| heptad | <chemistry> An atom which has a valence of seven, and which can be theoretically combined with, substituted for, or replaced by, seven monad atoms or radicals; as, iodine is a heptad in iodic acid. Also used as an adjective. Origin: L. Heptas the number seven. Gr, fr. "epta seven. Source: Websters Dictionary (01 Mar 1998) |
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| heptad repeat | <molecular biology> A heptad repeat is a type of tandem repeat sequence. It is a sequence of seven amino acids which is repeated multiple times in a row within certain proteins (the intermediate filament proteins) of nearly every animal in the animal kingdom. (09 Oct 1997) |