Gwendolyn A. Lawrie

Assessment of Course-Based Undergraduate Research Experiences: A Meeting Report

This report presents a summary of a meeting on assessment of course-based undergraduate research experiences (CUREs), including an operational definition of a CURE, a summary of research on CUREs, relevant findings from studies of undergraduate research internships, and recommendations for future research on and evaluation of CUREs.

Optical barcoding of colloidal suspensions: applications in genomics, proteomics and drug discovery

The enormous amount of information generated through sequencing of the human genome has increased demands for more economical and flexible alternatives in genomics, proteomics and drug discovery. Many companies and institutions have recognised the potential of increasing the size and complexity of chemical libraries by producing large chemical libraries on colloidal support beads. Since colloid-based compounds in a suspension are randomly located, an encoding system such as optical barcoding is required to permit rapid elucidation of the compound structures. We describe in this article innovative methods for optical barcoding of colloids for use as support beads in both combinatorial and non-combinatorial libraries. We focus in particular on the difficult problem of barcoding extremely large libraries, which if solved, will transform the manner in which genomics, proteomics and drug discovery research is currently performed.

Optical encoding of microbeads for gene screening: alternatives to microarrays

Abstract Rapid access to genetic information is central to the revolution presently occurring in the pharmaceutical industry, particularly in relation to novel drug target identification and drug development. Genetic variation, gene expression, gene function and gene structure are just some of the important research areas requiring efficient methods of DNA screening. Here, we highlight state-of-the-art techniques and devices for gene screening that promise cheaper and higher-throughput yields than currently achieved with DNA microarrays. We include an overview of existing and proposed bead-based strategies designed to dramatically increase the number of probes that can be interrogated in one assay. We focus, in particular, on the issue of encoding and/or decoding (bar-coding) large bead-based libraries for HTS.

The structure of mixed monolayer films of DPPC and hexadecanol

Abstract Although dipalmitoyl phosphatidycholine (DPPC) is the primary surface active component of natural lung surfactant (NLS), under physiological conditions it does not adsorb rapidly to the interface or respread efficiently or rapidly after compression beyond film collapse. Other materials must be present to enhance these functions and one synthetic exogenous surfactant used in replacement therapy mixes DPPC with hexadecanol and tyloxapol. In the present study the interactions of DPPC and hexadecanol in spread monolayers have been investigated by film balance measurements, and Brewster angle microscopy. Two phases can be observed when the surface pressure is low and the mole fraction of DPPC is high: a condensed phase of hexadecanol with some DPPC and an expanded phase. Increasing surface pressure generates a second condensed phase that is DPPC rich. On further compression the expanded phase disappears and the two condensed phases merge, but miscibility rules indicate that the expanded phases do not mix even though there is no evidence for two phases in the experimental data.

Atomic force microscopy studies of Bowen Basin coal macerals

The porous structure of Bowen Basin coal macerals is very important in the storage and transport of coal seam gases. As part of a full characterization of this porosity, several coal macerals were examined by atomic force microscopy. Mesopores of ≥ 8 nm deriving from different types of porosity were imaged. The pores were either formed by contact points between spherical clusters of molecules or were defined channels that had been created by some physical process. The potential of this technique for characterizing the porous structure in greater depth was demonstrated.

Synthesis and Application of FRET Nanoparticles in the Profiling of a Protease

A novel colloidal bar coding method utilizing nanoscale fluorescence resonance energy transfer (FRET) reporters decoded by confocal laser scanning microscopy combined with spectral unmixing, was reported. Succinimidyl ester dyes Atto-488, Atto-550, and Atto-590 were covalently linked to a silane coupling agent (3-aminopropyl)-trimethoxysilane, forming an APS-dye conjugate. The three dyes were incorporated into the reporters at five molar ratios. The reporters were loaded on 10μm amine functionalized polystyrene microspheres in eleven different combinations of between three and seven codes to evaluate the utility of the reporters to form a colloidal barcode. Following characterization, the reporters were used to encode a combinatorial peptide library that was applied to profiling the affinity of the West Nile flavivirus protease (WNV-pro). Varying the ratios of energy transfer dyes served as an innovative route to produce unique spectral signatures.

