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LIPIDS IN MEMBRANES
From the viewpoint of the Singer-Nicholson model, the lipid matrix of a
plasma membrane is only the frame for the elements which carry out the
cellular function, i.e. the membrane proteins which float laterally within
the membrane. However, a large variety of lipids of different structure
were found to reside in plasma membranes, much more than one would expect
for just performing the functions of frame giving / compartmentation.
Biophysicists started to characterize the lipids which became available
with chemically defined structures. Simple model membranes have been
investigated by different methods such as calorimetry, x-ray diffraction,
different spectroscopy methods, etc. The phase behavior of these model
systems depends on the structure of the lipid, temperature water content,
and further parameters. Thus, for an individual lipid, a rich
polymorphism can be found. Under specific conditions, even biologically
occurring lipids can also form phases other than the biologically relevant
lamellar liquid-crystalline (L) phase.
The picture of lipids became complicated and even more interesting when it
became clear that some lipids play also an important role in cellular
signaling. Furthermore, the finding of detergent resistant membranes gave
evidence for the lipid-raft hypothesis which tries to explain how lipid
microenvironments can take part in physiological processes.
We want to continue the previous work done in our lab on the diffusion
behavior of Langmuir monolayers at the air/water interface as model
membranes. Our aim is to extend the measurements to systems related to
lipid raft mixtures, and to investigate the influence of an antimicrobial
peptide on the monolayer properties.