Les complexes luminescents de lanthanides font l'objet d'une recherche importante dans le domaine de l'opto-électronique du fait de couleur pure et de rendements quantiques importants. Le développement de nouveaux chelates spécifiquement adaptés pour des applications opto-électroniques reste cependant un domaine moins développé par rapport à d'autres applications.<br /><br />Le but de ce travail est d'accéder à de nouvelles possibilités de synthèse dans le domaine des émetteurs moléculaires à base de lanthanides pour l'opto-electronique ; ceci, en concevant de nouveaux ligands adaptés à la complexation de ces métaux et l'étude des propriétés optiques des complexes formés.<br /><br />A cette fin nous avons synthétisés et étudiés une série de ligands basés sur des motifs terpyridine-, bipyridine- et pyridine-tetrazole. Divers substituants ont été ajoutés afin de moduler les propriétés électroniques de ces molécules avec, pour résultats, l'obtention de fortes efficacités lumineuses pour certains de ces complexes tant dans le visible que le proche infrarouge. Les effets induits par l'ajout des divers subtituants sur leurs propriétés photophysiques ont été clairement démontré. De plus, nous avons également synthétisés et testé en couche active de dispositifs OLED une nouvelle classe de complexes neutres complétées par des unités dicétonates.<br /><br />Nous avons par ailleurs explorés la sensibilisation des ions lanthanides par l'intermédiaire de complexes de métaux de transition d. Pour cela nous avons conçus une nouvelle architecture hétéro-métallique d-f où le complexe d'iridium est employé comme antenne. Finalement, nous avons étudiés les processus de transfert d'énergie par mesures de luminescence.

Förster Resonance Energy Transfer (FRET) plays an important role for biochemical applications such as DNA sequencing, intracellular protein-protein interactions, molecular binding studies, in vitro diagnostics and many others. For qualitative and quantitative analysis, FRET systems are usually assembled through molecular recognition of biomolecules conjugated with donor and acceptor luminophores. Lanthanide (Ln) complexes, as well as semiconductor quantum dot nanocrystals (QD), possess unique photophysical properties that make them especially suitable for applied FRET. In this work the possibility of using QD as very efficient FRET acceptors in combination with Ln complexes as donors in biochemical systems is demonstrated. The necessary theoretical and practical background of FRET, Ln complexes, QD and the applied biochemical models is outlined. In addition, scientific as well as commercial applications are presented. FRET can be used to measure structural changes or dynamics at distances ranging from approximately 1 to 10 nm. The very strong and well characterized binding process between streptavidin (Strep) and biotin (Biot) is used as a biomolecular model system. A FRET system is established by Strep conjugation with the Ln complexes and QD biotinylation. Three Ln complexes (one with Tb3+ and two with Eu3+ as central ion) are used as FRET donors. Besides the QD two further acceptors, the luminescent crosslinked protein allophycocyanin (APC) and a commercial fluorescence dye (DY633), are investigated for direct comparison. FRET is demonstrated for all donor-acceptor pairs by acceptor emission sensitization and a more than 1000-fold increase of the luminescence decay time in the case of QD reaching the hundred microsecond regime. Detailed photophysical characterization of donors and acceptors permits analysis of the bioconjugates and calculation of the FRET parameters. Extremely large Förster radii of more than 100 Å are achieved for QD as acceptors, considerably larger than for APC and DY633 (ca. 80 and 60 Å). Special attention is paid to interactions with different additives in aqueous solutions, namely borate buffer, bovine serum albumin (BSA), sodium azide and potassium fluoride (KF). A more than 10-fold limit of detection (LOD) decrease compared to the extensively characterized and frequently used donor-acceptor pair of Europium tris(bipyridine) (Eu-TBP) and APC is demonstrated for the FRET system, consisting of the Tb complex and QD. A sub-picomolar LOD for QD is achieved with this system in azide free borate buffer (pH 8.3) containing 2 % BSA and 0.5 M KF. In order to transfer the Strep-Biot model system to a real-life in vitro diagnostic application, two kinds of imunnoassays are investigated using human chorionic gonadotropin (HCG) as analyte. HCG itself, as well as two monoclonal anti-HCG mouse-IgG (immunoglobulin G) antibodies are labeled with the Tb complex and QD, respectively. Although no sufficient evidence for FRET can be found for a sandwich assay, FRET becomes obvious in a direct HCG-IgG assay showing the feasibility of using the Ln-QD donor-acceptor pair as highly sensitive analytical tool for in vitro diagnostics. / Förster Resonanzenergietransfer (FRET) spielt eine wichtige Rolle in biochemischen Anwendungen, wie z.B. DNA-Sequenzierung, intrazellulären Protein-Protein-Wechselwirkungen, molekularen Bindungsstudien, in-vitro-Diagnostik und vielen anderen. Zur quantitativen und qualitativen Analyse werden FRET Systeme normalerweise durch molekulare Erkennung von Biomolekülen, die mit Donator- und Acceptorluminophoren markiert sind, ermöglicht. Durch die besonderen photophysikalischen Eigenschaften sowohl von Lanthanidkomplexen (Ln-Komplexen), als auch Halbleiternanokristallen (sog. Quantenpunkten oder Quantumdots - QD), sind diese besonders für FRET Anwendungen geeignet. In der vorliegenden Arbeit wird effizienter FRET zwischen Ln-Komplexen und QD in biochemischen Systemen demonstriert. Die notwendigen theoretischen und praktischen Grundlagen über FRET, Ln-Komplexe, QD und die verwendeten biochemischen Modelle werden dargestellt, und wissenschaftliche als auch kommerzielle Anwendungen werden präsentiert. FRET kann zur Messung von strukturellen Veränderungen und Dynamiken im Bereich von ca. 1 bis 10 nm verwendet werden. Der sehr starke und gut charakterisierte Bindungsprozess zwischen Streptavidin (Strep) und Biotin (Biot) wird als biomolekulares Modellsystem eingesetzt. Ein FRET System wird durch Streptavidinkonjugation mit Ln-Komplexen und QD-Biotinylierung etabliert. Drei Ln-Komplexe (einer mit Tb3+ und zwei mit Eu3+ als Zentralion) werden als Donatoren verwendet, und neben QD werden zwei weitere Acceptoren, das lumineszierende, quervernetzte Protein Allophycocyanin (APC) und ein kommerzieller Fluoreszenzfarbstoff (DY633), untersucht. FRET kann für alle Donator-Acceptor Paare nachgewiesen werden, zum einen durch sensibilisierte Acceptorlumineszenz und zum anderen durch eine über 1000-fach erhöhte Lumineszenzabklingzeit der QD mit über 100 Mikrosekunden. Mittels detailierter photophysikalischer Charakterisierung der Donatoren und Acceptoren können die Biokonjugate analysiert und die FRET Parameter berechnet werden. Für die QD FRET Systeme ergeben sich extrem große Försterradien von über 100 Å, die wesentlich größer sind als für APC und DY633 (ca. 80 bzw. 60 Å). Besondere Aufmerksamkeit gilt der Wechselwirkung mit den Zusatzreagenzien Boratpuffer, Bovines Serumalbumin (BSA), Natriumazid und Kaliumfluorid (KF) in den wässrigen Lösungen. Im Vergleich zum ausgiebig charakterisierten und vielfach verwendeten Donator-Acceptor Paar aus Europium-tris(Bipyridin) (Eu-TBP) und APC wird eine mehr als 10-fache Senkung der Nachweisgrenze für das FRET-System, bestehend aus Tb-Komplex und QD, erreicht. In azidfreiem Boratpuffer (pH 8,3) mit 2 % BSA und 0,5 M KF wird eine subpicomolare QD-Nachweisgrenze für dieses System aufgezeigt. Um den Transfer des Strep-Biot Modellsystems in eine echte in-vitro-diagnostische Anwendung zu demonstrieren, werden zwei Immuntests zum HCG-(Humanes Choriongonadotropin)-Nachweis untersucht. Sowohl HCG als auch monoklonale anti-HCG Maus-IgG-(Immunoglobulin G)-Antikörper werden mit dem Tb-Komplex bzw. mit QD markiert. Obwohl kein ausreichender Nachweis für FRET in einem immunometrischen Assay (oder Sandwichassay) erbracht werden kann, wird FRET in einem direkten HCG-IgG Assay erzielt, wodurch die Realisierbarkeit von Ln-QD Donator-Acceptor Paaren zur hochsensitiven Anwendung in der in-vitro-Diagnostik gezeigt werden kann.

This thesis deals with the development of new methods for efficient synthesis and analysis in asymmetric catalysis. It focuses on the preparation of chiral cyanohydrins by enantioselective addition of cyanide to prochiral aldehydes. The initial part of the thesis describes the development of a dual Lewis acid– Lewis base activation system for efficient synthesis of chiral O-acylated and Ocarbonylated cyanohydrins. This system was used for the preparation of a variety of cyanohydrins in high isolated yields and with up to 96% ee. Activation of the cyanide by nucleophilic attack of the Lewis base at the carbonyl carbon atom was supported experimentally. Secondly, convenient procedures for the synthesis of polymer-bound chiral YbCl3-pybox and Ti-salen complexes are described. The polymeric complexes were employed in cyanation of benzaldehyde. A T-shaped microreactor was used for screening of reaction conditions for the enantioselective cyanation of benzaldehyde using trimethylsilyl cyanide and acetyl cyanide as cyanide sources. A microreactor charged with the polymeric Tisalen complex was used for enantioselective cyanation of benzaldehyde. Finally, an enzymatic method for high throughput analysis of ee and conversion of products from chiral Lewis acid–Lewis base-catalysed additions of α- ketonitriles to prochiral aldehydes was developed. The method could be used for the analysis of a variety of O-acylated cyanohydrins. Microreactor technology was successfully combined with high throughput analysis for efficient catalyst optimisation. / QC 20100809

Der Förster-Resonanzenergietransfer (FRET) liefert einen wichtigen Beitrag bei der Untersuchung kleinskaliger biologischer Systeme und Prozesse. Möglich wird dies durch die r-6-Abhängigkeit des FRET, die es erlaubt Abstände und strukturelle Änderungen weit unterhalb der Beugungsgrenze des Lichts mit hoher Sensitivität und geringem Aufwand zu bestimmen. Die besonderen photophysikalischen Eigenschaften von Terbiumkomplexen (LTC) und Quantenpunkten (QD) machen sie zu geeigneten Kandidaten für hochsensitive und störungsarme Multiplex-Abstandsmessungen in biologischen Systemen und Prozessen. Die Abstandsbestimmungen setzen jedoch eine genaueste Kenntnis des Mechanismus des Energietransfers von LTC auf QD ebenso voraus, wie das Wissen um Größe und Gestalt letzterer. Quantenpunkte haben im Vergleich zu biologischen Strukturen ähnliche Dimensionen und können nicht als punktförmig betrachtet werden, wie es bei einfacheren Farbstoffen möglich ist. Durch ihre Form kommt es zu einer Abstandsverteilung innerhalb des Donor-Akzeptorsystems. Dies beeinflusst den Energietransfer und damit die experimentellen Ergebnisse. In dieser Arbeit wurde der Energietransfer von LTC auf QD untersucht, um zu einer Aussage hinsichtlich des Mechanismus der Energieübertragung und der dabei zu berücksichtigenden photophysikalischen und strukturellen Parameter von LTC und QD zu gelangen. Mit der Annahme einer Abstandsverteilung sollten die Größen der Quantenpunkte bestimmt und der Einfluss von Form und Gestalt auf den Energietransfer betrachtet werden. Die notwendigen theoretischen und praktischen Grundlagen wurden eingangs dargestellt. Daran schlossen sich Messungen zur photophysikalischen Charakterisierung der Donoren und Akzeptoren an, die Grundlage der Berechnung der FRET-Parameter waren. Die Förster-Radien zeigten die für den FRET von LTC auf QD typischen extrem hohen Werte von bis zu 11 nm. Zeitaufgelöste Messungen der FRET-induzierten Lumineszenz der Donoren und Akzeptoren in den beiden biomolekularen Modellsystemen Zink-Histidin und Biotin-Streptavidin beschlossen den praktischen Teil. Als Donor wurde Lumi4Tb gebunden an ein Peptid bzw. Streptavidin genutzt, Akzeptoren waren fünf verschiedene, kommerziell erhältliche Quantenpunkte mit Carboxyl- bzw. Biotinfunktionalisierung. Bei allen Donor-Akzeptor-Paarungen konnte FRET beobachtet und ausgewertet werden. Es konnte gezeigt werden, dass die gesamte Emission des Terbiums zum Energietransfer beiträgt und der Orientierungsfaktor ² den Wert 2/3 annimmt. Die Charakterisierung der Bindungsverhältnisse innerhalb der FRET-Paare von LTC und QD über