Interactions of pyronin Y(G) with nucleic acids

Area of Science:

• Biophysical Chemistry
• Molecular Biology
• Spectroscopy

Background:

• Pyronin Y (PY) is a fluorescent dye used in nucleic acid staining.
• Understanding PY's spectral properties and binding interactions is crucial for accurate cytochemical analysis.

Purpose of the Study:

• To investigate the spectral properties of Pyronin Y alone and in complexes with various nucleic acids.
• To determine the binding characteristics and base-composition dependence of PY-nucleic acid interactions.

Main Methods:

• Spectrophotometry and spectrofluorometry were used to study PY in aqueous solutions with varying salt concentrations.
• Complexes of PY with single-stranded (ss) and double-stranded (ds) DNA and RNA were analyzed.
• Dimerization and association constants were determined.

Main Results:

• PY forms monomers and dimers in solution, with established absorption spectra.
• PY binding to ss nucleic acids causes a hypsochromic shift and >90% fluorescence quenching.
• PY binding to ds nucleic acids (DNA/RNA) results in a bathochromic shift; guanine strongly quenches fluorescence, while other bases have minor effects.
• Association constants for ds RNA and ds DNA were determined, with a binding site size of 2-3 base pairs.

Conclusions:

• The base-composition dependent fluorescence quenching by guanine is a key feature of PY binding to ds nucleic acids.
• These findings have implications for the qualitative and quantitative use of Pyronin Y in cytochemistry for nucleic acid analysis.