MAGNETIC SPIN-SPIN INTERACTIONS OF COENZYME B12

这个项目的目的是阐明 两个顺磁物种之间的磁自旋-自旋相互作用 辅酶B12均解钴-碳键断裂形成 以及相关的多晶态或多晶态的模型化合物 光诱导的模型膜。实验研究是 规划采用多频段(Q波段、X波段、S波段、L波段) 多晶的电子自旋共振(ESR)谱 辅酶B12及其已知结构的模型化合物 X射线测定。类似的研究将在 辅酶B12和与模型化合物分散在两个不同的 脂质双层：L-α-二肉豆蔻酰磷脂酰胆碱a 饱和脂肪和蛋黄磷脂酰胆碱和不饱和 脂类。关于血沉测量，线型将 使用矩阵对角化技术或 摄动法。钴自由基自旋自旋的值 耦合常数J0将根据两个线形确定 电渣重熔面积随温度变化的数值模拟 信号。中两个自旋之间的偶极距离 将使用两种线形模拟来估计三线态 和一个比较相对强度的一般关系 半场线VS全场线。相对的 Co(II)和自由基的位置可以是 是由“磁性几何”的概念决定的 由多频ESR线型定义。此外，我们 拟确定参数德尔塔不等于，德尔塔S 不等于和钴的键离解能- 辅酶B12的碳键及其模型化合物 光解均相速率与温度的关系 模型膜中的卵裂。参与或参与 轴向配体苯并咪唑在活性中的作用 而同质溶解的速度将会被确定 使用碱基和碱基脱基的辅酶B12模型化合物。 这些研究可能有助于更好地理解辅酶B12 在生化系统中。

The objectives of this project are to elucidate the nature of magnetic spin-spin interactions between two paramagnetic species formed in homolytic cobalt-carbon bond cleavage of coenzyme B12 and related model compounds in a polycrystalline state or in model membranes induced by light. Experimental studies are planned using multi-frequency (Q-band, X-band, S-band and L-band) electron spin resonance (ESR) spectroscopy on polycrystalline coenzyme B12 and model compounds with known structures based on X-ray determinations. Similar studies are to be performed on coenzyme B12 and with model compounds dispersed in two different lipid bilayers: L-alpha-dimyristoylphosphatidylcholine a saturated lipid and egg yolk phosphatidylcholine an unsaturated lipid. With regard to the ESR measurements, the lineshapes will be calculated using either matrix diagonalization techniques or perturbation methods. The values of the cobalt-radical spin-spin coupling constants, J0, will be determined from both lineshape simulation and the temperature dependence of the area of the ESR signals. The dipolar distance between the two spins in the triplet state will be estimated using both lineshape simulation and a general relationship comparing the relative intensity of the half-field line vs. the full-field line. The relative positions of the Co(II) and the free radical can then be determined from the "magnetic geometry" idea which is well defined by multi-frequency ESR lineshapes. In addition, we intend to determine parameters delta eta not equal to, delta S is not equal to and the bond dissociation energies of the cobalt- carbon bond of coenzyme B12 and the model compounds from the temperature dependence of the rate of homolysis by photolytic cleavage in model membranes. The participation or the contribution of the axial ligand benzimidazole in the activation and the rate of homolysis is of interest which will be determined using both base-on and base-off coenzyme B12 model compounds. These studies may lead to a better understanding of coenzyme B12 in biochemical systems.