Mechanism of the screw-sense reversal of tightly hydrogen-bonded α-helical network triggered by the side-chain conformation

The paper presents theoretical treatment of a screw-sense reversal of tightly hydrogen-bonded α-helical polypeptide chains. The transition is triggered by the conformational free-energy difference (s) of the side chain flanking the chiral (right(r)- or left(?)-handed) backbone. The two-parameter scheme (s, σ) corresponding to a zipper-type transition model starting from one terminal has been constructed and applied to the thermally-induced helix-helix transition characteristic of polyaspartic acid esters observed in the helicoidal solution. The weighting parameter σ takes care of the instability associated with the ?/r junction, i.e., the unfolded site where at least three successive hydrogen-bonds should become free to change their partner. The enthalpy of transition (ca. 2 kJ/mol) of poly(β-phenethyl l-aspartate) (PPLA) (Mv = 6 × 10⁴) observed in the lyotropic liquid crystalline state in 1,1,2,2-tetrachloroethane has been reproduced with the instability parameter σ = 0.001-0.0001. Attempts were further extended to interpret the thermally-induced helix-helix transition behaviors of the PPLA homopolymers and random copolymers involving benzyl l-aspartate residues observed under various conditions.     

Secretory production of recombinant human chymase as an active form in Pichia pastoris

We succeeded in expressing in a Pichia pastoris (P. pastoris) host a cDNA encoding a mature human chymase (h-chymase) which was secreted directly into the culture medium. Recombinant human heart chymase (rh-chymase) was purified from the culture medium via a single one-step heparin-agarose column chromatography tracing, using succinyl-Ala-Ala-Pro-Phe-para-nitroanilide (Suc-AAPF-pNA) hydrolysing activity. On SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the rh-chymase showed a diffused protein band with molecular weight of 32-37 kDa. After deglycosylation, however, rh-chymase changed to a sharp protein band with molecular weight 28 kDa, which is equal in size to deglycosylated h-chymase. The rh-chymase had an activity to convert one of the natural substrates, angiotensin I, to angiotensin II. Double reciprocal plot analysis revealed that the K(m) value ofrh-chymase against Suc-AAPF-pNA was approximately 5.1 mM, which is close to that of purified h-chymase.     

Spin gap and antiferromagnetic fluctuation in spin ladder system doped with nonmagnetic impurities

Effects of nonmagnetic impurity doping in a spin ladder system with a spin gap are investigated by the exact diagonalization and the variational Monte Carlo calculations. Small amount of impurity doping generates a nearly free spin bound to each impurity. These nearly free spins interact each other only weakly giving rise to gapless spin excitations. Another important aspect is that short-ranged antiferromagnetic correlation is enhanced especially around the impurity sites. We propose a possible scenario for this drastic change in the spin gapped ladder system. We also compare with the experimental results of Zn-doped SrCu₂O₃.     

Decoded-source sense amplifier for high-density DRAMs

The decoded-source sense amplifier (DSSA) for high-speed, high-density DRAMs is discussed. To prevent clamping of the common-source node of the sense amplifier caused by bit-line discharge current, the DSSA has an additional latching transistor with a gate controlled by a column decoder. The DSSA has been successfully installed in a 4-Mb DRAM and provided a RAS access time of 60 ns under a V_cc of 4 V at 85°C     

Human auditory cortical mechanisms of sound lateralization: II. Interaural time differences at sound onset

Neuromagnetic responses were recorded over the right temporal cortex using a 24-channel gradiometer. Stimuli were binaural click trains, presented with six separate interaural time differences (ITDs). N100m to sound onset was larger and earlier for stimuli presented with left- than with right-leading ITDs. With stimulus lateralization taken into account, monaural and binaural stimuli evoked responses of roughly equal amplitude. In selective adaptation and oddball experiments, stimuli presented with different ITDs excited overlapping neuronal populations, but the amount of overlap decreased as the ITD between the stimuli increased. There were no systematic differences in the cortical source locations of the N100m as a function of ITD, however. Thus it appears that ITD-sensitive neurons in the human auditory cortex are not organized into a large-scale, orderly representation, which could be resolved by MEG.     

The concept of uncertainty in animal experiments using aversive stimulation.

