Effect of polyethylenimine, a cell permeabilizer, on the photosensitized destruction of algae by methylene blue and nuclear fast red

The present study reports the effect a cell permeabilizer, polyethylenimine (PEI) has on the photodynamic effect of methylene blue (MB) and nuclear fast red (NFR) in the presence of hydrogen peroxide (H2O2). The photosensitized destruction of the algae Chlorella vulgaris under irradiation with visible light is examined. The photodynamic effect was investigated under aerobic and anaerobic conditions. The presence of a permeabilizer during the photosensitized destruction of C. vulgaris does not enhance the activity of the MB, MB/H2O2 system or the NFR, NFR/H2O2 system under aerobic conditions. However under anaerobic conditions we have determined that when a cell permeabilizer was added to the MB/H202 system, the photosensitized destruction of C. vulgaris proceeded via a combination of Type I and Type II mechanisms. The presence of PEI enforces MB/H2O2 to be active toward the destruction of C. vulgaris whether oxygen is present or absent. Under aerobic and anaerobic conditions the activity of NFR was suppressed in the presence of PEI as a result of electrostatic interactions between the photosensitizer and the cell permeabilizer. The decrease in fluorescence recorded is indicative of destruction of the chlorophyll a pigment.     

Baseline resolution of isomers by traveling wave ion mobility mass spectrometry: investigating the eff ects of polarizable drift gases and ionic charge distribution

We have studied the behavior of isomers and analogues by traveling wave ion mobility mass spectrometry (TWIM‐MS) using drift‐gases with varying masses and polarizabilities. Despite the reduced length of the cell (18 cm), a pair of constitutional isomers, N‐butylaniline and para‐butylaniline, with theoretical collision cross‐section values in helium (Ω_He) differing by as little as 1.2 Ų (1.5%) but possessing contrasting charge distribution, showed baseline peak‐to‐peak resolution (R_p‐p) for their protonated molecules, using carbon dioxide (CO₂), nitrous oxide (N₂O) and ethene (C₂H₄) as the TWIM drift‐gas. Near baseline R_p‐p was also obtained in CO₂ for a group of protonated haloanilines (para‐chloroaniline, para‐bromoaniline and para‐iodoaniline) which display contrasting masses and theoretical Ω_He, which differ by as much as 15.7 Ų (19.5%) but similar charge distributions. The deprotonated isomeric pair of trans‐oleic acid and cis‐oleic acid possessing nearly identical theoretical Ω_He and Ω_N2 as well as similar charge distributions, remained unresolved. Interestingly, an inversion of drift‐times were observed for the 1,3‐dialkylimidazolium ions when comparing He, N₂ and N₂O. Using density functional theory as a means of examining the ions electronic structure, and He and N₂‐based trajectory method algorithm, we discuss the effect of the long‐range charge induced dipole attractive and short‐range Van der Waals forces involved in the TWIM separation in drift‐gases of differing polarizabilities. We therefore propose that examining the electronic structure of the ions under investigation may potentially indicate whether the use of more polarizable drift‐gases could improve separation and the overall success of TWIM‐MS analysis. Copyright © 2013 John Wiley & Sons, Ltd.