WATER-NETWORK MEDIATED, ELECTRON INDUCED PROTON TRANSFER IN ANIONIC [C5H5N·(H2O)n]− CLUSTERS: SIZE DEPENDENT FORMATION OF THE PYRIDINIUM RADICAL FOR n ≥ 3

2015 ◽  
Author(s):  
Andrew DeBlase ◽  
Mark Johnson ◽  
Kenneth Jordan ◽  
Kaye Archer ◽  
Gary Weddle
Keyword(s):  
Proton Transfer ◽  
Water Network ◽  
Size Dependent

Introducing Water‐Network‐Assisted Proton Transfer for Boosted Electrocatalytic Hydrogen Evolution with Cobalt Corrole

2021 ◽  
Author(s):  
Xialiang Li ◽  
Bin Lv ◽  
Xue-Peng Zhang ◽  
Xiaotong Jin ◽  
Kai Guo ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Hydrogen Evolution ◽  
Water Network

scholarly journals Water network-mediated, electron-induced proton transfer in [C5H5N ⋅ (H2O)n]− clusters

2015 ◽  
Vol 143 (14) ◽  
pp. 144305 ◽  
Author(s):  
Andrew F. DeBlase ◽  
Conrad T. Wolke ◽  
Gary H. Weddle ◽  
Kaye A. Archer ◽  
Kenneth D. Jordan ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Water Network

scholarly journals Active-site solvent replenishment observed during human carbonic anhydrase II catalysis

IUCrJ ◽  
2018 ◽  
Vol 5 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Jin Kyun Kim ◽  
Carrie L. Lomelino ◽  
Balendu Sankara Avvaru ◽  
Brian P. Mahon ◽  
Robert McKenna ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Proton Transfer ◽  
Active Site ◽  
Water Reservoir ◽  
Bound Water ◽  
Nucleophilic Attack ◽  
Carbonic Anhydrase Ii ◽  
Intermediate Water ◽  
Water Network ◽  
Human Carbonic Anhydrase

Human carbonic anhydrase II (hCA II) is a zinc metalloenzyme that catalyzes the reversible hydration/dehydration of CO2/HCO3 −. Although hCA II has been extensively studied to investigate the proton-transfer process that occurs in the active site, its underlying mechanism is still not fully understood. Here, ultrahigh-resolution crystallographic structures of hCA II cryocooled under CO2 pressures of 7.0 and 2.5 atm are presented. The structures reveal new intermediate solvent states of hCA II that provide crystallographic snapshots during the restoration of the proton-transfer water network in the active site. Specifically, a new intermediate water (WI′) is observed next to the previously observed intermediate water WI, and they are both stabilized by the five water molecules at the entrance to the active site (the entrance conduit). Based on these structures, a water network-restructuring mechanism is proposed, which takes place at the active site after the nucleophilic attack of OH− on CO2. This mechanism explains how the zinc-bound water (WZn) and W1 are replenished, which are directly responsible for the reconnection of the His64-mediated proton-transfer water network. This study provides the first `physical' glimpse of how a water reservoir flows into the hCA II active site during its catalytic activity.

Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

Transfer Technique for Electron Microscopy of Membrance Filter Samples

1974 ◽  
Vol 32 ◽  
pp. 554-555
Author(s):  
Lawrence W. Ortiz ◽  
Bonnie L. Isom
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Pore Size ◽  
Membrane Filters ◽  
Size Dependent

A procedure is described for the quantitative transfer of fibers and particulates collected on membrane filters to electron microscope (EM) grids. Various Millipore MF filters (Millipore AA, HA, GS, and VM; 0.8, 0.45, 0.22 and 0.05 μm mean pore size) have been used with success. Observed particle losses have not been size dependent and have not exceeded 10%. With fibers (glass or asbestos) as the collected media this observed loss is approximately 3%.

Spindle scaling mechanisms

2020 ◽  
Vol 64 (2) ◽  
pp. 383-396
Author(s):  
Lara K. Krüger ◽  
Phong T. Tran
Keyword(s):  
Cell Size ◽  
Spindle Assembly ◽  
Dependent Manner ◽  
Post Translational Modification ◽  
Size Dependent ◽  
A Cell ◽  
Chromosome Separation ◽  
Spindle Elongation ◽  
Protein Gradients ◽  
Spindle Structure

Abstract The mitotic spindle robustly scales with cell size in a plethora of different organisms. During development and throughout evolution, the spindle adjusts to cell size in metazoans and yeast in order to ensure faithful chromosome separation. Spindle adjustment to cell size occurs by the scaling of spindle length, spindle shape and the velocity of spindle assembly and elongation. Different mechanisms, depending on spindle structure and organism, account for these scaling relationships. The limited availability of critical spindle components, protein gradients, sequestration of spindle components, or post-translational modification and differential expression levels have been implicated in the regulation of spindle length and the spindle assembly/elongation velocity in a cell size-dependent manner. In this review, we will discuss the phenomenon and mechanisms of spindle length, spindle shape and spindle elongation velocity scaling with cell size.

Sign in / Sign up

Export Citation Format

Share Document