Title: The role of momentum transfer during incoherent neutron scattering is explained by the energy landscape model

Abstract

We recently introduced a model of incoherent quasielastic neutron scattering (QENS) that treats the neutrons as wave packets of finite length and the protein as a random walker in the free energy landscape. We call the model ELM for “energy landscape model.” In ELM, the interaction of the wave packet with a proton in a protein provides the dynamic information. During the scattering event, the momentum Q(t) is transferred by the wave packet to the struck proton and its moiety, exerting the force F(t)=dQ(t)/dt. The resultant energy E* is stored elastically and returned to the neutron as it exits. The energy is given by E*=k_B(T₀+χQ), where T₀ is the ambient temperature and χ (≈ 91 K Å) is a new elastobaric coefficient. Experiments yield the scattering intensity (dynamic structure factor) S(Q;T) as a function of Q and T. To test our model, we use published data on proteins where only thermal vibrations are active. ELM competes with the currently accepted theory, here called the spatial motion model (SMM), which explains S(Q,T) by motions in real space. ELM is superior to SMM: It can explain the experimental angular and temperature dependence, whereas SMM cannot do so.

Authors:

Frauenfelder, Hans ^[1]; Young, Robert D. ^[2]; Fenimore, Paul W. ^[1]

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+ Show Author Affiliations

1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545,
2. Department of Physics, Illinois State University, Bloomington-Normal, IL 61790

Publication Date:

Tue May 16 00:00:00 EDT 2017

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1354751

Alternate Identifier(s):

OSTI ID: 1492533

Report Number(s):

LA-UR-16-20751
Journal ID: ISSN 0027-8424

Grant/Contract Number:  

LDRD DR200160044; 89233218CNA000001

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 114 Journal Issue: 20; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Biological Science; Incoherent quasi-elastic neutron scattering, protein dynamics