scholarly journals Molecular mechanism for thermal denaturation of thermophilic rhodopsin

2019 ◽  
Vol 10 (31) ◽  
pp. 7365-7374 ◽  
Author(s):  
Ramprasad Misra ◽  
Amiram Hirshfeld ◽  
Mordechai Sheves
Keyword(s):  
Schiff Base ◽  
Molecular Mechanism ◽  
Thermal Denaturation ◽  
Rate Determining Step ◽  
Hydrolysis Of ◽  
Denaturation Process

Studies of microbial rhodopsins revealed that hydrolysis of the retinal protonated Schiff base is the rate-determining step of the thermal denaturation process.

Schiff base equilibria. II. Beryllium complexes of N-n-butylsalicylideneimine and the hydrolysis of the Be2+ ion

1965 ◽  
Vol 18 (5) ◽  
pp. 651 ◽  
Author(s):  
RW Green ◽  
PW Alexander
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Complex Formation ◽  
Distribution Coefficient ◽  
Dilute Aqueous Solution ◽  
The Stability ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Beryllium Complexes ◽  
Equilibria In Aqueous Solution

The Schiff base, N-n-butylsalicylideneimine, extracts more than 99.8% beryllium into toluene from dilute aqueous solution. The distribution of beryllium has been studied in the pH range 5-13 and is discussed in terms of the several complex equilibria in aqueous solution. The stability constants of the complexes formed between beryllium and the Schiff base are log β1 11.1 and log β2 20.4, and the distribution coefficient of the bis complex is 550. Over most of the pH range, hydrolysis of the Be2+ ion competes with complex formation and provides a means of measuring the hydrolysis constants. They are for the reactions: Be(H2O)42+ ↔ 2H+ + Be(H2O)2(OH)2, log*β2 - 13.65; Be(H2O)42+ ↔ 3H+ + Be(H2O)(OH)3-, log*β3 -24.11.

A Selective Colorimetric and Fluorescent Chemodosimeter for Fe(III) Ion Based on Hydrolysis of Schiff Base

2015 ◽  
Vol 62 (4) ◽  
pp. 316-320 ◽  
Author(s):  
Haw-Tyng Tsai ◽  
Yeshwant Ramchandra Bhorge ◽  
Albert J. Pape ◽  
Sudhakar Narasimha Janaki ◽  
Yao-Pin Yen
Keyword(s):  
Schiff Base ◽  
Fluorescent Chemodosimeter ◽  
Hydrolysis Of

Effect of Medium on Reactivity for Alkaline Hydrolysis of p-Nitrophenyl Acetate and S-p-Nitrophenyl Thioacetate in DMSO-H2O Mixtures of Varying Compositions: Ground State and Transition State Contributions

2021 ◽  
Author(s):  
Ik-Hwan Um ◽  
Seungjae Kim
Keyword(s):  
Transition State ◽  
Alkaline Hydrolysis ◽  
Ground State ◽  
Rate Constants ◽  
Kinetic Data ◽  
Reaction Medium ◽  
Stepwise Mechanism ◽  
Rate Determining Step ◽  
Leaving Group ◽  
Hydrolysis Of

Second-order rate constants (kN) for reactions of p-nitrophenyl acetate (1) and S-p-nitrophenyl thioacetate (2) with OH‒ have been measured spectrophotometrically in DMSO-H2O mixtures of varying compositions at 25.0 ± 0.1 oC. The kN value increases from 11.6 to 32,800 M‒1s‒1 for the reactions of 1 and from 5.90 to 190,000 M‒1s‒1 for those of 2 as the reaction medium changes from H2O to 80 mol % DMSO, indicating that the effect of medium on reactivity is more remarkable for the reactions of 2 than for those of 1. Although 2 possesses a better leaving group than 1, the former is less reactive than the latter by a factor of 2 in H2O. This implies that expulsion of the leaving group is not advanced in the rate-determining transition state (TS), i.e., the reactions of 1 and 2 with OH‒ proceed through a stepwise mechanism, in which expulsion of the leaving group from the addition intermediate occurs after the rate-determining step (RDS). Addition of DMSO to H2O would destabilize OH‒ through electronic repulsion between the anion and the negative-dipole end in DMSO. However, destabilization of OH‒ in the ground state (GS) is not solely responsible for the remarkably enhanced reactivity upon addition of DMSO to the medium. The effect of medium on reactivity has been dissected into the GS and TS contributions through combination of the kinetic data with the transfer enthalpies (ΔΔHtr) from H2O to DMSO-H2O mixtures for OH‒ ion.

