38504-14-2Relevant academic research and scientific papers
Comparison of Proton- and Electron-Transfer Equilibria and Rates for Tetraalkylhydrazines
Nelsen, Stephen F.,Kinlen, Patrick J.,Evans, Dennis H.
, p. 7045 - 7050 (1981)
Relative electron-transfer equilibria for 17 tetralkylhydrazines (R4N2) were determined by measurement of their standard potentials for oxidation (E') and rates of electron loss by measurement of their standard heterogeneous electron-transfer rate constants (ks) determined from their cyclic voltammograms.These data are compared with equilibrium and rate constant measurements for proton transfer between R4N2 and salicylic acid.All measurements were in dimethyl sulfoxide containing 0.1 M tetraethylammonium perchlorate.Similar trends are found for electron and proton transfer; the most basic R4N2 examples are the most easily oxidized and the fastest both to protonate and lose an electron.The proton transfers run under these conditions show anomalous Broensted behavior; the rate of protonation of R4N2 is about twice as sensitive to change of the R groups as is the equilibrium constant, and the rate of deprotonation consequently becomes slower as the reaction becomes more exothermic.A Broensted-like plot for electron transfers was constructed by estimating the electron-transfer rate constants for all R4N2 as the same potential (called k0); electron transfer also gives anomalous Broensted behavior for R4N2.The electron-transfer rate has been previously shown to be far faster in anti lone pair conformations than in gauche ones, so that electron transfer from acrylic R4N2 involves a prior conformational equilibrium to the unstable but rapidly oxidized anti form.It is suggested that a similar gauche to anti conformational change precedes proton transfer under our conditions, and is a major contributing factor to the anomalous Broensted behavior of R4N2.
Entropic and enthalpic components of catalysis in the mutase and lyase activities of pseudomonas aeruginosa PchB
Luo, Qianyi,Meneely, Kathleen M.,Lamb, Audrey L.
, p. 7229 - 7233 (2011)
The isochorismate-pyruvate lyase from Pseudomonas aeruginosa (PchB) catalyzes two pericyclic reactions, demonstrating the eponymous activity and also chorismate mutase activity. The thermodynamic parameters for these enzyme-catalyzed activities, as well a
Effects of organic salts on the rate of intramolecular general base-catalyzed piperidinolysis of ionized phenyl salicylate in the presence of cationic micelles
Khan,Kun
, p. 1325 - 1330 (2001)
Pseudo-first-order rate constants (kobs), obtained for the cleavage of ionized phenyl salicylate (PS-) at constant [NaOH], [MeCN], [CTABr]T (total concentration of cetyltrimethylammonium bromide), [Pip]T (total
Binding of sodium salicylate by β-cyclodextrin or 2,6-di-o-methyl-β- cyclodextrin in aqueous solution
Junquera, Elena,Pena, Lourdes,Aicart, Emilio
, p. 86 - 90 (1998)
Speed of sound and conductivity experiments have been done at 298.15 K to study the encapsulation process of sodium salicylate (NASA) by β- cyclodextrin (β-CD) and 2,6-di-O-methyl-β-cyclodextrin (DIMEB) in aqueous solutions. Since the concentration of the salicyclic form (HSA), coming from the hydrolysis of SA-, is negligible at biological pH, the binding process studied in this work is that of the SA- species. The stoichiometries of the complexes DIMEB: SA- and β-CD:SA- have been found to be 1:1, as usually determined for most CD:drug complexes. Their association constants and their ionic molar conductivities at infinite dilution have been obtained by fitting the experimental conductivity data with a nonlinear regression method (NLR). For that purpose, a model based on that of Gelb and co-workers has been used. From the values of K(β-CD:SA-) = (105 ± 15) M-1 and K(DIMEB:SA-) = (140 ± 20) M-1 obtained, the bioavailability of the salicylate drug in the complexed form has been discussed.
