Doctoral Dissertations
Date of Award
5-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Chemistry
Major Professor
Thanh D. Do
Committee Members
Janice L. Musfeldt, Tessa R. Calhoun, Siris O. Laursen
Abstract
This dissertation presents an extensive and extremely thorough characterization of cyclosporines with the utilization of nuclear magnetic resonance spectroscopy (NMR) and ion mobility spectrometry-mass spectrometry (IMS-MS). Cyclosporines, flexible and diverse N-methylated macrocyclic peptides, display a wide variety of conformers and functions but the relationships between the two are still heavily unknown. Comprehensive analyses of the structures and dynamics of these macrocycles elucidate the key roles of specific ammino acid residues and shed light on membrane permeable conformers. Through various studies in the solution-, condensed-, and gas-phase, we elucidate the conformational ensembles of several cyclosporine derivatives. We uncover previously unreported cyclosporine A (CycA) and Alisporivir (ALI) conformers that are believed to be important for passive membrane permeation. We also propose a new mechanism for cyclosporine passive membrane permeation. Our data show common characteristics between cyclosporines with good membrane permeation, such as cis MeVal11-MeBmt1 containing conformers and similar conformational stability. These findings suggest that a biased two-state equilibrium between membrane-like and aqueous-like conformers is required for effective membrane permeation. Furthermore, we have established novel methods for employing traditional analysis techniques. For example, we have also utilized drift-tube IMS-MS as a conformational screening tool, established a set of routine NMR experiments for the thorough characterization of cyclsoproines in the solution-phase, pioneered the use of cyclic IMS MS for the conformational separation and dynamics evaluation of macrocyclic peptides, v and demonstrated the use of a standard solution-NMR spectrometer for the characterization of charged molecules in a solvent-free environment. Our studies push the boundaries of typical analysis and interweave fundamentals of analytical and physical chemistry to advance the knowledge of molecular structure-function relationships.
Recommended Citation
Limbach, Miranda N., "Elucidating Cyclosporine Properties with Nuclear Magnetic Resonance Spectroscopy and Ion Mobility Spectrometry – Mass Spectrometry. " PhD diss., University of Tennessee, 2025.
https://trace.tennessee.edu/utk_graddiss/12384