Artificial surfactants based on analogues of SP-B and SP-C

The hydrophobic proteins SP-B and SP-C are important components of natural surfactant preparations currently used in clinical practice, and physiologi cally active surfactants can be made from. isolated SP-B and/or SP-C recons tituted with synthetic lipids. Efforts have been made to produce these poly peptides, or analogues with similar function, by organic synthesis or expre ssion in heterologous systems. It is important to obtain proper folding of the synthetic peptides, as required for optimal interaction with the surfac tant lipids. Another issue is to avoid loss of SP-C activity due to alpha - helix to beta -sheet transition. This latter problem can be circumvented by replacing the polyvaline stretch of SP-C with a polyleucine stretch contai ning a few lysines. Palmitoylation of cysteines or serines at positions 5 a nd 6 also seems important for the properties of SP-C. SP-B, which is too bi g a molecule to be easily produced by organic synthesis, apparently can be replaced in an artificial surfactant by a peptide capable of cross-linking phospholipid bilayers. The development of synthetic analogues of the surfac tant proteins might make it possible to tailor artificial surfactants for s pecific therapeutic missions,for instance by enhancing resistance to inacti vation by meconium, plasma proteins, or oxygen radicals or maximizing bacte riostatic effects.