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1.
J Mol Model ; 25(8): 252, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31353431

RESUMO

The present study is aimed at probing the hydrogen bonding interaction between epinephrine and uracil by means of density functional theory calculations concerning their complexation's geometries, interaction energies, and vibrational frequencies. Geometry optimization was carried out giving 19 stable geometries of epinephrine-uracil complex with interaction energies in a range of - 21.51 to - 62.37 kJ mol-1 using the basis set superposition error (BSSE) correction. The analysis of structure and vibration shows that the hydrogen bonding elongates the length of corresponding bond O(N)-H and decreases the symmetric stretching vibrational frequency, which indicates red-shifted H-bonding interactions in all the geometries. Additionally, the analysis with theories of natural bond orbital (NBO), atoms in molecules (AIM), and the reduced density gradient (RDG) of hydrogen bonding properties and characteristics of the 19 geometries suggests that the hydrogen bonding in all the optimized structures of epinephrine-uracil complex is kind of a closed-shell interaction and mainly electrostatic dominant.


Assuntos
Epinefrina/química , Ligação de Hidrogênio , Uracila/química
2.
Exp Ther Med ; 17(5): 4109-4115, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30988787

RESUMO

The present study assessed the effects of poly-arginine R18 and its promotion of neurocyte cell growth via autophagy in traumatic brain injury (TBI), and aimed to determine the possible mechanism by which this occurs. Brain water content was measured to analyze the effects of poly-arginine R18 in TBI. MTT and lactate dehydrogenase activity assays were performed to measure N2A cell growth. Western blotting and immunofluorescence staining were also performed to determine the protein expression of Bcl-2 associated X, LC3, Beclin-1 and p62. The results demonstrated that poly-arginine R18 treatment reduced neurocyte apoptosis and promoted neurocyte cell growth via the activation of autophagy in a rat model of TBI. Furthermore, poly-arginine R18 treatment promoted neurocyte cell growth, reduced apoptosis, induced the protein expression of LC3 and Beclin-1, and suppressed p62 expression by promoting autophagy in vitro. In addition, the inhibition of autophagy attenuated the effects of poly-arginine R18 on cell growth in vitro. Collectively, the results demonstrate the effects of poly-arginine R18 on neurocyte cell growth via autophagy activation in a model of TBI, and poly-arginine R18 is therefore a potential therapeutic target in TBI.

3.
J Phys Chem A ; 122(8): 2297-2306, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29401396

RESUMO

Boron clusters and their oxides are electron-deficient species with (π and σ) aromaticity and antiaromaticity, enabling a structural and bonding analogy between them and the aromatic hydrocarbons. s-Indacene C12H8 is normally considered as a border system between the classes of aromatic and antiaromatic hydrocarbons. We show herein, via computer global-minimum searches and B3LYP and single-point CCSD(T) calculations, that boron oxide clusters D2h B8O8 (1, 1Ag) and D2h B8O8- (2, 2B2g) adopt planar tricyclic structures, which feature fused heterocyclic B3O2/B4O2/B3O2 rings and two boronyl (BO) terminals, a structural pattern analogous to the C5/C6/C5 rings in s-indacene. Bonding analyses indicate that B8O8 (1) is a formally antiaromatic 12π system, the molecular orbitals of which are largely similar to those of s-indacene. Infrared and ultraviolet-visible spectra of B8O8 (1) neutral, as well as the photoelectron spectrum of B8O8- (2) anion, are predicted computationally. The latter spectrum shows a sizable energy gap of 3.5 eV for 2, demonstrating the electronic robustness of 1. Our bonding analyses also shed critical light on the nature of bonding in s-indacene.

