No abstract

We obtained the first view in H 13 CO + J ¼ 1 0 and a high-resolution map in thermal SiO lines of G0.11À0.11, which is a molecular cloud situated between the Galactic Center radio arc and Sgr A. From a comparison with previous line observations, we found that the H 13 CO + J ¼ 1 0 line is optically thin, whereas the thermal SiO lines are optically thick. The line intensity in H 13 CO + J ¼ 1 0 shows that the cloud has a large column density, up to N (H 2 ) ¼ (6 7) ; 10 23 cm À2 , which corresponds to about 640-740 mag in A V or 10-12 mag in A 25 m . The estimated column density is the largest known of any even in the Galactic center region. We conclude from the intensity ratio of SiO J ¼ 1 0 to CS J ¼ 1 0 that emitting gas is highly inhomogeneous for SiO abundance on a scale smaller than the beam width $35 00 .

Animal hairs consist of aggregates of dead cells filled with keratin protein gel. We succeeded in preparing water-soluble hard-keratin proteins and reconstructing the keratin gels by heat-induced disulfide linkages in vitro. Here, the roles of intermolecular hydrophobic interaction and disulfide bonding between the proteins in the gel were discussed. Water-soluble keratin proteins consisting of mixtures of type I ( approximately 48 kDa) and type II ( approximately 61 kDa) were prepared from wool fibers as S-carboxymethyl alanyl disulfide keratin (CMADK). The gelation was achieved by heating an aqueous solution containing at least 0.8 wt % CMADK at 100 degrees C. CMADK solutions with different urea or N-ethylmaleimide concentrations or pH were exposed to dynamic light scattering (DLS) and circular dichroism (CD). DLS clarified the gelation point of CMADK solutions and provided information on the changes in keratin cluster size. DLS suggested two types of gelation mechanism. One was the regenerated chemical disulfide bonding between keratins from CMAD parts of chains. After the gel formed, this bond became important to maintain the gel structure. The other was the physical assembly due to hydrophobic interaction between alpha-helix parts of keratin chains. This hydrophobic assembly also played an important role during gelation. CD confirmed a conformational change in the keratin protein, resulting heat-induced gelation. CD clarified the relationship between keratin protein conformation and gelation, i.e., a rodlike conformation with many alpha-helix structures was necessary to associate keratin chains and form a gel network.

SYNOPSISCrosslinked structures of the permanent set wool fiber treated with boiling water at a 40% extension state and the control fiber were studied by analyzing the rubberlike force-extension curve of the swollen fiber in a mixed solution composed of equal volumes of 8M LiBr and butyl carbitol. The thiol and disulfide contents of set fibers were also determined. It was found that (1) the disulfide (SS) bonds in low-sulfur (LS) microfibril protein transform into new crosslinkages in boiling water, but the SS bonds in high-sulfur matrix protein remain intact, (2) the SS bonds in a-helical segments becomes reactive only at the extension state of fiber and produces a free thiol group, and (3) intramolecular SS bonds may exist in the a-helical segments. Discussion was also made about the closeness of the number of crosslinkage sites of SS bonds obtained from the present rubber elasticity theory and from the theoretical analysis of the amino acid sequence of the intermediate filament. The crosslinking structure model in LS protein was proposed. It was suggested further that the setting mechanism for new crosslinkage theory seems to be unsatisfactory, since the new crosslinkages do not contribute to stabilize the extended conformation of the wool chain.

No abstract