scholarly journals Photocrosslinked Alginate-Methacrylate Hydrogels with Modulable Mechanical Properties: Effect of the Molecular Conformation and Electron Density of the Methacrylate Reactive Group

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 534 ◽  
Author(s):  
Fernanda Araiza-Verduzco ◽  
Eustolia Rodríguez-Velázquez ◽  
Harold Cruz ◽  
Ignacio A. Rivero ◽  
Delvis R. Acosta-Martínez ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Density ◽  
Polymer Chain ◽  
Density Functional ◽  
Molecular Conformation ◽  
Structural Parameters ◽  
Density Functional Theory Method ◽  
Proton Nuclear Magnetic Resonance ◽  
Hydrogen Atoms ◽  
Tissue Replacement

Hydrogels for load-bearing biomedical applications, such as soft tissue replacement, are required to be tough and biocompatible. In this sense, alginate-methacrylate hydrogels (H-ALGMx) are well known to present modulable levels of elasticity depending on the methacrylation degree; however, little is known about the role of additional structural parameters. In this work, we present an experimental-computational approach aimed to evaluate the effect of the molecular conformation and electron density of distinct methacrylate groups on the mechanical properties of photocrosslinked H-ALGMx hydrogels. Three alginate-methacrylate precursor macromers (ALGMx) were synthesized: alginate-glycidyl methacrylate (ALGM1), alginate-2-aminoethyl methacrylate (ALGM2), and alginate-methacrylic anhydride (ALGM3). The macromers were studied by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), and density functional theory method (DFT) calculations to assess their molecular/electronic configurations. In parallel, they were also employed to produce H-ALGMx hydrogels, which were characterized by compressive tests. The obtained results demonstrated that tougher hydrogels were produced from ALGMx macromers presenting the C=C reactive bond with an outward orientation relative to the polymer chain and showing free rotation, which favored in conjunction the covalent crosslinking. In addition, although playing a secondary role, it was also found that the presence of acid hydrogen atoms in the methacrylate unit enables the formation of supramolecular hydrogen bonds, thereby reinforcing the mechanical properties of the H-ALGMx hydrogels. By contrast, impaired mechanical properties resulted from macromer conditions in which the C=C bond adopted an inward orientation to the polymer chain accompanied by a torsional impediment.

Vibrational spectroscopic and conformational studies of 1-(4-pyridyl)piperazine

2010 ◽  
Vol 64 (4) ◽  
Author(s):  
Özgür Alver ◽  
Mustafa Şenyel
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Density Functional Theory Method ◽  
Basis Set ◽  
Stable Form ◽  
Functional Theory ◽  
B3lyp Method ◽  
Ft Ir ◽  
Hybrid Density Functional ◽  
Ir And Raman

AbstractPossible stable conformers of the 1-(4-pyridyl)piperazine (1-4pypp) molecule were experimentally and theoretically studied by FT-IR and Raman spectroscopy. FT-IR and Raman spectra were recorded in the region of 4000–200 cm−1. Optimized geometric structures related to the minimum on the potential energy surface were investigated by the B3LYP hybrid density functional theory method using the 6-31G(d) basis set. Comparison of the experimental and theoretical results indicates that the density functional B3LYP method provides satisfactory results for the prediction of vibrational wavenumbers and structural parameters and equatorial-equatorial (e-e) isomer is supposed to be the most stable form of the 1–4pypp molecule.

MECHANICAL PROPERTIES OF CHIRAL SILICON CARBIDE NANOTUBES UNDER HYDROGEN ADSORPTION: A MOLECULAR MECHANICS APPROACH

NANO ◽  
2014 ◽  
Vol 09 (04) ◽  
pp. 1450043 ◽  
Author(s):  
R. ANSARI ◽  
M. MIRNEZHAD ◽  
H. ROUHI
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Molecular Mechanics ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Stable State ◽  
Future Research ◽  
Hydrogen Atoms ◽  
Hydrogenated Silicon ◽  
Silicon Carbide Nanotubes

This paper investigates the mechanical properties of hydrogenated silicon carbide nanotubes ( H - SiCNTs ) using a molecular mechanics model in conjunction with the density functional theory (DFT). Analytical expressions presented in this study can be employed for nanotubes with different chiralities. Four different positions of adsorptions are considered in this paper and it is shown that the most stable state happens when hydrogen atoms are adsorbed on silicon and carbon atoms at the two opposite sides of hexagonal phase of silicon carbide. This paper will contribute to future research on similar studies of H - SiCNTs in the specific area as the force constants used in the molecular mechanics models regarding the hydrogen adsorption are proposed. Also, the mechanical properties and atomic structure of hydrogenated silicon carbide ( H - SiC ) sheet for different states of adsorption are determined using the DFT. The results for bending stiffness of H - SiC sheets indicate the isotropic behavior of these materials.

