Synthesis,characterization, and solution properties of some new organotellurium compounds based on di(cyclohexylmethyl)telluride

A new series of organotellurium(IV) compounds based on di(cyclohexylmethyl)telluride ( 1 ) (i.e., (C₆H₁₁CH₂)₂TeX₂ and (C₆H₁₁CH₂)₂Te(R)X) was prepared by the reaction of compound 1 with halogens, N‐bromosuccinimide, and alkyl halides. Phenylation of (C₆H₁₁CH₂)₂TeX₂ with sodium tetraphenylborate gave di(cyclohexylmethyl)phenyltelluronium tetraphenylborate in good yield. Conductivity measurements in dimethylsulfoxide (DMSO) showed a considerable ionic character of these compounds and they behave as 1:1 electrolytes. ¹H NMR studies in CDCl₃ solution indicated that telluronium salts employed in this study are unstable toward reductive elimination. Reaction of di(cyclohexylmethyl)telluride, (C₆H₁₁CH₂)₂Te(CH₃)I, and (C₆H₁₁CH₂)₂Te(PhCH₂)Br with HgX₂ (X = Cl or Br) afforded 1:1 complexes. All compounds were characterized by elemental analyses and spectroscopic data. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:93–99, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20240     

碳酸氢盐活化的过氧化氢：一种有机废水处理的新技术

水污染问题已成为影响我国可持续发展的关键问题之一,为有效提高现有污水处理的效率及其回收利用,各种催化氧化技术受到了广泛的关注。目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制。因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注。
　　最近几年,利用碳酸氢盐活化过氧化氢,应用于有机废水的降解逐渐受到环境催化领域的关注。碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质,通过它活化过氧化氢产生过碳酸氢盐氧化剂,该氧化剂能够直接氧化有机物。同时,在各种过渡金属催化剂的存在下,通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等) 及高价态的过渡金属离子参与有机废水的降解。虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利,原因是认为它们能捕捉羟基自由基,形成氧化能力更低的碳酸根自由基。现有的研究已充分表明,较低浓度的碳酸氢盐能够加快有机废水的氧化降解,而且通常比单独使用过氧化氢效率更高,这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解。更为重要的是,在微量碳酸氢盐的存在下,其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命。该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战,原因是随着氧化降解的进行,废水体系由于有机酸的生成而逐渐酸化,进而引发氧化物催化剂的酸溶而流失。在这点上,碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势。
　　本文即是在本课题组工作基础上,对该领域内国内外研究进展加以总结,以期获得国内外同行的进一步关注。综述的主要内容包括：(1)碳酸氢氧活化过氧化氢的相关知识介绍,(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展,(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展,和(4)碳酸氢盐在其他高级氧化技术中的应用。虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段,还有很多基础科学问题如降解机理等值得进一步探索,期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解,进而推动该研究方向的发展,为有机废水的催化处理提供新的机会。     

Synthesis and reactions of 3-thioxo[1,2,4]-triazino[3,2-b]quinazolin-10-ones

Thiation of [1,2,4]triazino[3,2-b]quinazoline-3,10-dione 1 proceeds selectively to give the 3-thioxo-analog 3 . The latter was converted to the corresponding 3-methylthio derivative 4 which was reacted with aniline and hydrazine to give the corresponding anilino- and hydrazino derivatives 5 and 7 . Compound 7 was converted to the hydrazones 8a,b and into the novel heterocyclic ring systems [1,2,4]triazolo[4′,3′:4,5][1,2,4]triazino-[3,2-b]quinazolin-7-ones 9, 10a,b and tetrazolo[1′,5′:4,5][1,2,4]triazino[3,2-b]quinazolin-7-one 11 .     

Phytochemical investigation and hepatoprotective activity of Cupressus sempervirens L. leaves growing in Egypt

Three phenolic compounds cosmosiin, caffeic acid, and p-coumaric acid were isolated for the first time from the leaves of Cupressus sempervirens L., together with cupressuflavone, amentoflavone, rutin, quercitrin, quercetin, myricitrin. The isolated compounds were identified using (1)H- and (13)C-NMR spectra. The hepatoprotective activity of the MeOH extract was carried out in liver homogenate of normal and CCl(4)-treated rats; a significant decrease in glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, cholesterol level, and triglycerides, while a significant increase in the total protein level, was observed after the oral administration of MeOH extract. The free radical scavenging activity against stable 2,2-diphenyl-2-picrylhydrazyl (DPPH*) was measured for MeOH extract and some of the isolated phenolic compounds in comparison with alpha-tocopherol and butylated hydroxy toluene as standard antioxidants using ESR technique, showed high antioxidant activity for quercetin, rutin, caffeic acid, and p-coumaric acid.     

