4. Deuterium against the chain reaction of lipid peroxidation

If one of the milled grooves on your door key is particularly deep, then subjecting it to excessive tension, perhaps by accidentally squeezing a bunch of keys and coins in your pocket, may bend, or even break it at that point. Yet adding more metal to reinforce the weakest link would destroy its unique fingerprint: the key would no longer fit the lock. To fix the problem, one would need to use stronger metal, instead of soft brass.

Biomolecules we are made of often have their own “breaking points”, or the Achilles' heels, at which they can be attacked, and damaged, by various forms of oxygen. Yet these biomolecules, with PUFAs being a good example, have well-defined unique “shapes” which have to stay “carved in stone”: reinforcing them chemically would disfigure the molecules enough to make them unrecognizable, no longer fit for purpose, as building blocks, substrates, or what not.

We cannot live without PUFAs, yet oxygen and metals join forces to make a mockery of the antioxidants. And once enough PUFAs are damaged, pathologies and aging follow.

Is this a losing battle?

Enter the deuterium. Imagine two identical tennis balls. Use a syringe to fill one up with water. As the two balls are resting on the court, it is impossible to tell which one is heavier. But hit them with your racket, and the truth will come out, as more effort will be required to send the heavier ball the same distance (see Chapter 6.1).

In chemistry, the two balls may be referred to as isotopes. A good example would be hydrogen, and its heavy stable isotope, deuterium. As isotopes are forms of the same chemical element, they do not change the chemical identity of the molecules. One can swop a few hydrogens on a lipid molecule for a few deuteriums, or vice versa, and the molecule will still be the one, and the same, fatty acid molecule.

Plugging the weak spots

PUFAs have several “soft spots” on their molecules. Those points are particularly attractive for the oxygen gang, which rip off the “weak” hydrogens from them, initiating the chain reaction. And, courtesy of the isotope effect, deuterium can plug these holes.

Deuterate the PUFAs at the weak spots, and they will become resistant to oxidation!

Imagine having D-PUFAs in your lipid membranes. Like fire retardants, they prevent the chain reaction from propagating, all the while remaining essentially undistinguishable from the natural PUFAs. And you do not need all of your PUFAs to be reinforced in this way. A small fraction, about 30% of the total, will be enough!

Another illustration of the concept is based on a surprising natural phenomenon (see Chapter 2.6.1). Again, emperor penguins' golden collars symbolize the D-PUFAs here. This is not a bad colour scheme: D-PUFAs in oxidation-prone lipid membranes are the 24-carat gold of materials.