Relative affinities in solution of the RS20, A13L, V11L, V11F, and R16L peptides in the presence of calcium. The ratio of CaM, peptide1, peptide2, and CaCl2 was 1:1.5:1.5:5 in competition reactions. The relative intensities of CaM–peptide–Ca4 complexes at the 8+ charge-state were used for calculation. The values are the mean of three repeat experiments ± their standard deviation.