Equilibrium batch rebinding

Small scale procedures for the rapid synthesis and screening of large groups of MIPs have been recently developed [7,8], based on the preparation of 50 mg of materials (MiniMIPs) on the bottom of small vials or of 96-well plates [9] and their in situ testing by equilibrium batch rebinding. The preparation of the materials, which represents a scaled down version of the traditional monolith approach (Chapter 15), is outlined in Fig. 1. For each MiniMIP, a corresponding... 

Figure 2 Screening of MiniMIPs (1) in situ template extraction (2) equilibrium batch rebinding.

After complete extraction of the template, the polymers were submitted to equilibrium batch rebinding with a ImM solution of terbutylazine in CH2CI2. The imprinting factors ( mip/ np) of MIPs prepared using MAA and TFM as functional monomers were 11 and 6, respectively. 

The problem here was that the target molecule is very complex and unstable. The results of the rebinding test are shown after 1 and 26 h of equilibration (expressed as peak area values). The absolute absorbance decreased during this time due to template decomposition. 2-Vinyl pyridine appeared to be the most successful monomer based on the equilibrium batch rebinding tests (Fig. 15). The 2-VPY materials prepared on a larger scale and tested as chromatographic stationary phases also exhibited a certain selectivity towards the template (methotrexate, MTX) and its closely related analogues (leucovorin and folic acid) (Fig. 16). 

The relationship between K and k holds if both batch rebinding and chromatographic methods are under equilibrium conditions, allowing the equations derived for the bateh rebinding method to be converted to the following equations for ehromatographically derived data ... 

For determining the adsorption isotherm, the equilibrium concentrations of bound and free template must be reliably measured within a large concentration interval. Since the binding sites are part of a solid, this experiment is relatively simple and can be carried out in a batch equilibrium rebinding experiment or by frontal analysis. 

The template 7a can be split off by water or methanol to an extent of up to 95% (Scheme 2-5). The accuracy of the steric arrangement of the binding sites in the cavity can be tested by the ability of the polymer to resolve the racemate of the template, namely of phenyl-a-D,L-mannopyranoside. Therefore the polymer is equilibrated in a batch procedure with a solution of the racemate under conditions under which rebinding in equilibrium is possible. The enrichment of the antipodes on the polymer and in solution is determined by measuring the specific optical rotation and the separation factor a, i.e., the ratio of the distribution coefficients of the D and L compounds between polymer and solution, is calculated. After extensive optimization of the procedure, a values between 3.5 and 6.0 were obtained [10]. This is an extremely high selectivity for racemic resolution that cannot be reached by most other methods. 

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