Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 2Citation - Scopus: 2Gas Phase Fragmentation Behavior of Proline in Macrocyclic B7 Ions(American Chemical Society, 2023) Taşoğlu, Çağdaş; Arslanoğlu, Alper; Yalçın, TalatThefragmentation 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.Article Citation - WoS: 5Citation - Scopus: 5Non-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, TalatThe 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.]Article Citation - WoS: 1Citation - Scopus: 1Protonated Dipeptide Losses From B 5 and B 4 Ions of Side Chain Hydroxyl Group Containing Pentapeptides(American Chemical Society, 2013) Atik, Ahmet Emin; Yalçın, TalatIn this study, C-terminal protonated dipeptide eliminations were reported for both b 5 and b 4 ions of side chain hydroxyl group (-OH) containing pentapeptides. The study utilized the model C-terminal amidated pentapeptides having sequences of XGGFL and AXVYI, where X represents serine (S), threonine (T), glutamic acid (E), aspartic acid (D), or tyrosine (Y) residue. Upon low-energy collision-induced dissociation (CID) of XGGFL (where X = S, T, E, D, and Y) model peptide series, the ions at m/z 279 and 223 were observed as common fragments in all b 5 and b 4 ion (except b 4 ion of YGGFL) mass spectra, respectively. By contrast, peptides, namely SMeGGFL-NH2 and EOMeGGFL- NH2, did not show either the ion at m/z 279 or the ion at m/z 223. It is shown that the side chain hydroxyl group is required for the possible mechanism to take place that furnishes the protonated dipeptide loss from b 5 and b 4 ions. In addition, the ions at m/z 295 and 281 were detected as common fragments in all b 5 and b 4 ion (except b 4 ion of AYVYI) mass spectra, respectively, for AXVYI model peptide series. The MS4 experiments exhibited that the fragment ions at m/z 279, 223, 295, and 281 entirely reflect the same fragmentation behavior of [M + H]+ ion generated from commercial dipeptides FL-OH, GF-OH, YI-OH, and VY-OH. These novel eliminations reported here for b 5 and b 4 ions can be useful in assigning the correct and reliable peptide sequences for high-throughput proteomic studies. [Figure not available: see fulltext.]Article Citation - WoS: 22Citation - Scopus: 23A Systematic Study of Acidic Peptides for B-Type Sequence Scrambling(American Chemical Society, 2011) Atik, Ahmet Emin; Yalçın, TalatA systematic study was carried out to examine the effects of acidic amino acid residues and the position of the acidic group on the cyclization of b ions. The study utilized the model C-terminal amidated eptides AAAAAA, AXAAAAA, AAXAAAA, AAAXAAA, AAAAXAA, AAAAAXA, AAAAAAX, XXAAAAAA, AAXXAAAA, AAAAXXAA, and AAAAAAXX, where X is a glutamic acid (E) or aspartic acid (D) residue. The CID mass spectra of bn (where n=7 and 8) ions derived from XAAAAAA, AAAXAAA, AAAAAAX and XXAAAAAA, AAXXAAAA, AAAAXXAA, and AAAAAAXX exhibited very similar fragmentation patterns for both the glutamic and the aspartic acid peptide series. The CID mass spectra of MH+ derived from model peptides presented substantial direct and non-direct sequence bions. The results indicate that b ions produced from acidic peptides can also undergo head-to-tail cyclization, which is the reason for the formation of the non-direct sequence b ions. The bion spectra derived from the peptides became more complex as the number of acidic residues in the peptides increased. Side chains of glutamic and aspartic acid did not inhibit the cyclization of the b ions. Substantial water elimination was observed in all CID spectra of b7 and b8 ions. Finally, the preferential cleavage of glutamic or aspartic acid residues from macrocyclic structures of b ions was also investigated under various collision energy conditions.