Mechanism of charge transfer/disproportionation in LnCu3Fe4O12 (Ln: Lanthanides)

The Fe-Cu intersite charge transfer and Fe charge disproportionation are interesting phenomena observed in some LnCu3Fe4O12 (Ln: Lanthanides) compounds containing light and heavy Ln atoms, respectively. We show that a change in the spin state is responsible for the intersite charge transfer in the light Ln compounds. At the high spin state, such systems prefer an unusual Cu-d^8 configuration, whereas at the low spin state they retreat to the normal Cu-d^9 configuration through a charge transfer from Fe to Cu-3d_{xy} orbital. We find that the strength of the crystal field splitting and the relative energy ordering between Cu-3d_{xy} and Fe-3d states are the key parameters, determining the intersite charge transfer (charge disproportionation) in light (heavy) Ln compounds. It is further proposed that the size of Ln affects the onsite interaction strength of Cu-3d states, leading to a strong modification of the Cu-L_3 edge spectrum, as observed by the X-ray absorption spectroscopy.Comment: 6 pages, 5 figures, 1 table. To appear in PR

Hypoglycemic effect of Satureja montanum L. hydroethanolic extract on diabetic rats

ntroduction: Diabetes is one of the most prevalent metabolic disorders which is associated withseveral complications in different organs. Nowadays, medicinal herbs are being widely used totreat diseases. This study was conducted to study the hypoglycemic effect of Satureja montanum in diabetic male rats.Methods: In this study 42 male Wistar rats were randomly assigned to 7 equal groups includingcontrol, diabetic control, treatments 1, 2, and 3, metformin-treated diabetic, and healthytreated with Satureja montanum. To  induce diabetes streptozotocin (STZ) at 60 mg/kg wasintraperitoneally (ip) administered. The animals were treated daily with Satureja montanumextract (ip) for one week and their blood glucose was measured daily.Results: Satureja montanum extract could significantly decrease blood glucose. The greatest effectof the extract was seen on day 8 at 800 mg/kg (P < 0.001). Satureja montanum extract caused asignificant increase in serum insulin compared to the control group (P < 0. 001).Conclusion: The findings of this study indicate that Satureja montanum hydroethanolic extractis able to significantly decrease blood glucose of diabetic rats possibly with a stimulatory effect onbeta cells

Brand Value Co-Creation in the Social Commerce Era: Empirical Evidence From Iran

Brand value co-creation occurs when customers provide informational input to brand owners, which can be used to develop, refine or extend brands. Brand co-creation is an attractive and inexpensive marketing strategy for firms entering new markets and developing new brand meanings. The upward trend in social media use has transformed e-commerce by adding social support and information sharing features, resulting in social commerce. This research tests a framework that examines the e-commerce opportunities for firms from a branding perspective. Using a survey of Iranian consumers, SEM- PLS was used to analyse the data. Results provide new insights for a strategic approach to social media use in relation to the firm’s value co-creation objective. The results confirm the research model and emphasise the importance of social commerce constructs, social support, and relationship quality in brand value co-creation. The theoretical and practical implications are provided

Halotolerant Ability and α-Amylase Activity of Some Saltwater Fungal Isolates

Four halotolerant fungal isolates originating from the saltwater Lake Urmia in Iran were selected during a screening program for salt resistance and α-amylase activity. The isolates were identified based on sequencing the ITS region and a part of the β-tubulin gene, as Penicillium chrysogenum (isolate U1; CBS 132820), Fusarium incarnatum (isolate U2; CBS 132821), and Penicillium polonicum (isolate U3; CBS 132822, and isolate U4; CBS 132823). The growth of these isolates was determined by measuring the colony diameter and mycelia dry weight in Sabouraud dextrose agar and yeast nitrogen base medium supplemented with NaCl, KCl, and LiCl. Isolate U4 showed a growth up in 15% NaCl and U1 was the only isolate that could grow in 20% KCl. None of the strains grew in a media containing LiCl. The salt supplemented medium did not increase the size of colony diameter in all isolates (p > 0.05). The ability of the selected isolates for amylase production was quantitatively tested and showed that P. polonicum isolate U4 was the most potent producer of amylase with a yield of 260.9 U/L after 60 h, whereas P. polonicum isolate U3 was the lowest one with a production level of 97.9 U/L after 48 h. P. polonicum isolate U4 could be a suitable candidate for production of amylase on an industrial scale after optimization. © 2013 by School of Pharmacy

Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR

Heparins and heparan sulfate polysaccharides are negatively charged glycosaminoglycans and play important roles in cell-to-matrix and cell-to-cell signaling processes. Metal ion binding to heparins alters the conformation of heparins and influences their function. Various experimental techniques have been used to investigate metal ion-heparin interactions, frequently with inconsistent results. Exploiting the quadrupolar 23Na nucleus, we herein develop a 23Na NMR-based competition assay and monitor the binding of divalent Ca2+ and Mg2+ and trivalent Al3+ metal ions to sodium heparin and the consequent release of sodium ions from heparin. The 23Na spin relaxation rates and translational diffusion coefficients are utilized to quantify the metal ion-induced release of sodium ions from heparin. In the case of the Al3+ ion, the complementary approach of 27Al quadrupolar NMR is employed as a direct probe of ion binding to heparin. Our NMR results demonstrate at least two metal ion-binding sites with different affinities on heparin, potentially undergoing dynamic exchange. For the site with lower metal ion binding affinity, the order of Ca2+ > Mg2+ > Al3+ is obtained, in which even the weakly binding Al3+ ion is capable of displacing sodium ions from heparin. Overall, the multinuclear quadrupolar NMR approach employed here can monitor and quantify metal ion binding to heparin and capture different modes of metal ion-heparin binding

Reorientational dynamics of amyloid-β from NMR spin relaxation and molecular simulation.

Amyloid-β (Aβ) aggregation is a hallmark of Alzheimer's disease. As an intrinsically disordered protein, Aβ undergoes extensive dynamics on multiple length and time scales. Access to a comprehensive picture of the reorientational dynamics in Aβ requires therefore the combination of complementary techniques. Here, we integrate 15N spin relaxation rates at three magnetic fields with microseconds-long molecular dynamics simulation, ensemble-based hydrodynamic calculations, and previously published nanosecond fluorescence correlation spectroscopy to investigate the reorientational dynamics of Aβ1-40 (Aβ40) at single-residue resolution. The integrative analysis shows that librational and dihedral angle fluctuations occurring at fast and intermediate time scales are not sufficient to decorrelate orientational memory in Aβ40. Instead, slow segmental motions occurring at ∼5 ns are detected throughout the Aβ40 sequence and reach up to ∼10 ns for selected residues. We propose that the modulation of time scales of reorientational dynamics with respect to intra- and intermolecular diffusion plays an important role in disease-related Aβ aggregation

Dynamical component exchange in a model phase separating system: an NMR-based approach

Biomolecular phase separation plays a key role in the spatial organization of cellular activities. Dynamic formation and rapid component exchange between phase separated cellular bodies and their environment are crucial for their function. Here, we employ a well-established phase separating model system, namely, a triethylamine (TEA)–water mixture, and develop an NMR approach to detect the exchange of scaffolding TEA molecules between separate phases and determine the underlying exchange rate. We further demonstrate how the advantageous NMR properties of fluorine nuclei provide access to otherwise inaccessible exchange processes of a client molecule. The developed NMR-based approach allows quantitative monitoring of the effect of regulatory factors on component exchange and facilitates “exchange”-based screening and optimization of small molecules against druggable biomolecular targets located inside condensed phases