Statistical Physics of Macromolecules

Grosberg, Anna; Khokhlov, Alexei R.; Stanley, H. Eugene; Mallinckrodt, A. John; McKay, Susan R.

doi:10.1063/1.4823390

Cited by 445 publications

(349 citation statements)

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“…This behavior is different from that associated with the folding transition of the protein, which involves coexistence of two populations, folded and denatured. This observation strongly suggests that the expansion͞collapse transition is second-order in nature, as is usually observed for the CG transition of flexible polymers (2). The smFRET experiment thus is nicely capable of deciphering the order of a thermodynamic intramolecular transition in a protein.…”

Section: Resultssupporting

confidence: 63%

“…Flory-type mean-field theories of the CG transition treat the density of the polymer as an order parameter, from which changes in the radius of gyration can be readily calculated (1,2). It is much more difficult to calculate the effect of expansion on the hydrodynamic radius (but see refs.…”

Section: Resultsmentioning

confidence: 99%

“…When a polymer molecule is transferred from a good solvent to a bad one, it undergoes a collapse from an expanded coil-like conformation to a contracted, globule-like conformation. This collapse is typically a second-order phase transition and can be accounted well by mean-field theory (1,2). Proteins are heteropolymers and therefore should exhibit a similar transition.…”

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confidence: 95%

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Coil–globule transition in the denatured state of a small protein

Sherman

Haran

2006

Proc. Natl. Acad. Sci. U.S.A.

288

383

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Upon transfer from strongly denaturing to native conditions, proteins undergo a collapse that either precedes folding or occurs simultaneously with it. This collapse is similar to the well known coil-globule transition of polymers. Here we employ singlemolecule fluorescence methods to fully characterize the equilibrium coil-globule transition in the denatured state of the IgGbinding domain of protein L. By using FRET measurements on freely diffusing individual molecules, we determine the radius of gyration of the protein, which shows a gradual expansion as the concentration of the denaturant, guanidinium hydrochloride, is increased all the way up to 7 M. This expansion is observed also in fluorescence correlation spectroscopy measurements of the hydro- fluorescence correlation spectroscopy ͉ protein folding ͉ single-molecule fluorescence T he coil-globule (CG) transition is a hallmark of the physics of polymers in solution. When a polymer molecule is transferred from a good solvent to a bad one, it undergoes a collapse from an expanded coil-like conformation to a contracted, globule-like conformation. This collapse is typically a second-order phase transition and can be accounted well by mean-field theory (1, 2). Proteins are heteropolymers and therefore should exhibit a similar transition. Because proteins also undergo a first-order folding transition to form their native structure, it is of prime interest to deduce the relation between collapse and folding (3). If the CG transition precedes folding significantly, then the final rearrangements of the protein chain to form the native structure occur within a relatively limited configurational space, which might affect the efficiency and speed of the process. The CG transition of proteins is also important for the elucidation of the properties of their denatured states. Chain collapse can have an impact on secondary-structure formation in the denatured protein (4). Determining the energetics of the collapse, which involve changes in the solvation energy of the protein as the solution conditions are varied, might allow us to understand better the role of the denatured state in the folding transition (5).The occurrence of a collapse preceding protein folding was inferred from kinetic experiments (6-11) and also reported in equilibrium experiments, using small-angle x-ray scattering (SAXS) (12) and single-molecule fluorescence (13,14). However, the thermodynamics of the CG transition have not been characterized yet. In this work, we use two methods, singlemolecule FRET (smFRET) and fluorescence correlation spectroscopy (FCS), to measure the CG transition of a 64-amino acid protein exhibiting two-state folding, the IgG-binding domain of protein L (hereafter denoted simply as protein L) (15). The CG transition is driven by the chemical denaturant guanidinium hydrochloride (GuHCl). We then employ a version of the mean-field theory of Sanchez (16) to obtain a full thermodynamic characterization of the CG transition of a protein, identifying the transition point as well ...

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Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 95%

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Coil–globule transition in the denatured state of a small protein

Sherman

Haran

2006

Proc. Natl. Acad. Sci. U.S.A.

288

383

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“…This value suggests that denatured schizophyllan is a random coil swollen by an excluded-volume effect. 64,65 The polydispersity ratios shown in the last column of Tables II and III were obtained by the method of histograms described in Ref. 14.…”

Section: Resultsmentioning

confidence: 99%

Applications of fluorescence correlation spectroscopy: Measurement of size-mass relationship of native and denatured schizophyllan

2001

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“…In other words, the polyelectrolyte collapses to some extent and the cation is condensed together with the backbone charge. [17,24] The composition dependence described above for both the NMR and DSC data suggests that at higher LiAMPS content, polyelectrolyte condensation indeed occurs although ions can exchange between the two regions. This sort of behavior is also observed in micellar solutions beyond the critical micellar concentration.…”

Section: Structural Modelmentioning

confidence: 91%