A Comparison of Explanation Methods of Encapsulation Efficacy of Hydroquinone in a Liposomal System

     One of the most important parameters describing the liposomal formulation of hydroquinone is encapsulation efficacy. For the efficacy evaluation of hydroquinone trapped in liposomal structure, there is a need to first separate liposome from the matrix surrounding it. There are various separation techniques; however, in this study, the three techniques of centrifuges with and without washing and dialysis were used. From among the laboratory techniques, an appropriate method is the one that offers responses with a high repeatability. The statistical calculations revealed that encapsulation efficacy with a direct method resulted from a separation via the techniques of dialysis and centrifuge without washing had the highest dispersion with SDs of 6.1 and 8.7, respectively, while the SD value in the technique of centrifuge with washing was 5.2. Through an indirect method, hydroquinone encapsulation efficacy showed the best repeatability with SD values of 2.8 and 2.1 by using the two techniques of centrifuge and centrifuge filtration, respectively. It seems that the treatments leading to the dilution of hydroquinone formulation would result in hydroquinone leakage and a reduction of encapsulation efficacy. It seems that measurement of hydroquinone encapsulation efficacy with an indirect method is a better choice; therefore,  a centrifuge technique was utilized to report the mentioned efficacy at a speed of 45000 rcf and duration of 30 min due to having a reasonable price and ease of access.

The effects of amino acid sequence and solvent polarity on the self-assembling of cyclic peptide nanotubes and molecular channel formation inside the lipid bilayer

In this article, the effects of amino acid sequence and solvent polarity on the self-assembling process of cyclic peptides (CPs) were investigated by employing molecular dynamic (MD) simulations and quantum chemistry calculations. As a result, CP dimers are not stable in water, because of hydrogen bond (H-bond) lost between the CP units, while chloroform increases the stability of the CP dimers. MM-PBSA and MM-GBSA calculations confirmed that solvent polarity has an important effect on the stability of the CP dimers. Dynamical behavior of the cyclic peptide nanotubes (CPNTs) in chloroform indicates that CPNTs composed of leucine and phenylalanine are better molecular containers than that of isoleucine. At the next step, the ability of these CPNTs in molecular channel formation inside a fully hydrated DMPC (dimyristoylphosphatidylcholine) bilayer was investigated during 50 ns MD simulations. The obtained results show that only CPNT composed of isoleucine can form a molecular channel inside the DMPC membrane because isoleucine has a greater hydrophobicity than leucine and phenylalanine. This property increases the interactions between the CPNT and lipid residues, which elevates the stability of the CPNT inside the DMPC bilayer. Quantum chemistry calculations and non-covalent interactions analysis indicate that the solvent changes the stability and dynamical behavior of the CPNTs through the change in the H-bond strength. Finally, according to the different analyses, it can be concluded that the amino acid sequence in the CP units has an important role in designing specific nanostructures.Peer reviewe

Size Control of Iron Oxide Nanoparticles Using Reverse Microemulsion Method: Morphology, Reduction, and Catalytic Activity in CO Hydrogenation

Iron oxide nanoparticles were prepared by microemulsion method and evaluated in Fischer-Tropsch synthesis. The precipitation process was performed in a single-phase microemulsion operating region. Different HLB values of surfactant were prepared by mixing of sodium dodecyl sulfate (SDS) and Triton X-100. Transmission electron microscopy (TEM), surface area, pore volume, average pore diameter, pore size distribution, and XRD patterns were used to analyze size distribution, shape, and structure of precipitated hematite nanoparticles. Furthermore, temperature programmed reduction (TPR) and catalytic activity in CO hydrogenation were implemented to assess the performance of the samples. It was found that methane and CO 2 selectivity and also the syngas conversion increased as the HLB value of surfactant decreased. In addition, the selectivity to heavy hydrocarbons and chain growth probability ( ) decreased by decreasing the catalyst crystal size

Size Control of Iron Oxide Nanoparticles Using Reverse Microemulsion Method: Morphology, Reduction, and Catalytic Activity in CO Hydrogenation

Iron oxide nanoparticles were prepared by microemulsion method and evaluated in Fischer-Tropsch synthesis. The precipitation process was performed in a single-phase microemulsion operating region. Different HLB values of surfactant were prepared by mixing of sodium dodecyl sulfate (SDS) and Triton X-100. Transmission electron microscopy (TEM), surface area, pore volume, average pore diameter, pore size distribution, and XRD patterns were used to analyze size distribution, shape, and structure of precipitated hematite nanoparticles. Furthermore, temperature programmed reduction (TPR) and catalytic activity in CO hydrogenation were implemented to assess the performance of the samples. It was found that methane and CO2 selectivity and also the syngas conversion increased as the HLB value of surfactant decreased. In addition, the selectivity to heavy hydrocarbons and chain growth probability (α) decreased by decreasing the catalyst crystal size

