Tag Archives: Karplus Curve

RIP Martin Karplus and a Newman Anecdote

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Theoretical chemist Martin Karplus passed away 28 Dec., 2024, at age 94. Karplus shared the 2013 Nobel chemistry prize with Arieh Warshel and Michael Levitt for their work in “the development of multiscale models for complex chemical systems,” for computer programs they developed in the 1970s.

Those who have studied proton nuclear magnetic resonance will recall the Karplus equation or curve relating hydrogen-carbon-carbon-hydrogen dihedral bond angles to proton-proton coupling constants, 3JH,H, across 3 sigma bonds. If your molecule of interest is conformationally constrained such as an aliphatic ring, and there are coupled protons with the right splitting patterns, integrations and coupling constants, you may have some good data to prove/disprove a proposed structure in Acta Retracta.

The Karplus curve relating dihedral angle to proton-proton (1H-1H) coupling constants. The curve shown is the theoretical curve- measured coupling constants varied from the curve just a bit. Source: Wikipedia.

Newman Anecdote

Seeing the Newman projections above reminds me of the time I met him. It was 1993 and I and a faculty colleague found ourselves trudging through the hallowed chemistry department halls of her alma mater, The Ohio State University. We’re shuffling along when who should we spot working in his lab but the eminent Professor Mel Newman. Newman, who passed away later in 1993, was very near the end of his life then and looked every year of his age. My grad school research was in the area of stereochemistry and organic asymmetric synthesis, so I was naturally enthralled. We stepped in the lab like we owned the place and introduced ourselves. Newman was busy shaking a 2-Liter glass separatory funnel full of some jet-black liquid. We made sure not to startle him and let him set the funnel down into a ring stand before speaking. We exchanged pleasantries and I sputtered out words expressing my admiration and unexpected delight in meeting him- you know, fanboy stuff. He took the time to draw out the reaction chemistry he was performing and the target molecule. As I recall, it was a polyaromatic compound made with carbocation chemistry. Soon, we said our goodbyes and left.

On the way out of Columbus, OH, we stopped at a White Castle’s and enjoyed some sliders. It was a banner day- I met Mel Newman and had my first White Castle slider. It can get better than that, but probably not in Ohio.

For a chemist, the highest award is being recognized as an adjective for something, like Karplus Equation. Karplus made adjective status and that is an accomplishment most of us will never reach.