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Romanini M, Macovez R, Valenti S, Noor W, Tamarit JL. Dielectric Spectroscopy Studies of Conformational Relaxation Dynamics in Molecular Glass-Forming Liquids. Int J Mol Sci 2023; 24:17189. [PMID: 38139017 PMCID: PMC10743228 DOI: 10.3390/ijms242417189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 11/29/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
We review experimental results obtained with broadband dielectric spectroscopy concerning the relaxation times and activation energies of intramolecular conformational relaxation processes in small-molecule glass-formers. Such processes are due to the interconversion between different conformers of relatively flexible molecules, and generally involve conformational changes of flexible chain or ring moieties, or else the rigid rotation of planar groups, such as conjugated phenyl rings. Comparative analysis of molecules possessing the same (type of) functional group is carried out in order to test the possibility of assigning the dynamic conformational isomerism of given families of organic compounds to the motion of specific molecular subunits. These range from terminal halomethyl and acetyl/acetoxy groups to both rigid and flexible ring structures, such as the planar halobenzene cycles or the buckled saccharide and diazepine rings. A short section on polyesters provides a generalisation of these findings to synthetic macromolecules.
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Affiliation(s)
| | | | | | | | - Josep Lluís Tamarit
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Barcelona East School of Engineering (EEBE), Av. Eduard Maristany 10-14, E-08019 Barcelona, Spain; (M.R.); (R.M.); (S.V.); (W.N.)
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2
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Calderón JC, Herrera A, Heinemann FW, Langer J, Linden A, Chelouan A, Grasruck A, Añez R, Clark T, Dorta R. Stereochemical Stability of Planar-Chiral Benzazepine Tricyclics: Inversion Energies of P- and S-Alkene Ligands. J Org Chem 2023; 88:16144-16154. [PMID: 37944159 DOI: 10.1021/acs.joc.3c01447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Inversion barriers ΔG‡ for planar chiral phosphine-alkene and sulfonamide-alkene hybrid ligands based on phenyl-dibenz[b,f]azepine have been determined by density-functional theory calculations. Analysis of the structural and electronic characteristics of the minima and transition states explains the magnitudes of ΔG‡ and the geometrical changes during the inversion process. The steric repulsion caused by bulky substituents attached to the azepine nitrogen atom has a pronounced effect on the ΔG‡ value, explaining, inter alia, the stereochemical stability of the P- and S-alkene ligands when compared to the fluxional parent compound where X = H.
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Affiliation(s)
- Jacqueline C Calderón
- Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas, Venezuela
- Computer-Chemie-Centrum, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße. 25, 91052 Erlangen, Germany
| | - Alberto Herrera
- Anorganische und Allgemeine Chemie, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Frank W Heinemann
- Anorganische und Allgemeine Chemie, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Jens Langer
- Anorganische und Metallorganische Chemie, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Anthony Linden
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Ahmed Chelouan
- Anorganische und Allgemeine Chemie, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Alexander Grasruck
- Anorganische und Allgemeine Chemie, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Rafael Añez
- Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado 21827, Caracas, Venezuela
| | - Timothy Clark
- Computer-Chemie-Centrum, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstraße. 25, 91052 Erlangen, Germany
| | - Romano Dorta
- Anorganische und Allgemeine Chemie, Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
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3
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Valenti S, Del Barrio M, Negrier P, Romanini M, Macovez R, Tamarit JL. Correction to "Comparative Physical Study of Three Pharmaceutically Active Benzodiazepine Derivatives: Crystalline versus Amorphous State and Crystallization Tendency". Mol Pharm 2021; 18:3926-3927. [PMID: 34525808 PMCID: PMC8830214 DOI: 10.1021/acs.molpharmaceut.1c00654] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Low Temperature Dynamic Chromatography for the Separation of the Interconverting Conformational Enantiomers of the Benzodiazepines Clonazolam, Flubromazolam, Diclazepam and Flurazepam. Symmetry (Basel) 2021. [DOI: 10.3390/sym13061012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Benzodiazepines (BZDs) are an important class of psychoactive drugs with hypnotic-sedative, myorelaxant, anxiolytic and anticonvulsant properties due to interaction with the GABAa receptor in the central nervous system of mammals. BZDs are interesting both in clinical and forensic toxicology for their pharmacological characteristics and potential of abuse. The presence of a non-planar diazepine ring generates chiral conformational stereoisomers, even in the absence of stereogenic centers. A conformational enrichment of BZD at the binding sites has been reported in the literature, thus making interesting a stereodynamic screening of a wide range of BZDs. Herein, we report the investigation of three stereolabile 1,4-benzodiazepine included in the class of “designer benzodiazepines” (e.g., diclazepam, a chloro-derivative of diazepam, and two triazolo-benzodiazepines, flubromazolam and clonazolam) and a commercially available BZD known as flurazepam, in order to study the kinetic of the “ring-flip” process that allows two conformational enantiomers to interconvert at high rate at room temperature. A combination of low temperature enantioselective dynamic chromatography on chiral stationary phase and computer simulations of the experimental chromatograms allowed us to measure activation energies of enantiomerization (ΔG‡) lower than 18.5 kcal/mol. The differences between compounds have been correlated to the pattern of substitutions on the 1,4-benzodiazepinic core.
