Circularly polarized luminescence (CPL)-active lanthanide(III) complexes present a new method for chiral distinction of biomolecules upon metal binding or structural arrangements. This study is envisaged to understand the significantly different photophysical and chiroptical properties of the europium(III)-tetracycline (Eu:TC) complex. It is worth noting that the TC class of antibiotics has achieved importance beyond their therapeutic use as broad-spectrum antibiotics because many metal complexes utilizing TC have been used as luminescent probes for the investigation of biomolecular interactions. The method involves understanding the (a) speciation of TC, (b) conformation and ternary complexes formed between the Eu:TC complexes in aqueous and/or organic solvents at varied pH values and (c) variation of this Eu:TC complex using various TC-like derivatives. By identifying the structural changes of the various Eu:TC complexes, this CPL-active luminescent molecular probe can be designed and studied in diverse solutions at targeted pH values to allow for the molecular and chiral recognition/sensing of biomolecules such as amino acids, sugar derivatives, proteins, etc. Using luminescence, 5D0 7F0 Eu(III) excitation, and CPL spectroscopy, will allow for the study of the Eu:TC complex to recognize and interact with different chiral compounds in solution. The results from this study will explicate information on the local microenvironment about the lanthanide(III) metal by understanding the interactions of added analytes, in reference to chiral biomolecules like L-malic acid, human serum albumin (HSA), and bovine serum albumin (BSA), on the Eu:TC probe. CPL spectroscopy is used as a fingerprint to indicate the structural changes within the Eu:TC complex as a result in a chiral signal correlated to the molecular and chiral sensing of an added biomolecule. The use of molecular probing using luminescent lanthanide(III) metals will aid in understanding the structural and functional aspects of each essential metal ion within many biological systems. In addition, the development of a straightforward and sensitive CPL-based technique for chiral elucidation has the potential to become a standard technique in biology and biochemistry laboratories, so the broader impacts are significant.
The purpose of this project is to demonstrate the application of molecular probes using luminescent lanthanide(III) ions as a means of determining fundamental principles of bioinorganic functions within biological systems; in particular, the structural composition of circularly polarized luminescence-active tetracycline-like lanthanide complexes and the chiral sensing/recognition of biomolecules.
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