The e.s.r. technique has been applied to the study of primary processes occurring during photo-induced electron transfer reactions between metal ions and organic substrates. Photolysis of deoxygenated solutions of ceric perchlorate and ceric ammonium nitrate in alcoholic, aqueous alcoholic and water/alcohol/aceto-nitrile solutions at 770K by light of wavelength > 300 nm leads to formation of radicals derived from the alcohol. Primary alcohols, R CH2OH, yield R CHOH but secondary alcohols, R2CHOH, yield R' in addition to, and sometimes to the exclusion of, R2COH. Tertiary alcohols always give an alkyl fragment, e.g. C2H5', from 1,1-dimethylpropan-1-ol. Allylic alcohols produce the corresponding hydroxyallyl radical and 1,2-diphenylethanol gives a spectrum of benzyl radical, indicating C-C cleavage. The mode of photo-oxidation by CeIV clearly parallels that of the corresponding thermal reaction.

Single crystals of ND 4 DS0 4 and Sr(DCOO)2.2D 2 0 have been studied by deuteron magnetic resonance spectroscopy; the apparatus and techniques used are described in some detail. ND 4 DS0 4 has considerable interest because of its ferroelectric properties: spectra were recorded at 300 K and 230 K, within the paraelectric and ferroelectric phases respectively. Symmetry relationships were used in solving the structure, particularly for refining the orientation data. At room temperature, the two sets of bisu1phate deuterons were found to have (within xperimental error) the same quadrupole coupling constants and asymmetry parameters: h = 191.9 ± 3KHz, T1 = 0.094 ± 0.02 ~ h = 193.2 ± 3KHz, T1 = 0.070 ± 0.0l. The quadrupolar constants appear somewhat larger than expected from the known 0····0 distances. No evidence of disorder is apparent from the room temperature data. At 230 K, both groups of deuterons appear to have suffered small angular displacements, essentially planar and antisymmetric with relation to the room temperature positions. One type of deuteron undergoes movements of larger amplitude in a plane more favourably oriented with respect to the polar axis, [Cl], which suggests a definite contribution from these deuterons to the appearance of ferroelectricity. The Curie point has been determined independently by use of the radio frequency spectrometer; a value of 266 ± 2K was obtained, in reasonable agreement with the literature value from dielectric constant measurements. The ND4+ group is reorienting rapidly both at 230 K and 300 K. Little change seems to occur upon transition. Some distortion of the tetrahedral structure, a possible difference in the reorientation rate for the two kinds of ND4+ ions, and a slight difference in their respective environments could be the main causes for the fine structure observed in the ammonium resonance. The study of Sr(DCOO)2.2D 2 0 gave the following average values for the quadrupolar constants and asymmetry parameters at 300 K: 2 formate ion [DC(1)0(1)0(2)]- ~ = 167.6 + 3KHz 'T] = 0.043 ± 0.01, DB h = 170.3 ± 3KHz 'T] = 0.025 ± 0.01. formate ion [DC(2)0(3)0(4)]- DB= h 242.8 + 3KHz 'T] = O. 100 ± 0.005 2 ~ = 216.8 + 3KHz 'T] = O. 113 ± 0.005 Both formate ions give e.f.g. tensors very close to axial symmetry. For [DC(1)0(1)0(2)]-, the deuteron is approximately aligned with the C(1) 0(10(2) bisectrix in an essentially planar arrangement. For [DC(2)0(3)0(4)]- the deuteron shows a surprising deviation of 22̊ from the plane of the COO group, as determined from Osaki's X-ray data. A weak C-D---O bonding interaction is tentatively suggested to account for this anomaly. D 2 0(1) was easily localised in the surrounding structure as known from X-ray data; the electric field gradient constants indicate that this molecule is 'static' at room temperature. A-D-0-D angle of 107.8̊ is in good agreement with the value for H2O D 2 D0(2) gave rise to broad and rather weak resonances with marked fine structure: some poorly defined curves were analysed only approximately. The high quadrupolar constants (330 ± 30 KHz) and asymmetry parameters (0.2 ± 0.1) derived for one set of the curves suggest that this D 2 0 molecule is weakly hydrogen bonded (if at all), and may have a rather high degree of motional freedom. analysed only approximately. The high quadrupolar constants (330 ± 30 KHz) and asymmetry parameters (0.2 ± 0.1) derived for one set of the curves suggest that this D 2 0 molecule is weakly hydrogen bonded (if at all), and may have a rather high degree of motional freedom.

