A Family of PISEMA Experiments for Structural Studies of Biological Solids

Abstract

Narrowest heteronuclear dipolar coupling spectral lines provided by the two-dimensional polarization inversion spin exchange at the magic angle (PISEMA) technique lead to the development and application of a series of mul-tidimensional solid-state NMR methods for the structural studies of biological solids. Studies have shown that the measurement of structural and orientational constraints from uniformly labeled proteins using PISEMA is crucial, particularly in the structure determination of membrane-associated proteins. Excellent line-narrowing efficiency, high scaling factor, and performance at various magic-angle-spinning (MAS) speeds and radio frequency (rf) power are the main advantages of PISEMA. However, high rf power requirement and offset effects are the major limitations of this technique. In this chapter, these difficulties and methods to overcome them are discussed for both static and MAS experimental conditions. Experimental and simulated data to demonstrate the efficacy of newly developed PISEMA-type pulse sequences are also presented .