Preparation of antitumor platinum(II) complexes of 1,2-diphenylethylenediamine isomers and their interactions with DNA and its purine moieties

A series of Pt(II) complexes containing 1,2-diphenylethylenediamine (stien) isomers were synthesized and tested for their antitumor activity against leukemia L1210. Among the Pt(II) complexes examined water-soluble Pt(II) complexes with sulfate, nitrate and D-glucuronate ions as leaving groups exhibited relatively high antitumor activity. Furthermore, the interactions between calf-thymus DNA and Pt(SO4) (stein) complexes were investigated by means of circular dichroism spectrometry. Dichroism enhancements observed in the interaction between DNA and Pt(SO4) (stien) complexes were analysed to be contributable to two factors: (1) vicinal effects of DNA on the d-d transitions of Pt(II) ions and (2) conformational changes of DNA caused by the coordination of cis-configurational Pt(II) complexes.     

杂交水稻及其三系剑叶表面结构的扫描电镜比较观察

应用扫描电子显微镜,对野败型杂交水稻汕优50及其三系的剑叶表面进行了比较观察。结果表明:保持系和恢复系的气孔长度和气孔复体的表面积极为相似;不育系的气孔大于其父本;而杂交水稻的气孔最大,一定程度上体现了杂种优势。     

Determination of copper in biological materials by atomic absorption spectroscopy: a reevaluation of the extinction coefficients for azurin and stellacyanin

A new method for the determination of copper in biological materials by graphite furnace atomic absorption spectroscopy is presented. This new procedure is an extension of the classic method of standard additions, where the analyte concentration is determined in a series of identical samples to which various amounts of metal standard have been added. The concentration of metal in the original sample is determined from an extrapolation of a plot of absorbance versus added analyte. In the new method, the amount of copper is determined by the method of standard additions for different concentrations of the sample under investigation as well. From an extrapolation of the data, the concentration of copper in the absence of interfering matrix is obtained. Studies with fetal bovine serum demonstrate that the new extrapolation technique is precise. Furthermore, considerably more copper is detected than by the classic method of standard additions applied to a nitric acid treated sample. The matrix effects of phosphate, nitrate, albumin, and serum were also examined. Both phosphate and serum, at physiological pH, decrease the detectability of added copper, while nitrate and albumin were without effect. The accuracy of this method has been verified by determining the extinction coefficients of stellacyanin and azurin. The values obtained, 4.33 X 10(3) and 3.75 X 10(3) M-1 cm-1, respectively, are considerably different from those determined by the method of standard additions on nitric acid digests of these proteins, but were close to values previously reported and determined colorimetrically.     

Pigment organization of the B800–850 antenna complex of Rhodopseudomonas sphaeroides

The B800–850 antenna complex of Rhodopseudomonas sphaeroides was studied by comparing the spectral properties of several different types of complexes, isolated from chromatophores by means of the detergents lithium dodecyl sulfate (LDS) or lauryl dimethylamine N-oxide (LDAO). Fluorescence polarization spectra of the BChl 800 emission at 4 K indicated that rapid energy transfer between at least two BChl 800 molecules occurs with a rate constant of energy transfer k_ET > 3 · 10¹² s^?1. The maximal dipole-dipole distance between the two BChl 800 molecules was calculated to be 18–19 Å. The porphyrin rings of the BChl 800 molecules are oriented parallel to each other, while their Q_y transition moments are mutually perpendicular. The energy-transfer efficiency from carotenoid to bacteriochlorophyll measured in different complexes showed that two functionally different carotenoids are present associated with, respectively, BChl 800 and BChl 850. Fluorescence polarization and linear dichroism spectra revealed that these carotenoids have different absorption spectra and a different orientation with respect to the membrane. The carotenoid associated with BChl 800 absorbs some nanometers more to the red and its orientation is approximately parallel to the membrane, while the carotenoid associated with BChl 850 is oriented more or less perpendicular to the membrane. The fluorescence polarization of BChl 850 was the same for the different complexes. This indicates that the observed polarization of the fluorescence is determined by the smallest complex obtained which contains 8–10 BChl 850 molecules. The B800–850 complex isolated with LDAO thus must consist of a highly ordered array of smaller structures. On basis of these results a minimal model is proposed for the basic unit consisting of four BChl 850 and two BChl 800 and three carotenoid molecules.     

