Application of Phosphorus-31 Nuclear Magnetic Resonance Spectrosocopy for the Study of Human Diabetic Cataractogenesis

Intact human Senses incubated at 5.5 mM (normal) and 35.5 mM glucose were examined by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Lense in 35.5 mM glucose showed an altered metabolic steady-state characterized by a lowered adenosine triphosphate/inorganic orthophosphate ratio. ³¹P NMR spectroscopy can be used to measure metabolic changes in the lens. This model offers an important means to study dynamic metabolism in the human lens in the setting of diabetic cataractogenesis.     

Characterization of microwave-synthesized polydextrose and its radical-scavenging activity

Polydextrose (PD) was rapidly synthesized under microwave irradiation using glucose as substrate and phosphoric acid as catalyst. The reaction products were identified by methylation analysis, Fourier- Transform Infrared (FT-IR) and NMR spectroscopy. The FT-IR spectra confirmed the polymerization of glucose to form PD. Methylation analysis and ¹H NMR and ¹³C NMR assignments indicated that the PD was a highly branched polysaccharide. The results of radical scavenging activity assays showed that this PD exhibited a potent free hydroxyl radical scavenging activity. This synthetic method can be used to produce PD for the food industry.     

Study of Lysozyme Glycation Reaction by Mass Spectrometry and NMR Spectroscopy

The Advanced Glycation End Products (AGEs) are the causative substances of lifestyle‐habit illness. To elucidate the glycation mechanism of the protein, the reaction of lysozyme with D ‐glucose was analyzed by the fluorescence, TOF‐MS, and ¹³C‐NMR spectroscopy under the physiological condition. The fluorescence intensity of lysozyme in the glycation solution increased proportionally with a reaction time of ten weeks. The MALDI‐TOF‐MS spectra of the reaction solution after two weeks showed a peak at m/z 15066, which indicated the presence of a larger molecule than the native lysozyme (m/z 14331), and new peaks at m/z 30105 (dimer) and 45000 (trimer) were also observed. The spectral analysis supported the assumption of a continuous glycation reaction of D ‐glucose with lysozyme and a 30% transformation of lysozyme to the dimeric form during ten weeks. The ¹³C‐NMR spectra of lysozyme showed six [¹³C]‐labeled signals by the glycation reaction with [¹³C]‐glucose after two weeks of reaction. The combined analysis of TOF‐MS and ¹³C‐NMR spectra uncovered that first products of the glycation reaction of lysozyme with D ‐glucose can be observed already three hours after starting the reaction and that nine D ‐glucose units are attached during ten weeks at 37°.     

Latex‐state NMR spectroscopy for quantitative analysis of epoxidized deproteinized natural rubber

Method of quantitative analysis through latex‐state ¹³C NMR spectroscopy was established for in situ determination of epoxy group content of epoxidized natural rubber in latex stage. The epoxidized natural rubber latex was prepared by epoxidation of deproteinized natural rubber with freshly prepared peracetic acid in latex stage. The resulting epoxidized deproteinized natural rubber (EDPNR) latex was characterized through latex‐state ¹³C NMR spectroscopy. Chemical shift values of signals of latex‐state ¹³C NMR spectrum for EDPNR were similar to those of solution‐state ¹³C NMR spectrum for EDPNR. Resolution of latex‐state ¹³C NMR spectrum was gradually improved as temperature for the nuclear magnetic resonance (NMR) measurement increased to 70°C. Signal‐to‐noise ratio of latex‐state ¹³C NMR measurement was similar to that of solution‐state ¹³C NMR measurement at temperature above 50°C. The epoxy group content determined through latex‐state NMR spectroscopy was proved to be the same as that determined through solution‐state NMR spectroscopy. Copyright © 2017 John Wiley & Sons, Ltd.     

