RESUMEN
BACKGROUND: Interactions between adipocyte and breast cancer (BC) cells have yet to be fully elucidated. Here we investigated the prognostic impact of marginal adipose tissue invasion in both luminal breast cancer (HR+/HER2-) and triple-negative breast cancer (TNBC) (HR-/HER2-). METHODS: A total of 735 patients with early-stage invasive BC (1999-2014) were retrospectively registered. Median length of patient follow-up was 8.9 years. Survival curves were calculated using a Kaplan-Meier cumulative survival plot. The prognostic difference between two groups were assessed by the univariate Cox-proportional hazard regression model. RESULTS: Patients with adipose tissue invasion (n = 614) had a significantly poorer prognosis than those without adipose tissue invasion (n = 121) in overall survival (OS) (hazard ratio, 2.1; 95% Confidence interval [CI], 1.1 to 4.0; P = 0.025). While a poorer prognosis was observed in TNBC (n = 137) than in luminal BC patients (n = 496) (hazard ratio, 0.45; 95% CI, 0.30 to 0.68, P < 0.001), this aggressive nature of TNBC was noted in node-positive disease (hazard ratio, 0.3; 95% CI, 0.18 to 0.5, P < 0.001) but not in node-negative disease (hazard ratio, 0.78; 95% CI, 0.39 to 1.55, P = 0.472), and also noted in adipose tissue invasion-positive patients (hazard ratio, 0.4; 95% CI, 0.26 to 0.6, P < 0.001) but not in adipose tissue invasion-negative patients (hazard ratio, 0.73; 95% CI, 0.16 to 3.24, P = 0.675). In addition, although patients suffering from TNBC with adipose tissue invasion had a poorer outcome than those without adipose tissue invasion (hazard ratio, 3.63; 95% CI, 1.11 to 11.84; P = 0.033), the difference was not observed in luminal BC (hazard ratio, 1.75; 95% CI, 0.64 to 4.82; P = 0.277). CONCLUSIONS: Adipose tissue invasion was correlated with poor survival in TNBC. Cancer cell invasion into local fat may be a first step on cancer progression and systemic disease in TNBC.
Asunto(s)
Tejido Adiposo/patología , Neoplasias de la Mama Triple Negativas/patología , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores de Tumor , Comunicación Celular , Femenino , Humanos , Inmunohistoquímica , Estimación de Kaplan-Meier , Persona de Mediana Edad , Invasividad Neoplásica , Estadificación de Neoplasias , Pronóstico , Modelos de Riesgos Proporcionales , Estudios Retrospectivos , Neoplasias de la Mama Triple Negativas/etiología , Neoplasias de la Mama Triple Negativas/mortalidad , Neoplasias de la Mama Triple Negativas/terapia , Microambiente TumoralRESUMEN
We introduced trifluoromethyl (CF3) group(s) as heme side chain(s) of sperm whale myoglobin (Mb) in order to characterize the electronic nature of heme Fe(II) in deoxy Mb using 19F NMR spectroscopy. On the basis of the anti-Curie behavior of CF3 signals, we found that the deoxy Mb is in thermal equilibrium between the 5B2, (dxy)2(dxz)(dyz)(dz2)(dx2-y2), and 5E, (dxy)(dxz)2(dyz)(dz2)(dx2-y2), states of the heme Fe(II), i.e., 5B2 â 5E. Analysis of the curvature in Curie plots has yielded for the first time ΔH and ΔS values of â¼-20 kJ mol-1 and â¼-60 J K-1 mol-1, respectively, for the thermal equilibrium. Thus, the 5E state is slightly dominant over the 5B2 one at 25 °C. These findings provide not only valuable information about the ground state electronic structure of the high-spin heme Fe(II) in deoxy native Mb but also an important clue for elucidating the mechanism responsible for acceleration of the spin-forbidden oxygenation of the protein.
