CRYSTAL-STRUCTURE OF FORM-B MONOCLINIC CRYSTAL OF INSULIN

The form B monoclinic insulin crystal was crystallized in space group P2(1), with cell parameters a = 4.924 nm, b = 6.094 nm, c = 4.818 nm, beta = 95.8 degrees. There is one hexamer insulin molecule per asymmet ric unit. The structure determination was carried out by molecular rep lacement techniques and refined with 0.25 nm data to a crystallographi c R factor of 20.6%. The root mean-square deviation from ideal bond le ngths and ideal angles is 0.002 0 nm and 3.858 degrees respectively. E ach hexamer has 3-fold noncrystallographic symmetry and all six insuli n molecules have helical conformation from B1 to B20. Six phenol molec ules were found bonding specifically to each molecule, evidently stabi lizing the helical conformation.