Verteilungsfunktionen bietet über die Form der Verteilungskurve die Möglichkeit Aussagen über die Gestalt der FRET-Partner zu treffen. So war es möglich, die mittlere Form der Quantenpunkte als Sphäre zu bestimmen. Dies entsprach, insbesondere bei den in z-Richtung des Kristallgitters elongierten Quantenpunkten, nicht den Erwartungen. Dieser Befund ermöglicht daher bei zukünftigen Messungen eine Verbesserung der Genauigkeit bei Abstandsbestimmungen mit Quantenpunkten. Neben der Ermittlung der die FRET-Verteilung bestimmenden Gestalt der Quantenpunkte konnte im Rahmen dieser Arbeit anhand vergleichender Messungen die Dicke der Polymerhülle der QD bestimmt und so gezeigt werden, dass FRET-Paare aus lumineszenten Terbiumkomplexen und Quantenpunkten in der Lage sind, Abstände im Nano- bis Sub-Nanometerbereich aufzulösen. / Förster resonance energy transfer (FRET) plays an important role in the study of small-scale biological systems and processes. This is made possible by the r-6-dependence of FRET, which allows for determination of distances and structural changes far below the diffraction limit of light with high sensitivity and low costs. The unique photophysical properties of terbium complexes (LTC) and quantum dots (QDs) make them suitable candidates for high-sensitivity, low-noise multiplex distance measurements in biological systems and processes. Estimating distances with these FRET-pairs requires a precise knowledge of the mechanism of energy transfer from LTC to QD as well as the knowledge of size and shape of the latter. Quantum dots have, compared to biological structures, similar dimensions and therefore can not be considered as point-like, as it is possible with smaller dyes. Due to their shape, there is a distance distribution within the donor-acceptor system. This influences the energy transfer and hence the experimental results. In this work, the energy transfer from LTC to QD was examined to come to a conclusion regarding the mechanism of energy transfer and the photophysical and structural parameters of LTC and QD to be considered. The adoption of a FRET-distance distribution due to a size distribution of quantum dots should yield to a size estimation of the nanoparticles as well as a conclusion of the influence of shape and form on energy transfer. The necessary theoretical and practical principles were described at the outset of this work. This description of the basic concepts was followed by the photophysical characterization of the donors and acceptors and the calculation of FRET parameters. The calculated Förster radii were typical for the FRET from LTC to QD and showed extremely high values of up to 11 nm. Time-resolved measurements of the FRET-induced luminescence of donors and acceptors in two biomolecular model binding systems namely zinc-histidine and biotin-streptavidin binding rounded the practical part. FRET-donors used were commercially available Lumi4Tb complexes bound to streptavidin or a peptide, respectively. As FRET-acceptors five different commercially available quantum dots with carboxyl- or biotin-functionalisation were used. For all donor-acceptor pairs FRET could be observed and evaluated. It could be shown that the whole emission of terbium contributes to energy transfer. Furthermore the orientation factor ² was estimated to have a value of 2/3 when using LTC as FRET-donors and QD as FRET-acceptors. The characterization of the bonding within the FRET pairs of LTC and QD with distribution functions allows for statements about the shape of the FRET partners via shape of the distribution curves. It was possible to determine the average shape of the quantum dots as a sphere. This outcome was, especially for (in z-direction of the crystal lattice) elongated quantum dots, in the contrary to the expectations. This finding therefore allows for improving the accuracy of distance determinations with quantum dots. Based on comparative measurements it was also possible to determine the thickness of the polymer shell of the QD demonstrating that FRET pairs of luminescent terbium complexes and quantum dots are capable of determining distances in the nanometer to sub-nanometer range.

