Binding Energy

A novel technique for synthesizing a diamond-like carbon (DLC) film by pulsed laser deposition (PLD) is proposed. In the technique, additional lasers irradiated the plume in order to increase the density of the ionic carbon. By irradiating with an ArF excimer laser, the emission intensity of the atomic carbon was increased greatly. By irradiating with the third harmonic output and the fundamental output of an Nd:YAG laser, the emission intensity of the atomic and ionic carbon also increased greatly. The sp3 content increased from 51% without to 76% with two additional irradiation of the fundamental output of two Nd:YAG laser beams. The differences in the binding energy and surface morphology between the films with and without the irradiation of the additional lasers to the plume were observed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively.

We are reporting density functional theory results for the binding energies, structures, and vibrational spectra of (H-Cl)(2-6) and (H-F)(2-10) clusters. The performance of different functionals has been investigated. The properties of HF clusters predicted by hybrid functionals are in good agreement with experimental information. The HCl dimer binding energy DeltaE(e) is underestimated by hybrid functionals. The Perdew and Wang exchange and correlation functional (PW91) result for DeltaE(e) is -9.6 kJ mol(-1), in very good agreement with experiment (-9.5 kJ mol(-1)). However, PW91 overestimates binding energies of larger clusters. Hydrogen bonding cooperativity depends on the cluster size n but reaches a limit for moderately sized clusters (n=8 for HF). The average shift to low frequencies (Deltanu) of the X-H (X=Cl,F) stretching vibration relative to the monomer is in good agreement with experimental data for HF clusters in solid neon. However, some discrepancies with experimental results for HCl clusters were observed. The behavior of Deltanu as a function of the cluster size provides an interesting illustration of hydrogen-bond cooperative effects on the vibrational spectrum. The representation of the electronic density difference shows the rearrangement of the electronic density induced by hydrogen bonding in the clusters and supports the view that hydrogen-bond cooperativity is related to electronic sharing and delocalization.

Recent studies dealing with the structural, electronic, chemical and catalytic properties of well-defined bimetallic surfaces are reviewed. LEED and STM show that two metals interacting on a surface can form compounds with structures not seen in bulk alloys. Many novel phenomena related to the kinetics of growth of metals on metals have been discovered. The knowledge gathered in this area provides a solid basis for the synthesis of new materials with applications in areas of catalysis, electro-chemistry and microelectronics. In many cases, the formation of a surface bimetallic bond induces large changes in the band structure of the metals. For surfaces that contain transition or s,p metals, the strongest metal-metal interactions occur in systems that combine a metal with a valence band almost fully occupied and a metal in which the valence band is almost empty. A very good correlation is found between the electronic perturbations in a bimetallic system and its cohesive energy. Bimetallic bonds that display a large stability usually involve a significant redistribution of charge around the metal centers. The electronic perturbations affect the reactivity of the bonded metals toward small molecules (CO, NO, H2, O2, S2, C2H4, CH3OH, etc.). For supported monolayers of Ni, Pd, Pt and Cu a correlation is observed between the shifts in surface core-level binding energies and changes in the desorption temperature of CO from the metal adlayers. Examples are provided which demonstrate the utility of single-crystal studies for understanding the role of “ensemble” and “ligand” effects in bimetallic catalysts.

Enzymes utilize substrate binding energy both to promote ground state association and to selectively lower the energy of the reaction transition state.i The monomeric homing endonuclease I-AniI cleaves with high sequence specificity in the center of a 20 base-pair DNA target site, with the N-terminal domain of the enzyme making extensive binding interactions with the left (−) side of the target site and the similarly structured C-terminal domain interacting with the right (+) side.ii Despite the approximate two-fold symmetry of the enzyme-DNA complex, we find that there is almost complete segregation of interactions responsible for substrate binding to the (−) side of the interface and interactions responsible for transition state stabilization to the (+) side. While single base-pair substitutions throughout the entire DNA target site reduce catalytic efficiency, mutations in the (−) DNA half-site almost exclusively increase KD and KM*, and those in the (+) half-site primarily decrease kcat*. The reduction of activity produced by mutations on the (−) side, but not mutations on the (+) side, can be suppressed by tethering the substrate to the endonuclease displayed on the surface of yeast. This dramatic asymmetry in the utilization of enzyme-substrate binding energy for catalysis has direct relevance to the redesign of endonucleases to cleave genomic target sites for gene therapy and other applications. Computationally redesigned enzymes that achieve new specificities on the (−) side do so by modulating KM*, while redesigns with altered specificities on the (+) side modulate kcat*. Our results illustrate how classical enzymology and modern protein design can each inform the other.

Depression associated with poor general medical condition, such as post-stroke (PSD) or post-myocardial infarction (PMID) depression, is characterized by resistance to classical antidepressants. Special treatment strategies should thus be developed for these conditions. Our study aims to investigate the mechanism of action of 2-morpholino-5-phenyl-6H-1,3,4-thiadiazine, hydrobromide (L-17), a recently designed thiadiazine derivative with putative neuro- and cardioprotective and antidepressant-like effects, using combined in silico (for prediction of the molecular binding mechanisms), ex vivo (for assessment of the neural excitability using c-Fos immunocytochemistry), and in vivo (for direct examination of the neuronal excitability) methodological approaches. We found that the predicted binding affinities of L-17 to serotonin (5-HT) transporter (SERT) and 5-HT3 and 5-HT1A receptors are compatible with selective 5-HT serotonin reuptake inhibitors (SSRIs) and antagonists of 5-HT3 and 5-HT1A receptors, respectively. L-17 robustly increased c-Fos immunoreactivity in the amygdala and decreased it in the hippocampus. L-17 dose-dependently inhibited 5-HT neurons of the dorsal raphe nucleus; this inhibition was partially reversed by the 5-HT1A antagonist WAY100135. We suggest that L-17 is a potent 5-HT reuptake inhibitor and partial antagonist of 5-HT3 and 5-HT1A receptors; the effects of L-17 on amygdaloid and hippocampal excitability might be mediated via 5-HT, and putatively mediate the antidepressant-like effects of this drug. Since L-17 also possesses neuro- and cardioprotective properties, it can be beneficial in PSD and PMID. Combined in silico predictions with ex vivo neurochemical and in vivo electrophysiological assessments might be a useful strategy for early assessment of the efficacy and neural mechanism of action of novel CNS drugs.

A B S T R A C T Tetragonal zirconia (t-ZrO 2) nanoparticles were successfully prepared by a hydrothermal method and characterized by various measurement techniques. The tetragonal crystalline structure of ZrO 2 nanoparticles were confirmed by X-ray diffraction analysis. The binding energies of Zr and O were confirmed from the XPS spectrum. The band gap energy was estimated using optical absorption spectroscopy, found to be 4.8 eV. The UV (360 nm) and visible (403 nm and 537 nm) emissions were observed from PL spectrum. The thermal stability of the prepared ZrO 2 nanoparticles was studied by TG-DTA analysis. The photocatalytic degradation of the as-prepared ZrO 2 nanoparticles was studied under UV light irradiation using methyl orange (MO) as a model organic pollutant. Results showed that 99% degradation was achieved within 50 min. Photoelectrochemical studies were also supported the photocatalytic activities.