Three residues, Phe190, Leu193 and Val302, which have been proposed to define the S₁ site of prolidase of <i>Lactococcus lactis</i> NRRL B-1821 (<i>L. lactis</i> prolidase), may limit the size and polarity of specific substrates accepted by this enzyme (Yang, S. I., and Tanaka, T. 2008. Characterization of recombinant prolidase from <i>L. lactis</i> changes in substrate specificity by metal cations, and allosteric behavior of the peptidase. FEBS J. 275, 271-280). These residues form a hydrophobic pocket to determine the substrate specificity of <i>L. lactis</i> prolidase towards hydrophobic peptides, such as Leu-Pro and Phe-Pro, while little activity was observed for anionic Asp-Pro and Glu-Pro. It is hypothesized that the substrate specificity of <i>L. lactis</i> prolidase would be changed if these residues are substituted with hydrophilic amino acid residues individually or in combinations by site-directed mutagenesis (SDM). In addition to the changes in substrate specificity, other characteristics of wild type prolidase, such as allosteric behaviour and substrate inhibition may receive influences by the mutations (Yang & Tanaka, 2008). To test this hypothesis, mutations were conducted on these three residues at the S₁ site. Mutated <i>L. lactis</i> prolidases were subsequently analyzed in order to examine the roles of these residues in the substrate specificity, allosteric behaviour, pH dependency, thermal dependency and metal dependency of prolidase. The results showed the significant changes in these kinetic characteristics of single mutants, such as L193E, L193R, V302D and V302K and double mutants, L193E/V302D and L193R/V302D. Leu193 was suggested to be a key residue for substrate binding. The mutants L193R, V302D, L193R/V302D and L193E/V302D lost their allosteric behaviour, and the substrate inhibition of the wild type was no longer observed in V302D and L193E/V302D. The results indicated Val302 to be more important for these properties than other S₁ site residues. Moreover, together with the observations in molecular modelling of the mutants, it was proposed that interactions of Asp302 with Arg293 and His296 caused the loss of allosteric behaviour and substrate inhibition in the V302D mutant. The investigations on the pH dependency suggested that His296 acted as proton acceptor in <i>L. lactis</i> prolidase's catalysis. It was expected that the electrostatic microenvironment surrounding His296 was influenced by the charged mutated residues and side chains of dipeptide substrates, thus the protonation of His296 was affected. It was suggested that the introduced positive charge would stabilize the deprotonated form of His296 thus to maintain the activities of the mutants in more acidic condition compared to wild type prolidase. The study of thermal dependency revealed that all non-allosteric prolidases had higher optimum temperatures, suggesting that the loss of allosteric behaviour resulted in more rigid structures in these prolidases.

Ecosystems are disturbed to extract synthetic crude oil from the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada. Successful reclamation of mined oil sands sites depends on maximizing water storage and minimizing the potential for erosion. Soil water repellency in the AOSR affects undisturbed sites and consequently reclamation materials. Extreme water repellency may lead to low infiltration rates and hinder reclamation. There is a lack of information about the naturally occurring and pre-existing levels of soil water repellency in the AOSR. Thus, questions arise about the degree of naturally occurring water repellency and the potential for severe water repellency in reclamation soils. Studies were conducted on nine sites in the AOSR in the summers of 2008 and 2009. A range of undisturbed and reclaimed sites, as well as mineral and organic reclamation materials were examined. Five undisturbed Jack Pine stands (classified as A ecosites), four reclaimed sites and reclamation materials including mineral soil, peat and leaf and lichen covering the forest floor (LFH) were studied. For a comparison of methods, one grasslands site in central Saskatchewan was included. Mini and standard tension infiltrometers were compared as a means of measuring soil water repellency index (RI). There was strong variability in RI values between the infiltrometer methods. The mean RI values from the mini infiltrometers were higher than from the standard infiltrometer (9.61 and 3.46, respectively). The variability within sites dominated the variability in RI for the two methods. Despite these obvious trends, RI values between infiltrometer sizes were statistically different for only two individual sites. Increasing the number of sampling points in the second field season did not reduce the variability. The simpler, less expensive mini infiltrometer is as effective as the standard infiltrometer in measuring soil water repellency. This will enable more efficient and extensive monitoring of soil water repellency in reclaimed and undisturbed sites in the AOSR. Soil water repellency of reclaimed and undisturbed sites was investigated in situ using RI, the water droplet penetration time (WDPT) test, and the molarity of ethanol droplet (MED) test. These measures showed similar trends. Variability in soil water repellency was high at both reclaimed and undisturbed sites. The average RI value for the surface of reclaimed sites was higher than that of the subsurface at reclaimed sites; however, there were no statistical differences between RI values of surface reclaimed and undisturbed sites (P =0.213) due to high spatial variability. The critical water content (CWC) of reclamation materials was determined by measuring the contact angle (CA) and WDPT. Generally, CA and WDPT were inversely related to water content, though variability was high and the relationship between water content was weak. The clearest relationship between water repellency and water content was present for the mineral soil samples. Reclaimed mineral soil was generally wettable above gravimetric water contents of 5-10 %, while the coarse textured tarball affected materials were only subcritically water repellent. There was no relationship between water repellency and water content for peat and LFH. The degree of water repellency was statistically higher for peat materials with increasing decomposition levels. The average WDPT was 44, 128 and 217 s for fibric, mesic, and humic peat, respectively. With careful management and monitoring, water repellency may not be a major limitation to reclamation success. The mini tension infiltrometer is an effective method for monitoring soil water repellency in the AOSR.

