Coexistence of the spin-density-wave and superconductivity in the (Ba,K)Fe2As2

The relation between the spin-density-wave (SDW) and superconducting order is a central topic in current research on the FeAs-based high Tc superconductors. Conflicting results exist in the LaFeAs(O,F)-class of materials, for which whether the SDW and superconductivity are mutually exclusive or they can coexist has not been settled. Here we show that for the (Ba,K)Fe2As2 system, the SDW and superconductivity can coexist in an extended range of compositions. The availability of single crystalline samples and high value of the energy gaps would make the materials a model system to investigate the high Tc ferropnictide superconductivity.Comment: 4 pages, 5 figure

Melatonin the "light of night" in human biology and adolescent idiopathic scoliosis

Melatonin "the light of night" is secreted from the pineal gland principally at night. The hormone is involved in sleep regulation, as well as in a number of other cyclical bodily activities and circadian rhythm in humans. Melatonin is exclusively involved in signalling the 'time of day' and 'time of year' (hence considered to help both clock and calendar functions) to all tissues and is thus considered to be the body's chronological pacemaker or 'Zeitgeber'. The last decades melatonin has been used as a therapeutic chemical in a large spectrum of diseases, mainly in sleep disturbances and tumours and may play a role in the biologic regulation of mood, affective disorders, cardiovascular system, reproduction and aging. There are few papers regarding melatonin and its role in adolescent idiopathic scoliosis (AIS). Melatonin may play a role in the pathogenesis of scoliosis (neuroendocrine hypothesis) but at present, the data available cannot clearly support this hypothesis. Uncertainties and doubts still surround the role of melatonin in human physiology and pathophysiology and future research is needed

Circannual variation in the expression of beta 2-adrenoceptors on human peripheral mononuclear leukocytes (MNLs)

Peripheral mononuclear leukocytes (MNLs) are widely used as a tissue model in studies of beta-adrenoceptor disturbances in hypertension and asthmatic diseases. The beta 2-adrenoceptor density (Bmax), however, depends not only on the gender of the person under study and on the time of day the blood specimens are obtained. Evidence is now reported for a circannual variation in the expression of beta 2-adrenoceptor sites on peripheral MNLs. In male volunteers the 24-h mean was found to be highest in the men studied in April/May (1135 +/- 10 sites/cell) and decreased to 891 +/- 16 sites/cell in August and to 712 +r90 sites/cell in December (means +/- SE, P less than 0.01 April/May compared to December). Concomitantly the circadian amplitude increased from 17.3% +/- 6.4% of 24-h mean in April/May to 28.2% +/- 1.4% of 24-h mean in August and to 34.2% +/- 4.2% of 24-h mean in December (means +/- SE, P less than 0.05, April/May compared to December). The circadian acrophase remained constant (190 degrees +/- 30 degrees equivalent to 12 h 40 min +/- 2 h 00 min, means +/- SE)

Interplay of PDZ and protease domain of DegP ensures efficient elimination of misfolded proteins

Aberrant proteins represent an extreme hazard to cells. Therefore, molecular chaperones and proteases have to carry out protein quality control in each cellular compartment. In contrast to the ATP-dependent cytosolic proteases and chaperones, the molecular mechanisms of extracytosolic factors are largely unknown. To address this question, we studied the protease function of DegP, the central housekeeping protein in the bacterial envelope. Our data reveal that DegP processively degrades misfolded proteins into peptides of defined size by employing a molecular ruler comprised of the PDZ1 domain and the proteolytic site. Furthermore, peptide binding to the PDZ domain transforms the resting protease into its active state. This allosteric activation mechanism ensures the regulated and rapid elimination of misfolded proteins upon folding stress. In comparison to the cytosolic proteases, the regulatory features of DegP are established by entirely different mechanisms reflecting the convergent evolution of an extracytosolic housekeeping protease

Mutational Analysis of the Zippering Reaction during Flavivirus Membrane Fusion▿

The current model of flavivirus membrane fusion is based on atomic structures of truncated forms of the viral fusion protein E in its dimeric prefusion and trimeric postfusion conformations. These structures lack the two transmembrane domains (TMDs) of E as well as the so-called stem, believed to be involved in an intra- and intermolecular zippering reaction within the E trimer during the fusion process. In order to gain experimental evidence for the functional role of the stem in flavivirus membrane fusion, we performed a mutagenesis study with recombinant subviral particles (RSPs) of tick-borne encephalitis virus, which have fusion properties similar to those of whole infectious virions and are an established model for viral fusion. Mutations were introduced into the stem as well as that part of E predicted to interact with the stem during zippering, and the effect of these mutations was analyzed with respect to fusion peptide interactions with target cells, E protein trimerization, trimer stability, and membrane fusion in an in vitro liposome fusion assay. Our data provide evidence for a molecular interaction between a conserved phenylalanine at the N-terminal end of the stem and a pocket in domain II of E, which appears to be essential for the positioning of the stem in an orientation that allows zippering and the formation of a structure in which the TMDs can interact as required for efficient fusion