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1
White, Michael Jon. "Long-chain fatty acid incorporation into, and long-chain alcohol production by, yeasts." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760562.
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Gorce, Jean-Philippe. "Crystallisation and chain conformation of long chain n-alkanes." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/19705/.
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Hydrocarbon chains are a basic component in a number of systems as diverse as biological membranes, phospholipids and polymers. A better understanding of the physical properties of n-alkane chains should provide a better understanding of these more complex systems. With this aim, vibrational spectroscopy has been extensively used. This technique, sensitive to molecular details, is the only one able to both identify and quantify conformational disorder present in paraffinic systems. To achieve this, methyl deformations have been widely used as "internal standards" for the normalisation of peak areas. However, in the case of n-alkanes with short chain length, such as n-C[44]H[90] for example, the infrared spectra recorded at liquid nitrogen temperature and reported here show the sensitivity of these latter peaks to the various crystal structures formed. Indeed, the main frequencies of the symmetric methyl bending mode were found between 1384 cm[-1] and 1368 cm[-1] as a function of the crystal form. Changes in the frequency of the first order of the L.A.M. present in the Raman spectra were also observed. At higher temperatures, non all-trans conformers, inferred from different infrared bands present in the wagging mode region, were found to be essentially placed at the end of the n-alkane chains. At the monoclinic phase transition, the concentration of end-gauche conformers, proportional to the area of the infrared band at 1342 cm[-1], increases abruptly. On the contrary, in the spectra recorded at liquid nitrogen temperature no such band is observed. We also studied the degree of disorder in two purely monodisperse long chain n-alkanes, namely n-C[198]H[398] and n-C[246]H[494]. The chain conformation as well as the tilt angle of the chains from the crystal surfaces were determined by means of low frequency Raman spectroscopy and S.A.X.S. measurements on solution-crystallised samples. The increase in the number of end-gauche conformers which was expected to occur with the increase of the tilt angle as a function of the temperature was not detected due to a perfecting of the crystals. Indeed, due to successive heating and cooling to -173°C, the concentration of non all-trans conformers was found to decrease within the crystals. Their numbers were found to be up to six times higher in n-C[198]H[398] crystallised in once folded form than when crystallised in extended form. The C-C stretching mode region of the spectra was used to identify the chain conformation and to estimate the length of the all-trans stem passing through the crystal layers at -173°C. The transition between once folded and extended form crystals was indicated by the presence of additional bands in this region at 1089 cm[-1], 1078 cm[-1] and 1064 cm[-1]. Some of those bands may be related to the fold itself. At the same time, a strong decrease of the intensity of the infrared bands present in the wagging mode region was observed. Finally, the triple layered structure proposed on the basis of X-ray measurements obtained from the crystals of a binary mixture of long chain n-alkanes, namely n-C[162]H[326] and n-C[246]H[494], was confirmed from the study of the C-C stretching mode region of the infrared spectra.
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Cheng, Zijun. "Synthesis of long chain ammonium sulfobetaines." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39808.pdf.
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Hodgson, Lisa Frances. "Long-chain alcohol production by yeasts." Thesis, University of Bath, 1990. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278949.
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Thomas, Sydney. "Measurement and modelling of long chain branching in chain growth polymerization." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/NQ42769.pdf.
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Yildiz, Ünveren Hesna Hülya. "Hydroformylation of long chain olefins in microemulsion." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972892109.
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Putra, Edy Giri Rachman. "Solution crystallization of long chain n-alkanes." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401188.
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Liu, Gengxin. "Nonlinear Rheology of Long-Chain Branched Polymers." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1436977058.
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Jeffries, Kristen A. "Biosynthesis of Long-chain Fatty Acid Amides." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5850.
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The vast variety of long-chain fatty acid amides identified in biological systems is intriguing. The general structure of a fatty acid amide is R-CO-NH-X, where R is an alkyl group and X is derived from an immense variety of biogenic amines. Although structurally simple, the bioactivities of these molecules as signaling lipids are very diverse and have just recently begun to emerge in the literature. Interest in the long-chain fatty acid amides dramatically increased following the identification and characterization of one specific N-acylethanolamine, N-arachidonoylethanolamine (anandamide), as the endogenous ligand for the cannabinoid receptors in the mammalian brain. Since this discovery, the details of N-acylethanolamine metabolism have been elucidated. However, a lesser extent of progress has been made in the last twenty years to identify and study the non-N-acylethanolamine long-chain fatty acid amides. The focus of this dissertation is the elucidation of the biosynthetic pathways for long-chain fatty acid amides, including N-acylglycines, primary fatty acid amides, N-acylarylalkylamides, and N-acylethanolamines. The details of long-chain fatty acid amide metabolism will lead to the determination of possible therapeutic targets. We identified mammalian glycine N-acyltransferase like 3 as the enzyme that catalyzes the formation of long-chain N-acylglycines in mouse N18TG2 neuoblastoma cells, identified and quantified a panel of long-chain fatty acid amides in Drosophila melanogaster extracts by LC/QTOF-MS, established Drosophila melanogaster as a model system to study long-chain fatty acid amide metabolism, and identified arylalkylamine N-acyltransferase like 2 as the enzyme that catalyzes the formation of long-chain N-acylserotonins and N-acyldopamines in Drosophila melanogaster.
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Liu, Nannan 1973. "Molecular weight distribution of long chain branched polyethylene." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79248.
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To fully understand the properties of Long Chain Branched Metallocene Polyethylene (LCB mPE), we need to understand its molecular structure and Molecular Weight Distribution (MWD). Gel Permeation Chromatography (GPC) is the most important and widely applied technique to measure the MWD. In this analytical technique, polymer molecules are fractionated by their hydrodynamic volume (i.e. the sizes of polymer molecules in dilute solution). This work is focused on the simulation of GPC for the MWD of LCB mPE.The polymerization reaction mechanism of LCB mPE provides a method to simulate the generation of LCB mPE molecules thus allowing the development of a statistical model of the structure and molecular weight distribution of LCB mPE by previous researchers. This statistical model gives a theoretical MWD. In this work after simulating the generation of one million LCB mPE molecules, we calculate the sizes (i.e. radii of gyration) of molecules at both theta and good solvent conditions to obtain the molecular size distributions. Then we simulate the fractionation in GPC and the different GPC detector responses to obtain simulated GPC MWDs. The simulated MWDs are compared to real GPC results provided by the Dow Chemical Company. We analyze the performance of GPC for long chain branched polyethylene and relate the results to the theoretical MWD.
