Matching Items (14)
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- All Subjects: Photosynthesis
- Creators: Fromme, Petra
Description
The cyanobacterium Synechocystis sp. PCC 6803 performs oxygenic photosynthesis. Light energy conversion in photosynthesis takes place in photosystem I (PSI) and photosystem II (PSII) that contain chlorophyll, which absorbs light energy that is utilized as a driving force for photosynthesis. However, excess light energy may lead to formation of reactive oxygen species that cause damage to photosynthetic complexes, which subsequently need repair or replacement. To gain insight in the degradation/biogenesis dynamics of the photosystems, the lifetimes of photosynthetic proteins and chlorophyll were determined by a combined stable-isotope (15N) and mass spectrometry method. The lifetimes of PSII and PSI proteins ranged from 1-33 and 30-75 hours, respectively. Interestingly, chlorophyll had longer lifetimes than the chlorophyll-binding proteins in these photosystems. Therefore, photosynthetic proteins turn over and are replaced independently from each other, and chlorophyll is recycled from the damaged chlorophyll-binding proteins. In Synechocystis, there are five small Cab-like proteins (SCPs: ScpA-E) that share chlorophyll a/b-binding motifs with LHC proteins in plants. SCPs appear to transiently bind chlorophyll and to regulate chlorophyll biosynthesis. In this study, the association of ScpB, ScpC, and ScpD with damaged and repaired PSII was demonstrated. Moreover, in a mutant lacking SCPs, most PSII protein lifetimes were unaffected but the lifetime of chlorophyll was decreased, and one of the nascent PSII complexes was missing. SCPs appear to bind PSII chlorophyll while PSII is repaired, and SCPs stabilize nascent PSII complexes. Furthermore, aminolevulinic acid biosynthesis, an early step of chlorophyll biosynthesis, was impaired in the absence of SCPs, so that the amount of chlorophyll in the cells was reduced. Finally, a deletion mutation was introduced into the sll1906 gene, encoding a member of the putative bacteriochlorophyll delivery (BCD) protein family. The Sll1906 sequence contains possible chlorophyll-binding sites, and its homolog in purple bacteria functions in proper assembly of light-harvesting complexes. However, the sll1906 deletion did not affect chlorophyll degradation/biosynthesis and photosystem assembly. Other (parallel) pathways may exist that may fully compensate for the lack of Sll1906. This study has highlighted the dynamics of photosynthetic complexes in their biogenesis and turnover and the coordination between synthesis of chlorophyll and photosynthetic proteins.
ContributorsYao, Cheng I Daniel (Author) / Vermaas, Wim (Thesis advisor) / Fromme, Petra (Committee member) / Roberson, Robert (Committee member) / Webber, Andrew (Committee member) / Arizona State University (Publisher)
Created2011
Description
The need for a renewable and sustainable light-driven energy source is the motivation for this work, which utilizes a challenging, yet practical and attainable bio-inspired approach to develop an artificial oxygen evolving complex, which builds upon the principles of the natural water splitting mechanism in oxygenic photosynthesis. In this work, a stable framework consisting of a three-dimensional DNA tetrahedron has been used for the design of a bio-mimic of the Oxygen-Evolving Complex (OEC) found in natural Photosystem II (PSII). PSII is a large protein complex that evolves all the oxygen in the atmosphere, but it cannot be used directly in artificial systems, as the light reactions lead to damage of one of Photosystem II's core proteins, D1, which has to be replaced every half hour in the presence of sunlight. The final goal of the project aims to build the catalytic center of the OEC, including the Mn4CaCl metal cluster and its protein environment in the stable DNA framework of a tetrahedron, which can subsequently be connected to a photo-stable artificial reaction center that performs light-induced charge separation. Regions of the peptide sequences containing Mn4CaCl ligation sites are implemented in the design of the aOEC (artificial oxygen-evolving complex) and are attached to sites within the tetrahedron to facilitate assembly. Crystals of the tetrahedron have been obtained, and X-ray crystallography has been used for characterization. As a proof of concept, metal-binding peptides have been coupled to the DNA tetrahedron which allowed metal-containing porphyrins, specifically Fe(III) meso-Tetra(4-sulfonatophenyl) porphyrin chloride, to be encapsulated inside the DNA-tetrahedron. The porphyrins were successfully assembled inside the tetrahedron through coordination of two terminal histidines from the orthogonally oriented peptides covalently attached to the DNA. The assembly has been characterized using Electron Paramagnetic Resonance (EPR), optical spectroscopy, Dynamic Light Scattering (DLS), and x-ray crystallography. The results reveal that the spin state of the metal, iron (III), switches during assembly from the high-spin state to low-spin state.
