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Determination of the mutual orientation between proton CSA tensors mediated through band-selective 1H–1H recoupling under fast MAS 快速MAS下带选择性1H-1H重耦合介导的质子CSA张量相互取向的测定
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-06-01 DOI: 10.1016/j.ssnmr.2023.101874
Takeshi Kobayashi , Yusuke Nishiyama , Manoj Kumar Pandey

The mutual orientation of nuclear spin interaction tensors provides critical information on the conformation and arrangement of molecules in chemicals, materials, and biological systems at an atomic level. Proton is a ubiquitous and important element in a variety of substances, and its NMR is highly sensitive due to their virtually 100% natural abundance and large gyromagnetic ratio. Nevertheless, the measurement of mutual orientation between the 1H CSA tensors has remained largely untouched in the past due to strong 1H–1H homonuclear interactions in a dense network of protons. In this study, we have developed a proton-detected 3D 1H CSA/1H CSA/1H CS correlation method that utilizes three techniques to manage homonuclear interactions, namely fast magic-angle spinning, windowless C-symmetry-based CSA recoupling (windowless-ROCSA), and a band-selective 1H–1H polarization transfer. The asymmetric 1H CSA/1H CSA correlated powder patterns produced by the C-symmetry-based methods are highly sensitive to the sign and asymmetry parameter of the 1H CSA, and the Euler angle β as compared to the symmetric pattern obtained by the existing γ-encoded R-symmetry-based CSA/CSA correlation methods and allows a larger spectral area for data fitting. These features are beneficial for determining the mutual orientation between the nuclear spin interaction tensors with improved accuracy.

核自旋相互作用张量的相互取向在原子水平上为化学物质、材料和生物系统中分子的构象和排列提供了重要信息。质子是各种物质中普遍存在的重要元素,由于其几乎100%的天然丰度和较大的回旋磁比,其核磁共振具有很高的敏感性。然而,由于在密集的质子网络中强1H - 1H同核相互作用,1H CSA张量之间相互取向的测量在过去基本上没有受到影响。在这项研究中,我们开发了一种质子检测的3D 1H CSA/1H CSA/1H CS相关方法,该方法利用三种技术来管理同核相互作用,即快速神奇角旋转、基于无窗口c对称的CSA重耦合(无窗口rocsa)和波段选择性1H - 1H极化转移。与现有的基于γ编码r -对称的CSA/CSA相关方法得到的对称图相比,基于c -对称方法得到的不对称1H CSA/1H CSA相关图对1H CSA的符号和不对称参数以及欧拉角β高度敏感,并且可以获得更大的光谱面积用于数据拟合。这些特征有助于提高核自旋相互作用张量之间相互取向的确定精度。
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引用次数: 0
Site-specific protein backbone deuterium 2Hα quadrupolar patterns by proton-detected quadruple-resonance 3D 2HαcαNH MAS NMR spectroscopy 质子检测四共振3D 2Hαcα nh MAS核磁共振谱图的位点特异性蛋白主干氘2Hα四极性图谱
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-06-01 DOI: 10.1016/j.ssnmr.2023.101861
Ümit Akbey

A novel deuterium-excited and proton-detected quadruple-resonance three-dimensional (3D) 2HαcαNH MAS nuclear magnetic resonance (NMR) method is presented to obtain site-specific 2Hα deuterium quadrupolar couplings from protein backbone, as an extension to the 2D version of the experiment reported earlier. Proton-detection results in high sensitivity compared to the heteronuclei detection methods. Utilizing four independent radiofrequency (RF) channels (quadruple-resonance), we managed to excite the 2Hα, then transfer deuterium polarization to its attached Cα, followed by polarization transfers to the neighboring backbone nitrogen and then to the amide proton for detection. This experiment results in an easy to interpret HSQC-like 2D 1H–15N fingerprint NMR spectrum, which contains site-specific deuterium quadrupolar patterns in the indirect third dimension. Provided that four-channel NMR probe technology is available, the setup of the 2HαcαNH experiment is relatively straightforward, by using low power deuterium excitation and polarization transfer schemes we have been developing. To our knowledge, this is the first demonstration of a quadruple-resonance MAS NMR experiment to link 2Hα quadrupolar couplings to proton-detection, extending our previous triple-resonance demonstrations. Distortion-free excitation and polarization transfer of ∼160–170 kHz 2Hα quadrupolar coupling were presented by using a deuterium RF strength of ∼20 kHz. From these 2Hα patterns, an average backbone order parameter of S = 0.92 was determined on a deuterated SH3 sample, with an average η = 0.22. These indicate that SH3 backbone represents sizable dynamics in the microsecond timescale where the 2Hα lineshape is sensitive. Moreover, site-specific 2Hα T1 relaxation times were obtained for a proof of concept. This 3D 2HαcαNH NMR experiment has the potential to determine structure and dynamics of perdeuterated proteins by utilizing deuterium as a novel reporter.

