Reaction of the antitumor antibiotic CC-1065 with DNA: structure of a DNA adduct with DNA sequence specificity

Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.     

X-ray structure of racemic glycerol 1,2-(di-11-bromoundecanoate)-3-(-p-toluenesulfonate)

The single crystal x-ray structure of racemic glycerol 1,2-(di-11bromoundecanoate)-3-(p-toluenesulfonate), a sulfolipid analogous to the membrane phospholipids, reveals a folded conformation.     

Ce(NH4)2(NO3)6对水稻种子萌发及幼苗生理特性的影响

用不同浓度Ce(NH4)2(NO3)6对水稻种子浸种,探讨了外源Ce(NH4)2(NO3)6对种子萌发及幼苗生理特性的影响.结果表明,10～20mg·L-1Ce(NH4)2(NO3)6浸种24h,可增强水稻种子在萌发时的α-淀粉酶活性,提高种子活力及萌发率,根系活力增强,幼苗叶绿素含量提高,细胞膜相对透性及MDA含量降低.50～100 mg·L-1的Ce(NH4)2(NO3)6浸种后,种子活力及幼苗根系活力下降,幼苗叶绿素含量降低,细胞膜相对透性及MDA含量增加.     

苯并[a]芘对真鲷(Pagrosomus major)血细胞DNA损伤的慧星实验研究

对取自厦门海域养殖鱼排的真鲷以0.8、1.4、2.0μg.L-1不同浓度苯并[a]芘(BaP)分别进行4、24h的暴露染毒,用改进的慧星实验技术研究了BaP对真鲷血细胞DNA的损伤。结果表明:(1)通过慧星实验获得的DNA损伤指标显示,与空白对照组相比,暴露染毒组血细胞DNA均受到损伤且损伤存在显著性差异(P<0.01),剂量-效应关系明显,DNA损伤随着染毒时间的延长明显增加。(2)优化了适合检测真鲷血细胞DNA损伤的彗星实验电泳条件:20V、300mA、20min。(3)在样本数量较多的情况下,用细胞培养板板盖铺单层胶的彗星实验检测方式与用载玻片铺3层胶的“三明治”方式相比,具有操作简便、节省时间、制胶过程凝胶不易破损、重复性好等优点。     

An Inorganic Double Helix: Hydrothermal Synthesis, Structure, and Magnetism of Chiral [(CH3)2NH2]K4[V10O10(H2O)2(OH)4(PO4)7]{middle dot}4H2O

Very complicated inorganic solids can be self-assembled from structurally simple precursors as illustrated by the hydrothermal synthesis of the vanadium phosphate, [(CH(3))(2)NH(2)]K(4)[V(10)O(10)(H(2)O)(2)(OH)(4)(PO(4))(7)].4H(2)O, 1, which contains chiral double helices formed from interpenetrating spirals of vanadium oxo pentamers bonded together by P(5+). These double helices are in turn intertwined with each other in a manner that generates unusual tunnels and cavities that are filled with (CH(3))(2)NH(2)(+) and K(+) cations, respectively. The unit cell contents of dark blue phosphate 1, which crystallizes in the enantiomorphic space group P4(3) with lattice constants a = 12.130 and c = 30.555 angstroms, are chiral; only one enantiomorph is present in a given crystal. Magnetization measurements show that 1 is paramagnetic with ten unpaired electrons per formula unit at higher temperatures and that antiferromagnetic interactions develop at lower temperatures.     

Chemical etiology of nucleic acid structure: the alpha-threofuranosyl-(3'-->2') oligonucleotide system

TNAs [(L)-alpha-threofuranosyl oligonucleotides] containing vicinally connected (3'-->2') phosphodiester bridges undergo informational base pairing in antiparallel strand orientation and are capable of cross-pairing with RNA and DNA. Being derived from a sugar containing only four carbons, TNA is structurally the simplest of all potentially natural oligonucleotide-type nucleic acid alternatives studied thus far. This, along with the base-pairing properties of TNA, warrants close scrutiny of the system in the context of the problem of RNA's origin.     