A “turn-on” fluorescent and colorimetric chemodosimeter for selective detection of Au3+ ions in solution and in live cells via Au3+-induced hydrolysis of a rhodamine-derived Schiff base

2020 ◽  
Vol 44 (19) ◽  
pp. 7954-7961
Author(s):  
Sanchita Mondal ◽  
Saikat Kumar Manna ◽  
Sudipta Pathak ◽  
Aritri Ghosh ◽  
Pallab Datta ◽  
...  
Keyword(s):  
Schiff Base ◽  
Rhodamine B ◽  
Aqueous Media ◽  
Sensitive Detection ◽  
Live Cells ◽  
Selective Detection ◽  
Turn On ◽  
Hydrolysis Of

A chromogenic and “off–on” fluorogenic chemodosimeter (L) based on a naphthalene–rhodamine B derivative was designed, synthesized and characterized for the selective and sensitive detection of Au3+ ions in mixed acetonitrile aqueous media.

scholarly journals Thermal Healing, Reshaping and Ecofriendly Recycling of Epoxy Resin Crosslinked with Schiff Base of Vanillin and Hexane-1,6-Diamine

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 293 ◽  
Author(s):  
Van-Dung Mai ◽  
Se-Ra Shin ◽  
Dai-Soo Lee ◽  
Ilho Kang
Keyword(s):  
Schiff Base ◽  
Epoxy Resin ◽  
Elevated Temperatures ◽  
Relaxation Times ◽  
Diglycidyl Ether ◽  
Original Material ◽  
Crosslinked Polymer ◽  
Schiff Base Formation ◽  
Hydrolysis Of ◽  
Base Formation

A bio-derived dihydroxylimine hardener, Van2HMDA, for the curing of epoxy resin was prepared from vanillin (Van) and hexamethylene-1,6-diamine (HMDA) by Schiff base formation. The epoxy resin of diglycidyl ether of bisphenol A was cured with Van2HMDA in the presence of the catalyst, 2-ethyl-4-methylimidazole (EMI). The crosslinked epoxy resin showed thermal-healing properties at elevated temperatures. Moreover, the crosslinked epoxy resin can be reshaped by heating via imine metathesis of the hardener units. The imine metathesis of Van2HMDA was confirmed experimentally. Stress-relaxation properties of the epoxy resin crosslinked with Van2HMDA were investigated, and the activation energy obtained from Arrhenius plots of the relaxation times was 44 kJ/mol. The imine bonds in the epoxy polymer matrix did not undergo hydrolysis after immersing in water at room temperature for one week. However, in the presence of acid, the crosslinked polymer was easily decomposed due to the hydrolysis of imine bonds. The hydrolysis of imine bonds was used for the ecofriendly recycling of crosslinked polymer. It is inferred that thermal-healing, reshaping, and reprocessing properties can be implemented in the various crosslinked epoxy resins with the bio-derived dihydroxylimine hardener, albeit the recycled epoxy resin is of inevitably lower quality than the original material.

Effect of bromide salts on the acid hydrolysis of anti-bacterial hydrophilic Schiff base amino acid iron(II) complexes

2014 ◽  
Vol 84 (10) ◽  
pp. 2037-2042 ◽  
Author(s):  
Ali M. Shaker ◽  
Lobna A. E. Nassr ◽  
Mohamed S. S. Adam ◽  
Ibrahim M. A. Mohamed
Keyword(s):  
Schiff Base ◽  
Amino Acid ◽  
Acid Hydrolysis ◽  
Hydrolysis Of
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