We present a theoretical study of interactions of anionic and neutral serine (Ser) on pure or metal-doped graphene surfaces using density functional theory calculations. Interactions of both types of Ser with the pure graphene surface show weak non-covalent interactions due to the formation of -COOH…π, -COO-…π, and -OH…π interactions. On metaldoped graphene, covalent interactions to the surface dominate, due to the formation of strong metal-O and O-metal-O interactions. Furthermore, the doped Fe, Cr, Mn, Al, or Ti enhances the ability of graphene to attract both types of Ser by a combination of the adsorption energy, the density of states, the Mulliken atomic charges, and differences of electron density. At the same time, the interaction strengths of anionic Ser on various graphene surfaces are stronger than those of neutral Ser. These results provide useful insights for the rational design and development of graphene-based sensors for the two forms of Ser by introducing appropriate doped atoms. Ti and Fe are suggested to be the best choices among all doped atoms for the anionic Ser and neutral Ser, respectively. 相似文献
The effect of pressure on the microphase separation of diblock copolymer melts was investigated by dynamic density functional theory based on equation of state. The results correspond well with experiment data. With the application of high pressure, all of the phase regions corresponding to the different ordered morphologies become narrower. However, the pressure dependence of the order‐disorder transition temperature (TODT) relies on the symmetry of the diblock copolymer. In the very non‐symmetrical case when f is small, TODT decreases with increasing pressure, while in the symmetrical case when f = 0.5, TODT increases with increasing pressure. For the latter case, the increase in the total bead number of the system at the ODT is found, which is in good accordance with the experimental phenomenon that there is an increase in volume accompanying with the transition from ordered to disordered state. In contrast to the temperature, the pressure does not influence the starting time and the duration of microphase separation.
The focus of this study is on compound clusters and, due to the existence of many phases with different structural properties,
tin-based materials have been chosen as the reference case. The clusters considered below are of two types: in the first case
the clusters have the skeleton of the pure tin clusters and are doped with oxygen and aluminum atoms with composition SnxYywith Y = Al, O, x = 1, 10 and y = 1, 2. In the second case the clusters have a rutile lattice with a columnar or a spherical shape and a size up to 80 atoms
and are doped with a number of aluminum atoms up to 20. The calculations are based on the Density Functional Theory (DFT)
and the results describe the cluster structure, its binding energy and the density of states (DOS). The general indication
of the calculations is that the additive coordinates outside, rather than inside, the pristine skeleton with the formation
of hybrid bonds with properties similar to the ones of the host atoms. Also conspicuous effects of hybridization are observed
in the electronic structure and, due to these effects, the binding energy may decrease with respect to the one in the undoped
clusters. 相似文献
The mechanism of the Soai reaction has been thoroughly investigated at the M05‐2X/6‐31G(d) level of theory, by considering ten energetically distinct paths. The study indicates the fully enantioselective catalytic cycle of the homochiral dimers to be the dominant mechanism. Two other catalytic cycles are shown to both be important for correct understanding of the Soai reaction. These are the catalytic cycle of the heterochiral dimer and the non‐enantioselective catalytic cycle of the homochiral dimers. The former has been proved to be not really competitive with the principal cycle, as required for the Soai reaction to manifest chiral amplification, whereas the latter, which is only slightly competitive with the principal one, nicely explains the experimental enantioselectivity observed in the reaction of 2‐methylpyrimidine‐5‐carbaldehyde. The study has also evidenced the inadequacy of the B3LYP functional for mechanistic investigations of the Soai reaction. 相似文献
The anticonvulsant drug carbamazepine (−) is an emerging contaminant of considerable concern due to its hazard potential and environmental persistence. Previous experimental studies proposed hydrophobic zeolites as promising adsorbents for the removal of carbamazepine from water, but only a few framework types were considered in those investigations. In the present work, electronic structure calculations based on dispersion-corrected density functional theory (DFT) were used to study the adsorption of CBZ in eleven all-silica zeolites having different pore sizes and connectivities of the pore system (AFI, ATS, BEA, CFI, DON, FAU, IFR, ISV, MOR, SFH, SSF framework types). It was found that some zeolites with one-dimensional channels formed by twelve-membered rings (IFR, AFI) exhibit the highest affinity towards CBZ. A “good fit” of CBZ into the zeolite pores that maximizes dispersion interactions was identified as the dominant factor determining the interaction strength. Further calculations addressed the role of temperature (for selected systems) and of guest-guest interactions between coadsorbed CBZ molecules. In addition to predicting zeolite frameworks of particular interest as materials for selective CBZ removal, the calculations presented here also contribute to the atomic-level understanding of the interaction of functional organic molecules with all-silica zeolites. 相似文献
Imidazolium cations are promising candidates for preparing anion‐exchange membranes because of their good alkaline stability. Substitution of imidazolium cations is an efficient way to improve their alkaline stability. By combining density functional theory calculations with experimental results, it is found that the LUMO energy correlates with the alkaline stability of imidazolium cations. The results indicate that alkyl groups are the most suitable substituents for the N3 position of imidazolium cations, and the LUMO energies of alkyl‐substituted imidazolium cations depend on the electron‐donating effect and the hyperconjugation effect. Comparing 1,2‐dimethylimidazolium cations (1,2‐DMIm+) and 1,3‐dimethylimidazolium cations (1,3‐DMIm+) with the same substituents reveals that the hyperconjugation effect is more significant in influencing the LUMO energy of 1,3‐DMIms. This investigation reveals that LUMO energy is a helpful aid in predicting the alkaline stability of imidazolium cations. 相似文献
Introduction Palladium(II) complexes, as a promising artificial metallopeptidase, have been extensively studied for se-lective cleavage of methionine and histidine-containing dipeptides,1-11 oligopeptides12-16 and proteins.16-20 Dipeptides AcMet-aa and AcHis-aa, in which the amino-terminus is protected by acetylation and aa is an amino acid residue, are usually cleaved at the Met-aa and His-aa bond with a modest but significant turn-over.6,7,9 In oligopeptides which contain Met or His or b… 相似文献
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