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Side chain

noun, verb

Noun

1
That part of a molecule attached to some core structure; a radical.
2
Any of the variable parts of amino acids that extend from the peptide backbone in proteins; they are referred to as R-groups, which branch off the backbone at the alpha carbon (Cα).
3
Auxiliary audio input fed to a synthesizer etc. and used to selectively trigger an effect.
4
A separate blockchain attached to a parent blockchain (mainchain) to extend its functionalities.
"The Blockstream developers, meanwhile, were accused of working for the interests of their company, Blockstream, rather than the good of Bitcoin as a whole. Their company, after all, proposed breaking many smaller transactions off onto so called sidechains that would occasionally link back up with the main Bitcoin blockchain, […]"
5
On some railways, a chain fitted on both sides of a centre coupler or buffer at each end of a rail vehicle, which has a hook for connection to a corresponding chain on the next vehicle in a train.
"When the screw coupling replaced the old chain couplings on passenger stock, the latter were retained and still coupled up to prevent severance of a train in the event of a screw coupling breaking. The contingency is so remote, however, that the side chains have been abolished."

Verb

Unscramble this word: sidechain