Interaction of membrane skeletal proteins with membrane lipid domain

The object of this paper is to review briefly the studies on the interaction of red blood cell membrane skeletal proteins and their non-erythroid analogues with lipids in model systems as well as in natural membranes. An important question to be addressed is the physiological significance and possible regulatory molecular mechanisms in which these interactions are engaged.     

Host-Guest Chemistry and Chemical Sensors: FT-IR-Analysis and Spectra Simulation of CDCl<Subscript>3</Subscript> Inclusion

Host-guest principles are put into action advantageously by cyclodextrins that give remarkable sensor responses to halogenated hydrocarbons on mass-sensitive devices such as QMB (quartz micro balance) and SAW (surface acoustic wave) resonators. Modifications of the structure can tune the compound to different analytes and molecular modeling allows us to understand and predict specific host-guest interactions. The FT-IR analysis of CDCl₃, incorporated into a partially methylated cyclodextrine, yields an astonishingly strong band shift of about 50 cm^-1 to lower wave numbers, in contrast to the permethylated product that shows a displaced band of 10 cm^-1 for the C-D stretching vibration. The explanation can be given by semiempirical methods and force field calculations. Two CDCl₃ binding sites are revealed, one being a multicentered inclusion ([(n)\tilde] ~ 2195  cm^-1{\tilde\nu}\sim 2195\;cm^{-1} of CDCl₃ at the upper rim of the #-cyclodextrine cone, whereas the other is incorporated within the cavity ([(n)\tilde] ~ 2240  cm^-1{\tilde\nu}\sim 2240\;cm^{-1}.     

Development of a transient large strain contact method for biological heart valve simulations

A new 2D method to implement transient contact using Comsol Multiphysics (finite element analysis software that enables multiphysics simulations) is described, which is based on Hertzian contact. This method is compared to the existing (default) contact method that does not enable real transient simulations, but instead performs steady-state solutions where time is a constant. The two types of contact modelling have been applied to simple 2D biological heart valve models, undergoing strains in the region of 10% under 20 kPa pressure (applied over 0.3 s). Both the methods predicted comparable stress patterns, locations of peak stresses, deformations and directions of principal stress. The default contact method predicted slightly greater contact stresses, but spreads over a shorter surface length than the new contact method. The default contact method is useful for contact systems with little transient dependency, due to ease of use. However, where transient conditions are important the new contact method is preferred.     

Complete genome sequence of the thermophilic sulfur-reducer Desulfurobacterium thermolithotrophum type strain (BSA(T)) from a deep-sea hydrothermal vent

Desulfurobacterium thermolithotrophum L'Haridon et al. 1998 is the type species of the genus Desulfurobacterium which belongs to the family Desulfurobacteriaceae. The species is of interest because it represents the first thermophilic bacterium that can act as a primary producer in the temperature range of 45-75 °C (optimum 70°C) and is incapable of growing under microaerophilic conditions. Strain BSA(T) preferentially synthesizes high-melting-point fatty acids (C(18) and C(20)) which is hypothesized to be a strategy to ensure the functionality of the membrane at high growth temperatures. This is the second completed genome sequence of a member of the family Desulfurobacteriaceae and the first sequence from the genus Desulfurobacterium. The 1,541,968 bp long genome harbors 1,543 protein-coding and 51 RNA genes and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Complete genome sequence of Tsukamurella paurometabola type strain (no. 33)

Tsukamurella paurometabola corrig. (Steinhaus 1941) Collins et al. 1988 is the type species of the genus Tsukamurella, which is the type genus to the family Tsukamurellaceae. The species is not only of interest because of its isolated phylogenetic location, but also because it is a human opportunistic pathogen with some strains of the species reported to cause lung infection, lethal meningitis, and necrotizing tenosynovitis. This is the first completed genome sequence of a member of the genus Tsukamurella and the first genome sequence of a member of the family Tsukamurellaceae. The 4,479,724 bp long genome contains a 99,806 bp long plasmid and a total of 4,335 protein-coding and 56 RNA genes, and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Key amino acid residues of ankyrin-sensitive phosphatidylethanolamine/phosphatidylcholine-lipid binding site of βI-spectrin

It was shown previously that an ankyrin-sensitive, phosphatidylethanolamine/phosphatidylcholine (PE/PC) binding site maps to the N-terminal part of the ankyrin-binding domain of β-spectrin (ankBDn). Here we have identified the amino acid residues within this domain which are responsible for recognizing monolayers and bilayers composed of PE/PC mixtures. In vitro binding studies revealed that a quadruple mutant with substituted hydrophobic residues W1771, L1775, M1778 and W1779 not only failed to effectively bind PE/PC, but its residual PE/PC-binding activity was insensitive to inhibition with ankyrin. Structure prediction and analysis, supported by in vitro experiments, suggests that "opening" of the coiled-coil structure underlies the mechanism of this interaction. Experiments on red blood cells and HeLa cells supported the conclusions derived from the model and in vitro lipid-protein interaction results, and showed the potential physiological role of this binding. We postulate that direct interactions between spectrin ankBDn and PE-rich domains play an important role in stabilizing the structure of the spectrin-based membrane skeleton.     

Schmelztiegel Bodenbakterien

The melting point of soil bacteria Bacterial soil communities substancially drive the ecological functions of a healthy soil. The study of such communities is a highly challenging research field with multiple dimensions. Here, we briefly summarize, at different levels, the contextual relationship of technological, biological, theoretical and also legal aspects of bacterial soil biology.     

Expression of the Rickettsia prowazekii citrate synthase gene in Escherichia coli.

Recombinant DNA techniques were used to isolate the Rickettsia prowazekii citrate synthase gene on the plasmid vector pBR322 by functional complementation of a gltA mutation of Escherichia coli K-12. Analysis of citrate synthase activity in crude extracts revealed that the enzyme expressed in E. coli retains the regulatory control mechanisms characteristic of the rickettsial enzyme.