Probing the interaction of fisetin with human serum transferrin via spectroscopic and molecular docking approaches.

The binding of fisetin to human serum transferrin (HST) was investigated by spectroscopic (steady-state fluorescence, synchronous fluorescence, Förster resonance energy transfer) and molecular docking approaches. HST fluorescence is quenched by fisetin by a static process. The binding takes place with a moderate affinity and it is driven by hydrogen bonding and van der Waals forces. Synchronous fluorescence study indicates that Trp is more involved in the fluorescent quenching of HST by fisetin than Tyr. The energy transfer between HST and fisetin occurs at a distance of 2.31 nm confirming the results obtained by fluorescence. The binding of fisetin to HST favors thermal denaturation of HST conformation. The transition temperature for HST was obtained at 53.81 °C while the presence of the fisetin led to its change to 49.06 °C. The molecular docking of fisetin to HST confirms the results obtained by the spectroscopic experiments showing a moderate affinity of fisetin for HST.Communicated by Ramaswamy H. Sarma.

Structural and molecular aspects of flavonoids as ligands for serum transferrin.

Human serum transferrin (HST) acts as a carrier for Fe3+ and other ions. Binding of flavonoids to HST produces changes in the protein structure with direct implication on iron delivery into cells. We investigate the binding mechanism and affinity towards HST of three flavonoids: rutin, luteolin, and apigenin by different techniques: UV-Vis, fluorescence, fluorescence resonance energy transfer (FRET) combined with molecular docking. UV-Vis results indicate an interaction between flavonoids and HST. It was observed that HST fluorescence was quenched by these three flavonoids via a static process. All the interactions were moderate and the main driving forces are hydrophobic (ΔH > 0 and ΔS > 0) for rutin and luteolin binding or electrostatic (ΔH < 0 and ΔS > 0) for apigenin binding. FRET and molecular docking studies confirm the fluorescence static quenching mechanism by flavonoid binding. The binding of all three flavonoids increases HST stability. These results present the potential use of HST in target-oriented delivery of flavonoids and possibly other drugs into cells.

Treatment with Sildenafil and Donepezil Improves Angiogenesis in Experimentally Induced Critical Limb Ischemia.

Objectives. In this study, we aimed to demonstrate the role of sildenafil (an antagonist of phosphodiesterase type 5 (PDE-5)) and donepezil (a specific and reversible inhibitor of acetylcholinesterase (Ach)) in increasing ischemia-induced angiogenesis. Method. Critical limb ischemia was induced by ligation of the common femoral artery followed by ligation of the common iliac artery. The operated animals were divided into 3 groups: receiving sildenafil, receiving donepezil, and surgery alone; the contralateral lower limb was used as a negative control. The results were controlled based on clinical score and Doppler ultrasound. Gastrocnemius muscle samples were taken from all animals, both from the ischemic and nonischemic limb and were used for histopathological and immunohistochemical examination for the evaluation of the number of nuclei/field, endothelial cells (CD31), dividing cells (Ki-67), and vascular endothelial growth factor (VEGFR-3). Results. An increasing tendency of the number of nuclei/field with time was observed both in the case of sildenafil and donepezil treatment. The formation of new capillaries (the angiogenesis process) was more strongly influenced by donepezil treatment compared to sildenafil or no treatment. This treatment significantly influenced the capillary/fiber ratio, which was increased compared to untreated ligated animals. Sildenafil treatment led to a gradual increase in the number of dividing cells, which was significantly compared to the negative control group and compared to the ligation control group. The same effect (increase in the number of Ki-67 positive cells) was more obvious in the case of donepezil treatment. Conclusion. Donepezil treatment has a better effect in ligation-induced ischemia compared to sildenafil, promoting angiogenesis in the first place, and also arteriogenesis.

Evaluation of serum adipokines in peripheral arterial occlusive disease.

AIM: Out study aimed to assess the serum levels of adipokines in patients with peripheral arterial occlusive disease (PAOD) caused by atherosclerosis. METHODS: Serum samples were obtained from 221 patients. One hundred and forty patients, (26 females and 114 males) met the inclusion criteria and were assigned into the case group. Eighty one patients (17 females and 64 males), were included in the control group. Circulating plasma levels of adiponectin, leptin, resistin, and TNF-α were measured using the enzyme-linked immunosorbent assay (ELISA) method. RESULTS: Significant lower levels of adiponectin were present (P = 0.0061) in PAOD patients (2380.23 ± 1634.42 pg/mL) compared to the control group (3065.06 ± 1901.2 pg/mL). The mean value of leptin (2844.42 ± 3301.08 pg/mL) and resistin (2047.81±3301.08 pg/mL) patients included in the PAOD group was higher, as compared to the control group. Statistically significant difference was found between the two groups for leptin (P = 0.0332) and for resistin (P = 0.0352). No statistically significant difference for TNF-α was found between the two groups (P > 0.05). CONCLUSION: The markers of inflammation secreted by the adipose tissue (adiponectin, leptin, resistin) showed significant differences in patients from the case group (with PAOD) compared to the control group.

Diversity and distribution of Braconidae, a family of parasitoid wasps in the central European peatbogs of South Bohemia, Czech Republic.

An ecological overview of seven years investigation of Braconidae, a family of parasitoid wasps (Hymenoptera: Ichneumonoidea) and a tyrpho-classification of parasitoids in peatbog areas of South Bohemia, Czech Republic are given. A total of 350 species were recorded in investigated sites, but only five tyrphobionts (1.4%) are proposed: Microchelonus basalis, Microchelonus koponeni, Coloneura ate, Coloneura danica and Myiocephalus niger. All of these species have a boreal-alpine distribution that, in Central Europe, is associated only with peatbogs. Tyrphophilous behaviour is seen in at least four (1.1%) species: Microchelonus pedator, Microchelonus subpedator, Microchelonus karadagi and Microchelonus gravenhorstii; however, a number of other braconids prefer peatbogs because they were more frequently encountered within, rather than outside, the bog habitat. The rest of the braconids (342 species, 97.5%) are tyrphoneutrals, many of them being eurytopic components of various habitats throughout their current ranges. Lists of tyrphobiontic braconids and a brief commentary on species composition, distributional picture of actual ranges, and parasitoid association to bog landscape are provided. Being true refugial habitats for populations in an ever-changing world, peatbogs play a significant role in harboring insect communities.

Transbilayer pores induced by thickness fluctuations.

Thermally-induced fluctuations of individual phospholipids in a bilayer lipid membrane (BLM) are converted into collective motions due to the intermolecular interactions. Here, we demonstrate that transbilayer stochastic pores can be generated via collective thermal movements (CTM). Using the elastic theory of continuous media applied to smectic-A liquid crystals, we estimate the pore radius and the energetic requirements for pore appearance. Three types of thermally-induced transbilayer pores could be formed through BLMs: open and stable, open and unstable, and closed. In most of the situations, two open and stable pores with different radii could be generated. Notably, the two pores have the same generation probability. Unstable pores are possible to appear across thin bilayers that contain phospholipids with a large polar headgroup. Closed pores are present throughout the cases that we have inspected. The effects of hydrophobic thickness, polar headgroup size of phospholipids, temperature, surface tension, and elastic compression on the pore formation and pore stability have been examined as well.