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Differentiation of Boc-protected alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry.
J Mass Spectrom. 2010 Jun; 45(6):651-63.JM

Abstract

Two new series of Boc-N-alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptides containing repeats of L-Ala-delta(5)-Caa/delta(5)-Caa-L-Ala and beta(3)-Caa-delta(5)-Caa/delta(5)-Caa-beta(3)-Caa (L-Ala = L-alanine, Caa = C-linked carbo amino acid derived from D-xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MS(n) spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc-group, and the side chain. The dipeptide positional isomers are differentiated by the collision-induced dissociation (CID) of the protonated peptides. The loss of 2-methylprop-1-ene is more pronounced for Boc-NH-L-Ala-delta-Caa-OCH(3) (1), whereas it is totally absent for its positional isomer Boc-NH-delta-Caa-L-Ala-OCH(3) (7), instead it shows significant loss of t-butanol. On the other hand, second isomeric pair shows significant loss of t-butanol and loss of acetone for Boc-NH-delta-Caa-beta-Caa-OCH(3) (18), whereas these are insignificant for its positional isomer Boc-NH-beta-Caa-delta-Caa-OCH(3) (13). The tetra- and hexapeptide positional isomers also show significant differences in MS(2) and MS(3) CID spectra. It is observed that 'b' ions are abundant when oxazolone structures are formed through five-membered cyclic transition state and cyclization process for larger 'b' ions led to its insignificant abundance. However, b(1)(+) ion is formed in case of delta,alpha-dipeptide that may have a six-membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di-, tetra-, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers.

Authors+Show Affiliations

National Centre for Mass Spectrometry, Indian Institute of Chemical Technology, Hyderabad 500 007, India.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

20527034

Citation

Raju, G, et al. "Differentiation of Boc-protected Alpha,delta-/delta,alpha- and Beta,delta-/delta,beta-hybrid Peptide Positional Isomers By Electrospray Ionization Tandem Mass Spectrometry." Journal of Mass Spectrometry : JMS, vol. 45, no. 6, 2010, pp. 651-63.
Raju G, Ramesh V, Srinivas R, et al. Differentiation of Boc-protected alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry. J Mass Spectrom. 2010;45(6):651-63.
Raju, G., Ramesh, V., Srinivas, R., Sharma, G. V., & Shoban Babu, B. (2010). Differentiation of Boc-protected alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry. Journal of Mass Spectrometry : JMS, 45(6), 651-63. https://doi.org/10.1002/jms.1756
Raju G, et al. Differentiation of Boc-protected Alpha,delta-/delta,alpha- and Beta,delta-/delta,beta-hybrid Peptide Positional Isomers By Electrospray Ionization Tandem Mass Spectrometry. J Mass Spectrom. 2010;45(6):651-63. PubMed PMID: 20527034.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Differentiation of Boc-protected alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry. AU - Raju,G, AU - Ramesh,V, AU - Srinivas,R, AU - Sharma,G V M, AU - Shoban Babu,B, PY - 2010/6/8/entrez PY - 2010/6/9/pubmed PY - 2010/8/25/medline SP - 651 EP - 63 JF - Journal of mass spectrometry : JMS JO - J Mass Spectrom VL - 45 IS - 6 N2 - Two new series of Boc-N-alpha,delta-/delta,alpha- and beta,delta-/delta,beta-hybrid peptides containing repeats of L-Ala-delta(5)-Caa/delta(5)-Caa-L-Ala and beta(3)-Caa-delta(5)-Caa/delta(5)-Caa-beta(3)-Caa (L-Ala = L-alanine, Caa = C-linked carbo amino acid derived from D-xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MS(n) spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc-group, and the side chain. The dipeptide positional isomers are differentiated by the collision-induced dissociation (CID) of the protonated peptides. The loss of 2-methylprop-1-ene is more pronounced for Boc-NH-L-Ala-delta-Caa-OCH(3) (1), whereas it is totally absent for its positional isomer Boc-NH-delta-Caa-L-Ala-OCH(3) (7), instead it shows significant loss of t-butanol. On the other hand, second isomeric pair shows significant loss of t-butanol and loss of acetone for Boc-NH-delta-Caa-beta-Caa-OCH(3) (18), whereas these are insignificant for its positional isomer Boc-NH-beta-Caa-delta-Caa-OCH(3) (13). The tetra- and hexapeptide positional isomers also show significant differences in MS(2) and MS(3) CID spectra. It is observed that 'b' ions are abundant when oxazolone structures are formed through five-membered cyclic transition state and cyclization process for larger 'b' ions led to its insignificant abundance. However, b(1)(+) ion is formed in case of delta,alpha-dipeptide that may have a six-membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di-, tetra-, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers. SN - 1096-9888 UR - https://www.unboundmedicine.com/medline/citation/20527034/Differentiation_of_Boc_protected_alphadelta_/deltaalpha__and_betadelta_/deltabeta_hybrid_peptide_positional_isomers_by_electrospray_ionization_tandem_mass_spectrometry_ L2 - https://doi.org/10.1002/jms.1756 DB - PRIME DP - Unbound Medicine ER -