This thesis describes for the first time, how the membrane capacitance of pluripotent human embryonic stem cells (H1, H9, RCM1) increases with their differentiation (H1-MSC, H9-MSC, RCM1-trophoblast) based on the literature review. The method used to determine membrane capacitance was dielectrophoresis (DEP), which is an electrokinetic technique capable of characterising and sorting cells without the need for antibody-based cell surface markers, magnetic beads, or other chemical tags. This finding has potential biomedical importance because human embryonic stem cell (hESCs) isolated from early blastocyst-stage embryos and differentiated progeny have been identified to be of possible use in drug screening and regenerative cell based therapeutic treatment. Current cell sorting methods require membrane surface markers that limit their applicability in stem cell therapeutics, a limitation that is either removed or reduced if DEP-based sorting was used. The work described in this thesis consists of the design, fabrication and testing of DEP based microfluidic devices for characterization and separation of human embryonic stem cells. The cells studied were human undifferentiated hESC lines (H1, H9, RCM1, RH1, and T8) and their differentiated progeny (H1-MSC, H9-MSC, RCM1-trophoblast, hES-MP). The cell membrane capacitance (Cm) of the cells was determined by measuring a parameter known as the DEP cross-over frequency (fxo), where the electrical polarisability of a cell equals that of its suspending electrolyte and so experiences no DEP force. The studies of hESC lines cultured from different sources indicate, on the basis of their similar Cm values, that they have similar membrane morphologies. The change in calculated Cm value upon differentiation of these hESCs indicates that changes occur in their membrane morphology, texturing and possibly of their membrane thickness. Subsequent enrichment of these hESCs from human dermal fibroblasts (hDFs) has been achieved based on fxo measurements. The results presented in this thesis confirm the existence, previously indicated in the literature, of distinctive parameters for undifferentiated and differentiating cells on which future application of DEP in hESC manufacturing can be based.

The thesis constitutes an investigation into the production of floating photocatalytic particles (FPP) as a low cost, low carbon footprint and chemical-free wastewater treatment. It is anticipated that this approach would be particularly attractive for developing countries where it could reduce incidences of disease and pollution. The particles were manufactured from cocoa butter (CB), and contained either photocatalytic nanoparticle titanium dioxide TiO2 (P25) or silver-doped TiO2 (0.5% w/w). The photocatalytic activity of the particles was evaluated by means of the decolourisation of the dye indigo carmine (IC). Three arrangements were used; small scale treatment using Petri dishes, an 1800 ml batch-recirculation photoreactor and an 8 litre UV contactor. Membrane emulsification (ME) was the technique used here to generate particles of controlled size. The particles were in effect what are known as Pickering emulsions in which the solid fat core (CB) was stabilised by TiO2 nanoparticles, resulting in composite particles that float easily and can receive incident light to generate highly reactive free radical species. The FPPs were characterised by FEGSEM and EDs mapping analysis, and the images obtained displayed a spherical structure with a rough outer surface, and the EDs showed a good coverage of TiO2 on the surface of at a maximum loading of 10% w/w. Tests were conducted to assess the stability of the particles when used in repeated cycles. Reuse of the particles caused a significant drop of photodegradation activity after four cycles to 42% of that of freshly prepared particles. The correlation of photocatalytic activity with silver dosage was also investigated. The highest photocatalytic activity was achieved at 0.5 wt. % of silver doped TiO2 and was some 10% greater than for un- doped particles. The organic carbon release resulted from TOC analysis for the FPPs that were exposed to UV light for 8.5 hr in water was less than 1 wt. %. First order reaction kinetics were exhibited during decolourisation of IC dye with respect to the initial dye concentration, radiation intensity, percentage coverage of the liquid surface by the FPPs, and the catalytic loading. For a static system (i.e. no forced convection), the most effective surface coverage was identified as being in the range of 60 to 80%. A linear source spherical emission model (LSSE) was adopted to estimate the intensity of the incident radiation on the surface of the FPP layer in the photoreactor and validated. In addition, a preliminary kinetic model to describe of the effect of the photocatalytic active surface concentration of TiO2 as well as the efficient intensity flux in the kinetic model was developed for the FPP layer photoreactor.

