The human society of today has a significantly negative impact on the environment and needs to change its way of living towards a more sustainable path if to continue to live on a healthy planet. One path is believed to be an increased usage of naturally degradable and renewable raw materials and, therefore, attention has been focused on the highly abundant biopolymer cellulose. However, a large drawback with cellulose-based materials is the significant change of their mechanical properties when in contact with water. Despite more than a century of research, the extensively investigated interaction between water and cellulose still possesses many unsettled questions, and if the answer to those were known, cellulose-based materials could be more efficiently utilized. It is well understood that one interaction between cellulose and water is through hydrogen bonds, established between water and the hydroxyl groups of the cellulose. Due to the very similar properties of the hydroxyl groups in water and the hydroxyl groups of the cellulose, the specific interaction-induced effect on the hydroxyl groups at a cellulose surface is difficult to investigate.  Therefore, a method based on 2H MAS NMR spectroscopy has been developed and validated in this work. Due to the verified ability of the methodology to provide site-selective information regarding the molecular dynamics of the cellulose deuteroxyl groups (i.e. deuterium-exchanged hydroxyl groups), it was shown by investigating 1H-2H exchanged cellulose samples that only two of the three accessible hydroxyl groups (on the surface of cellulose fibrils) exchange with water. This finding was also verified by FT-IR spectroscopy, and together with MD simulations we could establish that it is O(2)H and O(6)H hydroxyl groups (of the constituting glucose units) that exchange with water. From the MD simulations additional conclusion could be drawn regarding the molecular interactions required for hydrogen exchange; an exchanging hydroxyl group needs to donate its hydrogen in a hydrogen bond to water. Exchange kinetics of thin cellulose films were investigated by monitoring two different exchange processes with FT-IR spectroscopy. Specific information about the two exchanging hydroxyl/deuteroxyl groups was then extracted by deconvoluting the changing intensities of the recorded IR spectra. It was recognized that the exchange of the hydroxyl groups were well described by a two-region model, which was assessed to correspond to two fibrillary surfaces differentiated by their respective positions in the fibril aggregate. From the detailed deconvolution it was also possible to estimate the fraction of these two surfaces, which indicated that the average aggregate of cotton cellulose is built up by three to four fibrils.                       2H MAS NMR spectroscopy was used to examine different states of water in cellulose samples, hydrated at different relative humidities of heavy water. The results showed that there exist two states of water adsorbed onto the cellulose, differentiated by distinct different mobilities. These two states of water are well separated and had negligible exchange on the time scale of the experiments. It was suggested that they are located at the internal and external surfaces of the fibril aggregates. By letting cellulose nanofibrils undergo an epoxidation reaction with a mono epoxide some indicative results regarding how to protect the cellulose material from the negative impact of water were presented. The protecting effect of the epoxidation were examined by mechanically testing and NMR spectroscopy. It was proposed that by changing the dominant interaction between the fibril aggregates from hydrophilic hydrogen bonds to hydrophobic π-interactions the sensitivity to moisture was much reduced. The results also indicated that the relative reduction in moisture sensitivity was largest for the samples with highest moisture content. / <p>QC 20161229</p>

