You are stranded on a leaky boat that is drifting toward shark-infested waters. Your primary radio is busted, but a backup is locked in a safe marked with the following: "When approaching shark-infested waters, unlock the safe using the isoelectric points of the peptide words."
The geniuses that set up the safe left you a hint (WHEN = 5).
You need to scramble your pH and amino acid knowledge to calculate the isoelectric points (round to the closest whole number) to unlock the safe and make the emergency call.
Hurry, the water is ankle deep and rising!
(1) APPROACHING has an isoelectric point around pH
NOTE The 'O' in APPROACHING represents ornithine – It is an amino acid but it is not utilized in protein synthesis. For the purposes of this question, treat it as a "Lysine" residue as the difference between them is a methylene group in the side chain.
(2) SHARK has an isoelectric point around pH
(3) INFESTED has an isoelectric point around pH
(4) WATERS has an isoelectric point around pH