Analysis, design and "in silico" evaluation of e-selectin antagonists

E-selectin, is member of a family of cell-adhesion proteins, which plays a crucial role in many physiological processes and diseases [1], and in particular, in the early phases of the inflammatory response. Its role is to promote the tethering and the rolling of leukocytes along the endothelial surface [2]. These steps are then followed by integrin-mediated firm adhesion and final transendothelial migration. Therefore, control of the leukocyte-endothelial cell adhesion process may be useful in cases, where excessive recruitment of leukocytes can contribute to acute or chronic diseases such as stroke, reperfusion injury, psoriasis or rheumatoid arthritis [3]. In this work, efforts to develop in silico-based protocols to study the interaction between E-selectin and its ligands, are presented. Hence, different protocols had to be developed and validated. In particular, a new procedure for the analysis of the conformational preferences of E-selectin antagonists was established and the results compared to those obtained with the MC(JBW)/SD approach, which had already demonstrated its validity in the past [161,168]. Thus, the comparison between the two protocols permitted to recognize a different conformational preference of the two methods for the orientation of the sialic acid moiety of sLex (3) (torsions Φ3 and Ψ3, Figure A), which reflects the contrasting opinions existing for the conformation adopted by sLex (3) in solution [150–168]. A more detailed analysis revealed that probably both approaches deliver only a partially correct view and that in reality, in solution, sLex (3) exists as a mixture of low energy conformers and not as supposed to date [150–154,161–163] as a population of a single conformer. In addition, a docking routine was established and the impact of different partialcharge methods and of explicit solvation on the binding mode studied. MD simulations enabled to gain an insight into the dynamical character of the protein-ligand interactions. In particular, the observations done in an atomic-force microscopy study [350], describing the interactions between the carboxylic group of sLex and Arg97, and between the 3– and 4–hydroxyls of fucose and the calcium ion, as the two main energy barriers for the dissociation process of the protein-ligand complex, found confirmation in our MD-investigations. Thus, these two contacts always lasted longer than any other in the MD simulation. QSAR-models with Quasar [270–272,351] and Raptor [315,316,335] were successfully derived and will permit a semi-quantitative in silico estimation of the binding affinity for the ligands that will be designed in the future. Finally, the developed protocols and models were applied for the development of new E-selectin antagonists. Unfortunately, to date, only few biological data is available to evaluate our design strategies. However, the impact of the ligand’s pre-organization on the binding affinity could be established at least for the Lexcore of sLex (3). Hence, the importance of the exo-anomeric effect, of the steric compression, and of the hydrophobic interaction between the methyl group of fucose and the β-face of galactose was clearly demonstrated

Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets.

In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus

Determination of Metal Content of Waste Mobile Phones and Estimation of Their Recovery Potential in Turkey

Waste mobile phones constitute one of the fastest growing Waste Electrical and Electronic Equipment (WEEE) types all over the world due to technological innovations and shortening of their life span. They contain a complex mix of various materials, such as basic metals, precious metals and rare earth elements and represent an important secondary raw metal source. The main objectives of this study were to characterize the metal concentration of waste mobile phones by optimizing the inductively coupled plasma optical emission spectrometer (ICP-OES) operation parameters and estimate the metal recovery potential of waste mobile phones in Turkey. Therefore, selected mobile phone samples collected from a recycling center in Turkey were analyzed to determine their metal concentrations. Then, the theoretical recovery potentials of precious and rare earth metals from waste mobile phones were estimated for Turkey. The analytical methods optimized in this study can help further research activities to obtain comprehensive data for determination of the critical metals (precious metals and rare earth elements) in WEEE samples so that proper recycling and recovery strategies can be selected and implemented

Biosorption of neodymium on <i>Chlorella vulgaris</i> in aqueous solution obtained from hard disk drive magnets

<div><p>In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (<i>Chlorella vulgaris</i>). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (<i>R</i>^<i>2</i> = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (<i>q</i>_<i>max</i>) of 188.68 mg/g, and Langmuir isotherm constant (<i>K</i>_<i>L</i>) of 0.029 L/mg. The corresponding separation factor (<i>R</i>_<i>L</i>) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R²>0.99), even at low initial concentrations. These results show that <i>Chlorella vulgaris</i> has greater biosorption affinity for Nd than activated carbon and other algae types such as: <i>A</i>. <i>Gracilis</i>, <i>Sargassum sp</i>. and <i>A</i>. <i>Densus</i>.</p></div

Experimental Nd uptake onto C. vulgaris at different temperature (21, 35 and 50°C) and pH (3, 4 and 5).

<p>Experimental Nd uptake onto C. vulgaris at different temperature (21, 35 and 50°C) and pH (3, 4 and 5).</p

Nd biosorption kinetics for pH 5, biosorbent dosage = 0.5 g/L, initial Nd concentration = 250 mg/L and for temperature 21, 35 and 50 oC.

<p>Curves were predicted by pseudo-second order model.</p

Summary of the experimental procedure.

<p>Summary of the experimental procedure.</p

The impact of hazelnuts in land-use changes on soil carbon and in situ soil respiration dynamics

Our study assessed the impact of hazelnuts (Coryllus avellena L) in land-use conversion from forest (F) to agricultural land (AL) on various attributes of soil respiration dynamics, such as soil elemental carbon (C %) content, microbial respiration, bulk density, soil pH, electrical conductivity, and seasonal variations. We developed soil C% models to compare soil C% between F and AL soils. Four field trips were conducted in the winter and summer of 2008 and the spring and fall of 2009 in the Karasu region of Turkey. During each trip, 42 sites were visited F (n = 21) and AL (n = 21). Our results showed that hazelnuts plantations in AL could reduce elemental C% by 27% (winter 2008), 16% (summer 2008), 41% (spring 2009), and 22% (fall 2009) in the four seasons studied when compared to F soils. In situ soil respiration was also reduced by 31% (spring 2008), 67% (fall 2008), 88% (spring 2009), and 79% (fall 2009) in AL soils over F soils. The percent of organic matter of AL soils was declined by 36% (winter 2008), 23% (summer 2008), 34% (spring 2009), and 26% (fall 2009) in comparison to F soils. Significant reductions in the correlation between C %-percent clay and C%-electrical conductivity were also recorded for AL soils over F soils. Furthermore, AL soils showed higher bulk density (7.4% and 7%) when compared to F soils. We also found that in situ soil respiration had significant seasonal correlations (p < 0.05) with soil pH (0.537), soil temperature, and percent clay (-0.486) in F soils (summer 2008, spring 2009). Additionally, we found that seasonal variations of four sampling seasons had a moderate impact on in situ respiration and that the differences were statistically significant, except for the winter-summer and spring-fall seasonal pairs. Linear regression C models showed significant differences for F and AL soils. (C) 2013 Elsevier Ltd. All rights reserved