title: Jumping mode atomic force microscopy on grana membranes from spinach.
abstract: The thylakoid membrane system is a complex membrane system that organizes and reorganizes itself to provide plants optimal chemical energy from sunlight under different and varying environmental conditions. Grana membranes are part of this system and contain the light-driven water-splitting enzyme Photosystem II (PSII) and light-harvesting antenna complexes. Here, we present a direct visualization of PSII complexes within grana membranes from spinach. By means of jumping mode atomic force microscopy in liquid, minimal forces were applied between the scanning tip and membrane or protein, allowing complexes to be imaged with high detail. We observed four different packing arrangements of PSII complexes, which occur primarily as dimers: co-linear crystalline rows, nanometric domains of straight or skewed rows, and disordered domains. Upon storing surface-adhered membranes at low temperature prior to imaging, large-scale reorganizations of supercomplexes between PSII and light-harvesting complex II could be induced. The highest resolution images show the existence of membrane domains without obvious topography extending beyond supercomplexes. These observations illustrate the possibility for diffusion of proteins and smaller molecules within these densely packed membranes.
authors.affiliation: Faculty of Sciences, Department of Physics and Astronomy, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands.
authors.forename: Kinga
authors.initials: K
authors.lastname: Sznee
authors.forename: Jan P
authors.initials: JP
authors.lastname: Dekker
authors.forename: Remus T
authors.initials: RT
authors.lastname: Dame
authors.forename: Henny
authors.initials: H
authors.lastname: van Roon
authors.forename: Gijs J L
authors.initials: GJ
authors.lastname: Wuite
authors.forename: Raoul N
authors.initials: RN
authors.lastname: Frese
mesh_terms: D018625:Microscopy, Atomic Force / Q000379:methods*; D045332:Photosystem II Protein Complex / Q000648:ultrastructure; D010940:Plant Proteins / Q000648:ultrastructure; D018724:Spinacia oleracea / Q000648:ultrastructure*; D020524:Thylakoids / Q000648:ultrastructure*
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins