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A three-winding transformer based asymmetrical dual active bridge (TWT-ADAB) isolated dc-dc converter is proposed in this study. The converter comprises of three stages: primary, isolation, and secondary. The primary stage consists of an H-bridge converter, the isolation stage consists of a three-winding transformer with one primary and two secondary windings, and the secondary stage consists of a bridge converter having three legs and six active switches. The load current is shared equally by the secondary windings of the transformer resulting in reduced currents through switches of the secondary converter. Therefore, the turn-off losses of these switches get reduced. Further, zero voltage switching turn-on can be achieved for all switches of the TWT-ADAB converter to reduce the switching losses. A detailed analysis of the modelling and control of the proposed TWT-ADAB converter is presented. The theoretical analysis is verified using the simulation and experimental results. These demonstrated results show that the proposed TWT-ADAB converter offers wider ranges of the output voltages and powers and higher efficiency as compared with the existing dual bridge isolated dc-dc converters. Therefore, it can be an eminent structure for high-power isolated dc-dc power conversion applications. [ABSTRACT FROM AUTHOR]

The pathogen Mycobacterium tuberculosis expresses two chaperonins, one (Cpn60.1) dispensable and one (Cpn60.2) essential. These proteins have been reported not to form oligomers despite the fact that oligomerization of chaperonins is regarded as essential for their function. We show here that the Cpn60.2 homologue from Mycobacterium smegmatis also fails to oligomerize under standard conditions. However, we also show that the Cpn60.2 proteins from both organisms can replace the essential groEL gene of Escherichia coli, and that they can function with E. coli GroES cochaperonin, as well as with their cognate cochaperonin proteins, strongly implying that they form oligomers in vivo. We show that the Cpn60.1 proteins, but not the Cpn60.2 proteins, can complement for loss of the M. smegmatis cpn60.1 gene. We investigated the oligomerization of the Cpn60.2 proteins using analytical ultracentrifugation and mass spectroscopy. Both form monomers under standard conditions, but they form higher order oligomers in the presence of kosmotropes and ADP or ATP. Under these conditions, their ATPase activity is significantly enhanced. We conclude that the essential mycobacterial chaperonins, while unstable compared to many other bacterial chaperonins, do act as oligomers in vivo, and that there has been specialization of function of the mycobacterial chaperonins following gene duplication. [ABSTRACT FROM AUTHOR]

Background and Purpose: Over the last decade apprehension has been growing over the effectiveness of existing parenteral vaccines for diphtheria and has created an interest in the development of a mucosally active vaccine. Oral immunization appears to be an effective alternative, but is not without the inherent disadvantages of antigen destruction and tolerance. Therefore, our objective was to investigate the incorporation of diphtheria toxoid (DTx) into bilosomes, which could provide protection as well as aid transmucosal uptake and subsequent immunization. Another objective was to determine the oral dose that will produce serum antibody titres comparable with those produced by i.m. doses of DTx.Experimental Approach: Bilosomes containing DTx were prepared by thin film hydration and characterized in vitro for their shape, size, percent antigen entrapment and stability. In the in vivo study the anti-DTx IgG and anti-DTx sIgA response was estimated using elisa, in serum and in various body secretions, respectively, following oral immunization with different doses of DTx entrapped in nano-bilosomes.Key Results: High dose loaded nano-bilosomes (DTxNB3, 2Lf) produced comparable anti-DTx IgG levels in serum to those induced by i.m. alum-adsorbed DTx (0.5Lf). In addition, all the nano-bilosomal preparations elicited a measurable anti-DTx sIgA response in mucosal secretion, whereas i.m. alum-adsorbed DTx (0.5Lf) was unable to elicit this response.Conclusions and Implications: The orally administered nano-bilosomal DTx formulation produced comparable serum antibody titres to i.m.alum-adsorbed DTx, at a fourfold higher dose and without the induction of tolerance. This approach will provide an effective and comprehensive immune protection against diphtheria with better patient compliance. [ABSTRACT FROM AUTHOR]

ESAT-6 is a well characterized secreted protein from Mycobacterium tuberculosis and represents the archetype of the WXG100 family of proteins. Genes encoding ESAT-6 homologues have been identified in the genome of the human pathogen Streptococcus agalactiae; one of these genes, esxA, has been cloned and the recombinant protein has been crystallized. In contrast to M. tuberculosis ESAT-6, the crystal structure of GBS1074 reveals a homodimeric structure similar to homologous structures from Staphylococcus aureus and Helicobacter pylori. Intriguingly, GBS1074 forms elongated fibre-like assemblies in the crystal structure. [ABSTRACT FROM AUTHOR]

The (β/α)8-barrel domain consists of eight topologically equivalent supersecondary structural motifs known as β/α-units. Each unit consists of a single β-strand, an α-helix, and two loops. Evidence collected in recent years indicates that the (β/α)8-barrel motif may not be a single, autonomously-folding domain, as was previously assumed. Segments of some (β/α)8-barrels appear to fold autonomously. However, the extent to which this is true of various (β/α)8-barrel domains remains to be explored. In this study, we have scrambled (reshuffled) the native order of β/α-units (1-2-3-4-5-6-7-8) comprising the polypeptide chain of a model (β/α)8-barrel from S. cerevisiae, triosephosphate isomerase (TIM). Total scrambling was effected in order to examine whether folding can still occur to yield β/α-structures in spite of a global 'destruction' of native hydrophobic and hydrogen bonding interactions among β/α-units, while still allowing the occurrence of native interactions within individual units. Our results demonstrate that scrambled full-barrel forms (2-4-6-8-1-3-5-7 and 1-3-5-7-2-4-6-8), as well as half-barrel (2-4-6-8) and quarter-barrel (1-3) forms of TIM fold into β/α-structures that sustain tertiary and quaternary structural interactions. In particular, one variant (2-4-6-8-1-3-5-7) was found to fold and form a stable dimer with native-like structural content and other characteristics. Our results demonstrate that (β/α)8-barrels can tolerate profound alterations of both strand-strand interactions responsible for the creation of the β-barrel and the geometry of presentation of nonpolar sidechains into the hydrophobic core of the β-barrel by individual β-strands. These findings lend support to our recent proposal that a hierarchy of interactions probably regulates structure formation and stability in (β/α)8-barrels, where folding proceeds successively through three stages: (i) the tentative formation of individual β/α-units which associate through 'near-neighbor' diffusion-collision interactions into (ii) curved assemblies of multiple β/α-units through sequence-independent hydrogen bonding of strands of neighboring units, leading finally to (iii) the association of curved (quarter/half-barrel) assemblies around a common hydrophobic core through packing interactions that remain plastic and amenable to change. Proteins 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Background Coal tar has been a very popular traditional treatment for various types of psoriasis for over a century. It is the first-line treatment for scalp, hand, and foot psoriasis. However, the application of coal tar on hair invariably causes staining, which results in a high degree of patient non-compliance, especially in patients with non-black hair. Thus, the treatment of scalp psoriasis with a topical coal tar formulation requires that special concern be paid to product esthetics. Objective This study aimed to evaluate the hair-staining characteristics of a novel lecithinized coal tar (LCT) formulation on different types of mammalian hair. Methods Samples of hair from different mammals, including human, sheep, rabbit, and goat, were repeatedly exposed to the LCT formulation over 14 days. The color of hair samples treated with LCT was compared with that of untreated control hair samples. Results The study revealed the distinct non-staining potential of the LCT formulation. Conclusions This LCT formulation lacks the propensity to stain hair and thus has excellent potential to be exploited in the treatment of scalp psoriasis. [ABSTRACT FROM AUTHOR]

The protein-folding catalyst SlyD, a peptidyl prolyl cis-trans isomerase regulated by metal binding, was initially discovered as a major contaminant of non-denaturing immobilized metal-affinity chromatography (IMAC)-based procedures for the purification of heterologously expressed 6xHis-tagged proteins from Escherichia coli. Given its ability to bind weakly to nickel-nitrilotriacetic acid (Ni(2+)-NTA), protocols for the purification of SlyD currently use an initial non-denaturing IMAC step, followed by an ion-exchange chromatographic step and occasionally also other chromatographic steps. Here we demonstrate that using denaturing conditions instead of non-denaturing conditions, and by processing of large quantities of culture through small volumes of Ni(2+)-NTA resin to increase competition for binding, single-step purification of SlyD to homogeneity can be achieved directly from E. coli extracts, as assessed through spectroscopic and electrophoretic methods. The purified, denatured SlyD is shown to be capable of refolding to give rise to a native-like CD spectrum, establishing the utility of the procedure. The procedure also establishes SlyD to be the only E. coli protein capable of contaminating denaturing IMAC-based procedures.