title: Effect of surfactants on apparent oxygen consumption of photosystem I isolated from Arthrospira platensis.
abstract: Surfactants play a significant role in solubilization of photosystem I (PSI) in vitro. Triton X-100 (TX), n-Dodecyl-β-D-maltoside (DDM), and sodium dodecyl sulfate (SDS) were employed to solubilize PSI particles in MES buffer to compare the effect of surfactant and its dosage on the apparent oxygen consumption rate of PSI. Through a combined assessment of sucrose density gradient centrifugation, Native PAGE and 77 K fluorescence with the apparent oxygen consumption, the nature of the enhancement of the apparent oxygen consumption activity of PSI by surfactants has been analyzed. Aggregated PSI particles can be dispersed by surfactant molecules into micelles, and the apparent oxygen consumption rate is higher for surfactant-solubilized PSI than for integral PSI particles. For DDM, PSI particles are solubilized mostly as the integral trimeric form. For TX, PSI particles are solubilized as incomplete trimeric and some monomeric forms. For the much harsher surfactant, SDS, PSI particles are completely solubilized as monomeric and its subunit forms. The enhancement of the oxygen consumption rate cannot be explained only by the effects of surfactant on the equilibrium between monomeric and trimeric forms of solubililized PSI. Care must be taken when the electron transfer activity of PSI is evaluated by methods based on oxygen consumption because the apparent oxygen consumption rate is influenced by uncoupled chlorophyll (Chl) from PSI, i.e., the larger the amount of uncoupled Chl, the higher the rate of apparent oxygen consumption. 77 K fluorescence spectra can be used to ensure that there is no uncoupled Chl present in the system. In order to eliminate the effect of trace uncoupled Chl, an efficient physical quencher of (1)O2, such as 1 mM NaN3, may be added into the mixture.
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, 266580, Shandong, China, daoyong@upc.edu.cn.
authors.forename: Daoyong
authors.initials: D
authors.lastname: Yu
authors.forename: Guihong
authors.initials: G
authors.lastname: Huang
authors.forename: Fengxi
authors.initials: F
authors.lastname: Xu
authors.forename: Baosheng
authors.initials: B
authors.lastname: Ge
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.forename: Hai
authors.initials: H
authors.lastname: Xu
authors.forename: Fang
authors.initials: F
authors.lastname: Huang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002734:Chlorophyll; D004735:Energy Transfer; D010100:Oxygen / Q000737:chemistry*; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D012995:Solubility; D053545:Spirulina / Q000378:metabolism*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D045331:Photosystem I Protein Complex; D013501:Surface-Active Agents; D002734:Chlorophyll; D010100:Oxygen