This thesis investigates membrane gas separation and its application to post-combustion carbon capture from coal-fired power plants as alternative to the conventional amine absorption technology. The attention is initially focused on membrane module modelling, with the aim of obtaining more detailed predictions of the behaviour of the separation though spiral-wound and hollow-fibre modules. Both one- and bi-dimensional models are implemented, compared and tested for different separations. Module geometry is investigated as well as the effect on the performances due to possible fabrication defects. A key part of the work involves the integration of the customised models into UniSim® Design, the Honeywell process simulator. Thanks to the developed interface, multi-stage process designs are developed, compared with the available literature and linked to a rigorous economic analysis. In particular, a long-term indicator such as the Levelised Cost Of Electricity (LCOE) is evaluated and parametric analyses are conducted with respect to both material and process parameters.

Thesis (M. Tech. Chemistry, Dept. of Chemistry, Faculty of Applied and Computer Sciences)--Vaal University of Technology, 2010. / Membrane separation processes offer a promising alternative to energy-intensive separation processes such as distillation and solvent extraction. NF and RO are among the most investigated membrane processes with a potential use in the chemical industry. Carbon-carbon coupling reactions feature in the top ten most used reactions in the chemical industry. These reactions often use homogeneous palladium, nickel and other precious catalysts which are often difficult to separate from reaction products. This leads to potential product contamination and loss of active catalysts. This not only poses a threat to the environment but is also costly to the chemical industry. The purpose of this study was to investigate the efficiency of the recovery of the metal catalysts by selected membrane processes. Four commercial polymeric NF and RO membranes (NF90, NF270, BW30 and XLE) were selected for the study. Palladium catalysts commonly used in Heck and Suzuki coupling reactions were selected. These are Pd(OAc)2, Pd(OAc)2(PPh3)2, PdCl2 and Pd(PPh3)2Cl2. A range of organic solvents were also selected for the study. All the membranes were characterized for pure water permeability, pure solvent permeability, swelling, surface morphology and chemical structure. The chemical and catalytic properties of the catalysts were determined. Catalytic activity was investigated by performing coupling reactions. These catalysts generally performed well in the Heck coupling reaction with sufficient yields realized. The catalysts showed poor activities in the Suzuki and Sonogashira coupling reactions. These coupling reaction systems were affected by rapid palladium black formation. vi Catalyst retention studies showed the influence of membrane-solute interactions such as steric hindrance and size exclusion. The larger catalyst, Pd(OAc)2(PPh3)2 was rejected better by all the membranes irrespective of the solvent used. The smaller catalyst, Pd(OAc)2 was the most poorly rejected catalyst. This catalyst showed signs of instability in the selected solvents. An interesting finding from this study is that of higher rejections in water compared to other solvents for a particular catalyst. In this regard, the influence of solventsolute effects was evident. Generally, higher rejections were observed in solvents with higher polarity. This has been explained by the concept of solvation. It has been shown that solvents with different polarity solvate solutes differently, therefore leading to a different effective solute diameter in each solvent. Catalyst separation using NF90 membrane was attempted for the Heck coupling reaction system. The reaction-separation procedure was repeated for two filtration cycles with rapid activity decline evident. This was regarded as very poor showing of the catalyst separation efficiency of the membrane. Other authors in similar studies using SRNF membranes have reported reaction-separation processes of up to seven cycles. This observation shows the inferiority of polymeric membranes in organic solvent applications such as catalyst separation.

School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa August 2017 / Global warming, resulting from emission of greenhouse gases (GHGs), is the cause of drastic climate changes that threatens the economy and living conditions on the planet. Currently, recovery and mitigation of these greenhouse gases remains a technological and scientific challenge. Various recovery processes for the mitigation of GHGs have been reported including among others carbon capture and storage (CCS). The most mature and applied technology in CCS process involves the absorption of carbon dioxide on amine based solvents. However, studies have shown that this process has several drawbacks that include low stability and high energy required to strip off the absorbed CO2 and regenerate the solvent. This presents an opportunity for the development of new materials for CO2 capture such as zeolite membranes. Previous studies have shown that the separation of CO2 can be achieved with high selectivity at low temperatures using thin-film SAPO-34 membranes (thin layers on supports). This is because CO2 adsorbs strongly on the membranes compared to other gases found in flue gas. In the thin-film membranes supported on ceramic or sintered stainless steel, thermal expansion mismatch may occur at higher operating temperatures resulting in loss of membrane selectivity due to the formation of cracks. A new method is required to overcome the aforementioned problems, thereby enhancing the separation