Electrochemiluminescence Distance and Reactivity of Coreactants Determine the Sensitivity of Bead-Based Immunoassays

Herein we report the study of electrochemiluminescence (ECL) generation by tris(2,2′-bipyridyl)ruthenium (Ru(bpy)₃²⁺) and five tertiary amine coreactants. The ECL distance and lifetime of coreactant radical cations were measured by ECL self-interference spectroscopy. And the reactivity of coreactants was quantitatively evaluated in terms of integrated ECL intensity. By statistical analysis of ECL images of single Ru(bpy)₃²⁺-labeled microbeads, we propose that ECL distance and reactivity of coreactant codetermine the emission intensity and thus the sensitivity of immunoassay. 2,2-bis(hydroxymethyl)-2,2′,2′′-nitrilotriethanol (BIS-TRIS) can well balance ECL distance-reactivity trade-off and enhance the sensitivity by 236 % compared with tri-n-propylamine (TPrA) in the bead-based immunoassay of carcinoembryonic antigen. The study brings an insightful understanding of ECL generation in bead-based immunoassay and a way of maximizing the analytical sensitivity from the aspect of coreactant.     

Bioprospecting Dodonaea viscosa Jacq.; a traditional medicinal plant for antioxidant,cytotoxic, antidiabetic and antimicrobial potential

Purpose of studyDodonaea viscosa Jacq. is an ethnomedicinal plant that has been extensively used for the treatment of gout, rheumatism and pain. Current study was undertaken to mine its antioxidant, antimicrobial, cytotoxic and antidiabetic potential. Chromogenic assays were employed to establish plant’s multimode antioxidant profile whereas HPLC fingerprinting was performed to quantify polyphenols. Standard brine shrimp lethality, MTT and SRB assays proved its cytotoxicity potential.ResultsAmong all the extracts (flower, leaf, stem and root), maximum extract recovery (22% w/w), gallic acid equivalent total phenolic content (20.11 ± 0.11 ug GAE/mg DW), ascorbic acid equivalent total antioxidant capacity (22.5 ± 0.07 µg/mg DW) and total reducing power (31.1 ± 1.13 µg/mg DW) were recorded in the distilled water + acetone extract of leaf. The acetone extract of leaf showed maximum quercetin equivalent total flavonoid content (4.78 ± 0.13 µg/mg DW). HPLC-DAD analysis revealed significant amount of rutin, vanillic acid, coumaric acid, ferulic acid, gallic acid, syringic acid, cinnamic acid, gentisic acid, catechin, caffeic acid, apigenin and myricetin in the different plant parts. Maximum scavenging potential was exhibited by methanol + ethyl acetate stem extract (IC₅₀ = 23.8 µg/ml). The highest antibacterial potential was found in flower (85.7%) and root (71.4%) extracts. The ethanol + ethyl acetate (1:1) leaf extract showed noteworthy toxicity against brine shrimps (LC₅₀ = 95.46 µg/ml) while a notable antiproliferative activity against THP-1 (IC₅₀ = 3.4 µg/ml) and Hep G2 (IC₅₀ = 20 µg/ml) cell lines was shown by ethanol + ethyl acetate extracts (1:1) of stem and root, respectively. A moderate inhibition of α-amylase enzyme was observed in all parts of the plant.ConclusionThe results of the present study suggest D. viscosa as a potential source of antioxidant, anticancer and α-amylase inhibitory phytochemicals.     

Radical cyclisation mediates the synthesis of a new base-ribose carbon bridged adenosine

Reaction of tributylstannyl, radical generated in situ with AIBN, with (2′,5′-di-O-tert-butyldimethylsilyl-3′-C-ethynyl-β-d-ribo-furanosyl)adenine (5) gave in 69% yield the new conformationally locked nucleosides 6 (E/Z).     

Unusual reduction of a lactone carbonyl in a Bu3SnCl and Na(CN)BH3 mediated radical cyclization of 3-(o-bromophenoxymethyl)coumarins

3-Chloromethyl coumarin was treated with different substituted 2-bromophenols in the presence of anhydrous potassium carbonate in refluxing acetone to afford a number of 3-(2-bromophenoxymethyl)coumarins 3a-f in 80-95% yield. These were then refluxed with tributyltin chloride and sodium cyanoborohydride in benzene under nitrogen, in the presence of a catalytic amount of azobisisobutyronitrile (AIBN) for 7-10 h to give spiro[chroman-3,3′-(2′H)-benzofurans] 4a-f in 60-75% yields.     

Tetrathiafulvalene-hydroxyamides and -oxazolines: hydrogen bonding, chirality, and a radical cation salt

Racemic and enantiopure ethylenedithio-tetrathiafulvalene (EDT-TTF) derivatives featuring β-hydroxyamide or oxazoline (OX) groups bearing methyl or isopropyl substituents have been synthesized starting from the corresponding amino alcohols. Crystal structure analysis shows in the case of the racemic methyl-β-hydroxyamide donor the development of a unique hydrogen bond network, characterized by short CO?H-O and N-H?O-H intermolecular distances. The enantiopure (S)-EDT-TTF-methyl-OX crystallizes in the monoclinic non-centrosymmetric space group P2₁, whereas the isopropyl counterparts, (R)-and (S)-EDT-TTF-isopropyl-OX, crystallize in the orthorhombic non-centrosymmetric space group P2₁2₁2₁. All of them adopt a s-trans conformation in which TTF and oxazoline units are coplanar. Electrocrystallization experiments with the racemic EDT-TTF-methyl-OX, in the presence of (nBu₄)₂Mo₆Cl₁₄ as supporting electrolyte, afford a radical cation salt, formulated as [(±)-EDT-TTF-methyl-OX]₂Mo₆Cl₁₄, in which the donors associate in strong dimers, which further stack along the b direction to form quasi-homochiral helix-like ribbons.     

