Decompaction of cationic gemini surfactant-induced DNA condensates by beta-cyclodextrin or anionic surfactant

Compaction of DNA by cationic gemini surfactant hexamethylene-1,6-bis-(dodecyldimethylammoniumbromide) (C12C6C12Br2) and the subsequent decompaction of the DNA-C12C6C12Br2 complexes by beta-cyclodextrin (beta-CD) or sodium dodecyl sulfate (SDS) have been studied by using zeta potential and particle size measurements, atomic force microscopy (AFM), isothermal titration microcalorimetry (ITC), and circular dichroism. The results show that C12C6C12Br2 can induce the collapse of DNA into densely packed bead-like structures with smaller size in an all-or-none manner, accompanied by the increase of zeta potential from highly negative values to highly positive values. In the decompaction of the DNA-C12C6C12Br2 complexes, beta-CD and SDS exhibit different behaviors. For beta-CD, the experimental results suggest that it can remove the outlayer hydrophobically bound C12C6C12Br2 molecules from the DNA-C12C6C12Br2 complexes by inclusion interaction, and the excess beta-CD may attach on the complexes by forming inclusion complexes with the hydrocarbon chains of the electrostatically bound C12C6C12Br2 that cannot be removed. The increase of steric hindrance due to the attachment of beta-CD molecules results in the decompaction of the DNA condensates though the true release of DNA cannot be attained. However, for SDS, the experimental results suggest that it can realize the decompaction and release of DNA from its complexes with C12C6C12Br2 due to both ion-pairing and hydrophobic interaction between SDS and C12C6C12Br2.     

杂元素冠醚研究(Ⅻ)──氧、硫、硒和碲杂冠醚的液膜迁移性能比较

报道了碲杂冠醚(TeB15C5)对Na⁺、K⁺、Ag⁺和Pb²⁺的液膜迁移能力,并与相应的全氧冠醚(B15C5)、硫杂冠醚(SB15C5)和硒杂冠醚(SeB15C5)作了比较;同时以SeB15C5对K⁺的迁移为例考察了冠醚浓度和盐浓度对迁移速率的影响,结果表明,TeB15C5对Na⁺、K⁺和Pb²⁺的迁移能力比SB15C5和SeB15C5强,但对Ag⁺的迁移速率比后两者慢;SeB15C5对Ag⁺的迁移速度比SB15C5快,两者对Ag⁺的选择性都相当高,可以用来分离和回收银等贵重金属。     

Ruthenium(II)‐Catalyzed C−C Arylations and Alkylations: Decarbamoylative C−C Functionalizations

Ruthenium(II)biscarboxylate catalysis enabled selective C−C functionalizations by means of decarbamoylative C−C arylations. The versatility of the ruthenium(II) catalysis was reflected by widely applicable C−C arylations and C−C alkylations of aryl amides, as well as acids with modifiable pyrazoles, through facile organometallic C−C activation.     

含水溶性碳笼烯的水凝胶

含水溶性碳笼烯的水凝胶陈立桅郑磊洪瀚李子臣周锡煌李福绵（北京大学化学系北京１００８７１）关键词水溶性碳笼烯，水凝胶，超氧负离子随着碳笼烯（Ｃ６０，Ｃ７０，ｆｕｌｅｒｅｎｅｓ）的简便制取方法［１］的问世，其应用，特别是其材料化自然被提到日程上来．...     

镧系金属杂—2,3,4,5—四苯基环戊二烯环状化合物的合成及其表征

二苯乙炔和金属锂在乙醚中反应得到1,4-二锂四苯基丁二烯,再与无水氧化希土反应得到了两种系金属条-2,3,4,5-四苯基环戊二烯环状化合物。通过元素分析、红外光谱、核磁共振谱、热失重及电子能谱的分析,对所合成的化合物进行了表征;并对化合物的水解产物作了红外光谱、质谱和核磁共振谱分析,确认下列两种化合物的存在:     

Kemp elimination in membrane mimetic reaction media: probing catalytic properties of catanionic vesicles formed from double-tailed amphiphiles