Ala. AT was purified from pig heart by a new procedure , which consisted of an homogenisation, ammonium sulphate fractionation, heat treatment and a second AS fractionation, followed by DEAE cellulose and Sephadex G200 chromatography Thee purified enzyme had a specific activity of 450 units/mg protein, and appeared to be at least 95 % pure, from electrophoresis. Sodium dodecyl sulphate - polyacrylamidee gel electrophoresis indicated a submit molecular weight of 52000. The concentration of' the coenzyme was measured: it was 1 mole/54 00 gm protein. The kinetic parameters for four different assays and the inhibitor constants for several inhibitors were determined, at 25°C, at several pHs. These parameters were found to vary considerably with buffer concentration. For this reason, the values of these parameterswere extrapolated to zero buffer concentration. From a study of the affinities of several different assays and the inhibitor from ala AT, at pH 8.0, it seems that the ˂(carboxyl end side group of the substrate, (as well as the <.amiro and ˂ (keto groups), are involved in binding to the enzyme. A Dixon analysis of the results shows the existence of certain catalytically important pKs in the free forms of the enzyme, the enzyme-substrate complexes, and the enzyme-inhibitor complexes. The nature and role of the enzyme groups that are involved in.substrate binding are deduced, in part. Visible absorption spectra were recorded at 25°C. PL-ala AT shows a spectral pK at pH 7.6. This pK is raised to about pH 8 by fumarate or acetate binding. The dissociation constants obtained are similar to the inhibition constants. TSC binding produces an intense absorbance peak at 390 nm: a similar result has been obtained with asp AT. Substrates were titrated with ala AT and spectra of the enzyme-substrate complexes were calculated. An absorbance peak at 490 nm is observed. It is very probably a deprotonated, (highly conjugated), complex: i.e. there are separate deprotonation and protonation steps. A rough estimate is made for the relative concentrations of the different spectral forms of the enzyme-substrate complex, at pH 7.0. The pH dependence of the L alanine-pyruvate equilibrium enzyme-substrate complex spectrum was studied. The changes between pH 5.5 and. 10.5 can be ascribed to three pKs, and were used to explain the pKs of the complex, that were shown by kinetic analysis. The inactivation of the enzyme was studies using heat, (65°C), 5.6 M urea, formaldehyde, nitrite, TNM, and. photo-oxidation by rose Bengal and methylene blue. Both methylene blue photo-oxidation and TNM inactivation of ala AT give results similar to those obtained by 1Martinez-Carrion, for asp AT. With methylene blue, an essential residue is modified, which has a low pK end is believed to be a catalytic base; it is probably a histidine. With rose Bengal phot-oxidation, nitrite and TNM, inactivation is incomplete and the nature end role of the modified residue is v most uncertain. The results with formaldehyde inactivation suggest that it inactivates by a reaction at the active site: the possibility that this reagent cross-links a histidine end a lysine group is discussed. The inactivation results, all together, indicate that two different conformational changes can occur, when substrate is bound to ala AT. The nature of these changes and their relation to the kinetic results are discussed. A detailed model of the catalytic activity of ala AT is presented.

Various physical techniques have been applied to the study of the primary processes involved in the photoreaction of uranyl ions with a variety of organic molecules. Electron spin resonance spectroscopy has been used to identify the primary radical products in many solid matrices at temperatures of down to 77 K and in the liquid state at 200 - 300 K in a slow flow system. In general, primary alcohols, R CH20H, yield R CHOH in the solid state whilst secondary and tertiary alcohols at 77 K undergo C - C cleavage to give alkyl radicals. Upon softening the matrices by warming, the radicals derived from tertiary alcohols attack parent molecules. Carboxylic acids undergo both abstraction of an α-hydrogen atom and C - C fission, the former process predominating with simple mono carboxylic acids and their esters and some dicarboxylic acids. The H-abstraction mechanism is also important with aldehydes, ketones and amides, the latter preferring to lose a hydrogen atom from N-alkyl substituents where applicable. Phosphorus-centred radicals exhibiting considerable g- and a- tensor anisotropy have been produced in the solid state. The radicals derived from primary alcohols and carboxylic acids in the flow apparatus are essentially the same as those observed at 77 K. n-Butyl lactate is shown to yield two conformational isomers of the radical CH3C(OH)C02C4H9 and mixtures of radicals were obtained from the ethers 1, 2-dimethoxyethane and 2-methoxyethanol. The mechanism of photochemical reaction of U(VI) with organic molecules is discussed. The final section of this work concerns the identification of the (excited state) absorption spectrum of the photoreactive state of the uranyl ion by (spectrographic) microsecond and (kinetic spectroscopic) nanosecond flash photolysis. By monitoring the decay of this absorption at ~590 nm, absolute values for second -order rate constants for the photoreaction with alcohol molecules have been determined and these are compared with the results of luminescence intensity and lifetime quenching by these molecules (the latter by the single-photon counting technique). The appreciable deuterium kinetic isotope effects on the rate constants are discussed in terms of the nature of the primary photochemical step.

