Rhomboids are a family of intramembrane serine proteases that cleave transmembrane protein substrates within the lipid membrane. They are involved in a wide range of biological processes, including signal transduction, parasite invasion, bacterial quorum sensing and apoptosis. While previous X-ray crystal structures and functional studies have provided some detailed insights into the mechanism of intramembrane hydrolysis, it is still not clear how the transmembrane substrate can gain access into the active site from the lipid environment. While several modes of action have been suggested, one hypothesis proposes a lateral movement of the fifth transmembrane helix, causing a displacement that would allow transmembrane substrates to enter the rhomboid active site. A powerful method that has the potential to yield insights into rhomboid dynamics is solution NMR; however, the large size of rhomboid protease samples has complicated conventional methods typically used to assess protein structure and dynamics. ¹⁹F NMR could allow the study of rhomboid conformational dynamics by providing a simplified spectrum with high sensitivity to changes in local chemical environments. In this thesis various methods of ¹⁹F incorporation were evaluated for utility in studying rhomboid conformational dynamics, focusing on the GlpG rhomboid from E. coli. First, GlpG samples were prepared with ¹⁹F incorporated into tryptophan sidechains, and 1D ¹⁹F NMR spectra were acquired. While spectra with decent spectral dispersion were obtained, the assignment process was complicated by low signal-to-noise, and multiple changes in the spectrum introduced by the mutation. Chemoselective labelling of cysteine residues with probes containing a trifluoromethyl group was also investigated and found to give rise to well resolved ¹⁹F NMR spectra with promising characteristics. In addition, protocols for incorporation of trifluoromethyl-phenylalanine using unnatural amino acid incorporation at introduced amber codon sites were also explored, since one of the long-term goals of this work is to study ¹⁹F-labelled GlpG in its native lipid environment. For this purpose, some protocol development was also performed to introduce GlpG into lipid nanoparticles using styrene maleic acid co-block polymers. However, low expression yields of trifluoromethyl-phenylalanine-labelled GlpG and the large size of the lipid nanoparticles are not yet compatible with solution NMR. Nonetheless, this thesis lays the groundwork for further development of these samples to allow the future study of conformational exchange of GlpG in native lipid membranes.

yes / Reproducible control of stoichiometry and difficulties in large scale production have been identified as two of the major challenges to commercial uptake of pharmaceutical co-crystals. The aim of this research was to extend the application of SFCC to control stoichiometry in caffeine: maleic acid co-crystals. Both 1:1 and 2:1 caffeine: maleic acid co-crystals were produced by control of the feedstock composition and process conditions. It was also observed that formation of 2:1 stoichiometry co-crystals involved formation of a 1:1 co-crystal which was subsequently transformed to 2:1 co-crystals. The investigation of stoichiometric transformation revealed that although 1:1 co-crystals could be converted into 2:1 form with addition of excess caffeine, the reverse was not possible in the presence of excess maleic acid. However, conversion from 2:1 into 1:1 was only achieved by melt seeding with the phase pure 1:1 co-crystals. This investigation demonstrates that stoichiometric control can be achieved by SFCC by control of parameters such as extrusion temperature.

In the past three decades, a new group of concrete admixtures, termed &ldquo / superplasticizers&rdquo / , were introduced to the concrete industry. They have gained wide acceptance because of their many advantages. The addition of superplasticizers to concrete improves the workability and strength of concrete. In this study, the effect of the chemical structure of poly (4-styrenesulfonic acid-co-maleic acid) sodium salt (SSAMA), which contains both sulfonic and carboxylic acid groups, which is a new superplasticizer, was analyzed. Two different molecular weights of PEG (polyethylene glycol monomethyl ether) were grafted to this water-soluble copolymer at different weight compositions. The structures of synthesized copolymers were verified by FTIR and NMR analyses. The molecular weight difference of the grafted copolymers with different side chain lengths was determined by dilute solution viscosimetry. The effects of chemical structure of grafted copolymers on the fluidity of cement paste and the mechanical properties of the mortars were investigated. The zeta potential measurements revealed the interactions between the cement particles and polycarboxylate type superplasticizers. The maximum fluidity was achieved for the PEG grafted copolymer with the weight ratio 3:3. The mechanical properties of this copolymer showed the highest flexural and compressive strength compared to other copolymers. The addition of various Li salts to SSAMA affected the ionic medium, therefore, the dispersion performance of cement paste and the mechanical properties of the mortars improved. The mixture of LiCl: SSAMA in 1:1 mol ratio exhibited the maximum fluidity compared to other Li salts and their compositions. This mixture gave the highest flexural strength but the mixture of Li2CO3 in 1:1 composition gave the highest compressive strength in each salt mixtures.

