The widespread interest in phase recognition of lipid membranes has led to the use of different optical techniques to enable differentiation of healthy and not fully functional cells. In this work, we show how the combination of different (non)linear optical methods such as one-photon absorption (OPA), two-photon absorption (TPA), and second harmonic generation (SHG) as well as the study of the fluorescence decay time leads to an enhanced screening of membrane phases using a fluorescent 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiD) probe. In the current study we consider the pure liquid disordered phases of DOPC (dioleoyl- sn-glycero-3-phosphocholine, room temperature) and DPPC (1,2-dipalmitoyl- sn-glycero-3-phosphocholine, 323 K), the solid gel phase of DPPC (298 K), and the liquid ordered phase of a 2:1 binary mixture of sphingomyelin and cholesterol. By means of extensive hybrid quantum mechanics-molecular mechanics calculations and based upon the (non)linear absorption of the embedded probes, it is found that DiD can be used to identify the lipid bilayer phase. The joint TPA and SHG as well as fluorescence analyses qualifies DiD as a versatile probe for phase recognition. In particular, the SHG data obtained by means of hyper-Rayleigh scattering and by electric field induced second harmonic generation reveal differences in polarization of the probe in the different environments. The TPA results finally confirm the particular location of the probe in between the polar headgroup region of the 2:1 SM:Chol mixture in the liquid ordered phase.

Biomedical Research Institute Hasselt University B 3590 Diepenbeek Belgium

Centre of Advanced Technologies and Materials Faculty of Science Palacký University tř 17 listopadu 12 771 46 Olomouc Czech Republic

Centre of New Technologies University of Warsaw Banacha 2C 02 097 Warsaw Poland

Department of Theoretical Chemistry and Biology School of Engineering Sciences in Chemistry Biotechnology and Health Royal Institute of Technology SE 10691 Stockholm Sweden

Faculty of Pharmacy UMR 1248 INSERM Limoges University 2 rue du Docteur Marcland 87025 Limoges Cedex France

LCSN EA1069 Faculty of Pharmacy Limoges University 2 rue du Dr Marcland 87025 Limoges Cedex France

Citace poskytuje Crossref.org

Influence of Membrane Phase on the Optical Properties of DPH