Dissertations / Theses on the topic 'Microspectrophotometry'

Syngnathidae (seahorse, pipefish, pipehorses & seadragons) are highly visual feeders with different species feeding on specific types of prey, a behaviour that has been related to snout length. Worldwide, many species have become threatened by habitat destruction, collection for the aquarium trade and exploitation for traditional medicine, as well as recreational and commercial bycatch. Attempts to establish aquaculture programs have been of limited success. Little is known about their visual capabilities in detail. The visual systems of fishes are known to have evolved specific adaptations that can be related to the colour of water in which they live and specific visual tasks such as predator detection and acquisition of food. This study examined the ocular and retinal morphology, photoreceptor structure and spectral sensitivity of adult individuals of a local pipefish (S. argus), local seahorse (Hippocampus subelongatus) which both inhabit green water seagrass beds, and a tropical species of seahorse (Hippocampus barbouri) from blue water coral reefs. Some juveniles were also investigated. Accordingly, we developed an understanding of the features that are common to all syngnathids and those that have evolved for specific environments. Cryosections of the eyes were taken to determine morphological distinctions of this group. Lens characteristics measured using a spectrophotometer determined 50% cut-off wavelengths below 408nm for all 3 species, hence no transmission of UV light to the retina. Histological examination determined a cone dominated fovea in the ventro-temporal retina and very large rods concentrated in the peripheral retina and adjacent to the optic nerve. Microspectrophotometry measured the absorption characteristics of the visual pigments within the photoreceptors showing the presence and maximum sensitivity (λmax) of rods, SWS single cones, and a broad, complex array of LWS double/twin cones. The results are discussed in relation to the light environment inhabited by each species and their feeding requirements. The implications for the design of suitable light environments for aquarium and aquaculture programs for the Syngnathidae are also discussed. Rearing success of this family of fish, for both the aquarium trade and re-stocking programs, would be advised to take lighting regimes and specifics of the animals’ vision into account

This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf
Bachelors
Arts and Sciences
Forensic Science

O presente trabalho tem como objetivo estudar as modificações ocorridas na cana-de-açúcar, com diferentes composições químicas e estruturais, pelo pré-tratamento sulfito alcalino. A remoção de lignina e hemicelulose, bem como a introdução de grupos sulfônicos em cana-de-açúcar que ocorrem durante o pré-tratamento sulfito alcalino tornam mais fácil a hidrólise da celulose. A compreensão das modificações químicas e físicas em materiais lignocelulósicos que ocorrem durante este pré-tratamento é fundamental para a geração de processos mais eficazes. Neste trabalho, bagaço e entrenós de cana-de-açúcar, selecionados de plantas híbridas com composição química variada, foram pré-tratados em condições brandas com 10% de sulfito e 5% de hidróxido de sódio por diferentes tempos. No início do pré-tratamento, a deslignificação aumentou rapidamente, o mesmo não aconteceu com a hemicelulose. Nos primeiros 30 min de pré-tratamento do bagaço de cana-de-açúcar houve remoção de 50% da lignina inicial e 30% da hemicelulose, o que ocasionou uma melhora significativa na conversão de celulose, atingindo 64%. Mesmo sem remoção adicional de lignina e hemicelulose, o processo continuou a introduzir os grupos ácidos, o que contribuiu para o inchamento da fibra. A largura da fibra do bagaço não tratado aumentou de 10,4 ?m para 30 ?m no material pré-tratado com 120 min. Estas modificações na fibra foram responsáveis pelo aumento na eficiência da hidrólise enzimática da celulose, a qual atingiu 92%. Híbridos experimentais com teores reduzidos de lignina apresentaram taxas iniciais de hidrólise mais elevadas e um menor tempo de pré-tratamento para alcançar a conversão total de celulose do que a cana de referência. Diferentes regiões (medula, interface, córtex e fração externa) dos entrenós das canas foram hidrolisadas por celulases. O pré-tratamento da interface, córtex e fração externa com sulfito-alcalino produziu substratos menos recalcitrantes com o aumento do tempo de reação e resultou na melhora da hidrólise enzimática. Foram utilizadas várias técnicas para avaliar as mudanças que ocorreram durante o pré-tratamento, as quais foram capazes de estudar a morfologia da superfície e as características químicas das amostras. O tratamento químico ocasionou uma intensa deslignificação e alterações morfológicas nas superfícies das fibras da cana-de-açúcar. A redução na absorção a 285 nm e 315 nm das paredes celulares das fibras, parênquima e dos vasos aumentou substancialmente os valores de conversão enzimática da celulose e da hemicelulose. Microscopia eletrônica de varredura por emissão de campo (FE-SEM) revelou que as fibras da região do córtex e, especialmente, da interface mostrou paredes celulares colapsadas após a parcial deslignificação. Após o tratamento sulfito alcalino, os dados de espectroscopia fotoelétrica de raio-X (XPS) e espectrometria de massa de íons secundários por tempo de vôo (TOF-SIMS) apresentaram um aumento das intensidades dos sinais nas superfícies das fibras, os quais foram atribuídos à presença de carboidratos em algumas amostras. Em conformidade, os sinais de lignina diminuíram nas superfícies das fibras das mesmas amostras.
The present work aims to study the changes occurring in sugar cane, with different in structure and chemical compositions, by sulfite-alkaline pre-treatment. Removing lignin and hemicellulose as well as introducing sulfonic groups in sugar cane pretreated with alkaline sulfite made cellulose hydrolysis easier. Understanding the chemical and physical alterations occurring during this pretreatment of lignocellulosic materials is fundamental for the generation of effective pretreatment methods. In the present work, sugarcane bagasse and also sugar cane internodes, selected from experimental hybrid plants, were pretreated with the alkaline-sulfite process under mild conditions with varied cooking times. The first 30 min of pretreatment of sugar cane bagasse, which removed approximately half of the initial lignin and 30% of hemicellulose seemed responsible for a significant enhancement of the cellulose conversion level, which reached 64%. After the first 30 min of pretreatment, delignification increased slightly and hemicellulose removal was not enhanced. However, the process continued to introduce acid groups into the residual lignin that enhanced the fiber swelling up to 120 min of cooking. The fiber widths increased from 10,4 ?m in the untreated bagasse to 30 ?m in the 120 min-pretreated material. These changes were responsible for an additional increase in the efficiency of enzymatic hydrolysis of the cellulose, which reached 92%. Experimental hybrids with less original lignin presented higher initial hydrolysis rates than reference sugar cane and required lower time of pretreatment to achieve the total cellulose conversion. Different regions (pith, interface, rind and outermost fraction) of the internodes of types of sugarcanes were hydrolyzed by cellulases. The pretreatment of the interface, rind and outermost fraction with alkaline sulfite produced less recalcitrant substrates with increasing reaction time and resulted in improvement enzymatic hydrolysis. Several techniques enabling the study of surface morphological and chemical characteristics were used to evaluate the changes occurring during the pretreatment step. The chemical treatment caused intense delignification and morphological changes on the sugar cane fiber surfaces. The reduction in the absorption at 285 nm and 315 nm of the cell walls of the fibers, parenchyma and vessel, substantially increased the values of enzymatic conversion of cellulose and hemicellulose. Field emission scanning electron microscopy (FE-SEM) indicated that the fibers from rind regions and especially from the interface showed collapsed cell walls after partial delignification. After the alkaline sulfite treatment, X-ray photoelectrom spectroscopy (XPS) and time-of-flight-secondary ion mass spectrometry (ToF-SIMS) data showed increased signal intensities on the fibers surfaces assigned to carbohydrates of some samples. In accordance, the lignin signals diminished on the fiber surfaces of the same samples.

