分子生物物理學(編輯修改稿)
2025-01-15 03:46 本頁面
【文章內(nèi)容簡介】 omewhatparedwiththestandardPaulingCoreymodel.Why?1. The packing of buried helices against other secondary structure elements in the core of the protein2. Proline residues induce distortions of around 20 degrees in the direction of the helix axis3. Solvent. Exposed helices are often bent away from the solvent region. This is because the exposed C=O groups tend to point towards solvent to maximise their Hbonding capacity, . tend to form Hbonds to solvent as well as NH groups.310helixintroductionOnly%oftheresiduesareinvolvedin310helices,andnearlyallthoseinhelicalsegmentscontainingii+3hydrogenbonds.Ideal(,)/found(and)COHNhydrogenbond:ii+3Standard 310 helixProlinehelixLeft handed helix residues per turnpitch = 197。 No hydrogen bonding in the backbone but helix still forms.Polyglycine also forms this type of helixCollagen:highinGlyProresidueshasthistypeofhelicalstructure?helicesintroductionThe pi helix is an extremely rare secondary structural element in proteins. the backbone C=O of residue i hydrogen bonds to the backbone HN of residue i+5.ii+5Hbonds1. the phi and psi angles of the pure pi helix ( , ) lie at the very edge of an allowed, minimum energy region of the Ramachandran (phi, psi) map. 2. the pi helix requires that the angle tau (NCaC39。) be larger () than the standard tetrahedral angle of degrees. 3. the large radius of the pi helix means the polypeptide backbone is no longer in van der Waals contact across the helical axis forming an axial hole too small for solvent water to fill. 4. side chains are more staggered than the ideal helix but not as well as the alpha helix.Hbond:15alphahelix, surface of protein, barrieramphiphilicproteindesign projects by Degrado, USAHelicalwheel
教學課件相關推薦
鄂ICP備17016276號-1