Extended thermodynamic approach to ion interaction chromatography: a thorough comparison with the electrostatic approach,and further quantitative validation

Based on a simple, chromatography-based analogy, a quantitatively exact explanation for the strong additional band broadening induced by the presence of the side-walls in flow channels with a large aspect-ratio rectangular cross-section is given and validated for two different flow types: pressure-driven and shear-driven flow.     

(π-Allyl)palladium coupling of 2-(tributylstannyl)cyclopent-2-enone for the synthesis of jasmonoid analogs

The coupling of 2-(tributylstannyl)cyclopent-2-enone with several (π-allyl)palladium complexes derived from allylic electrophiles was investigated as the key step in the synthesis of jasmonoids. These compounds have an important role in plant development, triggering direct and indirect responses when harmed to induce pest resistance. Palladium-catalyzed coupling conditions to obtain a jasmonoid library are described. The retention of geometry of the olefin in the allyl group is not always observed due to syn-anti isomerization of the (π-allyl)palladium complex. The methodology was employed for the synthesis of a simplified jasmonic acid analog.     

Binding of regulatory protein omega from Streptococcus pyogenes plasmid pSM19035 to direct and inverted 7‐base pair repeats of operator DNA

pSM19035‐encoded dimeric regulator omega (ω₂) belongs to the MetJ/Arc family of ribbon–helix–helix DNA binding proteins. ω₂ binds to a set of unspaced 7‐base pair repeat units with sequence 5′‐^A/_TATCAC^A/_T‐3′. Protein ω₂ and its variant ω₂ΔN18, lacking the first 18 N‐terminal amino acids, bind poorly to one heptad DNA, but the affinity to DNA markedly increases with two and more heptads organized in direct or inverted orientation. Raman difference spectra indicate that ω₂ and ω₂ΔN18 bind to operator DNA in the major groove and contact thymine, adenine and guanine residues. The mode of ω₂ or ω₂ΔN18 interaction with operator DNA is not affected by the orientation and number of heptads. The Raman data of ω₂T29A, an ω₂ variant with Ala instead of Thr at position 29 of the β‐sheet, show a sequence‐independent binding mode to DNA, which differs from the binding mode of wt ω₂ protein to its cognate site. The Raman data strongly support the notion that the 18 N‐terminal amino acids are not required for ω₂ activity, whereas Thr29 plays an essential role for operator DNA binding. The data suggest the formation of a hydrogen bond between Thr29 of wild‐type ω₂ to one of the bases in the central 5′‐TCA‐3′/5′‐TGA‐3′ stretch of the 7‐bp binding site. Copyright © 2006 John Wiley & Sons, Ltd.     

On oscillation and nonoscillation properties of Emden-Fowler difference equations

A characterization of oscillation and nonoscillation of the Emden-Fowler difference equation

Tricyclic heteroaromatic systems. 5H-1,2,3-triazolo[5,1-c][1,4]benzodiazepine

The synthesis of the new tricyclic system 5H-1,2,3-triazolo[5,1-c][1,4]benzodiazepine, diaza-analogue of 5H-pyrrolo[2,1-c][1,4]benzodiazepine, which is the common feature of some antitumor antibiotics, is reported. The structure of the new tricyclic system and of some of its key intermediates is assigned by means of a ¹³C nmr study.