4.
Phys Chem Chem Phys ; 19(3): 2479-2486, 2017 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-28058436

RESUMO

Boron-based heteroatomic rings can have exotic chemical bonding, in which the p lone-pairs of heteroatoms manage to participate in delocalized π bonding, compensating for boron's electron-deficiency. We explore herein the bonding properties of ternary B-N-H systems with a pentagonal ring, using the B3N2H50/-/2- clusters as examples. Computational structural searches lead to perfectly planar C2v B3N2H5 (1, 1A1) and C2v B3N2H5- (2, 2B1) as global minima for the neutral species and monoanion, which feature a pentagonal B3N2 ring. The corresponding dianion C2v B3N2H52- (3, 1A1) is a local minimum, whose global minimum adopts a chain-like open structure. Bonding analyses reveal a five-center four-electron (5c-4e) π system in 1, dubbed the 5c-4e o-bond. It is a 4π system in the bonding/nonbonding combination, originating from two N 2p lone-pairs, which can be considered as an extension of the concept of 3c-4e ω-bond. The extra electrons in 2 and 3 occupy a markedly destabilized π orbital. Thus, a 4π configuration, rather than a π sextet according to the (4n + 2) Hückel rule, is electronically robust for the B3N2H50/-/2- system. Infrared and photoelectron spectra are predicted for 1 and 2, respectively. Structural evolution of ring-like and chain-like isomers with charge-state in B3N2H50/-/2- is elucidated. B3N2H5- (2) is used as ligand for sandwich-type complexes: C2h [(B3N2H5)2Fe]2- and C2h [(B3N2H5)2Fe]Li2.

5.
Phys Chem Chem Phys ; 18(33): 23304-11, 2016 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-27499231

RESUMO

A chemical bonding model is presented for the bowl-like C5v B30 global-minimum cluster with a central pentagonal hole. The B30 cluster is composed of three concentric boron rings: first B5, second B10, and third B15. The first and second B rings constitute an inner double-chain ribbon and support a delocalized π sextet. The second and third rings form an outer double-chain ribbon, where 14π delocalized electrons are situated. The unique π systems lead to concentric dual π aromaticity for B30, a concept established from concerted computational data on the bases of canonical molecular orbital (CMO) analysis, adaptive natural density partitioning (AdNDP), nucleus-independent chemical shifts (NICS), and natural charge calculations. A proposal is put forward that the bowl-like B30 cluster is an exact all-boron analogue of corannulene (C20H10), a fragment of C60 fullerene. The bonding nature of corannulene is revisited and fully elucidated herein. A comparison of the bonding patterns in bowl-like C5v B30 cluster and two other structural isomers (Cs and C1) unravels the mechanism as to why the defective hole prefers to be positioned at the center.

6.
J Chem Phys ; 145(4): 044308, 2016 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-27475362

RESUMO

We report on the computational design of an all-metal aromatic sandwich, [Sb4Au4Sb4](2-). The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb4](+)[Au4](4-)[Sb4](+), showing ionic bonding characters with electron transfers in between the Sb4/Au4/Sb4 layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ← Au back-donation occur, redistributing electrons from the Sb4/Au4/Sb4 layers to the interlayer Sb-Au-Sb edges, which effectively lead to four Sb-Au-Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb4](+) ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ∼1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts.

7.
Phys Chem Chem Phys ; 18(31): 21412-20, 2016 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-27424889

RESUMO

Boron clusters can serve as inorganic analogues of hydrocarbons or polycyclic aromatic hydrocarbons (PAHs). We present herein, based upon global searches and electronic structural calculations at the B3LYP and CCSD(T) levels, the global-minimum structures of two boron-sulfur hydride clusters: C2v B3S2H3(-) (1, (2)B1) and C2v B3S2H3 (2, (1)A1). Both species are perfectly planar and feature a five-membered B3S2 ring as the structural core, with three H atoms attached terminally to the B sites. Chemical bonding analysis shows that C2v B3S2H3(-) (1) has a delocalized 5π system within a heteroatomic B3S2 ring, analogous to the π bonding in cyclopentadiene, D5h C5H5. The corresponding closed-shell C2v B3S2H3(2-) (3, (1)A1) dianion is only a local minimum. At the single-point CCSD(T) level, it is 5.7 kcal mol(-1) above the chain-like C1 ((1)A) open structure. This situation is in contrast to the cyclopentadienyl anion, C5H5(-), a prototypical aromatic hydrocarbon with a π sextet. The C2v B3S2H3 (2) neutral cluster is readily obtained upon removal of one π electron from C2v B3S2H3(-) (1). The anion photoelectron spectrum of C2v B3S2H3(-) (1) and the infrared absorption spectrum of C2v B3S2H3 (2) are predicted. The C2v B3S2H3(-) (1) species can be stabilized in sandwich-type C2h [(B3S2H3)2Fe](2-) and salt C2h [(B3S2H3)2Fe]Li2 complexes. An intriguing difference is observed between the pattern of π sextet in C2v B3S2H3(2-) (3) dianion and that in cyclopentadienyl anion. The present work also sheds light on the mechanism of structural evolution in the B3S2H3(0/-/2-) series with charge states.