Asunto(s)
Compuestos Ferrosos/química , Hemo/química , Mioglobina/química , Complejos de Coordinación/química , Electrones , Ligandos , Espectroscopía de Resonancia Magnética , TemperaturaRESUMEN
The interaction of mycophenolate mofetil (MMF) with ferrous ions (Fe(2+)) in the solid state, in water, and in polar organic solvents was investigated using (1)H-NMR, (13)C-NMR, IR, and UV-visible (Vis) spectroscopies. A red-purple colored substance was formed after grinding solid MMF and FeSO4·7H2O in a mortar. The IR spectrum of taken as a KBr tablet of the colored substance showed a new absorption band at 1651 cm(-1). Although the color disappeared when the sample was dissolved in water, it persisted in organic solvents such as MeOH or dimethyl sulfoxide (DMSO). The UV-Vis spectrum of a 0.25 mM MeOH solution of MMF showed a new absorption maximum at 507 nm in the presence of Fe(2+) ions, while an aqueous solution of the same mixture showed no significant change from the MMF solution. All the signals in the (13)C-NMR spectrum in DMSO-d6 solution were unambiguously assigned. Upon the addition of 0.5 eq. of Fe(2+) ions, all the carbon signals except those of the 2-morpholinoethyl group almost disappeared, which clearly indicated that the Fe(2+) ions were located far away from the 2-morpholinoethyl groups in the MMF molecules. On the basis of these results, we have concluded that the MMF-Fe(2+) complex is actually formed in the solid state as well as in polar organic solvents such as MeOH or DMSO.
Asunto(s)
Cationes Bivalentes/química , Compuestos Ferrosos/química , Inmunosupresores/química , Ácido Micofenólico/análogos & derivados , Dimetilsulfóxido/química , Espectroscopía de Resonancia Magnética , Metanol/química , Ácido Micofenólico/química , Solventes/química , Espectrofotometría Infrarroja , Espectrofotometría UltravioletaRESUMEN
The corrphycene mol-ecule of the title compound, [Cu(C(36)H(36)N(4)O(4))](0.034).0.966C(36)H(38)N(4)O(4), has an essentially planar macrocyclic framwork with a slightly distorted trapezoidal N(4) core; the r.m.s. deviation of the peripheral 20â C atoms and four N atoms is 0.054â (3)â Å. The surface area within the N(4)-coordinating core (8.358â Å(2)) is significantly smaller than that (8.503â Å(2)) of the corresponding free-base porphyrin. Two intra-molecular N-Hâ¯N hydrogen bonds are observed. Detailed structure analysis clarified that the co-crystallization of the free-base corrphycene together with a quite minor component (ca 3%) of corrphycenato-Cu(II) occurred in the recrystallization process.
RESUMEN
A series of low-spin, six-coordinate complexes [Fe(TBzTArP)L(2)]X (1) and [Fe(TBuTArP)L(2)]X (2) (X = Cl(-), BF(4)(-), or Bu(4)N(+)), where the axial ligands (L) are HIm, 1-MeIm, DMAP, 4-MeOPy, 4-MePy, Py, and CN(-), were prepared. The electronic structures of these complexes were examined by (1)H NMR and electron paramagnetic resonance (EPR) spectroscopy as well as density functional theory (DFT) calculations. In spite of the fact that almost all of the bis(HIm), bis(1-MeIm), and bis(DMAP) complexes reported previously (including 2) adopt the (d(xy))(2)(d(xz), d(yz))(3) ground state, the corresponding complexes of 1 show the (d(xz), d(yz))(4)(d(xy))(1) ground state at ambient temperature. At lower temperature, the electronic ground state of the HIm, 1-MeIm, and DMAP complexes of 1 changes to the common (d(xy))(2)(d(xz), d(yz))(3) ground state. All of the other complexes of 1 and 2 carrying 4-MeOPy, 4-MePy, Py, and CN(-) maintain the (d(xz), d(yz))(4)(d(xy))(1) ground state in the NMR temperature range, i.e., 298-173 K. The EPR spectra taken at 4.2 K are fully consistent with the NMR results because the HIm and 1-MeIm complexes of 1 and 2 adopt the (d(xy))(2)(d(xz), d(yz))(3) ground