Loria. "Conformational Motions Regulate Phosphoryl Transfer in Related Protein Tyrosine Phosphatases." Science 341, no. 6148 (2013): 899–903. http://dx.doi.org/10.1126/science.1241735.

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Many studies have implicated a role for conformational motions during the catalytic cycle, acting to optimize the binding pocket or facilitate product release, but a more intimate role in the chemical reaction has not been described. We address this by monitoring active-site loop motion in two protein tyrosine phosphatases (PTPs) using nuclear magnetic resonance spectroscopy. The PTPs, YopH and PTP1B, have very different catalytic rates; however, we find in both that the active-site loop closes to its catalytically competent position at rates that mirror the phosphotyrosine cleavage kinetics.

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5

Fauconnier, Theresa, Alex D. Bain, Paul Hazendonk, R. A. Bell, and Colin JL Lock. "Structure and dynamics of azapropazone derivatives studied by crystallography and nuclear magnetic resonance." Canadian Journal of Chemistry 76, no. 4 (1998): 426–30. http://dx.doi.org/10.1139/v98-031.

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The X-ray crystal structure of a derivative of the nonsteroidal anti-inflammatory drug, azapropazone, has been determined using a data set obtained from a charge-coupled device (CCD) area detector. Azapropazone itself, 5-(dimethylamino)-9-methyl-2-propyl-1H-pyrazolo[1,2-a][1,2,4]benzotriazine- 1,3(2H)-dione, has previously been shown to be nonplanar, probably due to steric interactions between the pyrazolidine ring and the exocyclic dimethylamino group. The derivative studied in this work, 3-dimethylamino-7-methyl-1,2,4-benzotriazine, does not have the pyrazolidine ring and is shown here to be

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6

Catchen, Gary L. "Perturbed-Angular-Correlation Spectroscopy: Renaissance of a Nuclear Technique." MRS Bulletin 20, no. 7 (1995): 37–46. http://dx.doi.org/10.1557/s0883769400037167.

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During the past decade, perturbed-angular-correlation (PAC) spectroscopy has emerged as an important technique in several areas of materials science. PAC spectroscopy is used to measure the effects of local fields at well-defined lattice sites in a crystal. These measurements can provide unique information about the structures, kinetics, and energetics associated with point defects, the mechanisms of phase transitions, and the strengths and symmetries of chemical bonds of atoms on surfaces and at interfaces. In what follows, I describe the PAC technique in the context of several examples of th

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7

Combourieu, B., P. Besse, M. Sancelme, et al. "Morpholine Degradation Pathway of Mycobacterium aurumMO1: Direct Evidence of Intermediates by In Situ 1H Nuclear Magnetic Resonance." Applied and Environmental Microbiology 64, no. 1 (1998): 153–58. http://dx.doi.org/10.1128/aem.64.1.153-158.1998.

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ABSTRACT Resting Mycobacterium aurum MO1 cells were incubated with morpholine, a waste from the chemical industry. The kinetics of biodegradation was monitored by using in situ nuclear magnetic resonance (NMR). The incubation medium was directly analyzed by1H NMR. This technique allowed the unambiguous identification of two intermediates of the metabolic pathway involved in the biodegradation process, glycolate and 2-(2-aminoethoxy)acetate. The latter compound, which was not commercially available, was synthesized, in three steps, from 2-(2-aminoethoxy)ethanol. Quantitative analysis of the kin

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8

Mattsson, Cecilia, Merima Hasani, Binh Dang, Maxim Mayzel, and Hans Theliander. "About structural changes of lignin during kraft cooking and the kinetics of delignification." Holzforschung 71, no. 7-8 (2017): 545–53. http://dx.doi.org/10.1515/hf-2016-0190.

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Abstract Wood meal was submitted to kraft cooking in a small-scale flow-through reactor and the structural changes of lignin have been investigated. The rate determining steps in kraft cooking were in focus. Based on two-dimensional nuclear magnetic resonance (2D-NMR) measurements on lignin fractions extracted at different cooking times from the black liquor, it was observed that the main lignin reactions occur within 10–20 min and thus the kinetics of the chemical reaction cannot be the rate-determining step. On the other hand, the molecular weight (MW) of lignin is shifted towards larger fra

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9

Saravanan, R., and L. Ravikumar. "Cellulose bearing Schiff base and carboxylic acid chelating groups: a low cost and green adsorbent for heavy metal ion removal from aqueous solution." Water Science and Technology 74, no. 8 (2016): 1780–92. http://dx.doi.org/10.2166/wst.2016.296.

