Ka Yee Lee Group
Professor
Postdoctoral Associates
Graduate Students
Research Interest: Interactions between cholesterol and phospholipids in model membranes
Abstract: The cell membrane is believed to be laterally heterogeneous due to the presence of ordered nanodomains enriched in cholesterol called lipid rafts. The role and importance of lipids rafts in cellular functions, such as signaling, trafficking, and protein attachment, are widely known and accepted, but their formation and the interactions involved in their assembly have yet to be determined. Using model lipid membranes containing cholesterol, I study the fundamental interactions between cholesterol and phospholipids found in the cell membrane. I am investigating if there is a propensity for these molecules to form complexes with characteristics distinct from the original lipid components and the chemical activity states of cholesterol.
Ka Yee C. Lee
kayeelee @ uchicago.edu Office: GCIS 139B Phone: 773-702-7068
Department of Chemistry, James Franck Institute, Materials Research Science and Engineering Center,
Institute for Biophysical Dynamics, The University of Chicago
Director, Chicago Materials Research Center
Jia-Yu Wang
jiayuwang @ uchicago.edu
Research Interest: Study the interaction of poloxamer with lipid membranes by use of model lipid systems (monolayers, supported bilayers, and unilamellar vesicles) as well as live cell systems
Undergraduate Students
Jaemin Chin
jchin87 @ uchicago.edu
Research Interest: Poloxamer 188 (P188) is one of a family of poly[ethylene oxide]-poly[propylene oxide]-poly[ethylene oxide] (PEO-PPO-PEO) triblock copolymers. All PEO-PPO-PEO copolymers consist of a central PPO chain that is hydrophobic relative to the bilateral PEO chains of equal length, which are hydrophilic. The members of the family have varying lengths of PEO and PPO chains, but they all are nonionic, amphiphilic surfactants. As much as the characters of P188 are very intriguing for their possible uses in other areas, at certain concentrations, P188 has shown to be effective in arresting the leakage of electroporated cells. In studying the interaction between P188 and a model system of giant unilamellar vesicles, I will examine the insertion of poloxamer into the membrane under different osmotic pressure and elucidate how this triblock copolymer restores integrity to the lipid membrane.
Niels Holten-Andersen
holten @ uchicago.edu
Research Interest: Lipid and protein interactions
Gregory Tietjen
gtietjen @ uchicago.edu
Oliver Shafaat
oshafaat @ uchicago.edu
Research Interests: Antimicrobial peptides (AMPs) are naturally-occurring cationic peptides (<100 amino acid residues) that have been shown to induce selective lytic activity in membranes. Protegrin-1 (PG-1) is an 18- residue AMP which forms an anti-parallel ß-hairpin structure in solution that is stabilized by two disulfide bonds. It was originally thought that electrostatic attraction of the cationic peptide side chains to the bacterial membrane anionic head groups was primarily responsible for selectivity. Antimicrobial peptides disrupt bacterial membranes in much lower concentrations then mammalian membranes. Recent work has shown that more subtle characteristics of membrane composition, such as fluidity and acyl chain length, affects the activity of PG-1. Cholesterol is a naturally occurring sterol found in eukaryotic cell membranes, and effects both the fluidity of the membrane as well as the acyl chain length.
I will explore the effects of cholesterol on the activity of PG-1. Cholesterol, along with other sterols and sterol-like molecules, is commonly found in eukaryotic membranes and causes the fluidity to decrease and the hydrophobic region to expand. This experimental system will allow us to determine the importance of cholesterol in membranes with respect to AMP activity. This is important to examine because of the prevalence of cholesterol and other sterols in eukaryotic membranes relative to prokaryotic membranes. This system will allow for better understanding of the selectivity of AMPs to membranes.
Ginevra Clark
Research Interest: I am interested in the role of lipid/protein interactions in the context of immune recognition. The immune system recognizes a vast array of chemical signatures as antigens although most research has focused on protein/protein recognition. Recently it has been appreciated that lipids can also be a potent stimulus for an immune response, both in the context of lipid-presenting molecules (such as CD1), and as a component of the cell membrane (phagocytosis receptors). I am studying the mechanisms by which these latter receptors can directly recognize “unusual” components of the lipid membrane and how this recognition process stimulates phagocytosis or an immune response.
Luka Pocivavsek
lukap @ uchicago.edu
Research Interest: Mechanical and thermodynamic focusing at membrane Interfaces
Research Interest: I am studying the influence of biopolymers and small molecules on lipid membranes.