Molecular Modelling Study of the 2:1 γ-Cyclodextrin:C⁶⁰ Complex. Dummy Atoms Simulating Bond Electron Distribution

Abstract

The 2:1 γ-cyclodextrin:C⁶⁰ inclusion complex was studied by molecular dynamics simulations with the AMBER package. Dummy atoms were used to incorporate the various electron densities on the fullerene bonds into the molecular mechanics scheme. According to our MD simulations, the two γ-cyclodextrins adopt a V-shape in the complex, which strengthens some intermolecular hydrogen bonds. Fullerene interacts better with O2 than with O3 oxygens (from the secondary hydroxyl groups on C2 and C3, respectively); no interactions with glycosidic O4 were detected.

Keywords:

• Cyclodextrins
• Inclusion complexes
• Molecular modelling
• Molecular dynamics
• Fullerene

Acknowledgements

Prof. E. Osawa, from Toyohashi University of Technology (Japan), is thanked for providing us with the fullerene atomic co-ordinates. Financial support was given by DGES through grant no. PB96-1181. CESCA-C⁴ is thanked for allocating computational time. The UAB and the TMR program of the European Community (Contract number ERB FMGE CT95 0062) are thanked for fellowships to two of us (I.B. and P.B, respectively).

Notes

^†The parameter used is: ANGLE OS–CT–OS: .

^‡For example, the C1–C2–C3 unit is now converted into the C1–D1–C2–D2–C3 unit. Consequently, C1 and C3 have strong repulsive vdW interactions.

^¶BOND DP–CA: BOND DN-CA: ANGLE CA–DP–CA:

^§This methodology was checked against its behavior with the benzene molecule.