Teresa (Barbie) and sidekick". In Life in the Dreamhouse Barbie states that all girls Teresa, Nikki, Summer, Midge, Raquelle & Grace are all her 'BFFs'. To counteract the criticisms that Barbie was a sex symbol, Mattel was compelled to issue companions for Barbie. Some of these are her boyfriend Ken, the African American Christie, Barbie's cousin Francie and Barbie's little sister Skipper. Midge appeared in 1963 and was marketed as Barbie's first best friend. Midge was discontinued in 1967. Over the years, Barbie's family tree expanded and soon Barbie would have many diverse and multicultural friends. Among these was Teresa, who was
S-tag S-tag S-tag is the name of an oligopeptide derived from pancreatic ribonuclease A (RNase A). If RNase A is digested with subtilisin, a single peptide bond is cleaved, but the resulting two products remain weakly bound to each other and the protein, called ribonuclease S, remains active although each of the two products alone shows no enzymatic activity. The N-terminus of the original RNase A, also called S-peptide, consists of 20 amino acid residues, of which only the first 15 are required for ribonuclease activity. This 15 amino acids long peptide is called S15 or S-tag. The amino acid sequence