Modulation of the distribution of small proteins within porous matrixes by smart-control of the immobilization rate

The distribution of enzymes attached to porous solid supports is a major concern in multienzymatic bioreactors. Herein, as proof of the concept that protein localization on porous surfaces can be controlled by tuning the protein immobilization rate. We study the distribution of two poly-histidine-tagged fluorescent proteins (His-GFP and His-mCherryFP) immobilized on different 4% crosslinked agarose-type carriers by confocal laser scanning microscopy. In this context, immobilization rate is easily modulated by controlling the (i) nature of physico-chemical interaction between protein and surface (reactive groups on surface), (ii) by controlling the reactive group density and (iii) by adding competitors to the immobilization process. His-GFP is 350-fold more rapid immobilized on agarose surfaces activated with either glyoxyl groups or chelates than the same matrix activated with primary amine groups instead. A similar effect is seen with agarose matrixes activated with lower glyoxyl densities that immobilize His-GFP roughly 350-fold slower than the corresponding highly activated matrix. When His-GFP is immobilized on agarose activated with chelates groups in presence of imidazol which competes with the protein for the reactive groups on the support, the immobilization rate is again 400-fold slower than when the same protein was immobilized on the same support but with no imidazol during the immobilization process. In all cases, it was observed that rapid immobilizations (quantitative immobilization in less than 10 min) located 100% of the loaded protein at the crown of the carrier beads, meaning that only the 10% of the bead radius was colonized by the protein. On the contrary, when immobilization is much slower, a homogeneous distribution is obtained, resulting in beads whose whole radius is occupied by the protein. Therefore, we set that the more rapid immobilization, the more heterogeneous distribution. All the knowledge gained in protein distribution by immobilization rate alteration of a single protein is applied to the co-immobilization of the two fluorescent proteins in order to develop four different co-immobilization patterns with an enormous applied potential to other multi-protein systems. (C) 2011 Elsevier B.V. All rights reserved.