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Dipolar couplings are an important source of structure as they provide sitespecific dipolar splittings for aligned samples and hence are extensively usedfor the study of membrane proteins in lipid bilayers, liquid crystals andsingle crystals. Of the many Separated Local Field (SLF) techniques existing toavail this information for static oriented systems, PISEMA (PolarizationInversion Spin Exchange at Magic Angle) has found to have wide application dueto its many favorable characteristics. However the pulse sequence suffers fromits inherent sensitivity to proton resonance frequency offset. We have recentlyproposed a sequence named DAPT (Dipolar Assisted Polarization Transfer: S.Jayanthi et al. Chem. Phys. Lett. 439, 407, 2007.) for dipolar couplingmeasurement which is found to be insensitive to proton offsets over wide range.In this presentation, we report the first implementation of the sequence onrigid systems. Experiments were done on a single crystal of N-Acetyl DL-Valine(NAV). Dipolar couplings measured from the 2D DAPT spectrum is used foridentifying the orientations of the magnetically in-equivalent molecules in theunit cell. SLF spectrum of NAV is complicated due to the presence of twomagnetically in-equivalent molecules in the unit cell and with pairs ofsplitting for each C(alpha) - 1H and C(beta) - 1H. The molecular orientationhas been identified by incorporating the crystal coordinates and constructing athree dimensional rotation matrix about an arbitrary axis using Rodrigues'rotation formula with the aid of a MATLAB program. Dipolar couplings measuredfrom the spectrum is used for all the calculations. The algorithm proposed hereis simple and hence can be easily accessible for various other studies aimedfor structural elucidation.

Offset-free Measurement of Dipolar Couplings in a Single Crystal and Determination of Molecular Orientation