Surface-induced unfolding of human lactoferrin

We have determined the structural conformations of human lactoferrin adsorbed at the air/water interface by neutron reflectivity (NR) and its solution structure by small angle neutron scattering (SANS). The neutron reflectivity measurements revealed a strong structural unfolding of the molecule when adsorbed at the interface from a pH 7 phosphate buffer solution (PBS with a total ionic strength at 4.5 mM) over a wide concentration range. Two distinct regions, a top dense layer of 15-20 angstroms on the air side and a bottom diffuse layer of some 50 angstroms into the aqueous subphase, characterized the unfolded interfacial layer. At a concentration around 1 g dm(-3), close to the physiological concentration of lactoferrin in biological fluids, the adsorbed amount was 5.5 x 10(-8) mol m(-2) in the absence of NaCl, but the addition of 0.3 M NaCl reduced protein adsorption to 3.5 x 10(-8) mol m(-2). Although the polypeptide distributions at the interface remained similar, quantitative analysis showed that the addition of NaCl reduced the layer thickness. Parallel measurements of lactoferrin adsorption in D2O instead of null reflecting water confirmed the unfolded structure at the interface. Furthermore, the D2O data indicated that the polypeptide in the top layer was predominantly protruded out of water, consistent with it being hydrophobic. In contrast, the scattering intensity profiles from SANS were well described by a cylindrical model with a diameter of 47 angstroms and a length of 105 angstroms in the presence of 0.3 M NaCl, indicating a retention of the globular framework in the bulk solution. In the absence of NaCl but with the same amount of phosphate buffer, the length of the cylinder increased to some 190 angstroms and the diameter remained constant. The length increase is indicative of changes in distance and orientation between the bilobal monomers due to the change in charge interactions. The results thus demonstrate that the surface structural unfolding was caused by the exposure of the protein molecule to the unsymmetrical energetic balance following surface adsorption.     

Isolation,structural elucidation and antiplasmodial activity of fucosterol compound from brown seaweed,Sargassum linearifolium against malarial parasite Plasmodium falciparum

The brown seaweed, Sargassum linearifolium (Turner) C. Agardh, 1820 is commonly available along the south-east coast of India. Its compound fucosterol was isolated and confirmed through spectral characterisation and chemical transformation methods. The antiplasmodial effect of the isolated fucosterol was investigated against the 3D7 chloroquine sensitive Plasmodium falciparum strain, parasitaemia percentage was determined at 48 h and morphological change was studied through microscopic examination after Giemsa staining. A perceptible antiplasmodial effect was produced by fucosterol compound against the P. falciparum and positive control, chloroquine with the IC₅₀ values (μg/mL) of 7.48 and 12.81, respectively. Fucosterol showed higher antiplasmodial activity as compared to chloroquine. It is inferred that both the fucosterol and chloroquine could have inhibited the schizont stage of the parasite during the intra-erythrocyte asexual development. The findings underline the usefulness of the seaweed-based fucosterol and further studies are warranted.     

Functionalized zinc(II) dithiocarbamate complexes: Synthesis,spectral and molecular structures of bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) and (2,2′-bipyridine)bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II)

Two new zinc and dithiocarbamate integrated metal complexes such as bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) (1) and (2,2′-bipyridine)bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) (2) have been synthesized and their spectral investigations viz., FT-IR, ¹H and ¹³C NMR as well as single crystal X-ray diffraction studies have been accomplished. Single crystal X-ray analysis of the complex 1 reveals the presence of distorted trigonal bipyramidal and tetrahedral coordination geometry around the zinc. The dithiocarbamate motif acts as bidentate chelating and bidentate bridging ligands between the zinc ions furnishing centrosymmetric dimeric molecules. In the complex 2, the zinc is in a distorted octahedral environment with a ZnS₄N₂ chromophore. The supramolecular frameworks in the complexes 1 and 2 have been sustained by CH?S, CH?O and CH?π (ZnCS₂, and chelate) interactions. Computational studies on complexes 1 and 2 have been executed utilizing DFT-B3LYP/ LANL2DZ method. In both the cases, the HOMO-LUMO calculations imply the occurrence of effective charge transfer within the molecule. Further, the MEP analysis of 1 and 2 implies the negative potential sites are sulfur of NCS₂ and oxygen of OCH₃ and the positive potential sites are nitrogen of NCS₂ in both the complexes along with 2,2′-bipyridine for complex 2. The former sites are susceptible for electrophilic reactions while the latter for nucleophilic reactions.     

