scholarly journals Experimental tests of the quantum property of protein folding

2016 ◽  
Author(s):  
Liaofu Luo
Keyword(s):  
Protein Folding ◽  
Conformational Changes ◽  
Experimental Tests ◽  
Spectral Lines ◽  
Short Time Scale ◽  
Quantum Property ◽  
Folding Rate ◽  
Arrhenius Temperature Dependence ◽  
Short Time ◽  
Arrhenius Temperature

Experimental tests on the quantum property of protein folding are discussed. It includes: the test of the instantaneousness of torsion transition through observation of protein structural change in a short time scale of microsecond; the test of non-Arrhenius temperature dependence of protein folding rate and other biomolecular conformational changes; and the search for the narrow spectral lines of the protein photo-folding.

scholarly journals Unentangled Vitrimer Melts: Interplay between Chain Relaxation and Cross-link Exchange Controls Linear Rheology

2020 ◽  
Author(s):  
RALM RICARTE ◽  
Sachin Shanbhag
Keyword(s):  
Activation Energy ◽  
A Priori ◽  
Relaxation Times ◽  
Cross Link ◽  
Time Dynamics ◽  
Temperature Dependences ◽  
Long Time ◽  
Arrhenius Temperature Dependence ◽  
Short Time ◽  
Arrhenius Temperature

<div>Using this theoretical approach, we explore the influence of molecular structure and temperature on vitrimer linear</div><div>viscoelasticity. We observe that vitrimers with uniform and random cross-link distributions exhibit larger viscosities</div><div>and relaxation times than gradient and blocky types. Polydimethylsiloxane vitrimer (which has a flexible backbone) shows an Arrhenius temperature dependence for viscosity, while polystyrene vitrimers (which has rigid backbones) are only Arrhenius at high temperatures. During stress relaxation, the short time dynamics represent monomer friction, while the long time dynamics encompass a combination of network strand relaxation and cross-link exchange. Because of the different temperature dependences of the processes, time-temperature superposition fails. We also show that the effective rheological activation energy can be estimated a priori using only the cross-link exchange activation energy and the backbone Williams-Landel-Ferry parameters.</div><div><br></div><div>(Submitted to Macromolecules)</div>

scholarly journals Unentangled Vitrimer Melts: Interplay between Chain Relaxation and Cross-link Exchange Controls Linear Rheology

2021 ◽  
Author(s):  
RALM RICARTE ◽  
Sachin Shanbhag
Keyword(s):  
Activation Energy ◽  
A Priori ◽  
Relaxation Times ◽  
Cross Link ◽  
Time Dynamics ◽  
Temperature Dependences ◽  
Long Time ◽  
Arrhenius Temperature Dependence ◽  
Short Time ◽  
Arrhenius Temperature

<div>Using this theoretical approach, we explore the influence of molecular structure and temperature on vitrimer linear viscoelasticity. We observe that vitrimers with uniform and random cross-link distributions exhibit larger viscosities and relaxation times than gradient and blocky types. Polydimethylsiloxane vitrimer (which has a flexible backbone) shows an Arrhenius temperature dependence for viscosity, while polystyrene vitrimers (which has rigid backbones) are only Arrhenius at high temperatures. During stress relaxation, the short time dynamics represent monomer friction, while the long time dynamics encompass a combination of network strand relaxation and cross-link exchange. Because of the different temperature dependences of the processes, time-temperature superposition fails. We also show that the effective rheological activation energy can be estimated a priori using only the cross-link exchange activation energy and the backbone Williams-Landel-Ferry parameters.</div><div><br></div><div>(Submitted to Macromolecules)</div>

scholarly journals The rapidly oscillating Ap star γ Equ: linear polarization as an enhanced pulsation diagnostic?

2021 ◽  
Vol 508 (1) ◽  
pp. L17-L21
Author(s):  
S Hubrig ◽  
S P Järvinen ◽  
I Ilyin ◽  
K G Strassmeier ◽  
M Schöller
Keyword(s):  
Magnetic Field ◽  
Polarized Light ◽  
Transverse Magnetic ◽  
Spectral Lines ◽  
Short Time Scale ◽  
Pulsation Period ◽  
Transversal Field ◽  
Short Time ◽  
The Impact ◽  
Landé Factors

ABSTRACT We present the first short time-scale observations of the rapidly oscillating Ap (roAp) star γ Equ in linear polarized light obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument installed at the Large Binocular Telescope. These observations are used to search for pulsation variability in Stokes Q and U line profiles belonging to different elements. The atmospheres of roAp stars are significantly stratified with spectral lines of different elements probing different atmospheric depths. roAp stars with strong magnetic fields, such as γ Equ with a magnetic field modulus of 4 kG and a pulsation period of 12.21 min, are of special interest because the effect of the magnetic field on the structure of their atmospheres can be studied with greatest detail and accuracy. Our results show that we may detect changes in the transversal field component in Fe i and rare earth element lines possessing large second-order Landé factors. Such variability can be due to the impact of pulsation on the transverse magnetic field, causing changes in the obliquity angles of the magnetic force lines. Further studies of roAp stars in linear polarized light and subsequent detailed modelling are necessary to improve our understanding of the involved physics.

