DNA loading dye contains a high density reagent. The high-density reagent is added to facilitate the sample to be placed in the well of the gel. Due to high density, DNA samples settle at the bottom of the well. It also helps DNA samples to be confined in the well without diffusing out. Commonly used high-density reagents for the preparation of DA loading dye are glycerol, sucrose and Ficoll 400.
An ideal High-density reagent used for the preparation of DNA loading dye/buffer should have the following characteristics.
- It should not interact with the DNA or component of electrophoresis buffer and gel.
- Its addition must make the sample heavier than the electrophoresis buffer.
- It should not have any effect on electrophoretic mobility of DNA.
- It should not modify agarose gel in any way.