Inhibition of UVB-mediated oxidative stress and markers of photoaging in immortalized HaCaT keratinocytes by pomegranate polyphenol extract POMx

In recent years there has been an increase in use of botanicals with antioxidant properties as skin photoprotective agents. Pomegranate (Punica granatum L.) fruit possesses strong antioxidant and antiinflammatory properties. Recently, we have shown that pomegranate-derived products rich in anthocyanidins and ellagitannins inhibit UVB-mediated activation of nuclear factor kappa B and modulate UVA-mediated cell proliferation pathways in normal human epidermal keratinocytes. In this study, we evaluated the effect of polyphenol-rich pomegranate fruit extract (POMx) on UVB-induced oxidative stress and photoaging in human immortalized HaCaT keratinocytes. Our data show that pretreatment of HaCaT cells with POMx (10-40 microg mL(-1)) inhibited UVB (15-30 mJ cm(-2))-mediated (1) decrease in cell viability, (2) decrease in intracellular glutathione content and (3) increase in lipid peroxidation. Employing immunoblot analysis we found that pretreatment of HaCaT cells with POMx inhibited UVB-induced (1) upregulation of MMP-1, -2, -7 and -9, (2) decrease in TIMP-1, (3) phosphorylation of MAPKs and (iv) phosphorylation of c-jun, whereas no effect was observed on UVB-induced c-fos protein levels. These results suggest that POMx protects HaCaT cells against UVB-induced oxidative stress and markers of photoaging and could be a useful supplement in skin care products.     

Lower homologues (methyl, ethyl) of diorganotin derivatives of germyl (substituted) propanoic acids: spectroscopic elucidations and biological studies

Some novel lower homologues of diorganotin derivatives of germyl substituted propanoic acids with general formula [Ar(3)GeCH(R(1))CH(R(2))COO](2)SnR(2)(3), where Ar = p-CH(3)C(6)H(4), C(6)H(5), R(1) = p-CH(3)C(6)H(4), p-CH(3)OC(6)H(4), o-CH(3)OC(6)H(4), C(6)H(5), R(2) = H, CH(3), R(3) = CH(3), C(2)H(5) have been prepared by the condensation reaction of dialkyltin oxide and triarylgermyl(substituted) propanoic acid in 1 : 2 M ratio, respectively, and were characterized by IR, multinuclear ((1)H, (13)C, (119)Sn) NMR, (119 m)Sn M?ssbauer spectroscopy. The synthesized compounds were also screened for their toxicity and possible antibacterial, antifungal activities and found some encouraging results.     

Asymmetric synthesis of mono- and dinuclear bis(dipyrrinato) complexes

The diastereoselective syntheses of Zn(II) bis(dipyrrinato) helicates is reported, involving ligands templated by the incorporation of homochiral binol within the linker joining the two dipyrrinato units. The most diastereoselective formation of dinuclear bis(dipyrrinato) helicates to date is reported. The formation of either mononuclear or dinuclear helicates can be tuned by varying the length of the linker between the dipyrrinato units and by varying the complexation procedure. The neutral dipyrrinato helicates were readily analyzed by HPLC to ascertain diastereoselectivity, and circular dichroism studies revealed the helical nature of the complexes. The molar ellipticities of the helicates produced by diastereoselective complexation are very large in the visible region and typically correspond to binol moieties in the UV region. Extensive X-ray crystallographic investigations further confirmed the helicity of the mononuclear Zn(II) helicates and identified significant interlayer displacement and bending within crystals.     

Differential scanning calorimetry and Fourier transform infrared spectroscopic studies of phospholipid organization and lipid-peptide interactions in nanoporous substrate-supported lipid model membranes

High-sensitivity differential scanning calorimetry was utilized to examine whether lipids capable of forming an inverted nonlamellar hexagonal II (HII) phase can be deposited into nanoporous substrate-supported arrays. Particularly, we compare the thermotropic phase properties of nanoconfined unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine lipid bilayers with unsupported dispersions to assess nanoconfinement effects, focusing on the lamellar fluid (Lalpha) to HII phase transition. Experimental results provide direct and clear evidence for the formation of an HII phase upon both heating and cooling. However, a small shift in the Lalpha/HII phase transition temperature, as well as an increase in the magnitude of the associated temperature hysteresis, was observed in the nanoporous substrate-supported system. Additionally, nanoconfinement effects on the interaction and location of the antimicrobial peptide gramicidin S (GS) with nanoporous substrate-supported cardiolipin bilayers were examined by Fourier transform infrared spectroscopy as a function of temperature and phospholipid phase state. Upon heating, GS molecules began to insert into nanoconfined, substrate-supported cardiolipin bilayers at lower temperatures relative to the gel/liquid-crystalline phase transition temperature than into unsupported bilayers. The reduction in the polarity and hydrogen-bonding potential environment of GS in the Lalpha state suggests that GS is located at the polar/apolar interfacial region in both supported and unsupported cardiolipin bilayers and that the capacity of GS to interact with nanoporous substrate-supported cardiolipin bilayers was not significantly hindered by nanoconfinement. These studies further demonstrate the usefulness of supported lipid bilayers inside nanoporous substrates.     

