Biosynthesis and characterization of novel elastin-basedbiomaterials and theoretical calculation of proline analogues Public
Tian, Ye (2008)
Published
Abstract
Abstract Biosynthesis and characterization of fluorinated elastin-mimetic polypeptides and theoretical calculation of proline analogues By Ye Tian Elastin is an important protein that provides connectivity and elasticity in the extracellular matrix. Elastin-mimetic polypeptides (EMPs) have been widely used as models for studying the structure and property of native elastin. In this study, two fluorinated amino acids, 4, 4, 4-trifluorovaline and 3-fluorovaline were incorporated into the isoleucine and valine codons of an elastin-mimetic polypeptide sequence. Both the two fluorinated EMPs underwent inverse temperature transitions. Structurally, these two proteins self-assembled from random coil to type II turn upon temperature increase. In addition, an EMP sequence comprised of repeating pentapeptide [Val-Pro-Gly-Ala-Gly] was designed to serve as the sequence for the incorporation of 4, 4-difluoroproline. The gene encoding this sequence was constructed by recursive directional ligation. Moreover, two plasmin-sensitive elastin-based triblock copolymers with different size in the mid-block were studied. It was revealed that these two proteins underwent inverse temperature transition upon a critical temperature of 19.8 and 20.0 , respectively. This transition was accompanied by a structure change from random coil to an ordered structure, which was confirmed by the CD results. Biodegradation of both proteins was demonstrated to be complete within six hours. Furthermore, two oxidation products of N-acetyl-thioproline-methyl ester were geometry-optimized by DFT computation. The calculation results revealed that the anti product preferred a C- exo pucker and a trans amide bond while the syn product preferred a C- endo pucker and a cis amide bond. It was shown that both the gauche effect between the sulfoxide bond and the amide nitrogen as well as the n* interaction between the nonbonding oxygen and the carbonyl group of the ester contributed to the conformational preferences.
Table of Contents
Table of contents Chapter 1. General Introduction .................................................................................1 Chapter 2. Biosynthesis and characterization of fluorinated elastin-mimetic polypeptides.................................................................................................9 Chapter 3. Design and construction of elastin-mimetic polypeptide gene suitable for the study of 4, 4-difluoroproline incorporation ............................26 Chapter 4. Characterization of biodegradable materials based on elastin-mimetic polypeptide.................................................................................................38 Chapter 5. DFT calculation of the conformational preference of thioproline derivatives ................................................................................................51 Chapter 6. Conclusions ..............................................................................................69
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