La fonctionnalisation sélective de BINOL en position 6 ou 6 et 6' par des groupements 3 - (diméthylamino)prop-1-yn-1-yl est décrite. Cette méthode constitue une stratégie prometteuse pour le développement de nouveaux ligands recyclables. Les complexes de La et Yb correspondants ont été testés dans la réaction d'époxydation des cétones α, β-insaturées. Les complexes d'ytterbium sont les plus efficaces, fournissant les époxydes chiraux attendus avec 90 ou 93% d'excès énantiomérique en conditions homogène et hétérogène, respectivement.Dans le cadre de nos études, nous avons également évalué de nouveaux catalyseurs comportant un ion de manganèse penta-coordinnée [LMn(III)OH]ClO4 et [LMnCl](MnCl4)0,5. Ces complexes ont été testés dans la réaction d'époxydation des oléfines terminales utilisant H2O2/NaHCO3 et PhIO comme oxydant. Il s'avère que le complexe [LMn(III)OH]ClO4 est le catalyseur le plus efficace de la série. Une autre approche également été envisagée : oxyder une molécule d'eau présente dans la sphère de coordination du métal par le Cerium Ammonium Nitrate (CAN) et utiliser l'espèce oxydante ainsi générée pour oxyder des substrats. Nos études ont montré que cette stratégie était possible et permettait d'oxyder des substrats organiques.

A summary of research conducted since September 2007 at the University of Toronto in the laboratory of Professor Robert A. Batey is presented in this thesis, which is divided into four chapters. The first chapter contains a two-part introduction, where aryl- and aliphatic-Claisen rearrangements are discussed in part 1, and the nucleophilic addition of organoboron reagents to unsaturated C–N functionalities is described in part 2. Chapter 2 contains research involving synthetic and theoretical studies of aryl-Claisen rearrangements and other sigmatropic reactions. The work towards developing the lanthanide-catalyzed domino aryl-Claisen rearrangement for the synthesis of contiguous aryl–C(sp³) moieties is presented first. This is followed by computational studies involving E/Z-selectivity differences for the aryl-Claisen rearrangement, which was an issue noted for the domino aryl-Claisen reaction of a linear substrate. The mechanistic origins of E/Z-selectivity differences for the mono aryl-Claisen rearrangement, which was experimentally ambiguous for over 40 years, is resolved through computational methods. A theoretical analysis of selectivity differences for the allylic azide rearrangement is also described. The third section contains a discussion of Eu(fod)3-catalyzed aryl-Claisen rearrangements on vinyl bromide systems and preliminary studies involving application of the substrates in cross-coupling reactions, and other attempted mono- and domino sigmatropic rearrangements are presented in the fourth section. In chapter 3, the search for computational methods that can accurately predict experimental free energy of activation barriers for the aliphatic-Claisen rearrangement through benchmarking studies with a priori kinetic barrier and kinetic isotope effect data is described. Methods were found to predict new valid transition states and predict ΔG‡ values with a mean unsigned error of 0.3 kcal/mol relative to experimental values. In chapter 4, the development of new allylboration reaction is outlined, involving the double allylboration of nitriles and anhydrides, and initial studies towards the first aminoallylboration reactions of N-aluminoaldimines to form 1,2-diamines.

In this thesis, solid state reactions of Ln2O3, Y2O3, B2O3 and (NH4)2HPO4 were investigated to synthesize LnBP2O8 (Ln= Dy, Ho, Er) and YBP2O8 type of borophosphates which were not reported before. The products were analyzed by XRD, IR, DTA, SEM and EDX methods. In the first part of this thesis, synthesis of YBP2O8 through the solid state reaction of Y2O3 + 4(NH4)2HPO4 + B2O3 have been studied in the range 800-1140 &deg / C. Orthophosphates of Dysprosium, Holmium, Erbium and Yttrium have tetragonal xenotime (YPO4) or zircon (ZrSiO4) structure. Examination of X-ray powder diffraction data at 1140 &ordm / C showed that the obtained structure was xenotime type together with weak BPO4 and Y(PO3)3 lines. The formula was calculated as YBxP1+xO4+4x through EDX and XRD data. The pattern was indexed in tetragonal system with the unit cell parameters of a= 6.8863, c= 6.016 &Aring / and s.g. is I41/amd. In the second part of this research, synthesis of LnBP2O8 through the solid state reaction of Ln2O3 + 4(NH4)2HPO4 + B2O3 (Ln= Dy, Ho, Er) have been studied in the range 800-1200 &ordm / C. At 1200 &ordm / C DyBP2O8 was obtained with tetragonal structure with the unit cell parameters of a= 6.905, c= 6.051 &Aring / and s.g. I41/amd. Using the same procedure HoBP2O8 was obtained at 1100-1200 &ordm / C and the XRD pattern was indexed in tetragonal system with the unit cell parameters of a= 6.887, c= 6.024 &Aring / and s.g. I41/amd. In the structural analysis of ErBP2O8 obtained by the same reaction, the system was found as tetragonal and was indexed with a= 6.849, c= 5.998 &Aring / and s.g. I41/amd. Examination of the unit cell parameters with respect to ionic radius showed that the unit cell parameters decrease depending on the lanthanide contraction. The structures of the compounds obtained throughout this thesis were examined by IR spectroscopy and relation between the spectra and IR vibrational modes were established. The presence of bands due to BO4 in the final products revealed that Boron is in the solid solution with the tentative formula YBxP1+xO4+4x for Y and LnBP2O8 for lanthanides.