提出了一种新的氘激发和质子检测的四共振三维(3D) 2Hαcα nh MAS核磁共振(NMR)方法,用于从蛋白质骨架中获得特定位点的2Hα氘四极偶联,作为先前报道的2D版本实验的扩展。与异核检测方法相比,质子检测结果具有较高的灵敏度。利用四个独立的射频通道(四共振),我们成功地激发2Hα,然后将氘极化转移到其附着的Cα上,然后将极化转移到邻近的主氮上,然后转移到酰胺质子上进行检测。本实验获得了易于解释的类hsqc的二维1H-15N指纹核磁共振谱,该谱在间接三维空间中包含特定位点的氘四极模式。如果有四通道核磁共振探针技术,利用我们已经开发的低功率氘激发和极化转移方案,2HαcαNH实验的设置相对简单。据我们所知,这是第一个将2Hα四极偶联与质子检测联系起来的四共振MAS NMR实验的演示,扩展了我们之前的三共振演示。利用氘射频强度为~ 20 kHz,研究了~ 160 ~ 170 kHz 2h - α四极耦合的无畸变激发和极化转移。从这些2Hα谱图中,氘化SH3样品的平均主链序参数S = 0.92,平均η = 0.22。这表明SH3骨架在微秒时间尺度上表现出相当大的动态,其中2Hα线形是敏感的。此外,还获得了特定位点的2Hα T1弛豫时间,以证明概念。这个3D 2HαcαNH NMR实验有潜力利用氘作为新的报告因子来确定过氘化蛋白的结构和动力学。
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引用次数: 1
Cryogen-free 400 MHz (9.4 T) solid state MAS NMR system with liquid state NMR potential 无低温400 MHz (9.4 T)固态MAS核磁共振系统与液态核磁共振电位
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-06-01 DOI: 10.1016/j.ssnmr.2023.101873
Eugeny Kryukov , Alexander Karabanov , Denis Langlais , Dinu Iuga , Rupert Reckless , Jeremy Good

We show that the temporal magnetic field distortion generated by the Cold Head operation can be removed and high quality Solid-State Magic Angle Spinning NMR results can be obtained with a cryogen-free magnet. The compact design of the cryogen-free magnets allows for the probe to be inserted either from the bottom (as in most NMR systems) or, more conveniently, from the top. The magnetic field settling time can be made as short as an hour after a field ramp. Therefore, a single cryogen-free magnet can be used at different fixed fields. The magnetic field can be changed every day without compromising the measurement resolution.

结果表明,使用无低温磁体可以消除冷头操作产生的时间磁场畸变,获得高质量的固态魔角自旋核磁共振结果。无低温磁体的紧凑设计允许探针从底部插入(如在大多数核磁共振系统中),或者更方便地从顶部插入。磁场斜坡后,磁场沉降时间可短至一小时。因此,单个无低温磁体可以用于不同的固定场。磁场可以每天改变而不影响测量分辨率。
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引用次数: 0
Indirectly detected satellite-transition quadrupolar NMR via progressive saturation of the proton reservoir 通过质子储层的逐渐饱和间接探测到卫星跃迁四极核磁共振
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-06-01 DOI: 10.1016/j.ssnmr.2023.101862
Tamar Wolf , Anna Eden-Kossoy , Lucio Frydman

