微波辐射下秸秆纤维微观结构的变化

利用原子力显微镜(AFM)对微波处理前后秸秆纤维表面的变化进行了研究,并结合XRD和FTIR研究了处理前后其化学结构及结晶形态的变化情况。结果表明,未经微波处理的秸秆纤维表面比较光滑,平均粗糙度(Ra)为(86.7±6.335)nm,均方根粗糙度(Rq)为(141.1±9.055)nm;经微波处理的秸秆纤维表面比较粗糙,并出现许多细小孔洞,其Ra为(445.0±28.14)nm,Rq为(558.9±33.458)nm,微波辐射处理前后秸秆纤维的表面形态差异较大。经微波辐射处理后,秸秆纤维在2θ=22.3°处的衍射峰移至21.8°,且峰宽稍有增加,在38.1°、44.3°、64.6°、78.9°处出现的4个衍射峰,除强度稍有增强,其峰形和位置与未经处理秸秆纤维的衍射峰基本一致,表明微波处理没有改变纤维的结晶形态。FTIR光谱表明,微波处理样中未产生新的官能团,但分子间氢键及分子内氢键发生变化。微波作用未引起秸秆纤维化学结构的变化。     

荧光光谱法研究木犀草素与牛血清白蛋白的相互作用

在pH为7.40的Tris-HCl缓冲体系中,采用荧光光谱技术研究了木犀草素与牛血清白蛋白(BSA)的相互作用。根据测定292K、299K、311K温度下的猝灭常数,证实了木犀草素对BSA的荧光猝灭为静态猝灭过程,根据Frster非辐射能量转移理论计算出木犀草素与BSA间的结合距离r=2.75nm,由热力学参数焓变(△H)小于零和熵变(△S)大于零,推断出木犀草素与BSA之间主要靠静电引力相结合,生成自由能变(△G)为负值,表明木犀草素与BSA的作用过程是一个自发过程;同时,应用同步荧光光谱考察了木犀草素对BSA构象的影响。     

米托蒽醌与B-DNA相互作用的分子模拟

针对嵌插型抗癌药物米托蒽醌(mitoxantrone,MTX)同B-DNA间作用模式的争议,采用分子模拟方法研究了米托蒽醌分子与B-DNA分子的相互作用.结果表明:米托蒽醌分子插入到B-DNA中有大小沟选择性及碱基对特异性,更倾向从小沟方向插入到DNA分子中;对5'-CG碱基对有特异性识别.通过详细能量项的分析,揭示了米托蒽醌插入DNA分子的驱动力及对碱基的特异性识别作用主要是空间相互作用特别是静电相互作用.在最佳作用位点复合物的构象分析则表明蒽醌环只有一部分插入碱基对中,侧链在小沟中延磷酸基骨架以3'-5'方向伸展,并通过静电作用进一步增强米托蒽醌与B-DNA的结合.     

Solid–liquid–gas equilibrium of the naphthalene–biphenyl–CO2 system: Measurement and modeling

The first and last melting points (FLMP) method was employed to measure the melting temperature–composition (T–w$T–w$) data at solid–liquid–gas (SLG) equilibrium for the naphthalene–biphenyl–CO₂ system. Results show that the system's phase diagram is simple eutectic under all investigated pressures (0.1, 3.0, 6.0 and 8.0 MPa), and the system's eutectic composition is almost constant. The (T–w$T–w$) data measured with a high-pressure differential scanning calorimetry are in good agreement with these from FLMP. The semi-predictive model using solubility data (SMS) and the calculation model combining with G^E models (CMG) for binary systems were extended to this ternary system. For the SMS model, the Peng–Robinson equation of state (PR-EoS) with the van der Waals one-fluid mixing rule was used to correlate the solubility data of the two solutes in CO₂ to obtain the two interaction parameters k₁₂ and k₁₃ and calculate the fugacity coefficients of the solutes in the liquid and vapor phases; the UNIFAC method was also applied to the activity coefficient of the solutes in the liquid phase. For the CMG model, the PR-EoS combining respectively the MHV1, LCVM, and modified LCVM (mLCVM) mixing rules was applied to the fugacity coefficients of the solutes. Results show that the CMG model with MHV1 gives the best prediction of the system's SLG equilibrium, while the SMS model and the CMG model with mLCVM provide comparable and acceptable results.     

Consensus model for identification of novel PI3K inhibitors in large chemical library

Phosphoinositide 3-kinases (PI3Ks) inhibitors have treatment potential for cancer, diabetes, cardiovascular disease, chronic inflammation and asthma. A consensus model consisting of three base classifiers (AODE, kNN, and SVM) trained with 1,283 positive compounds (PI3K inhibitors), 16 negative compounds (PI3K non-inhibitors) and 64,078 generated putative negatives was developed for predicting compounds with PI3K inhibitory activity of IC₅₀ ≤ 10 μM. The consensus model has an estimated false positive rate of 0.75%. Nine novel potential inhibitors were identified using the consensus model and several of these contain structural features that are consistent with those found to be important for PI3K inhibitory activities. An advantage of the current model is that it does not require knowledge of 3D structural information of the various PI3K isoforms, which is not readily available for all isoforms.     

