Protein crystal growth--microgravity aspects.

Area of Science:

• Crystallography
• Materials Science
• Biophysics

Background:

• Protein crystal quality varies significantly between Earth- and microgravity-grown samples.
• Existing models fail to explain reduced crystal quality observed in some low-gravity experiments.

Purpose of the Study:

• To propose a new rationale explaining the variable effects of microgravity on protein crystal growth.
• To link microgravity-induced changes in transport to crystal defect formation.

Main Methods:

• Theoretical modeling of solute and impurity transport under varying gravity conditions.
• Analysis of intrinsic growth rate fluctuations and their connection to interfacial kinetics.
• Ground-based experiments using lysozyme solutions with controlled impurity levels to validate transport enhancement predictions.

Main Results:

• A direct correlation was established between growth rate fluctuations, step bunching, and crystal defect formation.
• The proposed model predicts that microgravity can either enhance or suppress transport, influencing crystal perfection.
• Ground experiments confirmed that forced flow in solutions can reduce kinetic fluctuations.

Conclusions:

• The structural perfection of protein crystals in microgravity depends on the interplay between solute/impurity transport and nonlinear growth kinetics.
• Understanding these transport dynamics is crucial for optimizing protein crystallization in space for superior structural quality.
• The findings provide a framework for predicting and controlling protein crystal quality in reduced gravity environments.