Static satellite-transitions (ST) NMR line shapes from half-integer quadrupolar nuclei could be very informative: they can deliver insight about local motions over a wide range of timescales, and can report on small changes in the local electronic environments as reflected by variations in the quadrupolar parameters. Satellite transitions, however, are typically “invisible” for half-integer quadrupolar nuclei due to their sheer breadth, leading to low signal-to-noise ratio –especially for unreceptive low-gamma or dilute quadrupolar nuclei. Very recently we have introduced a method for enhancing the NMR sensitivity of unreceptive X nuclei in static solids dubbed PROgressive Saturation of the Proton Reservoir (PROSPR), which opens the possibility of magnifying the signals from such spins by repeatedly imprinting frequency-selective X-driven depolarizations on the much more sensitive 1H NMR signal. Here, we show that PROSPR's efficacy is high enough for enabling the detection of static ST NMR for challenging species like 35Cl, 33S and even 17O –all at natural-abundance. The ensuing ST-PROSPR NMR experiment thus opens new approaches to probe ultra-wideline (6–8 MHz wide) spectra. These highly pronounced anisotropies can in turn deliver new vistas about dynamic changes in solids, as here illustrated by tracking ST line shapes as a function of temperature during thermally-driven events.

来自半整数四极核的静态卫星跃迁(ST)NMR线形可能非常有用:它们可以提供关于宽时间尺度上局部运动的见解,并可以报告由四极参数变化反映的局部电子环境的微小变化。然而,由于半整数四极核的绝对宽度,卫星跃迁通常是“不可见的”,导致信噪比较低,尤其是对于不可接受的低伽马或稀释四极核。最近,我们介绍了一种提高静止固体中不可接收X核NMR灵敏度的方法,称为质子库的渐渗饱和(PROSPR),该方法通过在更灵敏的1H NMR信号上重复压印频率选择性X驱动的去极化,打开了放大此类自旋信号的可能性。在这里,我们表明PROSPR的功效足以检测35Cl、33S甚至17O等具有挑战性的物种的静态ST NMR——所有这些都处于自然丰度。因此,随后的ST-PROSPR NMR实验为探测超宽线(6-8 MHz宽)光谱开辟了新的途径。这些高度明显的各向异性反过来又可以提供关于固体动态变化的新视角,如这里通过跟踪热驱动事件期间作为温度函数的ST线形状所示。
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引用次数: 1
On the applicability of cosine-modulated pulses for high-resolution solid-state NMR of quadrupolar nuclei with spin > 3/2 余弦调制脉冲在自旋bbb3 /2的四极核的高分辨率固态核磁共振中的适用性
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-06-01 DOI: 10.1016/j.ssnmr.2023.101863
Akiko Sasaki , Julien Trébosc , Hiroki Nagashima , Jean-Paul Amoureux

In MQMAS-based high-resolution solid-state NMR experiments of half-integer spin quadrupolar nuclei, the high radiofrequency (RF) field requirement for the MQ excitation and conversion steps with two hard-pulses is often a sensitivity limiting factor in many practical applications. Recently, the use of two cosine-modulated (cos) low-power (lp) pulses, lasting one-rotor period each, was successfully introduced for efficient MQ excitation and conversion of spin-3/2 nuclei with a reduced RF amplitude. In this study, we extend our previous investigations of spin-3/2 nuclei to systems with higher spin values and discuss the applicability of coslp-MQ excitation and conversion in MQMAS and MQ-HETCOR experiments under slow and fast spinning conditions. For the numerical simulations and experiments we used a moderate magnetic field of 14.1 T. Two spin-5/2 nuclei (85Rb and 27Al) are mainly employed with a large variety of CQ values, but we show that the practical set up is also available for higher spin values, such as spin-9/2 with 93Nb in Cs4Nb11O30. We demonstrate for nuclei with spin value larger than 3/2 a preferential use of coslp-MQ acquisition for low-gamma nuclei and/or large CQ values with a much reduced RF-field with respect to that of hard-pulses used with conventional methods.

