Adsorption behavior of linear and cyclic genetically engineered platinum binding peptides

Recently, phage and cell-surface display libraries have been adapted for genetically selecting short peptides for a variety of inorganic materials. Despite the enormous number of inorganic-binding peptides reported and their bionanotechnological utility as synthesizers and molecular linkers, there is still a limited understanding of molecular mechanisms of peptide recognition of and binding to solid materials. As part of our goal of genetically designing these peptides, understanding the binding kinetics and thermodynamics, and using the peptides as molecular erectors, in this report we discuss molecular structural constraints imposed upon the quantitative binding characteristics of peptides with an affinity for inorganics. Specifically, we use a high-affinity seven amino acid Pt-binding sequence, PTSTGQA, as we reported in earlier studies and build two constructs: one is a Cys-Cys constrained "loop" sequence (CPTSTGQAC) that mimics the domain used in the pIII tail sequence of the phage library construction, and the second is the linear form, a septapeptide, without the loop. Both sequences were analyzed for their adsorption behavior on Pt thin films by surface plasmon resonance (SPR) spectroscopy and for their conformational properties by circular dichroism (CD). We find that the cyclic peptide of the integral Pt-binding sequence possesses single or 1:1 Langmuir adsorption behavior and displays equilibrium and adsorption rate constants that are significantly larger than those obtained for the linear form. Conversely, the linear form exhibits biexponential Langmuir isotherm behavior with slower and weaker binding. Furthermore, the structure of the cyclic version was found to adopt a random coil molecular conformation, whereas the linear version adopts a polyproline type II conformation in equilibrium with the random coil. The 2,2,2-trifluoroethanol titration experiments indicate that TFE has a different effect on the secondary structures of the linear and cyclic versions of the Pt binding sequence. We conclude that the presence of the Cys-Cys restraint affects both the conformation and binding behavior of the integral Pt-binding septapeptide sequence and that the presence or absence of constraints could be used to tune the adsorption and structural features of inorganic binding peptide sequences.     

Energetics and Structures of Charged Helium Clusters: Comparing Stabilities of Dimer and Trimer Cationic Cores

We present accurate ab initio calculations of the most stable structures of He_n⁺ clusters in order to determine the more likely ionic core arrangements existing after reaching structural equilibrium of the clusters. Two potential energy surfaces are presented: one for the He₂⁺ and the other with the He₃⁺ linear ion, both interacting with one He atom. The two computed potentials are in turn employed within a classical structure optimization where the overall interaction forces are obtained within the sum‐of‐ potentials approximation described in the main text. Because of the presence of many‐body effects within the ionic core, we find that the arrangements with He₃⁺ as a core turn out to be energetically preferred, leading to the formation of He₃⁺(He)_n?3 stable aggregates. Nanoscopic considerations about the relative stability of clusters with the two different cores are shown to give us new information on the dynamical processes observed in the impact ionization experiments of pure helium clusters and the importance of pre‐equilibrium evaporation of the ionic dimers in the ionized clusters.     

Bacillus sp. immobilized on Amberlite XAD-4 resin as a biosorbent for solid phase extraction of thorium prior to UV-vis spectrometry determination

A DNA biosensor is presented that is based on gold interdigitated nanoelectrodes of 100 nm width and 250 nm pitch. A single-strand oligonucleotide acts as the capture probe. Because of its nanometer dimensions, the device shows improved sensitivity when compared to similar systems. This encouraged us to perform a direct and unlabelled detection. After incubation with the DNA target, the impedance spectrum was recorded between 1 kHz and 10 MHz to obtain the net capacitance change. The use of a biotinylated DNA signalling probe permitted the integration of an amplification stage in a sandwich format that employs streptavidin-modified gold nanoparticles. The strategy was preliminarily tested by detecting the breast cancer related BRCA1 gene, where the noncomplementary, wild and mutated forms were easily differentiated at a concentration level of 3 μM (corresponding to a 30 pmol quantity).     

Stability-Indicating HPTLC Analysis of Flurbiprofen in Pharmaceutical Dosage Forms

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive, selective, precise, and stability-indicating high-performance thin-layer chromatographic (HPTLC) method has been...     

