The interaction of a bubble with solid surfaces, hydrophobic and hydrophilic, was investigated. When a bubble approaches towards a solid surface, a thin liquid film forms between them. The liquid in the film drains until an instability forms and film ruptures resulting in a three phase contact (TPC). Following rupture, the TPC line spreads on the solid surface. In the present study, glycerol-water solutions with varying percentages of water were used to investigate the effect of viscosity. Experiments were carried out with varying bubble size. The rupture and TPC line movement were recorded by high-speed digital video camera. The dependence of the TPC line movement on different parameters was investigated. The experimental results were compared with the existing theories for the TPC line movement. An empirical equation was developed to predict the TPC line movement. Formation or rupturing of the intervening film in case of a hydrophilic surfaces, which were glass surface cleaned by six cleaning techniques, was investigated. It was shown that a stable film forms for acid or alkali cleaning.

College level science is frequently taught as a recitation of facts in a lecture hall, and the students are expected to gain understanding and insight with their own study. Interactive learning is more effective than lecture based learning and more memorable for the students. Teaching with hands on models has been shown to specifically be beneficial in a college level molecular biology context. Included here is a guide for the instructor leading her through topic selection, activity development, and presentation to the class, as well as five complete and tested lesson plans with notes on alteration made and the reasons for them. / text

The overall objective of the present study was to evaluate the effectiveness of using a variety of hydrophobic biopolymers and hydrophobic biopolymer-coated sands as technically and economically feasible in-situ sediment amendments or alternative capping materials on a laboratory scale. Cutin from tomato peels, cellulolytic enzyme lignin from sitka spruce chips, and keratin azure from commercially dyed sheeps wool were isolated, prepared, tested, and evaluated as feasible hydrophobic biopolymers for the removal of selected Polycyclic Aromatic Hydrocarbons (PAHs). Testing included chemical and physical characterization, as well as the measurement of kinetics and equilibrium sorption parameters for the sorbates naphthalene, phenanthrene, and pyrene as model hydrophobic organic contaminants. Tomato peel cutin exhibited the largest overall affinity for PAHs, however, keratin azure was selected for further evaluation as the most feasible material due to its low preparation cost. Amendment of industrial sand with a stable, uniform, cross-linked keratin azure derivative was achieved to produce hydrophobic biopolymer-coated sand products containing zero, moderate, and high mass fractions of sand. Chemical and physical material parameters, as well as kinetics and equilibrium sorption parameters for the sorbates naphthalene, phenanthrene, and pyrene, were then obtained for the coated sand products. This allowed simple finite difference modeling of PAH fate and transport through a thin cap comprised of the same, insight into the specific sorption mechanisms involved, and information which could prove useful in predicting potential of keratin products to provide a suitable capping material. Conclusions and recommendations for future research focus on the technical and economical feasibility of the prepared hydrophobic biopolymers and hydrophobic biopolymer-coated sand products as capping or in-situ sediment amendments. / text

Most amino acid sequences are predicted to specify a single three-dimensional protein structure. However, the identification of "metamorphic" proteins, which can adopt two folds from a single amino acid sequence, has challenged the one sequence/one structure paradigm. Polar-to-hydrophobic substitutions have been suggested computationally as one mechanism to decrease structural specificity, allowing the population of novel folds. Here, we experimentally investigate the role of polar-to-hydrophobic substitutions on structural specificity in the homodimeric ribbon-helix-helix protein Arc repressor. Previous work showed that a single polar-to-hydrophobic surface substitution in the strand region of Arc repressor (Arc-N11L) populates the wild-type fold and a novel dimeric "switch" fold. In this work, we investigate an Arc repressor variant with the N11L substitution plus two additional polar-to-hydrophobic surface substitutions (Arc-S-VLV). We determine that this sequence folds into at least three structures: both dimer forms present in Arc-N11L, and a novel octamer structure containing higher stability and less helicity than the dimer folds. We are able to isolate and stabilize a core of the S-VLV octamer by limited trypsinolysis and deletion mutagenesis (Arc-VLV 4-44). The shortened construct contains only the octameric structure by removing disordered C-terminal segments nonessential for this fold. A two-dimensional NMR spectrum of VLV 4-44 and subsequent trypsinolysis of this construct suggests that at least two types of subunits comprise the S-VLV octamer: subunits structured from residues 4 to 44 and subunits structured from residues 4 to 31. Crystal trials of trypsinolyzed Arc-VLV 4-44 yielded several leads, suggesting that obtaining a high resolution structure of the S-VLV octamer is possible. Relatedly, we determine that the proline residues flanking the Arc repressor strand act in concert as "gatekeepers" to prevent aggregation in the S-VLV sequence. We also find that three highly hydrophobic surface substitutions in the Arc repressor strand region are necessary and sufficient to promote higher-order oligomer formation. In summation, this work reveals in an experimental context that progressive increases in polar-to-hydrophobic surface substitutions populate increasingly diverse, structurally degenerate folds. These results suggest that "metamorphic" as well as "polymetamorphic" proteins, which adopt numerous folds, are possible outcomes for a single protein sequence.

