Consequences of Sequential Ca²⁺ Occupancy for the Structure and Dynamics of Calbindin_D9K: Computational Simulations and Comparison to Experimental Determinations in Solution (10, 309, (1993))

Abstract

Due to the slow convergence of the atomic rms fluctuations with the length of time for which they are calculated, the entropic contribution to the cooperativity of Ca²⁺ binding to calbindin_D9k, discussed on pp. 329–330, has to be evaluated for a longer interval than used for the rms values given in Table 5. The value of ΔΔG obtained from the rms fluctuations given in Table 5 is about 0.5 Kcal/mole. For the longer interval of 179 ps the average rms values calculated for CAB₀, CAB₁ and CAB₂ (see original article for definitions) are 4.5 Å, 0.9 Å and 0.8 Å, respectively. The value of ΔΔG calculated from these rms fluctuations according to the equations in the the original article is about 1.0 Kcal/mole. It is noted that these trends do not affect the interpretation or conclusions regarding the significance of the configurational entropy for the cooperativity of binding in calbindin_D9k.