| 1. |
- Andersson, Åke, et al.
(author)
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Structure of Proton-Bound Methionine and Tryptophan Dimers in the Gas Phase Investigated with IRMPD Spectroscopy and Quantum Chemical Calculations
- 2020
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In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 124:12, s. 2408-2415
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Journal article (peer-reviewed)abstract
- The structures of three proton-bound dimers (Met(2)H(+), MetTrpH(+), and Trp(2)H(+)) are investigated in the gas phase with infrared multiple photon disassociation (IRMPD) spectroscopy in combination with quantum chemical calculations. Their IRMPD spectra in the range of 600-1850 cm(-1) are obtained experimentally using an FT-ICR mass spectrometer and the CLIO free electron laser as an IR light source. The most abundant conformers are elucidated by comparing the IRMPD spectra with harmonic frequencies obtained at the B3LYPGD3BJ/6-311++G** level of theory. Discrepancies between the experimental and theoretical data in the region of 1500-1700 cm(-1) are attributed to the anharmonicity of the amino bending modes. We confirm the result of a previous IRMPD study that the structure of gas-phase Trp(2)H(+) is charge-solvated but find that there are more stable structures than originally reported (Feng, R.; Yin, H.; Kong, X. Rapid Commun. Mass Spectrom. 2016, 30, 24-28). In addition, gas-phase Met(2)H(+) and MetTrpH(+) have been revealed to have charge-solvated structures. For all three dimers, the most stable conformer is found to be of type A. The spectrum of Met(2)H(+), however, cannot be explained without some abundance of type B charge-solvated conformers as well as salt-bridged structures.
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| 2. |
- Kulyk, Kostiantyn, et al.
(author)
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High-energy collisions of protonated enantiopure amino acids with a chiral target gas
- 2015
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In: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 388, s. 59-64
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Journal article (peer-reviewed)abstract
- We have studied the fragmentation of the singly protonated L- and D-forms of enantiomerically pure phenylalanine (Phe), tryptophan (Trp), and methionine (Met) in high-energy collisions with chiral and achiral gas targets. (S)-(+)-2-butanol, racemic (+/-)-2-butanol, and argon were used as target gases. At center-of-mass frame collision energy of I key, it was found that all of the ions exhibit common fragmentation pathways which are independent of target chirality. For all projectile ions, the elimination of NH3 and H2O + CO were found to be the main reaction channels. The observed fragmentation patterns were dominated by statistically driven processes. The energy deposited into the ions was found to be sufficient to yield multiple fragment ions, which arise from decomposition via various competitive reaction pathways.
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| 3. |
- Kulyk, Kostiantyn, et al.
(author)
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Low-Energy Collisions of Protonated Enantiopure Amino Acids with Chiral Target Gases
- 2017
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In: Journal of the American Society for Mass Spectrometry. - : American Chemical Society (ACS). - 1044-0305 .- 1879-1123. ; 28:12, s. 2686-2691
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Journal article (peer-reviewed)abstract
- Here we report on the gas-phase interactions between protonated enantiopure amino acids (l- and d-enantiomers of Met, Phe, and Trp) and chiral target gases [(R)- and (S)-2-butanol, and (S)-1-phenylethanol] in 0.1-10.0 eV low-energy collisions. Two major processes are seen to occur over this collision energy regime, collision-induced dissociation and ion-molecule complex formation. Both processes were found to be independent of the stereo-chemical composition of the interacting ions and targets. These data shed light on the currently debated mechanisms of gas-phase chiral selectivity by demonstrating the inapplicability of the three-point model to these interactions, at least under single collision conditions.
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| 4. |
- Poline, Mathias, et al.
(author)
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Theoretical studies of infrared signatures of proton‐bound amino acid dimers with homochiral and heterochiral moieties
- 2020
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In: Chirality. - : Wiley. - 0899-0042 .- 1520-636X. ; 32:3, s. 359-369
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Journal article (peer-reviewed)abstract
- Proton‐bound homochiral and heterochiral dimers, X‐H+‐X, of five amino acids (X = Ser, Ala, Thr, Phe, and Arg) are investigated theoretically using quantum chemical density functional theory (DFT) calculations and molecular dynamics simulations with the aim to unveil diastereomer‐specific mid‐infrared (mid‐IR) absorption bands in the spectral range of 1000 to 1800 cm−1. The theoretical calculations performed in this work imply that all systems, except Ala2H+, have distinct mid‐IR absorption bands in homochiral and heterochiral configurations, which make them appropriate systems to be studied experimentally with mid‐IR spectroscopy. We show that intermolecular interaction with the side chain, in the form of hydrogen bonding or cation‐π interaction, is necessary for chiral effects to be present in the mid‐IR spectra of proton‐bound dimers of amino acids. We also report new conformers for Ala2H+, Thr2H+, Phe2H+, and Arg2H+, which were not found in earlier studies of these dimers.