The practical applications of surfactant solutions in confined geometries require a thorough understanding of the system properties. Coarse-grained simulation techniques are useful for studying the qualitative behaviour of these systems, whereas the atomistic molecular dynamics (MD) technique can be used to obtain a molecular-level description. In this work, canonical MD simulations were performed using GROMACS version 4.0 to investigate the self-assembling behaviour of sodium octanoate (SO) confined between two parallel walls. In particular, the effects of gap size, wall type, and surfactant concentrations on the morphology of the surfactant aggregates were studied to gain in-depth knowledge of the system. The simulation results reveal that the morphology of the micelles formed between two parallel walls are affected not only by the gap size and surfactant concentration, but also by the nature and characteristics of the confining walls. With the graphite walls, most octanoate molecules are adsorbed at lower concentrations, but they form micellar aggregates as the surfactant concentration increases. Spherical micelles were found in the larger gaps (4 nm and 5 nm) but not in the smaller gap (3 nm), and the micellar shape also changes with increasing surfactant concentration. SO forms bilayer structures instead of spherical micelles between two silica walls. Interestingly, in the hydrophilic silica confinement, the orientation of these bilayers changes with gap sizes, whereas in the hydrophobic silica confinement, these bilayers remain perpendicular to the wall in all cases. Potentials of mean force between different molecules and atomic groups were determined under different conditions in order to develop a better understanding of the simulation results. It reveals, the presence of the confinement can alter the intermolecular interactions among the surfactant molecules, which, in turn, directly affects the self-assembling process, particularly the size and shape of the aggregates. Indeed, the formation of bilayers in silica wall confinement, as opposed to spherical micelles in graphite confinement, is caused by the enhanced electrostatic interactions between the charged atoms in the solution. The results of this study are expected to provide further insight into the self-assembling behaviour of confined surfactant systems, and may ultimately lead to the development of novel nanomaterials.

