Are zinc oxide nanoparticles safe? A structural study on human serum albumin using in vitro and in silico methods.

With due attention to adsorption of proteins on the nanoparticles surface and the formation of nanoparticle-protein corona, investigation of nanoparticles toxicity on the structure of proteins is important. Therefore, this work was done to evaluate toxicity of Zinc oxide nanoparticles (ZnO NPs) on the structure of human serum albumin (HSA) through in vitro and in silico studies. First, ZnO NPs were synthesized using hydrothermal method and their size and morphology were determined by SEM and TEM methods and then to study its toxicity on the HSA structure were used UV-Vis and fluorescence spectroscopy. Also, in order to investigate interaction mechanism of ZnO NP with HSA at the atomistic level was used molecular dynamics (MD) simulation. The obtained images from SEM and TEM showed that ZnO NPs were nanosheet with size of less than 40 nm. The results of spectroscopic studies showed ZnO NPs lead to significant conformational changes in the protein's absorption and emission spectra. Moreover, MD results indicated the minor structure changes in HSA due to interaction with ZnO NP during the 100 ns simulation, and the formation of nanoparticle-protein corona complex is mainly because of electrostatic interactions between charge groups of HSA and ZnO NP.Communicated by Ramaswamy H. Sarma.

Investigations of adsorption behavior and anti-inflammatory activity of glycine functionalized Al12N12 and Al12ON11 fullerene-like cages.

The adsorption behavior of the amino acid, glycine (Gly), via the carboxyl, hydroxyl, and amino groups onto the surfaces of Al12N12 and Al16N16 fullerene-like cages were computationally evaluated by the combination of density functional theory (DFT) and molecular docking studies. It was found that Gly can chemically bond with the Al12N12 and Al16N16 fullerene-like cages as its amino group being more favorable to interact with the aluminum atoms of the adsorbents compared to carboxyl and hydroxyl groups. Oxygen and carbon doping were reported to reduce steric hindrance for Glycine interaction at Al site of Al12ON11/Gly and Al12CN11/Gly complexes. Interaction was further enhanced by oxygen doping due to its greater electron withdrawing effect. Herein, the Al12ON11/Gly complex where two carbonyl groups of Gly are bonded to the aluminum atoms of the Al12N12 fullerene-like cage is the most stable interaction configuration showing ∆adsH and ∆adsG values of -81.74 kcal/mol and -66.21 kcal/mol, respectively. Computational studies also revealed the frequency shifts that occurred due to the interaction process. Molecular docking analysis revealed that the Al12N12/Gly (-11.7 kcal/mol) and the Al12ON11/Gly (-9.2 kcal/mol) complexes have a good binding affinity with protein tumor necrosis factor alpha (TNF-α). TNF-α was implicated as a key cytokine in various diseases, and it has been a validated therapeutic target for the treatment of rheumatoid arthritis. These results suggest that the Al12N12/Gly complex in comparison with the Al16N16/Gly, Al12ON11/Gly, and the Al12CN11/Gly complexes could be efficient inhibitors of TNF-α.

Theoretical study of nitrogen, boron, and co-doped (B, N) armchair graphene nanoribbons.

The electronic properties of the graphene nanoribbons (GNR) with armchair chirality were studied using the density functional theory (DFT) combined with non-equilibrium green's function method (NEGF) formalism. The role of donor and acceptor dopants of nitrogen and boron was studied separately and also in the situation of co-doping. The charge density, electronic density of states (DOS), and transmission coefficient at different bias voltages are presented for comparison between pure and doped states. It was found that this doping plays the main role in the distortion of the GNR lattices for cases of B and N as it affects straightly on the DOS and transmission coefficient of the systems under study. The band structure of edge was engineered by differently selecting the doping positions of B, N, and B-N hexagonal rings and it was found that there are significant changes in the electronic properties of these systems due to doping. This study can be used for developing GNR device based on doping B and N atoms.

Serine adsorption through different functionalities on the B12N12 and Pt-B12N12 nanocages.

