Exploring the intramolecular catalysis of the proton exchange process to modulate the relaxivity of Gd(iii)-complexes of HP-DO3A-like ligands

2018 ◽  
Vol 54 (72) ◽  
pp. 10056-10059 ◽  
Author(s):  
Irene Maria Carnovale ◽  
Marco Lucio Lolli ◽  
Sonia Colombo Serra ◽  
Alberto Fringuello Mingo ◽  
Roberta Napolitano ◽  
...  
Keyword(s):  
Exchange Process ◽  
Proton Exchange ◽  
Intramolecular Catalysis

The GdIII complex of Ph-HP-DO3A shows the highest contribution to the relaxivity by the intramolecular proton exchange of the –OH group.

H-Bonding and intramolecular catalysis of proton exchange affect the CEST properties of EuIII complexes with HP-DO3A-like ligands

2021 ◽  
Vol 57 (26) ◽  
pp. 3287-3290
Author(s):  
Simona Baroni ◽  
Irene Maria Carnovale ◽  
Carla Carrera ◽  
Mariangela Boccalon ◽  
Nicol Guidolin ◽  
...  
Keyword(s):  
Proton Exchange ◽  
Intramolecular Catalysis

CEST effects depend on the intramolecular proton exchange.

scholarly journals Synthesis of Propylene Oxide – Styrene Copolymers

2021 ◽  
Vol 10 (3) ◽  
pp. 2389-2395
Keyword(s):  
Propylene Oxide ◽  
Room Temperature ◽  
Structural Characteristics ◽  
Exchange Process ◽  
Proton Exchange ◽  
Styrene Copolymers ◽  
Forward Proton ◽  
Ft Ir ◽  
Ubbelohde Viscometer ◽  
Ft Ir Spectroscopy

The copolymerization of propylene oxide (PO) with styrene (St) catalyzed by Maghnite-H+ (Mag-H+) was investigated. Mag-H+, a nontoxic catalyst for cationic polymerization of vinylic and heterocyclic monomers, is a montmorillonite silicate sheet clay. This catalyst was prepared through a straight forward proton exchange process. It was found that Mag-H+ initiates the copolymerization in bulk at room temperature. Various techniques, including H1NMR, 13C-NMR, FT-IR spectroscopy, and Ubbelohde viscometer, were used to elucidate the resulting copolymers' structural characteristics. The effects of the amount of Mag-H+ and propylene oxide were studied. The yield of copolymerization depends on the amount of Mag-H+ used and the reaction time.

Hydrothermal Synthesis and Phase Formation Mechanism of TiO2(B) Nanorods via Alkali Metal Titanate Phase Transformation

2018 ◽  
Vol 283 ◽  
pp. 23-36 ◽  
Author(s):  
Yothin Chimupala ◽  
Rik Drummond-Brydson
Keyword(s):  
Phase Transformation ◽  
Intermediate Product ◽  
Intermediate Phase ◽  
Metastable Phase ◽  
Exchange Process ◽  
Titanium Isopropoxide ◽  
Growth Direction ◽  
Proton Exchange ◽  
Transformation Mechanism ◽  
Synthesis Conditions

Titanium dioxide (B phase) with 1-D structures was successfully fabricated via a hydrothermal method with a subsequent ion-exchange process and calcination. P25, titanium isopropoxide (TTIP), rutile and also anatase were used as Ti precursors in the alkali hydrothermal system. TTIP promoted an elongation of nanorod morphology whereas the other precursors produced short nanorod structures. The different types of titanium precursors did not have any influence on the phase transformation during the fabrication process. Na2Ti6O13 was the primary intermediate product after washing the hydrothermal sample. H2Ti3O7 was the secondary intermediate phase obtained following proton-exchange of Na2Ti6O13 in HNO3 solution. Finally, the TiO2(B) phase was the product of calcination of the secondary intermediate product at 400°C for 5 hr. A phase transformation mechanism is presented based on an investigation of products at each of the steps. The effects of the synthesis conditions on tailoring of the crystal morphology are discussed. The growth direction of the TiO2(B) nanorods was investigated by HR-TEM and SADP. Finally, the metastable phase of TiO2(B) was shown to be transformed to anatase during thermal treatment at temperatures higher than 400°C.