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Chemically modiﬁed cellulose bearing metal binding sites like Schiff base and carboxylic acid groups was synthesized and characterized through Fourier transform infrared and solid state 13C–nuclear magnetic resonance (NMR) analysis. The chemically modiﬁed cellulose (Cell-PA) adsorbent was examined for its metal ion uptake ability for Cu(II) and Pb(II) ions from aqueous solution. Kinetic and isotherm studies were carried out under optimum conditions. Pseudo-second-order kinetics and Langmuir isotherm fit well with the experimental data. Thermodynamic studies were also performed along with adsor

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10

Bouajila, J., G. Raffin, H. Waton, C. Sanglar, J. O. Païsse, and M. F. Grenier-Loustalot. "Phenolic Resins – Characterizations and Kinetic Studies of Different Resols Prepared with Different Catalysts and Formaldehyde/Phenol Ratios (I)." Polymers and Polymer Composites 10, no. 5 (2002): 341–60. http://dx.doi.org/10.1177/096739110201000502.

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The physicochemical and kinetic properties of resols prepared with different catalysts (NaOH, LiOH and Ba(OH)2) and variable formaldehyde/phenol ratios (2.5 £ R £ 3.5) were followed to determine their effects on the mechanisms and reaction products at a fixed pH and temperature. Kinetic monitoring and quantification of residual monomers were carried out by liquid chromatography coupled with mass spectrometry (LC/UV/MS), by 13C nuclear magnetic resonance (NMR) and by chemical assay for formaldehyde. Oligomer formation (n ≥ 2) was determined by LC/UV/MS, size exclusion chromatography (SEC) and 1

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11

Lundberg, Dan, and Krister Holmberg. "Nuclear magnetic resonance studies on hydrolysis kinetics and micellar growth in solutions of surface-active betaine esters." Journal of Surfactants and Detergents 7, no. 3 (2004): 239–46. http://dx.doi.org/10.1007/s11743-004-0307-9.

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Bourbiaux, Bernard, André Fourno, Quang-Long Nguyen, et al. "Experimental and Numerical Assessment of Chemical Enhanced Oil Recovery in Oil-Wet Naturally Fractured Reservoirs." SPE Journal 21, no. 03 (2016): 0706–19. http://dx.doi.org/10.2118/169140-pa.

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Summary Among various ways to extend the lifetime of mature fields, chemical enhanced-oil-recovery (EOR) processes have been subject of renewed interest in the recent years. Oil-wet fractured reservoirs represent a real challenge for chemical EOR because the matrix medium does not spontaneously imbibe the aqueous solvent of chemical additives. The present paper deals with chemical EOR by use of wettability modifiers (WMs). The kinetics of spontaneous imbibition of chemical solutions in oil-wet limestone plugs and mini-plugs was quantified thanks to X-ray computed-tomography (CT) scanning and n

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13

Fan, Yaqin, Chunlan Tang, Qing Hu, Yonglin Lei, and Jichuan Huo. "Evaluation on Curing Properties and Kinetics of Isophthalonitrile Oxide." Polish Journal of Chemical Technology 20, no. 3 (2018): 37–46. http://dx.doi.org/10.2478/pjct-2018-0036.

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Abstract N,N-dihydroxybenzene-1,3-dicarboximidoyl dichloride was synthesized from benzene-1,3-dicarboxaldehyde and characterized by fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H and 13C NMR). The elastomer was prepared through the 1,3-dipolar cycloaddition of reaction between liquid polybutadiene (LPB) and isophthalonitrile oxide in this work. The tensile strength of different elastomer was enhanced from 0.14 MPa to 0.33 MPa as the elongation at break decreased from 145% to 73%, and the modulus increased from 0.09 kPa to 0.47 kPa. The parameters of kinetic

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14

Tiecher, Tales, Mohsin Zafar, Fábio Joel Kochem Mallmann, et al. "Animal manure phosphorus characterization by sequential chemical fractionation, release kinetics and 31P-NMR analysis." Revista Brasileira de Ciência do Solo 38, no. 5 (2014): 1506–14. http://dx.doi.org/10.1590/s0100-06832014000500016.

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Phosphate release kinetics from manures are of global interest because sustainable plant nutrition with phosphate will be a major concern in the future. Although information on the bioavailability and chemical composition of P present in manure used as fertilizer are important to understand its dynamics in the soil, such studies are still scarce. Therefore, P extraction was evaluated in this study by sequential chemical fractionation, desorption with anion-cation exchange resin and 31P nuclear magnetic resonance (31P-NMR) spectroscopy to assess the P forms in three different dry manure types (

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15

Hajjaji, Mohamed, Abdellah Beraa, Yannick Coppel, Régis Laurent, and Anne-Marie Caminade. "Adsorption capacity of sodic- and dendrimers-modified stevensite." Clay Minerals 53, no. 3 (2018): 525–44. http://dx.doi.org/10.1180/clm.2018.39.

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ABSTRACTThe adsorption capacities of nano-sized organoclays composed of a stevensite-rich clay (R), phosphorus dendrimers (GC1 and GC2) and Na+-saturated clay were evaluated for their capacity to adsorb chromate and methylene blue (MB) in the range of 298–318 K. The adsorption kinetics and the isotherms were analysed based on kinetic equations and isotherm models and by adopting a non-linear regression procedure. In addition, the organoclays and the Na+-saturated clays were characterized principally by solid-state nuclear magnetic resonance spectroscopy. The pseudo-second-order rate equation d

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16

Korzhnev, Dmitry M., Tomasz L. Religa, Wiktor Banachewicz, Alan R. Fersht, and Lewis E. Kay. "A Transient and Low-Populated Protein-Folding Intermediate at Atomic Resolution." Science 329, no. 5997 (2010): 1312–16. http://dx.doi.org/10.1126/science.1191723.

