新型高分枝化PAM增强剂

一般增干强剂在纸张增强的同时具有对浆料的助滤、助留作用,尤其是PAM增强剂,在日本获得广泛应用。然而,由于废纸回用的增加、白水封闭循环以及大量填料的添加,使得普通PAM的效果下降。基于此,本文介绍了研发的新型PAM增强剂,具有高分枝化、高分子量和新型结构,与普通PAM相比,增强、助滤、助留效果优异,能够满足近年来苛刻的抄纸环境,生产出优良的纸和纸板。

天然红松林结实量预测模型的初步构建

以露水河林业局天然红松林为对象,基于在16块固定样地中测定的677株红松单株结实量和林木因子的实测数据,应用非线性回归方法建立预测模型,并进行评价.结果表明:胸径和树高与结实量存在显著的正相关关系(P<0.01),分枝高和冠幅与结实量未达到显著相关,但与胸径和树高关系显著(P<0.01).以胸径与树高、胸径与分枝高和胸径与冠幅的不同因子组合建立结实量预测模型.通过对7个模型的R^2、均方根误差(RMSE)、赤池信息准则(AIC)、平均绝对偏差(MAE)、平均相对偏差绝对值(MRAE)等拟合优度和检验参数的比较分析,选择模型y=a×(D^2×BH)~b作为天然红松林结实量的最优模型,其预测精度为89.35%,消除异方差后的残差分布均匀;模型y=a×(D^2×H)~b和y=a×(D^2×CW)~b虽然R^2和P略高,但其平均偏差(ME)和MRAE与最优模型相差较大;以D^2作为因子建立的模型y=a×(D^2×H)~b、y=a×(D2×BH)b和y=a×(D^2×CW)~b皆表现出良好的检验效果.

Interaction Mechanism of Nano-silicon Dioxide Modified by Poly（amidoamine） Dendrimers

To gain insight into the attachment of =Si^＋ （SC） ion （regarded as guest） to the lowest generation, NH2-terminated poly（amidoamine） （PAMAM） dendrimers （regarded as host） in the liquid phase, density functional theory is used to investigate the structures and energetics of the host-guest complex. The effect of solvent on the structures and energetics is also investigated. Various initial configurations of the ion bound to PAMAM are tested, and two stable conformers are found, i.e, types A （=Si^＋ is bound to the amine site） and C （=Si^＋ is bound to the amide site）. Types A and C are the most stable due to the chemical bond formations of Si-N° （amine nitrogen atoms） and Si-O, respectively. The IR spectra for the lowest energy conformers are thoroughly analyzed and compared with the available experimental data.

Quantification of seven phenylpropanoid compounds in Chinese Cinnamomi Cortex and Ramulus by HPLC

In the present study, we developed and validated a high-performance liquid chromatography method for the simultaneous determination of seven phenylpropanoid compounds （2-hydroxyl cinnamaldehyde, coumarin, cinnamyl alcohol, cinnamic acid, 2-methoxy cinnamic acid, cinnamaldehyde and 2-methoxy cinnamaldehyde） in Cinnamomi Cortex and Cinnamomi Ramulus. The levels of seven phenylpropanoid compounds in Cinnamomi Cortex and Cinnamomi Ramulus were compared using this method. A total of 48 samples （27 Cinnamomi Cortex and 21 Cinnamomi Ramulus） were purchased in China and analyzed. Quantities of seven phenylpropanoid compounds ranged from 17.5 to 61.6 mg/g in Cinnamomi Cortex and ranged from 9.91 to 23.4 mg/g in Ciunamomi Ramulus. The level of 2-methoxy cinnamic acid in the Cinnamomi Cortex samples was below the LOD, whereas it ranged from 0 to 0.119 mg/g in the Cinnamomi Ramulus samples. The （cinnamyl alcohol＋cinnamic acid）/cinnamaldehyde ratios （R346） of Ciunamomi Cortex and Cinnamomi Ramulus ranged from 0.0121 to 0.0467 and 0.0598 to 0.182, respectively. This ratio could be used to discriminate Cinnamomi Cortex （〈0.05） and Cinnamomi Ramulus （〉0.05）. The extraction rates （Dn） of seven compounds in boiling water were different, with the lowest dissolution for cinnamaldehyde （〈3%） and the highest for cinnamic acid （about 60%）.

Establishment and application of the screening model of the Mycobacterium tuberculosis β-lactamase BlaC inhibitors

With the continuous emergence and rapid spread of multidrug-resistant and extensively-drug-resistant Mycobacterium tuberculosis strains, it is imperative to develop novel therapies against this bacterium. The intrinsic β-lactam resistance of M. tuberculosis is primarily due to the production of an Ambler class-A β-lactamase BlaC, which limits the application of β-lactam antibiotics in the treatment of tuberculosis. Therefore, the inhibitors of BlaC could be novel anti-tuberculosis drug synergistic agents to recover the sensibility of M. Tuberculosis to the β-lactam antibiotics. In the present study, BlaC of M. tuberculosis was expressed and purified to establish a screening model of the BlaC inhibitors. The screening conditions were determined, and the screening model was evaluated to fit for the high throughput screening. A total of 22 BlaC inhibitors were screened out from 26 400 compound samples with a positive rate of 0.083%. Taken together, our findings lay the foundation for the discovery of novel anti-tuberculosis drug synergistic agents in clinic.

