Quantitative analysis of chemiluminescence signals using a cooled charge-coupled device camera

Chemiluminescence has been considered an alternative to radioisotopic detection of materials in the life sciences. One application of this nonradioisotopic method is the electrophoretic mobility shift assay. The essential requirement for quantitative applications is that the chemiluminescence signal is linearly proportional to the concentration. However, the generation of chemiluminescence is a multi-step process, therefore linearity cannot be assumed. Therefore, it is important to verify linearity before applying the method as a quantitative tool. We used a commercial chemiluminescence generating system to evaluate the validity of quantitative measurements of biotin-labeled tRNA and single-stranded DNA. The results indicate that the relationship between the chemiluminescence signals and the quantity of biotin-labeled nucleic acids is hyperbolic rather than linear. However, it was found that with less than 50 fmol of biotin-labeled nucleic acid, which corresponds to 2.5 nM in 20 μl, linearity can be demonstrated within 5% error. Therefore, chemiluminescence-based quantitative measurements are a reliable method within these limitations.