Hirsutellone F, a dimer of antitubercular alkaloids from the seed fungus Trichoderma species BCC 7579

[structure: see text] Hirsutellone F (7), a novel alkaloid dimer, was isolated together with known monomers, hirsutellones A (1), B (2), and C (3), from the seed fungus Trichoderma sp. BCC 7579. The structure of 7 was elucidated by spectroscopic analysis. Studies on biomimetic chemistry, using the dimer 7, suggested that compound 8 (17,1'-dehydrohirsutellone B) should be the precursor for all hirsutellones.     

Stereoselective Synthesis of the Decahydrofluorene Core of the Hirsutellones

A stereoselective synthesis of the decahydrofluorene core of the hirsutellones was accomplished in eight steps and in 43% overall yield. The key step of the synthesis is the highly stereoselective intramolecular Diels-Alder cyclization of the siloxacyclopentene-constrained tetraene 1.     

Hirsutellones A-E, antimycobacterial alkaloids from the insect pathogenic fungus Hirsutella nivea BCC 2594

Five new alkaloids, hirsutellones A-E, were isolated from the insect pathogenic fungus Hirsutella nivea BCC 2594. Their structures were elucidated by spectroscopic analysis and X-ray crystallography. Hirsutellones displayed significant growth inhibitory activity against Mycobacterium tuberculosis H₃₇Ra.     

Bioinspired synthesis of hirsutellones A, B, and C

The total synthesis of hirsutellones A (1), B (2), and C (3) has been achieved through a bioinspired late-stage sequence starting from advanced intermediate 6. The sequence proceeded via labile intermediate 17,1'-dehydrohirsutellone B (5) and delivered, in addition to the natural products (1-3), hirsutellone analogue 1',2',17-epi-hirsutellone C (1',2',17-epi-3).     

On the adequacy of modeling the concentration dependences of the activity coefficients for the components of solutions

An analysis of the accepted methods for calculating the activity coefficients for the components of binary aqueous solutions was performed. It was demonstrated that the use of the osmotic coefficients in auxiliary calculations decreases the accuracy of estimates of the activity coefficients. The possibility of calculating the activity coefficient of the solute from the concentration dependence of the water activity was examined. It was established that, for weak electrolytes, the interpretation of data on heterogeneous equilibria within the framework of the standard assumption that the dissociation is complete encounters serious difficulties.     

光亮剂对银电沉积行为的影响

用电势阶跃法和旋转圆盘电极法 (RDE)以及SEM和XRD测试手段 ,初步研究了光亮剂对氰化体系中银电沉积行为的影响 .研究表明 ,光亮剂的加入并未导致银电沉积成核机理的改变 ,但显著增强了镀液的微观平整效应 ,并且所得镀层的表观光滑程度明显改善 .XRD测试亦同时表明光亮剂的加入并未改变镀层的择优取向     

三种蒙药中微量元素含量与疗效相关性分析

用原子吸收分光光度计测定了蒙药扎木萨－4,阿拉坦－5,阿那日－5中多种微量元素及常量元素的含量。结果表明,这三种健胃消食蒙药中Mg、Fe、Mn、Zn均较高,呈一定相关性,而有害元素Pb、Cd很少,探讨了三种蒙药中微量元素与其疗效的关系。     

胶囊中铬的测定方法研究

通过对比不同的前处理措施,建立准确、快速测定胶囊中铬（Cr）的方法。分别采用微波消解和电热恒温自动消解法进行前处理,石墨炉原子吸收法进行测定。试验表明：该方法在0~40.0μg/L范围内呈线性相关,相关系数为0.997 7,检出限为0.017 mg/kg,样品的加标回收率在90%~110%之间。对标准物质圆白菜中铬的测定在所要求的准确度范围之内。同时作了原子吸收光谱仪和电感耦合等离子体（ICP）发射光谱仪两种仪器的对照试验,方法的稳定性良好。采用微波消解或电热恒温消解作为胶囊的前处理,通过原子吸收法或ICP法均能准确测定胶囊中的铬。     

On the properties of alpha-glucosidase and the binding of glucose to the enzyme.

