Intercalation of l-Alanyl-Glutamine Dipeptide into Layered Double Hydroxides:Configuration Stabilization in Confined Interlayer Region.

In this paper, an unstable chiral drug l-alanyl-glutamine(l-(Ala-Gln)) was intercalated into layered double hydroxides(LDHs) and a systematic study combining experimental and theoreticalinvestigation was carried out. Structural characterization revealsthe microstructure of LDHs and properties of the intercalated l-(Ala-Gln). Solid-state UV–vis spectroscopy is adoptedto observe the energy absorption. This result shows that LDHs canblock the UV light, and inhibition of configuration conversion worksin the LDH host. Circular dichroism (CD) spectra suggest that theintercalated l-(Ala-Gln) can maintain its configuration inthe interlayer even when irradiated under UV light. Density functionaltheory (DFT) computations at the B3PW91/6-31G(d, p) level have beencarried out to understand the mechanism of l-(Ala-Gln) racemization.The computed result demonstrates that the thermal energy based onthe reaction temperature cannot support l-(Ala-Gln) to givean excited state, but it can be excited under the irradiation of UVlight with a wavelength less than 240 nm and undergoes conformationaltransition. When intercalated in the interlayer of LDHs, l-(Ala-Gln) is involved in strong guest–host interaction withthe layers and thus inhibition of configuration conversion is effectivein the LDH interlayer. [ABSTRACT FROM AUTHOR]