state, as revealed by the rhombic-type spectra. The DMAP complex of 1 exists as a mixture of two electron-configurational isomers. All of the other complexes adopt the (d(xz), d(yz))(4)(d(xy))(1) ground state, as revealed by the axial-type spectra. Among the complexes adopting the (d(xz), d(yz))(4)(d(xy))(1) ground state, the energy gap between the d(xy) and d(π) orbitals in 1 is always larger than that of the corresponding complex of 2. Thus, it is clear that the benzoannelation of the porphyrin ring stabilizes the (d(xz), d(yz))(4)(d(xy))(1) ground state. The DFT calculation of the bis(Py) complex of analogous iron(III) porphyrinate, [Fe(TPTBzP)(Py)(2)](+), suggests that the (d(xz), d(yz))(4)(d(xy))(1) state is more stable than the (d(xy))(2)(d(xz), d(yz))(3) state in both ruffled and saddled conformations. The lowest-energy states in the two conformers are so close in energy that their ordering is reversed depending on the calculation methods applied. On the basis of the spectroscopic and theoretical results, we concluded that 1, having 4-MeOPy, 4-MePy, and Py as axial ligands, exists as an equilibrium mixture of saddled and ruffled isomers both of which adopt the (d(xz), d(yz))(4)(d(xy))(1) ground state. The stability of the (d(xz), d(yz))(4)(d(xy))(1) ground state is ascribed to the strong bonding interaction between the iron d(xy) and porphyrin a(1u) orbitals in the saddled conformer caused by the high energy of the a(1u) highest occupied molecular orbital in TBzTArP. Similarly, a bonding interaction occurs between the d(xy) and a(2u) orbitals in the ruffled conformer. In addition, the bonding interaction of the d(π) orbitals with the low-lying lowest unoccupied molecular orbital, which is an inherent characteristic of TBzTArP, can also contribute to stabilization of the (d(xz), d(yz))(4)(d(xy))(1) ground state.
Asunto(s)
Compuestos Férricos/química , Metaloporfirinas/química , Compuestos Férricos/síntesis química , Espectroscopía de Resonancia Magnética , Metaloporfirinas/síntesis química , Modelos Moleculares , Estructura Molecular , Teoría CuánticaRESUMEN
The title complex, [Fe(C(36)H(36)N(4)O(4))Cl], shows a domed structure with a slightly distorted trapezoidpyramidal core, in which the perpendicular displacements of the Fe(III) atom from the mean pyrrole N(4) plane are 0.418â (3) and 0.465â (3)â Å for the two crystallographically independent mol-ecules.
RESUMEN
A pair of myoglobins containing inherently distorted alpha-ethyl-2,4-dimethyldeuteroheme or undistorted 2,4-dimethyldeuteroheme were prepared, and the functional consequence of intrinsic heme deformation was investigated. The visible absorption peaks of the myoglobin bearing the distorted heme exhibited a bathochromic shift, indicating that the heme was deformed in the protein pocket. Ligand affinities for the ferric myoglobin with the distorted heme were found to be higher than those of the myoglobin bearing the undistorted heme. The observation suggested that the iron atom was more displaced toward the proximal histidine to weaken the coordination of the water molecule. In the paramagnetic proton NMR spectrum of ferrous deoxy protein, the deformed heme caused a 3.2 ppm lower-field shift of the proximal histidine signal, supporting an enhanced iron-histidine interaction. The deformed heme in ferrous myoglobin lowered the oxygen and carbon monoxide affinities by 25- and 480-fold, respectively, and caused the cleavage of the iron-histidine bond in a fractional population of the nitric oxide derivative. These results demonstrate a distinctive controlling mechanism for ligand binding by the deformed heme. Upon the heme distortion, the iron atom is more attracted by the proximal histidine to reduce the affinity of exogenous ligands for the ferrous heme.
