Complete 13C NMR Chemical Shifts Assignmentfor Cholesterol Crystals by Combined CP-MAS Spectral Editing and abInitio GIPAW Calculations with Dispersion Forces.

We report here the first fully ab initiodetermination of 13C NMR spectra for several crystalstructures of cholesterol, observedin various biomaterials. We combine Gauge-Including Projector AugmentedWaves (GIPAW) calculations at relaxed structures, fully includingdispersion forces, with Magic Angle Spinning Solid State NMR experimentsand spectral editing to achieve a detailed interpretation of the complexNMR spectra of cholesterol crystals. By introducing an environment-dependentsecondary referencing scheme in our calculations, not only do we reproducethe characteristic spectral features of the different crystallinepolymorphs, thus clearly discriminating among them, but also closelyrepresent the spectrum in the region of several highly overlappingpeaks. This, in combination with spectral editing, allows us to providea complete peak assignment for monohydrate (ChM) and low-temperatureanhydrous (ChAl) crystal polymorphs. Our results show that the synergybetween ab initio calculations and refined experimental techniquescan be exploited for an accurate and efficient NMR crystallographyof complex systems of great interest for biomaterial studies. Themethod is general in nature and can be applied for studies of variouscomplex biomaterials. [ABSTRACT FROM AUTHOR]