Figure 11 shows an efficiency profile that alternatively decreased and increased as the pH reduced from 9 to 2. The efficiency increase for pH ranges 3 2 and 8 5 was due to progressive proton donation.
The latter include for example hydrogen bond acceptors and donors for proton abstraction and proton donation, positive charges to stabilize developing negative charge in the transition state, etc.
In five-coordinate globins, His(E7) facilitates nitrite reduction, likely through proton donation.
EHOMO represents the proton acceptance ability in forming hydrogen bond, while ELUMO represents the proton donation ability in formation of hydrogen bond (Zhou et al., 2005).
EHOMO also represents the proton acceptance ability in forming hydrogen bond, while ELUMO represents the proton donation ability in forming hydrogen bond.
These water ligands would also contribute to the rapid DFP decay through proton donation to efficiently complete the ferroxidase reaction.
Large values of EHOMO and ELUMO would result in small values of KOW for PCB because EHOMO represents the proton acceptance ability in forming hydrogen bond, while ELUMO represents the proton donation ability in formation of hydrogen bond.
We hypothesized that, if proton donation from the ligand were needed for C4a-OO(H) formation (or breakdown), these steps should be significantly slowed in the presence of the methylated amino acids relative to their unfunctionalized counterparts.
It is possible that the 2′-OH acts in proton donation, eaither as a source or in relay, to the leaving group of the reaction, but this possibility remains to be tested.
The C=C double bond is oriented in ideal geometry and distance for proton donation (3.5 Å) from Y183 onto Cα, while at the same time Cβ is in hydride transfer distance (3.8 Å) from N5 of the isoalloxazine ring.
These phenolic acids disrupted the bacteria cell by hyperacidification of the plasma membrane via proton donation and acidification of the intracellular cytosolic; this low pH can inhibit the enzyme H+-ATPase necessary for the ATP production [ 32– 32].