ContributorsRendek, Kimberly Nicole (Author) / Fromme, Petra (Thesis advisor) / Chen, Julian (Committee member) / Ros, Alexandra (Committee member) / Arizona State University (Publisher)
Created2012
Description
The photosynthetic reaction center is a type of pigment-protein complex found widely in photosynthetic bacteria, algae and higher plants. Its function is to convert the energy of sunlight into a chemical form that can be used to support other life processes. The high efficiency and structural simplicity make the bacterial reaction center a paradigm for studying electron transfer in biomolecules. This thesis starts with a comparison of the primary electron transfer process in the reaction centers from the Rhodobacter shperoides bacterium and those from its thermophilic homolog, Chloroflexus aurantiacus. Different temperature dependences in the primary electron transfer were found in these two type of reaction centers. Analyses of the structural differences between these two proteins suggested that the excess surface charged amino acids as well as a larger solvent exposure area in the Chloroflexus aurantiacus reaction center could explain the different temperature depenence. The conclusion from this work is that the electrostatic interaction potentially has a major effect on the electron transfer. Inspired by these results, a single point mutant was designed for Rhodobacter shperoides reaction centers by placing an ionizable amino acid in the protein interior to perturb the dielectrics. The ionizable group in the mutation site largely deprotonated in the ground state judging from the cofactor absorption spectra as a function of pH. By contrast, a fast charge recombination assoicated with protein dielectric relaxation was observed in this mutant, suggesting the possibility that dynamic protonation/deprotonation may be taking place during the electron transfer. The fast protein dielectric relaxation occuring in this mutant complicates the electron transfer pathway and reduces the yield of electron transfer to QA. Considering the importance of the protein dielectric environment, efforts have been made in quantifying variations of the internal field during charge separation. An analysis protocol based on the Stark effect of reaction center cofactor spectra during charge separation has been developed to characterize the charge-separated radical field acting on probe chromophores. The field change, monitored by the dynamic Stark shift, correlates with, but is not identical to, the electron transfer kinetics. The dynamic Stark shift results have lead to a dynamic model for the time-dependent dielectric that is complementary to the static dielectric asymmetry observed in past steady state experiments. Taken together, the work in this thesis emphasizes the importance of protein electrostatics and its dielectric response to electron transfer.
ContributorsGuo, Zhi (Author) / Woodbury, Neal W (Thesis advisor) / Lindsay, Stuart M (Committee member) / Ross, Robert (Committee member) / Ozkan, Banu S (Committee member) / Moore, Thomas A. (Committee member) / Arizona State University (Publisher)
Created2012
Description
The heliobacterial reaction center (HbRC) is widely considered the simplest and most primitive photosynthetic reaction center (RC) still in existence. Despite the simplicity of the HbRC, many aspects of the electron transfer mechanism remain unknown or under debate. Improving our understanding of the structure and function of the HbRC is important in determining its role in the evolution of photosynthetic RCs. In this work, the function and properties of the iron-sulfur cluster FX and quinones of the HbRC were investigated, as these are the characteristic terminal electron acceptors used by Type-I and Type-II RCs, respectively. In Chapter 3, I develop a system to directly detect quinone double reduction activity using reverse-phase high pressure liquid chromatography (RP-HPLC), showing that Photosystem I (PSI) can reduce PQ to PQH2. In Chapter 4, I use RP-HPLC to characterize the HbRC, showing a surprisingly small antenna size and confirming the presence of menaquinone (MQ) in the isolated HbRC. The terminal electron acceptor FX was characterized spectroscopically and electrochemically in Chapter 5. I used three new systems to reduce FX in the HbRC, using EPR to confirm a S=3/2 ground-state for the reduced cluster. The midpoint potential of FX determined through thin film voltammetry was -372 mV, showing the cluster is much less reducing than previously expected. In Chapter 7, I show light-driven reduction of menaquinone in heliobacterial membrane samples using only mild chemical reductants. Finally, I discuss the evolutionary implications of these findings in Chapter 7.
