Project 03BMP03: Fresh from the press

We explore new methods to determine structure in structurally flexible proteins. One approach is to use two spin labels, which are incorporated into proteins by linking them to genetically engineered cysteins and measure the distance between them using specially designed EPR pulsed methods, such as double electron electron resonance - DEER (Drescher et al. JACS, 2008)

While nm-distance constraints can be measured by DEER, the method is not suitable to measure the distance between spin labels and paramagnetic metal centers. This is unfortunate because such centers are convenient native distance markers. We show that the relaxation induced dipolar magnetic resonance (RIDME) method (Kulik et al. (2002)) can do the trick. Our new sequence, 5p-RIDME, shown in the Figure (bottom) designed to remove the dead time makes it possible to measure the distance between a lowspin Fe(III) center and a spin label in spin-labeled cytochrome f . Read more: Journal of Magnetic Resonance 201 (2009) 48–56