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In binary systems, surfactant molecules can self-assemble into a large variety of structures depending on their chemical structure, concentration and temperature. The properties and stability of the phases, their coexistence regions and the formation of metastable structures is of great importance not only for fundamental understanding, but also for applications in many fields including industry and medicine. This thesis presents studies of the equilibrium and non-equilibrium behaviour of two widely used surfactant systems. The understanding of the equilibrium behaviour of an aqueous surfactant system is often incomplete or partly incorrect, which is caused by experimental difficulties, long equilibration times and the occurrence of long-lived metastable states. By applying a set of complementary techniques and recording changes on different length scales, the equilibrium phase diagram of the surfactant didodecyldimethylammonium bromide (DDAB) in water has been studied and amended. Differential scanning calorimetry has been used to obtain thermodynamic parameters. The structure of phases and biphasic regions have been characterised by small angle X-ray scattering and microscopy, while the conformational properties of the surfactant molecules have been investigated using Raman spectroscopy combined with computational methods. The effects of impurities have been studied using analytical techniques and a sufficient purity of the samples could be ensured. As a result of the studies, a new crystalline phase which exists at temperatures below 16°C was found. This phase replaces the frozen lamellar phase (Lβ) in the previously reported phase diagram. The Lβ phase has been found to be a long-lived metastable phase. The amended phase diagram has been tested by studying phase transitions along isoplethal and isothermal paths. All experimental results could be explained in terms of the new phase diagram. The study of phase transition along isoplethal paths focused on the transition between the new crystalline phase (XWn) coexisting with a dilute monomer solution (W) and the lamellar phase (Lα). This transition was (except for a single composition DDAB≈3% DDAB) a non-isothermal transition involving the phase sequence: XWn +W → XWn + Lα → Lα upon heating and Lα → overcooled Lα → XWn +W upon cooling. The structural changes within the phases and their relative ratios could be characterised using small angle X-ray scattering, microscopy and Raman spectroscopy. During the dissolution of lamellar phases along an isothermal path, multilamellar wormlike interface instabilities (so called myelins) were found to grow from the lamellar/water interface into the water. The growth of these myelins as well as changes in the lamellar phase have been investigated using optical microscopy and direct observation. This has provided detailed quantitative information on the dynamics of myelin growth and the effect of the initial structure of the lamellar phase on the myelin growth. The dependence of the growing rate on surfactant concentration could be explained in terms of a previously reported model in which the osmotic pressure was stated to be the driving force for the myelin kinetics. It has been found that for lamellar phases in coexistence with a sufficient amount of crystals, the myelin growth could be suppressed. Preliminary measurements of a tertiary system, where the pure lamellar phase of DDAB was mixed with a crystalline phase formed by dioctadecyldimethylammonium bromide (DODAB), a DDAB analogue, were carried out. The myelin growth has also been studied for a second system, the non-ionic surfactant triethylene glycol monododecyl ether (C12E3), known for its formation of myelins of great stability. The optical methods were extended to confocal microscopy, resulting in a 3D image of the myelin formation, providing detailed quantitative information on myelin growth as well as on myelin size.

Axons are directed along stereotypic pathways to their targets by cues arrayed in the extracellular environment. Identifying the cellular and molecular nature of these signals is of high interest and the developing optic pathway is a useful model system for achieving this. Although previous studies have identified several molecules essential for optic pathway formation, in vivo only subsets of retinal axons rely on them. I focused on the Dscam (Down’s syndrome cell adhesion molecule) and Sidekick (Sdk) cell adhesion molecules for potentially playing crucial roles in this system. In situ hybridisation in the embryonic mouse visual system showed Dscam and Sdk-1 expression in the RGC layer of the retina, along the optic pathway and in the visual targets. Sdk-2 was detected in the glia of the optic nerve and optic chiasm, marking the pathway that RGC axons follow, but not in RGCs. No DscamL1 was detected in RGCs or the optic pathway at the stages investigated and it was discounted from future analysis. In vitro, DSCAM promoted RGC axon outgrowth, whereas SDK 1 was inhibitory. SDK 2 had no effect on RGC axon outgrowth, suggesting it does not play a direct role in their pathfinding. Repeating this assay using retinal explants from the Dscamdel17 mouse mutant, showed that DSCAM enhanced retinal axon outgrowth, at least in part, through homophilic interactions. Analysis of visual system development in Dscam mutants showed DSCAM involvement in RGC axon fasciculation and in enhancing their growth, particularly within the ipsilateral optic tract. Retinal cell counts revealed that DSCAM played diverse roles in controlling cell number. Pre- and postnatal retinas lacking DSCAM contained more RGCs and mitotic cells. Postnatally, Dscam-/- retinas also show decreased cell death. In many cases, defect severity was dose-dependent, with an intermediate phenotype in the heterozygous mice, implicating DSCAM in the neurological defects of Downs’ Syndrome patients.

