Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

39-POS Board 20 Study of Lipid - Light Harvesting Complex II (LHC II) Model Membranes Using Nanoscale Infrared Spectroscopy

Andrzej J. Kulik 1 , Wieslaw I. Gruszecki 2 , Giovanni Dietler 1 . 1 EPFL, Lausanne, Switzerland, 2 UMCS, Lublin, Poland.

LHCII proteins are the most abundant trans-membrane protein on Earth, responsible for light harvesting in the photosynthetic apparatus of plants. Two types of pigment-protein complexes were analyzed: LHCII extracted from spinach leaves grown in dark condition and LHCII-HL extracted from pre-illuminated spinach leaves. Both proteins were embedded into artificial bi- layer lipid membranes. LHCII proteins interact to each-other forming characteristic pillars, contrary to LHCII-HL which are phosphorylated, and were randomly scattered. We applied here nanoscale Infrared (IR) Spectrometer (nanoIR) which uses tunable pulsed IR laser for excitation and AFM tip for detection. When particular wavelength is absorbed, sample is heated-up and expands. Thermal expansion of the sample is ‘kicking’ AFM cantilever, vibrating at resonant frequency to increase sensitivity of the method. Amplitude of vibrations is proportional to local IR absorption. Tuning the laser one can obtain IR absorption spectrum with spatial resolution down to 10 nm. Alternatively, one can get functional image of the absorption at single wavelength. It is very useful to study inhomogeneous thin samples. Using nanoIR method we could directly observe and confirm formation of the pillars (increasing efficiency of photosynthesis) in samples containing LHCII and random distribution of LHCII- HL, extracted from the leaves exposed to light. Using phosphorylation of LHCII complexes, nature is adjusting efficiency of photosynthesis to light conditions. 1. Janik E. et al., PLANT CELL, 25, 6, 2155-2170 (2013) 2. Gruszecki W.I. et al. NANOSCALE, 7, 35, 14659-14662 (2015)

107