What important tool did Linus Pauling use to determine the structure of proteins?

What important tool did Linus Pauling use to determine the structure of proteins?

• A. Electron microscopy
• B. Mass spectrometry
• C. X-ray crystallography
• D. NMR spectroscopy

Answer: (C)

X-ray crystallography reveals where atoms sit in a molecule by analyzing the pattern X-rays form when they pass through a protein crystal. Linus Pauling used this approach to interpret diffraction data from proteins and build models of how the polypeptide backbone could be arranged. By combining the repeating distances and angles implied by the diffraction pattern with what chemistry already tells us about peptide bonds and bond lengths, he identified regular, orderly motifs—most famously the alpha-helix and the beta-pleated sheet. The method translates those diffraction signals into an electron-density map or a structural model, showing how many residues per turn, the pitch, and the overall geometry that fits the data and chemical constraints. Other techniques exist, but at the time they didn’t provide the same level of atomic detail needed to propose these precise, repeatable structures.

X-ray crystallography reveals where atoms sit in a molecule by analyzing the pattern X-rays form when they pass through a protein crystal. Linus Pauling used this approach to interpret diffraction data from proteins and build models of how the polypeptide backbone could be arranged. By combining the repeating distances and angles implied by the diffraction pattern with what chemistry already tells us about peptide bonds and bond lengths, he identified regular, orderly motifs—most famously the alpha-helix and the beta-pleated sheet. The method translates those diffraction signals into an electron-density map or a structural model, showing how many residues per turn, the pitch, and the overall geometry that fits the data and chemical constraints. Other techniques exist, but at the time they didn’t provide the same level of atomic detail needed to propose these precise, repeatable structures.