8.
Phys Chem Chem Phys ; 18(19): 13423-31, 2016 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-27124821

RESUMO

In a recent communication, an all-metal aromatic sandwich [Sb3Au3Sb3](3-) was synthesized and characterized. We report herein a density-functional theory (DFT) study on the chemical bonding of this unique cluster, which makes use of a number of computational tools, including the canonical molecular orbital (CMO), adaptive natural density partitioning (AdNDP), Wiberg bond index, and orbital composition analyses. The 24-electron, triangular prismatic sandwich is intrinsically electron-deficient, being held together via six Sb-Sb, three Au-Au, and six Sb-Au links. A standard, qualitative bonding analysis suggests that all CMOs are primarily located on the three Sb3/Au3/Sb3 layers, three Au 6s based CMOs are fully occupied, and the three extra charges are equally shared by the two cyclo-Sb3 ligands. This bonding picture is referred to as the zeroth order model, in which the cluster can be formally formulated as [Sb3(1.5+)Au3(3-)Sb3(1.5+)](3-) or [Sb3(0)Au3(3-)Sb3(0)]. However, the system is far more complex and covalent than the above picture. Seventeen CMOs out of 33 in total involve remarkable Sb → Au electron donation and Sb ← Au back-donation, which are characteristic of covalent bonding and effectively redistribute electrons from the Sb3 and Au3 layers to the interlayer edges. This effect collectively leads to three Sb-Au-Sb three-center two-electron (3c-2e) σ bonds as revealed in the AdNDP analyses, despite the fact that not a single such bond can be identified from the CMOs. Orbital composition analyses for the 17 CMOs allow a quantitative understanding of how electron donation and back-donation redistribute the charges within the system from the formal Sb3(0)/Au3(3-) charge states in the zeroth order model to the effective Sb3(1.5-)/Au3(0) charge states, the latter being revealed from the natural bond orbital analysis.

9.
Phys Chem Chem Phys ; 18(14): 9594-601, 2016 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-26997584

RESUMO

The structural and electronic properties and chemical bonding of binary Be2O2 and Si2O2 clusters have been studied using quantum chemical calculations at the B3LYP level. For the Be2O2 cluster, the potential energy surface is probed by unbiased structural searches and the global-minimum structure was established using the B3LYP calculations, complemented by PBE0 and single-point CCSD(T) calculations for top isomers. The perfectly planar D2h Be2O2 ((1)Ag) global minimum is well defined, being at least 3.64 eV lower in energy than alternative structures at the CCSD(T)//B3LYP/aug-cc-pVTZ level. Chemical bonding analyses show that D2h Be2O2 and Si2O2 clusters possess the rhombic four-center four-electron (4c-4e) π bond, that is, the o-bond, a conception derived from electron-deficient boron oxide clusters lately. Furthermore, the Be2O2 and Si2O2 clusters also exhibit rhombic 4c-4e σ bonds, both for the radial and tangential σ frameworks (σr and σt). The σt framework is classified as an o-bond only formally, due to the secondary contribution from the Be/Si s component. The three-fold (π, σr, and σt) o-bonds in Be2O2 and Si2O2 are considered to resemble the three-fold aromaticity in all-metal Al4(2-) dianions. A 4c-4e o-bond makes use of four O 2p electrons, which would otherwise be two lone-pairs, for a delocalized and completely bonding orbital, as well as a residual nonbonding orbital. Three-fold o-bonds thus greatly stabilize the binary Be2O2 and Si2O2 clusters. We anticipate that the bonding concept should be applicable to additional molecular systems, including those with larger heterocyclic rings.