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Antipsychotic clozapine binding to alpha-2-macroglobulin protects interacting partners against oxidation and preserves the anti-proteinase activity of the protein. Int J Biol Macromol 2021; 183:502-512. [PMID: 33930446 DOI: 10.1016/j.ijbiomac.2021.04.155] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 04/23/2021] [Accepted: 04/24/2021] [Indexed: 12/20/2022]
Abstract
In this study, the interaction between clozapine, an atypical antipsychotic drug, and alpha-2-macroglobulin (α2M), a multipurpose anti-proteinase, was investigated under simulated (patho) physiological conditions using multiple spectroscopic techniques and molecular modeling. It was found that α2M binds clozapine with a moderate affinity (the binding constant of 0.9 × 105 M-1 at 37 °C). The preferable binding site for both clozapine's atropisomers was revealed to be a large pocket at the interface of C and D monomer subunits of the protein. Hydrogen bonds and the hydrophobic effect were proposed as dominant forces in complex formation. The binding of clozapine did not induce significant conformational change of the protein, as confirmed by virtually unaltered α2M secondary structure and anti-proteinase activity. However, both clozapine and α2M shielded each other from the deleterious influence of strong oxidants: sodium hypochlorite and 2,2'-azobis-2-methyl-propanimidamide dihydrochloride (AAPH). Moreover, clozapine in a concentration range that is usually targeted in the plasma during patients' treatment effectively protected the anti-proteinase activity of α2M under AAPH-induced free radical overproduction. Our results suggest that the cooperation between α2M and clozapine may be a path by which these two molecules synergistically protect neural tissue against injury caused by disturbed proteostasis or oxidative stress.
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Valenti S, Barrio M, Negrier P, Romanini M, Macovez R, Tamarit JL. Comparative Physical Study of Three Pharmaceutically Active Benzodiazepine Derivatives: Crystalline versus Amorphous State and Crystallization Tendency. Mol Pharm 2021; 18:1819-1832. [PMID: 33689364 PMCID: PMC8594866 DOI: 10.1021/acs.molpharmaceut.1c00081] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
![]()
Chemical derivatization and amorphization
are two possible strategies
to improve the solubility and bioavailability of drugs, which is a
key issue for the pharmaceutical industry. In this contribution, we
explore whether both strategies can be combined by studying how small
differences in the molecular structure of three related pharmaceutical
compounds affect their crystalline structure and melting point (Tm), the relaxation dynamics in the amorphous
phase, and the glass transition temperature (Tg), as well as the tendency toward recrystallization. Three
benzodiazepine derivatives of almost same molecular mass and structure
(Diazepam, Nordazepam and Tetrazepam) were chosen as model compounds.
