Fluorescence polarization and pulse width analysis of chromosomes by a flow system

Area of Science:

• Cytogenetics
• Biophysics
• Analytical Chemistry

Background:

• Characterizing individual chromosomes is crucial for genetic studies.
• Existing methods primarily rely on DNA content, limiting resolution.
• Novel parameters are needed to differentiate chromosomes effectively.

Purpose of the Study:

• To identify and utilize unique biophysical properties of Chinese hamster chromosomes for improved discrimination.
• To explore parameters beyond DNA content for chromosome analysis.
• To develop a theoretical model for interpreting experimental data.

Main Methods:

• Analysis of isolated Chinese hamster chromosomes using a multiparameter computer-controlled cell sorter.
• Measurement of polarized emission of Hoechst 33342, a DNA-specific dye.
• Quantification of emission anisotropy and pulse width for chromosome classification.
• Development of a theoretical model for rod-shaped particle pulse shape prediction.

Main Results:

• Emission anisotropy of Hoechst 33342-stained chromosomes was constant (0.30) across all classes, similar to purified DNA.
• Pulse width effectively resolved smaller chromosomes based on total emission.
• Pulse width also distinguished larger chromosomes based on their orientation and arm length.
• A theoretical model accurately predicted pulse shapes for arbitrarily oriented chromosomes.

Conclusions:

• Multiparameter flow cytometry, utilizing pulse width and polarized emission, enhances chromosome discrimination beyond DNA content.
• The study provides a robust method for analyzing chromosome structure and properties.
• The developed theoretical model aids in the interpretation of chromosome sorting data.