An alpha-glucosidase was purified from baker's yeast. The molecular weight was approximately 44 000 daltons. SDS-disc gel electrophoresis suggested that the enzyme consisted of four subunits. The isoelectric point was at pH 5.4. The Km values for p-nitrophenyl alpha-D-glucopyranoside and maltose were 2.9 X 10(-4) and 2.5 X 10(-2) M, respectively. Binding of 2-(p-toluidino)naphthalene-6-sulfonate to the alpha-glucosidase was associated with a strong increase in fluorescence. The dissociation constant of the enzyme-TNS complex was 8 X 10(-5) M. The fluorescent probe did not interfere with the binding of glucose to the enzyme although the alpha-glucosidase was inhibited by high concentrations of TNS. The formation of an enzyme-glucose complex was indicated by an increase of fluorescence and by a shift in the wavelength for maximal emission which suggests that the binding process is associated with a change in conformation. The dissociation constant of the glucose--alpha-glucosidase complex KD = 0.57 X 10(-3) M, was calculated from the increase in fluorescence as a function of glucose concentration.     

Construction of the Skeleton of Phthalascidin, Mechanism of the Formation of the Key Tricyclic Lactam Intermediate

Phthalascidin is a structurally simplified version of Et-743, which is a potent anti-tumor marine natural product isolated from Ecteinascidia turbinata. Its antiproliferative activity is greater than that of the agents taxol, camptothecin, adriamycin, mitomycin C, cisplatin, bleomycin, and etoposide by 1-3 orders of magnitude. An elegant synthesis of Et-743 and phthalascidin has been reported by E. J. Corey and co-workers1,2. As part of our continuing program, we have also engaged in dev…     

On the influence of the water electrostatic field on the amide group vibrational frequencies

For clusters of N-methylacetamide and water molecules the performance of the fixed-charged approximation was tested against continuum and explicit ab initio models. The dispersion of the vibrational frequencies when constant electrostatic potential was maintained at the solute atoms was compared to the distribution caused by geometry fluctuations.     

火灾探测器滤光片校准方法

以紫外可见近红外分光光度计为计量标准器建立火灾探测器滤光片校准方法。火焰探测器紫外滤光片校准选择波长范围150~300 nm进行光谱扫描,测量滤光片在紫外区域的透射比;红外滤光片校准选择波长范围800~1 100 nm进行光谱扫描,测量滤光片在红外区域的透射比。线型光束感烟火灾探测器滤光片校准波长扫描范围设置为700~1 100 nm,取850~950 nm透射比平均值计算减光值。火焰探测器紫外滤光片校准结果为220,240,260,280 nm波长下的透射比,红外滤光片校准结果为850,900,950,1 000 nm波长下的透射比,不作合格性判定。线型光束感烟火灾探测器滤光片减光值标称值为0.4,0.9 d B时,误差不超过±0.1 d B;减光值标称值为10.0 d B时,误差不超过±1.0 d B。     

Effect of the size of the charged group on the properties of alkoxylated NFCs

The impact of the size of the charged group on the properties of alkoxylated NFC was studied by two chloroalkyl acid reagents. It was found that the employment of the larger 2-chloropropionic acid reagent leads to improved properties, e.g. higher fraction of nano-sized materials, and significantly better redispersion as compared to when the smaller monochloroacetic acid was employed. The differences in the impacts of the different reagents were hypothesized to be due to a more efficient disruption of the cohesion between the nanofibrils when a larger charged group was employed.     

储氢合金电极的表面修饰研究

利用等离子体技术对AA型MH/Ni电池的储氢合金电极进行了镀覆导电膜层的表面修饰,用XRD及SEM对电极结构进行了表征.极片经过表面修饰的电池,其内阻降低了24％,放电容量有了明显提高,5C (7.5 A) 放电容量提高了200 mA•h,放电平台电压提高了约0.14 V,导电膜层还起到了电极保护层的作用,抑制了合金的粉化,提高了电池的循环稳定性.同时,电池内压显著降低,电池性能有了较大改善.     

