A bivalent cationic dye enabling selective photo-inactivation against Gram-negative bacteria.

A piperazine-modified Crystal Violet was found to be able to selectively inactivate Gram-negative bacteria upon visible light irradiation but left Gram-positive bacteria less damaged, which can serve as a blueprint for the development of novel narrow-spectrum agents to replenish the current arsenal of photodynamic antimicrobial chemotherapy (PACT).

Small change in structure leads to large difference in protein photocleavage: two porphyrins bearing rhodanine-based pendants.

Two 5,10,15,20-tetraphenylporphyrins with one phenyl group anchored to a rhodanine-terminated side chain, RhD-TPP and RhDCOOH-TPP, were designed and synthesized, and their protein photocleavage activities were investigated using bovine serum albumin (BSA) as a model protein. Both porphyrins exhibit similar absorption spectra, fluorescence spectra, fluorescence quantum yields, and singlet oxygen ((1)O(2)) quantum yields in organic solvents due to their structure similarity. They also show similar binding affinities and binding sites toward BSA. However, RhD-TPP is nearly inactive in protein photocleavage while RhDCOOH-TPP can lead to distinct photocleavage of BSA under the same experimental conditions. Such a difference may be attributed to the different binding modes of the two porphyrin derivatives toward BSA, though the apparent binding affinities and the binding sites are similar, and consequently a great difference in the (1)O(2) quantum yields of the two porphyrins bound on BSA. The presence of the COOH group in RhDCOOH is proposed to play an important role, leading to less hydrophobic character and additional interactions towards BSA.

A new Phenol Red-modified porphyrin as efficient protein photocleaving agent.

Protein affinity is of importance for porphyrins in their application in photodynamic therapy (PDT). A new Phenol Red-modified porphyrin (R-TPP) was designed and synthesized to fully take advantage of the binding character of Phenol Red towards protein. Detailed comparisons of absorption spectra, fluorescence spectra, n-octanol/water partition coefficients, (1)O(2) quantum yields, as well as protein photocleaving abilities between R-TPP and its parent porphyrin Br-TPP clearly demonstrate the benefits stemming from the modification of Phenol Red. On one hand, the presence of Phenol Red moiety greatly enhances the binding affinity of R-TPP towards model proteins (bovine serum albumin and hen egg lysozyme), and therefore improves the availability of (1)O(2). On the other hand, the presence of Phenol Red moiety provides R-TPP with amphiphilic character, and therefore restricts aggregation and favors the generation of (1)O(2). As a result, R-TPP photocleaves proteins efficiently, showing promising application potential in PDT.

Studies on the degradation of blue gel pen dyes by ion-pairing high performance liquid chromatography and electrospray tandem mass spectrometry.

Ion-pairing high performance liquid chromatography (IP-HPLC) was utilized to monitor the composition changes of blue gel pen ink entries on paper stored in different light conditions and natural environment. The chromatographic conditions were optimized by comparing the separation efficiencies of the blue gel pen inks using a series of ion-pairing reagents, including ammonium carbonate, ammonium acetate, triethylamine acetate, tributylamine acetate, tetrabutylammonium bromide and dihexylammonium acetate. It has been found that tributylamine acetate was a suitable ion-pairing reagent for separation of the inks on the common C18 column. The analysis results of the ink entries on paper in different aging conditions showed that the tendency of composition change in natural aging condition was similar with those in fluorescent light and UV light conditions, respectively. One main component dye of the blue gel pen ink, Acid Blue 9, and its degradation products were identified by ion-pairing high performance liquid chromatography coupled with electrospray tandem mass spectrometry. The results showed that the main degradation products originated from the Acid Blue 9. It gave a reasonable explanation for the changing rules of the relative content of the dyes in the blue gel pen ink. The results obtained can provide scientific evidences for dating of the blue gel pen ink entries on documents.