Synthesis, characterization and X-ray crystal structures of two polymorphs of a cobalt(III) complex with a N3O2 pentadentate Schiff base ligand, and benzylamine: spectral and electrochemical studies

The title complex [Co^III{(naph)₂dpt}(bzlan)]BPh₄, where (naph)₂dpt stands for bis-(2-hydroxy-1-naphthaldimine)-N-dipropylenetriamine dianion and bzlan for benzylamine, has been synthesized and characterized by elemental analyses, IR, UV–Vis and ¹H NMR spectroscopy. The structures of two possibly concomitant polymorphs, obtained from methanolic solution, [polymorph I (monoclinic, centrosymmetric, red-brown, thickish prismatic platelets) and polymorph II (orthorhombic, noncentrosymmetric, ochre olive-green, thin laths)] have been determined by X-ray crystallography. The geometry around the central cobalt ion is distorted octahedral in both polymorphs, but the benzylamine shows different kinds of orientation and disorder.     

Preconcentration of trace cadmium ion using magnetic graphene nanoparticles as an efficient adsorbent

Graphene-based magnetic nanoparticles (G-Fe₃O₄) were prepared and used as an effective adsorbent for the solid-phase extraction of trace quantities of cadmium from water and vegetable samples. The method avoids some of the time-consuming steps associated with traditional solid phase extraction. The excellent sorption property of the G-Fe₃O₄ system is attributed to π - π stacking interaction and hydrophobic interactions between graphene and the Cd-PAN complex. The effects of pH, the amount of G–Fe₃O₄, extraction time, type and volume of eluent, desorption time and interfering ions on the extraction efficiency were optimized. The preconcentration factor is 200. Cd(II) was then quantified by flame atomic absorption spectrometry with a detection limit of 0.32 ng mL^?1. The relative standard deviation (at 50 ng mL^?1; for n?=?10) is 2.45 %. The method has a linear analytical range from 1.1 to 150 ng mL^?1, and the recoveries in case of real samples are in the range between 93.1 % and 102.3 %.

Mild and Efficient One-Pot Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles from Nitriles Mediated by K3PO4

Potassium phosphate, K₃PO₄, has been proved to be a cheap, strong, and efficient reagent for the one-pot synthesis of 3,5-disubstituted-1,2,4-oxadiazoles from nitriles and acid chlorides under mild conditions.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Deconvolution and binding study of camel and human serum albumins upon interaction with sodium dodecyl sulphate

Interactions of camel serum albumin (CSA) and human serum albumin (HSA) with sodium dodecyl sulphate (SDS) were studied via fluorescence and circular dichroism (CD) spectroscopy and tensiometry. There was a good correlation between fluorescence intensity and surface tension changes of CSA and HSA versus SDS concentration in which both showed two main transitions. However, the CD signals of CSA at 222 nm versus SDS concentration showed only one transition. According to the obtained results, interaction of SDS with the proteins can be divided into four distinct regions; in the initial region, SDS binds specifically to high-affinity binding sites, in the second region, SDS binds to the lower affinity binding sites on the protein surface, in the third region, cooperative binding of SDS triggers the protein to unfold. Finally after saturation of protein with SDS, at the final stage, normal SDS micelles start to form. Our results indicated that the partial unfolding of HSA started at higher concentrations of SDS and proceeded with higher cooperativity compared to that of CSA. This may be attributed to a higher inner hydrophobicity and higher stability of HSA compared to CSA.     

Computational Study of the Dissolution of Some Atomic and Diatomic Species in the Square and Hexagonal 2‐D Helium Lattices

Dissolution of some industrially relevant atomic and diatomic species (Ar, Ne, H, O, H₂, N₂ and O₂) in the 5 × 5 2‐D hexagonal and square helium lattices, as the model of the liquid helium cryogen, has been studied using ab initio MP2/6‐31++G computations. Structural, electronic and thermochemical properties have been calculated and analyzed for these solution lattices. Results of these calculations show that dissolution of Ar, Ne, H and H₂ species is more favored at higher temperatures. A reverse trend is observed for the dissolution of O, N₂ and O₂ species. A staggered orientation is preferred by all diatomic species in both lattices. Results of this study also show that breakage of the O₂ molecule becomes slightly easier in the 2‐D helium lattices as compared with that of the H₂ molecule. Effect of the cavity geometry and size, and position of the solute in the lattice have also been studied. Analysis of the results shows that the range of the interaction between the solute and solvent atoms is only one helium layer.     

Synthesis and Reactivity of an Anionic Diazoolefin

Bent (hetero)allenes such as carbodicarbenes and carbodiphosphoranes can act as neutral C-donor ligands, and diverse applications in coordination chemistry have been reported. N-Heterocyclic diazoolefins are heterocumulenes, which can function in a similar fashion as L-type ligands. Herein, we describe the synthesis and the reactivity of an anionic diazoolefin. This compound displays distinct reactivity compared to neutral diazoolefins, as evidenced by the preparation of diazo compounds via protonation, alkylation, or silylation. The anionic diazoolefin can be employed as an ambidentate, X-type ligand in salt metathesis reactions with metal halide complexes. Extrusion of dinitrogen was observed in a reaction with PCl(NiPr₂)₂, resulting in a stable phosphinocarbene.     

Cloning and Expression of Functional Full-Length Human Tissue Plasminogen Activator in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Human tissue plasminogen activator (t-PA) plays a pivotal role in the treatment of acute myocardial infarction, ischemic stroke, and deep vein thrombosis. It has the benefit of generating no adverse effects such as fibrinogen depletion, systemic hemorrhage, and immunologic reactions. Human t-PA is a serine-protease enzyme containing 527 amino acid residues in five structural domains. The correct folding of t-PA requires the correct pairing of 17 disulfide bridges in the molecule. A gene encoding full-length human t-PA was cloned into pPICZαA expression vector downstream of alcohol oxidase promoter and α-mating signal sequence from Saccharomyces cerevisiae and flush with the kex2 cleavage site to express the protein with a native N terminus. The methylotrophic yeast, Pichia pastoris GS115 strain, was transformed with this cassette, and methanol utilizing (mut+) transformants were selected for production and secretion of human t-PA into culture media. SDS–PAGE and Western blot analysis showed the expressed bands of t-PA protein. Zymography test indicated suitable folding and proper function of the expressed recombinant human t-PA in conversion of plasminogen to plasmin and gelatin lysis. Amidolytic activity test showed the amidolytic activity of 1,650 IU/ml. The results of this study concluded that P. pastoris methylotrophic yeast can be a suitable alternative for mammalian and prokaryotic expression systems to produce t-PA.