(646g) Morphological Characterization of Detergent-Mediated Photosystem I (PS I)-Proteoliposome Formation

In-vitro functional and structural studies of membrane proteins rely on suitable choice of synthetic membrane mimics (e.g., detergents and liposomes) that maintain the protein function¹. To this end, we investigate the  interaction of two nonionic detergents n-dodecyl-β-D-maltoside (DDM) and Triton X-100 (TX-100) with two phospholipids, namely  DPhPC (1,2-diphytanoyl-sn-glycero-3-phosphocholine) and DPPG (1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol)), that commonly constitute the natural thylakoid membrane housing of Photosystem I (PS I), the photosynthetic protein complex. We use optical density and dynamic light scattering (DLS) measurements in conjunction with advanced transmission electron microscopy (TEM) techniques (namely, negative staining and cryo-TEM) to study the detailed mechanistic picture behind processes that drive membrane bilayers to undergo complex structural arrangements during different stages of detergent-mediated solublization.. Specifically, negative staining and cryo-TEM images are used to investigate the solution-phase morphological arrangement of PS I-proteoliposomes. These characterizations provide a fundamental understanding of the role of detergent-mediated protein reconstitution in driving unidirectional arrangements of PS I trimeric complexes within lipid vesicles during PS I-lipid interactions in colloidal solutions. In turn, the aforementioned studies provide valuable insight into mimicking the naturally occurring protein-phospholipid interactions in cell membranes. In future, these bio-mimetic systems shall facilitate easy incorporation of membrane protein-lipid complexes into novel bio-hybrid devices.

1. Dewald A.H., Hodges J.C., Columbus L. Biophys J. 2011; 100(9): 2131–2140