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A 310 helix is a type of secondary structure found (rarely) in proteins and polypeptides. ==Structure== The amino acids in a 310-helix are arranged in a right-handed helical structure. Each amino acid corresponds to a 120° turn in the helix (i.e., the helix has three residues per turn), and a translation of 2.0 Å (= 0.2 nm) along the helical axis, and has 10 atoms in the ring formed by making the hydrogen bond. Most importantly, the N-H group of an amino acid forms a hydrogen bond with the C = O group of the amino acid ''three'' residues earlier; this repeated ''i'' + 3 → ''i'' hydrogen bonding defines a 310-helix. Similar structures include the α-helix (''i'' + 4 → ''i'' hydrogen bonding) and the π-helix ''i'' + 5 → ''i'' hydrogen bonding). Residues in long 310-helices adopt (φ, ψ) dihedral angles near (−49°, −26°). Many 310-helices in proteins are short, so deviate from these values. More generally, residues in long 310-helices adopt dihedral angles such that the ψ dihedral angle of one residue and the φ dihedral angle of the ''next'' residue sum to roughly −75°. For comparison, the sum of the dihedral angles for an α-helix is roughly −105°, whereas that for a π-helix is roughly −125°. The general formula for the rotation angle Ω per residue of any polypeptide helix with ''trans'' isomers is given by the equation : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「310 helix」の詳細全文を読む スポンサード リンク
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