Nordazepam is the only one that displays N–H···O
hydrogen bonds both in crystalline and amorphous phases, which leads
to a significantly higher Tm (by 70–80
K) and Tg (by 30–40 K) compared
to those of Tetrazepam and Diazepam (which display similar values
of characteristic temperatures). The relaxation dynamics in the amorphous
phase, as determined experimentally using broadband dielectric spectroscopy,
is dominated by a structural relaxation and a Johari–Goldstein
secondary relaxation, both of which scale with the reduced temperature T/Tg. The kinetic fragility
index is very low and virtually the same (mp ≈ 32) in all three compounds. Two more secondary relaxations
are observed in the glass state: the slower of the two has virtually
the same relaxation time and activation energy in all three compounds,
and is assigned to the inter-enantiomer conversion dynamics of the
flexible diazepine heterocycle between isoenergetic P and M conformations.
We tentatively assign the fastest secondary relaxation, present only
in Diazepam and Tetrazepam, to the rigid rotation of the fused diazepine–benzene
double ring relative to the six-membered carbon ring. Such motion
appears to be largely hindered in glassy Nordazepam, possibly due
to the presence of the hydrogen bonds. Supercooled liquid Tetrazepam
and Nordazepam are observed to crystallize into their stable crystalline
form with an Avrami exponent close to unity indicating unidimensional
growth with only sporadic nucleation, which allows a direct assessment
of the crystal growth rate. Despite the very similar growth mode,
the two derivatives exhibit very different kinetics for a fixed value
of the reduced temperature and thus of the structural relaxation time,
with Nordazepam displaying slower growth kinetics. Diazepam does not
instead display any tendency toward recrystallization over short periods
of time (even close to Tm). Both these
observations in three very similar diazepine derivatives provide direct
evidence that the kinetics of recrystallization of amorphous pharmaceuticals
is not a universal function, at least in the supercooled liquid phase,
of the structural or the conformational relaxation dynamics, and it
is not simply correlated with related parameters such as the kinetic
fragility or activation barrier of the structural relaxation. Only
the crystal growth rate, and not the nucleation rate, shows a correlation
with the presence or absence of hydrogen bonding.
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Affiliation(s)
- Sofia Valenti
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Maria Barrio
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Philippe Negrier
- Université Bordeaux, Laboratoire Ondes et Matière d'Aquitaine, UMR 5798, 351 Cours de la Libération, Talence F-33400, France
| | - Michela Romanini
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Roberto Macovez
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
| | - Josep-Lluis Tamarit
- Grup de Caracterització de Materials, Departament de Física and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, EEBE, Campus Diagonal-Besòs, Av. Eduard Maristany 10-14, Barcelona, Catalonia 08019, Spain
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Franzini R, Pierini M, Mazzanti A, Iazzetti A, Ciogli A, Villani C. Molecular Recognition of the HPLC Whelk-O1 Selector towards the Conformational Enantiomers of Nevirapine and Oxcarbazepine. Int J Mol Sci 2020; 22:ijms22010144. [PMID: 33375681 PMCID: PMC7796420 DOI: 10.3390/ijms22010144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/16/2020] [Accepted: 12/23/2020] [Indexed: 01/19/2023] Open
Abstract
The presence of stereogenic elements is a common feature in pharmaceutical compounds, and affording optically pure stereoisomers is a frequent issue in drug design. In this context, the study of the chiral molecular recognition mechanism fundamentally supports the understanding and optimization of chromatographic separations with chiral stationary phases. We investigated, with molecular docking, the interactions between the chiral HPLC selector Whelk-O1 and the stereoisomers of two bioactive compounds, the antiviral Nevirapine and the anticonvulsant Oxcarbazepine, both characterized by two stereolabile conformational enantiomers. The presence of fast-exchange enantiomers and the rate of the interconversion process were studied using low temperature enantioselective HPLC and VT-NMR with Whelk-O1 applied as chiral solvating agent. The values of the energetic barriers of interconversion indicate, for the single enantiomers of both compounds, half-lives sufficiently long enough to allow their separation only at critically sub-ambient temperatures. The chiral selector Whelk-O1 performed as a strongly selective discriminating agent both when applied as a chiral stationary phase (CSP) in HPLC and as CSA in NMR spectroscopy.
