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Wilson, M. T., Ranson, R. J., Masiakowski, P., Czarnecka, E., & Brunori, M. (1977). A kinetic study of the pH-dependent properties of the ferric undecapeptide of cytochrome c (microperoxidase). Eur J Biochem, 77(1), 193–199.
Abstract: The ferric form of the haem undecapeptide, derived from horse cytochrome c by peptic digestion, undergoes at least three pH-induced transitions with pK values of 3.4, 5.8 and 7.6. Temperature-jump experiments suggest that the first of these is due to the binding of a deprotonated imidazole group to the feric iron while the second and third arise from the binding of the two available amino groups present (the alpha-NH2 of valine and the epsilon-NH2 of lysine). Molecular models indicate that steric retraints on the peptide dictate that these amino groups may only coordinate to iron atoms via intermolecular bonds, thus leading to the polymerization of the peptide. Cyanide binding studies are in agreement with these conclusions and also yield a value of 3.6 X 10(6) M-1 s-1 for the intrinsic combination constant of CN- anion with the haem. A model is proposed which describes the pH-dependent properties of the ferric undecapeptide.
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Kihara, H., Nakatani, H., Hiromi, K., & Hon-Nami, K. (1977). Kinetic studies on redox reactions of hemoproteins. I. Reduction of thermoresistant cytochrome c-552 and horse heart cytochrome c by ferrocyanide. Biochim Biophys Acta, 460(3), 480–489.
Abstract: The oxidation-reduction reaction of horse heart cytochrome c and cytochrome c (552, Thermus thermophilus), which is highly thermoresistant, was studied by temperature-jump method. Ferrohexacyanide was used as reductant. (Formula: see text.) Thermodynamic and activation parameters of the reaction obtained for both cytochromes were compared with each other. The results of this showed that (1) the redox potential of cytochrome c-552, + 0.19 V, is markedly less than that of horse heart cytochrome c. (2) deltaHox of cytochrome c-552 is considerably lower than that of horse heart cytochrome c. (3) deltaSox and deltaSred of cytochrome c-552 are more negative than those of horse heart cytochrome c. (4) kred of cytochrome c-552 is much lower than that of horse heart cytochrome c at room temperature.
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Tsong, T. Y. (1977). Conformational relaxations of urea- and guanidine hydrochloride-unfolded ferricytochrome c. J Biol Chem, 252(24), 8778–8780.
Abstract: Several recent studies of protein the unfolded proteins. In urea- and guanidine HCl-unfolded ferricytochrome c (horse heart), an acid-induced spin state transformation of the heme group has been detected by the heme absorptions, Trp-59 fluorescence, and the intrinsic viscosity of protein. Kinetics of this second conformational transition, by the temperature jump and stopped flow methods, are complex. One rapid reaction (tau1), pH-independent, occurs in a 50-mus range; the second reaction (tau2), in a 1-ms range, depends linearly upon pH and is faster at the alkaline side; a third reaction (tau3), in a 1-s range, shows a sigmoidal transition at pH 5.1 and is faster at the acidic side. The results are consistent with a kinetic scheme which involves protein conformational changes in the transformation of the heme coordination state. The kinetics, along with previous equilibrium studies, indicate that ligand or charge interactions within a protein molecule are not completely prohibited even in strongly denaturing conditions, such as in high concentrations of urea and guanidine HCl. Thus, local structures of peptide chain associated with these interactions can exist in the unfolded protein.
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Hinde, R. A. (1969). Analyzing the roles of the partners in a behavioral interaction--mother-infant relations in rhesus macaques. Ann N Y Acad Sci, 159(3), 651–667.
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Smith, L. A., Wells, K. L., Marion, G., Swain, D. L., & Hutchings, M. R. (). Effects of group composition on the grazing behaviour of herbivores. Anim. Behav., In Press, Corrected Proof.
Abstract: Animal behaviour is often a function of the animal's physiological state. Groups of animals will often contain individuals with a range of physiological states and the grazing behaviour of herbivores is affected by their physiological state. This study compared the grazing decisions of animals in groups of single and mixed physiological states. Using a grazing model that simulated individual herbivore behaviour in relation to environmental distributions of forage resource (grass) and parasites (faeces), we tested the hypothesis that an animal's level of parasite exposure via the faecal-oral route is affected by the composition of physiological states in the group. Four physiological states were considered: parasite-naïve, parasitized, lactating and parasite-immune animals. Baseline parasite exposure levels for each state were generated by simulating single-state groups and were compared to simulations of each of the six two-state combinations. In single-state groups parasitized animals had the least and lactating animals had the greatest levels of parasite exposure. When co-grazing with lactating animals, parasitized, immune and naïve animals increased their parasite exposure, relative to single-state groups. When co-grazing with parasitized animals, lactating, immune and naïve animals reduced their parasite exposure, relative to single-state groups. There was no difference in parasite exposure of the immune or naïve animals co-grazing together when compared to the single-state groups. These results highlight the need to recognize the impact of the individual when studying group-living animals.
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