Analysis of microliter volumes of dye-labeled nucleic acids

We describe methodology useful for determining the fluorescent activity of small volumes (e.g., 1 microL) of dye-labeled cDNAs using microabsorbance spectroscopy. A direct relationship was found between the average fluorescent hybridization signal from an array and the fluorescent activity of the cDNA used in the hybridization. The microabsorbance method makes possible the screening of small-volume samples before hybridization, allowing for a more efficient use of available microarrays. The standardization of the concentration of RNA samples contained in 1 microL before reverse transcription is also described.