application of the membranes at higher temperatures. The effective separation and capture of CO2 from the coal-fired power plant flue gas is an essential part in the CCS process (Figueroa et al., 2016; Yang et al., 2008). Currently, the capture stage is a huge contributor to the overall cost of CCS (Yang et al., 2008). This is due to the high-energy intensity and inefficient thermal processes applied in the separation and capture in various industrial applications (Yang et al., 2008). This work presents the use of nanocomposite SAPO-34 zeolite membranes synthesized via the pore-plugging hydrothermal method for the separation of CO2 during post-combustion CO2 capture. The SAPO-34 membranes used were supported on asymmetric α-alumina as membrane supports. The membranes were characterized with a combination of dynamic and static physicochemical techniques such as Basic Desorption Quality Test (BDQT), X-ray diffraction (XRD) spectroscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The characteristic peaks at 2θ = 21°, 26°, and 32° on the XRD pattern confirmed the presence of SAPO-34 with a rhombohedral crystalline structure. The SEM images showed the formation of the cubic crystalline which were consistent with the reported morphology of SAPO-34. FTIR spectra showed the presence of the essential double-6 membered rings (D6R) and TO4 structural groups in surface chemistry of crystalline materials further confirming the presence SAPO-34. The TGA confirmed that the membranes possessed high thermal stability. To assess the feasibility of the synthesis process, the nanocomposite zeolites were grown within the tubular supports. The SEM images of the cross-section of the membrane confirmed the presence of the zeolites within the pores of the support confirming the fabrication of nanocomposite membranes by the pore-plugging synthesis method. The permeation tests used a dead-end filtration mode to measure the single gas permeance and the ideal selectivity of CO2 and N2 were calculated. The BDQT was essential in the study of the quality of the as-synthesized nanocomposite membranes. The quality of the membranes increased with an increase in the synthesis layers of the membranes. However, with an increase in synthesis layers, the membrane thickness also increases. The membrane thickness affected the gas permeance for CO2 and N2 significantly. The permeance of the N2 gas decreased from 10.73 x10-7 mol.s-1.m2Pa-1 after the first synthesis to 0.31 x10-7 mol.s-1.m2Pa-1 after seven synthesis layers. Alternatively, the more adsorbing gas CO2 decreased from 12.85 x10-7 mol.s-1.m2Pa-1 to 2.44 x10-7 mol.s-1.m2Pa-1. The performance of these zeolite membranes depends significantly on the operating conditions. Hence, we studied extensively the influence of the various operating conditions such as temperature, feed pressure and feed flowrate in this work. Results indicated that the membrane separation performance in this study is largely dependent on the temperature. In addition, the ideal selectivity decreased significantly with an increase in temperature. High temperatures results in less adsorption of the highly adsorbing CO2 gas, the permeance reduces significantly, while the permeance of the less adsorbing N2 increased slightly. The feed flow rate has less effect on the adsorbing gas while the non-absorbing gas increased resulting in a decrease in the ideal selectivity as well. The nanocomposite membranes in this study have a low flux compared to their thin film counterparts. An increase in feed pressure significantly increased the flux significantly as well as the ideal selectivity. Maxwell-Stefan model simulation was done in this study to describe the permeance of pure CO2 single gas permeance as a function of temperature. This model considered explicitly the adsorption-diffusion mechanism, which is the transport phenomenon, involved in the transport of CO2 through the zeolite membrane. The description of the support material was included in the model as well. However, the model was only applied to the CO2 gas permeation well within the experimental data. We then compared the model was with the experimental results and a good correlation was observed. In conclusion, SAPO-34 nanocomposite zeolite membranes were obtained at low temperatures (150 °C) with a short synthesis time (6 h). In addition, the high thermal stability of the as-synthesized SAPO-34 membranes makes them ideal for high temperature CO2 separation such as the intended post-combustion carbon capture. The BDQT revealed that the quality of the membranes was related to the thickness of the membranes. Therefore, better membrane quality was obtained with relatively thicker membranes. The separation performance evaluation was conducted on the membrane with the greatest quality. Our findings demonstrate that the performance of the membranes depends extensively on the operating conditions. / MT2018

