W0367

Matthews Coefficient Probabilities: Improved Estimates for Unit Cell Contents. K. Kantardjieff^a and B. Rupp^b,c, ^aDept. of Chemistry and Biochemistry and W.M. Keck Foundation Center for Molecular Structure, California State Univ. Fullerton, Fullerton, CA 92834, ^bDept. of Biochemistry and Biophysics, Texas A&M Univ., College Station, TX 77843, ^cBiology and Biotechnology Research Program, L-448, Lawrence Livermore National Laboratory, Livermore, CA 94551.

Estimating the number of molecules in the crystallographic asymmetric unit is one of the first steps in a macromolecular structure determination. Based on a survey of 15,641 crystallographic Protein Data Bank entries, the distribution of V_M, the crystal volume per unit of protein molecular weight, known as Matthews coefficient, has been reanalyzed. The range of values and frequencies have changed in the 30 years since Matthews first analysis of protein crystal solvent content. In the statistical analysis, complexes of proteins and nucleic acids have been treated as a separate group. In addition, the V_M distribution for nucleic acid crystals has been examined for the first time. Observing that resolution is a significant discriminator of V_M, an improved estimator for the probabilities of the number of molecules in the crystallographic asymmetric unit has been implemented, using resolution as additional information.

LLNL is operated by the U. of California for the US DOE under contract W-7405-ENG-48. CMolS is supported by the California State University Program for Education and Research in Biotechnology.