Peptide/boron atom

Fig. 4.10 Polylysine with a total of 80 boron atoms in the periphery (according to Qualmann et al.). For the sake of clarity a - peptide bonded - lysine building block in one of the dendri-mer branches is shown in green (PEG = polyethylene glycol)...

Fig. 1. Complex formation between a peptide and boron atom.

A quite new type of antibiotic and one of the few naturally-occurring boron compounds is boromycin (86). Hydrolytic cleavage of D-valine with the M(7) hydroxides gave caesium and rubidium salts of this antibiotic, and crystal structure analysis established the formula as (XIIT). The rubidium ion is irregularly coordinated by eight oxygen atoms. Experiments with models showed that the cation site would be the natural place for the—NH3+ end of the D-valine residue, and the whole structure raises the possibility that transport of larger alkali metals is related to the N-ends of peptides and proteins. 

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