Highly Purified Glucose Isomerase Crystals Under Microgravity Conditions Grow as Fast as Those on the Ground Do

Abstract

Suppression of convection flows (solute transportation) and that of impurity incorporation into crystals seem to be the main reasons why the quality of protein crystals becomes better under microgravity conditions, whereas each precise mechanism has not been completely clarified yet. We tried to clarify the former reason by the in-situ observation of spiral growth hillocks on the {110} faces of highly purified glucose isomerase (GI) crystals under microgravity conditions and on the ground. Lateral growth rates Vlateral of a spiral hillock on the {110} face of a glucose isomerase crystal in situ under microgravity conditions and step velocities Vstep of the same configuration on the ground took similar values as far as the maximum values are compared each other. This similarity indicates there are less influences of the convection flows on the growth rates of protein crystals contrary to conventional expectations.