The landmark experiments of Schoenheimer and Rittenberg in the 1930s provided the scientific foundation for the ensuing development and application of stable isotope techniques in clinical diagnosis and research. Stable isotopes are non-radioactive atoms of the same chemical element, which diVer only in their number of neutrons. Many elements also have radioactive (non-stable) isotopes. Aspects...

Compound-speci®c D values recorded by means of gas chromatography±thermal conversion±isotope ratio mass spectrometry (GC±TC±IRMS) of the biomarker n-alkane (n-tricosane; n-C23) representative of the dominant Sphagnum species in a 40 cm peat pro®le from Bolton Fell Moss, Cumbria, UK, correlate with vegetation changes in the past >200 years (age depth model based on Pb dating). The bog vegetation...

Synthetic immune response modifiers (IRM) such as imidazoquinolines can selectively activate human TLR7 or TLR8. Although these endosomal TLRs are close relatives, TLR7-deficient mice are unresponsive to TLR8 agonist IRMs. Similarly, natural ssRNA cannot activate murine TLR8, leading to the belief that murine TLR8 is nonfunctional. In this study, we transfected HEK293 cells with murine TLR8 and...

Confirmation of a potential disinterred grave was sought by GC and GC/MS analyses of lipid extracts of whole soils and white particulate matter. Fatty acid profiles and concentrations determined for three of the soils correlated with the deposition of a large amount of exogenous organic matter, most likely adipocere and/or decomposed body fat. Determination of C16:0 and C18:0 fatty acid delta13...

In order to delineate the origin of soil fatty acids, crop soil samples have been incubated for 21 days in vitro either with unlabelled or 13C-labelled glucose. Analyses of C14-C32 n-alkanoic acids from monocarboxylic acid fractions, as methyl esters, by gas chromatography-combustion-isotope ratio monitoring mass spectrometry (GC-C-IRMS) show that C14, C16 and C18 n-alkanoic acids are 13C-label...

Stable isotopes of water have long been used to improve understanding of the hydrological cycle, catchment hydrology, and polar climate. Recently, there has been increasing interest in measurement and use of the lessabundant O isotope in addition to H and O. Off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and precise measurements δO, δO, and O-excess in liq...