As antibiotic resistance is increasing more rapidly than new antibiotics are produced and/or discovered, there is an increasing need to identify new ways to design novel antibiotics. A potential avenue for this, is the exploitation of Nonribosomal Peptide Synthetases (NRPSs) from bacteria and fungi which biosynthesise structurally complex biologically active peptide products, including numerous potential antibiotics and other molecules with pharmacologically attractive properties. In order to do so, however, a detailed molecular understanding of NRPSs is required. NRPSs are modular proteins, with each module comprising domains that each perform specific functions to select, activate, alter (optional) and combine amino/hydroxyl acid substrates to form a specific peptide product. The Adenylation domain (A domain) specifically selects and activates the substrate through a two step reaction. In the first half reaction, a highly reactive aminoacyl adenylate is formed by reaction with Mg-adenosine triphosphate (ATP) resulting in the release of pyrophosphate. In the second half reaction the A domain binds the phosphopantetheinyl (PPant) arm of the downstream domain, the Peptidyl Carrier Protein (PCP) domain. The terminal thiol of the PPant arm attacks the activated aminoacyl group displacing adenosine monophosphate (AMP), leaving the amino acid substrate tethered to the PCP domain as a thioester. The A domain is of particular interest as a target for engineering approaches as it is considered to be the primary determinant of substrate specificity. Little is understood, however, about the molecular basis of substrate selectivity or how the dynamics of the domain enable the two part reactions to take place. In 1997, the first A domain structure was determined; the L-phenylalanine (L-Phe) activating A domain (PheA) of the Gramicidin S synthetase from Bacillus brevis. All of the A domain structures determined to date are either unligated (apo form) or co-crystallised with reactants or products from the first half reaction. The NRPS A domains are members of the adenylate-forming superfamily which have been structurally characterised in three states, apo, with the first half reaction and second half reaction ligands. Comparison between these structures, suggested these enzymes use a domain alternation strategy to reconfigure a single active site to perform two different reactions. While the A domains have only been determined in the adenylate-forming conformation, similarities between members of the adenylate-forming superfamily suggest NRPS A domains may exploit of a similar strategy of domain alternation to reconfigure the enzyme’s single active site. To date, no molecular simulation study of any NRPS A domain has been reported in the literature. In this study, molecular dynamics (MD) simulations of the PheA have been carried out in the apo form, with the cognate substrate, and with noncognate substrates, to understand the molecular basis of substrate specificity and the effect of the substrate on the dynamics of the protein. Inter-domain rotation was observed in the apo and cognate holo simulations and with one of the noncognate substrates, L-Thr. This motion occurred between the Acore domain and Asub domain or part of the Asub domain. The rotation observed in the simulations with the cognate substrate creates a widening between the two domains of PheA on the side of the enzyme where the PPant arm is thought to bind. Results from one of the cognate holo simulations suggests the A3 motif loop may be important in stabilising the A domain to increase the domain rotation or maintaining the opening through with PPant is proposed to access the active site. Results from one of the noncognate substrate simulations, L-Asp substrate, suggests a role for the A3 motif loop in the removal of noncognate ligands from the binding site. Results from the simulation with noncognate substrate L-Tyr also suggest that interaction of the substrate with the key Asp and Lys binding pocket residues may be required for rotation of the Asub domain can occur. A homology model of the second A domain of the NRPS that forms Coelichelin has built and it is shown that the core regions of the model are stable in the MD simulations carried out in the apo form, with the cognate ligand (L-Thr) and noncognate ligands (L-Ser and L-Val). Some domain rotation was observed in the simulations with L-Thr and L-Ser. The findings from this study support the suggestion that interaction between the key Asp and Lys binding pocket residues and the substrate may be required for domain rotation. This work presented in this thesis useful insight into the dynamics of the A domain and provides evidence for the role of the conserved A3 motif loop in both domain rotation and removal of noncognate ligands from the binding pocket.