10.
J Chem Phys ; 143(6): 064303, 2015 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-26277134

RESUMO

The concept of boronyl (BO) and the BO/H isolobal analogy build an interesting structural link between boron oxide clusters and hydrocarbons. Based upon global-minimum searches and first-principles electronic structural calculations, we present here the perfectly planar C2v B5O5 (+) (1, (1)A1), C2v B5O5 (2, (2)A1), and tetrahedral Cs B5O5 (-) (3, (1)A') clusters, which are the global minima of the systems. Structural and molecular orbital analyses indicate that C2v B5O5 (+) (1) [B3O3(BO)2 (+)] and C2v B5O5 (2) [B3O3(BO)2] feature an aromatic six-membered boroxol (B3O3) ring as the core with two equivalent boronyl terminals, similar to the recently reported boronyl boroxine D3h B6O6 [B3O3(BO)3]; whereas Cs B5O5 (-) (3) [B(BO)3(OBO)(-)] is characterized with a tetrahedral B(-) center, terminated with three BO groups and one OBO unit, similar to the previously predicted boronyl methane Td B5O4 (-) [B(BO)4 (-)]. Alternatively, the 1-3 clusters can be viewed as the boron oxide analogs of phenyl cation C6H5 (+), phenyl radical C6H5, and chloromethane CH3Cl, respectively. Chemical bonding analyses also reveal a dual three-center four-electron (3c-4e) π hyperbond in Cs B5O5 (-) (3). The infrared absorption spectra of B5O5 (+) (1), B5O5 (2), and B5O5 (-) (3) and anion photoelectron spectrum of B5O5 (-) (3) are predicted to facilitate their forthcoming experimental characterizations. The present work completes the BnOn (+/0/-) series for n = 1-6 and enriches the analogous relationship between boron oxides and hydrocarbons.

11.
Phys Chem Chem Phys ; 17(26): 16798-804, 2015 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-26060130

RESUMO

Based upon global searches and electronic structure calculations at the B3LYP and CCSD(T) levels, we present the global-minimum structures of two ternary B-O-H and B-S-H rhombic clusters: D2h B2O2H2 (1, (1)Ag) and C2v B2S2H2 (2, (1)A1). Both species feature a B2X2 (X = O or S) four-membered ring as the core, with two H atoms attached terminally. The former cluster is perfectly planar, whereas the latter undergoes a slight butterfly distortion. Bonding analyses reveal a four-center four-electron (4c-4e) o-bond in these clusters, which are 4π systems in a nonbonding/bonding combination, in contrast to an antibonding/bonding combination in a classical 4π antiaromatic hydrocarbon such as cyclobutadiene (C4H4). Clusters 1 and 2 are considered to be aromatic. The present results also help elucidate the bonding nature in the relevant heteroatomic ring B2N2H4 system and suggest that it is not appropriate to consider B2N2H4 as an inorganic cyclobutadiene, a conception that has been in existence in the literature for over 40 years. The electronic properties of the global-minimum clusters 1 and 2 are predicted. It is shown that B2O2H2 (1) and B2S2H2 (2) may serve as effective inorganic ligands to form sandwich-type transition metal complexes, such as D2d [B2O2H2]2Ni (3) and D2d [B2S2H2]2Ni (4).

12.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 6): 712-5, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-26090158

RESUMO

In the title indolinone derivative, C10H10INO, all the non-H atoms, except the terminal methyl C atom, are almost coplanar. The mol-ecules are arranged into columns extending along the a-axis direction and inter-act with the mol-ecules in adjacent columns via C-H⋯O hydrogen bonds [H⋯O distance = 2.57 (3) Å] and I⋯I short contacts of 3.8986 (3) Å. A one-dimensional zigzag iodine chain along the a axis is apparent between two neighbouring columns.

