Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions

Anna Jawor-Baczynska, Barry D. Moore, Han Seung Lee, Alon V. McCormick, Jan Sefcik

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Aqueous solutions of highly soluble substances such as small amino acids are usually assumed to be essentially homogenous systems with some degree of short range local structuring due to specific interactions on the sub-nanometre scale (e.g. molecular clusters, hydration shells) usually not exceeding several solute molecules. However, recent theoretical and experimental studies have indicated the presence of much larger supramolecular assemblies or mesospecies in solutions of small organic and inorganic molecules as well as proteins. We investigated both supersaturated and undersaturated aqueous solutions of two simple amino acids (glycine and DL-alanine) using Dynamic Light Scattering (DLS), Brownian Microscopy/Nanoparticles Tracking Analysis (NTA) and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Colloidal scale mesospecies (nanodroplets), were previously reported in supersaturated solutions of these amino acids and were implicated as intermediates species on a non-classical crystallization pathway. Surprisingly, we have found that the mesospecies are also present in significant numbers in undersaturated solutions even when the solute concentration is well below the solid-liquid equilibrium concentration (saturation limit). Thus, mesopecies can be observed with mean diameters ranging from 100 to 300 nm and a size distribution that broadens towards larger size with increasing solute concentration. We note that the mesospecies are not a separate phase and the system is better described as a thermodynamically stable mesostructured liquid containing solute-rich domains dispersed within bulk solute solution . Hence, at a given temperature, if excess crystalline solid is present, the complete mesostructured liquid will be in equilibrium with the solid and solute molecules will be stably distributed between solute-rich mesospecies and the surrounding bulk solution.
LanguageEnglish
Pages425–440
Number of pages16
JournalFaraday Discussions
Volume167
Early online date24 May 2013
DOIs
Publication statusPublished - 1 Dec 2013

Fingerprint

Population distribution
amino acids
solutes
Amino Acids
Molecules
Liquids
liquids
aqueous solutions
molecules
molecular clusters
alanine
Dynamic light scattering
glycine
Crystallization
Hydration
Alanine
Cryogenics
Glycine
assemblies
cryogenics

Keywords

  • highly soluble substances
  • solute-rich mesospecies
  • amino acid solutions

Cite this

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Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions. / Jawor-Baczynska, Anna; Moore, Barry D.; Lee, Han Seung; McCormick, Alon V.; Sefcik, Jan.

In: Faraday Discussions, Vol. 167, 01.12.2013, p. 425–440 .

Research output: Contribution to journalArticle

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T1 - Population and size distribution of solute-rich mesospecies within mesostructured aqueous amino acid solutions

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AU - Moore, Barry D.

AU - Lee, Han Seung

AU - McCormick, Alon V.

AU - Sefcik, Jan

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