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Macromolecule classification using X-ray laser induced fragmentation simulated with hybrid Monte Carlo/Molecular Dynamics
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kemisk och biomolekylär fysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kemisk och biomolekylär fysik. European XFEL, Holzkoppel 4, DE-22869 Schenefeld, Germany.ORCID-id: 0000-0002-2926-5702
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kemisk och biomolekylär fysik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Kemisk och biomolekylär fysik.ORCID-id: 0000-0001-7328-0400
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(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Abstract [en]

We have developed a hybrid Monte Carlo and classical molecular dynamics code to follow the ultrafast atomic dynamics in biological macromolecules induced by a femtosecond X-ray laser. Our model for fragmentation shows good qualitative agreement with ab-initio simulations of small molecules, while being computationally faster.  We applied the code for macromolecules and simulated the Coulomb explosion dynamics due to the fast ionization in six proteins with different physical properties. The trajectories of the ions are followed and projected onto a detector, where the particular pattern depends on the protein, providing a unique footprint. We utilize algorithms such as principal component analysis  and t-distributed stochastic neighbor embedding to classify the fragmentation pattern. The results show that the classification algorithms are able to separate the explosion patterns into distinct groups. We envision that this method could be used to provide additional class information, like particle mass or shape, in structural determination experiments using X-ray lasers.

HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-519565OAI: oai:DiVA.org:uu-519565DiVA, id: diva2:1825065
Prosjekter
In thesis
Forskningsfinansiär
Swedish Research Council, 2018-00740, 2019-03935, 2021-05988Tilgjengelig fra: 2024-01-08 Laget: 2024-01-08 Sist oppdatert: 2024-01-09
Inngår i avhandling
1. Simulations of ultrafast photon-matter interactions for molecular imaging with X-ray lasers
Åpne denne publikasjonen i ny fane eller vindu >>Simulations of ultrafast photon-matter interactions for molecular imaging with X-ray lasers
2024 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Biological structure determination has had new avenues of investigation opened due to the introduction of X-ray free-electron lasers (XFELs). These X-ray lasers provide an extreme amount of photons on ultrafast timescales used to probe matter, and in particular biomolecules. The high intensity of the X-rays destroys the sample, though not before structural information has been acquired. The unique properties of the probe provide the unprecedented opportunity to study the un-crystallized form of biological macromolecules, small crystals of biomolecules and their dynamics. 

In this work, we study processes in XFEL imaging experiments that could affect the achievable resolution of the protein structure in a diffraction experiment. Elastic scattering is the process which provides structural information and leaves the sample unperturbed. This interaction occurs far less often compared to damage inducing processes, such as photoabsorption, which leads to rapid ionization of the studied sample. By using density functional theory, we study the effect of ultrahigh charge states in small systems, such as amino acids and peptides, on the subsequent bond breaking and charge dynamics. Reproducible fragmentation patterns are studied in order to find features that could be understood in larger systems, such as proteins. 

Biomolecules are dynamical systems, and the currently used pulse duration is not short enough to outrun the movement of the atoms. The diffraction patterns acquired in an experiment are therefore an incoherent sum of slightly different conformations of the same system. Water can help to reduce these structural variations, but the water molecules themselves will then be a source of noise. Using classical molecular dynamics, we study the optimal amount of water that should be used to achieve the highest resolution. 

To simulate ultrafast molecular dynamics of larger systems such as proteins, we develop a hybrid Monte Carlo/molecular dynamics model. We utilize it to simulate the fragmentation dynamics of small proteins and investigate the possibility to extract structural information from the fragmentation patterns. For larger systems exposed to X-ray lasers, such as viruses and crystals, we develop a hybrid collisional-radiative and classical molecular dynamics approach. The method is used in several projects, both in theoretical studies and to support experiments conducted at XFEL facilities. In particular, we simulate the interaction of hexagonal ice with an X-ray laser, and show the structure makes a phase transition from the native crystal state to a plasma, while still partly retaining structural order. Furthermore, we note that the structural changes occur in an anisotropic manner, where different local structural configurations in ice decay on different time-scales. 

Preliminary experimental results show this anisotropic dynamics in an X-ray pump-probe serial femtosecond X-ray crystallography experiment performed on  I3C crystals. The real space dynamics as a function of probe delay given by our theoretical model and the experiment both show good agreement, where the iodine atoms exhibit correlated motion. The model is also used to calculate the expected atomic displacement and ionization in a hemoglobin crystal, revealing the time and length scales of the dynamics in the protein during the experiment. 

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2024. s. 95
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2353
Emneord
X-ray free-electron laser, molecular dynamics, radiation damage, plasma simulations, density functional theory¸ coherent diffractive imaging, protein structure, X-ray crystallography, single particle imaging
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-519472 (URN)978-91-513-2005-2 (ISBN)
Disputas
2024-02-29, Häggsalen, Ångström, Lägerhyddsvägen 1, Uppsala, 13:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2024-02-08 Laget: 2024-01-09 Sist oppdatert: 2024-02-08

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