Characterization and deposition of various light-harvesting antenna complexes by electrospray atomization

Photosynthetic organisms have light-harvesting complexes that absorb and transfer energy efficiently to reaction centers. Light-harvesting complexes (LHCs) have received increased attention in order to understand the natural photosynthetic process and also to utilize their unique properties in fabricating efficient artificial and bio-hybrid devices to capture solar energy. In this work, LHCs with different architectures, sizes, and absorption spectra, such as chlorosomes, Fenna–Matthews–Olson (FMO) protein, LH2 complex, and phycobilisome have been characterized by an electrospray-scanning mobility particle-sizer system (ES-SMPS). The size measured by ES-SMPS for FMO, chlorosomes, LH2, and phycobilisome were 6.4, 23.3, 9.5, and 33.4?nm, respectively. These size measurements were compared with values measured by dynamic light scattering and those reported in the literature. These complexes were deposited onto a transparent substrate by electrospray deposition. Absorption and fluorescence spectra of the deposited LHCs were measured. It was observed that the LHCs have light absorption and fluorescence spectra similar to that in solution, demonstrating the viability of the process.     

Molecular drug design, synthesis and structure elucidation of a new specific target peptide based metallo drug for cancer chemotherapy as topoisomerase I inhibitor

To evaluate the biological preference of metallopeptide drugs in cancer cells, a new dinuclear copper(II) complex [Cu(2)(glygly)(2)(ppz)(H(2)O)(4)]·2H(2)O (1) (glygly = glycyl glycine anion and ppz = piperazine), was designed and synthesized as topoisomerase I inhibitor. The structural elucidation of the complex was done by elemental analysis, spectroscopic methods and single crystal X-ray diffraction. The in vitro DNA binding studies of complex 1 with CT DNA were carried out by employing different optical methods viz. UV-vis, fluorescence and circular dichroism. The molecular docking technique was also utilized to ascertain the mechanism and mode of action towards the molecular target DNA and enzymes. Complex 1 cleaves pBR322 DNA via an oxidative mechanism and strongly binds to the DNA minor groove. Furthermore, complex 1 exhibits significant inhibitory effects on the catalytic activity of topoisomerase I at a very low concentration, ~12.5 μM, in addition to its excellent SOD mimics (IC(50)~0.086 μM).     

Quaternary ammonium bromide surfactant adsorption on low-index surfaces of gold. 1. Au(111)

The coadsorption of the anionic and cationic components of a model quaternary ammonium bromide surfactant on Au(111) has been measured using the thermodynamics of an ideally polarized electrode. The results indicate that both bromide and trimethyloctylammonium (OTA(+)) ions are coadsorbed over a broad range of the electrical state of the gold surface. At negative polarizations, the Gibbs surface excess of the cationic surfactant is largely unperturbed by the presence of bromide ions in solution. However, when the Au(111) surface is weakly charged the existence of a low-coverage, gaslike phase of adsorbed halide induces an appreciable (~25%) enhancement of the interfacial concentration of the cationic surfactant ion. At more positive polarizations, the coadsorbed OTA(+)/Br(-) layer undergoes at least one phase transition which appears to be concomitant with the lifting of the Au(111) reconstruction and the formation of a densely packed bromide adlayer. In the absence of coadsorbed halide, the OTA(+) ions are completely desorbed from the Au(111) surface at the most positive electrode polarizations studied. However, with NaBr present in the electrolyte, a high surface excess of bromide species leads to the stabilization of adsorbed OTA(+) at such positive potentials (or equivalent charge densities).     

In silico characterization of alkaline proteases from different species of Aspergillus

A total of 49 protein sequences of alkaline proteases retrieved from GenBank representing different species of Aspergillus have been characterized for various physiochemical properties, homology search, multiple sequence alignment, motif, and super family search and phylogenetic tree construction. The sequence level homology was obtained among different groups of alkaline protease enzymes, viz alkaline serine protease, oryzin, calpain-like protease, serine protease, subtilisin-like alkaline proteases. Multiple sequence alignment of alkaline protease protein sequence of different Aspergillus species revealed a stretch of conserved region for amino acid residues from 69 to 110 and 130–204. The phylogenetic tree constructed indicated several Aspergillus species-specific clusters for alkaline proteases namely Aspergillus fumigatus, Aspergillus niger, Aspergillus oryzae, Aspergillus clavatus. The distributions of ten commonly observed motifs were analyzed among these proteases. Motif 1 with a signature amino acid sequence of 50 amino acids, i.e., ASFSNYGKVVDIFAPGQDILSCWIGSTTATNTISGTSMATPHIVGLSCYL, was uniformly observed in proteases protein sequences indicating its involvement with the structure and enzymatic function. Motif analysis of acidic proteases of Aspergillus and bacterial alkaline proteases has revealed different signature amino acid sequences. The superfamily search for these proteases revealed the presence of subtilases, serine-carboxyl proteinase, calpain large subunit, and thermolysin-like superfamilies with 45 representing the subtilases superfamily.     