The comparison of catalysts for producing chiral materials is of vital importance in the improvement of reaction scope and efficacy. Here we describe a new method of analysing the kinetics of the stereodetermining steps in asymmetric reactions by performing ligand/catalyst competition experiments against an internal standard and measuring the enantiomeric excess obtained at a variety of ratios of ligand/catalyst to internal standard. From these enantiomeric excess measurements, we can establish the relative rate of reaction between the ligand/catalyst systems and the internal standard, allowing us to make indirect comparisons of the rates at which the ligands/catalysts perform the reaction. Here we take this method and apply it to three common synthetic procedures: the Sharpless asymmetric dihydroxylation, the asymmetric Michael addition of malonates to nitroalkenes and palladium catalysed asymmetric allylation reaction.

PtIV-diazidodihydroxido complexes are inert in the dark, but can be selectively activated by irradiation with light and become potently cytotoxic towards cancer cells. By site-specific irradiation to tumour tissue, the side-effects to healthy tissue associated with conventional chemotherapeutics, such as cisplatin, can be circumvented. This thesis aims to develop design photoactivatable platinum(IV) diazidodihydroxido complexes to achieve higher photocytotoxicity, lower crossresistance and longer wavelength of activation. A series of PtIV diazidodihydroxido complexes with trans azido, trans hydryxido groups and mixed trans aliphatic/aromatic amines, was designed, synthesized and characterized. Trans, trans, trans-[Pt(N3)2(OH)2(MA)(Py)] (5) and trans, trans, trans-[Pt(N3)2(OH)2(MA)(Tz)] (8) are potently cytotoxic towards A2780, OE19 and HaCaT cell lines upon irradiation with UVA. Remarkably, they also showed potent cytotoxic effects towards A2780cis (cisplatin-resistant ovarian cancer cell subline). Also, the photocytotoxicity towards the A2780, A2780cis, OE19 and HaCaT cell lines upon irradiation with blue light (λmax = 420 nm) is still potent compared to that upon irradiation with UVA. These complexes are highly inert in the absence of light and have almost no dark toxicity. Upon irradiation with UVA/blue light, the complex 5 was observed to release free azide anions N3−, azidyl radicals N3•, nitrogen gas N2 and form nitrene intermediates. It was of importance to discover that singlet oxygen (1O2) is generated from photoreactions in the absence of an exogenous source of oxygen, whereas hydrogen peroxide (H2O2) and hydroxyl radical intermediates did not appear to be formed. Mono-functional and bi-functional Pt adducts were captured from the photoinduced binding of complexes 5 and 8 to 5'-GMP and a DNA oligonucleotide. It was discovered for the first time that the oxidation of 5'-GMP can occur during the photoreaction of complex 5 upon irradiation with UVA. Singlet oxygen and nitrene intermediate generated from this photoreaction are likely to be the cause of the oxidative damage to guanine. 4-Nitropyridine, 2,2'-bipyridine, and terpyridines were used as ligands in novel photoactivable PtIV (di)azido complexes and two were activated by green light. A new two-photon-activatable PtII complex, cis-[PtCl2(MOPEP)2](42), was also designed, synthesized and characterized. It was observed that this complex was sensitive to one-photon excitation below 500 nm and the ligand MOPEP underwent rapid solvent (acetonitrile) substitution upon irradiation. The same photoreaction was also triggered by two-photon excitation with fs-pulses laser light between 600 – 700 nm.

