I have a fun freelance gig, writing up public-facing papers that have won a genomics award. Most of it is embargoed as yet, but I wanted to share something that has me shook.

I get to interview some seriously fascinating researchers, many of whom are very, very generous with their time and explanations. It’s thanks to one of these interviewees that today I learned about ‘salt bridges’ in protein folding, and was reminded, once again, how incredibly intricate and elegant life is.

Figure from an old textbook showing the field of a bar magnet
Opposites attract: the basis of the building blocks of life, as well as being the basis of one of the most unsettling music videos of all time.

The sequence of bases in your DNA determines (in many cases at least) the sequence of amino acids that are assembled to form a protein. There are 20 different amino acids in human biology. Some of these are hydrophobic: they usually make up the core of the protein as they cluster together in the centre, away from the sogginess inside the cell.

But the rest of the protein also needs to fold. And one of the ways this happens is with something called a ‘salt bridge.’ Some amino acids tend to have a positive charge (arginine or lysine) or a negative charge (glutatmate or aspartate.) When two amino acids of opposite charge are close together in the sequence (close here being less than half a nanometer) they *boop* together and fold the protein. All these folds make the protein do whatever it needs to do, whether that’s help metabolise your food, build your body, fight off invaders, or carry messages.

A single mutation in the amino acid sequence can cause major problems. For example, the loss of a single negatively-charged amino acid (replaced with an uncharged version) is enough to cause progeria syndrome.

Just thinking about all these little tiny charges, making these tiny origami shapes, is enough to induce a kind of vertigo. Inside you, me, every living thing, there are billions of these electrostatic bonds snapping shut, time after time after time. The machinery of life is complex, beautiful, and common to us all. We are all fragile, precious beings made of fragile, precious things.

It’s a wild statistical improbability – a more spiritual person than me might just go ahead and say it’s a miracle – that any of us is here.

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