P. Borgnat et al., IMPROVED SENSITIVITY IN SELECTIVE NMR CORRELATION SPECTROSCOPY AND APPLICATIONS TO THE DETERMINATION OF SCALAR COUPLINGS IN PEPTIDES AND PROTEINS, Journal of the American Chemical Society, 118(39), 1996, pp. 9320-9325
A new method, providing a significant improvement in sensitivity, is p
resented for obtaining selective two-dimensional NMR correlation (COSY
) spectra. The method is demonstrated on a small molecule having nonli
near optical properties and is further demonstrated by the precise det
ermination of scalar coupling constants in the peptide gramicidin and
in a 57 amino acid fragment of the nucleocapsid of the hepatitis C vir
us, In these systems we observe sensitivity improvements of between a
factor of 2 and 6. In the case of the protein it was not practical to
record the selective COSY spectra using conventional techniques. The m
ethod makes use of the recently introduced concept of ''linear'' selec
tive pulses which provide a simple way of obtaining pure-phase band se
lective excitation with an arbitrary shape for the response. In a sele
ctive 2D COSY experiment the relative sensitivity improvement provided
by these pulses is cubed with respect to a 1D experiment. The resulti
ng pulse sequences are highly unusual in that they require a modulatio
n of the pulse shape and pulse length as the indirect detection period
is increased.