简介：Fluorescenceliftimeimaging(FLIM)ofmodifiedhydrophobicbodipydyesthatactasfluorescentmolecularrotorsshowsthatthefluorescencelifetimeoftheseprobesisafunctionofthemicroviscosityoftheirenvironment.Incubatingcellswiththesedyes,wefindapunctateandcontinuousdistributionofthedyeincells.Theviscosityvalueobtainedinwhatappearstobeendocytoticvesiclesinlivingcellsisaround100timeshigherthanthatofwaterandofcellularcytoplasm.Time-resolvedfluorescenceanisotropymeasurementsalsoyieldrotationalcorrelationtimesconsistentwithlargemicroviscosityvalues.Inthisway,wesuccessfullydevelopapracticalandversatileapproachtomapthemicroviscosityincellsbasedonimagingfluorescentmolecularrotors.