The pK(a), values of the conjugate acid of imidazole in water-ethanol mixtures The p K a values of protonated imidazole in 10 different water-ethanol mixtures were determined at 25掳 by potentiometric titration in a cell without liquid junction (glass and silver-silver bromide electrodes). The...
butnotbasic when it is part of an amide group. Recall that in an amide, there is significant double-bond character to the carbon-nitrogen bond, due to a minor but still important resonance contributor in which the nitrogen lone pair is part of a pi bond. ...
for the transfer of ubiquitin onto the substrate to proceed efficiently the incoming nucleophile, which is either the ε-amino group of a lysine side chain or the N-terminal side chains is around 10.5, meaning α- amino group of Met1, needs to be they are protonated at physiological...
A plot of the pseudo-first order rate constant for inactivation by 20 mM EDC at different pH values from 4.2 to 7.7 at 25°C shows that this inactivation is due to the modification of a protonated carboxyl with a p K a of 5.6. The rate of inactivation by EDC at pH 6.0 is reduced,...
pKa
of tetracyclines is the presence of multiple acidic groups: four equilibrium constants have been measured for the fully protonated tetracycline (TCH3+) but so far no clear information concerning the pKas of the various sites has been reported. We present here a computational investigation on the ...
We have re-measured titration curves for all carboxylates and His 15 in Hen Egg White Lysozyme (HEWL) by recording the pH-dependent chemical shifts of all backbone amide nitrogens and protons, Asp/Glu side chain protons and carboxyl carbons, and imidazole protonated carbons and protons in this...
A plot of the pseudo-first-order rate constant for inactivation by 20 mM EDC at different pH values from pH 4.0 to 7.7 at 25掳C shows that inactivation is critically dependent on the protonated form of an acidic side chain with a pK a of 5.51. Significant protection against inactivation ...
Due to the near neutral pKa of one of the N-bonded protons on the imidazole side chain of histidine (Figure 1), the histidine residue can act both as a base and, when protonated, as an acid, under physiological conditions. The pKa of histidine is sensitive to its specific chemical ...