The problem the prize solved
Switch between the three ways to model a molecule.Two worlds of physics, one molecule
Karplus’s step: the 1972 hybrid program
Karplus had been working on quantum calculations for molecules. Arieh Warshel arrived at Harvard as a postdoc in 1970 with a classical force-field program from the Weizmann Institute.
Together they wrote a program that treated some of a molecule’s electrons with quantum mechanics and its atomic nuclei and remaining electrons with classical physics. They published it in 1972 in the Journal of the American Chemical Society.
The target was retinal, the light-sensitive molecule in vision, and molecules like it. Follow-up work in 1974 modelled how retinal changes shape.
The Nobel scientific background calls this the first work to show that hybrid methods could combine the strengths of both approaches.
- Paper
- Calculation of ground and excited state potential surfaces of conjugated molecules. I. Formulation and parametrization
- Authors
- A. Warshel, M. Karplus
- Journal
- J. Am. Chem. Soc. 94, 5612 (1972)
- Record
- doi.org/10.1021/ja00771a014
- Nobel ref.
- Reference 15 in the scientific background
The path to the prize, 1968 to 2024
Step through the story or select any point.Two research lines that met in 2013
What the Nobel committee pointed to
The scientific background’s 26 references
Orange marks the three papers this research identified: 15 is the 1972 Warshel–Karplus program; 17–18 are the 1975 and 1976 Levitt–Warshel papers. The others are not itemized here.
From paper to prize
Nobel-citedKarplus’s wider workCalendar years from publication to 2013, by subtraction. Select a row to find it on the timeline.
“for the development of multiscale models for complex chemical systems.”
The prize was split three ways: one third each to Karplus, Levitt and Warshel, sharing SEK 8 million.
The scientific background names Karplus’s 1972 paper with Warshel, then two papers by Levitt and Warshel. One is a 1975 protein-folding simulation. The other is the 1976 lysozyme study, now widely described as the first QM/MM model of an enzyme reaction.
Karplus’s part was the opening move: the 1972 program showed classical and quantum physics could share one calculation. Warshel was the thread through all three cited papers. Levitt brought the protein-scale modelling the 1975 and 1976 papers needed.
That last paragraph is this page’s reading of the cited papers, not the committee’s wording.
Why it matters today
Examples from the Nobel press release. Select one to see it in the model above.The press release puts it plainly: today “the computer is just as important a tool for chemists as the test tube.”
Karplus beyond the cited paper
His wider record, kept separate from what the prize cites.Reading structure from NMR
Before simulation, Karplus was known for linking magnetic-resonance measurements to molecular structure, theory that chemists could apply directly.
Proteins in motion
With McCammon and Gelin he published the first molecular dynamics simulation of a protein (BPTI) in Nature. It showed proteins flex and fluctuate rather than sit still.
CHARMM
His group built CHARMM (Chemistry at HARvard Macromolecular Mechanics), still a standard tool for simulating proteins, DNA and membranes.
Whether the scientific background discusses the 1977 or 1983 work was not checked for this revision. Karplus died at home in Cambridge, Massachusetts, in December 2024, aged 94.
Where the method breaks
The first hybrid treatment split electrons using molecular symmetry, so it only worked for planar molecules. Later work generalized the split.
A 2024 study found that cutting covalent bonds where the quantum region meets the classical one can introduce appreciable errors in the calculations it tested. That is a limitation of boundary handling in those tests, not a refutation of multiscale modelling.
No comprehensive check for retractions or corrections affecting the prize papers has been done, so none is asserted.
Every claim on this page
Hover a square to read it; select it to open the source.Claims by topic and status
Claims ledger
Verified means two independent sources, or one primary source or peer-reviewed paper.| # | Claim | Number or date | Source type | Confidence | Status |
|---|
Gaps
Tick items off as you close them. Ticks stay in this browser only.A note on the book in the original brief
The first version of this desk was built around Atoms and Molecules (1970), a 620-page physical-chemistry textbook by Karplus and Richard N. Porter.
It is a teaching text, not the prize work. It is absent from the scientific background’s 26 references, and no passage in it has been tied to the hybrid method.
- Title
- Atoms and Molecules: An Introduction for Students of Physical Chemistry
- Authors
- Martin Karplus, Richard N. Porter
- Published
- W. A. Benjamin, 1970 · 620 pages
- Prize role
- None documented