The scope and limitations of nucleophilic substitutions of aryl halides have been studied using ethyl 3-mercaptopropionate as nucleophile and microwave heating. A diversity of aromatic compounds have been investigated according to different types of leaving groups, regio isomers and substituents. Experimental design has been used as a tool to optimize the reaction. An electron-withdrawing group in ortho or para position of the leaving group proved to be necessary for a positive outcome of the reaction. Fluorine was, without competition, the best leaving group. Some examples of how the synthesized aryl sulfanyl propionates can be used as starting material for producing aryl thio ethers, sulfoxides and unique benzothiophenes are described.

No description available.

This thesis deals with the synthesis and development of 18F-labelled alkyl etomidate and vorozole analogues, and their use as positron emission tomography (PET) tracers for the imaging of the steroid enzymes 11β-hydroxylase and aromatase. Two synthetic 18F-labelling approaches to the etomidate and vorozole analogues were developed, and the analogues were evaluated in some biological assays. The two-step labelling method was used to synthesise many compounds for biological evaluation. In the first step, a 18F-labelled intermediate based on a ditosylate or a halogenated diethyl ether was synthesised and used directly in the next alkylation step. The decay-corrected (d.c.) radiochemical yield was higher compared to other known two-step labelling methods. Once an appropriate candidate has been chosen for clinical evaluation, a one-step labelling method will be more suitable. We therefore developed a method based on precursors that had leaving groups at the end of their alkyl chains, and used these directly in the 18F-labelling synthesis. The one-step 18F-labelling synthesis required less reaction time and produced higher specific radioactivity and d.c. radiochemical yield than our two-step synthesis. With microwave heating, the reaction time was reduced to seconds and the d.c. radiochemical yield was better than that obtained with conventional heating. The one-step synthesis simplified the technical handling by allowing the tracer syntheses to be automated on the TRACERLab FXFN.

Det är en stor förändring för varje elev att lämna grundskolan och gåvidare till gymnasieskolan. Det ställs stora krav på att eleverna måstevälja rätt redan från början. Detta innebär att elevernas förkunskaper ärmycket viktiga dels för att få en bra start i utbildningen dels för attgenomföra sin gymnasieutbildning med en god måluppfyllelse.I denna undersökning kommer elever som går sitt första år på detnaturvetenskapliga programmet att få svara på frågor om förkunskapernai kemi var tillräckliga från grundskolan och hur starten på gymnasieutbildningenupplevdes.Kursplanen i kemi för grundskolans år 7-9 samt kursplanen för kemi A pågymnasieskolan ska analyseras utifrån hur kunskapsmålen i de olikaskolformerna möts när eleverna byter skolform.Respondenterna i denna undersökning fick svara på andelen lärarleddundervisning, svårighetsgraden i kemi på gymnasiet samt om derasslutbetyg från grundskolan mötte gymnasieskolans krav på kunskap.

Fyllning i kakor (s.k. bakfyllning) kan under bakning och särskilt under lagring ge negativa effekter så som migrering av fyllning och olja ut i kakdegen. Valet av fettsystem i fyllningen och dess smältpunkt är av stor betydelse för att erhålla önskvärd konsistens och textur. Syftet med examensarbetet var att minimera dessa negativa effekter samt att kartlägga faktorer som påverkar detta. Tidigare bakförsök vid AarhusKarlshamn har visat att fyllningens partikelstorlek påverkar migreringen, då migreringen tycks öka med ökande partikelstorlek. Examensarbetet innefattade provbakningar, fysikaliska analyser och sensoriska test. Baktemperatur och avsvalningshastigheten varierades. Kakdegens socker varierades med strö- och florsocker för att ge olika porositet. Fyllningarna baserades på tre olika fettsystem; A, B och B:C. Fettsystem B gav dock fyllningen för lös konsistens och uteslöts senare ur studien. Fyllningarnas normala (N) partikelstorlek var 50 μm och fyllning baserad på A valsades för att reducera partikelstorleken till 10, 20 respektive 40 μm, vilka namngavs A(10), A(20) respektive A(40). Oljemigrering studerades efter 3 dagar och 2,5 veckor genom sensorisk utvärdering och texturanalys. Differential scanning calorimetry och reologi användes för att studera fyllningens fysikaliska egenskaper. Ingen signifikant skillnad i textur kunde påvisas med olika socker i kakdegen eller med de olika använda baktemperaturerna (160 resp. 190 °C). Den sensoriska och visuella utvärderingen visade att för kakor med fyllning A(N) och A(40) gav mest oljemigrering. Detta styrktes med resultat från texturanalysen. Smältpunkten för fyllning baserad på A bestämdes till ~48,4 °C och fyllning baserad på B:C till 60,6 °C. Partikelstorlek visades således ha inverkan på oljemigreringen och en partikelstorlek ≤ 20 μm är nödvändig för att fyllningen ska vara stabil, dvs. ingen migrering av fyllning och olja.