ContributorsCowgill, John (Author) / Redding, Kevin (Thesis advisor) / Jones, Anne (Committee member) / Fromme, Petra (Committee member) / Arizona State University (Publisher)
Created2012
Description
In oxygenic photosynthesis, Photosystem I (PSI) and Photosystem II (PSII) are two transmembrane protein complexes that catalyze the main step of energy conversion; the light induced charge separation that drives an electron transfer reaction across the thylakoid membrane. Current knowledge of the structure of PSI and PSII is based on three structures: PSI and PSII from the thermophilic cyanobacterium Thermosynechococcus elonagatus and the PSI/light harvesting complex I (PSI-LHCI) of the plant, Pisum sativum. To improve the knowledge of these important membrane protein complexes from a wider spectrum of photosynthetic organisms, photosynthetic apparatus of the thermo-acidophilic red alga, Galdieria sulphuraria and the green alga, Chlamydomonas reinhardtii were studied. Galdieria sulphuraria grows in extreme habitats such as hot sulfur springs with pH values from 0 to 4 and temperatures up to 56°C. In this study, both membrane protein complexes, PSI and PSII were isolated from this organism and characterized. Ultra-fast fluorescence spectroscopy and electron microscopy studies of PSI-LHCI supercomplexes illustrate how this organism has adapted to low light environmental conditions by tightly coupling PSI and LHC, which have not been observed in any organism so far. This result highlights the importance of structure-function relationships in different ecosystems. Galdieria sulphuraria PSII was used as a model protein to show the amenability of integral membrane proteins to top-down mass spectrometry. G.sulphuraria PSII has been characterized with unprecedented detail with identification of post translational modification of all the PSII subunits. This study is a technology advancement paving the way for the usage of top-down mass spectrometry for characterization of other large integral membrane proteins. The green alga, Chlamydomonas reinhardtii is widely used as a model for eukaryotic photosynthesis and results from this organism can be extrapolated to other eukaryotes, especially agricultural crops. Structural and functional studies on the PSI-LHCI complex of C.reinhardtii grown under high salt conditions were studied using ultra-fast fluorescence spectroscopy, circular dichroism and MALDI-TOF. Results revealed that pigment-pigment interactions in light harvesting complexes are disrupted and the acceptor side (ferredoxin docking side) is damaged under high salt conditions.
ContributorsThangaraj, Balakumar (Author) / Fromme, Petra (Thesis advisor) / Shock, Everett (Committee member) / Chen, Julian (Committee member) / Arizona State University (Publisher)
Created2010
Description
Over the last century, X-ray crystallography has been established as the most successful technique for unravelling the structure-function relationship in molecules. For integral membrane proteins, growing well-ordered large crystals is a challenge and hence, there is room for improving current methods of macromolecular crystallography and for exploring complimentary techniques. Since protein function is deeply associated with its structural dynamics, static position of atoms in a macromolecule are insufficient to unlock the mechanism.
