5 mm outer diameter nmr tube

For functional assessment of Bifidobacterium strains, media in which the bacterial cells had been grown were analysed using ¹H-NMR Spectroscopy. Media samples were mixed (2:1) with 0.2M sodium phosphate buffer solution (pH 7.4) made in 100% deuterium oxide and 0.01% of sodium 3-(trimethylsilyl) [2,2,3,3,-2H4] propionate 3mM NaN₃. The mixture was vortexed and centrifuged and transferred to a 5mm outer diameter NMR tube (Wilmad). One-dimensional spectroscopic data were acquired using a 500MHz NMR spectrometer (Bruker Biospin, Germany) operating at 300K. A standard one-dimensional NMR pulse sequence with water pre-saturation was applied to acquire spectroscopic data, using 4 dummy scans followed by 64 scans and collected into 24K data points. ¹H NMR spectra were manually corrected for phase and baseline distortions and referenced to the TSP signal at δ 0.0, using the TopSpin 3.5 software package (Bruker Biospin, Germany). Spectra from the different bacterial strains grown under different conditions were overlaid in TopSpin and compared for differences. The integrate function was utilised to integrate peaks of interest. Spectral compound libraries (e.g. Human Metabolome DataBase (HMDB), Biological Magnetic Resonance Data Bank) published literature and in-house spectral reference libraries were used to confirm metabolite assignments.