Figure 7.
MALDI-TOF mass spectra of controlled exonuclease digests of DNA 11 mer 5′-CGG ACX AGA AG -3′ where X = 3: 3′→5′ digest with PDE 1 (A), digest with PDE 1 for extended time (B); 5′→3′ digest with PDE II (C) and digest with PDE II for extended time (D). The signals corresponding to doubly charged ions are marked with an asterisk (*).