scholarly journals Unentangled Vitrimer Melts: Interplay between Chain Relaxation and Cross-link Exchange Controls Linear Rheology

2020 ◽  
Author(s):  
RALM RICARTE ◽  
Sachin Shanbhag
Keyword(s):  
Activation Energy ◽  
A Priori ◽  
Relaxation Times ◽  
Cross Link ◽  
Time Dynamics ◽  
Temperature Dependences ◽  
Long Time ◽  
Arrhenius Temperature Dependence ◽  
Short Time ◽  
Arrhenius Temperature

<div>Using this theoretical approach, we explore the influence of molecular structure and temperature on vitrimer linear</div><div>viscoelasticity. We observe that vitrimers with uniform and random cross-link distributions exhibit larger viscosities</div><div>and relaxation times than gradient and blocky types. Polydimethylsiloxane vitrimer (which has a flexible backbone) shows an Arrhenius temperature dependence for viscosity, while polystyrene vitrimers (which has rigid backbones) are only Arrhenius at high temperatures. During stress relaxation, the short time dynamics represent monomer friction, while the long time dynamics encompass a combination of network strand relaxation and cross-link exchange. Because of the different temperature dependences of the processes, time-temperature superposition fails. We also show that the effective rheological activation energy can be estimated a priori using only the cross-link exchange activation energy and the backbone Williams-Landel-Ferry parameters.</div><div><br></div><div>(Submitted to Macromolecules)</div>

Periodic Variations in the Coronal Green Line Intensity and their Connection with the White-light Coronal Structures

2000 ◽  
Vol 179 ◽  
pp. 197-200
Author(s):  
Milan Minarovjech ◽  
Milan Rybanský ◽  
Vojtech Rušin
Keyword(s):  
Time Resolution ◽  
White Light ◽  
Short Time Scale ◽  
High Time Resolution ◽  
Green Line ◽  
Periodic Intensity ◽  
Coronal Green Line ◽  
Significant Intensity ◽  
Short Time ◽  
Coronal Structures

AbstractWe present an analysis of short time-scale intensity variations in the coronal green line as obtained with high time resolution observations. The observed data can be divided into two groups. The first one shows periodic intensity variations with a period of 5 min. the second one does not show any significant intensity variations. We studied the relation between regions of coronal intensity oscillations and the shape of white-light coronal structures. We found that the coronal green-line oscillations occur mainly in regions where open white-light coronal structures are located.

Predicting Protein Folding Rate From Amino Acid Sequence

2011 ◽  
Vol 37 (12) ◽  
pp. 1331-1338 ◽  
Author(s):  
Jian-Xiu GUO ◽  
Ni-Ni RAO ◽  
Guang-Xiong LIU ◽  
Jie LI ◽  
Yun-He WANG
Keyword(s):  
Protein Folding ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Folding Rate ◽  
Protein Folding Rate

An Effective Cumulative Torsion Angles Model for Prediction of Protein Folding Rates

2020 ◽  
Vol 27 (4) ◽  
pp. 321-328 ◽  
Author(s):  
Yanru Li ◽  
Ying Zhang ◽  
Jun Lv
Keyword(s):  
Protein Folding ◽  
Size Structure ◽  
Conformational Space ◽  
Coefficient Of Determination ◽  
Folding Rate ◽  
Torsion Angles ◽  
Folding Rates ◽  
Protein Folding Rate ◽  
Optimal Set ◽  
Conformation Space

Background: Protein folding rate is mainly determined by the size of the conformational space to search, which in turn is dictated by factors such as size, structure and amino-acid sequence in a protein. It is important to integrate these factors effectively to form a more precisely description of conformation space. But there is no general paradigm to answer this question except some intuitions and empirical rules. Therefore, at the present stage, predictions of the folding rate can be improved through finding new factors, and some insights are given to the above question. Objective: Its purpose is to propose a new parameter that can describe the size of the conformational space to improve the prediction accuracy of protein folding rate. Method: Based on the optimal set of amino acids in a protein, an effective cumulative backbone torsion angles (CBTAeff) was proposed to describe the size of the conformational space. Linear regression model was used to predict protein folding rate with CBTAeff as a parameter. The degree of correlation was described by the coefficient of determination and the mean absolute error MAE between the predicted folding rates and experimental observations. Results: It achieved a high correlation (with the coefficient of determination of 0.70 and MAE of 1.88) between the logarithm of folding rates and the (CBTAeff)0.5 with experimental over 112 twoand multi-state folding proteins. Conclusion: The remarkable performance of our simplistic model demonstrates that CBTA based on optimal set was the major determinants of the conformation space of natural proteins.

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