Uptake properties of lamivudine (3TC) by a continuous renal epithelial cell line

2001 ◽  
Vol 79 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Simon Leung ◽  
Reina Bendayan
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
Organic Cation ◽  
Exchange Process ◽  
Proton Exchange ◽  
Nucleoside Transport ◽  
Epithelial Cell Line ◽  
Dependent Manner ◽  
Renal Epithelial Cell ◽  
Renal Epithelial Cell Line

The purpose of this study was to characterize the renal uptake properties of the cytidine analog and antiretroviral agent 3TC. The uptake of radiolabelled 3TC was measured at 37°C in a continuous porcine renal epithelial cell line (i.e., LLC-PK1 cells) grown as a monolayer on an impermeable support. 3TC (5 µM) uptake (37°C) by the monolayer cells was saturable (Km = 1.2 ± 0.2 mM) but not significantly altered by various dideoxynucleoside analog drugs, nucleosides, and nucleoside transport inhibitors, suggesting that a nucleoside transporter is not involved in 3TC uptake. A number of endogenous organic cation probes and inhibitors significantly reduced 3TC uptake by the monolayer cells. Quinine, trimethoprim (TMP), and tetraethylammonium (TEA) inhibited 3TC uptake in a dose dependent manner with IC50 values of 0.6mM, 0.63mM, and 1.9 mM, respectively. In turn, the uptake of the typical organic cation substrate TEA was inhibited by high concentrations of 3TC. An outwardly directed proton gradient significantly increased the uptake of 3TC by the monolayer cells, suggesting the involvement of a proton exchange process. Conversely, in the presence of monensin, a Na+/H+ ionophore, the uptake of 3TC was significantly reduced. These results suggest that the uptake of 3TC by a cultured renal epithelium may be mediated by an organic cation-proton exchanger. The observed clinical interaction between 3TC and trimethoprim may be explained by competition for a common renal organic cation tubular transporter.Key words: 3TC, kidney, uptake, LLC-PK1, tubular elimination.

NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULPHURIC ACID: III. METHYLBENZENES AND ANISOLE

1964 ◽  
Vol 42 (3) ◽  
pp. 502-513 ◽  
Author(s):  
T. Birchall ◽  
R. J. Gillespie
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Carbon Atom ◽  
Proton Magnetic Resonance ◽  
Exchange Process ◽  
Proton Exchange ◽  
Magnetic Resonance Studies ◽  
Ring Carbon ◽  
Weak Bases ◽  
Ring Carbon Atom

The proton magnetic resonance spectra of solutions of mesitylene, durene, pentamethylbenzene, hexamethylbenzene, m- and p-xylenes, and anisole have been studied in fluorosulphuric acid and protonation on the ring carbon atom established. Rates of proton exchange have been measured and activation energies calculated for the proton exchange process. Intermolecular exchange with the solvent is suggested as the most probable exchange process in all cases.

Elastic-Recoil-Detection Measurement of Instabilities in Proton-Exchanged Lithium Niobate

1987 ◽  
Vol 101 ◽  
Author(s):  
G. W. Arnold ◽  
A. Carnera ◽  
G. Mazzi ◽  
P. Mazzoldi
Keyword(s):  
Crystal Orientation ◽  
Annealing Temperature ◽  
Exchange Process ◽  
Proton Exchange ◽  
Elastic Recoil ◽  
Elastic Recoil Detection ◽  
Simultaneous Measurements ◽  
Acid Proton ◽  
Proton Source ◽  
Orientation Time

ABSTRACTThe H and Li profiles in proton-exchanged (PE) LiNbO3, have been measured using elastic recoil detection (ERD). Profiles were determined as a function of crystal orientation, time after PE, annealing temperature, MgO-doping, and added Li-benzoate to the benzoic acid proton source. The proton-exchange process produces Hx Li1−x NbO3 structures where x stabilizes near values of x=0.5 or x=0.7-0.75 depending on specific conditions. The ERD measurements represent the first direct and simultaneous measurements of H- and Li-concentrations in PE LiNbO3 and their variation with process parameters.

Study of anomalous behaviour of LiTaO3 during the annealed proton exchange process of optical waveguide’s formation – comparison with LiNbO3

2007 ◽  
Vol 29 (7) ◽  
pp. 913-918 ◽  
Author(s):  
Linda Salavcova ◽  
Jarmila Spirkova ◽  
Frantisek Ondracek ◽  
Anna Mackova ◽  
Jiri Vacik ◽  
...  
Keyword(s):  
Exchange Process ◽  
Proton Exchange ◽  
Anomalous Behaviour
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