Impact of graphene-based nanomaterials (GBNMs) on the structural and functional conformations of hepcidin peptide

Graphene-based nanomaterials (GBNMs) are widely used in various industrial and biomedical applications. GBNMs of different compositions, size and shapes are being introduced without thorough toxicity evaluation due to the unavailability of regulatory guidelines. Computational toxicity prediction methods are used by regulatory bodies to quickly assess health hazards caused by newer materials. Due to increasing demand of GBNMs in various size and functional groups in industrial and consumer based applications, rapid and reliable computational toxicity assessment methods are urgently needed. In the present work, we investigate the impact of graphene and graphene oxide nanomaterials on the structural conformations of small hepcidin peptide and compare the materials for their structural and conformational changes. Our molecular dynamics simulation studies revealed conformational changes in hepcidin due to its interaction with GBMNs, which results in a loss of its functional properties. Our results indicate that hepcidin peptide undergo severe structural deformations when superimposed on the graphene sheet in comparison to graphene oxide sheet. These observations suggest that graphene is more toxic than a graphene oxide nanosheet of similar area. Overall, this study indicates that computational methods based on structural deformation, using molecular dynamics (MD) simulations, can be used for the early evaluation of toxicity potential of novel nanomaterials.     

A Categorical Definition of Semidirect Products

For any punctured category, a definition of a semidirect product and its dual counterpart, a semidirect sum, is given. Several examples are studied, among which are semidirect products of commutative Banach algebras and locally compact topological groups, and semidirect sums of compact Hausdorff spaces with basepoint. Also, further applications to commutative Banach algebras are given.     

Influence of polymeric additives on biomimetic silica deposition on patterned microstructures

Microstructured polymer films prepared by photochemical grafting of different polymers were used as restricted reaction areas in silica deposition experiments. Linear and branched poly(alkyleneimines) and poly(allylamine hydrochloride) in pure aqueous or phosphate-containing solutions were used as additives to silica precursor solutions. The silica deposits obtained by spin-coating these solutions onto microstructured polymer films were investigated by scanning electron microscopy and atomic force microscopy. Experiments with poly(alkylene imines) in the silica precursor solution show the deposition of smooth and granular silica structures that closely mimic the natural patterns. The structure formation can be explained by physicochemical processes. Hypotheses that have been made for the natural silification processes can be evaluated on this basis.     

Synthesis, structure, and metal complexation behavior of a new type of functionalized chiral phenanthroline derivative

SmI(2) serves as an effective promoter for the coupling of 1,10-phenanthroline with an epoxide to generate a new class of chiral, functionalized ligands that readily form complexes with metals. Structural studies of the resulting phenanthroline derivative and two of its metal complexes are reported.     

Mono- and diprotonation of the superbasic bisguanidine 1,2-Bis(N,N,N',N'-tetramethylguanidino)benzene (btmgb) and Pt II and Pt IV complexes of chelating bisguanidines and guanidinates

New Pt complexes of chelating bisguanidines and guanidinate ligands were synthesized and characterized. 1,2-Bis(N,N,N',N'-tetramethylguanidino)benzene (btmgb) was used as a neutral chelating bisguanidine ligand, and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate (hpp(-)) as a guanidinate ligand. The salts [btmgbH](+)[HOB(C(6)F(5))(3)](-) and [btmgbH(2)]Cl(2) and the complexes [(btmgb)PtCl(2)], [(btmgb)PtCl(dmso)](+)[PtCl(3)(dmso)](-), and [(btmgb)PtCl(dmso)](+)[Cl(-)] were synthesized and characterized. In the [btmgbH](+) cation the proton is bound to only one N atom. In the other complexes, both imine N atoms are coordinated to the Pt(II), thus adopting a eta(2)-coordinational mode. The hpp(-) anion, which usually prefers a bridging binding mode in dinuclear complexes, is eta(2)-coordinated in the Pt(IV) complex [(eta(2)-hpp)(hppH)PtCl(2){N(H)C(O)CH(3)}], which is formed (in low yield) by reaction between cis-[(hppH)(2)PtCl(2)] and H(2)O(2) in CH(3)CN.     

Solid-state NMR spectroscopy applied to a chimeric potassium channel in lipid bilayers

We show that solid-state NMR can be used to investigate the structure and dynamics of a chimeric potassium channel, KcsA-Kv1.3, in lipid bilayers. Sequential resonance assignments were obtained using a combination of (15)N- (13)C and (13)C- (13)C correlation experiments conducted on fully labeled and reverse-labeled as well as C-terminally truncated samples. Comparison of our results with those from X-ray crystallography and solution-state NMR in micelles on the closely related KcsA K (+) channel provides insight into the mechanism of ion channel selectivity and underlines the important role of the lipid environment for membrane protein structure and function.     

Synthesis and Characterization of Diorganocobalt Chlorides by Aliphatic Vinylic C–Cl Bond Activation

Three diorganocobalt chlorides [CoClMe(PMe₃)₂–{(C₅H₆)–CH=O}] ( 4 ), [CoClMe(PMe₃)₂–{(C₆H₈)–CH=O}] ( 5 ), and [CoClMe(PMe₃)₂–{(C₆H₇Memeta)–CH=O}] ( 6 ) were synthesized through cyclometalation reactions with aldehyde as an anchoring group involving aliphatic vinylic C–Cl bond activation. Complexes 4 – 6 were characterized by IR and NMR spectroscopy. The crystal and molecular structures of complexes 4 and 5 were determined by single‐crystal X‐ray diffraction. Complexes 4 – 6 are stable in solution at room temperature, but they decompose at above 30 °C affording C,C‐couplings products with the formation of [Co(PMe₃)₃Cl]. The results of this work will be important for people to deepen the understanding of the C–Cl bond activation mechanism.     

Biologically Inspired C−H and C=C Oxidations with Hydrogen Peroxide Catalyzed by Iron Coordination Complexes

The development of catalysts for the selective oxidation of readily available hydrocarbons or organic precursors into oxygenated products is a long‐standing goal in organic synthesis. In the last decade, some iron coordination complexes have shown the potential to fit this role. These catalysts can mimic the O?O activation mode of far more sophisticated iron oxygenase enzymes, generating powerful yet selective oxidants. In this review, we report state‐of‐the‐art C?H and C=C oxidations catalyzed by non‐heme iron complexes and H₂O₂ as the oxidant. Finally, we briefly describe some novel oxidative reactivity and the perspectives of this chemistry.     

Detection of bis(sulfosuccinimidyl) suberate binding in electrophoresis: determination of membrane sidedness of proteins

The applicability of the membrane-impermeant protein cross-linker bis(sulfosuccinimidyl) suberate (BS(3)) to the determination of membrane sidedness of proteins was tested in 3T3-L1 cells and in erythrocytes. Binding of BS(3) to proteins was apparent in electrophoresis. In three proteins of 3T3-L1 cells, protein kinase-Cepsilon, protein kinase-Czeta, and glyceraldehyde-3-phosphate dehydrogenase, BS(3) action was detectable in SDS-PAGE with immunoblotting. This enabled confirmation of the well-known intracellular localization of these proteins. In cathepsin E of erythrocytes, a mobility increase in nondenaturing PAGE was the most prominent effect of BS(3) treatment. A mechanism for the increase in mobility due to BS(3) binding is suggested. Cathepsin E was found to be located at the intracellular side of the membrane, in accordance with existing evidence.