Actuellement le criblage en vue de la recherche de nouveaux agents antitumoraux se base principalement sur la qualité cytotoxique d’une molécule. Le principal défaut de cette approche est qu’aucune sélection n’est faite sur le mode d’action du médicament. L’objectif de ce travail est la mise au point d’une méthode permettant un classement rapide et objectif du mode d’action de molécules à visée thérapeutique par spectroscopie infrarouge. La spectroscopie infrarouge est une technique d’absorption de la lumière fournit la signature chimique d’un échantillon. L’excellente qualité du signal rend possible son utilisation comme outil discriminant. En outre, cette technique d’analyse se démarque des autres par son caractère non destructif et la rapidité d’acquisition des données. Elle se révèlerait donc une méthode de choix pour effectuer du criblage de molécules en vue de la recherche de nouveaux agents thérapeutiques. Dans un premier temps nous avons voulu évaluer la possibilité d’utiliser la spectroscopie infrarouge pour isoler la signature spectrale du mode d’action induit par des concentrations sub-létales de ouabaïne, un composé de la famille des cardénolides, sur une lignée tumorale de prostate. Nous avons montré que cette signature évolue au cours du temps et peut-être corrélée aux données biologiques décrites dans la littérature. Nous avons également mis en évidence pour la première fois une modification de la composition lipidique de la cellule. Cette altération a été caractérisée au cours du temps par spectrométrie de masse. Nous avons ensuite voulu définir les limites de la méthode. La littérature souligne la diversité des modes d’action que peut induire un agent thérapeutique selon sa concentration. Nous avons montré que cette diversité se reflète sur le spectre infrarouge de cellules tumorales traitées à la ouabaïne en distinguant au moins deux modes d’action distincts, dépendant de la concentration en ouabaïne. Par ailleurs, nous avons montré que la confluence pouvait modifier significativement le spectre infrarouge d’une cellule. Neanmoins cette signature est unique et orthogonale à celle induite par la ouabaïne. Finalement, nous avons évalué le potentiel de la spectroscopie infrarouge à distinguer des modes d’action induits par des molécules à la structure chimique proche. Nous avons montré qu’il était possible de caractériser spécifiquement chacun des modes d’action. D’autre part nous avons mis en évidence que les modes d’action de molécules issues d’une même classe d’agent thérapeutique conduisaient à des signatures spectrales similaires. Cette partie du travail souligne la possibilité d’utilisation de la spectroscopie infrarouge pour un classement objectif, uniquement basé sur leur mode d’action d’agents thérapeutiques potentiels.

Protein based biopharmaceuticals are becoming increasingly popular therapeutic agents. Recent changes to the legislation governing stem cell technologies will allow many further developments in this field. Characterisation of these therapeutic proteins poses numerous analytical challenges. In this work we address several of the key characterisation problems; detecting glycosylation, monitoring conformational changes, and identifying contamination, using vibrational spectroscopy. Raman and infrared spectroscopies are ideal techniques for the in situ monitoring of bioprocesses as they are non-destructive, inexpensive, rapid and quantitative. We unequivocally demonstrate that Raman spectroscopy is capable of detecting glycosylation in three independent systems; ribonuclease (a model system), transferrin (a recombinant biopharmaceutical product), and GFP (a synthetically glycosylated system). Raman data, coupled with multivariate analysis, have allowed the discrimination of a glycoprotein and the equivalent protein, deglycosylated forms of the glycoprotein, and also different glycoforms of a glycoprotein. Further to this, through the use of PLSR, we have achieved quantification of glycosylation in a mixture of protein and glycoprotein. We have shown that the vibrational modes which are discriminatory in the monitoring of glycosylation are relatively consistent over the three systems investigated and that these bands always include vibrations assigned to structural changes in the protein, and sugar vibrations that are arising from the glycan component. The sensitivity of Raman bands arising from vibrations of the protein backbone to changes in conformation is evident throughout the work presented in this thesis. We used these vibrations, specifically in the amide I region, to monitor chemically induced protein unfolding. By comparing these results to fluorescence spectroscopy and other regions of the Raman spectrum we have shown that this new method provides improved sensitivity to small structural changes. Finally, FT-IR spectroscopy, in tandem with supervised machine learning methods, has been applied to the detection of protein based contaminants in biopharmaceutical products. We present a high throughput vibrational spectroscopic method which, when combined with appropriate chemometric modelling, is able to reliably classify pure proteins and proteins ‘spiked’ with a protein contaminant, in some cases at contaminant concentrations as low as 0.25%.

