The most common method of measuring FRET involves measuring the donor and acceptor intensities separately. To calculate the FRET efficiency, the two intensity values obtained are calibrated using a complex system of equations. Our aim was to determine the exact ratio of the intensities of the excited donor and excited acceptor, denoted by alpha, required for the calibration.
Traditionally, in FRET measurements, alpha is determined by determining the intensity of samples labelled with the same number of donors and acceptors. However, if it is determined on a small number of cells, e.g., in a microscope, this shortcoming introduces a large statistical error (A). The statistical error can be reduced by measuring the cells by flow cytometry, as much more cells can be examined in a short period of time.
One of the innovations introduced in our experiments was to use microbeads with a calibrated number of antibody binding sites, labelled with fluorescently stained antibodies, instead of cells. Much more accurate measurement results are obtained using the microbeads (B).
Further improvement in reproducibility was achieved by labeling cell or bead samples with a mixture of antibodies containing both donor and acceptor. This modification gave even better results as it eliminated the need for comparing the intensities of two different samples (C). Since the proposed method does not require specialized instrumentation, it can enjoy widespread application in the calibration of intensity-based FRET measurements.

Research carried out in collaboration between the Department of Biophysics and Cell Biology, and the Department of Genetics of Applied Microbiology at the University of Debrecen, and the Department of Organic Chemistry, Semmelweis University revealed that cellular uptake of cell penetrating peptides (CPP) depends on the membrane dipole potential and that it can be enhanced by reducing the dipole potential. Cell penetrating peptides are molecules capable of traversing the intact cell membrane even when loaded with cargo, e.g. membrane impermeable drugs. The research group of Peter Nagy found that this uptake takes place by endocytosis followed by endosomal escape. Since most cell penetrating peptides are positively charged, the intramembrane, positive dipole potential generated by the ordered arrangement of dipoles in the membrane, inhibits their membrane crossing. Atorvastatin, widely applied in the treatment of high blood cholesterol levels, decreases the membrane dipole potential and consequently enhances the cellular uptake of cell penetrating peptides. The findings lay the foundation for applying the revealed principle for boosting the cellular uptake of drugs in the treatment of human diseases.