Journal of Theoretical and Computational Chemistry

Since there is no exact solution for problems in physics and chemistry, extrapolation methods may assume a key role in quantitative quantum chemistry. Two topics where it bears considerable impact are addressed, both at the heart of computational quantum chemistry: electronic structure and reaction dynamics. In the first, the problem of extrapolating the energy obtained by solving the electronic Schrödinger equation to the limit of the complete one-electron basis set is addressed. With the uniform-singlet-and-triplet-extrapolation (USTE) scheme at the focal point, the emphasis is on recent updates covering from the energy itself to other molecular properties. The second topic refers to extrapolation of quantum mechanical reactive scattering probabilities from zero total angular momentum to any of the values that it may assume when running quasiclassical trajectories, QCT/QM-$\alpha$J. With the extrapolation guided in both cases by physically motivated asymptotic theories, realism is seeked by avoiding unsecure jumps into the unknown. Although, mostly review oriented, a few issues are addressed for the first time here and there. Prospects for future work conclude the overview.

The single crystal XRD analysis has been used to examine the structure of the centrosymmetric crystal 4-Methoxy acetanilide. The material delineated in orthorhombic system with the space group of Pbca. FTIR and Raman spectrum analysis have been executed to comprehend the molecular interactions and to study the vibrational nature of the functional groups presented in the title molecule. Characteristic studies like optical, dielectric and thermal stability have also been carried out. Detailed explorations have been conducted on the optical properties of the crystal using both quantum chemical calculations and experimental data.

Tumor dissemination and relapse in lung cancer were found to be due to the existence of cancer stem cells. In particular, the $\beta$-catenin pathway is found to be one of the crucial pathways in maintaining the stem-like properties of the cells. Thus, targeting the $\beta$-catenin family of proteins is a significant therapeutic route in the treatment of lung cancer. Therefore, in the present study, a pharmacophore-based drug repurposing approach was accomplished to pinpoint potent $\beta$-catenin inhibitors from the DrugBank database. Primarily, ligand-based pharmacophore hypothesis (AAHHR) was generated using existing $\beta$-catenin inhibitors available in the literature and utilized for library screening. Subsequently, the inhibitory activity of the screened compounds was examined by the hierarchical docking process and the Prime MM-GBSA algorithm. Moreover, quantum chemical calculations and molecular dynamics simulations were executed to analyze the inhibitory effects of the screened hit molecule. The results indicate that hit molecule, DB08047 was found to possess better binding free energy, favorable ligand strain energy, satisfactory pharmacokinetic properties and superior free energy landscape profile. Eventually, the pIC${}_{50}$ values of the lead compounds were predicted by the AutoQSAR algorithm. It is noteworthy to mention that DB08047 was found to possess pyrazole scaffolds which could downregulate $\beta$-catenin pathway and thus facilitate the controlled cell growth/inhibit tumor growth.

A new method of calculation of equilibrium compositions of single-phase multicomponent systems in a wide range of temperatures, pressures, and elemental compositions is proposed. It is based on the minimization of the integral characteristic of the slope of the thermodynamic potential surface in the space of coordinates of chemical reactions. The proposed algorithm is applied to the definition of area of the thermodynamic stability of freons in volcanic gases and to the construction of the equilibrium profiles of the height distribution of sulphur-containing components of Venusian atmosphere.

A comparative theoretical study of the kinetics of the Diels–Alder (DA) reaction between empty fullerene (C${}_{60}$) and lithium ion encapsulated fullerene (${Li}^{+}{@C}_{60}$) with 1,3 cyclohexadiene (C${}_6$H${}_8$) was carried out. This reaction takes place in a photovoltaic cell. The effect of the encapsulated ${\text{Li}}^{+}$ ion on the conversion rate of solar energy into electricity has been highlighted through calculations based on the density functional theory (DFT). In addition, a static study using the global conceptual DFT indices, as part of the demonstration of the significant electrophilic power of the fullerene nanostructure, was carried out to show the effect of encapsulating the ${\text{Li}}^{+}$ ion in this nanoparticle on the electrophilic power of Li${}^{+}$@C${}_{60}$ and therefore on the acceleration of the reaction. The relationship between the HOMO_donor–LUMO_acceptor energy difference and the DA reaction acceleration, and therefore the acceleration of light conversion (a rapid conversion implies a small gap), has been thoroughly examined. Moreover, a mechanistic study of the kinetics of the DA reaction of the fullerene involved in an organic photovoltaic cell has been carried out. In this section, a concerted synchronous mechanism with no effect of ${\text{Li}}^{+}$ encapsulation on the synchronicity of the reaction was observed. Finally, it was revealed that Li${}^{+}$@C${}_{60}$ reacted approximately 2466 times faster than C${}_{60}$. Moreover, the experimental results were found in good agreement with the computer calculations.

