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Improved sensitivity of laser-enhanced 1Hα-13Cα-correlation via suppression of Cα-C′ scalar-coupling evolution
摘要： Low-concentration photochemically induced dynamic polarization (LC-photo-CIDNP) enables the spectroscopic analysis of biomolecules containing the amino acids Trp and Tyr at sub-micromolar concentration in solution. Typical LC-photo-CIDNP pulse sequences involving 1H-13C correlation, however, perform well in the case of aromatic resonances but display a relatively poor signal-to-noise ratio for 13Ca and 13Cb resonances. Here, we develop a novel pulse sequence denoted as 13C perturbation-recovered selective-pulse photo-CINDP enhanced reverse INEPT, or 13C PRESPRINT, tailored to the LC-photo-CIDNP analysis of 1H-13Ca pairs. Our method, which is based on full suppression of 1-bond Ca-C0 scalar-coupling evolution during the constant-time delay, results into a sensitivity improvement by a factor of 2. The enhanced performance of this pulse sequence enabled us to improve the analysis of LC-photo-CIDNP laser-power dependence at very low (200 nM) sample concentration. An improved theoretical model, developed to quantitatively describe this laser-power dependence, shows excellent agreement with our 13C PRESPRINT experimental data.
关键词： LC-photo-CIDNP,Photo-CIDNP,Hyperpolarization,1H-13Ca correlation,NMR sensitivity
更新于2025-09-16 10:30:52
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Fast-pulsing LED-enhanced NMR: A convenient and inexpensive approach to increase NMR sensitivity
摘要： Low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) has recently emerged as a powerful technology for the detection of aromatic amino acids and proteins in solution in the low-micromolar to nanomolar concentration range. LC-photo-CIDNP is typically carried out in the presence of high-power lasers, which are costly and maintenance-heavy. Here, we show that LC-photo-CIDNP can be performed with light-emitting diodes (LEDs), which are inexpensive and much less cumbersome than lasers, laser diodes, flash lamps, or other light sources. When nuclear magnetic resonance (NMR) sample concentration is within the low-micromolar to nanomolar range, as in LC-photo-CIDNP, replacement of lasers with LEDs leads to no losses in sensitivity. We also investigate the effect of optical-fiber thickness and compare excitation rate constants of an Ar ion laser (488 nm) and a 466 nm LED, taking LED emission bandwidths into account. In addition, importantly, we develop a novel pulse sequence (13C RASPRINT) to perform ultrarapid LC-photo-CIDNP data collection. Remarkably, 13C RASPRINT leads to 4-fold savings in data collection time. The latter advance relies on the fact that photo-CID nuclear hyperpolarization does not suffer from the longitudinal-relaxation recovery requirements of conventional NMR. Finally, we combine both the above improvements, resulting in facile and rapid (≈16 s–2.5 min) collection of 1 and 2D NMR data on aromatic amino acids and proteins in solution at nanomolar to low micromolar concentration.
关键词： LED,LC-photo-CIDNP,13C RASPRINT,NMR sensitivity,laser,hyperpolarization
更新于2025-09-12 10:27:22