期刊：
JOURNAL OF ORGANIC CHEMISTRY,2004年69(19):6157-6164 ISSN：0022-3263
通讯作者：
Isaacs, L
作者机构：
[Isaacs, L] Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA.;Cent China Normal Univ, Coll Chem, Hubei 430079, Peoples R China.
通讯机构：
[Isaacs, L] U;Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA.
摘要：
Self-sorting-the ability to efficiently distinguish between self and nonself-is common in nature but is still relatively rare in synthetic supramolecular systems. We report a 12-component mixture comprising 1-11 and KCl that undergoes thermodynamically controlled self-sorting in aqueous solution based on metal-ligand, ion-dipole, electrostatic, charge-transfer interactions, as well as the hydrophobic effect. We refer to this molecular ensemble-characterized by high-fidelity host-guest interactions between components-as a social self-sorting system to distinguish it from narcissistic self-sorting systems based on self-association processes. The influence of several key variables-temperature, pH, concentration, and host/guest stoichiometry-was explored by a combination of simulation and experiment. Variable temperature NMR experiments, for example, revealed a kinetically controlled irreversible process upon cycling from 298 to 338 K, which is an emergent property of this molecular ensemble. Variable pH and concentration experiments, in contrast, did not reveal any emergent properties of the molecular ensemble. Simulations of a four-component mixture establish that by proper control of the relative magnitude of the various equilibrium constants, it is possible to prepare socially self-sorted mixtures that are responsive (irresponsive) to host/guest stoichiometry over narrow (broad) ranges. The 12-component mixture is relatively irresponsive to host/guest stoichiometry. Such social self-sorting systems, like their natural counterparts, have potential applications as chemical sensors, as artificial regulatory elements, and in the preparation of biomimetic systems.
作者机构：
[Lu, GH] Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.;Caohu Coll, Dept Chem, Anhui 238000, Peoples R China.
通讯机构：
[Lu, GH] C;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
摘要：
A chemically modified electrode based on a chitosan-multiwall carbon nanotube (MWNT) coated glassy carbon electrode (GCE) is described, which exhibits an attractive ability to determine dopamine (DA) and ascorbic acid (AA) simultaneously. The modified electrode exhibited a high differential pulse voltammetry (DPV) current response to DA at 0.144 V and AA at -0.029 V (vs. SCE) in a 0.1 mol l-1 phosphate buffer solution (pH = 7.2). The properties and behaviors of the chitosan-multiwall carbon nanotube modified electrode (MC/GCE) were characterized using cyclic voltammetry (CV) and DPV methods. The mechanism for the discrimination of dopamine from ascorbic acid at MC/GCE is discussed. The linear calibration range for DA and AA were 5 × 10-7 mol l-1 to 1 × 10-4 mol l -1 (r = 0.997), and 5 × 10-6 mol l-1 to 1 × 10-3 mol l-1 (r = 0.996), respectively. The MC/GCE showed good sensitivity, selectivity and stability.
期刊：
JOURNAL OF ORGANIC CHEMISTRY,2004年69(24):8451-8458 ISSN：0022-3263
通讯作者：
Zhan, CG
作者机构：
[Zhan, CG] Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.;Univ Kentucky, Coll Pharm, Dept Pharmaceut Sci, Lexington, KY 40536 USA.
通讯机构：
[Zhan, CG] C;Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.
