硝酸镍-硝酸镧基体改进剂石墨炉原子吸收测定硫磺中痕量砷

本文研究了以硝酸镍 硝酸镧为基体改进剂 ,石墨炉原子吸收法测定硫磺中痕量砷 ,还研究了硫磺的控温电热酸消解和高压坩埚酸消解。试验表明 ,硫磺试样经硝酸 高氯酸消解后测砷 ,用硝酸镍 硝酸镧基体改进剂 ,比只用硝酸镍基体改进剂 ,灵敏度明显提高。试样的分析结果与HG ICP AES相吻合 ,方法检出限为0 0 34 μg·mL- 1 ,RSD≤ 2 1% (n =4) ,回收率 97 5 %～ 110 %。     

利用聚四氟乙烯为化学改进剂降低电热原子吸收测定铬的基体干扰

本文研究了电热原子吸收光谱测定痕量铬时几种常见的金属离子的干扰作用。     

Low-molecular-weight poly-carboxylate as crystal growth modifier in biomineralization

Construction of modified inorganic mineral with controlled mineralization analogues of those produced by nature is now of current interest for understanding the mechanism of thein vivo biomineralization processes, as well as looking for fresh industrial and technological applications. Low-molecular-weight chiral poly-carboxylate ligands derived from naturally occurring L-α-amino acids have been used as model systems to study the effect of molecular properties on crystal growth modification.     

Influence of polar modifiers on microstructure of polybutadiene obtained by anionic polymerization. Part 4: Acid-base polar modifiers forming σ-μ complexes: Amine-alkoxide,amine-ether-alkoxide,and ether-alkoxide

The influence of acid-base polar modifiers (σ-μ complex): amine-alkoxide, amine-ether-alkoxide, and ether-alkoxide complexes on microstructure of polybutadiene obtained by anionic polymerization was studied. The content of butadiene isomeric structures was determined based on FT-IR-ATR, ¹H, and ¹³C NMR data analyses. The results obtained indicated a very similar influence of all types of polar modifiers forming σ-μ complex on polymer microstructure leading to high vinyl polybutadiene with nearly equal ratios of cis-1,4 and trans-1,4 butadiene isomeric structures.     

RNA-Targeting Splicing Modifiers: Drug Development and Screening Assays

RNA splicing is an essential step in producing mature messenger RNA (mRNA) and other RNA species. Harnessing RNA splicing modifiers as a new pharmacological modality is promising for the treatment of diseases caused by aberrant splicing. This drug modality can be used for infectious diseases by disrupting the splicing of essential pathogenic genes. Several antisense oligonucleotide splicing modifiers were approved by the U.S. Food and Drug Administration (FDA) for the treatment of spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD). Recently, a small-molecule splicing modifier, risdiplam, was also approved for the treatment of SMA, highlighting small molecules as important warheads in the arsenal for regulating RNA splicing. The cellular targets of these approved drugs are all mRNA precursors (pre-mRNAs) in human cells. The development of novel RNA-targeting splicing modifiers can not only expand the scope of drug targets to include many previously considered “undruggable” genes but also enrich the chemical-genetic toolbox for basic biomedical research. In this review, we summarized known splicing modifiers, screening methods for novel splicing modifiers, and the chemical space occupied by the small-molecule splicing modifiers.     

Preparation of Mitochondria- and Epigenetics-Targeting Nanoparticles for Suppression of Cancer Metastasis

Epithelial-to-mesenchymal transition (EMT) of carcinoma cells is a promising target for cancer therapy since it is closely related to tumor metastasis and therapeutic resistance. The process of EMT is strongly associated with epigenetic alterations in cancer cells. In addition, recent accumulating evidence suggests that EMT also has a significant influence on inducing cancer stem cells (CSCs). In this study, novel polymer core–lipid shell nanoparticles (PLNPs) are prepared to suppress cancer EMT by the combined effects of the antioxidant activity of core-encapsulated Mn imidazolium porphyrin (MnImP) and the epigenetic control by histone acetyltransferase-encoding plasmid DNA (pHAT) hybridized onto the shell surface. PLNPs show the ability to control the expression of EMT-related markers, resulting in the suppression of EMT in lung epithelial cancer cells (paraquat-treated A549 cells). Furthermore, PLNPs suppress the levels of intracellular mitochondrial ROS and the transformation to CSCs. The results of this study may provide a novel therapeutic strategy against tumor metastasis and treatment resistance.     