13.
J Chem Phys ; 142(1): 014302, 2015 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-25573556

RESUMO

Inorganic analogues of hydrocarbons or polycyclic aromatic hydrocarbons (PAHs) are of current interest in chemistry. Based upon global structural searches and B3LYP and CCSD(T) calculations, we present herein the perfectly planar dicyclic boron sulfide clusters: D2h B6S6 (1, (1)Ag), D2h B6S6(-) (2, (2)B3u), and D2h B6S6(2-) (3, (1)Ag). These are the global minima of the systems, being at least 0.73, 0.81, and 0.53 eV lower in energy, respectively, than their alternative isomers at the CCSD(T) level. The D2h structures feature twin B3S2 five-membered rings, which are fused together via a B2 unit and terminated by two BS groups. Bonding analyses show that the closed-shell B6S6(2-) (3) cluster possesses 10 delocalized π electrons, closely analogous to the bonding pattern of the aromatic naphthalene C10H8. The B6S6(-) (2) and B6S6 (1) species are readily obtained upon removal of one or two π electrons from B6S6(2-) (3). The results build a new analogous relationship between boron sulfide clusters and their PAH counterparts. The B6S6(-) (2) monoanion and B6S6(2-) (3) dianion can be effectively stabilized in neutral LiB6S6 and Li2B6S6 salts, respectively.

14.
J Mol Model ; 20(9): 2427, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25159274

RESUMO

The investigation on the geometrical and electronic properties of B(2)(BO)(6) (0/-) and B(2)(BS)(6) (0/-) has been performed by density functional theory (DFT) using the B3LYP and BP86 methods. The chemical bonding in B(2)A(6) (A = H, BO, and BS) series is elucidated through the recently developed adaptive natural density partitioning (AdNDP). D(2h) B(2)(BO)(6) and B(2)(BS)(6) were found to possess two bridging η (2)-BO or η (2)-BS groups, as well as four terminal BO or BS groups that are analogs of diborane B(2)H(6). D(2)h B(2)(BO)(6) (-) and B(2)(BS)(6) (-) with two bridging η (2)-BO or η (2)-BS groups which are more stable than their corresponding D(3d) structures. The binding energy of B(2)(BO)(6) and B(2)(BS)(6) with respect to B(2)(BO)(6) (D2h) → 2B(BO)(3) (D(3h)) and B(2)(BS)(6)(D(2h)) → 2B(BS)(3) (D(3h)) are estimated to be (△)E = 19.8 and 40.6 kcal mol(-1) at CCSD(T)//B3LYP level, respectively. This finding advances the boronyl chemistry and helps establish the isolobal analogy between boron-rich oxide clusters and boranes.


Assuntos
Boranos/química , Compostos de Boro/química , Sulfetos/química , Simulação por Computador , Transferência de Energia , Ligantes , Modelos Químicos , Modelos Moleculares , Estrutura Molecular , Relação Estrutura-Atividade
15.
Exp Ther Med ; 7(5): 1327-1331, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24940433

RESUMO

This study aimed to investigate the effect of Quanzhenyiqitang on alveolar macrophages (AMs) in a rat model of chronic obstructive pulmonary disease (COPD). In addition, the induction of apoptosis and regulation of histone deacetylase 2 (HDAC2) was studied to elucidate the underlying mechanisms of Quanzhenyiqitang treatment of COPD. Quanzhenyiqitang-treated serum was applied to AMs obtained from rats with COPD. A blank (control) group, an untreated serum group and an aminophylline group were also observed to evaluate the differences in AM apoptosis status, as well as the expression levels of caspase-9, caspase-8 and HDAC2. Compared with the control group, Quanzhenyiqitang-treated serum resulted in higher levels of caspase-9 and caspase-8 expression, increased apoptosis of AMs and increased expression of HDAC2 by AMs. In conclusion, Quanzhenyiqitang is capable of inducing apoptosis of AMs, which are the primary inflammatory cells in COPD, and modulating the expression of the important inflammatory factor HDAC2, producing an overall anti-inflammatory effect.

