Replacing alanine by which amino acid will increase UV absorbance of protein at 280nm wavelength?
**Core Concept**
The question tests the understanding of amino acid structure and their ultraviolet (UV) absorbance properties, specifically at a wavelength of 280nm. This is relevant to the quantification of proteins, as certain amino acids absorb UV light at this wavelength.
**Why the Correct Answer is Right**
The correct answer is related to the amino acids that have absorbance at 280nm, which are typically those with aromatic rings. Tryptophan, tyrosine, and phenylalanine are such amino acids, but tryptophan has the highest absorbance at 280nm due to its indole structure. Replacing alanine with tryptophan would increase UV absorbance at 280nm.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so its correctness cannot be assessed.
**Option B:** This option is not provided, so its correctness cannot be assessed.
**Option C:** This option is not provided, so its correctness cannot be assessed.
**Option D:** This option is not provided, so its correctness cannot be assessed.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that tryptophan has the highest molar absorptivity at 280nm among the amino acids, making it crucial for protein quantification methods like the Bradford assay.
**Correct Answer:** D. Tryptophan