scholarly journals Isotope separation by chemical exchange process: Final technical report

1987 ◽  
Author(s):  
A Schneider
Keyword(s):  
Chemical Exchange ◽  
Isotope Separation ◽  
Exchange Process ◽  
Technical Report

scholarly journals Research on chemical exchange process of boron isotope separation

2011 ◽  
Vol 18 ◽  
pp. 151-156 ◽  
Author(s):  
Yiping Huang ◽  
Shuang Cheng ◽  
Jiao Xu ◽  
Weijiang Zhang
Keyword(s):  
Chemical Exchange ◽  
Isotope Separation ◽  
Exchange Process ◽  
Boron Isotope

scholarly journals Study of the coordination of quinuclidine to a chiral zinc phthalocyanine dimer

2016 ◽  
Vol 20 (08n11) ◽  
pp. 1224-1232 ◽  
Author(s):  
Nelson Giménez-Agulló ◽  
Gemma Aragay ◽  
José Ramón Galán-Mascarós ◽  
Pablo Ballester
Keyword(s):  
Chemical Exchange ◽  
Variable Temperature ◽  
Exchange Process ◽  
Zinc Phthalocyanine ◽  
Hydrogen Atoms ◽  
Dimerization Constant ◽  
H Nmr ◽  
Dimerization Process ◽  
Nmr Titrations ◽  
Millimolar Concentration

We attempted the calculation of an accurate equilibrium constant for the dimerization process of enantiomerically pure Zn-1 using UV-vis dilution experiments. At millimolar concentration Zn-1 is involved in a chemical exchange process between its monomeric and dimeric state that is slow on the 1H NMR timescale. We performed variable-temperature 1H NMR experiments in CDCl3 solution to determine the dimerization constant value at different temperatures and performed a van’t Hoff plot to derive the thermodynamic parameters of the process. The calculated thermodynamic data revealed that the dimerization process is entropy-driven and enthalpically opposed. We also probed the coordination of quinuclidine, 1-azabicyclo[2.2.2]octane, 2, to the Zn-1 using UV-vis and 1H NMR titrations in CDCl3 solution. At micromolar concentration the Zn-1 exclusively exists in solution as a monomer and forms a simple 1:1, [Formula: see text], complex with quinuclidine having a stability constant of [Formula: see text]([Formula: see text]) [Formula: see text] 106 M[Formula: see text]. On the other hand, the 1H NMR titrations carried out at 298 K and at millimolar concentration showed that Zn-1 was present in solution as the dimer and formed 1:2, [Formula: see text], and 2:2, [Formula: see text] complexes by coordination to 2. In addition, the 1:1 complex, [Formula: see text] showed a reduced dimerization constant compared to the uncoordinated parent monomer Zn-1. At high quinuclidine concentration, the 1:1 complex, [Formula: see text], derived from the coordinated dimer dissociation was also detected. The 1H NMR spectra of the titrations displayed separate signals for some hydrogen atoms of the Zn-phthalocyanine in each one of the four species. Remarkably, the chemical exchange processes involving free and bound quinuclidine in the monomeric and dimeric complexes showed different kinetics on the NMR timescale.

Design of a Mixer Settler Plant for Isotope Separation by Chemical Exchange

1995 ◽  
Vol 110 (2) ◽  
pp. 220-227 ◽  
Author(s):  
David A. White ◽  
Fathurrachman
Keyword(s):  
Chemical Exchange ◽  
Isotope Separation

The A39G FF domain folds on a volcano-shaped free energy surface via separate pathways

2021 ◽  
Vol 118 (46) ◽  
pp. e2115113118
Author(s):  
Ved P. Tiwari ◽  
Yuki Toyama ◽  
Debajyoti De ◽  
Lewis E. Kay ◽  
Pramodh Vallurupalli
Keyword(s):  
Free Energy ◽  
Chemical Exchange ◽  
Exchange Process ◽  
Conformational Dynamics ◽  
Chemical Exchange Saturation Transfer ◽  
Folding Kinetics ◽  
Free Energy Surface ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Energy Surfaces

