RESUMEN
The past few years have seen the development of three- and four-dimensional heteronuclear nuclear magnetic resonance methods. Increased sophistication in labelling strategies, use of pulse-field gradients and the application of these methods at higher magnetic fields has, in combination with improved software, allowed studies of the structure, interactions and dynamics of significantly larger proteins (now up to approximately 270 amino acid residues).
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Conformación Proteica , Proteínas/química , Animales , Enzimas/química , Estructura Secundaria de Proteína , Sensibilidad y EspecificidadRESUMEN
The use of pulsed field gradients in multiple-pulse NMR experiments has many advantages, including the possibility of obtaining excellent water suppression without the need for selective presaturation. In such gradient experiments the water magnetization is dephased deliberately; exchange between the saturated protons of the solvent water and the NH protons of a protein transfers this saturation to the protein. As the solvent is in large excess and relaxes relatively slowly, the result is a reduction in the sensitivity of the experiment due to the fact that the NH proton magnetization is only partially recovered. These effects can be avoided by ensuring that the water magnetization remains intact and is returned to the +z-axis at the start of data acquisition. General procedures for achieving this aim in any triple-resonance experiment are outlined and two specific examples are given. Experimental results confirm the sensitivity advantage of the modified sequences.