Reactions of Trivalent Iodine Reagents with Classic Iridium and Rhodium Complexes

In this work, the reactions of iodine(iii) reagents (PhI(L)2: L = pyridine, acetate (OAc−), triflate (OTf−)) with iridium(i) and rhodium(i) complexes (Vaskas’s compound, Wilkinson’s catalyst, and bis[bis(diphenylphosphino)ethane]rhodium(i) triflate) are reported. In all cases, the reactions resulted in two-electron oxidation of the metal complexes. Mixtures of products were observed in the reactions of Iiii reagents with Vaska’s compound and Wilkinson’s catalyst via ligand exchange and anion scrambling. In the case of reacting Iiii reagents with chelating ligand-containing bis[bis(diphenylphosphino)ethane]rhodium(i) triflate, no scrambling was observed.

Vapour-liquid equilibria of pyridine + acetate mixtures at 101.325 kPa

Experimental vapour-liquid equilibrium data for the binary mixtures ethyl acetate + pyridine, n-propyl acetate + pyridine and n-butyl acetate + pyridine have been determined at 101.325 kPa. The Wilson, NRTL, LEMF, UNIQUAC and Effective UNIQUAC equations have been fitted to the data, which have also been used to establish UNIFAC parameters for interaction between CCOO and PYRIDINE groups.

Automated cation-exchange chromatography of peptides at a high sensitivity (0–0.1 absorbance range) (Short Communication)

A method is described where leaching of the column resin by pyridine–acetate buffers is minimal and excessive rise of the base-line of the chromatogram is avoided. The method can be used to fractionate peptide mixtures at a concentration of 2–20nmol/component.

An Improved Fractionation System for Pronase on CM-Sephadex

An efficient, single-column preparative-scale fractionation of pronase on CM-Sephadex using a linear gradient of pyridine-acetate, pH 5.0, has been developed. Under these conditions excellent resolution and minimal autolysis of the component proteolytic enzymes occurs. Only three major endopeptidases with caseinolytic activity are found. Streptomyces griseus trypsin (S.G.T.) is recovered in adequate purity for amino acid sequence studies. Streptomyces griseus Protease A and Protease B have been shown to correspond to PNPase I and II previously described by Wählby. Two aminopeptidases and a carboxypeptidase have also been demonstrated. Pronase appears to be a less complex mixture of proteolytic enzymes than had previously been appreciated.