Nanjiols D and E, Two New Uncommon Steroids from the Chinese Soft Coral Nephthea bayeri

Marine organisms have been found to be a storehouse of steroids, particularly in term ofunique side-chain structures and unusual functionalization. Marine steroids are oftenfound in highly oxygenated forms and possessing various biological activities1.Previously, we reported the isolation and structural elucidation of three new marinesteroids, nanjiols A-C, which showed cytotoxicity against HL-60 and BEL 7402 celllines, from a soft coral Nephthea bayeri in East China Sea2. In continuation …     

Agonist–PPARγ interactions: Molecular modeling study with docking approach

Docking simulation of 18 agonists with the ligand binding pocket (LBP) of PPARγ has been performed. The binding conformations and binding affinities of these agonists were obtained by use of the flexible docking protocol FlexX. Test compound calculations indicated that FlexX can reproduce the binding conformation of the crystal structure (root mean square deviation = 1.43 Å); moreover, the predicted binding affinities correlate well with the activities of these agonists. The interaction model and pharmacophore of PPARγ agonists were derived and the difference in biologic activities of these agonists can be well explained. The PPARγ agonists must have both polar head and the hydrophobic tail, which form hydrogen bonds and hydrophobic contacts with hydrophilic and hydrophobic regions of the LBP of PPARγ, respectively. In addition, a suitable linker is also necessary. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 405–410, 2003     

压力、温度和晶粒尺寸对Fe-N合金的合成及结构的影响

在 1× 1 0 - 3 Pa～ 4 GPa的压力和 5 80～ 930 K温度范围内 ,利用高压技术并结合机械球磨 ,研究了压力、温度和晶粒尺寸对α-Fe与非晶 BN的固态反应的影响 .发现高压和晶粒细化可以极大地促进α-Fe和非晶 BN的固态反应过程 ,α-Fe与非晶 BN发生固态反应的临界晶粒尺寸约 8nm.压力和温度对反应产物及其晶体结构有明显影响 .2 GPa和 80 0 K时 ,反应产物为具有正交结构的 Fe-N新相 ;在 3～ 4 GPa和 690～80 0 K时 ,可形成单一ε-Fex N合金相 ;而在 4 GPa和 930 K以上 ,反应产物由 Fe-N合金相转变为 Fe3B相     

Poly[μ‐aqua‐μ4‐naphthalene‐1,8‐dicarboxylato‐zinc(II)]

In the title complex, [Zn(C₁₂H₆O₄)(H₂O)]_n, a Zn^II polymer based on naphthalene‐1,8‐dicarboxylate (1,8‐nap), the Zn^II atoms adopt an elongated octahedral coordination geometry. A zigzag chain is formed by μ₂‐aqua ligands and μ₂‐carboxylate groups of the 1,8‐nap ligands. Adjacent parallel chains are further linked by 1,8‐nap ligands, forming a twisted two‐dimensional layer structure along the (100) plane.     

二苯硫腙-CCl4-萃取-分光光度法连续测定水样中铜和铅

应用二苯硫腙萃取分光光度法连续测定水样中铜(Ⅱ)和铅(Ⅱ).在pH 3.8的乙酸盐缓冲介质中,用四氯化碳作溶剂萃取铜(Ⅱ)和二苯硫腙的络盐并在551 nm波长处测定溶液的吸光度.在萃取铜(Ⅱ)后的水相中加入pH 10的氨性缓冲溶液,并用1 mol.L-1 NaOH溶液调节溶液的酸度为pH 9.2,仍用四氯化碳作溶剂萃取铅(Ⅱ)与二苯硫腙的络盐,在525 nm波长处测定其吸光度.测得铜(Ⅱ)及铅(Ⅱ)的二苯硫腙络盐在CCl4溶液中的摩尔吸光率依次为6.8×104及1.3×105L·mol-1·cm-1.应用此方法测定了一种水样中的铜(Ⅱ)和铅(Ⅱ),分析结果的RSD(咒=6)值依次为3.0 9/6及8.4 9/6.     

Charge transfer and electron backdonation in metallofullerenes encapsulating NSc3

Orbital interaction analysis is employed to understand the complex charge transfer mechanism operative in endohedral metallofullerenes of composition NSc₃@C_n (n = 68, 78). This phenomenon combines substantial electron transfer from the core to the cage with electron backdonation, involving the interaction between the occupied orbitals of the negatively charged cage and the unoccupied d orbitals of the positively charged core. This electron backdonation differs fundamentally from conventional orbital hybridization, which takes place primarily between the HOMO of the metal core and the LUMO of the fullerene cage. These findings imply the pronounced stability of NSc₃@C_n (n = 68, 78), especially for NSc₃ encapsulated in the non-IPR C₆₈ enclosure, as experimentally established.     

A study of substituent effect on 1H and 13C nmr spectra of N‐ and C‐substituted carbazoles

¹H and ¹³C nmr spectra of several N‐ and C‐substituted carbazoles (Series 1, 2, 3 and 4) were measured. Correlations between chemical shifts and substituent constants show that these parameters describe properly the substituent effect on the nmr phenomena. Atomic charge densities for carbazoles of Series 1, 2, 3 and 4 were calculated by using the semi empirical PM3 method. These values also show a linear correlation with the ¹³C chemical shifts. The synthesis of several carbazole derivatives 1a – 1g, 2a – 2g, 3a – 3j and 4a – 4g have been carried out according to literature procedures. The carbazoles 3i, 3j and 4c have been synthesized and fully characterized for the first time.     

十二烷基季铵盐及其与十二烷基硫酸钠混合体系的表面活性

通过表面张力测定，研究了十二烷基季铵盐Ｃ１２Ｈ２５Ｎ（ＣｎＨ２ｎ＋１）３Ｂｒ（ｎ＝１，２，３，４）及其与十二烷基硫酸钠混合体系的表面活性，应用规则溶液理论，计算了混合体系表面吸附层和胶团的组成及分子相互作用参数，对于季铵盐、极性基影响大：ｃｍｃ随ｎ增加而下降，γｃｍｃ则先上升，后下降，自极性基碳链的空间阻碍、疏水、弯曲效应，以及电荷屏蔽效应可对此予以解释，对于混合体系，极性基大小对其表面活性及胶团     

纸张保存的化学

讨论了纸张保存过程中的某些化学问题,对纸张的酸性、酸性来源和纤维系酸催化水解以及影响纸张变质的其它因素进行了分析,评述了近年来在纸张脱酸、脱色和利用新的浆内施胶剂等方面研究取得的一些成果。     

火焰原子吸收法快速分析硫酸中铅镉铜锌

文中直接取硫酸样品3ml于装有约10ml水的25ml比色管中,加入碘化钾溶液2ml,用水稀至刻度。加入甲基异丁酮5ml,萃取lmin,分层后,在有机相中测定铅、镉、铜含量;在水相中测定锌含量。方法的加标回收率为98.9％～103％,精密度1.8％～4.3％,标准曲线法和标准加入法结果相近,倍比试验结果亦相吻合,方法快速简便、准确,适合于工业中的快速分析。