Depuis la découverte de la protéine fluorescente verte (GFP), celle des protéines fluorescentes photoactivables (PAFPs) a initié une révolution dans le domaine de la technologie des FP. Certaines PAFPs sont capables d'être irréversiblement photo converties d'une couleur à une autre alors que d'autres peuvent être réversiblement commutées entre des formes allumées ou éteintes. Ces protéines son intensivement employées dans les techniques de microscopie optique, particulièrement en "nanoscopie" qui permet d'atteindre une résolution optique 1 0 fois meilleure que la limite d'Abbe. Afin de développer plus en avant ces techniques, la nécessité d'obtenir des sondes fluorescentes plus lumineuses pouvant se photoconvertir ou se photocommuter efficacement est cruciale. En même temps, les marqueurs fluorescents doivent être monomériques et photostables. Pour mieux comprendre les mécanismes des phototransformations des PAFPs, trois membres de la famille ont été étudiés: EosFP, Dendra2 et IrisFP. Le phénomène de photoconversion du vert au rouge de photocommutation réversible et de photoblanchiment ont été étudiés grâce à une combinaison de cristallographie des rayons X et dl microspectrophotométrie, en utilisant le laboratoire Cryobench de l'ESRF/IBS. Les résultats nous ont permis de proposer un mécanisme de photoconversion pour EosFP et Dendra2 et de découvrir et caractériser IrisFP, première PAFP combinant à la fois les propriétés de photoconversion et de photocommutation. Les modifications structurales du chromophore associées à la formation d'un état radicalaire induit par les rayons X, probablement impliqué dans la voie de photoblanchiment des P AFPs, ont aussi été caracterisées
Since the discovery of the green fluorescent protein (GFP), the one of photoactivatable fluorescent proteins (P AFPs), notably from Anthozoan species, triggered a revolution in the field of FP technology. Sorne PAFPs are capable of being irreversibly photoconverted from a green- to a red-emitting form while other ones can be reversibly switched on and off, depending on specific excitation wavelengths. These proteins are being extensively used in optical microscopy techniques, particularly in "nanoscopy", which pro vides optical resolution 10 fold beyond the Abbe limit. Ln order to further develop these techniques, notably in term of time-resolution, the need to obtain brighter fluorescent probes that photoconvert or photoswitch efficiently is crucial. At the same time, fluorescent highlighters generally need to be monomeric and photostable. Ln order to better understand the mechanisms of phototransformations in PAFPs, three members of the family have been studied: EosFP, Dendra2 and IrisFP. The phenomena of green-to-red photoconversion, reversible photoswitching and non-reversible photobleaching have been studied by a combination of X-ray crystallography and microspectrophotometry using the Cryobench laboratory of the ESRF/IBS. Together, the results have a\lowed us to propose a mechanism for the photo conversion of EosFP and Dendra2 and to discover and characterize IrisFP, the first PAFP combining both properties of photoconversion and photoswitching. The structural modifications of the chromophore associated with an X-ray induced radical state, likely to be involved in thé photobleaching pathway of PAFPs, were also characterized

[Truncated abstract] The aims of the study were twofold; firstly, to describe the inequality in infant mortality in Indonesia namely, to look at the extent and magnitude of the problem in terms of the estimated number of infant deaths, the differentials in infant mortality rates, the probability of infant deaths across provinces, urban and rural areas, and across regions of Indonesia. Secondly, to examine the effect of family welfare status and maternal educational levels on the probability of infant deaths. The study design was that of a population-based multistage stratified survey of the 1997 Indonesian Demographic and Health Survey. Results of the study were obtained from a sample of 28,810 reproductive women aged 15 to 49 years who belonged to 34,255 households. A binary outcome variable was selected, namely, whether or not each of the live born infant(s) from the interviewed women was alive or dead prior to reaching one year of age. Of interest were the variables related to socio-economic status, measured by Family Welfare Status Index and maternal educational levels. The following risk factors were also investigated: current contraceptive methods; birth intervals; maternal age at first birth; marital duration; infants’ size perceived by the mothers; infants’ birth weight; marital status; prenatal care by health personnel; antenatal TT immunization; place of delivery; and religion. Geographical strata (province) and residence (urban and rural areas) were also considered. Both descriptive and multivariate analyses were undertaken. Descriptive analysis was aimed at obtaining non-biased estimates of the infant mortality rates at the appropriate levels of aggregation. Multivariate analysis involved a logistic regression model using the Generalized Estimating Equations (GEE) model-fitting technique. The procedure, a multilog-cumlogit , uses the Taylor Series Linearization methods to compute modelbased variance, and which adjusts for the complex sampling design. Results of descriptive analysis indicate that, indeed, there are inequalities in infant mortality across administrative divisions of the country, represented by provinces and regions, as well as across residential areas, namely urban and rural areas. Also, the results suggested that there is socio-economic inequality in infant mortality, as indicated by a dose-response effect across strata of family welfare and maternal educational levels, both individually and interactively. These inequalities varied by residence (urban and rural), provinces and regions (Java Bali, Outer Java Bali I and Outer Java Bali II). Furthermore, the probability of infant mortality was significantly greater among highrisk mothers, characterized by a number of risk factors used in the study

