Microscopic Imaging of Chiral Amino Acids in Agar Gel through Circularly Polarized Luminescence of EuIII Complex

• Published in: Chemistry, an Asian journal an Asian journal, 2020-01, Vol.15 (1), p.85-90
• Main Authors: Koike, Hikaru, Nozaki, Koichi, Iwamura, Munetaka
• Format: Article
• Language: English
• Subjects: amino acid; Amino acids; Aqueous solutions; Chemistry; chiral sensing; Circular polarization; circularly polarized luminescence; Crystal structure; Dicarboxylic acids; fluorescence microscopy; Gels; Histidine; lanthanide complex; Luminescence
• ISSN: 1861-4728; 1861-471X
• DOI: 10.1002/asia.201901495

We recently found that [Eu(pda)2]− (pda: 1,10‐phenanthroline‐2,9‐dicarboxylic acid), which has an achiral structure in crystals, exhibits circularly polarized luminescence (CPL) in aqueous solutions containing chiral amino acids such as arginine and histidine. CPL measurements were performed for agar gel, which includes an aqueous solution of [Eu(pda)2]− and chiral arginine or histidine. The spectral shape, concentration, and pH dependences on CPL intensity in the agar gels were very close to those in aqueous solutions, indicating that the CPL of the EuIII complex in the agar gels was induced by mechanism similar to that in aqueous solutions. We performed spatially resolved CPL measurements using a laboratory‐built microscopic CPL spectroscopic system for agar‐gel samples, where d‐ and l‐ amino acids were separately dispersed. We successfully recorded CPL imaging maps showing spatial dispersions of d‐ and l‐amino acid in the agar gels. Spatially resolved CPL measurements were performed using a microscopic CPL spectroscopic system for agar‐gel samples containing a Eu complex (probe) and d‐ and l‐ amino acids (chiral agents). CPL imaging maps showing spatial dispersions of d‐ and l‐amino acid in the agar gels were successfully recorded.