Effect of distortion on optical-fiber waveguides

We analyze the modes and coupling efficiency of asymmetric optical-fiber waveguides. We treated the step index-asymmetric optical-fiber waveguide as a boundary-value problem and obtain the expressions for the modes under logical assumptions. Using these expressions, we describe the propagation constants, mode delay, and power distribution of two asymmetric optical-fiber waveguides under consideration. Based on the perturbation theory, we also present the coupling coefficients of these asymmetric optical-fiber waveguides. We show that the waveguide parameters are considerably changed in the presence of distortion, and one can tune these parameters at the desired level by choosing suitable distortions.     

An organocatalytic direct Mannich-cyclization cascade as [3+2] annulation: asymmetric synthesis of 2,3-substituted pyrrolidines

A new method for asymmetric synthesis of 2,3-substituted pyrrolidines from N-PMP aldimines and succinaldehyde via formal [3+2] cycloaddition is reported. This reaction involves proline catalyzed direct Mannich reaction and acid catalyzed reductive cyclization with high yields (up to 78%) and excellent enantioselectivities (up to >99%).     

Triblock Copolymer Based on Poly(propylene oxide) and Poly(1‐[11‐acryloylundecyl]‐3‐methyl‐imidazolium bromide)

The controlled atom transfer radical polymerization of an ionic liquid, 1‐(11‐acryloylundecyl)‐3‐methyl imidazolium bromide (ILBr), from both ends of a telechelic poly(propylene oxide) (PPO) macroinitiator, end‐functionalized with bromoisobutyryloyl is reported. The resulting highly water‐soluble triblock, poly(ILBr‐b‐PO‐b‐ILBr) is multistimuli responsive. This new class of triblocks exhibits classical surface activity in lowering surface tension at the air–water interface and in modifying wetting in waterborne coatings. It also immunizes model colloids against coagulation induced by Debye–Hückel (indifferent electrolyte) electrostatic screening. Further, sol–gel thermoreversibility is unexpectedly found as an additional form of stimuli responsiveness.     

Can functionalized cucurbituril bind actinyl cations efficiently? A density functional theory based investigation

The feasibility of using cucurbituril host molecule as a probable actinyl cation binders candidate is investigated through density functional theory based calculations. Various possible binding sites of the cucurbit[5]uril host molecule to uranyl are analyzed and based on the binding energy evaluations, μ(5)-binding is predicted to be favored. For this coordination, the structure, vibrational spectra, and binding energies are evaluated for the binding of three actinyls in hexa-valent and penta-valent oxidation states with functionalized cucurbiturils. Functionalizing cucurbituril with methyl and cyclohexyl groups increases the binding affinities of actinyls, whereas fluorination decreases the binding affinities as compared to the native host molecule. Surprisingly hydroxylation of the host molecule does not distinguish the oxidation state of the three actinyls.     

Reconciliation of size–density bivariate distributions over a separating node

Data reconciliation considers the restoration of mass balance among the noise prone measured data by way of component adjustments for the various particle size or particle density classes or assays over the separating node. In this paper, the method of Lagrange multipliers has been extended to balance bivariate feed and product size-density distributions of coal particles split from a settling column. The settling suspension in the column was split into two product fractions at 40% height from the bottom after a minute settling of homogenized suspension at start. Reconciliation of data assists to estimate solid flow split of particles to the settled stream as well as helps to calculate the profiles of partition curves of the marginal particle size or particle density distributions. In general, Lagrange multiplier method with uniform weighting of its components may not guarantee a smooth partition surface and thus the reconciled data needs further refinement to establish the nature of the surface. In order to overcome this difficulty, a simple alternative method of reconciling bivariate size-density data using partition surface concept is explored in this paper.