*2.1. Materials*

All chemical reagents were purchased from Sigma-Aldrich (St. Louis, MO, USA), unless stated otherwise. Fluorescent probes Fura-4F, Fura-4FAM, tetramethylrhodamine methyl ester perchlorate (TMRM) and <sup>2</sup>,7-Bis-(2-Carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester (BCECFAM) were purchased from Life Technologies (Eugene, OR, USA).
