A method for quantifying heterocyst glycolipids in biomass and sediments

Heterocyst glycolipids (HGs) are biomarkers for heterocystous N2-fixing cyanobacteria and consist of a sugar moiety bound to an even numbered C26-C32 alkyl chain, containing various alcohol or ketone groups. They have been reported in ancient sediments but, due to a lack of standards, they were quantified in terms of integrated peak area response. Here we describe the use of a commercially available glycolipid (n-dodecyl-β-d-glucopyranoside) as an internal standard (IS) for reliable quantitative analysis. The common HG 1-(O-hexose)-3,25-hexacosanediol was isolated using both normal and reversed phase chromatography and used to assess the relative response factor compared with the IS, allowing correction of difference in mass spectral response between the IS and the target HGs.