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| 5. |
- Rebrov, Oleksii, 1988-
(author)
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Chiral Recognition by Means of Mass Spectrometry
- 2016
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Licentiate thesis (other academic/artistic)abstract
- This thesis is based on experimental studies of chiral ions in gas-phase. Electrospray ion source platform (Stockholm University) and commercially available Quadrupole Time-of-Flight mass spectrometer have been used in our studies.Using the advantages of tandem mass spectrometry, we have investigated interactions between protonated amino acids, namely phenylalanine (Phe), tryptophan (Trp), and methionine (Met) and Trp containing diastereomeric complexes with chiral 2-butanol, and achiral (argon) targets. In high energy collisions of 1 keV in the center-of-mass (c.o.m.) frame, collision induced dissociation (CID) via multiple channels independent on the chirality of either projectile or target was observed. The fragmentation via loss of H2O + CO and NH3 were found to be the main reaction channels for all studied amino acids. The energy gained in collisions was found to be sufficient to initiate fragmentation via various competitive reaction pathways.Chiral recognition in CID of the diastereomeric proton-bound complexes of tryptophan and 2-butanol as a function of collision energy was studied. Stereo dependent dissociation of complexes was observed, and for the first time an energy dependence has been measured for such a complex. Where possible, the comparison with previously reported results have been performed.
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| 6. |
- Rebrov, Oleksii, et al.
(author)
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Chirally sensitive collision induced dissociation of proton-bound diastereomeric complexes of tryptophan and 2-butanol
- 2017
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In: Chirality. - : Wiley. - 0899-0042 .- 1520-636X. ; 29:3-4, s. 115-119
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Journal article (peer-reviewed)abstract
- In this work we report the stereo-dependent collision-induced dissociation (CID) of proton-bound complexes of tryptophan and 2-butanol. The dissociation efficiency was measured as a function of collision energy in single collision mode. The homochiral complex was found to be less stable against CID than a heterochiral one. Additional gas dependence measurements were performed with diastereomeric complexes that confirm the findings.
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| 7. |
- Rebrov, Oleksii, 1988-
(author)
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Interactions of chiral ions and molecules in gas phase : Towards an understanding of chiral recognition mechanism
- 2018
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Doctoral thesis (other academic/artistic)abstract
- This thesis comprises the research related to interactions of enantiopure amino acids with chiral and achiral molecules in gas phase. The investigation of the mechanism responsible for chiral discrimination is of the special interest in this work. An electrospray ion source platform (Stockholm University), quadrupole time-of-flight mass spectrometer (University of Oslo) and Fourier-transform ion cyclotron resonance mass spectrometer in combination with OPO laser (Centre Laser Infrarouge d'Orsay (CLIO), France) have been used in our studies. Results of experiments on collisions of enantiopure amino acids, namely phenylalanine (Phe), tryptophan (Trp), and methionine (Met) with chiral and achiral targets in high and low energy regimes are presented. The fragmentation process is discussed in detail and compared with generally accepted models of amino acid fragmentation. Formation of proton bound diastereomeric adducts of amino acid and chiral alcohols (2-butanol and 1-phenylethanol) in single collisions is reported. The emphasis was given to reveal stereochemical effects in above mentioned reactions. The structure and vibrational properties of diastereomeric dimers of tryptophan studied using infrared multiphoton dissociation (IRMPD) spectrometry are presented. Structures and energies of most stable conformers obtained with quantum chemical calculations are described and compared to the experimental data. The stereo-dependent features are underlined and the chiral discrimination using IRMPD is addressed.
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| 8. |
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| 9. |
- Rebrov, Oleksii, 1988-, et al.
(author)
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Non-covalently Bonded Diastereomeric Adducts of Amino Acids and (S)-1-Phenylethanol in Low-energy Dissociative Collisions
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Other publication (other academic/artistic)abstract
- We have studied the collision induced dissociation reactions of proton-bound diastereomeric adducts of S-(-)-1-phenylethanol and enantiomers of three different amino acids (tryptophan, phenylalanine, methionine) with argon at a collision energy of 0.5 eV in the center-of-mass frame. At this energy, fragmentation into the alcohol and the protonated amino acid was the only observed product channel. Contrary to anticipation, the fragmentation was found to be insensitive to the chirality of the constituents. The results obtained from quantum chemical calculations show that the hetero-chiral adducts are more stable than the homo-chiral forms. However, given the experimental conditions in the ion source, it is likely that multiple conformers which lie close in energy to the ground-state configuration are populated, limiting the experimental sensitivity to observe the predicted differences.
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| 10. |
- Rebrov, Oleksii, et al.
(author)
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Non-covalently bonded diastereomeric adducts of amino acids and (S)-1-phenylethanol in low-energy dissociative collisions
- 2020
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In: Molecular Physics. - : Informa UK Limited. - 0026-8976 .- 1362-3028. ; 118:4
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Journal article (peer-reviewed)abstract
- We have studied the collision induced dissociation reactions of proton-bound diastereomeric adducts of S-1-phenylethanol and enantiomers of three different amino acids (tryptophan, phenylalanine, methionine). In all cases, the loss of S-1-phenylethanol from the adduct ion is the only observed process, and the relative abundance is found to be independent of the chirality of the amino acid. This is in contrast to earlier experiments on the dissociation of protonated tryptophan-2-butanol adducts, where chirality affected the results. Results obtained from quantum chemical computations support and provide a rationale for the experimental observations and highlight temperature as a possible factor of importance for the chiral effect in these types of systems. [GRAPHICS] .
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