Context. Ammonia and its deuterated isotopologues probe physical conditions in dense molecular cloud cores. The time-dependence of deuterium fractionation and the relative abundances of different nuclear spin modifications are supposed to provide a means of determining the evolutionary stages of these objects. Aims. We aim to test the current understanding of spin-state chemistry of deuterated species by determining the abundances and spin ratios of NH2D, NHD2 and ND3 in a quiescent, dense cloud. Methods. Spectral lines of NH3, NH2D, NHD2, ND3 and N2D+ were observed towards a dense, starless core in Ophiuchus with the APEX, GBT and IRAM 30-m telescopes. The observations were interpreted using a gas-grain chemistry model combined with radiative transfer calculations. The chemistry model distinguishes between the different nuclear spin states of light hydrogen molecules, ammonia and their deuterated forms. Different desorption schemes can be considered. Results. High deuterium fractionation ratios with NH2D = NH3 similar to 0 : 4, NHD2 = NH2D similar to 0 : 2 and ND3 = NHD2 similar to 0 : 06 are found in the core. The observed ortho/para ratios of NH2D and NHD2 are close to the corresponding nuclear spin statistical weights. The chemistry model can approximately reproduce the observed abundances, but consistently predicts too low ortho/para-NH2D, and too large ortho/para-NHD2 ratios. The longevity of N2H+ and NH3 in dense gas, which is prerequisite to their strong deuteration, can be attributed to the chemical inertia of N-2 on grain surfaces. Conclusions. The discrepancies between the chemistry model and the observations are likely to be caused by the fact that the model assumes complete scrambling in principal gas-phase deuteration reactions of ammonia, which means that all the nuclei are mixed in reactive collisions. If, instead, these reactions occur through proton hop/hydrogen abstraction processes, statistical spin ratios are to be expected. The present results suggest that while the deuteration of ammonia changes with physical conditions and time, the nuclear spin ratios of ammonia isotopologues do not probe the evolutionary stage of a cloud.

The construction of mechanically interlocked molecules has been the subject of decades of research. The efficiency of strategies for preparing these molecules has increased continuously. In recent years, the transition metal templation strategy has played quite a remarkable role in the synthesis of entwined or mechanically bonded structures due to the metals’ diverse coordination chemistry and ability to chelate ligands. In the early stages of this method’s development, the metal ions were used as integral part of the scaffold for such components as rings and stoppers to generate the interlocked structures. In newly developed active metal templation strategies, metal ions are used to promote covalent bond forming reactions while simultaneously acting as structural supports. In this thesis, three main aspects are expanded for the discussion of the application of metal template strategies. First of all, the newly developed strategy - active metal template - will be described and exemplified using the Huisgen-Meldal-Fokin Cu(I)- catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC “click” reaction), the Cu(I)-mediated Cadiot-Chodkiewicz heterocoupling of an alkyne halide with a terminal alkyne, and the Ni(II)-catalyzed Csp3-Csp3 homocoupling reaction. Secondly, the thesis discusses the use of these strategies to obtain several hard-to-access structures, including the first high-yielding doubly threaded [3]rotaxanes, heterocircuitcatenanes and the one pot synthesis of homocircuit-catenanes, and the smallest molecular trefoil knot prepared to date. Lastly, as an extension of the metal temptation strategy, the final chapter of this thesis will discuss the assembly of inorganic metal-organic catenanes by metal coordination.

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