Distyrylbenzene-aldehydes: identification of proteins in water.

Three different, water soluble, aldehyde-appended distyrylbenzene (DSB) derivatives were prepared. Their interaction with different albumin variants (human, porcine, bovine, lactalbumin, ovalbumin) was investigated (pH 11). All three fluorophores exhibit graded, protein-dependent fluorescence turn-on at slightly differing wavelengths. Linear discriminant analysis (LDA) differentiated all of the investigated albumins and was used to discern commercially available protein shakes. The three DSB derivatives barely react with the constituting amino acids but cysteine. In the proteins significant fluorescence signals are generated, probably due to a combination of imine/N,S-aminal formation and hydrophobic interactions between the DSBs and the proteins.

Water-soluble cruciforms and distyrylbenzenes: synthesis, characterization, and pH-dependent amine-sensing properties.

Three water-soluble fluorescent aldehyde-substituted distyrylbenzene derivatives were prepared using Heck or Horner methodologies. Water solubility was achieved through the addition of branched oligoethylene glycol side chains; these are attached via an ether bridge to the aromatic nucleus. The aldehydes are almost nonfluorescent in water, but addition of primary amines turns the fluorescence on; formation of imines results. Control of the basicity of the media allows further discrimination of the analytes employed. 1,3-Diaminopropane reacts with these aldehydes. Instead of an imine, a brightly fluorescent aminal forms. Amino acids are almost always nonreactive toward these aldehydes. Exceptions are lysine and cysteine, which form an imine and a thioaminal, respectively, discreating the aldehyde unit under fluorescence turn-on in water. The detection limit and time of completion of the sensing event were evaluated. Dialdehydes 3 and 16 were comparable on both counts. The cross-shaped 16 did react approximately twice as quickly with 1,3-diaminopropane.