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林立基 and Lap-kay Wilson Lam. "Organometallic reactions involving long chain fatty acid esters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31231196.
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Shang, Yuan. "Teabag technology in long chain alkane selective oxidation." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/66336/.
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This thesis describes the searching, preparation, characterization and catalytic evaluation of active catalysts for the terminal selectivity of long chain linear alkanes. The focus of the thesis is the study of shape selective materials, including the organic material cyclodextrins, and the inorganic material, zeolite and zeolitic membranes. Prepared catalysts were performed with n-decane or n-hexane as models to produce the terminal oxidation products 1-decanol, 1-hexanol, decanoic acid and hexanoic acid. Studies with the Andrews glass reactor showed a stable terminal selectivity of 5%-9% in the autoxidation of n-hexane in short time reactions. A comparison between the Andrews glass reactor and Parr stainless steel reactor showed that the autoxidation reactions can get higher conversion but lower terminal selectivity in the stainless steel reactor than the glass reactor. Most of the metal/support catalysts showed very low conversion and very poor terminal selectivity. Increasing the temperature leads to higher conversion but results in more cracked products and less selectivity for oxygenated C10 products. The most active catalyst was 5 w.t.% Au/TiO2. However, these catalysts did not show good terminal alcohol selectivity (<3%); whereas the cracked acid selectivity was high (32.0%). Cyclodextrin covered Au/SiO2 catalysts showed limited changes in terminal selectivities (1-2%). Zeolite 4A, silicalite-1, ZSM-5, zeolite X/Y coated catalysts were successfully synthesized with alumina and silica sphere supports. The most attractive oxidation results were performed by zeolite X/Y and zeolite 4A coated silica catalysts in n-hexane liquid phase oxidation, iv especially for with short reaction time. With zeolite X/Y membrane, in a 30 min reaction, the terminal selectivity was 16%, while the terminal selectivity for the blank reactions was 0-9%. With longer reaction time, the terminal selectivity decreased to 6-7%. Zeolite 4A membrane can produce a terminal selectivity of 13% in 4 h reactions.
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Lam, Lap-kay Wilson. "Organometallic reactions involving long chain fatty acid esters /." [Hong Kong : University of Hong Kong], 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12362323.
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Maeda, Nobuo, and nobuo@engineering ucsb edu. "Phase Transitions of Long-Chain N-Alkanes at Interfaces." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20011203.151921.
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An experimental study of phase transitions of long-chain n-alkanes induced by the effect of interfaces is described.
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The phase behaviour of long-chain n-alkanes (carbon number 14, 16, 17, 18) adsorbed at isolated mica surfaces and confined between two mica surfaces has been studied in the vicinity of and down to several degrees below the bulk melting points, Tm. Using the Surface Force Apparatus we have measured the thickness of alkane films adsorbed from vapour (0.97 [equal to or greater-than] p/p[subscript o] [equal to or greater-than] 0.997), studied capillary condensation transition, subsequent growth of capillary condensates between two surfaces, and phase transitions in both the adsorbed films and the condensates. By measuring the growth rate of the capillary condensates we have identified a transition in the lateral mobility of molecules in the adsorbed films on isolated mica surfaces. This transition to greater mobility occurs slightly above Tm for n-hexadecane, n-heptadecane and n-octadecane but several degrees below Tm for n-tetradecane, and is accompanied by a change in wetting behaviour and a measurable decrease in adsorbed film thickness for n-heptadecane and n-octadecane. Capillary condensates that form below Tm remain liquid, but may freeze if the degree of confinement is reduced by separation of the mica surfaces. An increase in the area of the liquid-vapour interface relative to that of the liquid-mica interface facilitates freezing in the case of the long-chain alkanes, which show surface freezing at the liquid-vapour interface.
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Although thermodynamic properties of the surface freezing transition have been rather well documented, the kinetics involved in formation of such ordered monolayers has so far received very little attention. We studied the surface tension of n-octadecane as a function of temperature in the vicinity of Tm, using the static Wilhelmy plate and the dynamic maximum bubble pressure methods. The two methods give different results on cooling paths, where nucleation of the surface ordered phase is involved, but agree on heating paths, where both methods measure properties of the equilibrium surface phase. On cooling paths, the surface of bubbles may supercool below the equilibrium surface freezing temperature. The onset of surface freezing is marked by a sharp drop in the surface tension. The transition is accompanied by an increased stability of the films resulting in longer bubble lifetimes at the liquid surface, which suggests that the mechanical properties of the surfaces change from liquid-like to solid-like. Our results suggest occurrence of supercooling of the monolayer itself.
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Kling, Marcel Robert. "Synthesis of very long chain fatty acid methyl esters /." Title page, table of contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phk65.pdf.
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De, Silva D. S. M. "Crystallization and molecular conformation of long chain N alkanes." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246907.
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Davies, John. "The synthesis and characterisation of long-chain fatty acids." Thesis, University of South Wales, 1987. https://pure.southwales.ac.uk/en/studentthesis/the-synthesis-and-characterisation-of-longchain-fatty-acids(e4850400-9e3e-4f53-af6a-873cd09a0ace).html.