Reviews rat experiments using aversive stimuli in which some element of uncertainty was involved. Nine cases of conditions that produce uncertainty are described, and relevant experimental facts are examined. Rats were found to prefer situations involving certainty to those involving uncertainty, and the rats' basal rate of responding was found to be less in suppression situations involving uncertainty about aversive environmental events than in those involving relative certainty. Results are obtained when the aversive stimuli the rats received were physically matched in quantity among the conditions compared. Results are discussed with reference to the safety signal, preparatory response, time allocation, contextual fear, and information hypotheses. It is concluded that the function of the concept of uncertainty is to organize a class of studies that are otherwise unrelated. (59 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suppression of licking behavior in rats as a function of predictability of shock and probability of conditioned-stimulus-shock pairings.

In Exp I, the effects of various degrees of predictability of electric shock upon rats' licking behavior were studied using 45 male albino rats. The basal rate of licking became progressively lower as unpredictability of shock increased. It was also found that Ss could utilize "time" as a predictor of safety and danger. In Exp II, using 48 Ss, the relationship between conditioned emotional response (CER) and the probability of conditional stimulus (CS) being paired with shock was studied under the matched basal rate of licking by making all shocks predictable. The CER was an increasing function of the probability of CS-shock pairings. Results are discussed with reference to M. Seligman's (1969) safety-signal hypothesis and R. Rescorla's (1968) probabilistic theory. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A clinicopathologic study of thymomas: a review of 52 cases, with particular reference to results of treatment

The possible use of spleen-derived mononuclear cells (SPMC) for the intentional and economical adoptive immunotherapy of cancer patients was studied. SPMC were obtained from spleens resected surgically from patients with gastric cancer or idiopathic thrombocytopenic purpura (ITP). When SPMC were cultured in recombinant interleukin 2 (rIL2), SPMC, in the form of interleukin-activated killer spleen cells (IL-SP) proliferated in six of eight cases. CD8+ lymphocytes were the major expanding cell population in most SPMC cultures and IL-SP showed a significant cytolytic activity against cultured tumor cells during cell proliferation. When cultured with a streptococcal preparation, OK-432, for 24 to 48 h, SPMC showed cytotoxic activity against tumor cells and were expressed as OK-432 activated killer spleen cells (OK-SP). The effects of supernatants from IL-SP and OK-SP on tumor cell growth were also examined. The supernatants from IL-SP and OK-SP significantly inhibited cell growth in 3 and 10 out of 11 cases, respectively, while those from OK-SP showed higher growth inhibitory activity than those from IL-SP. The results of this study indicate the potential of SPMC as effector cells for the adoptive immunotherapy of cancer patients.     

Measurement of emotional reactivity and association ability of the Tsukuba emotional strains of rats (Rattus norvegicus) in licking and lever-pressing conditioned suppression situations.

The emotional reactivity and association ability of the Tsukuba High Emotional (THE), the Tsukuba Low Emotional (TLE), and the Wistar-Imamichi (WI) strains of rats were studied in two experiments. Suppression of licking and lever pressing by unsignaled shocks were used to measure emotionality in Experiments 1 and 2, respectively. Contrary to our expectations, the WI rats which had formed a part of the foundation population of the Tsukuba strains, proved to be the most emotional, and the THE and TLE did not differ in emotionality from each other in either experiment. Association ability was measured by the speed of discriminating dangerous and safe periods under matched levels of emotional arousal. Association ability proved to be best in TLE rats, especially in Experiment 2, in which the procedures were somewhat improved on the basis of the results of Experiment 1. We discuss the results in terms of the motivational system and of the behavioral characteristics established during the course of selective breeding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Critical properties of metal-insulator transition in low dimensions

Anomalous metallic states near the Mott insulator are analyzed in terms of the critical scaling toward the metal-insulator transition. Continuous transitions from a metal to the Mott insulator are characterized either by the mass divergence as in the bi-component systems or the vanishing carrier number as in the valence bond systems. A set of critical exponents in these two cases is deduced from the scaling theory. The correlation exponent v and the dynamical exponent z satisfy v = 1/2d and z = 2d when the mass diverges in d dimensions, while v = 1/2and z = 2 if the carrier number vanishes. Crossovers between quantum critical regime and thermal critical regime inferred from this theory shed light on understanding experimental indications in high-T_c cuprates and other strongly correlated systems.