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The legacies of Langmuir, Ising, and Pauling: Ligand binding and the helix–coil transition
Author(s) -
Saroff Harry A.,
Kiefer James E.
Publication year - 1999
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/(sici)1097-0282(199905)49:6<425::aid-bip1>3.0.co;2-3
Subject(s) - ising model , chemistry , k nearest neighbors algorithm , partition (number theory) , statistical physics , chemical physics , combinatorics , physics , mathematics , computer science , artificial intelligence
Multiple, independent sites or domains behave, on chemical change, in a manner predicted by Langmuir. Distortions of this behavior have been attributed to interactions between the domains, which vary with the progress of the changes occurring at the sites or domains. The two main models for nearest neighbor interactions perturbing the Langmuir prediction for independent domains are those of Ising and Pauling. If we designate the initial site as (−) and the changed site as (+), then the Langmuir requirement for independence of sites yields a set of nearest neighbor interactions such that the (− −), (− +), (+ −), and (+ +) interactions are all identical. This identity is usually characterized as “no interactions.” Ising, in dealing with electron pairs, invoked nearest neighbor interactions such that the interactions of the (− −) pairs equaled those of the (+ +) pairs, but with the (− +) and (+ −) pairs differing from the reference (− −) pair. Pauling, on the other hand, postulated that only the (− −) and (+ +) pairs interacted differently. A dichotomy has arisen in the application of these two models, with some investigators ignoring or overlooking one of the models. We explore these models, alone and combined, with exact partition functions generated in reasonable computer times for hundreds of sites employing our combinatorial algorithm. © 1999 John Wiley & Sons, Inc. Biopoly 49: 425–440, 1999