(A) Central steps of sample preparation for mass spectrometric quantification of
R-Ado. (B) PAR can be quantitatively detached from acceptor proteins by alkaline
treatment. Subsequent digestion of PAR with phosphodiesterase and alkaline phosphatase releases
adenosine from the PAR termini and other unique nucleosides, i.e., ribosyladenosine
(R-Ado) and diribosyladenosine (R2-Ado), which are characteristic for the linear or
branched part of the polymer, respectively. (C) LC-MS/MS chromatogram of Ado, R-Ado and
R2-Ado obtained from digested PAR synthesized in vitro.