Anorganisches

Ohne Zusammenfassung     

The mechanism of the reaction between hydroxyl ions and some internally hydrogen-bonded acids

The kinetics of the proton transfer between hydroxyl ions and phenylazoresorcinol, 4-(p-nitrophenylazo), and 4-(m-nitrophenylazo) resorcinol have been investigated at 25°C and an ionic strength of 0.1M, in a wider pH range than had been done by previous authors. The rate at first decreased with decreasing [OH^?], reached a minimum, and then started to increase with decreasing [OH^?]. This unusual effect is explained by a mechanism suggested earlier for tropaeolin O. Rate constants and equilibrium constants have been evaluated and discussed. The experimental data were obtained by the T-jump method.     

The synthesis of sulfurous diamide heterocycles through the cycloaddition reaction of n-sulfinylanilines with benzalanilines

The cycloaddition reaction of N-sulfinylanilines - serving as “dienes” — with aromatic Schiff bases provides a convenient access to the thiadiazine oxide system ($\text{3}$)     

The G553M Mutant of Peroxisomal Carnitine Octanoyltransferase Catalyses Acetyl Transfer and Acetyl-CoA Hydrolysis

Summary. The structure of carnitine acetyltransferase revealed a putative binding site for longer acyl chains but access was blocked by methionine 564 (G. Jogl and L. Tong (2003) Cell 112, 113–122). The equivalent residue in all long chain carnitine acyltransferases is a conserved glycine. Mutation of glycine 553 to methionine in bovine COT resulted in loss of activity with all acyl-CoA substrates except acetyl-CoA, supporting the hypothesis that the methionine blocks access for longer acyl chains. The kinetic characteristics of acetyl transfer to carnitine were identical in the native and mutant enzyme. However, rapid acetyl-CoA hydrolysis in the mutant but not the wild-type indicates perturbation of the catalytic site.     

Black and white – does melanin change the bulk carbon and nitrogen isotope values of feathers?

Bird feathers are employed in a wide range of carbon and nitrogen isotope studies relating to diet and migration. Feathers are chemically inert with respect to carbon and nitrogen, after synthesis. It has always been assumed that feathers show isotope values characteristic of keratin, a fibrous structural protein from which they are formed. Little attention has been paid to other components of feathers such as melanin or carotenoids. Melanin is synthesized from tyrosine, which is depleted in both ¹³C and ¹⁵N. We compared isotope values of coeval black and white feathers in four different species. Black feather parts were in all cases significantly depleted in ¹³C relative to white feather parts but in most species no clear trend was discernable for ¹⁵N. We suggest that additional evaluation may be required to characterize the carbon and nitrogen isotope contribution of feather pigments like carotenoids. Care should be taken in future stable isotope studies when comparing differently coloured feathers. Copyright © 2010 John Wiley & Sons, Ltd.