Synthesis of human haemoglobin for use as a blood substitute using recombinant DNA techniques. Scientists at the U.K. Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge, and Somatogen Inc., in the U.S. have produced a synthetic haemoglobin, the oxygen-carrying molecule in blood, using genetic engineering techniques on the bacterium E. coli. The bottle at left (NC alpha) contains bacterial cells producing haemoglobin (red colour) whilst the one at right (TG-1) shows no presence of haemoglobin. The need to develop a blood substitute has arisen because of concern over contamination of stocks by pathogens such as HIV, the virus causing AIDS. - Renal toxicity due to dissociation into dimers, overcome by expressing alpha chain as a fused dimer; assembly with 2 beta chains into stable dimers.