The role of highly conserved amino acids within the carboxy-terminal hydrophobic domain of herpes simplex virus I (HSV-I) glycoprotein gB was studied by introducing point mutations using the method of site directed mutagenesis. A segment of this hydrophobic domain of glycoprotein gB contains a nuclear envelope (NE) targeting signal and the effect of these point mutations on targeting to the nuclear envelope was determined. A complementation assay was employed to determine the effect these mutations have on HSV-I infectivity .The point mutations created within the transmembrane domain of glycoprotein gB had no effect on nuclear envelope targeting and localization. However, single point mutations introduced into the first and second hydrophobic domains of glycoprotein gB, G₇₄₃R and F₇₇₀S, affected the targeting and localization of full-length glycoprotein gB at the nuclear envelope. When the transmembrane domain ofHSV-I glycoprotein gB containing the following point mutations A₇₉₀Q, A₇₉₁S, A₇₈₆S, A₇₈₆Y and A₇₉₀S, was introduced into a chimeric protein consisting of the cytoplasmic domain and ectodomain of a plasma membrane protein, vesicular stomatitis virus glycoprotein G, NE targeting and localization were affected. These point mutations may affect the targeting of glycoprotein gB by altering the structure of the targeting signal within the protein. It can be hypothesized that the presence of the cytoplasmic domain. ectodomain domain, and the first and second transmembrane domains within full-length glycoprotein gB can compensate for the effect these point mutations have on nuclear envelope targeting. since the same point mutations had no effect on the targeting · and localization of full-length glycoprotein gB. Complementation assays showed that the glycoprotein gB mutants, A₇₈₆S, A₇₈₆Y, A₇₈₆N, A₇₉₀Q, A₇₉₁S, F₇₇₀S, or G₇₄₃R, were unable to complement a gB-null virus even though these mutant proteins are localized at the nuclear envelope. These proteins may not have been incorporated into the viral capsid due to misfolding or due to the fact that sequences required for interaction with other viral proteins were lost. Another possibility is that the mutant proteins were incorporated into the HSV virion but were not biologically active. / Thesis / Master of Science (MS)

Fundamental studies of surface forces in foam films are carried out to explain the stability of foams and froths in froth flotation. The thin film pressure balance (TFPB) technique was used to study the surface forces between air bubbles in water from equilibrium film thickness and dynamic film thinning measurements. The results were compared with the disjoining pressure predicted from the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The contribution from the non-DLVO force was estimated by subtracting the electrostatic double-layer and van der Waals forces from the total force (or pressure) measured. The results obtained in the present work suggest that a strong attractive force (referred to as hydrophobic force) exists at very low surfactant concentrations, and that it decreases with increasing surfactant and/or electrolyte concentrations. In contrast, pH changes have only minor effects on the hydrophobic force. The changes in the hydrophobic force observed at low surfactant concentration region have been related to foam stability in flotation. In addition, an analytical model applicable to a broad range of surfactant concentration was developed to calculate film elasticity from surface tension. The model finds, however, that the film elasticities change little at low surfactant concentrations. It is, therefore, suggested that bubble coalescence and foam stability at low surfactant concentrations may be largely affected by hydrophobic force. The TFPB technique was also used to study the surface forces in the foam films stabilized with various frothers such as pentanol, octanol, methyl isobutyl carbinol (MIBC), and polypropylene glycol (PPG). The results were compared with the foam stabilities measured using the shake tests and the film elasticity calculated using the model developed in the present work. It was found that at a low electrolyte concentration foam stability is controlled by film elasticity and surface forces, the relative contributions from each changing with frother concentration and type. It is, therefore, proposed that one can control the foam stability in flotation by balancing the elasticities of foam films and the disjoining pressure in the films, particularly the contributions from the hydrophobic force. / Ph. D.

