Doutoramento em Ciências Farmacêuticas / PhD in Pharmaceutical Sciences

Doutoramento em Ciências Farmacêuticas / PhD in Pharmaceutical Sciences

Doutoramento em Ciências Farmacêuticas / PhD in Pharmaceutical Sciences

Doutoramento em Ciências Farmacêuticas / PhD in Pharmaceutical Sciences

Doutoramento em Química Analítica / PhD Degree - Analytical Chemistry

The gas-phase proton affinities of several highly basic amino acids and diamines were determined using the extended kinetic method in an ESI-quadrupole ion trap instrument. The non-protein amino acid L-canavanine is structurally related to L-arginine with an oxygen substituted for the terminal methylene group of L-arginine and is highly toxic to humans. The proton affinity of L-arginine, a protein amino acid, was determined to be 1036 kJ mol -1, whereas the proton affinity of L-canavanine was determined to be 1005 kJ mol-1. Thus, substitution of an oxyguanidino group for the guanidine group in L-arginine results in a large decrease in basicity. This decrease in basicity mirrors the solution behavior of these two amino acids in which the oxygen atom substitution causes a 5 pKa unit drop in basicity of L-canavanine relative to L-arginine. In addition, the proton affinities of the NPAAs L-canaline and L-citrulline were determined to be 952 kJ mol-1 and 990 kJ mol-1, respectively. The proton affinity values presented here for the NPAAs L-canavanine, L-canaline, and L-citrulline represent the first measurements for these compounds. Experiments were complemented by high-level hybrid density functional theory calculations. Theory values obtained for proton affinities were consistent with the theoretical findings except for L-arginine, which was higher than the experimentally determined value. This may be due to the small number of reference bases in the high basicity range used to determine the experimental value.;The proton affinities of the highly basic diamines cis-1,5-diaminocyclooctane, tetramethylcadaverine, and hexamethylcadaverine were determined to be 1002 kJ mol-1, 1013 kJ mol-1, and 1031 kJ mol-1, respectively. These values are consistent with the theory that diamines display increased basicity due to the stabilization that intramolecular hydrogen bonding provides.

The aim with this project was to evaluate Waters AccQTag method which was ananalytical method that Waters Corporation provides for determination of aminoacids. The amino acid analysis was carried out by reversed-phase AQUITY UPLCH-Class, using a BEH C18-column and a PDA detector.Both primary and secondary amino acids were analyzed after precolumnderivatization with the AccQTag reagent kit by a manual procedure and, detected at260 nm. Fresenius Kabis existing products, Aminoven 10 % and Vamin 18EF wereused as samples. The evaluation was based on external calibration curves withprepared standard solutions from Fresenius Kabi, with the addition of the internalstandard L-Norvaline. Waters amino acid standard was used for the system suitabilitytest. A validation according to the ICH guidelines were performed with the followingparameters: specificity, linearity, precision, LOQ, LOD and robustness.Complementary parameters for system suitability test (SST) and stability of standardand reagent were also evaluated. The validation showed that the % RSD values forspecificity, system suitability test and robustness were within the acceptance criteriaof equal or less than 3 % for amino acids. Although the precision were between1.3-7.5 % which was higher than the acceptance criteria of equal or less than 3 %, thiswas likely due to sensitive sample preparation. The linearity was bad which made itimpossible to quantify the method since the calibration curves were below 0.999. Itwas concluded that the system was robust and can be used to analyze amino acids inAminoven 10 % and Vamin 18EF but the preparation step should if possible beautomatized to achieve better precision in the analytical work. Two amino acids,cysteine and histidine, needs to be studied further; cysteine gave three peaks insteadof one and histidine gave a peak split at higher injection volume than 0.5 uL.

<p>We have found that calixarenes are good receptors of choline (trimethylammonium group) and they have strong affinity to form host-guest complexes with a variety of molecules carrying this moiety. Furthermore, the ability of lower rim carboxylic acid calix[n]arenes and upper rim phosphonic acid functionalized calix[4]arene to transport choline-conjugated drugs through a liquid membrane was discovered. The results demonstrate that these systems are highly efficient toward transporting choline-conjugated targets, as well as neurotransmitters that possess ionizable amine termini. The breadth of compounds that are transported is significant, facing limitations only when the payloads become extremely lipophilic. These developments reveal new approaches towards attempting synthetic receptor mediated selective small molecule transport in vesicular and cellular systems.

Two-dimensional correlation spectroscopy in solid-state NMR is an immensely important tool for the analysis of materials, such as technologically interesting nano-materials or bio-materials. After detailing one method that returns high-resolution one-dimensional solid-state proton NMR spectra, high-resolution proton-proton two-dimensional correlation experiments are described and demonstrated. Subsequently, a new two-dimensional NMR experiment is described which is suitable for obtaining a high-resolution proton dimension in heteronuclear dipolar correlation spectra of solids. This new experiment has been used to characterise the interface between the organic and inorganic components of "coreshell" colloidal nanocomposite particles. In addition, a new two-dimensional NMR experiment is described which is suitable for obtaining homonuclear scalar correlation spectra in solids. This new experiment has several advantages, including increased cross peak intensities coupled with good suppression of the diagonal. Its utility is demonstrated via carbon-13 spectra of natural abundance samples as well as the polymer phase of caesium fulleride.

An advanced Electron Energy Loss Spectrometer has been used to study the formation of 3,3,3-trifluoropropylidyne on Pt (111). This has been compared to the results from the same system using the complementary vibrational spectroscopic technique of Reflection Absorption Infrared Spectroscopy (RAIRS). This study demonstrates the improved resolution of the new spectrometer. The thermal decomposition products, CF3 and CF2 have been detected in the Electron Energy Loss (EEL) spectra. The RAIR spectra of carbon monoxide on Cu (111) have been recorded using synchrotron radiation. An optical accessory has been used to record the RAIR spectra at an incident angle of 20°. The results have been compared to an incident angle of 87°. At 20° no conventional absorption band at 339 cm-l was observed and an anti absorption band at 274 em-l of similar magnitude to that at 87° was seen. This has confirmed the involvement of the parallel electric field in the observation of antiabsorption bands. The EEL spectra of hydrogen and deuterium adsorbed on Pt (111) at 160 K have been recorded. The data has been interpreted using the Nearest Neighbour Central Force Constant (NNCFC) model in terms of 3- fold and 2-fold bridging sites. It is the 2-fold site which offers the more complete assignment of the vibrational bands observed.