Quantitative theory of the globule-to-coil transition. 4. Comparison of theoretical results with experimental data

Grosberg, Alexander Y.; Кузнецов, Д. В.

doi:10.1021/ma00033a025

Cited by 82 publications

(60 citation statements)

References 24 publications

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“…1,4 The correct characteristic ratio could not be obtained at the temperature defined by A 2 ϭ0 in the presence of a preferential sorption. 23 In the present experiment, the PMMA chain in pure tertbutyl alcohol was found to collapse completely within 90 min after quenching for M ϭ1.22ϫ10 7 and within 30 min for M ϭ4.1ϫ10 6 . For PMMA in the mixed solvent tert-butyl alcoholϩwater͑2.5 vol %͒, the chain collapse process was observed over periods of hours to weeks depending on the temperature and the molecular weight.…”

Section: Discussionsupporting

confidence: 49%

“…The effect of chain aggregation indicated by these large apparent molecular weights made the determination of ͗s 2 ͘ unreliable, though the solutions were transparent by the eye. On the other hand, for PMMA in the mixed solvent tert-butyl alcohol ϩwater͑2.5 vol %͒, the increase in observed molecular weight due to chain aggregation was negligibly small for a day after quenching for M w ϭ4.0ϫ10 6 and at least for a week after quenching for M w ϭ1.22ϫ10 7 . Thus, it is obvious that the phase separation occurs much faster in pure tertbutyl alcohol than in the mixed solvent.…”

Section: Discussionmentioning

confidence: 92%

“…The chain aggregation due to phase separation causes an apparent molecular weight which can be used as a measure for the rate of phase separation. For PMMA in pure tert-butyl alcohol, the apparent molecular weight was obtained as 7ϫ10 6 for M w ϭ4.1ϫ10 6 at 60 min after quenching to 60.0°C and 1.7ϫ10 7 for M w ϭ1.22 ϫ10 7 at 24 h after quenching to 55.0°C. The effect of chain aggregation indicated by these large apparent molecular weights made the determination of ͗s 2 ͘ unreliable, though the solutions were transparent by the eye.…”

Section: Discussionmentioning

confidence: 99%

“…The observed expansion factor ␣ 2 ϭ͗s 2 ͘/͗s 2 ͘ 0 relative to ͗s 2 ͘ 0 at the temperature has been represented by 5,6 ␣ 3 Ϫ␣ϪC͑␣ Ϫ3 Ϫ1 ͒ϭBM 1/2 , ͑1͒…”

Section: Introductionmentioning

confidence: 99%

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Solvent effect on single-chain collapse of poly(methyl methacrylate) in tert-butyl alcohol

Nakamura

Sasaki

Nakata

2003

The Journal of Chemical Physics

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Kinetic and static properties of the coil-globule transition of poly͑methyl methacrylate͒ ͑PMMA͒ in pure tert-butyl alcohol were determined by static light scattering and compared with those of PMMA in the mixed solvent tert-butyl alcoholϩwater͑2.5 vol %͒ in order to examine the effect of water on the chain collapse. The measurements were carried out for the molecular weight M ϫ10 Ϫ6 ϭ4.1 and 12.2 in the concentration range of 0.6ϫ10 Ϫ4 -2.6ϫ10 Ϫ4 g/cm 3 , and the mean-square radius of gyration ͗s 2 ͘ was determined as a function of the time after an abrupt decrease of temperature.PMMA chains collapsed to equilibrium globules within 90 min after quenching for M ϭ1.22 ϫ10 7 and within 30 min for M ϭ4.1ϫ10 6 . Chain aggregation due to phase separation became noticeable after the collapse of the chain because of an increase of observed molecular weight. For PMMA in the mixed solvent tert-butyl alcoholϩwater͑2.5 vol %͒, the chain collapse process has been observed for periods from hours to weeks depending on the molecular weight and temperature, and the chain aggregation was negligibly small in the chain collapse process. The expansion factor ␣ 2 ϭ͗s 2 ͘/͗s 2 ͘ 0 obtained for fully collapsed chains in pure tert-butyl alcohol was represented by the theoretical prediction ␣ 3 Ϫ␣ϪC(␣ Ϫ3 Ϫ1)ϭB(1Ϫ /T)M 1/2 with the coefficients of Bϭ0.0179 and Cϭ0.054. For PMMA in the mixed solvent, the coil-globule transition curve has been expressed by the same equation with Bϭ0.0164 and Cϭ0.049, close to the above values. The small amount of water in the mixed solvent caused a drastic slowdown in the chain-collapse rate but had little effect on the coil-globule transition curve.

