title: Self-assembling peptide detergents stabilize isolated photosystem I on a dry surface for an extended time.
abstract: We used a class of designed peptide detergents to stabilize photosystem I (PS-I) upon extended drying under N2 on a gold-coated-Ni-NTA glass surface. PS-I is a chlorophyll-containing membrane protein complex that is the primary reducer of ferredoxin and the electron acceptor of plastocyanin. We isolated the complex from the thylakoids of spinach chloroplasts using a chemical detergent. The chlorophyll molecules associated with the PS-I complex provide an intrinsic steady-state emission spectrum between 650 and 800 nm at -196.15 degrees C that reflects the organization of the pigment-protein interactions. In the absence of detergents, a large blue shift of the fluorescence maxima from approximately 735 nm to approximately 685 nm indicates a disruption in light-harvesting subunit organization, thus revealing chlorophyll-protein interactions. The commonly used membrane protein-stabilizing detergents, N-dodecyl-beta-D-maltoside and N-octyl-beta-D-glucoside, only partially stabilized the approximately 735-nm complex with approximately 685-nm spectroscopic shift. However, prior to drying, addition of the peptide detergent acetyl-AAAAAAK at increasing concentration significantly stabilized the PS-I complex. Moreover, in the presence of acetyl-AAAAAAK, the PS-I complex is stable in a dried form at room temperature for at least 3 wk. Another peptide detergent, acetyl-VVVVVVD, also stabilized the complex but to a lesser extent. These observations suggest that the peptide detergents may effectively stabilize membrane proteins in the solid-state. These designed peptide detergents may facilitate the study of diverse types of membrane proteins.
authors.affiliation: Center for Biomedical Engineering NE47-379, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kiley
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Zhao
authors.forename: Michael
authors.initials: M
authors.lastname: Vaughn
authors.forename: Marc A
authors.initials: MA
authors.lastname: Baldo
authors.forename: Barry D
authors.initials: BD
authors.lastname: Bruce
authors.forename: Shuguang
authors.initials: S
authors.lastname: Zhang
mesh_terms: D003902:Detergents / Q000494:pharmacology*; D004123:Dimethylamines / Q000494:pharmacology; D005960:Glucosides / Q000494:pharmacology; D008320:Maltose / Q000031:analogs & derivatives / Q000494:pharmacology; D017830:Octoxynol / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000187:drug effects; D013499:Surface Properties
chemical_list: D003902:Detergents; D004123:Dimethylamines; D005960:Glucosides; D009842:Oligopeptides; D045331:Photosystem I Protein Complex; C508692:acetyl-alanyl-alanyl-alanyl-alanyl-alanyl-alanyl-lysine; C508693:acetyl-valyl-valyl-valyl-valyl-valyl-valyl-aspartic acid; C411362:dodecyl maltopyranoside; C018619:octyl-beta-D-glucoside; C014518:dodecyldimethylamine oxide; D008320:Maltose; D017830:Octoxynol