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Boraneamines tend to have close N-H δ+ ‚‚‚ δ-H-B contacts as a result of the intermolecular interaction of the NH proton with the BH bond by a novel type of hydrogen bond (the dihydrogen bond). A CSD structural search provides characteristic metric data for the interaction: the H‚‚‚H distance is in the range 1.7-2.2 Å, and the N-H‚‚‚H group tends to be linear while B-H‚‚‚H tends to be bent. The reported X-ray structure of BH 3 NH 3 seemed to provide a singular exception in having bent N-H‚‚‚H and linear B-H‚‚‚H. Our neutron diffraction structure of BH 3 NH 3 now shows that the B and N atoms must be reversed from the assignment previously published. With the correct assignment we find the expected bent B-H‚‚‚H and linear N-H‚‚‚H arrangement in the closest intermolecular N-H‚‚‚H-B interaction (d HH ) 2.02 Å).

The Protein Data Bank is a computer-based archival file for macromolecular structures. The Bank stores in a uniform format atomic co-ordinates and partial bond connectivities, as derived from crystallographic studies. Text included in each data entry gives pertinent information for the structure at hand (e.g. species from which the molecule has been obtained, resolution of diffraction data, literature citations and specifications of secondary structure). In addition to atomic co-ordinates and connectivities, the Protein Data Bank stores structure factors and phases, although these latter data are not placed in any uniform format. Input of data to the Bank and general maintenance functions are carried out at Brookhaven National Laboratory. All data stored in the Bank are available on magnetic tape for public distribution, from Brookhaven (to laboratories in the Americas), Tokyo (Japan), and Cambridge (Europe and worldwide). A master file is maintained at Brookhaven and duplicate copies are stored in Cambridge and Tokyo. In the future, it is hoped to expand the scope of the Protein Data Bank to make available co-ordinates for standard structural types (e.g. a-helix, RNA double-stranded helix) and representative computer programs of utility in the study and interpretation of macromolecular structures.The Protein Data Bank' [1,2] was established in 1971 as a computer-based archival file for macromolecular structures. The purpose of the Bank is to collect, standardize, and distribute atomic co-ordinates and other data from crystallographic studies. As the number of solved protein and nucleic-acid structures has grown to the point where some lo7 characters are necessary to represent the co-ordinate information currently held, the need for such a computer-readable file has become very clear, and demands for the Bank's services have increased accordingly. The Protein Data Bank is one of several data base activities in the field of crystallography, e.g. the Bibliographic