Conformational dynamics play critical roles in protein folding, misfolding, function, misfunction, and aggregation. While detecting and studying the different conformational states populated by protein molecules on their free energy surfaces (FESs) remain a challenge, NMR spectroscopy has emerged as an invaluable experimental tool to explore the FES of a protein, as conformational dynamics can be probed at atomic resolution over a wide range of timescales. Here, we use chemical exchange saturation transfer (CEST) to detect “invisible” minor states on the energy landscape of the A39G mutant FF domain that exhibited “two-state” folding kinetics in traditional experiments. Although CEST has mostly been limited to studies of processes with rates between ∼5 to 300 s−1 involving sparse states with populations as low as ∼1%, we show that the line broadening that is often associated with minor state dips in CEST profiles can be exploited to inform on additional conformers, with lifetimes an order of magnitude shorter and populations close to 10-fold smaller than what typically is characterized. Our analysis of CEST profiles that exploits the minor state linewidths of the 71-residue A39G FF domain establishes a folding mechanism that can be described in terms of a four-state exchange process between interconverting states spanning over two orders of magnitude in timescale from ∼100 to ∼15,000 μs. A similar folding scheme is established for the wild-type domain as well. The study shows that the folding of this small domain proceeds through a pair of sparse, partially structured intermediates via two discrete pathways on a volcano-shaped FES.

Isotope Separation by Chemical Exchange: A Computer Simulation

1991 ◽  
Vol 96 (3) ◽  
pp. 337-345 ◽  
Author(s):  
Heinrich R. Obermoller ◽  
David A. White
Keyword(s):  
Computer Simulation ◽  
Chemical Exchange ◽  
Isotope Separation

Modeling a Chemical Exchange Process for the 13C Isotope Enrichment

2015 ◽  
Vol 772 ◽  
pp. 27-32 ◽  
Author(s):  
Zoltan Kovendi ◽  
Vlad Mureşan ◽  
Mihail Abrudean ◽  
Iulia Clitan ◽  
Mihaela Ligia Ungureşan ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Process Modeling ◽  
Process Simulation ◽  
Control Structure ◽  
Chemical Exchange ◽  
Exchange Process ◽  
Open Loop ◽  
Isotope Enrichment ◽  
Isotope Concentration ◽  
Made In

This paper presents a solution for modeling a chemical exchange process carbon dioxide (CO2) – carbamate for the 13C isotope enrichment. A big difficulty in the process modeling procedure is the fact that it is a non-linear one. In order to solve this problem, an original modeling solution that permits the process simulation for the entire domain of the values of the input signal is used. The process modeling is made in order to include it in an automatic control structure of the 13C isotope concentration. Some relevant simulations of the open loop process are presented, both in the case when the disturbances do not occur and the case when they occur in the system.

A Chemical Exchange System for Isotopic Feed to a Nitrogen and Oxygen Isotope Separation Plant

1989 ◽  
Vol 24 (5-6) ◽  
pp. 415-428 ◽  
Author(s):  
T. R. Mills ◽  
M. G. Garcia ◽  
R. C. Vandervoort ◽  
B. B. McInteer
Keyword(s):  
Oxygen Isotope ◽  
Chemical Exchange ◽  
Isotope Separation ◽  
Exchange System ◽  
Separation Plant

Optimization of primary enrichment section of mono-thermal ammonia–hydrogen chemical exchange process

2008 ◽  
Vol 142 (3) ◽  
pp. 285-300 ◽  
Author(s):  
M.R. Sawant ◽  
K.V. Patwardhan ◽  
A.W. Patwardhan ◽  
V.G. Gaikar ◽  
M. Bhaskaran
Keyword(s):  
Chemical Exchange ◽  
Exchange Process

Advances in boron-10 isotope separation by chemical exchange distillation

2010 ◽  
Vol 37 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Shuang Song ◽  
Yujun Mu ◽  
Xiaofeng Li ◽  
Peng Bai
Keyword(s):  
Chemical Exchange ◽  
Isotope Separation
Sign in / Sign up

Export Citation Format

Share Document