A novel affinity "tag-receptor" pair was developed as a generic platform for the purification of fusion proteins. The hexapeptide RKRKRK was selected as the affinity tag and fused to green fluorescent protein (GFP). The DNA fragments were designed, cloned in Pet-21c expression vector and expressed in E. coli host as soluble protein. A solid-phase combinatorial library based on the Ugi reaction was synthesized: 64 affinity ligands displaying complementary functionalities towards the designed tag. The library was screened by affinity chromatography in a 96-well format for binding to the RKRKRK-tagged GFP protein. Lead ligand A7C1 was selected for the purification of RKRKRK fusion proteins. The affinity pair RKRKRK-tagged GFP with A7C1 emerged as a promising solution (Ka of 2.45×10(5) M(-1) ). The specificity of the ligand towards the tag was observed experimentally and theoretically through automated docking and molecular dynamics simulations.
Retroviral particles are expensive to manufacture, mostly due to the downstream processing steps which result in low recoveries (≈30%) and concentration factors. In this work, a dodecapeptide phage-display library was panned against retrovirus like particles expressing the envelope protein Ampho4070A (VLPs-AMPHO) and VLPs without the target protein, used as a negative control (VLPs). A depletion/selection panning protocol was successfully used to deal with the structural complexity of the target, and a total of three distinct peptide sequences displaying preferential binding towards VLPs-AMPHO were found. Peptide 3 (CAAALAKPHTENHLLT), which appeared as one lead candidate, was synthesized and immobilized onto two purification matrices, cross-linked agarose and magnetic particles. The matrices selectively bound VLPs-AMPHO and in both cases recovery yields higher than 90% were obtained when employing mild elution conditions, while maintaining viral particle morphology and size.
Affinity‐triggered assemblies rely on affinity interactions as the driving force to assemble physically crosslinked networks. WW domains are small hydrophobic proteins binding to proline‐rich peptides that are typically produced in the insoluble form. Previous works attempted the biological production of the full WW domain in tandem to generate multivalent components for affinity‐triggered hydrogels. In this work, an alternative approach is followed by engineering a 13‐mer minimal version of the WW domain that retains the ability to bind to target proline‐rich peptides. Both ligand and target peptides are produced chemically and conjugated to multivalent polyethylene glycol, yielding two components. Upon mixing together, they form soft biocompatible affinity‐triggered assemblies, stable in stem cell culture media, and display mechanical properties in the same order of magnitude as for those hydrogels formed with the full WW protein in tandem.
Adenoviruses are important platforms for vaccine development and vectors for gene therapy, increasing the demand for high titers of purified viral preparations. Monoliths are macroporous supports regarded as ideal for the purification of macromolecular complexes, including viral particles. Although common monoliths are based on synthetic polymers as methacrylates, we explored the potential of biopolymers processed by clean technologies to produce monoliths for adenovirus purification. Such an approach enables the development of disposable and biodegradable matrices for bioprocessing. A total of 20 monoliths were produced from different biopolymers (chitosan, agarose, and dextran), employing two distinct temperatures during the freezing process (-20 °C and -80 °C). The morphological and physical properties of the structures were thoroughly characterized. The monoliths presenting higher robustness and permeability rates were further analyzed for the nonspecific binding of Adenovirus serotype 5 (Ad5) preparations. The matrices presenting lower nonspecific Ad5 binding were further functionalized with quaternary amine anion-exchange ligand glycidyltrimethylammonium chloride hydrochloride by two distinct methods, and their performance toward Ad5 purification was assessed. The monolith composed of chitosan and poly(vinyl) alcohol (50:50) prepared at -80 °C allowed 100% recovery of Ad5 particles bound to the support. This is the first report of the successful purification of adenovirus using monoliths obtained from biopolymers processed by clean technologies.
Tissue
engineering and stem cell research greatly benefit from
cell encapsulation within hydrogels as it promotes cell expansion
and differentiation. Affinity-triggered hydrogels, an appealing solution
for mild cell encapsulation, rely on selective interactions between
the ligand and target and also on the multivalent presentation of
these two components. Although these hydrogels represent a versatile
option to generate dynamic, tunable, and highly functional materials,
the design of hydrogel properties based on affinity and multivalency
remains challenging and unstudied. Here, the avidin–biotin
affinity pair, with the highest reported affinity constant, is used
to address this challenge. It is demonstrated that the binding between
the affinity hydrogel components is influenced by the multivalent
display selected. In addition, the natural multivalency of the interaction
must be obeyed to yield robust multicomponent synthetic protein hydrogels.
The hydrogel’s resistance to erosion depends on the right stoichiometric
match between the hydrogel components. The developed affinity-triggered
hydrogels are biocompatible and support encapsulation of induced pluripotent
stem cells and their successful differentiation into a neural cell
line. This principle can be generalized to other affinity pairs using
multimeric proteins, yielding biomaterials with controlled performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.