• Decanniere, Klaas
• Sleutel, Mike
• Wyns, Lode
• Willaert, Ronnie
• Maes, Dominique
• Vanhee, Celine
• Weerdt, Cécile Van De

Abstract

ABSTRACT: In the protein crystallization process, a growth unit has two possible molecular pathways it can follow from solution <br/>to the crystal bulk, namely, the process of direct incorporation from solution or the process of surface diffusion preceded by surface <br/>adsorption. We use real time in situ atomic force microscopy to monitor the molecular processes that govern the crystallization of <br/>the protein triosephosphate isomerase. With this technique, we study the step edge dynamics on a molecular scale. We conclude that <br/>step reorganization as a result of line diffusion has a negligible effect on step dynamics. Therefore, step displacements are attributed <br/>to the exchange of growth units with the surrounding phases, i.e., the terrace and the solution. Triosephosphate isomerase (TIM) <br/>tetramers are identified to be the dominating growth units. From the statistics of molecular attachment and detachment from the <br/>step, we conclude that the incorporation of growth units occurs through surface diffusion. Additionally, in the tested supersaturation <br/>range, normal growth is dominated by the two-dimensional nucleation of triangular islands. The step edges of these islands have <br/>equal step formation energy.

Topics

• impedance spectroscopy
• surface
• phase
• atomic force microscopy
• two-dimensional
• crystallization