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Proteins can sample conformational states that are critical for function but are seldom detected directly because of their low occupancies and short lifetimes. In this work, we used chemical shifts and bond-vector orientation constraints obtained from nuclear magnetic resonance relaxation dispersion spectroscopy, in concert with a chemical shift–based method for structure elucidation, to determine an atomic-resolution structure of an “invisible” folding intermediate of a small protein module: the FF domain. The structure reveals non-native elements preventing formation of the native conformati

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17

Chmela, Štefan, Agnesa Fiedlerová, Tibor Liptaj, Yohann Catel, and Norbert Moszner. "Determination of homopolymerization kinetics and copolymerization with methyl methacrylate of diethyl 9-(methacryloyloxy)-2-oxo-nonylphosphonate, 9-(methacryloyloxy)-2-oxo-nonylphosphonic acid and diethyl 9-(methacryloyloxy)-nonylphosphonate." e-Polymers 18, no. 3 (2018): 205–16. http://dx.doi.org/10.1515/epoly-2017-0155.

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AbstractThe three polymerizable monomers diethyl 9-(methacryloyloxy)-2-oxo-nonylphosphonate M1, 9-(methacryloyloxy)-2-oxo-nonylphosphonic acid M2 and diethyl 9-(methacryloyloxy)-nonylphosphonate M3 are examined for their free radical polymerization and copolymerization activity in methanol between 40 and 65°C. Polymerization proceeds readily through a thermal free radical initiation. The intensity exponents for the monomer and initiator are only slightly over 1 and approximately 0.5, respectively. This is in accordance with the results typically observed for an ideal free radical polymerizatio

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18

Wang, C. X., and Q. P. Song. "Removal of Cu(II) ions from aqueous solutions using N-carboxymethyl chitosan." Water Science and Technology 66, no. 9 (2012): 2027–32. http://dx.doi.org/10.2166/wst.2012.419.

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N-carboxymethyl chitosan (NCMC) was synthesized by reacting chitosan with chloroacetic acid in water under triethylamine (Et3N) as catalyst. The chemical structures of NCMC were characterized by Fourier transform infrared (FT-IR) and hydrogen-1 nuclear magnetic resonance (1H-NMR) spectroscopy and confirmed that carboxymethylation occurred on the amino groups. Samples of NCMC were used for removal of Cu(II) from aqueous solution. The effects of degree of substitution of NCMC, initial pH value and adsorption kinetics on the adsorption were studied. Adsorption experiments showed that NCMC has a h

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19

Cohen, D. M., and R. N. Bergman. "Prediction of positional isotopomers of the citric acid cycle: the syntactic approach." American Journal of Physiology-Endocrinology and Metabolism 266, no. 3 (1994): E341—E350. http://dx.doi.org/10.1152/ajpendo.1994.266.3.e341.

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We propose a syntactic approach to modeling of biochemical fluxes that combines a rule-based description of atomic transfer in chemical reactions with a structurally oriented, stochastic model of chemical reaction kinetics. This approach avoids the use of differential equations to describe the production and disappearance of each molecule. The computer simulation predicts the changes over time in the abundance of each positional isotopomer of every metabolic intermediate in the citric acid cycle of heart cells, subsequent to administration of [2-13C]acetate (including natural abundance of 13C)

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20

Bou Orm, Nadine, Thomas Gréa, Marwa Hamandi, et al. "Design of Hybrid PAH Nanoadsorbents by Surface Functionalization of ZrO2 Nanoparticles with Phosphonic Acids." Nanomaterials 11, no. 4 (2021): 952. http://dx.doi.org/10.3390/nano11040952.

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This study focuses on the preparation of innovative nanocomposite materials based on surface modification of commercial nano-ZrO2 optimized from Brønsted acid–base surface reactions. This surface modification was carried out by direct grafting of suitable phosphonic acids bearing a vinylic or phenylic substituent in aqueous solution. Different loading quantities of the anchoring organophosphorus compounds were applied for each materials synthesis. The resulting nanohybrids were thoroughly characterized by infrared spectroscopy (DRIFT), solid-state nuclear magnetic resonance (NMR), nitrogen ads

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21

Paganini, A. T., J. M. Foley, and R. A. Meyer. "Linear dependence of muscle phosphocreatine kinetics on oxidative capacity." American Journal of Physiology-Cell Physiology 272, no. 2 (1997): C501—C510. http://dx.doi.org/10.1152/ajpcell.1997.272.2.c501.