Wood is used for many applications because of its excellent mechanical properties, relative abundance and as it is a renewable resource. However, its wider utilization as an engineering material is limited because it swells and shrinks upon moisture changes and is susceptible to degradation by microorganisms and/or insects. Chemical modifications of wood have been shown to improve dimensional stability, water repellence and/or durability, thus increasing potential service-life of wood materials. However current treatments are limited because it is difficult to introduce and fix such modifications deep inside the tissue and cell wall. Within the scope of this thesis, novel chemical modification methods of wood cell walls were developed to improve both dimensional stability and water repellence of wood material. These methods were partly inspired by the heartwood formation in living trees, a process, that for some species results in an insertion of hydrophobic chemical substances into the cell walls of already dead wood cells, In the first part of this thesis a chemistry to modify wood cell walls was used, which was inspired by the natural process of heartwood formation. Commercially available hydrophobic flavonoid molecules were effectively inserted in the cell walls of spruce, a softwood species with low natural durability, after a tosylation treatment to obtain “artificial heartwood”. Flavonoid inserted cell walls show a reduced moisture absorption, resulting in better dimensional stability, water repellency and increased hardness. This approach was quite different compared to established modifications which mainly address hydroxyl groups of cell wall polymers with hydrophilic substances. In the second part of the work in-situ styrene polymerization inside the tosylated cell walls was studied. It is known that there is a weak adhesion between hydrophobic polymers and hydrophilic cell wall components. The hydrophobic styrene monomers were inserted into the tosylated wood cell walls for further polymerization to form polystyrene in the cell walls, which increased the dimensional stability of the bulk wood material and reduced water uptake of the cell walls considerably when compared to controls. In the third part of the work, grafting of another hydrophobic and also biodegradable polymer, poly(ɛ-caprolactone) in the wood cell walls by ring opening polymerization of ɛ-caprolactone was studied at mild temperatures. Results indicated that polycaprolactone attached into the cell walls, caused permanent swelling of the cell walls up to 5%. Dimensional stability of the bulk wood material increased 40% and water absorption reduced more than 35%. A fully biodegradable and hydrophobized wood material was obtained with this method which reduces disposal problem of the modified wood materials and has improved properties to extend the material’s service-life. Starting from a bio-inspired approach which showed great promise as an alternative to standard cell wall modifications we showed the possibility of inserting hydrophobic molecules in the cell walls and supported this fact with in-situ styrene and ɛ-caprolactone polymerization into the cell walls. It was shown in this thesis that despite the extensive knowledge and long history of using wood as a material there is still room for novel chemical modifications which could have a high impact on improving wood properties. / Der nachwachsende Rohstoff Holz wird aufgrund seiner guten mechanischen Eigenschaften und der leichten Verfügbarkeit für viele Anwendungszwecke genutzt. Quellen und Schrumpfen bei Feuchtigkeitsänderungen des hygroskopischen Werkstoffs Holz limitieren jedoch die Einsatzmöglichkeiten. Ein weiteres Problem stellt der mitunter leichte Abbau – u.a. bei feuchtem Holz - durch Mikroorganismen und/oder Insekten dar. Durch chemische Modifizierungen können die Dimensionsstabilität, die Hydrophobizität und die Dauerhaftigkeit verbessert und damit die potentielle Lebensdauer des Werkstoffes erhöht werden. Dabei ist die dauerhafte Modifikation der Zellwand nur äußerst schwer realisierbar. Inspiriert von der Kernholzbildung in lebenden Bäumen, ein zellwandverändernder Prozess, der Jahre nach der Holzbildung erfolgt, wurden im Rahmen dieser Arbeit neue Ansätze zur chemischen Modifizierung der Zellwände entwickelt, um die Dimensionsstabilität und Hydrophobizität zu erhöhen. Der erste Teil der Arbeit ist stark vom Prozess der Kernholzbildung inspiriert, eine abgeleitete Chemie wurde verwendet, um die Zellwände von Fichte, einem Nadelholz von geringer natürlicher Dauerhaftigkeit, zu modifizieren. Kommerziell verfügbare hydrophobe Flavonoide wurden nach einem Tosylierungsschritt erfolgreich in die Zellwand eingebracht, um so „artifizielles Kernholz“ zu erzeugen. Die modifizierten Holzproben zeigten eine verringerte Wasseraufnahme, die zu erhöhter Dimensionsstabilität und Härte führte. Dieser Ansatz unterscheidet sich grundlegend von bereits etablierten Modifikationen, die hauptsächlich hypdrophile Substanzen an die Hydroxylgruppen der Zellwand anlagern. Der zweite Teil der Arbeit beschäftigt sich mit der Polymerisation von Styren in tosylierten Zellwänden. Es ist bekannt, dass es nur eine schwache Adhäsion zwischen den hydrophoben Polymeren und den hydrophilen Zellwandkomponenten gibt. Die hydrophoben Styren-Monomere wurden in die tosylierte Zellwand eingebracht und zu Polystyren polymerisiert. Wie bei der Modifikation mit Flavonoiden konnte eine erhöhte Dimensionsstabilität und reduzierte Wasseraufnahme der Zellwände beobachtet werden. Im dritten Teil der Arbeit wurde das biologisch abbaubare, hydrophobe poly(ɛ-caprolacton) in der Zellwand aufpolymerisiert. Die Ergebnisse deuten darauf hin, dass Polycaprolacton in der Zellwand gebunden ist und zu einer permanenten Quellung führt (bis zu 5 %). Die Dimensionsstabilität nahm um 40 % zu und die Wasseraufnahmerate konnte um mehr als 35 % reduziert werden. Mit dieser Methode kann nicht nur dimensionsstabileres Holz realisiert werden, auch biologische Abbaubarkeit und damit eine einfache Entsorgung sind gewährleistest.