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The commercial hydrogenation of oils and fats results in the formation of, among other components, geometrical and positional isomers of monounsaturated fatty acids. The view that there may be hazards associated with such oils have occasionally been expressed. Prior to an investigation of the levels of such acids in human tissue and UK dietary fats, the synthesis of a series of these acids, as standards, and their characterisation, was necessary. For the synthetic programme, the general scheme provided a convenient route for the synthesis of geometrical and positional isomers from common precursors. When condensation of the 1-alkyne and a-chloro-w-iodoalkane was performed via sodamide in liquid ammonia, the scheme was limited but was extended somewhat when performed via methyllithium in dioxan. Generally, yields decreased with the increasing chain length, and migration of the unsaturated bond to the extremities of the resulting molecule. Chromatographic separation, both capillary column GLC and reversephase HPLC, was readily achieved on the basis of chain length and configuration of the double bond. Furthermore, the partial separation of positional isomers was achieved. NMR spectroscopy unambiguously determined the configuration and position of unsaturation in virtually every fatty acid. Assignment is based on the fact that functional groups within an acid alter the chemical shift of neighbouring carbons in a characteristic manner. No one of these techniques alone is applicable to the determination of positional isomerism in a complex lipid mixture and must be used in combination. Whereas NMR is undoubtedly invaluable in the quantification of positional isomers on an individual basis, or in profiling simple mixtures, it is not as applicable to the direct analysis of complex lipid samples. Emphasis on the continuing development of capillary column GLC holds the most promise for the direct quantification of positional isomerism.
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Qian, Cheng. "Effect of Long-Chain Fatty Acids on Anaerobic Digestion." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23778.
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An investigation was carried out to study whether long-chain fatty acids (LCFAs) have an effect on digestion of waste sludge under anaerobic conditions. Four different kinds of LCFAs were used in this study. The 18 carbon series with 0, 1, 2 and 3 double bonds were studied to evaluate the degree of saturation on fatty acid degradation. Due to their molecular structure, unsaturated LCFAs are more soluble than saturated LCFAs. Oleic, linoleic, linolenic acid with an ascending number of double bonds were tested as representatives for three different degrees of saturation. In addition, stearic acid, a saturated fatty acid was also tested. LCFAs were added to sewage sludge at concentrations ranging from 5% to 20% on a weight basis and the pH, solids reduction and COD reduction were determined. The results suggested that in addition to degrading in the digesters, all unsaturated acids contributed additional solids removal, compared to the control group. In contrast, stearic acid did not affect the solids removal. The COD reduction was similar to solids reduction in that additional COD was destroyed when unsaturated LCFAs were added to the sludge. The mechanism for additional solids reduction is not known.Master of Science
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Maeda, Nobuo. "Phase transitions of long-chain n-alkanes at interfaces." View thesis entry in Australian Digital Theses Program, 2001. http://thesis.anu.edu.au/public/adt-ANU20011203.151921/index.html.
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Kheirandish, Saeid. "Constitutive equations for linear and long-chain-branched polymer melts." Berlin : Univ.-Verl. der TU, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=97819974X.
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Kheirandish, Saeid. "Constitutive equations for linerar and long chain branched polymer melts /." Berlin : Univ.-Verl. der TU, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014705968&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Jakobsson, Andreas. "Elovl3 and very long chain fatty acids : role in metabolism /." Stockholm : The Wenner-Gren institute, Stockholm university, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-398.
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周晞 and Hei Chau. "Synthesis and properties of tellurium-containing long chain fatty acidderivatives." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31233478.
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Koen, Matthew Anthony. "Hydrocracking of long chain n-Paraffins under Fischer-Tropsch conditions." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13260.
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Includes bibliographical references.A number of various iron-palladium loaded H-MFI zeolites used for the hydrocracking of n- hexadecane under Fischer-Tropsch conditions were tested to address the inherent low CO tolerance of the pure palladium noble metal hydrocracking catalysts. The hydrocracking mechanism consists of two functions, namely the metal de-/hydrogenation (HD/DHD) and the acidic -scission function. The addition of CO to reactions involving monometallic palladium hydrocracking catalysts has led to an imbalance between these functions due to the migration of the noble metal resulting in significant and undesirable secondary cracking. However, the inclusion of iron to the hydrocracking catalyst may allow for chemical anchoring of the noble metal (Wen et al., 2002) reducing the effect of the migration and thus retaining the bifunctional balance. The consequent palladium-iron alloy (Garten, 1976) also has the potential for an improved rate of de-/hydrogenation (Fukuoka et al., 1990) resulting in a greater rate of intermediary carbenium ions which in turn could lower any undesired secondary cracking reactions already present. The Fe/H-MFI precursor was prepared using a solid-state ion exchange after which incipient wetness impregnation was used to add the palladium. Different loadings of palladium and iron were used to prepare the PdFe/H-MFI catalysts in order to determine an optimum ratio loading. All experiments were conducted at standard low temperature Fischer-Tropsch conditions in a plug-flow fixed trickle-bed reactor equipped with a homogeneously operating evaporator and on-line GC-FID analysis. It was found that none of the bimetallic catalysts produced showed any greater tolerance to carbon monoxide when compared to the monometallic catalyst. The results indicated that the behaviour of the bimetallic catalyst was near identical to that of the monometallic catalyst in the presence of CO. It was thus concluded that the preparation method used, in particular the Fe/H- MFI precursor through solid state ion-exchange, was unsuitable for the production of an alloyed PdFe/H-MFI catalyst. An effect of iron was noted in the low palladium high iron loaded catalyst i.e. PdFe/H-MFI (16,12). In the absence of CO, this catalyst showed a significantly improved selectivity when com- pared to the low palladium low iron catalyst, PdFe/H-MFI (16,24). This effect of iron was attributed to the blockage of the H-MFI pores due to the large amount of iron present. As a consequence of this, access to the internal acid sites is severely limited and therefore are essentially removed from the hydrocracking reaction. As such the PdFe/H-MFI (16,12) has an improved metal:acid site balance. Poisoning by water (a Fisher-Tropsch product) was found to significantly reduce secondary cracking due to deactivation of the acid sites (lowering of total acidity) resulting in improved selectivity through intermediary olefin product promotion. From this, almost pure primary cracking was possible allowing the noble metal catalysts to retain its ideal hydrocracking properties at very high conversions (as evident by the high isomerization selectivity). This indicates that if the total acid strength of the H-MFI zeolite could be reduced (e.g. dealumination), the overall catalyst selectivity could be improved. Testing into whether the effect of water in reducing secondary cracking could be used to offset the effect of an increase in secondary cracking by CO addition, proved ineffective. It is therefore thought that CO not only causes palladium migration and clustering on the external zeolite but also poisons the active metal sites still available. As a result the balance between the metal and acid function could not be restored. It is thus recommended that for future work a zeolite with a lower total acid strength be used in conjunction with a alternate method for iron addition. Furthermore, testing into higher loadings of palladium may prove fruitful in balancing its migratory nature in the presence of carbon monoxide.
