The crystallographic structure of the B800-850 peripheral light harvesting complex, an integral membrane pigment-protein complex, from the non-sulphur purple bacteria Rhodopseudomonas acidophila, strain 10050, has been determined to a resolution of 2.5 A (McDermott et al., 1995). This thesis outlines the changes made to the purification and crystallisation protocols which produced crystals which diffracted reproducibly to high resolution. In addition, microspectroscopy was utilised to determine the integrity of the complex in the crystal and to determine the effect of 'heavy atom soaking' procedures on the crystal order. The latter allowed the development of a soaking solution which maintained crystal order during heavy atom derivatisation trials. The LH structure is described and some initial interpretations of the implications that the structure has for the study of bacterial photosynthesis