Asunto(s)
Hemo/química , Hemo/metabolismo , Mioglobina , Monóxido de Carbono/química , Monóxido de Carbono/metabolismo , Hemo/análogos & derivados , Hemoproteínas/metabolismo , Histidina/química , Histidina/metabolismo , Hierro/química , Hierro/metabolismo , Ligandos , Espectroscopía de Resonancia Magnética , Mioglobina/química , Mioglobina/genética , Mioglobina/metabolismo , Óxido Nítrico , Oxígeno/metabolismo , AguaRESUMEN
Bis(pyridine)[meso-tetrakis(heptafluoropropyl)porphyrinato]iron(III), [Fe(THFPrP)Py(2)](+), was reported to be the low-spin complex that adopts the purest (d(xz), d(yz))(4)(d(xy))(1) ground state where the energy gap between the iron d(xy) and d(π)(d(xz), d(yz)) orbitals is larger than the corresponding energy gaps of any other complexes reported previously (Moore, K. T.; Fletcher, J. T.; Therien, M. J. J. Am. Chem. Soc. 1999, 121, 5196-5209). Although the highly ruffled porphyrin core expected for this complex contributes to the stabilization of the (d(xz), d(yz))(4)(d(xy))(1) ground state, the strongly electron withdrawing C(3)F(7) groups at the meso positions should stabilize the (d(xy))(2)(d(xz), d(yz))(3) ground state. Thus, we have reexamined the electronic structure of [Fe(THFPrP)Py(2)](+) by means of (1)H NMR, (19)F NMR, and electron paramagnetic resonance (EPR) spectroscopy. The CD(2)Cl(2) solution of [Fe(THFPrP)Py(2)](+) shows the pyrrole-H signal at -10.25 ppm (298 K) in (1)H NMR, the CF(2)(α) signal at -74.6 ppm (298 K) in (19)F NMR, and the large g(max) type signal at g = 3.16 (4.2 K) in the EPR. Thus, contrary to the previous report, the complex is unambiguously shown to adopt the (d(xy))(2)(d(xz), d(yz))(3) ground state. Comparison of the spectroscopic data of a series of [Fe(THFPrP)L(2)](+) with those of the corresponding meso-tetrapropylporphyrin complexes [Fe(TPrP)L(2)](+) with various axial ligands (L) has shown that the meso-C(3)F(7) groups stabilize the (d(xy))(2)(d(xz), d(yz))(3) ground state. Therefore, it is clear that the less common (d(xz), d(yz))(4)(d(xy))(1) ground state can be stabilized by the three major factors: (i) axial ligand with low-lying π* orbitals, (ii) ruffled porphyrin ring, and (iii) electron donating substituent at the meso position.
Asunto(s)
Electrones , Compuestos Férricos/química , Flúor/química , Metaloporfirinas/química , Espectroscopía de Resonancia Magnética , Modelos MolecularesRESUMEN
Iron man or weakling? Ligand-field strengths are conveniently expressed by the empirical spectrochemical series. Although cyanide has been deeply entrenched as a strong-field ligand, a couple of recent examples cast doubt toward the position of this ligand, namely the high-spin (S = 2) states of [Cr(II)(CN)(5)](3-) and [Fe(II)(tpp)(CN)](-). tpp = meso-tetraphenylporphinate.
Asunto(s)
Cianuros/química , Cromo/química , Hierro/química , Ligandos , Compuestos Organometálicos/químicaRESUMEN
The intramolecular magnetic interactions in one-electron oxidized iron(iii) porphyrin π-radical cations, [Fe(OETPPË)Cl][SbCl6] (1), [Fe(OMTPPË)Cl][SbCl6] (2) and [Fe(TPPË)Cl][SbCl6] (3), have been compared by means of X-ray crystallography, SQUID magnetometry, cyclic voltammetry, UV-Vis spectroelectrochemical analysis, NMR spectroscopy analysis and unrestricted DFT calculations. Unlike a generally recognized antiferromagnetic coupling dxy↑dxz↑dyz↑dz2↑dx2-y2↑PË+(a2u)↓ (S = 2) state via a weak bonding interaction as in (3), we have disclosed that a strong bonding interaction among iron dx2-y2 and porphyrin a2u orbitals forms in (1) into a highly delocalized Ψπ = [PË+(a2u) + FeIII(dx2-y2, dz2)] orbital that is able to accommodate two spin-paired electrons to form the Ψπ2dxy1dxz1dyz1, dz21 (S = 2) ground state. Concurrently, the spin polarization effect is exerted on the paired spins in the Ψπ orbital by magnetic induction from the remaining unpaired electrons in the iron d orbitals. The interpretation mentioned above is further verified by the diamagnetic nature of the saddled copper(ii) porphyrin π-cation radical, CuII(OETPPË)(ClO4) (S = 0), where the strong bonding interaction leads to the Ψπ2dxy2dxz2dyz2dz22 (S = 0) ground state but no spin polarization exists. Thus, the magnetic nature of the iron(iii) porphyrin π-radical cation is tuneable by saddling the ring planarity.