The National Academy of Sciences recently published a report which calls for improvements to the field of forensic science. Their report criticized many forensic disciplines for failure to establish rigorously-tested methods of comparison, and encouraged more research in these areas to establish limitations and assess error rates. This study applies chemometric and statistical methods to current and developing analytical techniques in fiber analysis. In addition to analysis of commercially available dyed textile fibers, two pairs of dyes are selected for custom fabric dyeing based on the similarities of their absorbance spectra and dye molecular structures. Visible absorption spectra for all fiber samples are collected using microspectrophotometry (MSP) and mass spectra are collected using electrospray ionization (ESI) mass spectrometry. Statistical calculations are performed using commercial software packages and software written in-house. Levels of Type I and Type II error are examined for fiber discrimination based on hypothesis testing of visible absorbance spectra profiles using a nonparametric permutation method. This work also explores evaluation of known and questioned fiber populations based on an assessment of statistical p-value distributions from questioned-known fiber comparisons with those of known fiber self-comparisons. Results from the hypothesis testing are compared with principal components analysis (PCA) and discriminant analysis (DA) of visible absorption spectra, as well as PCA and DA of ESI mass spectra. The sensitivity of a statistical approach will also be discussed in terms of how instrumental parameters and sampling methods may influence error rates.
ID: 030423335; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.)--University of Central Florida, 2010.; Includes bibliographical references (p. 112-119).
M.S.
Masters
Department of Chemistry
Sciences

Indiana University-Purdue University Indianapolis (IUPUI)
Microspectrophotometry is a quick, accurate, and reproducible method to compare colored fibers for forensic purposes. The use of chemometric techniques applied to spectroscopic data can provide valuable discriminatory information especially when looking at a complex dataset. Differentiating a group of samples by employing chemometric analysis increases the evidential value of fiber comparisons by decreasing the probability of false association. The aims of this research were to (1) evaluate the chemometric procedure on a data set consisting of blue acrylic fibers and (2) accurately discriminate between yellow polyester fibers with the same dye composition but different dye loadings along with introducing a multivariate calibration approach to determine the dye concentration of fibers. In the first study, background subtracted and normalized visible spectra from eleven blue acrylic exemplars dyed with varying compositions of dyes were discriminated from one another using agglomerative hierarchical clustering (AHC), principal component analysis (PCA), and discriminant analysis (DA). AHC and PCA results agreed showing similar spectra clustering close to one another. DA analysis indicated a total classification accuracy of approximately 93% with only two of the eleven exemplars confused with one another. This was expected because two exemplars consisted of the same dye compositions. An external validation of the data set was performed and showed consistent results, which validated the model produced from the training set. In the second study, background subtracted and normalized visible spectra from ten yellow polyester exemplars dyed with different concentrations of the same dye ranging from 0.1-3.5% (w/w), were analyzed by the same techniques. Three classes of fibers with a classification accuracy of approximately 96% were found representing low, medium, and high dye loadings. Exemplars with similar dye loadings were able to be readily discriminated in some cases based on a classification accuracy of 90% or higher and a receiver operating characteristic area under the curve score of 0.9 or greater. Calibration curves based upon a proximity matrix of dye loadings between 0.1-0.75% (w/w) were developed that provided better accuracy and precision to that of a traditional approach.

Indiana University-Purdue University Indianapolis (IUPUI)
Automotive paints have used an ultraviolet (UV) absorbing clear coat system for nearly thirty years. These clear coats have become of forensic interest when comparing paint transfers and paint samples from suspect vehicles. Clear coat samples and their ultraviolet absorbers are not typically examined or characterized using Raman spectroscopy or microspectrophotometry (MSP), however some past research has been done using MSP. Chemometric methods are also not typically used for this characterization. In this study, Raman and MSP spectra were collected from the clear coats of 245 American and Australian automobiles. Chemometric analysis was subsequently performed on the measurements. Sample preparation was simple and involved peeling the clear coat layer and placing the peel on a foil-covered microscope slide for Raman or a quartz slide with no cover slip for MSP. Agglomerative hierarchical clustering suggested three classes of spectra, and principal component analysis confirmed this. Factor loadings for the Raman data illustrated that much of the variance between spectra came from specific regions (400 – 465 cm-1, 600 – 660 cm-1, 820 – 885 cm-1, 950 – 1050 cm-1, 1740 – 1780 cm-1, and 1865 – 1900 cm-1). For MSP, the regions of highest variance were between 230 – 270 nm and 290 – 370 nm. Discriminant analysis showed that the three classes were well-differentiated with a cross-validation accuracy of 92.92% for Raman and 91.98% for MSP. Analysis of variance attributed differentiability of the classes to the regions between 400 – 430 cm-1, 615 – 640 cm-1, 825 – 880 cm-1, 1760 – 1780 cm-1, and 1860 – 1900 cm-1 for Raman spectroscopy. For MSP, these regions were between 240 – 285 nm and 300 – 370 nm. External validation results were poor due to excessively noisy spectra, with a prediction accuracy of 51.72% for Raman and 50.00% for MSP. No correlation was found between the make, model, and year of the vehicles using either method of analysis.

