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Fluorescence lifetime imaging microscopy (FLIM) to demonstrate the nuclear binding of flavanols and (--epigallocatechin gallate

Mueller-Harvey, I., Botchway, S., Feucht, W., Polster, J., Burgos, P. and Parker, A. (2010) Fluorescence lifetime imaging microscopy (FLIM) to demonstrate the nuclear binding of flavanols and (--epigallocatechin gallate. Planta Medica, 76 (12). O_7. ISSN 1439-0221

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To link to this article DOI: 10.1055/s-0030-1264193

Abstract/Summary

The use of light microscopy and DMACA staining strongly suggested that plant and animal cell nuclei act as sinks for flavanols [1, 2]. Detailed uv-vis spectroscopic titration experiments indicated that histone proteins are the likely binding sites in the nucleus [2]. Here we report the development of a multi-photon excitation microscopy technique combined with fluorescent lifetime measurements of flavanols. Using this technique, (+) catechin, (-) epicatechin and (-) epigallocatechin gallate (EGCG) showed strikingly different excited state lifetimes in solution. Interaction of histone proteins with flavanols was indicated by the appearance of a significant τ2-component of 1.7 to 4.0ns. Tryptophan interference could be circumvented in the in vivo fluorescence lifetime imaging microscopy (FLIM) experiments with 2-photon excitation at 630nm. This enabled visualisation and semi-quantitative measurements that demonstrated unequivocally the absorption of (+)catechin, (-)epicatechin and EGCG by nuclei of onion cells. 3D FLIM revealed for the first time that externally added EGCG penetrated the whole nucleus in onion cells. The relative proportions of EGCG in cytoplasm: nucleus: nucleoli were ca. 1:10:100. FLIM experiments may therefore facilitate probing the health effects of EGCG, which is the major constituent of green tea.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Agriculture, Policy and Development > Food Production and Quality Division > Animal Science Research Group (ASRG)
Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Food and Nutritional Sciences > Food Microbial Sciences Research Group
ID Code:24949
Additional Information:Special issue of the proceedings of the 7th Tannin Conference (Presymposium) and 58th International Congress and Annual Meeting of the Society for Medicinal Plant and Natural Product Research: Berlin, Germany, 29th August - 2nd September 2010
Publisher:Thieme Medical Publishers, Inc.

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