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1
PADOAN, ANDREA. « Statistical methods for mass spectrometry data analysis and identification of prostaste cancer biomarkers ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/50248.
Texte intégralRésumé :
BACKGROUND
Prostate Cancer (PCa) is the most common cancer among males in Europe. Patients developing early PCa sometimes refer non-specific symptoms, namely lower urinary tract symptoms (LUTS), and they usually undergo medical investigations based on Prostate Specific Antigen (PSA) and Digital Rectal Examination (DRE). Suspicious results of one or both testings are prerequisite to Prostate Biopsy. However, due to PSA low sensitivity/specificity in predicting positive prostate biopsy, the identification of new PCa biomarkers is actually a real need. MALDI-TOF/MS protein profiling could be a valuable technology for biomarkers identification. However, up to now its use is laden with lack of reproducibility that confounds scientific inferences and limits its broader use.
AIMS
Goal of this study is to analyze urine collected after prostatic massage in patients referring LUTS, to identify candidate biomarker for PCa, by using MALDI-TOF/MS. We considered important aspects of MALDI-TOF/MS label-free proteomic profiling, in order to assess features reproducibility and to propose appropriate strategy to handle both measurement error and limit of detection (LOD) problems. The study results should aid in reducing the number of worthless first-biopsied and assist Urologists on differential diagnosis of PCa.
METHODS
In a cross-sectional study, we collected urine obtained after DRE from 205 patients that referred LUTS to consultants at the Urological Unit at University of Padova. All patients undergone to prostate biopsy for suspicious PCa. Urines were dialyzed and analyzed by MALDI-TOF/MS in reflectron mode. For the MALDI-TOF/MS reproducibility evaluation, we analyzed a urine pooled from 10 reference samples, spiked with 12.58 pmol of a 1589.9 m/z internal standard (IS) peptide. For the inter-run variability assessment, 14 aliquots were dialyzed by MALDI-TOF/MS. For the intra-run study, an aliquot was divided into 26 separate sub-aliquots and analyzed by MALDI- TOF/MS. To estimate the signal detection limit (sLOD), serial dilution up to 1/256 of a urine pool were analyzed in triplicate. We evaluated the sLOD and adjusted the data appropriately to reduce its variability. We investigated six data normalization approaches - the mean, median, internal standard, relative intensity, total ion current and linear rescaling normalization. Between-spectrum and the overall spectra variability were evaluated by the coefficient of variation (CV). An optimized signal detection strategy was also evaluated to overcome peak detection algorithms errors. Measurement errors and with-in subject variances were evaluated by an external dataset, made of urine repeatedly collected from 20 reference subjects. Intra class correlation coefficient (ICC), Regression Calibration (RCAL) and SIMEX analyses were used to estimate unbiased logistic regression coefficients relating MALDI-TOF/MS features with Patients biopsy outcome. Monte Carlo simulations were used to estimate influence of different LOD adjustment methods on ICC and RCAL.
RESULTS
Initially, we evaluated the intra- and inter-run on data obtained from automatic peak detection. Normalization methods performed almost similarly in both studies, except IS, which resulted in an increased CV. Calculated sLOD varied with spectra m/z. After sLOD adjustment, raw and normalized data showed a reduction in CVs, while median and mean normalizations performed better, especially in the intra-assay study. However, by optimizing the peak signal detection, the overall features variability drastically decreased. Median normalization with sLOD correction remained the preferable choice for further analyses. Evaluating the external dataset, we found that most of the MALDI-TOF/MS variability is intrinsic to the biological matrix. By using substitution of below LOD values by LOD/2, simulation studies showed that ICC estimations were poorly affected by LOD, when measurement error σ is less that 0.36 and values below LOD are less that 50%. Comparing results from naïve logistic regression, RCAL and SIMEX, measurement error appeared to cause a "bias toward the null". However, SIMEX estimations seemed to correct for a smaller amount of bias than RCAL. Overall, we found eight MALDI-TOF/MS features associated with positive biopsy results.
CONCLUSION
Findings from the reproducibility study showed that the major contributing factor for MALDI-TOF/MS profiling variability is the peak detection process. So, a new algorithm suited for MALDI-TOF reflectron mode is desirable for its applications in profiling studies. However, normalization strategies aid in increasing MALDI-TOF/MS label-free data reproducibility, especially with sLOD correction. Despite urine does not seem to be a promising biological fluid for proteomic biomarker discovers, RCAL and SIMEX appeared valuable approaches to obtain regression coefficients adjusted for biological and instrumental errors on MALDI-TOF/MS features.
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Nightingale, Philip D. « Low molecular weight halocarbons in seawater ». Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280971.
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Hoogland, J. S. « Properties of low molecular weight food surfactants ». Thesis, University of Bristol, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333908.
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Abdel-Hady, Mohamed Helmy Abdel-Rahman. « Molecular genetic profiling of low grade gliomas : towards a molecular genetic classification / ». The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486402957195399.
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Hettiarachchi, Rohan Jagath Kumara. « Venous thromboembolism, cancer and low molecular weight heparin ». [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/84386.
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Roberts-Thomson, Peter John. « Low molecular weight IgM in health and disease / ». Title page, index and abstract only, 1987. http://web4.library.adelaide.edu.au/theses/09MD/09mdr648.pdf.
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Mauron, Thomas. « Influence of low molecular weight heparin and low molecular weight dextran sulfate on the inhibition of coagulation factor XIa by serpins / ». Bern : Hämatologisches Zentrallabor der Universität Inselspital, 1998. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Chen, Qiang. « The major chloroplast low molecular weight heat shock protein ». Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185849.
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The goal of this dissertation is to provide information critical for understanding the function of the major chloroplast LMW HSP. The results of this research show that the production of a nuclear-encoded, chloroplast LMW HSP is a highly conserved event in the plant HS response, and that the HSP itself is highly homologous in divergent plant species. Three major conserved regions were identified in the chloroplast LMW HSP. The carboxyl-terminal HS domain of the chloroplast LMW HSP is also found in cytoplasmic LMW HSPs and identifies it as a member of the superfamily of eukaryotic LMW HSPs. The amino-terminal region is unique to the chloroplast LMW HSP and is capable of forming a Met-rich amphipathic α-helix. The chloroplast LMW HSP cannot be detected at normal growth temperatures, but accumulates dramatically in both leaves and roots during HS. The chloroplast LMW HSP is a stable protein with a half-life of approximately 52 h. In the chloroplast, the majority of PsHSP21 is localized in the soluble protein fraction. In its native state, PsHSP21 exists in a 200 kDa particle as is observed for cytoplasmic LMW HSPs. However, unlike the cytoplasmic LMW HSPs, the PsHSP21-containing particles do not aggregate into heat shock granules even under severe, abrupt HS conditions. The formation of the PsHPS21-containing particle can be replicated in isolated chloroplasts, but the chloroplasts must be from heat stressed plants. The protein sequence homology and the similar native structure of the LMW cytoplasmic and chloroplast HSPs suggests they perform similar functions in different cellular compartments. I propose that the 200 kDa particle is the functional form of PsHSP21. Furthermore, the chloroplast LMW HSP performs functions in all types of plastids similar to those of the cytoplasmic LMW HSPs, but with unique substrates within the special environment of plastids. This study provides the first information regarding the expression and structure of the chloroplast LMW HSP. Since the chloroplast contains only a single major LMW HSP, this study also provides the basis for developing a simple model system for studies of the function of all members of the ubiquitous LMW HSP family.