Ray-finned fish from a diversity of distantly related lineages have remarkably large visual opsin repertoires. Starry flounder (Platichthys stellatus) development, morphology, life history, and behavior make this species especially suitable for experiments designed to determine why fish have so many opsins. Human and bird colour vision uses three and five opsins, respectively. Fish often have many more opsins. We sequenced an eye transcriptome to determine the starry flounder opsin repertoire, and used high performance liquid chromatography to determine the chromophore content of the retina. We found eight visual opsins that utilize only 11-cis-retinal (vitamin A1). This species’ entire visual opsin toolkit appears to be functional. The number of distinct cone and rod cell absorbance profiles determined using microspectrophotomery are consistent with the number of visual opsins in the transcriptome. RH2 transcripts were more abundant and SWS1 and SWS2 transcripts were less abundant in the dorsal retina, where cone density was highest, outer segments the longest, and where we observed double cones with outer segments that differed in their wavelength of maximum absorbance. Regions of fish retinas appear to be specialized and I predict that this fine-tuning is enhanced by photoreceptor plasticity and opsin gene duplication and divergence. Studies that compare opsin expression patterns among individuals, populations, or species typically assume that the differences observed influence vision. Direct connections between opsin expression and quantitative behaviours are rare. This thesis aimed to test whether varying opsin expression affects vision by modifying opsin expression and characterizing vision in starry flounder. We held starry flounder in aquaria exposed to either broad spectrum sunlight or green-filtered light. We tested vision by quantifying the visually-mediated camouflage response and we measured opsin expression using digital-PCR. Granularity analysis of photographs of the camouflage response revealed higher overall pattern energy at each of the seven spatial frequency bands in fish exposed to broad spectrum sunlight compared to the green-filtered fish. However, no statistical difference in typical measurements of pattern or contrast (e.g., maximum filter size, the standard deviation of pattern energy, and the proportional power) was observed between the two groups. Opsin expression was different between fish held in the green light environment compared to those exposed to broad spectrum light. SWS1 (UV sensitive) and SWS2B (blue sensitive) were significantly down regulated in response to the green light environment. Surprisingly, this difference was lost after only three hours under a white LED light, suggesting rapid changes in opsin expression in response to the light environment. We found tantalizing, albeit not statistically significant evidence that fish with higher expression of UV- and blue-wavelength sensitive opsins could see more contrast in colour on blue-green checkerboards.
Graduate

博士
國立交通大學
光電工程研究所
104
We develop a confocal microspectrophotometer with a halogen lamp to directly scan the surface reflectivities on the end of the GRIN lens. The pure fused silica is used to be a reference standard for deducing the absolute reflectivities of the Ge-doped core. Then, multi-wavelength refractive index profiles of the Ge-doped core can be further determined based on the Fresnel equation. Moreover, this work shows a connection between the material dispersion of the GRIN rod and the Ge-doped concentrations measured by an energy dispersive spectrometer. A direct image method of surface reflectivities on a cleaved fiber end with a filtered halogen lamp and a TE-cooled CCD with high dynamic range is proposed to measure the multi-wavelength refractive index profiling (RIP). A polished black glass is used to be a reference standard for measuring the absolute reflectivity of the fiber end. With the developed calibration procedures, both the spatially dependent sensitivity and spectral responsivity of the CCD pixels can be eliminated to achieve the high spatial accuracy. Tested fiber is connected with a fiber terminator to prevent errors from the backside return light. With the present method, the RIP can be precisely measured for not only multi-mode fibers but also single-mode fibers. This study also proposes an innovative filter wheel for multi-channel polarization state switching. Two orthogonal linear polarization states or two orthogonal circular polarization states can be easily switched by this apparatus for the characteristic of linear dichroism and circular dichroism. The above methods have several merits such as easy operation, broadband measurement, high resolution, high accuracy and rapid measurement.