Electrophoretic sol–gel synthesis of SrBi<Subscript>2</Subscript>Ta<Subscript>2</Subscript>O<Subscript>9</Subscript> nanowires

We report the independent invention of perovskite ferroelectric nanowires strontium bismuth tantalate (SrBi₂Ta₂O₉, SBT). Electrophoretic sol–gel techniques have been used successfully. The morphology and structures are analyzed via SEM, TEM and XRD. SBT nanowires and nanoparticles filled template revealed 30 and 40 μm long, respectively. SBT are proved to be a single phase of orthorhombic perovskite structure. As it indicated, SBT nanowires has been crystallized at 700 °C. To minimize surface polarity, SBT nanowires oriented preferentially along the growing axis (c axis) by translation and rotation of atomic clusters of SBT.     

Real‐Time Monitoring of Mass‐Transport‐Related Enzymatic Reaction Kinetics in a Nanochannel‐Array Reactor

To understand the fundamentals of enzymatic reactions confined in micro‐/nanosystems, the construction of a small enzyme reactor coupled with an integrated real‐time detection system for monitoring the kinetic information is a significant challenge. Nano‐enzyme array reactors were fabricated by covalently linking enzymes to the inner channels of a porous anodic alumina (PAA) membrane. The mechanical stability of this nanodevice enables us to integrate an electrochemical detector for the real‐time monitoring of the formation of the enzyme reaction product by sputtering a thin Pt film on one side of the PAA membrane. Because the enzymatic reaction is confined in a limited nanospace, the mass transport of the substrate would influence the reaction kinetics considerably. Therefore, the oxidation of glucose by dissolved oxygen catalyzed by immobilized glucose oxidase was used as a model to investigate the mass‐transport‐related enzymatic reaction kinetics in confined nanospaces. The activity and stability of the enzyme immobilized in the nanochannels was enhanced. In this nano‐enzyme reactor, the enzymatic reaction was controlled by mass transport if the flux was low. With an increase in the flux (e.g., >50 μL min^?1), the enzymatic reaction kinetics became the rate‐determining step. This change resulted in the decrease in the conversion efficiency of the nano‐enzyme reactor and the apparent Michaelis–Menten constant with an increase in substrate flux. This nanodevice integrated with an electrochemical detector could help to understand the fundamentals of enzymatic reactions confined in nanospaces and provide a platform for the design of highly efficient enzyme reactors. In addition, we believe that such nanodevices will find widespread applications in biosensing, drug screening, and biochemical synthesis.     

Three New Sesquiterpenoids from Echinops ritro L.

From the whole plants of E. ritro L., the three new sesquiterpenoids (3α,4α,6α)‐3,13‐dihydroxyguaia‐7(11),10(14)‐dieno‐12,6‐lactone ( 1 ), (3α,4α,6α,11β)‐3‐hydroxyguai‐1(10)‐eno‐12,6‐lactone ( 2 ), and (11α)‐11,13‐dihydroarglanilic acid methyl ester (=(4β,6α,11α)‐4,6‐dihydroxy‐1‐oxoeudesm‐2‐en‐12‐oic acid methyl ester; 3 ), together with eight known sesquiterpenoids, were isolated. Their structures were elucidated through analysis of spectroscopic data including extensive 2D‐NMR.     

Three New Caged Prenylxanthones from Garcinia bracteata

Three new caged prenylxanthones (xanthone=9H‐xanthen‐9‐one), named neobractatin ( 1 ), 3‐O‐methylneobractatin ( 2 ), and 3‐O‐methylbractatin ( 3 ), along with eight known compounds, were isolated from the twig of Garcinia bracteata. The structures of the new compounds were elucidated on the basis of 1D‐ and 2D‐NMR experiments, including HMBC, HSQC, ¹H,¹H‐COSY, and ROESY, as well as HR‐MS analysis.     

Four New Terpenoids from Xylaria sp. 101

One new diterpenoid, xylarenolide ( 1 ), and three new sesquiterpenoids, xylaranol A ( 2 ), xylaranol B ( 3 ), and xylaranic acid ( 4 ), were obtained from the fungal strain Xylaria sp. 101, which was isolated from the fruiting body of Xylaria sp. collected in Gaoligong Mountain, Yunnan Province. Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR experiments, and by HR‐Q‐TOF mass spectrometry. Their antimicrobial activities were evaluated.