Prefolded Synthetic G‐Quartets Display Enhanced Bioinspired Properties

A water‐soluble template‐assembled synthetic G‐quartet (TASQ) based on the use of a macrocyclodecapeptide scaffold was designed to display stable intramolecular folds alone in solution. The preformation of the guanine quartet, demonstrated by NMR and CD investigations, results in enhanced peroxidase‐type biocatalytic activities and improved quadruplex‐interacting properties. Comparison of its DNAzyme‐boosting properties with the ones of previously published TASQ revealed that, nowadays, it is the best DNAzyme‐boosting agent.     

Oligocarbamate molecular transporters: design,synthesis, and biological evaluation of a new class of transporters for drug delivery

Molecular transporters have the ability to deliver drugs and probe molecules into cells and tissues irrespective of their physical properties. We now report the design, synthesis, and biological evaluation of a new family of molecular transporters, guanidinylated oligocarbamates that enable exceptionally efficient uptake into cells and tissues. The synthesis features a solid-phase stepwise oligomerization to obtain the oligocarbamates and a single step perguanidinylation for the facile introduction of up to nine guanidinium groups. The oligocarbamate 9-mer is found to be among the most efficient transporters known, entering cells faster than even d-Arg9 and HIV-1 Tat49-57. Significantly, this new family of transporters also enables uptake into the formidable skin barrier of a probe molecule that by itself does not penetrate skin.     

Energy dependence of the ionization probability of sputtered Cu and Ni

Despite its great sensitivity, the usefulness of secondary ion mass spectrometry (SIMS) for many applications has been limited by an inadequate understanding of the probability of sputtering an atom in an ionized state. To determine this ionization probability for clean Cu and Ni surfaces, I have measured the energy distribution of sputtered neutrals and ions by quadrupole mass filtering and retarding potential analysis using potential modulation differentiation. Analysis of sputtered neutrals was accomplished by electron impact ionization. Because the neutrals outnumber the ions by at least two orders of magnitude, the ratio of sputtered ions to neutrals is an accurate measure of the ionization probability. For energies below 20 eV the dependence of the ionization probability on energy goes as P(E) α Eⁿ, where n = 0.65 for clean Cu. The absorption of oxygen on the Cu surface increases the total ion yield while causing a reduction in the value of the exponent n. Similar results are found for nickel, where n = 0.54 for the clean surface.     

Adsorption of molecular nitrogen by the W(110) plane

Characteristics of the adsorption of nitrogen on the (110) plane of tungsten were determined by thermal desorption and work function measurements. The low temperature γ-N₂ state desorbs with first order kinetics and an activation energy of 6 kcal mole^?1. The absence of isotope mixing between ¹⁴N₂ and ¹⁵N₂ demonstrates γ-N₂ is adsorbed molecularly. Monolayer coverage shows a decrease of 0.19 eV in work function. A Topping model plot indicates the layer is immobile at 123 K.     

Approximation and the spectral multiplicity of special automorphisms

Summary Conditions have been given [7] under which a special automorphism over an automorphism admitting a simple approximation again admits a simple approximation, and so has simple spectrum.In this paper using different techniques to those employed in [7], we obtain improved results in the same direction. Specifically, conditions are given for a special automorphism over an automorphism, which admits either a simple approximation, or an approximation with suitable speed, to have bounded spectral multiplicity. Furthermore, we obtain as a corollary a result on primitive automorphisms, which partially generalises a result appearing in [4].     

Treatment of trigeminal ganglion neurons in vitro with NGF,GDNF or BDNF: effects on neuronal survival,neurochemical properties and TRPV1-mediated neuropeptide secretion

Background  

Nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) all play important roles in the development of the peripheral sensory nervous system. Additionally, these growth factors are proposed to modulate the properties of the sensory system in the adult under pathological conditions brought about by nerve injury or inflammation. We have examined the effects of NGF, GDNF and BDNF on adult rat trigeminal ganglion (TG) neurons in culture to gain a better understanding of how these growth factors alter the cytochemical and functional phenotype of these neurons, with special attention to properties associated with nociception.     

Negative differential conductance and hot phonons in suspended nanotube molecular wires

Freely suspended metallic single-walled carbon nanotubes (SWNTs) exhibit reduced current carrying ability compared to those lying on substrates, and striking negative differential conductance at low electric fields. Theoretical analysis reveals significant self-heating effects including electron scattering by hot nonequilibrium optical phonons. Electron transport characteristics under strong self-heating are exploited for the first time to probe the thermal conductivity of individual SWNTs (approximately 3600 W m-1 K-1 at T=300 K) up to approximately 700 K, and reveal a 1/T dependence expected for umklapp phonon scattering at high temperatures.     

Nanotube molecular transporters: internalization of carbon nanotube-protein conjugates into Mammalian cells

The interactions between various functionalized carbon nanotubes and several types of human cancer cells are explored. We have prepared modified nanotubes and have shown that these can be derivatized in a way that enables attachment of small molecules and of proteins, the latter through a novel noncovalent association. The functionalized carbon nanotubes enter nonadherent human cancer cells as well as adherent cell lines (CHO and 3T3) and by themselves are not toxic. While the fluoresceinated protein streptavidin (MW approximately 60 kD) by itself does not enter cells, it readily enters cells when complexed to a nanotube-biotin transporter and exhibits dose-dependent cytotoxicity. The uptake pathway is consistent with adsorption-mediated endocytosis. The use of carbon nanotubes as molecular transporters could be exploited for various cargos. The biocompatibility and unique physical, electrical, optical, and mechanical properties of nanotubes provide the basis for new classes of materials for drug, protein, and gene delivery applications.