PH dependence of catalysis by pseudomonas aeruginosa isochorismate - Pyruvate lyase: Implications for transition state stabilization and the role of lysine 42
Olucha, Jose,Ouellette, Andrew N.,Luo, Qianyi,Lamb, Audrey L.
, p. 7198 - 7207 (2011)
An isochorismate - pyruvate lyase with adventitious chorismate mutase activity from Pseudomonas aerugionsa (PchB) achieves catalysis of both pericyclic reactions in part by the stabilization of reactive conformations and in part by electrostatic transitio
Isochorismate pyruvate lyase: A pericyclic reaction mechanism?
DeClue, Michael S.,Baldridge, Kim K.,Kuenzler, Dominik E.,Kast, Peter,Hilvert, Donald
, p. 15002 - 15003 (2005)
Isochorismate pyruvate lyase (IPL) catalyzes the cleavage of isochorismate to give salicylate and pyruvate, a key step in bacterial siderophore biosynthesis. We investigated the enzyme from Pseudomonas aeruginosa using isochorismate selectively deuterated
Excited-state proton-coupled electron transfer within ion pairs
Hammarstr?m, Leif,Meyer, Gerald J.,Swords, Wesley B.
, p. 3460 - 3473 (2020/04/17)
The use of light to drive proton-coupled electron transfer (PCET) reactions has received growing interest, with recent focus on the direct use of excited states in PCET reactions (ES-PCET). Electrostatic ion pairs provide a scaffold to reduce reaction orders and have facilitated many discoveries in electron-transfer chemistry. Their use, however, has not translated to PCET. Herein, we show that ion pairs, formed solely through electrostatic interactions, provide a general, facile means to study an ES-PCET mechanism. These ion pairs formed readily between salicylate anions and tetracationic ruthenium complexes in acetonitrile solution. Upon light excitation, quenching of the ruthenium excited state occurred through ES-PCET oxidation of salicylate within the ion pair. Transient absorption spectroscopy identified the reduced ruthenium complex and oxidized salicylate radical as the primary photoproducts of this reaction. The reduced reaction order due to ion pairing allowed the first-order PCET rate constants to be directly measured through nanosecond photoluminescence spectroscopy. These PCET rate constants saturated at larger driving forces consistent with approaching the Marcus barrierless region. Surprisingly, a proton-transfer tautomer of salicylate, with the proton localized on the carboxylate functional group, was present in acetonitrile. A pre-equilibrium model based on this tautomerization provided non-adiabatic electron-transfer rate constants that were well described by Marcus theory. Electrostatic ion pairs were critical to our ability to investigate this PCET mechanism without the need to covalently link the donor and acceptor or introduce specific hydrogen bonding sites that could compete in alternate PCET pathways.
The thermal charge-transfer reduction of uranyl UO22+(VI) to UO2+(V) by various functionalized organic compounds, and evidence for possible spin-spin interactions between UO2+(V) and hydroxymethyl ([rad]CH2OH) radical and between UO2+(V) and diphenyl sulfide radical cation (Ph2S[rad]+)
Sun, Xiaoping,Kolling, Derrick R.J.,Deskins, Seth,Adkins, Ethan
, p. 12 - 20 (2018/08/09)
The linear uranyl UO22+(VI) cation (D∞h symmetry) exhibited strong and broad absorptions at 350–400 nm in anhydrous methanol and methanol-water mixtures in the UV-Vis spectra. The intensity of the absorptions (represented by absorbance at 375 nm) is directly proportional to molar concentrations of methanol and UO22+(VI), respectively. The linear relationships indicate formation of an electron-donor-acceptor (EDA) complex [UO22+, CH3OH]. The absorptions at 350–400 nm originate from the charge-transfer (single-electron transfer) from CH3OH (electron donor) to UO22+ (electron