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Affiliation(s)
- Roberta Franzini
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
- Correspondence: (R.F.); (C.V.)
| | - Marco Pierini
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
| | - Andrea Mazzanti
- Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, V. Risorgimento 4, 40136 Bologna, Italy;
| | - Antonia Iazzetti
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
| | - Alessia Ciogli
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
| | - Claudio Villani
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
- Correspondence: (R.F.); (C.V.)
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8
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Testa B, Vistoli G, Pedretti A. Mechanisms and pharmaceutical consequences of processes of stereoisomerisation — A didactic excursion. Eur J Pharm Sci 2016; 88:101-23. [DOI: 10.1016/j.ejps.2016.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 04/02/2016] [Accepted: 04/05/2016] [Indexed: 11/29/2022]
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9
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Pertejo P, Corres N, Torroba T, García-Valverde M. Reversal of Diastereoselectivity in the Synthesis of Peptidomimetic 3-Carboxamide-1,4-benzodiazepin-5-ones. Org Lett 2015; 17:612-5. [DOI: 10.1021/ol503628r] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Pablo Pertejo
- Chemistry Department, Faculty
of Science, University of Burgos, 09001 Burgos, Spain
| | - Nazaret Corres
- Chemistry Department, Faculty
of Science, University of Burgos, 09001 Burgos, Spain
| | - Tomás Torroba
- Chemistry Department, Faculty
of Science, University of Burgos, 09001 Burgos, Spain
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10
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Sabia R, Ciogli A, Pierini M, Gasparrini F, Villani C. Dynamic high performance liquid chromatography on chiral stationary phases. Low temperature separation of the interconverting enantiomers of diazepam, flunitrazepam, prazepam and tetrazepam. J Chromatogr A 2014; 1363:144-9. [DOI: 10.1016/j.chroma.2014.07.097] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 07/25/2014] [Accepted: 07/28/2014] [Indexed: 10/24/2022]
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11
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Harper B, Miladi M, Solouki T. Loss of internal backbone carbonyls: additional evidence for sequence-scrambling in collision-induced dissociation of y-type ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1716-1729. [PMID: 25070583 DOI: 10.1007/s13361-014-0955-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 05/14/2014] [Accepted: 06/19/2014] [Indexed: 06/03/2023]
Abstract
It is shown that y-type ions, after losing C-terminal H2O or NH3, can lose an internal backbone carbonyl (CO) from different peptide positions and yield structurally different product fragment ions upon collision-induced dissociation (CID). Such CO losses from internal peptide backbones of y-fragment ions are not unique to a single peptide and were observed in four of five model peptides studied herein. Experimental details on examples of CO losses from y-type fragment ions for an isotopically labeled AAAAHAA-NH2 heptapeptide and des-acetylated-α-melanocyte-stimulating hormone (dα-MSH) (SYSMEHFRWGKPV-NH2) are reported. Results from isotope labeling, tandem mass spectrometry (MS(n)), and ion mobility-mass spectrometry (IM-MS) confirm that CO losses from different amino acids of m/z-isolated y-type ions yield structurally different ions. It is shown that losses of internal backbone carbonyls (as CID products of m/z-isolated y-type ions) are among intermediate steps towards formation of rearranged or permutated product fragment ions. Possible mechanisms for generation of the observed sequence-scrambled a-"like" ions, as intermediates in sequence-scrambling pathways of y-type ions, are proposed and discussed.
