Presenter 1: David Poger (Research Fellow, Mark group, SCMB)

Title: Tackling lipid diversity in membranes: the effect on membrane and protein functions

Abstract: Biological membranes regulate a myriad of cellular processes through the modulation of essential properties such as membrane fluidity and the formation of lipid microdomains. Such differences in turn affect the function of membranes and membrane proteins. The chemical and structural diversity of lipids is only being uncovered. For example, the repertoire of lipids in bacterial membranes is much broader than in eukaryotic membranes. In many if not most bacteria, membrane lipids include branched-chain fatty acids. Hopanoids have been identified in a range of bacteria. Branched-chain fatty acids have been proposed to protect membranes against hostile conditions and hopanoids have long been hypothesised to be surrogates of sterols, but, in fact, little is known about their actual effect on membranes. Using atomistic simulations, I showed that the different types of branching and hopanoids have specific effects on membrane fluidity and structure that allow bacteria to finely tune the sensitivity of their membranes to the environment. Furthermore, branched-chain lipids could affect the activity of commonly used disinfectants such as triclosan and para-chloroxylenol on membranes by modulating the interaction of the biocides with lipids and how deep they could insert into a membrane. The membrane composition also plays a critical role in the function of proteins. In simulations of the type-I cytokine receptors for growth hormone (GHR), prolactin (PRLR) and erythropoietin (EPOR) embedded in membranes, the presence of cholesterol altered the behaviour of the transmembrane domains, suggesting a key role of cholesterol in the mechanical coupling of the receptors through the plasma membrane upon receptor activation. The lipid composition is thus critical in the function of membrane and membrane proteins.

Bio: Dr David Poger is a structural biologist at the School of Chemistry & Molecular Biosciences in Prof Alan E. Mark’s group at UQ. His primary research interest lies in membrane biophysics focusing on understanding the properties, structure and function of biological membranes at the level of individual molecules and in larger architectures to address biological questions such as bacterial resilience and receptor activation in the promotion of cancer. His work has three major themes: i. the properties of membranes and lipids and their interaction with proteins, including antimicrobial peptides; ii. the properties of bacterial lipids (branched-chain lipids, hopanoids, sporulenes) that favour resilience and resistance in bacteria against unfavourable conditions (e.g. high concentration of toxic molecules including antibacterials and disinfectants); iii. the molecular mechanism of signal transduction by cytokine receptors.


Presenter 2: Haifei Zhan (Lecturer, LAMSES, QUT)

Title: Diamond Nanothread as a Novel Candidate for Nanofiber Application

Abstract: Carbon nanotube (CNT) fibers have been witnessed as emerging multifunctional nano-textiles in recent years. They have outstanding mechanical, chemical and physical properties and well over-perform traditional carbon and polymeric fibres. Various appealing applications have been proposed for CNT fibers, such as twist-spun yarn based artificial muscles which can respond to the electrical, chemical, or photonic excitations, aerospace electronics and field emission, intelligent textiles and structural composites. Very recently, a new type of ultrathin 1D carbon nanostructure – diamond nanothread (DNT), was synthesized through solid-state reaction of benzene under high-pressure. Similar to the hydrogenated (3,0) CNT, DNT has a hollow tubular structure, which is interrupted by Stone-Wales (SW) transformation defects. Encouraged by this experimental success, researchers found that there are different kinds of stable DNT structures through first principle calculations. Preliminary studies have shown that the DNTs with SW transformation defects have excellent mechanical properties, a high stiffness of about 850 GPa, and a large bending rigidity of about 5.35 × 10-28 N∙m2. Our following works reveal that the brittleness of DNTs can be changed via controlling the density of the SW transformation defects. With these excellent mechanical properties, ultrathin dimensions and a non-smooth surface (compared to CNT), it is of great interest to determine how DNTs can be used in fiber applications. Our study shows that DNT is ideal candidate for fiber applications. Not only do they possess excellent torsional deformation capability, they possess excellent interfacial load transfer efficiency.

Bio: Dr Haifei Zhan is a lecturer in QUT, whose main research interests are nanomechanics and nanoscale thermal transport through molecular dynamics simulations and first principle calculations. He works on varies advanced carbon-based nanomaterials, metallic nanomaterials, and nanocomposites. Dr Zhan is a core member of the Laboratory for Advanced Modelling and Simulation in Engineering and Science (LAMSES) at QUT, led by Professor Yuantong Gu.


AIBN Seminar Room