The first bidentate phosphanylborohydride: Synthesis, structure, and reactivity towards [CpFe(CO)2I]

Deprotonation of the phosphane-borane adduct rac/meso-(HP(BH₃)(Ph)CH₂)₂ (2) with KH provides facile access to the bidentate phosphanylborohydride rac/meso-K₂[(P(BH₃)(Ph)CH₂)₂] (3). Treatment of 3 with two equivalents of [CpFe(CO)₂I] gives the dinuclear complex rac/meso-[(CpFe(CO)₂)₂-μ-(P(BH₃)(Ph)CH₂)₂] (4). Single crystals of the pure diastereomers meso-2, meso-3(thf)₄, and rac-4 have been grown from toluene/pentane, diethyl ether/thf, and benzene/pentane, respectively. The molecular structures of all three compounds have been determined by X-ray crystallography.     

Interconversions of the silylene-to-silene and germylene-to-germene types: direct spectroscopic studies and calculations

The recent advances in spectroscopic and quantum-chemical studies of carbene-to-olefin isomerization of carbene analogs of Group 14 elements are discussed. Primary attention is devoted to the use of matrix isolation spectroscopy, whose successful combination with modern calculation techniques has resulted in the first spectroscopic characterization of a number of novel short-lived silylenes and germylenes and their structural isomers with unsaturated Si=C, Ge=C, and Si=O bonds. Based on invited lecture given by Professor Dr. V. N. Khabashesku at the Sixth International Conference on Chemistry of Carbenes and Related Intermediates (May 28–30, 1998, St. Petersburg, Russia). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2027–2039, November, 1999.     

二茂铁基Tamoxifen类似物的合成、结构与性质

合成了一系列二茂铁基Tamoxifen类似物并作了初步生化试验(RBA试验),研究了代表化合物二茂铁基羟基Tamoxifen的晶体结构和顺-反异构化。     

Theoretical approach to the pharmacophoric pattern of GABAB analogs

In order to determine the structural requirements that are important for GABA_B binding affinity, a quantum-chemical-based conformational study has been performed, followed by a similarity analysis which includes 12 GABA_B analogs. Due to the flexibility of the structures, a semigrid GABA_B analog [2RS-(5,5-dimethyl) morpholinyl-acetic acid] has been used as a template for the amonium moiety in order to help to identify the active conformation. Both in vacuo, and solvent-simulated calculations, for the physiological media modeled as water molecules, have been compared, for this analog, at ab initio (G94, 6-31+G(d,p)) and semiempirical (PM3) levels, respectively. On the basis of this comparison, the results of in vacuo PM3 calculations have been chosen for the similarity analysis. We have included, in the calculations, a group of molecules heterogeneous enough to become representative of the different families that can bind to the GABA_B receptor site. Following their comparison we report the leading characteristics that can be related to their binding capability and define a pharmacophoric pattern for GABA_B analogs. The latter is compared with the one previously found for the binding affinity at the GABA_A receptor site. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1195–1208, 1998     

Self‐assembled Lipid Nanoparticles for Ratiometric Codelivery of Cisplatin and siRNA Targeting XPF to Combat Drug Resistance in Lung Cancer

DNA damage repair through the nucleotide excision repair (NER) pathway is one of the major reasons for the decreased antitumor efficacy of platinum‐based anticancer drugs that have been widely applied in the clinic. Inhibiting the intrinsic NER function may enhance the antitumor activity of cisplatin and conquer cisplatin resistance. Herein, we report the design, optimization, and application of a self‐assembled lipid nanoparticle (LNP) system to simultaneously deliver a cisplatin prodrug together with siRNA targeting endonuclease xeroderma pigmentosum group F (XPF), a crucial component in the NER pathway. The LNP is able to efficiently encapsulate both the platinum prodrug and siRNA molecules with a tuned ratio. Both platinum prodrug and XPF‐targeted siRNA are efficiently carried into cells and released; the former damages DNA and the latter specifically downregulates both mRNA and protein levels of XPF to potentiate the platinum drug, leading to enhanced expression levels of apoptosis markers and improved cytotoxicity in both cisplatin‐sensitive and ‐resistant human lung cancer cells. Our results demonstrate an effective approach to utilize a multi‐targeted nanoparticle system that can specifically silence an NER‐related gene to promote apoptosis induced by cisplatin, especially in cisplatin‐refractory tumors.     

