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Water-soluble phthalocyanine (Pc) derivatives have been studied extensively as not only effective photosensitizers for photodynamic therapy (PDT), but also G-quadruplex ligands which have the poten...

An all-parallel tetrameric G-quadruplex formed from a DNA/RNA chimera sequence, d(TTA)r(GGG)d(T) ([Chimera(7mer)]4), and its interaction with heme have been characterized. [Chimera(7mer)]4 was foun...

Heme in the ferric state (heme(Fe3+)) binds to G-quadruplex DNAs to form stable complexes that exhibit enhanced peroxidase activities. The complexes are considered DNAzymes possessing heme as a pro...

The molecular structure and heme electronic structure of a complex (heme–(d(TTAGGGT))4 complex) between heme and a parallel G-quadruplex DNA formed from heptanucleotide d(TTAGGGT), i.e., (d(TTAGGGT...

The stretching frequency of the coordination bond between the heme Fe atom and proximal histidine (His93) Ne atom (νFe–His), and the NMR shift of the His93NδH proton (His93NδH shift) of the deoxy f...

The non-native heme coordination structures emerging upon guanidine hydrochloric acid (GdnHCl)-induced unfolding of Pseudomonas aeruginosa ferricytochrome c 5 5 1 were characterized by absorption, circular dichroism, paramagnetic NMR, and resonance Raman spectroscopy. Hexacoordinated high-spin ferriheme bearing axial His and H 2 O ligands, and pentacoordinated high-spin ferriheme with an axial His ligand were identified in the presence of GdnHCl concentrations ≥ 1.5 M (M = mol dm - 3 ). These non-native species were rapidly interconverted to each other through cleavage/formation of the Fe-H 2 O coordination bond, and were also in dynamic equilibrium, at a rate of < 2 × 10 4 s - 1 , with the native species. Thus, the present study demonstrated the presence of dynamic equilibrium through cleavage/formation of a Fe-H 2 O coordination bond in an unfolding intermediate. These results provide a deeper insight into structure transitions of the heme active site upon folding and unfolding of cytochrome c.

13,17-Bis(2-carboxylatoethyl)-3,8-diethyl-2-fluoro-7,12,18-trimethylporphyrinatoiron(III) was reconstituted with sperm-whale apomyoglobin to investigate the molecular and electronic structures of the heme-active site by 19F NMR spectroscopy. The detection of the nuclear Overhauser effect between the substituted fluorine atom for a heme side-chain and an amino acid side-chain proton in the reconstituted myoglobin unequivocally determines the heme orientation relative to the protein matrix. The orientation of this fluorinated hemin in the protein was found to differ by a 180° rotation of the heme plane about its C2-axis from that of structurally analogous mesohemin in the active site of myoglobin. Thus, the difference between the methyl group and fluorine atom as the peripheral side-chain at the 2-position of the porphyrin is a critical determinant for the thermodynamical stability of the heme orientational isomers. The effects of the heme orientation on the electronic structure of the active site of myoglo...

The resolved heme peripheral side-chain proton resonances of sperm whale met-aquo myoglobin have been connected to the corresponding resonances in met-imidazole myoglobin by the magnetization transfer through the external ligand exchange. From the signal assignments in met-imidazole myoglobin, which have been independently obtained using conventional two-dimensional NMR and one-dimensional nuclear Overhauser effect difference spectroscopies, the observed connectivities unambiguously identified the corresponding resonances of met-aquo myoglobin. The calculation of the pseudo-contact shifts for the resonances of met-aquo myoglobin from the reported zero-field splitting constant [Y. -H. Kao, and J. T. J. Lecomte, J. Am. Chem. Soc., 115, 9754—9762 (1993) and J. Am. Chem. Soc., 116, 6991 (1994)] together with the diamagnetic shifts observed for carbonmonoxy myoglobin [B. C. Mabbutt, and P. E. Wright, Biochim. Biophys. Acta, 832, 175—185 (1985)], allowed the extraction of the contact shifts from their paramagne...

N-(N-Formyl-L-phenylalanyl)-6-deoxy-6-aminocyclomaltoheptaose (f-L-Phe-β-CD) is one of CD derivatives with excellent ability of chiral recognition. In order to make clear the mechanism of chiral recognition, the conformation of free f-L-Phe-β-CD has been studied by using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. From the measurement of 1H homonuclear Overhauser enhancement on the rotating frame, it is concluded that f-L-Phe- residue of the f-L-Phe-β-CD is inserted into its cavity from the upside of primary hydroxyl groups of the macrocyclic ring. Analysis of 1H and 13C spectra of f-L-Phe-β-CD and model compounds of f-L-Phe- residue also support this conclusion. The macrocyclic ring is found to be distorted.

