In 1996 the International Sorex araneus Cytogenetics Committee (ISACC) published a comprehensive list of 50 chromosome races of the common shrew Sorex araneus (Zima et . 1996). Since that time twenty one new races have been described and three races have been removed from the list. The present list summarises the data about races described since the 1996 publication. The rules introduced by Searle et ai (1991) and Hausser et al (1994) were followed in the compilation of the list. It can be considered a reference for further studies of evolutionary relationships between the chromosome races of Sorex araneus. A summary table of all the 68 known races, arranged alphabetically according to their names, is given. RESUMEEn suivant les principes de nomenclature des chromosomes de Sorex araneus (Searle et al. 1991) et ceux de la definition de ses races chromosomiques , PISACC (International Sorex araneus Cytogenetics Committee) a public en 1996 la premiere liste de races chromosomiques de 5. araneus (Zima et al., 1996). Elle comprenait 50 races chromosomiques. Depuis, 21 race nouvelles ont etc decrites et trois races ont etc eliminees de cette liste. Nous presentons ici la liste revisee des races chromosomiques de 5. araneus qui comprend actuellement 68 races.
Differential scanning calorimetry (DSC) and light scattering were used to analyze the interaction of duck gizzard tropomyosin (tropomyosin) with rabbit skeletal-muscle F-actin. In the absence of F-actin, tropomyosin, represented mainly by heterodimers, unfolds at 41 8C with a sharp thermal transition. Interaction of tropomyosin heterodimers with F-actin causes a 2±6 8C shift in the tropomyosin thermal transition to higher temperature, depending on the tropomyosin/actin molar ratio and protein concentration. A pronounced shift of the tropomyosin thermal transition was observed only for tropomyosin heterodimers, and not for homodimers. The most pronounced effect was observed after complete saturation of F-actin with tropomyosin molecules, at tropomyosin/actin molar ratios . 1 : 7. Under these conditions, two well-separated peaks of tropomyosin were observed on the thermogram besides the peak of F-actin, the peak characteristic of free tropomyosin heterodimer, and the peak with a maximum at 45±47 8C corresponding to tropomyosin bound to F-actin. By measuring the temperature-dependence of light scattering, we found that thermal unfolding of tropomyosin is accompanied by its dissociation from F-actin. Thermal unfolding of tropomyosin is almost completely reversible, whereas F-actin denatures irreversibly. The addition of tropomyosin has no effect on thermal unfolding of F-actin, which denatures with a maximum at 64 8C in the absence and at 78 8C in the presence of a twofold molar excess of phalloidin. After the F-actin±tropomyosin complex had been heated to 90 8C and then cooled (i.e. after complete irreversible denaturation of F-actin), only the peak characteristic of free tropomyosin was observed on the thermogram during reheating, whereas the thermal transitions of F-actin and actin-bound tropomyosin completely disappeared. Therefore, the DSC method allows changes in thermal unfolding of tropomyosin resulting from its interaction with F-actin to be probed very precisely.Keywords: differential scanning calorimetry; F-actin; thermal unfolding; tropomyosin.Tropomyosin is a coiled-coil actin-binding protein bound along the length of actin filament in all types of muscle [1,2]. One tropomyosin molecule spans the length of seven actin monomers in the filament. Tropomyosin molecules bind to themselves in a end-to-end manner [3,4], and form a continuous structure along the actin filament. The presence of tropomyosin on actin filaments confers co-operativity on the interaction between myosin heads and actin [5±7]. Together with the other regulatory proteins, troponin in striated skeletal muscle or caldesmon in smooth muscle, it takes part in the Ca 21 regulation of muscle contraction [8,9]. Recent structural studies on skeletal muscle thin filaments suggest that tropomyosin can occupy three different positions on the actin surface, depending on the presence or absence of troponin, myosin, and Ca 21 [10]. These results are consistent with independently proposed models of the regulation of actomyosin interaction by tropomyos...
Somatic angiotensin-converting enzyme (ACE) consists of two homologous domains, each domain bearing a catalytic site. Di¡erential scanning calorimetry of the enzyme revealed two distinct thermal transitions with melting points at 55.3 and 70.5 ‡C. which corresponded to denaturation of C-and N-domains, respectively. Di¡erent heat stability of the domains underlies the methods of acquiring either single active N-domain or active N-domain with inactive C-domain within parent somatic ACE. Selective denaturation of C-domain supports the hypothesis of independent folding of the two domains within the ACE molecule. Modeling of ACE secondary structure revealed the di¡erence in predicted structures of the two domains, which, in turn, allowed suggestion of the region 291 33 in amino acid sequence of the N-part of the molecule as responsible for thermostability of the N-domain. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.
We found that a 2-h incubation of potato virus X (PVX) virions in 10 mM Tris-HCl buffer pH 7.5 at -20 degrees C results in a strong but reversible drop in virion stability. Under these conditions, the PVX virions are completely disrupted by low (starting from 50 mM) concentrations of LiCl and CaCl(2) but not of NaCl. Incubation of PVX samples with 0.05-2 M LiCl at +4 degrees C did not result in virion disassembly and the virions were not disrupted upon incubation at -20 degrees C in 10 mM Tris-HCl buffer pH 7.5 without LiCl. We suggest that a 2-h incubation of the PVX virions at -20 degrees C in 10 mM Tris-HCl pH 7.5 results in a structural transition in the virus particles. A revised model of the three-dimensional organization of coat protein subunits in the PVX virions is proposed. This two-domain model explains better the high plasticity of the PVX CP structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.