Which of the following statements is true regarding the resolution of x-ray structures of proteins?
I. A resolution of 5 Å is needed to observe $\alpha$-helices as rods in an x-ray structure.
II. A resolution of 0.5 Å is needed to observe $\beta$-sheets in an x-ray structure.
III. An x-ray structure of a protein at a resolution of 1.0 Å is considered to be high resolution.
IV. A resolution of 2.0 Å is needed to distinguish side chains of amino acids in an x-ray structure.
V. A resolution of 1.5 Å is needed to observe hydrogen atoms in an x-ray structure.

Question

Quizplus · Accepted Answer

A resolution of 5 Å allows for the observation of secondary structures like ?-helices as rods. A resolution of 1.0 Å is indeed considered high resolution, allowing for detailed observation of the protein structure. At 2.0 Å resolution, side chains of amino acids can be distinguished, which is crucial for understanding the protein's function. Although a resolution of 1.5 Å is very high and can provide detailed information, it is generally not sufficient to reliably observe hydrogen atoms, which typically require even higher resolutions or specialized techniques. However, the statement regarding 0.5 Å for ?-sheets is incorrect, as ?-sheets, like ?-helices, can be observed at lower resolutions (around 3.5 to 5 Å). Therefore, the correct statements are I, III, and IV, making the choice D correct despite the slight inaccuracy in statement V's implication about hydrogen atoms.

Which of the Following Statements Is True Regarding the Resolution α\alphaα

Which of the Following Statements Is True Regarding the Resolution $\alpha$