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Affiliation(s)
- Brett Harper
- Institute of Biomedical Studies, Baylor University, Waco, TX, 76798, USA
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12
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Jahangir S, Khan KM, Fabian WM. Absolute configuration of 1,5-diazepin-2-ones: A critical test case for density functional theory. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2014.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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13
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Ramig K. Stereodynamic properties of medium-ring benzo-fused nitrogenous heterocycles: benzodiazepines, benzazepines, benzazocines, and benzazonines. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.10.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Pérez-Torralba M, Claramunt RM, Angeles García M, López C, Torralba MC, Rosario Torres M, Alkorta I, Elguero J. Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring. Beilstein J Org Chem 2013; 9:2156-67. [PMID: 24204428 PMCID: PMC3817505 DOI: 10.3762/bjoc.9.253] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 09/24/2013] [Indexed: 12/22/2022] Open
Abstract
Two novel tetrafluorinated 1,5-benzodiazepinones were synthesized and their X-ray structures determined. 6,7,8,9-Tetrafluoro-4-methyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one crystallizes in the monoclinic P21/c space group and 6,7,8,9-tetrafluoro-1,4-dimethyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one in the triclinic P−1 space group. Density functional theory studies at the B3LYP/6-311++G(d,p) level were carried out on these compounds and on four non-fluorinated derivatives, allowing to calculate geometries, tautomeric energies and ring-inversion barriers, that were compared with the experimental results obtained by static and dynamic NMR in solution and in solid state.
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Affiliation(s)
- Marta Pérez-Torralba
- Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED, Paseo Senda del Rey 9, 28040-Madrid, Spain
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15
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Miladi M, Harper B, Solouki T. Evidence for sequence scrambling in collision-induced dissociation of y-type fragment ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:1755-1766. [PMID: 23982935 DOI: 10.1007/s13361-013-0714-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2013] [Revised: 06/19/2013] [Accepted: 06/28/2013] [Indexed: 06/02/2023]
Abstract
Sequence scrambling from y-type fragment ions has not been previously reported. In a study designed to probe structural variations among b-type fragment ions, it was noted that y fragment ions might also yield sequence-scrambled ions. In this study, we examined the possibility and extent of sequence-scrambled fragment ion generation from collision-induced dissociation (CID) of y-type ions from four peptides (all containing basic residues near the C-terminus) including: AAAAHAA-NH2 (where "A" denotes carbon thirteen ((13)C1) isotope on the alanine carbonyl group), des-acetylated-α-melanocyte (SYSMEHFRWGKPV-NH2), angiotensin II antipeptide (EGVYVHPV), and glu-fibrinopeptide b (EGVNDNEEGFFSAR). We investigated fragmentation patterns of 32 y-type fragment ions, including y fragment ions with different charge states (+1 to +3) and sizes (3 to 12 amino acids). Sequence-scrambled fragment ions were observed from ~50 % (16 out of 32) of the studied y-type ions. However, observed sequence-scrambled ions had low relative intensities from ~0.1 % to a maximum of ~12 %. We present and discuss potential mechanisms for generation of sequence-scrambled fragment ions. To the best of our knowledge, results on y fragment dissociation presented here provide the first experimental evidence for generation of sequence-scrambled fragments from CID of y ions through intermediate cyclic "b-type" ions.
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Affiliation(s)
- Mahsan Miladi
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, 76798, USA
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16
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Ramig K, Greer EM, Szalda DJ, Karimi S, Ko A, Boulos L, Gu J, Dvorkin N, Bhramdat H, Subramaniam G. NMR Spectroscopic and Computational Study of Conformational Isomerism in Substituted 2-Aryl-3H-1-benzazepines: Toward Isolable Atropisomeric Benzazepine Enantiomers. J Org Chem 2013; 78:8028-36. [DOI: 10.1021/jo4013089] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Keith Ramig
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - Edyta M. Greer
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - David J. Szalda
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - Sasan Karimi
- Department of Chemistry, Queensborough Community College of the City University of New York, 222-05 56th Avenue, Bayside, New York 11364, United States
| | - Allen Ko
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - Laura Boulos
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - Jiansan Gu
