Studying Interactions with Biological Membranes using Neutron Scattering (original) (raw)
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Structural characterization in mixed lipid membrane systems by neutron and X-ray scattering
Biochimica et Biophysica Acta (BBA) - General Subjects, 2016
Lipids membranes, the primary component of the living cell, involve collective behaviour of numerous interacting molecules. The rich morphology and complex phase diagram of the lipid systems require different strategies in describing bio-membranes in order to capture the essential properties of self-assembly processes as well as the underling molecular collective phenomena involved in biological functions. Among the experimental methods used, the scattering techniques such as small angle neutrons and X-rays scattering (SANS and SAXS) are probably the most important experimental approaches for the structural investigation of bio-membranes and mixed lipids complex systems. In this tutorial review we describe the main approaches employed in the investigation of lipid bio-membranes by means of the neutron and x-ray scattering techniques. While introducing the main structural properties of lipid bio-membranes we highlight the important role of lipid components in different biological functions of living organisms. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.
Neutron Reflectometry for Studying Proteins/Peptides in Biomimetic Membranes
Neutron Scattering, 2016
The development of biomimetic surfaces for protein and peptide adsorptions is continuously expanding. Their biological functions can be influenced by the properties of the underlying artificial environment but the detailed mechanism is still not clear. In the past 30 years, neutron reflectometry has been widely applied to characterise the molecular structure of proteins or multi-protein complexes and their interactions with fluid artificial membrane that mimics the cellular environment. The specific interactions, bindings or structural changes between proteins and membranes play a crucial role in cellular responses and have promising potential in diagnostics and other biosensor applications. This chapter presents the progression of surface design for protein adsorption/interactions on membranes in detail, ranging from a simple phospholipid monolayer setup to more complicated artificial lipid bilayer systems. Furthermore, a new development of designed surfaces for studying the integral membrane protein system is also discussed in this chapter. A brief overview of various membrane mimetic surfaces is first outlined, followed by presenting specific examples of protein-membrane interactions studied by neutron reflectometry. The author demonstrates how to use neutron reflectometry as an advanced technique to provide step-by-step structural details for biomolecular applications in a well-controlled manner.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2014
Neutron reflectometry (NR) is an emerging experimental technique for the structural characterization of proteins interacting with fluid bilayer membranes under conditions that mimic closely the cellular environment. Thus, cellular processes can be emulated in artificial systems and their molecular basis studied by adding cellular components one at a time in a well-controlled environment while the resulting structures, or structural changes in response to external cues, are monitored with neutron reflection. In recent years, sample environments, data collection strategies and data analysis were continuously refined. The combination of these improvements increases the information which can be obtained from NR to an extent that enables structural characterization of proteinmembrane complexes at a length scale that exceeds the resolution of the measurement by far. Ultimately, the combination of NR with molecular dynamics (MD) simulations can be used to cross-validate the results of the two techniques and provide atomic-scale structural models. This review discusses these developments in detail and demonstrates how they provide new windows into relevant biomedical problems. This article is part of a Special Issue entitled: Interfacially active peptides and proteins. j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / b b a m e m Please cite this article as: F. Heinrich, M. Lösche, Zooming in on disordered systems: Neutron reflection studies of proteins associated with fluid membranes, Biochim. Biophys. Acta (2014), http://dx.
Diffusion and Domains: Membrane Structure and Dynamics Studied by Neutron Scattering
2013
Biological membranes play host to a number of processes essential for cellular function and are the most important biological interface. The structurally complex and highly dynamic nature of the membrane poses significant measurement challenges, requiring an experimental technique capable of accessing very short, nanometer length scales, and fast, micro-pico second time scales. The experimental work presented in this thesis uses a variety of neutron scattering techniques to study the structure and dynamics of biologically relevant model membrane systems. The main body of this work can be sub-divided into two distinct topics: (1) lateral diffusion of lipid molecules in a bilayer; and (2) the measurement of domains in the membrane. Diffusion is the fundamental mechanism for lipids and proteins to move throughout the lipid matrix of a biological membrane. Despite a strong effort to model lipid diffusion, there is still no coherent model which describes the motion of lipid molecules fro...
