Using alpha-helical coiled-coils to design nanostructured metalloporphyrin arrays

We have developed a computational design strategy based on the alpha-helical coiled-coil to generate modular peptide motifs capable of assembling into metalloporphyrin arrays of varying lengths. The current study highlights the extension of a two-metalloporphyrin array to a four-metalloporphyrin array through the incorporation of a coiled-coil repeat unit. Molecular dynamics simulations demonstrate that the initial design evolves rapidly to a stable structure with a small rmsd compared to the original model. Biophysical characterization reveals elongated proteins of the desired length, correct cofactor stoichiometry, and cofactor specificity. The successful extension of the two-porphyrin array demonstrates how this methodology serves as a foundation to create linear assemblies of organized electrically and optically responsive cofactors.     

Variability of volatile constituents in Artemisia maritima in western Himalaya

Chemical composition of the essential oil of Artemisia maritima, collected from three different high altitude locations in western Himalaya was studied by gas-chromatography mass spectrometry. Twenty-five constituents were identified in the oil distilled from the sample from Pooh, of which 1,8-cineole (23.8%) and chrysanthenone (17.54%) were the major constituents. Twenty volatile constituents were identified from the sample collected from Rhongtong pass, of which chrysanthenone (38.1%) and 1,8-cineole (37.3%) were the major constituents. In the oil distilled from the sample collected from Lahaul-Spiti 28 constituents were identified, of which 1,8-cineole (44.22%), camphor (9.16%) and borneol (10.94%) were the major constituents. In this sample chrysanthenone was present in very low percentage.     

Synthesis,characterization, and applications with the manifestation of antifungal activity and seed germination properties of nickel doped zinc oxide nano platform by biochemical contrivance

In the recent era, nanotechnology, a rapidly emerging field, has been explored as the most studied field worldwide. The goal of this study is to use neem leaves extract as an effective ‘reducing agent’ and ‘stabilizing agent’ in the green synthesis of bio-medically important Zn_1-XNi_XO (X = 0.00, 0.04, 0.08, 0.12) nanoparticles. The molar concentrations of nickel nitrate and zinc nitrate are varied to produce nickel-doped ZnO nanoparticles. Color change is the first indicator of nanoparticle formation during this biosynthesis. The hexagonal wurtzite structure with good crystallinity is confirmed by X-ray diffraction. FTIR analysis reveals the fact that the Zn–O stretching vibration shifts with the introduction of impurities into the ZnO matrix. UV–Vis spectra show the typical surface plasma resonance around 370 nm and the hydrodynamic diameter is larger than the size calculated from the XRD value, according to DLS. The main finding of this study is that Ni_0.12Zn_0.88O has a strong antifungal activity against and a significant growth rate after treating wheat seeds with biologically synthesized Ni_0.12Zn_0.88O nanoparticles.     

PE-CPE blends and their graphene oxide nanocomposites with reduced low temperature brittleness

The low-temperature flexibility of polyethylene (PE)–chlorinated polyethylene (CPE) blends and their composites with a small amount of graphene oxide filler was studied. Quantitative height variation in the AFM images, rheological as well as fracture analyses were employed to gain insights into the generation of flexibility in the matrix phase. The semi-crystalline CPE (CPE25) polymer did not induce viscoelastic behavior at temperatures lower than the glass transition temperature of PE, whereas the amorphous CPE (CPE35) had completely different behavior. The samples with CPE35 could not be sufficiently hardened even at ?180 °C and remained too soft for cryosectioning. Therefore, compression, which results in a 30–60 % reduction in length along the cutting direction with no change in the dimension perpendicular to it, was very prominent for both thin section and block face of the sample. The composites had even higher degree of compression due to additional effect of weak filler matrix interactions and as a consequence, the topographical variations led to filler pull out during sectioning. It was also confirmed using the rheological analysis that composites (and blends with 10 % CPE35 content) had phase immiscibility as CPE phase was suspected to concentrate near the graphene oxide phase leading to generation of chlorine-rich phases. The addition of graphene oxide did not lead to reduced flexibility and the composites also retained the modulus similar to pure polymer. The mechanical fracture of the samples also confirmed the flexibility of the CPE containing blends and composites as these samples were still flexible at ?195 °C.     

