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Oligomerization and Phase Transitions in Aqueous Solutions of Native and Truncated Human B1-Crystallin

Summary: Oligomerization and Phase Transitions in Aqueous Solutions of Native and
Truncated Human B1-Crystallin
Onofrio Annunziata,, Ajay Pande, Jayanti Pande, Olutayo Ogun, Nicolette H. Lubsen,| and
George B. Benedek*,
Department of Physics, Center for Materials Science and Engineering, and Materials Processing Center,
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Biochemistry,
UniVersity of Nijmegen, 6500 HB Nijmegen, The Netherlands
ReceiVed July 25, 2004; ReVised Manuscript ReceiVed NoVember 15, 2004
ABSTRACT: Human B1-crystallin is a major eye-lens protein that undergoes in vivo truncation at the
N-terminus with aging. By studying native B1 and truncated B1N41, which mimics an age-related in
vivo truncation, we have determined quantitatively the effect of truncation on the oligomerization and
phase transition properties of B1 aqueous solutions. The oligomerization studies show that the energy
of attraction between the B1N41 proteins is about 10% greater than that of the B1 proteins. We have
found that B1N41 aqueous solutions undergo two distinct types of phase transitions. The first phase
transition involves an initial formation of thin rodlike assemblies, which then evolve to form crystals.
The induction time for the formation of rodlike assemblies is sensitive to oligomerization. The second
phase transition can be described as liquid-liquid phase separation (LLPS) accompanied by gelation
within the protein-rich phase. We refer to this process as heterogeneous gelation. These two phase transitions
are not observed in the case of B1 aqueous solutions. However, upon the addition of poly(ethylene
glycol) (PEG), we observe heterogeneous gelation also for B1. Our PEG experiments allow us to estimate


Source: Annunziata, Onofrio - Department of Chemistry, Texas Christian University
Benedek, George B. - Department of Physics, Massachusetts Institute of Technology (MIT)


Collections: Chemistry; Physics