Figure 3.

Semi-quantitative analysis of LCM-procured samples by triple-quadrupole mass spectrometry. (A) One ng of ¹³C and ¹⁵N labeled reference peptide (APGLTQALNTK*) and 1 ng of unlabeled reference peptide (APGLTQALNTK) were added to all samples as a quality control (n = 72); (B) A total of 150 ng of maltose-binding protein (mbp) was added to all samples and the peak areas of three mbp unique peptides (mbp-Pa, DVGVDNAGAK; mbp-Pb, AGLTFLVDLIK; mbp-Pc, VNYGVTVLPTFK) were measured (n = 72). The peak area ratio of each mbp unique peptide to RP* is shown. RP, unlabeled reference peptide; RP*, labeled reference peptide.