Compact fibre-based coherent anti-Stokes Raman scattering spectroscopy and interferometric coherent anti-Stokes Raman scattering from a single femtosecond fibre-laser oscillator

We demonstrate a new approach to CARS spectroscopy by efficiently synthesizing synchronized narrow-bandwidth (less than 10 cm⁻¹) pump and Stokes pulses (frequency difference continuously tunable upto ≈3000 cm⁻¹) based on spectral compression together with second harmonic generation (in periodically-poled nonlinear crystals) of femtosecond pulses emitted by a single compact Er-fibre oscillator. For a far better signal to non-resonant background contrast, interferometric CARS (I-CARS) is demonstrated and CARS signal enhancement upto three orders of magnitude is achieved by constructive interference with an auxiliary local oscillator at anti-Stokes field, also synthesized by spectral compression of pulses emitted from the same fibre oscillator.     

Rapid and Sensitive LC–MS–MS Method for the Simultaneous Estimation of Alfuzosin and Dutasteride in Human Plasma

A simple, rapid, specific and sensitive liquid chromatography–tandem mass spectrometric method has been developed and validated for the simultaneous estimation of alfuzosin and dutasteride in human plasma. Both alfuzosin and dutasteride were extracted from human plasma by solid-phase extraction using terazosin and finasteride as the internal standards for alfuzosin and dutasteride, respectively. Chromatographic separation of analytes and their respective internal standards was carried out using a Hypurity C18 (50 × 4.6 mm i.d., 5 μm particle size) column followed by detection using an applied biosystems API 5000 mass spectrometer with a UPLC as the front end. The method involves a rapid solid phase extraction from plasma, simple isocratic chromatographic conditions and mass spectrometric detection in the positive ionization mode using multiple reactions monitoring that enables detection down to low nanogram levels with a total run time of 2.5 min only. The method was validated over a range of 0.25–20.0 ng mL^?1 for alfuzosin and 0.1–10.0 ng mL^?1 for dutasteride. The absolute recoveries for alfuzosin (65.57%), dutasteride (103.82%), terazosin (69.38%) and finasteride (102.25%) achieved from spiked plasma samples were consistent and reproducible. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. Due to the short run time of 2.5 min it was possible to analyze a throughput of more than 180 human plasma samples per day. The validated method can be successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailabilty or bioequivalence studies. As an example the application of this validated method to a bioequivalence study is also illustrated.     

Pd/C-Cu in coupling-cyclization process: a general synthesis of 2-substituted 6-oxopyrrolo[3,2,1-ij]quinoline derivatives

A general and practical synthesis of 2-substituted 6-oxopyrrolo[3,2,1-ij]quinolines has been achieved following a single-step Pd/C-mediated coupling-cyclization strategy. The methodology involves the reaction of 8-iodo-4-oxo-1,4-dihydro quinoline-3-carboxylic acid ethyl ester with a variety of terminal alkynes in the presence of 10% Pd/C-PPh₃-CuI as a catalyst system in EtOH. The reaction mechanism and utility of the methodology have been discussed.     

Computational design of a collagen A:B:C-type heterotrimer

We have successfully designed an A:B:C collagen peptide heterotrimer using an automated computational approach. The algorithm maximizes the energy gap between the target and competing misfolded states while enforcing a minimum target stability. Circular dichroism (CD) measurements confirm that all three peptides are required to form a stable, structured triple helix. This study highlights the power of automated computational design, providing model systems to probe the biophysics of collagen assembly and developing general methods for the design of fibrous proteins.     

Correcting for a density distribution: particle size analysis of core-shell nanocomposite particles using disk centrifuge photosedimentometry

Many types of colloidal particles possess a core-shell morphology. In this Article, we show that, if the core and shell densities differ, this morphology leads to an inherent density distribution for particles of finite polydispersity. If the shell is denser than the core, this density distribution implies an artificial narrowing of the particle size distribution as determined by disk centrifuge photosedimentometry (DCP). In the specific case of polystyrene/silica nanocomposite particles, which consist of a polystyrene core coated with a monolayer shell of silica nanoparticles, we demonstrate that the particle density distribution can be determined by analytical ultracentrifugation and introduce a mathematical method to account for this density distribution by reanalyzing the raw DCP data. Using the mean silica packing density calculated from small-angle X-ray scattering, the real particle density can be calculated for each data point. The corrected DCP particle size distribution is both broader and more consistent with particle size distributions reported for the same polystyrene/silica nanocomposite sample using other sizing techniques, such as electron microscopy, laser light diffraction, and dynamic light scattering. Artifactual narrowing of the size distribution is also likely to occur for many other polymer/inorganic nanocomposite particles comprising a low-density core of variable dimensions coated with a high-density shell of constant thickness, or for core-shell latexes where the shell is continuous rather than particulate in nature.