RESUMEN
Addition of tert-butylisocyanide (tBuNC) to a CD2Cl2 solution of the bis(perchlorato)(meso-tetramesitylporphyrinato) iron(III) cation radical leads to the formation of the corresponding bis(adduct), [Fe(TMP)(tBuNC)2]2+, whose electronic structure is in sharp contrast to that of the corresponding imidazole(HIm) complex, [Fe(TMP)(HIm)2]2+; the former adopts the S = 0 while the latter exhibits the S = 1 electronic ground state.
Asunto(s)
Compuestos Férricos/química , Metaloporfirinas/química , Ligandos , Espectroscopía de Resonancia Magnética/métodos , Nitrilos/química , Espectrofotometría Ultravioleta/métodosRESUMEN
The electronic structures of six-coordinate iron(III) octaethylmonoazaporphyrins, [Fe(MAzP)L 2] (+/-) ( 1), have been examined by means of (1)H NMR and EPR spectroscopy to reveal the effect of meso-nitrogen in the porphyrin ring. The complexes carrying axial ligands with strong field strengths such as 1-MeIm, DMAP, CN (-), and (t)BuNC adopt the low-spin state with the (d xy ) (2)(d xz , d yz ) (3) ground state in a wide temperature range where the (1)H NMR and EPR spectra are taken. In contrast, the complexes with much weaker axial ligands, such as 4-CNPy and 3,5-Cl 2Py, exhibit the spin transition from the mainly S = 3/2 at 298 K to the S = 1/2 with the (d xy ) (2)(d xz , d yz ) (3) ground state at 4 K. Only the THF complex has maintained the S = 3/2 throughout the temperature range examined. Thus, the electronic structures of 1 resemble those of the corresponding iron(III) octaethylporphyrins, [Fe(OEP)L 2] (+/-) ( 2). A couple of differences have been observed, however, in the electronic structures of 1 and 2. One of the differences is the electronic ground state in low-spin bis( (t)BuNC) complexes. While [Fe(OEP)( (t)BuNC) 2] (+) adopts the (d xz , d yz ) (4)(d xy ) (1) ground state, like most of the bis( (t)BuNC) complexes reported previously, [Fe(MAzP)( (t)BuNC) 2] (+) has shown the (d xy ) (2)(d xz , d yz ) (3) ground state. Another difference is the spin state of the bis(3,5-Cl 2Py) complexes. While [Fe(OEP)(3,5-Cl 2Py) 2] (+) has maintained the mixed S = 3/2 and 5/2 spin state from 298 to 4 K, [Fe(MAzP)(3,5-Cl 2Py) 2] (+) has shown the spin transition mentioned above. These differences have been ascribed to the narrower N4 cavity and the presence of lower-lying pi* orbital in MAzP as compared with OEP.
