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在 Oct 2, 2011，4:22 PM，Roger Rowlett <[email protected]> 写道： > You can't change the pKa of CO2, which is 6.3. Any attempt to grow bicarb > complexes below pH 7.5 will be problematic due to CO2 bubble formation, which > may crack the crystal. What we do in these situations is to soak crystals in > a cryo solution at a higher pH for as long as practical, then transfer to > another, identical solution with bicarbonate fo li and soak. This can be > tricky, because crystals may take a long time to pH equilibrate, crack, or > dissolve. At pH 7.5 or above, CO2 formation at chemical equilibrium is > minimal. At low pH, you can also consider using acetate as a bicarbonate > analog. > > Roger Rowlett > > On Oct 2, 2011 4:56 PM, "Jacob Keller" <[email protected]> wrote: > > Dear Crystallographers, > > > > I would like to soak my crystals in bicarbonate (a possible > > substrate), but the crystals have grown--and only grow--in pH 5.2-6.0, > > so the bicarb/CO2 will just keep evolving out of the solution and > > reliquishing its hydroxyls until the pH is elevated sufficiently out > > of range. Does anyone have a clever way of getting bicarb into these > > crystals? Grow them under CO2? Transfer them to higher pH, and hope > > for the best? > > > > Jacob Keller
