Salt-induced disintegration of lysozyme-containing polyelectrolyte complex micelles.
The salt-induced disintegration of lysozyme-filled polyelectrolyte complex micelles, consisting of positively charged homopolymers (PDMAEMA150), negatively charged diblock copolymers (PAA42-PAAm417), and lysozyme, has been studied with dynamic light scattering (DLS) and small-angle neutron scattering (SANS). These measurements show that, from 0 to 0.2 M NaCl, both the hydrodynamic radius (Rh) and the core radius (Rcore) decrease with increasing salt concentration. This suggests that the micellar structures rearrange. Moreover, from approximately 0.2 to 0.4 M NaCl the light-scattering intensity is constant. In this salt interval, the hydrodynamic radius increases, has a maximum at 0.3 M NaCl, and subsequently decreases. This behavior is observed in both a lysozyme-containing system and a system without lysozyme. The SANS measurements on the lysozyme-filled micelles do not show increased intensity or a larger core radius at 0.3 M NaCl. This indicates that from 0.2 to 0.4 M NaCl another structure is formed, consisting of just the diblock copolymer and the homopolymer, because at 0.12 M NaCl the lysozyme-PAA42-PAAm417 complex has disintegrated. One may expect that the driving force for the formation of the complex in this salt range is other than electrostatic.
Lindhoud
Saskia
S
Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands. saskia.lindhoud@wur.nl
Voorhaar
Lenny
L
de Vries
Renko
R
Schweins
Ralf
R
Cohen Stuart
Martien A
MA
Norde
Willem
W
D004573:Electrolytes / Q000737:chemistry*; D008027:Light; D008049:Lipase / Q000737:chemistry / Q000378:metabolism; D008823:Micelles; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D033363:Neutron Diffraction; D011108:Polymers / Q000737:chemistry*; D012492:Salts / Q000494:pharmacology*; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D017186:Titrimetry
D004573:Electrolytes; D008823:Micelles; D011108:Polymers; D012492:Salts; D008049:Lipase; D009113:Muramidase