Role of the (H2O)n (n = 1–3) cluster in the HO2 + HO → 3O2 + H2O reaction: mechanistic and kinetic studies

2018 ◽  
Vol 20 (12) ◽  
pp. 8152-8165 ◽  
Author(s):  
Tianlei Zhang ◽  
Xinguang Lan ◽  
Zhangyu Qiao ◽  
Rui Wang ◽  
Xiaohu Yu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Single Molecule ◽  
Kinetic Studies ◽  
Water Dimer ◽  
Water Trimer ◽  
Catalytic Effects

Upon incorporation of the catalyst (H2O)n (n = 1–3) into the reaction HO2 + HO → H2O + 3O2, the catalytic effects of water, water dimer, and water trimer mainly arise from the contribution of a single molecule of water vapor.

The localized electron: magnetic properties

2018 ◽  
Author(s):  
Jean-Pierre Launay ◽  
Michel Verdaguer
Keyword(s):  
Single Molecule ◽  
Model Systems ◽  
Ferromagnetic Coupling ◽  
Single Chain ◽  
Single Molecule Magnets ◽  
Magnetic Systems ◽  
Orbital Interactions ◽  
Prussian Blue Analogues ◽  
Mononuclear Complexes

After preliminaries about electron properties, and definitions in magnetism, one treats the magnetism of mononuclear complexes, in particular spin cross-over, showing the role of cooperativity and the sensitivity to external perturbations. Orbital interactions and exchange interaction are explained in binuclear model systems, using orbital overlap and orthogonality concepts to explain antiferromagnetic or ferromagnetic coupling. The phenomenologically useful Spin Hamiltonian is defined. The concepts are then applied to extended molecular magnetic systems, leading to molecular magnetic materials of various dimensionalities exhibiting bulk ferro- or ferrimagnetism. An illustration is provided by Prussian Blue analogues. Magnetic anisotropy is introduced. It is shown that in some cases, a slow relaxation of magnetization arises and gives rise to appealing single-ion magnets, single-molecule magnets or single-chain magnets, a route to store information at the molecular level.

Role of Lys-226 in the Catalytic Mechanism ofBacillus StearothermophilusSerine HydroxymethyltransferaseCrystal Structure and Kinetic Studies†,‡

Biochemistry ◽  
2005 ◽  
Vol 44 (18) ◽  
pp. 6929-6937 ◽  
Author(s):  
Siddegowda Bhavani ◽  
V. Trivedi ◽  
V. R. Jala ◽  
H. S. Subramanya ◽  
Purnima Kaul ◽  
...  
Keyword(s):  
Catalytic Mechanism ◽  
Kinetic Studies

scholarly journals Roles of the C-Terminal Amino Acids of Non-Hexameric Helicases: Insights from Escherichia coli UvrD

2021 ◽  
Vol 22 (3) ◽  
pp. 1018
Author(s):  
Hiroaki Yokota
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Single Molecule ◽  
Underlying Mechanism ◽  
Amino Acid Sequences ◽  
E Coli ◽  
X Ray Crystallography ◽  
Terminal Amino

Helicases are nucleic acid-unwinding enzymes that are involved in the maintenance of genome integrity. Several parts of the amino acid sequences of helicases are very similar, and these quite well-conserved amino acid sequences are termed “helicase motifs”. Previous studies by X-ray crystallography and single-molecule measurements have suggested a common underlying mechanism for their function. These studies indicate the role of the helicase motifs in unwinding nucleic acids. In contrast, the sequence and length of the C-terminal amino acids of helicases are highly variable. In this paper, I review past and recent studies that proposed helicase mechanisms and studies that investigated the roles of the C-terminal amino acids on helicase and dimerization activities, primarily on the non-hexermeric Escherichia coli (E. coli) UvrD helicase. Then, I center on my recent study of single-molecule direct visualization of a UvrD mutant lacking the C-terminal 40 amino acids (UvrDΔ40C) used in studies proposing the monomer helicase model. The study demonstrated that multiple UvrDΔ40C molecules jointly participated in DNA unwinding, presumably by forming an oligomer. Thus, the single-molecule observation addressed how the C-terminal amino acids affect the number of helicases bound to DNA, oligomerization, and unwinding activity, which can be applied to other helicases.