摘要：
Reaction pathways and free energy barriers for alkaline hydrolysis of the highly neurotoxic insecticide 2-trimethylammonioethyl methylphosphonofluoridate and related organophosphorus compounds were studied by performing first-principles electronic structure calculations on representative methylphosphonofluoridates, (RO)CH3P(O)F, in which R = CH2CH2N+(CH3)(3), CH3, CH2CH2C(CH3)(3), CH2CH2CH(CH3)(2), CH(CH3)CH2N+(CH3)(3), and CH(CH3)CH2N(CH3)(2). The dominant reaction pathway was found to be associated with a transition state in which the attacking nucleophile OH- and the leaving group F- are positioned on opposite sides of the plane formed by the three remaining atoms attached to the phosphorus in order to minimize the electrostatic repulsion between these two groups. The free energy barriers calculated for the rate-determining step of the dominant pathway are 12.5 kcal/mol when R = CH2CH2N+(CH3)(3), 15.5 kcal/mol when R = CH3, 17.9 kcal/mol when R = CH2CH2C(CH3)(3), 16.5 kcal/mol when R = CH2CH2CH(CH3)(2), 13.4 kcal/mol when R = CH(CH3)CH2N+(CH3)(3), and 18.7 kcal/mol when R = CH(CH3)CH2N(CH3)(2). The calculated free energy barriers are in good agreement with available experimentally derived activation free energies, i.e. 14.7 kcal/mol when R = CH3, 13.4 kcal/mol when R = CH2CH2N+(CH3)(3), and 13.9 kcal/mol when R = CH(CH3)CH2N+(CH3)(3). A detailed analysis of the calculated energetic results and available experimental data suggests that the net charge of the molecule (M) being hydrolyzed is a prominent factor affecting the free energy barrier (DeltaG) for the alkaline hydrolysis of phosphodiesters, phosphonofluoridates, and related organophosphorus compounds. The electrostatic interactions between the attacking nucleophile OH- and the molecule M being hydrolyzed favor such an order of the free energy barrier: DeltaG(M++OH-) < DeltaG(M-0+OH-) < DeltaG(M-+OH-), where M+, M-0, and M- represent the cationic, neutral, and anionic molecules, respectively. The change of the substituent R in (RO)CH3P(O)F from CH3 to CH2CH2N+(CH3)(3) is associated with both the electrostatic and steric effects on the free energy barrier, but the electrostatic effect dominates the substituent shift of the free energy barrier. This helps to better understand why the alkaline hydrolysis of (RO)CH3P(O)F with R = CH2CH2N+(CH3)(3) and CH(CH3)CH2N+(CH3)(3) is significantly faster than that with R = CH3. The effect of electrostatic interaction also helps to understand why the rate constants for the alkaline hydrolysis of phosphodiesters, such as intramolecular second messenger adenosine 3',5'-phosphate (cAMP), are generally smaller than those for the alkaline hydrolysis of the phosphonofluoridates and related phosphotriesters.
期刊：
Journal of Pharmaceutical and Biomedical Analysis,2004年34(2):247-254 ISSN：0731-7085
通讯作者：
Liu, ML
作者机构：
[Cui, YF] State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, PR China
通讯机构：
[Liu, ML ] ;Chinese Acad Sci, Wuhan Inst Phys & Math, State Key Lab Magnet Resonance & Atom & Mol Phys, Wuhan 430071, Peoples R China.
关键词：
NMR spectroscopy;H-1 relaxation rate;competitive binding;ibuprofen;salicylic acid;human serum albumin
摘要：
The competitive binding of two ligands, ibuprofen (IBP) and salicylic acid (SAL), to human serum albumin (HSA) was studied by using nuclear magnetic resonance (NMR) relaxation measurements. When the concentration of one ligand was increased in the solution containing IBP, SAL and HSA, the fractions of free IBP and SAL were increased because of the competitive binding. The 1H relaxation rates (R1) of both ligands were subsequently decreased. If a ligand is in fast exchanging between the free and bound forms, the observed 1H relaxation rate is a weighted average of that for the free ligand and the protein-ligand complex. The concentrations of the free and bound ligands can be quantitatively derived from the relaxation rates. The results presented in this work revealed that IBP and SAL shared certain low-affinity binding sites on the HSA molecule, in addition to the same high-affinity binding site of AIII.
