Hydration, proteins

Z1, P Cieplak, W D Cornell and P A Kolhnan 1993. A Well-Behaved Electrostatic Potential Based 5thod for Deriving Atomic Charges - The RESP Model. Journal of Physical Chemistry 97 10269-10280. sen H C, J P M Postma, W F van Gunsteren and J Hermans 1981. Interaction Models for Water in lation to Protein Hydration. In Pullman B (Editor). Intermolecular Forces. Dordrecht, Reidel, I. 331-342. 

HJC Berendsen, JPM Postma, WE van Gunsteren, J Hermans. Interaction models of water m relation to protein hydration. In B Pullman, ed. Intermolecular Eorces. Dordrecht, Holland Reidel, 1981, pp 331-341. 

The information obtained from X-ray measurements on the arrangement of the water molecules naturally depends very much on the resolution and state of refinement of the crystal structure investigated. For detailed information on the organization of water molecules in the protein hydration shell at the surface and on the bulk water in the crystals a 1,2 to 1,8 A resolution range is necessary 153>. 

Bone S, Pethig R (1985) Dielectric studies of protein hydration and hydration-induced flexibility. JMol Biol 181 323-326. 

Differential hydration of proteins has been little exploited as a selectivity factor in ion exchange, but it is simple to evaluate and can produce useful results. This technique relies on the preferential exclusion of certain solutes from protein surfaces to produce an exclusionary effect and favor their interaction with the column. Protein hydration is generally proportional to protein size and solubility. Among proteins of similar size, this predicts that retention will increase with protein solubility. Among proteins of similar solubility, retention increases with protein size.16... 

Initial screening conditions are suggested in Table 6.1. Multiple pH values are included because mobile-phase pH can significantly affect retention. Major selectivity shifts such as transpositions in elution order are fairly common changes in resolution are much more so.2,14-16 Changes in retention due to pH variation relate to protein hydration. Proteins are minimally charged at their isoelectric points (pis). This means that they carry the minimum of electrostricted hydration water. Both protein surface hydrophobicity and HIC retention should therefore reach their maximum at a protein s pi.6 As pH is either increased or... 

Membranes such as NC supported on glass may be more applicable for protein microarrays than glass substrates. Supported charged nylon membranes for microarrays are currently entering the marketplace as well. The essential ingredient for protein is water. Protein hydration reduces the likelihood for surface denaturation. Hydrophilic membranes allow proteins to... 

Rupley, J.A., Careri, G. (1991). Protein hydration and function. Advances in Protein Chemistry, 41,37-172. 

In sharp contrast to the large number of experimental and computer simulation studies reported in literature, there have been relatively few analytical or model dependent studies on the dynamics of protein hydration layer. A simple phenomenological model, proposed earlier by Nandi and Bagchi [4] explains the observed slow relaxation in the hydration layer in terms of a dynamic equilibrium between the bound and the free states of water molecules within the layer. The slow time scale is the inverse of the rate of bound to free transition. In this model, the transition between the free and bound states occurs by rotation. Recently Mukherjee and Bagchi [14] have numerically solved the space dependent reaction-diffusion model to obtain the probability distribution and the time dependent mean-square displacement (MSD). The model predicts a transition from sub-diffusive to super-diffusive translational behaviour, before it attains a diffusive nature in the long time. However, a microscopic theory of hydration layer dynamics is yet to be fully developed. 

Neurath. H. Protein Science, Cambridge University Press, New York, NY, 1991. Otring, G., E. Liepinsh, and K. Wuthrich Protein Hydration in Aqueous Solution, ... 

Table B5.1.1 Selected Tests of Protein Hydration Properties...

Solid-phase microextraction (SPME), volatile lipid analysis, 534-535 Solubility, protein hydration properties, 295 (table)... 

