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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Oscillations of chiral preference in proline clusters
Alison E Holliday1, Natalya Atlasevich, Sunnie Myung
1Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, Pennsylvania 19081, USA.
The Journal of Physical Chemistry. A
|June 7, 2012
Summary
Small proline clusters exhibit oscillating chiral preferences, favoring either homochiral or heterochiral arrangements depending on size and protonation state. This finding offers insights into molecular self-assembly and stability.
Area of Science:
- Chemical Physics
- Supramolecular Chemistry
- Biophysical Chemistry
Background:
- Chirality is fundamental in biological systems, with amino acids like proline existing as L- and D-enantiomers.
- The self-assembly of chiral molecules can lead to complex structures with specific properties.
- Understanding chiral preferences in small molecular clusters is key to predicting larger-scale organization.
Purpose of the Study:
- To investigate the chiral preferences of proline clusters of varying sizes (2-23 monomers).
- To determine how protonation state (singly or doubly protonated) influences cluster chirality.
- To correlate observed chiral preferences with potential stable structural geometries.
Main Methods:
- Utilized ion mobility/mass spectrometry (IM/MS) to analyze proline clusters.
- Generated clusters via electrospray ionization from solutions of varying enantiomeric purity (enantiopure L, enantiopure D, racemic).
- Analyzed cluster size and charge state ([xPro+H]+ and [xPro+2H]2+) to determine chiral preferences.
Main Results:
- Observed a distinct oscillation in chiral preference with increasing cluster size.
- Singly protonated clusters ([xPro+H]+) showed preference for homochiral assemblies at x=4, 6, 11, 12 and heterochiral at x=5, 7.
- Doubly protonated clusters ([xPro+2H]2+) favored homochiral for x=18, 19, 23 and heterochiral for x=14, 16, 17, 20, 21, 22.
Conclusions:
- Proline cluster chirality is size-dependent and influenced by protonation.
- Observed oscillations suggest specific stable geometric arrangements dictate chiral preference.
- Some heterochiral clusters may feature distinct homochiral domains of D- and L-proline.
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