Solution Properties of Synthetic Polypetides. VII. Approximate Expressions for Important Physical Quantities of Polypeptide Molecules

Abstract

Approximate expressions, which are amenable to straightforward numerical calculation, are derived from Nagai’s theory for such important molecular quantities of polypeptides in solution as helical content fN, number of helical sections gN, mean-square radius of gyration ‹S³›, and particle scattering function P(θ), subject to the condition that sqrt{σ}<<1,N⁻¹<<1, and Nsqrt{σ}>3. Here N denotes the degree of polymerization of the polypeptide molecule and σ the helix initiation parameter. The derived expressions are compared numerically with the exact ones for some typical cases of the parameters involved, and it is shown that they are accurate enough for practical purposes. A brief discussion is given on how each of them can be of use for characterizing polypeptides in dilute solution.