Oxidation of Vanadium(III) to Vanadium(IV) by L-Methionine and L-Threonine: an in vitro Investigation Regarding the Redox Behavior of Vanadium in the Vanadocyte of Ascidians

Mohammad K. Islam1*, Md. Nuruzzaman1, Rashedul I. Ripon1, Morium Rahaman Rupa1, Md. Shalauddin1 and Mohammad M. Hossain2

1Department of Chemistry, Mawlana Bhashani Science and Technology University, Santosh, Tangail-1902, BANGLADESH. 2Department of Chemistry, Jahangirnagar University, Savar, Dhaka-1342, BANGLADESH.


Certain ascidians accumulate high levels of vanadium from sea water and store in their blood cells (called vanadocytes), though the mechanism for this curious biofunction remains unrevealed. To better understand whether the accumulation process of vanadium by ascidians are redox or not, and to justify the persistence of large extent of vanadium(III) with small extent of vanadium(IV) in the vanadocytes, the oxidation behavior of vanadium(III) to vanadium(IV) pursued by several amino acids were investigated. UV-Visible and electron spin resonance (ESR) spectroscopy indicated that, among tested amino acids only L-Methionine and L-Threonine assist very fast oxidations adopting the physiological pH region (i.e., pH 4~5.5) relevant to vanadocyte. In particular, amino acids promote the oxidation of vanadium(III) which have smaller stability constant value with vanadium(III) and larger stability constant value with vanadium(IV), i.e., (log K1 and log K2)>7.4.

Keywords :Vanadium, Ascidian, L-Methionine, L-Threonine Oxidation behavior, Stability constant.