Investigation of adsorption behavior of mercury on Au(111) from first principles

The structural and electronic properties of Hg, SO(2), HgS, and HgO adsorption on Au(111) surfaces have been determined using density functional theory with the generalized gradient approximation. The adsorption strength of Hg on Au(111) increases by a factor of 1.3 (from -9.7 to -12.6 kcal/mol) when the number of surface vacancies increases from 0 to 3; however, the adsorption energy decreases with more than three vacancies. In the case of SO(2) adsorption on Au(111), the Au surface atoms are better able to stabilize the SO(2) molecule when they are highly undercoordinated. The SO(2) adsorption stability is enhanced from -0.8 to -9.3 kcal/mol by increasing the number of vacancies from 0 to 14, with the lowest adsorption energy of -10.2 kcal/mol at 8 Au vacancies. Atomic sulfur and oxygen precovered-Au(111) surfaces lower the Hg stability when Hg adsorbs on the top of S and O atoms. However, a cooperative effect between adjacent Hg atoms is observed as the number of S and Hg atoms increases on the perfect Au(111) surface, resulting in an increase in the magnitude of Hg adsorption. Details of the electronic structure properties of the Hg-Au systems are also discussed.     

Error Analysis of the Poisson P3M Force Field Scheme for Particle-Based Simulations of Biological Systems

The ability to accurately simulate electrolyte solutions is a strong requirement for the modeling of charge transport in ion channels. In this work, a Particle-Particle–Particle-Mesh (P³M) algorithm is used to model the electrostatic interactions governing the physics of electrolyte solutions. The goal of this study is to define the parameters relevant for this force field, and their respective influence on the accuracy of the simulation. Simulations have been performed for extended ranges of these parameters and the results are compared to theoretical models. Finally, the trade-offs between optimal algorithmic efficiency and accuracy are analyzed.     

Antioxidants and proteins in ethylene-treated kiwifruits

Ethylene-treated kiwifruit (Actinidia deliciosa) cultivar ‘Hayward’ was compared with the air-treated one. The correlation coefficients between total polyphenols and the antioxidant capacities measured by [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS) with Trolox equivalent antioxidant capacity (TEAC), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), and cupric reducing antioxidant capacity (CUPRAC) assays for ethylene-treated kiwifruits were as followed: 0.74; 0.93 and 0.98, in comparison with air-treated samples of 0.72, 0.88 and 0.97, respectively. CUPRAC produced the most consistent measurements for ethylene-treated kiwifruit. In extracted and separated, by electrophoresis, kiwifruit proteins differences were found in the sodium dodecyl sulfate–protein bands, in the region of 32 kDa, in samples after the first days of treatment. Based on antioxidant activity and the protein profiles it can be concluded that the ethylene treatment shortened the ripening process of the fruits.     

Relationship between seawater pollution and qualitative changes in the extracted proteins from mussels Mytilus galloprovincialis

The aim of this study was to find a reliable biomarker of seawater pollution. For this purpose the contents of Zn and Cu, proteins and antioxidant activity in mussels Mytilus galloprovincialis collected from polluted and non-polluted sites of the Bulgarian Black Sea coast were compared. To determine the above-mentioned indices atomic spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy, fluorescence, differential scanning calorimetry (DSC), and two antioxidant tests were used. It was found that the amounts of Zn and Cu were significantly higher in the mussel proteins from the polluted than from the non-polluted sites (P<0.05). FT-IR spectroscopy and fluorescence revealed specific qualitative changes in secondary and tertiary structures in mussel proteins in the samples from polluted sites. The thermodynamic properties of proteins and the changes upon denaturation were correlated with the secondary structure of proteins and disappearance of alpha-helix. Purified protein scavenging activity against 2, 2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS(*+)) was significantly higher in mussel samples from polluted than from non-polluted sites. Therefore, the changes in Zn and Cu concentration, in protein's secondary and tertiary structures and antioxidant activity in mussels M. galloprovincialis from polluted sites can be a reliable biomarker of the level of the seawater pollution.     