scholarly journals Role of the ribosomal protein L27 revealed by single-molecule FRET study

2012 ◽  
Vol 21 (11) ◽  
pp. 1696-1704 ◽  
Author(s):  
Yuhong Wang ◽  
Ming Xiao
Keyword(s):  
Ribosomal Protein ◽  
Single Molecule ◽  
Single Molecule Fret

Probing the Role of Tyr 64 ofTreponema denticolaCystalysin by Site-Directed Mutagenesis and Kinetic Studies†

Biochemistry ◽  
2005 ◽  
Vol 44 (42) ◽  
pp. 13970-13980 ◽  
Author(s):  
Barbara Cellini ◽  
Mariarita Bertoldi ◽  
Riccardo Montioli ◽  
Carla Borri Voltattorni
Keyword(s):  
Kinetic Studies ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis

Role of water vapor in oxidative decomposition of calcium sulfide

Fuel ◽  
2004 ◽  
Vol 83 (6) ◽  
pp. 671-677 ◽  
Author(s):  
Shengji Wu ◽  
Md.Azhar Uddin ◽  
Shinsuke Nagamine ◽  
Eiji Sasaoka
Keyword(s):  
Water Vapor ◽  
Calcium Sulfide ◽  
Oxidative Decomposition

scholarly journals Receptor compaction and GTPase rearrangement drive SRP-mediated cotranslational protein translocation into the ER

2021 ◽  
Vol 7 (21) ◽  
pp. eabg0942
Author(s):  
Jae Ho Lee ◽  
Ahmad Jomaa ◽  
SangYoon Chung ◽  
Yu-Hsien Hwang Fu ◽  
Ruilin Qian ◽  
...  
Keyword(s):  
Single Molecule ◽  
Protein Translocation ◽  
Molecular Model ◽  
Genetic Diseases ◽  
Signal Recognition Particle ◽  
Biological Regulation ◽  
Single Molecule Studies ◽  
Guanosine Triphosphatase ◽  
Gtpase Cycle

The conserved signal recognition particle (SRP) cotranslationally delivers ~30% of the proteome to the eukaryotic endoplasmic reticulum (ER). The molecular mechanism by which eukaryotic SRP transitions from cargo recognition in the cytosol to protein translocation at the ER is not understood. Here, structural, biochemical, and single-molecule studies show that this transition requires multiple sequential conformational rearrangements in the targeting complex initiated by guanosine triphosphatase (GTPase)–driven compaction of the SRP receptor (SR). Disruption of these rearrangements, particularly in mutant SRP54G226E linked to severe congenital neutropenia, uncouples the SRP/SR GTPase cycle from protein translocation. Structures of targeting intermediates reveal the molecular basis of early SRP-SR recognition and emphasize the role of eukaryote-specific elements in regulating targeting. Our results provide a molecular model for the structural and functional transitions of SRP throughout the targeting cycle and show that these transitions provide important points for biological regulation that can be perturbed in genetic diseases.

Extreme Surface Winds During Landfalling Atmospheric Rivers: The Modulating Role of Near-Surface Stability

2021 ◽  
Author(s):  
Terence J. Pagano ◽  
Duane E. Waliser ◽  
Bin Guan ◽  
Hengchun Ye ◽  
F. Martin Ralph ◽  
...  
Keyword(s):  
Water Vapor ◽  
Static Stability ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Surface Winds ◽  
Near Surface ◽  
Extreme Surface ◽  
Atmospheric Rivers ◽  
Explained Variance

