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

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.

Ask not what physics can do for biology--ask what biology can do for physics.

Stan Ulam, the famous mathematician, said once to Hans Frauenfelder: 'Ask not what Physics can do for biology, ask what biology can do for physics'. The interaction between biologists and physicists is a two-way street. Biology reveals the secrets of complex systems, physics provides the physical tools and the theoretical concepts to understand the complexity.

A wave-mechanical model of incoherent quasielastic scattering in complex systems.

Quasielastic incoherent neutron scattering (QENS) is an important tool for the exploration of the dynamics of complex systems such as biomolecules, liquids, and glasses. The dynamics is reflected in the energy spectra of the scattered neutrons. Conventionally these spectra are decomposed into a narrow elastic line and a broad quasielastic band.

Dynamics and the free-energy landscape of proteins, explored with the Mössbauer effect and quasi-elastic neutron scattering.

The Mössbauer effect and quasi-elastic neutron scattering (QENS) from hydrated proteins yield sharp elastic lines that are accompanied by broad wings. Conventionally, the elastic line and the broad wings are treated as separate phenomena. We show that there is no separation; the entire spectrum consists of Lorentzians with the natural line width.

Mössbauer effect in proteins.

In proteins, the Mössbauer effect and neutron scattering show a broad line and a rapid increase of the conformational mean-square displacement above about 180 K. The increase, dubbed the "dynamical transition," is controversial. We introduce a new interpretation of the Mössbauer effect in proteins and demonstrate that no dynamical transition is required.

Neutron scattering and protein dynamics.

Neutrons play an important role in the study of proteins. The best known example is the determination of protein structures using neutron diffraction. Less well known, but possibly even more important in the future, is the determination of protein fluctuations using neutron scattering.

A unified model of protein dynamics.

Protein functions require conformational motions. We show here that the dominant conformational motions are slaved by the hydration shell and the bulk solvent. The protein contributes the structure necessary for function.

Protein dynamics and function: insights from the energy landscape and solvent slaving.

Protein motions are complex and a good way to describe them is in terms of a very high-dimensional conformation space. We give here a simple explanation of the conformation space and the energy landscape, the conformational motions and protein reactions, based on an analogy to a traffic problem. The analogy provides insight into the slaving of protein processes to bulk solvent fluctuations, in both the native and unfolded states.

The association between cervical spine curvature and neck pain.

Degenerative changes of the cervical spine are commonly accompanied by a reduction or loss of the segmental or global lordosis, and are often considered to be a cause of neck pain. Nonetheless, such changes may also remain clinically silent. The aim of this study was to examine the correlation between the presence of neck pain and alterations of the normal cervical lordosis in people aged over 45 years.

Protein folding is slaved to solvent motions.

Proteins, the workhorses of living systems, are constructed from chains of amino acids, which are synthesized in the cell based on the instructions of the genetic code and then folded into working proteins. The time for folding varies from microseconds to hours. What controls the folding rate is hotly debated.

Mosaic energy landscapes of liquids and the control of protein conformational dynamics by glass-forming solvents.

Using recent advances in the Random First-Order Transition (RFOT) Theory of glass-forming liquids, we explain how the molecular motions of a glass-forming solvent distort the protein's boundary and slave some of the protein's conformational motions. Both the length and time scales of the solvent imposed constraints are provided by the RFOT theory. Comparison of the protein relaxation rate to that of the solvent provides an explicit lower bound on the size of the conformational space explored by the protein relaxation.

Energy landscape and dynamics of biomolecules extended abstract.

Proteins are not isolated homogeneous systems. Each protein can exist in a very large number of conformations (conformational substates) that are characterized by an energy landscape. The main conformational motions, similar to the α and β fluctuations in glasses, are linked to fluctuations in the bulk solvent and the hydration shell.

Picosecond thermometer in the amide I band of myoglobin.

The amide I and II bands in myoglobin show a heterogeneous temperature dependence, with bands at 6.17 and 6.43 microm which are more intense at low temperatures.

Bulk-solvent and hydration-shell fluctuations, similar to alpha- and beta-fluctuations in glasses, control protein motions and functions.

The concept that proteins exist in numerous different conformations or conformational substates, described by an energy landscape, is now accepted, but the dynamics is incompletely explored. We have previously shown that large-scale protein motions, such as the exit of a ligand from the protein interior, follow the dielectric fluctuations in the bulk solvent. Here, we demonstrate, by using mean-square displacements (msd) from Mossbauer and neutron-scattering experiments, that fluctuations in the hydration shell control fast fluctuations in the protein.

Slaving: solvent fluctuations dominate protein dynamics and functions.

Protein motions are essential for function. Comparing protein processes with the dielectric fluctuations of the surrounding solvent shows that they fall into two classes: nonslaved and slaved. Nonslaved processes are independent of the solvent motions; their rates are determined by the protein conformation and vibrational dynamics.

Hydration, slaving and protein function.

Protein dynamics is crucial for protein function. Proteins in living systems are not isolated, but operate in networks and in a carefully regulated environment. Understanding the external control of protein dynamics is consequently important.

Proteins: paradigms of complexity.

Proteins are the working machines of living systems. Directed by the DNA, of the order of a few hundred building blocks, selected from 20 different amino acids, are covalently linked into a linear polypeptide chain. In the proper environment, the chain folds into the working protein, often a globule of linear dimensions of a few nanometers.

Relaxations and fluctuations in myoglobin.

One major goal of biological physics is the discovery and understanding of the concepts and laws that govern biomolecules, in particular proteins. Since there exist at least 10(5) different proteins, the choice of a suitable prototype is necessary. Myoglobin (Mb) has for many years played the role of such a prototype.

The role of structure, energy landscape, dynamics, and allostery in the enzymatic function of myoglobin.

The grail of protein science is the connection between structure and function. For myoglobin (Mb) this goal is close. Described as only a passive dioxygen storage protein in texts, we argue here that Mb is actually an allosteric enzyme that can catalyze reactions among small molecules.