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Myoglobin temperature effects

The largest temperature difference occurs at the center of the tissue (z = 1), and for typical tissue fiber conditions, the maximum temperature difference is w/2 = 1.7 X 10 5oC at the tissue core. A similar increase with the effect of the chemical-binding reaction between myoglobin and oxygen is approximately 1.1 X 10-5oC. Equation (2) shows that the temperature difference increases with the square of the fiber thickness. Since the radii of skeletal muscle fibers are approximately 20 p.m. the temperature difference is not considerable. However, some experiments suggest that there is a temperature effect on the rate of facilitated transport (Dowd et al., 1991). [Pg.490]

Calculations on myoglobin mimics [34-39], provided a picture of the binding mode of O2 and ligands such as CO and NO. These studies have also shed light on the intricate interplay between structural and bonding properties of the complex and environment and temperature effects. [Pg.219]

Effects of solvent mixtures can be seen in biochemical systems. Ligand binding to myoglobin in aqueous solution involves two kinetic components, one extramolecular and one intramolecular, which have been interpreted in terms of two sequential kinetic barriers. In mixed solvents and subzero temperatures, the outer barrier increases and the inner barrier splits into several components, giving rise to fast intramolecular recombination. Measurements of the corresponding solvent structural relaxation rates by frequency resolved calorimetry allows the discrimination between solvent composition and viscosity-related effects. The inner barrier and its coupling to structural relaxation appear to be independent of viscosity but change with solvent composition (Kleinert et al., 1998). [Pg.74]

Fig. 4. Temperature dependence of the specific enthalpy of denaturation of myoglobin and ribonuclease A (per mole of amino acid residues) in solutions with pH and buffer providing maximal stability of these proteins and compensation of heat effects of ionization (see Privalov and Khechinashvili, 1974). The broken extension of the solid lines represents a region that is less certain due to uncertainty in the A°CP function (see Fig. 2). The dot-and-dash lines represent the functions calculated with the assumption that the denaturation heat capacity increment is temperature independent. Fig. 4. Temperature dependence of the specific enthalpy of denaturation of myoglobin and ribonuclease A (per mole of amino acid residues) in solutions with pH and buffer providing maximal stability of these proteins and compensation of heat effects of ionization (see Privalov and Khechinashvili, 1974). The broken extension of the solid lines represents a region that is less certain due to uncertainty in the A°CP function (see Fig. 2). The dot-and-dash lines represent the functions calculated with the assumption that the denaturation heat capacity increment is temperature independent.
Fig. 7. Microcalorimetric recording of the heat effect on cooling and subsequent heating of metmyoglobin solution at pH 3.83. The low temperature peaks correspond to heat release on cold denaturaton and heat absorption on subsequent renaturation of protein. The shift of these peaks in temperature is caused by slow kinetics of unfolding and folding of myoglobin structure at low temperature (for details, see Privalov et al 1986). Fig. 7. Microcalorimetric recording of the heat effect on cooling and subsequent heating of metmyoglobin solution at pH 3.83. The low temperature peaks correspond to heat release on cold denaturaton and heat absorption on subsequent renaturation of protein. The shift of these peaks in temperature is caused by slow kinetics of unfolding and folding of myoglobin structure at low temperature (for details, see Privalov et al 1986).
To provide an understanding of the importance of solvent mobility and the intrinsic protein energy surface, an MDS of proteins and surrounding solvent molecules at different temperatures has been performed. The simulation of myoglobin dynamics showed that solvent mobility is the dominant factor in determining protein atomic fluctuations above 180 K (Vitkup et ah, 2000). The drastic effects of water molecule dynamics on the intramolecular motion of RNase and xylase was demonstrated in recent computer simulation studies (Reat et al., 2000 Tarek et al, 2000). Extensive simulations were carried out to identify the time-scale of water attachment to lysozyme (Steprone et... [Pg.141]

FlGURE 7.7 Combined effects of two variables on conformational stability of globular proteins, (a) Denaturation (unfolding) temperature as a function of pH for papain (P), lysozyme (L), cytochrome C (C), parvalbumin (A), and myoglobin (M). (b) Effect of concentration of guanidinium chloride concentration and temperature on conformation of lysozyme at pH 1.7. (c) Effect of pressure (1 kbar= 10s Pa) and temperature on conformation of chymotrypsinogen. (d) Effect of pressure and pH on conformation of myoglobin (20°C). [Pg.245]


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See also in sourсe #XX -- [ Pg.159 ]




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