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The entropically favored osmotic “compression” of sickle cell hemoglobin gels
Author(s) -
Chik John K.,
Parsegian V. Adrian
Publication year - 2001
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(200108)59:2<120::aid-bip1011>3.0.co;2-m
Subject(s) - chemistry , monomer , polymerization , entropy (arrow of time) , hemoglobin , compressibility , chemical engineering , polymer chemistry , thermodynamics , polymer , chemical physics , organic chemistry , engineering , physics
Contrary to the accurate, hard‐sphere depiction of monomeric hemoglobin in solution, sickle cell hemoglobin (HbS) polymerization/gelation requires attention to molecular interactions. From the temperature dependence of the osmotic compressibility of HbS gels, we were able to extract the entropy increase for concentrating HbS in this phase. Normalized per mole of water removed, the entropy increase from gel compression Δ S gel is four times the previously measured Δ S trans , for the transition from monomeric HbS solution to HbS gel. The positive entropy change cannot emerge from the assembly of hard spheres but can indicate remodeling of HbS fibers driven by release of ordered water. The fourfold difference in Δ S gel and Δ S trans suggests that the act of initial fiber/gel formation from monomeric solution differs from the process of further polymerization due to tighter packing within the gel phase. © 2001 John Wiley & Sons, Inc. Biopolymers 59: 120–124, 2001