Chain dynamics segmental mobility

In general, incorporation of hydrophobic groups into PIPAAm chains decreases the LCST [29-31]. Hydrophobic groups alter the hydrophilic/ hydrophobic balance in PIPAAm, promoting a PIPAAm phase transition at the LCST, water clusters around the hydrophobic segments are excluded from the hydrophobicaUy aggregated inner core. The resulting isolated hydrophobic micellar core does not directly interfere with outer shell PIPAAm chain dynamics in aqueous media. The PIPAAm chains of the micellar outer shell therefore remain as mobile linear chains in this core-shell micellar structure. As a result, the thermoresponsive properties of PIPAAm in the outer PIPAAm chains of this structure are unaltered [23-27,32]. 

It is assumed that the limited proteolysis phenomenon derives from the fact that a specific polypeptide chain segment of the compact, folded protein substrate is exposed and flexible so that it can fit the active site of the appropriate peptidase for an efficient and selective limited hydrolysis. There is no doubt that enhanced chain flexibility or segment mobility is the key feature of the site of peptide bond hydrolysis demonstrated by a clear-cut correlation between sites of proteolytic attack and sites of enhanced chain flexibility. The present availability of automatic, efficient and sensitive techniques of protein sequencing and, particularly, the recent dramatic advances of mass spectrometry 361 in the analysis of peptides and proteins, allows a more systematic use of the limited proteolysis approach as a simple first step in the elucidation of structure-dynamics-function relationships for novel proteins which are only available in minute amounts. 

Conformational changes are expected to affect density (packing) and chain dynamics (mobility) such that surface/interface properties vary from that of the bulk glass. The surface effects are evident only within several chain segment diameters of the surface/interface 63), Chapter 6, by Haralampus et al., presents experimental and theoretical results on the effect of confinement on Tg. 

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