1. Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta- 700 032, India, Saha Institute of Nuclear Physics, Crystallography and Molecular Biology Division, Sector 1, Block “AF”, Bidhan Nagar, Calcutta-700064, India, Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Madras- 600 025, India, and X-ray Crystallography Unit, University Sains, Penang, Malaysia