Isotropic transition behaviour of an amphiphilic di-block copolymer under pressure

The present work deals with the interactions between carbon dioxide, used as pressure medium, either in the gas state (GCO₂) or in the supercritical state (SCCO₂) and amphiphilic di-block copolymers PEO_m-b-PMA(Az)_n. The effect of pressure on the isotropic transition of the PEO_m-b-PMA(Az)_n copolymer was investigated using scanning transitiometry (ST). The experimental results were compared with those measured when using ‘relatively inert’ mercury (Hg) as pressure medium. Morphological observation of a PEO_m-b-PMA(Az)_n thin film submitted to SCCO₂ was performed by atomic force microscopy (AFM) to investigate the nano-structure organization. These results indicate the possibility of modifying the nano-structure in a specific way depending on the CO₂ physical state.     

Rapid sequencing and disulfide mapping of peptides containing disulfide bonds by using 1,5-diaminonaphthalene as a reductive matrix

MS/MS is indispensable for the amino acid sequencing of peptides. However, its use is limited for peptides containing disulfide bonds. We have applied the reducing properties of 1,5-diaminonaphthalene (1,5-DAN) as a MALDI matrix to amino acid sequencing and disulfide bond mapping of human urotensin II possessing one disulfide bond, and human guanylin possessing two disulfide bonds. 1,5-DAN was used in the same manner as the usual MALDI matrices without any pre-treatment of the peptide, and MS/MS was performed using a matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight mass spectrometer (MALDI QIT TOFMS). The results demonstrated that MS/MS of the molecular ions reduced by 1,5-DAN provided a series of significant b-/y-product ions. All 11 amino acid residues of urotensin II were identified using 1,5-DAN, while only 5 out of 11 residues were identified using 2,5-dihydroxybenzoic acid (DHB); similarly 11 out of 15 amino acid residues of guanylin were identified using 1,5-DAN, while only three were identified using DHB. In addition, comparison of the theoretical and measured values of the mass differences between corresponding MS/MS product ions using 1,5-DAN and DHB narrowed down the possible disulfide bond arrangement candidates. Consequently, 1,5-DAN as a reductive matrix facilitates rapid amino acid sequencing and disulfide mapping for peptides containing disulfide bonds.     

Experimental investigation of amplitude death in delay-coupled double-scroll circuits with randomly time-varying network topology

Nonlinear Dynamics - The present study experimentally investigates amplitude death in delay-coupled double-scroll circuits with a time-varying network topology that randomly changes at a regular...     

Binary 1,4-asymmetric induction from a single allyltin reagent with a chiral nitrogen functional group toward aldehydes

Using a single allyltin reagent with a chiral nitrogen functionality, binary and remote asymmetric induction was realized toward various aldehydes. Either syn- or anti-1,4-amino-alcohols were selectively obtained with the use of Yb(OTf)₃ or SnCl₄, respectively. The structures of both diastereomers were identified by means of X-ray analysis.     

PETITE INDUCTION IN YEAST, Saccharomyces cerevisiae, BY PHOTOACTIVATION OF 3-A-ZIDO-6-A-MINO-10-M-ETHYLACRIDINIUM CHLORIDE

Abstract— The photoinduction of petite colonies and cell toxicity in non-growing yeast, Saccharomyces cerevisiae , by 3-a-zido-6-a-mino-10-m-ethylacridinium chloride (AAMAC) has been examined. The results presented here indicate that mitochondrial DNA damage in resting yeast which occurs following irradiation of AAMAC-treated cells for short time periods is probably mediated through a covalent adduct between AAMAC and DNA. Furthermore, the photoreaction which contributes to biological activity is dependent on the presence of oxygen. Pre-irradiated AAMAC, which no longer exhibited the short-term photo-induction of biological effects showed a second biological activity. In this case longer irradiation times, e.g. 30 min, were required to induce petites for resting yeast. Again there was a strong dependence on the presence of oxygen. These results suggest that both processes may be effected through oxygen intermediates (photodynamic processes).     

Long-wavelength luminescence from GaSb quantum dots grown on GaAs substrates

Self-assembled GaSb quantum dots (QDs) with a photoluminescence wavelength longer than 1.3 μm were successfully grown by suppressing the replacement of As and Sb on the surface of the GaSb QDs. This result means that GaSb can thus join InAs or GaInAs as a suitable material for QD lasers for optical communications.     

Electrostatic energies stored in dipolar films and analysis of decaying process of a large surface potential of Alq3 films

The decaying process of a large surface potential of as-deposited Alq₃ film was analyzed with consideration of electrostatic energies stored in the film. The analysis includes the cooperative molecular field effect and it shows that the derived equilibrium condition of dipolar films with electron traps supports the concept of the alignment of Fermi-level of metal and surface Fermi-level of dipolar films. The potential decay of Alq₃ films on Al electrodes by photo-exposure is explained due to detrapping of trapped electrons that are immediately transported to the injected electrodes along with the disordering of polar structure of Alq₃ films.     

Multi-dimensional tunneling and nuclear fission process

Semiclassical treatment of the tunneling through a multi-dimensional potential barrier is given. We discuss first about methods to calculate the minimum action trajectory. Next, we discuss the adiabatic approximation to the minimum action trajectory. We apply these two methods to the calculation of spontaneous fission. Finally we discuss some problems which should be solved to calculate more realistic penetration problems.     

Highly shape-selective guest encapsulation in the precisely defined cavity of a calix[4]arene-capped metalloporphyrin

We developed a metalloporphyrin-based molecular container capped with a calix[4]arene, and its rigid cavity distinguished the slight structural differences in the aromatic guests.