Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Poster: Heterogeneous Nucleation and Microstructure Formation (related to SYMF)

CPP 37.1: Poster

Wednesday, March 16, 2011, 17:00–19:00, P2

Crystallization of charged macromolecules — •Kai Kratzer and Axel Arnold — Institut für Computerphysik, Universität Stuttgart

The crystallization of charged macromolecules has a number of important applications in many fields, such as biology, pharmacology or materials design. For example, proteins are crystallized for purification or structure determination and colloidal crystals are promising candidates for photonic crystals. However, the crystallization of proteins or colloids is still more an art rather than a technique due to the poor understanding of the underlying physical mechanisms. To create defect-free crystals (or to prevent their growth), it is necessary to know the microscopic details of the onset of crystal growth, namely the nucleation. This process is described by the classical nucleation theory (CNT) as a balance of surface tension between liquid and crystal and the crystal's lower chemical potential. We performed computer simulations of the nucleation process to gain a better understanding of how charges carried by the macromolecules and the presence of neutralizing salt and precipitation agents influence nucleation. Since nucleation is a rare event, it is inaccessible to brute force computer simulations. We succeeded in this challenge by using the Forward Flux Sampling (FFS) method, which has only recently become available. We present first FFS results on systems of charged macromolecules in the presence of an explicit salt. This will help in developing a closed theory of protein and colloidal crystallization and thereby making targeted crystallization possible.