Plasmid Preparations with Diatomaceous Earth

Plasmid purification by alkaline lysis is one of the most generally used molecular biology techniques. Traditionally, the cleanest plasmid DNA has been made by banding the DNA on a cesium chloride gradient. This, however, is time-consuming and expensive, so alternative plasmid purification methods have been sought. One that is becoming more widespread is the use of silica-based DNA-binding matrices. Such matrices are available commercially, but can also be easily made in the laboratory. In this chapter, a protocol for large-scale plasmid DNA preparation using diatomaceous earth is presented. This protocol is based on methods of Boom et al. (1 ) and of Carter and Milton (2 ), as well as recommendations for homemade DNA purification kits in TIBS (3 ). Although this protocol is a large-scale preparation, “maxiprep” and yields milligrams of DNA, it can also be adapted for the small-scale, “miniprep” (2 ) to yield microgram quantities,