Superlattices of iron nanocubes synthesized from Fe[N(SiMe3)2]2

The reaction of the metal-organic precursor Fe[N(SiMe3)2]2 with H2 in the presence of a long-chain acid and a long-chain amine in various proportions produces monodisperse zerovalent iron nanoparticles. These Fe particles display magnetic properties that match those of bulk iron as evidenced by magnetic and M?ssbauer measurements. The nanoparticles adopt a cubic shape with edges of 7 nanometers and are incorporated into extended crystalline superlattices containing nanocubes in close proximity and with their crystallographic axes aligned. These superlattices are formed in solution, precipitate in high yield, and may be redissolved and redeposited as two-dimensional arrays.     

The S1-sensitive form of d(C-T)n.d(A-G)n: chemical evidence for a three-stranded structure in plasmids

Homopurine-homopyrimidine sequences that flank certain actively transcribed genes are hypersensitive to single strand-specific nucleases such as S1. This has raised the possibility that an unusual structure exists in these regions that might be involved in recognition or regulation. Several of these sequences, including d(C-T)n.d(A-G)n, are known to undergo a transition in plasmids to an underwound state that is hypersensitive to single strand-specific nucleases; this transition occurs under conditions of moderately acid pH and negative supercoiling. Chemical probes were used to examine the reactivity of a restriction fragment from a human U1 gene containing the sequence d(C-T)18.d(A-G)18 as a function of supercoiling and pH, and thus analyze the structure in this region. Hyperreactivity was seen in the center and at one end of the (C-T)n tract, and continuously from the center to the same end of the (A-G)n tract, in the presence of supercoiling and pH less than or equal to 6.0. These results provide strong support for a triple-helical model recently proposed for these sequences and are inconsistent with other proposed structures.     

X-ray diffraction and computation yield the structure of alkanethiols on gold(111)

The structure of self-assembled monolayers (SAMs) of long-chain alkyl sulfides on gold(111) has been resolved by density functional theory-based molecular dynamics simulations and grazing incidence x-ray diffraction for hexanethiol and methylthiol. The analysis of molecular dynamics trajectories and the relative energies of possible SAM structures suggest a competition between SAM ordering, driven by the lateral van der Waals interaction between alkyl chains, and disordering of interfacial Au atoms, driven by the sulfur-gold interaction. We found that the sulfur atoms of the molecules bind at two distinct surface sites, and that the first gold surface layer contains gold atom vacancies (which are partially redistributed over different sites) as well as gold adatoms that are laterally bound to two sulfur atoms.     

铵硝比(NH4+/NO3-)对不同氮素利用效率水稻的生理效应

采用控制条件下的水培试验方法,研究了不同铵硝配比(NH4 /NO3-分别为100/0、75/25、50/50和25/75)营养条件对8种不同氮素利用效率水稻苗期生长的影响.结果表明:在增硝营养条件下,不同水稻品种对硝态氮(NO3-)的反应不同.与纯铵营养条件相比,铵硝混合的营养条件对大多数氮高效水稻品种的生长都有显著促进作用,而对氮低效品种的生长没有显著影响.试验重点研究了增硝营养对氮高效水稻品种南光、云粳38和氮低效水稻品种ELIO生长的影响.结果发现,对于南光和云粳38,增硝营养可以使水稻的分蘖数和光合速率分别增加35%和24%,从而促进水稻生长和氮吸收,提高氮素利用率;而增硝营养对ELIO的生长并无显著影响.不同基因型水稻在增硝营养下氮积累量增幅不同主要是由于其生物量增幅不同造成的,而整株氮素含量增幅差异不大;NO3-的存在可增加干物质在水稻根系的积累,增加根系体积,促进水稻根系的生长.     

