二氧化碳基脂肪族聚碳酸酯的功能化研究进展

简要介绍了二氧化碳基塑料的工业化进程,同时针对当前二氧化碳共聚物结构中缺少可反应基团、难以进行化学修饰导致的品种和功能单一、亲水性差等问题,介绍了二氧化碳基脂肪族聚碳酸酯的功能化研究进展,主要包括侧链含有双键、碳酸酯键和液晶基团的侧基功能化二氧化碳共聚物的合成与性能研究,以及二氧化碳共聚物的亲水性调制和刺激响应行为探索,试图为丰富二氧化碳基聚碳酸酯结构和性能提供借鉴.     

气相色谱-质谱法同时测定葡萄酒中13种防腐剂

采用气相色谱-质谱法同时测定了葡萄酒中的乙酸、丙酸、富马酸二甲酯(DMF)、2,6-二叔丁基对甲酚(BHT)、山梨酸、脱氢乙酸、苯甲酸、叔丁基羟基茴香醚(BHA)、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯、4-苯基苯酚共等13种防腐剂,建立了测定方法。样品以乙醚作为提取溶剂,饱和NaCl溶液作为释放剂,提取后乙醚层经无水Na2SO4脱水干燥过滤,旋转蒸发仪上浓缩至近干,定容后进行分析。采用程序升温,将13种防腐剂完全分离,平均回收率为84%～107%,检出限为0.10～1.46 mg/kg,RSD(n=7)为0.8%～5.4%。     

Single‐Molecule Detection Reveals Knot Sliding in TrmD Denaturation

An increasing number of proteins are found to contain a knot in their polypeptide chain. Although some studies have looked into the folding mechanism of knotted proteins, why and how these complex topologies form are still far from being fully answered. Moreover, no experimental information about how the knot moves during the protein‐folding process is available. Herein, by combining single‐molecule fluorescence resonance energy transfer (smFRET) experiments with molecular dynamics (MD) simulations, we performed a detailed study to characterize the knot in the denatured state of TrmD, a knotted tRNA (guanosine‐1) methyltransferase from Escherichia coli, as a model system. We found that the knot still existed in the unfolded state of TrmD, consistent with the results for two other knotted proteins, YibK and YbeA. More interestingly, both smFRET experiments and MD simulations revealed that the knot slid towards the C‐terminal during the unfolding process, which could be explained by the relatively strong interactions between the β‐sheet core at the N terminal of the native knot region. The size of the knot in the unfolded state is not larger than that in the native state. In addition, the knot slid in a “downhill” mode with simultaneous chain collapse in the denatured state.     

羟基自由基引发的马来酸酐聚合反应机理AM1研究

用AM1方法计算了马来酸酐、羟基自由基及其加成产物α-羟基丁二酸酐基自由基的电子结构、电荷分布和键级.应用前线轨道理论和成键三原则研究了羟基自由基引发下马来酸酐聚合过程中α-羟基丁二酸酐基自由基活性中间体参与反应的可能性及其自由基聚合反应机理.计算结果表明:马来酸酐基态分子的HOMO和LUMO分别对应于双键CC的成键π-MO和反键π -MO;马来酸酐的羟基自由基加成反应活化能计算值为55 7kJ/mol;马来酸酐在羟基自由基引发下的自由基聚合产物是链式结构,与实验事实相符.     

CO2 and photo-controlled reversible conversion of supramolecular assemblies based on water soluble pillar[5]arene and coumarin-containing guest

In this communication,a new supramolecualr amphiphile was successfully constructed based on water soluble pillar[5]arene and a unique guest which contain a CO₂ responsive tertiary amine unit and a UV responsive coumarin group.When guest molecule 1 dispersed in water,it self-assembled into sheet-like structures.Upon bubbling CO₂,1 transformed into 1 H due to the tertiary amine unit was protonated,accompany the nano-sheets transformed into vesicles.Further irradiation of 1 H with 365 nm light for 3 h,the coumarin group reacted with each other to form bola-type amphiphie 2 H.In this case,vesicles collapsed and re-assembled into nano-tubes.However,when addition of WPS into the solution of 1 H,the vesicles transformed into micelles,this is due to the formation of supramolecular amphiphile WP5&1 H.Upon irradiation of WP5&1 H with 365 nm light for 3 h,nano-ribbons observed instead of micelles in the solution.Notably,nanotubes from 2 H could also transform into nano-ribbons after adding WPS.The selfassembly process and the resultant assemblies were characterized by TEM,SEM,DLS,SAXS and NMR technologies.Due to both CO₂ and light are "green" for living organisms,we anticipated our system can offer the possibilities in "on demand" drug absorption and release.     

Two-photon dual-channel fluorogenic probe for in situ imaging the mitochondrial H2S/viscosity in the brain of drosophila Parkinson’s disease model

H₂S is an essential gas signal molecule in cells, and viscosity is a key internal environmental parameter. Recent studies have shown that H₂S acts as a cytoarchitecture agent and gas transmitter in many tissues, e.g., as a regulator of neuroendocrine in the brain for mediating vascular tone in blood vessels. Mitochondrial viscosity is an important parameter for judging whether mitochondrial function is normal. It has been reported that oxidative stress and mitochondrial dysfunction are connected with Parkinson’s disease (PD), and the protective role of H₂S in PD models has been extensively demonstrated. Herein, Mito-HS, a new two-photon fluorescent probe was demonstrated to detect cross-talk between the two channels of mitochondrial viscosity and H₂S content. Moreover, this probe could detect the relative amount of and changes in mitochondrial H₂S in situ due to the reduced mitochondrial targeting ability after reaction with H₂S. The results show that H₂S in mitochondria is inversely related to viscosity. The PD model has a lower H₂S in mitochondria and a higher mitochondrial viscosity than did the normal. This result is important for our deep understanding of PD and its causes.     