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - Nathan Dvorkin
- Department of Natural Sciences, Baruch College of the City University of New York,
17 Lexington Avenue, New York, New York 10010, United States
| | - Hema Bhramdat
- Department of Chemistry and Biochemistry, Queens College of the City University of New York,
65-30 Kissena Boulevard, Flushing, New York 11367, United States
| | - Gopal Subramaniam
- Department of Chemistry and Biochemistry, Queens College of the City University of New York,
65-30 Kissena Boulevard, Flushing, New York 11367, United States
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A hybrid method for estimation of molecular dynamics of diazepam-density functional theory combined with NMR and FT-IR spectroscopy. Int J Pharm 2011; 404:19-26. [DOI: 10.1016/j.ijpharm.2010.10.044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 10/25/2010] [Accepted: 10/26/2010] [Indexed: 11/23/2022]
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18
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Zong W, Liu R, Sun F, Zhang P, Xu Q. Influence of charge distribution on the discrepant MS/MS fragmentation of the native and oxidized FMRF: evidence for the mobile proton model. J Pept Sci 2010; 16:687-92. [DOI: 10.1002/psc.1286] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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19
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Hsu DC, Lam PCH, Slebodnick C, Carlier PR. Complete mapping of the stereochemical course of retentive deprotonation/alkylation of 1H-benzo[e][1,4]diazepin-2(3H)-ones. J Am Chem Soc 2009; 131:18168-76. [PMID: 19921816 DOI: 10.1021/ja907507j] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Enantiopure amino-acid derived 1H-benzo[e][1,4]diazepin-2(3H)-ones (BZDs) undergo highly retentive deprotonation/alkylation reactions. To confirm the role of stereolabile, axially chiral intermediates in these reactions and to determine the precise stereochemical course of deprotonation and alkylation, a new alanine-derived BZD (S)-1d was prepared. Because of slow diazepine ring inversion of the C3-alkylated derivatives of 1d, it proved possible to determine that electrophiles react at the concave face of the enolate derived from 1d. Furthermore, an enantiopure silyl enol ether derivative of (S)-1d was prepared and characterized by X-ray crystallography, confirming that deprotonation resulted in an (M)-configured axially chiral enolate. Activation parameters for diazepine ring inversion in the potassium enolate of 1d were determined experimentally and are well-matched by density functional calculations. Finally, the factors leading to concave-face alkylation of the enolate derived from 1d are analyzed based on calculated alkylation transition structures. Minimization of torsional effects at the BZD ring fusion and maximization of imine and amide resonance are proposed to favor concave-face alkylation.
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Affiliation(s)
- Danny C Hsu
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
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20
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Abstract
Chiral substances possess a unique architecture such that, despite sharing identical molecular formulas, atom-to-atom linkages, and bonding distances, they cannot be superimposed. Thus, in the environment of living systems, where specific structure-activity relationships may be required for effect (e.g., enzymes, receptors, transporters, and DNA), the physiochemical and biochemical properties of racemic mixtures and individual stereoisomers can differ significantly. In drug development, enantiomeric selection to maximize clinical effects or mitigate drug toxicity has yielded both success and failure. Further complicating genetic polymorphisms in drug disposition, stereoselective metabolism of chiral compounds can additionally influence pharmacokinetics, pharmacodynamics, and toxicity. Optically pure pharmaceuticals may undergo racemization in vivo, negating single enantiomer benefits or inducing unexpected effects. Appropriate chiral antidotes must be selected for therapeutic benefit and to minimize adverse events. Enantiomers may possess different carcinogenicity and teratogenicity. Environmental toxicology provides several examples in which compound bioaccumulation, persistence, and toxicity show chiral dependence. In forensic toxicology, chiral analysis has been applied to illicit drug preparations and biological specimens, with the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse and "doping" screens. Adrenergic agonists and antagonist, nonsteroidal anti-inflammatory agents, SSRIs, opioids, warfarin, valproate, thalidomide, retinoic acid, N-acetylcysteine, carnitine, penicillamine, leucovorin, glucarpidase, pesticides, polychlorinated biphenyls, phenylethylamines, and additional compounds will be discussed to illustrate important concepts in "chiral toxicology."
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Affiliation(s)
- Silas W Smith
- New York University School of Medicine, New York, New York 10016, USA.
