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Updated: Jul 12, 2026
07:03
Measuring Photophysiology of Attached Stage of Colacium sp. by a Cuvette-Type Fast Repetition Rate Fluorometer
Published on: November 12, 2021
Summary
Keyhole limpet hemocyanin exhibits no Bohr effect, indicating stable oxygen binding across a pH range. Oxygenation involves positive cooperativity and releases significant heat.
Area of Science:
- Biochemistry
- Marine Biology
- Physiology
Background:
- Hemocyanins are copper-containing respiratory proteins in many marine invertebrates.
- The Bohr effect describes the influence of pH on oxygen affinity in respiratory proteins.
- Diodora aspera hemocyanin's physiological characteristics are not fully understood.
Purpose of the Study:
- To investigate the oxygen-binding properties of Diodora aspera hemocyanin.
- To determine the presence and extent of the Bohr effect in this hemocyanin.
- To characterize the thermodynamic and cooperativity aspects of oxygenation.
Main Methods:
- Oxygen equilibrium curves were measured for Diodora aspera hemocyanin.
- Experiments were conducted across a defined pH range (6.88–7.84) and at a constant temperature (10°C).
- Thermodynamic parameters, including the heat of oxygenation, were calculated.
Main Results:
- No significant Bohr effect was observed for Diodora aspera hemocyanin within the tested pH range.
- The pressure of half-saturation (P50) was determined to be 5 mm-Hg at 10°C.
- A moderately positive interaction (cooperativity) among oxygen-combining sites was detected during oxygenation.
- The calculated heat of oxygenation was approximately -12.6 kcal/mole of oxygen.
- The normal blood pH of Diodora aspera was found to be lower than that of many other marine molluscs.
Conclusions:
- Diodora aspera hemocyanin functions independently of pH changes within the physiological range studied.
- The observed positive cooperativity suggests an allosteric mechanism for oxygen binding.
- The significant negative heat of oxygenation indicates an exothermic binding process.
- The lower blood pH may have implications for hemocyanin function and other physiological processes in Diodora aspera.
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