Amorphous clusters across a vast range of sizes found to affect crystal nucleation
Amorphous clusters of amino acids and peptides formed in solution with sizes ranging from the molecular to micrometre scale influence crystal nucleation, according to research by a team in the UK. This new insight could allow scientists to better understand and control crystal growth of a range of compounds.
Klaas Wynne at the University of Glasgow and Rebecca Beveridge at the University of Strathclyde teamed up to explore the size distribution of aggregates formed in supersaturated solutions of amino acids and peptides. First they observed that amorphous nanoclusters form over several days, using dynamic light scattering. The data could be analysed using a stretched exponential function, which suggests a range of structures of different sizes were present. Next, Beveridge’s team used mass spectrometry to image small nanoclusters that aren’t visible using dynamic light scattering techniques.
They discovered that the aggregates, which vary in size from dimers up to the micrometre scale, play a crucial role in crystal nucleation. ‘Instead of overcoming a big barrier associated with this big interfacial tension of making a small crystal, you circumvent it by making an amorphous structure which has a very low surface tension,’ Wynne explains. The aggregates provide a site for nucleation, which lowers the energy barrier to crystal formation.
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