<p>This thesis presents two new concepts for separation of micro particles using dielectrophoresis, demonstrated by calculated examples, as well as a new method for obtaining dielectric data on living cells. The thesis is based on four papers.</p><p>Paper I describes how the trapping efficiency of micro particles may be significantly increased when superpositioned electric fields are employed in a high conductivity medium. Avoiding low conductivity media is important when working with living cells. Calculations were performed to predict trajectories of Escherichia coli bacteria in the system with superpositioned electric fields, and a model was developed which employed two arrays of interdigitated electrodes in a micro channel.</p><p>Paper II proposes a new concept for separation of micro particles, based on repetitive dielectrophoretic trapping and release in a flow system. Calculations show that the resolution increases as a direct function of the number of trap and release steps, and that a difference in size will have a larger influence on the separation than a difference in dielectrophoretic properties. Polystyrene beads in deionized water were used as a model, and calculations were performed to predict the particle behavior and the separation efficiency. It should be possible to separate particles with a size difference of 0.2 % by performing 200 trap-and-release steps. The enhanced separation power of multi step dielectrophoresis could have significant applications, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity.</p><p>Paper III presents a new calculation method for predicting dielectrophoretic motion of micro particles. The method is based on a soft sphere method often used in molecular dynamics. Results from the calculations are in good agreement with theoretical predictions as well as initial experimental results, showing that the method provides good efficiency and accuracy.</p><p>Paper IV describes a new method for measurements of conductivity of living bacteria. To obtain reliable conductivity values, it is important to handle the cells as gently as possible during the measurement process. A standard conductivity meter was used in combination with cross-flow filtration. In this way, repeated centrifugation and resuspension is avoided which otherwise may cause damage to the bacteria. The conductivity of Bacillus subtilis was determined to be 7000 μS/cm by means of the cross-flow filtration method, and the values differ from earlier published values by almost an order of a magnitude.</p><p>In addition to the work presented in the papers, some experimental dielectrophoresis work in chip-based systems was performed. The behavior of Escherichia coli and polystyrene beads at different voltages and frequencies were studied. Separation of beads with different sizes was achieved on an array of interdigitated electrodes. Using electrodes with a pointed shape, alignment in different directions, pearl-chain formation, rotation, and other dielectrophoretic motion of <i>E. coli</i> were observed.</p>

<p>A very important trend for studying biomolecules is computational chemistry. In particular, nowadays it is possible to use theoretical methods to figure out the catalytic mechanism of enzyme reactions. Quantum chemistry has become a powerful tool to achieve a description of biological processes in enzymes active sites and to model reaction mechanisms.</p><p>The present thesis uses Density Functional Theory (DFT) to investigate catalytic mechanism of methyltransferase enzymes. Two enzymes were studied – Glycine N-MethylTransferase (GNMT) and Guanidinoacetate Methyltransferase (GAMT). Different models of the enzyme active sites, consisting of 20 to 100 atoms, are employed. The computed energetics are compared and are used to judge the feasibility of the reaction mechanisms under investigation.</p><p>For the GNMT enzyme, the methyl transfer reaction was found to follow an SN2 reaction mechanism. The calculations demonstrate that the mechanism is thermodynamically reasonable. Based on the calculations it was concluded that hydrogen bonds to the amino group of the glycine substrate lower the reaction barrier, while hydrogen bonds to carboxylate group raise the barrier.</p><p>In the GAMT enzyme the methyl transfer reaction was found to follow a concerted asynchronous mechanism which includes transfer of a methyl group accompanied by a proton transfer taking place simultaneously in the same kinetic step. The calculated barrier agrees well with the experimental rate constant. i</p>