Comparison of bioactive compounds,antioxidant and antiproliferative activities of Mon Thong durian during ripening

The aim of this investigation was to compare the bioactive and nutrient compounds, fatty acids, and antioxidant and antiproliferative activities of Mon Thong durian at different stages of ripening. It was found that the total polyphenols, flavonoids, flavanols, ascorbic acid, tannins and the antioxidant activity determined by four assays (CUPRAC, DPPH, ABTS and FRAP) differed in immature, mature, ripe and overripe samples. The content of polyphenols and antioxidant activity were the highest in overripe durian, flavonoids were the highest in ripe durian, and flavanols and antiproliferative activity were the highest in mature durian (p < 0.05). FTIR spectra of polyphenols, HPLC profiles of fatty acids, the antioxidant and antiproliferative activities can be used as indicators to characterise different stages of durian ripening.     

Bioactive compounds and antioxidant potential in fresh and dried Jaffa® sweeties,a new kind of citrus fruit

Bioactive compounds in the edible parts of fresh and dried Jaffa^® sweeties, a new kind of citrus fruit, were analysed and their antioxidant capacities were assessed. Antioxidant‐rich fractions were extracted from fresh and dried sweeties with 1.2 M HCl in methanol/water (1:1 v/v), and the antioxidant activities of these extracts were evaluated. Using the β‐carotene/linoleate model system, the extracts from equivalent quantities of fresh and dried sweeties showed 89 and 87% antioxidant activity respectively. Similarly, using the DPPH radical‐scavenging method, the extracts showed 87 and 85% antioxidant activity respectively. The best correlations were between caffeic acid content and β‐carotene and DPPH antioxidant activity values (r = 0.9849 and 0.9798 respectively, p = 0.005). Both fresh and dried sweeties are bioactive natural products; when fresh fruits are not available, properly dried sweeties could be used as a substitute. Copyright © 2004 Society of Chemical Industry     

Antioxidant properties and bioactive constituents of some rare exotic Thai fruits and comparison with conventional fruits: In vitro and in vivo studies

The aim of this research was to investigate the bioactivity of durian, snake fruit and mangosteen, rare exotic Thai fruits. These fruits were compared among them and with conventional fruits: durian with mango and avocado, and snake fruit with mangosteen and kiwifruit in order to find the preferable diet for human consumption. The contents of polyphenols, flavonoids, flavanols, tannins, anthocyanins, ascorbic acid and carotenoids, and the level of antioxidant potential by ABTS, DPPH, FRAP and CUPRAC in different extracts (methanol, water, acetone, and hexane) were determined. The presence of polyphenols (flavonoids and phenolic acids) in the investigated samples was characterized by Fourier transform infrared (FT-IR) spectroscopy and three-dimensional fluorimetry (3D-FL).The in vivo studies were carried out on 25 male Wistar rats, divided into 5 diet groups, each of 5. During 30 days of the experiment the rats of all 5 groups were fed basal diet (BD), which included wheat starch, casein, soybean oil, vitamin and mineral mixtures. The rats of the Control group were fed only the BD. The BD of the other 4 groups was supplemented with 1% of nonoxidized cholesterol (NOC) (Chol group), 1% of NOC in each group and 5% of lyophilized fruits: durian (Chol/Durian), snake fruit (Chol/Snake), mangosteen (Chol/Mangosteen). After the experiment diets supplemented with exotic fruits significantly hindered the rise in plasma lipids and hindered the decrease in the plasma antioxidant activity. In conclusion, the contents of bioactive compounds and the antioxidant potential are relatively high in the studied fruits and varied among them depending on the extraction procedure. FT-IR and 3D-FL can be used as additional tools for identification and comparison of bioactive compounds. Supplementation of diets with exotic fruits positively affects plasma lipid profile and antioxidant activity in rats fed cholesterol-containing diets.     

Effects of artificial lighting on bioactivity of sweet red pepper (Capsicum annuum L.)

Recent studies have shown that artificial light effectively promotes the growth and development of red peppers when light spectra, intensities and duration are controlled. Cited reports deal mostly with studies involving with the growth stages of pepper. Changes in the biochemical status of plants were not studied. Therefore, this study focuses on the changes in the content of some bioactive compounds (polyphenols, flavonoids, tannins, ascorbic acid and antioxidant capacities) after artificial lightening [high‐pressure sodium and light‐emitting plasma (LEP) lamps] during the cultivation of sweet red pepper. The bioactive compounds differ slightly, depending on the source of light. Fluorescence spectra showed higher binding properties of LEP polyphenol extracts to human serum albumin (HSA) than other samples. FTIR peaks were similar in their polyphenols region for all investigated samples.