Buchanan Charles J, Bhole Gaurav, Karunanithy Gogulan, Casablancas-Antràs Virginia, Poh Adeline W J, Davis Benjamin G, Jones Jonathan A, Baldwin Andrew J
Kavli Institute of Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building, Oxford, UK.
Physical and Theoretical Chemistry, Oxford University, Oxford, UK.
Nat Commun. 2025 Aug 7;16(1):7276. doi: 10.1038/s41467-025-61663-8.
NMR experiments require sequences of radio frequency (RF) pulses to manipulate nuclear spins. Signal is lost due to non-uniform excitation of nuclear spins resonating at different energies (chemical shifts) and inhomogeneity in the RF unavoidably generated by hardware over the sample volume. To overcome this, we present Seedless, a tool to calculate NMR pulses that compensate for these effects to enhance control of magnetisation and boost signal. As calculations take only a few seconds using an optimised GRadient Ascent Pulse Engineering (GRAPE) implementation, this now allows pulses to be generated in a few seconds, allowing them to be optimised for individual samples and spectrometers ("on-the-fly"). Each calculated pulse requires bands of chemical shift to be identified, over which one of 4 transforms will be performed, selected from a set that covers all commonly used applications. Using imaging experiments, we demonstrate our pulses effectively both increase the size of the coil volume and signal-to-noise in all experiments. We illustrate the approach by showing sensitivity gains in 1, 2 and 3D applications suitable for chemical and biological NMR. Seedless provides a means to enhance sensitivity in all pulse sequences in a manner that can be tailored to different samples and hardware being used.
核磁共振（NMR）实验需要射频（RF）脉冲序列来操纵核自旋。由于在不同能量（化学位移）下共振的核自旋的非均匀激发以及硬件在样品体积上不可避免地产生的RF中的不均匀性，信号会丢失。为了克服这一问题，我们提出了Seedless，这是一种计算NMR脉冲的工具，可补偿这些影响，以增强对磁化的控制并提高信号强度。由于使用优化的梯度上升脉冲工程（GRAPE）实现方式进行计算仅需几秒钟，现在可以在几秒钟内生成脉冲，从而可以针对单个样品和光谱仪进行优化（“即时”）。每个计算出的脉冲都需要识别化学位移带，在该带上将执行4种变换之一，这些变换是从涵盖所有常用应用的集合中选择的。通过成像实验，我们证明了我们的脉冲在所有实验中均有效地增加了线圈体积的大小和信噪比。我们通过展示适用于化学和生物NMR的1D、2D和3D应用中的灵敏度增益来说明该方法。Seedless提供了一种以可针对不同样品和所使用硬件进行定制的方式来提高所有脉冲序列灵敏度的方法。