<p>This thesis deals with the influence of molecular adhesion on paper strength. By combining the use of high-resolution techniques and silica/cellulose surfaces, with various fibre–fibre and sheet testing techniques, new information regarding the molecular mechanisms responsible for paper strength has been obtained.</p><p>Large parts of this research were devoted to the polyelectrolyte multilayer (PEM) technique, i.e. a charged surface is consecutively treated with oppositely charged polyelectrolytes. Application of PEMs incorporating polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) onto dried, fully bleached softwood fibres, prior to sheet preparation, increased tensile strength. No linear relationship was detected between the amounts of PAH and PAA adsorbed onto the fibres and the developed tensile strength, which suggests that the adsorbed amount is not the only important factor determining the tensile strength. Closer examination of PEM formation on silica indicated that both exponential PEM film growth and the occurrence of a PEM film in which the polyelectrolytes are highly mobile, favour the strength-enhancing properties of sheets containing PEM-treated fibres. This indicates that a water-rich, soft PEM film allows the polyelectrolytes to diffuse into each other, creating a stronger fibre–fibre joint during consolidation, pressing, and drying of the paper. In addition, when PAH capped the PEM film, the paper strength was higher than when PAA capped the film; this could be related to the structure of the adsorbed layer. Further analysis of the sheets revealed that the increase in tensile strength can also be linked to an increase in the degree of contact within a fibre–fibre joint, the number of efficient joints, and the formation of covalent bonds. The relative bonded area (RBA) in the sheets, as determined using light-scattering measurements, indicated no significant change until a certain tensile strength was obtained. The RBA, as determined using nitrogen adsorption via BET analysis, did show significant changes over the whole investigated tensile strength range. From this it can be concluded that light scattering cannot give any direct information regarding molecular interactions within a sheet. Furthermore, it was shown that PEMs involving cationic and anionic starch display an almost linear relationship with out-of-plane strength properties regarding the amount of starch in the sheets, whereas the tensile strength was more dependent on the physical properties of the starch, as was the case with PAH and PAA.</p><p>Cationic dextran (DEX) and hydrophobically modified cationic dextran (HDEX) were used to test the importance of having compatible surface layers in order to obtain strong adhesive joints. DEX and HDEX phase separated in solution, however, this incompatibility of HDEX:DEX mixtures was not reflected in wet or dry joint strength. For both wet and dry measurements, adhesion between DEX and HDEX coated surfaces was intermediate to the adhesion of DEX:DEX and HDEX:HDEX surfaces.</p><p>In addition, various types of cellulose surfaces, different regarding their crystallinity, were investigated. Depending on the preparation techniques and solution conditions used, i.e. pH and salt concentration, steric, electrostatic, and van der Waals interactions were obtained between the surfaces in aqueous solutions. The adhesion forces between polydimethylsiloxane and cellulose surfaces, measured under ambient conditions, were influenced by the degree of crystallinity. This suggests that amorphous cellulose offers more possibilities for surface groups to arrange themselves to participate in molecular interactions in the joint. Higher relative humidity could increase this adhesion force further, water probably acting as a plasticizer during joint formation.</p>

<p>In this thesis, synthesis of structures related to antifreeze glycoproteins (AFGPs) are presented. Synthetic routes to a protected carbohydrate derivative, 2,3,4,6-tetra-O-benzyl-β-galactopyranosyl-(1→3)-2-deoxy-2-azido-4,6-di-O-benzyl-β-D-thio-1-galactopyranoside, and a tBu-Ala-Thr-Ala-Fmoc tripeptide, are described. These compounds are meant to be used in the assembly of AFGPs and analogues thereof. A Gal-GlcN disaccharide was synthesized via glycosylation between the donor, bromo-2-O-benzoyl-3,4,6-tri-O-benzyl-α-Dgalactopyranoside, and acceptor, ethyl 4,6-O-benzylidene-2-deoxy-2-N-phthalimido-β-D-1-thio-glucopyranoside, using silver triflate activation. Subsequent epimerization to a Gal-GalN disaccharide was achieved using Moffatt oxidation followed by L-selectride® reduction. The tripeptide was synthesized in a short and convenient manner using solid phase peptide synthesis with immobilized Fmoc-Ala on Wang® resins as starting point.</p>

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2009. / Härtill 4 uppsatser.