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?

Why can proteins be quantified directly using A280?

Tryptophan, tyrosine and cystine contribute to absorption at 280 nm. With a known extinction coefficient and path length, concentration can be calculated using Beer–Lambert.