Interaction of α-poly-L-lysine and ε-poly-L-lysine with methyl orange and its homologs in aqueous solution: Results from dialysis and spectroscopic measurements

The interaction of α-poly-L -lysine and ε-poly-L -lysine with methyl and ethyl orange was studied by equilibrium dialysis and spectroscopic methods. The results of the dialysis measurements indicated that the extent of binding by ε-polypeptide is substantially higher than that by α-polypeptide, despite the much greater molecular weight of the latter. This difference in binding affinity was interpreted in terms of the increased conformational adaptability of ε-polypeptide because of its highly flexible structure. Furthermore, ε-polypeptide exhibited strong cooperative binding. In addition, the effect of the successive addition of α- and ε-polypeptides on the absorption spectra of methyl and ethyl orange was investigated. The addition of α-polypeptide with a molecular weight of 400,000 produced a new absorption peak at a shorter wavelength, due to the stacked dye molecules on the polypeptide chain, whereas that of ε-polypeptide did not. From the results of spectroscopic measurements a possible mode of interaction between these two polypeptides and the small molecule is discussed.     

Protonation states of buried histidine residues in human deoxyhemoglobin revealed by neutron crystallography

The protonation states of buried histidine residues in human deoxyhemoglobin were unambiguously identified by using a neutron crystallographic technique. Unexpectedly, the neutron structure reveals that both the alpha- and beta-distal histidines (Hisalpha58 and Hisbeta63) adopt a positively charged, fully (doubly) protonated form, suggesting their contribution to the Bohr effect. In addition, the neutron data provide an accurate picture of the alpha1beta1 hydrogen-bonding network and allow us to observe unambiguously the nature of the intradimeric interactions at an atomic level.     

Effects of the Thermal Environment on Articular Chondrocyte Metabolism: A Fundamental Study to Facilitate Establishment of an Effective Thermotherapy for Osteoarthritis

Aim: To facilitate establishment of an effective thermotherapy for osteoarthritis (OA), we investigated the effects of the thermal environment on articular chondrocyte metabolism in vitro. Methods: Chondrocytes were isolated from porcine knee joints, and cultured at 32°C, 37°C and 41°C. Cell proliferation and viability were assessed at Days 2, 4 and 8. In addition, TdT-mediated dUTP nick end labeling (TUNEL) assay was performed at Day 3 to determine the proportion of apoptotic chondrocytes. Analysis of genes specific for factors related to the cartilage extracellular matrix (ECM), cartilage destruction, and cartilage protection was performed at Day 2. Furthermore, evaluation of heat stress tolerance, and heat shock protein 70 (HSP70) mRNA expression and protein synthesis was performed at Day 2 and 3, respectively. Results: Cell proliferation was more at 37°C than at 32°C and 41°C. Cell viability and the number of TUNEL-positive cells were not affected until Day 8 and 3, respectively. The expression of the ECM-related genes was up-regulated at higher temperature. The expression of MMP13, a type II collagen destructive enzyme, and that of TIMP1 and TIMP2, which are MMP inhibitors, were up-regulated at higher temperatures. Finally, the chondrocytes cultured at 41°C may acquire heat stress tolerance, in part, due to the up-regulation of HSP70, and may inhibit apoptosis induced by various stresses, which is observed in OA. Conclusions: The thermal environment affects articular chondrocyte metabolism, and a heat stimulus of approximately 41°C could enhance chondrocyte anabolism and induce heat stress tolerance.     

Novel catalyst system for the synthesis of poly(alkylene oxide) with controlled molecular weight

An organoaluminum compound with bulky phenoxide groups as a Lewis acid can accelerate much the living polymerization of alkylene oxide initiated with aluminum porphyrin by the coordinative activation of the monomer. This concept can be extented to the polymerization initiated with aluminum Schiff base and tetraazaannulene complexes.