Competition between native and monoacetylated polymyxin for charged adsorption sites

The native antibiotic polymyxin B, carrying five positive charges, displaces the monoacetylated on from its adsorbed state at the interface between negatively charged lipid layers ans water. A simulation model for asdorption, governed by electrostatic forces, is presented. The model adequently representes the competitive adsorption kinetics and equilibria.     

Metabolic behavior of acetyl glyceryl ether phosphorylcholine on interaction with rabbit platelets

The metabolic fate of 1-O-[³H]alkyl-2-acetyl-sn-glycero-3-phosphorylcholine ([³H]-AGEPC) upon interaction with rabbit platelets was investigated. [³H]AGEPC was converted to a product identified as the long-chain fatty acyl analog. The reaction was unaffected by extracellular calcium. After a lag time of 30 to 60 s the kinetics of the conversion was linear. The rate of the reaction was found to be a function of platelet and AGEPC concentrations. Of the [³H]AGEPC (10^?9m) 85 ± 5% was processed into the-long chain fatty acyl analog within 1 h when incubated at 37 2C with a 1.25 × 10⁹ platelets per milliliter suspension. A maximal number of 1200 to 3600 [³H]AGEPC molecules were converted to the long-chain fatty acyl derivative per minute per platelet in the presence of 2 mm EDTA. Under similar conditions the 1-O-[³H]alkyl-2-(lyso)-sn-glycero-3-phosphorylcholine ([³H]lysoGEPC) also was transformed to a comparable long-chain fatty acyl derivative at a much slower rate and to a lower extent. No significant increase in lysoGEPC was noted in incubation mixtures containing [³H]AGEPC. The possible direct transacylation of AGEPC upon interaction with platelets is discussed as well as the possible involvement of this reaction in directly triggering the platelet response to AGEPC stimuli.     

Deoxyribonucleic Acid Base Composition of Lactobacilli Determined by Thermal Denaturation

Moles per cent guanine plus cytosine content of 16 lactobacilli provided three taxonomic groups: I, 32.4 to 38.3% with five species; II, 42.7 to 48.0% with six species; III, 49.0 to 51.9% with five species.     

A role for the transmembrane domain in the trimerization of the MHC class II-associated invariant chain.

MHC class II and invariant chain (Ii) associate early in biosynthesis to form a nonameric complex. Ii first assembles into a trimer and then associates with three class II alphabeta heterodimers. Although the membrane-proximal region of the Ii luminal domain is structurally disordered, the C-terminal segment of the luminal domain is largely alpha-helical and contains a major interaction site for the Ii trimer. In this study, we show that the Ii transmembrane domain plays an important role in the formation of Ii trimers. The Ii transmembrane domain contains an unusual patch of hydrophilic residues near the luminal interface. Substitution of these polar residues with nonpolar amino acids resulted in a decrease in the efficiency of Ii trimerization and subsequent class II association. Moreover, N-terminal fragments of Ii were found to trimerize independently of the luminal alpha-helical domain. Progressive C-terminal truncations mapped a homotypic association site to the first 80 aa of Ii. Together, these results implicate the Ii transmembrane domain as a site of trimer interaction that can play an important role in the initiation of trimer formation.     

Bacteriophage Ø105clz induces the GroEL-homologue protein inBacillus subtilis

Using two-dimensional polyacrylamide gel electrophoresis, the GroEL homologue ofBacillus subtilis was shown to be induced upon infection with Ø105clz, a clear plaque mutant of the temperate bacteriophage Ø105. Western blotting of one dimensional polyacrylamide gels also showed the induction of the GroEL homologue when cells were infected with Ø105clz.     

The influence of limb alignment and transfemoral amputation technique on muscle capacity during gait

Many factors influence successful outcomes following transfemoral amputation. One factor is surgical technique. In this study, the influence of limb alignment and surgical technique on a muscle’s capacity to generate force was examined using musculoskeletal modeling. Non-amputee and transfemoral amputee models were analyzed while hip adduction, femur length, and reattached muscle wrap position, tension and stabilization technique were systematically varied. With muscle tension preserved, wrap position and femur length had little influence on muscle capacity. However, limb alignment, muscle tension and stabilization technique notably influenced muscle capacity. Overall, myodesis stabilization provided greater muscle balance and function than myoplasty stabilization.