Biotransformation of uridine monophosphate (UMP) and glucose to uridine diphosphate-glucose (UDPG) byCandida saitoana KCTC7249 cells

The present study investigates the biotransformation of glucose with uridine monophosphate (UMP) to obtain sugar nucleotide, UDP-glucose (UDPG), by the dried cells ofCandida saitoana KCTC7249. The biotransformation was optimized by varying the concentrations of substrates and phosphate ion. UDPG (24 mM) was biotransformed from 200 mM glucose and 37.5 mM UMP by dried cells of C.saitoana. The glucose yields about 64% UDP-glucose, based on UMP concentration. The addition of glucose-1-phosphate to the reaction mixture accelerated the formation of UDPG from a concentration of UMP. The structure of UDP-glucose obtained was determined with¹³C NMR and FAB mass spectra. These results indicate that the yeast-dried cells could be used for the production of nucleotide sugars for donor molecules of complex carbohydrate synthesis.     

Recent developments in the <Superscript>13</Superscript>C NMR spectroscopic analysis of paramagnetic hemes and heme proteins

Despite the wealth of information that has been obtained from the study of paramagnetic hemes and heme proteins by ¹H NMR spectroscopy, there are certain limitations imposed by the nature of paramagnetically affected resonances that are difficult to overcome. Although it has long been recognized that ¹³C NMR spectroscopy is likely to be a powerful complementary technique to overcome some of these limitations, the low sensitivity and low natural abundance of ¹³C nuclei has resulted in a lag in the application of ¹³C NMR spectroscopy to the study of paramagnetic hemes and heme proteins. The tremendous advances in methodology and instrumentation witnessed in the NMR field, coupled to the advent of recombinant DNA methods that have made possible the preparation and purification of significant quantities of proteins, and the biosynthesis of ¹³C-labeled heme, have contributed to an increased interest in the study of paramagnetic heme active sites by ¹³C NMR spectroscopy. As a consequence, ¹³C NMR spectroscopy is emerging as a powerful tool to study heme electronic structure and structure–function relationships in heme-containing proteins. In this report we strive to summarize some of the recent developments in the analysis of paramagnetic hemes and heme-containing proteins by ¹³C NMR spectroscopy.     

13C NMR spectroscopy of 4,5- and 5,6-double bond isomers of spiro-3-steroidal ketone derivatives : The determination of the structures of steroidal thiazolidines

The thiazolidine isomers obtained upon the reaction of aminoethanethiols with α,β-unsaturated steroidal ketones were found to be double bond positional isomers based on their optical rotations and ¹H and ¹³C NMR spectra. The ¹³C NMR spectra of analogous ketals, hemithioketals and a thioketal of steroidal ketones were also reported, and ¹³C NMR spectroscopy was shown to be a convenient method of assigning the position of the double bond in the double bond isomers for all four of these derivatives. Finally, ¹³C NMR spectroscopy was found to be useful in determining that thiazolidine formation was stereospecific to give only one C-3-isomer.     

NMR spectroscopic study of 3-nitrofurazans

3-Nitrofurazans with different substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between chemical shifts (CS) in the ¹³C NMR spectra of furazans and benzene with similar substituents was revealed. Increments for a series of new substituents were determined. The ¹³C and ¹⁴N CS values presented can be used as a reliable set of reference data.     

NMR Study of the Hydrolysis and Oligomerization of Alkyltrichlorosilanes in Silanizing Solutions Used to Prepare Alkylsiloxane Self-Assembled Monolayers

²⁹Si NMR spectroscopy is not suited to following a number of fast occurring processes involving silicon centres due to long accumulation times resulting from low detector sensitivity factors and poor natural abundance. By observing subtle changes in signals due to the methylene protons adjacent to the silicon centre, the hydrolysis of alkyltrichlorosilanes in tetrahydrofuran and acetone-d₆ solutions, and subsequent polycondensation reactions, were studied using ¹H and ¹³C NMR spectroscopy, to gain an understanding of the processes that lead to formation of oligomers in silanizing solutions. The hydroxysilanes formed by hydrolysis of alkyltrichlorosilanes were characterized by ¹H and ¹³C NMR studies at low temperatures. Formation of oligomeric and polymeric species from these hydroxysilanes at higher temperatures was monitored by ¹H NMR studies. The data for oligomer formation were fitted to the kinetic model of an acid-catalyzed stepwise condensation. The implications of these results for the problem of oligomer formation competing with self-assembly processes in formation of alkylsiloxane monolayers are discussed.     