The availability of X-ray free electron lasers presents an opportunity to study micron-sized crystals that could be triggered (using light, small molecules or physical conditions) to capture macromolecules in action. This method of ‘Time-resolved serial crystallography’ answers key biological questions by capturing snapshots of conformational changes associated with multi-step reactions. This dissertation describes approaches for studying structures of large membrane protein complexes. Both macro and micro-seeding techniques have been implemented for improving crystal quality and obtaining high-resolution structures. Well-diffracting 15-20 micron crystals of active Photosystem II were used to perform time-resolved studies with fixed-target Roadrunner sample delivery system. By employing continuous diffraction obtained up to 2 A, significant progress can be made towards understanding the process of water oxidation.
Structure of Photosystem I was solved to 2.3 A by X-ray crystallography and to medium resolution of 4.8 A using Cryogenic electron microscopy. Using complimentary techniques to study macromolecules provides an insight into differences among methods in structural biology. This helps in overcoming limitations of one specific technique and contributes in greater knowledge of the molecule under study.
The availability of X-ray free electron lasers presents an opportunity to study micron-sized crystals that could be triggered (using light, small molecules or physical conditions) to capture macromolecules in action. This method of ‘Time-resolved serial crystallography’ answers key biological questions by capturing snapshots of conformational changes associated with multi-step reactions. This dissertation describes approaches for studying structures of large membrane protein complexes. Both macro and micro-seeding techniques have been implemented for improving crystal quality and obtaining high-resolution structures. Well-diffracting 15-20 micron crystals of active Photosystem II were used to perform time-resolved studies with fixed-target Roadrunner sample delivery system. By employing continuous diffraction obtained up to 2 A, significant progress can be made towards understanding the process of water oxidation.
Structure of Photosystem I was solved to 2.3 A by X-ray crystallography and to medium resolution of 4.8 A using Cryogenic electron microscopy. Using complimentary techniques to study macromolecules provides an insight into differences among methods in structural biology. This helps in overcoming limitations of one specific technique and contributes in greater knowledge of the molecule under study.
ContributorsRoy Chowdhury, Shatabdi (Author) / Fromme, Petra (Thesis advisor) / Ros, Alexandra (Committee member) / Redding, Kevin (Committee member) / Arizona State University (Publisher)
Created2018
Description
Photosystem II (PSII) is a large protein-cofactor complex. The first step in
photosynthesis involves the harvesting of light energy from the sun by the antenna (made
of pigments) of the PSII trans-membrane complex. The harvested excitation energy is
transferred from the antenna complex to the reaction center of the PSII, which leads to a
light-driven charge separation event, from water to plastoquinone. This phenomenal
process has been producing the oxygen that maintains the oxygenic environment of our
planet for the past 2.5 billion years.
The oxygen molecule formation involves the light-driven extraction of 4 electrons
and protons from two water molecules through a multistep reaction, in which the Oxygen
Evolving Center (OEC) of PSII cycles through 5 different oxidation states, S0 to S4.
Unraveling the water-splitting mechanism remains as a grant challenge in the field of
photosynthesis research. This requires the development of an entirely new capability, the
ability to produce molecular movies. This dissertation advances a novel technique, Serial
Femtosecond X-ray crystallography (SFX), into a new realm whereby such time-resolved
molecular movies may be attained. The ultimate goal is to make a “molecular movie” that
reveals the dynamics of the water splitting mechanism using time-resolved SFX (TRSFX)
experiments and the uniquely enabling features of X-ray Free-Electron Laser
(XFEL) for the study of biological processes.
This thesis presents the development of SFX techniques, including development of
new methods to analyze millions of diffraction patterns (~100 terabytes of data per XFEL
experiment) with the goal of solving the X-ray structures in different transition states.
ii
The research comprises significant advancements to XFEL software packages (e.g.,
Cheetah and CrystFEL). Initially these programs could evaluate only 8-10% of all the
data acquired successfully. This research demonstrates that with manual optimizations,
the evaluation success rate was enhanced to 40-50%. These improvements have enabled
TR-SFX, for the first time, to examine the double excited state (S3) of PSII at 5.5-Å. This
breakthrough demonstrated the first indication of conformational changes between the
ground (S1) and the double-excited (S3) states, a result fully consistent with theoretical
predictions.
