The effect of viscosity, solvent polarity and pH of the medium on the reaction of a protein, bovi... more The effect of viscosity, solvent polarity and pH of the medium on the reaction of a protein, bovine serum albumin (BSA), with organohalo-peroxyl radical in aqueous solution has been studied using pulse radiolysis technique. Unlike in dilute aqueous solution, electron transfer from tyrosine to tryptophan radical in BSA has been clearly observed at a viscosity of 7.7 centiPoise (cP). The oxidation of BSA, tryptophan and tyrosine in different media has also been compared with those taking place in dilute aqueous solution. The effect of solvent characteristics on the observed charge transfer has been discussed.
Reactions of sulfasalazine (SAZ) and its metabolites, 5-aminosalicylic acid (5-ASA) and sulfapyri... more Reactions of sulfasalazine (SAZ) and its metabolites, 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), with various oxidizing and reducing free radicals (hydroxyl, haloperoxyl, one-electron oxidizing, lipid peroxyl, glutathiyl, superoxide, tryptophanyl, etc.) have been studied to understand the mechanistic aspects of its action against free radicals produced during inflammation. Nanosecond pulse radiolysis technique coupled with transient spectrophotometry has been used for in situ generation of free radicals and to follow their reaction pathways. The transients produced in these reactions have been assigned and radical scavenging rate constants have been measured. In addition to scavenging of various primary and secondary free radicals by SAZ, 5-ASA and SP, 5-ASA has also been observed to efficiently scavenge radicals of biomolecules. 5-ASA has been found to be the active moiety of SAZ involved in the scavenging of oxidizing free radicals whereas reduction of SAZ produced molecular radical anion. The study suggests that free radical scavenging activity of 5-ASA may be a major path of pharmacological action of SAZ against inflammatory bowel diseases (IBD).
Sesamol (from Sesamum indicum) is a dietary compound, which is soluble in aqueous as well as lipi... more Sesamol (from Sesamum indicum) is a dietary compound, which is soluble in aqueous as well as lipid phases. Free radical scavenging reactions of sesamol, 5-hydroxy-1,3-benzodioxole, have been studied using a nanosecond pulse radiolysis technique. Sesamol efficiently scavenges hydroxyl, one-electron oxidizing, organo-haloperoxyl, lipid peroxyl, and tryptophanyl radicals. Its antioxidant activity has also been evaluated with cyclic voltammetry. In biochemical studies, it has been found to inhibit lipid peroxidation, hydroxyl radical-induced deoxyribose degradation, and DNA cleavage. These antioxidant and free radical scavenging activities of sesamol have been reported in the paper.
Abstract--Reduction reactions of bovine serum albumin (BSA), lysozyme (Lz) and dimethyldisulfide ... more Abstract--Reduction reactions of bovine serum albumin (BSA), lysozyme (Lz) and dimethyldisulfide (DMDS) with hydrated electron in quaternary micro emulsion were studied using pulse radiolysis. The reduction of proteins in this organized assembly is found to be dependent ...
Redox reactions of pyridoxal (P-OH) with e¯aq, . OH, N. 3, SO. 4¯ and various organo-haloperoxyl ... more Redox reactions of pyridoxal (P-OH) with e¯aq, . OH, N. 3, SO. 4¯ and various organo-haloperoxyl radicals have been studied using pulse radiolysis technique. The rate constants for the reaction of P-OH or P-O¯ with the above-mentioned radicals and the transient absorption spectra have been measured. The transients formed in the reaction of hydrated electron and oxidizing radicals with pyridoxal have been assigned. An attempt has been made to find a correlation between the rate constants and Taft parameter for the reactions with the organo-haloperoxyl radicals. It has also been observed that the one-electron oxidized radical of pyridoxal is repaired by uric acid. The reduction potential for the P-OH.+/P-OH couple at pH 7, as measured by cyclic voltammetry, has been found to be +1.11 V vs. NHE.
Pulse radiolytic reduction of bovine serum albumin (BSA) and lysozyme by CO 2 radical in presence... more Pulse radiolytic reduction of bovine serum albumin (BSA) and lysozyme by CO 2 radical in presence of polyvinyl alcohol (PVA) has been studied. At pH 6.8 in presence of 2% (w/v) PVA, reduction of BSA and lysozyme (both at 1×10 −4 mol dm −3 ) give an additional transient peak at ...
