蛋白质的结构英文版.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 12.4 Molten globules are formed early in folding. 12.4.1 Molten gobule state contains native secondary but not tertiary structure (an experimental observation). 12.4.2 Hydrophobic collapse and acquisition of stable secondary structure are mutually reinforcing events in the formation of molten globules (synergistic, helping each other). 学习文档 12.5 Partially folded intermediates can be detected, trapped, and characterized. 12.5.1 Rapid-kinetics studies, where protein secondary structures are monitored by spectroscopic methods (e.g., fluorescence, circular dichroism), can reveal the progression of distinctive intermediates during refolding processes. 12.5.2 Disulfide-bonded intermediates can be trapped covalently by blocking uncombined cysteines with iodoacetate. 12.5.3 Pulsed hydrogen-deuterium exchange can be used to monitor the acquisition of secondary structures in protein folding. 学习文档 12.5.4 Our understanding of protein folding can be stringently tested by designing novel proteins with distinctive functions. For example, encouraging starts have been made in synthesizing new scaffolds, metal-binding proteins, channels, and catalysts. 12.6 Protein folding in vivo is sometimes catalyzed by isomerases and chaperone proteins. 12.6.1 The formation of correct disulfide pairing in nascent proteins is catalyzed by protein disulfide isomerase (PDI), which is especially important I accelerating disulfide interchange in kinetically trapped folding intermediates. 学习文档 12.6.2 Peptidyl prolyl isomerases (PPIases) accelerate cis-trans isomerization of Pro residues during protein folding. 12.6.3 Molecular chaperones in cells facilitate the correct assembly (including folding, refolding, formation of oligomeric complexes, … etc) of other polypeptides but are not themselves part of the assembled, functional structure. Are they enzymes? Facilitated search (e.g., avoiding aggregate