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21
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Branca M, Alezra V, Kouklovsky C, Archirel P. Accurate conformation analysis in solution: NMR and DFT/PCM study of the S-3-(1-naphthoyl)-4-isopropyl-2,2-dimethyloxazolidin-5-one in CDCl3. Tetrahedron 2008. [DOI: 10.1016/j.tet.2007.12.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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22
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Lee YS, Pike VW, Hodoscek M. Identification of the Transition States in the Inversion of 1,4-Benzodiazepines with the Ab Initio Replica Path Method. J Phys Chem A 2008; 112:1604-11. [DOI: 10.1021/jp077738o] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yong-Sok Lee
- Center for Molecular Modeling, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Building 12A, Room 2049, Bethesda, Maryland 20892, Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3C 346A, 10 Center Drive, Bethesda, Maryland 20892, National Heart, Lung and Blood Institute, National Institutes of Health, DHHS, Bethesda, Maryland 20892, National Institute of Chemistry, Ljubljana, Slovenia
| | - Victor W. Pike
- Center for Molecular Modeling, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Building 12A, Room 2049, Bethesda, Maryland 20892, Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3C 346A, 10 Center Drive, Bethesda, Maryland 20892, National Heart, Lung and Blood Institute, National Institutes of Health, DHHS, Bethesda, Maryland 20892, National Institute of Chemistry, Ljubljana, Slovenia
| | - Milan Hodoscek
- Center for Molecular Modeling, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Building 12A, Room 2049, Bethesda, Maryland 20892, Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Building 10, Room B3C 346A, 10 Center Drive, Bethesda, Maryland 20892, National Heart, Lung and Blood Institute, National Institutes of Health, DHHS, Bethesda, Maryland 20892, National Institute of Chemistry, Ljubljana, Slovenia
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23
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Altamura M, Dapporto P, Guidi A, Harmat NJS, Jierry L, Libralesso E, Paoli P, Rossi P. Investigation on the flexibility of chiral tricyclic derivatives. NEW J CHEM 2008. [DOI: 10.1039/b801569d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Fedurcová A, Májek P, Lehotay J, Čižmárik J. HPLC Behaviour of Diazepam on β‐Cyclodextrin Chiral Stationary Phase. Evidence of Conformational Change. J LIQ CHROMATOGR R T 2007. [DOI: 10.1080/10826070600832913] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Andrea Fedurcová
- a Department of Analytical Chemistry, Institute of Analytical Chemistry , Slovak University of Technology , Bratislava, Slovakia
| | - Pavel Májek
- a Department of Analytical Chemistry, Institute of Analytical Chemistry , Slovak University of Technology , Bratislava, Slovakia
| | - Jozef Lehotay
- a Department of Analytical Chemistry, Institute of Analytical Chemistry , Slovak University of Technology , Bratislava, Slovakia
| | - Jozef Čižmárik
- b Department of Pharmaceutical Chemistry , Commenius University , Bratislava, Slovakia
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Fedurcová A, Lehotay J, Liptaj T, Prónayová N, Čižmárik J. HPLC Separation of Diazepam Conformers Coupled with Off‐Line NMR Experiment. J LIQ CHROMATOGR R T 2007. [DOI: 10.1080/10826070600598852] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Andrea Fedurcová
- a Department of Analytical Chemistry, Faculty of Chemical and Food Technology , Slovak University of Technology , Bratislava, Slovakia
| | - Jozef Lehotay
- a Department of Analytical Chemistry, Faculty of Chemical and Food Technology , Slovak University of Technology , Bratislava, Slovakia
| | - Tibor Liptaj
- b Central Laboratory, Faculty of Chemical and Food Technology , Slovak University of Technology , Bratislava, Slovakia
| | - Nad'a Prónayová
- b Central Laboratory, Faculty of Chemical and Food Technology , Slovak University of Technology , Bratislava, Slovakia
| | - Jozef Čižmárik
- c Department of Pharmaceutical Chemistry, Faculty of Pharmacy , Commenius University , Bratislava, Slovakia
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26
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Lam PCH, Carlier PR. Experimental and Computational Studies of Ring Inversion of 1,4-Benzodiazepin-2-ones: Implications for Memory of Chirality Transformations. J Org Chem 2005; 70:1530-8. [PMID: 15730270 DOI: 10.1021/jo048450n] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We recently reported the enantioselective syntheses of quaternary 1,4-benzodiazepin-2-ones via memory of chirality. The success of this method depends on formation of conformationally chiral enolates that racemize very slowly under the reaction conditions. As a prelude to undertaking experimental and computational studies on the racemization of these enolates, we have studied the ring-inversion process of the parent 1,4-benzodiazepin-2-ones. In this paper, we use dynamic and 2D-EXSY NMR to characterize inversion barriers. Using DFT calculations, we reproduce the experimental results with high accuracy (within 1-2 kcal/mol). Structural parameters obtained from DFT calculations provide valuable insights into the important effect of the N1 substituent on the ring-inversion barrier and shed light on the mechanism of the memory of chirality method. These measurements and calculations provide a foundation for future studies of benzodiazepine enolates and will be valuable in the design of new memory of chirality reactions.
