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Understanding the shape of sickled red cells
Garrott W Christoph1, James Hofrichter, William A Eaton
1Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
Biophysical Journal
|November 16, 2004
Summary
Sickle cell anemia red blood cell shapes result from hemoglobin S fiber formation. High protein concentration sensitivity explains varied cell morphology and rapid polymerization, preventing sickling.
Area of Science:
- Biophysics
- Hematology
- Polymer Science
Background:
- Sickle cell anemia is characterized by abnormal red blood cell (RBC) shapes.
- Deoxygenated sickle cells contain polymerized hemoglobin S fibers.
- RBC morphology is linked to the physical properties of hemoglobin S polymerization.
Purpose of the Study:
- To investigate the physical basis for diverse deoxygenated RBC shapes in sickle cell anemia.
- To measure the formation rate and volume distribution of hemoglobin S fiber domains.
Main Methods:
- Quantified domain formation rate and volume distribution of hemoglobin S fibers.
- Analyzed concentration dependence of domain formation and pre-fiber delay time.
Main Results:
- Domain formation rate shows an ~80th power dependence on protein concentration.
- Pre-fiber delay time shows an ~40th power dependence on protein concentration.
- Domain volumes exhibit an exponential distribution.
Conclusions:
- The double nucleation model explains observed concentration dependencies and domain volume distributions.
- High sensitivity of domain formation rate to intracellular hemoglobin S concentration dictates RBC morphology.
- Rapid polymerization can lead to cells that do not appear sickled, despite deoxygenation.