Oxygen binding by single crystals of hemoglobin

Area of Science:

• Biochemistry
• Biophysics
• Crystallography

Background:

• Hemoglobin's oxygen binding is crucial for physiological transport.
• Previous studies suggest cooperative binding and Bohr effect in solution.
• Crystal structure provides insights into molecular interactions.

Purpose of the Study:

• To investigate hemoglobin's oxygen binding properties within a crystal.
• To compare crystal binding with solution-based hemoglobin behavior.
• To test hypotheses regarding salt bridges and subunit cooperativity.

Main Methods:

• Microspectrophotometry used for reversible oxygen binding curves.
• Linear polarized light along crystal axes (a and c) for saturation.
• Visible spectra analysis for quantitative measurements.

Main Results:

• Oxygen binding in crystals is noncooperative.
• Bohr effect and chloride ion influence are absent in crystals.
• Lower oxygen affinity observed in crystals compared to solution.

Conclusions:

• Crystal environment significantly alters hemoglobin's oxygen binding.
• Findings support the role of intact salt bridges in crystal binding.
• A modified MWC-PSK model explains observed crystal properties.