Current diagnostic and therapeutic nanocarriers, including liposomes, micelles, and polymeric- and protein-based nanoparticles, are designed to have key functional properties such as: (i) longevity in the bloodstream, leading to accumulation of therapeutic cargos in neoplastic areas with leaky vasculatures; (ii) targeting of specific pathological sites through surface modification with targeting ligands; (iii) stimuli-responsive characteristics for controlled drug release under specific conditions. While some of these drug delivery systems have advanced into clinical stages, other nanocarriers remain under development to overcome issues with effective delivery such as lack of target-ability and fast clearance from circulation. Self-assembling peptides have recently shown great potential as nanocarrier materials for drug and gene delivery, owing to their safety, efficiency, and targeting capabilities. An amino acid pairing strategy enables us to design self/co-assembling peptides with multiple functionalities to fulfill drug delivery requirements. This thesis focuses on functionalization and characterization of self/co-assembling peptides as nanocarriers for hydrophobic anticancer drug delivery. Diethylene glycol (DEG) conjugation and protein binding are the two modification strategies used in this thesis to impart longevity and target-ability upon the peptide-based delivery system. The studies include: (i) characterization of self-assembling properties of the diethylene glycol (DEG)-conjugated amino acid pairing peptide AAP8, (ii) investigation of the self/co-assembling features of a model ionic-complementary peptide (EAR8-II) in complex with the hydrophobic drug pirarubicin, and the anticancer activity of the complex, (iii) the interactions between peptide-drug complexes and serum proteins from the thermodynamic viewpoint, (iv) quantification of the effect of protein binding to the peptide-based delivery system on immune responses and biocompatibility, and (v) exploration of the targeting capability of albumin-bound peptide-drug complexes towards lung cancer cells. Uncontrollable aggregation of AAP8 was the first issue to address in order to develop a promising platform for the peptide-based delivery system. Diethylene glycol (DEG), a short segment of polyethylene glycol (PEG), was conjugated to AAP8 either at one or both terminals, and then self-assembling and drug encapsulation properties of both functionalized AAP8s were characterized to evaluate the effect of DEG-modification. The results illustrated a significant reduction in uncontrollable aggregation, and the formation of uniform fibular nanostructures. In addition, DEG conjugation provided the peptide with safer features towards immune cells by reducing cellular toxicity to macrophages. Moreover, DEG-functionalization improved hydrophobic drug stabilization, as demonstrated by sustained cytotoxic efficacy against lung carcinoma cells over a relatively long time compared to the non-functionalized AAP8. Protein binding strategy was the second approach to utilize the peptide-based delivery system with more biocompatibility and target-ability features. EAR8-II was studied as a model ionic-complementary peptide with high capability of pirarubicin encapsulation and anticancer activities against different cancer cells. Albumin as a most abundant protein in serum was selected to assess its binding affinity to the delivery system, and evaluate its binding effect on immune responses and anticancer activities. The results showed a central role of albumin in the in vitro delivery of peptide-drug complexes to target lung cancer cells based on the following characteristics: (a) Non-covalent binding of albumin to the complex through hydrogen bonding and Van der Waals interactions. The interaction was confirmed by physicochemical methods such as fluorescence quenching and isothermal titration calorimeter (ITC). (b) Shielding properties of albumin for the complex against macrophages and blood components (erythrocytes and complement protein C5b-9). In the presence of albumin, phagocytosis and cytokine expression level of macrophages and hemolytic activity of the peptide-drug complex reduced significantly due to the smaller particle size of the albumin-bound complexes compared to unprotected ones. (c) Targeting the lung cancer cells, possibly because of the inhibition of the albumin-binding protein SPARC (secreted protein, acidic and rich in cysteine). SPARC is a glycoprotein over expressed in lung cancer cells with high affinity to albumin. The results from in vitro SPARC expression in A549 cells, a type of human non-small cell lung carcinoma (NSCLC), showed a significant drop by the albumin-bound complex at the mRNA level evaluated by qRT-PCR. This effect can be explained by transporting the albumin-bound complex into the cell surface, binding to the SPARC proteins, and so inhibiting the SPARC expressions. This work lays out a foundation for modification and characterization of the self/co-assembly peptide-based nanocarriers for hydrophobic anticancer drug delivery, especially to improve longevity and target-ability properties.

