Complete free energy landscape and statistical thermodynamics of single poly(ethylene glycol) molecules

An inverse gas chromatographic (IGC) study of the sorption properties of poly(ethylene glycol) modified with tosylate (PEG-TOS) was presented. PEG-TOS was synthesized via the tosylation of the corresponding poly(ethylene glycol) (PEG) withp-toluenesulfonyl chloride in the basic medium. The synthesized PEG-Tos was characterized by FTIR-ATR and1HNMR techniques. The retention diagrams of n-hexane, n-heptane, n-octane, n-nonane, n-decane, dichloromethane, chloroform, acetone, tetrahydrofuran, ethyl acetate, and ethanol on the PEG and PEG-Tos were plotted at temperatures in K between 303 and 373 by inverse gas chromatography technique. The dispersive component of the surface-free energy,γSD, of studied adsorbent surface was estimated using retention times of different nonpolar organics in the infinite dilution region. Thermodynamic parameters of adsorption (free energy,ΔGAS, enthalpy,ΔHAS, and entropy,ΔSAS), dispersive components of the surface energies,γSD, and the acid,KA, and base,KD, constants for the PEG and PEG-Tos were calculated and the results were discussed.

Download Full-text

PIEZOELECTRIC PROPERTIES OF POLY(3-HYDROXYBUTYRATE-CO-3-HEDROXYBUTYRATE)-CO-POLY(ETHYLENE GLYCOL) PRODUCED BY CONTROLLED MICROBIOLOGICAL BIOSYNTHESIS

Biological journal ◽

10.32743/2658-6460.2019.10.10.184 ◽

2019 ◽

Vol 10 (10) ◽

Author(s):

Anton Bonartsev ◽

Vera Voinova ◽

Elizaveta Akoulina ◽

Andrey Dudun ◽

Irina Zharkova ◽

...

Keyword(s):

Ethylene Glycol ◽

Piezoelectric Properties ◽

Poly Ethylene Glycol ◽

Poly Ethylene

Download Full-text

Determination of Base Flipping Free Energy Landscapes from Nonequilibrium Stratification

10.26434/chemrxiv.7376081 ◽

2019 ◽

Author(s):

Xiaohui Wang ◽

Zhaoxi Sun

Keyword(s):

Free Energy ◽

Energy Landscape ◽

Sampling Technique ◽

Umbrella Sampling ◽

Energy Simulation ◽

Nonlinear Dependence ◽

Free Energy Landscape ◽

Convergence Criterion ◽

Base Flipping ◽

Convergence Behavior

<p>Correct calculation of the variation of free energy upon base flipping is crucial in understanding the dynamics of DNA systems. The free energy landscape along the flipping pathway gives the thermodynamic stability and the flexibility of base-paired states. Although numerous free energy simulations are performed in the base flipping cases, no theoretically rigorous nonequilibrium techniques are devised and employed to investigate the thermodynamics of base flipping. In the current work, we report a general nonequilibrium stratification scheme for efficient calculation of the free energy landscape of base flipping in DNA duplex. We carefully monitor the convergence behavior of the equilibrium sampling based free energy simulation and the nonequilibrium stratification and determine the empirical length of time blocks required for converged sampling. Comparison between the performances of equilibrium umbrella sampling and nonequilibrium stratification is given. The results show that nonequilibrium free energy simulation is able to give similar accuracy and efficiency compared with the equilibrium enhanced sampling technique in the base flipping cases. We further test a convergence criterion we previously proposed and it comes out that the convergence behavior determined by this criterion agrees with those given by the time-invariant behavior of PMF and the nonlinear dependence of standard deviation on the sample size. </p>

Download Full-text