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Section: Discussionsupporting

confidence: 49%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

“…The observed expansion factor ␣ 2 ϭ͗s 2 ͘/͗s 2 ͘ 0 relative to ͗s 2 ͘ 0 at the temperature has been represented by 5,6 ␣ 3 Ϫ␣ϪC͑␣ Ϫ3 Ϫ1 ͒ϭBM 1/2 , ͑1͒…”

Section: Introductionmentioning

confidence: 99%

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Solvent effect on single-chain collapse of poly(methyl methacrylate) in tert-butyl alcohol

Nakamura

Sasaki

Nakata

2003

The Journal of Chemical Physics

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“…In this review, we focus on a description of the concepts borrowed directly from polymer physics [20][21][22][23][24][25][26][27][28] that provide the necessary framework for understanding the driving forces and mechanisms for protein aggregation. In our parlance, protein aggregation refers is allencompassing because we do not distinguish between ordered versus amorphous aggregates.…”

Section: Introductionmentioning

confidence: 99%

A polymer physics perspective on driving forces and mechanisms for protein aggregation

Pappu

Wang

Vitalis

et al. 2008

Archives of Biochemistry and Biophysics

154

172

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Protein aggregation is a commonly occurring problem in biology. Cells have evolved stress-response mechanisms to cope with problems posed by protein aggregation. Yet, these quality control mechanisms are overwhelmed by chronic aggregation-related stress and the resultant consequences of aggregation become toxic to cells. As a result, a variety of systemic and neurodegenerative diseases are associated with various aspects of protein aggregation and rational approaches to either inhibit aggregation or manipulate the pathways to aggregation might lead to an alleviation of disease phenotypes. To develop such approaches, one needs a rigorous and quantitative understanding of protein aggregation. Much work has been done in this area. However, several unanswered questions linger, and these pertain primarily to the actual mechanism of aggregation as well as to the types of intermolecular associations and intramolecular fluctuations realized at low protein concentrations. It has been suggested that the concepts underlying protein aggregation are similar to those used to describe the aggregation of synthetic polymers. Following this suggestion, the relevant concepts of polymer aggregation are introduced. The focus is on explaining the driving forces for polymer aggregation and how these driving forces vary with chain length and solution conditions. It is widely accepted that protein aggregation is a nucleation-dependent process. This view is based mainly on the presence of long times for the accumulation of aggregates and the elimination of these lag times with "seeds". In this sense, protein aggregation is viewed as being analogous to the aggregation of colloidal particles. The theories for polymer aggregation reviewed in this work suggest an alternative mechanism for the origin of long lag times in protein aggregation. The proposed mechanism derives from the recognition that polymers have unique dynamics that distinguish them from other aggregation-prone systems such as colloidal particles.

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DNA condensation by multivalent cations

1997

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In the presence of multivalent cations, high molecular weight DNA undergoes a dramatic condensation to a compact, usually highly ordered toroidal structure. This review begins with an overview of DNA condensation:condensing agents, morphology, kinetics and reversibility, and the minimum size required to form orderly condensates. It then summarizes the statistical mechanics of the collapse of stiff polymers, which shows why DNA condensation is abrupt and why toroids are favored structures. Various ways to estimate or measure intermolecular forces in DNA condensation are discussed, all of them agreeing that the free energy change per base pair is very small, on the order of 1% of thermal energy. Experimental evidence is surveyed showing that DNA condensation occurs when about 90% of its charge is neutralized by counterions. The various intermolecular forces whose interplay gives rise to DNA condensation are then reviewed. The entropy loss upon collapse of the expanded wormlike coil costs free energy, and stiffness sets limits on tight curvature. However, the dominant contributions seem to come from ions and water. Electrostatic repulsions must be overcome by high salt concentrations or by the correlated fluctuations of territorially bound multivalent cations. Hydration must be adjusted to allow a cooperative accommodation of the water structure surrounding surface groups on the DNA helices as they approach. Undulations of the DNA in its confined surroundings extend the range of the electrostatic forces. The condensing ions may also subtly modify the local structure of the double helix.

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Quantitative theory of the globule-to-coil transition. 4. Comparison of theoretical results with experimental data

Cited by 82 publications

References 24 publications

Solvent effect on single-chain collapse of poly(methyl methacrylate) in tert-butyl alcohol

Solvent effect on single-chain collapse of poly(methyl methacrylate) in tert-butyl alcohol

A polymer physics perspective on driving forces and mechanisms for protein aggregation

DNA condensation by multivalent cations

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