1H and 13C nuclear relaxation of paramagnetic iron(III) tetraphenylporphyrin–imidazole complexes has been investigated in order to gain insight into the relationship between the paramagnetic relaxation rate and the electron-nucleus distance. The analysis of the nuclear spin–lattice relaxation time (T1) in terms of the distance indicated that, for the iron porphyrin complexes used, the contribution of the electron-nucleus dipolar coupling no longer contributes significantly to the relaxation process of a proton located at more than 0.75 nm away from the iron. For the complexes studied, the electron spin–lattice relaxation time (T1e) of 6.4 ps was calculated from the T1 values measured at 26°C.

Conformation of viologen-linked porphyrins (p-PCnV, n=4–7), which are capable of intramolecular electron transfer, was studied by 1H NMR in order to gain insight into the relative geometry of the donor and acceptor during the electron transfer process. The orientation of the viologen with respect to the porphyrin was interpreted in terms of the rate of the intramolecular electron transfer between the two π-systems.

The aqueous solutions containing KCl or NaCl at various concentrations have been studied by 17O NMR. The line width of the signal increases and decreases with an addition of KCl above and below 55 °C, respectivly, and these results indicate that the effect of KCl on the water structure depends on temperature.

A 19F NMR study on myoglobin reconstituted with a ring-fluorinated C2 symmetric heme, 13,17-bis(2-carboxylatoethyl)-2,8,12,18-tetramethyl-3,7-difluoroporphyrinatoiron(II), demonstrated that the por...

The metal-centered pseudo-contact shift contribution in the hyperfine shift of NMR resonance of paramagnetic hemin dicyano complex ([FeIII(proto)(CN)2]) in solution was quantitatively determined from the combined use of 1H and 13C NMR data. Taking advantage of the axially symmetric magnetic property for [FeIII(proto)(CN)2] in solution, the paramagnetic metal-centered dipolar field was quantitatively mapped. The highly solvent-dependent magnetic anisotropy, (g2⁄⁄–g2⊥), of this complex in CD3OD was estimated to be 7.2 and the obtained value is placed between the values in D2O (4.4) and in CDCl3 (9.7).

Novel porphyrins to which the viologen is linked (m-PCnV) were synthesized. The linkage methylene chain between the porphyrin and the bipyridine moieties was systematically changed from (CH2)3 to (CH2)6. The molecular structure of m-PCnV was characterized by 1H NMR in some detail. The orientation of the viologen with respect to the porphyrin plane in m-PCnV was semiquantitatively estimated from the porphyrin ring current induced chemical shift changes on the resonances from the viologen moiety. The NMR conformational analyses on m-PCnV in dimethyl sulfoxide and acetonitrile clearly revealed the effect of the solvent on its molecular structure.

Intramolecular hydrogen bonding of α-, β-, and γ-cyclodextrins, and α- and β-dimethyl cyclodextrins has been investigated in dimethyl sulfoxide-d6 by 1H NMR spectroscopy. The temperature dependence of 1H chemical shifts of secondary hydroxyl protons of cyclodextrins and dimethyl cyclodextrins reveals the existence of the intramolecular hydrogen bond. The strength of hydrogen bond becomes stronger as the ring size becomes smaller and by methylation. The intramolecular hydrogen bond in which the OH(3) is proton donor is preferred in α-cyclodextrin as well as in α- and β-dimethyl cyclodextrins. The orientation of secondary hydroxyl groups was estimated with the Karplus-type equation and the orientation is found to be suitable for making intramolecular hydrogen bond.

6-O-α-D-Glucopyranosyl-α-cyclodextrin (G1-α-CD)-p-nitrophenol (pNP) inclusion complex has been characterized by high resolution 1H and 13C NMR. From 1H NMR measurements it is concluded that G1-α-CD forms a 1 : 1 inclusion complex with pNP at both pD 7 and 10, and the dissociation constants for their complexation are quite similar to those for α-CD–pNP complexation, suggesting that G1-α-CD and α-CD have a similar ability of complexation with pNP. The geometry of G1-α-CD–pNP complex was found to be similar to that of α-CD–pNP complex. Analysis on the NMR spectral parameters of G1-α-CD have revealed that the asymmetric nature of G1-α-CD molecule is enhanced by complexation with pNP.