Principles of self-assembly of helical pores from dendritic dipeptides

doi:10.1073/pnas.0509676103

Principles of self-assembly of helical pores from dendritic dipeptides

*Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323; and
^‡Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104-6396

Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved December 27, 2005 (received for review November 7, 2005)

Abstract

The self-assembly of the dendritic dipeptides (4-3,4-3,5)nG2-CH₂-Boc-l-Tyr-l-Ala-OMe and their achiral dendritic alcohol (4-3,4-3,5)nG2-CH₂OH precursors, both with n = 1–16, where n represents the number of methylenic units in the alkyl groups of the dendron, are reported. All chiral dendritic dipeptides and achiral dendritic alcohols self-assemble into helical porous columns that are stable in both solution and solid state. The pore diameter (D_pore) of the columns self-assembled from dendritic dipeptides is ≈10 Å larger than that of structures assembled from dendritic alcohols. The increase of the D_pore at the transition from dendritic alcohol to dendritic dipeptide is accompanied by a decreased solid angle of the building block. This trend is in agreement with previous pore size-solid angle dependences observed with different protective groups of the dipeptide and primary structures of the dendron. However, within the series of dendritic alcohols and dendritic dipeptides with various n, the D_pore increases when the solid angle increases. The results of these investigations together with those of previous studies on the role of dipeptide stereochemistry and protective groups on this self-assembly process provide the molecular principles required to program the construction of supramolecular helical pores with diameter controlled at the Å level from a single dendritic dipeptide architecture. These principles are expected to be valid for libraries of dendritic dipeptides based on dendrons and dipeptides with various primary structures.

Footnotes

^†To whom correspondence should be addressed. E-mail: percec{at}sas.upenn.edu
Author contributions: V.P. designed research; A.E.D., M.P., M.I., S.N., and M.J.S. performed research; A.E.D. and M.P. contributed new reagents/analytic tools; V.P., A.E.D., M.P., M.I., and P.A.H. analyzed data; and V.P. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

DSC,

differential scanning calorimetry;

XRD,

x-ray diffraction;

Φh,

hexagonal columnar lattice;

Φr,

rectangular columnar lattice;

Φr-c,

centered rectangular columnar lattice;

Φr-s,

simple rectangular columnar lattice;

io,

intracolumnar order;

Dcol,

column diameter;

Dpore,

pore diameter.