Table 1.

The five pairs of synthetic peptides, their chirality-reporting fragment ions and the corresponding chiral recognition factors.

(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.) R_chiral is distinct for each pairs of chirality reporters, R_L and R_D 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 R_chiral. With such adducts, a higher discrimination power is measured but with higher standard deviation.