MECHANISM OF THE RMAL MIXING DYNAMIC NUCLEAR POLARIZATION IN 4 AMINO TEMPO

4 氨基速度下的正常混合动态核极化机制

• 批准号: 6279713
• 负责人: DENNIS A HALL
• 金额: $ 1.18万
• 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/6279713
• 关键词: biological products; biomedical equipment development; biomedical resource; proteins; technology /technique

The mechanism of electron-nuclear polarization transfer from the TEMPO free radical to proton spins relies on a thermal mixing mechanism. In DNP experiments at lower fields, the solid effect (direct irradiation of simultaneous electron-nuclear transitions) is typically exploited. However, at higher fields, the solid effect efficiency drastically decreases because it relies on a ncmina]ly forbidden, second-order transition. Thermal mixing is driven by direct irradiation of EPR transitions, and thus does not have the stringent requirements on microwave power which the solid effect possesses. However, while thermal mixing at low fields typically involves a homogeneous EPR line, the TEMPO EPR line at 5 T is inhomogenously broadened, primarily by g-anisotropy. We have performed a number of experiments which elucidate the mechanism at high field, suggesting that electron-electron cross relaxation allows spin diffusion across the EPR line, rendering it effectively homogeneous at high radical concentrations. Electron-electron double resonance (ELDOR) experiments and EPR saturation recovery experiments both provide clear evidence of cross-relaxation across the TEMPO line.

电子-核极化转移机制 TEMPO 自由基到质子自旋依赖于热混合 机制。 在较低场的 DNP 实验中，固体效应 （同时电子-核跃迁的直接照射）是 通常被利用。 然而，在更高的场，固体效应 效率急剧下降，因为它依赖于 禁止的二阶跃迁。 热混合由以下因素驱动 直接照射 EPR 跃迁，因此不具有 对微波功率的严格要求，固效 拥有。 然而，虽然低场下的热混合通常 涉及同质 EPR 线，5 T 下的 TEMPO EPR 线为 不均匀地展宽，主要是由于 g 各向异性。 我们有 进行了许多实验来阐明其机制 高场，表明电子-电子交叉弛豫允许 自旋扩散穿过 EPR 线，有效渲染它 在高自由基浓度下均匀。 电子-电子双 共振（ELDOR）实验和EPR饱和恢复实验 两者都提供了跨 TEMPO 线交叉松弛的明确证据。