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The goal of this thesis was to develop a method for efficiently synthesizing a large suite of asymmetric oligoester ion channel-forming compounds. A solid-phase organic synthesis (SPOS) approach on Wang resin was used to generate the ion channel candidates. A follow-on goal is to survey the compounds produced to uncover structure-related controls on ion transport activity. Two classes of building blocks were used to generate the oligoesters – head groups and cores. The core building blocks were three omega-hydroxy acid derivatives six, eight and twelve carbons in length and the alcohol protected as a tetrahydropyranyl ether. The head group building blocks were either a glutaric acid monoester derivative of varying lipophilicity (12 to 16 carbon long alkyl tail) or a beta-hydroxy acid derivative; these building blocks used a tert-butyldimethylsilyl ether for alcohol protection. Optimized conditions for building block coupling, deprotection, and product cleavage were first established by the generation of dimeric and trimeric products. The building blocks were coupled using diisopropylcarbodiimide/ dimethylaminopyridine conditions. The deprotection of the tetrahydropyranyl ether group from the alcohol used a dilute acid solution in methanol and dichloromethane. A fluoride solution (from tetrabutylammonium fluoride) in tetrahydrofuran was used to deprotect the tert-butyldimethylsilyl ether group. Cleavage of the product synthesized on Wang resin was achieved by treatment with a trifluoroacetic acid/dichloromethane or ethereal hydrogen chloride solution. The products were then isolated by gel filtration. Mass spectrometry was used to identify the minor impurities which were quantified by proton nuclear magnetic resonance integrations. With the nine building blocks, many tetrameric and pentameric structures can be made, but a directed-library approach was used to address structure-activity related questions. Three pentameric oligoester products were the largest products synthesized to determine the scope and limitations of the SPOS methodology. The oligoester ion channel candidates were tested for ion transport activity using a 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt fluorescence vesicle assay. For each compound a pseudo-first order rate constant was derived at a particular concentration. A more useful normalized rate constant was calculated for an interpolated transporter concentration which allowed for transport activity comparison between compounds. The results from the fluorescence assay showed that some compounds and some isomers were substantially more active than others. There appeared to be an optimal core length and lipophilicity for relatively high activity. The aggregation of the compounds in buffer solution was probed using a pyrene fluorescence experiment. The solid-phase methodology was extended to include coupling of amino acids. A tryptophan derivative was made from one of the most active SPOS oligoester ion channel-forming compounds. The integrity of the molecules synthesized by SPOS which contain the tryptophan group could then be determined by high performance liquid chromatography. The fluorescence of the indole is quenched by acrylamide. By first equilibrating the vesicles with the tryptophan-containing oligoesters and then adding a fluorescence quencher, the resulting indole fluorescence was monitored as a function of quencher concentration. A Stern-Volmer plot was derived based on the quenching data which reported the possible orientations of the tryptophan-containing oligoester within the vesicle.

Plant oriented movements, or tropisms allow the plant to actively respond to environmental stimuli to get more light, better access to nutrients and to grow roots deeper into the soil. Gravitropism drives the growth of roots along the gravity vector. Perception of gravity is triggered by the sedimentation of statoliths in columella root cap, but the exact signalling pathway behind this process is not known. Perception of gravity results in an unequal redistribution of the phytohormone auxin in the outer cell layers which leads to different rate of growth on the root's upper and lower side and bending of the root. The changes in auxin redistribution are accompanied by changes in apoplastic pH. Knowing an exact pattern of these pH changes could shed light on the mechanisms laying behind the gravitropic response pathway. While microelectrodes can be used to measure pH precisely, they are not suitable for the long-term imaging of growing roots. In the past few years, several pH sensitive dyes and genetically encoded sensors emerged. These can be used for long-term live in vivo imaging of pH changes in growing roots. In this thesis, I analysed the performance of several published pH sensitive genetically encoded sensors and available dyes in the roots of Arabidopsis thaliana. I observed that dyes varied...

The deprotonation characteristics of fluorescent probes -naphthol and 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS) were studied in this diploma thesis, using steady-state and time-resolved fluorescence spectroscopy. Two cationic surfactants, Septonex and cetyltrimethylammonium bromide (CTAB), were studied. These surfactants were measured in the complex with hyaluronan (1.75 MDa, 1 MDa and 300 kDa). Steady-state fluorescence was used for determination of critical aggregation concentration of each surfactant and pKa*. Time-resolved fluorescence decays were used to calculate the average lifetimes and the deprotonation constants of naphthol and HPTS. The measurement with hyaluronan were compared with the polystyrenesulfonate (PSS) – surfactant system. The effect of hydration shell of hyaluronan on hyaluronan – surfactant complex formation results from the comparison of above mentioned systems. Large differences were found in the deprotonation characteristic between surfactants and even between individual molecular weights of hyaluronan. The measurement shows that the hydration shell is located near to the dissociated carboxyl groups of hyaluronan chain, where the interaction with the positively charged surfactants occurs. Furthermore, the aggregation number of Septonex was determined by quenching of pyrene using cetylpyridinium chloride (CPC) as a quencher. The aggregation number for 20 mM Septonex solution was determined as a value of 104 molecules. CPC was used for confirmation of the localization of -naphthol in the micelles of CTAB and polymer – CTAB, respectively.