CPMAS spectra of crystalline (a) and amorphous (b) disaccharides -trehalose, -lactose, and sucrose. The assignment of the NMR lines is presented for the two carbons involved in the glycosidic bond.
Ramachandran relaxed maps of -trehalose, -lactose, and sucrose, calculated with the molecular mechanics BIO85 force field. The origin of energies is placed at the lowest minimum for each sugar with contour lines labeled every . Dots show the conformation of the anhydrous (crossed circle) or hydrated (crossed square) crystalline forms.
isotropic chemical shift surfaces of the carbons involved in the glycosidic bond of -trehalose, -lactose, and sucrose. The maps were calculated by DFT on the same molecular conformations defining the energy maps . The contour lines are labeled every .
Lower line: best fits of the experimental CPMAS spectrum (dashed line) with the chemical shift distributions for the glycosidic carbons of -trehalose, -lactose, and sucrose, using Gaussian (solid black line) or Boltzmann (solid gray line) conformational probability . Upper line: corresponding best-fit Gaussian probability surfaces .
Plot of the inverse nonergodicity parameter as a function of . The values of have been calculated according to Bordat et al. (Ref. 14). The scaling glass transition temperatures are the experimental and for trehalose and sucrose, respectively.
Dihedral angles and defining the glycosidic torsion angles of -trehalose, -lactose, and sucrose.
Coefficients of the linear conversion from calculated magnetic shielding to chemical shift .
Lowest energy conformations calculated from the BIO85 force field for trehalose, lactose, and sucrose, compared to the dihedral angles observed in crystalline forms (Refs. 23, 24, 26, 34, and 42) of trehalose, lactose and sucrose.
Parameters of the best-fit populations of the Gaussian form (see Fig. 4) and of the Boltzmann partition on the maps calculated with the BIO85 force field (see Fig. 2).
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