Molar masses and structure in solution of haemoglobin hyperpolymers--a common calibration of size exclusion chromatography of these artificial oxygen carriers

Supramolecular assembling systems formed by heme-heme pocket interactions in hemoproteins

A native protein in a biological system spontaneously produces large and elegant assemblies via self-assembly or assembly with various biomolecules which provide non-covalent interactions. In this context, the protein plays a key role in construction of a unique supramolecular structure operating as a functional system. Our group has recently highlighted the structure and function of hemoproteins reconstituted with artificially created heme analogs. The heme molecule is a replaceable cofactor of several hemoproteins. Here, we focus on the successive supramolecular protein assemblies driven by heme-heme pocket interactions to afford various examples of protein fibers, networks and three-dimensional clusters in which an artificial heme moiety is introduced onto the surface of a hemoprotein via covalent linkage and the native heme cofactor is removed from the heme pocket. This strategy is found to be useful for constructing hybrid materials with an electrode or with nanoparticles. The new systems described herein are expected to lead to the generation of various biomaterials with functions and characteristic physicochemical properties similar to those of hemoproteins.

New artificial oxygen carriers made of pegulated polymerised pyridoxylated porcine haemoglobin (P(4)Hb)

Oxygen-carrying plasma expanders are designed for use as iso-oncotic 'blood substitutes' to combat oxygen deficiencies caused by blood loss. In contrast, a hypo-oncotic artificial oxygen carrier can be added to existing blood - as a 'blood additive'. It has potential therapeutic use for deficiencies of oxygen which are not entailed by blood (volume) lack, and can therefore not be treated by a 'blood substitute', e.g. anaemias, local ischaemias and their complications such as stroke or myocardial infarction, or lack of oxygen in tumours, reducing the effectiveness of anti-cancer treatments by irradiation or chemotherapy. For such a novel approach haemoglobin-based oxygen-carrying additive, the haemoglobin must be highly polymerised in order to decrease the oncotic pressure, which can be received many times lower compared with smaller molecular size haemoglobins. Our aim is to produce haemoglobin polymers with narrow distributions of molecular weights of approximately 1,000,000 g/mol, preferably produced in high yield and at low cost. But polymerising haemoglobin by cross-linking normally results in a so-called percolation distribution of molecular weights, with a large amount of insoluble material, and with only poor yields of the desired polymers. A newly developed one-vessel synthesis procedure, which includes a controlled marked dilution of the synthesis medium during the cross-linking reaction, enables yields of polymerised haemoglobin (P(4)Hb) of over 80 %. Those preparations are easy and cheap to perform at large scales. P(4)Hb hyperpolymers (the high molecular moiety of P(4)Hb) are suitable for an oxygen-carrying blood additive: their oxygen-binding properties are sufficient, they are fully compatible with human blood plasma, and at the intended therapeutic concentration of approximately 30 g/l oncotic pressures are very low, and the impact on blood viscosity is tolerable.