Understanding biological phenomena at atomic resolution is one of the keys to modern drug design. In particular, knowledge of 3D structures of proteins and their interactions with other macromolecules are necessary for designing chemical compounds that modify biological processes. Conventional methods for protein structure determinations comprise X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. These techniques can also determine the binding mode of chemical compounds. Either technique can be slow and costly, making it highly relevant to explore alternative strategies. Paramagnetic NMR spectroscopy is emerging as such an alternative technique. In order to measure the paramagnetic effects, two NMR spectra are compared that have been measured with and without a bound paramagnetic metal ion. In particular, pseudocontact shifts (PCS) of nuclear spins are easily measured as the difference (in ppm) of the chemical shifts between the two spectra. PCSs provide long range and orientation dependent restraints, allowing positioning of the spin with respect to the magnetic susceptibility tensor anisotropy (Δχ-tensor) of the metal ion. In this thesis, I used the PCS effect to computationally extract information from NMR spectra. I developed (i) a tool (called Possum) to automatically assign diamagnetic and paramagnetic spectra of the methyl groups of amino acid side chains, given structural information of the protein studied and prior knowledge of the Δχ-tensor; (ii) I designed a comprehensive software package (called Numbat) to extract Δχ-tensor parameters from assigned PCS values and the available 3D structure; and (iii) I incorporated PCS-based restraints into the protein structure prediction software CS-ROSETTA and demonstrated that this combination (PCS-ROSETTA) presents a significant improvement for de novo structure determination. The three projects serve different purposes at different stages of protein NMR studies. They could be combined in the following manner: Starting from assigned backbone PCSs, PCS-Rosetta could be used to determine the 3D structure of the protein. Possum can then be used to automatically assign the NMR resonances of the methyl groups using PCSs. Finally, Numbat can be used to fit improved Δχ-tensors to all the PCS data, analyze the quality of the Δχ-tensors and identify possible wrong assignments. Iterative repetition of this protocol would give a 3D structural model of the protein with a minimum of data. Alternatively, the Δχ-tensor parameters and PCSs could be used as input for a traditional software package such as Xplor-NIH to compute a 3D structure of the protein.

Understanding biological phenomena at atomic resolution is one of the keys to modern drug design. In particular, knowledge of 3D structures of proteins and their interactions with other macromolecules are necessary for designing chemical compounds that modify biological processes. Conventional methods for protein structure determinations comprise X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. These techniques can also determine the binding mode of chemical compounds. Either technique can be slow and costly, making it highly relevant to explore alternative strategies. Paramagnetic NMR spectroscopy is emerging as such an alternative technique. In order to measure the paramagnetic effects, two NMR spectra are compared that have been measured with and without a bound paramagnetic metal ion. In particular, pseudocontact shifts (PCS) of nuclear spins are easily measured as the difference (in ppm) of the chemical shifts between the two spectra. PCSs provide long range and orientation dependent restraints, allowing positioning of the spin with respect to the magnetic susceptibility tensor anisotropy (Δχ-tensor) of the metal ion. In this thesis, I used the PCS effect to computationally extract information from NMR spectra. I developed (i) a tool (called Possum) to automatically assign diamagnetic and paramagnetic spectra of the methyl groups of amino acid side chains, given structural information of the protein studied and prior knowledge of the Δχ-tensor; (ii) I designed a comprehensive software package (called Numbat) to extract Δχ-tensor parameters from assigned PCS values and the available 3D structure; and (iii) I incorporated PCS-based restraints into the protein structure prediction software CS-ROSETTA and demonstrated that this combination (PCS-ROSETTA) presents a significant improvement for de novo structure determination. The three projects serve different purposes at different stages of protein NMR studies. They could be combined in the following manner: Starting from assigned backbone PCSs, PCS-Rosetta could be used to determine the 3D structure of the protein. Possum can then be used to automatically assign the NMR resonances of the methyl groups using PCSs. Finally, Numbat can be used to fit improved Δχ-tensors to all the PCS data, analyze the quality of the Δχ-tensors and identify possible wrong assignments. Iterative repetition of this protocol would give a 3D structural model of the protein with a minimum of data. Alternatively, the Δχ-tensor parameters and PCSs could be used as input for a traditional software package such as Xplor-NIH to compute a 3D structure of the protein.

