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Exploring the conformational energy landscape of glassy disaccharides by cross polarization magic angle spinning nuclear magnetic resonance and numerical simulations. II. Enhanced molecular flexibility in amorphous trehalose
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10.1063/1.2409935
/content/aip/journal/jcp/126/1/10.1063/1.2409935
http://aip.metastore.ingenta.com/content/aip/journal/jcp/126/1/10.1063/1.2409935

Figures

Image of FIG. 1.
FIG. 1.

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.

Image of FIG. 2.
FIG. 2.

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.

Image of FIG. 3.
FIG. 3.

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 .

Image of FIG. 4.
FIG. 4.

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 .

Image of FIG. 5.
FIG. 5.

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.

Tables

Generic image for table
Table I.

Dihedral angles and defining the glycosidic torsion angles of -trehalose, -lactose, and sucrose.

Generic image for table
Table II.

Coefficients of the linear conversion from calculated magnetic shielding to chemical shift .

Generic image for table
Table III.

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.

Generic image for table
Table IV.

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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/content/aip/journal/jcp/126/1/10.1063/1.2409935
2007-01-05
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Exploring the conformational energy landscape of glassy disaccharides by cross polarization magic angle spinning C13 nuclear magnetic resonance and numerical simulations. II. Enhanced molecular flexibility in amorphous trehalose
http://aip.metastore.ingenta.com/content/aip/journal/jcp/126/1/10.1063/1.2409935
10.1063/1.2409935
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