Improvements of the membrane filter method for DNA:rRNA hybridization

Area of Science:

• Molecular Biology
• Biochemistry

Background:

• DNA:rRNA membrane filter hybridization is a crucial technique in molecular biology.
• Optimizing hybridization conditions is essential to prevent sample loss and ensure reliable results.

Purpose of the Study:

• To describe and recommend improvements for DNA:rRNA membrane filter hybridization methods.
• To minimize DNA release from filter discs during hybridization.

Main Methods:

• Hybridization performed in 2x SSC with 20% formamide at 50°C for 16 hours.
• RNAase treatment using 250 μg/5 ml 2x SSC per filter at 37°C for 1 hour.
• Stepwise thermal denaturation conducted in 5°C increments from 50°C to 90°C in 1.5x SSC with 20% formamide.

Main Results:

• High purity formamide (O.D. ≤ 0.2/cm at 270 nm) is critical.
• Single-stranded DNA on filters is stable for up to 20 months when stored at 4°C in a vacuum.
• Concentrated DNA can be stored at -90°C for up to 2 years with minimal change.
• Ribosomal RNA (rRNA) remains stable for 20 months at -12°C in SSC or 2x SSC.

Conclusions:

• Recommended hybridization conditions improve DNA:rRNA membrane filter assays.
• Optimized storage protocols enhance the long-term usability of DNA and rRNA samples.
• Careful formamide purity and RNAase treatment are key factors for successful hybridization.