Dissertação de Mestrado em Química Forense apresentada à Faculdade de Ciências e Tecnologia
Atualmente, os documentos impressos ainda são bastante utilizados apesar de vivermos na era digital. As tecnologias de impressão estão, cada vez mais, acessíveis a todos podendo, por isso, ser usadas para fins ilegais, como por exemplo contrafação ou falsificação de documentos. A análise forense a documentos tem como objetivo primordial averiguar a autenticidade dos mesmos, sendo uma das vertentes a análise da tinta presente. O objetivo deste trabalho, realizado no Laboratório de Polícia Científica da Polícia Judiciária, foi estudar a eventual influência de alguns fatores nos resultados da análise de tinta de jato de tinta, através das técnicas de microespectrofotometria e de cromatografia de camada fina. Realizou-se um estudo comparativo não só entre a tinta obtida por impressão nos diferentes níveis de qualidade disponíveis nas opções das impressoras, mas também com a tinta recolhida diretamente dos tinteiros. Foram igualmente efetuadas comparações entre a tinta impressa em diversos papéis de marcas, gramagens e cores diferentes. Procedeu-se também à comparação da tinta, impressa no mesmo modo de impressão e no mesmo suporte, mas após sujeita a diferentes tratamentos físicos, químicos e de exposição à luz. Demonstrou-se que as técnicas usadas são muito robustas, uma vez que, os resultados da análise à tinta de impressão são idênticos entre si, independentemente da forma de obtenção da amostra de tinta (qualidade de impressão e/ou recolha direta do tinteiro), do papel utilizado e do tratamento a que o conjunto tinta + papel foi sujeito. Porém, concluiu-se que a cor de fundo do papel pode alterar os espectros de absorção da tinta, dificultando deste modo a análise por microespectrofotometria.
Although we live in the digital era, printed documents still have a very important role in our daily life. Printing technologies became more accessible and affordable leading to its illegally misuse, such as in fraud and document forgeries. The forensic analysis of documents aims to verify their authenticity. One of its fields of study is the analysis of the printed ink used in those documents. The purpose of this research, that took place at the Forensic Science Laboratory (LPC) of the Portuguese Criminal Police (Polícia Judiciária), was to study the influence of some factors on the analysis of inkjet ink, using microspectrophotometry and thin-layer chromatography. To accomplish these objectives, it was carried out a comparative study between several ink samples obtained from different printing modes, offered on the printing properties menu, as well as ink collected directly from selected cartridges. Comparisons have also been made between the printed ink on various papers brands, weights and different colours. Furthermore, comparisons between ink samples were performed after the paper support was subjected to different physical, chemical and light exposure treatments.This investigation has proven that both applied techniques are very robust, since the results were similar to each other, regardless of the origin of the ink sample (printing modes and/or collected directly from cartridge) and the type of paper selected. Even ink subjected to physical and chemical treatments presented similar results. Nevertheless, this project showed that coloured paper can interfere with absorption spectra, causing difficulties on microspectrophotometry analysis.

L'objectif de la thèse était de regarder l'acétylcholinestérase (AChE) en mouvement. L'AChE est une enzyme très rapide qui met fin à la transmission de l'influx nerveux au sein des synapses cholinergiques. À l'aide de la cristallographie aux rayons X, des sous-états conformationnels de l'AChE de Torpedo californica (Tc) ont été piégés par sa liaison à des drogues anti-Alzheimer putatives. Les formes, non vieillie et vieillie, de la TcAChE conjuguée au soman ont été caractérisées structuralement, éclairant ainsi le mécanisme de vieillissement de la TcAChE inhibée par les organophosphorés (OP). La structure du complexe ternaire du conjugué vieilli avec un réactivateur a également été résolue. Toutes ces structures guideront l'élaboration de médicaments (drogues anti-Alzheimer ou antidotes contre l'empoisonnement par des OP) en prenant en compte la flexibilité de l'enzyme et ses conformations minoritaires. La structure du complexe de la TcAChE avec un inhibiteur de son site périphérique (PAS), l'aflatoxine B1 (AB1), a été résolue dans deux formes cristallines. Ce travail a mis en évidence des artefacts de la cristallographie nuisibles à l'interprétation biologique des structures. La mesure du temps de vie de phosphorescence de l'AB1 a permis de sonder les mouvements du PAS à l'échelle de la seconde et de révéler des différences de flexibilité liées à l'empilement cristallin de la TcAChE. Cette méthode spectroscopique est complémentaire à la cristallographie cinétique. La gamme de températures cryogéniques identifiée pourrait en effet faciliter l'exploration du mécanisme réactionnel de l'AChE, en ralentissant l'enzyme sans pour autant la figer.