The present work reports the adsorption of serine in the neutral and zwitterionic forms on the pure and Pt-decorated B12N12 fullerenes by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The binding energy of serine over the fullerene has been studied through its hydroxyl (-OH), carboxyl (-COOH), and amine (-NH2) functional groups. Based on our analysis, the binding energy of serine in zwitterionic form (F: -1.52 eV) on B12N12 fullerene is less stable than that of the neutral form (C: -1.61 eV) using the M06-2X functional. Our results indicated that the most stable chemisorption state for serine is through its amine group (I: -2.49 eV) interacting with the Pt-decorated B12N12 fullerene in comparison with the carbonyl group (J: -1.92 eV). The conductivity of the B12N12 and Pt-decorated B12N12 fullerenes is influenced by the energy band gap variation when serine is adsorbed upon the outer surface of fullerenes. Understanding the adsorption of serine on B12N12 and Pt-decorated B12N12 fullerenes provide fundamental knowledge for future applications in biomolecules and metal surfaces.

Small cobalt clusters encapsulated inside Si30C30 nanocages: electronic and magnetic properties.

We investigated the structural, electronic, and magnetic properties of small Co(n) clusters (n = 2-6) when they were endohedrally doped into Si30C30 nanocages using ab initio calculations based on density functional theory. Two different spin-polarized functionals based on the generalized gradient and local density approximations were used to characterize Co(n)@Si30C30. It was found that the Co(n) clusters encapsulated inside Si30C30 nanocages can form stable structures due to their significant binding energies. Among the various encapsulated clusters studied, the Co4 cluster was the most stable in a Si30C30 nanocage. We also found that the magnetic moments of the clusters decreased during the encapsulation process due to substantial hybridization between the cobalt cluster and the Si30C30 nanocage structure, although the encaged Co2 cluster presented somewhat different behavior. It was found that significant magnetic moments are induced in the wall of the nanocage, and that Co(n)@Si30C30 presents higher total magnetic moments than Co(n)@C60.

Oxygen doped SiC nanocrystals: first principles study of the optical properties.

We have studied a typical spherical SiC nanocrystal with a diameter of 1.2 nm (Si43C44H76) using linear combination of atomic orbitals in combination with pesudopotential density functional calculation. The role of fluorine and oxygen impurities was investigated on the electronic and optical properties of the Si43C44H76 nanocrystal. Total energy calculations show that the fluorine doped Si43C44H76 nanocrystals are unstable. Oxygen doped Si43C44H76 have different binding energies in various substitutional and interstitial defects. The maximum binding energy of the oxygen at carbon substitutional defect is about -0.5 eV and at interstitial defect is -0.18 eV. The HOMO-LUMO gap of the pure Si43C44H76 is about 6.71 eV and after doping with oxygen changes on the order of 0.1 eV. Our studies show that the refractive index of the doped Si43C44H76 nanocrystal significantly dispersed in comparison with pure SiC nanocrystal especially at the range of 6 to 8 eV.

Optical properties of GaAs nanocrystals: influence of an electric field.

A study of the electronic and optical properties of the hydrogen-terminated GaAs nanocrystals Ga68As68H96 and Ga92As80H108 is presented. In this study, their dielectric functions, refractive indices, and absorption coefficients were calculated using density functional theory (DFT). The influence of a uniform external electric field on the optical properties of the nanocrystals was also explored. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for each nanocrystal were studied in the absence and the presence of the uniform external electric field. Our results indicate that the HOMO-LUMO gap decreases with increasing electric field strength. The calculated density of states revealed that the main reason for this shrinking gap is an increase in the delocalization of the gallium π-orbitals under the influence of an increasing external electric field. The permanent dipole moment and the polarizability of the nanocrystals under the induced electric field increased with increasing nanocrystal radius. The induced electric field caused a noticeable redshift in the absorption peaks. The electric field also increased the absorption intensity, particularly when the field strength was >0.25 V/Å.