6027-15-2Relevant articles and documents
Electrocatalytic oxidation and determination of homocysteine at nanotubes-modified carbon paste electrode using dopamine as a mediator
Mohammadzadeh, Safoora,Fouladgar, Masoud
, p. 1595 - 1607 (2013)
A carbon paste electrode modified with multiwall carbon nanotubes (MWCNTPE) was prepared to study the electrocatalytic activity of dopamine (DP) in the presence of homocysteine (HCy) and it was used for the determination of HCy. The diffusion coefficient of HCy (D = 6.79×10-6cm 2s-1),and the kinetic parameters of its oxidation, such as electron transfer coefficient (a = 0.46), and rate constant (kh= 7.44×102dm3mol-1s-1)were also determined using electrochemical approaches. Under the optimum pH of 5.0, the peak current of oxidation of HCy at MWCNTPE in the presence of DP occurred at a potential of about 530 mV and the results showed that the oxidation peak current of HCy at the modified carbon nanotubes electrode was higher than on the unmodified electrode. The peak current of differential pulse voltammograms of HCy solutions increased linearly in the range 3.0-600 μM HCy with a detection limit of 2.08 μM HCy. This method was also examined for determination of HCy in physiological serum and urine samples.
S-Adenosylhomocysteine Analogue of a Fairy Chemical, Imidazole-4-carboxamide, as its Metabolite in Rice and Yeast and Synthetic Investigations of Related Compounds
Ouchi, Hitoshi,Namiki, Takuya,Iwamoto, Kenji,Matsuzaki, Nobuo,Inai, Makoto,Kotajima, Mihaya,Wu, Jing,Choi, Jae-Hoon,Kimura, Yoko,Hirai, Hirofumi,Xie, Xiaonan,Kawagishi, Hirokazu,Kan, Toshiyuki
supporting information, p. 453 - 458 (2021/02/05)
During the course of our investigations of fairy chemicals (FCs), we found S-ICAr-H (8a), as a metabolite of imidazole-4-carboxamide (ICA) in rice and yeast (Saccharomyces cerevisiae). In order to determine its absolute configuration, an efficient synthetic method of 8a was developed. This synthetic strategy was applicable to the preparation of analogues of 8a that might be biologically very important, such as S-ICAr-M (9), S-AICAr-H (10), and S-AICAr-M (11).
METHOD OF PRODUCING S-ICA RIBOSYLHOMOCYSTEINE
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Paragraph 0055-0057, (2020/02/14)
PROBLEM TO BE SOLVED: To provide novel techniques regarding a method of producing S-ICA ribosylhomocysteine. SOLUTION: A method of producing a compound represented by formula (1) or a salt thereof comprises reacting a compound represented by formula (2) with a compound represented by formula (3) to generate a compound represented by formula (4), and subjecting the obtained compound represented by formula (4) to a treatment of removing a protecting group. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
Crystal-facet-dependent denitrosylation: Modulation of NO release from S-nitrosothiols by Cu2O polymorphs
Ghosh, Sourav,Roy, Punarbasu,Prasad, Sanjay,Mugesh, Govindasamy
, p. 5308 - 5318 (2019/05/29)
Nitric oxide (NO), a gaseous small molecule generated by the nitric oxide synthase (NOS) enzymes, plays key roles in signal transduction. The thiol groups present in many proteins and small molecules undergo nitrosylation to form the corresponding S-nitrosothiols. The release of NO from S-nitrosothiols is a key strategy to maintain the NO levels in biological systems. However, the controlled release of NO from the nitrosylated compounds at physiological pH remains a challenge. In this paper, we describe the synthesis and NO releasing ability of Cu2O nanomaterials and provide the first experimental evidence that the nanocrystals having different crystal facets within the same crystal system exhibit different activities toward S-nitrosothiols. We used various imaging techniques and time-dependent spectroscopic measurements to understand the nature of catalytically active species involved in the surface reactions. The denitrosylation reactions by Cu2O can be carried out multiple times without affecting the catalytic activity.