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Song, Yang. « OXIDATIVE DEPOLYMERIZATION OF LIGNIN TO LOW MOLECULAR WEIGHT AROMATICS ». UKnowledge, 2019. https://uknowledge.uky.edu/chemistry_etds/114.
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To date, most lignocellulosic biorefinery strategies have focused on optimizing conversion of cellulose to ethanol, leaving lignin as an underutilized biomass constituent. Lignin is engineered by nature with the intent to protect plants from chemical and biological attack; this leaves lignin with high structural irregularity and recalcitrance, rendering conversion of the lignin macromolecule to valuable products particularly challenging. Nevertheless, given that the economics of cellulosic ethanol production are strongly dependent on the value that can be obtained for the lignin co-product, the successful valorization of lignin is a crucial step in the transition towards a bio-based economy.
This thesis focuses on lignin depolymerization using oxidative methods, specifically, the oxidation and cleavage of the β-O-4 linkage. Heterogeneous catalysis in this case is more desirable than homogenous catalysis as the catalyst easily recovered, and it is better suited for industrial applications. Initially, layered double hydroxide (LDH) supported gold nanoparticles were characterized and screened in the oxidation of various lignin model compounds using molecular oxygen, leading to the discovery of an Au/Li-Al LDH heterogeneous catalyst active for oxidative cleavage of the β-O-4 linkage. The Au/Li-Al LDH catalyst was then applied to oxidatively depolymerize Indulin AT kraft lignin and γ-valerolactone (GVL) extracted lignin, high yields of monomers being observed when the oxidized lignins underwent subsequent base-catalyzed hydrolysis. Thereafter, different literature oxidative lignin depolymerization methods were tested on kraft lignin and GVL lignin, and the results compared to the Au/Li-Al LDH catalyst (coupled with hydrolysis) system to determine the most effective oxidative depolymerization method.
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Rodríguez, Seco Cristina. « Low-Molecular Weight Semiconductors for Organic and Perovskite Solar Cells ». Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/667660.
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Actualment, les fonts d'energia renovables estan atraient molta atenció degut a l'impacte negatiu que els combustibles
fòssils estan causant al planeta. Les tecnologies basades en les cel·les fotovoltaiques són una alternativa sostenible
per cobrir la demanda energètica mundial.
El principal objectiu d'aquest treball és el disseny i la síntesis de noves molècules per tal de reemplaçar els polímers
habitualment utilitzats com a molècules captadores de llum en cel·les solars orgàniques i el spiro-OMeTAD usat com a
transportador de buits (HTM per les sigles en anglès "hole transporting material") en dispositius solars de perovskita.
D'una banda, els polímers són coneguts per ser bons transportadors de buits, posseir una elevada solubilitat i una
bona habilitat per a la formació de capes, però entre els diferents lots existeix una baixa reproductibilitat degut a la
seva síntesi complexa. D'altra banda, el spiro-OMeTAD és la molècula que millor reproductibilitat i eficiència presenta
en cel·les solars de perovskita. No obstant això, la seva síntesi complexa i d’alt cost impedeix la possibilitat d'escalat a
nivell industrial.
Per tal de solucionar aquests problemes, aquesta tesi s'ha enfocat en el disseny, síntesi i caracterització d'un conjunt
de molècules petites de baix pes molecular per a la seva aplicació en aquests dispositius.Actualmente, las fuentes de energía renovables están atrayendo mucha atención debido al impacto negativo que los combustibles fósiles están causando al planeta. Las tecnologías basadas en las celdas fotovoltaicas son una alternativa sostenible para cubrir la demanda energética mundial. El principal objetivo de este trabajo fue el diseño y la síntesis de nuevas moléculas que reemplacen los polímeros comúnmente utilizados como moléculas captadoras de luz en celdas solares orgánicas y el spiro-OMeTAD usado como transportador de huecos (HTM por sus siglas en inglés “hole transporting material”) en dispositivos solares de perovskita. Por una parte, los polímeros son conocidos por ser buenos transportadores de huecos, su alta solubilidad y su favorable habilidad en la formación de capas, pero tienen muy poca reproducibilidad entre distintos lotes. Por otra parte, el spiro-OMeTAD es la molécula que mejor reproducibilidad y eficiencia presenta en celdas solares de perovskita. Sin embargo, su síntesis compleja y de alto coste impide la posibilidad de escalado a nivel industrial. Con el fin de solucionar estos problemas, esta tesis se ha enfocado en el diseño, síntesis y caracterización de un conjunto de moléculas pequeñas de bajo peso molecular para su aplicación en dichos dispositivos
Nowadays, renewable energy sources are attracting a lot of attention due to the undesired environmental impact the fossil fuels are causing to the Earth. Solar cells technologies are a sustainable alternative to the increasing world energy demand. The main aim of this work was to design and synthetize novel molecules that could replace the polymers widely used as absorbers in organic solar cells and spiro-OMeTAD used as a hole transporting material (HTM) in perovskite solar cells. On the one hand, polymers are known for their good hole transporting properties, high solubility and good film forming abilities but they have a poor batch-to-batch reproducibility. Furthermore, spiro-OMeTAD is the best molecule to achieve reproducible and highly efficient perovskite solar cells. However, its complex and expensive synthesis and purification hinder its usage in industrial scale photovoltaics. In order to overcome these problems, the rational design, synthesis and characterization of a variety of small molecules for both applications have been on a focus of this thesis.
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Cheuk, Sherwin. « Glucose and Glucosamine Derivatives as Novel Low Molecular Weight Gelators ». ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/868.
