1. Are the probes stable at room temperature?
Yes, the probes are stable at room temperature for a few days. However it strongly depends on the probe and the solvent. It is recommended to store all the probes or solutions thereof at -20°C.
2. Are SiR- or SPY-probes toxic to the cells?
Yes, above a certain threshold both probes show some effect on cell proliferation and altered actin or microtubule dynamics. However, the probes are orders of magnitude less toxic that their parent drug. For SiR-probes we recommend using 100 nM concentration and for SPY-probes we recommend diluting the DMSO stock 1:1000.
3. After dissolving the probe in DMSO, the solution is colorless, is this normal?
Yes, in DMSO the probe is mainly in the colorless spiro form and the color of the solution can vary, depending on the probe, from colorless to mildly colored. This does not influence the staining efficiency of the probe.
4. Do the probes work on fixed cells?
Our SiR- and SPY-probes for actin and DNA and lysosomes can be used with PFA fixed cells. SiR- and SPY-probes for microtubules do not work on fixed cells nor survive the fixation step, if the cells were labeled before the fixation.
5. Is it possible to image live cells labeled with SiR- or SPY-probes by STORM?
No, under the very high light intensities typically used in STORM imaging, phototoxicity of the excitation light is usually observed on live-cells. SMLM techniques that require less excitation light power may be suited
6. Which organisms and tissues are stained by Sir-probes?
This list is only reporting known working cell lines, tissues or organisms. If a cell line, tissue or organism is not present in the list, it does not mean that it will not be stained by our Probes.

Homo sapiens : U2OS, fibroblasts, HeLa, HUVEC, MCF-10A, HCT-116, A549, erythrocytes.

Mus musculus : C2C12, IA32, skeletal muscle, primary cardiomyocyte, primary oocyte.

Rattus norvegicus : primary hyppocampal neurons, primary cortex neurons, NRK.

Cercopithecus aethiops : COS-7.

Mesocricetus auratus : BHK.

Drosophila melanogaster : Notum epithelium, S2.

Didelphis marsupialis : OK-cells.

Carassius auratus (goldfish) : retina bipolar cells

Danio rerio (zebrafish) : retina bipolar cells

Help us to complete the List by reporting your positive experiences!

7. Do SiR-probes work in 3D cell cultures?
Yes, the probes are able to stain cells in a 3D growth environment such as spheroids and organoids.
8. What are the correction factors CF260 and CF280 for SiR fluorophore?
CF260 = 0.116

CF280 = 0.147