Etoposide interferes with the process of chromatin condensation during alga Chara vulgaris spermiogenesis

DNA topoisomerase II plays an essential role in animal spermiogenesis, where changes of chromatin structure are connected with appearance of transient DNA breaks. Such topo II activity can be curtailed by inhibitors such as etoposide and suramine. The aim of the present study was to investigate, for the first time, the effect of etoposide on spermatid chromatin remodeling in the green alga Chara vulgaris. This inhibitor prolonged the early spermiogenesis stages and blocked the formation of the phosphorylated form of histone H2AX at stages VI–VII. The lack of transient DSBs at these stages impairs the elimination of supercoils containing nucleosomes which lead to disturbances in nucleoprotein exchange and the pattern of spermatid chromatin fibrils at stages VI–VIII. Immunofluorescent and ultrastructural observations revealed that during C. vulgaris spermiogenesis topo II played an important role similar to that in mammals. Some corresponding features had been pointed out before, the present studies showed further similarities.     

A study of the ground states of CaC2H2+,CaC2D2+ and CaC2H4+

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Raman and IR spectra of K4Nb6O17and K4Nb6O17·3H2O single crystals

Polarised Raman and IR spectra of K₄Nb₆O₁₇ and K₄Nb₆O₁₇· 3H₂O single crystals were measured. The obtained spectra are discussed using the factor group approach for the orthorhombic P2₁nb space group and assignment of bands to the respective motions of atoms is proposed. In particular, we have shown that the bands above 770 cm⁻¹ can be attributed to the stretching modes of short niobium–oxygen bonds, which are present in this material due to the pronounced layered structure, whereas the potassium atoms contribute to the bands observed below 180 cm⁻¹. Our studies have revealed that intercalation of water molecules leads to shifts, broadening and changes in intensity of some bands. These changes have been attributed to slight changes in the bond lengths and angles, interactions of the water molecules with K atoms and structural disorder introduced by the intercalated water molecules. However, the main structural framework was preserved. Copyright © 2010 John Wiley & Sons, Ltd.     

2,3-二取代喹唑啉-4(3H)-酮化合物结构和活性的密度泛函理论研究

采用密度泛函理论中的广义梯度近似(DFT/GGA)方法,在PW91/DNP水平上研究了21种2,3-二取代喹唑啉-4(3H)-酮化合物的结构、化学活性和前线轨道.结果表明:此类化合物的能隙E_g大部分都在3.50~3.60 e V之间,其中在喹唑啉环3位上取代甲氧基苄基,或是在8位上取代甲基,化合物的能隙降低,而且甲氧基在苄基的间位比对位降低得更厉害.通过比较还发现,2,3-二取代喹唑啉-4(3H)-酮化合物对水稻纹枯菌(Rhizoctonia solani bacteria)的杀菌活性与哌啶并噻吩并嘧啶酮衍生物对水稻纹枯菌的杀菌活性相当,而哌啶并噻吩并嘧啶酮衍生物比2,3-二取代喹唑啉-4(3H)-酮化合物对苹果轮纹病(Botryospuaeria gregaria bacteria)杀菌活性好.     

Calorimetric and computational study of 2H-1, 4-benzoxazin-3(4H)-one and of related species

The standard molar enthalpy of formation in the gas phase of 2H-1,4-benzoxazin-3(4H)-one was derived from the standard energy of combustion determined by static bomb combustion calorimetry in oxygen atmosphere and from the standard sublimation enthalpy determined by Calvet microcalorimetry. In addition, we report the results of a systematic theoretical study of the keto and enol tautomers in benzoxazinones and diones using density functional theory. The keto tautomers are computed to be more stable than the enols. Tautomerization energies are reported.     

1H and 13C NMR Spectral Study of Some 2r-Aryl-6c-phenylthian-4-ones,Their 1-Oxides and 1,1-Dioxides

ABSTRACT

Four 2r-aryl-6c-phenylthian-4-ones 1b?1e and their 1-oxides 2b?2e and 1,1-dioxides 3b?3e have been newly synthesized. ¹H and ¹³C NMR spectra have been recorded for all these compounds and 2r,6c-diphenylthian-4-one 1-oxide 2a. ¹³C NMR spectrum has been recorded for the sulfone 3a of 1a. For selected compounds ¹H-¹H COSY, HSQC, HMBC, and NOESY spectra have been recorded. The vicinal proton–proton coupling constants suggest that in all these compounds, the heterocyclic ring adopts chair conformation with equatorial orientations of the aryl and phenyl groups. Proton and carbon chemical shifts suggest that in the sulfoxides, the S=O bond is axial and enhances the J _aa value by some special effect. The S = O bond causes a significant upfield shift even on carbons without hydrogens. Significant solvent shifts also were observed.     