Method for the calculation of the species balance in the reaction zone

A class of processes for which the problem of species balance can be solved without using any assumptions concerning the mechanism of the chemical event of the reaction was found in the problem of species balance in the reaction zone. The mathematical statement of the problem in this case was discussed; it was shown that the solution is mainly determined by the system geometry. The method for reducing the problem to determination of the probability of species entering the chemical event zone is substantiated; this can be done by the Green function method.     

Probing the role of the mycosamine C2'-OH on the activity of amphotericin B

A synthetic route to a mycosamine donor was designed and provided access to a set of AmB derivatives targeted to probe the effect of the C2'-OH. It was determined that the configuration of the C2'-position is inconsequential but that O-methylation of this alcohol was deleterious to its mode of action. Additionally, the analog incorporating a mycosamine derivative from the enantiomeric series was devoid of activity.     

Investigation of the mechanism of the polarographic reduction of the sydnoneimmonium cation

The polarographic reduction of the sydnoneimmonium cation (I) was investigated in the case of 3--phenylisopropylsydnoneimine hydrochloride (sydnophen). The effect of the pH, alcohol concentration, ionic strength, and surface-active substances was studied, and the electrolysis was carried out at a controllable potential under various conditions. The cyclic voltampefograms were recorded. A mechanism for the reduction of I is proposed. Cleavage of the ring of I in the near-electrode space is observed in unbuffered media. The first direct proof of the existence of the unstable sydnoneimine base was obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1042–1048, August, 1975.     

国产硅藻土吸附尿激酶机理的研究

在常温下, 尿激酶在浙江土和吉林土表面的吸附等温线分别为V型和II型; 焙烧后两者皆转为III型。吸附等温线类型与硅藻土表面结构、孔结构、表面ζ电位有关。在400℃焙烧的硅藻土等电点值最低, 吸附量最大; 改性后, 吸附量也发生改变。本文还测定了尿激酶在硅藻土表面的吸附形态, 其吸附等温线方程符合0/(1-0)=(Kc)^1/β, 并讨论了平衡常数K和尿激酶吸附功能链段数β随温度的变化。     

Effect of the thermal history on the phase transition and the liquid crystalline structure of thermotropic polyesters

A series of triad type thermotropic polyesters based on phenylsulfonyl hydroquinone and α,ω-bis(4-carboxyphenoxy)alkane was prepared, and the effect of the thermal history on the phase transition and the liquid crystalline structure of the polyesters was studied. The phase transition was significantly affected by the thermal history. When annealed at various temperatures, multiple endotherms were observed for all polyesters in DSC thermograms. A phase stability concept was employed to explain the complicated phase transitions. The time evolution of the liquid crystalline structure was investigated by optical microscopy and transmitted light intensity measurement under crossed polars during annealing. The steady decrease in the density of disclinations with accompanying increase of transmitted light intensity was observed. Depending on the surface conditions of the liquid crystal polymer film, two markedly different domain growth patterns and different textures were found on isothermal annealing; the continuous wormlike texture and the discontinuous droplet texture. The structural relaxation of the deformed texture during annealing was also studied. When shear was applied, the characteristic banded texture was formed in all polyesters.     

Effect of the pH of the medium on the chemical shifts in the PMR spectra and on the distribution of the π-electron density

The dependence of the chemical shifts of the ring protons on the pH of the medium for a number of 4-hydroxyquinoline derivatives was studied by means of PMR spectroscopy. The dipolar and uncharged hydroxy forms exist in equilibrium in aqueous solutions. The effect of intramolecular hydrogen bonding on the character of the dependence of the chemical shift on the pH of the medium in the case of 3-piperidinomethyl-4-hydroxyisoquinoline was investigated. The possibility of the separate protonation of the ring nitrogen and the side-chain nitrogen in 3-piperidinomethyl-4-hydroxyisoquinoline was established. The distribution of the -electron density in 4-hydroxyisoquinoline is in good agreement with its chemical behavior.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1546–1549, November, 1971