A Molecular Ferromagnet with a Curie Temperature of 6.2 Kelvin: [Mn(C5(CH3)5)2]+[TCNQ]-

The study of magnetic phase transitions in insulating molecular solids provides new insights into mechanisms of magnetic coupling in the solid state and into critical phenomena associated with these transitions. Only a few such materials are known to display cooperative magnetic properties. The use of high-spin molecular components would enhance intermolecular spin-spin interactions and thus a series of chargetransfer (CT) salts have been synthesized that utilize the spin S = 1 molecular cation, [Mn(C(5)(CH(3))(5))(2)](+) (decamethylmanganocenium). The structure and cooperative magnetic behavior of [Mn(C(5)(CH(3))(5))(2)](+)[TCNQ(-) (decamethylmanganocenium 7,7,8,8-tetracyano-p-quinodimethanide) are reported. This salt is a bulk molecular ferromagnet with the highest critical (Curie) temperature (T(c) = 6.2 K) and coercive field (3.6 x 10(3) gauss), yet reported for such a material.     

A crystal structure of the complex between human complement receptor 2 and its ligand C3d

The interaction of complement receptor 2 (CR2)--which is present on B cells and follicular dendritic cells--with its antigen-bound ligand C3d results in an enhanced antibody response, thus providing an important link between the innate and adaptive immune systems. Although a cocrystal structure of a complex between C3d and the ligand-binding domains of CR2 has been published, several aspects of this structure, including the position in C3d of the binding interface, remained controversial because of disagreement with biochemical data. We now report a cocrystal structure of a CR2(SCR1-2):C3d complex at 3.2 angstrom resolution in which the interaction interfaces differ markedly from the previously published structure and are consistent with the biochemical data. It is likely that, in the previous structure, the interaction was influenced by the presence of zinc acetate additive in the crystallization buffer, leading to a nonphysiological complex. Detailed knowledge of the binding interface now at hand gives the potential to exploit the interaction in vaccine design or in therapeutics directed against autoreactive B cells.     

苯胺铝-三乙胺盐酸盐/三氯化铝离子液体催化烷基化制备2,6-二异丙基苯胺的研究

[目的]优化苯胺铝和[Et3NH]Cl/AlCl3离子液体催化苯胺与丙烯烷基化反应条件。[方法]考察了催化剂的组成和用量、苯胺/催化剂摩尔比、反应温度、反应压力以及反应时间等因素对反应结果的影响。[结果]反应的较优条件为:n(Al)∶n(AlCl3)∶n(Et3HCl)=3∶1∶1,n(苯胺)/n(催化剂)=15∶1,反应温度为305～315℃,反应压力为4.0～8.0 MPa,苯胺转化率大于90%,2,6-二异丙基苯胺选择性大于50%。[结论]与铝-三氯化铝混合催化剂相比,离子液体催化剂在较低反应温度和反应压力下均能有效提高烷基化反应的转化率和选择性。     

温度对硫酸亚铁铵抑制血吸虫毛蚴趋向运动的影响

目的:观察硫酸亚铁铵对毛蚴的趋向作用及温度的影响。方法:采用改良的Rorbert比较法。以0.2 mol/L硫酸亚铁铵溶液为实验组,等量去离子水作为对照组,检测不同温度下硫酸亚铁铵对日本血吸虫毛蚴趋向作用的影响。结果:15℃左右环境下,硫酸亚铁铵显示为吸引作用,随温度升高出现排斥现象,尤其在27℃左右,药物排斥作用极为明显,此温度也正是毛蚴活动、繁殖的适宜温度;在31~35℃,药物仍然能够发挥有效的排斥作用。结论:硫酸亚铁铵具良好的抑制毛蚴侵入钉螺的作用,在血吸虫流行地区,春夏之交可能是最适应施用该药的季节。     

A sharp peak of the zero-temperature penetration depth at optimal composition in BaFe2(As(1-x)P(x))2

In a superconductor, the ratio of the carrier density, n, to its effective mass, m*, is a fundamental property directly reflecting the length scale of the superfluid flow, the London penetration depth, λ(L). In two-dimensional systems, this ratio n/m* (~1/λ(L)(2)) determines the effective Fermi temperature, T(F). We report a sharp peak in the x-dependence of λ(L) at zero temperature in clean samples of BaFe(2)(As(1)(-x)P(x))(2) at the optimum composition x = 0.30, where the superconducting transition temperature T(c) reaches a maximum of 30 kelvin. This structure may arise from quantum fluctuations associated with a quantum critical point. The ratio of T(c)/T(F) at x = 0.30 is enhanced, implying a possible crossover toward the Bose-Einstein condensate limit driven by quantum criticality.     

