Conformation and assembly of polypeptide scaffolds in templating the synthesis of silica: an example of a polylysine macromolecular "switch".
Although the role of polycationic macromolecules in catalyzing the synthesis of silica structures is well established, detailed understanding of the mechanisms behind the production of silica structures of controlled morphologies remains unclear. In this study, we have used both poly-L-lysine (PLL) and/or poly-D-lysine (PDL) for silica synthesis to investigate mechanisms controlling inorganic morphologies. The formation of both spherical silica particles and hexagonal plates was observed. The formation of hexagonal plates was suggested, via circular dichroic spectroscopy (CD), to result from the assembly of helical polylysine molecules. We confirm that the formation of PLL helices is a prerequisite to the hexagonal silica synthesis. In addition, we present for the first time that the handedness of the helicity of the macromolecule does not affect the formation of hexagonal silica. We also show, by using two different silica precursors, that the precursor does not have a direct effect on the formation of hexagonal silica plates. Furthermore, when polylysine helices were converted to beta-sheet structure, only silica particles were obtained, thus suggesting that the adoption of a helical conformation by PLL is required for the formation of hexagonally organized silica. These results demonstrate that the change in polylysine conformation can act as a "switch" in silica structure formation and suggest the potential for controlling morphologies and structures of inorganic materials via control of the conformation of soft macromolecular templates.
Department of Chemical and Material Engineering, University of Cincinnati, Ohio 45221-0012, USA. Siddharth.Patwardhan@ntu.ac.uk
Siddharth V
SV
Patwardhan
Ronak
R
Maheshwari
Niloy
N
Mukherjee
Kristi L
KL
Kiick
Stephen J
SJ
Clarson
D002942:Circular Dichroism / Q000379:methods; D046911:Macromolecular Substances / Q000737:chemistry*; D010316:Particle Size; D010455:Peptides / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000138:chemical synthesis* / Q000737:chemistry; D013696:Temperature
D046911:Macromolecular Substances; D010455:Peptides; D011107:Polylysine; D012822:Silicon Dioxide