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Characterization of various Avidin variants

Streptavidin and its variants were produced by cytoplasmic expression in E. coli in inclusion bodies. After stabilization and refolding of the functional tetrameric and monomeric variants, purification was carried out by ammonium sulfate precipitation, Ion Exchange Chromatography and size exclusion chromatography. Samples of each required step were analysed by SDS-PAGE. Finally each of the successfully purified variants were characterized. Mass spectrometry was used to confirm the expected size, circular dichroism spectroscopy to determine folding states, fluorescence titration and surface plasmon resonance for determining binding affinities.

Results can be seen in Table 1.

Table 1: Properties of various Avidin variants.

protein	amino acids (without Met)	molecular weight monomer [Da]	molecular weight tetramer [Da]	theoretical isoelectric proint (pI)	pI (Isoelectric focusing)	extinction coefficient (monomer, ε280) [M-1 cm-1]
Streptavidin wt	126	13200.34	52801.36	6.09		41940
Traptavidin	126	13129.22	52516.88	5.14		41940
Streptactin	126	13241.44	52516.88	8.32		41940
enhanced monomeric Avidin	138	15220.30	/	5.91		35075
single chain Avidin	567	61530.65	/	9.84		94460

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Literaturreferenz

Literaturreferenz^[1]

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Introduction

Design

Experiments

Proof of concept

Demonstrate

Discussion

References

1. ↑ Schmidt, T. G., & Skerra, A. (2007). The Strep-tag system for one-step purification and high-affinity detection or capturing of proteins. Nature protocols, 2(6), 1528-1535.