Linked peptide nucleic acids

A compound comprising a, first peptide nucleic acid segment and a second peptide nucleic acid segment, wherein said segments are joined via at least one linking segment;

• and wherein said linking segment comprises a compound of the formula:
• —[NH—(CH2—CH2—O—)j—CH2—C(═O)—]i
• wherein:
• j is 1 to 6;
• and
• i is 1 to 6.

A compound comprising a first peptide nucleic acid segment and a second peptide nucleic acid segment wherein one of said first and second peptide nucleic acid segments includes at least one pyrimidine nucleobase;

• wherein:
• said segments are joined via at least one linking segment;
• and
• said linking segment is not a peptide nucleic acid or an oligonucleotide.

A compound comprising a first peptide nucleic acid segment and a second peptide nucleic acid segment wherein one of said first and second peptide nucleic acid segments includes at least one pyrimidine nucleobase;

• wherein at least one of said pyrimidine nucleobases of one of said first or said second peptide nucleic acid segments comprises a C-pyrimidine heterocyclic base or an iso-pyrimidine heterocyclic base;
• wherein:
• said segments are joined via at least one linking segment;
• and
• said linking segment is not a peptide nucleic acid or an oligonucleotide.

A multiple stranded structure comprising:

• a nucleic acid strand, at least a portion of which forms a target nucleotide sequence;
• and
• a further strand, said further strand including first and second peptide nucleic acid segments that are joined together via a linker wherein one of said segments includes at least one pyrimidine nucleobase;
• wherein:
• said first peptide nucleic acid segment has a nucleobase sequence that is complementary to the target nucleotide sequence in the 5′ to 3′ direction of said target nucleotide sequence;
• said second peptide nucleic acid segment has a nucleobase sequence that is complementary to the target nucleotide sequence in the 3′ to 5′ direction of said target nucleotide sequence;
• and
• said nucleic acid strand is a double stranded DNA.

A multiple stranded structure comprising:

• a nucleic acid strand, at least a portion of which forms a target nucleotide sequence;
• and
• a further strand, said further strand including first and second peptide nucleic acid segments that are joined together via a linker wherein one of said segments includes at least one pyrimidine nucleobase;
• wherein:
• said first peptide nucleic acid segment has a nucleobase sequence that is complementary to the target nucleotide sequence in the 5′ to 3′ direction of said target nucleotide sequence;
• said second peptide nucleic acid segment has a nucleobase sequence that is complementary to the target nucleotide sequence in the 3′ to 5′ direction of said target nucleotide sequence;
• one of said first or second peptide nucleic acid segments exhibits Watson/Crick binding to said target nucleotide sequence and the other of said first and second peptide nucleic acid segments exhibits Hoogsteen binding to said target nucleotide sequence;
• and
• said one of said first or second peptide nucleic acid segments that exhibits Hoogsteen binding to said target nucleotide sequence includes C-pyrimidine heterocyclic nucleobases or iso-pyrimidine heterocyclic nucleobases in at least one of the positions that are complementary to nucleobases in said target nucleotide sequence.

A compound comprising a first peptide nucleic acid segment and a second peptide nucleic acid segment wherein at least one of said segments comprises at least one pyrimidine heterocyclic base wherein:

• said segments are joined via at least one linking segment;
• and
• said linking segment is of the formula:
• —[NH—Z—C(═O)]n—
• wherein:
• n is an integer from 1 to 3;
• Z is C1 to C20 alkyl, C2 to C20 alkenyl, C2 to C20 alkynyl, C1 to C20 alkanoyl having at least one O or S atom, C7 to C34 aralkyl, C6-C14 aryl or an amino acid.