Magnetic interaction of manganese with pheophytin anion-radical and chlorophyll cation-radical in reaction centers of the photosystem II

The influence of Mn on saturation curves of ESR spectra of Ph(-) and P(+)(680) at 1-200K in samples with different content of Mn has been studied. An analysis of these data and those on photoinduced changes of fluorescence yield of chlorophyll leads to the conclusion that the Mn-containing centre in Photosystem 2 is a cluster of 4 Mn atoms, two of which can be replaced by Mg(2+) or any other divalent metal. The distances between Mn Na Ph as well as between Mn and P(680) have been estimated.     

Big flies, small repeats: the "Thr-Gly" region of the period gene in Diptera

The region of the clock gene period (per) that encodes a repetitive tract of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran species both within and outside the Drosophilidae. All the non- Drosophilidae sequences in this region are short and present a remarkably stable picture compared to the Drosophilidae, in which the region is much larger and extremely variable, both in size and composition. The accelerated evolution in the repetitive region of the Drosophilidae appears to be mainly due to an expansion of two ancestral repeats, one encoding a Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and asparagine or threonine. In some drosophilids the expansion involves a duplication of the pentapeptide sequence, but in Drosophila pseudoobscura both the dipeptide and the pentapeptide repeats are present in larger numbers. In the nondrosophilids, however, the pentapeptide sequence is represented by one copy and the dipeptide by two copies. These observations fulfill some of the predictions of recent theoretical models that have simulated the evolution of repetitive sequences.      

Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene

We have analyzed the conserved regions of the gene coding for the circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria parasite. The closest evolutionary relative of P. falciparum, the agent of malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is consistent with the hypothesis that P. falciparum is an ancient human parasite, associated with humans since the divergence of the hominids from their closest hominoid relatives. Three other human Plasmodium species are each genetically indistinguishable from species parasitic to nonhuman primates; that is, for the DNA sequences included in our analysis, the differences between species are not greater than the differences between strains of the human species. The human P. malariae is indistinguishable from P. brasilianum, and P. vivax is indistinguishable from P. simium; P. brasilianum and P. simium are parasitic to New World monkeys. The human P. vivax-like is indistinguishable from P. simiovale, a parasite of Old World macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are evolutionarily recent human parasites, the first two at least acquired only within the last several thousand years, and perhaps within the last few hundred years, after the expansion of human populations in South America following the European colonizations. We estimate the rate of evolution of the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year. The divergence between the P. falciparum and P. reichenowi lineages is accordingly dated 8.9 Myr ago. The divergence between the three lineages leading to the human parasites is very ancient, about 100 Myr old between P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between P. falciparum and the other two.      

Excitation of System I and System II in Photosynthesis as a Possible Control Mechanism of Glycolate Metabolism in the Blue-Green Alga Anacystis nidulans

Photosynthetic enhancement studies performed at 619 nm (excitation of Systems I and II) and at 446 nm (mainly excitation of System I) revealed an 18% photosynthetic enhancement simultaneously with a 31% reduction in glycolate excretion. This observation supports the hypothesis that some glycolate may be consumed in an oxidation process associated with System I when System II is poorly excited and the supply of electrons from the water splitting process of photosynthesis is low.     

Preparation of androsta-1,4-diene-3,17-dione from sterols using Mycobacterium neoaurum VKPM As-1656 strain

A product of microbiological cleavage of the sterols side chain, androsta-1,4-diene-3,17-dione, is toxic for bacteria, in particular, actinobacteria of the genera Mycobacterium and Arthrobacter. Sterols were transformed into androsta-1,4-diene-3,17-dione by culturing the M. neoaurum VKPM An-1656 strain in a high yield, provided that a sorbent was used for elimination of contact between the bacterial cells and the product. Unlike the cholesterol side chain, the more branched chains of phytosterols were cleaved in the presence of M. neoaurum at a high rate only under turbulent stirring of the culture medium, which intensified the formation of hydrocarbonate ion from NaNI3 in situ.     

