9 research outputs found
Ion-Induced Dipole Interactions and Fragmentation Times : C -C Chromophore Bond Dissociation Channel
The fragmentation times corresponding to the loss of the chromophore
(C-- C bond dissociation channel) after photoexcitation at 263
nm have been investigated for several small peptides containing tryptophan or
tyrosine. For tryptophan-containing peptides, the aromatic chromophore is lost
as an ionic fragment (m/z 130), and the fragmentation time increases with the
mass of the neutral fragment. In contrast, for tyrosine-containing peptides the
aromatic chromophore is always lost as a neutral fragment (mass = 107 amu) and
the fragmentation time is found to be fast (\textless{}20 ns). These different
behaviors are explained by the role of the postfragmentation interaction in the
complex formed after the C--C bond cleavage
Dynamique de photofragmentation de molĂ©cules d'intĂ©rĂȘt biologique protonĂ©es
The Arc-En-Ciel experiment allows the investigation of UV photo-fragmentation dynamics of protonated biomolecules produced by an electrospray ion source. The specificity of the set-up is based on the detection in coincidence of ionic and neutral photo-fragments coming from the same fragmentation event. The study of simple charged molecules allows the identification of each fragmentation channel by the mass of the emitted ionic fragment. With the time and spatial correlation of the information of detected photo-fragments we identify:- the number of neutral fragments as well as their masses associated with each ionic fragment- the number of fragmentation steps of each channel as well as their fragmentation times (20 ns â€ Ï < 1 ÎŒs)This information provides a comprehensive understanding of the photo-fragmentation dynamics.The photo-fragmentation dynamics of protonated Tryptophan is driven by concerted electron and proton transfers in the excited state. When protonated Tryptophan is complexed witha crown-ether, proton transfers are inhibited and dynamics is modified.The excited state dynamics of small protonated peptides containing Tryptophan is governed by the position of Tryptophan in the peptide chain. The specific fragmentation channels involved are explained by concerted electron and proton transfers. We show how these mechanisms change with the composition of peptides.LâexpĂ©rience Arc-En-Ciel permet dâĂ©tudier la dynamique de photofragmentation UV de biomolĂ©cules produites par une source « Ă©lectrospray ». La spĂ©cificitĂ© du dispositif expĂ©rimental utilisĂ© repose sur la dĂ©tection en coĂŻncidence des photo-fragments ioniques et neutres issus dâun mĂȘme Ă©vĂšnement physique de fragmentation. LâĂ©tude de molĂ©cules simplement chargĂ©es permet dâidentifier chaque canal de fragmentation par la masse du fragment ionique Ă©mis. En corrĂ©lant les informations temporelles et spatiales des photo-fragments dĂ©tectĂ©s, on dĂ©finit :- le nombre et la masse des fragments neutres associĂ©s Ă chaque fragment ionique- le nombre dâĂ©tapes de fragmentation de chaque canal et leurs temps caractĂ©ristiques(20 ns â€ Ï < 1 ÎŒs).Lâensemble de ces informations permet une description complĂšte de la dynamique de photofragmentation du systĂšme Ă©tudiĂ©.La dynamique de photofragmentation du tryptophane protonĂ© est rĂ©gie par des transferts concertĂ©s dâĂ©lectron et de proton Ă lâĂ©tat excitĂ©. Lorsque le tryptophane protonĂ© est complexĂ© Ă un Ă©ther-couronne, les transferts de protons sont inhibĂ©s. Nous observons alors une modification de la dynamique de fragmentation.Pour de petits peptides protonĂ©s contenant le tryptophane, la dynamique Ă lâĂ©tat excitĂ© est gouvernĂ©e par la position du tryptophane dans la chaĂźne peptidique. Les voies de fragmentation spĂ©cifiques UV, mises en Ă©vidence pour ces peptides, sont expliquĂ©es par les mĂȘmes mĂ©canismes de transfert concertĂ© dâĂ©lectron et de proton. Nous montrons cependant que ces mĂ©canismes diffĂšrent suivant la composition du peptide
Photofragmentation dynamics of small protonated biomolecules