Structure of the hydrated alpha-Al(2)O(3) (0001) surface

The physical and chemical properties of the hydrated alpha-Al(2)O(3) (0001) surface are important for understanding the reactivity of natural and synthetic aluminum-containing oxides. The structure of this surface was determined in the presence of water vapor at 300 kelvin by crystal truncation rod diffraction at a third-generation synchrotron x-ray source. The fully hydrated surface is oxygen terminated, with a 53% contracted double Al layer directly below. The structure is an intermediate between alpha-Al(2)O(3) and gamma-Al(OH)(3), a fully hydroxylated form of alumina. A semiordered oxygen layer about 2.3 angstroms above the terminal oxygen layer is interpreted as adsorbed water. The clean alpha-Al(2)O(3) (0001) surface, in contrast, is Al terminated and significantly relaxed relative to the bulk structure. These differences explain the different reactivities of the clean and hydroxylated surfaces.     

水稻、玉米生产中磷酸二铵合理用量探讨

根据磷酸二铵（ＤＡＰ）肥效试验结果,讨论了磷酸二铵不同用量对水稻，玉米产量效应及构成因素的影响，试验结果表明在施用等量Ｎ，Ｋ养分基础上，每公顷施ＤＡＰ２２５kg与施ＤＡＰ１９５kg,279kg和ＳＳＰ７５０kg相比，有明显的增产作用。     

硫酸铈铵对玉米根尖细胞的遗传毒性研究

通过不同梯度质量浓度的叠氮化钠与硫酸铈铵对玉米根尖进行处理,研究其对玉米根尖细胞的遗传毒性。结果表明,硫酸铈铵对玉米根尖细胞的微核和有丝分裂的影响存在一定的剂量关系。当用叠氮化钠处理玉米根尖时,微核率先升后降,迭氮化钠为20 mg/L时微核率最高,有丝分裂指数随质量浓度升高递减;当用硫酸铈铵处理玉米根尖时,微核率随质量浓度升高而升高,浓度为20 mg/L时微核率显著升高,有丝分裂指数随质量浓度升高而降低,说明硫酸铈铵对玉米根尖细胞具有一定的遗传毒性,但毒性比叠氮化钠要缓和一些。     

Synthesis of Methyl 7-chlor-2 ,5-dihydroindeno[ 1,2-e ] [ 1,3,4] oxadiazine-4a-(3H) -carboxylate

[目的]探讨合成7-氯-2,5-二氢茚并[1,2-e][1,3,4]噁二嗪-4a-(3H)-羧酸甲酯的新方法.[方法]以5-氯-1-氧-2,3-二氢茚-2-羧酸甲酯为起始原料,先后经过不对称氧化、肟化、环合、取代反应得到目标化合物.[结果]目标产物及中间体的结构已通过质谱、1H NMR进行表征.[结论]该合成方法具有原材料易得、收率高、成本低等优点.     

氟罗沙星-铜络合物与DNA的电化学研究

采用单扫描法和循环伏安法研究了氟罗沙星-铜-DNA三元体系的电化学行为,建立了利用电活性物质氟罗沙星-铜测定DNA的新方法。在0 05mol/L、pH=7 12的KH2PO4-NaOH缓冲溶液中,氟罗沙星-铜络合物在-0 36V(vs.SCE)处产生一个不可逆的并具有吸附性质的还原峰,DNA的加入使其峰电流降低,但峰电位不变。在最佳实验条件下,峰电流的差值(Δip)与DNA的浓度成正比,小牛胸腺DNA的线性范围为5 0×10-7～2 0×10-5g/mL,检出限为8 0×10-8g/mL。采用本方法测定了合成样品中DNA的含量,结果满意。