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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.
Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation .
All beta-barrel transmembrane proteins have simplest up-and-down topology, which may reflect their common evolutionary origin and similar folding mechanism. [7] In addition to the protein domains, there are unusual transmembrane elements formed by peptides. A typical example is gramicidin A, a peptide that forms a dimeric transmembrane β-helix ...
The pitch of the alpha-helix (the vertical distance between consecutive turns of the helix) is 5.4 Å (0.54 nm), which is the product of 1.5 and 3.6. The most important thing is that the N-H group of one amino acid forms a hydrogen bond with the C=O group of the amino acid four residues earlier; this repeated i + 4 → i hydrogen bonding is the ...
When Pauling and Corey first proposed the alpha sheet, they suggested that it agreed well with fiber diffraction results from beta-keratin fibers. [2] However, since the alpha sheet did not appear to be energetically favorable, they argued that beta sheets would occur more commonly among normal proteins, [3] and subsequent demonstration that beta-keratin is made of beta sheets consigned the ...
beta sheet. Beta strand. alpha helix. ribbon diagram. creator. some value. ... Template:Alpha beta structure; Metadata. This file contains additional information ...
In biochemistry, a Ramachandran plot (also known as a Rama plot, a Ramachandran diagram or a [φ,ψ] plot), originally developed in 1963 by G. N. Ramachandran, C. Ramakrishnan, and V. Sasisekharan, [1] is a way to visualize energetically allowed regions for backbone dihedral angles ( also called as torsional angles , phi and psi angles ) ψ ...
The Rossmann fold is a tertiary fold found in proteins that bind nucleotides, such as enzyme cofactors FAD, NAD +, and NADP +.This fold is composed of alternating beta strands and alpha helical segments where the beta strands are hydrogen bonded to each other forming an extended beta sheet and the alpha helices surround both faces of the sheet to produce a three-layered sandwich.