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The influence of muscle oxidative capacity on phosphocreatine (PCr) changes during and after stimulation was examined in the superficial (fast-twitch) section of rat gastrocnemius muscles. Muscle mitochondrial enzymes were increased in one group of rats by 8-10 wk of training on a running wheel (to a final regimen of 50 min/day at 38 m/min, 5 days/wk) and decreased in another group by chemical thyroidectomy [0.025% methimazole (MMI) in drinking water for 8 wk]. After these treatments, muscle citrate synthase activity was 179 and 29%, respectively, of that in corresponding control groups. Muscl

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22

Liu, Bo, and Wei Wu. "Influence of epoxidized ethylene propylene diene rubber on nonisothermal crystallization kinetics and mechanical properties of poly(butylene terephthalate)/polypropylene blend." Journal of Polymer Engineering 39, no. 3 (2019): 216–27. http://dx.doi.org/10.1515/polyeng-2018-0283.

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Abstract The epoxidized ethylene propylene diene rubber (eEPDM) was successfully prepared by the epoxidation of ethylene propylene diene rubber (EPDM) using t-butyl hydroperoxide as the oxidant in association with molybdenum oxide as the catalyst and characterized by Fourier-transform infrared (FTIR) spectrometer and 1H-nuclear magnetic resonance analyses. Then the poly(butylene terephthalate) (PBT)/eEPDM/polypropylene (PP) blends with different eEPDM contents were prepared using a twin-screw extruder, and the effect of eEPDM on nonisothermal crystallization kinetics of PBT/PP blend was invest

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23

Halmen, Norbert, Christoph Kugler, Eduard Kraus, Benjamin Baudrit, Thomas Hochrein, and Martin Bastian. "Single-sided NMR for the measurement of the degree of cross-linking and curing." Journal of Sensors and Sensor Systems 7, no. 1 (2018): 21–30. http://dx.doi.org/10.5194/jsss-7-21-2018.

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Abstract. The degree of cross-linking and curing is one of the most important values concerning the quality of cross-linked polyethylene (PE-X) and the functionality of adhesives and resin-based components. Up to now, the measurement of this property has mostly been time-consuming and usually destructive. Within the shown work the feasibility of single-sided nuclear magnetic resonance (NMR) for the non-destructive determination of the degree of cross-linking and curing as process monitoring was investigated. First results indicate the possibility of distinguishing between PE-X samples with dif

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24

Hu, K. S., A. I. Darer, and M. J. Elrod. "Thermodynamics and kinetics of the hydrolysis of atmospherically relevant organonitrates and organosulfates." Atmospheric Chemistry and Physics Discussions 11, no. 5 (2011): 14383–416. http://dx.doi.org/10.5194/acpd-11-14383-2011.

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Abstract. The presence of alcohol, organonitrate, and organosulfate species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has suggested that certain isoprene-derived organonitrates are able to efficiently convert to organosulfates and alcohols on ambient SOA. In order to better understand the structure activity relationships previously observed for the isoprene-derived organonitrates and organosulfates, the hydrolysis reactions of a number of monofunctional and difun

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Hu, K. S., A. I. Darer, and M. J. Elrod. "Thermodynamics and kinetics of the hydrolysis of atmospherically relevant organonitrates and organosulfates." Atmospheric Chemistry and Physics 11, no. 16 (2011): 8307–20. http://dx.doi.org/10.5194/acp-11-8307-2011.

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Abstract. The presence of alcohol, organonitrate, and organosulfate species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has suggested that certain isoprene-derived organonitrates are able to efficiently convert to organosulfates and alcohols on ambient SOA. In order to better understand the structure activity relationships previously observed for the isoprene-derived organonitrates and organosulfates, the hydrolysis reactions of a number of monofunctional and difun

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26

Frukhtbeyn, S., K. Van Dongen, and J. Sun. "Stoichiometry and Kinetics of Sequential Dimethacrylate Enzymolysis." Journal of Dental Research 98, no. 9 (2019): 1037–44. http://dx.doi.org/10.1177/0022034519858975.

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The increasing use of methacrylate-based materials in tissue engineering and dental restorations demands detailed evaluation of enzymolysis of these materials due to toxicity, durability, and biocompatibility concerns. The objective of this study is to develop tools for assessing and ranking the enzymolysis kinetics of dimethacrylate (DMA) compounds. Triethyleneglycol DMA and diurethane DMA are employed as model DMAs for kinetic studies of 2-step enzymolysis by 2 esterases, pseudocholine esterase and cholesterol esterase. In addition, the intermediate hydrolysis products, mono-methacrylates (m

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Birdsall, A. W., C. A. Zentner, and M. J. Elrod. "Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid." Atmospheric Chemistry and Physics Discussions 12, no. 11 (2012): 30039–80. http://dx.doi.org/10.5194/acpd-12-30039-2012.

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Abstract. The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear

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Birdsall, A. W., C. A. Zentner, and M. J. Elrod. "Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid." Atmospheric Chemistry and Physics 13, no. 6 (2013): 3097–109. http://dx.doi.org/10.5194/acp-13-3097-2013.

