UVA and UVB‐Induced 8‐Methoxypsoralen Photoadducts and a Novel Method for their Detection by Surface‐Enhanced Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry (SELDI‐TOF MS)

UVA‐activated psoralens are used to treat hyperproliferative skin conditions due to their ability to form DNA photoadducts, which impair cellular processes and may lead to cell death. Although UVA (320–400 nm) is more commonly used clinically, studies have shown that UVB (280–320 nm) activation of psoralen can also be effective. However, there has been no characterization of UVB‐induced adduct formation in DNA alone. As psoralen derivatives have a greater extinction coefficient in the UVB region (11 800 cm^?1 M^?1 at 300 nm) compared with the UVA region (2016 cm^?1 M^?1 at 365 nm), a greater extent of adduct formation is expected. SELDI‐TOF, a proteomic technique that combines chromatography with mass spectrometry, was used to detect photoadduct formation in an alternating A–T oligonucleotide. 8‐Methoxypsoralen (8‐MOP) and DNA solutions were irradiated with either UVA or UVB. An adduct peak was obtained with SELDI‐TOF. For UVB‐activated 8‐MOP, the extent of adducts was three times greater than for UVA. HPLC ESI‐MS analysis showed that UVB irradiation yielded high levels of 3,4‐monoadducts (78% of total adducts). UVA was more effective than UVB at conversion of 4′,5′‐monoadducts to crosslinks (17% vs 4%, respectively). This report presents a method for comparing DNA binding efficiencies of interstrand crosslink inducing agents.     

Ring signatures for benzenoids with up to seven rings,Part 2: Pericondensed systems

An array of integers p_ij indicate in how many of the K resonance structures one finds 6 > i > 0 π‐electrons in the corresponding ring (which is labeled with capital letters A through a subsequent letter up to G). The index j for the rows indicates the ring type, denoted by capital letters (that is, j = 1 stands for A, j = 2 stands for B, etc.). Row sums lead to π‐electron ring partitions after division by the number K of resonance structures. Column sums lead to a sequence of seven integers (R_i sequence) which after division by K affords the r_i sequence; this is finally converted into the signature of the benzenoid s_i sequence). The analysis of signatures for pericondensed benzenoids with h = 4 through 7 benzenoid rings has revealed interesting regularities and correlations with structure, and has also allowed a confirmation of Clar's theory by investigating five isomeric dibenzopyrenes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

A new yardstick for benzenoid polycyclic aromatic hydrocarbons

The newly introduced signature of benzenoids (a sequence of six real numbers Si with i = 6-1) shows the composition of the pi-electron partition by indicating the number of times all rings of the benzenoid are assigned 6, 5, 4, 3, 2, or 1 pi-electrons. It allows the introduction of a new ordering criterion for such polycyclic aromatic hydrocarbons by summing some of the terms in the signature. There is an almost perfect linear correlation between sums S6 + S5 and S4 + S3 for isomeric cata- or peri-fused benzenoids, so that one can sort such isomers according to ascending s 6 + S5 or to descending S4 + S3 sums (the resulting ordering does not differ much and agrees with that based on increasing numbers of Clar sextets and of Kekule structures). Branched cata-condensed benzenoids have higher S6 + S5 sums than isomeric nonbranched systems. For nonisomeric peri-condensed benzenoids, both sums increase with increasing numbers of benzenoid rings and decrease with the number of internal carbon atoms. Other partial sums that have been explored are S6 + S5 + S3 And S6 + S2 + S1, and the last one appears to be more generally applicable as a parameter for the complexity of benzenoids and for ordering isomeric benzenoids.     

Structure characterization of free-standing filaments drawn in the liquid crystal state

Stable free-standing liquid filaments formed by some layered mesophases of bent-core mesogens are unique structures. Some of their physical properties have been analyzed in recent studies, but their microscopic structure and conditions for stability have still been unclear. We explore details of filament shapes and surface profiles of filaments drawn in liquid crystal phases of bent-core mesogens by AFM and SEM measurements, and we present a microscopic structure model. Conclusions on the stabilizing mechanisms are drawn. Qualitative differences in mechanical properties are found for different mesophases, even though the macroscopic appearance of the filaments is very similar.     

Bifibrations and Weak Factorisation Systems

We review a theorem of A. Roig about Quillen model structures on Grothendieck bifibrations and observe that it contains a gap. We reformulate one of its assumptions in order to validate it. As an application to the new version, we introduce the fibred model structure on the category of small categories enriched in a suitable monoidal model category.     

