Research

Biomembranes

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This is an image of the chemical structure of 1,2-dipalmitoylgalloylglycerol (DPGG)

Chemical structure of 1,2-dipalmitoylgalloylglycerol (DPGG)

Interfacial interactions govern many important biological processes, e.g. enzyme activity, transmembrane signaling and membrane structure. Lipid monolayers and bilayers provide well-defined model systems for examining lipid-lipid miscibility and lipid-protein interactions. Our recent work has focused on the structural parameters governing lipid behaviour and miscibility, however we are also interested in lipid-protein interactions. The specificity of this molecular recognition is complex and can depend not only on the presence of certain components but also on their orientation, conformation and localization.

Work continues on the phosphoinositide (PI) lipids a minor group of membrane lipids yet play a key role in signal transduction. It has been reported that these lipids are localized into rafts which induces sufficient local concentrations for them to interact preferentially with proteins. We are investigating the conditions under which PIs form lipid rafts by investigating their phase behaviour and miscibility properties. The role of structure and weak interactions in governing lipid phase behaviour and miscibility have led us to the study of lipid with strong potential hydrogen bonding capabilities. We have synthesized a family of polyphenolic lipid molecules with systematic variation in the number and position of hydroxyl groups which yields methodical variation of hydrogen bonding capacity. Furthermore polyphenolic compounds are found in a vast array of natural systems and are known to interact with other biomolecules through hydrogen bonding and in particular they can bind/precipitate proteins. Understanding how such biomolecules interact with each other not only provides insight into structure-function relationships in biological systems but enables the design of molecules for bioapplications (see Design of functional materials).

Our recent work on the ozonolysis of atmospheric aerosols has led us to study the influence of ozone on the properties and functioning of lung surfactant. Ozone is also known to be a powerful respiratory irritant and the extent of damage to lung surfactant due to increased levels of ozone, in particular in smog and pollution, has yet to be quantified from a molecular perspective. Given the proportion of unsaturated lipid in lung surfactant it is likely that processing and oxidation of these lipids due to ozone exposure may significantly affect their rheological properties which allow them to carry out their biological function. Therefore, we seek use model membranes to quantify the effect of ozone exposure on the dilational rheology of these films in order to address the roles of ozone pollution on human health.

Finally we are interested in the mechanism of action of both synthetic and natural antimicrobial peptides/protein (AMPs) for the development of new antibiotics. Adsorption kinetics and selectivity are both important for AMPs, the former important as a fast-acting AMP reduces the ability of bacteria to build up resistance and the latter in order to selectively target bacterial and not mammalian cells. The selectivity is dependent on the nature of the surface interactions. We are studying the specificity of protein and peptides with demonstrated antimicrobial activity with regards to their binding to, penetration and disruption of lipid monolayers and bilayers.


 

Concordia University