TMR biocytin is a cell-impermeant, fixable polar tracer that combines the tetramethylrhodamine (TAMRA) with biotin and an aldehyde-fixable primary amine. Polar tracers are commonly used to investigate cell-cell and cell-liposome fusion as well as membrane permeability and transport through gap junctions or cell uptake during pinocytosis. TMR biocytin proved to be an effective neuronal tracer in live tissue when applied by electroporation. We also offer CF® Dye Biocytin with a selection of our superior CF® dyes.