The Role of Ovalbumin in Manganese Homeostasis during Chick Embryogenesis: An EPR Spectroscopic Study

Ovalbumin (OVA), a protein vital for chick embryo nutrition, hydration, and antimicrobial protection, together with other egg-white proteins, migrates to the amniotic fluid and is orally absorbed by the embryo during embryogenesis. Recently, it has been shown that for optimal eggshell quality, the hen diet can be supplemented with manganese. Although essential for embryonic development, manganese in excess causes neurotoxicity. This study investigates whether OVA may be involved in the regulation of manganese levels. The binding of Mn(II) to OVA was investigated using electron paramagnetic resonance (EPR) spectroscopy. The results show that OVA binds a maximum of two Mn(II) ions, one with slightly weaker affinity, even in a 10-fold excess, suggesting it may have a protective role from Mn(II) overload. It seems that the binding of Mn(II), or the presence of excess Mn(II), does not affect OVA’s tertiary structure, as evidenced from fluorescence and UV/vis measurements. Comparative analysis with bovine and human serum albumins revealed that they exhibit higher affinities for Mn(II) than OVA, most likely due to their essentially different physiological roles. These findings suggest that OVA does not play a role in the transport and storage of manganese; however, it may be involved in embryo protection from manganese-induced toxicity

Aminoalcoholate-driven tetracopper(II) cores as inhibitors of aggregation of β-amyloid

Fourth WG Meeting CA15135 : Final status of WG activities within MuTaLig COST Action, 5-6 March 2020, Izmir, Turkiye [http://www.mutalig.eu/wp-content/uploads/2020/03/Book_of_abstracts_WG_Izmir.pdf

Oxidative stress responses of 12-Tungstosilicic and 12-Tungstophosphoric acid

In vitro oxidative stress responses of two Keggin-type polyoxotungstates, 12- tungstosilicic (WSiA) and 12-tungstophosphoric acid (WPA), were investigated using rat synaptosomes as a model system. WSiA induced concentration-dependent increase in catalase activity, up to about 6 times compared to the control activity in untreated synaptosomes, and glutathione peroxidase was not significantly affected after WSiA treatment. On the contrary, WPA treatment resulted in the increase of glutathione peroxidase activity, while synaptosomal catalase was even reduced related to the control, at all investigated WPA concentrations. Both investigated polyoxotungstates did not significantly change malondialdehyde content in synaptosomal preparations. It could accordingly be concluded that WSiA and WPA probably induce reactive oxygen species generation, resulting in the activation of the antioxidant defense enzymes. However, these polyoxotungstates are not strong prooxidants being able to cause oxidative stress, and consequently synaptosomal membrane lipid damage.14th international conference on fundamental and applied aspects of physical chemistry; 24-28 September 2018, Belgrade, Serbia

“Soft Protein Corona” as the Stabilizer of the Methionine-Coated Silver Nanoparticles in the Physiological Environment: Insights into the Mechanism of the Interaction

The study of the interactions between nanoparticles (NPs) and proteins has had a pivotal role in facilitating the understanding of biological effects and safe application of NPs after exposure to the physiological environment. Herein, for the first time, the interaction between L-methionine capped silver nanoparticles (AgMet), and bovine serum albumin (BSA) is investigated in order to predict the fate of AgMet after its contact with the most abundant blood transport protein. The detailed insights into the mechanism of interaction were achieved using different physicochemical techniques. The UV/Vis, TEM, and DLS were used for the characterization of the newly formed “entity”, while the kinetic and thermodynamic parameters were utilized to describe the adsorption process. Additionally, the fluorescence quenching and synchronous fluorescence studies enabled the prediction of the binding affinity and gave us insight into the influence of the adsorption on the conformation state of the BSA. According to the best of our knowledge, for the first time, we show that BSA can be used as an external stabilizer agent which is able to induce the peptization of previously agglomerated AgMet. We believe that the obtained results could contribute to further improvement of AgNPs’ performances as well as to the understanding of their in vivo behavior, which could contribute to their potential use in preclinical research studies

Modulation of acetylcholinesterase activity induced by polyoxotungstates

The in vitroinfluence of five polyoxotungstates containing various central atoms on acetylcholinesterase (AChE) activity was investigated. K6[PV3W9O40] × 3H2O, K6H2[TiW11CoO40] × 13H2O, (NH4)14[NaP5W30O110] × 31H2O, K7[SiV3W9O40] × 10H2O, and K7[Ti2PW10O40] induced the enzyme inhibition in a concentration-dependent manner. Inhibitory power of the investigated compounds was evaluated using IC50values. K7[SiV3W9O40] × 10H2O affected AChE activity with lowest potency (IC50 = 4.80 × 10-4mol/L). K6H2[TiW11CoO40] × 13H2O and K7[Ti2PW10O40] exhibited high affinity toward the enzyme, inducing half-maximuminhibition at micromolar concentrations (1.14 × 10-6and 1.04 × 10-6mol/L, respectively), while the same effect was achieved in the presence of about fifty times higher concentration of K6[PV3W9O40] × 3H2O. Finally, (NH4)14[NaP5W30O110] × 31H2O was foundas the most potent inhibitor of AChE activity (IC50 = 6.36 × 10-7mol/L), and consequently the most promising candidate for the treatment of neurological diseases associated with acetylcholine leakage.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 2016