<p>The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood.</p><p>The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material.</p><p>Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material.</p>

The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood. The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material. Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material. / QC 20101123

Several traditional methods have been used to characterise bacteria, such as biochemical, morphological and molecular tests; however, these methods are time-consuming and not always reliable. Recently, modern analytical techniques have emerged as powerful tools offering high-throughput, reliable and rapid analysis in applications, such as clinical and microbiology studies. A variety of modern analytical techniques have been employed for bacterial characterisation, including matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), liquid chromatography-mass spectrometry (LC-MS), Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy. This thesis focused on developing a robust MALDI-TOF-MS methodology to generate mass spectra profiles for the discrimination of clinically-significant bacteria. The data generated from MALDI-TOF-MS analysis are significantly influenced by a number of experimental factors, namely instrument settings, sample preparation, the choice of matrix, matrix additives and matrix preparation as well as sample-matrix deposition methods. The need to optimise experimental variables for bacterial analysis using MALDI-TOF-MS was evident despite the increased application of this analytical tool for clinical microbiology. Experimental optimisation revealed that the choice of matrix is the most important element in MALDI-TOF-MS analysis. Based on this study, a number of different matrices were used to obtain more reproducible mass spectra to classify bacterial samples using a rapid and effective approach. Studies in this thesis indicated that sinapinic acid (SA) is the best matrix for the analysis of proteins from intact bacteria, while 6-aza-2-thiothymine (ATT) and 2,5-dihydroxybenzoic acid (DHB) produced promising results for the analysis of lipid extracts from bacteria. Analytical techniques in combination with multivariate analysis, such as principal components analysis (PCA) and principal component-discriminant function analysis (PC-DFA), were used for bacterial discrimination. Classification was initially undertaken using MALDI-TOF-MS analysis, and subsequently FT-IR spectroscopy, Raman spectroscopy and LC-MS were performed to confirm the classification results. Two main types of bacteria were used for this analysis: 34 strains from seven Bacillus and Brevibacillus species and 35 isolates from 12 Enterococcus faecium strains. The findings showed that the four analytical techniques provide clear discrimination between bacteria at these different levels. Classification of different Bacillus and Brevibacillus bacteria using MALDI-TOF-MS analysis of extracted lipids was confirmed by LC-MS data. In addition, MALDI-TOF-MS data based on extracted lipids and intact bacterial cell proteins were very similar. MALD-TOF-MS analysis of intact enterococci cells produced successful classification with 78% correct classification rate (CCR) at the strain level. FT-IR and Raman spectroscopic data produced very similar bacterial classification with CCR of 89% and 69% at the strain level, respectively. However, classification based on MALDI-TOF-MS data and that based on spectroscopic data were slightly different (Procrustes distance of 0.81, p < 0.001, at the species level). Overall, the findings in this thesis indicate the potential of MALDI-TOF-MS as a rapid, robust and reliable method for the classification of bacteria based on different bacterial preparations.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-01-26T14:34:24Z No. of bitstreams: 1 2016 - Danielle Affonso Sampaio.pdf: 3006939 bytes, checksum: 839c5d77a13fd99ad3c749c33dc2530a (MD5) / Made available in DSpace on 2017-01-26T14:34:25Z (GMT). No. of bitstreams: 1 2016 - Danielle Affonso Sampaio.pdf: 3006939 bytes, checksum: 839c5d77a13fd99ad3c749c33dc2530a (MD5) Previous issue date: 2016-05-19 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / Seed integument plays an important role in the plant life cycle, monitoring the embryo development and germination. Informations about cell structure and physico-chemical characteristics of the Araucaria angustifolia seed coat are important to its correct functional interpretation. Thus, the aim of this