Fig. 5.

MALDI-TOF mass spectrum of siRNA duplex consisting of RNAs 3 + 4 (50 μM) incubated with 10% mouse serum for 5 days using matrix c. Evidence of cleavage at several other pyrimidine nucleoside sites at long time periods. The circled U in both strands of RNA 3 and 4 denote that these are 2′-OMeU derivatives; 3′ inverse deoxythymidine is denoted with idT; cP denotes 2′,3′-cyclic phosphate; P denotes 2′- (3′-) phosphate.