Thesis advisor: Jianmin Gao / My graduate research career has focused on studying the principles that underlie molecular recognition, which include protein folding, protein-membrane interactions, structural preoranization for target binding and non-covalent interactions. This thesis will present an overview of this work through three different projects. I) Synthetic receptors for target binding in water. Molecular interactions in water provide the foundation for life. More specifically, the interactions between one or more molecules, through hydrogen bonding, π-effects, hydrophobic interactions and electrostatic interactions, all play a significant role essential to biological processes. This chapter will present an overview of supramolecular chemistry in water, with a focus on small molecule receptor “warheads” that target biomolecules of interest. The discussion will then move towards the ability to preorganize these “warheads” on a scaffold to improve their potency towards a target. The fundamental principles discussed in this section will provide a foundation for the following chapter in this thesis.II) Understanding Phosphatidylserine Recognition Using the Model cLac Peptide. The plasma membrane serves as a defining feature of the cell membrane, acting as a barrier for material exchange between a cell and its local environment. More importantly, membrane lipids are involved in mediating numerous cell-signaling events and acting as receptors to recruit proteins that carry out a specific function. Due to the important role that lipids play, it is highly desirable to develop affinity ligands for the diverse range of lipid headgroup structures on a cell membrane. Although prevalent, proteins have intrinsic limitations due to their size, low stabilities and slow clearance rates. This chapter will focus on the model peptide, cLac, which was previously developed as an affinity ligand for phosphatidylserine recognition. We will focus on understanding the key properties that contribute to PS selectivity and affinity, then attempt to improve this scaffold through structural preorganization. III) A prolinomycin-based scaffold for developing functional peptides. Nature has evolved proteins to bind cell-signaling molecules with exquisite affinity and specificity, making molecular recognition an essential part of biology. It has been a highly sought after goal within the chemistry field to be able to mimic the structure and function of certain proteins with smaller molecules, such as peptides. Specifically, cyclic peptides are showing promise as therapeutic agents due to their high proteolytic stabilities, faster clearance rates and ease of synthesis compared to proteins. One challenge, however, is that peptides generally do not possess the ability to properly fold and display their side chains for target binding, as proteins do. In this chapter, I will present a prolinomycin-based scaffold, which can fold in the presence of K+ ions to preorganize its side chains for target binding. Moreover, the focus will be on the structural aspects of this cyclic peptide, along with proof-of-concept studies demonstrating its ability to recognize a target under physiological conditions. The findings in this study will be useful in developing peptide-based tools that recognize various targets. IV) Dissecting the energetic consequences of fluorinating a protein core. Proteins have emerged as a powerful class of therapeutic agents due to their superior properties over small molecules in the clinic. Some of the key advantages include their large surface areas and highly defined structures, which allow them to perform very specific functions that are generally not reproducible with traditional small molecule scaffolds. In addition, proteins possess the ability to properly fold under physiological conditions through precise, noncovalent interactions between their side chain residues. Perhaps the most relevant interactions arise from aromatic side chains, which can interact in a variety of ways to help proteins fold. In this chapter, we will focus on the model protein, VHP35, which contains a hydrophobic core of three interacting Phe residues, to study the effects of fluorination on an edge-face interaction. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Jianmin Gao / The oligomerization of membrane proteins has been shown to play a critical role in a myriad of cellular processes, some of which include signal propagation, cell-to-cell communication, and a cell's ability to interact with its surroundings. Diseases that are associated with disruption of protein-protein interactions in the membrane include cystic fibrosis, certain cancers, and bone growth disorders. Although significant progress has been made in our mechanistic understanding of protein-protein interactions in membranes, it remains difficult to predict the oligomerization state of transmembrane domains and explain the physiological consequences of a point mutation within a membrane embedded protein. The development of novel classes of chemical tools will allow us to better understand the energetics of transmembrane domain association at the molecular level. Herein, we demonstrate that fluorinated aromatic amino acids offer intriguing potential as chemical mediators of transmembrane protein association. We have systematically examined the effects of fluorination on the physical properties of aromatic systems in the context of a soluble protein model system. Our results illustrate the ability of fluorinated aromatic amino acids to simultaneously stabilize protein structure and facilitate highly specific protein self-assembly. An improved understanding of the fundamental energetics of aromatic interactions should allow for their more efficient incorporation into designed inhibitors of transmembrane protein association. In addition to chemical tools, the development of simple methods for directly monitoring transmembrane domain association in vitro and in vivo is necessary to advance our understanding of these interactions. Towards this goal, we have established FlAsH-tetracysteine display as an effective approach to quantifying the association propensities of transmembrane α-helices (TMHs) in vitro. Our assay is compatible with two of the most commonly utilized model membrane systems, detergent micelles and vesicles. The high spatial resolution of FlAsH binding (˂ 10 Å) allows for the differentiation of parallel and antiparallel oligomerization events. Importantly, preliminary studies suggest the assay's ability to detect inhibition from exogenous TMHs. Encouraged by our understanding of aromatic interactions and the success of our assay, we are beginning to incorporate fluorinated aromatics in the model TMHs and monitoring their ability to associate. The ultimate goal is to modulate the association of endogenous TMHs such as ErbB2. Research in this direction is ongoing. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