This thesis describes the development of an electrochemical scanned probe microscope, SECCM, outlining the need for such a development, by highlighting previous techniques and their limitations. SECCM consists of a double barrel capillary pulled to small dimensions, filled with electrolyte solution and a redox mediator of choice, with a QRCE is inserted into each channel. A potential is applied between the QRCEs, whilst modulating the pipet normal to the surface. The probe is translated towards the surface and once contact is established, a modulation in the ion current arises due to the physical oscillation of the probe, which is then used as a feedback parameter for imaging. The potential at the working electrode substrate is also controlled. SECCM is introduced using a model test substrate, gold bands on glass, showing that the probe is able to track topographical features, making simultaneous electrochemical measurements. Ion conductance measurements between the two QRCEs, are shown to be sensitive to the nature of the substrate investigated. The fundamental electrochemical behaviour of CVD graphene and SWNT is investigated. A multimicroscopy approach is used for CVD graphene studies, correlating surface structure and activity, deducing heterogeneous electron transfer kinetics through simulation. The SWNT samples are studied in two different morphologies: as 3D forests; and, as a 2D network. In the forests, the probe is positioned at the ends and sidewalls, making spot measurements. The voltammetric behaviour shows very similar responses, whilst in the network, a nanosized probe is scanned across the surface, showing relatively uniform activity across an entire tube. These new insights indicate that SWNTs are highly active electrode materials. The fabrication and characterisation of SECM-SICM probes, in a straightforward manner is also presented. These types of probes were found to be ideal for the investigation of biological samples, being extremely easy and quick to fabricate.

Owing to its extraordinary electrical, optical, and mechanical properties, graphene has emerged as a promising material for a variety of applications in the future. However, not all these applications will be able to employ or require pristine graphene; hence several alternative methods have developed for the mass production of graphene and related materials. Graphene oxide (GO), a material closely related to graphene, allows engineering of its chemical composition by means of chemical, thermal, and electrochemical methods. This provides an opportunity to tune physical and chemical properties of graphene. This work reports on investigations of the structure of chemically modified graphenes (CMGs) derived from GO, interactions of metals and organic thin films with CMG, and application of metal-CMG as a hydrogen gas sensor. GO was fabricated by a modified Hummers method. GO, being insulating, was reduced by hydrazine and thermal annealing to produce reduced graphene oxide (rGO). The CMG sheets were deposited on TEM grids and on Si/SiO2 substrates for characterization by atomic force microscopy, transmission electron microscopy (TEM), xray photoelectron spectroscopy, and Raman spectroscopy. The structural analysis of GO performed by TEM revealed that in GO, on average, the underlying carbon lattice maintains the symmetry and lattice-spacings of graphene. Compositional analysis disclosed that the as-produced GO is actually made of oxidized graphene like sheets strongly attached with oxidative debris that make the as produced GO hydrophilic and insulating. In the TEM, both GO and reduced GO (rGO) were nearly transparent and stable under the electron beam and hence they made excellent supports to study the growth of thin organic and metal films deposited by physical vapour deposition. The study revealed the interactions of organic molecules, fluorinated copper phthalocyanine, with CMG and packing of the molecules in the crystal structure. Film-thicknesses from sub-monolayer to tens of monolayers were analysed. In the study of metal thin film growth, the factors determining the growth and morphology of different metals-on-CMG were studied. Fine control over the size and coverage of nanoparticles were achieved. This control was used to combine Pd nanoparticles and rGO to design selective, highly sensitive, and practical hydrogen gas sensor.

Chapter 1 is the main introduction of this work and it features the two main concepts of this study. First living polymerisation techniques are introduced with a special focus into RAFT and ROP. Secondly solution self-assembly is briefly discussed. In Chapter 2 we describe the synthesis of an amphiphilic block copolymer where the two blocks are connected through a reversible bond. A Diels-Alder (DA) adduct consisted of a maleimide-furan pair was chosen as the reversible linker. The solution self-assembly of this polymer was studied by TEM and DLS giving rise to the unexpected formation of cylindrical micelles. In Chapter 3 the main objective was to synthesise new amphiphilic block copolymers without the DA motif in order to investigate their self-assembly behaviour compared to those for DA containing polymers obtained in Chapter 2. To further understand this self-assembly behaviour our method has been extended to the synthesis of other hydrophilic blocks and end group modified polymers. In addition, some key properties of the polymers synthesised have been investigated. In Chapter 4 our main goal is to understand the origins of the cylindrical micelle formation seen in Chapter 2. We investigated the aggregation behaviour under the aqueous thermal conditions in which the PTHPA block hydrolysis is performed. Studies at different concentrations and solvent mixtures provide valuable information regarding the self-assembly mechanism. In addition, the polymers with modified end groups and the triblock copolymers synthesised in Chapter 3 are studied and all the results compared. In Chapter 5 we explore the living crystallisation driven self-assembly of PLA-b- PAA block copolymers in aqueous media towards the formation of cylindrical micelles of controlled length. Interestingly, in many of the unstained TEM images presented in this work the particles demonstrate a non-uniform contrast along their width. This unexpected result is fully investigated in Chapter 6.