Leading RNA tertiary interactions: structures, energies, and water insertion of A-minor and P-interactions. A quantum chemical view

Complex molecular shapes of ribosomal RNA molecules are stabilized by recurrent types of tertiary interactions involving highly specific and conserved non-Watson-Crick base pairs, triplets, and quartets. We analyzed the intrinsic structure and stability of the P-motif and the four basic types of A-minor interactions (types I, II, III, and 0), which represent the most prominent RNA tertiary interaction patterns refined in the course of evolution. In the studied interactions, the electron correlation component of the stabilization usually exceeds the Hartree-Fock (HF) term, leading to a strikingly different balance of forces as compared to standard base pairing stabilized primarily by the HF term. In other words, the A-minor and P-interactions are considerably more influenced by the dispersion energy as compared to canonical base pairs, which makes them particularly suitable to zip the folded RNA structures that are substantially hydrated even in their interior. Continuum solvent COSMO calculations confirm that the stability of the canonical GC base pair is affected (reduced) by the continuum solvent screening considerably more than the stability of the A-minor interaction. Among the studied systems, the strong A-minor II and weak A-minor III interactions require water molecules to stabilize the experimental geometry. Gas-phase optimization of the canonical A-minor II A/CG triplet without water results in a geometry that is clearly inconsistent with the RNA structure. The gas-phase structure of the P-interaction and the most stable A-minor I interaction nicely agrees with the geometries occurring in the ribosome. A-minor I can also adopt an alternative water-mediated substate rather often observed in X-ray and molecular dynamics studies. The A-minor I water bridge, however, does not appear to stabilize the tertiary contact, and its role is to provide structural flexibility to this binding pattern within the context of the RNA structure. Interestingly, the insertion of a polar water molecule in the A-minor I A/CG tertiary contact occurring in the A/C tertiary pair is stabilized primarily by the HF (electrostatic) interaction energy, while the dispersion-controlled A/G contact remains firmly bound. Thus, the intrinsic balance of forces as revealed by quantum mechanics (QM) calculations nicely correlates with many behavioral aspects of the studied interactions inside RNA. The comparison of interaction energies computed using quantum chemistry and an AMBER force field reveals that common molecular mechanics calculations perform rather well, except that the strength of the P-interaction is modestly overestimated. We also briefly discuss the non-negligible methodological differences when evaluating simple base-base nucleic acids base pairs and the complex RNA tertiary base pairing patterns using QM procedures.     

Thermocapillary convection in double-layer fluid structures within a two-dimensional open cavity

Thermocapillary convection within a differentially-heated open rectangular cavity containing two immiscible liquid layers is considered in the absence of gravitational effects. The temperature and flow fields in the two layers are computed using domain mapping in conjunction with a finite-difference scheme on a staggered grid. The melt-encapsulant and air-encapsulant interfaces are allowed to deform, with the contact lines pinned on the solid boundaries. The presence of a free surface at the top leads to increased convection in the encapsulant phase while retarding thermocapillary flow in the melt. The intensity of thermocapillary convection in the encapsulated layer is reduced as the viscosity of the encapsulant is increased or the thickness of the encapsulant layer is decreased. Choosing an encapsulant with a greater sensitivity of interfacial tension to temperature (as compared to that of the melt phase) can almost completely suppress thermocapillary convection in the melt. Deformations of the melt-encapsulant interface in an open cavity are found to be larger than those in a closed cavity with a rigid top surface, due to higher pressure gradients realized in the encapsulant phase. In contrast to interface deformation behavior reported earlier for a double-layer system in a closed cavity, the shape of the melt-encapsulant interface is qualitatively similar for all values of the viscosity ratio, with the interface dipping into the melt near the cold wall, and into the encapsulant near the hot wall. For the double-layers considered in this study, a free surface at the top of the encapsulant layer was found to be more effective than a rigid top in reducing the intensity of thermocapillary convection in the melt.