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Abstract. The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear

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29

Guzmàn, M. C. Carmona, M. Balôn Almeida, J. Hidalgo Toledo, M. A. Munoz Perez та M. Lopez Poveda. "Sulfonation reactions of (β-carbolines". Canadian Journal of Chemistry 67, № 4 (1989): 720–26. http://dx.doi.org/10.1139/v89-110.

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The homogeneous sulfonations of (β-carboline derivatives norharmane 2, harmane 3, harmine 4, harmol 5, -N,N′-dimethyl-harmane 6, and harmaline 7 have been studied in 80–90% w/w sulfuric acid solutions at 25 °C. Ultraviolet–visible and 13C nuclear magnetic resonance spectra and chemical analysis of the reaction mixtures show that for all the substrates studied only C-6 sulfonated products are obtained. The sulfonation reactions of the benzene unsubstituted substrates 2, 3, and 6 and the partially aromatic substrate 7 proceed by direct electrophilic attack of the H3SO4+ cation on the benzene rin

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Patel, Rakesh B., Umesh P. Tarpada, and Dipak K. Raval. "Study on copolymers synthesized from 2,3-epoxypropyl-3-(2-furyl) acrylate – styrene and their glass fiber reinforced composites." Journal of Polymer Engineering 33, no. 4 (2013): 303–14. http://dx.doi.org/10.1515/polyeng-2013-0054.

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Abstract 3-(2-Furyl) acrylic acid (FAA) and 2,3-epoxypropyl-3-(2-furyl) acrylate (EPFA) were synthesized. EPFA was characterized by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1HNMR) spectroscopy. Copolymerization of prepared EPFA was carried out with styrene as the comonomer, by varying the mole ratio of EPFA:styrene at different reaction times, using benzoyl peroxide as an initiator at 80°C in toluene. FAA, EPFA and copolymers were characterized by FTIR and 1HNMR spectroscopy, as well as viscosity, gel permeation chromatography (GPC) and epoxy equivalent

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Pokorny, Diana, Lothar Brecker, Mateja Pogorevc та ін. "Proton-Nuclear Magnetic Resonance Analyses of the Substrate Specificity of a β-Ketolase from Pseudomonas putida, Acetopyruvate Hydrolase". Journal of Bacteriology 181, № 16 (1999): 5051–59. http://dx.doi.org/10.1128/jb.181.16.5051-5059.1999.

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ABSTRACT A revised purification of acetopyruvate hydrolase from orcinol-grown Pseudomonas putida ORC is described. This carbon-carbon bond hydrolase, which is the last inducible enzyme of the orcinol catabolic pathway, is monomeric with a molecular size of ∼38 kDa; it hydrolyzes acetopyruvate to equimolar quantities of acetate and pyruvate. We have previously described the aqueous-solution structures of acetopyruvate at pH 7.5 and several synthesized analogues by1H-nuclear magnetic resonance (NMR)-Fourier transform (FT) experiments. Three 1H signals (2.2 to 2.4 ppm) of the methyl group are ass

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Oh, Sung Joon, and Jack L. Koenig. "Studies of Peroxide Curing of cis-1,4-Polyisoprene/Diallyl Phthalate Blends by Spectroscopic Techniques." Rubber Chemistry and Technology 72, no. 2 (1999): 334–42. http://dx.doi.org/10.5254/1.3538805.

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Abstract Peroxide curing of cis-1,4-polyisoprene/diallyl phthalate blends was studied by the analytical techniques of equilibrium swelling, differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), and solid-state nuclear magnetic resonance (NMR). Although the overall curing kinetics are controlled by the peroxide decomposition rate, the addition of a coagent into the rubber matrix catalyzes the curing reactions. The increase in peroxide and coagent concentrations in the blend results in a decrease in T2 relaxation times, which is caused by restricted segmental mobility due

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Castiglione Morelli, Maria Antonietta, Angela Ostuni, Brunella Giangaspero, Stefano Cecchini, Augusto Carluccio, and Raffaele Boni. "Relationships between Seminal Plasma Metabolites, Semen Characteristics and Sperm Kinetics in Donkey (Equus asinus)." Animals 11, no. 1 (2021): 201. http://dx.doi.org/10.3390/ani11010201.

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This study aimed to evaluate donkey seminal plasma metabolites and relate this information to the main characteristics of sperm quality. Sperm kinetics from 10 donkey stallions were analyzed with a computerized system at the time of collection (T0) and after 24 h storage at 4 °C (T24). Seminal plasma was frozen at −80 °C for subsequent proton nuclear magnetic resonance (1H NMR) spectroscopy. On three stallions, semen collection was repeated monthly for three times and sperm analysis also included mitochondrial activity and oxidative status. One stallion was azoospermic and a second semen colle

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Wang, Jun, Shuangshuang Gu, Na Pang, Fangqin Wang, and Fuan Wu. "A study of esterification of caffeic acid with methanol using p-toluenesulfonic acid as a catalyst." Journal of the Serbian Chemical Society 78, no. 7 (2013): 1023–34. http://dx.doi.org/10.2298/jsc120802101w.

