I have done diaotization of light chain silk for modification of tyrosine present in it. I tried H1-NMR and ATR-FTIR on these modified silk. But no peak was observed, from dizonium salts in both of these characterization, Is there any technique to determine that silk material is diotized and %diaotization done after completion of experiment?
Diazonium salts with aliphatic substituent ( like in tyrosine) are unstable and rapidly lost nitrogen with building of alcohol (in water media). This is good method of R-NH2 -> R-OH transformation.
Dry diazonation Ar-NH2 -> Ar-N=S=O + NO+BF4- -> Ar-N≡N+ BF4- + SO2 is known for aromatics but to be explored in aliphatics.
I am not sure if this paper describes exactly what you are trying to quantify, but the Kaplan lab has used the extinction coefficient of the azo group to estimate the degree of modification. "Modification of silk fibroin using diazonium coupling chemistry and the effects on hMSC proliferation and differentiation."
I fully agree with Andrei and Jeannine. Concentration on reaction with diazonium comounds will help. For example the Pauli diazo reaction using diazobenzenesulfonic acid should result in a red colour which can be determined e.g. by UV-vis.
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