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Low molecular weight gelators (LMWGs) are small molecules that are capable of entrapping solvents to form a gel in organic solvents or aqueous solution. These compounds rely solely on noncovalent forces to form the fibrous networks necessary to entrap a variety of solvents. The organogels and hydrogels thus formed could have applications in a variety of fields from environmental to biological to medicinal. Carbohydrates are ideal starting materials to synthesize LMWGs, because of their natural abundance, dense chirality, and biocompatibility. D-Glucose is the most common monosaccharide and D-glucosamine is isolated from natural sources, such as crab shells. Several series of compounds were synthesized using compounds 1-3 as the starting materials. These include esters, carbamates, amides, and ureas. The structure and gelation relationship was analyzed to obtain guidelines for designing new LMWGs. Compound 1 is a simple derivative of D-glucose and its terminal alkynyl esters and saturated carbamates are effective gelators. Compound 2 is a simple derivative of D-glucosamine and its amide and urea derivatives are also effective gelators. Compound 3 is formed from the deoxygenation of D-glucose. 1OOHOOCH3OHOPh2OOHOOCH3NH2OPh3OOHOOHOPh The design, synthesis and gelation properties of several classes of sugar based low molecular organo/hydrogelators will be discussed in this thesis in chapters 2, 3, and 4. After obtaining highly effective organo/hydrogelators, potential applications of these novel molecular systems can be explored. Some preliminary study on using one of the gelator in enzyme assay has shown that it is possible to utilize the hydrogels to immobilize enzymes. However, future research can explore further on the applications of these gelators.
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Williams, Kristopher Aaron. « Synthesis and Characterization of Monosaccharide-derived Low Molecular Weight Gelators ». ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/135.
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Low molecular weight gelators (LMWGs) are interesting materials whose applications are as diverse and wide ranging as their molecular structures. These materials self-assemble through the formation of non-covelent intermolecular forces and interactions to form supramolecular assemblies that trap solvent within their matrices. Because of the non-covalent nature of the forces of self-assembly, the gelation process is typically thermally reversible. In addition, low molecular weight gelators can also be modified to respond to various stimuli, such as change in pH, presence of enzymes or metal cations, or exposure to light. The design of low molecular weight gelators is often difficult, and most new classes of low molecular weight gelators are discovered by serendipity. As such, it is often useful to use structural templates in the design of LMWGs. Biomolecules, such as steroids, amino acids and peptides, and carbohydrates make excellent templates due to their inherent propensity to self assemble. A review of the current literature regarding the use of biomolecules as templates for the design and synthesis of LMWGs will be presented in chapter 1. Our research group has been active in the research of carbohydrate-based LMWGs for several years, and these results are also briefly reviewed in the related chapters. The synthesis and characterization of ester derivatives of D-galactose, D-glucose, and amide derivatives of D-glucosamine will be discussed in chapters 2-4, along with their evaluation for gelation in aqueous and organic solvents, such as hexane, ethanol, water, and aqueous DMSO or ethanol mixtures.
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Yang, Hao. « Synthesis and characterization of sugar based low molecular weight gelators ». ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1496.
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Low molecular weight gelators (LMWGs) have gained great attention over the past two decades. These compounds form self-assembled fibrous networks like micelles, cylindrical, sheets, fibers, layers and so on. The fibrous network entraps the solvent and form gel. LMWGs are interesting compounds with many potential applications in material and biomedical sciences.
Many different structures have been found to be good LMWGs. Our interests focus on the carbohydrate based LMWGs. Previously, we have found that several ester derivatives of methyl 4, 6-O-benzylidene-α-D-glucopyranoside are good gelators for organic solvents and aqueous solutions. In this study, in order to understand the structure requirement, we systematically investigated the influence of sugar head groups and the attached hydrophobic tails towards gelation. The design, synthesis and gel properties of esters, amides, ureas, carbamates which derived from sugar head groups show above will be discussed in chapter II, III, IV.
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Brás, Ana Rita Elias. « Influence of constraining and confinement in the molecular mobility of low molecular weight materials ». Doctoral thesis, FCT - UNL, 2009. http://hdl.handle.net/10362/2670.
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Dissertation presented to obtain a Ph.D. Degree in Chemical PhysicsDespite the importance that the glassy state has nowadays, the transition from liquid to the glass, glass transition, still remains a matter of debate which constitutes one of the great condensed matter physics challenges. Since this fact is closely related to the cooperativity dynamics, the study of this phenomenon in glass-forming liquids under confinement in the nanometer scale, has recently emerged as a strategy to clarify factors such as the existence of an inherent length scale of the cooperative dynamics that determines the glass transition temperature. In this context, this thesis represents an additional contribution to the study of molecular dynamics of glass-forming liquids under confinement in nanoporous inorganic materials. As target compounds the liquid crystal E7 and the drug Ibuprofen were selected. Since the first exhibit various transitions makes it more sensitive to perturbations and thus appears as the ideal candidate to evaluate confinement effects. The study of ibuprofen is of particular interest because confinement emerges as a method of stabilizing the amorphous phase that is mostly important in pharmaceutical applications. Dielectric Relaxation Spectroscopy(DRS) is the main technique used to obtain detailed information about the molecular mobility in a wide range of frequencies (10-2-109Hz) (Chapter I and II). The first part of the thesis is devoted to the characterization of the two target compounds in the bulk state. The combination of DRS with the specific heat spectroscopy allowed to determine which of the E7 observed relaxation processes (a process in the isotropic phase and two processes in the nematic phase: δ and tumbling) is responsible for the glass transition temperature Tg (tumbling process). Detailed studies of ibuprofen molecular mobility in the liquid, supercooled liquid and glassy states are also presented in this chapter, where four relaxation processes are detected: two secondary processes (γ and β), the cooperative process related to Tg (α ) and the Debye process (D), probably related to the hydrogen bonding dynamics. This study was preceded by an optimization of the conditions to obtain amorphous Ibuprofen which is a crystal in its natural state (Chapter III). In the next chapter (Chapter IV), the molecular dynamics of E7 confined to untreated and phospholipid lecithin treated rigid inorganic membranes with 20 nm pore diameter was evaluated. It was found that both the liquid crystal alignment, as well as the dynamics is influenced by confinement and treatment of the surface pores. Additionally, E7 was further studied confined to the mesoporous materials MCM-41 and SBA-15 type, 100% silica composition and pore size between the 2.8 and 6.8 nm. A multiplicity of relaxation processes was revealed by DRS, including the modes already observed in the bulk E7. In addition, two
Fundação para a Ciência e Tecnologia (FCT),financial support by means of the PhD grant SFRH/BD/23829/2005
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Gao, Karen Ging. « Photoresist removal using low molecular weight alcohols and IPA-based solutions ». Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/11875.