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Okihara, Takumi. "Crystallization Behavior of Long Chain Compounds on Polyolefin Thin Films." Kyoto University, 1991. http://hdl.handle.net/2433/74581.
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Subramanian, Vivek. "Effects of long-chain surfactants, short-chain alcohols and hydrolyzable cations on the Hydrophobic and Hydration Forces." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30137.
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The DLVO theory states that the interaction between two lyophobic particles in aqueous media can be predicted by the sum of two surface forces, i.e., the electrical double-layer and van der Waals forces. This theory, which was developed 50 years ago, served as a backbone for colloid chemistry. However, various experiments conducted in recent years showed that it is applicable only to those particles whose advancing water contact angles (qa) are in the range of 15-60o. For example, direct surface force measurements conducted between silica substrates, whose qa values are less than 15o, exhibited the existence of repulsive hydration forces at relatively short separation distances. On the other hand, substrates, for which qa is greater than 60o, exhibit long-range attractive hydrophobic forces not considered in the DLVO theory . These extraneous attractive forces play important roles in many industrial applications. It is, therefore, the objective of the present study to measure the hydrophobic and hydration forces under different conditions. The measurements were conducted using both the Surface Forces Apparatus (SFA) and the Atomic Force Microscope (AFM). Mica and Silica were used as substrates, and the effects of dioctylammonium-hydrochloride (DOAHCl), octanol, methanol, ethanol, trifluoroethanol (TFE), pyridine, CaCl2, MgCl2 and sodium oleate were studied.
A Mark IV SFA was used to conduct force measurements between mica surfaces in aqueous solutions of DOAHCl, which is a secondary amine. At 7x10-6M DOAHCl, the mica surfaces were rendered electrically neutral, and net attractive hydrophobic forces were observed. The measured forces can be represented by a double-exponential function with the larger decay length (D2) of 5.1 nm. The measured hydrophobic forces are substantially stronger than those reported in literature between self-assembled monolayers of soluble single-chain surfactants such as dodeylammonium hydrochloride (DAHCl) and cetyltrimethylammonium bromide (CTAB). Appearance of the strong hydrophobic forces is due to the likelihood that the double-chain cationic surfactant can create a higher hydrocarbon chain packing density than the single-chain cationic surfactants such as DAHCl and CTAB.
Force measurements were also conducted using the AFM between a silica plate and a glass sphere in aqueous solutions of methanol, ethanol, TFE and pyridine to study their effect on the hydration force. It was observed that in Nanopure water, silica surfaces exhibit a strong short-range hydration repulsion, which can be represented by a double-exponential function with its longer decay length (D2) of 2.4 nm. In solutions containing 15% methanol, however, the hydration force disappears completely. This observation can be attributed to the displacement of the water molecules H-bonded to the silanol group by methanol, which in turn destroys the water structure in the vicinity of the silica surface. Methanol can displace water from the silanol group because it is more basic than the water. Ethanol, on the other hand, cannot cause the hydration forces to disappear, suggesting that it is less effective than methanol in displacing the H-bonded water molecules from the silanol groups, possibly due to steric hindrance. In the presence of triflouroethanol (TFE) and pyridine, hydration forces change little, which suggest that they are not effective in disturbing the water structure in the vicinity of silica.
Finally, an AFM was used to measure the hydrophobic forces between silica surfaces coated with oleate. Since this surfactant is anionic, and the silica surface is negatively charged in alkaline solutions, it was necessary to reverse the charge of the silica substrate. In the present work, CaCl2 and MgCl2 were used as activators. It was found that hydrophobic forces are observed at pHs where the CaOH+ or MgOH+ ion concentrations reach maximum, suggesting that the singly charged hydroxo-complexes are the activating species. A model developed in the proposed work suggests that a significant part of the free energy of adsorption comes from the lateral interactions between neighboring hydroxo-complexes on the surface. It is also suggested that oleate adsorbs on silica as basic calcium oleate and basic magnesium oleate. These species may be H-bonded to the silanol groups on surface.
The force measurements were also conducted between hydrophobic (silanated) silica surfaces in CuCl2 solutions. The results show that the hydrophobic force decreases most significantly at the pH where the concentration of the CuOH+ ions reaches maximum, which suggests that the singly charged hydroxo-complexes are more surface-active than their unhydrolyzed counterpart. The driving forces for the adsorption of the CaOH+ ions may include the electrostatic attraction from the surface and the lateral interaction between neighboring hydroxo-complexes on the surface.Ph. D.
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Nelson-Moon, Zararna Louise. "Myosin heavy chain expression in the human masseter muscle and vertical facial form." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252100.
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Dai, Honghao. "Optimization of Financial Decision for Elder Care Services Using Markov Chain Modeling." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491559313631188.
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Beigzadeh, Daryoosh. "Long-chain branching in ethylene polymerization using combined metallocene catalyst systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/NQ52024.pdf.
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Marin, Joseph R. "Production of sophorolipids from long-chain fatty acids by candida bombicola." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79250.
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Tall oil, a mixture of long-chain oleic and linoleic acids, was found to be a suitable lipophilic substrate for the production of sophorolipid, an extracellular glycolipid surfactant, by Candida bombicola ATCC 22214. Oxygen limitation was found to decrease sophorolipid production in this system. Partitioning experiments with sophorolipid revealed that the surfactant increases the affinity of oleic acid for the aqueous phase of a two phase system. C. bombicola therefore has potential applications in the remediation of pulp and paper effluent containing recalcitrant long-chain fatty acids; both for its ability to degrade the acids and for the tendency of sophorolipid to make fatty acids more bioavailable to organisms involved in downstream activated sludge treatment. A novel capillary gas chromatography method was developed to rapidly and quantitatively analyze long-chain fatty acids.
