Cross-reactions residues detection

Houk RJT, Wallace KJ, Hewage HS, Anslyn EV (2008) A colorimetric chemodosimeter for Pd(II) a method for detecting residual palladium in cross-coupling reactions. Tetrahedron 64 8271-8278... 

These initial findings do not exclude other possible formaldehyde-induced reactions with tissue proteins. Notably, this first model system was not designed to detect the role of lysine residues. Lysine has a propensity to react with and form a variety of different types of cross-links with other amino acids in the presence of formaldehyde.1,3 417 Therefore, it is likely to also be important in reactions with formaldehyde. In fact, peptides with internal lysine residues were purposefully excluded from this initial study for technical reasons. To explore the importance of lysine residues in antigen retrieval, an alternative method was employed. 

The strains due to the platinated macrocycle and the double helix are necessary to induce the linkage isomerization reaction. The DNA duplex containing the central sequence G AG CTC (G indicating the platinated guanine residue) in which the half-life of the intrastrand cross-link G AG is about 2 h, is taken as reference. The cleavage of the phosphodiester backbone at the level of the macrocycle decreases the rate of the rearrangement by at least a factor of ten. Over a period of 48 h, no rearrangement was detected when the 1,3-intrastrand cross-link is at the 3 - or 5 -end of the platinated strand in the duplex. 

Intermediates occurring in these mechanisms have been identified by ESR measurements and by flash photolysis studies using optical absorption detection. For example, ESR measurements on wool keratins revealed the formation of sulfur-centered radicals of the structure RCH2S, which, in this case, are assumed to result from a reaction of electronically excited tyrosine moieties with cystine residues [11]. In many proteins, cross-links are formed. In the case of keratin and collagen, the cross-links are of the tryptophan-histidine and dityrosine types [11]. Cross-links formed by the combination of R-S or R-S-S radicals, both intermolecularly and intramolecularly, with incorrect sites are considered to be an important source of photoaggregation effects [8]. ESR measurements have also yielded evidence of C-H and C-N bond ruptures [8]. 

A Dubna-LLNL team (Oganessian et al. 2009) recently reported an unsuccessfid attempt to synthesize element 120 at Dubna via the Pu( Fe,xn) 120 reaction. The sensitivity of the experiment corresponded to a cross section of 0.4 pb for the detection of one decay. The production cross section of the evaporation residues in this reaction appeared to be lower by more than an order of magnitude compared to that of the same target with Ca. They considered various explanations for this and concluded that additional attempts to synthesize element 120 in this reaction would require much increased sensitivity and proposed... 

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