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Iodide is considered a chaotrope. Maybe it’s denaturing your enzyme. > On 5 Aug 2015, at 1:38 PM, rohit kumar <[log in to unmask]> wrote: > > Hi Shane, > > I am measured decrees in NADH absorption in a recording uv/spectrophotometer for 3-5 min, at 340nm. > > > On Wed, Aug 5, 2015 at 11:03 PM, Shane Caldwell <[log in to unmask]> wrote: > Hi Rohit, > > How does your assay work? Iodide can interfere with spectroscopic methods. It's also more reactive than F, Cl, or Br, and can participate in redox chemistry. Without additional information, I'm afraid it's really difficult for anyone to make any concrete recommendations... > > Shane Caldwell > McGill University > > > On Wed, Aug 5, 2015 at 12:52 PM, rohit kumar <[log in to unmask]> wrote: > Dear All, > > I am trying to check the affect of different halide on our enzyme. The reaction assay have > 50 mM TAPS, pH 8.5, 0.2 mM NADH, 1.0 mM DTT, 1.0 mM EDTA, 5.0 mM substarte1, excess amount of PGDH, 5.0 mM substrate 2, and 4 µg of enzymes (enzyme of interast). I am using 200 mM of halids (NaF, NaCl, NaBr and NaI) in separate reactions. > > In prsence of 200 mM NaF, NaCl, and NaBr the enzyme activity is not affected. But in case of NaI > 50% activity is decreased. > > our enzyme does not have any halide binding site. > > Can any one just tell me why NaI give such affect? > Is it because of bigger size of I (iodide ion)? or something else.... > > > Please suggest > > > > -- > WITH REGARDS > > Rohit Kumar Singh > > Research Scholar > > > > > -- > WITH REGARDS > Rohit Kumar Singh > Lab. no. 430, > P.I. Dr. S. Gourinath, > School of Life Sciences, > Jawaharlal Nehru University > New Delhi -110067