A nuclear magnetic resonance study of the kinetics and equilibria for the oxidation of penicillamine and N-acetylpenicillamine by glutathione disulfide

1984 ◽  
Vol 62 (9) ◽  
pp. 1672-1680 ◽  
Author(s):  
Dallas L. Rabenstein ◽  
Yvon Theriault
Keyword(s):  
Equilibrium Constants ◽  
Reducing Power ◽  
Thiol Group ◽  
Nuclear Magnetic Resonance Study ◽  
Second Step ◽  
Glutathione Disulfide ◽  
Exchange Reactions ◽  
H Nmr ◽  
Mixed Disulfide ◽  
Ph Range

The kinetics and equilibria of the oxidation of penicillamine by glutathione disulfide to form, in the first step, penicillamine–glutathione mixed disulfide and glutathione and, in the second step, penicillamine disulfide and glutathione have been studied over the pH range 4–9 by 1H nmr. The reactive species are found to be penicillamine with its amino group protonated and its thiol group deprotonated and glutathione disulfide and penicillamine–glutathione mixed disulfide with their two amino groups protonated. The rate and equilibrium constants for the first step are much larger than those for the second step, indicating a small tendency for penicillamine to form its symmetrical disulfide by thiol/disulfide exchange reactions. This and the smaller reducing power of penicillamine as compared to glutathione are attributed to steric hindrance from the methyl groups adjacent to the sulfur. The kinetics and equilibria of the oxidation of N-acetylpenicillamine by glutathione disulfide were studied at neutral pH. Conditional equilibrium and rate constants for the oxidation of penicillamine by glutathione disulfide at pH 7.4 are presented and discussed in terms of the metabolism of penicillamine.

A nuclear magnetic resonance study of the equilibria and kinetics of the reaction of penicillamine with cystine and related disulfides

1985 ◽  
Vol 63 (8) ◽  
pp. 2225-2231 ◽  
Author(s):  
Yvon Theriault ◽  
Dallas L. Rabenstein
Keyword(s):  
Random Distribution ◽  
Ph Dependence ◽  
Thiol Group ◽  
Nuclear Magnetic Resonance Study ◽  
Mercaptoacetic Acid ◽  
Exchange Reactions ◽  
H Nmr ◽  
Mixed Disulfide ◽  
Ph Range ◽  
Kinetics Of

The thiol/disulfide exchange reactions of penicillamine (PSH) with cystine and several related disulfides (RSSR) have been studied by 1H nmr. The reactions take place in two steps:[Formula: see text]The equilibria and kinetics of the reactions of PSH with cystine were characterized over the pH range 5–8, while the reactions with the disulfides of cysteamine, homocysteine, 2-mercaptoethanol, mercaptoacetic acid, 3-mercaptopropionic acid, and mercaptosuccinic acid were studied at neutral pH. From the pH dependence of the rate of the reaction of PSH with cystine, the reactive species are identified as penicillamine with its amino group protonated and its thiol group deprotonated and cystine and penicillamine–cysteine mixed disulfide with their amino groups protonated. For all the disulfides studied, the extent to which the first reaction occurs is within a factor of 2–3 of that predicted by a random distribution, while the extent to which the second reaction occurs is considerably less than for a random distribution. This is attributed to steric effects due to the two methyl groups next to the sulfur of penicillamine.

A 19F nuclear magnetic resonance study of the conjugate Brønsted–Lewis superacid HSO3F–SbF5. Part II.

2002 ◽  
Vol 80 (9) ◽  
pp. 1265-1277 ◽  
Author(s):  
Jobst Kühn-Velten ◽  
Matthias Bodenbinder ◽  
Raimund Bröchler ◽  
Gerhard Hägele ◽  
Friedhelm Aubke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Acid System ◽  
Exchange Reactions ◽  
Magnetic Resonance Study ◽  
Dilute Solutions ◽  
H Nmr ◽  
Anionic Species ◽  
High Concentrations ◽  
Initial Process

