In what respect do prontosil and salvarsan resemble? Is there any resemblance between azo dye and prontosil? Explain.

(N/A) Paul Ehrlich,a German bacteriologist,investigated arsenic-based structures to produce less toxic substances for the treatment of syphilis. He developed the medicine,arsphenamine,known as $Salvarsan$. It was the first effective treatment discovered for syphilis.
Ehrlich also worked on azo dyes and noted a structural similarity between $Salvarsan$ and azo dyes. The $-As=As-$ linkage present in arsphenamine resembles the $-N=N-$ linkage present in azo dyes,where the arsenic atom replaces the nitrogen atom.
Regarding the resemblance between azo dyes and $Prontosil$,$Prontosil$ is an azo dye itself. It contains the $-N=N-$ linkage,which is the characteristic functional group of all azo dyes. $Prontosil$ was developed based on the observation that certain dyes could selectively stain and bind to bacteria,leading to the search for compounds that structurally resemble azo dyes and exhibit antibacterial properties.