Incorporation of plastoquinone and ubiquinone into liposome membranes studied by HPLC analysis. The effect of side chain length and redox state of quinone

The efficiency of incorporation of plastoquinones and ubiquinones into phos pholipid liposomes has been studied. The representatives of short (PQ1 and UQ1) middle (PQ4 and UQ4) and long (PQ9, UQ9 and UQ10) prenylquinones have been used to investigate the effect of quinone side chain length. The prope rties of hydroquinones have been also thoroughly examined in relation to th e quinone forms. The extraction procedure was modified and further develope d which enables removing of nonincorporated quinone by pentane washing and then determination of quinone content inside the lipid bilayer. The quantit atively evaluation of the amount of prenylquinone was assayed by means of H PLC analysis which offers much greater sensitivity and could be easily appl ied in case of hydroquinones. It has been found that PQ1 and UQ1 as well as their reduced forms were present mainly (about 80%) in the aqueous phase, when attempting to introduce them into phospholipid bilayer. In case of qui nones having four and more isoprenyl units in side chain, a high level of q uinone incorporation, ranging about 95%, was observed. The results pointed out that when comparing the effects of different exogenous quinones on memb rane related processes, one has to consider the effectiveness of their inco rporation within lipid bilayer. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.