study was the anatomical and physico-chemical characterization of the Araucaria angustifolia seed integument. Anatomical features were observed using different microscopy techniques (brightfield microscopy, fluorescence microscopy and scanning electron microscopy) and histochemical tests (Lugol, Wiesner, Sudan IV and potassium dichromate ? K2Cr2O7). Chemical analysis included the extractive, holocelulose and Klason lignin contents (untreated and treated with sodium hydroxide ? NaOH). Functional groups of the integument layers and lignin were observed by Fourier transformed infrared spectroscopy using a VARIAN 640-IR FT-IR spectrometer. Colour analyses were performed in CIE 1976 L*a*b* space colour according to ISO 11664-4:2008 standard using CM 2600d spectrometer. Wettability of the layers was evaluated by contact angle analysis with the drop shape analyser DSA 100. The Araucaria angustifolia seed integument is composed by three distinct layers: exotesta, mesotesta and endotesta. The layers have different chemical and anatomical characteristics. Lignin structure of the integument layers was classified as guayacil (G) type. The endotesta was the layer with higher chromaticity due to higher extractive content and phenolic substances. The wettability varied between layers according to ther strusture. The results of this study contribute to a better understanding of the functioning of the Araucaria angustifolia seed integument and corroborate to future studies on seed physiology / O tegumento de semente desempenha um papel importante no ciclo de vida do vegetal, controlando o desenvolvimento do embri?o e a germina??o. O conhecimento da estrutura celular e das caracter?sticas f?sico-qu?micas do tegumento da semente de Araucaria angustifolia ? importante para a correta interpreta??o funcional do mesmo. Sendo assim, o objetivo deste estudo consistiu na caracteriza??o anat?mica e f?sico-qu?mica do tegumento da semente de Araucaria angustifolia. As caracter?sticas anat?micas foram observadas atrav?s de diferentes t?cnicas de microscopia (microscopia de campo claro, microscopia de fluoresc?ncia e microscopia eletr?nica de varredura) e testes histoqu?micos (Lugol, Wiesner, Sudan IV e dicromato de pot?ssio ? K2Cr2O7). Nas an?lises qu?micas, determinou-se os teores de extrativos, holocelulose e lignina de Klason tratada e n?o-tratada com hidr?xido de s?dio ?NaOH. Os grupos funcionais das camadas do tegumento e da lignina foram observados por espectroscopia no infravermelho por transformada de Fourier atrav?s do espectr?metro VARIAN 640-IR FT-IR. As an?lises colorim?tricas foram realizadas no espa?o de cor L*a*b* CIE 1976 segundo a norma ISO 11664-4: 2008 utilizando o espectrofot?metro CM 2600d. A molhabilidade das camadas foi avaliada atrav?s de an?lises de ?ngulo de contato com o sistema de formato da gota DSA 100. O tegumento da semente de Araucaria angustifolia ? composto por tr?s camadas distintas: exotesta, mesotesta e endotesta. As camadas apresentam caracter?sticas qu?micas e anat?micas distintas. A estrutura da lignina das camadas do tegumento foi classificada como guaiac?lica (G). A endotesta foi a camada com maior cromaticidade devido ao maior teor de extrativos e subst?ncias fen?licas. A molhabilidade variou entre as camadas em fun??o da sua estrutura. Os resultados deste estudo contribuem para uma melhor compreens?o do funcionamento do tegumento da semente de Araucaria angustifolia, podendo corroborar com estudos futuros sobre a fisiologia da semente

Šiame darbe nagrinėjami radiaciniai defektai bei jų tarpusavio reakcijos silicyje. Atlikti eksperimentai, kurių metu pasitelkus minkštąją Rentgeno spinduliuotę buvo generuojami defektai. Vėliau bandiniai buvo tiriami FT-IR spektroskopijos metodais. Darbo apimtis 52 puslapiai. Darbas susideda iš 5 dalių. Pirmoje dalyje apžvelgiami Rentgeno spinduliuotės šaltiniai ir spinduliuotės savybės. Antroje - dalyje radiaciniai defektai silicyje. Trečioje - defektų tyrimo metodai. Ketvirtoje - dalyje defektų reakcijos. Penktoje - eksperimento metodika ir eksperimento rezultatai. / In this work, we are researching radiation defects and their reactions in silicon. During experiments defects were generated using soft Rentgen radiance. Later samples were researched using FT-IR methods of spectroscopy. Work amount is 52 pages. Work consists from 5 parts. First part - overview of sources and features of Rentgen radiance. Second part – radiation defects in silicon. Third part – methods of defect researching. Fourth part – reactions of defects. Fifth part – Methods and results of experiment.

