The Experts below are selected from a list of 47631 Experts worldwide ranked by ideXlab platform
Yi Wu - One of the best experts on this subject based on the ideXlab platform.
-
Quantification of load-dependent changes in the Collagen Fiber architecture for the strut chordae tendineae-leaflet insertion of porcine atrioventricular heart valves
Biomechanics and Modeling in Mechanobiology, 2020Co-Authors: Colton J. Ross, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Yi WuAbstract:Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of Collagen Fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the Collagen Fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue’s Collagen Fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the Collagen Fiber architecture of the mitral and tricuspid valve’s strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the Collagen Fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.
-
quantification of load dependent changes in the Collagen Fiber architecture for the strut chordae tendineae leaflet insertion of porcine atrioventricular heart valves
Biomechanics and Modeling in Mechanobiology, 2020Co-Authors: Colton J. Ross, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Yi WuAbstract:Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of Collagen Fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the Collagen Fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue’s Collagen Fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the Collagen Fiber architecture of the mitral and tricuspid valve’s strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the Collagen Fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.
-
load dependent Collagen Fiber architecture data of representative bovine tendon and mitral valve anterior leaflet tissues as quantified by an integrated opto mechanical system
Data in Brief, 2020Co-Authors: Samuel Jett, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Luke T Hudson, Bradley N Bohnstedt, Yi WuAbstract:Abstract The data presented in this article provide load-dependent Collagen Fiber architecture (CFA) of one representative bovine tendon tissue sample and two representative porcine mitral valve anterior leaflet tissues, and they are stored in a MATLAB MAT-file format. Each dataset contains: (i) the number of pixel points, (ii) the array of pixel's x- and y-coordinates, (iii) the three acquired pixel intensity arrays, and (iv) the Delaunay triangulation for visualization purpose. This dataset is associated with a companion journal article, which can be consulted for further information about the methodology, results, and discussion of the opto-mechanical characterization of the tissue's CFA's (Jett et al. [1]).
Louis J. Soslowsky - One of the best experts on this subject based on the ideXlab platform.
-
tensile mechanical properties and dynamic Collagen Fiber re alignment of the murine cervix are dramatically altered throughout pregnancy
Journal of Biomechanical Engineering-transactions of The Asme, 2017Co-Authors: Carrie E Barnum, Brianne K. Connizzo, Jennifer L Fey, Stephanie N Weiss, Guillermo Barila, Amy Brown, Snehal S Shetye, Michal A Elovitz, Louis J. SoslowskyAbstract:The cervix is a unique organ able to dramatically change its shape and function by serving as a physical barrier for the growing fetus and then undergoing dramatic dilation allowing for delivery of a term infant. As a result, the cervix endures changing mechanical forces from the growing fetus. There is an emerging concept that the cervix may change or remodel "early" in many cases of spontaneous preterm birth (sPTB). However, the mechanical role of the cervix in both normal and preterm birth remains unclear. Therefore, the primary objective of this study was to determine the mechanical and structural responses of murine cervical tissue throughout a normal gestational time course. In this study, both tissue structural and material properties were determined via a quasi-static tensile load-to-failure test, while simultaneously obtaining dynamic Collagen Fiber re-alignment via cross-polarization imaging. This study demonstrated that the majority of the mechanical properties evaluated decreased at midgestation and not just at term, while Collagen Fiber re-alignment occurred earlier in the loading curve for cervices at term. This suggests that although structural changes in the cervix occur throughout gestation, the differences in material properties function in combination with Collagen Fiber re-alignment as mechanical precursors to regulate term gestation. This work lays a foundation for investigating cervical biomechanics and the role of the cervix in preterm birth.
-
diabetes alters mechanical properties and Collagen Fiber re alignment in multiple mouse tendons
Annals of Biomedical Engineering, 2014Co-Authors: Brianne K. Connizzo, Pankti R Bhatt, Kenneth W Liechty, Louis J. SoslowskyAbstract:Tendons function to transfer load from muscle to bone through their complex composition and hierarchical structure, consisting mainly of type I Collagen. Recent evidence suggests that type II diabetes may cause alterations in Collagen structure, such as irregular fibril morphology and density, which could play a role in the mechanical function of tendons. Using the db/db mouse model of type II diabetes, the diabetic skin was found to have impaired biomechanical properties when compared to the non-diabetic group. The purpose of this study was to assess the effect of diabetes on biomechanics, Collagen Fiber re-alignment, and biochemistry in three functionally different tendons (Achilles, supraspinatus, patellar) using the db/db mouse model. Results showed that cross-sectional area and stiffness, but not modulus, were significantly reduced in all three tendons. However, the tendon response to load (transition strain, Collagen Fiber re-alignment) occurred earlier in the mechanical test, contrary to expectations. In addition, the patellar tendon had an altered response to diabetes when compared to the other two tendons, with no changes in Fiber re-alignment and decreased Collagen content at the midsubstance of the tendon. Overall, type II diabetes alters tendon mechanical properties and the dynamic response to load.