The effect of viscosity, solvent polarity and pH of the medium on the reaction of a protein, bovi... more The effect of viscosity, solvent polarity and pH of the medium on the reaction of a protein, bovine serum albumin (BSA), with organohalo-peroxyl radical in aqueous solution has been studied using pulse radiolysis technique. Unlike in dilute aqueous solution, electron transfer from tyrosine to tryptophan radical in BSA has been clearly observed at a viscosity of 7.7 centiPoise (cP). The oxidation of BSA, tryptophan and tyrosine in different media has also been compared with those taking place in dilute aqueous solution. The effect of solvent characteristics on the observed charge transfer has been discussed.
Reactions of sulfasalazine (SAZ) and its metabolites, 5-aminosalicylic acid (5-ASA) and sulfapyri... more Reactions of sulfasalazine (SAZ) and its metabolites, 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), with various oxidizing and reducing free radicals (hydroxyl, haloperoxyl, one-electron oxidizing, lipid peroxyl, glutathiyl, superoxide, tryptophanyl, etc.) have been studied to understand the mechanistic aspects of its action against free radicals produced during inflammation. Nanosecond pulse radiolysis technique coupled with transient spectrophotometry has been used for in situ generation of free radicals and to follow their reaction pathways. The transients produced in these reactions have been assigned and radical scavenging rate constants have been measured. In addition to scavenging of various primary and secondary free radicals by SAZ, 5-ASA and SP, 5-ASA has also been observed to efficiently scavenge radicals of biomolecules. 5-ASA has been found to be the active moiety of SAZ involved in the scavenging of oxidizing free radicals whereas reduction of SAZ produced molecular radical anion. The study suggests that free radical scavenging activity of 5-ASA may be a major path of pharmacological action of SAZ against inflammatory bowel diseases (IBD).
Sesamol (from Sesamum indicum) is a dietary compound, which is soluble in aqueous as well as lipi... more Sesamol (from Sesamum indicum) is a dietary compound, which is soluble in aqueous as well as lipid phases. Free radical scavenging reactions of sesamol, 5-hydroxy-1,3-benzodioxole, have been studied using a nanosecond pulse radiolysis technique. Sesamol efficiently scavenges hydroxyl, one-electron oxidizing, organo-haloperoxyl, lipid peroxyl, and tryptophanyl radicals. Its antioxidant activity has also been evaluated with cyclic voltammetry. In biochemical studies, it has been found to inhibit lipid peroxidation, hydroxyl radical-induced deoxyribose degradation, and DNA cleavage. These antioxidant and free radical scavenging activities of sesamol have been reported in the paper.
Abstract--Reduction reactions of bovine serum albumin (BSA), lysozyme (Lz) and dimethyldisulfide ... more Abstract--Reduction reactions of bovine serum albumin (BSA), lysozyme (Lz) and dimethyldisulfide (DMDS) with hydrated electron in quaternary micro emulsion were studied using pulse radiolysis. The reduction of proteins in this organized assembly is found to be dependent ...
Redox reactions of pyridoxal (P-OH) with e¯aq, . OH, N. 3, SO. 4¯ and various organo-haloperoxyl ... more Redox reactions of pyridoxal (P-OH) with e¯aq, . OH, N. 3, SO. 4¯ and various organo-haloperoxyl radicals have been studied using pulse radiolysis technique. The rate constants for the reaction of P-OH or P-O¯ with the above-mentioned radicals and the transient absorption spectra have been measured. The transients formed in the reaction of hydrated electron and oxidizing radicals with pyridoxal have been assigned. An attempt has been made to find a correlation between the rate constants and Taft parameter for the reactions with the organo-haloperoxyl radicals. It has also been observed that the one-electron oxidized radical of pyridoxal is repaired by uric acid. The reduction potential for the P-OH.+/P-OH couple at pH 7, as measured by cyclic voltammetry, has been found to be +1.11 V vs. NHE.
Pulse radiolytic reduction of bovine serum albumin (BSA) and lysozyme by CO 2 radical in presence... more Pulse radiolytic reduction of bovine serum albumin (BSA) and lysozyme by CO 2 radical in presence of polyvinyl alcohol (PVA) has been studied. At pH 6.8 in presence of 2% (w/v) PVA, reduction of BSA and lysozyme (both at 1×10 −4 mol dm −3 ) give an additional transient peak at ...
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