AbstractAtmospheric rivers (ARs) are long and narrow regions of strong horizontal water vapor transport. Upon landfall, ARs are typically associated with heavy precipitation and strong surface winds. A quantitative understanding of the atmospheric conditions that favor extreme surface winds during ARs has implications for anticipating and managing various impacts associated with these potentially hazardous events. Here, a global AR database (1999–2014) with relevant information from MERRA-2 reanalysis, QuikSCAT and AIRS satellite observations are used to better understand and quantify the role of near-surface static stability in modulating surface winds during landfalling ARs. The temperature difference between the surface and 1 km MSL (ΔT; used here as a proxy for near-surface static stability), and integrated water vapor transport (IVT) are analyzed to quantify their relationships to surface winds using bivariate linear regression. In four regions where AR landfalls are common, the MERRA-2-based results indicate that IVT accounts for 22-38% of the variance in surface wind speed. Combining ΔT with IVT increases the explained variance to 36-52%. Substitution of QuikSCAT surface winds and AIRS ΔT in place of the MERRA-2 data largely preserves this relationship (e.g., 44% compared to 52% explained variance for USA West Coast). Use of an alternate static stability measure–the bulk Richardson number–yields a similar explained variance (47%). Lastly, AR cases within the top and bottom 25% of near-surface static stability indicate that extreme surface winds (gale or higher) are more likely to occur in unstable conditions (5.3%/14.7% during weak/strong IVT) than in stable conditions (0.58%/6.15%).

The Role of Binary and Ion Nucleation of Sulfuric Acid and Water Vapor in the Dynamics of Sulfate Aerosol Formation in the Atmosphere

2021 ◽  
pp. 53-60
Author(s):  
A. E. Aloyan ◽  
◽  
A. N. Yermakov ◽  
V. O. Arutyunyan ◽  
◽  
...  
Keyword(s):  
Water Vapor ◽  
Sulfuric Acid ◽  
Three Dimensional ◽  
Ionization Rate ◽  
Sulfate Aerosol ◽  
Aerosol Formation ◽  
Three Dimensional Model ◽  
Aerosol Composition ◽  
Transport And Transformation

The results of one-dimensional calculations of the height profiles of nucleated sulfate aerosol particles for the northern mid-latitudes and tropics in winter are presented. Numerical calculations were performed using a three-dimensional model of the transport and transformation of multicompo- nent gas and aerosol substances in the atmosphere, incorporating photochemistry, nucleation involving neutral molecules and ions, as well as condensation/evaporation and coagulation. It is found that the resulting dynamics of the formation of aerosol particle nuclei is not a simple sum of ion and binary (water vapor/sulfuric acid) nucleation rates. This dynamics is determined by the ratio of critical radii of nucleated particles due to binary and ion nucleation of these substances (rcr_bin and rcr_ion) depending on temperature, relative humidity, and ionization rate. This should be taken into account in modeling the gas and aerosol composition of the atmosphere and comparing calculated and observed data.

scholarly journals Upper Tropospheric Water Vapor Transport from Indian to Sahelian Regions

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 403 ◽  
Author(s):  
Abdoulaye Sy ◽  
Bouya Diop ◽  
Joël Van Baelen ◽  
Christophe Duroure ◽  
Yahya Gour ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Monsoon ◽  
Water Vapor Transport ◽  
Substantial Part ◽  
Monsoon Region ◽  
Direct Role ◽  
Air Masses ◽  
Upper Troposphere ◽  
Tropical Easterly Jet

We present a study of upper tropospheric westward transport of air masses coming from the Indian monsoon zone over the period 1998–2008. The objective is to characterize upper tropospheric transport of water vapor from the Indian to Sahelian regions, and to improve the understanding of the dynamical mechanisms that govern water vapor variations in West Africa and the interconnections between India and the Sahel, focusing on the direct role of the Indian monsoon region on Sahel tropospheric water vapor and precipitation. The calculations of forward trajectories with LACYTRAJ (LACY TRAJectory code) and humidity fluxes show that a substantial part (40 to 70% at 300 hPa) of trajectories coming from the upper troposphere of the monsoon region crossed the Sahelian region in a few days (3–14 days), and water vapor fluxes connecting these two regions are established when the Indian monsoon begins at latitudes higher than 15° N in its south–north migration. The intensity and orientation of water vapor fluxes are related to the tropical easterly jet, but they are from the east above the high convection zones. Between 1998 and 2008, these fluxes between the 500–300 hPa pressure levels are associated with precipitation in Sahel only if they are from the east and with an intensity exceeding 8 kg·(m·s)−1.

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