Preparation of horseradish peroxidase-labeled probes

The direct labeling of nucleic acid probes with horseradish peroxidase (HRP) may be used in many membrane hybridization applications, including Southern blots, Northern blots, colony and plaque screening, PCR products detection/identification. This article describes the preparation method, which involves the labeling of a single-stranded nucleic acid probe with a positively charged HRP-parabenzoquinone-polyethyleneimine complex (labeling reagent). The associated hybridization and posthybridization protocols are relatively simple, which makes probes labeled directly with HRP particularly suitable for large scale screening, where tens or hundreds of blots are processed weekly.