Application of cationic polymerization to grafting and coating of silica particles

The cationic polymerization of electron rich monomers such as vinyl ethers, vinyl furane, and cyclopentadiene on silica surfaces can be initiated by aryl methyl halides. The reactions yield always soluble polymers (by heterogeneous catalysis) and novel polymer/silica hybrid materials. The link between polymer and solid is caused by covalent Si-O-C bonds, by network formation of the polymers during the chain growth, or by a combination of both of them. The analysis of the polymer structures on the surface by ¹H MAS NMR spectroscopy in suspension and by solid state ¹³C CP MAS NMR spectroscopy is described. Proof of Si-O-C bonds via DRIFT spectroscopy and ¹³C CP MAS NMR spectroscopy is given. The most effective method of irreversibly linking the polymer to the silica surface is the network formation. Polyvinyl ethers are bound strongly to the surface, as can be shown by FTIR measurements, but the linkage is not stable due to the Si-O-C bonds' susceptibility to hydrolysis. Poly-cyclopentadienes (PCPD) are linked to the surface by Si-O-C bonds, which show an extraordinary high resistance to acids and bases. Si-O-C bond formation of poly-2-vinyl furane could not yet be detected by ¹³C CP MAS NMR spectroscopy and DRIFT spectroscopy. In this case the high degree of coating derives from the bifunctionality of 2-vinyl furane: it may undergo Friedel-Crafts-alkylation at the 5-position of the furane ring as well as chain polymerization via the vinyl group at the 2-position.     

Synthesis of Glucose‐Containing Polyaniline by the Oxidative Polymerization of N‐Glucosylaniline

Summary: The oxidative polymerization of N‐glucosylaniline was carried out using ammonium persulfate as the oxidant in phosphate buffer. The structure of the isolated polymer was determined by ¹H NMR, ¹³C NMR, and UV‐vis spectroscopy to be the polyaniline having glucose residues attached to the general polyaniline unit. Participation of the ortho‐position of the aromatic ring in the polymerization was also confirmed by the analyses.

The oxidative polymerization of N‐glucosylaniline.     

Real‐Time Interrogation of Aspirin Reactivity,Biochemistry, and Biodistribution by Hyperpolarized Magnetic Resonance Spectroscopy

Hyperpolarized magnetic resonance spectroscopy enables quantitative, non‐radioactive, real‐time measurement of imaging probe biodistribution and metabolism in vivo. Here, we investigate and report on the development and characterization of hyperpolarized acetylsalicylic acid (aspirin) and its use as a nuclear magnetic resonance (NMR) probe. Aspirin derivatives were synthesized with single‐ and double‐¹³C labels and hyperpolarized by dynamic nuclear polarization with 4.7 % and 3 % polarization, respectively. The longitudinal relaxation constants (T₁) for the labeled acetyl and carboxyl carbonyls were approximately 30 seconds, supporting in vivo imaging and spectroscopy applications. In vitro hydrolysis, transacetylation, and albumin binding of hyperpolarized aspirin were readily monitored in real time by ¹³C‐NMR spectroscopy. Hyperpolarized, double‐labeled aspirin was well tolerated in mice and could be observed by both ¹³C‐MR imaging and ¹³C‐NMR spectroscopy in vivo.     

