Alanine Radicals: Structure Determination by EPR and ENDOR of Single Crystals X-Irradiated at 295 K
Alanine Radicals: Structure Determination by EPR and ENDOR of Single Crystals X-Irradiated at 295 K
复制标题
丙氨酸自由基：通过 EPR 和 ENDOR 对 295 K 下 X 辐照的单晶进行结构测定
DOI：
10.1021/jp972158k
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发表时间：
1997
影响因子：
2.9
通讯作者：
W. Nelson
中科院分区：
文献类型：
--
作者：
E. Sagstuen;E. Hole;Andreas Haugedal;W. Nelson
在室温下对氨基酸l-α-丙氨酸的单晶进行X射线辐照，并在220 - 295 K的温度区间内使用X-带和K-带EPR、ENDOR和EIE（ENDOR诱导EPR）光谱研究了自由基的形成。借助于EIE的结果，以及ENDOR从选定的磁场位置，九个超精细耦合张量，并分配到三个不同的自由基。室温下的松弛行为，其特征在于有效的W1 x和W1 e和缓慢的W1 n弛豫速率允许测定的各种超精细耦合的迹象，在室温下获得的ENDOR光谱。定性地讨论了W1 x弛豫的温度依赖性。从丙氨酸的EPR光谱是由众所周知的共振的“稳定的丙氨酸自由基”，SAR，由质子化的丙氨酸阴离子的净脱氨基形成的。精确的超精细耦合张量，由于α-质子耦合，甲基耦合，和偶极…
Single crystals of the amino acid l-α-alanine have been X-irradiated at room temperature, and the free radical formation has been studied using X-band and K-band EPR, ENDOR, and EIE (ENDOR-induced EPR) spectroscopy in the temperature interval 220−295 K. Aided by the results from EIE, as well as ENDOR from selected magnetic field positions, nine hyperfine coupling tensors were obtained and assigned to three different radicals. Room-temperature relaxation behaviors characterized by efficient W1x and W1e and by slow W1n relaxation rates allowed for determination of the signs of the various hyperfine couplings from the ENDOR spectra obtained at room temperature. The temperature dependence of the W1x relaxation is qualitatively discussed. The EPR spectra from alanine are dominated by the well-known resonance of the “stable alanine radical”, SAR, formed by a net deamination of the protonated alanine anion. Precise hyperfine coupling tensors due to the α-proton coupling, the methyl group coupling, and a dipolar ...