Single Green Fluorescence Protein in Nanocapsules

F.Cannone (1); G.Chirico(1); S.Krol(2) and A.Diaspro(2)

(1) Dipartimento Fisica Università Milano Bicocca Milan Italy ; (2) Dipartimento Fisica Università Genova Genoa Italy

Nanocapsules, assemblies of multiple layers of polyelectrolytes, are of promising biomedical interest. Here we show that they can be used to immobilize single proteins to study protein-protein interactions and protein photo-isomerizations. We have focused our attention on the mutant of GFP (Green Fluorescence Protein)): GFPmut2 , and we have studied, with Two-Photon Excitation (TPE)its fluorescence emission, bleaching time, lifetimes and unfolding process, in different parts of the capsules. The measurements of the brightness and lifetime of single GFP on the surface and inside the nanocapsules, indicate that this system does not perturb the protein spectroscopy properties. Rather a large fraction of single GFP protein turn out to be stabilized. When GFP is linked between two polyelectrolyte layers, a systematic variation of the fluorescence emission and lifetimes is found. Linking single GFP among the polyelectrolyte layer, different population are recorded. Each population represent a specific interaction of single GFP protein – environment. Moreover , denaturation experiments prove measurement proves that the single GFP bound binding to the capsules is more robuststurdy than single protein in other environments. (for examples silica gels). These results set a good basis for the use of nanocapsules as a multipurpose protein carrier

Email: fabio.cannone@mib.infn.it

Address: Fabio Cannone, Dipartimento di Fisica, Università di Milano Bicocca, Piazza della Scienza n.3, 20132 Milan Italy