Real‐Time Interrogation of Aspirin Reactivity,Biochemistry, and Biodistribution by Hyperpolarized Magnetic Resonance Spectroscopy

Hyperpolarized magnetic resonance spectroscopy enables quantitative, non‐radioactive, real‐time measurement of imaging probe biodistribution and metabolism in vivo. Here, we investigate and report on the development and characterization of hyperpolarized acetylsalicylic acid (aspirin) and its use as a nuclear magnetic resonance (NMR) probe. Aspirin derivatives were synthesized with single‐ and double‐¹³C labels and hyperpolarized by dynamic nuclear polarization with 4.7 % and 3 % polarization, respectively. The longitudinal relaxation constants (T₁) for the labeled acetyl and carboxyl carbonyls were approximately 30 seconds, supporting in vivo imaging and spectroscopy applications. In vitro hydrolysis, transacetylation, and albumin binding of hyperpolarized aspirin were readily monitored in real time by ¹³C‐NMR spectroscopy. Hyperpolarized, double‐labeled aspirin was well tolerated in mice and could be observed by both ¹³C‐MR imaging and ¹³C‐NMR spectroscopy in vivo.     

Immobilization of Optically Active and Complexing Olefins Using Solid- and Liquid-Phase Catalytic Hydrosilylation

It was shown that chiral stationary phases and complexing sorbents can be synthesized by hydrosilylation of the respective functional olefins and sol–gel transformations in the surface layer of silica. The modified matrices were characterized by UV spectroscopy, diffuse reflectance IR spectroscopy, and ¹³C NMR spectroscopy.     

13C isotope effects on 1H chemical shifts: NMR spectral analysis of 13C‐labelled D‐glucose and some 13C‐labelled amino acids

The one‐ and two‐bond ¹³C isotope shifts, typically ?1.5 to ?2.5 ppb and ?0.7 ppb respectively, in non‐cyclic aliphatic systems and up to ?4.4 ppb and ?1.0 ppb in glucose cause effects that need to be taken into account in the adaptive NMR spectral library‐based quantification of the isotopomer mixtures. In this work, NMR spectral analyses of some ¹³C‐labelled amino acids, D ‐glucose and other small compounds were performed in order to obtain rules for prediction of the ¹³C isotope effects on ¹H chemical shifts. It is proposed that using the additivity rules, the isotope effects can be predicted with a sufficient accuracy for amino acid isotopomer applications. For glucose the effects were found strongly non‐additive. The complete spectral analysis of fully ¹³C‐labelled D ‐glucose made it also possible to assign the exocyclic proton signals of the glucose. Copyright © 2009 John Wiley & Sons, Ltd.     

Solid-state NMR studies of pharmaceutical solids in polymer matrices

Biodegradable drug-delivery systems can be formulated to release drug for hours to years and have been used for the controlled release of medications in animals and humans. An important consideration in developing a drug-delivery matrix is knowledge of the long-term stability of the form of the drug and matrix after formulation and any changes that might occur to the drug throughout the delivery process. Solid-state NMR spectroscopy is an effective technique for studying the state of both the drug and the matrix. Two systems that have been studied using solid-state NMR spectroscopy are presented. The first system studied involved bupivacaine, a local anesthetic compound, which was incorporated into microspheres composed of tristearin and encapsulated using a solid protein matrix. Solid-state ¹³C NMR spectroscopy was used to investigate the solid forms of bupivacaine in their bulk form or as incorporated into the tristearin/protein matrix. Bupivacaine free base and bupivacaine-HCl have very different solid-state NMR spectra, indicating that the molecules of these compounds pack in different crystal forms. In the tristearin matrix, the drug form could be determined at levels as low as 1:100 (w/w), and the form of bupivacaine was identified upon loading into the tristearin/protein matrix. In the second case, the possibility of using solid-state ¹³C NMR spectroscopy to characterize biomolecules lyophilized within polymer matrices is evaluated by studying uniformly ¹³C-labeled asparagine (Asn) in 1:250 (w/w) formulations with poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA). This work shows the capability of solid-state NMR spectroscopy to study interactions between the amino acid and the polymer matrix for synthetic peptides and peptidomimetics containing selective ¹³C labeling at the Asn residue.     

