Final answer:
Linus Pauling first described the alpha helix structure of proteins using X-ray crystallography in the early 1950s.
Step-by-step explanation:
The individual who first described the alpha helix structure of proteins is Linus Pauling. Pauling, along with his colleague Robert Corey, used X-ray crystallography to discern the secondary structures of proteins. This pivotal discovery was made in the early 1950s and provided a significant advancement in the field of molecular biology. The alpha helix is a right-handed coiled structure resembling a spiral, which is stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen four amino acids away. This helical structure is pivotal in the formation of proteins' three-dimensional shapes and is found in many types of proteins, contributing to their unique functional properties.