o-iodoxybenzoic-acid and 2-iodosobenzoic-acid

The gas phase anion proton affinities of the periodinane anions IBX- and IBA- were examined using mass spectrometry-based experiments, and estimated as 1300 +/- 25 and 1390 +/- 10 kJ mol(-1), respectively. The experimental results were supported by theoretical calculations, which yielded proton affinities of 1336 and 1392 kJ mol(-1) for IBX- and IBA- respectively, at the B3LYP/aug-cc-PVDZ level of theory.

Topics: Anions; Gases; Iodobenzenes; Iodobenzoates; Kinetics; Mass Spectrometry; Protons

o-Iodoxybenzoic acid, a disproportionation product of o-iodosobenzoic acid, has been identified as a contaminant in most preparations of o-iodosobenzoic acid capable of both modifying and cleaving certain tyrosyl residues. A new synthetic approach for the production of o-iodosobenzoic acid containing low amounts of o-iodoxybenzoic acid combined with preincubation of the reagent with p-cresol to destroy the remaining o-iodoxybenzoic acid prior to the reaction with a polypeptide allows preparation of reagent solutions in which tyrosyl residues remain intact during tryptophanyl bond cleavage. In addition, the product produced by the action of o-iodosobenzoic acid upon tryptophanyl bonds has been identified as N-acyldioxindolylalanine. It is inferred from that structure that the chemical reaction proceeds via a two-step oxidation of the tryptophanyl residue followed by formation of an iminospirolactone which hydrolyzes, cleaving the peptide chain. Small peptides ending with dioxindolylalanine can be coupled to aminopropyl glass in high yield and are suitable for solid-phase Edman degradation.

Topics: Amino Acids; Animals; Cattle; Chemical Phenomena; Chemistry; Chromatography, High Pressure Liquid; Iodobenzenes; Iodobenzoates; Kinetics; Myoglobin; Peptide Fragments; Proteins; Trypsinogen; Tyrosine; Whales