Dynamics of Bengal Rose Encapsulated in the Meijer Dendrimer Box
Miklis, P, Cagin, T. and Goddard, W. A.
J. Amer. Chem. Soc.131, 7458 (1997)
We used molecular dynamics (MD) techniques to examine the
encapsulation of Bengal Rose (BR) molecules in the Meijer Dendrimer Box
(DBox) formed by the addition of
tert-butyloxycarbonyl-L-Phe (tBOC-L-Phe) cap molecules to the 64 terminal
amines of a fifth generation poly(propyleneimine) (PPI-5) dendrimer. Using
a large periodic box (including DBox, 4 to 6 BR, and
CH2Cl2 solvent, totaling ~25,000 atoms),
we examined the MD of
these systems for ~0.5 ns. Without the cap we find that BR
molecules establish a concentration dependent equilibrium between the
interior and surface regions of PPI-5 and the solvent region outside the
dendrimer. The number of BR molecules calculated to associate with the
interior of the PPI-5 dendrimer agrees
exactly with experiment (at the same BR/PPI concentration).
MD simulations on the DBox in CH2Cl2
show that the tBOC-L-Phe surface is completely impermeable to
encapsulated BR molecules, even when an excess is forced inside the box.
correspondence of the theory with experiment suggests that these methods
can be used to design such systems in advance of experiment.