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Unusual diffraction geometries

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

Unusual diffraction geometries may seem a curiosity but may stimulate novel avenues of application. Not least they illustrate a diversity of diffraction‐measuring possibilities. Laue diffraction ... More

Unusual diffraction geometries may seem a curiosity but may stimulate novel avenues of application. Not least they illustrate a diversity of diffraction‐measuring possibilities. Laue diffraction including 3‐dimensional detector arrangements is described. The particular congestion of neutron Laue diffraction patterns with big crystals is highlighted. The large‐angle oscillation technique is discussed including the principle with the Ewald sphere construction and practical examples of ‘LOT’ diffraction patterns. Ultra‐fine‐phi‐slicing with perfect or near‐perfect crystals is described. Particular success has been obtained with Laue diffraction where applications to time‐resolved structural intermediates using synchrotron radiation as well as hydrogen and hydration in macromolecular structure are described.Less

Overall summary and future thoughts

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

This chapter summarizes the state‐of‐the‐art in the field and discusses upcoming techniques to solve and to improve the current problems.

Membrane proteins

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

The structural studies of membrane proteins lag those of their soluble counterparts. This is mainly due to the difficulty in crystallizing membrane proteins that have large hydrophobic regions that ... More

The structural studies of membrane proteins lag those of their soluble counterparts. This is mainly due to the difficulty in crystallizing membrane proteins that have large hydrophobic regions that are in contact with the alkyl chains of the lipids in the membrane. This chapter describes specific methods for membrane protein crystal growth including screening with detergents, lipidic cubic‐phase crystallization and antibody fragment approaches.Less

Beyond existence

Louis A. Girifalco

in The Universal Force: Gravity - Creator of Worlds

Gravity is responsible not only for the existence of stars and planets; it also creates the weirdest objects imaginable. A body with mass greater than 1.4 solar masses cannot remain a white dwarf and ... More

Gravity is responsible not only for the existence of stars and planets; it also creates the weirdest objects imaginable. A body with mass greater than 1.4 solar masses cannot remain a white dwarf and will collapse into a neutron star. But if the mass is greater than about two and a half solar masses, the collapse will continue until it becomes a black hole. This is the strangest object in the universe. Its gravity is so strong that even light cannot get out of it. Anything near it is sucked in, crushed to a point, and approaches infinite density. The laws of physics as now known do not apply at the centre of a black hole and the very meaning of its existence is in doubt.Less

NEUTRON ABSORPTION TOMOGRAPHY

Eberhard Lehmann and Nikolay Kardjilov

in Advanced Tomographic Methods in Materials Research and Engineering

This chapter discusses neutron absorption tomography. Topics covered include the interaction of neutron radiation with matter and comparison to x-rays, specifics of neutron tomography, limitations in ... More

This chapter discusses neutron absorption tomography. Topics covered include the interaction of neutron radiation with matter and comparison to x-rays, specifics of neutron tomography, limitations in neutron tomography, and selected applications and experimental options.Less

NEUTRON BEAM MAGNETIC RESONANCE

Norman F. Ramsey

in Molecular Beams

Neutron beam magnetic resonance experiments with slow neutrons are very similar to corresponding molecular beam experiments. Methods of polarizing neutron beams by total reflection and other means ... More

Neutron beam magnetic resonance experiments with slow neutrons are very similar to corresponding molecular beam experiments. Methods of polarizing neutron beams by total reflection and other means are discussed. The neutron beam experiments that measure the magnetic moment of the neutron are described. Magnetic resonance experiments in which the static magnetic fields are changed from parallel to anti-parallel provide a sensitive upper limit to the neutron electric dipole moment.Less

The Progenitors of Gamma-Ray Bursts

Joshua S. Bloom

in What Are Gamma-Ray Bursts?

