1 research outputs found
Melting transitions in biomembranes
We investigated melting transitions in biological membranes in their native
state that include their membrane proteins. These membranes originated from
\textit{E. coli}, \textit{B. subtilis}, lung surfactant and nerve tissue from
the spinal cord of several mammals. For some preparations, we studied the
pressure, pH and ionic strength dependence of the transition. For porcine
spine, we compared the transition of the native membrane to that of the
extracted lipids. All preparations displayed melting transitions of 10-20
degrees below physiological or growth temperature, independent of the organism
of origin and the respective cell type. The position of transitions in
\textit{E. coli} membranes depends on the growth temperature. We discuss these
findings in the context of the thermodynamic theory of membrane fluctuations
that leads to largely altered elastic constants, an increase in fluctuation
lifetime and in membrane permeability associated with the transitions. We also
discuss how to distinguish lipid transitions from protein unfolding
transitions. Since the feature of a transition slightly below physiological
temperature is conserved even when growth conditions change, we conclude that
the transitions are likely to be of major biological importance for the
survival and the function of the cell.Comment: 12 pages, 6 Figures, 1 supplement with 1 figur