Colorimetric and fluorometric determination of homocysteine and cysteine
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Page/Page column 8; 9, (2015/12/18)
Colorimetric and fluorometric methods are disclosed for the rapid, accurate, selective, and inexpensive detection of homocysteine, or of homocysteine and cysteine, or of cysteine. The methods may be employed with materials that are readily available commercially. The novel methods are selective for homocysteine, for cysteine, or for total homocysteine and cysteine, and do not cross-react substantially with chemically-related species such as glutathione. The homocysteine-selective method does not have substantial cross-reactivity to the very closely related species cysteine. The cysteine-selective method does not have substantial cross-reactivity to the very closely related species homocysteine. The methods may be used, for example, in a direct assay of human blood plasma for homocysteine levels.
A study of the glutathione metaboloma peptides by energy-resolved mass spectrometry as a tool to investigate into the interference of toxic heavy metals with their metabolic processes
Rubino, Federico Maria,Pitton, Marco,Brambilla, Gabri,Colombi, Antonio
, p. 1578 - 1593 (2007/10/03)
To better understand the fragmentation processes of the metal-biothiol conjugates and their possible significance in biological terms, an energy-resolved mass spectrometric study of the glutathione conjugates of heavy metals, of several thiols and disulfides of the glutathione metaboloma has been carried out. The main fragmentation process of γ-glutamyl compounds, whether in the thiol, disulfide, thioether or metal-bis-thiolate form, is the loss of the γ-glutamyl residue, a process which ERMS data showed to be hardly influenced by the sulfur substitution. However, loss of the γ-glutamyl residue from the mono-S-glutathionyl-mercury (II) cation is a much more energetic process, possibly pointing at a strong coordination of the carboxylic group to the metal. Moreover, loss of neutral mercury from ions containing the γ-glutamyl residue to yield a sulfenium cation was a much more energetic process than those not containing them, suggesting that the redox potential of the thiol/disulfide system plays a role in the formal reduction of the mercury dication in the gas phase. Occurrence of complementary sulfenium and protonated thiol fragments in the spectra of protonated disulfides of the glutathione metaboloma mirrors the thiol/disulfide redox process of biological importance. The intensity ratio of the fragments is proportional to the reduction potential in solution of the corresponding redox pairs. This finding has allowed the calculation of the previously unreported reduction potentials for the disulfide/thiol pair of cysteinylglycine, thereby confirming the decomposition scheme of bis- and mono-S-glutathionyl-mercury (II) ions. Finally, on the sole basis of the mass spectrometric fragmentation of the glutathione-mercury conjugates, and supported by independent literature evidence, an unprecedented mechanism for mercury ion-induced cellular oxidative stress could be proposed, based on the depletion of the glutathione pool by a catalytic mechanism acting on the metal (II)-thiol conjugates and involving as a necessary step the enzymatic removal of the glutamic acid residue to yield a mercury (II)-cysteinyl-glycine conjugate capable of regenerating neutral mercury through the oxidation of glutathione thiols to the corresponding disulfides. Copyright
Characterization of the disulfides of bio-thiols by electrospray ionization and triple-quadrupole tandem mass spectrometry
Rubino, Federico Maria,Verduci, Cinzia,Giampiccolo, Rosario,Pulvirenti, Salvatore,Brambilla, Gabri,Colombi, Antonio
, p. 1408 - 1416 (2007/10/03)
Glutathione and other intracellular low molecular mass thiols act both as the major endogenous antioxidant and redox buffer system and, as recently highlighted, as an important regulator of cellular homeostasis. Such cellular functions are mediated by protein thiolation, a newly recognized post-translational modification which involves the formation of mixed disulfides between GSH and key disulfide-linked Cys residues in the native protein structure. It is also well known that thiol-seeking heavy metals, such as mercury, cadmium and lead, may interfere in this regulatory system, thus disrupting the cellular functioning. To identify such mixed disulfides in order to investigate their biological role, 15 homo- and heterodimeric disulfides were prepared by air oxidation of binary mixtures containing cysteine, homocysteine, penicillamine, N-acetylcysteine, N-acetylpenicillamine and glutathione and their protonated molecules were characterized by mass spectrometry. Collisionally activated unimolecular decomposition of protonated homo- and heterodimeric disulfides generated by electrospray ionization gives rise to fission of the disulfide system both between the two sulfur atoms and across the C-S bonds, to yield structurally specific fragments which allow one to define the structure of the compounds and to discriminate between isomeric compounds. Fission between the sulfur atoms yields a pair of R-S? ions and, in some cases, also the complementary fragments corresponding to the protonated amino acids. Fission across the C-S bonds mainly occurs in the disulfides of N-acetylcysteine and N-acetylpenicillamine and gives rise to non-S-containing fragments formally similar to those obtained from some mercapturic acids. The complementary fragments, formally connected as R-S-S+ ions are also observed. Fragmentation of glutathione disulfides mainly shows the characteristic loss of the terminal γ-linked glutamic acid and little, if any, fragmentation of the disulfide system. Copyright
The first asymmetric syntheses of L-homocysteine and L-homocystine
Adamczyk, Maciej,Fishpaugh, Jeffrey R.,Thiruvazhi, Mohan
, p. 4151 - 4156 (2007/10/03)
Asymmetric syntheses of L-homocysteine 1 and L-homocystine 2 are described. Alkylation of the carbanion derived from Schollkopf reagent 3 and ensuing hydrolyses gave S-triphenylmethyl-L-homocysteine 6. Removal of the triphenylmethyl group gave L-homocysteine 1 and subsequent oxidation provided L-homocystine 2.
