Semisynthesis of a Homogeneous Glycoprotein Enzyme: Ribonuclease C: Part 2

Active RNase glycoprotein from three pieces : The glycoprotein enzyme ribonuclease C, which contains a complex saccharide N‐glycan, was synthesized by sequential native chemical ligation. An optimized ligation and isolation protocol allowed the efficient assembly and refolding of the 124 amino acid enzyme.

     

“Helter‐Skelter‐Like” Perylene Polyisocyanopeptides

Exciton migration! Spectroscopic analyses and extensive molecular dynamics studies revealed a well‐defined 4₁ helix in which the perylene molecules (see figure) form four “helter‐skelter‐like” overlapping pathways along which excitons and electrons can rapidly migrate.

     

Tuning intermolecular interactions in a rodlike polymer assembled at surfaces and in solution

The isolation of single polyelectrolyte chains of water-soluble poly(isocyanodipeptide)s (PICs) bearing carboxylic acid terminated side chains occurring both at surfaces and in solution was accomplished by reducing the intermolecular interactions through complexation with cations or positively charged surfactants.Scanning force microscopy and viscosity analyses revealed that this method allows to tune the conformation of the macromolecule, which is of importance for tailoring the physicochemical properties of the material.This is particularly significant for the use of these polymer chains as seed for biomineralization processes.     

Continuous monitoring of ascorbate transport through neuroblastoma cells with a ruthenium oxide hexacyanoferrate modified microelectrode

The uptake of ascorbate by neuroblastoma cells using a ruthenium oxide hexacyanoferrate (RuOHCF)-modified carbon fiber disc (CFD) microelectrode (r = 14.5 microm) was investigated. By use of the proposed electrochemical sensor the amperometric determination of ascorbate was performed at 0.0 V in minimum essential medium (MEM, pH = 7.2) with a limit of detection of 25 micromol L(-1). Under the optimum experimental conditions, no interference from MEM constituents and reduced glutathione (used to prevent the oxidation of ascorbate during the experiments) was noticed. The stability of the RuOHCF-modified electrode response was studied by measuring the sensitivity over an extended period of time (120 h), a decrease of around 10% being noticed at the end of the experiment. The rate of ascorbate uptake by control human neuroblastoma SH-SY5Y cells, and cells transfected with wild-type Cu,Zn-superoxide dismutase (SOD WT) or with a mutant typical of familial amyotrophic lateral sclerosis (SOD G93A), was in agreement with the level of oxidative stress in these cells. The usefulness of the RuOHCF-modified microelectrode for in vivo monitoring of ascorbate inside neuroblastoma cells was also demonstrated.     

Functional polymers: scanning force microscopy insights

Scanning force microscopy (SFM) and related techniques make it possible to visualize polymer systems with a molecular resolution. Beyond imaging, they also enable the unveiling of a variety of (dynamic) physico-chemical properties of both isolated polymer chains and their supramolecular architectures, including structural, mechanical and electronic properties. This article reviews recent progress in the use of SFM on polymers, with a particular emphasis on the mechanical properties of copolymers and single polymer chains, as well as on the bottom-up fabrication of supramolecular polymeric (helical) nanostructures in particular based upon pi-conjugated macromolecules as building blocks for nanoelectronics. Through a detailed understanding of the polymer behavior, we propose solutions for the generation of organic functional (nano)systems.     

Reversible interconversion between a supramolecular polymer and a discrete octameric species from a guanosine derivative by dynamic cation binding and release

[reaction: see text] The tunable interconversion between two highly ordered supramolecular motifs (G-quartet K(+)-templated column and G-ribbon) of a lipophilic guanosine derivative fueled by cation complexation and release in a cryptand [2.2.2] containing guanosine solution is reported. The process is controlled by the sequential addition of acid and base.     

A general model for non-autocatalytic zymogen activation in the presence of two different and mutually exclusive inhibitors. I. Kinetic analysis

The kinetic study carried out in paper I of this series (preceding article) on enzyme systems involving zymogen activation and the simultaneous action of two different, mutually exclusive inhibitors (Scheme 1) allows, new dimensionless kinetic parameters to be suggested. These parameters furnish quantitative information about the relative weight of the activation and inhibition routes, i.e. the conditions under which the activation prevails over the inhibition and vice versa, as well as the absolute and relative contributions to overall inhibition of each of the inhibition routes and their synergistic effect. These results can be easily and directly applied to any of the thousands of particular cases of the model. Examples are given for different particular cases.     

DNA codes for nanoscience

The nanometer scale is a special place where all sciences meet and develop a particularly strong interdisciplinarity. While biology is a source of inspiration for nanoscientists, chemistry has a central role in turning inspirations and methods from biological systems to nanotechnological use. DNA is the biological molecule by which nanoscience and nanotechnology is mostly fascinated. Nature uses DNA not only as a repository of the genetic information, but also as a controller of the expression of the genes it contains. Thus, there are codes embedded in the DNA sequence that serve to control recognition processes on the atomic scale, such as the base pairing, and others that control processes taking place on the nanoscale. From the chemical point of view, DNA is the supramolecular building block with the highest informational content. Nanoscience has therefore the opportunity of using DNA molecules to increase the level of complexity and efficiency in self-assembling and self-directing processes.