Practice question

Maxam-Gilbert chemistry employs formic acid as a depurinating agent. Formic acid weakens the N-glycosidic bond of purines by protonation, leading to loss of adenine and guanine bases and formation of apurinic sites. Subsequent treatment with piperidine cleaves the phosphodiester backbone at those abasic positions, generating fragments ending at purines. Hence formic acid produces an A plus G specific ladder, whereas dimethyl sulfate is tuned for G alone. Pyrimidines C and T are not targeted by formic acid; hydrazine targets them instead.