Protein crystallization driving force

For the electron transfer reactions to amieyanin from the 0-quinol, 0-semiquinone and N-semiquinone, Fej is the slowest step in the overall reaction (Bishop and Davidson, 1998). The rates of these reactions vary predictably with driving force (i.e. the redox potential difference between the reactants) (Figure 9). Independent analyses by Eqs. 4 and 5 of the AG and temperature dependencies of the electron transfer rate of each of these reactions (Brooks and Davidson, 1994ab Bishop and Davidson, 1998) yielded identical values of k and H b, and predicted the electron transfer distance that is seen in the crystal structure. Furthermore, the rates of each of these reactions were relatively insensitive to pH and buffer composition (Table 1), as would be expected for an electron transfer reaction occurring within a protein complex. 

In a saturated solution, including one saturated with respect to protein, two states exist in equilibrium the solid phase and one consisting of molecules free in solution. At saturation, no net increase in the proportion of solid phase can accrue, since it would be counterbalanced by an equivalent dissolution. Thus crystals do not grow from a saturated solution. The system must be in a nonequilibrium, or supersaturated state to provide the thermodynamic driving force for crystallization. 

Although one can have a broad picture of how Type A function comes about, the detailed kinetics and thermodynamics still present unsolved problems. The planar, hydrophobic, aromatic face presented by all the protein folds that have Type A function suggests that the driving force is hydrophobic and that therefore Type A CBDs should bind preferentially to hydrophobic faces of the polysaccharide crystal. Indeed, with gold-labelled CBM 1 and CBM 3 binding to cellulose lo, (triclinic) crystals of Valonia ventricosa, electron microscopy reveals just that - preferential binding to the (110) face of the crystal. 

DRIVING FORCE OF PROTEIN CRYSTALLIZATION THERMODYNAMICAL ASPECTS... 

From the perspective of thermodynamics and experimental kinetics, the driving force of crystallization is the difference of the chemical potential (A/r) of the protein molecule in solution and in the crystal ... 

When a medical device is in contact with body fluid such as blood, the first thing that occurs on the surface is protein adsorption [96-98]. Proteins in solution trying to minimize the total surface energy is the thermodynamic driving force of protein adsorption on solid surfaces. In blood contact protein adsorption is believed to be the initial event in thrombus formation [99-101], calcification [102-104], and biofilm attachment [105-107], which leads to the failure of implanted devices. Therefore, protein-reducing surface modifications of polyurethane biomaterials have been applied to improve the service life of implants. Previous studies of protein adsorption have focused on adsorption of albumin, IgG, and Fg, which are the predominant three proteins in blood plasma. Surface protein adsorption can be quantitated by several methods such as quartz crystal microbalance (QCM) [108-112], surface plasmon resonance (SPR) [113-118], and iodonization radiolabeling [78,119-125]. 

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