TY - JOUR
T1 - Can di-4-ANEPPDHQ reveal the structural differences between nanodiscs and liposomes?
AU - Chmielińska, Anna
AU - Stepien, Piotr
AU - Bonarek, Piotr
AU - Girych, Mykhailo
AU - Enkavi, Giray
AU - Rog, Tomasz
AU - Dziedzicka-Wasylewska, Marta
AU - Polit, Agnieszka
PY - 2021/9
Y1 - 2021/9
N2 - The potential-sensitive di-4-ANEPPDHQ dye is presently gaining popularity in structural studies of the lipid bilayer. Within the bilayer, dye environmental sensitivity originates from the excitation induced charge redistribution and is usually attributed to solvent relaxation. Here, di-4-ANEPPDHQ is utilized to compare the structure of neutral and negatively charged lipid bilayers between two model systems: the nanodiscs and the liposomes. Using the well-established approach of measuring solvatochromic shifts of the steady-state spectra to study the bilayer structural changes has proved insufficient in this case. By applying an in-depth analysis of time-resolved fluorescence decays and emission spectra, we distinguished and characterized two and three distinct emissive di-4-ANEPPDHQ species in the liposomes and the nanodiscs, respectively. These emissive species were ascribed to the dual emission of the dye rather than to solvent relaxation. An additional, long-lived component present in the nanodiscs was associated with a unique domain of high order, postulated recently. Our results reveal that the di-4-ANEPPDHQ steady-state fluorescence should be interpreted with caution. With the experimental approach presented here, the di-4-ANEPPDHQ sensitivity was improved. We confirmed that the bilayer structure is, indeed, altered in the nanodiscs. Moreover, molecular dynamic simulations showed a distribution of the probe in the nanodiscs plane, which is sensitive to lipid composition. In POPC nanodiscs, probe frequently interacts with MSP, while in POPC-POPG nanodiscs, such interactions are rare. We did not observe, however, any impact of those interactions on the probe fluorescence.
AB - The potential-sensitive di-4-ANEPPDHQ dye is presently gaining popularity in structural studies of the lipid bilayer. Within the bilayer, dye environmental sensitivity originates from the excitation induced charge redistribution and is usually attributed to solvent relaxation. Here, di-4-ANEPPDHQ is utilized to compare the structure of neutral and negatively charged lipid bilayers between two model systems: the nanodiscs and the liposomes. Using the well-established approach of measuring solvatochromic shifts of the steady-state spectra to study the bilayer structural changes has proved insufficient in this case. By applying an in-depth analysis of time-resolved fluorescence decays and emission spectra, we distinguished and characterized two and three distinct emissive di-4-ANEPPDHQ species in the liposomes and the nanodiscs, respectively. These emissive species were ascribed to the dual emission of the dye rather than to solvent relaxation. An additional, long-lived component present in the nanodiscs was associated with a unique domain of high order, postulated recently. Our results reveal that the di-4-ANEPPDHQ steady-state fluorescence should be interpreted with caution. With the experimental approach presented here, the di-4-ANEPPDHQ sensitivity was improved. We confirmed that the bilayer structure is, indeed, altered in the nanodiscs. Moreover, molecular dynamic simulations showed a distribution of the probe in the nanodiscs plane, which is sensitive to lipid composition. In POPC nanodiscs, probe frequently interacts with MSP, while in POPC-POPG nanodiscs, such interactions are rare. We did not observe, however, any impact of those interactions on the probe fluorescence.
KW - CD
KW - ITC
KW - Liposomes
KW - MD simulations
KW - Nanodiscs
KW - TCSPC
KW - di-4-ANEPPDHQ
UR - http://www.scopus.com/inward/record.url?scp=85105724210&partnerID=8YFLogxK
U2 - 10.1016/j.bbamem.2021.183649
DO - 10.1016/j.bbamem.2021.183649
M3 - Article
SN - 0005-2736
VL - 1863
JO - Biochimica et Biophysica Acta: Biomembranes
JF - Biochimica et Biophysica Acta: Biomembranes
IS - 9
M1 - 183649
ER -