An NMR study of the temperature dependence of the coefficient of water self-diffusion through lipid bilayer membranes

The temperature dependence of the coefficient of water self-diffusion through plane-parallel lipid multilayers of the phospholipid dioleoylphosphatidylcholine oriented on a glass support has been studied in the temperature range of 20-60 degrees C by the method of NMR with magnetic field pulse gradient. The values of the coefficients of transbilayer water diffusion are by four orders of magnitude less than for bulky water and ten times less than the coefficients of lateral diffusion of the lipid under the same conditions. The temperature dependence of the coefficient of water diffusion is described by the Arrhenius law with an apparent activation energy of about 41 kJ/mol, which far exceeds the activation energy for the diffusion of bulky water (18 kJ/mol). The experimental data were analyzed using a "dissolving-diffusion" model, by simulating the passage of water through membrane channels, and by analyzing the exchange of water molecules in states with different modes of translation mobility, including pore channels and bilayer "defects". Each of the approaches used made it possible to take the significance of bilayer permeability for the apparent energy of activation of water diffusion into account and estimate the energies of activation of water diffusion in the hydrophobic moiety of the bilayer, which were found to be close to the values for bulky water. The coefficients of water diffusion in the system under examination and the coefficients of permeation of water through the bilayer were estimated, and the effect of bilayer "defects" on the coefficients of water diffusion along and across bilayers was studied.     

Occurrence and genetic typing of infectious hematopoietic necrosis virus in Kamchatka, Russia

Infectious hematopoietic necrosis virus (IHNV) is a well known rhabdoviral pathogen of salmonid fish in North America that has become established in Asia and Europe. On the Pacific coast of Russia, IHNV was first detected in hatchery sockeye from the Kamchatka Peninsula in 2001. Results of virological examinations of over 10,000 wild and cultured salmonid fish from Kamchatka during 1996 to 2005 revealed IHNV in several sockeye salmon Oncorhynchus nerka populations. The virus was isolated from spawning adults and from juveniles undergoing epidemics in both hatchery and wild sockeye populations from the Bolshaya watershed. No virus was detected in 2 other watersheds, or in species other than sockeye salmon. Genetic typing of 8 virus isolates by sequence analysis of partial glycoprotein and nucleocapsid genes revealed that they were genetically homogeneous and fell within the U genogroup of IHNV. In phylogenetic analyses, the Russian IHNV sequences were indistinguishable from the sequences of North American U genogroup isolates that occur throughout Alaska, British Columbia, Washington, and Oregon. The high similarity, and in some cases identity, between Russian and North American IHNV isolates suggests virus transmission or exposure to a common viral reservoir in the North Pacific Ocean.     

11S storage globulin from pumpkin seeds: Regularities of proteolysis by papain

Limited proteolysis of the α- and β-chains and deep cleavage of the αβ-subunits by the cooperative (one-by-one) mechanism was observed in the course of papain hydrolysis of cucurbitin, an 11S storage globulin from seeds of the pumpkin Cucurbita maxima. An independent analysis of the kinetics of the limited and cooperative proteolyses revealed that the reaction occurs in two successive steps. In the first step, limited proteolysis consisting of detachments of short terminal pep-tides from the α- and β-chains was observed. The cooperative proteolysis, which occurs as a pseudo-first order reaction, started at the second step. Therefore, the limited proteolysis at the first step plays a regulatory role, impacting the rate of deep degradation of cucurbitin molecules by the cooperative mechanism. Structural alterations of cucurbitin induced by limited proteolysis are suggested to generate its susceptibility to cooperative proteolysis. These alterations are tentatively discussed on the basis of the tertiary structure of the cucurbitin subunit pdb|2EVX in comparison with previously obtained data on features of degradation of soybean 11S globulin hydrolyzed by papain.     

Improving the specificity of high-throughput ortholog prediction

Background  

Orthologs (genes that have diverged after a speciation event) tend to have similar function, and so their prediction has become an important component of comparative genomics and genome annotation. The gold standard phylogenetic analysis approach of comparing available organismal phylogeny to gene phylogeny is not easily automated for genome-wide analysis; therefore, ortholog prediction for large genome-scale datasets is typically performed using a reciprocal-best-BLAST-hits (RBH) approach. One problem with RBH is that it will incorrectly predict a paralog as an ortholog when incomplete genome sequences or gene loss is involved. In addition, there is an increasing interest in identifying orthologs most likely to have retained similar function.     

The effect of the infectious hematopoietic necrosis virus on the population of sockeye salmon <Emphasis Type="Italic">Oncorhynchus nerka</Emphasis> (Salmoniformes,Salmonidae) from Lake Nachikinskoe

The results of virological examination of adult sockeye salmon Oncorhynchus nerka in Lake Nachikinskoe from 2003 to 2008 demonstrated high values of prevalence of the infectious hematopoietic necrosis virus (IHNV) in the fish population (up to 100%). In the studied water reservoir there are optimal conditions for the development and revealing of the epizootic of infectious hematopoietic necrosis (IHN). In Lake Nachikinskoe, two natural epizootics of IHN in juvenile sockeye salmon were recorded in 2003 and 2006. The tendencies for change of prevalence of IHNV by years were analyzed, and their relation to the numbers of adult sockeye salmon at the spawning grounds of Lake Nachikinskoe was determined. The correlation of IHNV prevalence with the numbers of adult sockeye salmon in the studied water reservoir is direct but insignificant (r _s = 0.695, p < 0.05). It was shown that the epizootic of 2003 could affect the fact that fish return in 2007 and 2008 was minimum for the considered time interval while the numbers of their parents were, on the other hand, very high.     

Effect of surface-active agents (tween-21) on indices of energy metabolism in oleandomycin producers

The specific growth rate of Streptomyces antibioticus, a producer of oleandomycin, and the specific rate of the antibiotic accumulation in the culture medium during fermentation were investigated. On the basis of the results obtained the fermentation period was divided into 7 phases of development. The culture treated with the surfactant (Tween-21) is characterized by a higher specific growth rate during the whole fermentation and a higher specific rate of the antibiotic accumulation at the stage of the highest production as compared to the control. The ATP content, the value of the adenylate energy charge and the contents of high-molecular weight polyphosphates in the mycelium were examined. In the phase of the intensive growth St. antibioticus was characterized by a higher ATP level and a higher energy charge. More active accumulation of polyphosphates was observed in the late intensive growth phase. It was also found that after the treatment of the culture with Tween-21 it utilized polyphosphates more actively during the antibiotic biosynthesis.