Determination of the Stereochemistry of Substituted 4-(Sulfo- and Sulfonamidoalkyl) piperidine-2-carboxylic Acids with H NMR,COSY, and Homonuclear NOE Experiments

Basically the aim of this work is to define the accurate configuration of 4-substituted (sulfo- and sulfonamidoalkyl)piperidine-2-carboxylic acids which have been conceived as potential NMDA antagonists. H NMR and 2D NMR (COSY) followed by qualitative Homonuclear NOE have led to the assignement of the (±) cis and (±) trans configuration of the whole family's compounds.     

Mixed alkali metal selenate proton conductors: Phase transitions and crystal structure of [Rb0.54(Nh4)0.46]3H(SeO4)2

Optical birefringence, calorimetric, thermal expansion, powder and single crystal X-ray diffraction investigations of mixed proton conductors [Rb_1-x(NH₄)_x]₃H(SeO₄)₂ were performed with the aim of studying the influence of partial substitution of cations on the superprotonic phase transition, on the atomic structure and on other characteristic features of this type of crystals.     

An unexpected tetracyclic product isolated during the synthesis of biscoumarins catalyzed by [MIM(CH2)4SO3H][HSO4]: Characterization and X-ray crystal structure of 7-(2-hydroxy-4-oxo-4H-chromen-3-yl)-6H,7H-chromeno[4,3-b]chromen-6-one

Under solvent-free conditions and in the presence of 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [MIM(CH₂)₄SO₃H][HSO₄], a Brønsted acidic ionic liquid, the reaction of aromatic aldehydes with 4-hydroxycoumarin has been investigated. A wide range of aromatic aldehydes easily undergoes condensation with 4-hydroxycoumarin to afford biscoumarins with good purity in excellent yields. However, reaction of 2-hydroxybenzaldehyde with 4-hydroxycoumarin gave, not the corresponding biscoumarin, but a tetracyclic compound, 7-(2-hydroxy-4-oxo-4H-chromen-3-yl)-6H,7H-chromeno[4,3-b]chromen-6-one, in high yield.     

Polarised IR and Raman spectra of non‐centrosymmetric Na3Li(MoO4)2· 6H2O crystal—a new Raman laser material

Polarised IR and Raman spectra of Na₃Li(MoO₄)₂· 6H₂O single crystal were measured. Discussion of the results is based on the factor group approach for the trigonal R 3c(C_3v⁶) space group with Z = 2. The assignment of the observed bands was performed on the basis of their polarisation behaviour and literature data. The obtained results for the spontaneous Raman scattering were used in the analysis of the stimulated Raman spectra of the material studied—a new Raman laser crystal. The promoting modes of the stimulated effect were identified. Copyright © 2009 John Wiley & Sons, Ltd.     

1H and 13C NMR Determination of the Enantiomeric Purity of Substituted 4-Amino-3- (thien-2-Yl)-Butyric Acids and 4-Amino-3-(Benzo[b]Furan-2-yl)-Butyric Acids,Ligands of the GabaB Receptor.

The enantiomeric composition and absolute configuration of 4-Amino-3-(benzo[b]furan-2-yl)-Butanoic Acids and of 4-Amino-3-(thien-2-yl)-Butanoic Acids 1 may be accurately determined by ¹H and ¹³C nuclear magnetic resonance analysis of the corresponding derivatives 3 prepared by reaction with chiral reagents. Correlation with HPLC is signaled.     

The 2D {P} Spin-Echo-Difference Constant-Time [C, H]-HMQC Experiment for Simultaneous Determination of JH3′P and JC4′P in C-Labeled Nucleic Acids and Their Protein Complexes

A two-dimensional {³¹P} spin-echo-difference constant-time [¹³C, ¹H]-HMQC experiment (2D {³¹P}-sedct-[¹³C, ¹H]-HMQC) is introduced for measurements of ³J_C4′P and ³J_H3′P scalar couplings in large ¹³C-labeled nucleic acids and in DNA–protein complexes. This experiment makes use of the fact that ¹H–¹³C multiple-quantum coherences in macromolecules relax more slowly than the corresponding ¹³C single-quantum coherences. ³J_C4′P and ³J_H3′P are related via Karplus-type functions with the phosphodiester torsion angles β and ε, respectively, and their experimental assessment therefore contributes to further improved quality of NMR solution structures. Data are presented for a uniformly ¹³C, ¹⁵N-labeled 14-base-pair DNA duplex, both free in solution and in a 17-kDa protein–DNA complex.