Field-induced phase transition in the periodic Anderson model

We investigate the effect of magnetic fields on a Kondo insulator by using the periodic Anderson model. The analysis by dynamical mean field theory combined with quantum Monte Carlo simulations reveals that the magnetic field drives the Kondo insulator to a transverse antiferromagnetic insulator at low temperatures. We calculate the staggered spin susceptibility and find its divergence signaling the antiferromagnetic instability. Further investigation of the spin correlation functions and the magnetization process clarifies how the magnetic field suppresses the Kondo singlet formation and induces the transverse antiferromagnetic ordering.Comment: 2 pages, 2 figures, submitted to SCES200

Alcohols increase calmodulin affinity for Ca2+ and decrease target affinity for calmodulin

AbstractIt has been proposed that alcohols and anesthetics selectively inhibit proteins containing easily disrupted motifs, e.g., α-helices. In this study, the calcineurin/calmodulin/Ca2+ enzyme system was used to examine the effects of alcohols on calmodulin, a protein with a predominantly α-helical structure. Calcineurin phosphatase activity and Ca2+ binding were monitored as indicators of calmodulin function. Alcohols inhibited enzyme activity in a concentration-dependent manner, with two-, four- and five-carbon n-alcohols exhibiting similar leftward shifts in the inhibition curves for calmodulin-dependent and -independent activities; the former was slightly more sensitive than the latter. Ca2+ binding was measured by flow dialysis as a direct measure of calmodulin function, whereas, with the addition of a binding domain peptide, measured calmodulin–target interactions. Ethanol increased the affinity of calmodulin for Ca2+ in the presence and absence of the peptide, indicating that ethanol stabilizes the Ca2+ bound form of calmodulin. An increase in Ca2+ affinity was detected in a calmodulin binding assay, but the affinity of calmodulin for calcineurin decreased at saturating Ca2+. These data demonstrate that although specific regions within proteins may be more sensitive to alcohols and anesthetics, the presence of α-helices is unlikely to be a reliable indicator of alcohol or anesthetic potency

Characteristic expression of twelve rice PR1 family genes in response to pathogen infection, wounding, and defense-related signal compounds (121/180)

Pathogenesis-related (PR) proteins have been used as markers of plant defense responses, and are classified into 17 families. However, precise information on the majority members in specific PR families is still limited. We were interested in the individual characteristics of rice PR1 family genes, and selected 12 putatively active genes using rice genome databases for expressed genes. All were upregulated upon compatible and/or incompatible rice-blast fungus interactions; three were upregulated in the early infection period and four in the late infection period. Upon compatible rice–bacterial blight interaction, four genes were upregulated, six were not affected, and one was downregulated. These results are in striking contrast to those among 22 ArabidopsisPR1 genes where only one gene was pathogen-inducible. The responses of individual genes to salicylic acid, jasmonic acid, and ethylene induced defense signaling pathways in rice are likely to be different from those in dicot plants. Transcript levels in healthy leaves, roots, and flowers varied according to each gene. Analysis of the partially overlapping expression patterns of rice PR1 genes in healthy tissues and in response to pathogens and other stresses would be useful to understand their possible functions and for use as characteristic markers for defense-related studies in rice