acceptor) within the [UO22+, CH3OH] complex. Electron paramagnetic resonance (EPR) studies of various mixtures of UO22+-CH3OH and UO22+-CH3OH-H2O have shown that the charge-transfer also took place slowly in the dark, resulting in thermal reduction of UO22+(VI) to UO2+(V) (singlet, g = 2.08) by CH3OH, and CH3OH was oxidized to the hydroxymethyl [rad]CH2OH radical (generating an axial signal). The charge-transfer oxidation-reduction reaction is believed to take place via the EDA [UO22+, CH3OH] complex. EPR studies suggested spin-spin coupling between UO2+(V) and [rad]CH2OH in anhydrous methanol, supporting the formation of a [UO2+, [rad]CH2OH] ion-radical pair. The EPR studies have also shown that UO22+(VI) was reduced to UO2+(V) thermally by other alcohols (ethanol, 2-propanol, and cyclohexanol), and by diphenyl sulfide (Ph2S), L-ascorbic acid (AA), and 2-methyl-5-(propan-2-yl)phenol (carvacrol, ArOH), respectively. Ph2S, AA, and ArOH were oxidized to the diphenyl sulfide Ph2S+[rad] radical cation (singlet, g = 2.00), ascorbic acid AA[rad] radical (singlet, g = 2.00), and carvacrol ArO[rad] radical (singlet, g = 1.98), respectively. Both EPR and UV-Vis studies indicate that the reactions followed the ground-state charge-transfer mechanisms similar to that of the UO22+/methanol reaction. EPR evidence supported formation of the [UO2+, Ph2S+[rad]] ion-radical pair in the charge-transfer reaction of UO22+ and Ph2S and spin-spin interactions within the ion-radical pair. The sulfuric-acid-catalyzed isomerization of [rad]CH2OH to CH3O[rad] was found by EPR studies.
Conversion of Anthranilate Synthase into Isochorismate Synthase: Implications for the Evolution of Chorismate-Utilizing Enzymes
Plach, Maximilian G.,L?ffler, Patrick,Merkl, Rainer,Sterner, Reinhard
supporting information, p. 11270 - 11274 (2016/07/06)
Chorismate-utilizing enzymes play a vital role in the biosynthesis of metabolites in plants as well as free-living and infectious microorganisms. Among these enzymes are the homologous primary metabolic anthranilate synthase (AS) and secondary metabolic i
Synthesis and chemical and biological comparison of nitroxyl- and nitric oxide-releasing diazeniumdiolate-based aspirin derivatives
Basudhar, Debashree,Bharadwaj, Gaurav,Cheng, Robert Y.,Jain, Sarthak,Shi, Sa,Heinecke, Julie L.,Holland, Ryan J.,Ridnour, Lisa A.,Caceres, Viviane M.,Spadari-Bratfisch, Regina C.,Paolocci, Nazareno,Velázquez-Martínez, Carlos A.,Wink, David A.,Miranda, Katrina M.
supporting information, p. 7804 - 7820 (2013/11/06)
Structural modifications of nonsteroidal anti-inflammatory drugs (NSAIDs) have successfully reduced the side effect of gastrointestinal ulceration without affecting anti-inflammatory activity, but they may increase the risk of myocardial infarction with chronic use. The fact that nitroxyl (HNO) reduces platelet aggregation, preconditions against myocardial infarction, and enhances contractility led us to synthesize a diazeniumdiolate-based HNO-releasing aspirin and to compare it to an NO-releasing analogue. Here, the decomposition mechanisms are described for these compounds. In addition to protection against stomach ulceration, these prodrugs exhibited significantly enhanced cytotoxcity compared to either aspirin or the parent diazeniumdiolate toward nonsmall cell lung carcinoma cells (A549), but they were not appreciably toxic toward endothelial cells (HUVECs). The HNO-NSAID prodrug inhibited cylcooxgenase-2 and glyceraldehyde 3-phosphate dehydrogenase activity and triggered significant sarcomere shortening on murine ventricular myocytes compared to control. Together, these anti-inflammatory, antineoplasic, and contractile properties suggest the potential of HNO-NSAIDs in the treatment of inflammation, cancer, or heart failure.