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Gauthier, Elisabeth. « Utilization of low molecular weight substrates by psychrotrophic meat spoilage organisms ». Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59274.
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Four meat spoilage organisms were grown at 4$ sp circ$C for 7 d, in an aqueous extract of meat (Meat Juice Medium), and the levels of various nutrients in the extracts were measured. At an agitation rate of 50 rev$ cdot$min$ sp{-1},$ the four species reached viable counts of 10$ sp8$ Colony Forming Units (CFU)$ cdot$ml$ sp{-1},$ and the order of nutrient utilization was as follows: (1) glucose, (2) gluconate and urea, (3) glycerol, (4) glucose-6-phosphate. Several substrates were still present in the growth medium at the end of the growth period, namely lactate, glucose-6-phosphate and the two unknowns. At a higher agitation rate (100 rev$ cdot$min$ sp{-1}),$ the non-fluorescent pseudomonad reached final counts of ca. 10$ sp{10}$ CFU$ cdot$ml$ sp{-1},$ 2 logs higher than those of the other three organisms present in the mixed culture. The order of nutrient utilization was: (1) glucose, (2) gluconate, urea and glycerol, (3) lactate and glucose-6-phosphate, (4) unknowns 1 and 2. At day 7, none of the nine substrates studied remained in the growth medium.
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Lo, Wendy. « Thermo-chemical recovery of low molecular weight oligomers from polyethylene waste ». Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61313.
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This study focused on the chemical recycling of polyethylene using controlled thermo-chemical degradation. Polyethylene was degraded in a stirred, batch reactor under a nitrogen atmosphere. The reaction temperatures that were investigated ranged between 375$ sp circ$C and 421$ sp circ$C. The reaction time ranged between 20 and 50 minutes. Three major products were collected, an insoluble solid residue, a condensable wax that was volatile during the reaction, and a residual wax that was not volatile during the reaction. It was determined that above 409$ sp circ$C, 90% of the original resin weight was converted to both the volatile and residual wax. Both waxes had a final Mn of 400 to 500. Analysis revealed that the volatile wax was a mixture of straight chain hydrocarbons, with 4% of the carbon bonds unsaturated. The residual wax was a mixture of hydrocarbons, both straight and branched components. No liquid product was collected, and gaseous components did not exceed 10% of the original resin weight. It was also determined that silica alumina did not enhance degradation.
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Cotterill, Sally L. « Purification of a low molecular weight heat shock protein from plants ». Thesis, Bangor University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262239.
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Danesh, Mesgaran Mohsen. « Ruminal accumulation and fate of low molecular weight peptides in sheep ». Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295475.
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Crawford, S. M. « Low molecular weight proteinuria and the natural history of multiple myeloma ». Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382055.
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Parikh, Bhargiv. « Design, Synthesis and Characterization of D-glucosamine Low Molecular Weight Gelators ». ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/1110.
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Low molecular weight gelators (LMWGs) have gained much attention over the last few decades, because of their ability to form supramolecular architectures as well as their many potential applications in biomedical research and as advanced materials. Most of the gelators were discovered through serendipity, and their structural requirements are somewhat ambiguous. This is due, in part, to the fact that the supramolecular gelation phenomenon is not yet fully understood, though many structural classes have been found to be excellent organogelators. Carbohydrates are abundant natural resources that are useful in preparing advanced materials. We have previously showed that monosaccharide derivatives can form effective low molecular weight gelators for both organic solvents and aqueous mixtures. In this research, we have studied the gelation capability of several glucosamine derivatives. Several series of 4,6-O-acetal protected glucosamine derivatives were synthesized and screened for their gelation properties in several solvents.
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Aktaş, Ece. « Low-Molecular Weight Molecules as Selective Contacts for Perovskite Solar Cells ». Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/672777.
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La tecnologia fotovoltaica és una de les fonts d'energia neta i renovable més prometedores per reduir l'impacte ambiental dels combustibles fòssils en les últimes dècades. en aquest context, les perovskites són un material que ha atret recentment una atenció important a causa de la seva capacitat per aconseguir eficiències de conversió molt elevades. Les capes de càrrega selectiva juguen un paper crucial en el ràpid augment del rendiment del dispositiu i en l'estabilitat de les cel·les solars de perovskita. Recentment, l'aplicació de mono-capes auto-assemblades formades per molècules orgàniques que funcionen com a capes selectives de càrrega en cel·les solars de perovskita ha atret una gran atenció a causa d'avantatges com la rendibilitat, l'estabilitat i l'absència d'additius. L'objectiu d'aquesta tesi és el disseny i la síntesi de noves molècules que formen mono-capes auto-assemblades que funcionin com a capes selectives de forats en cel·les solars de perovskita per aconseguir una eficiència de conversió d'alta d'energia i una vida d'envelliment d'alt rendiment feta a mida.La tecnología fotovoltaica es una de las fuentes de energía limpia y renovable más prometedoras para reducir el impacto ambiental de los combustibles fósiles en las últimas décadas. en este contexto, las *perovskites son un material que ha atraído recientemente una atención importante a causa de su capacidad para conseguir eficiencias de conversión muy elevadas. Las capas de carga selectiva juegan un papel crucial en el rápido aumento del rendimiento del dispositivo y en la estabilidad de las celdas solares de *perovskita. Recientemente, la aplicación de *mono-capes auto-asemejadas formadas por moléculas orgánicas que funcionan como capas selectivas de carga en celdas solares de *perovskita ha atraído una gran atención a causa de ventajas como la rentabilidad, la estabilidad y la ausencia de aditivos. El objetivo de esta tesis es el diseño y la síntesis de nuevas moléculas que forman *mono-capes auto-asemejadas que funcionen como capas selectivas de agujeros en celdas solares de *perovskita para conseguir una eficiencia de conversión de alta de energía y una vida de envejecimiento de alto rendimiento hecha a medida.
Photovoltaic technology is one of the most promising clean and renewable energy sources to reduce the environmental impact of fossil fuels in recent decades. In this context, perovskites are a material that has recently attracted significant attention due to their ability to achieve very high conversion efficiencys. Selective charge layers play a crucial role in rapidly increasing device performance and in the stability of perovskite solar cells. Recently, the application of self-assembly mono-caps made up of organic molecules that function as selective layers of charge in solar perovskite cells has attracted great attention due to advantages such as profitability, stability and the absence of additives. The goal of this thesis is the design and synthesis of new molecules that form self-assembly mono-layers that function as selective layers of holes in solar perovskite cells to achieve high-energy conversion efficiency and a high-performance aging life tailored to size.
