Aggregation of a peptide antibiotic alamethicin at the air-water interface and its influence on the viscoelasticity of phospholipid monolayers

The aggregation properties of an antibiotic membrane-active peptide alamethicin at the air-water interface have been studied using interfacial rheology and fluorescence microscopy techniques. Fluorescence microscopy of alamethicin monolayers revealed a coexistence of liquid expanded (LE) and solid phases at the surface concentrations studied. Interfacial oscillatory shear measurements on alamethicin monolayers indicate that its viscoelastic properties are determined by the area fraction of the solid domains. The role of zwitterionic phospholipids dioleoylphosphatidyl choline (DOPC) and dioleoylphosphatidyl ethanolamine (DOPE) on the peptide aggregation behavior was also investigated. Fluorescence microscopy of alamethicin/phospholipid monolayers revealed an intermediate phase (I) in addition to the solid and LE phase. In mixed monolayers of phospholipid (L)/alamethicin (P), with increase in L/P, the monolayer transforms from a viscoelastic to a viscous fluid with the increase in area fraction of the intermediate phase. Further, a homogeneous mixing of alamethicin/lipid molecules is observed at L/P > 4. Our studies also confirm that the viscoelasticity of alamethicin/phospholipid monolayers is closely related to the alamethicin/phospholipid interactions at the air-water interface.     

A Review of Recent Progress in Solid State Fabrication of Composites and Functionally Graded Systems Via Friction Stir Processing

Friction stir processing (FSP) is a rapidly emerging newer solid-state technique for composite fabrication. It involves surface modification which in turn enables successful adaptation of surface properties through plastic deformations in solid state. During initial years of FSP inception, it was primarily employed in development of metal matrix composites of light metal alloys like aluminum. However, recently, it has gained an alluring role in fabrication of composites of various nonferrous and ferrous metal alloys as well as of polymers. In addition to composite fabrication, FSP has evolved as a revolutionary technique in developing functionally graded systems/surfaces (FGS) of metal matrix. This article covers all aspects of FSP in which reinforcement particles are embedded in the base matrix to develop composites and FGS. It presents a critical review on domains of recent developments, effects of different types of reinforcement particles and properties enhancement of composites, and FGS fabrication. In addition to this, various issues, challenges, and future work that demand attention are systematically addressed.     

Iridoid glycosides-Kutkin,Picroside I,and Kutkoside from Picrorrhiza kurroa Benth inhibits the invasion and migration of MCF-7 breast cancer cells through the down regulation of matrix metalloproteinases: 1st Cancer Update

Ethnopharmacological relevanceIridoid glycosides have been associated with decreased risks of cancer, such as hepatocarcinoma. Although Picrorrhiza kurroa has shown activity against hepatocarcinogenesis, its mechanism of action is poorly understood, further the anticancer activity of iridoid glycosides present in this plant has not been tested so far.Aim of the studyHere, MCF-7 cell lines (Human breast cancer) were used to test whether P. kurroa extract (PE) and its isolated iridoid glycosides Picroside I (PS), Kutkoside (KS), and Kutkin (KT) exerts the anti-invasion activity via down-regulation of the expression of matrix metalloproteinases (MMPs). MMPs play an important role in solid tumor invasion and migration.Materials and methodsThe activity and expression of gelatinases (MMP-2 and MMP-9) and collagenases (MMP-1 and MMP-13), protein, and mRNA were detected by gelatin zymography, and RT-PCR. The migratory and invasive capacities of MCF-7 cell lines were measured by the wound scratch migration assay. The preliminary cytotoxicity testing was done by MTT assay and propidium iodide staining. Further the inhibition of inflammatory mediators was also done by quantification of nitrite inflammatory mediators.ResultsThe study showed that PE and its isolated iridoids glycosides PS, KS, and KT exhibited considerable cytotoxic potential in a dose-dependent manner. Further PE, PS, KS, and KT inhibited MCF-7 cell invasion and migration, and decreased MMP-2, 9 and MMP-1, 13 activities. Furthermore, PS, KS, and KT reduced MMPs expression at protein and mRNA levels, and suppression of the inflammatory mediators was also exhibited.ConclusionsOur results suggest that PS, KS, and KT may be the valuable anti-invasive drug candidates for cancer therapy by suppressing Collagenases and Gelatinases. PS, KS, and KT showed good results in comparison with PE. PS and KS exhibit almost comparable down regulation while KT exhibited maximum suppression of invasion, migration, and expression of MMPs.     

Remediation of environmentally hazardous organophosphates by artificial metalloenzymes

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Rotational spectra and structure of the Ar2-H2S complex: pulsed nozzle Fourier transform microwave spectroscopic and ab initio studies

This paper reports the rotational spectrum and structure of the Ar2-H2S complex and its HDS and D2S isotopomers. The ground state structure has heavy-atom C2v symmetry with the two Ar atoms indistinguishable and H2S freely rotating as evinced by the fact that asymmetric top energy levels with Kp=odd levels are missing. The rotational constants for the parent isotopomer are: A=1733.115(1) MHz, B=1617.6160(5) MHz and C=830.2951(2) MHz. Unlike the Ar-H2S complex, the Ar2-H2S does not show an anomalous isotopic shift in rotational constants on deuterium substitution. However, the intermolecular potential is still quite floppy, leading to very different centrifugal distortion constants for the three isotopomers. The Ar-Ar and Ar-c.m.(H2S) distances are determined to be 3.820 A and 4.105 A, respectively. The A rotational constants for Ar2-H2S/HDS/D2S isotopomers are very close to each other and to the B constant of free Ar2, indicating that H2S does not contribute to the moment of inertia about the a-axis. Ab initio calculations at MP2 level with aug-cc-pVQZ basis set lead to an equilibrium C2v minimum structure with the Ar-Ar line perpendicular to the H-H line and the S away from Ar2. The centrifugal distortion constants, calculated using the ab initio force field, are in reasonable agreement with the experimental values. However, they do not show the variation observed for different isotopmers. The binding energy of Ar2-H2S has been determined to be 507 cm-1(6.0 kJ mol-1) by CBS extrapolation after correcting for basis set superposition error. Potential energy scans point out that the barrier for internal rotation of H2S about its b axis is only 10 cm-1 and it is below the zero point energy (13.5 cm-1) in this torsional degree of freedom. Internal rotation of H2S about its a- and c-axes also have small barriers of about 50 cm-1 only, suggesting that H2S is extremely floppy within the complex.