Folate-Targeted Polyacrylamide/Punicic Acid Nanomicelles for Flutamide Delivery in Prostate Cancer: Characterization, In Vitro Biological Evaluation, and its DFT Study

2020 ◽  
Vol 14 (4) ◽  
pp. 360-374
Author(s):  
Razieh Mirsafaei ◽  
Jaleh Varshosaz ◽  
Seyed N. Mirsattari
Keyword(s):  
Prostate Cancer ◽  
Density Functional ◽  
Structural Parameters ◽  
Density Functional Theory Method ◽  
Biological Evaluation ◽  
Chemotherapeutic Agents ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Punicic Acid

Background: Targeted nanocarriers can be used for reducing the unwanted side effects of drugs in non-target organs. Punicic acid, the polyunsaturated fatty acid of pomegranate seed oil, has been shown to possess anti-cancer effects on prostate cancer and the study also covers recent patents related to prostate cancer. The objective of the current study was to synthesize a co-polymeric micelle for delivery of Flutamide (FL) in prostate cancer using Polyacrylamide (PAM) and Punicic Acid (PA). Methods: The co-polymer of PAM and PA was synthesized and conjugated to folic acid. The successful conjugation was studied computationally by the density functional theory method and was confirmed by the FT- IR and 1HNMR. The folate-PAMPA micelles produced by the film casting method were characterized physically. FL was loaded in the nanomicelles and its release test was done at different pH. The Critical Micelle Concentration (CMC) was measured by pyrene as a fluorescent probe. Their cellular uptake and cytotoxicity were evaluated on PC3 prostate cancer cells. The molecular geometry and vibrational frequencies of two different possibilities for conjugation were calculated using the B3LYP/6-31G basis set. Results: The CMC of the micelles and their particle size were 79.05 μg/ml and 88 nm, respectively. The resulting nanocarriers of FL showed significantly more cytotoxic effects than the free drug at a concentration of 25 μM. The calculated results showed that the optimized geometries could well reproduce the structural parameters, and the theoretical vibrational frequencies were in good agreement with the experimental values. Conclusion: Folate-PAMPA nanomicelles may be promising for the enhancement of FL cytotoxicity and seem to potentiate the effect of chemotherapeutic agents used in prostate cancer treatment.

scholarly journals Physical and Chemical Aspects of the interaction of Chitosan and Cellulose acetate with ions Ca2+ and K+ using   DFT methods

2021 ◽  
Author(s):  
Hajar Atmani ◽  
Abdelkhalk Aboulouard ◽  
Fatima Ezzahra Bakkardouch ◽  
Latifa Laallam ◽  
Ahmed Jouaiti ◽  
...  
Keyword(s):  
Cellulose Acetate ◽  
Density Functional ◽  
Structural Parameters ◽  
Density Functional Theory Method ◽  
Reactivity Index ◽  
Electron Interaction ◽  
Qtaim Analysis ◽  
Reactivity Indexes ◽  
Organic Matrices ◽  
Physical And Chemical

Abstract Motivated by the use of chitosan (Ch), and cellulose acetate (AC) as organic matrices in several therapeutic drugs, a theoretical study has been elaborated through the density functional theory method (DFT) to investigate the interaction mechanism between two essential ions for the human body Ca2+, K+ and two organic matrices chitosan (Ch), and cellulose acetate (AC). Many physical and chemical aspects have been carried out after the achievement of structural optimization. This involves structural parameters, molecular electrostatic potential (MEPs), interaction energy, reactivity indexes, frontier molecular orbitals (FMOs), quantum theory atoms in molecules (QTAIM) analysis and non-covalent interaction (NCI) analysis. The results of FMOs, MEPs and reactivity index studies have revealed that the site of interaction can be predicted. The calculation of electron interaction energies shows that those ions interact with the matrix of AC and Ch. Concretely, the Ca2+ ion interacted efficiently with the AC matrix. The structural analysis results show that the interaction of Ch and ions appear spontaneously (ΔG < 0) while the interaction of AC and ions (ΔG > 0), requires more energy to occur. Finally, the QTAIM analysis data indicates that the interactions of AC -ions and Ch-ions are non-covalent presenting an electrostatic character.

