Waterloo Soft Matter Theory 2013
Collagen is the main component of connective tissue and the most abundant protein in mammals. The structure of collagen is hierarchical with the triple-helical molecules organizing into fibrils and fibrils contained in higher-order arrangements. A fibril may be considered as a liquid crystal of individual triple helices. Their chiral molecular structure can lead to a macroscopic helical arrangement known as the cholesteric phase which has been observed in fragments of collagen fibrils. The cholesteric orientation can vary with radial distance in the fibril as a double twist.
Lipid bilayers form the basic structure of cellular membranes creating a semi-permeable barrier necessary for separating distinct chemical environments. Hydrophilic pores can form in bilayers that breach the barrier potentially causing cell death or enhance the uptake of hydrophilic molecules. We use molecular dynamics simulations and free energy calculations to investigate pore formation in model bilayers. The free energy barrier for pore formation is much lower in thinner phosphatidylcholine bilayers compared to thicker bilayers.
Recently there has been a large growth of research effort for nanoelectronic devices.Investigations of quantumly coherent nano-meter scale systems whose fabrication has been made possible by recent advances in experimental and sample preparation techniques have revealed that transport properties could be non-Ohmic and G could be quantized. Understanding electron conduction in such devices is an extremely active research topic.
Antimicrobial peptides (AMPs) are known to be active against a wide range of microbes. Cell selectivity is an important quality of AMPs which enables them to preferentially bind to and kill the microbes over host cells. Despite its significance in determining the cell selectivity however the cell-concentration dependence of AMP activity has not been criticality examined. Here we present a coarse-grained model for describing how cell concentrations are implicated in AMP's membrane-perturbing activity and selectivity.
C. elegans is a millimeter-sized nematode which has served as a model organism in biology for several decades primarily due to its simple anatomy. Using an undulatory form of locomotion this worm is capable of propelling itself through various media. Due to the small length scales involved swimming in this regime is qualitatively different from macroscopic locomotion because the swimmers can be considered to have no inertia. In order to understand the microswimming that this worm exhibits it is crucial to determine the viscous forces experienced during its motion.
Undulatory motion is utilized by crawlers and swimmers such as snakes and sperm at length scales spanning more than seven orders of magnitude. The understanding of this highly efficient form of locomotion requires an experimental characterisation of the passive material properties of the organism as well as of its active force output on the surrounding medium. The millimeter-sized nematode Caenorhabditis elegans provides an excellent biophysical system for both static and dynamic biomechanical studies.
We simulated Ni disc immersed in a liquid crystal using a lattice Boltzmann algorithm for liquid crystals. In the absence of external torques discs with homeotropic anchoring align with their surface normal parallel to the director of the nematic liquid crystal. In the presence of a weak magnetic field (
In eukaryotic organisms, DNA replication is initiated at “origins,” launching “forks” that spread bidirectionally to replicate the genome. The distribution and firing rate of these origins and the fork progression velocity form the “replication program.” With Antoine Baker, I generalize a stochastic model of DNA replication to allow for space and time variations in origin-initiation rates, characterized by a function I(x,t). We then address the inverse problem of inferring I(x,t) from experimental data concerning replication in cell populations.
This talk will focus on the behavior of colloidal crystals, and will describe both the nucleation and growth of crystals and their melting. The nucleation and growth of colloidal crystals is experimentally observed to be much faster than expected theoretically or through simulation. The discrepancy can be as much as 10150! I will describe some new experiments that suggest a possible reason for this. I will also describe the melting of colloidal crystals formed with highly charged particles that form a Wigner lattice.