<p>Producing bio-based commodity chemicals, such as polymers and fuels, is of significant interest as petroleum reserves continue to decline. A major roadblock to bio-based production is high processing costs. These costs are associated with the need for highly-specialized catalysts to produce bio-based commodity chemicals from agricultural products and wastes. This prevents bioprocessing facilities from fully taking advantage of commodities of scale, where purchasing materials in greater quantities reduces the material cost. Discovering catalysts capable of being used in multiple production pathways could reduce the per unit processing of a biorefinery. <br> Recent works have shown that maleic acid can be used for multiple conversion reactions of plant material to valuable products: xylose to furfural, glucose to hydroxymethylfurfural (HMF), and the pretreatment of lignocellulosic material for second generation biofuel production. This work evaluates the use of maleic acid as a catalyst for producing HMF from corn starch, with a specific focus on reducing operating costs. Additionally, the use of maleic acid as a liquefaction catalyst for producing corn stover slurries is tested. </p> <p>To evaluate HMF production from starch, a combined computational and experimental approach is used. Through modelling and experimental validation, molar HMF yields of ~30% are reached by incorporating dilute dimethylsulfoxide and acetonitrile into the reaction mixture. However, HMF yield was limited by low stability in the reaction media. The addition of activated carbon to the reactor overcomes challenges with second order side reactions, resulting in HMF selling prices that are competitive with similar petroleum-derived chemicals. The key technical roadblocks to commercialization of HMF production are identified as solvent recycling and HMF separation efficiency in a sensitivity analysis. During liquefaction of corn stover, maleic acid was found to reduce the yield stress required to begin slurry flow through a pipe. However, a reduction in the free water content of the reactor through binding of water in the matrix of biomass limited liquefaction, resulting in solids concentrations not financially feasible at scale. To overcome this, maleic acid treatment was performed at solids contents of 25%, followed by a water removal step and enzymatic liquefaction at 30% solids. Yield stress was reduced from >6000 Pa for untreated samples to ~50 Pa for samples treated with maleic acid and enzymes sequentially. Such treatment reduces the challenges associated with feeding solid biomass into a pretreatment reactor. Additionally, reduced slurry yield stress results in lower capital costs, since smaller pumps can be used in the production facility. </p> This work provides a step forward in transitioning away from a petroleum-based economy to a bio-based economy without significant disruptions in product pricing and availability.

This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated. The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored. Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding. / QC20100608

<p>This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated.</p><p>The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm^-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored.</p><p>Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding.</p> / QC20100608

