NMR determination of the conformation of a trimethylene interstrand cross-link in an oligodeoxynucleotide duplex containing a 5'-d(GpC) motif

Malondialdehyde interstrand cross-links in DNA show strong preference for 5'-d(CpG) sequences. The cross-links are unstable and a trimethylene cross-link has been used as a surrogate for structural studies. A previous structural study of the 5'-d(CpG) cross-link in the sequence 5'-d(AGGCGCCT), where G is the modified nucleotide, by NMR spectroscopy and molecular dynamics using a simulated annealing protocol showed the guanine residues and the tether lay approximately in a plane such that the trimethylene tether and probably the malondialdehyde tether, as well, could be accommodated without major disruptions of duplex structure [Dooley et al. J. Am Chem. Soc. 2001, 123, 1730-1739]. The trimethylene cross-link has now been studied in a GpC motif using the reverse sequence. The structure lacks the planarity seen with the 5'-d(CpG) sequence and is skewed about the trimethylene cross-link. Melting studies indicate that the trimethylene cross-link is thermodynamically less stable in the GpC motif than in the 5-d(CpG). Furthermore, lack of planarity of the GpC cross-link precludes making an isosteric replacement of the trimethylene tether by malondialdehyde. A similar argument can be used to explain the 5'-d(CpG) preference for interchain cross-linking by acrolein.     

On the number of limit cycles which appear by perturbation of Hamiltonian two-saddle cycles of planar vector fields

We find an upper bound to the maximal number of limit cycles, which bifurcate from a hamiltonian two-saddle loop of an analytic vector field, under an analytic deformation.     

Polymer Carriers for Anticancer Drugs Targeted to EGF Receptor

A novel actively targeted polymer carrier for anticancer drugs based on an N‐(2‐hydroxypropyl)methacrylamide copolymer (PHPMA) is proposed. An oligopeptide sequence GE7, attached to the polymer, is a specific ligand for the EGF receptor overexpressed on most tumor cells. Co‐attachment of selected chemotherapeutics will therefore lead to formation of tumor‐specific polymer therapeutics, further enhanced by the EPR effect. FACS measurements prove elevated binding activity of the fluorescently labeled PHPMA/GE7 conjugate in EGFR‐rich cells (FaDu, MCF‐7), compared to conjugates of scrambled peptides. Cell lines with low EGFR level (SW620, B16F10) bind the GE7 conjugate significantly less.

     

Glass formation and confined melting in sol–gel derived nano-ZnO aggregates

Sol–gel processing of ZnO nanocolloids has been revisited to prepare various alkaline metal acetate (MAc: K, Na, Li-acetates) containing ZnO nanopowders. Using differential scanning calorimetry and X-ray diffraction investigations, several new relationships between the morphology and the thermodynamic behavior in the aforementioned particulate ZnO/MAc nanocomposites were noticed: (1) large MAc melting depression shifts ?ΔT_m ~ 80 °C due to salt confinement within porous ZnO aggregates, (2) corresponding MAc crystallization and re-crystallization temperature depression shifts, (3) presence of multimodal pore size distributions within nanoaggregates and (4) glass formation at temperatures T_g between ?40 and 130 °C. We also note that the T_g value drops with rising alkaline metal size, increasing water content and decreasing ZnO particle size. In contrast, T_g rises in the case of co-doped Fe–LiAc/ZnO compositions.     

PHAISTOS: A framework for Markov chain Monte Carlo simulation and inference of protein structure

We present a new software framework for Markov chain Monte Carlo sampling for simulation, prediction, and inference of protein structure. The software package contains implementations of recent advances in Monte Carlo methodology, such as efficient local updates and sampling from probabilistic models of local protein structure. These models form a probabilistic alternative to the widely used fragment and rotamer libraries. Combined with an easily extendible software architecture, this makes PHAISTOS well suited for Bayesian inference of protein structure from sequence and/or experimental data. Currently, two force‐fields are available within the framework: PROFASI and OPLS‐AA/L, the latter including the generalized Born surface area solvent model. A flexible command‐line and configuration‐file interface allows users quickly to set up simulations with the desired configuration. PHAISTOS is released under the GNU General Public License v3.0. Source code and documentation are freely available from http://phaistos.sourceforge.net . The software is implemented in C++ and has been tested on Linux and OSX platforms. © 2013 Wiley Periodicals, Inc.     

