Quantitative Functionalization of the Tyrosine Residues in Silk Fibroin through an Amino‐Tyrosine Intermediate

Here, a reaction sequence that can be used to quantitatively modify the tyrosine residues in silk protein from B. mori silkworms is demonstrated. A primary amine is installed ortho to the hydroxyl group on the tyrosine ring using a diazonium coupling reaction followed by reduction of the azo bond. T...

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Bibliographic Details
Published in:Macromolecular chemistry and physics 2022-09, Vol.223 (17), p.n/a
Main Authors: Hausken, Kian G., Frevol, Romane L., Dowdle, Kimberly P., Young, Aleena N., Talusig, Jeremy M., Holbrook, Carolynne C., Rubin, Benjamin K., Murphy, Amanda R.
Format: Article
Language:English
Subjects:
Alkynes
amino‐tyrosine
azobenzene
Carboxylic acids
Cycloaddition
Functional groups
HMBC
Hydroxyl groups
Microparticles
NHS‐ester
NMR spectroscopy
Reagents
Residues
Room temperature
silk
Silk fibroin
Silkworms
Tyrosine
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Summary:Here, a reaction sequence that can be used to quantitatively modify the tyrosine residues in silk protein from B. mori silkworms is demonstrated. A primary amine is installed ortho to the hydroxyl group on the tyrosine ring using a diazonium coupling reaction followed by reduction of the azo bond. The resulting amine is then acylated using carboxylic acid or NHS‐ester derivatives at room temperature and neutral pH conditions. The silk derivatives are characterized using 1H NMR, UV–vis spectroscopy, ATR‐FTIR, and a unique method to follow this reaction sequence using isotopically labeled reagents and 2D NMR spectroscopy is also used. This study further demonstrates that this sequence can be used to install alkyne or azide functional groups which can undergo further bio‐orthogonal cycloaddition reactions under mild conditions. Finally, methods to carry out these modifications on solid silk microparticles and electrospun mats are also described. A fast, simple reaction sequence capable of conjugating a high degree of non‐native functional groups to silk is demonstrated. First, the native tyrosine rings are quantitatively converted to azobenzene derivatives. Subsequent reduction of the azo bond produces electron‐rich amino‐tyrosine groups which can be easily acylated under very mild conditions, resulting in a broad variety of functional silk derivatives.
ISSN:1022-1352
1521-3935
DOI:10.1002/macp.202200119