Single molecule spectroscopy of bioobjects

This project is related to the following Fields, Subjects and Techniques:

This work is being carried out in close collaboration with the Centre of Organic Electronics (COE) supported by the Swedish Foundation for Strategic Research. The head of the COE is Prof. Olle Inganas, the Group of biomolecular and organic electronics, Department of Physics, Linkoping University, Sweden.

Combination of special conjugated polymers with bio-molecules like DNA is a step forward towards "smart self-assembled materials" where DNA molecules of controlled size and structure work as frames for functional supramolecular nano-structures. Due to inherent large inhomogeneity of such complexes SMS is absolutely necessary in order to rationalize the properties of those promising nano-materials. We also use SMS to study biospecific interactions between CPs and DNAs providing a basis for biodetection where conjugated polymers work as very stable fluorescence probes sensitive to DNA conformation.

Fluorescence image of stretched DNAs decorated by a conjugated polymer

Single Molecular Imaging and Spectroscopy of Conjugated Polyelectrolytes Decorated on Stretched Aligned DNA
P.Bjork, A.Herland, I.G.Scheblykin and O.Inganas,Nano Lett, 2005, 5, 1948

We also studied amyloid fibrils from bovine insulin decorated with an alternating polyfluorene derivative (APFO-12). Decorated fibrils were partially aligned on hydrophobic surfaces as separate and bundled fibrils, by means of molecular combing. Single molecule spectroscopy technique utilizing excitation by rotating linearly polarized light and fluorescence detection through a rotating polarizer showed a high degree of anisotropy of the polymer chains on the individual fibrils. The high degree of polarization indicated highly oriented polymer chains with the preferential orientation of the polymer backbone along the fibrils. The anisotropy ratios are comparable with well-oriented polymer chains in films.

Fluorescence micrographs of partially aligned insulin fibrils decorated with APFO-12	Emission intensity from a part of an insulin fibril decorated with APFO-12 recorded with rotating polarizer in excitation and emission beams. The two modulation frequencies were 0.15 Hz and 0.012 Hz for excitation and emission respectively

Alignment of a conjugated polymer onto amyloid-like protein fibrils
A.Herland, P.Bjork, P.R.Hania, I.G.Scheblykin, and O.Inganas, Small 2007, 3, 318

Decoration of amyloid fibrils with luminescent conjugated polymers
Anna Herland, Daniel Thomsson, Oleg Mirzov, Ivan G. Scheblykin, Olle Inganäs, J. Mater. Chem., 2008, 1, 126