A NOVEL METHOD IN STUDIES OF DYNAMICAL PROPERTIES IN PLANT MEMBRANES - LAURDAN FLUORESCENCE SPECTROSCOPY

A new method to study dynamical properties of biological membranes, ex citation generalized polarization (excitation GP) of Laurdan (6-lauroy l-2-dimethylaminonaphtalene) fluorescence, has for the first time been used in plant science. This method allows the determination of the mo lecular dynamics in biological membranes, using simple steady-state fl uorescence measurements. Laurdan spectroscopy also determines the phas e state of the membranes, and separation into co-existing gel- and liq uid-crystalline phases can be revealed. A protocol for labelling wheat (Triticum aestivum L.) plasma membranes with Laurdan have been establ ished. The method has been used to probe the dynamical alterations tha t occur in wheat plasma membranes at changed temperatures. The method detects changes in plasma membrane dynamics induced by alterations in temperature of 2 degrees C. The results for plasma membranes are simil ar to those obtained for animal cell membranes, and show that isolated wheat plasma membranes occur in a homogenous liquid-crystalline phase at all temperatures tested, from 4 degrees C to 28 degrees C. Laurdan fluorescence spectroscopy is a promising tool in plant membrane resea rch, acid it is suggested that the temperature dependence of excitatio n GP is a suitable parameter to use in determing the effect on membran e dynamics by altered membrane lipid composition.