| Abstract | The membrane lipids of Methanothrix concilii are based on two types of core lipid structures, namely, the ubiquitous 2,3-di-O-phytanyl-sn-glycerol and a second previously unidentified diether core lipid, each accounting for 70 and 30% (wt. %), respectively, of the total polar lipids. Preparation of the novel diether core lipid from either purified glycolipid-1 (GL-1) or total polar lipid in 2.5% methanolic HCl resulted in the formation of several lipid artifacts, thereby necessitating the utilization of new hydrolytic conditions. We found that mild acid hydrolysis in 0.18% methanolic HCl produced only one core lipid product from GL-1 or two core lipids from the total polar lipid fraction. This new core lipid material differed from the authentic C20,20 diether in that it contained a hydroxyl group on C-3 of the phytanyl chain at the sn-3 position of glycerol. The full chemical designation for this novel diether is: 2-O-[3,7,11,15-tetramethyl]hexadecyl-3-O-[3′ -hydroxy-3′,7′,11′,15′-tetramethyl]hexadecyl-sn-glycerol. 1H-NMR of the total polar lipid extract could detect the presence of this new core lipid by exploiting the appearance of the methyl (C-17′) singlet at 1.24 ppm. The presence of this methyl singlet in the 1H-NMR spectrum would subsequently determine whether a strong or a mild acid hydrolysis should be used for the preparation of core lipids in methanogens. |
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