Proton-proton correlation via carbon-carbon couplings: a three-dimensional NMR approach for the assignment of aliphatic resonances in proteins labeled with carbon-13
Proton-proton correlation via carbon-carbon couplings: a three-dimensional NMR approach for the assignment of aliphatic resonances in proteins labeled with carbon-13
复制标题
通过碳-碳耦合的质子-质子关联：一种三维 NMR 方法，用于分配碳 13 标记的蛋白质中的脂肪族共振
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
A. Bax
中科院分区：
文献类型：
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作者：
L. Kay;M. Ikura;A. Bax
在2D 13 C TOCSY-REVINEPT实验中，在MLEV-17混合时间之后立即进行。这导致了一个实验，其中13 CNMR信号和标量相关的I3 C自旋分别在wI和wz中被检测到，并且附着到碳（wz）上的质子在w3中被检测到。[13 C，1 SN] T4溶菌酶的3D [13 C-13 C-1H] TOCSY-REVINEPT光谱的横截面（~ 1，0 3）如图1、B和C所示。与2D“C TOCSY-REVINEPT光谱相比，该光谱明显简化，便于鉴定氨基酸自旋系统。例如，从位于69.2 ppm（q）的（w I，w ~）平面，三种氨基酸自旋系统的I3 C光谱被解析，并从特征I3 C化学位移被鉴定为苏氨酸。由于该平面位于这些残基的@-碳的典型频率处，因此也获得了@-质子化学位移（w3）。苏氨酸自旋系统的其他质子的位移由位于C1 a和C1 y碳的w2频率（等于w1频率）处的平面确定。如图C中的y质子所示，这些质子频率可以容易地从更拥挤的平面中提取，因为它们包含与B质子相同的I3 C（al）子光谱（图B）。总之，2D和3D NMR实验描述了采用各向同性13 C-13 C磁化转移，以提供大蛋白质光谱中的I3 C和'H信号的自旋系统分配。这些分配，这不能从经典的质子2D实验中获得，是必要的识别用于大蛋白质的结构测定的NOES。
directly after the MLEV-17 mixing time in the 2D 13C TOCSY-REVINEPT experiment. This leads to an experiment in which 13C N M R signals and the scalar correlated I3C spins are detected in wI and wz, respectively, and the protons attached to the carbons (wz) are detected in w3. Cross-sections ( ~ l , 0 3 ) of a 3D [13C-13C-1H] TOCSY-REVINEPT spectrum of [13C,1SN] T4 lysozyme are shown in Figure 1, B and C. The spectra are markedly simplified compared to the 2D "C TOCSY-REVINEPT spectra, facilitating the identification of the amino acid spin systems. For example, from the ( w I , w ~ ) plane located at 69.2 ppm (q), the I3C spectra of three amino acid spin systems are resolved and identified as threonines from the characteristic I3C chemical shifts. Since this plane is located at a frequency typical for @-carbons of these residues, the @-proton chemical shifts (w3) are also obtained. The shifts of the other protons of the threonine spin systems are determined from planes located at the w2 frequencies (equal to the wl frequencies) of the C a and C y carbons. As illustrated for the y protons in panel C, these proton frequencies can easily be extracted from more crowded planes because they contain the same I3C (al) subspectrum as the B protons (panel B). In conclusion, 2D and 3D NMR experiments are described that employ isotropic 13C-13C magnetization transfer to provide spin system assignments for both I3C and 'H signals in the spectra of large proteins. These assignments, which cannot be obtained from classical proton 2D experiments, are necessary for the identification of NOES used in the structure determination of large proteins.