Question

When solving a protein structure using X-ray crystallography, the crystallographer generates a 3-D grid called an electron density map based on the observed diffraction pattern. The higher the resolution, the more detailed the electron density map and therefore the easier it is to identify what atoms (and therefore what amino acids) are in a given position. Based on the three choices below, in which of the following groups could the two of amino acids be the easiest to differentiate regardless of resolution?

I. Leucine vs. Isoleucine II. Phenylalanine vs. Alanine III. Glutamate vs. Glutamic acid
A
Option A: Those in both groups I and III could be differentiated.
B
Option B: Only those in group II could be differentiated.
C
Option C: Only those in group III could be differentiated.
D
Option D: Those in both groups I and II could be differentiated.
E
Option E: Only those in group I could be differentiated.

Answer 1

Option B is the correct answer. Regardless of Resolution the amino acid which can easily be differentiated is phenylalanine and alanine amino acid

Step-by-step explanation:

Phenylalanine and Alanine amino acid both are hydrophobic in nature but Phenylalanine is aromatic amino acid (containing benzene ring shaped) and Alanine is aliphatic amino acid (linear or chain)

While Isoleucine and leucine both are aliphatic and hydrophobic in nature

And glutamate & glutamic acid both are acidic amino acid. Glutamate is the dissociated or ionic form in aqueous solution of glutamic acid.

With respect to resolution or electron density map generated by X-Ray Crystallographer, option C will be more relevant as the amino acid glutamate will be determined by its dissociated form as compared to glutamic acid