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Three of the authors (from left: Sissel Juul, Megan Yi-Ping Ho and Magnus Stougaard) of the article that describes the development of a new method that enables the measurement of enzyme activities in individual human cells. The researchers hope that the method can be used to target chemotherapy to patients. Click photo for enlargement. Photo: Lisbeth Heilesen
Measurement of DNA topoisomerase activity. A. Cells, DNA sensors and a special buffer – which destroys the cell membrane and allows the cellular topoisomerase enzymes to react with DNA sensors – are loaded into each channel of the system. B. The reaction of the topoisomerases with the DNA sensor, which consists of a piece of self-folding DNA transformed into a closed DNA circle upon reaction with the topoisomerase. C. After this reaction, the mixture is transferred onto a glass plate that is already activated with so-called DNA primers. These support a so-called DNA amplification process resulting in products consisting of 103 copies of the circular DNA sensors that can be made visible at the single-molecule level through hybridisation to fluorescent probes. In addition to the described topoisomerase sensor, a pre-made DNA circle that serves as a control is added to the system. The circular topoisomerase sensors are visualised with green fluorescent probes, while the control circles are visualised with blue fluorescent probes. D. Example of the detection of topoisomerase activity (green signals) and control circles (blue signals) in the system. Each field displays the contents of a single lipid-encapsulated droplet. Figure: Sissel Juul

2011.09.30 | Public / media, Department of Molecular Biology and Genetics

New method for single cell analysis may improve cancer treatment

A collaboration between Danish and American researchers has resulted in the development of a new method that enables the measurement of enzyme activities in individual human cells. This method can be used to measure how cell-to-cell variation in tumours affects the overall response to chemotherapy and thus clarify some of the molecular causes of…