Phthalocyanine macrocycle as stabilizer for gold and silver nanoparticles

A one-step process was used for the preparation of gold and silver nanoparticles stabilized by an aminophthalocyanine macrocycle. The resultant nanoparticles were characterized by absorption spectra, infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The nanoparticles were found to possess relatively narrow size distribution. The gold nanoparticles have an average diameter of ~2 nm, while silver particles have 4–5 nm. Preliminary studies on fluorescence and surface enhanced Raman spectroscopy were carried out using these nanoparticles. Fluorescence studies indicate that gold nanoparticles do not quench the fluorescence, while silver nanoparticles do. The stabilized nanoparticles showed enhancement of the Raman signals, thus revealing that they are good substrates for surface enhanced Raman scattering studies.     

A designed glycoprotein analogue of Gc-MAF exhibits native-like phagocytic activity

Rational protein design has been successfully used to create mimics of natural proteins that retain native activity. In the present work, de novo protein engineering is explored to develop a mini-protein analogue of Gc-MAF, a glycoprotein involved in the immune system activation that has shown anticancer activity in mice. Gc-MAF is derived in vivo from vitamin D binding protein (VDBP) via enzymatic processing of its glycosaccharide to leave a single GalNAc residue located on an exposed loop. We used molecular modeling tools in conjunction with structural analysis to splice the glycosylated loop onto a stable three-helix bundle (alpha3W, PDB entry 1LQ7). The resulting 69-residue model peptide, MM1, has been successfully synthesized by solid-phase synthesis both in the aglycosylated and the glycosylated (GalNAc-MM1) form. Circular dichroism spectroscopy confirmed the expected alpha-helical secondary structure. The thermodynamic stability as evaluated from chemical and thermal denaturation is comparable with that of the scaffold protein, alpha3W, indicating that the insertion of the exogenous loop of Gc-MAF did not significantly perturb the overall structure. GalNAc-MM1 retains the macrophage stimulation activity of natural Gc-MAF; in vitro tests show an identical enhancement of Fc-receptor-mediated phagocytosis in primary macrophages. GalNAc-MM1 provides a framework for the development of mutants with increased activity that could be used in place of Gc-MAF as an immunomodulatory agent in therapy.     

Hydroxyapatite coating on stainless steel pre-coated with bovine serum albumin at ambient conditions

A biomimetic process for coating of nanosized hydroxyapatite on stainless steel, which capitalises the dual nature of the protein bovine serum albumin in both metal binding and a strong affinity for calcium ions, has been developed. The novelty of the process lies in pre-conditioning the metallic surface using the above protein prior to its mineralization with hydroxyapatite at ambient conditions. The microporous morphology of these coatings may provide favourable solubility and resorbability as desired by many orthopaedic and orthodontic applications.     

Cobalt perchlorate hexahydrate catalyzed one-pot synthesis of dihydropyrimidin-ones/-thiones through sonochemistry and its mechanistic study using density functional theory calculations

A cobalt(II) perchlorate hexahydrate coordinated synthesis of dihydropyrimidin-ones and -thiones through sonochemistry is developed. Herein, the reaction was demonstrated as a simple, efficient, and one-pot method for synthesizing a series of interesting 3,4-dihydropyrimidin-2(1H)-ones. Further, the reaction mechanism was investigated using mass spectrometry and density functional theory calculations suggesting that a Lewis acid character of cobalt(II) perchlorate hexahydrate plays a crucial role in coordinating carbonyl functionalities and stabilizing the polar intermediates like imine–enamine which further led to cyclized dihydropyrimidin-ones and -thiones. This methodology was further explored to synthesize a gram-scale synthesis of monastrol drug, a kinase inhibitor.     

The Structure of [HSi9]3− in the Solid State and Its Unexpected Highly Dynamic Behavior in Solution

We report on the first unambiguous detection of the elusive [HSi₉]^3? anion in solutions of liquid ammonia by various ²⁹Si and ¹H NMR experiments including chemical exchange saturation transfer (CEST). The characteristic multiplicity patterns of both the ²⁹Si and ¹H resonances together with CEST and a partially reduced ¹H,²⁹Si coupling constant indicate the presence of a highly dynamic Si₈ entity and a Si?H moiety with slow proton hopping. Theoretical calculations corroborate both reorganization of Si₈ on the picosecond timescale via low vibrational modes and proton hopping. In addition, in a single‐crystal X‐ray study of (K(DB[18]crown‐6))(K([2.2.2]crypt))₂[ HSi₉ ]?8.5 NH₃, the H atom was unequivocally localized at one vertex of the basal square of the monocapped square‐antiprismatic cluster. Thus experimental studies and theoretical considerations provide unprecedented insight into both the structure and the dynamic behavior of these cluster anions, which hitherto had been considered to be rigid.     

Unusual transformation of benzil monooxime coumarin ethers into carboxamides

Oxime ethers obtained from benzil monooxime and 4-bromomethy coumarins have undergone an unusual transformation into coumarin-4-carboxamides. Structures of the products have been supported by X-ray studies and robustness of the reaction has been investigated for a variety of substituent.     

MgSiO3 nanoparticle‐catalyzed 1,3‐dipolar cycloaddition reactions in the synthesis of novel spiroindane‐1,3‐diones derived from substituted chalcones

Employment of metal nanoparticles has been one of the most promising synthetic strategies for a number of chemical transformations. New spiroindane‐1,3‐diones were synthesized through [3 + 2] cycloaddition in moderate to high yields by a three‐component reaction of heterocyclic chalcone derivatives, ninhydrin, and sarcosine/L‐proline. The presence of heterogenous MgSiO₃ nanoparticles (NPs) under microwave irradiation showed a robust effect in improving the yield of the desired products. Furthermore, the catalyst may be recovered and reused without significant loss of activity.     

Self-assembled supramolecular array of polymeric phthalocyanine on gold for the determination of hydrogen peroxide

This Article describes for the first time the formation of a supramolecular self-assembled monolayer of polymeric phthalocyanine (poly(CuPc)) onto a gold substrate. The latter is established through the interaction of the cyano group, belonging to the poly(CuPc), with the metal substrate. The functionalized gold substrate was characterized using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and electrochemical methods. Results clearly demonstrated the interaction between gold and the nitrogen atom of cyano group and showed at the same time the formation of a completely covered polymeric monolayer on the gold surface. In addition, the modified gold surface seems to exhibit a reversible redox behavior and is found to act as an electronic conductor, which allows rapid electron transfer. Electrochemical impedance spectroscopy (EIS) analyses in the presence of [Fe(CN)(6)](3-/4-) as a redox couple revealed that the modified electrode showed a much lower electron transfer resistance compared with bare gold. In addition, the modified electrode is found to catalyze the H(2)O(2) reduction very effectively, showing a catalytic current that varies linearly with the peroxide concentration in the range of 0.35 to 70 μM with a detection limit of 0.25 μM.