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The main chain–main chain hydrogen bond is replaced by a side chain–main chain hydrogen bond. 3D computer superimposition shows that, in proteins, they occur [12] as one of the same four types that beta turns do, except that their relative frequency of occurrence differs: type II’ is the most common, followed by types I, II and I’.
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 .
For example, a beta hairpin connects two hydrogen-bonded, antiparallel β-strands (a rather confusing name, since a β-hairpin may contain many types of turns – α, β, γ, etc.). Beta hairpins may be classified according to the number of residues that make up the turn - that is, that are not part of the flanking β-strands. [7]
Protein secondary structure is the local spatial conformation of the polypeptide backbone excluding the side chains. [1] The two most common secondary structural elements are alpha helices and beta sheets , though beta turns and omega loops occur as well.
All-β proteins are a class of structural domains in which the secondary structure is composed entirely of β-sheets, with the possible exception of a few isolated α-helices on the periphery.
The other type is the G1 beta bulge, of which there are two common sorts, both mainly occurring in association with antiparallel sheet; one residue has the α L conformation and is usually a glycine. In one sort, the beta bulge loop , one of the hydrogen bonds of the beta-bulge also forms a beta turn or alpha turn, such that the motif is often ...
The beta subunits in turn bind the αε polymerase complex. The α subunit possesses DNA polymerase activity and the ε subunit is a 3’-5’ exonuclease. [9] The beta chain of bacterial DNA polymerase III is composed of three topologically equivalent domains (N-terminal, central, and C-terminal). Two beta chain molecules are tightly ...
Beta scission is an important reaction in the chemistry of thermal cracking of hydrocarbons and the formation of free radicals. Free radicals are formed upon splitting the carbon-carbon bond . Free radicals are extremely reactive and short-lived.