Standardization of Methods for Characterizing the Surface Geometry of Solids

Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals.     

Molecular addressing? Studies on light-induced reorientation in liquid-crystalline side chain polymers

Polarized light leads to an effective reorientation of the optic axis in the glassy state of liquid-crystalline side chain polymers containing azobenzene mesogenic groups, via a trans-cis and cis-trans isomerization. Using a combination of U V and IR dichroitic studies it is shown for copolymers consisting of chromophores (azobenzene) and non-chromophores (phenylbenzoate) that only the chromophores are reoriented by light as far as the glassy state is concerned. Individual chromophores are thus addressed by photoselection. Photoselection in the fluid nematic state, on the other hand, leads also to a reorientation of the non-chromophores.     

New disc-shaped mesogens based on pentakis(phenylethynyl)benzene derivatives

First examples of amphiphilic alkyl pentakis(phenylethynyl)benzene ethers containing functional groups at the terminal position of their alkoxy chains were synthesized by etherification of pentabromophenol with 11-bromoundecan-1-ol and 11-bromoundecanoic acid ethyl ester, respectively, and subsequent palladium catalyzed, fivefold coupling reactions with the substituted phenylacetylene. Two undecanoic acid derivatives with different pentakis(phenylethynyl)phenoxy substituents in the ω-position were prepared by ester cleavage from the corresponding ethyl esters. The thermal behaviours of five penta-alkynes in their pure states, as well as of their charge transfer complexes formed from mixtures with 2,4,7-tri-nitrofluorenone, were examined.     

Isotope dilution mass spectrometry for micro- and trace-element determination

Isotope dilution mass spectrometry is an important method for accurate and precise determination of trace- and micro-amounts of the elements. Using different ionization techniques in the mass spectrometer most of the elements of the periodic table can be analysed.     

CHEMILUMINESCENCE FROM THE OXIDATION OF AUXIN DERIVATIVES

Abstract— The thiophenyl ester of indole-3-acetic acid and indole-3-acetonitrile produce chemiluminescence in aerated dimethylsulfoxide in the presence of potassium t -butoxide. The emitter is the aromatic aldehyde. In the case of acetonitrile, the other product expected from the cleavage of an intermediate dioxetane, cyanate/isocyanate, has also been identified. Other auxins also chemiluminesce under similar conditions, but the emitters have not been properly identified.
These systems are models for the peroxidase catalyzed oxidation of indole-3-acetic acid to indole-3-carboxaldehyde and as such support the earlier inference (Vidigal et al , 1975) that the excited aldehyde is generated in the enzymic process.
An additional result is the observation of an exciplex between excited indole-3-carboxaldehyde and the thiophenylester of indole-3-acetic acid. This appears to be the first case of chemical generation of an exciplex by a route other than radical ion reaction, presumably by the dioxetane route.     

Das Grenzflächenverhalten von Carboxymethylcellulose an Baumwolle

Ohne Zusammenfassung     

THE SYNERGISTIC ACTION OF ULTRAVIOLET AND X RADIATION ON MUTANTS OF ESCHERICHIA COLI K-12

Abstract— Prior UV irradiation increased the X-ray sensitivity of wild-type E. coli K-12. This synergistic effect of combined UV and X irradiation was also observed, but to a reduced extent, in uvrA, uvrB, uvrC , and polA mutants, but was absent in exrA, recA, recB , or recC mutants of E. coli K-12. Alkaline sucrose gradient studies demonstrated that the wand err gene-controlled, growth-medium-dependent (Type III) repair of X-ray-induced DNA single-strand breaks was inhibited by prior UV irradiation. This inhibition probably explains the synergistic effect of these two radiations on survival.     

Design,synthesis, and evaluation of 6-carboxyalkyl and 6-phosphonoxyalkyl derivatives of 7-oxo-8-ribitylaminolumazines as inhibitors of riboflavin synthase and lumazine synthase

A series of 6-carboxyalkyl and 6-phosphonoxyalkyl derivatives of 7-oxo-8-D-ribityllumazine were synthesized as inhibitors of both Escherichia coli riboflavin synthase and Bacillus subtilis lumazine synthase. The compounds were designed to bind to both the ribitylpurine binding site and the phosphate binding site of lumazine synthase. In the carboxyalkyl series, maximum activity against both enzymes was observed with the 3'-carboxypropyl compound 22. Lengthening or shortening the chain linking the carboxyl group to the lumazine by one carbon resulted in decreased activity. In the phosphonoxyalkyl series, the 3'-phosphonoxypropyl compound 33 was more potent than the 4'-phosphonoxybutyl derivative 39 against lumazine synthase, but it was less potent against riboflavin synthase. Molecular modeling suggested that the terminal carboxyl group of 6-(3'-carboxypropyl)-7-oxo-8-D-ribityllumazine (22) may bind to the side chains of Arg127 and Lys135 of the enzyme. A hypothetical molecular model was also constructed for the binding of 6-(2'-carboxyethyl)-7-oxolumazine (15) in the active site of E. coli riboflavin synthase, which demonstrated that the active site could readily accommodate two molecules of the inhibitor.