The rate-determining deprotonation of 5-nitrobenzisoxazole (Kemp elimination) by hydroxide is efficiently catalyzed by vesicles formed from dimethyldioctadecylammonium chloride (C(18)()C(18)()(+)()). Gradual addition of sodium didecyl phosphate (C(10)()C(10)()(-)()) leads to the formation of catanionic vesicles, which were characterized by cryo-electron microscopy, and their main phase transition temperatures (DSC) and zeta-potentials. Increasing percentages of C(10)()C(10)()(-)() in the vesicular bilayers decrease the catalysis of the Kemp elimination. A detailed kinetic analysis, supported by consideration of substrate binding site polarities and counterion binding percentages, suggest that the catalytic effects of C(18)()C(18)()(+)()/C(10)()C(10)()(-)() catanionic vesicles are primarily determined by the binding of catalytically active hydroxide ions to the vesicular surface area. The formation of neutral microdomains between 10 and 30 mol % of C(10)()C(10)()(-)() in the bilayer, as revealed by DSC, is not apparent from the catalytic effects found for these vesicles. Interestingly, the catalytic effects observed for 50 mol % C(10)()C(10)()(-)() in the catanionic vesicles indicate an asymmetric distribution of C(18)()C(18)()(+)() and C(10)()C(10)()(-)() over the bilayer leaflets. The overall kinetic results illustrate the highly complex mix of factors which determines catalytic effects on reactions occurring in biological cell membranes.     

In the first proven SN2' fullerene reaction,both C3 and C1 C60F36 hydrolyse to C1 isomers of C60F35OH that eliminate HF to give epoxides C60F34O; C60F36O oxides are shown to be ethers,and a fourth isomer of C60F36 exists

On standing in organic solvents containing traces of water, C3 and C1 isomers of C60F36 slowly convert to C1 isomers of C60F35OH. Both fluorofullerenols eliminate HF during EI mass spectrometry to give C60F34O epoxides, one fullerenol being much less stable than the other to the extent that the mass spectrum shows only the epoxide. Both C60F35OH isomers have C1 symmetry, one being identified by the remarkable linear relationship between chemical shifts in its 19F NMR spectrum and those in the spectrum of C1 C60F36; the spectrum of the other shows the pattern of C3 C60F36 rendered asymmetrical by the replacement of one F by OH. The reactions are facilitated by the presence of isolated double bonds, and provide the first proven examples of an SN2' reaction of a fullerene derivative. Our observation explains why only a limited number of fluorines are readily replaced in C60F36 and why C60F18 is by contrast much more resistant to hydrolysis. We have isolated also a pure isomer of C60F36O, which is shown to be an oxahomofullerene (ether) apparently derived from C1 C60F36, and an impure fraction comprising a fourth isomer of C60F36, a trifluoromethyl derivative of C60F36, a second isomer of C60F36O, and an unknown species of 1392 u.     

Determination of clethodim and its oxidation metabolites in crops by liquid chromatography with confirmation by LC/MS

A method was developed for determination of the herbicide clethodim (C0) and its oxidation metabolites clethodim sulfoxide (C1) and clethodim sulfone (C2) in agricultural products. Upon extraction, both C0 and C1 were oxidized to C2 by m-chloroperoxybenzoic acid, and C2 was determined by liquid chromatography (LC). The C2 peak was confirmed by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI). Recoveries of C0 from radish, tomato, onion, sweet potato, kidney bean, carrot, cabbage, and lettuce ranged from 91 to 118% following fortification at 0.05-1.0 ppm. The detection limit of C2 in crops was 0.01 ppm (S/N > 3). The fortified samples of onion, sweet potato, kidney bean, and carrot were confirmed by LC/MS (ESI), and the peak of C2 was detected.     

Site‐Selective Remote Radical C−H Functionalization of Unactivated C−H Bonds in Amides Using Sulfone Reagents

A general and practical strategy for remote site‐selective functionalization of unactivated aliphatic C?H bonds in various amides by radical chemistry is introduced. C?H bond functionalization is achieved by using the readily installed N‐allylsulfonyl moiety as an N‐radical precursor. The in situ generated N‐radical engages in intramolecular 1,5‐hydrogen atom transfer to generate a translocated C radical which is subsequently trapped with various sulfone reagents to afford the corresponding C?H functionalized amides. The generality of the approach is documented by the successful remote C?N₃, C?Cl, C?Br, C?SCF₃, C?SPh, and C?C bond formation. Unactivated tertiary and secondary C?H bonds, as well as activated primary C?H bonds, can be readily functionalized by this method.     

