A metal-chelate affinity reverse micellar system for protein extraction.

Area of Science:

• Biochemistry
• Materials Science
• Chemical Engineering

Background:

• Nonionic surfactants Triton X-45 and Span 80 form stable reverse micelles.
• Di(2-ethylhexyl) phosphoric acid (HDEHP) chelates transition metals like copper, zinc, and nickel.
• These metal chelates bind to histidine-rich proteins.

Purpose of the Study:

• To develop a novel nonionic reverse micellar system for selective protein purification.
• To characterize copper-chelate reverse micelles (Cu-RM) and their properties.
• To demonstrate the system's utility in isolating and refolding histidine-tagged proteins.

Main Methods:

• Blending Triton X-45 and Span 80 to create reverse micelles.
• Introducing HDEHP for transition metal chelation.
• Characterizing Cu-RM by water content (W(0)), hydrodynamic radius (R(h)), and aggregation number (N(ag)).
• Performing selective protein extraction using Cu-RM and subsequent protein recovery via stripping.

Main Results:

• Thermodynamically stable reverse micelles formed with W(0) up to 30.
• Cu-RM exhibited a linear relationship between R(h) and W(0).
• Aggregation number of Cu-RM was 30-90 at W(0) of 5-30.
• Successfully achieved selective extraction of myoglobin using Cu-RM.
• Demonstrated recovery of solubilized protein using imidazole or EDTA.

Conclusions:

• The developed nonionic reverse micellar system is effective for selective metal-chelation and protein purification.
• This system shows potential for simultaneous isolation and refolding of recombinant histidine-tagged proteins.
• The findings suggest broad applicability in bioprocessing and protein recovery.