Fragment collection, nucleic acid

Much useful information in crystal structure studies is often passed over by the authors themselves and has to be actively sought and recovered, either from the original publications or from databases. From the very early days, isolated bits of information were collected and used to construct tables of standard distances for various types of covalent bonds and of van der Waals radii for intermolecular contact distances, as collected in Pauling s influential book [41] and elsewhere, as well as standard dimensions for structural fragments that are important in biomolecular crystallography, such as the peptide moiety and the nucleic acid bases. 

A wide range of nucleic acids including RNAs, DNA fragments, plasmids, and oligonucleotides can be separated effectively by SEC on the basis of molecular size. Accordingly, it is possible to adopt SEC as an alternative to gel electrophoresis for analytical purposes. Furthermore, because the separated components in samples can be recovered easily and yet almost quantitatively by collection of column effluent, SEC should be superior to gel electrophoresis for preparative purposes. Consequently, SEC seems to be a useful technique for the separation and purification of nucleic acids. 

DNA and RNA chromatography require that the instrument, column and eluent be completely free of metal contamination. The effect, source, and control of metal contamination wiU be discussed. A high-quality oven must be used. The instrument normally includes the option of collecting the nucleic acid in a fragment collector for further research and processing. 

The components of the HPLC system are quite similar to what is used for standard ion chromatography with some important refinements in the general flow path, oven, and detector. In many cases, the nucleic acid that is separated is collected in a fragment collector to be used for further research. These instrument refinements are described in this section. 

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