Characterization of atomic layer deposition coated cutting tools by X-ray photoelectron spectroscopy and examination of cutting performance

Abstract

The performance of cutting tools was examined, involving synthesis of a 10?nm thin film of Aluminum oxide using atomic layer deposition. Characterization of coated and uncoated cutting tools was done by several methods. scanning electron microscopy was used and the images were compared with each other. Chemical characterization was performed by X-ray diffraction and X-ray photoelectron spectroscopy. Coated and uncoated cutting tools were tested with steel material in turning tests. After turning, it was observed that the adhesion effect was reduced to a large extent in turning with coated tool. It was observed that the coating showed stability at high temperatures during cutting and the cutting performance was increased. The main advantage of the coating was that the tools produced were more environmentally friendly, with a longer useful life and they were easier to recycle.     

Weighted Harmonic Bloch Spaces on the Ball

We study the family of weighted harmonic Bloch spaces \(b_\alpha , \alpha \in {\mathbb {R}}\), on the unit ball of \({\mathbb {R}}^n\). We provide characterizations in terms of partial and radial derivatives and certain radial differential operators that are more compatible with reproducing kernels of harmonic Bergman–Besov spaces. We consider a class of integral operators related to harmonic Bergman projection and determine precisely when they are bounded on \(L^\infty _\alpha \). We define projections from \(L^\infty _\alpha \) to \(b_\alpha \) and as a consequence obtain integral representations. We solve the Gleason problem and provide atomic decomposition for all \(b_\alpha , \alpha \in {\mathbb {R}}\). Finally we give an oscillatory characterization of \(b_\alpha \) when \(\alpha >-1\).     

Synthesis and optimization of permselective polymer (polyindoline) film

A polyindoline permselective polymer film was readily synthesized by an electrochemical polymerization of indoline in an aqueous solution of KCl at a potential of 0.4 V vs Ag/AgCl. The amperometric responses of the polyindoline film-coated platinum electrodes to electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) substances were measured at a potential of 0.7 V. Effects of various variables such as film thickness, concentrations of monomer and electrolyte, and pH on the permselective behavior of the polymeric membrane were systematically investigated and the optimal values were determined. It was found that permselective polyindoline-coated electrodes prepared in this one-step procedure permitted hydrogen peroxide oxidation while it prevented interference due to oxidizable species such as ascorbic acid and oxalic acid. As a result, it is believed that this polymeric membrane, owing to its permselective character, can be used as the protective material in the construction of hydrogen peroxide-based biosensors. Received: 10 November 1997 / Accepted: 27 January 1998     

Phytochemical compounds and antiradical,antimicrobial, and cytotoxic activities of the extracts from Hypericum scabrum L. Flowers

Abstract

Hypericum scabrum L. has been widely used in traditional medicine for the treatment of many diseases just as the other Hypericum species. In the present study, the antiradical, antimicrobial and cytotoxic activities of water and ethanol extracts of H. scabrum flowers were investigated. Their phytochemical contents and composition were also determined. The water and ethanol extracts are better scavenged ABTS (97.89 and 98.99%) and OH radicals (96.36 and 97.33%); the water extract is better scavenged DPPH radicals (91.66%) than the standard antioxidant BHA (94.33, 85.19, 90.16%, respectively). Flowers of H. scabrum contain flavonoids, phenolic acids, vitamins and phytosterols, dominated by catechin, vanillic acid, vitamin K and ergosterol. The extracts exhibit a strong cytotoxic activity against MCF-7, HCT-116, and LNCaP cancer cell lines. It is found that their antimicrobial activities are higher than the standard antibiotics. These results indicate that H. scabrum flowers have potent antiradical, antimicrobial and cytotoxic activities.     

Synthesis of block copolymers by the transformation of cationic polymerization into reversible atom transfer radical polymerization

Azo-containing polytetrahydrofuran (PTHF) obtained by cationic polymerization was used as a macroinitiator in the reverse atom transfer radical polymerization (RATRP) of styrene and methyl acrylate in conjunction with CuCl₂/2,2′-bipyridine as a catalyst. Diblock PTHF–polystyrene and PTHF–poly(methyl acrylate) were obtained after a two-step process. In the first step of the reaction, stable chlorine-end-capped PTHF was formed with the thermolysis of azo-linked PTHF at 65–70 °C in the presence of the catalyst. Heating the system at temperatures of 100–110 °C started the polymerization of the second monomer, which resulted in the formation of block copolymers. The decomposition behavior of the azo-linked PTHF and the structure of the block copolymers were determined by ¹H NMR and gel permeation chromatography (GPC). Kinetic studies and GPC analyses further confirmed the controlled/living nature of the RATRP initiated by the polymeric radicals. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2199–2208, 2002