"Water behavior in pure silicalite and Dealuminated Zeolite Y (DAY), two highly hydrophobic zeolites, was investigated at different temperatures in the range 100-600 K by molecular dynamics simulations. The Compass forcefield was used to carry out the study. A full flexibility of water molecules and of the zeolite framework was considered. The results show that water behavior is more complex in silicalite than in zeolite DAY. Three different activation energies for water diffusion were obtained in silicalite in the range 250-600 K compared to two for DAY. The values of these activation energies are discussed in detail and are related to the hydrogen bond‘s strength and the zeolite structure. Moreover, from the radial distribution functions (rdfs), it is shown that water mostly exists in the gas phase at room temperature in silicalite whereas liquid water is observed in DAY in agreement with previous experimental observations. The self-diffusion coefficients of water and the rdfs are obtained as a function of temperature in order to explain the behavior differences of water in the two all-silica zeolites. The loading influence on the self-diffusion coefficients is also investigated for both crystals. The results are compared with previous experimental and theoretical studies."

It is well known that water molecules at room temperature tend to form ‘iceberg’ structures around the hydrocarbon chains of surfactant molecules dissolved in water. The entropy reduction (times the absolute temperature T) associated with the iceberg structure can be considered as the net driving force for self-assembly. More recently, many investigators measured long-range attractive forces between hydrophobic surfaces, which are likely to result from structuring of the water molecules in the vicinity of the hydrophobic surfaces. Similarly, the hydrophobic nature of most gas hydrate formers may induce ordering of water molecules in the vicinity of dissolved solutes. In the present work, the surface forces between thiolated gold surfaces have been measured using an atomic force microscope (AFM) to obtain information on the structure of the thin films of water between hydrophobic surfaces. The results have been used to develop a new concept for the formation of gas hydrates.

In the past decade, the condensation on superhydrophobic surfaces has been investigated abundantly to achieve dropwise condensation. There is not a specific approach in choosing the size of the roughness of the superhydrophobic surfaces and it was mostly selected arbitrarily to investigate the behavior of condensates on these surfaces. In this research, we are optimizing the size of the roughness of the superhydrophobic surface in order to achieve dropwise condensation. By minimizing the resistances toward the transition of the tails of droplets from the cavities of the roughness to the top of the roughness, the size of the roughness is optimized. It is shown that by decreasing the size of the roughness of the superhydrophobic surface, the resistances toward the transition of the tails of droplets from Wenzel state to Cassie state decrease and consequently dropwise condensation becomes more likely.

The condition of no relative velocity of fluid past solid is termed as ‘no-slip boundary condition’. This condition is a general observation in fluid mechanics. However, several research groups have recently reported slip of water for surfaces with water repelling chemistry (referred to as hydrophobic surfaces). The effect has been attributed to disruption of H-bonding network of water molecules at such surfaces and resulting nucleation of dissolved gases and even reduced water density locally in absence of dissolved air. Slip of water on hydrophobic surfaces has been demonstrated to get amplified by high degree of roughness and patterning. Trapping of air in the surface asperities has been cited as the possible reason. The present work focuses on the study of effect of surface chemistry and roughness on flow behavior close to solid surfaces. Superhydrophobic surfaces have been generated by novel methods and wet-etching has been used to generate well-defined patterns on silicon surfaces. For flow characterisation, a micrometre resolution Particle Image Velocimetry (micro-PIV) facility has been developed and flow measurements have been carried out with a spatial resolution of less than 4 µm. It has been found from the experiments that flow of water on smooth surfaces, with or without chemical modification, conforms to the no-slip within the resolution limits of experiments. Deviation is observed in case of rough and patterned hydrophobic surfaces, possibly because of trapped air in asperities. Total Internal Reflection experiments, used to visualise the air pockets, confirmed the trapping of air at asperities. Diffusion of air out of the crevices seems to be the limiting factor for the utility of these surfaces in under-water applications.

