Polypeptides with Nucleic Acid Base Derivatives

Polypeptides with Nucleic Acid Base Derivatives 

An interesting approach to obtain peptides in which the purine or pyrimidine residues were correctiy spaced for interaction with the nucleic acids, was made by using a spacer amino acid [49]. Serine was used as a spacer and several protected tetrapeptides, e.g., a-N-t-BOC-L-seryl-D,L-P-(thymin-l-yl)ala-nyl-L-seryl-D,L-P-(thymin-l-yl)alanine, ethyl ester, were synthesized but little was reported about their solution properties and interactions with the nucleic acids. The polymerization of the nucleic acid base-substituted L-lysine derivatives by N-carboxyamino acid anhydride method was also reported [52, 53]. 

In circular dichroism study on the binding of an octamer of PepNA having thymine and a terminal lysine, a right-handed triplex was found to form between the PepNA and poly(dA) [60]. Since PepNA was achiral except for the terminal lysine, it showed a very weak CD spectrum. When 1 mole of poly(dA) was mixed with 2 moles of the PepNA, the CD spectrum of poly(dA) was chan- 

Polymer 30 was named a-PepNA. Nucleobases were attached to a-position via ethylene linkages of L-a-amino acids. The amino acids were coupled with glycine to yield optically pure monomers of a-PepNA [68]. 

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Polypeptides with Nucleic Acid Base Derivatives... 

Studies of the specificities of experimentally induced antipolynucleotide antibodies have yielded some information on the antigenic determinants which could exist in a molecule of nucleic acid. Like the antibodies to proteins or synthetic polypeptides, antibodies to polynucleotides can be directed against different antigenic determinants derived from sequential regions as well as conformational factors in the molecule. Since antibodies in which the specificity is associated with the heterocyclic bases are obtained by use of single-stranded polynucleotides or certain components of nucleic acids it is thus evident that the bases themselves can be included among the antigenic determinants of polynucleotides. 

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