![[University of Cambridge]](graphics/identifier2.gif){kind=small} |
Department of Applied Mathematics and Theoretical Physics |
Aurelia R. Honerkamp-SmithPostdoctoral researcherfellow of Churchill CollegeCurrent workI'm currently a postdoctoral researcher in the Goldstein lab. I'm an experimentalist, and I'm studying the interactions between fluid flow, lipid membranes and the cytoskeleton. 
CharaOne of the model organisms used in the Goldstein lab is Chara australis, also known as stonewort. It is a freshwater algae with large cells in which cytoplasmic streaming is easily visible, and streaming in Chara has been studied for many years. Each individual cell of the plant, seen in the image at left, is about 1 mm wide, and can be many centimeters long. 
VesiclesI'm interested in looking at the interactions between lipid bilayers, cytoskeleton proteins, and fluid flow. The image at left shows actin polymerized inside a lipid vesicle. I hope this model will help us to understand how the proteins inside cells organize to result in cytoplasmic streaming like that observed in Chara cells. Below, movies of polystyrene beads (green) flowing inside and outside a hemispherical vesicle (red) show the transmission of shear flow through the membrane. This work is motivated by a recently published calculation by Francis G. Woodhouse.
Volvox inversionVolvox carteri is a microscopic, colonial algae that forms a hollow sphere. The sphere consists of somatic cells, each of which has a photoreceptor and two flagella. Inside of the sphere are the germ cells which will become the next generation. The colony coordinates the beating of its flagella to steer towards light. Each colony arises from a germ cell that initially develops inside out, with the flagella pointing towards the center. The developing colony therefore inverts as soon as cell division has finished. I'm cooperating with Jocelyn Dunstan to study the material properties of inverting Volvox embryos: we hope to describe fluid mechanical contributions to the organization of the adult colony. Previous work
I did my PhD research with Prof. Sarah L. Keller in the Department of Chemistry at the University of Washington, on critical phase transitions in giant unilamellar vesicles. Giant unilamellar vesicles, like the one at left, can separate into coexisting liquid phases made from certain lipid mixtures. The cell membranes of animals contain multiple lipid types, and membrane proteins. Protein configuration can be altered by the lipid composition of the surrounding membrane. Biological membranes are thought to contain small, dynamic inhomogeneities in lipid composition, called rafts.
Static critical exponentsI used fluorescence microscopy and image analysis to show that the fluctuations that appear in ternary lipid bilayers are consistent with the universality class of the 2D Ising model. This work was done in collaboration with Marcel den Nijs (UW Physics), Michael Schick (UW Physics), Marcus Collins (UW Chemistry, currently Biochemistry), Pietro Cicuta (University of Cambridge Physics) and Sarah Veatch (formerly at Cornell, currently at University of Michigan). The paper is here. Similar results are found in plasma membrane vesicles isolated directly from living cells (experiments done by Sarah Veatch, here). 
Dynamic critical exponentMore recently, I used similar techniques to find the dynamic critical exponent for bilayer concentration fluctuations. Once dynamics are considered, the 2-D Ising universality class breaks into multiple sub-classes that depend on the mechanism by which lipid momentum is dissipated. Critical dynamics in lipid membranes are governed not only by membrane properties, but also by how the membrane couples to the surrounding bulk fluid. Ben Machta at Cornell was instrumental in interpreting and analyzing this experiment, which is now published. |