Daily Archives: October 28, 2010

peptide

This word looks as though it’s formed by bonding two somewhat disparate parts, one suggesting liveliness (not just pep but pepper, Pepsi, peppermint, and for that matter those yummy peppermint patties called Pep), the other suggesting massive fluid action (or laundry detergent, or perhaps a time of the year, as in Christmastide) – in other words, two parts suggesting action but otherwise some distance apart, sort of like two distant mountain states (say, Colorado and New Hampshire). On the other hand, it could be the cheerleading squad of the University of Alabama (whose sports teams are called the Crimson Tide).

One could also think of it as pept with the ide ending, of course – that chemical ide that shows up in bromide and hydride and other such things as may be pipetted in a lab. And in fact that’s where it comes from. The pept comes from peptone, which is not some group of harmony singers from a pep rally but rather (per the OED) “a mixture of proteins made soluble by partial digestion or hydrolysis”; peptone in turn comes from German Pepton, which comes from ancient Greek πεπτος peptos “cooked”, source in turn of pepsin and, from that, Pepsi.

What is a peptide? Even if you haven’t been tipped off, you probably have a sense that it’s something biochemical; I’m quite sure some of you reading know exactly what it is, and in much greater depth than I do. But, in short, it’s a chain of amino acids of the same type as a protein, but generally shorter (there is some overlap). When two amino acid residues are held together to make a chain (a peptide chain), the bond that holds them gets a name that is a common collocation for this word: a peptide bond. That’s specifically a carbon-nitrogen bond, CO linked with NH.

CO-NH peptide bond, eh… Makes me think of a ski chase in some Bond flick (Bond? Peptide Bond), taking place on the mountains of Colorado and New Hampshire. Or maybe he goes to the ocean and encounters a rip tide… Or maybe he just has too much dodgy food (with his martinis) and takes some Pepcid.