Proteins temperature interval

Proteins may be covalently attached to the latex particle by a reaction of the chloromethyl group with a-amino groups of lysine residues. We studied this process (17) using bovine serum albumin as a model protein - the reaction is of considerable interest because latex-bound antigens or antibodies may be used for highly sensitive immunoassays. The temperature dependence of the rate of protein attachment to the latex particle was unusually small - this rate increased only by 27% when the temperature was raised from 25°C to 35°C. This suggests that non-covalent protein adsorption on the polymer is rate determining. On the other hand. the rate of chloride release increases in this temperature interval by a factor of 17 and while the protein is bound to the latex particle by only 2 bonds at 25°C, 22 bonds are formed at 35°C. 

Should the process take place with some number of intermediate steps, such as the unfolding of only part of the protein chain or an incomplete unzipping of the duplex, then the fractional change in the absorbance will not be linearly related to the composition of the mixture A + B. Under these circumstances, the melting curve is often broader and spread out over a larger temperature interval than would occur for the simple two-state process. The broadening leads to a... 

Applying an all-atom parallel tempering simulation of the protein HP-36 in the ECEPP/2 force field [33] using an implicit solvent model [34] the authors of [27] have measured the diffusion of labeled replicas in temperature space. The simulated temperature interval is chosen such that at the lowest temperature = 250 K the protein is in a folded state and the highest temperature T ax = 1000 K ensures that the protein can fully unfold for the simulated force field. The measured local diffusivity for the random walk between these two extremal temperatures is shown in Fig. 7. A very strong modulation of the local diffusivity is found along the temperature. Note the logarithmic scale of the ordinate. The pronounced minimum of the local diffusivity around T 500 K points to a severe bottleneck in the simulation which by measurements of the specific heat has been identified as the helix-coil... 

Figure 16.8 by A,ransCp, but Privalov uses the notation A Cp, which we will adopt here.) That is, near Td, A C/ = C d - Cp< n > 0. As the temperature interval over which proteins have been studied has increased, it has become clear that A Cp is not constant over extended temperatures. The observed trend suggests that the value for A°CP decreases to zero at about 415 K for all the proteins studied. A consequence of the decreasing A Cp is that the enthalpy and entropy of denaturation approach constant values as T approaches 415 K,... 

The sigmoid-shaped curves of Figure 2.6A represent the shortening of contraction that occurs on raising the temperature through the relevant temperature interval for the particular extent of oil-like character of the model protein. Elastic-contractile model proteins of more oillike composition contract at lower temperatures and over narrower temperature intervals. 

Figure 5.5. Transitions, plotted as independent variable versus dependent variable, showing a response limited to a partieular range of independent variable. (A) Representation of the thermally driven contraction for an elastic-contractile model protein, such as the cross-linked poly(GVGVP), plotted as the percent contraction (dependent variable) versus temperature (independent variable). The plot shows a poorly responsive range below the onset of the transition, the temperature interval of the inverse temperature transition for hydrophobic association, and another poorly responsive region above the tem-...

Certain vitamins like B2 (riboflavin) and B3 (niacin) become chemically dressed up for attachment to proteins. As such these attached vitamins become redox couples that can accept electrons (become reduced) and give up electrons (become oxidized). A change in the redox state changes the temperature interval for the phase transition, that is, moves the T,-divide. Just as protonation of a carboxylate lowers the temperature interval, so too does adding electrons to the oxidized state of a redox couple. Lowering the temperature interval from above to below the operating temperature by reduc-... 

As mentioned above in reference to Figure 5.5A, as the temperature is raised, contraction of a band composed of elastic-contractile model protein occurs. Contraction occurs as the temperature is raised through a temperature interval. Crossing over the T,-divide, defined in Figure 5.3, is to pass through the temperature interval over which contraction occurs it is the result of the phase separation, specifically of the inverse temperature transition. Furthermore, the temperature interval for contraction occurs at a lower temperature when the model protein is more hydrophobic and at a higher temperature when the model protein is less hydrophobic. 

As noted above, the temperature interval shifts on changing the concentration of a chemical, that is, on changing the chemical potential of a chemical for which the model protein is responsive, as in protonation of a carboxylate. Similarly, the temperature interval shifts on changing the availability of electrons, that is, on changing the electrochemical potential, such that an oxidized component of a redox couple becomes reduced. 

Axiom 1 The change in temperature interval, over which occurs the oil-like folding and assembly transition of a host model protein on introduction of different guest substituents, becomes a functional measure of relative oil-like character of the substituents, that is, of their relative hydrophobicity, and it provides a measure of the change in free energy of the hydrophobi-cally associated state. 

Contraction of elastic matrices occurs as the temperature is raised through the temperature interval of Figure 5.5A this constitutes the input of thermal energy (TE), measurable as the heat of the transition seen in Figure 5.1C. Visible contraction also occurs as any of the independent variables move through the transition zone in Figure 5.5B. Depending on the composition of the model protein that consti-... 

Axiom 2 Heating to raise the temperature from below to above the temperature interval for hydrophobic association of cross-linked elastic model protein chains drives contraction with the performance of mechanical work. 

Axiom S At constant temperature, an energy input that changes the temperature interval for thermally driven hydrophobic association in a model protein can drive contraction, that is, oillike folding and assembly, with the performance of mechanical work in other words, the energy input moves the system through the transition zone for contraction due to hydrophobic association. 

Increasing the concentration of acid, constitutes a particular chemical energy input. The addition of acid (H ), over the concentration range that protonates the carboxylate, lowers the temperature interval for the model protein, drives contraction, and defines the transition zone for this energy input indicated as c in Figure 5.18A. Figure 5.18B, 2a), represents the contraction and relaxation by reversible protonation and deprotonation of the carboxyl functional group, i.e., chemo-mechanical transduction. 

Figure 5.17 shows direct experimental results, which give rise to the generalized representation in Figure 5.18,3). In the case of Figure 5.17, for every 100 residues of model protein, there are 5.4 lysine residues to each of which is attached an N-methyl nicotinamide (NMeN) group. When oxidized, the circumstance is as indicated by temperature interval b of Figure...

When the transition zone is specifically the temperature interval, any change in oil-like character of the model protein-based machine moves... 

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