In order to measure the thickness of a protein layer on a structured surface of silicon rubber, we have used ellipsometry and Fourier transform infrared (FTIR)-spectroscopy. The aim was to determine whether this type of measurement method can be used on protein layers or not. By hot-embossing a specific pattern of micrometre-sized pillars was created on the surface of the silicon rubber, which then was exposed to a phosphate buffer solution (PBS) containing human serum albumin (HSA) protein. FTIR measurements confirmed that proteins had attached to the surface. Ellipsometric studies were made and even though the protein layer was too thin to be measured, a simulation was made that revealed that a protein layer needs to be at least 1,5 nm to be measured properly with this method. We can also see that the protein molecules can get out of the solution, to find their way into the small pits of the samples.

Torrefaction has become a topic of interest in recent times not only because farmers could increase their income due to more farming activities for biomass feedstock demands but also it promotes opportunities for green job creation, provides alternative fuel source for coal fired plants, and contributes to greenhouse gas emission mitigation. Hence, this thesis explored the torrefaction behaviour of both herbaceous (switchgrass, miscanthus, wheat straw) and short rotation (willow) agricultural energy crops in terms of hydrophobicity, grindability and energy density. The lignocellulosic compositions of raw and treated switchgrass and bulk density of raw and treated miscanthus were also determined. Hence, the outcomes of these experimental investigations facilitated the development of a torrefaction definition. The research also studied the heat transfer mechanisms of torrefaction and developed mathematical models to simulate the heat generation profile due to the internal and spontaneous combustion of a cylindrically-shaped poplar wood. COMSOL modeling software was used to analyze and simulate the heat generation profiles that were closely similar to those from the experiments; hence led to a development of a correction factor to scale treatment inputs. / Thesis / OMAFRA HQP

The purpose of this study is to investigate the torrefaction and pelletization behavior, hydrophobicity, storage behavior, ash analysis on three different biomasses: one (willow pellets) from wood products, one (oat pellets) from agricultural products and one (poultry litter) from the non-lignocellulosic biomass products during the processes. Four different torrefaction temperatures from 200°C-300°C, at 10-60 minute residence times, 0%-2.4% oxygen concentration, were considered. Of these, 285°C for willow pellets, 270°C for oat pellets and 275°C for poultry litter were found to be optimum for hydrophobicity. Studies of XRD and SEM of biomass ash at 800°C, 900°C and 1000°C were also carried out. The aforementioned results indicate that torrefaction is a feasible alternative to improve energy properties of ordinary biomass and prevent moisture re-absorption during storage.

No description available.

