High-density small-volume gel loading directly from capillary tubes

A technique has been developed for high lane density loading of small-volum e DNA samples in a horizontal agarose gel. This technique has been investig ated with a simple hand-held tool that is made to couple to sample output f rom a new capillary-based sample automation system. The approach consists o f piercing the gel with pressurized sample capillaries and relieving the pr essure shortly before withdrawal. The pressurization prevents the capillary from aspirating the gel buffer and keeps the sample at the tip of the capi llary, so that it may be sucked into the gel during withdrawal. This method is shown to be adequate for a wide range of DNA ladders and PCR-based scre ening. In addition to allowing smaller lanes and a higher lane density than is achievable with traditional well-forming techniques, it relaxes the nee d for well formation and the alignment of the sample loader with those well s, providing an easy, efficient means of loading agarose gels.