Proteins hydration environment

Since DNA is a highly charged polyanion, it is always hydrated by water molecules [in the dry state (under moist air) it contains 12 water molecules per nucleotide subunit]. In a cellular environment, proteins (histones in eukaryotic cells) are always attached to DNA or are at least surrounded by proteins as in viruses. In order to attack DNA, radicals have to be sufficiently mobile in such a partially hydrophilic environment. For this reason, typical lipid radicals confined to the membranes will not be discussed here, although one must keep in mind that small fragments of free-radical nature maybe able to escape the lipid environment and can, in principle, also react with DNA. 

In acid environments proteins may form protein-phosphate complexes of low solubility. The metaphosphates, which are less hydrated than the ortophosphates, form complexes that are less soluble than those with ortophosphates. This has been utilized for the modification of functional properties of protein concentrates and preparations, for separation of proteins in different food processing operations, and in treatment of protein-containing food plant effluents. 

Ion-specific effects on enzyme activity could be explained through their kosmo-tropicity (Hofmeister series) [80]. The Hofmeister series describes the strength of interaction of ions with water. Kosmotropic ions interact strongly with water and tend to produce ordered water structures, while chaotropic ions interact less with water than water itself The ability of ions to modify the water structure influences the protein hydration environment, and combined with direct interactions between ions and proteins, the protein structure can be affected. The suggested hypothesis is that kosmotropic anions and chaotropic cations stabilize enzymes, while chaotropic anions and kosmotropic cations destabilize them [80]. In a number of reports. 

In addition to an array of experimental methods, we also consider a more diverse assortment of polymeric systems than has been true in other chapters. Besides synthetic polymer solutions, we also consider aqueous protein solutions. The former polymers are well represented by the random coil model the latter are approximated by rigid ellipsoids or spheres. For random coils changes in the goodness of the solvent affects coil dimensions. For aqueous proteins the solvent-solute interaction results in various degrees of hydration, which also changes the size of the molecules. Hence the methods we discuss are all potential sources of information about these interactions between polymers and their solvent environments. 

Fig. 1.52. Schematic model of CPA action in protein solutions during freezing and freeze drying. (Fig. 10 from [1.36]). Top row Without CPA the hydrate water of the ovalbumin has migrated into the ice and the freed valences are exposed to the influence of the environment. Second row With CPA a part of the hydrate water of the proteins becomes replaced by CPA molecules. These, together with the remaining water molecules and the protein molecule, form a quasi (replacement) hydrate layer.

Hydration of phospholipid head groups is essential properties not only for stabilizing bilayer structures in an aqueous environment, but also for fusion or endocytosis of biological membranes including protein transfers [33-35]. Hydration or swelling behavior has only been studied by indirect methods such as X-ray diffraction [36], differential scanning calorimetry (DSC) [37], and H-NMR [38,39]. 

In protein solutions the water protons may be considered to reside in two different environments, i.e. the bulk water, and the hydration spheres of the protein molecules. If there is fast exchange of protons between these environments a single proton nuclear magnetic resonance will be observed, which corresponds to the average of the resonances in the different environments. Following McConnell (74) the observed longitudinal relaxation time is to a good approximation... 

One of the key arguments for neutral site binding is the presence of (3-turns and associated conformations. This puts certain restrains on the structure of the fibrous protein. For elastin, conformations with bound calcium are likely to be inside-out with respect to hydrophobicity. Such structures are acceptable only for molecules functioning in a non-polar environment (cell-membranes) but not for a hydrated elastin fibre. Binding of calcium would stabilize a rigid inside-out conformation437. ... 

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