This study is based on the valuation of a few model molecules. The objective of this research is focussed on the nonlinear optical (NLO) improvement of four organometallic molecules and one organic molecule. These molecules have been subjected to several calculations by different functionals: CAM–B3LYP, LC–BLYP, LC–wPBE, wB97X, M11, M06–2X, M08–HX and M08–SO. These functionals gave three orders of classification of the ${\beta }_{\mathrm{\text{tot}}}$ parameters. The CAM–B3LYP functional recorded very good agreement between ${\beta }_{\mathrm{\text{tot}}}$ parameters and gaps ($\mathrm{\Delta }{E}_{\text{H}-\text{L}})$. Significant first hyperpolarizabilities (${\beta }_{\mathrm{\text{tot}}})$ have been obtained around 880 * 10${}^{-30}$esu. The mechanisms of intramolecular charge transfer (ICT) have shown energetic passages from donor groups to acceptors and vice versa. The substitution of metals influences the location of $\pi$ electrons at the level of the chromophores. Finally, the lengthening of the aromatic chains between the acceptor and donor groups shows significant NLO improvements. The first and second hyperpolarizabilities (${\beta }_{\mathrm{\text{tot}}})$ and (${\gamma }_{\mathrm{\text{tot}}})$ for a chain of several benzene rings are of the order of 21,663.16 * 10${}^{-30}$esu and 16,464.65 * 10${}^{-35}$esu, respectively.

Human glucokinase (GK) is a potentially attractive target for diabetes, playing a prominent role in the control of glucose homeostasis. Dorzagliatin is the first GK activator (GKA) to enter phase III clinical trial. In this study, the possible binding mode of dorzagliatin with GK was investigated via the molecular simulation method. Two other systems in the absence of dorzagliatin and glucose were also studied to disclose the roles of dorzagliatin and glucose. The outcomes revealed that dorzagliatin can create the characteristic hydrogen bonds of GKA with Arg63, and Arg63 can form hydrogen bonds with nearby residues, making a tight binding hydrogen bond network around dorzagliatin. The presence of dorzagliatin can stabilize glucokinase for a period of time, and the binding of glucose may prevent the GK conformational change to a certain extent. Our results may be beneficial to mechanism understanding of GKA, and will be useful in design of novel GKAs for treating metabolic diseases.

Humanity is facing a grieve danger of coronavirus disease-19 caused by severe acute respiratory syndrome novel coronavirus-2 (SARS nCov-2). There is an urgent need of therapeutics that can help in overcoming this global pandemic. Identifying novel therapeutic target and screening already approved drug is a faster approach in this situation. Spike glycoprotein (Sgp) of SARS nCoV-2 is potentials target where in researchers have targeted receptor binding domain (RBD) of S1 domain. The S2 domain of Sgp also plays a pivotal role in viral entry, but the mechanism is less understood. We analyzed the structure of Sgp S2 domain in pre-fusion state and Heptad repeat region in its post-fusion state available from protein data bank. Sgp shows three major regions in S2 domain, the fusion peptide (FP), heptad repeat 1 (HR1) and central helical (CH) region. The HR1 region undergoes structural changes by flipping approximately 180^∘ and coil up to form a rod like structure during fusion process implying its role in viral entry into the host cell. This structural change in S2 domain helices is crucial step, if this process is hindered by targeting the HR1 and CH region then the progression of virus can be stopped. Possible binding cavity was identified near the HR1 and CH region in S2 domain and docking-based virtual screening of FDA approved drugs was performed. Promising candidates like Troxerutin, Thymopentin and Daclatasvir can be used as therapeutics provided an immediate in-vitro and clinical studies are carried out by research groups.