Catalysis by Cu2+ of nitric oxide release from S-nitrosothiols (RSNO)
Askew, Stuart C.,Barnett, D. Jonathan,McAninly, John,Williams, D. Lyn H.
, p. 741 - 746 (2007/10/02)
The decomposition of a range of S-nitrosothiols (thionitrites) RSNO, based on cysteine derivatives, yields in water at pH 7.4 nitrite ion quantitatively.If oxygen is rigorously excluded then no nitrite ion is formed and nitric oxide can be detected using an NO-probe.The reaction is catalysed by trace quantities of Cu2+ (there is often enough present in distilled water samples) and also to a lesser extent by Fe2+, but not by Zn2+, Cu2+, Mg2+, Ni2+, Co2+, Mn2+, Cr3+ or Fe3+.The rate equation (measuring the disappearance of the absorption at ca. 350 nm due to RSNO) was established as v = k*2+> + k' over a range of 2+> typically 5-50 μmol dm-3.The constant term k' represents the component of the rate due to residual Cu2+ in the solvent and buffer components, together with the spontaneous thermal reaction.Decomposition can be virtually halted by the addition of EDTA.Reactions carried out in the presence of N-methylaniline gave a quantitative yield of N-methyl-N-nitrosoaniline, but a negligible yield when oxygen was rigorously excluded.Values of the second-order rate constant k were obtained for a range of S-nitrosothiols.Reactivity is highest for the S-nitrosothiols derived from cysteamine and penicillamine, when Cu2+ can be complexed both with the nitrogen atom of the nitroso group and the nitrogen atom of the amino group, via a six-membered ring intermediate.If there is no amino (or other electron donating group) present, reaction is very slow (as for RSNO derived from a tert-butyl sulfide).N-Acetylation of the amino group reduces the reactivity drastically as does the introduction of another CH2 group in the chain.There is evidence of a significant gem-dimethyl effect.Kinetic results using the S-nitrosothiols derived from mercaptoacetic, thiolactic and thiomalic acids suggests that coordination can also occur via one of the oxygen atoms of the carboxylate group.EPR experiments which examined the Cu2+ signal showed no spectral change during the reaction suggesting that the mechanism does not involve oxidation and reduction with Cu2+ Cu+ interconversion.
Preparations of Optically Active Homocysteine and Homocystine by Asymmetric Transformation of (RS)-1,3-Thiazane-4-carboxylic Acid
Miyazaki, Hideya,Ohta, Atsushi,Kawakatsu, Nobuyuki,Waki, Yukitaka,Gogun, Yasuhiro,et al.
, p. 536 - 540 (2007/10/02)
DL-Homocysteine from (RS)-homocysteine thiolactone hydrochloride was subjected to reaction with formaldehyde in acetic acid to give (RS)-1,3-thiazane-4-carboxylic acid monohydrate .An asymmetric transformation of (RS)-THA*H2O was achieved via salt formation with optically active tartaric acid in the presence of salicylaldehyde in acetic acid.The (R)- and (S)-THA obtained, respectively, from the salt of (R)-THA with (2R,3R)-tartaric acid and its enantiomeric salt were treated with hydroxylamine hydrochloride to give D- and L-Hcy of 100percent optical purity, respectively, in 50percent yield from (RS)-HTL*HCl.Oxidation of D- and L-Hcy with hydrogen peroxide gave D- and L-homocystine, respectively, in 47percent yield.
