Structural Reorganization of a Synthetic Mimic of the Oxygen-Evolving Center in Multiple Redox Transitions Revealed by Electrochemical FTIR Spectra

2021 ◽  
pp. 9830-9839
Author(s):  
Mohan Wang ◽  
Ying Zhang ◽  
Changhui Chen ◽  
Chunxi Zhang ◽  
Junguang Jiang ◽  
...  
Keyword(s):  
Ftir Spectra ◽  
Structural Reorganization ◽  
Redox Transitions ◽  
Oxygen Evolving

Kinetics of manganese redox transitions in the oxygen-evolving apparatus of photosynthesis

1984 ◽  
Vol 767 (1) ◽  
pp. 176-179 ◽  
Author(s):  
Jan P. Dekker ◽  
Johan J. Plijter ◽  
Luberthus Ouwehand ◽  
Hans J. Van Gorkom
Keyword(s):  
Redox Transitions ◽  
Oxygen Evolving ◽  
Kinetics Of

Characterization of photosystem II with the atomic-force microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1146-1147
Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon
Keyword(s):  
Photosystem Ii ◽  
Atomic Force Microscope ◽  
Three Dimensional ◽  
Biologically Active ◽  
Atomic Force ◽  
Freeze Etching ◽  
Image Averaging ◽  
Oxygen Evolving ◽  
Averaging Techniques

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

2017 ◽  
Author(s):  
Massimiliano Galluzzi ◽  
Simone Bovio ◽  
Paolo Milani ◽  
Alessandro Podestà
Keyword(s):  
Ionic Liquid ◽  
Electrical Properties ◽  
Electric Fields ◽  
Relative Dielectric Constant ◽  
Ionic Mobility ◽  
Electric Properties ◽  
Bulk Liquid ◽  
Structural Reorganization ◽  
Surface Confinement ◽  
Insulator Layers

We report on the modification of the electric properties of the imidazolium-based [BMIM][NTf2] ionic liquid upon surface confinement in the sub-monolayer regime. Solid-like insulating nanostructures of [BMIM][NTf2] spontaneously form on a variety of insulating substrates, at odd with the liquid and conductive nature of the same substances in the bulk phase. A systematic spatially resolved investigation by atomic force microscopy of the morphological, mechanical and electrical properties of [BMIM][NTf2] nanostructures showed that this liquid substance rearranges into lamellar nanostructures with a high degree of vertical order and enhanced resistance to mechanical compressive stresses and very intense electric fields, denoting a solid-like character. The morphological and structural reorganization has a profound impact on the electric properties of supported [BMIM][NTf2] islands, which behave like insulator layers with a relative dielectric constant between 3 and 5, comparable to those of conventional ionic solids, and significantly smaller than those measured in the bulk ionic liquid. These results suggest that in the solid-like ordered domains confined either at surfaces or inside the pores of the nanoporous electrodes of photo-electrochemical devices, the ionic mobility and the overall electrical properties can be significantly perturbed with respect to the bulk liquid phase, which would likely influence the<br>performance of the devices.<br>

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