Elongational flow studies on the molecular properties of collagen and its thermal denaturation

Sasaki, Naoki; Atkins, E. D. T.; Fulton, W. Stephen

doi:10.1002/app.1991.070421115

Cited by 17 publications

(10 citation statements)

References 10 publications

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“…Figure 7 shows the rotational diffusion coefficient ( D r ) for the HPC solution of 4.98 g/L, which was derived from Figure 6. D r is determined from the birefringence intensity Δ n by the following relation:10, 13, 23 where Δ n 0 is the birefringence at a steady state in a rigid rod‐like pattern. As the temperature increased, D r gradually decreased.…”

Section: Resultsmentioning

confidence: 99%

“…Then, the birefringence increases rapidly with This phenomenon is a manifestation of the coil‐stretch transition. On the other hand, rod‐like molecules become aligned along the flow direction with an increase in Their birefringence pattern differs significantly from that of a flexible chain at the point that there is no criticality in the appearance of Δ n , and the birefringence does not localize along the pure elongational field 10–13. If a polymer chain undergoes a conformational transition from a rod‐like structure to a flexible coil and vice versa, the transition process will be well documented by the observation of an elongational Δ n .…”

Section: Introductionmentioning

confidence: 99%

“…If a polymer chain undergoes a conformational transition from a rod‐like structure to a flexible coil and vice versa, the transition process will be well documented by the observation of an elongational Δ n . On the basis of this concept, a conformational change of macromolecules, such as the collapsing of a secondary structure of DNA and collagen or a morphological variation in a single polymer chain, has been investigated 11–14…”

Section: Introductionmentioning

confidence: 99%

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Elongational flow studies on the phase separation of hydroxypropylcellulose solution

Fujii

Sasaki

Nakata

2002

J of Applied Polymer Sci

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ABSTRACT:The phase separation of hydroxypropylcellulose (HPC) in a mixed solvent of glycerol and water was investigated by an elongational flow birefringence method. In the one-phase region, the elongational flow birefringence had the characteristics of a typical coil-stretch transition-like pattern with a critical elongational strain rate c . c increased monotonously with temperature, but in the vicinity of the phase-separation point, c began to decrease even in the one-phase region. In the two-phase region, the flow-induced birefringence pattern contained both a rigid rod-like response and the coil-stretch transition-like response of a flexible polymer. The appearance of the rod-like birefringence pattern indicates the association of HPC chains to form a precursor of the liquid-crystalline phase formation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Elongational flow studies on the phase separation of hydroxypropylcellulose solution

Fujii

Sasaki

Nakata

2002

J of Applied Polymer Sci

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“…This behavior is characteristic of flexible molecules and is explained by a change of the conformation of the collagen molecule to a hinged-rod structure before melting. 49 Models of collagen containing internal distortions have previously been obtained in studies of the effect of mutations in which Gly is replaced by other amino acids. In an earlier model building study of a triple helix with a Gly to Cys mutation, 50 the bulky Cys was accommodated by a small local distortion that disrupted interchain contacts and…”

Section: Discussionmentioning

confidence: 99%

The energy of formation of internal loops in triple‐helical collagen polypeptides

Némethy

1995

Biopolymers

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The sequence-dependent local destabilization in the interior of the collagen triple helix has been evaluated by means of conformational energy computations. Using a model poly(Gly-Pro-Pro) triple helix as the reference state, a method was developed for generating local loops, i.e., internal deformations, and analyzing their conformations. A seven-residue Gly-Pro-Pro- Gly-Pro-Pro-Gly fragment was replaced by the Gly-Pro-Ala-Gly-Ala-Ala-Gly sequence in one, two, or all three of the strands of the loop region. A set of loop conformations was generated in which the ends of the loop were initially fixed in the triple-helical structure. The potential energy of the entire deformed triple helix was then minimized, resulting in a variety of structures that contained deformed loops. The conformations of the triple helices at the two ends of the loops remained essentially unchanged in many of the low-energy conformations. In numerous high-energy conformations, however, the triple-helical segments were also partially or totally disrupted. The minimum-energy conformations of the whole structures were compared in terms of rms deviations of atomic coordinates with respect to the original triple helix, and of the shapes of the loops (using a distance function derived from differential geometry). Three new geometrical parameters-stretch S, kink K, and unwinding U-were defined to describe the changes in the overall orientation of the triple helices at the two ends of the loop. It is shown that, when the number of Pro residues in a short fragment is reduced, the triple helical structure can accomodate internal loops (i.e., distortions) within a 5 kcal/mol cutoff from the essentially unperturbed triple helical structure. For structures with a Gly-Pro-Ala-Gly-Ala-Ala-Gly sequence in all three strands, the probability of finding conformations with internal loops is small, i.e., 0.06. Internal loops affect the overall orientation of these structures, as measured by the helix-distortion parameters S, K, and U.

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“…By making use of these differences in the response of polymers to the elongational flow field, conformational transitions of biopolymers have been successfully investigated. [13][14][15][16] The elongational flow field has been shown to be a new useful tool for studying the conformational transition of both synthetic and biological polymers. Results from hydrodynamic studies have contributed to an understanding of the global properties of macromolecules.…”

Section: Introductionmentioning

confidence: 99%

Elongation flow studies of DNA as a function of temperature

Sasaki

Maki

Nakata

2001

J of Applied Polymer Sci

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ABSTRACT:The response of T4-phage DNA molecules to an elongational flow field was monitored by flow-induced birefringence as a function of temperature. The flow-induced birefringence observed in this study was localized in the pure elongational flow area with a critical strain rate, indicating that the birefringence was attributed to a coilstretch transition of DNA molecules. The slight decrease in the birefringence intensity with increases in temperature to 40°C was explained by a thermal-activation process. At temperatures above 50°C, flow-induced birefringence decreased remarkably, and no birefringence was observed at temperatures above 60°C. After the flow experiments, ambient temperature was reduced back to room temperature, and flow experiments at room temperature were performed again. Flow-induced birefringence was recovered almost completely in samples for which the first flow measurements were made at temperatures below 53°C. Irreversible changes were observed for samples for which the first flow experiments were performed at temperatures above 55°C. The temperature dependence of UV-absorption spectra revealed that the double-strand DNA helix began to partially untwine at a temperature over 50°C, and duplexes became almost completely untwined at a temperature over 55°C. A comparison of electrophoresis patterns for untwined molecules showed that flow-induced scission of DNA molecules occurred in a sample solution in flow experiments performed at 65°C, while no molecular weight reduction was observed in the sample solution at 55°C. In this article, this difference between the untwined DNA molecules is discussed on the basis of the thermally activated bond scission (TABS) model.

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Elongational flow studies on the molecular properties of collagen and its thermal denaturation

Cited by 17 publications

References 10 publications

Elongational flow studies on the phase separation of hydroxypropylcellulose solution

Elongational flow studies on the phase separation of hydroxypropylcellulose solution

The energy of formation of internal loops in triple‐helical collagen polypeptides

Elongation flow studies of DNA as a function of temperature

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