Spacer molecules in peptide sequences: Incorporation into analogues of atrial natriuretic factor

In the present study, 10 modified human atrial natriuretic factor (hANF) analogues were designed using solid phase synthesis. This was carried out by replacing 'alkyl or glycol' spacer with octapeptide sequence within the cyclic portion of hANF in each analogue synthesised. The unnatural amino acid spacers (1b) and (2d) have been synthesised using solution chemistry. The latter spacers were successfully incorporated into the peptide structure, using solid phase synthesis assembly. Amongst the ten analogues, thus prepared, two in which the alkyl spacer was used to substitute amino acid residues Gly(15), to Gly(22) and Arg(14) to Leu(21) to give 4a and 4b, successively. In the purification process of the latter analogues (4a, 4b), problems of their severe solubility were encountered. The eight glycol-spaced analogues (5a-5h) were successfully synthesised and purified using HPLC. The structure of(5a-5h) was confirmed by the presence of mass ion peaks in the atom bombardment mass spectroscopy (FAB MS) and by NMR. The latter analogues were tested, in vivo, for their ability to bind to specific hANF receptors, as agonists or antagonists. The biological results have showed that none of these analogues (5a-5h) were active. (C) 1997 Elsevier Science Ltd.