Asunto(s)
Compuestos Férricos/química , Metaloporfirinas/química , Compuestos Aza/síntesis química , Compuestos Aza/química , Cianuros/química , Espectroscopía de Resonancia por Spin del Electrón , Compuestos Férricos/síntesis química , Ligandos , Espectroscopía de Resonancia Magnética/métodos , Metaloporfirinas/síntesis química , Piridinas/químicaRESUMEN
Six-coordinate low-spin iron(III) porphyrinates adopt either common (d(xy))(2)(d(xz),d(yz))(3) or less common (d(xz),d(yz))(4)(d(xy))(1) ground state. In this review article, three major factors that affect the electronic ground state have been examined. They are (i) nature of the axial ligand, (ii) electronic effect of peripheral substituents, and (iii) deformation of porphyrin ring. On the basis of the (1)H NMR, (13)C NMR, and EPR data, it is now clear that (i) the axial ligands with low-lying pi* orbitals such as tert-butylisocyanide and 4-cyanopyridine, (ii) the electron donating groups at the meso-carbon atoms, and (iii) the ruffled deformation of porphyrin ring stabilize the (d(xz),d(yz))(4)(d(xy))(1) ground state. By manipulating these factors, we are able to prepare various low-spin iron(III) porphyrinates with unusual electronic structures such as bis(imidazole) complexes with the (d(xz),d(yz))(4)(d(xy))(1) ground state or bis(tert-butylisocyanide) complexes with the (d(xy))(2)(d(xz),d(yz))(3) ground state; bis(imidazole) and bis(tert-butylisocyanide) complexes usually adopt the (d(xy))(2)(d(xz),d(yz))(3) and (d(xz),d(yz))(4)(d(xy))(1) ground state, respectively.
Asunto(s)
Hemina/química , Hemina/metabolismo , Catálisis , Sistema Enzimático del Citocromo P-450/metabolismo , Espectroscopía de Resonancia por Spin del Electrón , Espectroscopía de Resonancia Magnética , Modelos Biológicos , Modelos Moleculares , Estructura MolecularRESUMEN
A subchronic oral toxicity study of purple corn color (PCC), a natural food colorant, was performed with groups of 10 male and 10 female F344 rats fed the agent at dietary levels of 0%, 0.5%, 1.5% and 5.0% for 90 days. No mortalities occurred during the treatment period. No treatment-related changes in the body weight, food and water consumption, ophthalmology, hematology, organ weight data and histopathology were observed. Regarding general conditions and gross pathology, staining of fur and black feces were noted in rats of the 1.5% and 5.0% diet groups. Moreover, brown urine and black material in the stomach, small and large intestine were evident in rats receiving 5.0%. These changes were considered due to the anthocyanin content. On clinical chemistry analysis, total cholesterol, phospholipid and triglyceride were significantly lowered in both sexes of the 5.0% group, but these were not considered to be toxicologically significant. Thus, the No-observed-adverse-effect-level (NOAEL) was judged to be 5.0% in diet for both sexes (male: 3542 mg/kg/day, female: 3849 mg/kg/day) for PCC under the present experimental conditions.
Asunto(s)
Antocianinas/toxicidad , Dieta , Colorantes de Alimentos/toxicidad , Animales , Antocianinas/metabolismo , Relación Dosis-Respuesta a Droga , Femenino , Colorantes de Alimentos/metabolismo , Masculino , Nivel sin Efectos Adversos Observados , Tamaño de los Órganos/efectos de los fármacos , Ratas , Ratas Endogámicas F344 , SeguridadRESUMEN
Pyrrocorphin is an air-sensitive porphyrinoid with a highly reduced hexahydroporphyrin core. In contrast, pyrrolidine-fused pyrrocorphin (Pyr) obtained by successive 1,3-dipolar cycloaddition reactions of azomethine ylide to 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin is less air-sensitive. In order to reveal the effect of highly reduced porphyrin rings on the physicochemical properties of their metal complexes, we have prepared diamagnetic (S=0) Ni(II) complex Ni(II)(Pyr). The addition of excess pyridine (Py) to the toluene solution of Ni(II)(Pyr) yielded five-coordinate Ni(II)(Pyr)(Py), which was then completely converted to six-coordinate paramagnetic (S=1) Ni(II)(Pyr)(Py)2. The latter was characterized by UV-Vis, 