Micro/nano-patterning of supported lipid bilayers (SLBs) has shown considerable potential for addressing fundamental biophysical questions about cell membrane behavior and the creation of a new generation of biosensors. Herein are presented several novel lithographic methods for the size-controlled patterning of SLBs from the microscale to the nanoscale. Using these methods, chemically distinct types of phospholipid bilayers and/or Escherichia Coli (E. Coli) membranes can be spatially addressed on a single microchip. These arrays can, in turn, be employed in the studies of multivalent ligand-receptor interactions, enzyme kinetics, SLBs size limitation, and membrane-associated species separation. The investigations performed in the Laboratory for Biological Surface Science include the following projects. Chapters II and III describe the creation of lab-on-a-chip based platforms by patterning SLBs in microfluidic devices, which were employed in high throughput binding assays for multivalent ligand-receptor interactions between cholera toxin B subunits (CTB) and ganglioside GM1. The studies on the effect of ligand density for multivalent CTB-GM1 interactions revealed that the CTB-GM1 binding weakened with increasing GM1 density. Such a result can be explained by the clustering of GM1 on the supported phospholipid membranes, which in turn inhibits the binding of CTB. Chapter IV characterizes the enzymatic activity of phosphatase tethered to SLBs in a microfluidic device. Higher turnover rate and catalytic efficiency were observed at low enzyme surface densities, ascribing to the low steric crowding hindrance and high enzyme fluidity, as well as the resulting improvement of substrate accessibility and affinity of enzyme catalytic sites. Chapter V presents sub-100 nm patterning of supported biomembranes by atomic force microscopy (AFM) based nanoshaving lithography. Stable SLBs formed by this method have a lower size limit of ~ 55 nm in width. This size limit stems from a balance between a favorable bilayer adhesion energy and an unfavorable bilayer edge energy. Finally, chapter VI demonstrates the electrophoretic separation of membrane-associated fluorophores in polymer-cushioned lipid bilayers. This electrophoretic method was applied to the separation of membrane proteins in E. Coli ghost membranes.

This dissertation focuses on the study of inverse temperature transition processes of the poly(N-isopropylacrylamide) (PNIPAM) and the elastin-like polypeptides (ELPs). A novel temperature jump microfluidic system is introduced and this system shows the ability to measure the kinetics of the PNIPAM and the ELPs collapse without a heat transfer problem. The conformational change of the ELPs during the phase transition process is utilized as a nanoscale protein filter to modulate ligandreceptor binding events on supported lipid bilayers (SLBs). This research study is divided into three main parts. The first part is the development of the temperature jump microfluidics. The kinetics of PNIPAM collapse is used as a model system to show the capability of this new device to measure millisecond time scale phase transition processes. The effects of salts on the kinetics of PNIPAM collapse are also shown in this part. To our knowledge, this is the first study which shows the effects of salts on PNIPAM collapse kinetics. The second part of this research is the application of the novel temperature jump microfluidics. The hydrophobic collapse of ELPs composed of identical sequence but different chain length is investigated. By controlling the molecular weight of the ELPs, the thermodynamic contributions from intermolecular hydrophobic interactions, and intramolecular hydrophobic interactions could be calculated individually for this unique system. The third part is the application of the phase transition property of ELPs. The ELPs are conjugated on the surface of the SLBs as a nanoscale protein filter. The conformation of the ELPs can be modulated by ionic strength of the buffer solution or ambient temperature. The ELPs conjugated SLBs platform showed the ability to block IgG binding to biotin conjugated on the SLBs when the ELPs were in the extended coil state and open the access for protein to bind to biotin in compact globule conformation.

Thesis (doctoral)--Universität St. Gallen, 1999.

Thesis (doctoral)--Universität St. Gallen, 1998.

