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The corrosion hindrance impact of Syzygium aromaticum fruit extract has been analyzed on mild steel (MS) corrosion in 0.5M H₂SO₄ by utilizing weight reduction estimations, potentiodynamic polarization estimations and electrochemical impedance spectroscopy (EIS) procedures. This Eugenol- and Eugenol-acetate-containing extract diminishes the corrosion rate of MS in acidic medium. The greatest corrosion restraint effectiveness was observed at 500mg/L inhibitor concentration in 0.5M H₂SO₄. The adsorption of Syzygium aromaticum extract on the surface of MS has been analyzed by utilizing atomic force microscopy (AFM), scanning electron microscopy (SEM) study and spectroscopic strategies.

Multi-branched oligomers F1, F2 and F3 were investigated by spectroscopic experiments as well as quantum chemical calculations to elucidate the structure–property relationships and intramolecular charge transfer (ICT) characteristics of typical nonlinear optical materials. A better ICT property of F2 is obtained by replacing terminal electron donors with stronger electron-donating ability. The degree of ICT is effectively increased, which can be clearly seen from the frontier molecular orbitals contribution of central anthracene between HOMO and LUMO. The central group plays a major role in the direction as well as effective path of ICT process. In the X-shaped oligomers with anthracene as central group, ICT process takes place from terminal groups of 1,8 position branches, to the central anthracene group. However, the electron distribution as well as the ICT of tri-branched oligomer F3 with triazine as central group is not symmetric. ICT process of F3 takes place from terminal triphenylamine groups to the central triazine and two fluorene groups at 4,6 position branches. Y-shaped oligomer F3 has a longer lifetime of ICT state as well as a higher fluorescence quantum yield, which is consistent with the results of time-resolved fluorescence spectroscopy. Z-scan results show that the TPA cross-section value of F3 is 10.6 and 2.9 times higher than that of X-shaped F1 and F2. The dynamics curves of transient absorption spectroscopy also indicate that oligomer F3 structure has relatively stronger ICT properties. To verify the substituent effect, two linear molecules F4 and F5 were also calculated. The quantum chemical calculations result shows that the branches at positions 4 and 11 of the central anthracene group have little effect on the electron cloud distribution, and there are indeed significant differences in the contributions of branches at different positions. Our results may provide some reference for molecular design.

The structural and energetic properties of polyfluorene and its derivatives were investigated, using quantum chemical calculations. Conformational analysis of bifluorene was performed by using ab initio (HF/6-31G* and MP2/6-31G*) and density functional theory (B3LYP/6-31G*) calculations. The results showed that the local energy minimum of bifluorene lies between the coplanar and perpendicular conformation, and the B3LYP/6-31G* calculations led to the overestimation of the stability of the planar pi systems. The HOMO-LUMO energy differences of fluorene oligomers and its derivatives — 9,9-dihexylfluorene (DHPF), 9,9-dioctylfluorene (PFO), and bis(2-ethylhexyl)fluorene (BEHPF) — were calculated at the B3LYP/6-31G* level. Energy gaps and effective conjugation lengths of the corresponding polymers were obtained by extrapolating HOMO-LUMO energy differences and the lowest excitation energies to infinite chain length. The lowest excitation energies and the maximum absorption wavelength of polyfluorene were also performed, employing the time-dependent density functional theory (TDDFT) and ZINDO methods. The extrapolations, based on TDDFT and ZINDO calculations, agree well with experimental results. These theoretical methods can be useful for the design of new polymeric structures with a reducing energy gap.

While there has been no pandemic outbreak of influenza evolving from the H5N1 strain yet, the virus has already killed people. This suggests that without any significant mutations the influenza virus can live within the human body for days in which its life cycles can continue. The first step for infection is the host cell surface binding which is the function of the glycoprotein hemagglutinin (HA). In this investigation, quantum chemical calculations were performed on the systems comprising four structures coming from parts of the HA, with its cell receptor-analog substrate, determined from X-ray structures of the 1934 Spanish flu and avian influenza antigens. The calculations are aimed at partitioning the system into several parts, thus obtaining global and partial contributions of binding energy from each of them. As a result, it was possible to propose quantitatively the main contributions of key amino residues of the avian influenza virus glycoprotein around the binding pocket relevant to the binding process.

The main binding energy contributions of the Spanish flu HA were from Tyr95, Val135, Thr136, Ala137, Glu190, Asp225, and Gln226, while the main contributions of the avian flu HA were from Ser129, Val131, Ser132, and Ser133. It was also found that the effect from the HA with an avian characteristic, Gln226 and Gly228, was not relatively high according to the contributed binding energy, whereas the effect from nearby water molecules was significant. Thus, it was concluded that both human and avian virus HA could recognize human cell receptors better than the avian cell receptors according to the binding energy. Therefore, the preference to any particular cell receptor types might involve some other factors rather than being determined solely by the HA binding process.

