Inverse temperature transitions provided

Inverse Temperature Transitions Provide Negative Entropy to Protein... 

It is quite clear that the ion-pairing approach using hydrophobic-induced, pKa-shifted, anionic sites within polymers capable of inverse temperature transitions provides a means of achieving constant release of positively charged drugs over substantial periods of time. As discussed below, similar results have been obtained for the narcotic antagonist naltrexone. 

The azo-modified, elastin-like polypeptide XIV illustrated in Scheme 9 exhibits a so-called inverse temperature transition" that is, the compound gives cross-linked gels that remain swollen in water at temperature below 25 °C but deswell and contract upon a rise of temperature. The trans-cis photoisomerization of the azo units, obtained through alternating irradiation at 350 and 450 nm, permits photomodulation of the inverse temperature transition.[S9] The result indicates that attachment of a small proportion of azobenzene chromophores is sufficient to render inverse temperature transition of elastin-like polypeptides photoresponsive, and provides a route to protein-based polymeric materials capable of photomechanical transduction. 

The inverse temperature transition is a specific mechanism whereby thermal energy (heat) provides an increase in order of the protein part of the system. A decrease in entropy of this sort has been termed negative entropy by Schrodinger. ° While the total entropy (disorder) for the complete system of protein and water increases as the temperature is raised, the structural protein component, critical to the conversion of thermal energy to mechanical work, increases in negative entropy. The protein component increases in order by the folding that shortens length and by the assembly of oillike domains that builds structures. 

A smart plastic would harmlessly disintegrate once its useful Life were completed. Plastics made of plastic-contractile model proteins with controllable inverse temperature transitions can be designed as smart plastics. A smart protein-based plastic, having fulfilled its role, would swell and become a fragile, edible gelatin-like substance. Rather than foretell death for the fishes, a smart protein-based plastic could provide food for the fishes, once its useful Life as a plastic were complete. 

T, to a new value of T, caused by an energy input represented by % to provide a measure of the change in Gibbs free energy for hydrophobic association of the protein-based polymer. Therefore, Tt, the onset temperature for the inverse temperature transition, represents an intrinsic property of the hydrophobic consilient mechanism of energy conversion. 

Now, it has been shown for materials such as poly(propylene diol) (wherein both the absorption maximum for loss shear modulus and loss permittivity overlap near the frequency of IHz) that their normalized curves perfectly superimpose over their frequency band width. - As shown in Figure 9.15, the lower frequency loss shear modulus curves uniquely overlap with the loss permittivity data at higher frequency. As such the former is melded to calibrate the loss permittivity data to obtain a coarse estimate of the elastic modulus values. This provides an independent demonstration of the mechanic il resonance near 3 kHz and also allows reference to the 5 MHz dielectric relaxation as a mechanical resonance. Thus, as the folding and assembly of the elastic protein-based polymers proceed through the phase (inverse temperature) transition, the pentamers wrap up into a structurally repeating helical arrangement like that represented in Figure 9.17. 

The presence of phase transitions at 19 and 30°C provides an opportunity to test the proposed deformation model. Below 19°C the lattice contracts into a triclinic structure witli strong intermolecular interaction. 5,26 sjamplcs deformed below 19°C should develop off-c-axis orientation while samples deformed above 30°C should not. Figures 1.12 and 1.13 show inverse pole figures for samples deformed at 2 and 70°C. The observed orientation agrees with our proposed model. - With tlris set of experiments, it is possible to activate the oblique slip process or, alternatively, to deactivate it in the high-temperature phase above 30°C. 

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