The reactions of the "clamshell" 1,2-bis(imino)acenaphthene (BIAN) ligand with decamethyleuropocene, boron triiodide, phosphorus triiodide, and tellurium tetraiodide have been investigated. The "clamshell" ligand undergoes one-electron reduction with decamethyleuropocene while treatment of this ligand with boron triiodide generates a BIAN-supported boron monoiodide via two-electron reduction. The reaction of the "clamshell" ligand with phosphorus triiodide involves a two-electron reduction of the BIAN backbone while that with tellurium tetraiodide yields a TeI2 complex without intermolecular charge transfer. / text

The market for local organic foods in the United States has grown tremendously in recent years. Compared to a meager existence just a decade ago, local organic options now flourish through the form of Community Supported Agriculture (CSA), thousands of farmers markets, community cooperative grocery stores, and upscale restaurants. Interestingly, the greatest percentage of growth in farmers markets in the US has occurred in the last 2-3 years during the Great Recession despite economic downturn. This changing nature of agriculture and new developments of alternative niche markets have captured the attention of scholars. Most studies tend to focus on economic, organizational, or even nutritional elements reflected in the food industry. Less emphasis, however, has been devoted to the roles of cultural consumption, values, and desires that have propagated the swift and substantial growth of this movement. Direct sales in local organic niche markets and the CSA model provide an atmosphere for repetitive interpersonal interaction between farmer and buyer around a product infused with shared meaning. I utilize ethnographic data from an extended case of a local organic farm in Southern Arizona and interviews with over 50 of their CSA members. This dissertation addresses how and why both producers and consumers co-produce alternative visions and meanings that sustain a viable local niche food economy. I argue that the members involved in this niche market sector hold unified reactions against the global expansionary aims of food corporations. Inverse to market forces, the cultural and economic ethos driving this movement originates from appreciation for craft production as an expression of commodity de-fetishization, personal investment and embeddedness in local economies, and desires for authenticity in community and consumption.

The work described here has focused on two types of supramolecular assemblies, supported lipid bilayers (SLBs) and giant vesicles (GVs) from polymerizable lipids. SLBs are explored extensively as structural models in biophysical studies of cell membranes and biosensor coatings. With regard to implementation as biocompatible scaffoldings for receptor-based molecular devices, fluid SLBs lack chemical, thermal and mechanical stability as lipids are self-organized by weak, noncovalent forces. One possible solution is to use synthetic lipid monomers that can be polymerized to form robust bilayers. A key question is how polymerization affects transmembrane protein structure and activity. Specifically it is unclear if lipid cross-linking can be achieved without adversely affecting the activity of incorporated proteins. In this work the effect of lipid polymerization on transmembrane protein activity was studied with rhodopsin. The protein was reconstituted into SLBs composed of polymerizable lipids, bis-SorbPC, bis-SorbPC:mono-SorbPC, bis-DenPC and bis-SorbPC:mono-SorbPE. Rhodopsin photoactivity was monitored using plasmon waveguide spectroscopy. The results show that reconstitution of rhodopsin into SLBs composed of phosphatidylcholine with the polymerizable moiety in the acyl chain terminus, followed by photoinduced cross-linking of the lipids, does not significantly perturb protein function. A possible explanation is that a bilayer with relatively low Xn retains sufficient elasticity to accommodate the membrane deformation that accompanies the conformational change associated with rhodopsin photoactivation when polymerized in the acyl chain terminus. GVs have diameters ranging from several to few hundred micrometers and thus can be observed by optical microscopic methods. This allows manipulation of individual vesicles and observation of their transformations in real time. GVs have attracted attention as microcontainers for enzymes and drugs, and as biosensors. With the aim of increasing stability for these types of applications, GVs were prepared from synthetic dienoyl lipids that can be polymerized to form robust vesicles. The stability of these vesicles after polymerization was investigated by surfactant treatment, drying and rehydration, and temperature variations. The structure of poly(GVs) was largely retained under these conditions which destroy unpolymerized vesicles. Permeability studies on poly(GVs) suggests that they could be potentially used in a variety of technological applications, including sensors, macromolecular carriers, and microreactors.

