I am working on hemolymph of lepidopteran insect and want to calculate the PO activity in the hemolymph. For control group, I need to add 10% PTU solution, but it is not soluble in water/ PBS. How should I make the solution and/or dissolve PTU? Thanks in Advance.
Dear Istkhat,
Phenylthiourea is soluble in 400 parts cold water, 17 parts boiling water; soluble in alcohol.
As you can see its solubility in water is not good even in hot water 1g is dissolved in 17 ml hot water. I siggest that you dissolve it in ethanol or DMSo, in both solvents PTU is soluble. Alternatively you can dissolve it in mixtures of PBS/DMSO, PBS/EtOH, water/DMSO or water/EtOH.
Hoping this will be helpful,
Rafik
Dear RafiK Sir
Thanks for the suggestion. The solubility and nonsolubility of PTU in alcohol and water respectively are well known. I just want to know it I dissolve it in alcohol or PBS/EtOH, will it make any effect on hemocytes or phenoloxidase activity. Further, If in PBS/EtOH in what ratio should I dissolve? Waiting for your valuable response.
Dear Istkhar,
You can use mixtures up to 50% ethanol or 50% DMSO; EtOH/water 50/50; DMS/water 50/50; EtOH/PBS 50/50 or DMSO/PBS 50/50.
Good luck,
Rafik
Dear Isthkar,
a late reply on your question, I hope it is not to late. You must take care when adding ethanol (or acetone or methanol...) since prophenoloxidase can be transformed to active phenoloxidase by adding ethanol which might result in false positive reactions (at least of the non-inhibited samples to which you add the solution containing no PTU) (see Ashida M., Brey P. (1997). Recent advances on the research of the insect prophenoloxidase cascade, in Molecular Mechanisms of Immune Responses in Insects, eds Brey P., Hultmark D., editors. (London: Chapman & Hall; ), 135–172). You should consider using an aqueous PTU solution with lower concentration if possible. I do not know if DMSO has any effects on prophenoloxidase activation or PO activity.
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