After it has been shown that removal of residues B26-B30 leaves insulin with full biological activity, provided the new C-terminus is amidated (Fischer et al. (1985) Biol. Chem. Hoppe-Seyler 366, 521-525), it is demonstrated here that it does not even preclude enhancement of potency. 7 analogues of des-(B26-B30)-insulin-B25-amide were prepared by trypsin-mediated semisynthesis, the replacements being D-Phe B24 ; His B2S , D-Phe B2S , Trp B25 ,Tyr B25 ;D-Phe B24 ' B2S and D-Phe B24 , Tyr B2S . Mere conversion of the configuration of B25-phenylalanine reduces in vitro potency to 0.5%. If B25-phenylalanine is, however, substituted by histidine or tyrosine activity is in-
Verkürzte Insuline mit erhöhter AktivitätZusammenfassung: Nachdem sich erwiesen hatte, daß die Abspaltung der Reste B26 bis B30 ein biologisch voll aktives Insulin hinterläßt, vorausgesetzt der neue C-Terminus ist amidiert (Fischer et al. (1985) Biol Chem. Hoppe-Seyler 366, 521-525), wird jetzt gezeigt, daß sie sogar mit erhöhter Aktivität vereinbar ist. Durch Trypsin-vermittelte Semisynthese wurden 7 Analoge von Des-(B26-B30)-insulin-B25-amid hergestellt, und zwar mit den Substitutionen D-Phe B24 ; His B2S , D-Phe B25 , Trp B2S , Tyr B2S ; D .p he B24,B25 und D -Phe B24 , Tyr B25 ßloße Um _
Next to in vitro-cultured autogeneic keratinocytes for the restoration of epidermis, a suitable dermal matrix is a mandatory component of an artificial skin substitute for the permanent covering of full thickness skin defects. In our model a xenogeneic membrane, consisting of processed native collagen and elastin of porcine origin is meant to serve as a template for the formation of a neo-dermis. In order to improve the resistance of this matrix against enzymatical degradation, we cross-linked it by using the carbodiimide 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) together with N-hydroxysuccinimide. Chemical cross-linking by these agents at two different degrees (shrinkage temperatures 63 degrees C and 81 degrees C) had no relevant effect on mechanical features or water-uptake capacity. The time needed for enzymatic digestion was increased by cross-linking. Concerning growth and spreading of fibroblasts and keratinocytes on and within the structure of this membrane, we did not observe a difference between cross-linked and non-cross-linked material (shrinkage temperature 48 degrees C). We therefore expect that cross-linking by EDC is an effective means to control the degradation of the collagen/elastin membranes in vivo without a significant influence on their biocompatibility.
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