MOLECULAR REPLACEMENT STUDY ON FORM-B MONOCLINIC CRYSTAL OF INSULIN

The form-B monoclinic insulin crystal was obtained from the sodium cit rate buffer with 1% zinc chloride, keeping phenolic content between 0. 76% and 1.25%. Its space group is P2(1), cell constants are: a=4.924nm , b-6.094nm, c=4.818nm, beta=95.8 degrees. There are 6 insulin molecul es which form a hexamer. The initial phase was obtained by Lsing rotat ion function program of X-PLOR program package and molecular packing p rogram of our laboratory. The molecular model was chosen from 4 zinc b ovine insulin hexamer. After the preliminary refinement by using the m acromolecular rigid body refinement technique, the molecular model was further refined and adjusted by using the energy-minimizing stereoche mically restrained least-squared refinement on the difference Fourier maps, The final R-factor is 22.4% at 0.3 nm resolution, the r.m.s. dev iations from standard bond length and bond angle are 0.0022 nm and 4.7 degrees, respectively.