The power of the TR-SFX technique was further demonstrated with proof-of principle
experiments on Photoactive Yellow Protein (PYP) micro-crystals that high
temporal (10-ns) and spatial (1.5-Å) resolution structures could be achieved.
In summary, this dissertation research heralds the development of the TR-SFX
technique, protocols, and associated data analysis methods that will usher into practice a
new era in structural biology for the recording of ‘molecular movies’ of any biomolecular
process.
photosynthesis involves the harvesting of light energy from the sun by the antenna (made
of pigments) of the PSII trans-membrane complex. The harvested excitation energy is
transferred from the antenna complex to the reaction center of the PSII, which leads to a
light-driven charge separation event, from water to plastoquinone. This phenomenal
process has been producing the oxygen that maintains the oxygenic environment of our
planet for the past 2.5 billion years.
The oxygen molecule formation involves the light-driven extraction of 4 electrons
and protons from two water molecules through a multistep reaction, in which the Oxygen
Evolving Center (OEC) of PSII cycles through 5 different oxidation states, S0 to S4.
Unraveling the water-splitting mechanism remains as a grant challenge in the field of
photosynthesis research. This requires the development of an entirely new capability, the
ability to produce molecular movies. This dissertation advances a novel technique, Serial
Femtosecond X-ray crystallography (SFX), into a new realm whereby such time-resolved
molecular movies may be attained. The ultimate goal is to make a “molecular movie” that
reveals the dynamics of the water splitting mechanism using time-resolved SFX (TRSFX)
experiments and the uniquely enabling features of X-ray Free-Electron Laser
(XFEL) for the study of biological processes.
This thesis presents the development of SFX techniques, including development of
new methods to analyze millions of diffraction patterns (~100 terabytes of data per XFEL
experiment) with the goal of solving the X-ray structures in different transition states.
ii
The research comprises significant advancements to XFEL software packages (e.g.,
Cheetah and CrystFEL). Initially these programs could evaluate only 8-10% of all the
data acquired successfully. This research demonstrates that with manual optimizations,
the evaluation success rate was enhanced to 40-50%. These improvements have enabled
TR-SFX, for the first time, to examine the double excited state (S3) of PSII at 5.5-Å. This
breakthrough demonstrated the first indication of conformational changes between the
ground (S1) and the double-excited (S3) states, a result fully consistent with theoretical
predictions.
The power of the TR-SFX technique was further demonstrated with proof-of principle
experiments on Photoactive Yellow Protein (PYP) micro-crystals that high
temporal (10-ns) and spatial (1.5-Å) resolution structures could be achieved.
In summary, this dissertation research heralds the development of the TR-SFX
technique, protocols, and associated data analysis methods that will usher into practice a
new era in structural biology for the recording of ‘molecular movies’ of any biomolecular
process.
ContributorsBasu, Shibom, 1988- (Author) / Fromme, Petra (Thesis advisor) / Spence, John C.H. (Committee member) / Wolf, George (Committee member) / Ros, Robert (Committee member) / Fromme, Raimund (Committee member) / Arizona State University (Publisher)
Created2015
Description
Photosystem I (PSI) is a multi-subunit, pigment-protein complex that catalyzes light-driven electron transfer (ET) in its bi-branched reaction center (RC). Recently it was suggested that the initial charge separation (CS) event can take place independently within each ec2/ec3 chlorophyll pair. In order to improve our understanding of this phenomenon, we have generated new mutations in the PsaA and PsaB subunits near the electron transfer cofactor 2 (ec2 chlorophyll). PsaA-Asn604 accepts a hydrogen bond from the water molecule that is the axial ligand of ec2B and the case is similar for PsaB-Asn591 and ec2A. The second set of targeted sites was PsaA-Ala684 and PsaB-Ala664, whose methyl groups are present near ec2A and ec2B, respectively. We generated a number of mutants by targeting the selected protein residues. These mutations were expected to alter the energetics of the primary charge separation event.
