Development of a high-throughput technique for screening Archaeal tetraether lipid cores and other alcohols in sediments and microbial cultures

Abstract

A mild and effective protocol for the derivatisation of Archaeal tetraether lipid cores and other alcohols from cultured and sedimentary material has been developed using N-protected amino acids. The derivatives were prepared in excellent to near quantitative yields in approx. 2 h. The N-Boc and N-Fmoc derivatives exhibit very good chromatographic properties and considerable signal intensity improvement, in MS, of up to two orders of magnitude, relative to the native species. The fluorescence properties of the derivatives containing a strong chromophore (Fmoc), showed excellent detector response and allow very favourable detection limits to be achieved, comparable to those of MS detection. Derivatisation of a total lipid extract from a soil using Fmoc-lysine(Boc) amino acid permitted the derivatives of sterols and alkanols to be chromatographed and detected by reversed phase LC-MS in under 20 min, which is significantly faster than the standard gas chromatography method. Due to the ability to selectively screen the mass spectral data for characteristic losses associated only with the derivatives, this approach enabled the identification a number of lipid components that were omitted during GC-MS analysis. The novel APCI-LC-MS method was shown to be suited to application in rapid screening of GDGT tetraether lipids from Archaeal cultures and sediment extracts, with drastically reduced analytical run times and markedly improved separation of the cyclopentane ring-containing GDGT lipids. Although, the lack of resolution of crenarchaeol and its regioisomer precluded use of the TEX86 index to reconstruct the geological temperature, the calculation of TEX86Lafforded an estimate of SST temperature that is very close to the value obtained from the native GDGTs using the normal phase based method with TEX86