SYNTHESIS AND CHARACTERIZATION OF POLYROTAXANES MADE FROM α-CDs THREADED ONTO TRIBLOCK COPOLYMERS WITH PEG AS A CENTRAL AXLE AND FLANKED BY TWO LOW MOLECULAR WEIGHT POLYSTYRENES AS OUTER STOPPERS

A study has been conducted on the synthesis and characterization of a kind of novel polyrotaxanes comprisingα- cyclodextrins (α-CDs) threaded on triblock eopolymers with poly(ethylene glycol) (PEG) as a central axle and flanked by two low molecular weight polystyrenes as outer stoppers.Styrene was allowed to telomerize with polypseudorotaxanes as chain transfer agents made from the self-assembly of a distal thiol-capped PEG with a varying amount ofα-CDs in the presence of a redox initiation system at 40~C in aqueous solutions.The resulting polyrotaxanes were characterized in detail by ~1H-NMR,FTIR,XRD,TG and DSC analyses.The findings from the study demonstrated that the low molecular weight polystyrenes were successfully attached to two axle terminals of polypseudorotaxanes,and the number ofα-CDs threaded onto the PEG backbone was tunable by varying its molar feeding ratio to some extent,while the polymerization degree of PS nearly remained constant in this radical telomerization process.     

Stereoselective synthesis of 2-iodo-1-perfluoroalkyl-2(Z)-alkenes and E or Z-4-perfluoroalkylmethyl-4-en-2-ynol via Na2S2O4-promoted radical addition reaction of perfluoroalkyl iodides with allenes and the palladium-catalyzed kinetic resolution with Sonogashira coupling reaction

A Na₂S₂O₄-promoted radical addition reaction of perfluoroalkyl iodides with allenes has been studied in which a Z/E mixture of 2-iodo-1-perfluoroalkyl-2-alkenes 3 were afforded in 52-69% yields. A kinetic resolution using Sonogashira coupling reaction in MeCN using Et₂NH as the base was developed to synthesize the 2-iodo-1-perfluoroalkyl-2(Z)-alkenes (Z-3) and E-4-perfluoroalkylmethylalk-4-en-2-ynols (E-5) stereoselectively. A complete Sonogashira coupling procedure in Et₂NH at 40 °C was also developed affording a mixture of E and Z-4-perfluoroalkylmethyl-4-en-2-ynols (E-5 and Z-5), which may be easily separated by chromatography on silica gel.     

光学活性N-邻噁唑啉苯基甲基丙烯酰胺聚合物的合成及其手性光学性质

在三氟甲磺酸稀土盐(Ln(OTf)3,Ln=La,Nd,Sm,Y)的存在下,光学纯N-邻唑啉苯基甲基丙烯酰胺((S)-MeOPMAM)经自由基聚合反应得到相应的光学活性聚合物.考察了稀土盐种类、用量及溶剂性质等因素对聚合反应立体化学的影响.研究发现,以Y(OTf)3为调节剂、正丁醇为溶剂的体系能在一定程度上提高聚合反应的全同立体定向性.聚合物的手性光学性质明显依赖于立构规整度,随全同含量增大,聚合物的比旋光度和π-π*电子跃迁区域的Cotton效应强度呈下降趋势.利用1H-NMR技术研究了上述聚合物与1,1′-联-2-萘酚(BINOL)的对映选择性相互作用,结果表明,全同三元组含量较高的聚合物不仅使酚羟基质子峰向低场位移,而且导致信号分裂.     

基于EPR方法的天然产物抗氧化性能研究(英文)

自旋捕捉EPR、用于动物模型的低温EPR以及自旋标记EPR等多种EPR方法已经用于天然产物的抗氧化活性研究中.虽然对于抗氧化剂而言其必备条件之一就是具有体外清除自由基的能力,但是外源性抗氧化剂在生物体内抗氧化剂抗氧化能力评价的方法更有实际意义.通过对超过200种中药和一些传统中药处方的研究,已经建立并详细描述了用于评价天然产物抗氧化能力的EPR筛选方法.通过EPR方法可以获得天然产物在分子水平、细胞水平以及组织水平抗氧化能力的比较全面的评价.     

Chemical capture of an unprecedented oxatetramethyleneethane radical cation with a through-space electronic coupling

A photoinduced electron-transfer reaction of 2,2-dianisyl-4-isopropylidene-3,3-dimethylcyclobutanone (5) in acetonitrile containing molecular oxygen or water gave 4,4′-dimethoxybenzophenone (7) and 2,2-dianisyl-4-isopropylidene-5,5-dimethylhydrofuran-3-one (8), demonstrating the chemical capture of an unprecedented oxatetramethyleneethane-type radical cation intermediate (6⁺). A density functional theory calculation suggests through-space electronic coupling between the tetramethylallyl and joined dianisylmethyl carbonyl subunits in 6⁺.