The adsorption of SO2 on TiO2 anatase nanoparticles: a density functional theory study

2016 ◽  
Vol 94 (1) ◽  
pp. 78-87 ◽  
Author(s):  
Amirali Abbasi ◽  
Jaber Jahanbin Sardroodi ◽  
Alireza Rastkar Ebrahimzade
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Gas Sensing ◽  
Structural Parameters ◽  
Density Functional Theory Method ◽  
Functional Theory ◽  
Tio2 Anatase ◽  
Nitrogen Doped ◽  
Adsorption Processes ◽  
Anatase Nanoparticles

First-principles calculations have been carried out to investigate the adsorption properties of SO2 molecules on nitrogen-doped TiO2 anatase nanoparticles using the density functional theory method to fully exploit the gas-sensing capabilities of TiO2 particles. For this purpose, we have mainly studied the adsorption of the SO2 molecule on the dangling oxygen atom and doped nitrogen atom sites of the TiO2 nanoparticles because these sites are more active than other sites in the adsorption processes. The complex systems consisting of the SO2 molecule positioned toward the undoped and nitrogen-doped nanoparticles have been relaxed geometrically. The results presented include structural parameters such as bond lengths and bond angles and energetics of the systems such as adsorption energies. The electronic structure and its variations resulting from the adsorption process, including the density of states, molecular orbitals, and the charge transfer, are discussed. We found that the adsorption of the SO2 molecule on the nitrogen-doped TiO2 nanoparticles is energetically more favorable than the adsorption on the undoped ones. These results thus provide a theoretical basis for the potential applications of TiO2 nanoparticles in the removal and sensing of SO2 and give an explanation for helping in the optimization of improved gas removers and sensor devices.

scholarly journals A Molecular Electron Density Theory Study of the Chemoselectivity, Regioselectivity, and Diastereofacial Selectivity in the Synthesis of an Anticancer Spiroisoxazoline derived from α-Santonin

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 832 ◽  
Author(s):  
Luis Domingo ◽  
Mar Ríos-Gutiérrez ◽  
Nivedita Acharjee
Keyword(s):  
Double Bond ◽  
Electron Density ◽  
Density Functional ◽  
Nitrile Oxide ◽  
Complete Agreement ◽  
Hydrogen Atoms ◽  
Conceptual Density Functional Theory ◽  
Electronic Interactions ◽  
Molecular Electron ◽  
Molecular Electron Density Theory

The [3 + 2] cycloaddition (32CA) reaction of an α-santonin derivative, which has an exocyclic C–C double bond, with p-bromophenyl nitrile oxide yielding only one spiroisoxazoline, has been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. Analysis of the conceptual density functional theory (CDFT) reactivity indices and the global electron density transfer (GEDT) account for the non-polar character of this zwitterionic-type 32CA reaction, which presents an activation enthalpy of 13.3 kcal·mol−1. This 32CA reaction takes place with total ortho regioselectivity and syn diastereofacial selectivity involving the exocyclic C–C double bond, which is in complete agreement with the experimental outcomes. While the C–C bond formation involving the β-conjugated carbon of α-santonin derivative is more favorable than the C–O one, which is responsible for the ortho regioselectivity, the favorable electronic interactions taking place between the oxygen of the nitrile oxide and two axial hydrogen atoms of the α-santonin derivative are responsible for the syn diastereofacial selectivity.

scholarly journals Hirshfeld atom like refinement with alternative electron density partitions

IUCrJ ◽  
2020 ◽  
Vol 7 (6) ◽  
pp. 1199-1215 ◽  
Author(s):  
Michał Leszek Chodkiewicz ◽  
Magdalena Woińska ◽  
Krzysztof Woźniak
Keyword(s):  
Quantum Chemistry ◽  
Electron Density ◽  
Structural Parameters ◽  
Accurate Determination ◽  
Basis Set ◽  
Hydrogen Atoms ◽  
Minimal Basis ◽  
Bond Lengths ◽  
Hartree Fock ◽  
Systematic Effects

