Acta biochimica et biophysica; Academiae Scientiarum Hungaricae最新文献

The absorption characteristics of bacteriorhodopsin chromophore cannot be understand on the basis of a simple protonated Schiff-base linkage. A possible hypothetical explanation may be an interaction of the aromatic amino acid residues also with retinal. Mixtures of retinal and tryptophan analogues were reacted in organic solvents. Many similarities were found in the absorption spectra of the different products of these reactions and in those of the main forms of bacteriorhodopsin photocycle. Such products are suggested to model the purple complex of bacteriorhodopsin as well as the chromophores of the photointermediates.

Aminoacylase (E.C. 3.5.1.14) was isolated from the kidneys of different mammalian species (horse, cattle, rabbit and pig) by extracting the organ with water and subjecting the extract to heat treatment at 70 degrees C for 10 min, then, after having removed denatured proteins by fractionating those remaining in the solution by ammonium sulfate. The enzyme obtained in this way can either be used directly for practical purposes (e.g. preparation of immobilized aminoacylase) or further purified by chromatography. For the further purification of porcine kidney aminoacylase we applied a combination of ion exchange chromatography and gel filtration.

Experiments were performed to decide between the alternatives a) the ionized K+ is in a dissolved state in the muscle water, or b) a part of the muscle potassium is in a "bound' state. Sartorius muscles of Rana esculenta were put into glicerol for about one hour at 0-2 degrees C. Most of muscle water came out, but most of muscle potassium remained in the muscles. In contrast to this: from muscle in heat rigor more potassium was released due to glicerol treating than from the intact ones. 1. Supposition a) is experimentally refuted. 2. Supposition b) corresponds to the experimental results.

65Zn2+ was given to rats per os and intraperitoneally for in vivo labelling of Zn2+-metalloproteins of cytosol. At the chromatographic analysis of the cytosol, two 65Zn2+-containing protein peaks were found in per os, while an additional low molecular weight third peak appeared in the intraperitoneal dosing samples. The chromatographic fractions were further separated by a non-denaturing gradient polyacrylamide electrophoresis technique. At the electrophoretic analysis of the chromatographic fractions the recovery of 65Zn2+ was the highest in samples taken from a second chromatographic peak (88%), which indicates the presence of proteins with exceptionally strong Zn2+-binding character in the 30-40 000 molecular weight fraction of the cytosol.

Polynucleotide kinase was purified from crude extracts of rat liver nuclei by affinity chromatography on DNA agarose. At optimal pH (5.5) and at saturating concentrations of ATP and DNA, the purified enzyme was found to express maximal activity in the presence of 0.10-0.15 M NaCl; higher salt concentrations inhibited the activity. At the optimal pH and NaCl concentration, the apparent KM for 5'-OH-DNA at 100 microM ATP was 46.2 microM and the apparent KM for ATP at 1 mM 5'-OH-DNA was 15.8 microM. Polynucleotide kinase was protected against heat inactivation by ATP as well as by 5'-OH-DNA at low and moderately high NaCl concentrations, which suggests that under these conditions the enzyme reacts according to a random reaction mechanism. Studies on the heat inactivation of the enzyme in the presence of 5'-OH- or 5'-P-DNA revealed the protection occurs only if 5'-OH-DNA is present, at NaCl concentrations permitting the enzyme to bind DNA.

Acetylcholine in concentrations of 10-5, 2 x 10-5, 5 x 10-5 and 10-4 in normal Ringer's solution causes contracture of different muscles of Rana esculenta. The similar effect brought about by KCl solution does not necessarily mean the same basic process leading to similar changes in muscle mechanics. Experiments made on many particular questions of muscle mechanics will possibly clarify the real role of single factors (e.g. transmitters, kations, anions, acids, alkalis. ATP, heat etc.) changing the mechanical state of muscular organs.