Water droplets tend to bead up on rough or textured hydrophobic surfaces by trapping air on the crevices underneath resulting in “Cassie” state of wetting. When a textured hydrophobic surface is immersed in water, the resulting underwater “Cassie” state can lead to significant drag reduction. The entrapped air pockets act as shear free regions and the composite interface consisting of alternate no slip and no shear regions thus formed can deliver substantial drag reduction during flow. The magnitude of drag reduction depends not only on the fractional coverage of air on the surface, but also on the size of the air pockets, with larger sized air pockets facilitating larger drag reduction. It is a common observance that Lotus leaf when kept immersed in water for a few minutes loses its water repellency due to the loss of entrapped air on the surface. Underwater Cassie state on textured hydrophobic surfaces is also not sustainable because of the depletion of air pockets caused by the diffusion of trapped air into water. This causes the drag reduction to diminish with time. Rate of diffusion of air across the water–air interface depends on the concentration gradient of air across the interface. Under flow conditions, removal of entrapped air is further enhanced by convection, leading to more rapid shrinkage of the air pockets. In order to sustain the Cassie state, it is thus necessary to continuously supply air to these air pockets. In this work, we explore the possibility of supplying air to the cavities on the textured surface inside a microchannel by controlling the solubility of air in water close to the surface. The solubility is varied by i) Controlling the absolute pressure inside the channel and ii) Localized heating of the surface To trap uniform air pockets, a textured surface containing a regular array of blind holes is used. The textured surface is generated by photo etching of brass and is rendered hydrophobic through a self-assembled monolayer. The sustainability of the underwater Cassie state of wetting on the surface is studied at various flow conditions. The air trapped on the textured surface is visualized using total internal reflection based technique, with the pressure drop (or drag) being simultaneously measured. Water which is initially saturated with air at atmospheric conditions, when subjected to sub-atmospheric pressures within the channel becomes supersaturated causing the air bubbles to grow in size. Further growth causes the bubbles to merge and eventually detach from the surface. The growth and subsequent merging of the air bubbles leads to a substantial increase in the pressure drop because as the air pockets grow in size, they project into the flow and start obstructing the flow. On the other hand, a pressure above the atmospheric pressure within the channel makes the water undersaturated with air, leading to gradual shrinkage and eventual disappearance of air bubbles. In this case, the air bubbles do cause reduction in the pressure drop with the minimum pressure drop (or maximum drag reduction) occurring when the bubbles are flush with the surface. The rate of growth or decay of air bubbles is found to be significantly dependent on the absolute pressure in the channel. Hence by carefully controlling the absolute pressure, the Cassie state of wetting can be sustained for extended periods of time. A drag reduction of up to 15% was achieved and sustained for a period of over 5 hours. Temperature of water also influences the solubility of air in water with higher temperatures resulting in reduced solubility. Thus locally heating the textured hydrophobic surface causes the air bubbles to grow, with the rate of growth being dependent on the heat input. The effect of trapped air bubbles on thermal transport is also determined by measuring the heat transfer rate through the surface in the presence and absence of trapped air bubbles. Even though the trapped air bubbles do cause a reduction in the heat transfer coefficient by about 10%, a large pressure drop reduction of up to 15% obtained during the experiments helps in circumventing this disadvantage. Hence for the same pressure drop across the channel, the textured hydrophobic surface helps to augment the heat transfer rate. The experiments show that, by varying the solubility of air in water either by controlling the pressure or by local heating, underwater Cassie state of wetting can be sustained on textured hydrophobic surfaces, thus delivering up to 15% drag reduction in both cases for extended periods of time. The results obtained hold important implications towards achieving sustained drag reduction in microfluidic applications.

β-lactoglobulin (β-Lg), bovine serum albumin (BSA), α-lactalbumin (α-Lac), and β-casein were adsorbed onto silanized silica surfaces of low and high hydrophobicity for 8 h, and β-Lg and BSA for 1 h. The surfaces were incubated in buffer for 0, 5, 10, or 15 h and then contacted with Listeria monocytogenes for 3 h. Cell adhesion was quantified using image analysis. Following 8 h of protein contact, adhesion to both surfaces was greatest when β-Lg was present and lowest when BSA was present. Preadsorption of α-Lac and β-casein showed an intermediate effect on cell adhesion. Adsorption of β-Lg for 1 h resulted in lower numbers of cells adhered as compared to the 8 h adsorption time, while the opposite was observed with BSA, but adhesion to BSA was observed to decrease slowly with film age to values comparable to the 8 h tests. The adsorption of BSA and β-Lg to both surfaces was also carried out where each protein was allowed to contact the surface in sequence and simultaneously. In sequential tests performed with an 8 h contact/protein, cell numbers on each surface were near that expected for the bare hydrophobic surface when β-Lg contact preceded introduction of BSA, whereas adhesion was reduced to values below that expected for the bare hydrophilic surface when BSA preceded β-Lg contact. In short-term sequential tests (1 h contact/protein), adhesion was lower than that recorded on bare hydrophilic surfaces in each case. Adhesion to each surface following contact with an equimolar mixture of β-Lg and BSA was lower than that measured on the bare hydrophilic surface in each case, with adhesion following 1 h contact being greater than that following 8 h contact. Adhesion following competitive adsorption was greater to hydrophobic than to hydrophilic surfaces. These results were explained with reference to the surface passivating character of BSA, and its ability to rapidly attain a nonexchangeable state upon adsorption, relative to β-Lg. / Graduation date: 1995

