Substituent, temperature and solvent effects on tautomeric equilibria in several β-ketoamides have been investigated by means of nuclear magnetic resonance spectroscopy (NMR). Keto-enol equilibrium predominates over the amide-imidol one. The relative stability of the individual tautomers and the corresponding equilibrium shifts are explained considering electronic and steric effects and tautome...

Density functional theory (DFT) calculations have been performed to calculate the optimized geometries of stepwise fluorinated methylenecyclopropanes and 1-methylcyclopropenes. Increasing the number of fluorine atoms caused a destabilization of methylenecycopropane. Perfluorinated 1-methylcyclopropene was found to be present in substantial concentration. This is supported by calculations of the...

This thesis presents computational chemistry studies of keto-enol reactions and chromophores of photobiological significance. The first part of the thesis is concerned with two protein-bound chromophores that, depending on the chemical conditions, can exist in a number of different ketonic and enolic forms. The first chromophore is astaxanthin, which occurs in the protein complex responsible fo...

(a) Draw the bi-molecular complex (see Figure 2 in the paper) using Avogadro. (b) Optimize the structure at B3LYP/6-31G** level of theory. (c) Prepare an input file for a relaxed scan (same level of theory) of the proton transfer using the modredundant option (check the manual page for opt ). Please include the option maxcyc=8 regarding the optimization. (Hint: which geometrical parameter do yo...

Because carbonyl groups can participate in both hydrogen bonds and n→π* interactions, these two interactions likely affect one another. Herein, enhancement of an amidic n→π* interaction is shown to reduce the ability of β-keto amides to tautomerize to the enol, indicating decreased hydrogen-bonding capacity of the amide carbonyl group. Thus, an n→π* interaction can have a significant effect on ...

zoanthamine-type alkaloids display a wide spectrum of biological effects. this study aimed to examine the inhibitory effects of norzoanthamine and its ten homologues of zoanthamine class on human fibroblast collagenase by modeling a three-dimensional structure of the ligands at collagenase using energy minimization, docking, molecular dynamics simulation and mm-pb/gbsa binding free energy calcu...

Photoexcitation with blue light of the flavin chromophore in BLUF photoreceptors induces a switch into a metastable signaling state that is characterized by a red-shifted absorption maximum. The red shift is due to a rearrangement in the hydrogen bond pattern around Gln63 located in the immediate proximity of the isoalloxazine ring system of the chromophore. There is a long-lasting controversy ...

Increasingly grim environmental pollutions are closely related with the occurrence and development of diseases. However, it’s obscure how stress disturbs normal physiological process, then endogenous reactive species mend cases. Hypoxia/reperfusion (H/R), a common intractable injury in aquaculture clinic, can induce oxidative ultimately cause irreversible to organism. Cysteine (Cys) plays essen...

Pulse Radiolysis, OH Radicals, Acetylacetone, Reaction Mechanisms Pulse radiolysis experiments monitoring optical absorbance as well as conductivity and in-situ ESR radiolysis studies show that the OH radical reacts with the enol (k = 8.6 x 109 M_1 s_1) and the enolate (k = 7.4 X 109 M_1 s-1) forms of acetylacetone by addition to the C = C double bond in aqueous N2O saturated solution. The OH r...