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林正乾 and Ching-kin Lam. "Oxidation reaction of unsaturated long chain fatty esters: a sonochemical approach." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31212384.
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Grasso, Giuseppe. "Solid-state NMR studies of alkali fullerides and long-chain alkanes." Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/10051/.
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The main focus of this thesis is the investigation of structure and motion of different materials by applying different solid-state NMR techniques. In the first section (1) some of the bases of NMR are described both in a Classical (1.1) and Quantum Mechanical (1.2) approach, while the next two sections deal with the experimental part of the work. In section 2 solid-state NMR studies of CsC60 are described and an unambiguous assignment of the 13C NMR spectrum of the polymer phase of CsC60, which is based solely on our experimental data, is presented. In contrast to previous work, the assignment does not rely on the knowledge of the electronic structure of this material and our results support a fully three-dimensional electronic structure as opposed to a quasi one-dimensional one. This is achieved using a two-dimensional 13C MAS NMR correlation experiment, which identifies nuclei coupled via a through-bond scalar interaction, the Refocused INADEQUATE. In section 3 solid-state NMR experiments performed on polyethylene and long-chain n-alkanes corresponding to the formula C246H494 are described. Particular attention is given to some specific issues such as chain folding and a detailed study of the saturation-recovery curves (T1) obtained is carried out for different materials. The model elaborated is able to simulate all the data recorded and the presence of an interphase between the crystalline and the amorphous parts of the samples is proposed. To help the understanding of the structure and the motion of long-chain n-alkanes in section 3 some deuterated samples such as C216H434-d24 and C12H25(CH2)192CHDC11D23+C162H326 ("the mixture") are also studied. Deuterium NMR is widely used and we fit all the experimental line shape of the different samples at different temperatures. Diverse models for the structure and motion of such materials are given, which take into account all the experimental results obtained.
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Walker, Michael. "Influence of long chain fatty acids on the epidermal permeability barrier." Thesis, Cardiff Metropolitan University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288513.
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Knox, T. "Synthesis of long chain esters by a fungal cell-bound enzyme." Thesis, University of the West of Scotland, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370509.
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Buchanan, Paul George. "The synthesis and characterisation of novel long-chain dimethyl siloxane surfactants." Thesis, Sheffield Hallam University, 1994. http://shura.shu.ac.uk/19403/.
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A basic introduction to liquid crystals and surfactants has been given, along with a description of the main techniques employed in the study of liquid crystals (in particular optical polarising microscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy and x-ray diffraction studies). Conventional surfactants comprise a polar head group and a hydrophobic, hydrocarbon chain ie. they are amphiphilic. Because long chains have high melting points the length of the alkyl chain in these compounds is limited to < ca C[18], as long chain surfactants are usually insoluble. Therefore, in this project the alkyl group has been replaced by a long, hydrophobic polydimethylsiloxane chain. Polydimethylsiloxanes are low melting materials (glass transition at ca -120°C) with very flexible chains, hence surfactants based on them might be readily soluble in water. This project involves chemical attachment of amphiphilic mesogens to alpha-SiH terminated siloxanes of varying lengths and the examination of their surfactant properties. The following type of structure was successfully synthesised: CH[3]CH[2]CH[2]CH[2](Si (CH[3]) [2]O)n Si(CH[3])[2] - m where n = integer; m = amphiphilic mesogen. The amphiphilic head groups of these novel surfactants contained the salts of either a mono-, or a dicarboxylic acid. After the synthesis of these surfactants, the liquid crystal and micelle properties of the sodium and calcium salts, were investigated utilising a number of physical techniques eg. optical microscopy and differential scanning calorimetry. Finally, some work on synergism has been described. When different types of surfactants are purposely mixed, what is sought is synergism, the condition when the properties of the mixture are better than those attainable with the individual components by themselves.
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Gragert, Maria Magdalena. "Catalyst design for ethylene polymerisation : a study on long-chain branching." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44956.
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Polyethylene (PE) is the most produced polyolefin worldwide. Since recently discovered long-chain branches (LCB) have been shown to improve the processability, this thesis concentrates on the synthesis of new catalysts capable of producing long-chain branched polyethylene (LCB PE), the investigation of the mechanism which leads to LCB, and the control of the branching degree. The synthesis of new Group IV metal complexes with aromatic carbon-donor ligands which are η1-bound to the metal centre is described. These ligands include biphenyls, diphenylpyridines and terphenyls. Furthermore, an amido complex has been prepared and its synthesis and characterisation is presented herein. All complexes with carbon-based ligands are highly sensitive to air and moisture. Only the use of metal precursors with electron donating ligands enabled the formation of such complexes and it is concluded that electron donating ligands stabilise the electron deficient metal centre and metal-carbon bond. Polymerisation studies showed that the new complexes are active ethylene polymerisation catalysts. Their activity usually increases with temperature. The effect of hydrogen on the polymerisation activity cannot be predicted. Sensitive rheology measurements of the polymer melts revealed the presence of long-chain branches and it has been shown that the Group IV metal complexes with carbon-based ligands described in this thesis are producing LCB PE. Initial experiments towards the investigation of the long-chain branch forming mechanism are described within this thesis. Although not finished, a suitable route to complexes bearing a long alkyl chain has been established, which can be pursued in further studies. A series of tertiary-alkyl amines has been prepared and reacted with a silane to give the targeted aminosilane ligand. The effect of alkyl chain substituents on a cyclopentadienyl ligand in metallocenes has additionally been investigated with respect to the formation of LCB. In order to control the number of LCB in a PE resin, a bicatalytic system involving a bis(imino)pyridineiron catalyst that produces linear PE, an α-diiminenickel catalyst that produces branched PE and a chain transfer agent (CTA) was investigated. The combination of chain shuttling and chain walking as common mechanisms involved in ethylene polymerisation with late transition metal complexes showed to be a promising approach for the control of branching in PE while using ethylene as only monomer feed. Not only can branching be induced by carefully selecting the catalyst ratio and amount of CTA, but it has been shown that chain straightening occurs.
