Biomimetic polyamines

E. (2003) Biomimetic control of size in the polyamine-directed formation of silica nanospheres. Angewandte Chemie-Intemational Edition, 42, 5192— 5195. 

As part of a biomimetic study for the enzyme class II aldolase" the equilibrium was reported for the cyclen complex, hydroxo-Zn(II)-l-(4-bromophenacyl)-l,4,7,10-tetraaza-cyclododecane and the intramolecular enolate 20, formed from Zn(II) and the enolate of l-(4-bromophenacyl)cyclen. This cyclization reaction was shown to be endothermic by 8.7 kJmol. However, with an entropy of 19 JmoU K it proceeds readily enough to show facile H/D exchange from the CH2 group of the exocyclic ligand. We wonder about the enthalpy and entropy changes associated with a different choice of other polyamines and/or central metals. 

The biomimetic studies of biomineralization have also provided inspiration to explain biopolymer-mediated silica formation in the diatoms. As mentioned in the previous section, biogenic silica contain small proteins and polyamines such as the silaffins. 

Polyamines Nonpeptide biomimetic analogues to siUca-precipitating peptides are drawn from the isolated LCPAs found on the cell walls of diatoms. Some of these polyamines include poly(allylamine) [79], (PEI) [73], N-methylpropylamine (PA) [76] and amine-terminated dendrimers [62, 68-70]. Each of these classes of compound represents a different structural aspect to silica templating, including the number of amines, the number of spacer atoms between the amines, its relative degree of methylation, and the presence and number of branching elements. All of these factors affect the resultant physical properties and subsequent reactivity of the siUca nanoparticle produced. 

Lutz, K., Groger, C., Sumper, M. and Brunner, E. (2005) Biomimetic silica formation analysis of the phosphate-induced self-assembly of polyamines. Physical Chemistry Chemical Physics, 7, 2812-15. 

Xu, M., Gratson, G.M., Duoss, E.B., Shepherd, R.F. and Lewis, J.A. (2005) Biomimetic silicification of 3D polyamine-rich scaffolds assembled by direct ink writing. Soji Matter, 2, 205. 

Bernecker, A., Wieneke, R., Riedel, R., Seibt, M., Geyer, A., and Steinem, C. (2010) Tailored synthetic polyamines for controlled biomimetic silica formation. /. Am. Chem. Soc., 132,1023-1031. 

Brunner, E., Lutz, K., Sumper, M. Biomimetic synthesis of silica nanospheres depends on the aggregation and phase separation of polyamines in aqueous solution. Phys. Chem. Chem. Phys. 6, 854-857 (2004)... 

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