16.
J Chem Phys ; 138(24): 244304, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23822241

RESUMO

Inorganic benzene-like compounds such as boroxine and borazine are of interest in chemistry. Here we report on theoretical prediction of a new member of the inorganic benzene family: boronyl boroxine. This perfectly planar D3h B6O6 (1, (1)A1') cluster is identified as the global minimum of the system at density functional theory (B3LYP) and molecular orbital theory levels, which lies at least ∼20 kcal∕mol lower in energy than alternative structures. It can be formulated as B3O3(BO)3 and features a boroxol B3O3 ring as the core with three boronyl (BO) groups attached terminally, closely resembling boroxine and obtainable from the latter via isovalent BO∕H substitution. Detailed bonding analyses reveal weak π aromaticity in boronyl boroxine, rendering it a true analog to boroxine and borazine. Upon electron attachment, the slightly distorted C2v B6O6(-) (2, (2)A2) anion is also perfectly planar, and its electronic properties are calculated. A huge energy gap (4.83 eV) is predicted for B6O6(-) (2) at B3LYP level, which is characteristic of a stable closed-shell neutral cluster. Similar to benzene, boronyl boroxine is also predicted to be an effective inorganic ligand to form sandwich-type complexes, such as D3d [B3O3(BO)3]2Cr (4, (1)Ag).


Assuntos
Benzeno/química , Compostos de Boro/química , Teoria Quântica
17.
J Mol Model ; 19(8): 3219-24, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23636641

RESUMO

A density functional theory (DFT) investigation into the structures and bonding characteristics of [(B3O3H3)nM](+)(n = 1, 2;M = Cu, Ag, Au) complexes was performed. DFT calculations and natural bond orbital (NBO) analyses indicate that the ΙB metal complexes of boroxine exhibit intriguing bonding characteristics, different from the typical cation-π interactions between ΙB metal-cations and benzene. The complexes of [B3O3H3M](+) and [(B3O3H3)2 M](+) (M = Cu, Ag, and Au) favor the conformation of perfectly planar structures with the C2v and D2h symmetry along one of the threefold molecular axes of boroxine, respectively. Detailed natural resonance theory (NRT) and canonical molecular orbitals (CMOs) analyses show that interaction between the metal cation and the boroxine in [B3O3H3M](+) (M = Cu, Ag, and Au) is mainly ionic, while the ΙB metal-cations←π donation effect is responsible for the binding site. In these complexes, boroxine serves as terminals η(1)-B3O3H3 with one O atom of the B3O3 ring. The infra-red (IR) spectra of [B3O3H3M](+) were simulated to facilitate their future experimental characterization. The complexes all give two IR active modes at about 1,300 and 2,700 cm(-1), which are inactive in pure boroxine. Simultaneously, the B-H stretching modes of the complexes are red-shifted due to the interaction between the metal-cation and boroxine. To explore the possibility of the structural pattern developed in this work forming mesoporous materials, complexes [(B3O3H3M)6](6+) (M = Cu, Ag, and Au) were also studied, which appear to be unique and particular interesting: they are all true minima with D6h symmetries and pore sizes ranging from 12.04 Å to 13.65 Å.


Assuntos
Compostos de Boro/química , Complexos de Coordenação/química , Cobre/química , Ouro/química , Prata/química , Modelos Químicos , Teoria Quântica , Espectrofotometria Infravermelho
18.
Phys Chem Chem Phys ; 14(43): 14769-74, 2012 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-22678105