期刊：
JOURNAL OF ORGANIC CHEMISTRY,2004年69(24):8366-8371 ISSN：0022-3263
通讯作者：
Ding, MW
作者机构：
[Zhao, JF; Xu, SZ; Ding, MW] Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.
通讯机构：
[Ding, MW] C;Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.
摘要：
The bis(carbodiimides) 4, obtained from bis-aza-Wittig reactions of bis(iminophosphorane) 3 with 2 equiv of aromatic isocyanates, were reacted with secondary amine to give symmetrically substituted 2,7-diaminothieno[2,3-d:5,4-d']dipyrimidine-4,5(3H,6H)-dione 6 in the presence of a catalytic amount of EtO(-)Na(+). Reactions of 4 with phenols or ROH in the presence of a catalytic amount of potassium carbonate or RO(-)Na(+) gave symmetrically substituted 2,7-diaryl(alkyl)oxythieno[2,3-d:5,4-d']dipyrimidine-4,5(3H,6H)-diones 6 in satisfactory yields. However, iminophosphoranes 9 were obtained via reaction of bis(iminophosphorane) 3 with 1 equiv of aromatic isocyanate and subsequent reaction with an amine in the presence of a catalytic amount of EtO(-)Na(+). Further reaction of iminophosphoranes 9 with aromatic isocyanates and various nucleophile generated unsymmetrically substituted thieno[2,3-d:5,4-d']dipyrimidine-4,5(3H,6H)-diones 12 in good yields.
摘要：
The crystal structure and catecholase-like activity of a mononuclear complex, Cu(EDTB)(NO3)(2) (.) C2H5OH (here EDTB stands N,N,N',N'-tetrakis(2'-benzimidazolyl methyl)-1,2-ethanediamine) has been studied in comparison with a binuclear complex Cu-2(EDTB)(NO3)(4) (.) 3H(2)O. The results show that the reactive rate constants increase with increases of reaction temperature and pH value of intermediate. Electrospray ionization mass spectrum (ESI-MS) shows that tautomerism isomers of catechol with the title complex exist in reaction solution, and catechol is oxidized to quinone, then it is further oxidized resulting in muconic acid and its derivatives via an intradiol mechanism, just like that catalyzed by a mononuclear non-heme iron-containing dioxygenase. (C) 2004 Elsevier Inc. All rights reserved.
期刊：
Journal of Computational Chemistry,2004年25(15):1827-1832 ISSN：0192-8651
通讯作者：
Wan, J
作者机构：
[Zhang, L; Wan, J; Yang, GF] Cent China Normal Univ, Coll Chem, Minist Educ, CCNU, Wuhan 430079, Peoples R China.
通讯机构：
[Wan, J] C;Cent China Normal Univ, Coll Chem, Minist Educ, CCNU, Wuhan 430079, Peoples R China.
关键词：
density functional theory;quantitative structure-activity relationships;inhibitors
摘要：
The equilibrium geometries, electronic structures, and electrostatic potentials of a series of substituted phenyl triazolinones of protoporphyrinogen oxidase (PPO) inhibitors have been investigated by using the density functional theory (DFT) method. The quantum chemical descriptors, highest occupied molecular orbital and lowest unoccupied molecular orbital energy gap (DeltaE), weighted electrophilic, and nucleophilic atomic frontier electron density (FAE and FAN), and net atomic charge (QA), were computed at the same DFT level. Based on these precise quantum chemical descriptors, a quantitative structure-activity relationships study has been carried out and shown that QC11, FN5E, FC10N, and DeltaE of individual molecules are most likely to be responsible for the in vitro biological activity and greenhouse preemergence activity of phenyl triazolinones. The ability to quite accurately predict the biological activity of phenyl triazolinones by using DFT-based QSAR can be expected to help facilitate the design of additional substituted phenyl triazolinones as PPO inhibitors with good biological activity.
