HOMO NUCLEAR RADIO FREQUENCY DRIVEN RECOUPLING IN ROTATING SOLIDS

旋转固体中的同质核射频驱动的重新耦合

• 批准号: 6279726
• 负责人: ANDREW E BENNETT
• 金额: $ 0.24万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-01 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6279726
• 关键词: biological products; biomedical resource; human tissue; nucleic acids; proteins

We have explored in more detail the underlying spin physics of RFDR, in order to facilitate the accurate measurement of weak dipole-dipole couplings between rare spins, and to understand the behavior of dipolar trajectories in multiple spin environments. RFDR has frequently been used as a tool for homonuclear 13C-13C (and 15N-5N) chemical shift correlation spectroscopy. We have presented in more detail several aspects of homonuclear recoupling and longitudinal exchange using rotor-synchronized spin echo sequences in solid state magic angle spinning (MAS) experiments. These experiments include in one limit (where N= 1 and ,z=0, one It pulse per rotor period) the standard version of RFDR, and in other cases (e.g., N=4, n=2) frequency-selective versions. The recoupling effect can be quenched in a manner similar to R2 so that only particular chemical shift differences are recoupled; in addition, selective RFDR permits recoupling of spins for which the chemical shift differences are not a small integer multiple of the MAS rate. This frequency-selective approach has possible utility in examining weak dipole-dipole couplings in the presence of strong interactions. To describe dipolar trajectories accurately, we have adopted an approach to the simulation of these experiments which includes finite pulses and the influence of coherence decay. The latter effect becomes competitive with the strength of weak couplings in many experiments, and a simple empirical approach has been outlined for the selection of decay parameters. In multi-spin systems, dipolar trajectories are shown to be dominated by the largest couplings. This has been demonstrated in two- and three-spin model compounds, as well as numerous U- 3C, 5N-labeled peptides, nucleoside monophosphates, and amino acids. For example, two-dimensional correlation spectroscopy based on dipolar exchange among proximate nuclei has been demonstrated in a uniformly 15Nj3C-labeled sample of the tetrapeptide achatin-Il (Gly-L-Phe-L-Ala-L-Asp).

我们已经更详细地探讨了 RFDR，以便于准确测量弱 偶极偶极耦合之间的罕见自旋，并了解 多自旋环境中偶极轨道的行为。 RFDR 经常用作同核13 C-13 C（和 15 N-5 N）化学位移相关光谱。 我们已经介绍了在 更详细的几个方面的homecoupling和纵向 使用固态转子同步自旋回波序列进行交换 魔角旋转（MAS）实验。 这些实验包括在 一个极限（其中N= 1，z=0，每个转子周期一个It脉冲）， RFDR的标准版本，而在其他情况下（例如，N=4，n=2） 频率选择版本。 再耦合效应可以被抑制 以类似于R2的方式， 差异被重新耦合;此外，选择性RFDR允许 化学位移差不为零的自旋的再耦合 MAS速率的小整数倍。 这种频率选择性 这种方法在研究弱偶极-偶极 在强相互作用的存在下的耦合。 来描述偶极 轨迹准确，我们采用了一种方法来模拟 这些实验，其中包括有限脉冲和影响， 相干衰减 后一种效应与 在许多实验中弱耦合的强度，和一个简单的经验 的方法已被概述的衰变参数的选择。 在 多自旋系统，偶极轨迹被证明是占主导地位的 最大的耦合。 这已经在两个方面得到了证明， 三自旋模型化合物，以及许多U- 3C，5 N标记的 肽、核苷一磷酸和氨基酸。 比如说， 偶极交换二维相关光谱 在最近的核之间，已经证明了在一个统一的 15 Nj 3 C标记的四肽achatin-Il样品 （Gly-L-Phe-L-Ala-L-Asp）。