| Abstract: | Ca2+ (1-5 mM) and lanthanide (20-250 microM) ions enhance the rate of polymerization of purified calf skin collagen (1.5 mg/ml) at pH 7.0 in the presence of 30mM-Tris/HCl and 0.2 M-NaCl. Both the nucleation phase and the growth phase of polymerization are accelerated. The activation energy of the growth phase, 239.3 +/- 24.3 kJ/mol (57.2 +/- 5.8 kcal/mol), is decreased to 145.6 +/- 9.6 kJ/mol (34.8 +/- 2.3 kcal/mol) by 5 mM-Ca2+ and to 75.3 +/- 4.6 kJ/mol (18.0 +/- 1.1 kcal/mol) by 25 microM-Sm3+. In contrast, the activation energy of the nucleation phase, 191.6 +/- 23.4 kJ/mol (45.8 +/- 5.6 kcal/mol), is only slightly decreased by Ca2+ or Sm3+. Collagen fibrils formed in the presence of Sm3+ are thinner than control fibrils, and more thermoresistant. |