ABSTRACT The Chloride Intracellular Channel (CLIC) proteins are a family of amphitropic proteins that can convert from soluble to integral membrane forms. CLIC1 is a member of this family that functions as a chloride channel in the plasma and nuclear membranes of cells. Although high-resolution structural data exists for the soluble form of monomeric CLIC1, not much is known about the integral membrane forms’ structure. The exact mechanism and signals involved in the conversion of the soluble form to membrane-inserted form are also not clear. Studies were undertaken in the absence and presence of membrane models. Analysis of the structure and stability of CLIC1 in the absence of membrane investigated the effect of possible signals or triggers that may play a crucial role in the conversion of the soluble form to integral membrane form. Exposing CLIC1 to oxidizing conditions results in the formation of a dimeric form. The CLIC1 dimer was found to be less stable than the monomeric form based on unfolding kinetic studies. The stability of the dimer was also less influenced by salt concentration, compared with the monomer. The effect of pH on the structure of CLIC1 is of physiological relevance since the movement of soluble CLIC1 in the cytoplasm or nucleoplasm toward the membrane will involve the protein being exposed to a lower pH micro-environment. Hydrogen exchange mass spectrometry was used to study the structural dynamics of CLIC1 at pH 7.0 and pH 5.5. At neutral pH, domain II is more stable than the more flexible thioredoxin domain I. The thioredoxin-fold therefore is more likely to unfold and rearrange to insert into membranes. Because of the high stability of domain II this region is probably where the folding nucleus of the protein is. At pH 5.5 it was found that the a1, a3 and a6 helices, which are spatially adjacent to one another across the domain interface, were destabilized. This destabilization may be the trigger for CLIC1 to unfold and rearrange into a membrane insertion-competent form. The role of the primary sequence and unique three-dimensional structure of CLIC1 in membrane insertion was investigated in a bioinformatics-based study that looked at conserved residue features such as hydropathy and charge. Hidden helical propensities and Ncapping motifs in the a1-b2 region were found, which may have important implications for locating putative transmembrane regions. Analysis of the structure and thermodynamics of CLIC1 interacting with membranes investigated changes in secondary structure, tertiary structure, hydrodynamic volume and thermodynamics when CLIC1 is exposed to membrane-mimicking models. The effect of a variety of conditions such as pH and redox, cysteine-modifiying agents (NEM), ligands (GSH), and inhibitors (IAA) on CLIC1 membrane interaction were studied. It was found that CLIC1 interacted with membranes more favourably at lower pH and that NEM completely inhibited CLIC1 interaction with micelles.

1 Summary The first part of this thesis is preoccupied with the identification of protein alterations in the membrane fraction of HEK293-E2M11 cells after prolonged TRH treatment. The isolated membrane fraction enriched in plasma membranes contained markedly increased the amount of Na,K-ATPase, TRH receptor and G-proteins compared to the postnuclear supernatant. By using 2D electrophoresis and mass spectrometry, the levels of 42 proteins were identified to be altered in samples of PM- enriched fractions from TRH-treated (16 h; 10 μM) cells. Out of these proteins only ezrin and stomatin-like 2 are known to be localized in the plasma membrane. Five proteins (mitofilin, MTHSP75, prohibitin, stomatin like-2, peroxiredoxin III) whose levels were increased after the prolonged TRH treatment represent proteins localized in mitochondria. All of them are important for proper structure and function of mitochondria. The ratio of anti-apoptotic Bcl-2 to pro-apoptotic Bax was markedly higher in cells treated with TRH than in control untreated cells. Hence, it can be concluded that prolonged TRH treatment may significantly affect mitochondrial membrane and function of mitochondria. The second part of this thesis deals with the identification of molecular protein complexes of TRH-R and/or Gq/11 protein. The presumed...

Thesis advisor: Jianmin Gao / A common method of studying proteins is to introduce mutations into the amino acid sequence of the system. Incorporating phenylalanine analogs of varying degrees and sites of fluorination on the aromatic system gave substantial insight into the structure—function relationship of model peptide systems. By strategically placing tetrafluorinated phenylalanine mutants into the villin headpiece, HP35, increased thermodynamic and thermal stability was achieved. Using these highly but not fully fluorinated novel amino acid analogs allowed for the retention of the important ArH•••π interactions of the system. Furthermore, fluorinated amino acid residues were introduced into peptide systems known to form pores in lipid membrane systems. Certain fluorinated mutants of the membrane pore-forming peptides (MPP) showed increased membrane activity. Thus, fluorinated amino acids have tremendous potential to create hyperstable protein conformations, as well as increase the activity of proteins in membranes. / Thesis (BS) — Boston College, 2009. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Chemistry.