Table 4.

Comparison of predicted and observed retention times.

Column Number
	1	2	3	4	5	6	7	8	9	10	11
Amino Acid Substitution at Position Xa	Obs.b (min)	Pred 1c (min)	Pred 1 - Obs (min)	Pred 2d (min)	Pred 2 - Obs (min)	Pred 3e (min)	Pred 3 - Obs (min)	Pred 4f (min)	Pred 4 - Obs (min)	Pred 5g (min)	Pred 5 - Obs (min)
Trp	76.3	107.9	31.6	56.8	−19.5	76.8	0.5	59.6	−16.7	76.7	0.4
Phe	73.3	104.9	31.6	55.3	−18.0	73.8	0.5	57.3	−16.0	73.7	0.4
Leu	68.5	100.1	31.6	52.9	−15.6	69.0	0.5	53.5	−15.0	68.9	0.4
Ile	66.8	98.4	31.6	52.1	−14.7	67.3	0.5	52.0	−14.8	67.2	0.4
Met	57.5	89.1	31.6	47.4	−10.1	58.0	0.5	47.9	− 9.6	57.9	0.4
Tyr	55.2	86.8	31.6	46.3	− 8.9	55.7	0.5	44.9	−10.3	55.6	0.4
Val	56.3	87.9	31.6	46.8	− 9.5	6.8	0.5	45.3	−11.0	56.7	0.4
Pro	48.5	80.1	31.6	42.9	− 5.6	49.0	0.5	40.3	− 8.2	48.9	0.4
Cys	47.1	78.7	31.6	42.2	− 4.9	47.6	0.5	42.7	− 4.4	47.5	0.4
Ala	41.3	72.9	31.6	39.3	− 2.0	41.8	0.5	39.5	− 1.8	41.7	0.4
Glu	38.4	70.0	31.6	37.9	− 0.5	38.9	0.5	39.0	0.6	38.8	0.4
Thr	39.9	71.5	31.6	38.6	− 1.3	40.4	0.5	38.2	− 1.7	40.3	0.4
Arg	38.8	70.4	31.6	38.1	− 0.7	39.3	0.5	35.6	− 3.2	39.2	0.4
Asp	37.7	69.3	31.6	37.5	− 0.2	38.2	0.5	38.2	0.5	38.1	0.4
Gln	36.3	67.9	31.6	36.8	0.5	36.8	0.5	37.5	1.2	36.7	0.4
Gly	36.3	67.9	31.6	36.8	0.5	36.8	0.5	36.7	0.4	36.7	0.4
His	36.3	67.9	31.6	36.8	0.5	36.8	0.5	34.3	− 2.0	36.7	0.4
Ser	35.5	67.1	31.6	36.4	0.9	36.0	0.5	37.3	1.8	35.9	0.4
Lys	35.3	66.9	31.6	36.3	1.0	35.8	0.5	34.4	− 0.9	35.7	0.4
Asn	34.0	65.6	31.6	35.6	1.6	34.5	0.5	36.2	2.2	34.4	0.4

^aThe L-amino acid substitutions at position X in the peptide sequences shown in Table 1.

^bObserved retention times of the twenty peptides differing at position X of peptide 1 shown in Table 2.

^cPredicted peptide retention time (τ) using the C-terminal X-carboxyl coefficients for all residues in the peptide sequence (column 2) and the difference between predicted and observed (column 3).

^dτ using weighted C-terminal carboxyl coefficients (weighting factor 0.5) for all residues in the peptide sequence (column 4) and the difference in predicted and observed (column 5).

^eτ using the weighted C-terminal carboxyl coefficients for all residues except the C-terminal residue which uses the C-terminal X-carboxyl coefficients (column 6) and the difference in predicted and observed (column 7).

^fτ using experimentally derived internal coefficients (peptide 5, Table 3) for all residues in the sequence (column 8) and the difference in predicted and observed (column 9)

^gτ using the internal coefficients for all residues except the C-terminal residue which uses the C-terminal X-carboxyl coefficients (column 10) and the difference in predicted and observed (column 11).