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Funkey, Carolina P. « Abiotic Release of Low Molecular Weight Nitrogen from Effluent Organic Nitrogen ». W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539617906.
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Matthíasson, Stefán E. « Low molecular weight heparin and dextran in thromboprophylaxis human and experimental studies / ». Malmö : Dept. of Surgery, Lund University, Malmö General Hospital, 1994. http://books.google.com/books?id=9OxsAAAAMAAJ.
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Chen, Yuan. « Low-molecular-weight chromium-binding substance advanced studies from aves to human / ». Thesis, [Tuscaloosa, Ala. : University of Alabama Libraries], 2009. http://purl.lib.ua.edu/2167.
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Alshahrani, Rasha. « Liquid Organic Electrolytes : Blends of Low Molecular Weight Methoxyoligooxyethylene (MPEGs)/LiTFSI Salt ». DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2017. http://digitalcommons.auctr.edu/cauetds/111.
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Blends containing methoxyoligooxyethyleneglycol (MPEGs) (MW 350 and 550) and bis(trifluoromethane)sulfonimide lithium (LiTFSI) salt were prepared by solution blending process using tetrahydrofuran (THF) as a solvent. The ionic conductivity of the blends of different compositions were determined at four temperatures i.e. 25°C, 40°C, 60°C and 70°C. A maximum ionic conductivity value of 3.9x10-3 S cm-1 at 25°C was obtained for the blends containing MPEG-350 at an ethylene oxide to lithium salt ratio of 1:10. The ionic conductivity increases with increasing temperature and shows that the ion transport is aided by the segmental motion of the MPEG chains. 7Li NMR spectroscopy was used to study the nature and dynamics of the salt clusters in the blends
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Hoang, Tiffany Truc. « Speciation and identification of low molecular weight organoselenium metabolites in human urine ». Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/30671.
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Griffin, Jonathan Hrothgar. « Low molecular weight proteomic analysis of Arabidopsis thaliana and Oryza sativa seeds ». Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414173.
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Lima, Juliana Pego. « Development of Nanoparticles as Low Molecular Weight Heparins Carriers for Oral Administration ». Master's thesis, Faculdade de Farmácia da Universidade do Porto, 2007. http://hdl.handle.net/10216/7486.
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Sivakova, Sona. « Supramolecular Polymers via Nucleobase Directed Self-Assembly of Low-Molecular Weight Monomers ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1112726513.
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Verghese, Jenson. « SYNTHESIS AND BIOCHEMICAL STUDIES ON SULFATED MONOMERS OF LOW MOLECULAR WEIGHT LIGNINS ». VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1868.
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Anticoagulants are used as the first line therapy for management and prevention of thrombotic disorders. Thrombin and factor Xa have been the prime targets for regulation of the coagulation cascade. In this work, a small library of 17 benzofuran derivatives were synthesized and screened against thrombin and factor Xa. The derivatives that displayed inhibitory potential were docked on the exosite-II of factor Xa using a docking protocol that was developed in our research group. These compounds were based on the β-5 structural unit found in the oligomer -'CDSO3‘, which was prepared in our lab and was found to inhibit both thrombin and factor Xa by an exosite-II mediated allosteric disruption of the catalytic triad.The results revealed that these β-5 like derivatives are inhibitory against thrombin and factor Xa, although their potency is weak. Thrombin and factor Xa appear to recognize different structural features suggesting a significant selectivity in recognition. Furthermore, a slight preference for the benzofuran scaffold was observed with factor Xa. Probing the mechanism of inhibition using Michaelis-Menten kinetics reveal that these compounds display uncompetitive inhibition of these proteases and the mechanism of inhibition is allosteric. Docking of these compounds on factor Xa were done using GOLD (Genetic algorithm for ligand docking) and the results, explain the observed inhibition profile. The computed docked poses also give an idea of the residues on the exosite-II of factor Xa critical for inhibition. The molecules studied here are radically different in terms of structure and mechanism of inhibition from any other ligand described in literature. This represents an opportunity to discover novel molecules with a possibly different pharmacological and toxicological profile.
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Lima, Juliana Pego. « Development of Nanoparticles as Low Molecular Weight Heparins Carriers for Oral Administration ». Dissertação, Faculdade de Farmácia da Universidade do Porto, 2007. http://hdl.handle.net/10216/7486.
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Goh, Ching Yong. « Amino acid functionalised calixarenes : crystal growth modifiers and low molecular weight gelators ». Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1894.
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A selection of amino acid functionalised calix[4]arenes was studied. Acidic amino acid functionalised calixarenes were investigated as crystal growth modifiers. The self-assembly behaviour of proline functionalised calixarenes were also examined.Calix[4]arenes functionalised at the wide-rim with acidic amino acids were investigated as potential crystal growth modifiers on model mineral systems and were compared with previously investigated narrow-rim analogues. This study found that the wide-rim aspartic acid and glutamic acid functionalised calix[4]arenes had an impact on the morphology of calcium carbonate and barium sulfate. The iminodiacetic acid calix[4]arene was found to have minor impact on the morphology of calcium carbonate.In comparison with the narrow-rim analogues, the wide-rim and narrow-rim aspartic acid calix[4]arenes had similar potency on calcium carbonate while the wide-rim glutamic acid calix[4]arene appeared to be more potent than the narrow-rim calix[4]arene. Calcium carbonate crystallised in the presence of wide-rim aspartic acid and glutamic acid calix[4]arenes and their narrow-rim analogues had stepped edges which resembled calcium carbonate found in biomineral systems (e.g. mollusc shells). Desupersaturation experiments showed the wide-rim aspartic acid calix[4]arene to be a more potent inhibitor of barium sulfate crystallisation than the wide-rim glutamic acid calix[4]arene.An aqueous solution of L-proline calix[4]arene exhibited surfactant-like properties. The self-assembly behaviour of L-proline calix[4]arene in solution was characterised by UV-visible and NMR spectroscopy. The critical aggregation concentration of L-proline calix[4]arene was determined to be 4–9 mM by monitoring a selection of dye compounds using UV-visible spectroscopy. The interaction of L-proline calix[4]arene with small molecules and in the presence of electrolytes was also characterised by NMR spectroscopy. The 1H NMR spectra of L-proline calix[4]arene in the presence of small molecules (tetrahydrofuran, 1-methyl-2-pyrrolidinone, and tert-butyl alcohol) suggested that the calixarene was either acting as a host or selfassembling into larger aggregates. Variable temperature NMR experiments showed