Weak Intercalation Research Articles

Spectroscopic and voltammetric studies of the cobalt (II) complex of Morin bound to calf thymus DNA

Absorption and emission spectra, viscometric and electrochemical studies have been carried out on the interaction of Morin (2′, 3, 4′, 5, 7-pentahydroxyflavone) and its Co complex, CoL2·3H2O[L = Morin (2′-OH group deprotonated)], with calf thymus DNA. In the presence of DNA, the complex exhibits a hypochromism in the u.v.–vis. spectra and a large enhancement in emission spectra suggests that the complex binds to DNA via a weak partial intercalation, revealed by competitive experiments, viscosity and by electrochemical studies. The binding constant is ca. 2 × 103 M−1 at 20 °C. Both ZnL2·3H2O and CoL2·3H2O complexes have the same molecular structure, ZnL2·3H2O shows the spectral characteristics and electrochemical behaviour which agrees with observations for other intercalators in the presence and absence of DNA, whereas the CoL2·3H2O complex shows different spectral characteristics and electrochemical behaviour to that of ZnL2·3H2O, which suggests that the mode and affinity of the complex CoL2·3H2O binding to DNA are different from that of ZnL2·3H2O. Both ZnL2·3H2O and CoL2·3H2O complexes exhibited different antitumour activity. So the binding mode and affinity of complexes to DNA may play an important role in determining the antitumour activity.

Inhibition of DNA Topoisomerase I by Dihydrotanshinone I, Components of a Medicinal Herb Salvia miltiorrhiza Bunge.

Dihydrotanshinone I induced topoisomerase I-mediated DNA cleavage in vitro as strongly as camptothecin, but topoisomerase II-mediated DNA cleavage was not affected. In a DNA relaxation assay using calf thymus DNA topoisomerase I and supercoiled pBR322 plasmid DNA, dihydrotanshinone I reduced topoisomerase I-mediated DNA relaxation in a dose-dependent manner. Heat treatment (65°C) of the reaction mixture containing dihydrotanshinone I and topoisomerase I resulted in a substantial reduction in DNA cleavage, suggesting topoisomerase I and dihydrotanshinone I may form a reversible cleavable complex to induce DNA damage. A DNA unwinding assay using T4 DNA ligase showed that dihydrotanshinone I is a very weak DNA intercalator. These results suggest that dihydrotanshinone I inhibits the catalytic activity of topoisomerase I by the formation of a cleavable complex and at least in part through the intercalation into DNA.

RNA-Diethylstilbestrol Interaction Studied by Fourier Transform Infrared Difference Spectroscopy

Diethylstilbestrol (DES), a synthetic estrogen, is known to be a carcinogen in human and in animals. This study was designed to examine the interaction of DES with yeast RNA in aqueous solution at physiological pH with drug/RNA-phosphate (P) molar ratios of 1/80, 1/40, 1/20, 1/10, 1/4, and 1/2. Fourier transform infrared (FTIR) difference spectroscopy was used to determine the drug binding mode, the binding constant, the sequence selectivity, and RNA secondary structure in the RNA.DES complexes. Spectroscopic evidence showed that at low drug concentration (1/80 and 1/40), DES is intercalating through both Gua-Cyt and Ade-Urd base pairs with minor interaction with the backbone PO2 group (external binding). The calculated binding constant of K approximately 8.5 x 10(4) M-1 at a drug concentration of 3.12 x 10(-4) M shows that DES is a weaker intercalator than those of the methylene blue, acridine orange, and ethidium bromide. At high drug content (r > 1/40, where r represents the DES/RNA-phosphate molar ratio), a partial helix destabilization occurs with no alteration of RNA conformation upon drug complexation. However, a comparison with DNA.DES complexes showed that drug intercalation causes major reduction of the B-DNA structure in favor of A-DNA with no participation of the backbone PO2 group in the DES. DNA complexation.