LâexpĂ©rience Arc-En-Ciel permet dâĂ©tudier la dynamique de photofragmentation UV de biomolĂ©cules produites par une source « Ă©lectrospray ». La spĂ©cificitĂ© du dispositif expĂ©rimental utilisĂ© repose sur la dĂ©tection en coĂŻncidence des photo-fragments ioniques et neutres issus dâun mĂȘme Ă©vĂšnement physique de fragmentation. LâĂ©tude de molĂ©cules simplement chargĂ©es permet dâidentifier chaque canal de fragmentation par la masse du fragment ionique Ă©mis. En corrĂ©lant les informations temporelles et spatiales des photo-fragments dĂ©tectĂ©s, on dĂ©finit :- le nombre et la masse des fragments neutres associĂ©s Ă chaque fragment ionique- le nombre dâĂ©tapes de fragmentation de chaque canal et leurs temps caractĂ©ristiques(20 ns â€ Ï < 1 ÎŒs).Lâensemble de ces informations permet une description complĂšte de la dynamique de photofragmentation du systĂšme Ă©tudiĂ©.La dynamique de photofragmentation du tryptophane protonĂ© est rĂ©gie par des transferts concertĂ©s dâĂ©lectron et de proton Ă lâĂ©tat excitĂ©. Lorsque le tryptophane protonĂ© est complexĂ© Ă un Ă©ther-couronne, les transferts de protons sont inhibĂ©s. Nous observons alors une modification de la dynamique de fragmentation.Pour de petits peptides protonĂ©s contenant le tryptophane, la dynamique Ă lâĂ©tat excitĂ© est gouvernĂ©e par la position du tryptophane dans la chaĂźne peptidique. Les voies de fragmentation spĂ©cifiques UV, mises en Ă©vidence pour ces peptides, sont expliquĂ©es par les mĂȘmes mĂ©canismes de transfert concertĂ© dâĂ©lectron et de proton. Nous montrons cependant que ces mĂ©canismes diffĂšrent suivant la composition du peptide.The Arc-En-Ciel experiment allows the investigation of UV photo-fragmentation dynamics of protonated biomolecules produced by an electrospray ion source. The specificity of the set-up is based on the detection in coincidence of ionic and neutral photo-fragments coming from the same fragmentation event. The study of simple charged molecules allows the identification of each fragmentation channel by the mass of the emitted ionic fragment. With the time and spatial correlation of the information of detected photo-fragments we identify:- the number of neutral fragments as well as their masses associated with each ionic fragment- the number of fragmentation steps of each channel as well as their fragmentation times (20 ns â€ Ï < 1 ÎŒs)This information provides a comprehensive understanding of the photo-fragmentation dynamics.The photo-fragmentation dynamics of protonated Tryptophan is driven by concerted electron and proton transfers in the excited state. When protonated Tryptophan is complexed witha crown-ether, proton transfers are inhibited and dynamics is modified.The excited state dynamics of small protonated peptides containing Tryptophan is governed by the position of Tryptophan in the peptide chain. The specific fragmentation channels involved are explained by concerted electron and proton transfers. We show how these mechanisms change with the composition of peptides
Vacuum Ultraviolet Photoionization Study of Gas Phase Vitamins A and B1 Using Aerosol Thermodesorption and Synchrotron Radiation
International audienceGas-phase studies of biomolecules are often difficult to initiate because of the thermolability of these systems. Such studies are nevertheless important to determine fundamental intrinsic properties of the molecules. Here we present the valence shell photoionization of gas-phase vitamins A and B1 close to their ionization threshold. The study was performed by means of an aerosol thermodesorption source coupled to an electron/ion coincidence spectrometer and synchrotron radiation (SOLEIL facility, France). Ion yield curves were recorded for both molecules over a few electronvolt energy range and the threshold photoelectron spectrum was also obtained for vitamin A. Some fundamental properties were extracted for both ions such as adiabatic and the three first vertical ionization energies of retinol (IEad = 6.8 ± 0.2 eV and IEvert = 7.4, 8.3, and 9.2 eV) and dissociation appearance energies for the main fragment ions of vitamin B1. Analysis of the data was supported by ab initio calculations which show a very good agreement with the experimental observations
Determination of Peptide Topology through Time-Resolved Double-Resonance under Electron Capture Dissociation Conditions.
