Thermal fluctuations and deformations upon binding

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. 

Most remarkably, the bundle of the four specific heat curves splits into the two groups of pairs SI, S3 and S3, SI. To repeat this, sequences of these pairs differ mainly by the location of the amino acid proline. Thus, it seems that changes of the thermodynamic behavior of these synthetic peptides are virtually controlled by proline only. The knowledge that individual amino acids or segments of the sequence are particularly relevant for a certain structural behavior is of obvious value for the design of sequences with specific functions. The example discussed here is certainly simple, but any systematic attempt to design 

6 Sequence-specific peptide adsorption at siiicon (100) surface 

Considering the previous argument about structural properties of these peptides in solvent only, we also expect that the adsorbed conformations are not supposed to exhibit clear symmetries. However, good binding properties are only possible if the peptide forms comparatively flat structures, enabling it to maximize the number of substrate contacts. Thus, at room temperature, surface-attached peptides are expected to be compact without noticeable internal structure. The deformation of the peptides due to adsorption is apparent if we analyze the gyration tensor components perpendicular and parallel to the substrate separately. Let the gyration radius of the heavy atoms be 

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