在半整数自旋四极核的基于MQMAS的高分辨率固态NMR实验中,在许多实际应用中,具有两个硬脉冲的MQ激发和转换步骤的高射频(RF)场要求通常是灵敏度限制因素。最近,成功地引入了两个余弦调制(cos)低功率(lp)脉冲的使用,每个脉冲持续一个转子周期,用于降低RF振幅的自旋3/2核的有效MQ激发和转换。在这项研究中,我们将之前对自旋3/2核的研究扩展到具有更高自旋值的系统,并讨论了coslp MQ激发和转换在慢自旋和快自旋条件下的MQMAS和MQ-HETCOR实验中的适用性。在数值模拟和实验中,我们使用了14.1T的中等磁场。两个自旋为5/2的核(85Rb和27Al)主要用于各种CQ值,但我们表明,实际设置也适用于更高的自旋值,例如Cs4Nb11O30中具有93Nb的自旋为9/2的核。我们证明,对于自旋值大于3/2的核,对于低伽马核和/或大CQ值的核,优先使用coslp MQ采集,与传统方法使用的硬脉冲相比,RF场大大降低。
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引用次数: 0
Cryogen-free 400 MHz (9.4 T) solid state MAS NMR system with liquid state NMR potential. 无低温400 MHz (9.4 T)固态MAS核磁共振系统与液态核磁共振电位。
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-05-01 DOI: 10.2139/ssrn.4377536
E. Kryukov, A. Karabanov, D. Langlais, D. Iuga, Rupert Reckless, J. Good
We show that the temporal magnetic field distortion generated by the Cold Head operation can be removed and high quality Solid-State Magic Angle Spinning NMR results can be obtained with a cryogen-free magnet. The compact design of the cryogen-free magnets allows for the probe to be inserted either from the bottom (as in most NMR systems) or, more conveniently, from the top. The magnetic field settling time can be made as short as an hour after a field ramp. Therefore, a single cryogen-free magnet can be used at different fixed fields. The magnetic field can be changed every day without compromising the measurement resolution.
我们表明,冷头操作产生的时间磁场畸变可以消除,并且使用无冷冻剂磁体可以获得高质量的固态魔角自旋NMR结果。无冷冻剂磁体的紧凑设计允许探针从底部插入(如在大多数NMR系统中),或者更方便地从顶部插入。磁场稳定时间可以在磁场斜坡后短至一小时。因此,单个无冷冻剂磁体可以用于不同的固定场。磁场可以每天改变,而不会影响测量分辨率。
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引用次数: 0
Asynchronising five-fold symmetry sequence for better homonuclear polarisation transfer in magic-angle-spinning solid-state NMR 在魔角自旋固体核磁共振中,采用异步五重对称序列实现更好的同核极化转移
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-04-01 DOI: 10.1016/j.ssnmr.2023.101858
Vaishali Arunachalam, Kshama Sharma, Kaustubh R. Mote, P.K. Madhu

Recoupling, decoupling, and multidimensional correlation experiments in magic-angle-spinning (MAS) solid-state NMR can be designed by exploiting the symmetry of internal spin interactions. One such scheme, namely, C521, and its supercycled version SPC521, notated as a five-fold symmetry sequence, is widely used for double-quantum dipole-dipole recoupling. Such schemes are generally rotor synchronised by design. We demonstrate an asynchronous implementation of the SPC521 sequence leading to higher double-quantum homonuclear polarisation transfer efficiency compared to the normal synchronous implementation. Rotor-synchronisation is broken in two different ways: lengthening the duration of one of the pulses, denoted as pulse-width variation (PWV), and mismatching the MAS frequency denoted as MAS variation (MASV). The application of this asynchronous sequence is shown on three different samples, namely, U–13C-alanine and 1,4-13C-labelled ammonium phthalate which include 13Cα-13Cβ, 13Cα-13Co, and 13Co13Co spin systems, and adenosine 5′- triphosphate disodium salt trihydrate (ATP⋅3H2O). We show that the asynchronous version performs better for spin pairs with small dipole-dipole couplings and large chemical-shift anisotropies, for example, 13Co13Co. Simulations and experiments are shown to corroborate the results.