International audienceCharacterizing the conformation of biomolecules by mass spectrometry still represents a challenge. With their knotted structure involving a N-terminal macrolactam ring where the C-terminal tail of the peptide is threaded and sterically trapped, lasso peptides constitute an attractive model for developing methods for characterizing gas-phase conformation, through comparison with their unknotted topoisomers. Here, the kinetics of electron capture dissociation (ECD) of a lasso peptide, capistruin, was investigated by electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry and compared to that of its branched-cyclic topoisomer, lactam-capistruin. Both peptides produced rather similar ECD spectra but showed different extent of H(*) transfer from c(i)' to z(j)(*) ions. Time-resolved double-resonance experiments under ECD conditions were performed to measure the formation rate constants of typical product ions. Such experiments showed that certain product ions, in particular those related to H(*) transfer, proceeded through long-lived complexes for capistruin, while fast dissociation processes predominated for lactam-capistruin. The formation rate constants of specific ECD product ions enabled a clear differentiation of the lasso and branched-cyclic topoisomers. These results indicate that the formation kinetics of ECD product ions constitute a new way to explore the conformation of biomolecules and distinguish between topoisomers and, more generally, conformers
Caractérisation de peptides lasso par EPD et EDD
communication par afficheNational audienceLes peptides lasso sont des peptides bioactifs d'origine bactĂ©rienne. L'extrĂ©mitĂ© C-terminale de ces peptides est enchĂąssĂ©e dans un cycle macrolactame formĂ© entre le rĂ©sidu N-terminal et le carboxylate de la chaĂźne latĂ©rale d'un rĂ©sidu glutamate ou aspartate en position 8 ou 9. La maturation d'un prĂ©curseur linĂ©aire sous l'action de deux enzymes permet d'obtenir cette structure compacte et rigide. Notre travail consiste Ă caractĂ©riser par spectromĂ©trie de masse la topologie de ces peptides en forme de lasso. Leur fragmentation est comparĂ©e Ă celle de peptides synthĂ©tiques possĂ©dant une topologie diffĂ©rente avec le mĂȘme enchaĂźnement d'acides aminĂ©s: peptide lactame non-lasso ou peptide linĂ©aire. La microcine J25 (MccJ25), peptide lasso antibactĂ©rien produit par Escherichia coli AY25 [1], a d'abord Ă©tĂ© Ă©tudiĂ©e par spectromĂ©trie de masse en mode positif (CID, IRMPD et ECD) [2]. Dans cet exposĂ© nous prĂ©senterons les rĂ©sultats obtenus sur cette molĂ©cule en mode nĂ©gatif par activation vibrationnelle (CID) et Ă©lectronique (EDD, EPD). Les expĂ©riences EPD (Electron Photodetachment Dissociation) ont Ă©tĂ© rĂ©alisĂ©es sur un LTQ modifiĂ© Ă©quipĂ© d'un laser Ă 266 nm [3], tandis que les expĂ©riences EDD (Electron Detachment Dissociation) ont Ă©tĂ© rĂ©alisĂ©es sur un FTICR [2] avec des Ă©lectrons d'environ 20 eV. La MccJ25 contient deux tyrosines capables d'absorber l'UV Ă 266 nm, induisant le dĂ©tachement d'Ă©lectron Ă l'origine des fragmentations observĂ©es en EPD. Afin de prĂ©ciser le rĂŽle de chaque tyrosine en EPD, nous avons Ă©tudiĂ© deux variants de MccJ25 produits par mutagenĂšse dirigĂ©e, dans lesquels chaque tyrosine est sĂ©lectivement substituĂ©e par une phĂ©nylalanine. Par ailleurs des expĂ©riences de double-rĂ©sonance ont Ă©tĂ© rĂ©alisĂ©es en EDD sur le FT-ICR en faisant varier l'amplitude d'Ă©jection de l'ion de charge rĂ©duite au cours de l'irradiation par les Ă©lectrons [4]. Ces expĂ©riences fournissent des informations sur la cinĂ©tique de formation des fragments et nous ont permis de diffĂ©rencier plusieurs mĂ©canismes de fragmentation
Electron detachment/photodetachment dissociation of lasso peptides
International audienceno abstrac
Determination of Peptide Topology through Time-Resolved Double-Resonance under Electron Capture Dissociation Conditions
International audienceCharacterizing the conformation of biomolecules by mass spectrometry still represents a challenge. With their knotted structure involving a N-terminal macrolactam ring where the C-terminal tail of the peptide is threaded and sterically trapped, lasso peptides constitute an attractive model for developing methods for characterizing gas-phase conformation, through comparison with their unknotted topoisomers. Here, the kinetics of electron capture dissociation (ECD) of a lasso peptide, capistruin, was investigated by electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry and compared to that of its branched-cyclic topoisomer, lactam-capistruin. Both peptides produced rather similar ECD spectra but showed different extent of H(*) transfer from c(i)' to z(j)(*) ions. Time-resolved double-resonance experiments under ECD conditions were performed to measure the formation rate constants of typical product ions. Such experiments showed that certain product ions, in particular those related to H(*) transfer, proceeded through long-lived complexes for capistruin, while fast dissociation processes predominated for lactam-capistruin. The formation rate constants of specific ECD product ions enabled a clear differentiation of the lasso and branched-cyclic topoisomers. These results indicate that the formation kinetics of ECD product ions constitute a new way to explore the conformation of biomolecules and distinguish between topoisomers and, more generally, conformers