that these interactions were thermoreversible.The formation of a hydrogel by proline calix[4]arenes in the presence of electrolytes was a serendipitous discovery. Investigations with selected electrolytes showed that the anion was the dominant factor in determining if a hydrogel formed, with lesser influence from the cation. The thermostability of the calixarene-electrolyte hydrogels tended to follow the Hofmeister series, where more stable hydrogels formed in the presence of anions towards the chaotropic end of the series. A racemic mixture of the proline calixarenes gave a less stable hydrogel compared with hydrogels of the enantiopure compounds. The calixarene-electrolyte hydrogels had a fibrous appearance, as characterised by atomic force microscopy. Some hydrogels collapsed slowly and deposited crystals of sufficient quality for single crystal x-ray crystallography. These structures gave some insights into how intermolecular forces may give rise to the fibrous gel structures; in particular hydrogen bonds between proline moieties, and the inclusion of a proline group into the cavity of a neighbouring calixarene, leading to spiral-like structures. A sarcosine functionalised calix[4]arene also formed hydrogels upon addition of some electrolytes, whereas the proline-functionalised calix[5]arene analogue did not.Since a range of hydrogels have been used as matrices to control crystal growth, a proline calix[4]arene-lithium nitrate hydrogel was used as a potential template for barium sulfate crystallisation. The results suggested that lithium nitrate was the main factor in modification of the barium sulfate morphology. The hydrogel did have a minor impact by slowing the diffusion of sulfate anions into the barium-containing gel phase resulting in smaller particles.The versatility of amino acid functionalised calix[4]arenes has been highlighted here. Wide-rim functionalised acidic amino acid calix[4]arenes were found to be effective crystal growth modifiers; having an impact on the morphology and growth kinetics of model crystallisation systems, calcium carbonate and barium sulfate. Interesting supramolecular chemistry was observed with proline functionalised calix[4]arenes; the proline calixarene interacts with small molecules in solution and either act as a host or self-assembles into large aggregates. The formation of proline calix[4]arene aggregates is interesting as they give rise to hydrogels in the presence of selected electrolytes.
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Ferrari, Dante F. « Aminolysis kinetics of low molecular weight and polymer-bound anhydride moieties in low and high viscosity media ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20633.pdf.
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Lambourne, John Joseph. « Elucidating the role of low molecular weight glutenin subunits in determining wheat quality ». Thesis, University of Reading, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506122.
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Gräßler, Jürgen, Matthias Gruber, Rolf-Bernd Radke, Steffi Kopprasch, Peter E. H. Schwarz, Wolfram Kamke, Stefan R. Bornstein et Sabine Fischer. « Type 2 Diabetes in Octogenarians Is Associated with Decreased Low Molecular Weight Adiponectin ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-134756.
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Background: Adiponectin circulates in the blood in three different multimer isoforms, of which the high molecular weight form (HMW) is presumed to mediate insulin sensitivity. We examined whether adiponectin oligomer distribution is associated with aging and type 2 diabetes (T2D) in octogenarians without characteristic features of metabolic syndrome. Methods: The study included 154 octogenarians (58 men, 96 women), 24 normoglycemic middle-aged controls (11 men, 13 women; mean age 44 years), and 33 middle-aged individuals (14 men, 19 women; mean age 55 years) with T2D. Based on oral glucose tolerance test 62 octogenarians had normal, 63 impaired glucose tolerance, and 29 octogenarians had newly detected T2D. Serum adiponectin multimer isoforms were measured after overnight fast by enzyme-linked immunosorbent assays. Results:Compared to the normoglycemic middle-aged control group, male normoglycemic octogenarians revealed significantly higher total adiponectin and all adiponectin isoforms. The same was true for females with the exception of low molecular weight (LMW) adiponectin, which was not statistically higher in octogenarians. Male and female octogenarians with T2D had significantly higher levels of total, HMW, and middle molecular weight (MMW) adiponectin, but not LMW adiponectin, than middle-aged individuals with T2D. Female, but not male, octogenarians revealed significantly lower total adiponectin than normoglycemic octogenarians. Compared with normoglycemic octogenarians, male and female octogenarians with T2D were characterized by significantly lower LMW adiponectin. In male and female octogenarians, total adiponectin and all multimer isoforms were directly correlated with HDL cholesterol. LMW adiponectin in octogenarians of both sexes was inversely correlated with glucose level at 2-hour oral glucose tolerance test. Conclusions: Serum levels of total adiponectin as well as its HMW and MMW isoforms were significantly higher in octogenarians with normoglycemia or T2D than in corresponding middle-aged control groups. In male and female octogenarians without metabolic syndrome, T2D was associated with lower LMW adiponectin, while the HMW and MMW isoforms were not statistically differentDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Barrett, Perry. « The regulation of expression of low molecular weight RNA species in amphibian oocytes ». Thesis, University of St Andrews, 1987. http://hdl.handle.net/10023/14292.
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During early oogenesis in Xenopus laevis about half of the 5S ribosomal RNA and most of the transfer RNA produced is stored in a ribonucleoprotein (RNP) complex that sediments at 42S. The other half of the 5S RNA produced is stored in a separate 73 RNP particle. As ribosome production gets underway in mid-oogenesis both the 1|2S and 7S particles disappear, the 5S rRNA being incorporated into the ribosomes, the tRNA being released as a slower sedimenting particle. Heterogeneity in the composition of the 42S particle was observed with respect to both protein and RNA components. The proteins of the 423 particle, Mr 48000 (P48) and Mr 43000 (P43) appear to be cleaved to smaller proteins. A derivative of P43 of Mr 17000 (P17) possibly becomes a ribosomal protein. Several observations are consistent with the view that P43 may accompany 53 RNA to the nucleolus before its cleavage product (P17) becomes incorporated into the ribosome. The chemical and structural relationships of P48, P43 and the protein component of the 73 RNP particle, transcription factor IIIA were studied and it was established that they are the products of three different genes. The 423 particle proteins have also been shown to have a binding affinity for 53 RNA genes (P48), tRNA genes (P43) or ribosomal genes (P43). In vivo inhibition of 5S RNA transcription by an anti-P48 antibody or tRNA transcription by an anti-P43 antibody suggest that these proteins may have a role in the transcription of these genes. Interactions between P43 and tRNA genes were analysed in most detail and indicating a specific interaction between these two components. The results taken as a whole suggest a central role for 42S particle proteins in particular P43, in co-ordinating the formation of the protein translational machinary.
