Environmental Metabolomics: NMR Techniques

Environmental metabolomics is a rapidly growing area of research and, over the past decade, has focused on organism responses to various types of environmental stressors such as pollutants, nutritional shifts, and global climate change. NMR is playing a major role in this field of research because as an analytical detector, it is nonselective, sensitive, rapid, and quantitative. It is able to analyze biofluids or tissue extracts with nominal sample pretreatment making it highly versatile for studying a wide range of samples from different types of environmental organisms. Most NMR-based environmental metabolomic studies focus on aqueous tissue extracts and, as such, employ water suppression NMR methods to obtain 1H NMR spectra. The use of water suppression not only avoids the loss of information near the water resonance but also improves baseline quality and prevents signal distortion due to receiver overload. However, metabolite resonance overlap has prompted the investigation of using other methods, such as 1H–1H J-resolved (JRES), 1H–1H COSY and TOCSY, and 1H–13C heteronuclear single quantum coherence (HSQC) NMR for metabolite identification. In addition to these pulse sequences, NMR developments such as microcoil and cryogenically cooled probes and flow injection have increased the use of NMR as a fundamental discovery platform to study a wide array of environmental organisms. Future pulse program and hardware developments will only increase the versatility of NMR for environmental metabolomic studies, and NMR will continue to be a central tool for the foreseeable future. Keywords: environmental metabolomics; water suppression; metabolite quantification; NMR methods; JRES