Undergraduate Research Summary

Dr. Audra Goach Sostarecz

Chemistry Department

Monmouth College

 

Investigating Molecular Interactions in Relation to Membrane Domain Formation

 

 

 


 

Text Box: Lipid bilayer Text Box: Lehninger; Nelson; Cox; Principles of Biochemistry, 1993

 

 

 

 

 

 

BACKGROUND

 

1. the cellular membrane is extremely complex consisting of lipids, in particular phospholipids and cholesterol, and proteins

2. the important aspects of the membrane that we are interested in include:

            a. the ability of the cellular membrane to serve as a barrier to the cell due to the amphiphilic nature of the lipids (hydrophilic head groups (purple) hydrophobic tail groups (yellow))

            b. the degree of order of the lipids in the lipid bilayer represented by the fluid  (disordered) and gel (ordered) phases

 

 fluid phase (disordered phase)            gel phase (ordered phase)

 

            c. the ability of cholesterol to induce order in fluid phase phospholipids resulting in a liquid ordered phase

 

  liquid ordered phase

 

3.  the liquid ordered phase is often referred to as domains or “rafts” and is governed by molecular interactions of phospholipids and cholesterol

            a.  rafts are the vehicle of transportation for proteins involved in such processes as disease progression

            b. evidence that cholesterol domains may play a role in HIV-1 assembly by protein interaction where disruption or depletion of cholesterol induces changes in HIV-1 assembly (reference: Ono and Freed, Proc. Nat. Acad. Sci. 2001)

 

GOALS of PROJECT

 

To obtain a clear and concise picture of membrane domains (liquid ordered phase) through the use of model systems to allow us to investigate the structure of cellular molecules along with their interactions.

 

GENERAL QUESTIONS to ANSWER

 

1. Which lipids form domains with cholesterol?

2. Which lipids do not form domains?

3. What induces these domains?

4. What is the best way to represent the lipid bilayer?

5. How should domains be analyzed?

 

PROJECTS

 

1. Comprehensive Look at Cholesterol Domains in the Inner Leaflet

2. Improving Upon the Types of Model Membranes Currently Used to Investigate Domain Formation

3. Proteins and Cholesterol Domains in Disease

 

PHOSPHOLIPIDS to INVESTIGATE

 

1. Phosphatidylcholine (PC)

2. Phosphatidylethanolamine (PE)

3. Phosphatidylserine (PS)

 

Text Box: PC headgroup

 

 

 

INSTRUMENTATION used to make MODEL SYSTEMS – Kibron Micro Trough -the main instrumentation that will be used in our lab

 

1.Pictorial of Langmuir Trough – air-water interface

Text Box: Headgroups of lipids are in the water and tailgroups are out of water

 

 

 

П = surface pressure

γ = surface tension of pure water

γ = surface tension of pure water + monolayer of lipids

 

 

 

 

 

 

 

 

2. Actual Langmuir Trough

 www.kibron,com

 

 

 

 

 

 

 

3. Langmuir trough produces surface pressure vs area graphs known as isotherms which allow us to investigate molecular interactions

            a. The 2-D gas phase is similar to the fluid phase of the lipid bilyaer

            b. The 2-D solid phase is similar to the gel phase of the lipid bilayer

  

Text Box: fluid

  

 

ACCESIBILITY to UNDERGRADS!

 

1. The LB trough is small and user-friendly

2. Projects are not time consuming and therefore useful data may be   obtained within a semester or summer

3. Projects are attractive to students since they involve aspects of chemistry, biology, and physics in the form of biochemistry and biophysics

4. Students will gain valuable experience in laboratory research