Facile measurement of polypeptide JHNHα coupling constants from HMQC-J spectra.

A method, based on linewidth measurements, is described which permits the rapid and facile determination of J_HNHα coupling constants from ¹⁵N labeled proteins. Using appropriately processed HMQC-J data, we have found that a simple linear relationship exists between the half-height linewidth (Δν_1/2) of ¹⁵N–¹H cross peaks and their corresponding J_HNHα coupling constants. Tests indicate that this technique permits the accurate measurement of up to 100 J_HNHα coupling constants in less than 30 min. Furthermore, the J_HNHα measurements can be done manually – without the need of any computer-based curve-fitting or minimization. Comparisons between J_HNHα values predicted from high resolution X-ray structures and those determined using this technique indicate that the method is both accurate and precise (correlation coefficient = 0.90, rmsd = 0.75 Hz). [ABSTRACT FROM AUTHOR]