The structure of vitamin B 12 - IV. The X-ray analysis of air-dried crystals of B 12

Abstract

Measurements were made during 1948-9 of all the intensities of hkl reflexions observable with chromium Koc X-radiation from air-dried crystals of vitamin B 12 . Calculations parallel with those of J. G. White were carried out on these data. The positions of the cobalt atoms in the crystal structure were found from three-dimensional Patterson series and the positions of 90 atoms of the B 12 molecule and 7 water molecules were derived through three successive approximations to the three-dimensional electron density distribution. The choice of atomic positions was checked against superposition maps derived from the original Patterson series, and assisted by comparisons with other B 12 derivatives. Minor differences appear between the positions derived here and in III; some of these may be real differences due to the state of dryness of the crystals.