Substrate-specific peptide adsorption

Influence of temperature and solubility on substrate-specific peptide adsorption... 

In the following, we first discuss the substrate specificity of heteropolymer adhesion by employing a simple hybrid lattice model [284, 303, 306, 309, 318]. After having gained this qualitative insight into the structural binding behavior of heteropolymers, an exemplary realistic hybrid peptide-semiconductor system is investigated to verify the sequence specificity of peptide adsorption [274-276,340]. 

Various bacterial, fungal and plant lipases have been described to hydrolyze PET (Table 15.1). Lipases catalyze the hydrolysis of long chain water insoluble triglycerides and, unlike cutinase they are interfacially activated in the presence of a water-lipid interface [63-65]. The active site of lipases is covered with a peptide segment called lid while upon opening the active site becomes accessible to the substrate. Consequently, it as been indicated that PET hydrolysis by lipase can be improved in the presence of detergents [55, 66]. Apart from typical lipases and cutinases, other esterases have been shown to hydrolyze PET. Nevertheless, it is not quite clear yet what constitues a PET-hydrolase. On the one hand a comprehensive comparison of all reported enzymes on typical lipase and cutinase substrates in addition to PET is not available. On the other hand, apart from the active site architecture and specificities on water soluble substrates, the adsorption behavior onto polymers will also play a major role. 

The adsorption of the peptides at the semiconductor surface is a conformational pseudophase transition and accompanied by structural changes of the peptides during the adsorption process. The energetic response of the peptides upon binding can be obtained from Fig. 14.9, where the specific heat curves are plotted for each of the peptides. The peaks for SI and S3 and the increase toward lower temperatures for S3 and SI indicate energetic activity that signals the onset of a crossover between random-coil structures in solvent and adsorbed conformations at the substrate. 

---