L'IRM (Imagerie par Résonance Magnétique) est une technique de choix pour l'imagerie moléculaire, soit la visualisation d'événements biologiques à l'échelle moléculaire. En effet, elle est non invasive et possède une haute résolution. Cependant, elle manque de sensibilité. L'utilisation d'agents de contraste commerciaux, qui sont pour la plupart des chélates de Gd(III), peut pallier à ce problème lors d'examens cliniques mais ils ne sont pas assez efficaces en vue de l'imagerie moléculaire. Leur efficacité, définie par leur relaxivité, peut être améliorée en optimisant les paramètres qui la gouvernent, comme le nombre de molécules d'eau coordinées, la vitesse d'échange de l'eau ou la dynamique de rotation du complexe. Deux stratégies sont envisagées pour améliorer la sensibilité : la première est de rassembler un grand nombre de complexes de Gd(III) possédant une haute relaxivité dans une seule entité ; la seconde est la conception de sondes bimodales IRM/imagerie optique, permettant de tirer profit à la fois de la haute résolution de l'IRM et de la très bonne sensibilité de l'imagerie optique.Ce travail de thèse a consisté à incorporer des agents de contraste à base de Gd(III) possédant des propriétés de relaxivité améliorées dans des systèmes macromoléculaires ou des nanobjets. Pour cela, des complexes ayant des paramètres de relaxivité optimisés connus au laboratoire ont été fonctionnalisés pour être greffés sur des quantum dots, pour le caractère bimodal et sur des oligonucléotides afin de réaliser des sondes ADN. L'utilisation de billes de silice a permis d'incorporer des complexes de Gd(III) de manière non covalente et d'obtenir à la fois une relaxivité par Gd(III) et par particule très élevée. L'incorporation simultanée de complexes d'Yb(III) permet également d'obtenir une sonde bimodale avec une émission dans le proche infrarouge. Tous ces systèmes ouvrent la possibilité au développement de sondes IRM avec des propriétés optimisées, prometteuses pour l'imagerie moléculaire. / Magnetic Resonance Imaging (MRI) is a widely used diagnostic method in medicinal practice. It is the ideal technique for molecular imaging, which allows biological events to be observed at the molecular scale thanks to its high resolution. However it has a very low sensitivity. Commercial contrast agents can palliate this lack of sensitivity, but their efficiency, defined as relaxivity, is too low for molecular imaging. The relaxivity of Gd(III) chelates depends on parameters such as the hydration number, the exchange rate and the rotational dynamics of the complex, which can be optimized to improve the relaxivity. Two strategies can be considered to improve the sensitivity: the first one is to gather a high number of complexes demonstrating an optimized relaxivity on a nanoobject ; the second one is the design of a bimodal probe MRI/Optical imaging to combine the high resolution of MRI and the high sensitivity of optical imaging.In this work we present the incorporation of gadolinium chelates into macromolecular systems and two different types of nanoobjects. Gd(III) chelates with improved relaxometric properties have been functionalized and grafted onto quantum dots for the design of a bimodal probe and into oligonucleotides for the conception of a DNA probe. The non-covalent incorporation of Gd(III) in silica spheres allows both a high relaxivity per Gd(III) and per particle. The simultaneous incorporation of Yb(III) complexes emitting in the near infrared permits the design of a bimodal probe. All of these systems lead to the development of a new class of promising probes for molecular imaging.