POLYMER NUCLEOTIDES, PEPTIDES, SACCHARIDES AND THE PDB. Wolfram Saenger, Institut fur Kristallographie, Freie Universitat Berlin Takusk.6, 14195 Berlin, FRG

In modern days, publication of the crystal or NMR structure of a biological macromolecule is linked with deposition of atomic parameters in the PDB. Problems arise with older data in the literature which were not deposited, in those days, with the data bank. Notorious are data from X-ray fiber diffraction analyses on polynucleotides, -peptides and -saccharides. Another problem may be faced if a crystal structure determination is only available at such low resolution that a complete chain tracing is not possible. Presented here are our own experiences with cellulose and photosystem I.