反应修饰剂ZnSO_4和预处理对苯选择加氢制环己烯Ru-Zn催化剂性能的影响

共沉淀法制备了Ru-Zn催化剂,考察了反应修饰剂ZnSO_4和预处理对苯选择加氢制环己烯Ru-Zn催化剂性能的影响。结果表明,反应修饰剂ZnSO_4可以与Ru-Zn催化剂中助剂Zn O反应生成(Zn(OH)2)3(ZnSO_4)(H_2O)盐。随反应修饰剂ZnSO_4浓度增加,(Zn(OH)2)3(ZnSO_4)(H_2O)盐量逐渐增加,Ru-Zn催化剂活性逐渐降低,环己烯选择性逐渐升高。因为(Zn(OH)2)3(ZnSO_4)(H_2O)盐中的Zn2+可以使Ru变为有利环己烯生成的缺电子的Ruδ+物种,而且还可以占据不适宜环己烯生成的强Ru活性位。但当反应修饰剂ZnSO_4浓度高于0.41 mol·L-1后,继续增加ZnSO_4浓度,由于Zn2+水解浆液酸性太强,可以溶解部分(Zn(OH)2)3(ZnSO_4)(H_2O)盐,RuZn催化剂活性升高,环己烯选择性降低。环己烯选择性略微降低,是由于ZnSO_4溶液中大量的Zn2+可以与生成的环己烯形成配合物,稳定生成的环己烯,抑制环己烯再吸附到催化剂表面并加氢生成环己烷。在ZnSO_4最佳浓度0.61 mol·L-1下对Ru-Zn催化剂预处理15 h,Ru-Zn催化剂中助剂Zn O可以与ZnSO_4完全反应生成(Zn(OH)2)3(ZnSO_4)(H_2O)盐,在该催化剂上25 min苯转化68.2%时环己烯选择性和收率分别为80.2%和54.7%。而且该催化剂具有良好的稳定性和重复使用性能。     

石墨炉原子吸收光谱法测定锌基体物料中微量铊

采用B-HNO3-A溶解样品,硝酸钯作基体改进剂,通过优化仪器分析条件,灰化温度为500℃,原子化温度为1 800℃,成功实现了石墨炉原子吸收光谱法测定湿法冶炼锌基体物料锌精矿、锌焙砂、氧化锌、锌粉等物料中微量铊。方法对照实验结果与电感耦合等离子体质谱法(ICP-MS)测定值基本一致。方法的相对标准偏差(RSD,n≤8)为1.7%~7.8%,加标回收率为99%~103%。     

冠醚化合物在制备外延卤化银乳剂中的作用

自从冠醚于六十年代末问世以来^[1,2],科学家们对它进行了大量的研究。它以遮盖力大,对金属离子络合性能好而著称于化学领域。在感光化学领域,它的主要应用在于对乳剂晶体的尺寸及分布产生影响,使之均一,且颗粒增大^[3-6];作为调变剂,促进外延乳剂晶体的生长^[7-8];提高乳剂的感光性能^[5,9-11]。     

石墨炉原子吸收光谱法测定锌基体物料中微量铊

采用B-HNO3-A溶解样品,硝酸钯作基体改进剂,通过优化仪器分析条件,灰化温度为500℃,原子化温度为1 800℃,成功实现了石墨炉原子吸收光谱法测定湿法冶炼锌基体物料锌精矿、锌焙砂、氧化锌、锌粉等物料中微量铊。方法对照实验结果与电感耦合等离子体质谱法(ICP-MS)测定值基本一致。方法的相对标准偏差(RSD,n≤8)为1.7%⁷.8%,加标回收率为99%7.8%,加标回收率为99%¹03%。