Acid sensitive doxorubicin-PAMAM with tumor targeting profile

Poly （amidoamine） dendrimers are emerging as versatile and derivatizable nano-scale drug delivery vehicles. In our study, cis-4,7,10,13,16,19-docosahexenoic acid and doxorubicin were conjugated to generation 2.5 PAMAM. The molecular architecture of the carrier was designed for optimized blood circulation and optimized drug release through the use of pH-sensitive hydrazone linkages. In vitro, DHA-PAMAM-DOX conjugates were able to release twice as much doxorubicin at pH 4.5 （lysosomal pH） as at pH 7.4, ensuring more pronounced antitumor activity. Upon intravenous administration to ICR mice, the DHA-PAMAM-DOX delivery systems resulted in more plasma exposure of doxorubicin than free doxorubicin solution. In efficacy studies performed with B6D2F1 mice bearing B16 melanoma tumors, DHA-PAMAM-DOX was significantly more efficient in inhibiting tumor growth than free doxorubicin at the dose equivalent to 5 mg/kg doxorubicin. Our research provides evidence that DHA-PAMAM-DOX conjugates have the potential to enhance the effect of cancer therapy in the course of delivering anticancer drugs to their target sites.

Graphene-induced Pd nanodendrites： A high performance hybrid nanoelectrocatalyst

A facile and green approach has been developed for the in situ synthesis of hybrid nanomaterials based on dendrite-shaped Pd nanostructures supported on graphene （RG）. The as-synthesized hybrid nanomaterials （RG-PdnDs） have been thoroughly characterized by high resolution transmission electron microscopy, X-ray photoelectron spectroscop）~ atomic force microscop）~ Raman spectroscopy and electrochemical techniques. The mechanism of formation of such dendrite- shaped Pd nanostructures on the graphene support has been elucidated using transmission electron microscopy （TEM） measurements. The RG induces the formation of, and plays a decisive role in shaping, the dendrite morphology of Pd nanostructures on its surface. Cyclic voltammetry and chronoamperometry techniques have been employed to evaluate the electrochemical performance of RG-PdnDs towards oxidation of methanol. The electrochemical （EC） activities of RG-PdnDs are compared with graphene-supported spherical-shaped Pd nanostructures, Pd nanodendrites alone and a commercial available Pd/C counterpart. The combined effect of the graphene support and the dendrite morphology of RG-PdnDs triggers the high electrocatalytic activity and results in robust tolerance to CO poisoning.

Recent advances of the Bergman cyclization in polymer science

The Bergman cyclization has strongly impacted on a number of fields including pharmaceutics, synthetic chemistry, and material science. The diradical intermediates stemmed from enediynes can not only cause DNA cleavage under physiological conditions but also function as monomer or initiator participants in polymer science. The homo-polymerization of enediynes through the Bergman cyclization to fabricate conjugated polymers is a fascinating strategy due to the advantages of facial operation, high efficiency, tailored structure, and catalyst-free operation. Moreover, conjugated polymers generated through the Bergman cyclization show many remarkable properties, such as excellent thermal stability, good solubility, and processability, which enables these polymers to be further manufactured into carbon-rich materials. Recent times have seen extensive efforts devoted to the application of the Bergman cyclization in polymer science and materials chemistry. A variety of synthetic strategies have been developed to fabricate structurally unique materials via the Bergman cyclization, including the fabrication of rod-like polymers with polyester, dendrimers and chiral imide side chains, functionalization of carbon nanomaterials by surface-grafting conjugated polymers, formation of nanoparticles by intramolecular collapse of single polymer chains, and the construction of carbon nanomembranes with different morphologies. Future developments involving the Bergman cyclization in polymer science, probably by altering the reaction mechanism to precisely control the microstructure of polymeric products, are also proposed in this review article.

Polymer-mediated immunocamouflage of red blood cells: Effects of polymer size on antigenic and immunogenic recognition of allogeneic donor blood cells

Developing a practical means of reducing alloimmunization in chronically transfused patients would be of significant clinical benefit. Immunocamouflaging red blood ceils （RBCs） by membrane grafting of methoxypoly（ethylene glycol） （mPEG） may reduce the risk of allo-immunization. The results of this study showed that antibody recognition of non-ABO antigens was sig- nificantly reduced in an mPEG-dose- and polymer size-dependent manner, with higher molecular weight mPEGs providing better immunoprotection. Furthermore, in vivo immunogenicity was significantly reduced in mice serially transfused with mPEG-modified xenogeneic （sheep; sRBCs）, allogeneic （C57B1/6）, or syngeneic （Balb/c） RBCs. Following a primary transfu- sion of sRBCs, mice receiving mPEG-sRBCs showed a 〉90% reduction in anti-sRBC IgG antibody levels. After two transfusions, mice receiving mPEG-sRBCs showed reductions of 〉80% in anti-sRBC IgG levels. Importantly, mPEG-modified autologous cells did not induce neoantigens or an immune （IgG or IgM） response. These data suggest that the global immuno- camouflage of RBCs by polymer grafting may provide a safe and cost-effective means of reducing therisk of alloimmunization.