alpha -helical peptide nucleic acids (alpha PNAs) are synthetic molecules t
hat merge the a-helix secondary structure of peptides with the codified Wat
son-Crick base pairing capability of nucleic acids. It is now demonstrated
that aPNAs made up of either L- Or D-amino acids are resistant to degradati
on by the proteases present in human serum. The increased stability of aPNA
s towards proteases may be attributable to the presence of unnatural nucleo
amino acid residues [-NHCH(CH2OCH2B)CO, where B = thymine or cytosine] sinc
e the replacement of these amino acids by serine yields a control peptide t
hat does break down in human serum. The stability of alpha PNAs towards pro
teases makes them attractive candidates for further development as antisens
e agents. (C) 2001 Elsevier Science Ltd. All rights reserved.