Analysis of solid state C-13 NMR spectra of biologically active compounds

The characteristic features of C-13 solid state NMR applications are discus sed. The spectra are routinely measured with cross-polarisation (CP) pulse sequence and fast spinning under magic angle (MAS). Additional techniques ( dipolar dephase, variation of cross-polarisation contact time) influence th e signal intensities and enable selective observation of nonprotonated or p rotonated carbons. Solid state NMR is complementary to X-ray diffraction an d provides structural information about solids when the attempts to grow su itable single crystals have failed. However the combination of both methods is more successful in characterisation of solid state conformations and dy namic processes. Many medium sized molecules such as: saccharides, amino acids, peptides, st eroids, polyphenols (flavonoids), and tocopherol derivatives have been stud ied. Samples that are insoluble in commonly used solvents or easily decompo se in solution should be investigated by solid state NMR. Since the method can be applied to crystalline as well as to amorphous powders it is especia lly interesting tool in the studies of macromolecules. Numerous results con cerning peptides, proteins and polysaccharides are reported.