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Caffeic acid (CA) can be considered as an important natural antioxidant. However, the low solubility and stability of CA in various solvent systems is a major limiting factor governing the overall application in the lipid industry, so the synthesis of methyl caffeate (MC)using CA and methanol is a feasible way to improve its lipophilicity. Here, the reaction conditions and kinetic parameters for the synthesis of MC using p-toluenesulfonic acid (PTSA) as a catalyst were firstly investigated, and the product was confirmed byliquid chromatography-mass spectrometry (LC-MS),Fourier transform infrar

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Shushakov, Oleg A. "Groundwater NMR in conductive water." GEOPHYSICS 61, no. 4 (1996): 998–1006. http://dx.doi.org/10.1190/1.1444048.

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A surface method of groundwater prospecting using nuclear magnetic resonance (NMR) in the Earth’s magnetic field is under study. The technique is employed for hydrogeological surveys down to a depth of about 100 m. The advantage of this method is that an NMR signal can be observed only in the presence of groundwater. A circular wire loop with a diameter of 100 m is laid out on the ground to excite and receive the NMR signal. An oscillating current with a rectangular pulse‐shape is passed through the loop, with the carrier‐frequency being equal to the proton‐resonance frequency in the Earth’s f

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Saliba, Daniel, and Mazen Al-Ghoul. "Kinetics of intercalation of fluorescent probes in magnesium–aluminium layered double hydroxide within a multiscale reaction–diffusion framework." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2080 (2016): 20160138. http://dx.doi.org/10.1098/rsta.2016.0138.

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We report the synthesis of magnesium–aluminium layered double hydroxide (LDH) using a reaction–diffusion framework (RDF) that exploits the multiscale coupling of molecular diffusion with chemical reactions, nucleation and growth of crystals. In an RDF, the hydroxide anions are allowed to diffuse into an organic gel matrix containing the salt mixture needed for the precipitation of the LDH. The chemical structure and composition of the synthesized magnesium–aluminium LDHs are determined using powder X-ray diffraction (PXRD), thermo-gravimetric analysis, differential scanning calorimetry, solid-

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Ahmed, Abdul Baquee, and Iman Bhaduri. "CHEMICAL MODIFICATION, CHARACTERIZATION AND EVALUATION OF MUCOADHESIVE POTENTIALITY OF ASSAM BORA RICE STARCH." International Journal of Pharmacy and Pharmaceutical Sciences 9, no. 9 (2017): 132. http://dx.doi.org/10.22159/ijpps.2017v9i9.20108.

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Objective: The objective of the present study was to chemical modification, characterization and evaluation of mucoadhesive potentiality of Assam bora rice starch as potential excipients in the sustained release drug delivery system. Methods: The starch was isolated from Assam bora rice and esterified using thioglycolic acid and characterized by Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC) and Nuclear magnetic resonance (NMR). The 10% w/v gel formulation based on modified bora rice starch loaded with irinotecan (0.6%) was prepared and evaluated for v

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Brandão, Deysiane Oliveira, Geovani Pereira Guimarães, Ravely Lucena Santos, et al. "Model Analytical Development for Physical, Chemical, and Biological Characterization ofMomordica charantiaVegetable Drug." Journal of Analytical Methods in Chemistry 2016 (2016): 1–15. http://dx.doi.org/10.1155/2016/7528297.

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Momordica charantiais a species cultivated throughout the world and widely used in folk medicine, and its medicinal benefits are well documented, especially its pharmacological properties, including antimicrobial activities. Analytical methods have been used to aid in the characterization of compounds derived from plant drug extracts and their products. This paper developed a methodological model to evaluate the integrity of the vegetable drugM. charantiain different particle sizes, using different analytical methods.M. charantiawas collected in the semiarid region of Paraíba, Brazil. The herb

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Wang, Xiujuan, Xiuting Zheng, Meng Song, and Sizhu Wu. "A study on the relationship between polycarbonate microstructure and performance as determined by a combined experimental and molecular dynamics simulation method." e-Polymers 14, no. 6 (2014): 407–15. http://dx.doi.org/10.1515/epoly-2014-0065.

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AbstractThe influence of the microstructure of polycarbonate (PC) on performance was systematically investigated by both experimental method and molecular simulation. Yield stress, impact strength, molecular weight, and transmittance were used to distinguish the degradation processes between different PCs, and thermal degradation kinetics was studied to obtain the activation energy. At the molecular level, through 13C nuclear magnetic resonance (NMR) spectroscopy, it was observed that PCs have a more polar group of benzene rings, resulting in the high density, dielectric constant, and tensile

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Du, Bo-Wei, Ching-Chang Lin, and Fu-Hsiang Ko. "Trivalent Cations Detection of Magnetic-Sensitive Microcapsules by Controlled-Release Fluorescence Off-On Sensor." Nanomaterials 11, no. 7 (2021): 1801. http://dx.doi.org/10.3390/nano11071801.

