Understanding metal inhibition: The effect of copper (Cu2+) on DNA containing samples

- Copper ion carry-over during sample purification affects the DNA typing process.
- Aggregation, charge effects, and conformational changes affect amplification and/or electrophoretic mobility.
- Solid phase sample purification decreases copper carryover to subsequent steps.

Copper wires are a common component of improvised explosive devices (IEDs) and are increasingly found in forensic evidence. When processed for DNA, ions from the metal can be co-extracted with the genetic material, and potentially cause complications during the analysis procedure. It was determined in this project that copper ions do have adverse effects on DNA processing by either interacting directly with the DNA or affecting the electrophoretic mobility of the molecule. It was also found that these negative effects could be improved by utilizing a purification method capable of reducing the amount of copper carry-over into the sample.

This diagram illustrates the effects of a copper containing sample on the DNA processing workflow. During the purification process, copper ions interact with the nucleic acid causing aggregation and conformational changes which can affect electrophoretic conductivity. The end result is usually an inhibited profile.109