During ageing of the mix, interfacial milk protein hydration also increases simultaneously with protein desorption from the fat globules. The water content of the isolated cream layers after centrifugation of ice cream mix can be analyzed by Karl Fischer titration. From such analyses, interfacial protein hydration can be calculated (Figure 13). 

The voluminosity or hydration of interfacially bound protein may be calculated from the amount of water bound per gram of fat divided by the amount of protein bound per gram of fat. This corresponds to the volume of water per gram interfacial protein. Calculations show that emulsifiers facilitate interfacial protein hydration. This property is probably connected with their ability to desorb protein from the interface (Figure 14). 

For an example of structure analysis by X-ray scattering, see D. I. Svergun, S. Richard, M. H. Koch, Z. Sayers, S. Kuprin, and G. Zaccai, Protein hydration in solution experimental observation by X-ray and neutron scattering, Proc. Natl Acad. 3d. USA 95,2267-2272, 1998. 

S. N. Timasheff, Protein hydration, thermodynamic binding, and preferential hydration, Biochemistry 2002, 41, 13473-13482. 

Kunz, D. and Brassfield, T.S., Hydration of macromolecules. II. Effects of urea on protein hydration, Arch. Biochem. Biophys., 142, 660, 1971. 

Berendsen HJ, Postma JP, van Gunsteren WF, Hermans J (1981) Interaction models for water in relation to protein hydration. In Pullman B (ed) Intermolecular forces. D. Reidel, Dordrecht, pp 331-342... 

Dalvit C, Hommel U, Sensitivity-improved detection of protein hydration and its extension to the assignment of fast-exchanging resonances, J. Magn. Resort. Series B, 109 334-338, 1995. 

Molecular dynamics (MD) simulations [29-31], coupled with experimental observations, have played an important role in the understanding of protein hydration. They predicted that the dynamics of ordered water molecules in the surface layer is ultrafast, typically on the picosecond time scales. Most calculated residence times are shorter than experimental measurements reported before, in a range of sub-picosecond to 100 ps. Water molecules at the surface are very mobile and are in constant exchange with bulk water. For example, the trajectory study of myoglobin hydration revealed that among 294 hydration sites, the residence times at 284 sites (96.6% of surface water molecules) are less than lOOps [32]. Furthermore, the population time correlation functions... 

Femtosecond spectroscopy has an ideal temporal resolution for the study of ultrafast water motions from femtosecond to picosecond time scales [33-36]. Femtosecond solvation dynamics is sensitive to both time and length scales and can be a good probe for protein hydration dynamics [16, 37-50]. Recent femtosecond studies by an extrinsic labeling of a protein with a dye molecule showed certain ultrafast water motions [37-42]. This kind of labeling usually relies on hydrophobic interactions, and the probe is typically located in the hydrophobic crevice. The resulting dynamics mostly reflects bound water behavior. The recent success of incorporating a synthetic fluorescent amino acid into the protein showed another way to probe protein electrostatic interactions [43, 48]. 

With site-directed mutation and femtosecond-resolved fluorescence methods, we have used tryptophan as an excellent local molecular reporter for studies of a series of ultrafast protein dynamics, which include intraprotein electron transfer [64-68] and energy transfer [61, 69], as well as protein hydration dynamics [70-74]. As an optical probe, all these ultrafast measurements require no potential quenching of excited-state tryptophan by neighboring protein residues or peptide bonds on the picosecond time scale. However, it is known that tryptophan fluorescence is readily quenched by various amino acid residues [75] and peptide bonds [76-78]. Intraprotein electron transfer from excited indole moiety to nearby electrophilic residue(s) was proposed to be the quenching... 

Figure 46. A unified molecular mechanism of protein hydration dynamics and coupled water-protein fluctuations. The initial ultrafast dynamics in a few picoseconds (ii) represents local collective orientation or small translation motions, which mainly depend on local electrostatic interactions. On the longer time (12), the water networks undergo structural rearrangements in the layer, which are strongly coupled with both protein fluctuations and bulk-water dynamic exchange.

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