期刊：
Journal of Chemical Information and Modeling,2004年44(6):2099-2105 ISSN：1549-9596
通讯作者：
Yang, GF
作者机构：
[Yang, GF] Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.;Univ Kentucky, Coll Pharm, Dept Pharmaceut Sci, Lexington, KY 40536 USA.
通讯机构：
[Yang, GF] C;Cent China Normal Univ, Coll Chem, Key Lab Pesticide & Chem Biol, Minist Educ, Wuhan 430079, Peoples R China.
摘要：
This study examined the applicability of various density functional theory (DFT)-based descriptors, such as energy gap (ΔE) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), weighted nucleophilic atomic frontier electron density (WNAFED, F <inf>i</inf><sup>N</sup>), mean molecular polarizability (α), and net atomic charge (Q<inf>i</inf>), in quantitative structure-activity relationship (QSAR) studies on a class of important protoporphyrinogen oxidase (Protox) inhibitors including a series of cyclic imide derivatives with various heterocyclic rings and substituents. Our QSAR analysis using the quantum chemical descriptors calculated at the B3LYP/6-31G(d,p) level led to a useful explicit correlation relationship, i.e. pI<inf>50</inf> = -5.7414 + 0.1424α- 0.0003α<sup>2</sup> - 0.4546F<inf>C.</inf><sup>N</sup> + 0.2974Q<inf>N.</inf> (n=26, R<sup>2</sup>=0.87), showing that descriptors mean molecular polarizability, α, and WNAFED F<inf>C.</inf><sup>N</sup> of a critical carbon atom and net atomic charge (Q<inf>i</inf>) in the molecules are most likely responsible for the in vitro biological activity of cyclic imides. It has been shown that the use of the DFT-based quantum chemical descriptors indeed led to a better QSAR equation than that obtained from the use of the corresponding descriptors calculated at a semiempirical PM3 level. The present work demonstrates that the DFT-based quantum chemical descriptors are potentially useful in the future QSAR studies for quantitatively predicting biological activity, and, therefore, the DFT-based QSAR approach could be expected to help facilitate the design of additional substituted cyclic imide derivatives of Protox inhibitors with the potentially higher biological activity.
期刊：
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,2004年126(32):10035-10043 ISSN：0002-7863
通讯作者：
Isaacs, L
作者机构：
[Isaacs, L] Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA.;Cent China Normal Univ, Coll Chem, Wuhan 430079, Peoples R China.
通讯机构：
[Isaacs, L] U;Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA.
摘要：
We report the synthesis and characterization of eight C-shaped methylene-bridged glycoluril dimers (1-8) bearing hydrogen-bonding amide groups on their aromatic rings. Compounds 1-6 undergo tight dimerization in CDCl <inf>3</inf> solution (K<inf>s</inf> >9 ×10<sup>5</sup> M <sup>-1</sup>);binary mixtures of 1-7 form mixtures of homodimers and heterodimers in moderately selective dimerization processes (0.23 &le K <inf>eq</inf> &le 768;0.253 &le χAB <0.933). The high affinity formation of 1·1-6·6 is due to the commensurate nature of the geometrical constraints imposed by the π-πinteractions and only two hydrogen bonds. The differential response of the strengths of the π-πinteractions and H-bonds of 2·2 to changes in solvent polarity-from C<inf>6</inf>D<inf>6</inf> to D<inf>2</inf>O-results in the formation of a solvent-independent isostructural aggregate that exhibits high affinity dimerization across the full range of solvents.
作者机构：
[Cao, YC; Liu, MX; Huang, GL] School of Life Science and Technology, Huazhong University of Science and Technology (East Campus), 1037 Luoyu Lu, Wuhan, 430074, China;[Mei, XY] School of Chemistry, Central China Normal University, 100 Luoyu Lu, Wuhan, 430079, China
通讯机构：
[Huang, GL ] ;Huazhong Univ Sci & Technol, Sch Life Sci & Technol, East Campus,1037 Luoyu Lu, Wuhan 430074, Peoples R China.
