Exploratory Purification of Compounds from Aqueous Extracts of <Emphasis Type="Italic">Pinus massoniana</Emphasis> Lamb. by Two-Dimensional Preparative Liquid Chromatography

An off-line orthogonal two-dimensional preparative liquid chromatography method was developed for isolation of high-purity compounds from aqueous extracts of Pinus massoniana Lamb., which has efficient therapeutic properties in recipes of traditional Chinese medicines. A polar-enhanced reversed-phase (RP) column, XAqua C18 was selected for the first-dimensional separation. A HILIC column and a hydrophobic RP column were both explored in the second dimension. The preparation results indicated hydrophilic RP × HILIC mode would provide better separation efficiency for polar complexes, i.e., the second-dimensional separation was finished in less than 30 min and high-purity compounds were obtained. In this work, 16 fractions were collected efficiently in the first dimension with a recovery up to 96%, and six compounds with high purity and enough quantity were identified by NMR and high resolution mass spectrometry, including epicatechin, betuloside, taxifolin-3-O-xyloside, cedrusin-4-O-glucoside, massonianoside C and massonianoside D, and five are glycosides, including flavonoid glycosides, lignanoid glycosides and an arylbutanoid glycoside. Betuloside was first reported in the preparation of Pinus massoniana Lamb. This work demonstrated a flexible strategy of compromise in between time and resolution for selecting solvent and column to enhance preparative efficiency of polar complex systems.     

Ultrasensitive amperometric determination of PSA based on a signal amplification strategy using nanoflowers composed of single-strand DNA modified fullerene and Methylene Blue,and an improved surface-initiated enzymatic polymerization

The authors describe a signal amplification strategy for highly sensitive detection of the prostate-specific antigen (PSA). This is accomplished by a combination of two methods, viz. (a) improved surface-initiated enzymatic polymerization (SIEP), and (b) the use of nanoflowers prepared from C₆₀ fullerene and Methylene Blue (C₆₀/MB) modified with a long single-strand DNA. C₆₀/MB acts as a novel electrochemical indicator. The C₆₀/MB nanoflowers improve the load of MB and promote the electron transfer. The integration of the SIEP technique and the C₆₀/MB nanomaterial also results in improved loading of MB on the nucleic acid. Ultimately, dual cascade signal amplification is accomplished. The biosensor was constructed as follows: (a) Gold nanospheres were modified with antibody 2 (Ab₂) and a thiolated oligonucleotide (referred to as S₀). (2) S₀ is then extended by the SIEP reaction. (3) The redox indicator C₆₀/MB is then connected to the extended guanine-rich ssDNA which then yields the amperometric signal. (4) A sandwich immunoassay is performed by capturing the nanoprobe oy type Ab₂-Au-S₀ on the gold electrode modified with multi-walled carbon nanotubes (MWCNTs) and protein A. Current is measured by using differential pulse voltammetry (DPV). The synergic effect of the biofunctional nanomaterial and the signal amplification strategy greatly improves the performance of this immunoassay. Under optimized conditions and at a working voltage of typically ?0.18 V (vs Ag/AgCl), the assay has a linear range that extends from 15 pg·mL^?1 to 8 ng·mL^?1 of PSA. The detection limit is as low as 1.7 pg·mL^?1 (at an S/N ratio of 3). In our perception, this dual amplification scheme has a wide scope in that it may become applicable to numerous other immunoassays.

Open image in new window

Graphical abstract C₆₀/Methylene blue nanoflowers, a novel electrochemical indicator, connect with the long single-stranded DNA (ssDNA) extended by the improved surface-initiated enzymatic polymerization method. This amplification strategy is utilized to construct a sandwich prostate-specific antigen (PSA) immunosensor.

     

Synthesis and biological evaluation of oxoapratoxin E and its C30 epimer

30R- and 30S-oxazoline analogues of apratoxin E have been prepared with late-stage formation of an oxazoline ring. These two compounds have a potent inhibitory effect on HCT-116 cell proliferation with IC₅₀ values of 345 and 638 nM, respectively. These results suggest that apratoxin E oxazoline bioisosteres are approximately 6-fold less potent than their thiazoline parent compounds. A positive impact of the 30R conformation on antiproliferative activity was also observed, with approximately 2-fold enhancement when compared to the 30S epimer.     

12-磷钨酸插层MgAl水滑石的合成、表征及催化酯化原油脱酸性能

采用离子交换法合成了不同Mg/Al物质的量比的12-磷钨酸(H_3PW_(12)O_(40),HPW)插层水滑石(LDHs),采用XRD、FT-IR、Raman、ICP-AES、TG-DSC等分析手段表征其物化性质,Hammett指示剂-正丁胺滴定法测定其酸强度和酸量分布。进一步将其用于原油催化酯化脱酸反应,并与NO_3型LDHs对比,探讨酯化活性与催化剂性质之间的关系。结果表明,催化剂的活性主要受酸性和比表面积的影响。HPW插层LDHs的酯化活性明显优于NO3型LDHs,归因于增强的酸性和增大的比表面积。对于弱酸性的NO_3型LDHs,酯化活性与比表面积呈正向关系,Mg/Al物质的量比为4时,具有最大的比表面积和脱酸活性。而对于较强酸性的HPW插层LDHs,酯化活性主要受到酸量的影响,Mg/Al物质的量比为2的催化剂具有最高的酸量和脱酸活性。     

