I. Di Liegro

Organometallic complexes with biological molecules: VII. Dialkyl- and trialkyl-tin (IV)[meso-tetra(4-carboxyphenyl)porphinate] derivatives : Solid-state, solution-phase structural aspects and in vivo effects

The synthesis, the structural features and the in vivo biological activity of diorganotin(IV) and triorganotin(IV) derivatives of [meso-tetra(4-carboxyphenyl)porphine] (H 4 TPPC) are reported. Derivatives with general formula (R 2 Sn) 2 TPPC and (R 3 Sn) 4 TPPC (R=Me, Bu, and Ph) were obtained, and the main information extracted from the infrared and Mossbauer spectral data, in the solid state, was in favor of the occurrence of five-coordinated tin(IV) atoms, in a polymeric trigonal-bipyramidal configuration, attained through two differently coordinated, estertype and chelating respectively, carboxylate anions in [R 2 Sn] 2 TPPC, while in [Alk 3 Sn] 4 TPPC five-coordination of the tin(IV) atom is reached through bridging carboxylate groups. 1 H and 13 C NMR spectra, in DMSO-d 6 or CDCl 3 suggested that the soluble derivatives, at room temperature or at 342K, were present in solution as simple monomers. The interactions of (trimethyltin) 4 [meso-tetra(4-carboxyphenyl)porphinate] (TMTPPC) and (tributyltin)4[mesa-tetra(4-carboxyphenyl)porphinate] (TBTPPC) with Bluescript KS(+) plasmid and cultured 3T3 fibroblasts were studied. Both compounds have a clear inhibitory effect on the growth of cultured mouse embryonal fibroblasts (NIH-3T3), TBTPPC being much more active. No evidence was found, however, for DNA cleavage by the compounds at molar ratios as high as 1:10 (TMTPPC, TBTPPC/DNA base pairs). According toour observations, the cytotoxicity of TBTPPC and TMTPPC does not seem to be besed on direct interation with DNA

Organometallic complexes with biological molecules: XII. Solid‐state and solution studies on dialkyltin(IV)– and trialkyltin(IV)–thiaminepyrophosphate derivatives

Dialkyltin(IV) and trialkyltin(IV) derivatives of the coenzyme thiaminepyrophosphate (H2TPP) have been synthesized with general formula R2Sn(HTPP)2·nH2O (Alk = Me, n = 2; Alk = Bu, n = 4) and R3SnHTPP·nH2O (R=Me, n = 2; R = Bu, n = 1), respectively. The solid-state structure of the complexes has been investigated through infrared and Mossbauer spectroscopy. The infrared data suggest the involvement of only phosphate oxygen atoms in the coordination of both dialkyl- and trialkyl-tin(IV) moieties, with phosphate anions behaving as monoanionic bidentate bridging or chelating groups, with the tin(IV) involved in six- and five-fold coordination geometries, respectively, in R2Sn(HTPP)2·nH2O (R = Me, n = 2; R = Bu, n = 4) and R3SnHTPP·nH2O (R = Me, n = 2; R = Bu, n = 1). The 119Sn Mossbauer data, and in particular rationalization of the experimental nuclear quadrupole splittings, Δ, through the point-charge model formalism, suggests the occurrence of an octahedral trans-R2 structure in R2Sn(HTPP)2·nH2O (R = Me, n = 2; R = Bu, n = 4) and a trigonal-bipyramidal structure in R3SnHTPP·nH2O (R = Me, n = 2; R = Bu, n = 1). 1H and 13C NMR spectra, in D2O, suggested that the soluble derivatives, at room temperature, in solution, maintained the solid-state structure. The interactions of dibutyltin(IV)–thiaminepyrophosphate (DBTPP) and tributyltin(IV)–thiaminepyrophosphate (TBTPP) complexes with Bluescript KS(+) plasmid and immortalized 3T3 fibroblasts were studied. Both compounds have a clear inhibitory effect on the growth of immortalized mouse embryonal fibroblasts (NIH-3T3), TBTPP being the much more active. No evidence was found, however, for DNA cleavage by the compounds at molar ratios as high as 1:10 (DBTPP, TBTPP/DNA base pairs). According to our observations, the cytotoxicity of TBTPP does not seem to be based on direct interaction with DNA, but in the presence of TBTPP (1:10, TBTPP/DNA bp), plasmid DNA seems to be more susceptible to cleavage by UV. Copyright

Unusual properties of sea urchin unfertilized egg chromatin

A typical nucleosomal pattern is not detected by electrophoretic analysis of sea urchin mature egg chromatin, following digestion with micrococcal nuclease. Moreover, at least 80% of the egg nuclear DNA is resistant to nuclease attack. These unusual features of unfertilized egg chromatin, not shared by oocytes or sperms, are discussed in view of the unique properties and fate of mature female germ cells.

Identification in the rat brain of a set of nuclear proteins interacting with H1° mRNA.

Synthesis of H1° histone, in the developing rat brain, is also regulated at post-transcriptional level. Regulation of RNA metabolism depends on a series of RNA-binding proteins (RBPs); therefore, we searched for H1° mRNA-interacting proteins. With this aim, we used in vitro transcribed, biotinylated H1° RNA as bait to isolate, by a chromatographic approach, proteins which interact with this mRNA, in the nuclei of brain cells. Abundant RBPs, such as heterogeneous nuclear ribonucleoprotein (hnRNP) K and hnRNP A1, and molecular chaperones (heat shock cognate 70, Hsc70) were identified by mass spectrometry. Western blot analysis also revealed the presence of cold shock domain-containing protein 2 (CSD-C2, also known as PIPPin), a brain-enriched RBP previously described in our laboratory. Co-immunoprecipitation assays were performed to investigate the possibility that identified proteins interact with each other and with other nuclear proteins. We found that hnRNP K interacts with both hnRNP A1 and Hsc70 whereas there is no interaction between hnRNP A1 and Hsc70. Moreover, CSD-C2 interacts with hnRNP A1, Y box-binding protein 1 (YB-1), and hnRNP K. We also have indications that CSD-C2 interacts with Hsc70. Overall, we have contributed to the molecular characterization of a ribonucleoprotein particle possibly controlling H1° histone expression in the brain.

Chromatin organization in Paracentrotus lividus eggs

After purification by buoyant density centrifugation in ethidium bromide - CsCl gradient and electrophoretic fractionation, the DNA fragments isolated from P. lividus egg nuclei incubated with micrococcal nuclease exhibit a typical oligomeric pattern. Analysis of chromatin samples digested to an increasing extent by micrococcal nuclease reveals that the structural organization of egg chromatin is heterogeneous, both in terms of repeat size and degree of sensitivity to nuclease attack. The nucleosomal repeats of P. lividus sperms and embryos up to the mesenchyme blastula stage have also been determined, for comparison.

Effects of triiodothyronine (T3) on differentiation of rat cortical neurons in primary cultures.

Some of the events which characterize neuronal terminal differentiation have been studied in rat cortical neurons cultured in a selective synthetic medium for a period which corresponds to terminal brain maturation in vivo. In particular, we have studied the effect of T3 on the synthesis of nuclear proteins and the expression of the mRNAs which encode different variants of T3 nuclear receptors (c erb A proteins). We have shown that: a) T3 stimulates the turnover of nuclear proteins, with a more evident effect on the non-histone component; b) for the whole lifespan of cultures the predominant form of c erb Aα mRNA is the α2 variant (which encodes a protein unable to bind T3); whatever the function of α2 protein this finding suggests that its predominance on α1 is settled very early during mammalian brain maturation.