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The activation volume, Δ V‡, of the solute incorporation process at the kink site of a glucose isomerase (GI) crystal was estimated using the pressure dependency of the step kinetic coefficient, βstep, and the three-dimensional nucleation rates J of GI crystals were analyzed using classical nucleation theory. Δ V‡ took a negative value. The sticking parameter, s, for the addition of a GI tetramer to a critical nucleus drastically increased with increasing pressure. This was probably due to the decrease in the activation energy needed for the addition of the GI tetramer. [ABSTRACT FROM AUTHOR]

Solubility of tetragonal lysozyme crystal was measured by using two different methods. The solubility measured by using growth rates of the crystal corresponded well to that measured by using change in the concentration of the supernatant of the solution. Our data also corresponded well to the data obtained by Sazaki et al. and Gray et al., while not to those obtained by Howard et al. and Rosenberger et al. The discrepancies are due to the difference in the principles of the methods. We also checked effects of different initial concentrations on the solubility. Contrary to previous reports, the solutions of the different initial concentrations did not reach equilibrium when their concentrations attained to a same value. [ABSTRACT FROM AUTHOR]

Abstract: Equilibrium temperatures, T e , of tetragonal hen egg-white lysozyme crystals were determined by in situ observation of apex regions formed by the (110), (11̄0) and (101) faces of the crystals. We could precisely measure T e within 60min, and with an error margin ±0.7°C or less. This is largely because growth and dissolution can be detected more rapidly at the apex than at the steps at the center of the crystal faces. [Copyright &y& Elsevier]

Abstract: We measured the temperature dependence of the solubility, C e , of triclinic lysozyme crystals on temperature at two pressures (0.1 and 100MPa) and five pHs (4.3, 4.4, 4.5, 4.6, and 4.7) by in situ observation of the morphological changes in the crystals. The solubility increased with increase in temperature and pressure. The enthalpies of dissolution (ΔH) decreased with increase in pressure when we used the same 50mM sodium acetate buffer solution (pH=4.5 at 0.1MPa). The effects of pH on solubility were somehow complicated. Although the solubilities at pH 4.7 did not differ from those at pH 4.5, those at pH 4.3 were significantly larger than those at pH 4.5. Since the pH of an acetate buffer is known to decrease from 4.71 to 4.52 at 98.1MPa and 25°C , the pH of the acetate buffer (pH 4.5 at 0.1MPa) decreased to pH∼4.3 as pressure increased to 100MPa. Thus, from the viewpoint of “constant pH”, ΔH increased with increase in pressure, since ΔH at pH 4.3 and 0.1MPa was smaller than that at 100MPa. This inconsistency is probably due to the change in the hydration state of the crystal and solution with decreasing pH (from 4.5 to 4.3). [Copyright &y& Elsevier]