Spectroscopy check: at what wavelengths do nucleotide bases and aromatic amino acids absorb most strongly (respectively)? Choose the correct pairing of peak absorbance maxima.

Introduction / Context:Ultraviolet absorbance is routinely used to quantify biomolecules. Nucleic acids and proteins have distinct absorbance peaks due to their chromophores, enabling rapid purity checks (for example, A260/A280 ratios).

Given Data / Assumptions:

• Nucleotide bases have conjugated ring systems with maxima near 260 nm.
• Aromatic amino acids (tryptophan, tyrosine, phenylalanine) dominate protein absorbance near 280 nm.
• “Respectively” means first value corresponds to nucleotides, second to aromatic amino acids.

Concept / Approach:DNA/RNA quantification uses A260 because nucleobases absorb strongly there. Protein quantification and contamination checks often reference A280. The A260/A280 ratio guides assessments of nucleic acid purity.

Step-by-Step Solution:Map chromophores to peaks: nucleotides → 260 nm; aromatics → 280 nm.Select the option listing 260 nm first and 280 nm second.

Verification / Alternative check:Laboratory spectrophotometer protocols standardize nucleic acid measurements at 260 nm and protein measurements at 280 nm, confirming the assignment.

Why Other Options Are Wrong:Reversed or shifted values do not reflect the canonical maxima used in routine assays.

Common Pitfalls:For proteins lacking Trp/Tyr, A280 underestimates concentration; complementary dye-binding methods may be preferred.

Final Answer:260 nm and 280 nm.