Solutions of SbF5 in HSO3F with xSbF5 = 0.012 to 0.405 are studied by 500 MHz 1H NMR (299 K) and 471 MHz 19F NMR (213–250 K), using NMR tubes fitted with fluoropolymer lining. The initial process during dissolution is the fast solvolysis of monomeric SbF5 in HSO3F according to SbF5 + nHSO3F [Formula: see text] SbF5 – n(SO3F)n + nHF (n = 1, 2). All HF formed during solvolysis will no longer be removed by reaction with glass, but will remain in the superacid system. Besides participation in the fast formation of various fluoro-fluorosulfato anions [SbF6 – n(SO3F)n]– (n = 0, 1, 2) and acidium ions [H2X]+(solv.) (X= F, SO3F), HF is involved in slow-exchange reactions of the type [SbF6 – n(SO3F)n]–(solv.) + HF [Formula: see text] [SbF7 – n(SO3F)n– 1]–(solv.) + HSO3F (n = 1, 2) detected because of a delay of 3 months between sample preparation and measurements and confirmed by repeating theses measurements after a further 3 months. There are three notable differences to our earlier study, affecting concentrations of the fluoro-fluorosulfato antimonate anions observed: (i) in dilute solutions [SbF6]– is formed in high concentrations (34.7–76.1%), with [Sb2F11]– now clearly detected at intermediate to high SbF5 concentrations (up to 5.8%); (ii) bis-fluorosulfato anions (cis-, trans-[SbF4(SO3F)2]–) are found in much lower concentrations only, which decrease further with time, while tris-fluorosulfato anions ([SbF3(SO3F)3]–) are now no longer observed; (iii) these reduced concentrations of poly-fluorosulfato anions in dilute solutions are responsible for the formation of fewer µ-SO3F-oligomers at lower concentrations, when more SbF5 is added. As a consequence, the HSO3F–SbF5 magic acid system is now less complex than found previously and only seven anionic species are clearly observed. Key words: superacids, antimony(V) fluoroanions, 1H NMR, 19F NMR, solvolysis.

Isotopic exchange reactions of amines. Part 1. An 2H nuclear magnetic resonance study of the amino to methyl group deuteron exchange in methylamine

1976 ◽  
Vol 54 (23) ◽  
pp. 3775-3782 ◽  
Author(s):  
James D. Halliday ◽  
Patrick E. Bindner
Keyword(s):  
Thermal Decomposition ◽  
Isotopic Exchange ◽  
Equilibrium Mixture ◽  
Nuclear Magnetic Resonance Study ◽  
Exchange Reactions ◽  
Amino Groups ◽  
Thermal Decomposition Product ◽  
First Order ◽  
H Nmr ◽  
Exchange Kinetics

Deuteron exchange kinetics between the methyl and amino groups in methylamine, catalyzed by potassium methylamide (PMA), have been studied by 2H nmr.[Formula: see text]Typical values of kobs, the observed pseudo first-order exchange rate, are 1.0 × 10−5 s−1 at 0.21 M PMA and 323 K. Effects of added potassium methylamide and temperature are described. The rate is unaffected by the thermal decomposition product of PMA and there is little or no catalysis by an equilibrium mixture of the solvated electron species e−, (e−K+), and K−. The active catalyst in solution is shown to be monomeric PMA in equilibrium with relatively inactive dimers, …, n-mers. A mechanism that describes the exchange and relates it to the thermal decomposition of the amide is discussed.

Anesthetic-membrane interaction: A 2H nuclear magnetic resonance study of the binding of specifically deuterated tetracaine and procaine to phosphatidylcholine

1984 ◽  
Vol 62 (2-3) ◽  
pp. 178-184 ◽  
Author(s):  
Eric C. Kelusky ◽  
Ian C. P. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Local Anesthetics ◽  
Nuclear Magnetic Resonance Study ◽  
Weakly Bound ◽  
Slow Exchange ◽  
H Nmr ◽  
Line Shapes ◽  
Acyl Chains ◽  
Nuclear Magnetic

The binding of the local anesthetics tetracaine and procaine with multilamellar dispersions of egg phosphatidylcholine has been studied by 2H nuclear magnetic resonance (NMR). The 2H-NMR line shapes of specifically deuterated local anesthetics are found to be very dependent on the attainment of a true equilibrium. The equilibrium could be most properly reached by the use of repeated freeze–thaw–vortex cycles. The data for tetracaine are consistent with the three-site exchange model proposed earlier. Tetracaine is in slow exchange between a strongly bound site and a weakly bound site and in fast exchange between the weakly bound site and free in solution. The slow exchange rate is estimated, from temperature and dilution studies, to be approximately 1.5 × 103 s−1 at pH 5.5 and slightly faster at pH 9.5. Comparisons of the quadrupole splittings with those seen for our earlier work in egg phosphatidylethanolamine suggest that the location of the strongly bound site in phosphatidylcholine is dependent on the anesthetic charge. This is in contrast to egg phosphatidylethanolamine, where molecular shapes appear to be the determining factor for the location of the anesthetic. Procaine bound very weakly to the model membranes, to yield only a broad resonance and no quadrupole splitting. It appears that procaine, unlike tetracaine, is not bound by the ordered acyl chains.

