Support inert spacer

The described bioaffinity separations demonstrate that polyacrylamide spacers aid the selective binding of highly complex and delicate biomacromolecules and their associates. Moreover, these solutes remain biologically active after desorption probably due to the high inertness and flexibility of the surrounding polymer chains fixed on the solid support. The unbound parts of serum usually show no loss of the activities of their constituents. Thus we evaluate the surface of inorganic supports coated with chemisorbed iV-hydroxyethyl polyacrylamide and its derivatives as being biocompatible. 

The requirements for solid-phase synthesis are diverse. The support must be insoluble, in the form of beads of sufficient size to allow quick removal of solvent by filtration, and stable to agitation and inert to all the chemistry and solvents employed. For continuous-flow systems, the beads also must be noncompressible. Reactions with functional groups on beads imply reaction on the inside of the beads as well as on the surface. Thus, it is imperative that there be easy diffusion of reagents inside the swollen beads and that the reaction sites be accessible. Accessibility is facilitated by a polymer matrix that is not dense and not highly functionalized. A matrix of defined constitution allows for better control of the chemistry. Easier reaction is favored by a spacer that separates the matrix from the reaction sites. Coupling requires an environment of intermediate polarity such as that provided by dichloromethane or dimethylformamide benzene is unsuitable as solvent. 

Y. F. Ng, J. C. Meillon, T. Ryan, A. P. Dominey, A. P. Davis and J. . M. Sanders, Gel-phase MAS NMR spectroscopy of a polymer-supported pseudorotaxane and rotaxane Receptor binding to an inert polyethylene glycol spacer, Angewandte Chemie-International Edition, 2001, 40, 1757-1760. 

It should be emphasized that the spacer bearing support modified in this way is indeed uniformly functionalized. The tertiary glycolic group was found entirely inert to the reaction conditions of the Merrifield synthesis, if low concentrations of trifluoroacetic acid (< 10%, in dichloromethane) are used in the deprotection procedures [81]. The subsequent elimination of water from the remaining tertiary alcoholic function of the glycolic handle which leads to the activation of the C-termini of peptides synthetized on this support, will be described in Sect. 3.5.3.1. 

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