Hirshfeld atom refinement is one of the most successful methods for the accurate determination of structural parameters for hydrogen atoms from X-ray diffraction data. This work introduces a generalization of the method [generalized atom refinement (GAR)], consisting of the application of various methods of partitioning electron density into atomic contributions. These were tested on three organic structures using the following partitions: Hirshfeld, iterative Hirshfeld, iterative stockholder, minimal basis iterative stockholder and Becke. The effects of partition choice were also compared with those caused by other factors such as quantum chemical methodology, basis set, representation of the crystal field and a combination of these factors. The differences between the partitions were small in terms of R factor (e.g. much smaller than for refinements with different quantum chemistry methods, i.e. Hartree–Fock and coupled cluster) and therefore no single partition was clearly the best in terms of experimental data reconstruction. In the case of structural parameters the differences between the partitions are comparable to those related to the choice of other factors. We have observed the systematic effects of the partition choice on bond lengths and ADP values of polar hydrogen atoms. The bond lengths were also systematically influenced by the choice of electron density calculation methodology. This suggests that GAR-derived structural parameters could be systematically improved by selecting an optimal combination of the partition and quantum chemistry method. The results of the refinements were compared with those of neutron diffraction experiments. This allowed a selection of the most promising partition methods for further optimization of GAR settings, namely the Hirshfeld, iterative stockholder and minimal basis iterative stockholder.

scholarly journals Synthesis, Antioxidant Activity and DFT Study of Some Novel N-Methylated Indole Incorporating Isoxazole Moieties

2019 ◽  
Vol 32 (2) ◽  
pp. 244-248
Author(s):  
J. Jani Matilda ◽  
T.F. Abbs Fen Reji
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Analytical Data ◽  
Radical Scavenging ◽  
Density Functional Theory Method ◽  
Basis Set ◽  
Anticancer Activities ◽  
Functional Theory ◽  
Radical Scavenging Ability ◽  
Isoxazole Derivatives

A novel series of indolyl isoxazole derivatives were synthesized and the structure of the products is confirmed on the basis of IR, 1H NMR, MS and analytical data. The synthesized compounds were evaluated for their antioxidant and anticancer activities. The results revealed clearly those compounds 4b and 4d exhibited better radical scavenging ability. The optimized structural parameters of all compounds was carried out at the B3LYP/6-311++G (d, p) level of DFT basis set implemented in Gaussian 09 program package. Theoretical calculation of the title compounds were carried out using density functional theory method (DFT).

Structure and Properties of Diamond-Like Phases

2016 ◽  
Vol 845 ◽  
pp. 231-234 ◽  
Author(s):  
Vladimir Greshnyakov ◽  
Evgeniy A. Belenkov
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Density Functional Theory Method ◽  
Theory Method ◽  
Structure And Properties ◽  
Functional Theory ◽  
Graphene Layers ◽  
The Density Functional Theory

The geometrically optimized structures of twenty three carbon diamond-like phases obtained by linking graphene layers, carbon nanotubes, and three-dimensional graphites has been calculated using the density functional theory method and the structural parameters, densities, sublimation energies, electronic properties, and bulk moduli have been calculated.

Quantum Mechanical Investigation of Geometrical Structure and Dynamic Behavior of h-BNNT (9,9-5) and h-AlNNT (9,9-5)Single-Walled Nanotubes: NBO Analysis

2019 ◽  
Vol 16 (9) ◽  
pp. 705-717
Author(s):  
Mehrnoosh Khaleghian ◽  
Fatemeh Azarakhshi
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Structural Parameters ◽  
Energy Levels ◽  
Nbo Analysis ◽  
Electronic Energy ◽  
Boron Nitride Nanotubes ◽  
Basis Set ◽  
B3lyp Method ◽  
Mechanical Investigation

In the present research, B45H36N45 Born Nitride (9,9) nanotube (BNNT) and Al45H36N45 Aluminum nitride (9,9) nanotube (AlNNT) have been studied, both having the same length of 5 angstroms. The main reason for choosing boron nitride nanotubes is their interesting properties compared with carbon nanotubes. For example, resistance to oxidation at high temperatures, chemical and thermal stability higher rather than carbon nanotubes and conductivity in these nanotubes, unlike carbon nanotubes, does not depend on the type of nanotube chirality. The method used in this study is the density functional theory (DFT) at Becke3, Lee-Yang-Parr (B3LYP) method and 6-31G* basis set for all the calculations. At first, the samples were simulated and then the optimized structure was obtained using Gaussian 09 software. The structural parameters of each nanotube were determined in 5 layers. Frequency calculations in order to extract the thermodynamic parameters and natural bond orbital (NBO) calculations have been performed to evaluate the electron density and electrostatic environment of different layers, energy levels and related parameters, such as ionization energy and electronic energy, bond gap energy and the share of hybrid orbitals of different layers.

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