I. Equilibrium Sedimentation of Macromolecules in Density Gradients with Application to the Study of Deoxyribonucleic Acid. II. The Crystal Structure of N, N'-Dimethyl Malonamide

Citation

Meselson, Matthew Stanley (1957) I. Equilibrium Sedimentation of Macromolecules in Density Gradients with Application to the Study of Deoxyribonucleic Acid. II. The Crystal Structure of N, N'-Dimethyl Malonamide. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/5PJC-KZ44. https://resolver.caltech.edu/CaltechETD:etd-06102004-145206

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract in included in .pdf document. 1. A method is presented for the study of the molecular weight and composition of macromolecules by observing in the ultracentrifuge their equilibrium distribution in a density gradient. The macromolecular material is centrifuged to near equilibrium in a solution of a low molecular weight solute. Under these conditions, sedimentation of the low molecular weight solute results in a continuous increase of density along the direction of the centrifugal field. The macromolecules collect in a band where their effective density is the same as that of the solution. Analysis of the shape and position of such bands yields information regarding molecular weight and composition. By this method, a deoxyribonucleic acid sample from bacteriophage is shown to be monodisperse with molecular weight [...]. Bacteriophage DNA containing 5-bromouracil instead of thymine has been prepared and found to differ considerably in effective density from normal DNA. II. The crystal structure of N,N'-dimethyl malonamide has been determined by two-dimensional methods. A type of weighted density projection has been devised which is especially suited to the refinement of projections complicated by atomic overlap. The crystal is monoclinic with space group [...]. A network of N-H...0 hydrogen bonds ties molecules into extended sheets parallel to the [...] plane. Although the configuration and dimensions found for the amide group conform quite closely to previous findings for related compounds, there is some indication of an especially large double bond character for the [...] bond.

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