Photoionization and excitation processes in proteins and peptides

Dmitrii Egorov

Photoionization and excitation processes in proteins and peptides

Dmitrii Egorov

Quantum interactions and structural dynamics

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Samenvatting

Wij kijken naar moleculaire fragmentatiepatronen van peptiden en eiwitten en hun niet-dissociatieve ionisatie-opbrengsten als een functie van de moleculaire grootte en structuur. De moleculaire ionisatie- en fragmentatieprocessen zijn op gang gebracht door absorptie van energetische fotonen.

Wij introduceren de resultaten van near-edge X-ray absorption massaspectrometrie van peptiden en eiwitten met diverse massa's. De massa's van de gebruikte moleculen variëren van 500 Da tot meer dan 12 kDa. Voor de kleinere moleculen, tot ongeveer 2 kDa, worden de massaspectra gedomineerd door kleine fragmenten, terwijl voor grotere moleculen, met een massa groter dan ~8 kDa, de prominente kenmerken het gevolg zijn van niet-dissociatieve ionisatie.

Met 20 eV VUV-fotonen de overgang van fragmentatie naar het niet-dissociërende ionisatieregime treedt op bij veel kleinere molecuulgrootte in vergelijking tot de zachte röntgens. Bovendien bestuderen wij de invloed van de fotonenenergie op de fotofragmentatiepatronen.

In de finale wij voeren een case-study voor zachteröntgenabsorptie uit met melittine. We constateren een duidelijke afname van deze niet-dissociatieve dubbele ionisatie onder de ionisatiedrempel voor een toenemende protoneringstoestand van melittine. De hoofdverklaring is de kleinere kans op secundaire ionisatie vanwege de minder compacte structuur van melittine voor hogere protonatietoestanden. Naast niet-dissociërende ionisatie, hebben we gestudeerd verlies van kleine neutrale moleculen en vorming van ionen als gevolg van backbone-splitsing.

Originele taal-2	English
Kwalificatie	Doctor of Philosophy
Toekennende instantie	Rijksuniversiteit Groningen
Begeleider(s)/adviseur	Hoekstra, Ronnie, Supervisor Schlathölter, Thomas, Co-supervisor
Datum van toekenning	12-mrt-2018
Plaats van publicatie	[Groningen]
Uitgever	Rijksuniversiteit Groningen
Gedrukte ISBN's	978-94-034-0436-3
Elektronische ISBN's	978-94-034-0435-6
Status	Published - 2018

Toegang tot document

Title and contentsFinal publisher's version, 906 KB
Chapter 1Final publisher's version, 5,81 MB
Chapter 2Final publisher's version, 12,6 MB
Chapter 3Final publisher's version, 2,93 MB
Chapter 4Final publisher's version, 2,44 MB
Chapter 5Final publisher's version, 5,79 MB
Chapter 6Final publisher's version, 4,02 MB
SamenvattingFinal publisher's version, 340 KB
List of publicationsFinal publisher's version, 236 KB
AcknowledgementsFinal publisher's version, 222 KB
Complete thesisFinal publisher's version, 33 MB
PropositionsFinal publisher's version, 126 KB

Citeer dit

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title = "Photoionization and excitation processes in proteins and peptides",

abstract = "We have performed systematic studies of molecular fragmentation patterns of peptides and proteins and their non-dissociative ionization yields as a function of molecular size and conformation. The molecular ionization and fragmentation processes have been triggered by absorption of energetic photons.We presented the results of near-edge X-ray absorption mass-spectrometry of peptides and proteins of various masses. The molecular masses ran from 500 Da to more than 12 kDa. For the smaller molecules up to approximately 2kDa the fragment mass spectra were dominated by small fragments while for larger molecules with masses exceeding ~8 kDa the prominent mass-spectral features were due to non-dissociative ionization.For 20 eV VUV photons the transition from the extensive fragmentation to the non-dissociative ionization regime occured at much smaller molecule size compared to soft X-ray. Additionally, the influence of the photon energy on the photofragmentation patterns was studied.In the final we performed a soft X-ray absorption spectroscopy case study for the melittin peptide. We observed a clear decline of non-dissociative double ionization below the ionization threshold with increasing melittin protonation state. This was explained by the lower probability of secondary electron ionization by the Auger electrons due to the less compact structure of melittin for higher charge states. In addition to non-dissociative ionization, we studied small neutral molecule loss and formation of ions due to backbone scission.",

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N2 - We have performed systematic studies of molecular fragmentation patterns of peptides and proteins and their non-dissociative ionization yields as a function of molecular size and conformation. The molecular ionization and fragmentation processes have been triggered by absorption of energetic photons.We presented the results of near-edge X-ray absorption mass-spectrometry of peptides and proteins of various masses. The molecular masses ran from 500 Da to more than 12 kDa. For the smaller molecules up to approximately 2kDa the fragment mass spectra were dominated by small fragments while for larger molecules with masses exceeding ~8 kDa the prominent mass-spectral features were due to non-dissociative ionization.For 20 eV VUV photons the transition from the extensive fragmentation to the non-dissociative ionization regime occured at much smaller molecule size compared to soft X-ray. Additionally, the influence of the photon energy on the photofragmentation patterns was studied.In the final we performed a soft X-ray absorption spectroscopy case study for the melittin peptide. We observed a clear decline of non-dissociative double ionization below the ionization threshold with increasing melittin protonation state. This was explained by the lower probability of secondary electron ionization by the Auger electrons due to the less compact structure of melittin for higher charge states. In addition to non-dissociative ionization, we studied small neutral molecule loss and formation of ions due to backbone scission.

AB - We have performed systematic studies of molecular fragmentation patterns of peptides and proteins and their non-dissociative ionization yields as a function of molecular size and conformation. The molecular ionization and fragmentation processes have been triggered by absorption of energetic photons.We presented the results of near-edge X-ray absorption mass-spectrometry of peptides and proteins of various masses. The molecular masses ran from 500 Da to more than 12 kDa. For the smaller molecules up to approximately 2kDa the fragment mass spectra were dominated by small fragments while for larger molecules with masses exceeding ~8 kDa the prominent mass-spectral features were due to non-dissociative ionization.For 20 eV VUV photons the transition from the extensive fragmentation to the non-dissociative ionization regime occured at much smaller molecule size compared to soft X-ray. Additionally, the influence of the photon energy on the photofragmentation patterns was studied.In the final we performed a soft X-ray absorption spectroscopy case study for the melittin peptide. We observed a clear decline of non-dissociative double ionization below the ionization threshold with increasing melittin protonation state. This was explained by the lower probability of secondary electron ionization by the Auger electrons due to the less compact structure of melittin for higher charge states. In addition to non-dissociative ionization, we studied small neutral molecule loss and formation of ions due to backbone scission.

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