Immobilization of a photosystem ii submembrane fraction in a glutaraldehyde cross-linked matrix

Cryostructuring of polymer systems. 44. Freeze-dried and then chemically cross-linked wide porous cryostructurates based on serum albumin

Spongy cryostructurates based on bovine serum albumin (BSA) have been prepared via freezing the aqueous solutions of the protein followed by freeze-drying and subsequent cross-linking BSA macromolecules each together within the macropore walls using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) dissolved in ethanol. The gel-fraction yield values testifies high efficiency (>93%) of the protein building-up into the 3D polymeric network. Poor swelling of the pore walls of BSA-based sponges in water (1–2 g H2O per 1 g of dry polymer) and even in the powerful protein-solubilizing media (8 m urea, 5 m guanidine hydrochloride, 1% SDS) indicates the multipoint character of albumin cross-linking via the pendant peptide bonds. As a result, strong cross-linking is able (as revealed by HS-DSC) to inhibit BSA thermal denaturation. The size of wide pores in the obtained cryostructures ranges from 40 to 250 μm and mainly depends on the freezing temperature.

Cryostructuring of polymer systems. Proteinaceous wide-pore cryogels generated by the action of denaturant/reductant mixtures on bovine serum albumin in moderately frozen aqueous media

Freeze-thaw processing of bovine serum albumin (BSA) aqueous solutions, which contain also the additives of denaturants (urea in this case) and thiol-bearing reductants [cysteine (Cys) in this case] leads to the formation of wide-pore cryogels. The properties and porous morphology of these spongy gel matrices were demonstrated to depend on the initial concentration of all precursors and on the freezing/frozen storage temperature. The optimum conditions for preparing such BSA-based cryogels were found to be as follows: [BSA] = 3-5 g dL(-1), [urea] = 0.5-2.0 mol L(-1), [Cys] = 0.01 mol L(-1), and freezing temperatures in the range of -15 to -20 °C. The size of gross pores in thus prepared cryogels is ∼50-150 μm. The spatial network of BSA-cryogels was shown to be cross-linked chemically via interchain disulfide bridges. The significant role of hydrophobic interactions in the stabilization of 3D networks of these cryogels is inferred, as well as the supposition about the relay-race sequence mechanism of the intermolecular disulfide cross-link formation is made.

Physical and chemical immobilization methods of photosynthetic materials

Isolated photosynthetic materials have a relatively short active life time that limits their effective use. To circumvent this limitation, various immobilization techniques have been designed to improve their stability both under storage and working conditions. The immobilization methods are identified either as chemical or physical procedures depending on whether covalent bonds are established or not. In this chapter, two immobilization methods frequently used are described: a physical one based on the entrapment of photosynthetic materials in photo-crosslinkable poly(vinylalcohol) polymer bearing styrylpyridinium groups (PVA-SbQ) and a chemical one where the photosynthetic materials are immobilized by coreticulation in an albumin-glutaraldehyde cross-linked matrix (BSA-Glu). Different immobilization procedures in relation with various photosynthetic materials are mentioned.