High blood glucose levels induce metabolic disorders that initiate a sequence of events including renal, arterial, cardiac and retinal disorders. Diabetes mellitus increases oxidative stress in tissues of animals including humans. The resulting oxidative stress might play role in the development of diabetic complications. In the present study, 36 male Wistar rats (250-300g) were divided into 5 groups as Control (n=6), Diabetic (n=7), Diabetic + Vit C (n=7), Diabetic + &amp / #945 / -Lipoic acid (n=6) and Diabetic + Combination of Vit C and &amp / #945 / -Lipoic acid (n=10). From the livers of all groups cytoplasmic and microsomal membrane fractions were prepared from liver and antioxidant enzymes namely, superoxide dismutase, glutathione peroxidase, catalase and glutathione S-transferase activities were measured. Microsomal lipid peroxidation, total lipid, total protein, reduced glutathione levels of each group was determined and compared. Microsomal fractions were also analyzed by FT-IR spectroscopy. The total protein levels of diabetic rats were found to be decreased significantly (p&lt / 0.05) compared to controls and the &amp / #945 / -lipoic acid and vitamin C supplemented groups tend to compensate the decreased levels of total proteins. Decreased catalase activity in diabetic group compared to control was restored by &amp / #945 / -lipoic acid, vitamin C treatment and/or combination of both. Increased glutathione peroxidase activity was decreased to control levels by the treatement of both &amp / #945 / -lipoic acid and vitamin C. Superoxide dismutase activities of diabetic rats were increased (p&lt / 0.05) compared to control group. Whereas glutathione S-transferase activities though showed some fluctuations, the results were not statistically significant. Total glutathione levels decreased in all groups significantly (p&lt / 0.0.5) compared to control group but any of the agent failed to compensate the reduced levels of glutathione. As an index of lipid peroxidation, TBA-reactivity (MDA) levels increased significantly in all diabetic groups and only combination group&rsquo / s TBARS levels decreased significantly compared to diabetic group. FT-IR study of rat liver microsomal membranes was carried out in order to understand the effects of diabetes on membrane order, dynamics and lipid peroxidation status. For this purpose CH2 symmetric wavenumber, CH2 antisymmetric bandwidth, =CH olefinic band area were compared. In temperature dependent FT-IR studies microsomal membrane phase behavior, order and dynamics were analyzed. Diabetic samples showed apparent decrease in both frequency and bandwidth. =CH olefinic band integrated area was increased for diabetic samples compared to controls. Alpha-lipoic acid and vitamin C supplemented groups showed similar effects. They tend to restore decreased levels of band frequency and bandwidth. Additive effect between &amp / #945 / -lipoic acid and vitamin C was seen in some cases that only the combination group achieved to restore control values while &amp / #945 / -lipoic acid and vitamin C were failed to restore alone. In conclusion, STZ-induced diabetes mainly caused an increase in antioxidant enzyme activities. Also, increase in lipid peroxidation caused a decrease in the fluidity and order of the membrane resulting in more rigid membrane structures. The loss of cooperation between the antioxidant network may play a role in the secondary complications of diabetes.

Previous research has underscored the importance of protein dynamics during light-induced electron transfer; however, specific interactions have not been well characterized. It is of particular importance to understand the role of protein dynamics and cofactor interactions in controlling electron transfer in oxygenic photosynthesis. These factors include hydrogen bonding, ð-stacking and electrostatic interactions. Reaction-induced FT-IR spectroscopy is sensitive to these interactions as well as isotopic incorporation, and is useful to probe protein dynamics associated with light-induced electron transfer in Photosystem I (PSI). Density functional theory (DFT) provides information concerning the vibrational frequencies of molecules as well as the amplitudes of the vibrations and sensitivity to isotope incorporation. Combining these approaches, protein dynamics associated with light-induced electron transfer in PSI were studied. The work presented here describes specific protein cofactor interactions and specific protein relaxation events associated with light-induced electron transfer. The results reported here are consistent with noncovalent protein cofactor interactions that modulate the redox potential of the secondary electron acceptor of PSI. Furthermore, the studies presented here describe novel protein dynamics associated with the oxidation of the terminal electron donor of PSI. These results characterize specific protein dynamics that may be associated with interactions of the soluble electron donors. These studies highlight the importance of protein dynamics in oxygenic photosynthesis.