Effect of ionic liquid on the fluorescence of an intramolecular exciplex forming probe

The effects of ionic liquid addition on the spectroscopic properties of a pyrene-tryptophan-containing fluorescent intramolecular complex in polar-aprotic and polar-protic solvents, specifically, acetonitrile and ethanol, are assessed.

Deboronation of New Clarithromycin-Benzo[c][1,2]oxaborole Conjugates

<P>Background: The conjugates of antibiotics are new molecules that might show new antibacterial spectrum and overcome resistance of insusceptible bacterial strains. Modification of known antibiotics like Clarithromycin with active fragments is laborious and proven method to overcome resistance of such strains. Methods: The conjugates of Clarithromycin and Benzo[c][1,2]oxaboroles were synthesized using long linkers to extend antimicrobial spectrum of this antibiotic. Results and Discussion: Unexpected intramolecular deboronation of these bioconjugated was found to occur when the linker contained two or more CH2-groups. Molecular modeling was used to understand the source of instability and show a possibility of intramolecular complex of carbonyl group at C-9 in Clarithromycin core and hydroxy-borole moiety. This could facilitate nucleophilic attack of methanol used in reactions to destroy benzo[c][1,2]oxaboroles fragments and leave stable hydroxyl-aryl molecules. Conclusion: The loss of boron from benzo[c][1,2]oxoborole fragments leads to the significant decrease of antimicrobial activity of synthesized antibiotics.</P>

A tryptophan-containing fluorescent intramolecular complex as a designer peptidic proton sensor

Pyrene and tryptophan groups judiciously placed on a molecular scaffold, namely, bispidine exhibited fluorescence due to the formation of an emissive intramolecular complex.

Crystallization and diffraction of an Isl1–Ldb1 complex

A stable intramolecular complex comprising the LIM domains of the LIM-homeodomain protein Isl1 tethered to a peptide region of Ldb1 has been engineered, purified and crystallized. The orthorhombic crystals belonged to space groupP2221, with unit-cell parametersa= 57.2,b= 56.7,c= 179.8 Å, and diffracted to 3.10 Å resolution.

Photocyclisation of o-Xylylbischromones: Proximity Effect

The photocyclisation of thiophene and furan substituted o-xylylbischromones is described. The reaction occurs through a 1,4-biradical species. The proximity of the two chromophores due to intramolecular complex formation affects the chemical efficiency of the reaction.