Backbone hydration

External backbone hydration is more common than the other two types and may be especially relevant to aqueous solution studies as it is typical... 

The baseline structural deficiency Y = 20 represents the maximum of a tight distribution (standard deviation a = 2.25) of T-values for the structural deficiency of soluble proteins with no disulfide bridges. This baseline T-value implies that soluble proteins are not perfectly packed and maintain at least 20% of unburied backbone hydrogen bonds. Since such structural deficiencies locally promote backbone hydration, they belong to an intermediate region between order and disorder and hence represent markers of structural flexibility. Thus, because of its universality, the Y = 20 constant may be interpreted as the baseline flexibility needed for protein function. 

In this chapter, dehydrons were characterized as structural deficiencies. These deficiencies are of a special kind They are promoters of backbone hydration [4] and hence destabilizers of the native structure. On the other hand, disulfide bonds pre-formed in the denatured state reduce the structure-destabilizing conformational entropy cost associated with the folding process [12], hence stabilizing the native... 

Fig. 3.1 The cross-over behavior from backbone hydration to dehydration of backbone hydrogen bonds triggered by hydrophobic collapse translates at the ensemble folding-kinetics level into a commitment of the chain to fold as the folding reaction progresses beyond the transition state...

Ghosh, T., Grade, S. and Garcia, A.E. (2003) Role of Backbone Hydration and Salt-Bridge Formation in Stability of Alpha-Helix in Solution. Biophys. J., 85, 3187-3193. 

The slightly galactosylated mannans are essentially linear polymers. As a result of their cellulose-like (1 4)-/3-D-mannan backbone, they tend towards self-association, insolubility, and crystallinity. Crystallographic study of C. spectabilis seed GaM [180] with a Man Gal ratio 2.65 1 suggested an orthorhombic unit cell with lattice constants of a = 9.12, b = 25.63, and c = 10.28 the dimension b was shown to be sensitive to the degree of galactose substitution and the hydration conditions [180 and references therein, [191]]. 

It has been suggested by Ikegami (1968) that the carboxylate groups of a polyacrylate chain are each surrounded by a primary local sphere of oriented water molecules, and that the polyacrylate chain itself is surrounded by a secondary sheath of water molecules. This secondary sheath is maintained as a result of the cooperative action of the charged functional groups on the backbone of the molecule. The monovalent ions Li", Na and are able to penetrate only this secondary hydration sheath, and thereby form a solvent-separated ion-pair, rather than a contact ion-pair. Divalent ions, such as Mg " or Ba +, cause a much greater disruption to the secondary hydration sheath. 

Ion exchangers are polymer electrolytes prepared a priori as insoluble solids (salts, acids, bases hydrated, possibly gel-Uke). Their polymer backbone is three-dimensional. Many are polyvinyl compounds (substituted polyethylenes) having the general formula [-CH2-CXH-] , where different substituents X lead to rather different products ... 

Thomas, S. T., Loladze, V. V., and Makhatadze, G. I. (2001). Hydration of the peptide backbone largely defines the thermodynamic propensity scale of residues at the i position of the c-capping box of a helices. Proc. Natl. Acad. Sci. USA 98, 10670-10675. 

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