Self-assembly of synthetic peptides control conformation and optical properties of a zwitterionic polythiophene derivative

^†Biomolecular and Organic Electronics and ^¶Organic Chemistry, Department of Physics and Measurement Technology, Biology, and Chemistry, Linköping University, SE-581 83 Linköping, Sweden

Communicated by Alan J. Heeger, University of California, Santa Barbara, CA, July 15, 2003 (received for review April 24, 2003)

Abstract

The optical transitions of a chiral, three-substituted polythiophene with an amino acid function can be tuned by interactions with synthetic peptides. The addition of a positively charged peptide with a random-coil formation will force the polymer to adopt a nonplanar conformation, and the intensity of the emitted light is increased and blue-shifted. After the addition of a negatively charged peptide with a random-coil conformation, the backbone of the polymer adopts a planar conformation and an aggregation of the polymer chains occurs, seen as a red shift and a decrease of the intensity of the emitted light. By adding the positively charged peptide designed to form a four-helix bundle with the negatively charged peptide, the polymer aggregates are disrupted and the intensity of the emitted light is increased because of separation of the polymer chains. This technique could be used as a platform for making novel sensors and biomolecular switches.

Footnotes

↵ § To whom correspondence should be addressed. E-mail: petni{at}ifm.liu.se.
↵ ‡ There is a patent application concerning the technique described in this article: detection of biospecific interactions with a fluorescent zwitterionic CP.
Abbreviations: CP, conjugated polymer; POWT, poly{3-[(S)-5-amino-5-carboxyl-3-oxapentyl]-2,5-thiophenylene hydrochloride}; ICD, induced CD.