The study of liposomes, lamellae and membranes using neutrons and X-rays
Current Opinion in Colloid & Interface Science, 2007
Advances in colloid and interface science have stimulated a renewed interest in the study of lipid-water systems. In recent years, much progress has been achieved in the domains of sample preparation and sample environments, offering the unique possibility of studying these systems under physiologically relevant conditions. In the case of neutron reflectometry, new experimental protocols allow for the unique structural determination of one-dimensional membrane profiles, while the advantages offered by synchrotron radiation (e.g., high flux and spatial resolution) make X-rays an excellent tool for addressing questions pertaining to membrane interactions. Most recently, holographic techniques are evolving so that one day they may be able to resolve, to atomic resolution, the structure of poorly crystallized membrane associated proteins.
Hydration dependent studies of highly aligned multilayer lipid membranes by neutron scattering
The Journal of Chemical Physics, 2010
We investigated molecular motions on a picoseconds timescale of 1,2-Dimyristoyl-sn-Glycero-3-Phosphocholine (DMPC) model membranes as a function of hydration by using elastic and quasielastic neutron scattering. Two different hydrations corresponding to approximately nine and twelve water molecules per lipid were studied, the latter being the fully hydrated state. In our study we focused on head group motions by using chain deuterated lipids. Information on in-plane and out-of-plane motions could be extracted by using solid supported DMPC multilayers. Our studies confirm and complete former investigations by K¨onig et al. and Rheinst¨adter et al. who describe the dynamics of lipidmembranes, but did not explore the influence of hydration on the head group dynamics as presented here. From the elastic data a clear shift of the main phase transition from the Pβ ripple phase to the Lα liquid phase was observed. A decreasing water content moves the transition temperature to higher temperatures. The quasielastic data permit a closer investigation of the different types of head group motion of the two samples. Two different model are needed to fit the elastic incoherent structure factor (EISF) and corresponding radii were calculated. Therefore the presented data show the strong influence hydration has on the head group mobility of DMPC.
Molecular motions and hydration of purple membranes and disk membranes studied by neutron scattering
European Biophysics Journal, 1998
Fast stochastic equilibrium fluctuations (time scale: 10 -10 -10 -13 seconds) in purple membranes (PM) and in disk membranes (DM) have been measured with quasielastic incoherent neutron scattering. The comparison of predominantly stochastic motions occurring in purple membranes and in disk membranes revealed qualitatively similar dynamical behaviour. Models of internal motions within restricted volumes have been shown to be useful to fit the spectra from both samples. From fits using these models we found "amplitudes" 15 to 20% larger for motions in DM samples compared to PM samples. This indicates a higher internal flexibility of the DM. Because the dynamical behaviour is very sensitive to the hydration of the protein-lipid complex, we also performed neutron diffraction experiments to determine lamellar spacings as a measure of level of hydration and as a function of temperature. From these studies the interaction of solvent molecules with the surface of the protein-lipid complex appears to be qualitatively similar for both types of membranes.
Physical Review E, 2008
We designed artificial models of biological membranes by deposition of synthetic glycolipid membrane multilayers on planar silicon substrates. In contrast to commonly used phospholipid membranes, this offers the unique possibility to study the influence of membrane-bound saccharide chains ͑cell glycocalix͒ on the membrane mechanics. Taking advantage of the planar sample geometry, we carried out specular and off-specular neutron scattering experiments to identify out-of-plane and in-plane scattering vector components. By considering the effects of finite sample sizes, we were able to simulate the measured two-dimensional reciprocal space maps within the framework of smectic liquid-crystal theory. The results obtained both at controlled humidity and in bulk water clearly indicate that a subtle change in the molecular chemistry of the saccharides strongly influences intermembrane interactions and membrane bending rigidities.