Effect of Agave americana L. on the human,and Aspergillus oryzae S2 α-amylase inhibitions

Among phenolic compounds, Agave americana L. extract contained puerarin (38.4%) and p-coumaric acid (12.29%) (pCa). From the Lineweaver–Burk plots, pCa and puerarin demonstrated a competitive and a non competitive inhibitions towards human α-amylase activity, respectively. PCa exhibited a higher human inhibitory activity with an IC₅₀ of 98.8 μM which was about 2.3 times than acarbose. Puerarin (IC₅₀ = 3.87 μM) and pCa (IC₅₀ = 10.16 μM) also showed an excellent inhibition for Aspergillus oryzae S2 α-amylase activity. The inhibitions of the described biocatalysts compounds towards both amylases were significantly decreased when they were pre-incubated with starch. The binding modes of these compounds were evaluated in silico. The binding efficiency order of these molecules in terms of polar contact numbers for both enzymes was in agreement with the in vitro studies. These findings provided a rational reason to establish the isolated compounds capability as therapeutic target for hyperglycaemia modulation and antifungal therapy.     

Clay‐Na as a sorbent for the extraction of anti‐inflammatory compounds in water samples

In this work, clay‐Na particles are used as the adsorbent for the solid‐phase extraction of acidic compounds. The novel sorbent under study is based on high‐specific surface area, cation‐exchange capacity designed specifically to offer ion‐exchange properties with the goal being to selectively extract a group of acidic compounds. The effects of the extraction parameters including extraction elution solvent, sample volume and pH. In optimum conditions, the repeatability for one fiber (n = 3), expressed as % relative standard deviation, was between 0.3 and 4.3% for the acid compounds. The detection limits for the studied acidic compounds were between 0.1–0.6 μg/L. The developed method offers the advantages of being simple to use and having a low cost of equipment.     

Local Delaminations Induced by Interaction Between Intralaminar Cracking and Specimen Edge in Quasi-Isotropic CF/EP NCF Composites in Fatigue Loadings

Mechanics of Composite Materials - Experimental results are presented on the onset and propagation of local delaminations caused by the interaction between specimen edges and intralaminar cracks in...     

Positive linear relations between Riesz spaces

In the present paper we introduce the notion of a positive linear relation and we investigate the class of such operators. As well as placing the theory of positive operators in a natural setting, this structure seems to be interesting for the study of abstract boundary value problems.     

Preparation and characterization of n-type conductive (Al, Co) co-doped ZnO thin films deposited by sputtering from aerogel nanopowders

Highly transparent, n-type conducting ZnO thin films were obtained by low temperature magnetron sputtering of (Co, Al) co-doped ZnO nanocrystalline aerogels. The nanoparticles of ∼30 nm size were synthesized by a sol-gel method using supercritical drying in ethyl alcohol. The structural, optical and electrical properties of the films were investigated. The ZnO films were polycrystalline textured, preferentially oriented with the (0 0 2) crystallographic direction normal to the film plane. The films show within the visible wavelength region an optical transmittance of more than 90% and a low electrical resistivity of 3.5 × 10⁻⁴ Ω cm at room temperature.     

Molecular modeling study of DNA abasic sites

We use molecular modeling calculations to study the structure and the flexibility of abasic (AP sites) and for the design of anticancer drugs targeted against AP sites. For either adenine or cytosine on the opposing strand within the same sequence context, the results are in line with experimental data which show that the two unpaired bases lead to intrahelical forms, but with differences in induced curvature. Results on flexibility, indicate that the two duplexes have the same bending rigidity for cytosine. In previous work a series of polyfunctional molecules, such as ATAc, were designed to selectively recognize and cleave abasic sites in DNA. The nitrobenzamide group which was added to the ATAc molecule to obtain a new molecule, termed ATAc4, can induce a second lesion under irradiation in close proximity to the abasic site. The different conformations of ATAc4 interacting with a DNA oligomer containing a stable analog of the abasic site were compared to the photoinduced cleavage pattern observed experimentally. Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 12 May 2000     

Magnetization reversal dynamics in Au/Co/Au(111) ultrathin films: Effect of roughness of the buffer layer

We present a study of the magnetization reversal dynamics in ultrathin Au/Co/Au films with perpendicular magnetic anisotropy, for a Co thickness of 0.5, 0.7 and 1 nm. In these films, the magnetization reversal is dominated by domain nucleation for t_Co=0.5, 0.7 nm and by domain wall propagation for t_Co=1 nm. The prevalence of domain nucleation for the thickness range 0.5-0.7 nm is different from results reported in the literature, for the same system and for the same thickness range, where the magnetization reversal took place mainly by domain wall motion. We attribute this difference to the effect of roughness of the Au buffer layer on the morphology of the magnetic layer.