The conformational analysis of HIV-1 Reverse Transcriptase Inhibitor, nevirapine, 11-cyclopropyl-5,-11dihydro-4-methyl-6H-dipyrido[3,2-b2′,3′-e][1,4]diazepin-6-one, was investigated using ab initio and density functional theory calculations. The fully optimized structures and rotational potential energies of the nitrogen and carbon bonds in the cyclopropyl ring (C15-N11-C17-C19, α) were examined in detail. Geometries obtained from all applied calculations show similarities to the complex structure with HIV-1 reverse transcriptase. To obtain more information on the structure, conformational minima of nevirapine, optimized at the B3LYP/6-31G** level, were calculated for the ¹H, ¹³C, and ¹⁵N-NMR chemical shifts at the B3LYP/6-311++G** level using the GIAO approach in DMSO and chloroform IEFPCM solvation models. The calculated ¹H, ¹³C-NMR chemical shifts agree well with the experimental data, which indicates that the geometry of nevirapine in solution is similar to that of the molecule in the inhibition complex. Solvation free energies (ΔG_sol) of nevirapine in DMSO and chloroform were also obtained.

The ground-state geometries of 2-cyano-5-(4-(phenyl(4-vinylphenyl)amino)phenyl) penta-2,4-dienoic acid (TC4) derivatives have been optimized by using density functional theory (DFT) at B3LYP/6-31G** level of theory. The effect of bridge has been investigated on the electronic and charge transfer properties. The distortion between triphenylamine unit and acceptor moieties revealed there would be recombination barrier. The excitation energies have been computed by time dependent DFT at PCM-CAM-B3LYP/6-31G** and PCM-LC-BLYP/6-31G** level of theories. The absorption spectrum of TC4 computed at PCM-CAM-B3LYP/6-31G** level of theory is in good agreement with the experimental evidence while PCM-LC-BLYP/6-31G** level of theory underestimate it. The electron injection, electronic coupling constant and light harvesting efficiency (LHE) improved by elongating the bridge. The superior electron injection, electronic coupling constant, LHE, LUMO lying above the conduction band of TiO₂ and HOMO below the redox couple compared to parent molecule revealed that new designed materials would be efficient photosensitizers.

The present work deals with the theoretical investigation of electronic structure features and stability of adenine–thymine (AT) and rare tautomer of adenine–thymine (rAT) base pairs along with their complexes with Cu²⁺ cation and their interactions with BN doped fullerene (C₅₈BN). All the calculations have been performed with density functional theory using B3LYP functional. Electronic structures of the two base pairs are almost identical. Hence, it is rather difficult to distinguish between the two base pairs on the basis of their electronic properties. As per our theoretical calculations, we have observed that, BN modified fullerene could act as a nano-biosensor for detection of mispairing between these two complementary bases as well as their Cu²⁺ complexes.

Molecular docking and charge density analysis were carried out to understand the geometry, charge density distribution and electrostatic properties of one of newly synthesized 4-substituted-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylates (PDE), which is regarded as the best $\alpha$-Glucosidase inhibitor among the hydropyridine dicarboxylate derivatives. The different bonding models of the PDE molecule in the active sites of proteins Human serum albumin (HSA) and Saccharomyces cerevisiae$\alpha$-glucosidase (SAG) are firstly compared, which is important to understand the different intermolecular interactions between drug-transport protein and drug-target protein. The deformation density maps suggest that the electron densities of the PDE molecule are redistributed when it presents in the active sites. When the molecule presents in the active site of the SAG, it is evident to find that the negative region does not appear at the vicinity of the oxygen atoms on one of the carboxylic acid dimethyl ester group. Frontier molecular orbital density distributions for the PDE molecule are similar in all forms. The highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) energy gaps in the active sites are higher than that of the molecule in pure solution phase. It is generally noticed that all of the orientations of the dipole moment vectors are reoriented in both active sites. These fine details at electronic level allow to better understand the exact drug-transport protein and drug-target protein interactions.

As sensitizers, a series of organic dyes containing phenoxazine is synthesized for use in dye-sensitized solar cells (DSSCs). The dyes were characterized using FT-IR, NMR and UV experiments. Quantum chemical calculations were used to gain insight into the structural, electronic and photophysical properties including its as-synthesized sensitizers, as well as to allocate experimental spectroscopic results. It has been observed that increasing the electron-donor potential and the $\pi$-conjugated bridge of the dyes would increase the photovoltaic performance. The obtained two dyes have substantially higher efficiency of 6.6 and 6.4%, respectively, under the modeled AM1.5G conditions. Efficient electron injection from the excited sensitizer to the conduction band of TiO₂ film occurs due to further delocalizing electrons in the $\pi$-conjugated bridge and donor areas of the dyes. Using cyclic voltammetry, the electrochemical efficiency of BPA and BPCA was evaluated, and reversible oxidation signals were reported.