Using both artificial and natural templates, biomimetic micro-structures are fabricated on conventional coating materials (epoxy and silicone elastomers) to mimic both artificial and natural templates through effective pattern transfer processes. The pattern transfer processes use a soft-polymer negative stamp, where the flexibility of the stamp allows for easy conformation to both flat and curved surfaces. Patterns have been successfully transferred as a rigid epoxy to complex surfaces or as a soft elastomer replica of a hydrophobic Trembling Aspen leaf. The hydrophobicity and friction behaviour of the resulting micro-patterned surfaces are systematically investigated, showing that surface patterning can be used as an effective way to improve hydrophobicity while reducing the surface adhesion and friction without a loss of the structural integrity or rigidity typical of epoxy coatings. The relative strength of the micro-pattern was determined through indentation testing in order to support the claim of a robust pattern on the micro-scale that is able to withstand the harsh environment of industrial application or weather exposure. With the well characterized patterned epoxy material fabricated and able to be transferred to many different surfaces, the potential for the patterned surface to act as an icephobic coating was pursued. The robustness of the epoxy material with the unique ability to coat surfaces that are typically unable to possess a micro-structure makes this coating an ideal candidate for large-scale icephobic application. The potential use of a micro-patterned epoxy coating is investigated against comparable surface coatings within an innovative experimental set-up to measure the relative ice-adhesion strength of different substrates. In characterizing the relative shear-force required to remove frozen water droplets from the coating surface at the interface, several variables and factors were explored. The addition of a surface pattern was found to impact the icephobic ability of several materials, where different materials with the same pattern were compared to identify that the surface energy of the substrate influences the icephobic nature of a surface. Moreover, previous studies that relate the water contact angle or hysteresis to ice-adhesion strength are questioned through a preliminary qualitative analysis of ice adhesion strength data. This work demonstrates a potential process for the utilization of biomimetic epoxy micro-patterns as an enhanced hydrophobic and icephobic option for large scale protective coatings.

Hydrophobicity is the generalized characteristic of non-polar substances that brings about their exclusion from aqueous phases. This property, entropic in its nature, drives key self-assembly and phase separation processes in water. Protein folding, the formation of DNA double helix, the existence of lipid bilayers and the wetting properties of leaf surfaces are all due to hydrophobic interactions. Inspired by Nature, we aimed to use hydrophobicity for creating novel and improved catalytic systems. (I) A number of fluorous amphiphilic star block-copolymers containing a tris(benzyltriazolylmethyl)amine motif have been prepared. These polymers assembled into well-defined nanostructures in water, and their mode of assembly could be controlled by changing the composition of the polymer. The polymers were used for enzyme-inspired catalysis of alcohol oxidation. (II) An enzyme-inspired catalytic system based on a rationally designed multifunctional surfactant was developed. The resulting micelles feature metal-binding sites and stable free radical moieties as well as fluorous pockets that attract and preconcentrate molecular oxygen. In the presence of copper ions, the micelles effect chemoselective aerobic alcohol oxidation under ambient conditions in water, a transformation that is challenging to achieve nonenzymatically. (III) Development of a facile means of photo/electrocatalytic water splitting is one of the main barriers to establishing of a solar hydrogen economy. Of the two half-reactions involved in splitting water into O2 and H2, water oxidation presents the most challenge due to its mechanistic complexity. A practical water oxidation catalyst must be highly active, yet inexpensive and indefinitely stable under harsh oxidative conditions. Here, I shall describe the synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine, (BimH)3. A wide range of catalysts differing in their electronic properties, surface affinity, and steric bulk was explored. We identified hydrophobicity as the key variable in mediating the catalytic competence of Co-(BimH)3 complexes. The change in this parameter correlates both with the conformational mobility of the ligand core and the structural changes in the local solvent environment around the catalytic metal site. The optimal ligand identified is superhydrophobic due to three fluorinated side chains. The corresponding Co complex catalyzes water electrooxidation efficiently, with an onset potential equal to that for the well-established CoPi heterogeneous system, albeit with a dramatically higher turnover frequency (TOF) and in the absence of soluble Co salts. As an added benefit, the hydrophobic catalyst can be immobilized through physisorption, and remains stable after prolonged controlled-potential electrolysis. A DFT calculation was also performed to understand the catalytic pathway.

No description available.

Four casein-derived peptides fractions of varying hydrophobicity were obtained from á-chymotryptic digest of acid casein using hydrophobic interaction chromatography, termed fractions one through four (abbreviated, F1, F2, F3, and F4). Four standard methods involving alkoxyl, peroxyl, 2, 2-diphenyl-1-picrylhydrazl (DPPH), and 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) ABTS•+ radicals, were used to measure antioxidative properties. While significantly superior efficacy was exhibited by F2 for all tests except against DPPH, no correlation between antioxidant efficacy and surface hydrophobicity was found. By using capillary electrophoresis and high performance liquid chromatography, the detection of aromatic chromophores by ultraviolet at 280 nm in the fractions revealed that F2 contained the highest concentration of aromatic amino acids and a unique peptide. Result from circular dichroism exhibited remaining residual structure in F2 compared with undigested casein. The F2 possesses a high potential to be used in food industry as a natural source of antioxidant with pronounced antioxidant capacity.