-
effect of age and proteoglycan deficiency on Collagen Fiber re alignment and mechanical properties in mouse supraspinatus tendon
Journal of Biomechanical Engineering-transactions of The Asme, 2013Co-Authors: Brianne K. Connizzo, Joseph J Sarver, Renato V Iozzo, David E Birk, Louis J. SoslowskyAbstract:Collagen Fiber realignment is one mechanism by which tendon responds to load. Re-alignment is altered when the structure of tendon is altered, such as in the natural process of aging or with alterations of matrix proteins, such as proteoglycan expression. While changes in re-alignment and mechanical properties have been investigated recently during development, they have not been studied in (1) aged tendons, or (2) in the absence of key proteoglycans. Collagen Fiber re-alignment and the corresponding mechanical properties are quantified throughout tensile mechanical testing in both the insertion site and the midsubstance of mouse supraspinatus tendons in wild type (WT), decorin-null (Dcn(-/-)), and biglycan-null (Bgn(-/-)) mice at three different ages (90 days, 300 days, and 570 days). Percent relaxation was significantly decreased with age in the WT and Dcn(-/-) tendons, but not in the Bgn(-/-) tendons. Changes with age were found in the linear modulus at the insertion site where the 300 day group was greater than the 90 day and 570 day group in the Bgn(-/-) tendons and the 90 day group was smaller than the 300 day and 570 day groups in the Dcn(-/-) tendons. However, no changes in modulus were found across age in WT tendons were found. The midsubstance Fibers of the WT and Bgn(-/-) tendons were initially less aligned with increasing age. The re-alignment was significantly altered with age in the WT tendons, with older groups responding to load later in the mechanical test. This was also seen in the Dcn(-/-) midsubstance and the Bgn(-/-) insertion, but not in the other locations. Although some studies have found changes in the WT mechanical properties with age, this study did not support those findings. However, it did show Fiber re-alignment changes at both locations with age, suggesting a breakdown of tendon's ability to respond to load in later ages. In the proteoglycan-null tendons however, there were changes in the mechanical properties, accompanied only by location-dependent re-alignment changes, suggesting a site-specific role for these molecules in loading. Finally, changes in the mechanical properties did not occur in concert with changes in re-alignment, suggesting that typical mechanical property measurements alone are insufficient to describe how structural alterations affect tendon's response to load.
-
characterizing local Collagen Fiber re alignment and crimp behavior throughout mechanical testing in a mature mouse supraspinatus tendon model
Journal of Biomechanics, 2012Co-Authors: Kristin S. Miller, Brianne K. Connizzo, Elizabeth Feeney, Louis J. SoslowskyAbstract:Abstract Background Collagen Fiber re-alignment and uncrimping are two postulated mechanisms of tendon structural response to load. Recent studies have examined structural changes in response to mechanical testing in a postnatal development mouse supraspinatus tendon model (SST), however, those changes in the mature mouse have not been characterized. The objective of this study was to characterize Collagen Fiber re-alignment and crimp behavior throughout mechanical testing in a mature mouse SST. Method of approach A tensile mechanical testing set-up integrated with a polarized light system was utilized for alignment and mechanical analysis. Local Collagen Fiber crimp frequency was quantified immediately following the designated loading protocol using a traditional tensile set up and a flash-freezing method. The effect of number of preconditioning cycles on Collagen Fiber re-alignment, crimp frequency and mechanical properties in midsubstance and insertion site locations were examined. Results Decreases in Collagen Fiber crimp frequency were identified at the toe-region of the mechanical test at both locations. The insertion site re-aligned throughout the entire test, while the midsubstance re-aligned during preconditioning and the test's linear-region. The insertion site demonstrated a more disorganized Collagen Fiber distribution, lower mechanical properties and a higher cross-sectional area compared to the midsubstance location. Conclusions Local Collagen Fiber re-alignment, crimp behavior and mechanical properties were characterized in a mature mouse SST model. The insertion site and midsubstance respond differently to mechanical load and have different mechanisms of structural response. Additionally, results support that Collagen Fiber crimp is a physiologic phenomenon that may explain the mechanical test toe-region.