Analysis of protein synthesis in morphologically classified bovine follicular oocytes before and after maturation in vitro

Bovine cumulus oocyte complexes (COCs) were isolated from antral ovarian follicles (4-8 mm). Immature COCs were classified into four categories, based on the homogeneity and clearness of the ooplasm and the transparency and compactness of the cumulus investment. In this study, the incorporation of TCA-precipitable 35S-methionine and the protein synthesis patterns of oocytes of these four categories were examined. Before maturation in vitro, similar incorporation rates and identical protein synthesis patterns were observed between oocytes of categories 1-3. Immature oocytes of category 4 showed reduced incorporation rates and exhibited aberrant protein synthesis patterns. After maturation in vitro, the patterns of category 4 oocytes were identical with the patterns of those in categories 1-3. The incorporation of 35S-methionine into in vitro matured oocytes was lower (P less than .001) in all categories. Based on these results, it is concluded that the initial classification of oocytes into four categories can be reduced to two categories.     

Structural analysis of EcoRI-DNA complexes as revealed by electron microscopy

Electron microscopy of negatively stained isolated restriction enzyme EcoRI revealed particle projections with triangular or square outlines, indicating that the enzyme, in its tetrameric state, is tetrahedron-like. The two dimers making up the tetramer appear to be arranged in two planes orthogonal to each other. Complexes formed by EcoRI with the plasmids pBR322 or pGW10 were investigated by electron microscopic spreading techniques. In the presence of Mg²⁺, EcoRI was bound to the DNA molecules to form pearl necklace-like aggregates. The number of bound EcoRI particles was much higher as the sum of EcoRI-and 5..AATT..3 sites (with exceptions, the 5..AATT..3 sites may function as one type of EcoRI^* sites) along the DNAs, indicating unspecific binding. In the absence of Mg²⁺, EcoRI was bound to the DNA only at the recognition site for EcoRI and the sites where the tetranucleotide sequence 5..AATT..3 was present. A direct correlation of the local concentrations of the bases A and T within the flanking sequences of the binding sites with the frequency of EcoRI to the DNA was observed. Dimers and tetramers of the enzyme was found to bind to the DNA. Tetramers occasionally exhibited two binding sites for DNA as indicated by the observation of DNA loops originating at the sites of bound tetrameric EcoRI particles.Abbreviations BAC Benzyldimethylalkylammoniumchloride - bp base pairs - Kb kilobases - SDS sodium dodecylsulfate Enzymes (EC 3.1.23.13) Restrictionendonuclease EcoRI - (EC 3.1.23.21) Restrictionendonuclease HindIII - (EC 3.1.23.37) Restrictionendonuclease SalGI Dedicated Professor H. G. Schlegel on occasion of this 60th birthday     

Studies on decomposition of humus in clay-humus complexes

Summary Decomposition studies with humic acids (HAs) present in HA-clay complexes revealed that such decomposition decreases at higher clay concentrations. At high clay concentration, moreover, it has also been observed that smaller and more flexible humic molecules are less susceptible to the said decomposition as compared to larger and more rigid structures.     

Photodynamic inactivation of Aeromonas hydrophila by cationic phthalocyanines with different hydrophobicity

Antibacterial photodynamic therapy is a pioneering method for the inactivation of pathogenic bacteria. Four tetra alkyl-substituted cationic phthalocyanines with different hydrocarbon chains attached to the pyridyloxy group were synthesized. These photodynamic sensitizers were studied for antibacterial inactivation of a multidrug-resistant strain of Gram-negative bacterium Aeromonas hydrophila. Aeromonas species are recognized as etiological agents of a wide spectrum of diseases in humans and animals. The uptake of phthalocyanines by the bacterial cells decreased with an increase in cell density. Following the phthalocyanine solubility from hydrophilic to hydrophobic complexes, the accumulation capacity increased. Full inactivation was achieved with phthalocyanine with (methoxy) pyridyloxy substitution following a short exposure time, low drug concentration and mild irradiation. Although the phthalocyanine with the longest hydrocarbon chain (C12) has some toxic effect in the absence of light, substantial phototoxic effect was obtained with the optimal combination of drug-irradiation parameters.