PRODAN differentially influences its local environment

Abstract

Environmentally-sensitive membrane dyes have been extensively used to study the different liquid phases, (liquid-ordered (Lo) and liquid-disordered (Ld)) of the heterogenous cellular membrane. However, it is not yet well understood how these dyes affect membrane properties upon and post insertion. Using a combination of molecular dynamics (MD) simulations and fluorescence microscopy, we study the effect of PRODAN insertion upon its local environment. We firstly present the results of the MD simulations of PRODAN interacting with lipid bilayers of various compositions, specifically the resultant hydration and lipid order of the system. Experimentally, the lipid order of Lo and Ld vesicles containing various concentrations of PRODAN are inferred from their Generalised Polarisation (GP) values, calculated using their fluorescence spectra. We then apply the methodology to a more complex biological system, the HeLa cell line. For both systems, the presence of PRODAN influences its local environment differently between the Lo and Ld phases. In the simulated systems, the presence of PRODAN lowers the lipid order in the Ld phase and increases the order in the Lo phase, whilst experimental data demonstrates that even a small increase in PRODAN concentration significantly lowers the order of both phases. We suggest this discrepancy may be ascribed to the differing localisations of the dye molecules within the bilayer, and their effect on the hydration of adjacent lipids.

Lipid vesicle composition influences the incorporation and fluorescence properties of the lipophilic sulphonated carbocyanine dye SP-DiO

“…39 Alternatively, differences in orientation and penetration of the dye molecules into the bilayer could affect its spectral properties, as suggested for other environmentally sensitive dyes. 40,41 Taken together, our results suggest that SP-DiO incorporates most efficiently into DOPC membranes, whereas the fluorescence lifetime is highest in DSPC membranes. Therefore, the higher labeling efficiency with DOPC is counter-balanced by a considerably weaker fluorescence of the SP-DiO dye in a DOPC membrane and vice versa, clearly demonstrating how both binding and brightness contributes to the total fluorescence intensity of the labelled membrane.…”

Targeted fluorescence lifetime probes reveal responsive organelle viscosity and membrane fluidity

“…As we have done previously for the environmentally sensitive fluorescent dye, PRODAN [33], we have used all-atom classical molecular dynamics (MD) simulations to investigate the effect that the FMR-2 dye has on the molecular scale properties of a model lipid bilayer. Therefore, two systems were simulated: (a) a DOPC bilayer consisting of 288 lipid molecules (144 molecules in each leaflet) and (b) the same bilayer interacting with a single FMR-2 molecule.…”

Making Nitronaphthalene Fluoresce

“…Carbonyl groups tend to drive triplet formation in quantitative yields, and alkanionyls of naphthalene are no exception. Inducing a CT character in the singlet excited state of such compounds can suppress their propensity for ISC and result in strongly fluorescent dyes, such as 1-[6-(dimethylamino)-2-naphthalenyl]-1-propanone (prodan). − 5-(Dimethylamino)­naphthalene-1-sulfonamide (dansylamide) presents another example of an immensely popular fluorescent photoprobe with a naphthalene push–pull architecture (Chart ). , Carbonyls and sulfonamides, on the other hand, are considerably weaker electron-withdrawing substituents than the nitro group, and with reduction potentials of about −2.1 V vs SCE, prodan and dansylamide are pronouncedly weaker electron acceptors than nitronaphthalenes (Chart ).…”