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Affiliation(s)
- Polo C-H Lam
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
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27
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Carlier PR, Zhao H, DeGuzman J, Lam PCH. Enantioselective synthesis of "quaternary" 1,4-benzodiazepin-2-one scaffolds via memory of chirality. J Am Chem Soc 2003; 125:11482-3. [PMID: 13129335 DOI: 10.1021/ja0365781] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glycine-derived 1,4-benzodiazepine-2-ones such as diazepam are chiral by virtue of the boat-shaped conformation of the diazepine ring and exist as a racemic mixture of conformational enantiomers. However, the presence of a chiral center at C-3 of the benzodiazepine perturbs this equilibrium and preferentially stabilizes one ring conformer. We report that N-i-Pr 1,4-benzodiazepine-2-ones derived from (S)-Ala and (S)-Phe can be deprotonated and alkylated in 86-99% ee, despite the fact that the original chiral center is destroyed in the deprotonation step. We attribute this highly enantioselective alkylation to the chiral memory of the benzodiazepine ring. This protocol provides easy access to the previously unexplored "quaternary" 1,4-benzodiazepine-2-ones.
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Affiliation(s)
- Paul R Carlier
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
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28
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Csonka IP, Paizs B, Lendvay G, Suhai S. Proton mobility in protonated peptides: a joint molecular orbital and RRKM study. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2000; 14:417-431. [PMID: 10717650 DOI: 10.1002/(sici)1097-0231(20000331)14:6<417::aid-rcm885>3.0.co;2-j] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The mobile proton model was critically evaluated by using purely theoretical models which include quantum mechanical calculations to determine stationary points on the potential energy surface (PES) of a model compound, and Rice-Ramsperger-Kassel-Marcus (RRKM) calculations to determine the rate constants of various processes (conformational changes, proton transfer reactions) which occur during mass analysis of protonated peptides. Extensive mapping of the PES of protonated N-formylglycinamide resulted in various minima which were stabilized by one or more of the following types of interaction: internal hydrogen bond, charge transfer interaction, charge delocalization, and ring formation. The relative energies of most of the investigated minima are less then 20 kcal mol(-1) compared with the most stable species. More importantly, the relative energies of the transition structures connecting these minima are fairly low, allowing facile transitions among the energetically low-lying species. It is demonstrated that a path can be found leading from the energetically most stable species, protonated on an amide oxygen, to the structure from which the energetically most favorable fragmentation occurs. It is also shown that the added proton can sample all protonation sites prior to fragmentation. The RRKM calculations applied the results of ab initio computations (structures, energetics, vibrational frequencies) to the reactions (internal rotations, proton transfers) occurring in protonated N-formylglycinamide, and clearly lend additional evidence to the mobile proton model. Based on the results of the PES search on protonated N-formylglycinamide, we also comment on the mechanism proposed by Arnot et al. (Arnot D, Kottmeier D, Yates N, Shabanowitz J, Hunt D F. 42(nd) ASMS Conference on Mass Spectrometry, 1994; 470) and Reid et al. (Reid G E, Simpson R J, O'Hair R A J. J. Am. Soc. Mass Spectrom. 1998; 9:945) for the formation of b(2)(+) ions. According to the high level ab initio results, the mechanism relying on amide oxygen protonated species seems to be less feasible than the one which involves N-protonated species.
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Affiliation(s)
- I P Csonka
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
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