There is little evidence that Health Technology Assessment (HTA) is much used in dentistry. Dental implant technology is an example of innovative oral health technology. The objectives of this research were to gather the evidence needed for the assessment of overdenture implant treatment so that both patients and dental practitioners can make informed decisions about this technology. These objectives included 1) investigating what types of dental clinicians adopt and provide dental implants 2) determining the effect of the clinicians' experience in the provision of implant supported prostheses and 3) measuring the patients' preference in provision of mandibular 2-implants overdenture technology. / For the first part, a cross-sectional survey was sent to all licensed Canadian Dentists to measure the adoption and provision of implant technology. For the second part, we used the data on the first 140 edentulous elders who were enrolled in a randomized controlled clinical trial to compare the effects of mandibular conventional (CD) and 2-implant overdentures (IOD) on nutrition. The change in patient ratings of satisfaction after treatment, laboratory costs and the number of unscheduled visits were compared. For the last part, edentulous elders (N=36) who were wearing maxillary dentures and either a mandibular conventional denture (CD, n=13) or a two-implant overdenture (IOD, n=23) participated in this study. Participants' preference was measured during a 20-minute interview. / Multivariate regression analysis on the data from the first part of the study shows that the Dentist's gender, province of practice, specialty, and whether they practice alone or in association with other practitioners, are significantly associated with the adoption of implant technology (p<0.05). It is also shown that there was no difference in satisfaction scores for either prosthesis between the groups treated by experienced specialists or new dentists. Furthermore, it is shown that IOD wearers were willing to pay three times more than the current cost of conventional dentures for implant prostheses (p<0.05). / Overall, the results of this study 1) inform decision makers on what types of clinicians provide implant technology and 2) suggest that, with minimal training, all dental clinicians irrespective of their specialty, can provide successful implant overdenture prostheses that edentulous patients are willing to pay for.

This study investigates the participation patterns of employer-sponsored adult education and training by Swedish workers over the period of 1975 - 1995, and evaluates the importance of the determinants of such provision. The study also explores the ways participation experiences in employer-sponsored education and training influence subsequent participation, occupational mobility and economic outcomes for Swedish workers. Data collected from 1975 to 1995 in The Swedish Living Conditions Survey (ULF), both the cross-sectional data and its panel component, have been analyzed. Contained in the panel are 3,319 Swedish adults who have been followed up in the ULF from 1979 to 1995. The study employs measures of work and job characteristics such as indicators of occupational status, wage, union membership, length of employment, job type, job responsibilities, influence on decision-making at the workplace, learning opportunities at the workplace, enterprise ownership, as well measures of personal characteristics, such as age, gender, level of formal education. The approach taken in the evaluation of the influences of work, job and demographic characteristics on the likelihood of receiving employer-sponsored education and training has been to develop and estimate logistic regression models by means of which these effects during different periods (1975, 1979, 1986/7, 1994/5) can be assessed and compared. Another three models have been investigated, using the panel data, namely: (1) a logistic regression model predicting subsequent participation in employer-sponsored education and training by similar experiences at earlier career stages; (2) a multiple regression model predicting 1994/5 annual income with participation history as a predictor; (3) a discriminant function analytical model predicting 1994/5 occupational status with participation history as a discriminating variable. The departure point of this study is that separate analyses have been done with the public sector and private sector sub-data sets. The findings indicate that occupational status, level of education, age, gender and to a less extent, union membership, and other work and job characteristics are the more important predictors of the likelihood of participation in employersponsored education and training for the Swedish workers in the private sector. For those working in the public sector, institutional factors relating to management style and job responsibility as well as age play an important part in training decisions. The findings also indicate that youth and older age groups, particularly those with the private sector, have been consistently under-served by provision of employer-sponsored education and training throughout the period investigated. The results reveal that by the mid-1990s, gender was not a issue in the public sector in terms of the participation rate but female workers were still disadvantaged in the private sector. The findings verify a trend that the participation gaps between the well-educated and the undereducated, and those between professionals and non-skilled and semi-skilled have narrowed by a great magnitude, yet not adequately to close up the gaps. In 1975, the likelihood of participation for a professional worker was nine times as high as that for a non-skilled worker in the private sector. By 1995, the comparable figure was three times. The findings from panel data analysis show that, for workers in the private sector, their participation status as of the mid-1990s was significantly correlated with their participation status back in the mid-1980s and late 1970s, even after the statistical adjustment. For the public sector employees, their participation status as of the mid-1990s is related to participation status in the mid-1980s only. The results of income estimation models show that all three indicators of participation status are significantly associated with higher earnings, but a further analysis that separates the private sector from the public sector indicates that the result applied more in the case of the private sector employees. In contrast, none of the measures of participation status are significantly associated with higher earnings for employees with the public sector. The findings, as a result of discriminant function analysis, indicate that participation undertaken in the mid- 1980s, together with the earlier status of occupation and formal education background, form the first discriminant function that classify occupational status of 1994/5, explaining 54% of the explained variance.

No description available.