The two limiting cases of the metal completely free (K - 00) or completely bound (K - 0), where K is the dissociation constant of the CM complex, would give [Pg.133]

When the CM complex is fully formed, [M] = 0 and [CM] = Cm, therefore, from Eq. (4.40), e = So- w thus defined as the enhancement factor measured in a solution where all the metal is complexed. Since usually q p,eo should be smaller than unity if the intrinsic nuclear relaxation times are the same in the metal complex and in the aquaion. However, as often T cm T m owing to a longer correlation time xc in the complex (Chapter 3), q can be larger than unity. This is particularly true when C is a macromolecule (e.g. a protein) and M is a metal ion with long electronic relaxation times. [Pg.134]

As it appears in Eq. (4.40), eo is defined only in terms of the molar fraction of bound metal ion that is, independently of the actual concentrations. By using an equation for /b analogous to Eq. (4.32), the enhancement factor can be expressed as [Pg.134]

Both K and o can be obtained through a two-parameter fitting of the s data obtained at various Cc and/or Cm concentrations. [Pg.134]

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