Structure of the new iron(II) oxalate potassium salt K2Fe[(C2O4)2(H2O)2]·0.18H2O.

The discovery of a new FeII oxalate framework of composition K2Fe[(C2O4)2(H2O)2]·0.18H2O is reported. Its crystal structure was solved by means of single crystal and powder X-ray diffraction. The new organic-inorganic hybrid compound crystallizes in the orthorhombic space group Pca21 with unit-cell parameters: a = 12.0351 (4) Å, b = 15.1265 (5) Å, c = 10.5562 (4) Å. This crystal structure, containing eight chemical formula, consists of a succession of FeO4(H2O)2 octahedra and K+ cations growing along b direction. Magnetization measurements indicate that the title compound is paramagnetic over the investigated temperature range (2-300 K). Both magnetization and 57Fe Mössbauer data indicate that Fe2+ is in a high-spin state.

Correlations between stacked structures and weak itinerant magnetic properties of La2 - x Y x Ni7 compounds.

Hexagonal La2Ni7 and rhombohedral Y2Ni7 are weak itinerant antiferromagnet (wAFM) and ferromagnet (wFM), respectively. To follow the evolution between these two compounds, the crystal structure and magnetic properties of A 2 B 7 intermetallic compounds (A = La, Y, B = Ni) have been investigated combining x-ray powder diffraction and magnetic measurements. The La2-x Y x Ni7 intermetallic compounds with 0 ⩽ x ⩽ 1 crystallize in the hexagonal Ce2Ni7-type structure with Y preferentially located in the [A 2 B 4] units. The compounds with larger Y content (1.2 ⩽ x < 2) crystallize in both hexagonal and rhombohedral (Gd2Co7-type) structures with a substitution of Y for La in both [A 2 B 4] and [AB 5] units. Y2Ni7 crystallizes in the rhombohedral structure only. The average cell volume decreases linearly versus Y content, whereas the c/a ratio presents a minimum at x = 1 due to geometric constrains. The magnetic properties are strongly dependent on the structure type and the Y content. La2Ni7 displays a complex metamagnetic behavior with split AFM peaks. Compounds with x = 0.25 and 0.5 display a wAFM ground state and two metamagnetic transitions, the first one toward an intermediate wAFM state and the second one toward a FM state. T N and the second critical field µ 0 H c2 increase with the Y content, indicating a stabilization of the AFM state. LaYNi7, which is as the boundary between the two structure types, presents a very wFM state at low field and an AFM state as the applied field increases. All the compounds with x > 1, and which contains a rhombohedral phase are wFM with T C = 53(2) K. In addition to the experimental studies, first principles calculations using spin polarization have been performed to interpret the evolution of structural phase stability for 0 ⩽ x ⩽ 2.

Differential regulation of the parathyroid hormone-related protein gene P1 and P3 promoters by cAMP.

The role of calcitonin, and other agonists which activate the cAMP pathway, in regulating transcription of the human parathyroid hormone-related protein (PTHrP) gene was investigated in a human lung cancer cell line (BEN). Both calcitonin and forskolin caused a 5-6-fold increase in transcription initiated from both the P1 and P3 promoters, but with no observed effect on the P2 promoter. Maximal 6-fold activation of the P1 promoter occurred at 16 h post-stimulation and effects of calcitonin were observed within the pM range. The PKC agonist, phorbol 12-myristate 13-acetate diester (PMA), did not modulate transcription initiated from the P1 promoter. The ionophore ionomycin had a small effect on transcription of the P1 promoter, and transcriptional control may involve an interaction between the cAMP and intracellular calcium second messenger pathways. Deletion mapping studies indicated that increases in transcription of the human PTHrP gene is being mediated via a CRE element situated at -3313 to -3306 upstream of the P1 promoter. Mutational analysis of this CRE element confirmed a role for this sequence in mediating the increase in transcription effected by cAMP. Consistent with these transfection studies, RT-PCR of PTHrP mRNA also indicated a significant increase in transcripts generated from the P1 promoter. Gel retardation assays utilising a fragment of the P1 promoter region, encompassing the putative CRE, determined that nuclear proteins were binding to this region. Competition binding studies with labelled probe and cold competitors determined that the binding was specific for this sequence. A wild-type CRE consensus oligonucleotide also competed for binding with this sequence.

Calcitonin increases transcription of parathyroid hormone-related protein via cAMP.

Transcriptional regulation of the human parathyroid hormone-related protein (PTHrP) gene by calcitonin was examined in a lung cancer line (BEN cells). Northern analysis demonstrated that calcitonin caused a rapid 4.5-fold elevation in PTHrP mRNA. Transient transfection of a construct containing 1119 base pairs of the human PTHrP gene 5' to the ATG start site of translation, fused to the CAT reporter sequence, was used to demonstrate a five-fold increase in transcription by calcitonin. Similar increases were also observed when transfected cells were exposed to a number of cAMP agonists including forskolin, as well as isobutyl-methylxanthine. A putative cAMP responsive element (5'-TGACTTCA-3') present within exon 4 was placed upstream of the heterologous SV40 promoter. Expression of this construct was elevated 4.5-fold in response to calcitonin and 7-fold in response to forskolin. Similar responses to calcitonin occurred with a smaller construct (pZMR30) containing 530 bp of sequence upstream of the ATG start site. Thus we postulate that calcitonin acts at least partially via cAMP through this element in exon 4 of the human PTHrP gene.

Activity of platinum(II) intercalating agents against murine leukemia L1210.

Four series of intercalating, square-planar Pt(II) complexes derived from the ligands 2,2'-bipyridine, 2,2':6',2"-terpyridine, 1,10-phenanthroline, and 3,4,7,8-tetramethyl-1,10-phenanthroline were synthesized and aspects of their activity against murine leukemia L1210 cells investigated. The 2,2':6',2"-terpyridine-thiolato complexes are growth inhibitory in culture, with IC50 values in the range 6-32 microM, and cause cell lysis at high concentrations. Of the remaining three series, the 2,2'-bipyridine complexes are the least potent in their effects. There is a general enhancement in activity on moving from the 1,10-phenanthroline complexes to the 3,4,7,8-tetramethyl-1,10-phenanthroline analogues. Flow cytometric analysis on representative complexes shows that they are not cell cycle specific. Alkaline elution experiments indicate no damage to DNA of cells exposed to (thiophenolato)(2,2':6',2"-terpyridine)platinum(II) chloride monohydrate and (ethylenediamine)(1,10-phenanthroline)platinum(II) dichloride dihydrate although (ethylenediamine)(3,4,7,8-tetramethyl-1,10-phenanthroline)platinum(II) dichloride dihydrate causes both single-strand breaks and DNA cross-links. Compounds 2a, 5a, and 6a showed no antitumor activity against L1210 in mice.