Dichlorobis(cycloalkylamine)platinum(II) complexes. Structure activity relationship on the human MDA-MB-231 breast cancer cell line

The syntheses of dichlorobis(cycloalkylamine)platinum(II) complexes with cis and trans cycloalkylamine ligands [cis-PtCl2(C3H5NH2)2 to cis-PtCl2(C8H15NH2)2 and trans-PtCl2(C7H13NH2)2 and trans-PtCl2(C8H15NH2)2 are described. The distinction between cis and trans isomers was achieved by 1H-NMR spectroscopy. The antitumor activity was detd. on the cell proliferation of the human MDA-MB-231 breast cancer cell line during long-term drug exposure. The complexes with small cycloalkylamine ligands were inferior, those with large cycloalkylamine ligands were comparable or superior to cisplatin. All cycloalkylamine ligands were inactive. IR spectroscopic studies showed that the size of the cycloalkylamine ring does not lead to significant differences in the Pt-Cl binding strength. Therefore it is assumed that the markedly stronger antitumor activity of the higher homologs is not the result of a faster reaction with bionucleophiles such as DNA. A possible explanation of the high activity of some of the isomers is the strong lipophilicity of the complexes. This assumption was confirmed by toxicity tests against confluent cultures

Relating critical phonon occupation to activation barrier in fast lithium-ion conductors

Phonon-based (vibrational) theories of ion transport are likely key to developing new design strategies for solid-state ionic conductors. However, they are not often utilized because it is difficult to ascertain which vibrational frequencies are important, even in describing fundamental parameters such as the activation barrier. This is perpetuated by the fact that it is difficult to tune vibrational frequencies directly, without changing the chemical structure, in order to study underlying phonon relations. Using isotopic substitution of 6Li for 7Li, we are able to change the mobile ion vibrations in the two exemplary ion conductors Li10SnP2S12 and Li6PS5Cl without altering their structure. Using a combination of nuclear magnetic resonance spectroscopy and ab initio molecular dynamics simulations to characterize temperature-dependent ion transport, it is demonstrated that the isotopic substitution of 6Li for 7Li increases the activation barrier for Li-ion transport. The magnitude of this isotope effect cannot be explained by changes in the zero-point vibrational energy alone. Therefore, we propose that the observed change in the activation barrier is related to the differences in the average critical phonon occupation needed to overcome the activation barrier. Our hypothesis is supported by an analytical model, based on the physics of quantum harmonic oscillators, that gives good agreement with the experimental results. Thus, isotopic substitution provides unique insights into the vibrational perspective and frequency dependence of the activation barrier in fast Li-ion conductors

Genome-wide association study of L-arginine and dimethylarginines reveals novel metabolic pathway for symmetric dimethylarginine.

BACKGROUND: -Dimethylarginines (DMA) interfere with nitric oxide (NO) formation by inhibiting NO synthase (asymmetric dimethylarginine, ADMA) and L-arginine uptake into the cell (ADMA and symmetric dimethylarginine, SDMA). In prospective clinical studies ADMA has been characterized as a cardiovascular risk marker whereas SDMA is a novel marker for renal function and associated with all-cause mortality after ischemic stroke. The aim of the current study was to characterise the environmental and genetic contributions to inter-individual variability of these biomarkers. METHODS AND RESULTS: -This study comprised a genome-wide association analysis of 3 well-characterized population-based cohorts (FHS (n=2992), GHS (n=4354) and MONICA/KORA F3 (n=581)) and identified replicated loci (DDAH1, MED23, Arg1 and AGXT2) associated with the inter-individual variability in ADMA, L-arginine and SDMA. Experimental in-silico and in-vitro studies confirmed functional significance of the identified AGXT2 variants. Clinical outcome analysis in 384 patients of the Leeds stroke study demonstrated an association between increased plasma levels of SDMA, AGXT2 variants and various cardiometabolic risk factors. AGXT2 variants were not associated with post-stroke survival in the Leeds study, nor were they associated with incident stroke in the CHARGE consortium. CONCLUSIONS: -These GWAS support the importance of DDAH1 and MED23/Arg1 in regulating ADMA and L-arginine metabolism, respectively, and identify a novel regulatory renal pathway for SDMA by AGXT2. AGXT2 variants might explain part of the pathogenic link between SDMA, renal function, and outcome. An association between AGXT2 variants and stroke is unclear and warrants further investigation