Table I. List of identified non-glycopeptides, their calculated hydrophobicity values (ΔGoctw, kcal/mol), and IP-NPLC retention times from the RNase B and fetuin tryptic digest.
Sequences in italic letters are from RNase B; Glu0, Asp0, His+, Lys+, Arg+, N-T NH3+, and C-T COO− are used for calculation of the charged non-glycopeptides (pH 1.1) using MPExTotalizer (35, 37). A value of 4.1 kcal/mol was further added to the calculated value for peptide xiv of fetuin due to likely salt bridge formation of this peptide (36). A value of 2 kcal/mol was further added to the calculated values for peptides xxiv–xxv due to losses of NH3 at C-terminal, respectively (35, 38). The tryptic digest of RNase B and fetuin mixture was injected with 0.25% HCl in 80% ACN/20% H2O for IP-NPLC-MS. CamC, carboxyamidomethylcysteine.
| Peptide no. | Sequnece of identified non-glycopeptides | Calculated hydrophobicity values | IP-NPLC retention time (RT) | Error of RT |
|---|---|---|---|---|
| ΔGoctw, kcal/mol | min | % | ||
| i | (K)VWPR | −8.0 | 3.8 | 42.7 |
| ii | (R)AQFVPLPVSVSVEFAVAATDcamCIAK(E) | −8.5 | 4.2 | 36.4 |
| iii | (K)FER(Q) | −8.8 | 5.0 | 0.6 |
| iv | (R)YFK(I) | −8.9 | 4.3 | 3.5 |
| v | (K)QDGQFSVLFTK(B) | −10.1 | 5.1 | 5.8 |
| vi | (K)camCNLLAEK(Q) | −10.3 | 5.2 | 8.1 |
| vii | (R)LcamCPGR(I) | −10.4 | 5.5 | 5.2 |
| viii | (K)HIIVACEGNPYVPVHFDASV(−) | −10.7 | 5.8 | 2.9 |
| viv | R)VVHAVEVALATFNAESNGSYLQLVEISR(A) | −10.7 | 5.4 | 6.9 |
| x | (K)QYGFcamCK(G) | −10.9 | 5.5 | 1.7 |
| xi | (K)YPNcamCAYK(T) | −11.4 | 5.7 | 4.6 |
| xii | (K)HLPR(G) | −11.6 | 6.2 | 11.5 |
| xiii | (R)AHYDLR(H) | −11.7 | 6.2 | 11.5 |
| xiv | (−)IPLDPVAGYKEPAcamCDDPDTEQAALAAVDYINK(H) | −11.9 | 6.0 | 0.6 |
| xv | (K)ALGGEDVR(V) | −12.0 | 5.3 | 1.7 |
| xvi | (K)GSVIQK(A) | −12.2 | 5.9 | 3.5 |
| xvii | (K)NVACK(N) | −12.2 | 6.2 | 0.6 |
| xviii | (K)TPIVGQPSIPGGPVR(V) | −12.7 | 5.3 | 1.7 |
| xix | (K)camCDSSPDSAEDVR(K) | −13.3 | 6.7 | 3.5 |
| xx | (K)HTLNQIDSVK(V) | −13.6 | 6.6 | 0.6 |
| xxi | (R)ETGSSK(Y) | −13.8 | 6.9 | 0.6 |
| xxii | (K)TTQANK(H) | −14.0 | 7.0 | 1.7 |
| xxiii | (K)NGQTNcamCYQSYSTMSITDcamCR(E) | −14.1 | 7.0 | 0.0 |
| xxiv | (R)camCKPVNTFVHESLADVQAVcamCSQK(N) | −14.9 | 6.5 | 0.6 |
| xxv | (R)pyroQQTQHAVEGDcamCDIHVLK(Q) | −15.9 | 6.9 | 2.9 |
| xxvi | (K)camCDSSPDSAEDVRK(L) | −16.1 | 7.4 | 0.6 |
| xxvii | (R)QQTQHAVEGDcamCDIHVLK(Q) | −17.9 | 7.5 | 0.6 |
| xxviii | (R)HTFSGVASVESSSGEAFHVGK(T) | −18.4 | 7.1 | 0.6 |
| xxix | (R)QHMDSSTSAASSSNYcamCNQMMK(S) | −18.6 | 7.7 | 0.6 |