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Hussein, Nahed Mohamed. "Nutritional studies of long chain conversion of dietary polyunsaturated fatty acids." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/844191/.
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Growing evidence suggests that dietary n-3 very long chain polyunsaturated fatty acids (eicosapentaenoic acid; EPA and docosahexaenoic acid; DHA) reduce the risk of coronary heart disease and stroke, alpha-linolenic acid (alpha-LNA) is the natural precursor of EPA and DHA and is an abundant and accessible source of dietary n-3 PUFA that can be further elongated and unsaturated in vivo. The overall aim of the project is to examine the conversion of alpha-LNA to its long chain metabolite, most importantly DHA. This aim was accomplished by a combination of a human dietary intervention study to assess accumulation of EPA and DHA from dietary alpha-LNA, and 13C-tracer studies of alpha-LNA & linoleic acid (LA) conversion to their long-chain metabolites. The dietary intervention trial was a 12-week parallel design in men expressing an atherogenic lipoprotein phenotype, a common source of lipid-mediated coronary heart disease risk. Diets were enriched with 18 g of alpha-LNA as flaxseed oil (n=21), with a high LA oil (n=17), or with fish-oil (6g/d n=19) as a positive control group. Thus the intention was to provide an increased intake of alpha-LNA with a low ratio of n-6 to n-3 PUFA (1:1 or less), minimizing competition between alpha-LNA and the abundant LA and, in theory, increasing the conversion of alpha-LNA to LC n-3 PUFA. The results from the dietary intervention indicate that, dietary alpha-LNA as flaxseed oil can increase n-3 membrane fatty acid contents, through a 3-fold increase in alpha-LNA (p <0.001)) and 2.5 fold increase in EPA (p<0.001) at week-12, decreasing in n-6:n-3 ratio (p =0.001), but not changing DHA level. In contrast the fish oil diet increased both EPA and DHA. Dietary alpha-LNA had 7% of the efficacy of preformed EPA from fish oil to increase membrane EPA levels. Subjects on the 13C tracer study were a sub-group of the intervention study, studied after 12-weeks on the high alpha-LNA (n=6) or high n-6 (n=5) diets. Subjects were given an oral mixture of 400 mg each of uniformly 13C labelled alpha-LNA and LA in a milk shake after an overnight fast. 13C enrichment was measured in fatty acids isolated from plasma at 1,2,3,7,10 and 14 days after the dose. Of the dose appearing in the plasma 35-45% was converted to EPA with no dietary effects. Some conversion to DHA did occur especially in the high n-6 group (3.9% of dose) compared with the flaxseed-oil group (mean value 0.8% of the dose; p < 0.05). In the single subject studied on the fish-oil diet there was a much lower conversion rate compared to the flaxseed-oil diet. The variability between subjects for percent conversion to DHA ranged from zero to 6.2% of the dose appearing in plasma. Taken together these results clearly establish the effectiveness of dietary alpha-LNA as a method of increasing the concentration of EPA, but not DHA, in membrane phospholipids, with up to 7% of the efficacy of preformed EPA. The increase in the EPA: AA ratio (eicosapentanoic: arachidonic acid) in membrane phospholipids with dietary alpha-LNA is likely to reduce the overall inflammatory environment with beneficial effects for long-term health.
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Binneman, Jacqueline. "The hydrocracking of long chain n-paraffins under Fischer-Tropsch conditions." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/14415.
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Includes bibliographical references.Interest in the area of hydrocracking has grown rapidly over the years. In the early 1960's companies such as Chevron and Universal Oil Products (UOP) introduced new hydrocracking processes to manufacture high octane gasoline. The demand for transportation fuels such as diesel and jet fuel has increased significantly which results in the continuous development of hydrocracking techniques and catalysts. The conversion of normal long chain paraffins from the Fischer-Tropsch synthesis to clean distillate fuels is a particular area of interest. The objective of this project is to investigate the hydrocracking of long chain paraffins under F-T conditions. The aim is to achieve in situ, the hydrocracking of low temperature Cobalt-based F-T wax by combining F-T synthesis and hydrocracking in a single reactor. For the purpose of this thesis, it involves subjecting the hydrocracking catalyst to F-T conditions. Synthesis gas (carbon monoxide and hydrogen), the paraffin n-C16 and water were co-currently fed to a fixed-bed reactor containing only the hydrocracking catalyst. Therefore care was taken to match the experimental conditions of the hydrocracking experiments to those that prevail in the Fischer-Tropsch synthesis. Practically this means the hydrocracking of n-hexadecane was studied at the space velocity, the reaction temperature and pressure and under partial pressure of H2, CO and water, at which n-hexadecane is produced in F-T process assuming that n-hexadecane is the only hydrocarbon product and that n-hexadecane is a model compound for the low temperature F-T process. The results of this investigation show that the hydrocracking reaction over a Pd catalyst supported on H-MFI Zeolite under F-T conditions is non-ideal. At low feed (n-C16) conversions, product distributions are strongly dominated by secondary reactions. The ability of the metal site is significantly inhibited by the presence of CO and water. The product distributions show exactly this due to the increase in unsaturated and more branched species. Feed conversion in the presence of water and CO increase with increasing reaction temperature. The absence of methane in the product spectrum is an indication that the hydrogenolysis reaction is an unfavorable pathway for the catalyst used. The data obtained from this investigation suggests that the combination of low temperature Fischer-Tropsch and hydrocracking into a single reaction step is feasible.
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Bach, Liên. "@Role of very long chain fatty acid in arabidopsis thaliana development." Paris 11, 2010. http://www.theses.fr/2010PA112030.
