In memory of Prof. Lowell D. Kispert (June 9, 1940– February 8, 2026), his transformative contributions to the field of carotenoid radicals are recognized here. Although Prof. Kispert had been a pioneer in studying organic radicals with EPR (Electron Paramagnetic Resonance) since 1960s, his first major carotenoid-focused study entitled “Carotenoid cation radicals: electrochemical, optical, and EPR study” appeared on March 1, 1988. Published in the Journal of the American Chemical Society, this landmark paper detailed the EPR detection of the carotenoid radical cation for the first time in solution. This paper followed a 1985 proposal Kispert submitted to the U.S. Department of Energy, which shifted his career focus toward the role of carotenoids in plant photosynthesis. These radical cations are crucial for understanding how plants dissipate excess light energy (photoprotection) and the antioxidant behavior of carotenoid pigments. For the next four decades, until his passing on February 8, 2026 at the age of 85, he dedicated his life’s work to carotenoids, producing about 125 publications in this area. In total, Prof. Kispert authored more than 300 scientific publications over the course of his nearly 60-year career.
Prof Kispert pioneered the use of simultaneous electrochemical and EPR (SEEPR) techniques to characterize the two-electron transfer character of carotenoids. Through the use of EPR and ENDOR (Electron-Nuclear Double Resonance), he elucidated the complex electron transfer processes occurring when carotenoids are adsorbed on solid matrices or in biological systems like Photosystem II. His work established the correlation between the redox properties of carotenoids and their ability to scavenge free radicals, providing keyinsights into how they protect plants from oxidative stress.
For researchers continuing his work, the following recent publications establish the prevailing analytical framework for carotenoid EPR and ENDOR methodology:
- EPR at 80: Carotenoid Radical Cation Detection (2024) Published in Applied Magnetic Resonance, this review summarizes the beginning of his carotenoid chemistry started in middle 1980s, specifically highlighting how Simultaneous Electrochemical EPR (SEEPR) and High-Field/High-Frequency EPR (HFEPR) have become tools for resolving the structures and stability of carotenoid radical cations.
- The Endless World of Carotenoids—Structural, Chemical and Biological Aspects (2023) This work in the International Journal of Molecular Sciences details the use of HFEPR (up to 330 GHz) to resolve g-anisotropy. This high-frequency resolution is essential for distinguishing between cylindrically symmetrical p-radical cations and other species that appear as single unresolved peaks at standard X-band frequencies.
- Chemistry of Carotenoid Radicals and Complexes (2023) This book by Kispert and Focsan provides a centralized reference for the entire suite of EPR techniques—including spin-trapping and pulsed ENDOR—used to study carotenoids in both artificial matrices and biological systems like Photosystem II.
- Carotenoids: Importance in Daily Life—Insight Gained from EPR and ENDOR (2021) This comprehensive review in Applied Magnetic Resonance establishes the protocols for using ENDOR and DFT calculations to distinguish between carotenoid radical cations and neutral radicals, which often share similar hyperfine couplings.
Dr. Kispert’s transition from 1960s organic radical chemistry—utilizing traditional X-band EPR—to the sophisticated carotenoid research of the 21st century stands as a testament to a lifetime of intellectual curiosity. Over four decades, he moved beyond standard measurements to master advanced EPR techniques to study carotenoid radicals. By integrating these with simultaneous electrochemical methods and computational DFT modeling, he pushed the boundaries of the field to better understand how these vital molecules protect life through electron transfer.
