Simultaneous determination of <Superscript>89</Superscript>Sr and <Superscript>90</Superscript>Sr: comparison of methods and calculation techniques

The presence of ⁸⁹Sr and ⁹⁰Sr in the biosphere constitutes a biological hazard. There are several analytical methods for the determination of ⁸⁹Sr and ⁹⁰Sr. Three analytical methods of various application fields using selective Sr resin for Sr separation and DGA resin for Y separation and measuring techniques, i.e. liquid scintillation spectrometry and Cerenkov counting are discussed in the paper. The calculation techniques are compared in the aspects such as trueness and accuracy of the results and the limit of detection. Uncertainties and detection limits are calculated using the spreadsheet method.     

Interview with Eric Scerri

Foundations of Chemistry - Eric Scerri is the world-leading expert on (the history of) Periodic Table and was quite recently named the second-most influential academic in the field of chemistry...     

Development of Electrophoretic Methods for Simultaneous Determination of Enantiomeric Ratio and Composition of Diastereomeric Salt Mixtures

Obtaining enantiomeric pure compounds is—among other techniques—possible in a resolvation experiment via diastereomeric salt formation, excellently exemplified by a modified Pope–Peachy method performed in supercritical carbon dioxide as solvent. The salt precipitation is followed by supercritical fluid extraction (SFE) to separate the diastereomeric salts and the unreacted enantiomers. To evaluate the extraction efficiency, conversion and enantioselectivity achieved, it is essential to determine the enantiomer excess and the residual resolving agent content in extracts and raffinates. Carefully chosen experimental parameters enable the simultaneous determination of certain anions and cations in capillary electrophoresis in a single run, which has not been reported for diastereomeric mixtures so far. In this paper, a partially validated chiral selective cyclodextrin enabled capillary electrophoresis method is presented for the characterization of cis-permethrinic acid samples resolved with (R)-1-phenylethylamine prepared by the SFE-based resolvation technique. To evaluate the efficiency of the resolvation, a cyclodextrin enabled chiral separation method was developed applying permethylated-β-cyclodextrin as chiral selector. The theoretical possibility of the widespread application of the developed method (with minor adjustments) is justified for other selectands and selectors. The developed methods can be thereby applied for the fast and reliable control of resolvation experiments.     

Targeting an Interaction Between Two Disordered Domains by Using a Designed Peptide

Intrinsically disordered regions in proteins (IDRs) mediate many disease-related protein–protein interactions. However, the unfolded character and continuous conformational changes of IDRs make them difficult to target for therapeutic purposes. Here, we show that a designed peptide based on the disordered p53 linker domain can be used to target a partner IDR from the anti-apoptotic iASPP protein, promoting apoptosis of cancer cells. The p53 linker forms a hairpin-like structure with its two termini in close proximity. We designed a peptide derived from the disordered termini without the hairpin, designated as p53 LinkTer. The LinkTer peptide binds the disordered RT loop of iASPP with the same affinity as the parent p53 linker peptide, and inhibits the p53–iASPP interaction in vitro. The LinkTer peptide shows increased stability to proteolysis, penetrates cancer cells, causes nuclei shrinkage, and compromises the viability of cells. We conclude that a designed peptide comprising only the IDR from a peptide sequence can serve as an improved inhibitor since it binds its target protein without the need for pre-folding, paving the way for therapeutic targeting of IDRs.     

Different ortho and para electronic effects on hydrolysis and cytotoxicity of diamino bis(phenolato) "salan" Ti(IV) complexes

Bis(isopropoxo) Ti(IV) complexes of diamino bis(phenolato) "salan" ligands were prepared, their hydrolysis in 1:9 water/THF solutions was investigated, and their cytotoxicity toward colon HT-29 and ovarian OVCAR-1 cells was measured. In particular, electronic effects at positions ortho and para to the binding phenolato unit were analyzed. We found that para substituents of different electronic features, including Me, Cl, OMe, and NO(2), have very little influence on hydrolysis rate, and all para-substituted ortho-H complexes hydrolyze slowly to give O-bridged clusters with a t(1/2) of 1-2 h for isopropoxo release. Consequently, no clear cytotoxicity pattern is observed as well, where the largest influence of para substituents appears to be of a steric nature. These complexes exhibit IC(50) values of 2-18 μM toward the cells analyzed, with activity which is mostly higher than those of Cp(2)TiCl(2), (bzac)(2)Ti(OiPr)(2) and cisplatin. On the contrary, major electronic effects are observed for substituents at the ortho position, with an influence that exceeds even that of steric hindrance. Ortho-chloro or -bromo substituted compounds possess extremely high hydrolytic stability where no major isopropoxo release as isopropanol occurs for days. In accordance, very high cytotoxicity toward colon and ovarian cells is observed for ortho-Cl and -Br complexes, with IC(50) values of 1-8 μM, where the most cytotoxic complexes are the ortho-Cl-para-Me and ortho-Br-para-Me derivatives. In this series of ortho-substituted complexes, the halogen radius is of lesser influence both on hydrolysis and on cytotoxicity, while OMe substituents do not impose similar effect of hydrolytic stability and cytotoxicity enhancement. Therefore, hydrolytic stability and cytotoxic activity are clearly intertwined, and thus this family of readily available Ti(IV) salan complexes exhibiting both features in an enhanced manner is highly attractive for further exploration.     

Rate constant for the reaction of CH3C(O)CH2 radical with HBr and its thermochemical implication

The fast flow method with laser induced fluorescence detection of CH₃C(O)CH₂ was employed to obtain the rate constant of k₁ (298 K) = (1.83 ± 0.12 (1σ)) × 10¹⁰ cm³ mol^?1 s^?1 for the reaction CH₃C(O)CH₂ + HBr ? CH₃C(O)CH₃ + Br (1, ?1). The observed reduced reactivity compared with n‐alkyl or alkoxyl radicals can be attributed to the partial resonance stabilization of the acetonyl radical. An application of k₁ in a third law estimation provides Δ_fH(CH₃C(O)CH₂) values of ?24 kJ mol^?1 and ?28 kJ mol^?1 depending on the rate constants available for reaction ( ‐1 ) from the literature. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 32–37, 2006     

Preparation and X-ray characterization of two-coordinate Cu(I) complex of aliphatic thiolato ligand: Effect of steric bulk on coordination features

We have synthesized in a single-step procedure from available copper(I) precursor at RT two Cu(I) thiolato clusters of the formula [Cu₄(μ-SCH(CH₃)₂)₆]²⁻ and [Cu₅(μ-SC(CH₃)₃)₆]⁻ as revealed by X-ray crystallography, where increased steric bulk leads to a bigger cage with some two-coordinate metal centers. In addition, we identified a mononuclear two coordinate thiolato complex with the bulkier ligand, of the formula NEt₄[Cu(SC(CH₃)₃)₂]. This is only the second example of such a complex of an aliphatic ligand that is structurally characterized. The X-ray structure reveals an S–Cu–S angle of 176.7–179.5°, with Cu–S distances of 2.14 Å.