1H NMR, CV, SQUID, and X-ray crystallography as well as DFT calculations. As compared with analogous complexes of porphyrin (Por), chlorin (Chl), and isobacteriochlorin (Iso) reported by Herges and co-workers (R. Herges et al., Inorg. Chem. 2015), Ni(II)(Pyr)(Py)2 has longer equatorial NiN and shorter axial NiN bonds. The CV study has shown a large decrease in HOMO-LUMO gap as the reduction of porphyrin ring proceeds, which has further been confirmed by UV-Vis and DFT calculation. Titration studies using 1H NMR and UV-Vis have shown that the first binding constant of pyridine toward Ni(II)(Pyr) is ca. 4 times as large as that of Ni(II)(Iso) and ca 230 times as large as that of Ni(II)(Por). Thus, we have concluded that the binding constant of pyridine to Ni(II) porphyrinoid increases by the following order: PorAsunto(s)
Complejos de Coordinación/química
, Níquel/química
, Porfirinas/química
, Cristalografía por Rayos X
, Electroquímica
, Espectroscopía de Resonancia Magnética
, Estructura Molecular
, Oxidación-Reducción
RESUMEN
Isocyanide-bound model hemes always adopt the (dxz, dyz)4(dxy)1 ground state, however, we have found that the replacement of porphyrin by diazaporphyrin leads to the formation of an unprecedented low-spin bis(tert-butylisocyanide) complex with the (dxy)2(dxz, dyz)3 ground state.
Asunto(s)
Electrones , Compuestos Férricos/química , Hemo/química , Metaloporfirinas/química , Nitrilos/química , Espectroscopía de Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética/normas , Teoría Cuántica , Estándares de Referencia , TemperaturaRESUMEN
A novel spin transition between S = 5/2 and S = 3/2 has been observed for the first time in five-coordinate, highly saddled iron(III) porphyrinates by EPR and SQUID measurements at extremely low temperatures.
Asunto(s)
Frío , Hemina/química , Azufre/química , Espectroscopía de Resonancia por Spin del Electrón , Magnetismo , Modelos Moleculares , Estructura MolecularRESUMEN
In contrast to the general tendency that six coordinate iron(iii) porphyrin complexes with neutral oxygen ligands adopt a high-spin state in a wide range of temperature, some complexes with substituted pyridine N-oxides have exhibited spin-crossover from high-spin to low-spin states with decreasing temperature both in solution and in the solid state.
RESUMEN
The 13C NMR chemical shifts of all the carbons in an a2u type iron(III) porphyrin radical cation, [Fe(TPP)Cl]+, have been determined for the first time by the titration method as well as by the chemical shift correlation; they are 2230, 1050, and -1910 ppm for the alpha-pyrrole, beta-pyrrole, and meso carbon atoms, respectively.
Asunto(s)
Compuestos Férricos/análisis , Espectroscopía de Resonancia Magnética/normas , Metaloporfirinas/análisis , Isótopos de Carbono , Cationes/análisis , Radicales Libres/análisis , Espectroscopía de Resonancia Magnética/métodos , Estándares de ReferenciaRESUMEN
Modifying potential of annatto extract (norbixin) on liver carcinogenesis was investigated in male F344/DuCrj rats initially treated with N-nitrosodiethylamine (DEN). Two weeks after a single dose of DEN (200 mg/kg, intraperitoneally), rats were given annatto extract at dietary levels of 0, 0.03, 0.1 and 0.3%, or phenobarbital sodium at 0.05% as a positive control for 6 weeks. All animals were subjected to partial hepatectomy at week 3, and were killed at week 8. There were no deaths related to annatto extract ingestion, and the treatment had no effects on body weights, or food and water consumption. Statistically significant increases of absolute and relative liver weights were apparent in the 0.1 and 0.3% groups. However, annatto extract did not significantly increase the quantitative values for glutathione S-transferase placental form positive liver cell foci observed after DEN initiation, in clear contrast to the positive control case. The results thus demonstrate that annatto extract at a dietary level of 0.3% (200 mg/kg/day) lacks modifying potential for liver carcinogenesis in our medium-term bioassay system.