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A pyrene-based derivative, 2-((pyrene-1-ylmethylene)amino)ethanol (PE) nanoparticle, was encapsulated via water-in-oil-in-water (W/O/W) double emulsion with the solvent evaporation method by one-pot reaction and utilized as a fluorescence turn-on sensor for detecting Fe3+, Cr3+, and Al3+ ions. Magnetic nanoparticles (MNPs) embedded in polycaprolactone (PCL) were used as the magnetic-sensitive polyelectrolyte microcapsule-triggered elements in the construction of the polymer matrix. The microcapsules were characterized by ultraviolet–visible (UV–Vis) and photoluminescence (PL) titrations, quant

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Wiśniewska-Wrona, Maria, and Mirosława El Fray. "FUNCTIONAL THREE-COMPONENT POLYMERIC BIOCOMPOSITES FOR THE TREATMENT OF BEDSORES." Progress on Chemistry and Application of Chitin and its Derivatives XXIII (September 10, 2018): 185–206. http://dx.doi.org/10.15259/pcacd.23.019.

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Presented here are the results of investigations into the preparation of three-component dressing materials from various biopolymers in the form of a single-layer film which is suitable as a carrier for pain-relieving (lidocaine) and bacteriostatic (sulphanilamid) therapeutic agents. Physical-chemical, biological and usable properties of the prepared materials were tested and assessed. The amount of added active substance was adopted based on the dose recommended by the Polish Pharmacopeia for external medicinal preparations. Antibacterial activity against gram (-) Escherichia coli and gram (+

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Ribeiro, Ana C. F., and Miguel A. Esteso. "Transport Properties for Pharmaceutical Controlled-Release Systems: A Brief Review of the Importance of Their Study in Biological Systems." Biomolecules 8, no. 4 (2018): 178. http://dx.doi.org/10.3390/biom8040178.

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: The goal of this work was to comprehensive study the transport properties of controlled-release systems for the safe and reliable delivery of drugs. Special emphasis has been placed on the measurement of the diffusion of drugs, alone or in combination with carrier molecules for enhanced solubility and facilitated transport. These studies have provided detailed comprehensive information—both kinetic and thermodynamic—for the design and operation of systems for the controlled release and delivery of drugs. Cyclodextrins are among the most important carriers used in these systems. The basis for

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Jacobs, M. I., W. J. Burke, and M. J. Elrod. "Kinetics of the reactions of isoprene-derived hydroxynitrates: gas phase epoxide formation and solution phase hydrolysis." Atmospheric Chemistry and Physics 14, no. 17 (2014): 8933–46. http://dx.doi.org/10.5194/acp-14-8933-2014.

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Abstract. Isoprene, the most abundant non-methane volatile organic compound (VOC) emitted into the atmosphere, is known to undergo gas phase oxidation to form eight different hydroxynitrate isomers in "high-NOx" environments. These hydroxynitrates are known to affect the global and regional formation of ozone and secondary organic aerosol (SOA), as well as affect the distribution of nitrogen. In the present study, we have synthesized three of the eight possible hydroxynitrates: 4-hydroxy-3-nitroxy isoprene (4,3-HNI) and E / Z-1-hydroxy-4-nitroxy isoprene (1,4-HNI). Oxidation of the 4,3-HNI iso

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Eykyn, Thomas R., Stuart J. Elliott, and Philip W. Kuchel. "Extended Bloch–McConnell equations for mechanistic analysis of hyperpolarized <sup>13</sup>C magnetic resonance experiments on enzyme systems." Magnetic Resonance 2, no. 1 (2021): 421–46. http://dx.doi.org/10.5194/mr-2-421-2021.

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Abstract. We describe an approach to formulating the kinetic master equations of the time evolution of NMR signals in reacting (bio)chemical systems. Special focus is given to studies that employ signal enhancement (hyperpolarization) methods such as dissolution dynamic nuclear polarization (dDNP) and involving nuclear spin-bearing solutes that undergo reactions mediated by enzymes and membrane transport proteins. We extend the work given in a recent presentation on this topic (Kuchel and Shishmarev, 2020) to now include enzymes with two or more substrates and various enzyme reaction mechanism

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Vala, Masoud Mohamadi, Yadollah Bayat, and Mohammad Bayat. "Synthesis and Thermal Decomposition Kinetics of Epoxy Poly Glycidyl Nitrate as an Energetic Binder." Defence Science Journal 70, no. 4 (2020): 461–68. http://dx.doi.org/10.14429/dsj.70.15470.

