Relationships between amino-acid side-chain volume at position 337, single channel conductance, and SCN– permeability. a Conductance as a function of side-chain volume. The solid lines represent a linear regression fitted to all data points (R2 0.39), while the dotted line is a similar fit excluding wild-type (R2 0.35). b PSCN/PCl as a function of side-chain volume, fitted by linear regression to all data points (R2 0.45). c Same as b but with polar side-chains (open symbols) and non-polar side-chains (filled symbols) fitted separately by linear regression (R2 0.62 for polar and 0.53 for non-polar side-chains). d Relationship between PSCN/PCl and conductance, fitted by linear regression (R2 0.20). In each panel, letters indicate the amino-acid present at position 337, i.e. F represents wild-type (represented by solid symbol in a, b and d). Conductance and PSCN/PCl values taken from Figs. 3c and 5b. Amino-acid side-chain volumes estimated according to Richards (1974)