Glu35 acts as a proton donor to the glycosidic bond, cleaving the C-O bond in the substrate, whereas Asp52 acts as a nucleophile to generate a glycosyl enzyme intermediate.
22.
It has been hypothesized that a nearby tyrosine acts as the proton donor and acceptor during the transaldimination step as well as the pK of the tyrosine, making proton transfers more facile.
23.
There exist three residues in the enzyme within a suitable distance of the C-4 that could be potential proton donors : Tyr-48, His-110 and Cys-298.
24.
In this reaction, the two aldehydes serve different purposes; one aldehyde donates a proton and one aldehyde accepts a proton . 4-Dimethylaminobenzaldehyde is an efficient proton donor while benzaldehyde is both a proton acceptor and donor.
25.
In "'acid catalysis "'and "'base catalysis "'a chemical reaction is proton donor and the base is the proton acceptor, known as Bronsted-Lowry acid and base respectively.
26.
Hydrogenation with Raney nickel gives the diol "'9 "'which on a double Mitsunobu reaction ( with an amine proton donor ) gives the azafenestrane "'10 "'as the borane salt.
27.
Although, is protonated acetic acid in ether a particularly good proton donor when " needed ", i . e . when it arrives at the reaction site ? talk ) 23 : 36, 19 August 2010 ( UTC)
28.
Arguing by analogy to the well known tunneling-inversion spectrum of ammonia, Klemperer recognized that the key to understanding the spectrum was to recognize that HF HF was undergoing quantum tunnelling to FH FH, interchanging the roles of proton donor and acceptor.
29.
The acids include bisphenol A, parabens, 1, 2, 3-triazole derivates, and 4-hydroxycoumarin and act as proton donors, changing the dye molecule between its leuco form and its protonated colored form; stronger acids would make the change irreversible.
30.
The acidity of hydronium is the implicit standard used to judge the strength of an acid in water : strong acids must be better proton donors than hydronium, otherwise a significant portion of acid will exist in a non-ionized state ( i . e . : a weak acid ).
