Table 1.
(M+H)+M/Z (mono) | Peptide | Sequence | Chirality-reporting fragments | Ratio of chirality-reporting fragments (measured by peak intensity) | Rchiral=RD/RL |
---|---|---|---|---|---|
465.2 | N(l/d)WFa | Asn-Trp-Phe-NH2 | b3 and b2 | 1.28 ± 0.03 | 2.97 |
Asn-DTrp-Phe-NH2 | 3.78 ± 0.06 | ||||
641.3 | Y(l/d)AEFLa | Tyr-Ala-Glu-Phe-Leu-NH2 | b4 and y2 | 0.043 ± 0.002 | 2.51 |
Tyr-DAla-Glu-Phe-Leu-NH2 | 0.111 ± 0.002 | ||||
485.2 | G(l/d)FFD | Gly-Phe-Phe-Asp | Y2 and MH+H2O | 0.13 ± 0.02 | 1.78 |
Gly-DPhe-Phe-Asp | 0.23 ± 0.02 | ||||
599.3 | F(l/d)MRFa | Phe-Met-Arg-Phe-NH2 | b3 (or y3-NH3) and y3 (or c3) | 7.65 ± 0.18 | 1.14 |
Phe-DMet-Arg-Phe-NH2 | 8.7 ± 0.2 | ||||
657.3 | F(d/l)MRFa Cobalt adduct | [M−H++Co]+ | b3+Co and 615 | 0.30 ± 0.1 | 2.80 |
0.73 ± 0.09 | |||||
b3+Co and 612 | 0.10 ± 0.03 | 2.88 | |||
0.33 ± 0.05 | |||||
b3+Co and a3+Co | 0.26 ± 0.01 | 1.62 | |||
0.40 ± 0.03 | |||||
b3+Co and c3 (or y3) | 0.101 ± 0.008 | 1.60 | |||
0.16 ± 0.02 | |||||
409.2 | G(l/d)FAD | Gly-Phe-Ala-Asp | b3 and y2 | 1.00 ± 0.02 | 1.20 |
Gly- DPhe-Ala-Asp | 1.21 ± 0.01 | ||||
431.2 | G(d/l)FAD Sodium adduct | [M+Na]+ | c3+Na and y2-H2O | 7.6 ± 5.3 | 3.44 |
26 ± 12 | |||||
c3+Na and a3+Na | 2.02 ± 0.08 | 1.29 | |||
2.6 ± 0.1 | |||||
c3+Na and b3+Na | 1.9 ± 0.2 | 1.28 | |||
2.4 ± 0.3 |
Single letter codes are used for the amino acids, with a terminal “a” indicating an amidated C-terminus, and a small “l” or “d” denoting that the following residue is in the L- or the D-form.) Rchiral is distinct for each pairs of chirality reporters, RL and RD calculated by dividing the peak area of the former by the latter chirality reporters in the table. Enhanced discrimination power of this method on F(l/d)MRFa and G(l/d)FAD are realized via metal-complexed cations (cobalt adducts and sodium adducts respectively) instead of protonated peptides as precursors for fragmentation. A different set of product ions are found with metal adducts, which have different Rchiral. With such adducts, a higher discrimination power is measured but with higher standard deviation.