- Staining of viable and dead cells
- Detection of cellular structures
- Suited for e.g. fluorescence microscopy/flow cytometry
- High quality
- Thoroughly tested
- Highly sensitive
Nerve Terminal Probes
PromoKine's Nerve Terminal Probes are a series of fluorescent cationic styryl dyes developed to follow synaptic activities at neuromuscular junctions or synapses. These dyes typically have a lipophilic tail (two carbon chains) at one end and a highly hydrophilic, cationically charged head group at the other end.
These nerve terminal probes were originally called FM dyes, and now they are available from PromoKine under own trademark names depending on the wavelength of the dyes (SynapseGreen and SynapseRed).
We also offer a series of fixable nerve terminal dyes, known as AM dyes, which are closely related to the FM dyes. The primary difference between the fixable and nonfixable dyes is that the formers have an additional amino group attached to the positively-charged head group of the dyes. The amino group reacts with formaldehyde fixative, thus crosslinking the dye with membrane proteins. AM2-10, AM1-43 and AM1-44 are derivatives of SynapseGreen dyes that have relatively shorter wavelengths, while AM4-64 and AM4-65 are based on SynapseRed dyes that have relatively longer wavelengths.
When using these nerve terminal dyes, one frequent problem is the background fluorescence due to nonspecific membrane staining. Although most of the background fluorescence can be removed by repeated washings with a buffer, the problem is still significant with dyes that have a longer tail or more double bonds, particularly when the dyes are used in tissue preparations. To reduce the background fluorescence, we offer three quencher or dye-clearing agents: ADVASEP-7, a sulfonated cyclodextrin, forms a water soluble inclusion complex with SynapseGreen C4, thus leaving the dye in the aqueous phase. The dye-dextrin inclusion complex is actually much more fluorescent than the free dye in solution. However, repeated washings remove the inclusion complex and thus lower the background fluorescence. Our unique quencher, SCAS, reduces background fluorescence as soon as it is added to the preparation without the need for repeated washings. Sulforhodamine 101 has also been used to reduce SynapseGreen C4 background staining via fluorescent resonance energy transfer (FRET).