Influence of 12-Tungstosilicic acid and 12-Tungstophosphoric acid on the activity and secondary structure of acetylcholinesterase

Inhibition of acetylcholinesterase (AChE) is presented as a promising strategy in the treatment of Alzheimer disease providing inspiration for new discoveries and investigations less toxic and more effective potential anti Alzheimer drugs. In this paper, it demonstrated that the activity of acetylcholinesterase can be effectively inhibited by polyoxometalates (POMs), 12-tungstosilicic acid (WSiA) and 12-tungstophosphoric acid (WPA) without significant changes on the secondary structure of this enzyme. The obtained values of partition coefficient implicated on smooth pass of these POMs trough cell membrane and satisfied necessary criteria for the drugs used in the treatment of the central nervous system disease. Based on these obtained results it is possible to conclude that POM could represent new generation of potential anti Alzheimer drugs.14th international conference on fundamental and applied aspects of physical chemistry; 24-28 September 2018, Belgrade, Serbia

Conjugates of Gold Nanoparticles and Antitumor Gold(III) Complexes as a Tool for Their AFM and SERS Detection in Biological Tissue

Citrate-capped gold nanoparticles (AuNPs) were functionalized with three distinct antitumor gold(III) complexes, e.g., [Au(N,N)(OH)2][PF6], where (N,N)=2,2′-bipyridine; [Au(C,N)(AcO)2], where (C,N)=deprotonated 6-(1,1-dimethylbenzyl)-pyridine; [Au(C,N,N)(OH)][PF6], where (C,N,N)=deprotonated 6-(1,1-dimethylbenzyl)-2,2′-bipyridine, to assess the chance of tracking their subcellular distribution by atomic force microscopy (AFM), and surface enhanced Raman spectroscopy (SERS) techniques. An extensive physicochemical characterization of the formed conjugates was, thus, carried out by applying a variety of methods (density functional theory—DFT, UV/Vis spectrophotometry, AFM, Raman spectroscopy, and SERS). The resulting gold(III) complexes/AuNPs conjugates turned out to be pretty stable. Interestingly, they exhibited a dramatically increased resonance intensity in the Raman spectra induced by AuNPs. For testing the use of the functionalized AuNPs for biosensing, their distribution in the nuclear, cytosolic, and membrane cell fractions obtained from human lymphocytes was investigated by AFM and SERS. The conjugates were detected in the membrane and nuclear cell fractions but not in the cytosol. The AFM method confirmed that conjugates induced changes in the morphology and nanostructure of the membrane and nuclear fractions. The obtained results point out that the conjugates formed between AuNPs and gold(III) complexes may be used as a tool for tracking metallodrug distribution in the different cell fractions

Organocatalytic, Organic Oxidant Promoted, Enamine C−H Oxidation/Cyclopropanation Reaction

Herein, we demonstrate that organic, single-electron oxidant in the presence of diarylprolinol silylether type catalyst serves as a tool for the transformation of electron-rich enamines to iminium ions. These iminium ions take part in a subsequent Michael-initiated ring-closure (MIRC) reaction with in situ present nucleophile giving rise to overall cyclopropanation reaction of saturated aldehydes. Stereodefined cyclopropanes are obtained in high yields and selectivities. This one-pot transformation represents the additional example of saturated aldehydes being used in the coupled one-pot processes. (Figure presented.)

pi-Annulation reactions of 4-thiazolidinone enaminones in the synthesis of fused bi- and tri-cyclic compounds

The a-C position in 4-oxo thiazolidinones functions as one of the three possible nucleophilic sites in these molecules. We used the inherent reactivity of alpha-C of the exocyclic double bond (a so called push pull system) to obtain bicyclic fused thiazolidinones via pi-annulation cyclization. Appropriate reaction conditions to selectively activate this position and secondary nitrogen towards N, pi-annulation were found. Furthermore, the intramolecular vinylogous iminium ion 6-exo-trig cyclization was used to access fused bicyclic precursors for the pi-annulation in order to obtain the novel tricyclic structures stereoselectively

Visible-light promoted photoredox catalysis in flow: addition of biologically important α‑amino radicals to michael acceptors

Visible light promoted photoredox catalyzed formation of α-amino radicals from cyclic tertiary amine compounds and their subsequent addition to Michael acceptors performed in flow conditions allowed access to a wide range of functionalized N-aryl-substituted tetrahydroisoquinolines (THIQs) and N-aryl-substituted tetrahydro-β-carbolines (THBCs). Visible light in conjunction with Ru(bpy)3Cl2 photocatalyst allowed the formation and high reactivities of α-amino radicals in flow conditions at room temperature. These reactions gave valuable products with high efficiencies; some previously unavailable reaction pathways photo or thermal reaction conditions; i.e. direct synthesis of 1-substituted (THBCs) via α-amino radical path were successfully realized in flow. The use of custom-made FEP tube microreactor proved to be the key to succesfull α-amino-radical formation and overall reaction performance in flow. Three types of light transparent custom-made microfluidic devices were tested, among them glass/silicon and FEP type reactor showed very good results in the conversion of tested compounds. Plausible reaction mechanism is proposed in accordance with known principles of photo activation of tertiary amines