魔角自旋(MAS)固态NMR中的重耦合、解耦和多维关联实验可以通过利用内部自旋相互作用的对称性来设计。一种这样的方案,即C521及其超循环版本SPC521,记为五重对称序列,被广泛用于双量子偶极-偶极重耦合。这种方案通常通过设计实现转子同步。我们展示了SPC521序列的异步实现,与正常同步实现相比,该序列具有更高的双量子同核极化转移效率。转子同步以两种不同的方式中断:延长其中一个脉冲的持续时间,表示为脉冲宽度变化(PWV),以及失配MAS频率,表示为MAS变化(MASV)。该异步序列在三种不同的样品上的应用,即U–13C-丙氨酸和1,4-13C-标记的邻苯二甲酸铵,包括13Cα-13Cβ、13Cα-13 Co和13Co–13Co自旋系统,以及腺苷5′-三磷酸二钠盐三水合物(ATP·3H2O)。我们表明,异步版本对于具有小偶极-偶极耦合和大化学位移各向异性的自旋对(例如13Co–13Co)表现更好。仿真和实验证实了这一结果。
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引用次数: 0
On the applicability of cosine-modulated pulses for high-resolution solid-state NMR of quadrupolar nuclei with spin > 3/2. 关于余弦调制脉冲在自旋>3/2的四极核的高分辨率固态NMR中的适用性。
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-04-01 DOI: 10.2139/ssrn.4359541
Akiko Sasaki, J. Trébosc, H. Nagashima, J. Amoureux
In MQMAS-based high-resolution solid-state NMR experiments of half-integer spin quadrupolar nuclei, the high radiofrequency (RF) field requirement for the MQ excitation and conversion steps with two hard-pulses is often a sensitivity limiting factor in many practical applications. Recently, the use of two cosine-modulated (cos) low-power (lp) pulses, lasting one-rotor period each, was successfully introduced for efficient MQ excitation and conversion of spin-3/2 nuclei with a reduced RF amplitude. In this study, we extend our previous investigations of spin-3/2 nuclei to systems with higher spin values and discuss the applicability of coslp-MQ excitation and conversion in MQMAS and MQ-HETCOR experiments under slow and fast spinning conditions. For the numerical simulations and experiments we used a moderate magnetic field of 14.1 T. Two spin-5/2 nuclei (85Rb and 27Al) are mainly employed with a large variety of CQ values, but we show that the practical set up is also available for higher spin values, such as spin-9/2 with 93Nb in Cs4Nb11O30. We demonstrate for nuclei with spin value larger than 3/2 a preferential use of coslp-MQ acquisition for low-gamma nuclei and/or large CQ values with a much reduced RF-field with respect to that of hard-pulses used with conventional methods.
在基于mqmas的半整数自旋四极核高分辨率固体核磁共振实验中,两个硬脉冲的MQ激发和转换步骤的高射频场要求在许多实际应用中往往是灵敏度限制因素。最近,成功地引入了两个余弦调制(cos)低功率(lp)脉冲,每个脉冲持续一个转子周期,用于有效的MQ激励和自旋3/2核的转换,并降低了射频振幅。在本研究中,我们将先前对自旋为3/2的原子核的研究扩展到更高自旋值的体系,并讨论了coslp-MQ激发和转换在慢速和快速自旋条件下MQMAS和MQ-HETCOR实验中的适用性。对于数值模拟和实验,我们使用了14.1 t的中等磁场,主要使用两个自旋为5/2的原子核(85Rb和27Al),其CQ值变化很大,但我们表明,实际设置也适用于更高的自旋值,例如Cs4Nb11O30中自旋为9/2的93Nb。我们证明了对于自旋值大于3/2的原子核,对于低伽马原子核和/或大CQ值的低伽马原子核和/或大CQ值的coslp-MQ采集的优先使用,相对于传统方法使用的硬脉冲的rf场要小得多。
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引用次数: 0
Selective excitation with recoupling pulse schemes uncover properties of disordered mineral phases in bone-like apatite grown with bone proteins 选择性激发与耦合脉冲方案揭示无序矿物相的性质在骨样磷灰石生长与骨蛋白
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-04-01 DOI: 10.1016/j.ssnmr.2023.101860
Irina Matlahov , Alexey Kulpanovich, Taly Iline-Vul, Merav Nadav-Tsubery, Gil Goobes

Bone construction has been under intensive scrutiny for many years using numerous techniques. Solid-state NMR spectroscopy helped unravel key characteristics of the mineral structure in bone owing to its capability of analyzing crystalline and disordered phases at high-resolution. This has invoked new questions regarding the roles of persistent disordered phases in structural integrity and mechanical function of mature bone as well as regarding regulation of early events in formation of apatite by bone proteins which interact intimately with the different mineral phases to exert biological control.

Here, spectral editing tethered to standard NMR techniques is employed to analyze bone-like apatite minerals prepared synthetically in the presence and absence of two non-collagenous bone proteins, osteocalcin and osteonectin. A 1H spectral editing block allows excitation of species from the crystalline and disordered phases selectively, facilitating analysis of phosphate or carbon species in each phase by magnetization transfer via cross polarization. Further characterization of phosphate proximities using SEDRA dipolar recoupling, cross-phase magnetization transfer using DARR and T1/T2 relaxation times demonstrate that the mineral phases formed in the presence of bone proteins are more complex than bimodal. They reveal disparities in the physical properties of the mineral layers, indicate the layers in which the proteins reside and highlight the effect that each protein imparts across the mineral layers.

