So this is the histidine 141 residue found on the beta one subunit. And this is a nearby residue on the same beta one subunit, the aspartate 94. Now, notice in this particular case, so at a relatively high PH of, let's say, 7.4, which is the PH inside our lungs, this nitrogen. So by the way, this is the nitrogen. These are carbons, and these blue ones are oxygen atoms. And this orange one is an H ion.