Ar离子束作用下C60薄膜的结构稳定性研究

利用XPS和AES研究了在Ar离子束作用下C60薄膜的分子结构的稳定性．研究发现C60分子与Ar离子束作用后，C1s结合能从284．7eV逐步下降到284．4eV，CKLL俄歇动能从270．0eV增加到271．3eV．并且C60薄膜在与氩离子束作用后，其C60分子结构特征的C1s携上峰及价带峰均消失．表明Ar离子束可以促使C60分子的C＝C双键断裂，离域π键消失，C60分子分解为单质碳．C＝C双键断裂过程与离子束的能量和辐照时间有一定的函数关系．     

Stereoselective synthesis of the C-11 to C-19 segment of macrolactin 3 via a center inversion followed by Oxa-Michael addition approach

An efficient and short stereoselective synthesis of C11–C19 fragment of Macrolactin 3 was achieved. The vic-triol moiety (C15–C17) was derived from the C2–C4 chiral centers of D-mannose. The C-1 of D-mannose was utilized for the Wittig-olefination followed by hydroxylation using hydroboration reaction to introduce C11–C13 carbon chain in the C11–C19 fragment, whereas C5–C6 carbon chain of mannose was converted into C18–C19 of the target by dehydration reactions. Thus, the main strategy was (a) two consecutive Wittig-olefination reactions on C1 carbon of mannose, (b) inversion of C4 stereocenter, and (c) dehydration of C5–C6 vic-diol to olefin to result in the C11–C19 fragment.     

Preparation, characterization, and chemical stability of gold nanoparticles coated with mono-, bis-, and tris-chelating alkanethiols

A systematically varying series of monolayer-protected clusters (MPCs) was prepared by exposing small gold nanoparticles ( approximately 2 nm in diameter) to the following four adsorbates: n-octadecanethiol ( n - C18), 2-hexadecylpropane-1,3-dithiol ( C18C2), 2-hexadecyl-2-methylpropane-1,3-dithiol ( C18C3), and 1,1,1-tris(mercaptomethyl)heptadecane ( t - C18). The resultant MPCs were characterized by solubility studies, UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FT-IR). All of the MPCs were soluble in common organic solvents; moreover, analysis by TEM showed that the core dimensions were unaffected by exposure to any of the adsorbates. Separate studies by XPS revealed that the sulfur atoms in all MPCs were predominantly bound to the surface of gold (i.e., approximately 85% or better). Analysis by FT-IR showed that MPCs functionalized with n - C18 possessed alkyl chains having the greatest conformational order in both the solid-state and dispersed in solution; in contrast, those generated from the other three adsorbates were more liquid-like with reduced conformational order (or crystallinity). The rate of nanoparticle decomposition induced by cyanide ions was monitored by UV-vis spectroscopy. While MPCs functionalized with n - C18 showed the fastest rate of decomposition, those functionalized with C18C3 were the most resistant to decomposition. Overall, the following trend in chemical stability was observed, C18C3 > C18C2 > t - C18 > n - C18.     

Total synthesis of phorboxazole A. 2. Assembly of subunits and completion of the synthesis

[Structure: see text] Subunits of phorboxazole A containing C1-C2, C3-C8, C9-C19, C20-C32, C33-C41, and C42-C46 were connected in a sequence that first linked C32 with C33 and then C41 with C42. A C3-C8 fragment was joined to C9-C19, and the assembled unit was then joined with the left half of 1. Closure of the macrolide was accomplished by esterification of the C24 alcohol followed by intramolecular Horner-Wadsworth-Emmons condensation to set the (E)-C2-C3 alkene.     

C1 C70F38 contains four planar aromatic hexagons; the parallel between fluorination of [60]- and [70]fullerenes

The main C(1) isomer of C(70)F(38) is shown by single-crystal X-ray analysis to contain four planar aromatic hexagons and four isolated C=C bonds, has two fluorines on the equator, and is related to C(2) C(70)F(38) by means of three 1,3-fluorine shifts. The C(1) and C(2) isomers thus parallel the T and C(3)/C(1) isomers of C(60)F(36) in containing three and four aromatic rings, respectively, and in the fluorine shift relationship.     

Structural and magnetic properties of Zn-substituted cobalt ferrites prepared by co-precipitation method

Zn substituted cobalt ferrite spinels with the general formula Zn(x)Co(1-x)Fe(2)O(4) (with x varying from 0 to 0.5) were synthesized by a co-precipitation method and calcined at 500 °C and 800 °C. It was found that Zn substitution has a big effect in decreasing the Curie temperature (T(c)), from around 440 °C for the undoped sample to ~180 °C with x = 0.5. However, these values were also strongly affected by the pre-calcination temperature of the samples, thus T(C) shifts from ~275 °C for the x = 0.3 sample to ~296 °C after calcination at 500 °C and 800 °C respectively. These effects are due to facilitation of demagnetisation by substitution of the non-magnetic Zn ions and by production of very small nanoparticles. The latter are removed by higher temperature calcinations and so T(C) increases.     