多年来,骨结构一直在使用多种技术进行严格审查。固态核磁共振波谱有助于揭示骨骼中矿物结构的关键特征,因为它能够以高分辨率分析结晶相和无序相。这引发了关于持久性无序相在成熟骨的结构完整性和机械功能中的作用的新问题,以及关于通过与不同矿物相密切相互作用以发挥生物控制的骨蛋白对磷灰石形成的早期事件的调节的新问题。在这里,使用与标准NMR技术相关的光谱编辑来分析在存在和不存在两种非胶原蛋白骨钙素和骨连蛋白的情况下合成的类骨磷灰石矿物。1H光谱编辑块允许选择性地激发来自结晶相和无序相的物种,有助于通过交叉极化的磁化转移分析每个相中的磷酸盐或碳物种。使用SEDRA偶极重耦合、使用DARR和T1/T2弛豫时间的跨相磁化转移对磷酸盐接近性的进一步表征表明,在骨蛋白存在的情况下形成的矿物相比双峰更复杂。它们揭示了矿物层物理性质的差异,指示了蛋白质所在的层,并突出了每种蛋白质在矿物层中的作用。
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引用次数: 0
Theoretical description of pulse induced resonances in the homonuclear PIRATE experiment 同核PIRATE实验中脉冲诱导共振的理论描述
IF 3.2 3区 化学 Q1 Physics and Astronomy Pub Date : 2023-04-01 DOI: 10.1016/j.ssnmr.2023.101859
Orr Simon Lusky , Matthias Ernst , Amir Goldbourt

Rotor-synchronous π pulses applied to protons (S) enhance homonuclear polarisation transfer between two spins (I) such as 13C or 15N as long as at least a single I–S heteronuclear dipolar-coupling interaction exists. The enhancement is maximum when the chemical-shift difference Δν between two spins equals an integer multiple, n, of the pulse-modulation frequency, which is half the rotor frequency νr. This condition, applied in the Pulse Induced Resonance with Angular dependent Total Enhancement (PIRATE) experiment, can be generalised for any spacing of the pulses kr such that Δν=nνr2k . We show, using average Hamiltonian theory (AHT) and Floquet theory, that the resonance conditions promote a second-order recoupling consisting of a cross-term between the homonuclear and heteronuclear dipolar interactions in a three-spin system. The minimum requirement is a coupling between the two I spins and a coupling of one of the I spins to the S spin. The effective Hamiltonian at the resonance conditions contains three-spin operators of the form 2I1±I2Sz with a non-zero effective dipolar coupling. Theoretical analysis shows that the effective strength of the resonance conditions decreases with increasing values of k and n. The theory is backed by numerical simulations, and experimental results on fully labelled 13C-glycine demonstrating the efficiency of the different resonance condition for k=1,2 at various spinning frequencies.

施加在质子(S)上的转子同步π脉冲增强了两个自旋(I)(如13C或15N)之间的同核极化转移,只要至少存在单个I–S异核偶极耦合相互作用。当两个自旋之间的化学位移差ΔΓ等于脉冲调制频率的整数倍n时,增强最大,脉冲调制频率是转子频率Γr的一半。这一条件应用于具有角度相关总增强的脉冲诱导共振(PIRATE)实验,可以推广到脉冲k/μr的任何间隔,使得Δμ=nμr2k。使用平均哈密顿理论(AHT)和Floquet理论,我们证明了共振条件促进了由三自旋系统中同核和异核偶极相互作用之间的交叉项组成的二阶重新耦合。最低要求是两个I自旋之间的耦合以及其中一个I自旋与S自旋的耦合。共振条件下的有效哈密顿量包含三个形式为2I1±I2∓Sz的自旋算符,具有非零有效偶极耦合。理论分析表明,共振条件的有效强度随着k和n值的增加而降低。该理论得到了数值模拟的支持,并且在完全标记的13C-甘氨酸上的实验结果表明,在不同的自旋频率下,k=1,2的不同共振条件的效率。
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引用次数: 0
期刊
Solid state nuclear magnetic resonance
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