Distribution of dopamine, an essential neurotransmitter in mammalian central and peripheral nervous systems, in a lipid bilayer and at the surface of 1,2-ditetradecanoyl-sn-glycero-3-phospho-(1'-rac-glycerol) vesicles has been studied herein. To track the progress of dopamine through different regions of the lipid vesicle, these were synthesized using 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-labeled phospholipid molecules tagged to either the headgroup (NBDPE) or the acyl chain (NBDPG). Dopamine-induced quenching of NBD fluorescence in the lipid vesicles demonstrates that dopamine has a preference to diffuse into the lipid bilayer. The change in the excited state lifetime obtained for NBDPG clearly indicates the preference in dopamine binding. The propositions were supported by fluorescence lifetime imaging microscopy.
Thiazole
orange (TO) exists mainly as a monomer in aqueous medium,
where its fluorescence is negligibly small due to intramolecular movements.
In the present study, it has been shown that in presence of giant
unilamellar vesicles, produced from anionic lipid molecules, TO prefers
to form H-dimer and H-aggregates at low lipid concentrations. The
nonfluorescent form of TO (monomer) starts fluorescing in the aggregated
or dimeric forms. At higher 1,2-dimyristoyl-
sn
-glycero-3-phospho-(1′-rac-glycerol)
concentration, the TO aggregates disintegrate to the monomeric variants.
This is principally due to generation of more surface of residence
for the TO molecules. The dye molecules/aggregates reside on the outer
surface as well as percolate inside the lipid vesicles toward the
inner water pool due to the presence of anionic charges at the interface.
We adopted fluorescence lifetime imaging to find out the heterogeneity
in photophysics of the different forms of TO inside the lipid vesicles
supported by fluorescence correlation spectroscopy to characterize
the formation or disintegration of the TO aggregates.
Harmful
UVC (200–280 nm) radiation is entirely screened
by a combination of dioxygen and ozone in the stratosphere. However,
because of environmental pollution, depletion of stratospheric ozone
layer is increasing alarmingly, ensuing danger of penetration of the
harmful UVC through the earth’s atmosphere to reach the living
world. Studies have shown that UVC radiation accelerates aging of
albumin solutions along with other qualitative changes. Herein, we
have used in situ grown and ex situ added gold nanoclusters (AuNCs)
to minimize the damage in the protein structure caused by long-term
UVC exposure. The effects were demonstrated in the absence and presence
of lipid vesicles to mimic the biological environment. Bovine serum
albumin (BSA) has been used as the model protein that contains ∼50–60%
helicity. It is observed that UVC converts most of α-helix into
β-sheet, leading to the aggregation of protein. The ingrown
AuNCs could provide about 23–40% protection to the secondary
structure, whereas the externally added AuNCs preserved almost 73–82%.
To generalize this finding, we have also studied the effect of AuNC
protection on the UVC-exposed lysozyme protein. The results show that
the proposed method is indeed helpful for life.
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