Η αλληλεπίδραση μεταξύ συνθετικών πολυηλεκτρολυτών και ιόντων στοιχείων μετάβασης, και κατ επέκταση η δημιουργία συμπλόκου μεταξύ τους, έχει τύχει μεγάλου ενδιαφέροντος από τους ερευνητές τις τελευταίες δεκαετίες. Αυτό το ενδιαφέρον αποδίδεται στις μοναδικές ιδιότητες των σχηματιζόμενων συμπλοκών, καθώς μπορούν να χρησιμοποιηθούν σε διάφορα πεδία όπως στην ιατρική, την τεχνολογία και τις βιομηχανίες τροφίμων ή την αποκατάσταση των περιβαλλοντολογικών προβλημάτων. Σε αυτή την εργασία προχωρήσαμε στη παρασκευή των συμπολυμερών P(EV2-PDMAM) που αποτελείται από ένα συμπολυμερές (EV2) του αιθυλενίου με το μηλεϊνικό οξύ ως σκελετό, επί των οποίων έχουν εμβολιαστεί αλυσίδες πολυ(Ν,Ν-διμεθυλακρυλαμιδίου) (PDMAM). Η γραμμομοριακή σύσταση των συμπολυμερών, εκφρασμένη σε δομικές μονάδες DMAM, ήταν 25, 50 και 75%. Η φυσικοχημική μελέτη της αλληλεπίδρασης των ιόντων δισθενούς χαλκού με τα συμπολυμερή P(EV2-PDMAM) πραγματοποιήθηκε με μια σειρά τεχνικών όπως η ιξωδόμετρα, η pHμετρία και η φασματοσκοπία υπεριώδους-ορατού (UV-vis). Η δημιουργία συμπλόκου οδηγεί σε σημαντική συρρίκνωση της πολυμερικής αλυσίδας, όπως διαπιστώθηκε από τη σημαντική μείωση του ανηγμένου ιξώδους. Από την pHμετρική μελέτη παρατηρούμε ότι καθώς αυξάνεται η συγκέντρωση των ιόντων δισθενούς χαλκού μειώνεται σημαντικά η τιμή του pH. Τέλος, η συμπλοκοποίηση των ιόντων Cu2+ με τα συμπολυμερή διαπιστώθηκε και με φασματοσκοπία υπεριώδους-ορατού, καθώς η κορυφή απορρόφησης των ιόντων Cu2+ μετατοπίζεται και ενισχύεται σημαντικά, σε σχέση με την αντίστοιχη συμπεριφορά των ελεύθερων ιόντων Cu2+. / The interaction between synthetic polyelectrolytes with transition metal ions leading to complex formation has attracted the research interest during the last decades. This interest is attributed to the unique properties of the complexes formed, as they can find uses in many fields, like medicine, food industries or remedation of environmental problems. In this work we proceeded to the synthesis of comb-like copolymer, denoted P(EV2-PDMAM). These copolymers are based on a poly(ethylene-co-maleic acid) backbone (EV2), onto which poly(N,N-dimethylacrylamide), (PDMAM) side chains were grafted. The molar composition of the copolymers, expressed in DMAM structural units was 25, 50 and 75%. The physicochemical study of the interaction of Cu2+ with the P(EV2-PDMAM) was performed using a series of techniques, such as viscometry, potentiometry and UV-vis spectrometry. Complex formation leads to a vey significant shrinkage of the polymer chain, as it is revealed by the decrease of the reduced viscosity. The potentiometric study revealed that the pH of the aqueous polymer solution decreases considerably upon increasing the concentration of Cu2+ ions. Finally, the UV-vis investigation also verified the polymer-Cu2+ complexation, since the absorption peak of Cu2+ ions shifts towards lower wavelengths and the intensity of the band is significantly enhanced as compared to the respective properties of free Cu2+ ions.

Metal nanoclusters exhibit unique properties which differ from their bulk materials, owing to the quantum size effects. For example, the catalytic activity of transition metal nanoclusters generally increases with decreasing particle size. However, nanoclusters tend to be fairly unstable with respect to the agglomerate into bulk metal in solution and thus special precautions have to be taken to avoid their aggregation or precipitation during the preparation of such nanoclusters in solution. In order to obtain stable nanoclusters dispersed in solution, a stabilizing agent is usually added into the reaction system. The stabilization of metal nanoclusters in solution can be achieved either by electrostatically by using charged ions such as acetate ion or sterically by long chain molecules such as polymers. Polymers are one of the most widely used steric stabilizers for the preparation of stable metal nanoclusters in solution. The use of polymers as stabilizer for the synthesis of transition metal nanoclusters provides advantegous regarding solubility, conductivity, thermal stability and reusability. The metal nanoclusters stabilized by polymers generally show higher catalytic activity, stability and optical properties. In this dissertation we report the preparation and characterization of water soluble polymer stabilized transition metal(0) (metal= Ni, Co and Ru) nanoclusters and their v catalysis in hydrogen generation from the hydrolysis of sodium borohydride (NaBH4) and ammonia borane (AB) which are the best candidates as chemical hydrogen storage materials for on-board applications. The water soluble polymer stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters were prepared by using two different facile methods / (i) the reduction of metal precursors by sodium borohydride in the presence poly(N-vinyl pyrrolidone) (PVP) in methanol solution after 1h reflux, (ii) the in situ generation during the hydrolysis of ammonia borane in the presence of poly(4-styrene sulfonicacid-co-maleic acid) (PSSA-co-MA). The characterization of both type of polymer stabilized transition metal(0) nanoclusters were done by using UV-Visible electronic absorption spectroscopy (UV-Vis), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and FT-IR techniques. The catalytic activity of PVP stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters was tested in the hydrolysis of NaBH4 and AB. The catalytic acitivity of PSSA-co-MA stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters was tested only in the hydrolysis of AB in which they were in situ generated. The kinetics of hydrogen generation from both hydrolysis reactions in the presence PVP or PSSA-co-MA stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters were studied depending on the polymer to metal ratio, catalyst concentration, substrate concentration and temperature as well as the activation parameters (Arrhenius activation energy (Ea), activation enthalpy (