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Gräßler, Jürgen, Matthias Gruber, Rolf-Bernd Radke, Steffi Kopprasch, Peter E. H. Schwarz, Wolfram Kamke, Stefan R. Bornstein et Sabine Fischer. « Type 2 Diabetes in Octogenarians Is Associated with Decreased Low Molecular Weight Adiponectin ». Karger, 2011. https://tud.qucosa.de/id/qucosa%3A27595.
Texte intégralRésumé :
Background: Adiponectin circulates in the blood in three different multimer isoforms, of which the high molecular weight form (HMW) is presumed to mediate insulin sensitivity. We examined whether adiponectin oligomer distribution is associated with aging and type 2 diabetes (T2D) in octogenarians without characteristic features of metabolic syndrome. Methods: The study included 154 octogenarians (58 men, 96 women), 24 normoglycemic middle-aged controls (11 men, 13 women; mean age 44 years), and 33 middle-aged individuals (14 men, 19 women; mean age 55 years) with T2D. Based on oral glucose tolerance test 62 octogenarians had normal, 63 impaired glucose tolerance, and 29 octogenarians had newly detected T2D. Serum adiponectin multimer isoforms were measured after overnight fast by enzyme-linked immunosorbent assays. Results:Compared to the normoglycemic middle-aged control group, male normoglycemic octogenarians revealed significantly higher total adiponectin and all adiponectin isoforms. The same was true for females with the exception of low molecular weight (LMW) adiponectin, which was not statistically higher in octogenarians. Male and female octogenarians with T2D had significantly higher levels of total, HMW, and middle molecular weight (MMW) adiponectin, but not LMW adiponectin, than middle-aged individuals with T2D. Female, but not male, octogenarians revealed significantly lower total adiponectin than normoglycemic octogenarians. Compared with normoglycemic octogenarians, male and female octogenarians with T2D were characterized by significantly lower LMW adiponectin. In male and female octogenarians, total adiponectin and all multimer isoforms were directly correlated with HDL cholesterol. LMW adiponectin in octogenarians of both sexes was inversely correlated with glucose level at 2-hour oral glucose tolerance test. Conclusions: Serum levels of total adiponectin as well as its HMW and MMW isoforms were significantly higher in octogenarians with normoglycemia or T2D than in corresponding middle-aged control groups. In male and female octogenarians without metabolic syndrome, T2D was associated with lower LMW adiponectin, while the HMW and MMW isoforms were not statistically different.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Giuri, Demetra <1993>. « Peptide-based low molecular weight gelators for the preparation of self-assembled materials ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9612/1/Giuri_Demetra_tesi.pdf.
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Low molecular weight gelators (LMWGs) based on pseudo-peptides are here studied for the preparation of supramolecular materials. These compounds can self-assemble through non-covalent interactions such as hydrogen bonds and π-π stacking, forming fibres and gels. A wide variety of materials can be prepared starting from these building blocks, which can be tuned and functionalised depending on the application. In this work, derivatives of the three aromatic amino acids L-Phenylalanine, L-Tyrosine and L-DOPA (3,4-dihydroxiphenylalanine) were synthesised and tested as gelators for water or organic solvents. First, the optimal gelating conditions were studied for each compound, varying concentration, solvent and trigger. Then the materials were characterised in terms of mechanical properties and morphology. Water remediation from dye pollution was the first focus of this work. Organogels were studied as absorbent of dyes from contaminated water. Hydrogels functionalised with TiO2 nanoparticles and graphene platelets were proposed as efficient materials for the photo-degradation of dyes. An efficient method for the incorporation of graphene inside hydrogels using the gelator itself as dispersant was proposed. In these materials a high storage modulus coexists with good self-healing and biocompatibility. The incorporation of a mineral phase inside the gel matrix was then investigated, leading to the preparation of composite organic/inorganic materials. In a first study, the growth of calcium carbonate crystals was achieved inside the hydrogel, which preserved its structure after crystal formation. Then the self-assembled fibres made of LMWGs were used for the first time instead of the polymeric ones as reinforcement inside calcium phosphate cements (CPCs) for bone regeneration. Gel-to-crystal transitions occurring with time in a metastable gel were also examined. The formation of organic crystals in gels can be achieved in multicomponent systems, in which a second gelator constitutes the independent gel network. Finally, some compounds unable to gelate were tested as underwater adhesives.
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Costa, Coto Daniel 1977. « High-throughput molecular profiling of the fetal inflammatory response in extremely low gestational age newborns ». Doctoral thesis, TDX (Tesis Doctorals en Xarxa), 2019. http://hdl.handle.net/10803/671727.
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Preterm birth is the leading cause of neonatal morbidity and mortality worldwide. Preterm newborns require special care for surviving and may develop severe diseases related to prematurity, especially those born very early. The fetal inflammatory response (FIR) to intraamniotic infection is characterized by high levels of cytokines in umbilical cord (UC) blood and it is diagnosed by the identification of pathological vasculitis of vessels of fetal origin in the umbilical cord and the placenta. The FIR jointly with neonatal diseases with systemic inflammation increase the risk of perinatal brain injury. In this thesis we explore the molecular changes associated with FIR in UC and in dried blood spots, collected during the first postnatal week and archived at the newborn screening program, using technologies for high-throughput molecular profiling. The results of this thesis provide new insights into the molecular mechanisms of FIR at birth and postnatally, which can help the identification of biomarkers and therapeutic targets of FIR and FIR-associated disordersEl part preterme és una de les principals causes de mortalitat i morbiditat neonatal. Els nadons prematurs requereixen atenció mèdica especialitzada per sobreviure i poden patir freqüentment malalties greus associades a la prematuritat, especialment aquells més prematurs. La resposta fetal inflamatòria (FIR) és caracteritza per l’elevació de citoquines en sang de cordó umbilical i es diagnostica a nivell patològic per la presència de vasculitis dels vasos d’origen fetal en el cordó umbilical i la placenta. FIR conjuntament amb d’altres malalties neonatals associades amb inflamació sistèmica incrementen el risc de dany cerebral perinatal. En aquesta tesis explorem el canvis moleculars associats a FIR en el cordó umbilical i en sang seca de taló, recollida durant la primera setmana postnatal i emmagatzemada en el programa de cribatge neonatal, ulitzant tecnologies de perfilatge molecular d’alt rendiment. Els resultats aquí obtinguts mostren mecanismes moleculars de FIR, els quals poden ajudar a la recerca de nous biomarcadors i dianes terapèutiques per FIR i patologies neonatals associades.
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Tartsch, Bernd. « Organization, manipulation and motion of brush polymers and low molecular weight amphiphiles at interfaces ». [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=979080673.
