Routine high-resolution 5 mm cryoprobes at 16.45–18.8 Tesla typically have and SNR of 6000–8000:1 for 0.1% ethyl benzene in CDCl 3.
When samples are severely limited, such as for tissue biopsy, microprobes outperform standard diameter probes. The salt-associated losses however are somewhat offset by using smaller diameter microprobes, such as 3 mm or 1.7 mm compared with the “standard” 5 mm probe. However, this may be optimistic for salty samples, and the loss of sensitivity due to the presence of mobile ions increases with increasing magnetic field strength. Cryoprobes may yield a sensitivity enhancement of 3–4 fold compared with an RT probe counterpart, which corresponds to about ≥10-fold reduction in experimental time for a given signal-to-noise ratio (SNR). Sensitivity theoretically scales as B 0 1.5, though in practice it is closer to linear in B 0 especially for the now prevalent cryoprobes. The sensitivity of an NMR experiment is determined primarily by the amount (concentration) of each analyte and the nature of the detector system, primarily the probe type and magnetic field strength. It should be noted that the experiments and analyses can be used for those with or without stable isotope enrichment. The goal of this chapter is to provide detailed experimental procedures for NMR identification and quantification of metabolites and their isotopomer distributions in Stable Isotope-Resolved Metabolomics (SIRM) studies. isotopomers (v) isotope editing capabilities for spectral simplification in complex mixtures. These are (i) quantification without the need for authentic standards (ii) reliable quantitation with high dynamic ranges (iii) ability to elucidate molecular structures with multidimensional and multinuclear capabilities (iv) ability to determine distributions of labeled atom position(s), i.e. Although NMR is much less sensitive than most MS detection methods, it has several unique advantages for metabolite analysis. įor stable isotope tracing, there are two main analytical approaches that are widely applied, mass spectrometry (MS) and NMR. In metabolic research, stable isotope tracing provides much more rigorous metabolic pathway details than total metabolite profiling, as it can help resolve which intersecting pathways are active, and be used for estimating network fluxes. Thus cellular metabolism provides a very rich and molecular readout of the functional state of cells. Metabolic activity is both quantitatively and qualitatively specific to tissue and cell types, and is generally highly responsive to changes in external (environmental) or internal (e.g.
0 kommentar(er)