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An energetic binder epoxy poly glycidyl nitrate (e-PGN) with a molecular weight of about 1244 gr/mol was synthesised via end modified poly glycidyl nitrate (PGN) is presented in the paper. This structure was characterised by the number of epoxy groups, infrared spectroscopy, and nuclear magnetic resonance. The thermal degradation behavior of e-PGN was studied by thermo gravimetric analysis (TG) and differential scanning calorimetry (DSC) under nitrogen atmosphere at different heating rates. The glass transition temperature (Tg) was measured to determine the compatibility of energetic plasticiz

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León-Boigues, Laia, Luis Andrés Pérez, and Carmen Mijangos. "In Situ Synthesis of Poly(butyl methacrylate) in Anodic Aluminum Oxide Nanoreactors by Radical Polymerization: A Comparative Kinetics Analysis by Differential Scanning Calorimetry and 1H-NMR." Polymers 13, no. 4 (2021): 602. http://dx.doi.org/10.3390/polym13040602.

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In this work, we explore the ability to generate well-defined poly(butyl methacrylate) (PBMA) nanostructures by “in situ” polymerization of butyl methacrylate monomer (BMA). PBMA nanostructures of high and low aspect ratios have been successfully obtained through the free radical polymerization (FRP) of a BMA monomer in anodic aluminum oxide (AAO) nanoreactors of suitable size. A polymerization kinetics process has been followed by differential scanning calorimetry (DSC) and proton Nuclear Magnetic Resonance spectroscopy (1H-NMR).The determination of the kinetics of polymerization through DSC

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Li, Xiaohua, Vishal Agarwal, Meilin Liu, and William S. Rees. "Investigation of the mechanism of sol-gel formation in the Sr(NO3)2/citric acid/ethylene glycol system by solution state 87 Sr nuclear magnetic resonance spectroscopy." Journal of Materials Research 15, no. 11 (2000): 2393–99. http://dx.doi.org/10.1557/jmr.2000.0344.

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The polymerization mechanism of a modified Pechini process was investigated by 87Sr nuclear magnetic resonance spectroscopy for the mixed solution of strontium nitrate, citric acid, and ethylene glycol. The C-ratio (the ratio of citric acid to metal ions in the polymer complex) is suggested to have a strong influence on the quality of the derived film. An analysis of the chemical shift variation, as a function of C-ratio, indicates the presence in the solution of two species: solvated strontium ions and strontium ions bound to the polymer complex, with a stoichiometry of 1:7. A polymeric precu

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Bezerra, Roosevelt Delano Sousa, A. I. S. Morais, Josy Anteveli Osajima, Lívio César Cunha Nunes, and Edson Cavalcanti Silva Filho. "Cellulose Phosphate Applied in the Removal of the Drug Acetaminophen from Aqueous Media." Materials Science Forum 869 (August 2016): 745–49. http://dx.doi.org/10.4028/www.scientific.net/msf.869.745.

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The cellulose phosphate used for this work was obtained by a reaction between cellulose and sodium trimetaphosphate (STMP) at pH 10. The material obtained was characterized by 31P nuclear magnetic resonance (31P NMR) spectrometry and energy-dispersive X-ray spectroscopy (EDS). In the 31P NMR results, the two peaks at 2.05 and 7.96 ppm are related to phosphorous. The EDS indicated the presence of 5.47% of incorporated phosphorus which proved the modification. The material obtained was applied in the removal of the pharmaceutical drug acetaminophen (acetaminophen) from aqueous media. The maximum

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Errich, A., K. Azzaoui, E. Mejdoubi, et al. "Toxic heavy metals removal using a hydroxyapatite and hydroxyethyl cellulose modified with a new Gum Arabic." Indonesian Journal of Science and Technology 6, no. 1 (2021): 41–64. http://dx.doi.org/10.17509/ijost.v6i1.31480.

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The objective of this work was to develop a process that allows the synthesis of an apatitic material of controlled composition and morphology, which could be used for medical and environmental applications. The adsorbent was synthesized, and characterized using scanning electron microscopy, nuclear magnetic resonance, Thermal analysis and other techniques, Atomic Force Microscopy, X-ray photoelectron spectroscopy and Total organic carbon. Different experimental parameters such as the effect of the amount of adsorbent, solution pH and temperatures and contact times were studied. Pseudo-order k

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Alberdi-Cedeño, Jon, María L. Ibargoitia, and María D. Guillén. "Oxylipins Associated to Current Diseases Detected for the First Time in the Oxidation of Corn Oil as a Model System of Oils Rich in Omega-6 Polyunsaturated Groups. A Global, Broad and in-Depth Study by 1H NMR Spectroscopy." Antioxidants 9, no. 6 (2020): 544. http://dx.doi.org/10.3390/antiox9060544.

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For the first time, an important number of oxylipins have been identified and quantified in corn oil submitted to mild oxidative conditions at each time of their oxidation process. This oil can be considered as a model system of edible oils rich in polyunsaturated omega-6 groups. The study was carried out using 1H nuclear magnetic resonance spectroscopy (1H NMR), which does not require chemical modification of the sample. These newly detected oxylipins include dihydroperoxy-non-conjugated-dienes, hydroperoxy-epoxy-, hydroxy-epoxy- and keto-epoxy-monoenes as well as E-epoxy-monoenes, some of wh

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