Vegetation plays an important role in the partitioning, transport and fate of hydrophobic organic contaminants (HOCs) in the environment. This thesis aimed at addressing two key knowledge gaps in our understanding of how plants exchange HOCs with the atmosphere: (1) To improve our understanding of the uptake of HOCs into, and transfer through, leaves of different plant species which can significantly influence the transport and fate of HOCs in the environment; and (2) To evaluate an experimental approach to measure fluxes of HOCs in the field. The methods presented in papers I, II and III contribute to increasing our understanding of the fate and transport of HOCs in leaves by offering straightforward ways of measuring mass transfer coefficients through leaves and partition ratios of HOCs between leaves, leaf lipids and lipid standards and reference materials like water, air and olive oil. The passive dosing study in paper III in particular investigated the role of the composition of the organic matter extracted from leaves in determining the capacity of the leaves to hold chemicals and found no large differences between 7 different plant species, even though literature data on leaf/air partition ratios (Kleaf/air) varies over 1-3 orders of magnitude. In paper IV we demonstrated that the modified Bowen ratio method can be extended to measure fluxes of persistent organic pollutants (POPs) if the fluxes do not change direction over the course of the sampling period and are large enough to be measured. This approach thus makes it possible to measure fluxes of POPs that usually require sampling times of days to weeks to exceed method detection limits. The experimental methods described in this thesis have the potential to support improved parameterization of multimedia models, which can then be evaluated against fluxes measured in the field using the modified Bowen ratio approach. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>

Background: Despite the numerous pharmaceutical applications of alcohols andglycols, the interspecies differences with respect to their pharmacokinetics (PK) arepoorly understood. The aim of this research was to use in-vivo and in-vitro approaches to compare and model the PK characteristics across various species.Methods: Appropriate published in-vivo studies (in different species) foralcohols and glycols were carefully selected. PK analysis was performed using (a) noncompartmental analysis and (b) compartmental modeling to estimate relevant dose-independent PK parameters. Next, six alcohols (methanol, ethanol, 1 -propanol, 1 -butanol, 1-hexanol, and 1-octanol), two glycols (ethylene glycol and propylene glycol)and one secondary alcohol (2-propanol) were examined as in-vitro substrates for equine ADH using a UV spectrophotometric assay to evaluate the effect of molecular structure. Furthermore, in-vitro metabolism of ethanol and propylene glycol was also characterized in hepatic cytosolic fractions from rat, rabbit, dog and human and in-vitro in-vivo correlation for the hepatic disposition parameters was assessed. Finally, allometric scaling relationships for ethanol and propylene glycol PK parameters (in-vivo and in-vitro) were developed and validated.Results: Alcohols and glycols exhibited nonlinear PK due to saturable hepaticmetabolism in all species. The reported in-vivo data were well described by oneltwo compartment PK models with parallel saturable metabolism and first-order renalexcretion. In-vitro equine ADH experiments revealed differences in affinity andturnover between the substrates: Enzyme affinity (1/Km) and in-vitro intrinsic clearance (CLintin-vitro) correlated positively with logP values; glycols showed lower CLintin-vitro values than straight-chain alcohols. In-vitro hepatic cytosol studies yielded acceptable in-vivo predictions for the metabolic clearance (CLmet) of ethanol and propylene glycol in the rat, dog and human, but not the rabbit. Vdss, Vmax, CLintin-vitro, CLmet scaled allometrically across species with similar powers for both ethanol and propylene glycol, and good agreement between in-vivo and in-vitro scaling was noted. The allometric scaling models gave excellent predictions when externally validated against in-vivo concentration-time data. Conclusions: The present research demonstrates .the successful application of amodeling-based approach to elucidate interspecies relationships for alcohols andglycols, compounds which exhibit nonlinear PK and mainly low hepatic extractionbehavior. The in-vitro experimental systems have been used successfully forcharacterizing alcohol/glycol metabolism and predicting in-vivo disposition.