-
examining differences in local Collagen Fiber crimp frequency throughout mechanical testing in a developmental mouse supraspinatus tendon model
Journal of Biomechanical Engineering-transactions of The Asme, 2012Co-Authors: Kristin S. Miller, Brianne K. Connizzo, Elizabeth Feeney, Jennica J Tucker, Louis J. SoslowskyAbstract:Crimp morphology is believed to be related to tendon mechanical behavior. While crimp has been extensively studied at slack or nondescript load conditions in tendon, few studies have examined crimp at specific, quantifiable loading conditions. Additionally, the effect of the number of cycles of preconditioning on Collagen Fiber crimp behavior has not been examined. Further, the dependence of Collagen Fiber crimp behavior on location and developmental age has not been examined in the supraspinatus tendon. Local Collagen Fiber crimp frequency is quantified throughout tensile mechanical testing using a flash freezing method immediately following the designated loading protocol. Samples are analyzed quantitatively using custom software and semi-quantitatively using a previously established method to validate the quantitative software. Local Collagen Fiber crimp frequency values are compared throughout the mechanical test to determine where Collagen Fiber frequency changed. Additionally, the effect of the number of preconditioning cycles is examined compared to the preload and toe-region frequencies to determine if increasing the number of preconditioning cycles affects crimp behavior. Changes in crimp frequency with age and location are also examined. Decreases in Collagen Fiber crimp frequency were found at the toe-region at all ages. Significant differences in Collagen Fiber crimp frequency were found between the preload and after preconditioning points at 28 days. No changes in Collagen Fiber crimp frequency were found between locations or between 10 and 28 days old. Local Collagen Fiber crimp frequency throughout mechanical testing in a postnatal developmental mouse SST model was measured. Results confirmed that the uncrimping of Collagen Fibers occurs primarily in the toe-region and may contribute to the tendon’s nonlinear behavior. Additionally, results identified changes in Collagen Fiber crimp frequency with an increasing number of preconditioning cycles at 28 days, which may have implications on the measurement of mechanical properties and identifying a proper reference configuration.
Gerhard A. Holzapfel - One of the best experts on this subject based on the ideXlab platform.
-
Quantification of load-dependent changes in the Collagen Fiber architecture for the strut chordae tendineae-leaflet insertion of porcine atrioventricular heart valves
Biomechanics and Modeling in Mechanobiology, 2020Co-Authors: Colton J. Ross, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Yi WuAbstract:Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of Collagen Fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the Collagen Fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue’s Collagen Fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the Collagen Fiber architecture of the mitral and tricuspid valve’s strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the Collagen Fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.
-
quantification of load dependent changes in the Collagen Fiber architecture for the strut chordae tendineae leaflet insertion of porcine atrioventricular heart valves
Biomechanics and Modeling in Mechanobiology, 2020Co-Authors: Colton J. Ross, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Yi WuAbstract:Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of Collagen Fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the Collagen Fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue’s Collagen Fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the Collagen Fiber architecture of the mitral and tricuspid valve’s strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the Collagen Fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.
-
load dependent Collagen Fiber architecture data of representative bovine tendon and mitral valve anterior leaflet tissues as quantified by an integrated opto mechanical system
Data in Brief, 2020Co-Authors: Samuel Jett, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Luke T Hudson, Bradley N Bohnstedt, Yi WuAbstract:Abstract The data presented in this article provide load-dependent Collagen Fiber architecture (CFA) of one representative bovine tendon tissue sample and two representative porcine mitral valve anterior leaflet tissues, and they are stored in a MATLAB MAT-file format. Each dataset contains: (i) the number of pixel points, (ii) the array of pixel's x- and y-coordinates, (iii) the three acquired pixel intensity arrays, and (iv) the Delaunay triangulation for visualization purpose. This dataset is associated with a companion journal article, which can be consulted for further information about the methodology, results, and discussion of the opto-mechanical characterization of the tissue's CFA's (Jett et al. [1]).
-
a phenomenological approach toward patient specific computational modeling of articular cartilage including Collagen Fiber tracking
Journal of Biomechanical Engineering-transactions of The Asme, 2009Co-Authors: David M Pierce, Werner Trobin, Siegfried Trattnig, Horst Bischof, Gerhard A. HolzapfelAbstract:To model the cartilage morphology and the material response, a phenomenological and patient-specific simulation approach incorporating the Collagen Fiber fabric is proposed. Cartilage tissue respon ...
Colton J. Ross - One of the best experts on this subject based on the ideXlab platform.
