Skip to main content
. Author manuscript; available in PMC: 2011 Aug 1.
Published in final edited form as: J Am Soc Mass Spectrom. 2010 Apr 24;21(8):1432–1445. doi: 10.1016/j.jasms.2010.04.004

Figure 3.

Figure 3

Enrichment of Azide-DSG cross-linked Ac-myelin peptides by chemical conjugation. A–C) Cross-linked products of Ac-myelin prior to enrichment: A) structural illustration of cross-linked peptides, R represents either an additional peptide for inter-linked or a hydroxyl group for a dead-end modified Ac-myelin peptides; MS spectra of B) inter-link (observed: [M+6H]6+ 467.07, [M+5H]5+ 560.29, [M+4H]4+ 700.11; theoretical: [M+6H]6+ 467.07, [M+5H]5+ 560.29, [M+4H]4+ 700.11) and C) dead-end (observed: [M+3H]3+ 508.26; theoretical: [M+3H]3+ 508.25) modified Ac-myelin. D–I) Cross-linked products of Ac-myelin after copper catalyzed click chemistry (D–F), and affinity purification/TFA cleavage (H–I): D) structural illustration of conjugated products after click chemistry; MS spectra of E) inter-linked (observed: [M+6H]6+ 594.48, [M+5H]5+ 713.18, [M+4H]4+ 891.21; theoretical: [M+6H]6+ 594.47, [M+5H]5+ 713.16, [M+4H]4+ 891.20;) and F) dead-end (observed: [M+3H]3+ 763.06; theoretical: [M+3H]3+ 763.05) products; G) structural illustration of final cross-linked products after affinity purification and TFA cleavage; MS spectra of H) inter-linked (observed: [M+6H]6+ 490.28, [M+5H]5+ 588.13, [M+4H]4+ 734.92; theoretical: [M+6H]6+ 490.26, [M+5H]5+ 588.11, [M+4H]4+ 734.88;) and I) dead-end (observed: [M+3H]3+ 554.65; theoretical: [M+3H]3+ 554.62) modified peptides. J–O) Cross-linked products of Ac-myelin after Staudinger ligation (J–L) and affinity purification/TFA cleavage (M–O): J) structural illustration of Staudinger ligation conjugates; MS spectra of E) inter-linked (observed: [M+6H]6+ 609.96, [M+5H]5+ 728.16, [M+4H]4+ 909.94; theoretical: [M+6H]6+ 609.96, [M+5H]5+ 728.15, [M+4H]4+ 909.94) and F) dead-end (observed: [M+3H]3+ 788.03; theoretical: [M+3H]3+ 788.03) products; M) structural illustration of the final cross-linked peptides after affinity purification and TFA cleavage; MS spectra of N) inter-linked (observed: [M+6H]6+ 537.11, [M+5H]5+ 644.33, [M+4H]4+ 805.15; theoretical: [M+6H]6+ 537.10, [M+5H]5+ 644.32, [M+4H]4+ 805.15) and O) dead-end (observed: [M+4H]4+ 486.49; theoretical: [M+4H]4+ 486.49) modified peptides. Note: E, F, H and I were acquired by QSTAR MS. The rest of MS spectra were acquired by LTQ-Orbitrap XL MS.