Repolarization of canine ventricular myocardium under the supraventricular rhythm

The ventricular myocardium is characterized by heterogeneity of activation-recovery interval durations. The transmural ARI gradients are present in the right ventricular apex (ARIs monotonically decreased as one moved from the endocardium to the epicardium), and in the left ventricular base (repolarization in the subepicardial layers was significantly shorter than that in the midmyo cardial layers whereas subendocardial ARIs did not differ from the others). The repolarization pattern of these myocardial regions is governed by the distribution of ARIs. In the apical left ventricular and basal right ventricular areas, no significant transmural differences in the repolarization durations were found. The repolarization pattern of these myocardial regions is governed by the activation sequence. In the right ventricle, ARIs were significantly longer at the base and shorter at the apex. In contrast, in the left ventricle, the apical ARIs were prolonged whereas the basal ARIs were abbreviated. The apex-to-base sequence of myocardial repolarization seems to depend on apex-to-base gradient of activation-recovery intervals durations.     

Protein splicing

Inteins are internal polypeptide sequences that are posttranslationally excised from a protein precursor by a self-catalyzed protein-splicing reaction. Most of inteins consist of N- and C-terminal protein splicing domain and central endonuclease domain. The endonuclease domain can initiate mobility of the intein gene, this process being named intein homing. This review is focused on the recent data about the structure and function of inteins. Main intein-mediated protein-engineering applications, such as protein purification, ligation and cyclization, new forms of biosensors, are presented.     

Identification of Ca(2+)-activated Mg(2+)-dependent ATP-hydrolase activity of membrane microsomal fraction of loach embryo (Misgurnus fossilis L.)

The functional confirmation of availability of Ca2+ transport initially-active systems in the embryo cells of loach Misgurnus fossilis L. has been obtained. Using thapsigargin, the specific inhibitor of endoplasmic reticulum of Ca2+, Mg(2+)-ATPase, this enzyme activity was divided into thapsigargin-sensitive (actually endoplasmic reticulum Ca2+, Mg(2+)-ATPase) and thapsigargin-insensitive (plasma membrane Ca2+, Mg(2+)-ATPase) constituents. The Ca(2+)-independent Mg(2+)-dependent ATPase activity makes above 39.7% of the common Ca2+, Mg(2+)-ATPase activity of embryo loach. The periodic changes of Ca2+, Mg(2+)-ATPase activity (except for the changes of plasma membrane Ca2+, Mg(2+)-ATPase activity) were found out, which coincide with periodic [Ca2+]i oscillations during the synchronous divisions of loach blastomers embryos.     

Profiles of the utilization of 20 amino acids as the only source of nitrogen and carbon in bacteria of the genera Klebsiella, Enterobacter, Serratia, Escherichia

The profiles of the utilization of 20 protein amino acids in 118 Klebsiella pneumoniae sub- sp. pneumoniae, K. oxytoca, K. planticola, K. mobilis, Enterobacter cloacae, Serratia marscescens, S. liquefaciens, Escherichia coli strains isolated from clinical material were studied. The utilization of amino acids was determined on minimal saline agar containing amino acid as the only source of nitrogen and carbon; the results were evaluated after 72-hour incubation at 37 degrees C. 17 profiles of amino-acid utilization were thus determined, most of them genus-specific in enterobacteria: Klebsiella (profiles No. 1--6, 9, 10), Enterobacter (No. 11--13), Serratia (No. 14--16), Escherichia (No. 17). The full coincidence of amino-acid utilization profiles in bacteria of K. mobilis (No. 1, 6) and K. pneumoniae subsp. pneumoniae with out of such profiles in bacteria of the genera Enterobacter, Serratia, Escherichia was established, which confirmed that K. mobilis (formerly Enterobacter aerogenes) belonged to the genus Klebsiella.     

Activity of the climbing fiber innervating various Purkinje cells

Low-amplitude potentials (10-130 microV) related to the action of a distant branch of the climbing fiber, which elicits complex spikes of the reference Purkinje cell were revealed by means of potential averaging synchronously with complex spikes of Purkinje cells in 10 out of 255 paired records of cerebellar Purkinje cells activity and extracellular field potentials at interelectrode distances of 200-1500 microns. These potential waves had a stable form in independent sets of data. In 3 out of 10 cases, the low-amplitude potentials included a slow (about 100 ms in duration) component. In one case, both test and reference electrodes recorded both simple and complex spikes of different Purkinje cells so that complex spikes of both cells were practically synchronous (conditional probability of complex spikes p = 0.97, onset time difference 0.54 ms). Thus for the first time in cerebellar physiology both simple and complex spikes activity of two Purkinje cells controlled by the same climbing fiber was recorded.