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Laschewsky, André, W. Paulus, Helmut Ringsdorf, A. Schuster, G. Frick et A. Mathy. « Mixed polymeric monolayers and Langmuir-Blodgett multilayers with functional low molecular weight guest compounds ». Universität Potsdam, 1992. http://opus.kobv.de/ubp/volltexte/2008/1723/.
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Mixed monolayers and Langmuir-Blodgett multilayers of functional low molecular weight guest compounds, especially nonlinear optical (NLO) dyes, within the matrix of an amphotropic spacer polymer have been prepared. The polymer matrix enabled the transfer of guest compounds not capable of self-organizing at the air-water interface by themselves. The structure of the LB multilayers and the transfer process were studied by small angle X-ray scattering and UV-visible spectroscopy. Good NLO coefficients were found in the mixed films.
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Saito, Takashi. « DESIGN AND CHARACTERIZATION OF GELATIN HYDROGELS INCORPORATING LOW-MOLECULAR-WEIGHT DRUGS FOR TISSUE REGENERATION ». 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199334.
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Moosavi-Nasab, Marzieh. « Identification of low molecular weight compounds produced or utilized by psychrotrophic meat spoilage organisms ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0024/MQ37151.pdf.
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Jiang, Lu. « Oligomer-supported solution synthesis of oligosaccharides using low molecular weight poly(ethylene glycol) linkers ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0025/NQ50194.pdf.
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Hedeland, Ylva. « Chiral Separation of Amines by Non-Aqueous Capillary Electrophoresis using Low Molecular Weight Selectors ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6759.
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Holmström, Margareta. « Clinical aspects on treatment of deep venous thrombosis with a low molecular weight heparin / ». Stockholm, 1998. http://diss.kib.ki.se/1998/91-628-2989-0/.
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Jiang, Lu 1967. « Oligomer-supported solution synthesis of oligosaccharides using low molecular weight poly(ethylene glycol) linkers ». Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35712.
Texte intégralRésumé :
A new approach has been studied for solution-phase oligosaccharide syntheses using low molecular weight poly(ethylene glycol) monomethyl ethers (MPEG, average Mn = 550 and 750) as oligomer supports. A complex branched mannononaose (Man9) has been synthesized by this method in a very concise way to yield a large quantity of final product. Attempt has been made towards the synthesis of a heptasaccharide phytoalexin elicitor (HPE).Model linear mannotetraose and branched mannopentaose were first tested using the novel HMB low molecular weight poly(ethylene glycol) linker. The use of this linker as the oligomer support retains the normal advantages of polymer-supported solution synthesis of oligosaccharides. Purification of the supported synthons by flash column chromatography on silica gel is greatly simplified. Another advantage of this approach is that the reaction can be monitored readily by the usual arsenal of spectroscopic techniques. Both compounds were obtained in over 10% overall yields.
In order to synthesize properly protected glycosyl donors for the construction of the mannononaose, the regioselective reductive ring opening of benzylidene acetals in carbohydrates with BH3/Bu2BOTf and regioselective acylation of hexopyranosides with pivaloyl chloride have been developed. BH 3/Bu2OTf is an effective reagent to reductively cleave 4,6- O-benzylidene acetals of various hexopyranosides to the corresponding 4-O-benzyl ethers. 4,6-O-isopropylidene acetals can be similarly cleaved. Common protecting groups are stable to the reaction conditions. On the other hand, the regioselectivity in the acylation of hexopyranosides with pivaloyl chloride in pyridine was studied. Manno- and galacto-pyranosides were regioselectively acylated to give the 3- O-pivaloylated compounds in good yields. Both methodologies have been used to provide properly protected mannoside donors and acceptors for polymannan syntheses. The regioselective reductive ring opening of 4,6- O-benzylidene acetals of hexopyranosides has also been demonstrated by concise syntheses of two building blocks of a heptasaccharide phytoalexin elicitor (HPE).
A concise synthesis of the mannan residue of a highly branched mannose type oligosaccharide present on the viral coat of HIV-1 from only two monosaccharide building blocks was achieved. The synthesis requires only five coupling steps instead of the seven or more steps required for the conventional block synthesis. In addition, even though the synthesis of HPE has not been completed to the last step, it showed that adjustment of the length of the poly(ethylene glycol) oligomer support could result in better overall yields. In both cases, 1H-1H COSY and 1H-13C HMQC NMR spectroscopies have proven to be extremely useful in monitoring the progress of oligosaccharide construction. These syntheses demonstrate that oligomer-supported solution synthesis using low molecular weight poly(ethylene glycol) is a powerful tool for the rapid and efficient preparation of complex oligosaccharides.
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Moosavi-Nasab, Marzieh. « Identification of low molecular weight compounds produced or utilized by pychrotrophic meat spoilage organisms ». Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27892.
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Meat Juice Medium (MJM), an aqueous extract of meat, was inoculated with Pseudomonas aeruginosa and incubated for 7 d at 4$ sp circ$C under shaking conditions (100 rev.min$ sp{-1}$). Two predominant compounds produced during spoilage of MJM were detected using HPLC. These compounds with retention times (RT) of 21.48 and 32.04 min were tentatively identified as acetic and butyric acids, respectively. These compounds were also produced when MJM was replaced with Brain Heart Infusion Broth medium. In later experiments, the effect of glucose supplementation on the rate of MJM spoilage was examined. Glucose 0.5% (wt/vol) was added to the MJM, inoculated with P. aeruginosa and incubated at 30$ sp circ$C under shaking conditions (100 rev.min$ sp{-1}$). HPLC of samples after 1d of incubation indicated the presence of 8 predominant compounds including acetic and butyric acids. Their concentrations were, in general, higher in control samples of MJM without added glucose. Using HPLC, TLC, Pyrolysis/GC/MS, FTIR and GC-MS methodologies, the compounds with RT of 8.91, 9.67, 11.96, 13.33, 17.74, 21.48, 26.07 and 32.04 min were tentatively identified as cadaverine, 2-keto gluconic acid, fructose, lactic acid, acetic acid, methanol and butyric acid. In contrast to the results of previous researchers, cadaverine was produced in large amounts while no putrescine was produced by P. aeruginosa. During the spoilage period, the levels of glucose, fructose and total carbohydrate were monitored. Addition of glucose to MJM delayed slime production by 4 days and increase to maximum pH of 8.3 by 7 days. Results suggest that addition of glucose to MJM delays spoilage by P. aeruginosa.
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Kwaambwa, Habauka Majority. « Rheological studies of concentrated sterically stabilized colloidal dispersions with added low molecular weight polymers ». Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259438.
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