Search results for "Phi value analysis"
showing 4 items of 4 documents
Site-Specific Information on Membrane Protein Folding by Electron Spin Echo Envelope Modulation Spectroscopy
2010
Compared to folding of soluble proteins, folding of membrane proteins is complicated by the fact that it requires an amphiphilic environment. Few existing techniques can provide structurally resolved information on folding kinetics. For the major plant light harvesting complex LHCII, it is demonstrated that changes in water accessibility of a particular amino acid residue can be followed during folding by measuring the hyperfine interaction of spin labels with deuterium nuclei of heavy water. The incorporation of residue 196 into the hydrophobic core of a detergent micelle was investigated. The technique provides a time constant that is similar to the one found with fluorescence spectroscop…
Two-state protein-like folding of a homopolymer chain
2010
Many small proteins fold via a first-order "all-or-none" transition directly from an expanded coil to a compact native state. Here we study an analogous direct freezing transition from an expanded coil to a compact crystallite for a simple flexible homopolymer. Wang-Landau sampling is used to construct the 1D density of states for square-well chains of length 128. Analysis within both the micro-canonical and canonical ensembles shows that, for a chain with sufficiently short-range interactions, the usual polymer collapse transition is preempted by a direct freezing or "folding" transition. A 2D free-energy landscape, built via subsequent multi-canonical sampling, reveals a dominant folding …
Folding energetics and oligomerization of polytopic α-helical transmembrane proteins
2014
While interactions of single-span transmembrane helices have been studied to a significant extent in the past years, the folding of polytopic α-helical transmembrane proteins as well as their oligomerization, are far less analyzed and understood. The goal of the few thus far performed thermodynamic studies, in which unfolding of polytopic TM proteins was described, was to achieve a mild, potentially reversible unfolding process, to finally derive thermodynamic parameters for the reverse folding pathway. In the first part of this review, we summarize the studies analyzing the thermodynamic stability and folding pathways of polytopic transmembrane proteins. Based on these studies, we deduce s…
Template-Directed Protein Folding into a Metastable State of Increased Activity
1995
The principal objective of this work was to distinguish between kinetic and thermodynamic reaction control in protein folding. The deleterious effects of a specific mutation on spontaneous refolding competence were analyzed for this purpose. A Bowman-Birk-type proteinase inhibitor of trypsin and chymotrypsin was selected as a double-headed model protein to facilitate the detection of functional irregularities by the use of functional assays. The parent protein spontaneously folds into a single, fully active and thermodynamically stable state in a redox buffer after reduction/denaturation. By contrast, the properties of a P'1Ser--Pro variant in the trypsin-reactive subdomain differ before an…