Thermal interactions with proteins

Heinz P, Bretagnol F, Mannelli I, Sirghi L, Valsesia A, Ceccone G, et al. Poly(N-isopropyla-crylamide) grafted on plasma-activated poly(ethylene oxide) thermal response and interaction with proteins. Langmuir 2008 24(12) 6166—75. 

The interest in vesicles as models for cell biomembranes has led to much work on the interactions within and between lipid layers. The primary contributions to vesicle stability and curvature include those familiar to us already, the electrostatic interactions between charged head groups (Chapter V) and the van der Waals interaction between layers (Chapter VI). An additional force due to thermal fluctuations in membranes produces a steric repulsion between membranes known as the Helfrich or undulation interaction. This force has been quantified by Sackmann and co-workers using reflection interference contrast microscopy to monitor vesicles weakly adhering to a solid substrate [78]. Membrane fluctuation forces may influence the interactions between proteins embedded in them [79]. Finally, in balance with these forces, bending elasticity helps determine shape transitions [80], interactions between inclusions [81], aggregation of membrane junctions [82], and unbinding of pinched membranes [83]. Specific interactions between membrane embedded receptors add an additional complication to biomembrane behavior. These have been stud-... 

Common bean protein and procyanidin interactions can be hydrophilic or hydrophobic, depending on the sites on the protein available for interaction. Thermal processing can denature the protein and change the type of interaction possible. Once bean protein is denatured, hydrophobic interactions between the protein and procyanidin are likely. Since the strength of hydrophobic interactions increases with increased in temperature, the interaction between protein and procyanidin will be enhanced during thermal processing. Removal of procyanidin will be easiest prior to thermal processing. 

Results from thermal denaturation and heat capacity studies have shown that the proteins are not necessarily completely unfolded in this process. The volume observations also suggest that the denatured state is not one in which all hydrophobic groups are exposed to water. But the results can also be understood from the effect of close polar and electrostatic groups interacting with the water structure surrounding the hydrophobic groups. The volume change is heavily... 

The importance of direct gas chromatography and combined direct GC/MS to the food industry is demonstrated by the analysis of volatile flavor components and contaminants in experimental samples of rice, food blends, and raw and roasted peanuts. By examining these samples, we are able to investigate flavor systems that are probably associated with lipid oxidation, thermal degradation of protein, or protein interactions with other compounds. 

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