scholarly journals Chaperone-Mediated Sec61 Channel Gating during ER Import of Small Precursor Proteins Overcomes Sec61 Inhibitor-Reinforced Energy Barrier

Cell Reports ◽  
2018 ◽  
Vol 23 (5) ◽  
pp. 1373-1386 ◽  
Author(s):  
Sarah Haßdenteufel ◽  
Nicholas Johnson ◽  
Adrienne W. Paton ◽  
James C. Paton ◽  
Stephen High ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Channel Gating ◽  
Precursor Proteins ◽  
Sec61 Channel

scholarly journals The signal peptide plus a cluster of positive charges in prion protein dictate chaperone-mediated Sec61 channel gating

Biology Open ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. bio040691 ◽  
Author(s):  
Anke Ziska ◽  
Jörg Tatzelt ◽  
Johanna Dudek ◽  
Adrienne W. Paton ◽  
James C. Paton ◽  
...  
Keyword(s):  
Prion Protein ◽  
Signal Peptide ◽  
Channel Gating ◽  
Sec61 Channel

Structure of contact sites between the outer and inner mitochondrial membranes investigated by HVEM tomography

1996 ◽  
Vol 54 ◽  
pp. 966-967
Author(s):  
C.A. Mannella ◽  
K.F. Buttle ◽  
K.A. O‘Farrell ◽  
A. Leith ◽  
M. Marko
Keyword(s):  
Liver Mitochondrion ◽  
Adenine Nucleotide ◽  
Protein Complexes ◽  
Mitochondrial Membranes ◽  
Electron Microscopic ◽  
Contact Sites ◽  
Transmission Electron ◽  
Precursor Proteins ◽  
Membrane Contacts ◽  
And Function

Early transmission electron microscopy of plastic-embedded, thin-sectioned mitochondria indicated that there are numerous junctions between the outer and inner membranes of this organelle. More recent studies have suggested that the mitochondrial membrane contacts may be the site of protein complexes engaged in specialized functions, e.g., import of mitochondrial precursor proteins, adenine nucleotide channeling, and even intermembrane signalling. It has been suggested that the intermembrane contacts may be sites of membrane fusion involving non-bilayer lipid domains in the two membranes. However, despite growing interest in the nature and function of intramitochondrial contact sites, little is known about their structure.We are using electron microscopic tomography with the Albany HVEM to determine the internal organization of mitochondria. We have reconstructed a 0.6-μm section through an isolated, plasticembedded rat-liver mitochondrion by combining 123 projections collected by tilting (+/- 70°) around two perpendicular tilt axes. The resulting 3-D image has confirmed the basic inner-membrane organization inferred from lower-resolution reconstructions obtained from single-axis tomography.

Exchange-Biasing in a Dinuclear Dysprosium(III) Single-Molecule Magnet with a Large Energy Barrier for Magnetization Reversal

2019 ◽  
Author(s):  
Tian Han ◽  
Marcus J. Giansiracusa ◽  
Zi-Han Li ◽  
You-Song Ding ◽  
Nicholas F. Chilton ◽  
...  
Keyword(s):  
Single Molecule ◽  
Magnetization Reversal ◽  
Energy Barrier ◽  
Magnetic Hysteresis ◽  
Large Energy ◽  
Magnetic Studies ◽  
Bridging Ligands ◽  
Single Molecule Magnet ◽  
Exchange Biasing

A dichlorido-bridged dinuclear dysprosium(III) single-molecule magnet [Dy<sub>2</sub>L<sub>2</sub>(<i>µ</i>-Cl)<sub>2</sub>(THF)<sub>2</sub>] has been made using a diamine-bis(phenolate) ligand, H<sub>2</sub>L. Magnetic studies show an energy barrier for magnetization reversal (<i>U</i><sub>eff</sub>) around 1000 K. Exchange-biasing effect is clearly seen in magnetic hysteresis with steps up to 4 K. <i>Ab</i> initio calculations exclude the possibility of pure dipolar origin of this effect leading to the conclusion that super-exchange <i>via</i> the chloride bridging ligands is important.

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

AMPA and Kainate Receptors

2020 ◽  
Author(s):  
G. Brent Dawe ◽  
Patricia M. G. E. Brown ◽  
Derek Bowie
Keyword(s):  
Ion Channel ◽  
Glutamate Receptor ◽  
Single Channel ◽  
Channel Gating ◽  
Regulatory Proteins ◽  
Kainate Receptors ◽  
Mammalian Brain ◽  
Receptor Field ◽  
Neuronal Excitation ◽  
Ion Channel Proteins

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate-type glutamate receptors (AMPARs and KARs) are dynamic ion channel proteins that govern neuronal excitation and signal transduction in the mammalian brain. The four AMPAR and five KAR subunits can heteromerize with other subfamily members to create several combinations of tetrameric channels with unique physiological and pharmacological properties. While both receptor classes are noted for their rapid, millisecond-scale channel gating in response to agonist binding, the intricate structural rearrangements underlying their function have only recently been elucidated. This chapter begins with a review of AMPAR and KAR nomenclature, topology, and rules of assembly. Subsequently, receptor gating properties are outlined for both single-channel and synaptic contexts. The structural biology of AMPAR and KAR proteins is also discussed at length, with particular focus on the ligand-binding domain, where allosteric regulation and alternative splicing work together to dictate gating behavior. Toward the end of the chapter there is an overview of several classes of auxiliary subunits, notably transmembrane AMPAR regulatory proteins and Neto proteins, which enhance native AMPAR and KAR expression and channel gating, respectively. Whether bringing an ion channel novice up to speed with glutamate receptor theory and terminology or providing a refresher for more seasoned biophysicists, there is much to appreciate in this summation of work from the glutamate receptor field.

Transfer of particles over a randomly fluctuating energy barrier

1989 ◽  
Vol 128 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Piotr Warszynski ◽  
Jan Czarnecki
Keyword(s):  
Energy Barrier

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

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