RELAXATION TIME MEASUREMT OF NITROXIDE PROBES FOR SCANNED-PROBE MAGNETIC FORCE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 John Marohn开发了一种方法，将磁共振超灵敏力量梯度检测的适用范围扩展到自旋晶格弛豫时间(T1)短至单悬臂周期的样品。通过在4.2K和0.6T下用T1=1ms氮氧化物自旋探针(TEMPAMINE)在4.2K和0.6T下检测薄膜中的电子自旋共振，证明了该方法的一般性，该方法依赖于检测悬臂梁频率或相位，并使用定制的直径为4Mu m的镍尖悬臂梁在1 Hz的带宽内获得了410个玻尔磁子的磁共振灵敏度。这个实验背后的理论定量地预测了观测到的悬臂频移的线形和大小，作为场和悬臂-样品分离的函数。这种新的方法有许多优点，使其非常适合于单个大分子中单自旋敏感的氮氧化物自旋标记的磁共振检测和成像。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. John Marohn has developed an approach that extends the applicability of ultrasensitive force gradient detection of magnetic resonance to samples with spin-lattice relaxation times (T1) as short as a single cantilever period. The generality of the approach, which relies on detecting either cantilever frequency or phase, was demonstrated by detecting electron spin resonance from a T1 = 1 ms nitroxide spin probe (TEMPAMINE) in a thin film at 4.2 K and 0.6 T. A custom fabricated cantilever with a 4 Mu m diameter nickel tip, was used to achieve a magnetic resonance sensitivity of 410 Bohr magnetons in a 1 Hz bandwidth. The theory underlying this experiment quantitatively predicts both the lineshape and the magnitude of the observed cantilever frequency shift as a function of field and cantilever-sample separation. The new approach has a number of advantages that make it well suited for magnetic resonance detection and imaging of nitroxide spin labels in an individual macromolecule at single-spin sensitivity