Incorporating C2 into C60 films

The material formed by depositing C(2)(-) anions onto/into thin C(60) films (on graphite) at room temperature has been studied by means of thermal desorption mass spectroscopy, ultraviolet photoionization spectroscopy, atomic force microscopy (AFM), and surface enhanced Raman spectroscopy. As-prepared, C(2)/C(60) films manifest thermal desorption behaviour which differs significantly from pure C(60) films. Whereas the latter can be fully sublimed, we observe decomposition of C(2)/C(60) films to a high-temperature-stable material while predominantly C(60), C(62), and C(64) are desorbed in parallel. Deposition of C(2)(-) also leads to significantly modified electronic and vibrational properties. Based on DFT model calculations of the Raman spectra, we suggest that as-prepared C(2)/C(60) films contain appreciable amounts of polymeric networks comprising -C(2)-C(60)-C(2)-C(60)- chains. Detection of sublimed C(62) and C(64) upon heating implies that thermal decomposition of C(2)/C(60) films involves addition/uptake of C(2) units into individual fullerene cages. Correspondingly, annealing films up to various intermediate temperatures results in significant modifications to valence-band UP spectra as well as to surface topographies as imaged by AFM. The novel carbonaceous material obtained by heating to T > 950 K has a finite density of states at the Fermi level in contrast to as-prepared C(2)/C(60). It comprises fused fullerene cages.     

Synthetic study of azaspiracid-1: synthesis of the EFGHI-ring fragment

Here, we report a synthesis of the lower half C21-C40 fragment of the shellfish toxin, azaspiracid-1. The C28-C40 fragment was synthesized by a coupling between the C28-C35 epoxide and the C36-C40 dithioacetal anion, followed by the HI-ring spiroaminal formation. An aldehyde corresponding to the C28-C40 fragment was then coupled with the C21-C27 allylic stannane by using InCl3. Finally, the FG-ring was constructed by HF.pyridine to accomplish the synthesis of the suitably protected C21-C40 fragment.     

C60 and C70 fullerene isomers generated in flames. Detection and verification by liquid chromatography/mass spectrometry analyses.

Fullerenes C60 and C70, generated by combustion, have been shown previously to be produced in controlled laminar flames accompanied by other compounds having fullerene-like characteristics. Analysis of these additional compounds by high-performance liquid chromatography, coupled on-line with mass spectrometry has identified them as isomers of the C60 and C70 fullerenes. The newly observed isomers have characteristic UV spectra and are thermally unstable, undergoing conversion to the more stable fullerenes with a half-life of about 1 h in boiling toluene (111 degrees C). Isomers of C60 and C70 fullerenes previously have been studied theoretically, but not observed experimentally. The flame-generated material also contains C60O and C70O compounds, as well as C76 and higher carbon clusters.     

Stereoselective synthesis of the middle (C10–C17) and right (C18–C30) segments and their coupling to complete a formal synthesis of the polyether antibiotic salinomycin

The middle (C10–C17) and right (C18–C30) segments of the polyether antibiotic salinomycin were stereoselectively synthesized from D-glucose, D-mannitol and ethyl L-lactate. Coupling of the two segments followed by construction of the bisketal ring system gave the C10–C30 segment, which was already converted to salinomycin by Kishi.     

Cu(II)、Ni(II)配合物的合成、抗肿瘤作用及其对细胞周期分布的影响

以2-氨基-5-氯苯酚和2-喹啉甲醛合成的席夫碱作为配体,分别与氯化镍、氯化铜反应合成了2个金属配合物C1和C2,其结构通过单晶X-射线衍射进行了解析。采用MTT法测试了配合物C1和C2对不同人肝癌细胞系和正常肝细胞系HL-7702增殖抑制活性,结果表明C1、C2对人肝癌细胞系的抑制活性均优于顺铂,且对正常肝细胞系HL-7702的毒性要弱于顺铂。通过活性氧实验、细胞周期等实验,可以推断出配合物C1、C2抗肿瘤机制是通过产生活性氧造成肿瘤细胞的氧化损伤,以及使细胞周期停滞在G0/G1期阻滞细胞复制。