DNA does not have a single, universally agreed-upon isoelectric point (pI). The pI of DNA is highly dependent on several factors, including its base composition (the ratio of guanine-cytosine (GC) to adenine-thymine (AT) pairs), the solution's pH and ionic strength, and the presence of any bound proteins or other molecules. While the provided references mention the isoelectric points of proteins and the use of propidium iodide (PI) for DNA staining in flow cytometry, they don't offer a definitive pI value for DNA itself. ResearchGate discussions (https://www.researchgate.net/post/Isoelectric-point-of-DNA) highlight the variability in reported pI values for nucleic acids.
The references do, however, provide relevant information regarding the components of DNA and their properties:
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Phosphate Groups: The phosphate backbone of DNA significantly influences its overall charge. The primary dissociation pKa of phosphate groups in nucleotides is approximately 0.7 to 0.9 (https://www.creative-proteomics.com/pronalyse/resource-what-is-isoelectric-point.html). This means that at physiological pH, the phosphate groups are negatively charged.
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Base Composition: The ratio of GC to AT base pairs influences the overall charge and hydrogen bonding within the DNA molecule. While not directly defining the pI, this ratio contributes to the overall electrostatic properties.
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Propidium Iodide (PI): PI is a fluorescent dye used to stain DNA, indicating its ability to interact with the DNA molecule, but it doesn't define the pI (https://biotium.com/product/propidium-iodide-pi/).
In summary, while a precise pI for DNA cannot be stated without specifying the conditions (pH, ionic strength, DNA sequence, etc.), it is understood to be significantly influenced by the negatively charged phosphate backbone and the solution's environment.