alkalis when permissible provides the additional advantages described herein in a preferred embodiment dtpa chelant rather than edta can be used as a general thiol stabilizer and protectant in thiol reactions another significant application of dtpa direct thiolation of amino derivatives i e proteins via 2 iminothiolane it or traut 39 s reagent which is described in pierce reagents for thiolation not requiring ha or cma involves concurrent functionalization of protein amino groups and thiol generation with one reagent in one step this reaction is carded out in the ph range of 7 10 generally for several hours or overnight with or without edta present there is a potential for significant losses of thiol through oxidation depending on the effectiveness of light air exclusion and the absence of redox active metallic contaminants in the buffers generally the iminothiolated protein is then purified by gel filtration prior to reaction with a thiol reactive reagent in a subsequent step in view of the demonstrated ability of dtpa but not edta to protect the thiol group of cysteine for 24 60 hrs comparable protection will be expected for the iminothiolated product during the generation purification and conjugation steps and thus significant improvements in conjugation efficiencies 8 tlc plates whatman mk6f silica gel 60a 1 u00d7 3 inches cat no 4861 110 9 pauly 39 s reagent store 3 components in refrigerator and mix before use mix 5 ml a plus 5 ml b let stand at room temperature for 2 min and add 10 ml c mix and use immediately spray dried tlc plates in the hood wear gloves iodinated or unsubstituted phenols yield orange.