The PsaA-A684N mutants exhibited increased ET on the B-branch as compared to the A-branch in both in vivo and in vitro conditions. The transient electron paramagnetic resonance (EPR) spectroscopy revealed the formation of increased B-side radical pair (RP) at ambient and cryogenic temperatures. The ultrafast transient absorption spectroscopy and fluorescence decay measurement of the PsaA-A684N and PsaB-A664N showed a slight deceleration of energy trapping. Thus making mutations near ec2 on each branch resulted into modulation of the charge separation process. In the second set of mutants, where ec2 cofactor was target by substitution of PsaA-Asn604 or PsaB-Asn591 to other amino acids, a drop in energy trapping was observed. The quantum yield of CS decreases in Asn to Leu and His mutants on the respective branch. The P700 triplet state was not observed at room and cryogenic temperature for these mutants, nor was a rapid decay of P700+ in the nanosecond timescale, indicating that the mutations do not cause a blockage of electron transfer from the ec3 Chl. Time-resolved fluorescence results showed a decrease in the lifetime of the energy trapping. We interpret this decrease in lifetime as a new channel of excitation energy decay, in which the untrapped energy dissipates as heat through a fast internal conversion process. Thus, a variety of spectroscopic measurements of PSI with point mutations near the ec2 cofactor further support that the ec2 cofactor is involved in energy trapping process.
The PsaA-A684N mutants exhibited increased ET on the B-branch as compared to the A-branch in both in vivo and in vitro conditions. The transient electron paramagnetic resonance (EPR) spectroscopy revealed the formation of increased B-side radical pair (RP) at ambient and cryogenic temperatures. The ultrafast transient absorption spectroscopy and fluorescence decay measurement of the PsaA-A684N and PsaB-A664N showed a slight deceleration of energy trapping. Thus making mutations near ec2 on each branch resulted into modulation of the charge separation process. In the second set of mutants, where ec2 cofactor was target by substitution of PsaA-Asn604 or PsaB-Asn591 to other amino acids, a drop in energy trapping was observed. The quantum yield of CS decreases in Asn to Leu and His mutants on the respective branch. The P700 triplet state was not observed at room and cryogenic temperature for these mutants, nor was a rapid decay of P700+ in the nanosecond timescale, indicating that the mutations do not cause a blockage of electron transfer from the ec3 Chl. Time-resolved fluorescence results showed a decrease in the lifetime of the energy trapping. We interpret this decrease in lifetime as a new channel of excitation energy decay, in which the untrapped energy dissipates as heat through a fast internal conversion process. Thus, a variety of spectroscopic measurements of PSI with point mutations near the ec2 cofactor further support that the ec2 cofactor is involved in energy trapping process.
