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| Bernhard Rupp - | |
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TB Structural Genomics Consortium, U. of California - LLNL, Livermore, CA 94551
Crystallization of proteins is a nontrivial task, and despite the substantial efforts in
robotic automation, crystallization screening is still largely based on trial-and error
sampling of a limited subset of suitable reagents and experimental parameters. From a
phenomenological viewpoint, crystallization is phase separation in a thermodynamically
metastable supersaturated system under the control of kinetic parameters, with the
favorable outcome being the formation of a crystal. Fulfillment of thermodynamic
criteria only implies that crystallization is possible, i.e. it is a necessary but not
sufficient condition for crystallization. Whether the thermodynamically possible outcome
is realized, depends on the kinetic parameters controlling the process. While the
thermodynamic parameters (classifiable into extensive ones like protein or reagent
concentrations, and intensive ones such as temperature or pH) are deceptively easy
controlled by the experimenter, we have only limited influence on (and knowledge about)
the pathway-dependent kinetic parameters such as equilibration rates, molecular
association, preassembly, nucleation and growth kinetics.
We will discuss basics of protein solubility to establish the foundation of solubility
diagrams and discuss different methods with respect to their pathways through the phase
diagrams - keeping in mind that these phase diagrams are more of playground for
imagination and conceptual aid than true phase diagrams in a physico-chemical sense.
Lawrence Livermore National Laboratory is operated by the University of California for
the United States Department of Energy under contract no. W-7405-ENG-48. Work funded
by NIH P50 GM62410 (TB Structural Genomics) center grant.
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