Constitutive relationship for plastic dilatancy due to weak intercalations in rockmasses : He Manchao Proc 26th Annual Conference of the Engineering Group of the Geological Society, The Engineering Geology of Weak Rock, Leeds, 9–13 September 1990P243–249. Publ Rotterdam: A A Balkema, 1993 (Engineering Geology Special Publication No. 8)

Constitutive relationship for plastic dilatancy due to weak intercalations in rockmasses : He Manchao Proc 26th Annual Conference of the Engineering Group of the Geological Society, The Engineering Geology of Weak Rock, Leeds, 9–13 September 1990P243–249. Publ Rotterdam: A A Balkema, 1993 (Engineering Geology Special Publication No. 8)

Studies on the principal factors affecting shear strength of weak intercalations and the correlation between them : Zhang Xiangong; Nie Dexin; Han Wenfeng Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990V4, P2579–2583. Publ Rotterdam: A A Balkema, 1990

Studies on the principal factors affecting shear strength of weak intercalations and the correlation between them : Zhang Xiangong; Nie Dexin; Han Wenfeng Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990V4, P2579–2583. Publ Rotterdam: A A Balkema, 1990

Experimental study on the brittle failure of weak intercalations in dam foundation by physical modelling : Yang Guohua; Lu Jiayou Proc International Symposium on Rock Joints, Loen, 4–6 June 1990P495–502. Publ Rottendam: A A Balkema, 1990

Experimental study on the brittle failure of weak intercalations in dam foundation by physical modelling : Yang Guohua; Lu Jiayou Proc International Symposium on Rock Joints, Loen, 4–6 June 1990P495–502. Publ Rottendam: A A Balkema, 1990

Acoustic environment and physico‐mechanical properties of the shelf seabed off the pearl river mouth

Abstract The vast shallow sea off the Pearl River mouth in the northern South China Sea is an important prospecting area for offshore oil development. In recent years, the authors have investigated acoustic and geotechnical characteristics of marine sediments in this area. An intercalated layer of low sound velocity and low compressive strength has been found within the seabed, in which the median diameter of sediment grains is fine and the sound velocity is 100–200 m/s lower than that of the overlying and underlying layers. The minimum unconfined compressive strength of this layer is 0.075 kg/cm2, which is lower than that of the over‐ and underlying layers by an order of magnitude. Such an intercalation often constitutes a threat to the stability of shallow foundation soil. In case of overloading, the layer may be weakened, and seafloor sliding between different sediment layers may occur. The regional distribution of these kinds of weak intercalations of low sound velocity may be traced by a subbottom profiler and by means of sediment acoustical investigations. Correlation between the gray level of a layer on subbottom profile records and physical properties of the layer (including sound velocity and reflectivity) suggests that the layer of sufficient bearing capacity must be searched by means of sediment acoustics at least to the depth of a high‐velocity substratum of stronger reflection.

The elasto-visco-plastic analysis for rock displacement of the foundation pit of a water power plant

The Elasto-Visco-Plastic Analysis for Rock Displacement of the Foundation Pit of a Water Power Plant In this paper a method used in the elasto-visco-plastic analysis is proposed. It has been employed for deformation analysis of the foundation pit of a large water power plant in China. The back analysis of this rock engineering problem shows that the relief of the rock initial stresses due to excavation and the rheological properties of the weak intercalations and the rock masses as well are the main factors which caused the large deformation of the foundation pit. The results from the calculations are coincided fairly well with the data measured and observed in situ.

Non‐linear analysis of a joint element and its application in rock engineering

AbstractIn this paper models are given for analysis and description of non‐linear properties of joints, weak intercalations and interfaces in rock masses.Models for analysis consist of four parts, i.e. shear displacement model, normal deformation model, shear strength model and a relationship between unit shear stiffness and normal stress.The method of non‐linear analysis given in this paper is based on an incremental procedure.The proposed method is available for different types of shear‐displacement curves, and also adapted to the complicated process of loading‐unloading‐reloading.The results of computer simulation of an in‐situ shear test obtained by this method gave a good fit to the measured data.The method of non‐linear analysis of joint elements has been used in some practical rock engineering problems, and some interesting results and conclusions have been obtained.