Tham khảo tài liệu 'protein purification part 9', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Purification Systems Based on Bacterial Surface Proteins 113 helix version of the Z-domain an elastin sequence was inserted in the inter-helix turn Reiersen Rees 1999 . This modification dramatically altered the helical structure of the resulting protein. However in contrast to the starting molecule the elastin-turn mutant exhibited a more than 20-fold improvement of Fc-binding affinity when the temperature was increased. This effect is hypothesized to arise through a temperature- or salt-induced formation of a fi-turn that stabilizes the alignment of the Fc-binding helices and represents a modular switch to alter structure and activity Reiersen Rees 1999 2000 . For small protein domains synthesis provides a straightforward means for site-specific labeling chemical cross-linking or introduction of non-natural building blocks to make novel variants available for different applications. Deeper understanding of interaction interfaces between proteins may also facilitate rational design of small molecular weight mimics Wells et al. 2002 miniaturized proteins only represent intermediates for the challenging task of designing small molecule mimetics. In rational molecular design starting from a structurally defined scaffold and a binding surface rather than a sequential stretch of amino acids such as a loop region usually results in a more defined binding molecule Stahl Nygren 1997 . For example the key determinants of the interaction site between the IgG-binding domains of SPA and Fc have stood model for the generation of several small protein mimetic organic molecules. This concept was beautifully demonstrated for the interaction between the B-domain of SPA and the Fc-part of IgG Li et al. 1998 . Using the hydrophobic core dipeptide Phe132-Tyr133 as a starting point a novel triazine mimetic was rationally designed synthesized and utilized for purification of antibodies Li et al. 1998 . Since then mimetics have also been developed for other antibody-binding proteins .