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Chez les plantes, les acides gras à très longues chaînes (AGTLCs) sont les composants des triacyglycerols, des cires épicuticulaires, de la suberine ainsi que des lipides membranaires comme les phospholipides et spingolipides. Leur synthèse s’effectue au niveau du Reticulum Endoplasmique (RE) par le complexe élongase. PASTICCIN02 (PAS2) est l’homologue de la 3-hydroxy-acyl-CoA-dehydratase Phs1p chez la levure Saccharomyces cerevisae. Nous avons montré que PAS2 est un gène essentiel. A l’inverse, l’expression du gène Phs1 est capable de complémenter les défauts de développement du mutant pas2-1. De plus, la protéine PAS2 interagit directement au niveau du RE avec la dernière enzyme du complexe, CER10. Nous avons montré qu’une altération de l’activité de PAS2 entraîne une réduction générale des teneurs en AGTLCs dans toutes les classes lipidiques. La réduction ou l’augmentation des teneurs en AGTLLCs obervés respectivement chez un mutant pas2-1 ou chez des plantes surexprimant le gène Phs1, sont associées avec de fortes altérations développementales. En particulier, une mutation pas2-1 entraîne une réduction de la croissance racinaire associée paradoxalement avec une augmentation du nombre de cellules en division. Nos résultats ont montré que cette augmentation est due à des retards et/ou défauts de mise en place de la plaque cellulaire au cours de la cytokinèse. De plus, une mutation pas-2-1 conduit à des altérations de la dynamique membranaire au niveau de la voie sécrétoire et de l’endocytose. L’ensemble de ces résultats a permis de démontrer que la protéine PAS2 est la 3-acyl-CoA déshydratase du complexe élongase chez Arabidopsis et que les AGTLCs sont des composants essentiels du développement de la planteIn plants, very long chain fatty acids (VLCFAs) are building blocks of triacylglycerols, epicuticular waxes, suberin and membrane lipids such as phospholipids and sphingolipids. They are synthesized by the ER membrane bound elongase complex, which requires four enzymatic steps. PASTICCINO2 (PAS2) is the putative homolog of the yeast 3-hydroxy-acyl-CoA dehydratase (Phs1), the third enzyme of the elongase complex. We showed that Arabidopsis PAS2 is an essential gene and that it was able to complement phs1 lethality. Conversely, the expression of Phs1 was able to complement the developmental defects of the pas2-1 mutant. Moreover, PAS2 protein was found to interact directly in the Endoplasmic Reticulum with CER10, the last enzyme of the elongase complex. We showed that PAS2 impairement led to a strong reduction of VLCFAs in different lipid classes. Reduced or enhanced VLCFAs levels in respectively pas 2-1 mutant Phs1 overexpressing plants were associated with developmental defects. In particular, pas 2-1 mutation led to reduced root growth and paradoxically to a higher incidence of cell divisions. We demonstrated that higher incidence of cell divisions resulted from delayed or defective cell plate formation during cytokinesis. Moreover, our results indicated that VLCFA-dependent membrane dynamics during endocytosis and secretion, was required for the establishment of the cell plate. Collectively our data identified PAS2 as the unique 3-hydroxy-acyl-CoA dehydratase in Arabidopsis and highlighted the essential role of VLCFAs in plant development
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Bakare, Oladapo. "Synthesis and properties of sulphur-containing long chain fatty acid derivatives." Thesis, [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13544561.
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Lam, Ching-kin. "Oxidation reaction of unsaturated long chain fatty esters : a sonochemical approach /." [Hong Kong] : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B14777460.
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Chau, Hei. "Synthesis and properties of tellurium-containing long chain fatty acid derivatives /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13554566.
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Haarmann, Niklas [Verfasser]. "Thermodynamic Modeling of Long-Chain Molecules and Related Mixtures / Niklas Haarmann." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219476307/34.
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Yang, Xiaoyan. "Long-Range Side Chain-Main Chain Hydrogen Bonds: A Molecular Signature of the TIM Barrel Architecture: A Dissertation." eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/430.
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The hydrophobic effect and hydrogen bonding interactions have long been considered to be the dominant forces in protein folding. However, the contribution of hydrogen bonds to stabilizing proteins has been difficult to clarify. As the intramolecular hydrogen bonds are formed in place of hydrogen bonds with solvent during folding, measures of stability fail to give a significant change in free energy. Previous studies on hydrogen bonding interactions have shown that they are only marginally important.
Three long-range side chain-main chain hydrogen bonds have been found in the alpha subunit of tryptophan synthase (αTS), a (βα)8TIM barrel protein. These long-range noncovalent interactions connect either the N-terminus of one β-strand with the C-terminus of the succeeding and anti-parallel α-helix (F19-D46 and I97-D124) or the N-terminus of an α-helix with the C-terminus of the succeeding β-strand (A103-D130). By analogy, these interactions are designated as βα- or αβ-hairpin clamps. Surprisingly, the removal of any one of these clamp interactions, by replacement of the aspartic acid with alanine, results in significantly decreased thermodynamic stability for the native state and a substantial loss of secondary structure. When compared to several other side chain-side chain and short-range side chain-main chain interactions in αTS, these hairpin clamps clearly play a unique role in the structure and stability of αTS.
The generality of these observations for βα-hairpin clamps in TIM barrel proteins was tested by experimental analysis of the clamps in a pair of homologous indole-3-glycerol phosphate synthase (IGPS) TIM barrels of low sequence identity. The results suggest that only the subset of conserved βα-hairpin clamps with hydrogen bond length less than 2.80 Å make substantive contributions to stability and/or structure. Those clamps with longer hydrogen bonds make modest contributions to stability and structure, similar to other types of side chain-main chain or side chain-side chain hydrogen bonds. The role of these clamps in defining the structures of the super-family of TIM barrel proteins was examined by a survey of 71 TIM barrel proteins from the structural database. Conserved features of βα-hairpin clamps are consistent with a 4-fold symmetry, with a predominance of main chain amide hydrogen bond donors near the N-terminus of the odd-number β-strands and side chain hydrogen bond acceptors in the loops between the subsequent α-helices and even-numbered β-strands. In this configuration, the clamps provide an N-terminal cap to odd-number β- strands in the β-barrel.
