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)Those in both groups I and II could be differentiated
B)Those in both groups I and III could be differentiated
C)Only those in group II could be differentiated
D)Only those in group III could be differentiated
E)Only those in groupI could be differentiated

Question

Quizplus · Accepted Answer

Group II (Phenylalanine vs. Alanine) involves amino acids with significantly different side chains, making them easier to differentiate in an electron density map regardless of resolution. Leucine and Isoleucine (I) have very similar structures, making them harder to distinguish. Glutamate and Glutamic acid (III) are actually the same molecule (Glutamic acid is the name of the amino acid, and Glutamate is its anionic form), so this option is incorrect.

When Solving a Protein Structure Using X-Ray Crystallography,the Crystallographer Generates