DFT study of the interaction free energy of π–π complexes of fullerenes with buckybowls and viologen dimers

2011 ◽  
Vol 35 (7) ◽  
pp. 1453 ◽  
Author(s):  
Girolamo Casella ◽  
Giacomo Saielli
Keyword(s):  
Free Energy ◽  
Dft Study ◽  
Interaction Free Energy

Effect of Fluctuations in the Brush Conformation on the Interaction Between Polymer Brushes in a Good Solvent

2008 ◽  
Vol 75 (5) ◽  
Author(s):  
Yan Xing Shen ◽  
Jen Fin Lin
Keyword(s):  
Free Energy ◽  
Polymer Brushes ◽  
High Surface ◽  
Current Method ◽  
Interaction Force ◽  
Height Distribution ◽  
Parallel Plates ◽  
Surface Separation ◽  
Brush Height ◽  
Interaction Free Energy

This study presents a novel approach for analyzing the interaction between two parallel surfaces grafted with polymer brushes in a good solvent. In the proposed approach, molecular dynamics simulations are performed to establish the mean brush height and the standard deviation of the brush height distribution for a given value of the surface separation. The corresponding probability density function (PDF) of the brush height is then determined and a statistical technique is applied to compute the corresponding interaction free energy per unit area of the grafted substrates. Finally, the Derjaguin approximation is employed to determine the corresponding value of the interaction force between the two surfaces. At relatively high surface grafting density as well as under low to moderate compressions of these two parallel plates, the interdigitation effect of the brushes is quite weak and is not considered in the present study. The results obtained for the interaction free energy and interaction force are compared with those derived using the Alexander and de Gennes (AdG) model [1977, “Adsorption of Chain Molecules With a Polar Head. A Scaling Approach,” J. Phys. (Paris), 38, pp. 983–989, 1985, “Films of Polymer-Solutions,” C. R. Acad. Sci., 300, pp. 839–843] and the Milner, Witten, and Cates (MWC) model [1988, “Theory of the Grafted Polymer Brush,” Macromolecules, 21, pp. 2610–2619], respectively. The value of the normalized interaction free energy computed using the present method is higher than that obtained from the AdG and MWC models at larger surface separations. However, the three sets of results are in good agreement particularly at smaller values of the surface separation. In addition, the results obtained by the current method for the interaction force are found to be in better agreement with the experimental data than those obtained using the AdG or MWC models. The enhanced performance of the proposed method is attributed primarily to the use of an adaptive non-Gaussian PDF of the brush height to model the effects of fluctuations in the brush conformation at different distances from the grafting plane.

scholarly journals Casimir-Foucault interaction: Free energy and entropy at low temperature

2010 ◽  
Vol 82 (3) ◽  
Author(s):  
Francesco Intravaia ◽  
Simen Å. Ellingsen ◽  
Carsten Henkel
Keyword(s):  
Free Energy ◽  
Low Temperature ◽  
Interaction Free Energy

scholarly journals The miRNA COMPLEXES AGAINST CORONAVIRUSES SARS-CoV-2, SARS-CoV, and MERS-CoV

2020 ◽  
Author(s):  
Aizhan Rakhmetullina ◽  
Anatoliy Ivashchenko ◽  
Aigul Akimniyazova ◽  
Dana Aisina ◽  
Anna Pyrkova
Keyword(s):  
Free Energy ◽  
Side Effects ◽  
Binding Sites ◽  
Untranslated Region ◽  
Messenger Rnas ◽  
High Concentration ◽  
Human Genes ◽  
Weak Binding ◽  
Simultaneous Inhibition ◽  
Interaction Free Energy

Abstract Background: In the past twenty years humankind has effected from infections caused by SARS-CoV (severe acute respiratory syndrome), MERS-CoV (Middle East respiratory syndrome) and SARS-CoV-2 coronaviruses, which have caused significant harm to human health and resulted in high mortality. The possibility of using miRNA (mRNA-inhibiting RNA) to inhibit infections caused by the coronaviruses SARS-CoV-2, SARS-CoV, and MERS-CoV has been shown. Methods: The MirTarget program determines the following characteristics of interaction between miRNAs and messenger RNAs (mRNAs): the start of the miRNA binding site on the mRNA; the locations of the miRNA binding sites in the 3'-untranslated region (3'UTR), 5'-untranslated region (5'UTR), or coding sequence (CDS); the interaction free energy (∆G, kJ/mole); and nucleotide interaction schemes between miRNAs and mRNAs.Results: Using bioinformatics approaches, completely complementary miRNA (cc-miRNA) complexes were predicted to be able to bind and inhibit the translation of coronavirus proteins and the replication of SARS-CoV-2, SARS-CoV, and MERS-CoV genomes. For complexes of seven completely complementary miRNA of SARS-CoV-2 (cc-miRc), seven completely complementary miRNA of SARS-CoV (cc-miRs), and eight completely complementary miRNA of MERS-CoV (cc-miRm), the interactions with the RNA genomes (gRNAs) of the corresponding coronaviruses was evaluated. The free energy of the interactions of cc-miRNAs with binding sites was significantly higher than the free energy of the interactions with other regions in gRNA, which ensures high selectivity of the binding of cc-miRNAs. Weak binding of cc-miRNAs to the mRNAs of 17508 human genes was shown, which suggests the absence of side effects of the cc-miRNAs in humans. A feature of this method is the simultaneous inhibition of translation and replication by several cc-miRNAs binding from the 5' end to the 3' end of gRNA. Conclusion: The use of several cc-miRNAs to suppress infections allows each of them to be used at a lower concentration to avoid side effects when one cc-miRNA is introduced into humans at a high concentration.

scholarly journals DFT Study on the Oxidative Addition of 4-Substituted Iodobenzenes on Pd(0)-Phosphine Complexes

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Tímea R. Kégl ◽  
László Kollár ◽  
Tamás Kégl
Keyword(s):  
Free Energy ◽  
Dissociation Energy ◽  
Linear Correlation ◽  
Oxidative Addition ◽  
Dft Study ◽  
Solvation Effect ◽  
Dispersion Correction ◽  
Phosphine Complexes ◽  
Hammett Constants ◽  
Reaction Free Energy

The oxidative addition of 4-substituted iodobenzenes on Pd(0)-PMe3 complexes has been studied at the BP86 level of theory including dispersion correction and solvation effect, with tetrahydrofuran as solvent. The bisphosphine pathway was found to be barrierless, whereas the monophosphine route is hampered by the high dissociation energy of trimethylphosphine. The reaction free energy of this step shows linear correlation with the Hammett constants of the para substituents with the most electron withdrawing groups being the most exergonic.

Sign in / Sign up

Export Citation Format

Share Document