Structural Dependence of Aromatic Ring Stacking and Related Weak Interactions in Ternary Amino Acid−Copper(II) Complexes and Its Biological Implication

Abstract

Structures and stabilization due to stacking of ternary copper(II) complexes containing an aromatic amino acid (AA) and an aromatic diamine (DA), Cu(AA)(DA), have been investigated by potentiometric, spectroscopic, and X-ray diffraction methods. For the systems with AA ) para-X-substituted L-phenylalanine (L-XPhe; X ) H, NO 2 , OH, NH 2 ) and DA ) 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen), the difference absorption spectra in the region 320-400 nm exhibited a peak assignable to the charge transfer interaction between the aromatic rings of DA and L-XPhe, the intensity being in the order NH 2 > OH > H . NO 2 with respect to X. The stability constants of Cu(AA)(DA) determined for AA ) DL-XPhe (X ) F, Cl, Br) and L-XPhe (X ) NH 2 , NO 2 , I) at 25 °C and I ) 0.1 M (KNO 3 ) indicated that stabilization of Cu(L-XPhe)(DA) relative to Cu(L-Ala)(en) (Ala ) alanine; en 3), and [Cu(L-Phe)-(bpy)]ClO 4 ‚H 2 O (4), isolated as crystals, were determined by the X-ray diffraction method: 1, orthorhombic,All of the complexes have a similar distorted square-pyramidal structure around the central Cu(II) ion. While 1 and 2 have a structure involving aromatic ring stacking in the solid state, 4 has a structure without it and 3 has both types of structures in the unit cell.

The Structure and Unusual pH Dependence of Plastocyanin from the Fern Dryopteris crassirhizoma

“…A stacking interaction between the coordinated imidazole ligand of histamine and the phenyl group of phenylalanine was demonstrated in the previous studies of the stability and structure of copper complexes (41). Yamauchi and co-workers (42) have pointed out that the stacking interaction induces stronger imidazole-copper bonding due to the delocalization of electron density on the copper center. By the comparison of electronic absorption spectra of usual seed plant plastocyanins, the electronic absorption spectrum of Dryopteris plastocyanin indicates the 7 nm blue-shifted charge transfer band, and an additional absorption band at 410 nm is recognized in the electronic absorption spectrum (see above).…”

“…The resonance Raman excitation profile of poplar plastocyanin has suggested that the charge transfer band from His 1 to Cu 2ϩ should be lying into the most intense absorption band around at 600 nm (38). On the other hand, the charge transfer band between stacked Phe 12 and His 90 residues would be expected around 300 -400 nm region (42). The differences of electronic absorption spectra between Dryopteris and usual higher plant plastocyanins may reflect the stacking structure on the active site electronic structures.…”

“…A great deal of evidence from kinetics measurements suggests that the adjacent and remote sites are the sites of electron transfer to [Fe(CN) 6 ] 3Ϫ and [Co(phen) 3 ] 3ϩ , respectively (16). In higher plant plastocyanins, the adjacent site consists of conserved hydrophobic amino acid residues surrounding the solvent-exposed His 87 , and the remote site is an acidic patch comprising Asp 42 , Glu 43 , Asp 44 , Glu 59 , Glu 60 , Asp 61 , and Glu 68 as well as the invariant residue Tyr 83 (9). Electron transfer reaction studies of the nitrated plastocyanin at the remote site Tyr 83 indicated the possible interaction with cytochrome f at the site of Tyr 83 (17).…”

Modelling of copper(II) binding to pentapeptides related to atrial natriuretic factor using the 3χv connectivity index / Modeliranje vezivanja bakra(II) za pentapeptide povezane s atrijalnim natriuretičkim faktorom pomoću indeksa povezanosti 3χv

“…The most interesting question, however, is how copper interacts with aromatic residues, phenylalanine and tyrosine in particular. We know that cation-π interactions enhance the stability of coordination compounds such as Cu(II) chelates with amino acids (6,7), but interactions with aromatic side chains may also include π-π stacking as well as other hydrophobic interactions (8)(9)(10)(11)(12)(13).…”

1H-NMR Study of Ternary Platinum(II) Complexes with N-(1-Naphtyl)methyl-1,2-ethanediamine or N-(9-Anthrylmethyl)-1,2-ethanediamine and Bipyridine or Phenanthroline and Restricted Single Bond Rotation Due to Aromatic-Aromatic Ring Interaction

“…[1][2][3][4][5][6][7][8] Ternary complexes of platinum(II) or palladium(II) containing 2,2Ј-bipyridine (bpy) or 1,10-phenanthroline (phen) and an amino acid bearing an aromatic side chain such as tyrosine and tryptophan have been reported to show aromatic p-p interactions. [9][10][11][12][13] The crystal structures of ternary complexes of platinum(II), bpy, and N-benzyl-1,2-ethanediamine (Been), N-(1-naphthylmethyl)-1,2-ethanediamine (Npen), or N-(9-anthrylmethyl)-1,2-ethanediamine (Aten) indicate that intramolecular aromatic p-p interactions occur in the cases of Npen and Aten complexes.…”