Chromomycin A3

Chromomycin A3 or Toyomycin is an anthraquinone antibiotic glycoside produced by the fermentation of a certain strain of Streptomyces griseus.

Fluorescence properties

In the presence of Mg²⁺ ions, Chromomycin A₃ binds reversibly to DNA, preferentially to contiguous G/C base pairs.
When bound to DNA, Chromomycin A₃ has a maximum excitation wavelength of 445 nm, and a maximum emission wavelength of 575 nm.

Uses

in-vitro membrane-impermeant G/C-specific fluorescent DNA-binding dye.
in-vitro antibiotic of gram-positive bacteria, through inhibition of the incorporation of P_i in the RNA.
in-vitro anticancer drug that inhibits RNA synthesis.
Evaluation of male fertility: Chromomycin A₃ and protamines compete for the same binding sites in the DNA, so CMA₃ positivity in spermatozoa reflects protamine deficiency.