Vanadium in ascidians: changes in vanadium coordination and oxidation state upon cell lysis

Area of Science:

• Biochemistry
• Biophysics
• Marine Biology

Background:

• Ascidian blood cells accumulate high concentrations of vanadium.
• The coordination state of vanadium in these cells is not fully understood.
• Cell lysis is known to affect the chemical environment of vanadium.

Purpose of the Study:

• To investigate changes in vanadium coordination during cell lysis in ascidian blood cells.
• To elucidate the chemical forms of vanadium in different cellular states.
• To correlate vanadium release with biological processes like wound repair.

Main Methods:

• Electron Paramagnetic Resonance (EPR) spectroscopy was used to analyze vanadium coordination.
• Blood and tissue samples from Ascidia ceratodes and Phallusia julinea were studied.
• Samples were analyzed in both freshly frozen and thawed (lysed) states.

Main Results:

• EPR spectra indicated aquated oxovanadium(IV) in lysed A. ceratodes blood.
• Freshly frozen blood showed broadened signals, attributed to damaged cells in a low-sulfate, low-acid environment.
• Thawed blood showed narrowed signals due to acid and sulfate release upon lysis.
• P. julinea samples exhibited intermediate EPR parameters between aquated oxovanadium(IV) and 'type I' complexes.
• Tissue samples suggested a more stable, 'resting' vanadium state due to buffering capacity.

Conclusions:

• Cellular lysis in ascidians is accompanied by vanadium oxidation and chelate exchange.
• Released protons during lysis contribute to the acidity of blood cell lysates.
• The release of vanadium and tunichrome from blood cells has implications for wound repair.