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Hoechst S769121 (Nuclear Yellow) is a cell-permeant yellow-emitting fluorescent dye that binds strongly to adenine-thymine-rich regions in the minor groove of double-stranded DNA. Although Nuclear Yellow can bind to all nucleic acids, AT-rich dsDNA strands enhance its fluorescence considerably.

Nuclear Yellow is used in fluorescence microscopy, fluorometry, and flow cytometry to stain and measure DNA content in live and fixed cells. It is commonly used in combination with retrograde tracers such as True Blue for two-color neuronal imaging. Nuclear Yellow can also be used to photoconvert diaminobenzidine (DAB) into an electron-dense reaction product for light and electron microscopy applications.

The commonly used dye concentration to stain bacteria or eukaryote cells is 0.1–10 μg/mL.

Hoechst S 769121 is a marker dye in Hoechst series. Hoechst is A live nuclear marker dye. Hoechst binds to the grooves in the DNA double strand, which tends to be A/ T-rich DNA strand. Although it binds to all nucleic acids, the A/ T-rich double strand DNA significantly enhances fluorescence intensity Therefore,Hoechst dye can be used for living cell labeling. The fluorescence intensity of Hoechst dye increases with the increase of pH of solution[1].

[1] Latt SA, Stetten G, Juergens LA, Recent developments in the detection of deoxyribonucleic acid synthesis by 33258 Hoechst fluorescence. The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society 23 (7): 493-505. DOI:10.1177/23.7.1095650
[2] a b c "Hoechst Stains". Invitrogren (Molecular Probes).
[3] Portugal J, Waring MJ. Assignment of DNA binding sites for 4',6-diamidine-2-phenylindole and bisbenzimide (Hoechst 33258). A comparative footprinting study. Biochimica et Biophysica Acta 949 DOI:10.1016/0167-4781(88)90079-6

360 (complex)/505 (complex) nm