Figure 1. SIMS images of double-labeled ( ¹³C, ¹⁵N) chromosomal Bacillus subtilis DNA.

The DNA was combed at 0.2 μg/mL on a Si_C14 wafer using the lift method, the wafer surface was covered with cesium and analyzed with a NanoSIMS 50. Primary beam intensity, 1 pA; dwell time, 30 ms; field of view, 15 μm × 15 μm; 256 × 256 pixels; scale bar = 1 μm. ( a) ¹³C ¹⁵N, ( b) ¹³C ¹⁴N, ( c) Isotope ratio ¹³C/ ¹²C, and ( d) ¹³C ¹⁵N+ ¹³C ¹⁴N. ( a) and ( b) are the results of adding the counts from three successive sputter sections, ( c) is the ratio between the two sets ( ¹³C and ¹²C) of three successive sputter sections, and ( d) is the three sputter sections of ( a) plus the three of ( b). The count numbers of ( a), ( b) and ( d), and the count ratio of ( c) are given on the linear color scales.