A fundamental understanding of the enantiospecific interactions between chiral adsorbates and understanding of their interactions with chiral surfaces is key to unlocking the origins of enantiospecific surface chemistry. Herein, the adsorption and decomposition of the amino acid proline (Pro) have been studied on the achiral Cu(110) and Cu(111) surfaces and on the chiral Cu(643)
- Award ID(s):
- 1764252
- NSF-PAR ID:
- 10224449
- Date Published:
- Journal Name:
- Nanomaterials
- Volume:
- 10
- Issue:
- 9
- ISSN:
- 2079-4991
- Page Range / eLocation ID:
- 1716
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract R&S surfaces. Isotopically labelled 1‐13C‐l‐ Pro has been used to probe the Pro decomposition mechanism and to allow mass spectrometric discrimination ofd ‐Pro and 1‐13C‐l ‐Pro when adsorbed as mixtures. On the Cu(111) surface, X‐ray photoelectron spectroscopy reveals that Pro adsorbs as an anionic species in the monolayer. On the chiral Cu(643)R&S surface, adsorbed Pro enantiomers decompose with non‐enantiospecific kinetics. However, the decomposition kinetics were found to be different on the terraces versus the kinked steps. Exposure of the chiral Cu(643)R&S surfaces to a racemic gas phase mixture ofd ‐Pro and 1‐13C‐l ‐Pro resulted in the adsorption of a racemic mixture; i.e., adsorption is not enantiospecific. However, exposure to non‐racemic mixtures ofd ‐Pro and 1‐13C‐l ‐Pro resulted in amplification of enantiomeric excess on the surface, indicative of homochiral aggregation of adsorbed Pro. During co‐adsorption, this amplification is observed even at very low coverages, quite distinct from the behavior of other amino acids, which begin to exhibit homochiral aggregation only after reaching monolayer coverages. The equilibrium adsorption ofd ‐Pro and 1‐13C‐l ‐Pro mixtures on achiral Cu(110) did not display any aggregation, consistent with prior scanning tunneling microscopy (STM) observations ofdl ‐Pro/Cu(110). This demonstrates convergence between findings from equilibrium adsorption methods and STM experiments and corroborates formation of a 2D random solid solution. -
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Abstract The hydration kinetics of enantiomerically pure propylene oxide (PO, CH3*CHCH2O) to chiral propylene glycol (PG, CH3*CH(OH)CH2OH) in aqueous solution have been studied using FTIR while simultaneously monitoring the net chirality of the reaction mixture. The hydration reaction appears to be first‐order in the PO concentration with a rate constant of
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The enantiomers of chiral amino acids play versatile roles in biological systems including humans. They are also very useful in the asymmetric synthesis of diverse chiral organic compounds. Therefore, identifying a specific amino acid and distinguishing it from its enantiomer are of great importance. Although significant progress has been made in the development of fluorescent probes for amino acids, most of them are not capable of conducting simultaneous chemoselective and enantioselective detection of a specific amino acid enantiomer. In this article, several fluorescent probes have been designed and synthesized for chemoselective as well as enantioselective recognition of certain amino acid enantiomers. ( S )-1 shows greatly enhanced fluorescence in the presence of l -glutamic acid and l -aspartic acid, but produces no or little fluorescence response toward their opposite enantiomers and other amino acids. ( R )-4 in combination with Zn 2+ shows greatly enhanced fluorescence in the presence of l -serine. ( S )-6 is designed for the selective recognition of histidine. Micelles made of an amphiphilic diblock copolymer are used to encapsulate the water-insoluble compound ( S )-8 which shows chemoselective as well as enantioselective fluorescence enhancement with l -lysine in the presence of Zn 2+ in aqueous solution. The same micelles are also used to encapsulate several ( S )-1,1′-binaphthyl-based monoaldehydes ( S )-10 for the chemoselective and enantioselective fluorescence recognition of l -tryptophan in the presence of Zn 2+ in aqueous solution. These findings have demonstrated that highly selective fluorescence identification of a specific amino acid enantiomer can be achieved by incorporating certain functional groups at the designated locations of the 1,1′-binaphthyls. The binaphthyl core structure of these probes provides both a chirality source and highly tunable fluorescence properties. Matching the structure and chirality of these probes with those of the specific amino acid enantiomers can generate structurally rigid reaction products and give rise to greatly enhanced fluorescence. The strategies of this work can be further expanded to develop fluorescent probes for the specific identification of many amino acids of interest. This should facilitate the analysis of chiral amino acids in various applications. The outlook of this research and its comparison with other methods are also discussed.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/nano10091716