ContributorsBadshah, Syed Lal (Author) / Redding, Kevin E (Thesis advisor) / Fromme, Petra (Committee member) / Gould, Ian (Committee member) / Arizona State University (Publisher)
Created2014
Description
A vast amount of energy emanates from the sun, and at the distance of Earth, approximately 172,500 TW reaches the atmosphere. Of that, 80,600 TW reaches the surface with 15,600 TW falling on land. Photosynthesis converts 156 TW in the form of biomass, which represents all food/fuel for the biosphere with about 20 TW of the total product used by humans. Additionally, our society uses approximately 20 more TW of energy from ancient photosynthetic products i.e. fossil fuels. In order to mitigate climate problems, the carbon dioxide must be removed from the human energy usage by replacement or recycling as an energy carrier. Proposals have been made to process biomass into biofuels; this work demonstrates that current efficiencies of natural photosynthesis are inadequate for this purpose, the effects of fossil fuel replacement with biofuels is ecologically irresponsible, and new technologies are required to operate at sufficient efficiencies to utilize artificial solar-to-fuels systems. Herein a hybrid bioderived self-assembling hydrogen-evolving nanoparticle consisting of photosystem I (PSI) and platinum nanoclusters is demonstrated to operate with an overall efficiency of 6%, which exceeds that of land plants by more than an order of magnitude. The system was limited by the rate of electron donation to photooxidized PSI. Further work investigated the interactions of natural donor acceptor pairs of cytochrome c6 and PSI for the thermophilic cyanobacteria Thermosynechococcus elogantus BP1 and the red alga Galderia sulphuraria. The cyanobacterial system is typified by collisional control while the algal system demonstrates a population of prebound PSI-cytochrome c6 complexes with faster electron transfer rates. Combining the stability of cyanobacterial PSI and kinetics of the algal PSI:cytochrome would result in more efficient solar-to-fuel conversion. A second priority is the replacement of platinum with chemically abundant catalysts. In this work, protein scaffolds are employed using host-guest strategies to increase the stability of proton reduction catalysts and enhance the turnover number without the oxygen sensitivity of hydrogenases. Finally, design of unnatural electron transfer proteins are explored and may introduce a bioorthogonal method of introducing alternative electron transfer pathways in vitro or in vivo in the case of engineered photosynthetic organisms.
ContributorsVaughn, Michael David (Author) / Moore, Thomas (Thesis advisor) / Fromme, Petra (Thesis advisor) / Ghirlanda, Giovanna (Committee member) / Redding, Kevin (Committee member) / Arizona State University (Publisher)
Created2014
Description
Membrane proteins are a vital part of cellular structure. They are directly involved in many important cellular functions, such as uptake, signaling, respiration, and photosynthesis, among others. Despite their importance, however, less than 500 unique membrane protein structures have been determined to date. This is due to several difficulties with macromolecular crystallography, primarily the difficulty of growing large, well-ordered protein crystals. Since the first proof of concept for femtosecond nanocrystallography showing that diffraction patterns can be collected on extremely small crystals, thus negating the need to grow larger crystals, there have been many exciting advancements in the field. The technique has been proven to show high spatial resolution, thus making it a viable method for structural biology. However, due to the ultrafast nature of the technique, which allows for a lack of radiation damage in imaging, even more interesting experiments are possible, and the first temporal and spatial images of an undamaged structure could be acquired. This concept was denoted as time-resolved femtosecond nanocrystallography.
This dissertation presents on the first time-resolved data set of Photosystem II where structural changes can actually be seen without radiation damage. In order to accomplish this, new crystallization techniques had to be developed so that enough crystals could be made for the liquid jet to deliver a fully hydrated stream of crystals to the high-powered X-ray source. These changes are still in the preliminary stages due to the slightly lower resolution data obtained, but they are still a promising show of the power of this new technique. With further optimization of crystal growth methods and quality, injection technique, and continued development of data analysis software, it is only a matter of time before the ability to make movies of molecules in motion from X-ray diffraction snapshots in time exists. The work presented here is the first step in that process.
This dissertation presents on the first time-resolved data set of Photosystem II where structural changes can actually be seen without radiation damage. In order to accomplish this, new crystallization techniques had to be developed so that enough crystals could be made for the liquid jet to deliver a fully hydrated stream of crystals to the high-powered X-ray source. These changes are still in the preliminary stages due to the slightly lower resolution data obtained, but they are still a promising show of the power of this new technique. With further optimization of crystal growth methods and quality, injection technique, and continued development of data analysis software, it is only a matter of time before the ability to make movies of molecules in motion from X-ray diffraction snapshots in time exists. The work presented here is the first step in that process.
ContributorsKupitz, Christopher (Author) / Fromme, Petra (Thesis advisor) / Spence, John C. (Thesis advisor) / Redding, Kevin (Committee member) / Ros, Alexandra (Committee member) / Arizona State University (Publisher)
Created2014