Biopolymers, hydration

In biopolymers hydrates may enforce special conformations141. For example, the harmone oxy tocine of the hypophysis conforms with all hydrophobic groups on one side1271 (Fig. 26) and the hydrophilic groups on the other12 (Fig. 27). Similarity the A-chain and the B-chain of insulin can be arranged to form a disc with a... 

A possible explanation of the hysteresis could be the non-equilibrium of the DNA hydration. In that case the value of hysteresis has to depend on the size of the experimental sample. However, such a dependence is not observed in the wide range of DNA film thicknesses (0.05-0.2 fmi) [14], [12]. Thus, hysteresis cannot be a macroscopic phenomenon and does reflect the molecular interaction of water and the biopolymer. 

D. Beglov and B. Roux. Dominant solvations effects from the primary shell of hydration Approximation for molecular dynamics simulations. Biopolymers, 35 171-178, 1994. 

Fig. 7. Besides direct interactions between functional groups of the biopolymer molecule itself there are also various kinds of interactions with water molecules. These hydrophilic and hydrophobic interactions are essential for stabilizing the native conformation of biopolymers. In the last few years some progress was made in elucidating the hydration of these molecules.

Protein crystals contain between 25 and 65 vol% water, which is essential for the crystallisation of these biopolymers. A typical value for the water content of protein crystals is 45% according to Matthews et al. l49,150). For this reason it is possible to study the arrangement of water molecules in the hydration-shell by protein-water and water-water interactions near the protein surface, if one can solve the structure of the crystal by X-ray or neutron diffraction to a sufficiently high resolution151 -153). 

The amount of water boimd to the proteins and polysaccharides depends primarily on the ratio of water to the biopolymer in the investigated system The two extreme cases are the dry biopolymer (water content tend to zero) and highly diluted aqueous solutions of the biopolymers. The dry biopolymer undergoes hydration if is exposed to the water vapor of increased vapor pressure. The extent of hydration can be determined y measuring the... 

The amount of hydrated biopolymer and of free water in the biopolymer-water system, the thermodynamic notion of partial specific volume has been introduced and is frequently determined. The relation to Vsp, the specific volume, is shown by the equation ... 

The stability of a colloid such as gelatin in water is determined by the electric charge and hydration. The addition of large amounts of electrolytes to colloids (biopolymers) causes... 

For many solubilized enzymes the greatest catalytic activity and/or changes in conformation are found at R < 12, namely, when the competition for the water in the system between surfactant head groups and biopolymers is strong. This emphasizes the importance of the hydration water surrounding the biopolymer on its reactivity and conformation [13], It has been reported that enzymes incorporated in the aqueous polar core of the reversed micelles are protected against denaturation and that the distribution of some proteins, such as chymotrypsine, ribonuclease, and cytochrome c, is well described by a Poisson distribution. The protein state and reactivity were found markedly different from those observed in bulk aqueous solution [178,179],... 

The hydration of propylene with sulfuric acid catalyst in high-temperature water was investigated using a flow reaction system.31 The major product is isopropanol. A biopolymer-metal complex, wool-supported palladium-iron complex (wool-Pd-Fe), has been found to be a highly active catalyst for the hydration of some alkenes to the corresponding alcohols. The yield is greatly affected by the Pd/Fe molar ratio in the wool-Pd-Fe complex catalyst and the catalyst can be reused several times without remarkable change in the catalytic activity.32... 

Grant, J. A., R. L. Williams, and H. A. Scheraga. 1990. Ab Initio Self-Consistent Field and Potential-Dependent Partial Equalization of Orbital Electronegativity Calculations of Hydration Properties of N-Acetyl-N -Methyl-Alanineamide. Biopolymers 30, 929-949. 

As stated previously, the total normal cytoplasmic free copper concentration is less than 10 18 M or less than one copper ion per cell. In thermodynamic terms, almost all hydrated copper ions are immediately and tightly coordinated by amino acids or biopolymers—peptides, proteins, and other species with free sulfur ligands. An excess of copper ions activates metallothionein synthesis for storage or removal of the excess. Copper chaperones mediate transfer of copper ions from extracellular or storage locations to their target proteins. Instability of copper ion concentrations in vivo results in various disease states. Three of these—FALS, Menkes, and Wilson s diseases—are described below. 

V.I. Gol danskii, Yu. F. Krupyanskii, and V. N. Fleurov, Rayleigh scattering of Mossbauer radiation (RSMR) data, hydration effects and glass-like dynamical model of biopolymers, Phys. Scr. 33, 527-540 (1986). 

In addition to the considerations mentioned above, it is rather important to keep in mind that a common aspect in determining the overall thermodynamic behaviour of a biopolymer solution/dispersion is the necessity of taking into account all of the component interactions. This includes the interactions of the biopolymer(s) with the water molecules, including both hydration (attraction) and dehydration (release), as well as the interactions amongst the water molecules themselves. 

MCC and carboxymethylcellulose sodium Avicel RC-581, RC-591, CL-611 FMC BioPolymer, Newark, Delaware, U.S.A. Viscosity regulator and modifier, thixotropic characteristics, heat and freeze-thaw stable, long shelf-life stability, lengthy hydration times eliminated, stable at pH range 4-11... 

If we calculated with the idealized co-operative model by the content of spectroscopic determined Op values the number Nei of H-bonded water molecules we would get — with different 1 molar salt solutions — the result of Fig. 11. The values Nei with salt additions depend strongly on the salt concentrations because of the disturbance of the big H-bonded system3At small concentrations the Nel-N0 numbers (7V0 association number in pure water) of structure-makers are in size of the order of Debye-Sack s or Azzam s calculations. They are of the same size of order as the secondary hydration numbers calculated by solubility measurements of organic substances in water (Chapter b) or as the hydration numbers of hydrophilic organic molecules (Chapter lld-e) or biopolymers (Chapter III). 

The large water contents of the organic PIOP-w phases indicate that biopolymers may contain hydrates too. This possibility is neglected by some authors. The positions of polar groups of the solute in relation to the size of the non-polar group is a further parameter which induces the big scale of aqueous-mixtures properties. 

The effect of salts on the biopolymers is clearly shown by the results of v. Hippel and Wong218 (Fig. 32). Salts with possibility of giving salt-in effects reduce Tm of ribonuclease. Salt-out effects giving ions like sulfate increase 7, they reduce the interactions of biopolymere bulk water. Using models, there are opinions that proteins are preferentially hydrated in the presence of SO4 , less with Cl- > Br- > CNS- > J-218. If this is true, weaker interaction with the bulk water should strengthen the stability of fixed hydrates on the polymers. 

He estimated a thickness of about 25 A of the bond water layer. This value is similar to the extension of the H-bonds in bulk water and would mean in a simple model that the biopolymer surface prevents the flickering of the defects in water. Garlid has found too that the bound water on mitochondria is a solvent of H-bonding organic molecules275. If his interpretation is correct, solutes in the secondary hydrate sphere would get more immobile. The time for transfer in cells is increased. —... 

Summarizing Chapter 3 we can conclude there are many indications that biopolymers may have different hydrations 1. Primary hydrate 1 -2 H20 per unit 2. bonded water 10-20 H20 3. secondary hydrate shells up to 50 H20 and 4. bulk water. The secondary hydrates may solve ions. 

Berisio, R., Vitagliano, L., Mazzarella, L., and Zagari, A. (2001). Crystal structure of a collagen-like polypeptide with repeating sequence Pro-Hyp-Gly at 1.4A resolution Implications for collagen hydration. Biopolymers 56, 8-13. 

---