Ammonium bicarbonate buffer system for DNA hybridization and quantification by LC-ESI-MS/MS.

Area of Science:

• Biochemistry
• Analytical Chemistry
• Molecular Biology

Background:

• Traditional DNA detection methods like UV/VIS and radiometric assays often use high salt buffers.
• High salt concentrations are incompatible with sensitive electrospray mass spectrometry, limiting direct DNA analysis.
• Colorimetric DNA hybridization assays can detect HIV DNA but require specific buffer conditions.

Purpose of the Study:

• To develop a mass spectrometry-compatible method for sensitive DNA detection.
• To identify alternative buffer systems that support DNA hybridization and mass spectrometry.
• To establish a novel enzyme-linked mass spectrometric assay (ELiMSA) for direct DNA analysis.

Main Methods:

• Utilized alkaline phosphatase-streptavidin (APSA) enzyme conjugate for DNA hybridization.
• Tested ammonia bicarbonate (AMBIC) and ethanolamine as high salt buffer alternatives to NaCl.
• Employed mass spectrometry to detect adenosine, a product of substrate conversion, via precursor and fragment ion monitoring (m/z 268→ m/z 136).

Main Results:

• AMBIC and ethanolamine buffers supported DNA hybridization comparable to NaCl.
• AMBIC buffer was compatible with sensitive mass spectrometry, unlike high salt buffers.
• Achieved linear and Gaussian analysis of HIV DNA from femtomolar to picomolar concentrations with low error.
• Demonstrated direct DNA analysis using as little as 0.1 μL of sample via ELiMSA.

Conclusions:

• Ammonia bicarbonate (AMBIC) is a suitable alternative to NaCl for DNA hybridization assays compatible with mass spectrometry.
• The developed enzyme-linked mass spectrometric assay (ELiMSA) enables sensitive and specific direct DNA detection in the femtomolar to picomolar range.
• This method overcomes the limitations of high salt buffers in mass spectrometry-based DNA analysis.