In the alpha helix, there is not an integral number of amino acid residues per turn of the helix. There are 3.6 residues per turn in the alpha helix; in other words, the helix will repeat itself every 36 residues, with ten turns of the helix in that interval. Beta sheet. The beta sheet involves H‐bonding between backbone residues in adjacent chains. Beta sheets come in two flavors: parallel (shown on this slide) and anti parallel. The geometry of the individual beta strand is are almost identical in these two forms of beta sheet. The difference is in the relative direction of neighboring strands and in the way they hydrogen bond. Either way, just as an alpha helix, a

series of alpha helices and beta sheets, joined by loops of less regular protein structure. An alpha helixis a compact right-handed helix, with 3.6 amino acids per turn of the helix. The amino acid sidechains are bonded to the alpha carbon of each amino acid and radiate outward from the helix. The alpha helix is stabi-lized by hydrogen bonds ... The most common secondary structures are alpha helices and beta sheets. Other helices, such as the 3 10 helix and π helix, are calculated to have energetically favorable hydrogen-bonding patterns but are rarely observed in natural proteins except at the ends of α helices due to unfavorable backbone packing in the center of the helix. The two most common secondary structures are the alpha helix and the beta pleated sheet. The secondary structure is maintained by hydrogen bonds between the backbone atoms. These form between the H of the N (amide hydrogen) and the O of C=O (carbonyl oxygen). Alpha Helices. Alpha helices form a right-handed corkscrew within a protein.