RESUMO

Based upon comprehensive theoretical investigations and known experimental observations, we predict the existence of the double-chain planar D(2h) B(4)H(2)(1), C(2h) B(8)H(2)(3), and C(2h) B(12)H(2)(5) which appear to be the lowest-lying isomers of the systems at the density functional theory level. These conjugated aromatic borenes turn out to be the boron hydride analogues of the conjugated ethylene D(2h) C(2)H(4)(2), 1,3-butadiene C(2h) C(4)H(6)(4), and 1,3,5-hexatriene C(2h) C(6)H(8)(6), respectively, indicating that a B(4) rhombus in B(2n)H(2) borenes (n = 2, 4, 6) is equivalent to a C=C double bond unit in the corresponding C(n)H(n+2) hydrocarbons. Detailed canonical molecular orbital (CMO), adaptive natural density partitioning (AdNDP), and electron localization function (ELF) analyses unravel the bonding patterns of these novel borene clusters and indicate that they are all overall aromatic in nature with the formation of islands of both σ- and π- aromaticity. The double-chain planar or quasi-planar C(2v) B(3)H(2)(-)(7), C(2) B(5)H(2)(-)(8), and C(2h) B(6)H(2)(9) with one delocalized π orbital, C(2v) B(7)H(2)(-)(10), C(2) B(9)H(2)(-)(11), and C(2h) B(10)H(2)(12) with two delocalized π orbitals, and C(2v) B(11)H(2)(-)(13) with three delocalized π orbitals are found to be analogous in π-bonding to D(2h) B(4)H(2)(1), C(2h) B(8)H(2)(3), and C(2h) B(12)H(2)(5), respectively. We also calculated the electron affinities and ionization potentials of the neutrals and simulated the photoelectron spectroscopic spectra of the monoanions to facilitate their future experimental characterization. The results obtained in this work enrich the analogous relationship between hydroborons and their hydrocarbon counterparts and help to understand the high stability of the theoretically predicted all-boron nanostructures which favor the formation of double-chain substructures.

19.
Curr Microbiol ; 65(3): 304-12, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22674174

RESUMO

Xanthomonas axonopodis pv. citri (Xac) is the causal agent of citrus bacterial canker, an economically important disease to world citrus industry. To monitor the infection process of Xac in different citrus plants, the enhanced green florescent protein (EGFP) visualizing system was constructed to visualize the propagation and localization in planta. First, the wild-type Xac was isolated from the diseased leaves of susceptible 'Bingtang' sweet orange, and then the isolated Xac was labeled with EGFP by triparental mating. After PCR identification, the growth kinetics and pathogenicity of the transformants were analyzed in comparison with the wild-type Xac. The EGFP-labeled bacteria were inoculated by spraying on the surface and infiltration in the mesophyll of 'Bingtang' sweet orange leaves. The bacterial cell multiplication and diffusion processes were observed directly under confocal laser scanning microscope at different intervals after inoculation. The results indicated that the EGFP-labeled Xac releasing clear green fluorescence light under fluorescent microscope showed the infection process and had the same pathogenicity as the wild type to citrus. Consequently, the labeled Xac demonstrated the ability as an efficient tool to monitor the pathogen infection.


Assuntos
Citrus sinensis/microbiologia , Proteínas de Fluorescência Verde/química , Doenças das Plantas/microbiologia , Xanthomonas axonopodis/química , Xanthomonas axonopodis/patogenicidade , Análise de Variância , Citrus sinensis/química , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Folhas de Planta/química , Folhas de Planta/microbiologia , Xanthomonas axonopodis/genética , Xanthomonas axonopodis/metabolismo
20.
J Mol Model ; 18(7): 3161-7, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22231982

RESUMO

Based upon extensive density functional theory and wave function theory calculations performed in this work, we predict the existence of the perfectly planar triangle C(3h) B(6)H(3)(+) (1, (1)A') and the double-chain stripe C(2h) B(8)H(2) (9, (1)A(g)) which are the ground states of the systems and the inorganic analogues of cyclopropene cation D(3h) C(3)H (3) (+) and cyclobutadiene D(2h) C(4)H(4), respectively. Detailed adaptive natural density partitioning (AdNDP) analyses indicate that C(3h) B(6)H (3) (+) is π plus σ doubly aromatic with two delocalized π-electrons and six delocalized σ-electrons formally conforming to the 4n + 2 aromatic rule, while C(2h) B(8)H(2) is π antiaromatic and σ aromatic with four delocalized π-electrons and ten delocalized σ-electrons. The perfectly planar C(2h) B(8)H(4) (5, (1)A(g)) also proves to be π antiaromatic analogous to D(2h) C(4)H(4), but it appears to be a local minimum about 50 kJ mol(-1) less stable than the three dimensional C(s) B(8)H(4)(6, (1)A'). AdNDP, nucleus independent chemical shifts (NICS) and electron localization function (ELF) analyses indicate that these boron hydride clusters form islands of both σ- and π-aromaticities and are overall aromatic in nature in ELF aromatic criteria.


Assuntos
Boranos/química , Modelos Químicos , Modelos Moleculares
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