| Fluoro-Gold (FG) is a highly effective fluorescent retrograde tracer used in neuroanatomical research to map the connections between neurons. It is primarily composed of hydroxystilbamidine (specifically its bis-methanesulfonate or di-hydroxyethanesulfonate salt), a stilbene derivative that emits an intense yellow or gold light when viewed under ultraviolet (UV) light. The use of Fluoro-Gold is essentially the same as other fluorescent tracers. The main difference is that Fluoro-Gold is more flexible in terms of post-injection survival times, concentration range, tissue treatment, and compatibility with other histochemical techniques. Fluoro-Gold has been successfully used at concentrations ranging from 1-10%. Initially, a 4% concentration is advised. If undesirable necrosis occurs at the injection site, or labeling is too intense, reduce the concentration to a 2% solution. If you need to use more precise measurements, the molecular weight of Fluoro-Gold is 532.6 Daltons. Fluoro-Gold can be injected using several different methods, including pressure, iontophoretic and other applications developed by a variety of researchers. See Schmued and Fallon, Fluoro-Gold: A fluorescent retrograde axonal tracer with numerous unique properties, Brain Research, 377 (1986) 147- 154 as well as Pieribone and Aston-Jones, The Iontophoretic Application of Fluoro-Gold for the study of afferents to deep brain nuclei, Brain Research, 475 (1988) 259-271. Many researchers have developed their own modified procedures. Excitation/Emission: Peak excitation at ~361nm, peak emission at ~536nm (UV/Yellow) Active Constituent: Hydroxystilbamidine (MW ~280.3Da) is the membrane-impermeant active component Applications: Suitable for use in Immunohistochemistry Other applications not tested. Recommended Dilutions: Immunohistochemistry (Frozen): Aliquot is at a dilution of 1:100 which can be further diluted 1:10,000 to 1:100,000 times in BSA diluent (50mM KPBS, 0.4% Triton, 1% BSA, 1% NGS) to produce 50-100ml of working titer. Cryostat sections of unfixed tissue (10um), frozen sections of fixed tissue (20um), and thin sections cut from tissue imbedded in either plastic (0.2-4um) or paraffin (3-10um). Frozen sections of fixed tissue. After fixation, sections may be further processed for a second marker such as autoradiography, HRP histochemistry, immunocytochemistry, a second fluorescent tracer, fluorescent counterstain, etc. Optimal dilutions to be determined by the researcher. Storage and Stability: Light Sensitive. Lyophilized and reconstituted products are stable for 6 months after receipt at 4C. Reconstitute with sterile ddH2O or buffer. Aliquot to avoid repeated freezing and thawing. Store at 4C. Do not freeze. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. US Patent No. 4,716,905 UK Patent No. 2,181,545 |