Taken together, these findings suggest that βα-hairpin clamps are a vestigial signature of the fundamental βαβ building block for the (βα)8 motif and an integral part of the basic TIM barrel architecture. The relative paucity of βα-hairpin clamps remaining in TIM barrel structures and their variable contributions to stability imply that other determinants for structure and stability of the barrel have evolved to render a subset of the clamp interactions redundant. Distinct sequence preferences for the partners in the βα-hairpin clamps and the neighboring segments may be useful in enhancing algorithms for structure prediction and for engineering stability in TIM barrel proteins.
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Teo, William W. J. "A natural language processing approach to improve demand forecasting in long supply chains." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127104.
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Thesis: M. Eng. in Supply Chain Management, Massachusetts Institute of Technology, Supply Chain Management Program, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 74-80).
Information sharing is one of the established approaches to improve demand forecasting and reduce the bullwhip effect, but it is infeasible to do so effectively in a long supply chain. Using the polystyrene industry as a case study, this thesis explores the usage of modern natural language processing (NLP) techniques in a deep learning model, known as NEMO, to forecast the demand of a commodity -- without requiring downstream companies to share information. In addition, this thesis compares the effectiveness of such an approach with other non-deep learning approaches, specifically an ARIMA model and a gradient boosting model, XGBoost, to demand forecasting. All three models returned large forecast errors. However, NEMO tracked the volatility of actual data better than the ARIMA model. NEMO also had better success in predicting demand than the XGBoost model, returning approximately 20% better Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) scores. This result suggests that NEMO can be improved with better data, but other issues, such as legality of text mining, need to be considered and addressed before NEMO can be used in day-to-day operations. In its current form, NEMO can be used alongside other forecasting models and provide invaluable information about upcoming demand volatility.
by William W.J. Teo.
M. Eng. in Supply Chain Management
M.Eng.inSupplyChainManagement Massachusetts Institute of Technology, Supply Chain Management Program
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Kolodka, Edward B. "Synthesis, characterization, thermomechanical and rheological properties of long chain branched metallocene polyolefins /." *McMaster only, 2003.
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Panagopulos, Michael. "The role of long-chain sphingoid base kinases in plant cell signalling." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520228.
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Chippington-Derrick, T. C. "Models, methods and algorithms for constraint dynamics simulations of long chain molecules." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234776.
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Raihan, Sheikh Zahir. "Desensitisation of the human long chain fatty acid receptors FFA1 and FFA4." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8144/.
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G protein-coupled receptors (GPCRs) constitute the largest, most ubiquitous and most versatile family of membrane proteins encoded by the human genome. Due to diverse ligands and multiple physiological activities, this set of receptors has frequently been explored as potential drug targets. Deorphanisation of GPCRs successfully identified FFA1 and FFA4 (previously named GPR40 and GPR120) as long chain free fatty acid receptors. With diverse expression patterns and close association to pathophysiology of metabolic diseases, both receptors are being studied to understand both receptor pharmacology and their potential for drug development. Due to the overlap in the activation of FFA1 and FFA4 by endogenous fatty acid ligands, selective synthetic ligands have been developed for these receptors. Using a number of biochemical and biophysical assays, I have characterised TUG-770, TUG-905 and GW-1100 as FFA1 ligands and TUG-891, TUG-1197 and TUG-1275 as FFA4 ligands. TUG-905 was found to be most potent and selective FFA1 agonist and GW-1100 showed insurmountable antagonism at FFA1. At FFA4, TUG-1197 was found to be a highly potent and selective agonist. TUG-1275 showed insurmountable antagonism at FFA4 in β-arrestin2 recruitment, receptor internalisation and inositol monophosphate accumulation studies and showed complete selectivity for hFFA4. Agonist exposure rapidly phosphorylated FFA4 in an agonist-concentration-dependent fashion which was totally blocked by TUG-1275. The protein kinase C activator PMA was also noted to phosphorylate FFAA in a concentration-dependent manner. Thus both homologous and heterologous phosphorylation is involved in FFA4 regulation. The FFA4-agonist TUG-891 produced robust internalisation of FFA4 as detected by each of confocal microscopy, and both cell surface ELISA and biotinylation. PMA was able to internalise FFA4 although it was unable to recruit β-arrestin2 to FFA4 suggesting that this internalisation might not be β-arrestin2-dependent. Constitutive internalisation was seen for FFA1, where the selective FFA1 antagonist GW-1100 had no effect. Repeated agonist-exposure desensitised both FFA1 and FF4 as revealed in single-cell calcium imaging studies. Although there was a small reduction of FFA4-internalisation and a slight elevation of total calcium levels from a single-chronic exposure of agonist, elimination of β-arrestin1/2 from HEK293 cells by genome editing did not significantly change the desensitisation of FFA4 to repeated exposure of agonist and did not prevent agonist-promoted internalisation. These studies indicate that β-arrestins are not the sole factors in desensitisation of human FFA4. Gαq/11 elimination by genome editing completely blocked intracellular calcium mobilisation and accumulation of inositol monophosphates mediated by both FFA1 and FFA4 indicating that Gαq/11 coupling to agonist-activated receptors is essential for this functional signalling outcome via both receptors. FFA4 expressed in Gαq/11-null cells was found to be phosphorylated by agonist, indicating that phosphorylation-mediated desensitisation of this receptor is not dependent on Gαq/11 proteins. FRET and BRET experiments revealed for the first time homo and hetero-oligomerisation of both FFA1 and FFA4. Although ligand regulation of oligomerisation was not investigated these preliminary observations of oligomerisation may help in the future to answer many questions of regulation and desensitisation of these receptors. The selective FFA1 and FFA4 ligands characterised here in this project might be used as tool compounds to further explore the physiology and pharmacology of these therapeutically important receptors.
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Prabhavathi, Kalluri. "Ultrasound-assisted synthesis of some N-heterocyclic long-chain fatty ester derivatives." Thesis, Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17592185.
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