K11[HSn(PWO34)2] · 27 H2O – Synthese und Struktur

K₁₁[HSn (PW O₃₄)₂] · 27 H₂O – Synthesis and Structure K₁₁[HSn (PWO₃₄)₂] · 27 H₂O 1 can be synthesized in an “one-pot reaction” from commercially obtainable educts (SnCl₂; Na₂HPO₄ · 7 H₂O, Na₂WO₄ · 2 H₂O) in high yields and has been characterized by elemental analysis, IR/Raman-, UV/Vis-spectroscopy as well as by X-ray crystal structure analysis. The example of 1 again demonstrates the validity of our working hypothesis, that polyoxometalates can be obtained by linking highly charged, transferable building blocks by cationic centres within the scope of an optimal charge control. For structural details see “Inhaltsübersicht”.     

Spectral Automorphisms in Quantum Logics

In quantum mechanics, the Hilbert space formalism might be physically justified in terms of some axioms based on the orthomodular lattice (OML) mathematical structure (Piron in Foundations of Quantum Physics, Benjamin, Reading, 1976). We intend to investigate the extent to which some fundamental physical facts can be described in the more general framework of OMLs, without the support of Hilbert space-specific tools. We consider the study of lattice automorphisms properties as a “substitute” for Hilbert space techniques in investigating the spectral properties of observables. This is why we introduce the notion of spectral automorphism of an OML. Properties of spectral automorphisms and of their spectra are studied. We prove that the presence of nontrivial spectral automorphisms allow us to distinguish between classical and nonclassical theories. We also prove, for finite dimensional OMLs, that for every spectral automorphism there is a basis of invariant atoms. This is an analogue of the spectral theorem for unitary operators having purely point spectrum.     

Surface-enhanced spectroscopic investigation of the adsorption properties of hydroxybenzoic acid isomers onto metallic surfaces

Surface-enhanced Raman Spectroscopy (SERS), surface-enhanced infrared absorption spectroscopy (SEIRA), temperature-programmed desorption (TPD), and density functional theory were used to characterize the adsorption properties of the hydroxybenzoic acid (HBA) isomers including ortho-hydroxybenzoic acid (OHA), meta-hydroxybenzoic acid (MHA), and para-hydroxybenzoic acid (PHA) using various deposition solvents with different polar properties. SERS typically enhances the Raman shifts of the monolayer, while SEIRA is a longer range effect, often providing vibrational enhancement to both the monolayer and multilayer. TPD analysis showed that OHA adsorption to silver is weaker than MHA/PHA, most likely as a result of the strong OHA intramolecular hydrogen-bonding. SERS and SEIRA demonstrated that OHA ionized efficiently in the monolayer and multilayer independent of the solvent polarity because of OHA's low pK_a (2.98). MHA/PHA ionized better than OHA in the multilayer in less polar deposition solvents, and a decrease in the polarity of the deposition solvent created additional ordering in the MHA monolayer while inducing stronger adsorption in the PHA monolayer. It is believed that a lower level of solvation with less polar deposition solvents allowed for more adsorbate/substrate interaction and more intermolecular attraction. The addition of more MHA to a multilayer resulted only in stronger SEIRA peaks. As a PHA multilayer thickened there was significant structural changes represented by new bands and spectral peak shifts with greater intermolecular attraction as the multilayer approached bulk properties. Due to the range of applications involving HBA isomers, these studies could find significant applications in biochemistry, medicine, nanotechnology and environmental science.     

4‐(Azulen‐1‐yl) six‐membered heteroaromatics substituted with thiophen‐2‐yl or furan‐2‐yl moieties in 2 and 6 positions

Pyranylium perchlorates with azulen‐1‐yl moiety in 4‐position and thiophen‐2‐yl or furan‐2‐yl in 2 and 6‐positions were obtained by the substitution of 4‐chloro corresponding salts with azulenes. The pyranylium salts are used as starting materials for the synthesis of pyridine and pyridinium salts. The products were characterized and for pyridines pKa was spectroscopically determined. Several attempts were made for pyridine complexation with metal cations as Hg²⁺ or Ag⁺. J. Heterocyclic Chem., (2011).     

Significance of local density of states in the scanning tunneling microscopy imaging of alkanethiol self-assembled monolayers

A systematic scanning tunneling microscopy (STM) study of alkanethiol self-assembled monolayers (SAMs) is presented as a function of the bias voltage, tunneling current, and tip-termini separation. Stable and etch-pit free SAMs of close-packed undecanethiol/Au(111) were obtained after annealing in ultrahigh vacuum. STM revealed two distinct c(4x2) structures with four nonequivalent molecules per unit cell. For both structures, reversible contrast variations occur upon systematically tuning the bias voltage, the current, and the tip-termini distance. These contrast transitions originate from probing the corresponding local density of states (LDOS) of each molecule and not from the reorientation of the alkanethiol chains. The STM contrast is particularly sensitive to the tip-termini separation in the range of 0.5-2.5 A, reflecting the distance-dependence of LDOS. At a fixed tip elevation, the STM contrast is less sensitive to changes in bias within 0.1-1.2 V. For the first time, we demonstrate that LDOS may override the physical height variations in the STM topographic contrast for alkanethiol SAM systems.