Multiple selective excitation as a tool for NMR studies of paramagnetic metalloproteins

The original use of shifted laminar pulses to excite selectively several hy perfine-shifted signals spread over a spectral window as large as 100 ppm i s presented. As an application of such a multi-site selective excitation we developed a multiNOE difference experiment which permits one to detect dip ole-dipole couplings arising from various well separated hyperfine-shifted signals within a single one-dimensional experiment. Although typical inform ation on a 1D NOE experiment is lost when several signals are simultaneousl y irradiated, the experiment can be useful for collecting selective relaxat ion rates from NOE build-up curves. This will provide a significant gain in experimental time with respect to a series of individual NOE build-up expe riments. Such experiments can also be used as a building block for multi-di mensional experiments such as multiNOE-NOESY, which maintains the selective information of 1D NOE and can, therefore, be used for assignment purposes. This constitutes the first application of a chemical shift-based filter as a complement to relaxation-based filters, generally used when dealing with paramagnetic systems. The application of multiple selective pulses in para magnetic systems is expected to be particularly useful when dealing with do uble and triple resonance experiments on isotopically enriched samples. Coh erence transfer pathways involving only resonances affected by the hyperfin e interactions could be selected by this approach. Copyright (C) 2000 John Wiley & Sons, Ltd.