Protein porous assembly

In this chapter we describe the basic principles involved in the controlled production and modification of two-dimensional protein crystals. These are synthesized in nature as the outermost cell surface layer (S-layer) of prokaryotic organisms and have been successfully applied as basic building blocks in a biomolecular construction kit. Most importantly, the constituent subunits of the S-layer lattices have the capability to recrystallize into iso-porous closed monolayers in suspension, at liquid-surface interfaces, on lipid films, on liposomes, and on solid supports (e.g., silicon wafers, metals, and polymers). The self-assembled monomolecular lattices have been utilized for the immobilization of functional biomolecules in an ordered fashion and for their controlled confinement in defined areas of nanometer dimension. Thus, S-layers fulfill key requirements for the development of new supramolecular materials and enable the design of a broad spectrum of nanoscale devices, as required in molecular nanotechnology, nanobiotechnology, and biomimetics [1-3]. 

Fig. 4.8 Preparation of a porous protein assembly using mesoporous silica as a hard template.

C. Duan and M.E. Meyerhoff, Immobilization of proteins on gold coated porous membranes via an activated self-assembled monolayer of thioctic acid. Mikrochim. Acta 117,195-206 (1995). 

Figure B3.2.3 Electroblotting with a semidry transfer unit. In most cases, the lower electrode is the anode, as shown. Position the Mylar mask (optional) directly over the anode. Layer on three sheets of filter paper that have been wetted in transfer buffer. For negatively charged proteins, place the preequilibrated transfer membrane on top of the filter paper followed by the gel and three additional sheets of wetted filter paper. If multiple gels are to be transferred, separate the transfer sandwiches by inserting a sheet of porous cellophane or dialysis membrane between each stack. Place the cathode on top of the assembled transfer stack(s). Transfer the proteins by applying a maximum current of 0.8 mA/cm2 gel area.

Each mitochondrion (plural mitochondria) is bounded by two membranes (Figure 2.24a). The smooth outer membrane is relatively porous, because it is permeable to most molecules with masses less than 10,000 D. The inner membrane, which is impermeable to ions and a variety of organic molecules, projects inward into folds that are called cristae (singular crista). Embedded in this membrane are structures composed of molecular complexes and called respiratory assemblies (described in Chapter 10) that are responsible for the synthesis of ATP. Also present are a series of proteins that are responsible for the transport of specific molecules and ions. 

Nanocasting Strategies and Porous Materials, p. 950 Protein Supramolecular Chemistry, p. 1161 Self-Assembling Catenanes, p. 1240 Self-Assembly in Biochemistry, p. 1257... 

We can also mention the use of bio-sourced building blocks based on cellulose or dextran. Kadla et al. described value-added materials from naturally abundant polymers for system that may serve as a platform for the design and development of biosensors [197]. A hierarchically strucmred honeycomb film from dextran-ft-PS amphiphilic linear diblock copolymers has also been described by Chen et al. leading to ordered porous bio-hybrid films. [198] Honeycomb patterned surfaces functionalized with biomolecules for specific recognition of proteins or bacteria have been also achieved either by self-assembly of amphiphilic copolymers based on galactose moieties [155] or by post-modification with peptide sequences [199]. 

---