A molecule according to formula which comprises or consists of: w - x -C1-L2-B1-L3-C2-L4-B2-L5-C3- y - z wherein B1 and B2 are single-domain antibodies (sdAbs); wherein sdAb is an antigen-binding antibody or antibody fragment, wherein said antibody or antibody fragment consists of a single VH domain; wherein C1, C2 and C3 are collagen XV or collagen XVIII trimerizing structural elements; wherein a "collagen XV TSE" is a polypeptide which comprises or consists of a polypeptide having the amino acid sequence shown in SEQ ID NO: 1, or to a polypeptide having at least 60%, preferably at least 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or at least 99% amino acid sequence identity with the sequence shown in SEQ ID NO: 1, and maintains the ability to form trimers and/or produce intramolecular trimerization; wherein a "collagen XVIII TSE" is a polypeptide which comprises or consists of a polypeptide having the amino acid sequence shown in SEQ ID NO: 2, or to a polypeptide having at least 60%, preferably at least 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or at least 99% amino acid sequence identity with the sequence shown in SEQ ID NO: 2, and maintains the ability to form trimers and/or produce intramolecular trimerization; wherein L1, L2, L3, L4, L5 and L6 are flexible peptide linkers, wherein the term flexible peptide linker refers to peptide linkers which comprise 2 or more amino acids selected from the group consisting of Gly, Ser, Ala and Thr, and wherein L2 and L4 have a length from 5 to 40 amino acids; wherein C1-L2-B1-L3-C2-L4-B2-L5-C3 is a recombinant single-chain polypeptide, C1 being located at the N-terminus of the polypeptide and C3 at the C-terminus of the polypeptide; wherein w, x, y and z can be 1 or 0; wherein when w is 1 and A is a moiety with binding, detection and/or effector properties, then A is directly or indirectly covalently linked to the N-terminus of said single-chain polypeptide; and wherein when z is 1 and D is a moiety with binding, detection and/or effector properties then D is directly or indirectly covalently linked to the C-terminus of said single-chain polypeptide. wherein B1 and B2 are single-domain antibodies (sdAbs); wherein sdAb is an antigen-binding antibody or antibody fragment, wherein said antibody or antibody fragment consists of a single VH domain; wherein C1, C2 and C3 are collagen XV or collagen XVIII trimerizing structural elements; wherein a "collagen XV TSE" is a polypeptide which comprises or consists of a polypeptide having the amino acid sequence shown in SEQ ID NO: 1, or to a polypeptide having at least 60%, preferably at least 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or at least 99% amino acid sequence identity with the sequence shown in SEQ ID NO: 1, and maintains the ability to form trimers and/or produce intramolecular trimerization; wherein a "collagen XVIII TSE" is a polypeptide which comprises or consists of a polypeptide having the amino acid sequence shown in SEQ ID NO: 2, or to a polypeptide having at least 60%, preferably at least 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or at least 99% amino acid sequence identity with the sequence shown in SEQ ID NO: 2, and maintains the ability to form trimers and/or produce intramolecular trimerization; wherein L1, L2, L3, L4, L5 and L6 are flexible peptide linkers, wherein the term flexible peptide linker refers to peptide linkers which comprise 2 or more amino acids selected from the group consisting of Gly, Ser, Ala and Thr, and wherein L2 and L4 have a length from 5 to 40 amino acids; wherein C1-L2-B1-L3-C2-L4-B2-L5-C3 is a recombinant single-chain polypeptide, C1 being located at the N-terminus of the polypeptide and C3 at the C-terminus of the polypeptide; wherein w, x, y and z can be 1 or 0; wherein when w is 1 and A is a moiety with binding, detection and/or effector properties, then A is directly or indirectly covalently linked to the N-terminus of said single-chain polypeptide; and wherein when z is 1 and D is a moiety with binding, detection and/or effector properties then D is directly or indirectly covalently linked to the C-terminus of said single-chain polypeptide.