重组内切纤维素酶Fpendo5A转化三七总皂苷

从嗜热细菌基因组中克隆到1个新的纤维素酶基因,并在大肠杆菌中进行了高效可溶性表达,粗酶液经镍柱亲和层析进行分离纯化.利用快速分离液相色谱-四极杆飞行时间质谱联用仪(RRLC/Q-TOF-MS)对重组内切纤维素酶Fpendo5A转化三七总皂苷的产物结构进行了鉴定,并进一步阐明其转化机制.结果表明,该酶的最适反应温度和pH值分别为80℃和5.5.Fpendo5A能够催化三七总皂苷中的主要皂苷成分,即Ra_1,Rb_1,Rc,Rd和Rg_3的侧链糖基的水解反应,但对于不同的皂苷底物,Fpendo5A选择性催化的侧链糖基类型不同.经鉴定,Fpendo5A转化Ra_1,Rb_1,Rc,Rd和Rg_3的转化产物分别为Rb_2,GypⅩⅦ,CMC_1,F_2和Rh_2.由此可见,Fpendo5A通过水解Rb_1,Rc,Rd和Rg3的C3位的β-(1,2)糖苷键分别生成GypⅩⅦ,CMC1,F2和Rh2.在转化Ra_1时,Fpendo5A通过水解Ra_1的C20位的α-(1,4)木糖苷键生成Rb2.     

血管紧张素转换酶与抑制肽结合模式的分子动力学研究

应用分子模拟方法研究了血管紧张素转换酶(Angiotensin-converting enzyme,ACE)C端结构域(C-domain)与两种抑制肽(RIGLF/AHEPVK)的结合机制,预测了两个体系的结合模式,提出在C-domain-RIGLF中His353,Asp377,Asp453,Phe457,His513,Tyr523和Phe527为RIGLF主要结合残基,而在C-domainAHEPVK中Gln281,His353,Ser355,Glu384,Lys511,His513和Tyr523等残基起关键作用.应用结合自由能计算比较了两个体系的结合能力,结果表明,RIGLF和AHEPVK均与C-domain活性位点残基存在较强作用,且AHEPVK对C-domain的结合能力较强,与实验结果一致.     

Multi-bond network hydrogels with robust mechanical and self-healable properties

Multi-bond network(MBN) which contains a single network with hierarchical cross-links is a suggested way to fabricate robust hydrogels. In order to reveal the roles of different cross-links with hierarchical bond energy in the MBN, here we fabricate poly(acrylic acid) physical hydrogels with dual bond network composed of ionic cross-links between carboxylFe3+ interactions and hydrogen bonds, and compare these dually cross-linked hydrogels with singly and ternarily cross-linked hydrogels. Simple models are employed to predict the tensile property, and the results confirm that the multi-bond network with hierarchical distribution in the bond energy of cross-links endows hydrogel with effective energy-dissipating mechanism. Moreover, the dually cross-linked MBN gels exhibit excellent mechanical properties(tensile strength up to 500 k Pa, elongation at break ~ 2400%) and complete self-healing after being kept at 50 °C for 48 h. The factors on promoting self-healing are deeply explored and the dynamic multi-bonds are regarded to trigger the self-healing along with the mutual diffusion of long polymer chains and ferric ions.     

Comparison of Gasoline-Ranged <Emphasis Type="Italic">n</Emphasis>-Alkanes Conversions Using Dielectric Barrier Discharge: A Kinetic Study

Here, we compared the conversion of gasoline-ranged n-alkanes (C₆–C₉) using dielectric barrier discharge. For an energy density of ~68 J/L and an initial n-alkane concentration of ~230 ppm, when carbon number increased from 6 to 9, the energy efficiency of n-alkane conversion increased from 117 to 240 mmol/kWh, CO _x selectivity decreased from 46 to 20%, and ozone concentration increased from 216 to 240 ppm. The effect of energy density and initial n-alkane concentration were also investigated. The understanding of initial step of conversion was greatly aided by a proposed kinetic model. The pathways of consecutive reactions from the initiation to products were also discussed.     

A Competitor-switched Electrochemical Sensor for Detection of DNA

A competitor‐switched electrochemical sensor based on a generic displacement strategy was designed for DNA detection. In this strategy, an unmodified single‐stranded DNA (cDNA) completely complementary to the target DNA served as the molecular recognition element, while a hairpin DNA (hDNA) labeled with a ferrocene (Fc) and a thiol group at its terminals served as both the competitor element and the probe. This electrochemical sensor was fabricated by self‐assembling a dsDNA onto a gold electrode surface. The dsDNA was pre‐formed through the hybridization of Fc‐labeled hDNA and cDNA with their part complementary sequences. Initially, the labeled ferrocene in the dsDNA was far from surface of the electrode, the electrochemical sensor exhibited a "switch‐off" mode due to unfavorable electron transfer of Fc label. However, in the presence of target DNA, cDNA was released from hDNA by target DNA, the hairpin‐open hDNA restored its original hairpin structure and the ferrocene approached onto the electrode surface, thus the electrochemical sensor exhibited a "switch‐on" mode accompanying with a change in the current response. The experimental results showed that as low as 4.4×10⁻¹⁰ mol/L target DNA could be distinguishingly detected, and this method had obvious advantages such as facile operation, low cost and reagentless procedure.     

高粘度枯基酚甲醛树脂的固体酸催化法合成新工艺研究

以对枯基苯酚和甲醛为原料,运用正交实验法,经过固体酸(阳离子交换树脂)催化缩合、过滤、蒸馏等过程,研制出合成枯基酚甲醛树脂产品的一种新型工艺路线。产品外观为红棕色粘稠液体,pH值接近7,能够耐水和酸碱,稳定性好,主要用于电绝缘体、涂料和橡胶制品等领域。