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Toxic Effects and Biodistribution of Ultrasmall Gold Nanoparticles *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Gunter Schmid, Wolfgang G. Kreyling, Ulrich Simon
Whereas in a bulk metal, the electrons are distributed in so-called electronic bands. In small molecules like Fe3(CO)12 or Co4(CO)12 the electrons are located in the so-called molecular orbitals. The important question is: Where is the transition from bulk to molecule? Obviously, Au55(PPh3)12Cl6 performs all necessary conditions at room temperature. At low temperatures, larger particles also fulfill all the conditions to serve as intermediates between bulk and molecule. Figures 15.8 and 15.9 show current (I)-voltage (U) results that clearly show the situation.
Crocus sativus and the Prized Commodity, Saffron
Published in Raymond Cooper, Jeffrey John Deakin, Natural Products of Silk Road Plants, 2020
Jeffrey John Deakin, Raymond Cooper
Chromophores arise from conjugated unsaturated systems of covalent bonds within organic molecules, such as crocin and β-carotene. A chromophore is the part of a molecule responsible for its color, which arises when a molecule absorbs certain wavelengths of visible light and transmits or reflects others. The chromophore is a region in the molecule where the energy difference between two different molecular orbitals falls within the range of the visible spectrum. Visible light reaching the chromophore can thus be absorbed in a narrow band of frequencies by exciting an electron from a molecular orbital in the ground state to one in an excited state. It is important to bear in mind that these electronic transitions are from one molecular orbital to another.
Receptor Binding Studies: General Considerations
Published in William C. Eckelman, Lelio G. Colombetti, Receptor-Binding Radiotracers, 2019
Ehrlich’s observations on the rigid structural requirements for antibody-antigen (and later chemotherapeutic agent-parasite) interactions provided the basis for the earliest, and one of the most productive modes of inquiry into receptor biochemistry, the structure-activity relationship (SAR). In this approach, it is assumed that there is a high degree of complementarity between the stereochemical configuration of a compound and the site with which it interacts. Comparisons of biological potency and chemical composition provide information on minimal structural requirements for effective drug action, suggest the presence of specific chemical groups within the binding site, permit the subclassification of receptors which recognize the same biological ligand, provide direction in the design of new synthetic drugs and afford insight into the relationship between receptor agonists and antagonists, the effects of which are frequently elucidated subsequent to interaction with overlapping sites. The application of molecular orbital theory has promised to extend the usefulness of SAR studies. In certain variations of this approach, attention is shifted away from “atom-to-atom” resemblances between molecules acting at a common site to a consideration of the overall electrostatic potential energy contours which determine the approach and the sites of interaction involved in the earliest stages of ligand recognition by a receptor (e.g., References 3 and 4). These long-range intermolecular forces during the early stages of drug-receptor interaction may be the greatest source of “specificity” in the interaction.4
Synthesis, X-ray diffraction analysis, quantum chemical studies and α-amylase inhibition of probenecid derived S-alkylphthalimide-oxadiazole-benzenesulfonamide hybrids
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Bilal Ahmad Khan, Syeda Shamila Hamdani, Muhammad Naeem Ahmed, Shahid Hameed, Muhammad Ashfaq, Ahmed M. Shawky, Mahmoud A. A. Ibrahim, Peter A. Sidhom
To verify the experimental results, versatile quantum mechanical calculations are carried out on the two hybrids (1 and 2). The studied hybrids are first optimised at the B3LYP/6-31G* level of theory50–51. Upon the optimised geometries, the vibrational frequency and single-point energy calculations are executed. Molecular electrostatic potential (MEP) maps are then generated using a 0.002 au electron density envelope according to the previous recommendations52. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributions are also visualised for the optimised geometries. Moreover, the quantum theory of atoms in molecules (QTAIM)53 along with noncovalent interaction (NCI) index54 are utilised to identify the origin of interactions within the dimeric form of the studied hybrids based on the crystallographic coordinates. The QTAIM and NCI calculations are executed using Multiwfn 3.7 package55 and are graphed using Visual Molecular Dynamics (VMD) software56. All the adopted quantum mechanical calculations are performed at the B3LYP/6-31G* level of theory with the help of Gaussian 09 software 57.
Modeling of the structure and forecasting properties of dihydroquercetin derivatives
Published in Drug Development and Industrial Pharmacy, 2022
A. K. Boshkayeva, R. A. Omarova, S. K. Ordabayeva, A. D. Serikbayeva, G. G. Umurzakhova, A. J. Massakbayev
Using the AM1, PM3, and RM1 methods, spatial characteristics were calculated in order to select the most optimal method for further calculations. The results of quantum-chemical studies of model derivatives of dihydroquercetin carried out by the RM1 method have been obtained. The most optimal calculation method was chosen on the data basis of calculating the bond lengths between atoms. Calculations of the enthalpies of formation of model molecules made it possible to evaluate their thermodynamic stability. An analysis of these charge characteristics on atoms in model molecules made it possible to determine the reaction center for each molecule. The reactivity of the studied models was evaluated by comparing the energies of the boundary Molecular Orbitals (HOMO and LUMO), as well as the difference in their values. An analysis of the electric dipole moments allowed us to determine the preferred (polar) nature of the solvents for the studied model molecular systems. Using benzoyl chloride acylation, new compounds are obtained - as derivatives of DHQ.
Exploring space-energy matching via quantum-molecular mechanics modeling and breakage dynamics-energy dissipation via microhydrodynamic modeling to improve the screening efficiency of nanosuspension prepared by wet media milling
Published in Expert Opinion on Drug Delivery, 2021
Jing Tian, Fangxia Qiao, Yanhui Hou, Bin Tian, Jianhong Yang
The aggregation characteristics of drug molecules can affect the stability of nanosuspensions. If bulk drug molecules readily aggregate, then the interactions between the drug molecules may be stronger and nanosuspensions with larger particles are more likely to be produced. The intermolecular interactions might be caused by acceptance/donor and transfer of the electrons, and the frontier molecular orbitals can be used to evaluate the electron regions of molecules to assess where the possible adsorption sites may occur [66,67]. The highest occupied molecular orbital (HOMO) of the donor electrons has the highest energy and the lowest occupied molecular orbital (LUMO) receives electrons with the lowest energy, and they are collectively referred to as the frontier orbitals. The electron cloud regions in HOMO may affect LUMO or electron transition phenomenon can even occur to allow their interaction [38]. After obtaining the adsorption sites, the adsorption module can be used to determine the aggregation conditions for different amounts of drug molecules based on diagrams.