Anodic dissolution of iron microparticles in chloride-containing acetate buffer electrolytes studied by elimination voltammetry

Elimination voltammetry with linear scan (EVLS) was used for the study of the anodic dissolution process of iron microparticles immobilized on paraffin-impregnated graphite electrode. This process was investigated in acetate buffer solutions in the range of pH 4 to 6 and the effect of chloride ions was evaluated. It was found that the anodic dissolution process of iron powder proceeded in two peaks with different pH and KCl-dependent characterizations. Both the more negative process at about ?300 mV and the positive process at about 1,200 mV are influenced by chloride and hydroxyl ions. Chloride ions incorporate into the intermediate species and form more soluble species in the passivation layer, leading to its degradation. Detailed information about the processes was provided by the EVLS functions conserving diffusion current components. The mechanism of anodic dissolution of iron powder in acetate solutions representing passive ions and chloride ions appearing in the role of corrosion activators was discussed.     

Acetylcholinesterase and butyrylcholinesterase inhibitory compounds from Corydalis cava (Fumariaceae)

Tubers of Corydalis cava were extracted with ethanol and fractionated using n-hexane, chloroform and ethanol. Repeated column chromatography, preparative TLC and crystallization led to the isolation of fifteen isoquinoline alkaloids. The chemical structures of the isolated compounds were determined on the basis of spectroscopic techniques and by comparison with literature data. All isolated compounds were tested for human blood acetylcholinesterase (HuAChE) and human plasma butyrylcholinesterase (HuBuChE) inhibitory activity. (+)-Canadaline inhibited acetylcholinesterase as well as butyrylcholinesterase in a dose-dependent manner with IC50 values of 20.1 +/- 1.1 microM and 85.2 +/- 3.2 microM, respectively. (+)-Canadine, with an IC50 value of 12.4 +/- 0.9 microM, was the most potent inhibitor of acetylcholinesterase, whilst (+/-)-corycavidine and (+)-bulbocapnine were effective inhibitors of butyrylcholinesterase with IC50 values of 46.2 +/- 2.4 microM and 67.0 +/- 2.1 microM, respectively. The other isolated alkaloids were considered inactive (IC50 > 100 microM).     

Posicast control of a class of fractional-order processes

The number of studies on the control of fractional-order processes—processes having dynamics described by differential equations of arbitrary order—has been increasing in the past two decades and it is now ubiquitous. Various methods have emerged and have been proven to effectively control such processes—usually resulting in fractional-order controllers similar to their conventional integer-order counterparts, which include, but are not limited to fractional PID and fractional lead-lag controllers. However, such methods require a lot of computational effort and fractional-order controllers could be challenging when it comes to their synthesis and implementation. In this paper, we propose a simple yet effective delay-based controller with the use of the Posicast control methodology in controlling the overshoot of a fractional-order process of the class $\mathcal{P}:\left\{ {P\left( s \right) = {1 \mathord{\left/ {\vphantom {1 {\left( {as^\alpha + b} \right)}}} \right. \kern-0em} {\left( {as^\alpha + b} \right)}}} \right\}$ having orders 1 < α < 2. Such controllers have proven to be easy to implement because they only require delays and summers. In this paper, the Posicast control methodology introduced in the past few years is modified to minimize the overshoot of the processes step response to a level that is acceptable in control engineering and automation practices. Furthermore, proof of the existence of overshoot for such class of processes, as well as the determination of the peak-time of the open-loop response of a fractional-order process of the class P is presented. Validation through numerical simulations for a class of fractional-order processes are presented in this paper.     

Polyhydroxybutyrate/Chitosan 3D Scaffolds Promote In Vitro and In Vivo Chondrogenesis

Applied Biochemistry and Biotechnology - The articular cartilage is an avascular and aneural tissue and its injuries result mostly in osteoarthritic changes and formation of fibrous tissue. Efforts...     

On the cyclicity of weight-homogeneous centers

Let W be a weight-homogeneous planar polynomial differential system with a center. We find an upper bound of the number of limit cycles which bifurcate from the period annulus of W under a generic polynomial perturbation. We apply this result to a particular family of planar polynomial systems having a nilpotent center without meromorphic first integral.