The cryopreservation of cells and tissues requires the addition of a cryoprotectant in order to prevent cellular damage caused by ice. Unfortunately, common cryoprotectants such as DMSO and glycerol exhibit significant toxicity which makes their use unfeasible for many clinical procedures. Our laboratory is interested in the development of alternative, non-toxic cryoprotectants which possess ice recrystallization inhibition (IRI) activity. Potent IRI activity has recently been discovered in certain small molecules, but the structural features required for this process are unclear. Herein we report the development of a library of O-aryl glycosides in order to probe the importance of electron density and hydrophobic moieties for IRI activity. It was found that the degree of electron density at the anomeric oxygen does not correlate with IRI ability in para-substituted aryl glycosides, nor does changing the position of the aryl substituent impart a predictable effect on activity. However, the addition of hydrophobic alkyl or acyl chains was beneficial for IRI activity; generally, increasing chain length was found to correlate with increasing activity. In some instances, an optimal alkyl chain length was identified, after which continued lengthening results in a loss of potency. We conclude from this study that a certain extent of hydrophobic character is beneficial for the IRI activity of aryl glycosides, and that a balance between hydrophobicity and hydrophilicity is required for optimum IRI ability. It is hoped that these findings will aid future efforts towards the rational design of novel cryoprotectants.

The recognition of modified amino acids by reader proteins is governed by the competing interplay of weak, attractive, intermolecular forces and solvation effects. For the recognition of hydrophobic cations like methyl-lysines and methyl-arginines, native reader proteins utilize structural cages always containing multiple aromatic amino acids and sometimes an occasional acidic residue. Through the highly ordered arrangement of multiple aromatic surfaces, reader proteins can invoke the attractive forces of electrostatic, cation-pi, and in the case of arginine, pi-pi interactions. The hydrophobic effect can also significantly affect these binding events in aqueous environments. In this thesis, a number of small molecule, synthetic cages containing significant aromatic surface area have been synthesized. Variation in both total host hydrophobicity and degree of flexibility were explored to determine what effect they have on the overall binding of methylated amino acids in water. Significant flexibility in the first generation of highly aromatic hosts was shown to be detrimental to binding. However, strong binding was observed for guests with significant hydrophobic character despite this flexibility. The cause of the strong affinities in this family of synthetic cages was shown to be due to the hydrophobic effect, rather than any attraction due to cation-pi interactions. Synthetic efforts towards hosts with more rigid structures led to the use of Tröger’s base as a structural building block. Hosts incorporating Tröger’s bases into well-defined aromatic cavities were found to exhibit strong binding to both methyl-lysine and methyl-arginine derivatives in pure water. Differences in guest selectivity were due to the rigid altered host geometry introduced by the Tröger’s base cleft. / Graduate

In our study, the superhydrophobic surface based on biomimetic lotus leave is explored to maintain the desired properties for self-cleaning. In controlling bead-up and roll-off characteristics of water droplets the contact angle and contact angle hysteresis were very important and we investigated the determining conditions on different model surfaces with micro- and nanostructures. Two governing equations were proposed, one for contact angle based on Laplace pressure and one for contact angle hysteresis based on Young-Dupré equation. Based on these understanding on superhydrophobicity, possible applications of the superhydrophobicity for self-cleaning and water repellency were explored and application related technical issues were addressed. Based on our understanding of the roughness effect on superhydrophobicity (both contact angle and hysteresis), structured surfaces from polybutadiene, polyurethane, silica, and Si etc were successfully prepared. For engineering applications of superhydrophobic surfaces, stability issues regarding UV, mechanical robustness and humid environment need to be investigated. Among these factors, UV stability is the first one to be studied. Silica surfaces with excellent UV stability were prepared. UV stability on the surface currently is 5,500 h according the standard test method of ASTM D 4329. No degradation on surface superhydrophobicity was observed. New methods for preparing superhydrophobic and transparent silica surfaces were investigated using urea-choline chloride eutectic liquid to generate fine roughness and reduce the cost for preparation of surface structures. Another possible application for self-cleaning in photovoltaic panels was investigated on Si surfaces by construction of the two-scale rough structures followed by fluoroalkyl silane treatment. Regarding the mechanical robustness, epoxy-silica superhydrophobic surfaces were prepared by O2 plasma etching to generate enough surface roughness of silica spheres followed by fluoroalkyl silane treatment. A robustness test method was proposed and the test results showed that the surface is among the most robust surfaces for the superhydrophobic surfaces we prepared and currently reported in literature.