Non-linear electron spin resonance study of archaebacteria lipid dynamics

Abstract

The spectral diffusion occurring in non-linear electron spin resonance experiments performed at a suitable frequency of field modulation is exploited to gain dynamical information on an unusual class of lipids extracted from bacteria living in extreme physical conditions (high temperature and very low pH). These lipids are quite different from the usual fatty acid lipids and their molecular structure seems to play a particular role in the stability of the plasma membrane of these bacteria. An accurate and extensive determination of the magnetic instrumental parameters allowed a reliable calculation of the rotational correlation time of suitable spin labelled lipids which mimic the dynamical behaviour of the lipids under investigation. The lipids investigated have been shown to undergo an anisotropic molecular motion characterized by a very slow correlation time even at very high temperatures. The very slow anisotropic motion of these lipids indicates the ability of their nonitol polar heads to establish strong cooperative interactions which, from a biophysical point of view, could be invoked to explain the great stability of the plasma membrane even under those extreme environmental conditions.