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.     

A neighbouring group effect leading to enhanced nucleophilic substitution of amines at the hindered α-carbon atom of an α-hydroxyphosphonate

Diethyl α-hydroxy-benzylphosphonate undergoes nucleophilic substitution with primary amines of sufficient reactivity at around 100 °C to afford the corresponding α-aminophosphonates. The substitution can be enhanced by microwave irradiation. The reaction takes place with surprising ease due to the neighbouring group effect of the PO moiety as was justified by DFT calculations carried out to evaluate the mechanism of the substitution under discussion.     

Role of structure-proteins in the porphyrin–DNA interaction

We studied the complexation of meso-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP) with HeLa nucleosomes and compared it to our earlier results on T7 phage nucleoprotein complex (NP) and isolated DNA. To identify binding modes and relative concentrations of the bound TMPyP forms, the porphyrin absorption spectra were analyzed at various base pair/porphyrin ratios. Spectral decomposition and circular dichroism measurements proved that the two main binding modes of TMPyP, i.e., external binding and intercalation occur also in the nucleosomes. The DNA superstructure maintained by the proteins decreases its accessibility for TMPyP similarly in both nucleoproteins. A difference is observed between the partitioning of the two binding modes: in the case of nucleosome the ratio of intercalation to groove-binding is changed from 60/40 to 40/60 as determined for T7 NP and for isolated DNA-s. Using UV and CD melting studies, we revealed that TMPyP destabilizes the DNA–protein interaction in the nucleosomes but not in the T7 phage. Lastly, photoinduced reaction of bound TMPyP caused alterations in DNA structures and DNA–protein interactions within both nucleoprotein complexes; the nucleosomes were found to be more sensitive to the photoreaction.     

Unusually large reactivity differences in the transformation of cyclopropane lactones to 1‐aminocyclopropane‐1‐phosphonic acids and their carboxylic acid analogues

Starting from a cyclopropane lactone 5 , the synthesis of a 1‐aminocyclopropane‐1‐phosphonic acid derivative 11 is described. The considerable differences in the reactivity of the lactone ring opening in the case of a cyclopropane lactone substituted by a phosphonic acid ester 5 and their carboxylic acid ester analogue 2 toward ammonia or amines have been compared and interpreted by using the map of electrostatic potentials. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:90–96, 2001