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Surface-induced unfolding of human lactoferrin
Jian R Lu1, Shiamalee Perumal, Xiubo Zhao
1Biological Physics Group, School of Physics and Astronomy, the University of Manchester, Sackville Street Building, Sackville Street, Manchester M60 1QD, UK. j.lu@manchester.ac.uk
Langmuir : the ACS Journal of Surfaces and Colloids
|April 6, 2005
Summary
Human lactoferrin unfolds at the air/water interface, forming distinct layers. Salt concentration affects protein adsorption and layer thickness, while solution structure remains globular.
Area of Science:
- Biophysics
- Surface Science
- Protein Chemistry
Background:
- Human lactoferrin is a key protein in innate immunity.
- Understanding protein behavior at interfaces is crucial for biomaterial design and biological processes.
- The structural changes of proteins upon adsorption influence their function.
Purpose of the Study:
- To determine the structural conformations of human lactoferrin at the air/water interface and in solution.
- To investigate the effect of salt concentration on lactoferrin adsorption and structure.
- To elucidate the driving forces behind protein unfolding at interfaces.
Main Methods:
- Neutron reflectivity (NR) to study interfacial structure.
- Small angle neutron scattering (SANS) to determine solution structure.
- Adsorption measurements at varying NaCl concentrations.
Main Results:
- Neutron reflectivity revealed significant structural unfolding of lactoferrin at the air/water interface, forming a two-layered structure.
- Protein adsorption decreased with increasing NaCl concentration, and layer thickness was reduced.
- SANS data indicated that lactoferrin retained its globular structure in solution, though its dimensions changed with ionic strength.
- D2O measurements suggested hydrophobic interactions in the interfacial layer.
Conclusions:
- Human lactoferrin undergoes substantial structural unfolding at the air/water interface.
- Surface adsorption leads to an unfolded state driven by an asymmetric energetic balance.
- Ionic strength significantly modulates lactoferrin adsorption and interfacial structure, while preserving the globular state in solution.