Study of the Porosity of Carbonaceous Materials and Organic Polymers by Thermal Analysis

The thermal desorption of benzene from rigid and swelling materials was investigated by means of a thermogravimetric technique. Pore volumes and pore size distributions were calculated from the isobars of desorption.The results are compared with those derived from nitrogen adsorption data and mercury intrusion.     

Rotational Spectra of cis-HCOOH, trans-HCOOH, and trans-HCOOH

While the rotational spectrum of trans-HCOOH is well known, the cis-rotamer was known previously only from a few microwave transitions. The spectra of cis- and trans-HCOOH and of trans-H¹³COOH have been identified in the far infrared Fourier transform spectrum recorded in the range 20-100 cm⁻¹. The measurements were performed using an 80-cm base length White-type multipass absorption cell in combination with a Bruker IFS 120 HR spectrometer. The White cell was set up for 90 passes (total path length=72 m) and the spectrum was measured with a resolution (FWHM) of 0.0012 cm⁻¹. Submillimeter-wave transitions, just under 1 terahertz, of the same three species of formic acid were measured in the range from 835 to 993 GHz (27.8-33.1 cm⁻¹) and it was possible to assign b-type Q-branch transitions of both cis- and trans-HCOOH in this region, and also transitions of trans-H¹³COOH. These measurements served furthermore as a check on the calibration of the FTIR measurement. Furthermore, new millimeter-wave measurements in the range 172-366 GHz were made, bridging the gap between the MW and FIR lines for cis-HCOOH and providing important data for trans-H¹³COOH. The assigned FTIR, submillimeter- and millimeter-wave data reported in this work were fitted together with previously published rotational transitions to obtain rotational constants, using Watson's A-reduced Hamiltonian, for cis-HCOOH, trans-HCOOH, and trans-H¹³COOH.     

In vitro investigation on the pH dependence of the absorption and fluorescence properties of the photosensitizer mTHPC

Fluorescence excitation efficiency is of great importance for photodynamic diagnosis. Because usually a difference in the interstitial pH between normal and tumor tissue occurs, it is necessary to assess the impact of pH on the fluorescence emission intensity of the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) in this context. The results obtained by in vitro fluorescence measurements clearly indicate that pH values below 6 lead to a significant decrease in the fluorescence intensity. In the physiological range of pH 6.5-7.2, however, no pH dependence was found. Besides the decrease in the fluorescence intensity of mTHPC for pH < 6, changes in the spectral shape of the absorption were found. These changes can be utilized for "dual-wavelength ratio imaging," using mTHPC as a pH-sensitive indicator with the excitation pair 405 nm/436 nm in the range of pH 3.5-6.     

Study of fungal degradation products of polycyclic aromatic hydrocarbons using gas chromatography with ion trap mass spectrometry detection

Representatives of polycyclic aromatic hydrocarbons (PAHs) were degraded by ligninolytic fungus Irpex lacteus. The products were analyzed by GC-Ion trap mass spectrometry. The combination of full scan mass spectra, product ion scans (MS-MS) and derivatization of the degradation products of anthracene, phenanthrene, fluoranthene and pyrene provided further insight in the degradation mechanism initiated by I. lacteus. Particularly, the product ion scans enabled the interpretation of unknown degradation products, even though they were only produced at trace level. Most of the structures suggested were later confirmed with authentic standards.     

Fock space multireference coupled cluster method with full inclusion of connected triples for excitation energies

We report the initial Fock space multireference coupled cluster method with the full inclusion of single, double, and triple excitations (FS-CCSDT) for the (1,1) sector. We present pilot applications for calculating excitation energies for the N(2) molecule and the Ne atom. The performance of the current model, along with the FS-CCSD one, has been studied in comparison with the equation-of-motion coupled-cluster and the similarity transformed methods.     

1,3-Diphenyl-1H-pyrazolo[3,4-b]quinoline: a versatile fluorophore for the design of brightly emissive molecular sensors

[structure: see text] The 1,3-diphenyl-1H-pyrazolo[3,4-b]-quinoline chromophore is a versatile building block for the construction of brightly fluorescent molecular sensors. Facile synthetic procedures allow integration of the chromophore into fluorophore-spacer-receptor systems as well as fluoroionophores operating via intramolecular charge transfer. Whereas the former photoinduced electron-transfer probes show strong analyte-induced fluorescence enhancement, the latter exhibit bright ratiometric dual emission. Employing prototype macrocyclic receptors, the favorable signaling features for metal ion recognition are demonstrated.     

Solid-phase synthesis of thioether-linked glycopeptide mimics for application to glycoprotein semisynthesis

[reaction: see text]. Glycoproteins are particularly suited to protein semisynthesis since homogeneous samples for biological analyses are not readily available using traditional recombinant techniques. Here we apply glycosyl iodoacetamides, normally used for the modification of bacterially derived proteins, to solid-phase glycopeptide synthesis. This provides access to glycopeptide alpha-thioesters, which may lend themselves to the semisynthesis of homogeneous N-linked glycoprotein mimics and novel glycopeptide libraries.     

Inclusion Compounds of Nitrosobenzenes with Cholic Acid and Deoxycholic Acid

The crystalline inclusion compounds of cholic acid (CA) and deoxycholic acid (DCA) with several nitrosobenzenes were prepared. The IR spectra and crystal structures of these compounds confirmed inclusion of the monomeric form of the C-nitroso compounds. The DCA compounds have 2 : 1 host:guest stoichiometry and P2₁ symmetry. Guest molecules are enclosed in channels and disordered. In the CA-nitrobenzene inclusion compound (1·CA) the host:guest stoichiometry is 1 : 1. The host molecules form typical CA bilayer aggregates and guest molecules are accommodated in helicoidal channels. The guest nitroso group is not coplanar with the phenyl ring; the torsion angle on the C–N bond is 8.6(8)°. The solid-state circular dichroism spectrum of 1·CA shows the negative Cotton effect at 780 nm corresponding to the n–^* electronic transition that can be associated with the P helicity of the guest molecule. The extremely weak magnitude of the Cotton effects exhibited by the DCA complexes points to a nearly planar arrangement of the NO group and the phenyl ring in the guest molecules.