Disulfonated rhodamines were considered cell impermeable and not applicable for specific labeling in live cells. Surprisingly, in spite of the double negative charge of the molecules, the conjugates of these popular dyes with the HaloTag

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13C and 15N Benchtop NMR Detection of Metabolites via Relayed Hyperpolarization
Von Wiley-VCH zur Verfügung gestellt
Parahydrogen-relayed hyperpolarization is used for enhancing 13C and 15N benchtop NMR signals of key metabolites – urea, ammonium, glycine, glucose – and a drug precursor benzamide. After sample optimization, a 17,100-fold 15N NMR signal enhancement of [13C, 15N2]-urea 1 T was reached. The presented method opens ways of enhancing NMR signals of various molecules for benchtop NMR spectroscopy.
Abstract
Parahydrogen-based nuclear spin hyperpolarization allows various magnetic-resonance applications, and it is particularly attractive because of its technical simplicity, low cost, and ability to quickly (in seconds) produce large volumes of hyperpolarized material. Although many parahydrogen-based techniques have emerged, some of them remain unexplored due to the lack of careful optimization studies. In this work, we investigate and optimize a novel parahydrogen-induced polarization (PHIP) technique that relies on proton exchange referred to below as PHIP-relay. An INEPT (insensitive nuclei enhanced by polarization transfer) sequence is employed to transfer polarization from hyperpolarized protons to heteronuclei ( 15 ${^{15} }$ N and 13 ${^{13} }$ C) and nuclear signals are detected using benchtop NMR spectrometers (1 T and 1.4 T, respectively). We demonstrate the applicability of the PHIP-relay technique for hyperpolarization of a wide range of biochemicals by examining such key metabolites as urea, ammonium, glucose, amino acid glycine, and a drug precursor benzamide. By optimizing chemical and NMR parameters of the PHIP-relay, we achieve a 17,100-fold enhancement of 15 ${^{15} }$ N signal of [ 13 ${^{13} }$ C, 15 ${^{15} }$ N 2 ${_2 }$ ]-urea compared to the thermal signal measured at 1 T. We also show that repeated measurements with shorter exposure to parahydrogen provide a higher effective signal-to-noise ratio compared to longer parahydrogen bubbling.
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