41Can UV absorbance distinguish dsDNA, ssDNA and RNA?42Why does RNA contamination lead to an overestimate of DNA concentration?43How do absorbance and fluorescence methods differ?44Can purity ratios indicate nucleic acid integrity?45Why can proteins be quantified directly using A280?46Can all proteins use the same A280 conversion factor?47What are the limitations of direct A280 quantification?48What is the basic principle of the BCA assay?49What commonly interferes with the BCA assay?50What is the basic principle of the Bradford assay?

How do absorbance and fluorescence methods differ?

Absorbance measures light attenuation and provides a concentration estimate and spectral context, but nucleic acids, free nucleotides and other UV absorbers may contribute. Fluorescence uses a dye response; selectivity and working range depend on the assay.

When results disagree, check target type, units, dilution factor, blank and fluorescence standards before investigating additional absorbers or substances affecting the dye reaction.

Do not simply average the values. Choose quantification appropriate to the downstream application and retain the spectrum for troubleshooting: the methods do not measure exactly the same contributions.