Synthesis and structural study of thiacyclophanes utilizing dibromides and methane dithiolate

The synthesis of a series of thiacyclophanes and optically active binaphthol-based chiral thiacyclophanes is reported with XRD structure. Two diastereomeric tetrathiacyclophanes are designed and synthesized. The two diastereomers are evidenced by crystal structure; the single-crystal X-ray studies reveal that one of the isomers possesses an inherent property of self-assembling into a vertical stack of tunnel-like structures.     

Amperometric detection of nitric oxide using a glassy carbon electrode modified with gold nanoparticles incorporated into a nanohybrid composed of reduced graphene oxide and Nafion

Microchimica Acta - The authors show that the electrocatalytic performance toward the detection of nitric oxide (NO) can be enhanced by making use of gold nanoparticles (AuNP) in a matrix...     

Hydrogen bonding due to regioisomerism and its effect on the supramolecular architecture of diethyl 2‐[(2/4‐hydroxyanilino)methylidene]malonates

Diethyl 2‐[(2‐hydroxyanilino)methylidene]malonate, (I), and diethyl 2‐[(4‐hydroxyanilino)methylidene]malonate, (II), both C₁₄H₁₇NO₅, crystallize in centrosymmetric orthorhombic and monoclinic crystal systems, respectively. Compound (I) resides on a crystallographic mirror plane and displays bifurcated intramolecular hydrogen bonding, as well as intermolecular hydrogen bonding due to the position of the hydroxy group. Compound (II) has a single intramolecular N—H...O hydrogen bond. Infinite one‐dimensional head‐to‐tail chains formed by O—H...O hydrogen bonding are present in both structures. The molecular packing is mainly influenced by the intermolecular O—H...O interactions. Additionally, C—H...O interactions crosslinking the chains are found in (II).     

CONDENSATION OF SOME AROMATIC ALDEHYDES WITH DIMETHYL SULFONE

Abstract

Condensation of some aromatic aldehydes with dimethyl sulfone using sodium amide has been studied. Majority of the aldehydes afforded cis-2,6-diaryl-1,4-oxathian-4,4-dioxides as the exclusive product. 4-Methoxybenzaldehyde, in addition, provided the bis α,β-unsaturated sulfone as the major product while 4-nitrobenzaldehyde yielded only the Tischenko product by self-condensation. The products have been characterised by elemental analysis and spectral data.     

Stannous chloride mediated one pot synthesis of functionalized indole-3-yl pyridines using 3-cyanoacetylindoles and 3-formylchromones

An efficient one-pot synthesis of functionalized indole-3-yl pyridines by condensation of 3-formylchromones, cyanoacetylindoles and ammonium acetate has been achieved. A series of 17 new compounds were synthesized and all of them were characterized by FT-IR and NMR. The crystal structure of a typical compound was determined by X-ray diffraction. A variety of substrates can participate in the process resulting in high purity and good yields, making this methodology suitable for library synthesis in drug discovery.     

The Locally Conservative Galerkin (LCG) Method — a Discontinuous Methodology Applied to a Continuous Framework

This paper presents a comprehensive overview of the element-wise locally conservative Galerkin (LCG) method. The LCG method was developed to find a method that had the advantages of the discontinuous Galerkin methods, without the large computational and memory requirements. The initial application of the method is discussed, to the simple scalar transient convection-diffusion equation, along with its extension to the Navier-Stokes equations utilising the Characteristic Based Split (CBS) scheme. The element-by-element solution approach removes the standard finite element assembly necessity, with an face flux providing continuity between these elemental subdomains. This face flux provides explicit local conservation and can be determined via a simple small post-processing calculation. The LCG method obtains a unique solution from the elemental contributions through the use of simple averaging. It is shown within this paper that the LCG method provides equivalent solutions to the continuous (global) Galerkin method for both steady state and transient solutions. Several numerical examples are provided to demonstrate the abilities of the LCG method.