A 19F nuclear magnetic resonance study of the conjugate Brönsted-Lewis superacid HSO3F-SbF5. Part 1

1999 ◽  
Vol 77 (11) ◽  
pp. 1869-1886 ◽  
Author(s):  
Dingliang Zhang ◽  
Markus Heubes ◽  
Gerhard Hägele ◽  
Friedhelm Aubke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Formation Reaction ◽  
H Nmr ◽  
Acid Conjugate ◽  
Nmr Methods ◽  
Cis And Trans

The Brönsted-Lewis superacid HSO3F-SbF5 or "magic acid" is re-investigated by modern 19F NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6]-, [SbF5(SO3F)]-, cis- and trans-[SbF4(SO3F)2]-, and mer-[SbF3(SO3F)3]- gradually decreases. Except for [Sb2F11]-, which is present in very small concentrations only, the formation of oligomers involves exclusively μ-fluorosulfato bridges. In addition to donor (SO3F)- and acceptor (SbF5) complex formation to give [SbF5(SO3F)]- and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O]+, which has previously been identified by 1H NMR and structurally characterized as [H3O][Sb2F11] by us.Key words: magic acid, conjugate superacid, fluorosulfuric acid, 19F NMR spectra.

scholarly journals Hydrolysis of Methionine- and Histidine-Containing Peptides Promoted by Dinuclear Platinum(II) Complexes with Benzodiazines as Bridging Ligands: Influence of Ligand Structure on the Catalytic Ability of Platinum(II) Complexes

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Snežana Rajković ◽  
Beata Warżajtis ◽  
Marija D. Živković ◽  
Biljana Đ. Glišić ◽  
Urszula Rychlewska ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Amide Bond ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
Bridging Ligands ◽  
Metal Centers ◽  
H Nmr ◽  
Dinuclear Platinum ◽  
Ph Range ◽  
Hydrolysis Of

Dinuclear platinum(II) complexes, [{Pt(en)Cl}2(μ-qx)]Cl2·2H2O (1), [{Pt(en)Cl}2(μ-qz)](ClO4)2(2), and [{Pt(en)Cl}2(μ-phtz)]Cl2·4H2O (3), were synthesized and characterized by different spectroscopic techniques. The crystal structure of1was determined by single-crystal X-ray diffraction analysis, while the DFT M06-2X method was applied in order to optimize the structures of1–3. The chlorido Pt(II) complexes1–3were converted into the corresponding aqua species1a–3a, and their reactions with an equimolar amount of Ac–L–Met–Gly and Ac–L–His–Gly dipeptides were studied by1H NMR spectroscopy in the pH range 2.0 < pH < 2.5 at 37°C. It was found that, in all investigated reactions with the Ac–L–Met–Gly dipeptide, the cleavage of the Met–Gly amide bond had occurred, but complexes2aand3ashowed lower catalytic activity than1a. However, in the reactions with Ac–L–His–Gly dipeptide, the hydrolysis of the amide bond involving the carboxylic group of histidine was observed only with complex1a. The observed disparity in the catalytic activity of these complexes is thought to be due to different relative positioning of nitrogen atoms in the bridging qx, qz, and phtz ligands and consequent variation in the intramolecular separation of the two platinum(II) metal centers.

scholarly journals Mechanochemo-enzymatic Synthesis of Aromatic Aldehyde Oxime Esters

2018 ◽  
Vol 13 (7) ◽  
pp. 1934578X1801300
Author(s):  
Margarita A. Arthur-Santiago ◽  
Rosa María Oliart-Ros ◽  
María G. Sánchez-Otero ◽  
Gerardo Valerio-Alfaro
Keyword(s):  
Aromatic Aldehyde ◽  
Candida Rugosa ◽  
Hydroxylamine Hydrochloride ◽  
Aromatic Aldehydes ◽  
Second Step ◽  
Acyl Donor ◽  
Porcine Pancreas ◽  
H Nmr ◽  
Novozyme 435 ◽  
Porcine Pancreas Lipase

The synthesis of aromatic aldehyde oxime esters (considered fragrances, antifungal and antimicrobial compounds) was achieved by two reactions which combine the advantage of green chemistry and biocatalysis. In the first step, the mechanochemical oxime synthesis by means of grindstone milling of six solid aromatic aldehydes and hydroxylamine hydrochloride in the presence of FlorisilR, as the best support, yielded the aromatic aldehyde oximes 1–6 with high purity and good yields. In the second step the lipase catalyzed acetylation reaction at 40°C for three days of those oximes with vinyl and isopropenyl acetates as acyl donor substrates and ethyl acetate as the solvent, yielded the aromatic aldehyde oxime esters. With Candida antarctica lipase (Novozyme 435), the conversions of oximes 1–6 into their esters were ≥ 99% according to the 1H NMR results and it was the best biocatalyst compared with others such as Candida rugosa (CRL), porcine pancreas lipase and the recombinant lipase LipMatCCR11 from the thermophilic strain Geobacillus thermoleovorans CCR11 cloned and expressed in Escherichia coli BL21 (DE3), all of which showed lower yields.

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