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Computer models of a new deoxy-sickle cell hemoglobin fiber based on x-ray diffraction data
1College of Physicians & Surgeons, Columbia University, New York, New York.
Biophysical Journal
|June 1, 1992
Summary
New research reveals distinct x-ray diffraction patterns for deoxygenated sickle cell erythrocytes, showing a 109 A periodicity. Computer modeling identified twelve zigzag protofilament models, contrasting with classic sickle cell hemoglobin (HbS) fibers.
Area of Science:
- Biophysics
- Structural Biology
- Hematology
Background:
- Sickle cell hemoglobin (HbS) polymerization in erythrocytes causes disease pathology.
- Previous models of HbS fibers exhibit a 64 A periodicity.
Purpose of the Study:
- To investigate the structural basis of deoxygenated sickle cell erythrocytes using x-ray fiber diffraction.
- To develop and evaluate computational models of HbS protofilaments and fibers.
Main Methods:
- X-ray fiber diffraction analysis of deoxygenated sickle cell erythrocytes.
- Computer-based modeling and energy calculations for HbS protofilament and fiber structures.
- Systematic searches across parameter space to identify valid structural models.
Main Results:
- Observed a new x-ray fiber diffraction pattern with 14 layer lines and 109 A periodicity.
- Generated twelve distinct zigzag mono-strand protofilament models satisfying structural and energetic constraints.
- Identified four pseudo-hexagonally packed fiber models with low association energies (R-factor < 0.24).
Conclusions:
- The deoxygenated sickle cell erythrocyte structure differs from the classic HbS fiber model.
- Multiple protofilament arrangements can form fibers consistent with observed diffraction data.
- Further data is required to uniquely determine the precise in vivo HbS fiber structure.