TiO_2空心微球负载钒、铈催化剂的制备及其对氯苯催化燃烧性能研究

采用水热法制备TiO2空心球,以TiO2空心球为载体,采用等体积浸渍法分别制备了不同V负载量(3%~10%)的V2O5/TiO2和稀土改性后的V2O5-CeO2/TiO2催化剂,利用XRD,SEM,EDS,TEM对TiO2空心球及V2O5-CeO2/TiO2催化剂进行了表征,结果表明,空心球TiO2分散性良好,粒径在1.5μm左右,且其为锐钛矿结构,负载的V和大部分的Ce均匀分散在TiO2空心球体内部或者表面而未破坏TiO2空心球结构。考察了催化剂对氯苯的催化燃烧性能,活性评价结果表明当V负载量在5%时,V2O5/TiO2催化剂对氯苯催化燃烧性能最佳,在掺杂10%的稀土Ce后,催化燃烧氯苯的活性得到明显提高。     

Preparation of <Superscript>99m</Superscript>Tc-PQQ and preliminary biological evaluation for the NMDA receptor

Pyrroloquinoline quinone (PQQ), an essential nutrient, antioxidant, redox modulator and nerve growth factor found in a class of enzymes called quinoproteins, was labeled with ^99mTc by using stannous fluoride (SnF₂) method. Radiolabeling qualification, quality control and characterization of ^99mTc-PQQ and its biodistribution studies in mice were performed and discussed. Effects of pH values, temperature, time and reducing agents concentration on the radiolabeling yield were investigated. The quality control procedure of ^99mTc-PQQ was determined by thin layer chromatography (TLC), radio high-performance liquid chromatography (RHPLC) and paper electrophoresis methods. The average radiolabeling yield was 94 ± 1% under optimum conditions of 0.99 mg of PQQ, 30 μg of SnF₂, 0.5 mg of ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) and 18.5 MBq of Na^99mTcO₄ at pH 6 and 25 °C with a response volume of 1 ± 0.1 mL. ^99mTc-PQQ was stable and anionic. Lipid–water partition coefficient of ^99mTc-PQQ was −1.49 ± 0.16. The pharmacokinetics parameters of ^99mTc-PQQ were t _1/2α = 18.16 min, t _1/2β = 100.45 min, K ₁₂ = 0.013 min⁻¹, K ₂₁ = 0.017 min⁻¹, K _e = 0.016 min⁻¹, AUC (area under the curve) = 1040.78 ID% g⁻¹ min and CL (plasma clearance) = 0.096 mL min⁻¹. The dual-exponential equation was Y = 10.88e^−0.038t  + 5.21e^−0.0069t . The biodistribution of ^99mTc-PQQ was studied in ICR (Institute for Cancer Research 7701 Burhelme Are., Fox Chase, Philadelphia, PA 1911 USA) mice. In vitro autoradiographic studies clearly showed that the ^99mTc-PQQ radioactivity accumulated predominantly in the hippocampus and cortex, which had a high density of N-methyl-d-aspartate Receptor (NMDAR). The enrichment can be blocked by NMDAR redox modulatory site antagonists-ebselen (EB) and ^99mTc-PQQ is therefore a promising candidate for the molecular imaging of NMDAR. To date, however, there have been no studies characterizing ^99mTc-PQQ.     

Reversible high‐temperature phase transition of a manganese(II) formate framework with imidazolium cations

A new metal–formate framework, poly[1H‐imidazol‐3‐ium [tri‐μ₂‐formato‐manganese(II)]], {(C₃H₅N₂)[Mn(HCOO)₃]}_n, was synthesized and its structural phase transition was studied by thermal analysis and variable‐temperature X‐ray diffraction analysis. The transition temperature is around 435 K. The high‐temperature phase is tetragonal and the low‐temperature phase is monoclinic, with a β angle close to 90°. The relationship of the unit cells between the two phases can be described as: a_HT = 0.5a_LT + 0.5b_LT; b_HT = −0.5a_LT + 0.5b_LT; c_HT = 0.5c_LT. In the high‐temperature phase, both the framework and the guest 1H‐imidazol‐3‐ium (HIm) cations are disordered; the HIm cations are located about 2mm sites and were modelled as fourfold disordered. The Mn and a formate C atom are located on fourfold rotary inversion axes, while another formate C atom is on a mirror plane. The low‐temperature structure is ordered and consists of two crystallographically independent HIm cations and two crystallographically independent Mn²⁺ ions. The phase transition is attributable to the order–disorder transition of the HIm cations.     

Global variations in peak bone mass as studied by dual-energy X-ray absorptiometry

In 1994, the International Atomic Energy Agency (IAEA) initiated a 5-year Co-ordinated Research Project (CRP) to determine geographical and racial differences in peak bone mineral density (BMD) in men and women aged 15-49 years. The study demonstrates that there are distinct global differences in BMD at the hip and spine in both men and women approximating to one population standard deviation between populations with the highest and lowest BMD. These differences persist following adjustments for age, sex and body size. Such information is valuable in understanding the reasons for global differences in fracture rate and predicting future trends in fracture incidence. This revised version was published online in August 2006 with corrections to the Cover Date.