Effects of temperature, pressure, and pH on the solubility of triclinic lysozyme crystals

✍ Scribed by Yoshihisa Suzuki; Emi Konda; Hironori Hondoh; Katsuhiro Tamura

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 277 KB
• Volume: 318
• Category: Article
• ISSN: 0022-0248
• DOI: 10.1016/j.jcrysgro.2010.11.107

✦ Synopsis

We measured the temperature dependence of the solubility, C e , of triclinic lysozyme crystals on temperature at two pressures (0.1 and 100 MPa) 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 (DH) decreased with increase in pressure when we used the same 50 mM sodium acetate buffer solution (pH ¼4.5 at 0.1 MPa). 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 98.1 MPa and 25 1C [22], the pH of the acetate buffer (pH 4.5 at 0.1 MPa) decreased to pH $ 4.3 as pressure increased to 100 MPa. Thus, from the viewpoint of ''constant pH'', DH increased with increase in pressure, since DH at pH 4.3 and 0.1 MPa was smaller than that at 100 MPa. 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).