Sensing Ability of Hybrid Cyclic Nanopeptides Based on Thiourea Cryptands for Different Ions, A Joint DFT-D3/MD Study

Theoretical studies, including quantum chemistry (QM) calculations and 25 ns molecular dynamic (MD) simulations, were performed on two types of hybrid cyclic nanopeptides (HCNPs) that are constructed of tren-capped cryptand (HCNP1) and 1,3,5-triethylbenzene-capped cryptand (HCNP2) for selective complex formation with OAC^–, NO₃^–, HSO₄^–, F^–, Br^–, and Cl^– ions in the gas phase and DMSO. Obtained data by M05-2X, M05-2X-D3, B3LYP, and B3LYP-D3 functionals indicated that HCNPs form a stable complex with F^– in comparison to other ions. DFT-D3 results and quantum theory of atoms in molecules (QTAIM) analysis indicated that dispersion and electrostatic interactions are the most important driving forces in HCNP–ion complex formation, respectively. Moreover, HOMO–LUMO analysis reveals that the reactivity of HCNP2, due to a lower band gap, is more than HCNP1. High sensing ability of the studied HCNPs for different ions was confirmed by Fermi level shifting of HNCPs to higher values during the complex formation. Finally, MD simulation results in DMSO are in good agreement with QM calculations and indicate that F^– forms the most stable complexes with HCNPs because of stronger electrostatic interactions

Molecular dynamic simulation and DFT study on the Drug-DNA interaction; Crocetin as an anti-cancer and DNA nanostructure model

<p>In this research, the interaction of Crocetin as an anti-cancer drug and a Dickerson DNA has been investigated. 25 ns molecular dynamic simulations of Crocetin and DNA composed of 12 base pairs and a sequence of d(CGCGAATTCGCG)₂ were done in water. Three definite parts of the B-DNA were considered in analyzing the best interactive site from the thermodynamic point of view. Binding energy analysis showed that van der Waals interaction is the most important part related to the reciprocal O and H atoms of the Crocetin and DNA. Stabilizing interactions, obtained by ΔG calculations, showed that maximum and minimum interactions are related to the <b>S1</b> and <b>S3</b> regions, respectively. This means that the most probable van der Waals interaction site of the Dickerson B-DNA and Crocetin is located in the minor groove of DNA. Two sharp peaks at 2.55 and 1.75 Å in radial distribution functions of the PO⋯HO and NH⋯OC parts are related to new hydrogen bonds between the Crocetin and DNA in the complex which can be considered as the driving force of the anti-cancer mechanism of the Crocetin. Average values of 0.3 au and zero for the electron densities of the H⋯O bonds for DNA and complex, obtained by Quantum theory of atoms in molecules (QTAIM), means that the origin of DNA instability after complexation may be related to the H-bond denaturation by Crocetin. Finally, the evaluation of the dispersion interactions using the dispersion functional, -148.76 kcal.mol⁻¹, confirmed the importance of the dispersion interaction in drug-DNA complex.</p

DFT study on the selective complexation of B₁₂N₁₂ nanocage with alkali metal ions

<p>Quantum chemistry calculations indicate that BN nanocage is a good candidate for selective complex formation with Li⁺ in the presence of different alkali metal ions.</p> <p>Density functional theory (DFT) calculations were applied at the M05-2X/6-311++G(d,p) level of the theory to investigate the interaction of the B₁₂N₁₂ nanocage (BN) and alkali metal ions (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) in the gas phase and in water. On the basis of the results, BN nanocage is able to form a selective complex with Li⁺. Water, as a solvent, reduces the stability of the metal ion-BN complexes in comparison with the gas phase. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses, reveal that the electrostatic interaction between the BN and metal ions can be considered as the driving force for complex formation in which the role of water is of significance. Density of states (DOSs) analysis of the BN nanocage structure in the presence of different metal ions showed a noticeable change in the frontier orbitals, especially in the gas phase, and Fermi level shifting toward the lower values.</p

Quantum Chemistry Aspects of the Solvent Effects on 3,4-Dimethyl-2,5-dihydrothiophen-1,1-dioxide Pyrolysis Reaction

A theoretical density functional theory (DFT) study was employed to investigate solvent effects on a retro-cheletropic ene reaction. The use of a nonpolar solvent in this retro-ene reaction is desirable to improve the reaction rate. Interactions between 14 different solvents and the reaction mixtures (reactant and transition state) were considered using DFT solvation calculations. These results were used to determine the role of solvents on the rate constants. Theoretical calculations at the B3LYP/6-311++G­(d,p) level revealed that in the presence of solvents with low polarity the reaction becomes faster, which is in accordance with experimental data. Transition state–solvent interactions were analyzed by the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis. Finally, several correlations between electron densities in bond critical points of the C–S bond and interaction energy as well as vibrational frequencies at the transition state have been investigated