GCRIS

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Citation - WoS: 2
Citation - Scopus: 2
Gas Phase Fragmentation Behavior of Proline in Macrocyclic B7 Ions
(American Chemical Society, 2023) Taşoğlu, Çağdaş; Arslanoğlu, Alper; Yalçın, Talat
Thefragmentation characteristics of b (7) ionsproduced from proline-containing heptapeptides have been studiedin detail. The study has utilized the following C-terminally amidatedmodel peptides: PA(6), APA(5), A(2)PA(4), A(3)PA(3), A(4)PA(2), A(5)PA, A(6)P, PYAGFLV, PAGFLVY, PGFLVYA, PFLVYAG,PLVYAGF, PVYAGFL, YPAGFLV, YAPGFLV, YAGPFLV, YAGFPLV, YAGFLPV, YAGFLVP,PYAFLVG, PVLFYAG, A(2)PXA(3), and A(2)XPA(3) (where X = C, D, F, G, L, V, and Y, respectively). The resultshave shown that b (7) ions undergo head-to-tailcyclization and form a macrocyclic structure. Under the collision-induceddissociation (CID) condition, it generates nondirect sequence ionsregardless of the position of the proline and the neighboring aminoacid residues. This study highlights the unusual and unique fragmentationbehavior of proline-containing heptapeptides. Following the head-to-tailcyclization, the ring opens up and places the proline residue in theN-terminal position while forming a regular oxazolone form of b (2) ions for all peptide series. Then, the fragmentationreaction pathway is followed by the elimination of proline with itsC-terminal neighbor residue as an oxazolone (e.g., PXoxa) for all proline-containing peptide series.
Citation - WoS: 7
Citation - Scopus: 7
Investigation of Peptide Size, Residue Position, Neighbor Amino Acid and Side Chain Effect on Macrocyclization of B N (n = 5-7) Ions
(Elsevier Ltd., 2012) Taşoğlu, Çağdaş; Görgülü, Güvenç; Yalçın, Talat
A systematic study was carried out to examine the effects of the side chain, peptide size, residue position, and neighboring amino acid on the macrocyclization of b ions. The work utilized isomeric model peptides YAGFLV-NH 2, AGFLVY-NH 2, GFLVYA-NH 2, FLVYAG-NH 2, LVYAGF-NH 2, VYAGFL-NH 2, which all have the same amino acid sequence in cyclic form. The b 6 ions derived from all these isomeric peptides form the same macrocyclic structure due to the generation of the same amino acid sequence order upon cyclization. Hence, the MS/MS spectra and breakdown graphs of b 6 ions derived from these peptides are similar to each other. However, the relative intensities of the non-direct sequence ions in both the MS/MS spectra and breakdown graphs of the b 6 ions derived from FAYVGL-NH 2, GVYALF-NH 2 and VFYLAG-NH 2 show a different distribution from each other and the first series, even though they are all isomeric peptides. This could be due to the different amino acid sequence order in the cyclic forms of these peptides. It is clearly shown that the neighboring amino acid influences the selective opening of the macrocyclic form. Additionally, XYAGFLV-NH 2 and YAGXFLV-NH 2 (where X = C, D, E, H, K, M, N, P, Q, S, T, and W are amino acid residues) were also studied in order to examine the influence of the peptide size, amino acid side chain, and position on the ring formation and cleavage of macrocyclic b 5, b 6 and b 7 ions. The results have clearly shown that b 6 and b 7 ions have a higher tendency of macrocyclization compared to b 5 ions with the exception of QYAGFLV-NH 2. Additionally, it was observed that selective ring opening is also dependent on the size of the b ions and the position of the amino acid residue. From our study of the macrocyclic b 6 ions of our model peptides, the Q, W, K, and M residues were found to be more favorable eliminations when compared to C, D, E, H, N, P, S, and T. Based on the results, no preferential cleavage order can be specified depending on the nature of amino acid side chain.
Citation - WoS: 5
Citation - Scopus: 5
Non-Direct Sequence Ions in the Tandem Mass Spectrometry of Protonated Peptide Amides - an Energy-Resolved Study
(American Chemical Society, 2013) Harrison, Alex G.; Taşoğlu, Çağdaş; Yalçın, Talat
The fragmentation reactions of the MH+ ions of Leu-enkephalin amide and a variety of heptapeptide amides have been studied in detail as a function of collision energy using a QqToF beam type mass spectrometer. The initial fragmentation of the protonated amides involves primarily formation of bn ions, including significant loss of NH3 from the MH+ ions. Further fragmentation of these bn ions occurs following macrocyclization/ring opening leading in many cases to bn ions with permuted sequences and, thus, to formation of non-direct sequence ions. The importance of these non-direct sequence ions increases markedly with increasing collision energy, making peptide sequence determination difficult, if not impossible, at higher collision energies. [Figure not available: see fulltext.]

Chemistry / Kimya

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