WWWWhy does nature stutter? A survey of strands of repeated amino acids

Human stuttering is a simple example of the repetition of sounds or symbols , sometimes associated with single letters, and may be used to illustrate t he amazing repetition of amino acids (symbolized by a letter, e.g. W) in pr oteins. A survey of available databases with highly improbable strings of s ingle amino acids is tabulated. This paper concludes with a challenge to th e crystallographic community to probe the structural origins of the structu re-function relationship in this neglected area. When nature stutters, we s hould pay attention.