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BioMed Research International
Volume 2013 (2013), Article ID 329087, 6 pages
http://dx.doi.org/10.1155/2013/329087
Research Article

Enhanced EGFP Fluorescence Emission in Presence of PEG Aqueous Solutions and - - Copolymer Vesicles

1Department of Biotechnology (Biology VI), RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
2Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat 26000, Pakistan
3Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
4Department of Biology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany
5Technische Universität Darmstadt, Center of Smart Interfaces, Petersenstraße 32, 64287 Darmstadt, Germany
6Konrad-Müller Straße 17, 52249 Eschweiler, Germany

Received 22 April 2013; Accepted 13 June 2013

Academic Editor: Jason Shearer

Copyright © 2013 Noor Muhammad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An EGFP construct interacting with the PIB1000-PEG6000-PIB1000 vesicles surface reported a ~2-fold fluorescence emission enhancement. Because of the constructs nature with the amphiphilic peptide inserted into the PIB core, EGFP is expected to experience a “pure” PEG environment. To unravel this phenomenon PEG/water solutions at different molecular weights and concentrations were used. Already at ~1 : 10 protein/PEG molar ratio the increase in fluorescence emission is observed reaching a plateau correlating with the PEG molecular weight. Parallel experiments in presence of glycerol aqueous solutions did show a slight fluorescence enhancement however starting at much higher concentrations. Molecular dynamics simulations of EGFP in neat water, glycerol, and PEG aqueous solutions were performed showing that PEG molecules tend to “wrap” the protein creating a microenvironment where the local PEG concentration is higher compared to its bulk concentration. Because the fluorescent emission can be perturbed by the refractive index surrounding the protein, the clustering of PEG molecules induces an enhanced fluorescence emission already at extremely low concentrations. These findings can be important when related to the use of EGFP as reported in molecular biology experiments.