A structural study of hybrid organosilica materials for colloid-based DNA biosensors

Organosilane hybrid materials are of interest in the development of diagnostic devices and drug-delivery applications. Here we report a spectroscopic study involving the chemical and structural modification of thiol-functionalised organosilica particles with aminosilane to produce a bifunctional silica hybrid. The aminosilane was revealed to be distributed throughout the microsphere as opposed to being surface-localised as is commonly reported for modifications of pure silica. Spectroscopic methods including NMR, XPS, Ninhydrin and gravimetric measurements were employed to investigate the surface and internal elemental composition of the particles independently. A multiplexed model bioassay is presented to demonstrate the advantage of organosilane bifunctionality, enabling separate covalent attachment strategies for both homogeneous incorporation of fluorescent dyes and surface-specific biomolecule attachment. This study represents an advance in the understanding of organosilane chemistry resulting in versatile materials with a range of functionalities for covalent attachment.

Dimyristoyl phosphatidylcholine: equilibrium spreading behaviour

Abstract The equilibrium spreading behaviour of dimyristoyl phophatidylcholine has been studied at the air—water interface. The lipid was examined both as a dispersion (prepared by vortexing) and as the bulk solid (dropped onto the surface of water). The physical properties of the lipid in the aqueous media were examined by optical microscopy and cryo transmission electron microscopy. It was found that the nature of the sample was a key factor in the formation of a monolayer, spreading being dependent on the hydration of the bulk lipid and the formation of bilayers in the subphase. A model of bilayer formation is used to relate discrepancies in previously reported values of the equilibrium spreading pressure to a shift in the chain melting transition temperature Tm.

Interactions between Chitosan and Alginate Dialdehyde Biopolymers and Their Layer-by-Layer Assemblies

Biopolymers are researched extensively for their applications in biomaterials science and drug delivery including structures and complexes of more than one polymer. Chemical characterization of complexes formed between chitosan (CHI) and alginate dialdehyde (ADA) biopolymers established that while electrostatic interactions dominate (as determined from X-ray photoelectron spectroscopy (XPS)) covalent cross-linking between these biopolymers also contribute to their stability (evidenced from immersion in salt solution). It was furthermore found that imine bond formation could not be directly detected by any of the techniques XPS, FTIR, (1)H NMR, or fluorescence. The layer-by-layer assemblies of the biopolymers formed on silica colloids, glass slides, and alginate hydrogel beads were evaluated using XPS, as well as zeta potential measurements for the silica colloids and changes to hydration properties for the hydrogels. It was found that the degree of oxidation of ADA affected the LbL assemblies in terms of a greater degree of CHI penetration observed when using the more conformationally flexible biopolymer ADA (higher degree of oxidation).

Self-assembled films of dimyristoylphosphatidylcholine

Abstract Self-assembled films of dimyristoylphosphatidylcholine (DMPC) have been generated at the air/water interface and examined to identify structural characteristics. Powdered lipid, small unilamellar vesicles and multilamellar vesicles have been used as precursors to form interfacial films. Lipids were transported to the air/water interface either from the subphase dispersion or via a bridge from a remote reservoir. The isolation of the self-assembled film from the source of lipid molecules in the latter method has enabled studies of compressional behaviour and neutron reflectivity to be carried out directly at the interface, and for films to be deposited for atomic force microscopy. It was found that the structure of a DMPC self-assembled film was highly dependent on the lipid form from which the film was derived and also on the conditions of spreading. Self-assembled films derived from powder and multilamellar liposomes had bilayer structures associated with them. In contrast, the films formed from unilamellar vesicles behaved as isolated monolayers. The structure of the film formed by self-assembly from the powder form of the lipid was related to the surface pressure to which the film had been allowed to spread before transfer from the reservoir was interrupted.