Longitudinal optical binding refers to the light induced self organisation of micro particles in one dimension. In this thesis I will present experimental and theoretical studies of the separation between two dielectric spheres in a counter-propagating (CP) geometry. I will explore the bistable nature of the bound sphere separation and its dependency on the refractive index mismatch between the spheres and the host medium, with an emphasis on the fibre separation. The physical under pining principle of longitudinal optical binding in the Mie regime is the refocusing effect of the light field from one sphere to its nearest neighbour. In a second set of experiments I developed means to visualise the field intensity distribution responsible for optical binding using two-photon fluorescence imaging from fluorescein added to the host medium. The experimental intensity distributions are compared to theoretical predictions and provide an in situ method to observe the binding process in real time. This coupling via the refocused light fields between the spheres is in detailed investigated experimentally and theoretically, in particular I present data and analysis on the correlated behaviour of the micro spheres in the presence of noise. The measurement of the decay times of the correlation functions of the modes of the optically bound array provides a methodology for determining the optical restoring forces acting in optical binding. Interestingly micro devices can be initiated by means of the light-matter interaction. Light induced forces and torques are exerted on such micro-objects that are then driven by the optical gradient or scattering force. I have experimentally investigate how the driving light interacts with and diffracts from the motor, utilising two-photon imaging. The micromotor rotation rate dependence on the light field parameters is explored and theoretically modelled. The results presented will show that the model can be used to optimise the system geometry and the micromotor.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

published_or_final_version / Biochemistry / Master / Master of Philosophy

This dissertation reports on the recent discovery that calix[4]pyrrole not only functions as an anion receptor, but also has the ability to act as an ion pair receptor. It was discovered that in the solid state large diffuse cations, such as Cs+ and imidazolium, will occupy the electron-rich cone-like cavity that is formed upon anion binding to the NH region of the calix[4]pyrrole core. Also discussed are efforts devoted to improving the anion binding ability of calixpyrroles and fine-tuning their inherent selectivity. This has been probed through a variety of structural modifications. One of the most attractive of the modification strategies currently being explored involves expansion of the central binding cavity by using higher order β-fluorinated calix[n]pyrroles; n = 5, 6, and 8. An advantage of β-fluorinated calix[4]pyrrole is that it shows enhanced anion binding affinities toward several anions compared to the parent calix[4]pyrrole. Fluorinated calixpyrroles have also shown an ability to extract anions from aqueous environments into organic media. An alternative strategy has been to attach “straps” resulting in bicyclic systems, which further define the binding cavity achieving higher affinity and anion selectivity. The binding interactions of calixpyrrole and it derivative have been quantified using analytical techniques, such as nuclear magnetic resonance spectroscopy and isothermal titration calorimetry. The results of these latter studies will be discussed herein. / text

Arabidopsis thaliana Acyl-CoA-Binding Protein 3, one of six acyl-CoA-binding proteins, is unique by the C-terminal location of its acyl-CoA-binding (ACB) domain. It promotes autophagy (ATG)-mediated leaf senescence and confers resistance to Pseudomonas syringae pv. tomato DC3000. To understand the regulation of ACBP3, a 1.7 kb 5’-flanking region of ACBP3 and its deletion derivatives were characterized using β-glucuronidase (GUS) reporter gene fusions. A 374 bp minimal fragment (-151/+223) could drive GUS expression while a 1698 bp fragment (-1475/+223) conferred maximal activity. Further, histochemical GUS staining analysis on transgenic Arabidopsis harboring the largest (1698 bp) ACBP3pro::GUS fusion displayed ubiquitous expression in floral organs and vascular bundles of leaves and stems, consistent with previous results that extracellularly localized ACBP3 functions in plant defense. A 160 bp region (-434/-274) induced GUS expression in extended darkness and conferred down-regulation in extended light. Electrophoretic mobility shift assay (EMSA) and DNase I footprinting assay showed that the DNA binding with one finger box (Dof-box, -341/-338) interacted specifically with leaf nuclear proteins from dark-treated Arabidopsis while GT-1 (-406/-401) binds both dark- and light-treated Arabidopsis, suggesting that Dof and GT-1 motifs are required to mediate circadian regulation of ACBP3. Moreover, GUS staining and fluorometric measurements revealed that a 109 bp region (-543/-434) was responsive to phytohormones and pathogens. Within this 109 bp region, an S-box of AT-rich sequence (-516/-512) was identified to bind nuclear proteins from pathogen-infected Arabidopsis leaves, providing the basis for pathogen-inducible regulation of ACBP3 expression. Hence, three cis-responsive elements (Dof, GT-1 and S-box) in the 5’-flanking region of ACBP3 were demonstrated to participate in the regulation of ACBP3. The regulation of ACBP3 by circadian control is not surprising given that defense genes are now known to be circadian-regulated; infection being anticipated at dawn coinciding with pathogen activity in spore dispersal during the light period. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

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