两个取代苄基锡配合物的合成、抗癌活性及其与DNA相互作用

利用二(2,4-二氯苄基)二氯化锡分别与对甲基苯甲酰肼或对叔丁基苯甲酰肼、丙酮酸钠在甲醇中发生反应,合成了2个二(2,4-二氯苄基)锡配合物(C1、C2),通过元素分析、IR、¹H NMR、¹³C NMR、¹¹⁹Sn NMR、HRMS以及X射线单晶衍射表征了配合物结构。测试了配合物C1、C2的热稳定性以及配合物对NCI-H460(人肺癌细胞)、HepG2(人肝癌细胞)和MCF7(人乳腺癌细胞)的体外抑制活性,发现配合物C1对癌细胞均表现较好的抑制作用。利用UV-Vis光谱、荧光光谱以及黏度法研究了2个配合物与ct-DNA之间的相互作用,结果表明配合物是以经典的嵌入模式与DNA结合。     

Preparation of sol�Cgel hybrid materials from ��-methacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions

Organic?Cinorganic hybrid materials suitable for the development of sol?Cgel coatings for metallic surfaces were prepared by hydrolysis and condensation of ??-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). The hydrolysis of MAPTMS/TMOS was carried out in an ethanol/water solution. The prehydrolysis stage of MAPTMS/TMOS system was monitored by Fourier transform infrared spectroscopy (FTIR) and liquid-state ²⁹Si and ¹³C nuclear magnetic resonance (²⁹Si and ¹³C NMR). FTIR analysis indicated that the hydrolysis of MAPTMS/TMOS was accomplished as far as the (SiOMe) band corresponding to unhydrolyzed silane disappeared. The concentration of the alkoxy groups and the extent of self-condensation of mono-, di-, and trisubstituted siloxanes (T species) in the sol were estimated by using liquid-state ²⁹Si NMR spectroscopy. The hydrolysis of the prepared sol was also evaluated by liquid-state ¹³C NMR spectroscopy. The results indicated that under the adopted synthesis strategy conditions, the hydrolysis process requires 4?h to be completed.     

Ammonolysis of 1,2‐Bis[dichloro(methyl)silyl]ethane. On the Structure of 1,3,6,8‐Tetramethyl‐2,7,11,12‐tetraaza‐1,3,6,8‐tetrasila‐tricyclo[6.2.1.13,6]‐dodecane

Ammonolysis of 1,2‐bis[dichloro(methyl)silyl]ethane afforded a crystalline tricyclic silazane along with polymeric material. The crystalline material could be isolated in pure state. It was analyzed by ¹H, ¹³C, ¹⁵N and ²⁹Si NMR spectroscopy in solution, by ¹³C, ¹⁵N and ²⁹Si MAS NMR spectroscopy in the solid state, as well as by single‐crystal and powder X‐ray diffraction. The title compound exists as a single isomer in solution, whereas in the solid state the presence of several modifications is indicated, in particular by the solid‐state MAS NMR spectra.     

A Strategy to Design Hyperpolarized 13C Magnetic Resonance Probes Using [1‐13C]α‐Amino Acid as a Scaffold Structure

Hyperpolarization is an emerging method that dramatically enhances NMR signal intensity. As a result of their increased sensitivity, hyperpolarized (HP) NMR molecular probes can be used to perform time‐resolved spectroscopy and imaging in vitro and in vivo. It is, however, challenging to design such probes de novo. Herein, the [1‐¹³C]α‐amino acid is reported as a scaffold structure to design HP ¹³C NMR molecular probes. The [1‐¹³C]α‐amino acid can be converted to various HP ¹³C chemical probes that show sufficient chemical shift change by altering the chemical state of the α nitrogen upon interaction with the target. Several previously reported HP probes could be explained by this design principle. To demonstrate the versatility of this approach, two α‐amino‐acid‐based HP ¹³C chemical probes, sensitive to pH and Ca²⁺ ion, were developed and used to detect targets.