基于微流控芯片的72重单核苷酸多态性族群推断系统的构建

建立了常染色体单核苷酸多态性（SNPs）复合检测芯片体系,用于未知个体的族群来源推断。基于前期筛选的74-SNPs组合,采用竞争性等位基因特异性聚合酶链式反应（PCR）的原理构建SNPs的扩增体系,在微流控芯片的每个反应孔内完成一个SNP的检测,通过高通量PCR微流控芯片实现了其中72个SNPs的同步检测。芯片的扩增由平板PCR仪完成,反应孔的荧光信号通过激光共聚焦扫描仪检测,最终通过提取的荧光值进行结果分析。使用该芯片检测获得52份样本的SNPs分型,分型结果的准确率为100%。以57个人群的3628个样本为参考人群数据库,进行20份样本的族群来源推断,推断结果与样本的实际来源一致。本研究建立的常染色体72个SNPs微流控芯片体系可以有效地进行SNP多态性分析检测,基于参考数据库,20份检测样本族群推断的准确性为100%。     

Isolation and characterization of related impurities in 24-epibrassinolide

Two extra-hydroxylated analogs of 24-epibrassinolide (2), 17-hydroxy-24-epibrassinolide (4), 25-hydroxy-24-epibrassinolide (5), and two oxo-analogs of 24-epibrassinolide 22-oxo-23S-24-epibrassinolide (6), 22R-23-oxo-24-epibrassinolide (7) as impurities were isolated and identified from the initial material [purity: 2 and its 22S, 23S-isomer (3) >95%] by using various chromatographic methods and repeated crystallization. Among them, compound 4 and compound 6 were first reported. Their structures were established by spectrometric analysis and X-ray crystallography study. Formation of mixed crystals of 6 and 7 in the crystallization process was postulated and further confirmed.     

Polymorphisms of COTL1 gene identified by proteomic approach and their association with autoimmune disorders

To select candidate genes, we attempted to comparative analysis of protein levels between rheumatoid arthritis (RA) patients and healthy controls by two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS). We identified 17 proteins that showed up- or down-regulated spots in RA patients. We found that coactosin-like1 (COTL1) were highly expressed in RA patients compared with healthy controls. We performed a case-control study to determine whether the COTL1 gene polymorphisms were associated with RA and systemic lupus erythematosus (SLE). The genotype frequency of c.-1124G>T and the allelic frequency of c.484G>A in RA patients, and the genotype frequency of c.484G>A in SLE patients were significantly different from healthy controls (P = 0.009, 0.027, and 0.025, respectively). We also investigated the correlation with the levels of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibody in RA patients, and anti-nuclear antibodies (ANA) in SLE patients. The c.484G>A polymorphism in RA patients has significant association with the levels of anti-CCP antibody (P = 0.03). Our findings demonstrated that c.-1124G>T and c.484G>A polymorphisms of the COTL1 gene might be associated with the genetic susceptibility of autoimmune disorders.     

Synthesis and RNA-selective hybridization of α-l-ribo- and β-d-lyxo-configured oligonucleotides

Three α-l-ribofuranosyl analogues of RNA nucleotides (α-l-RNA analogues) have been synthesized and incorporated into oligonucleotides using the phosphoramide approach on an automated DNA synthesizer. The 4′-C-hydroxymethyl-α-l-ribofuranosyl thymine monomer was furthermore synthesized. Relative to the unmodified duplexes, incorporation of a single α-l-RNA monomer into a DNA strand leads to reduced thermal stability of duplexes with DNA complements but unchanged thermal stability of duplexes with RNA complements, whereas incorporation of more than one α-l-RNA monomer lead to moderately decreased thermal stability also of duplexes with RNA complements. Efficient hybridization with an RNA complement and no melting transition with a DNA complement were observed with stereoregular chimeric oligonucleotides composed of a mixture of α-l-RNA and affinity enhancing α-l-LNA monomers (α-l-ribo-configured locked nucleic acid). Furthermore, duplexes formed between oligodeoxynucleotides containing an α-l-RNA monomer and complementary RNA were good substrates for Escherichia coli RNase H. RNA-selective hybridization was also achieved by the incorporation of 1-(4-C-hydroxymethyl-β-d-lyxofuranosyl)thymine monomers into a DNA strand, whereas stable duplexes were formed with both complementary DNA and RNA when these monomers were incorporated into an RNA strand.     

Numerical characterization of DNA sequences based on the k-step Markov chain transition probability

A DNA sequence can be regarded as a discrete-time Markov chain. Based on k-step transition probabilities, we construct a series of 4 x 4 k-step transition matrices to characterize the DNA primary sequences. According to the properties of Markov chains, we obtain distributions of A, T, C and G, and analyze the changes among them from yesterday to tomorrow. We can calculate the probabilities of nucleotide triples of DNA primary sequences. Finally, we introduce a correlation of this kind of transition matrices and consider it as an invariant to analyze the similarities/dissimilarities of DNA sequences.