-
Quantification of load-dependent changes in the Collagen Fiber architecture for the strut chordae tendineae-leaflet insertion of porcine atrioventricular heart valves
Biomechanics and Modeling in Mechanobiology, 2020Co-Authors: Colton J. Ross, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Yi WuAbstract:Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of Collagen Fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the Collagen Fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue’s Collagen Fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the Collagen Fiber architecture of the mitral and tricuspid valve’s strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the Collagen Fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.
-
quantification of load dependent changes in the Collagen Fiber architecture for the strut chordae tendineae leaflet insertion of porcine atrioventricular heart valves
Biomechanics and Modeling in Mechanobiology, 2020Co-Authors: Colton J. Ross, Ryan Baumwart, Harold M. Burkhart, Gerhard A. Holzapfel, Yi WuAbstract:Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of Collagen Fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the Collagen Fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue’s Collagen Fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the Collagen Fiber architecture of the mitral and tricuspid valve’s strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the Collagen Fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.
Thirumalachari Ramasami - One of the best experts on this subject based on the ideXlab platform.
-
effect of hydrogen bond breaking reagent urea on the dimensional stability of rat tail tendon rtt Collagen Fiber
Journal of Applied Polymer Science, 2002Co-Authors: R Usha, Thirumalachari RamasamiAbstract:Influence of hydrogen-bond-breaking reagents such as urea on shrinkage temperature, isometric tension, swelling behavior, tensile strength, and percentage extension of native rat tail tendon (RTT) were examined. The swelling behavior was observed with polarizing optical microscopy and scanning electron microscopy. The results show that the lyotropic swelling increased the width of the Fiber and was associated with the action of urea on the Collagen Fiber. Hydration properties led to significant variations in the swelling phenomenon. Lyotropic swelling produced opaque, limp, and flaccid Fibers that did not change appreciably in length. The melting behavior and the swollen fascicles were clearly seen in scanning electron micrographs of 3 and 6M urea-treated RTT. The reduction in the dimensional stability of native RTT Collagen Fiber on treatment with urea demonstrated the role of secondary structure in the dimensional stabilization of Collagen. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 975–982, 2002; DOI 10.1002/app.10262
-
effect of ph on dimensional stability of rat tail tendon Collagen Fiber
Journal of Applied Polymer Science, 2000Co-Authors: R Usha, Thirumalachari RamasamiAbstract:The organized molecular structure of Collagen is related to its dimensional stability. The dimensional stability of Collagen arises from the interplay of various intermolecular forces such as covalent, hydrogen bonding, electrostatic interactions, hydrophobic interactions, London or van der Waals forces, and weak interactions. A structure–function relationship exists in Collagen. Electrostatic interactions play an important role in dimensional stabilization. The dimensional stability of rat tail tendon (RTT) Collagen Fiber is affected by the change in the net fixed charge on the molecule as a function of pH. Thermal and mechanical properties are dependent on molecular and lattice orders. The pH dependence of thermal shrinkage, isometric tension, differential scanning calorimetry, swelling behavior, tensile strength, and percent extension and stress relaxation behavior are studied in 0.02M Tris-maleate buffer at pH 4–8. The observed experimental results provide compelling evidence that electrostatic interactions play an important role in the dimensional stability of RTT Collagen. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1577–1584, 2000
-
role of aliphatic alcohols on the stability of rat tail tendon rtt Collagen Fiber
Journal of Polymer Science Part B, 1999Co-Authors: R Usha, Thirumalachari RamasamiAbstract:The dimensional stability of Collagen is related to hydrogen bonding, electrostatic, hydrophobic, London, or van der Waals forces, and weak interactions. To assess the influence of dielectric constant of solvents on the ion pair interactions, in this work, influence of different aliphatic alcohols viz., methanol, ethanol, and n-propanol on thermomechanical behavior of rat-tail tendon (RTT) Collagen Fiber has now been investigated. The results show that the shrinkage temperature of native RTT decreases in aqueous alcoholic mixtures with increasing mol proportions of alcohol up to the level of 10 mol %, and when the mol proportion of alcohol exceeds 10 mol %, shrinkage temperature increases, possibly due to a desolvational effect. Further, the thermal and mechanical stability of native RTT is lower in n-propanol medium. The stress relaxation behavior of RTT is explained in terms of a two-element model, involving two superposed exponentials, and the rate constants corresponding to two relaxation processes have been computed using a nonlinear least square fit of experimental data. The activation energy values E0 and E′0 corresponding to the two relaxation processes identified, have been computed and the differential scanning calorimetric studies have been made to assess the enthalpy changes associated with the heat denaturation processes. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1397–1405, 1999