M.Sc. (Chemistry) / Please refer to full text to view abstract

No description available.

No description available.

No description available.

No description available.

Call number: LD2668 .T4 1960 Z57

Call number: LD2668 .T4 1961 M32

Call number: LD2668 .T4 1964 D69 / Master of Science

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The deposition of atmospheric nitrogen is now recognized as a major driver of biodiversity changes at mid to high latitudes. It has previously been shown that regional variations in wet nitrogen deposition in the British Isles are reflected in broad targeted chemical parameters in the common heathland lichen Cladonia portentosa. A more detail analysis of alterations in the metabolic pathways in Cladonia portentosa collected from different locations within the UK was undertaken by applying the environmental metabolomics approach. Fourier transform infrared spectroscopy (FTIR) and liquid chromatography mass spectrometry (LC-MS) were applied in combination with principal component analysis (PCA) and partial least squares regression analysis (PLSR). The latter statistical method was used to correlate measured variables with modelled atmospheric data including wet nitrogen deposition, nitrogen concentration and precipitation. While FTIR in combination with PCA and PLSR revealed signatures of broad metabolic classes, LC-MS in combination with PCA and PLSR allowed the identification of betaine lipids (BL) as potential biomarkers of nitrogen enrichment. A compound tentatively identified as monoacylglycerol-(N,N,N trimethyl)-homoserine (MGTS) showed the strongest positive relation to increasing wet nitrogen deposition regimes and consequent phosphorus deficiency. In contrast, the structurally related phosphatidylcholine containing a C18:2 ester showed the opposite trend in natural populations of C. portentosa. Results obtained for C. portentosa collected from the N manipulation site Whim Moss indicated that ammonium is causal for the increase of two of the identified betaine lipids in natural populations in C. portentosa. Betaine lipids as well as the phosphatidylcholine biomarker could potentially be used to monitor nitrogen regimes and resulting phosphorus limitation on the lichen C. portentosa. The approach used for this study represented an effective integration of the complementary analytical techniques of FTIR and LC-MS in combination with multivariate statistical tools for environmental metabolomic studies.