This chapter discusses the object or objects responsible for gramma-ray bursts (GRBs). Until now, there are few absolute certainties with regard to the progenitors of GRBs. One clear standout is the ... More

This chapter discusses the object or objects responsible for gramma-ray bursts (GRBs). Until now, there are few absolute certainties with regard to the progenitors of GRBs. One clear standout is the progenitors of soft gamma-ray repeaters (SGRs) which are very obviously neutron stars. There are a number of corroborating lines of evidence for this progenitor association: (1) some well-localized SGRs are associated with supernova remnants, suggesting they are byproducts of recent supernovae; (2) there is quiescent X-ray emission from the sites of SGRs, similar to a class of neutron stars called “anomalous X-ray pulsars”; (3) Galactic SGRs tend to be found in the Galactic plane, where most young neutron stars reside; and (4) the ringdown emission after SGR pulses is periodic, with periods comparable to that of slowly rotating neutron stars (few seconds).Less

The basic principles and experimental configurations of neutron diffraction experiments

Nobuo Niimura and Alberto Podjarny

in Neutron Protein Crystallography: Hydrogen, Protons, and Hydration in Bio-macromolecules

The basic principles and experimental configurations of neutron diffraction experiments are given in this chapter. First, the physics of neutrons and neutron diffraction, such as neutron-scattering ... More

The basic principles and experimental configurations of neutron diffraction experiments are given in this chapter. First, the physics of neutrons and neutron diffraction, such as neutron-scattering lengths and neutron absorption, are reviewed briefly, with special emphases on the comparison of neutron and X-ray diffraction phenomena and on specific features of the interactions between neutrons and bio-macromolecules. The basic principles of neutron protein crystallography (NPC) and the method of obtaining the positions of hydrogen atoms in proteins are also discussed. Two types of neutron sources—steady-state, reactor neutron sources and pulsed, accelerator-driven neutron sources—are then introduced, along with the different techniques used with each source. Because neutron detection is a key technique in NPC, a section is devoted to describing different types of neutron detectors. Based on the preceding knowledge, reactor sources and pulsed sources, as used for NPC, can finally be compared at the end of the chapter.Less

Introduction to neutron powder diffraction

Erich H. Kisi and Christopher J. Howard

in Applications of Neutron Powder Diffraction

This chapter opens with brief descriptions of neutrons, powders (polycrystalline materials), and diffraction, followed by an account of how the unique properties of neutrons and their interaction ... More

This chapter opens with brief descriptions of neutrons, powders (polycrystalline materials), and diffraction, followed by an account of how the unique properties of neutrons and their interaction with matter define a role for neutron powder diffraction in the study of condensed matter. The concepts are refined within an historical account of the development of neutron powder diffraction and its applications. Reference are made to the earliest demonstration of neutron diffraction, to the development of neutron sources (research reactors and accelerator-based sources), and to applications ranging from early investigation of simple crystal and magnetic structures to the more recent investigations of kinetic processes and complex crystal structures (high-temperature superconductors, fullerenes).Less

OBSERVATION OF MICROSCOPIC MAGNETISM

Dante Gatteschi, Roberta Sessoli, and Jacques Villain

in Molecular Nanomagnets

This chapter is devoted to the observation of microscopic magnetism, working out in some detail the most commonly used magnetic techniques. The basic aspects of these techniques are only briefly ... More

This chapter is devoted to the observation of microscopic magnetism, working out in some detail the most commonly used magnetic techniques. The basic aspects of these techniques are only briefly recalled, and indication is given of relevant text books which will give a sound background knowledge. However, it is the goal of the chapter to allow the reader to be able to read the current literature with some acceptable understanding. The magnetic techniques include microSQUID and micro Hall probe techniques and torque magnetometry; specific heat measurements, including equilibrium and out of equilibrium measurements; and magnetic resonance techniques, including EPR, NMR, and muon spin resonance. Mention of neutron techniques, including polarized neutron diffraction and inelastic neutron scattering, will conclude the section.Less

Introduction

Rolf Hempelmann

in Quasielastic Neutron Scattering and Solid State Diffusion

This chapter introduces the basic idea of quasielastic neutron scattering as a probe for diffusion processes in condensed matter. Neutron scattering and solid state diffusion have in common that they ... More

This chapter introduces the basic idea of quasielastic neutron scattering as a probe for diffusion processes in condensed matter. Neutron scattering and solid state diffusion have in common that they both can be separated into two problems: the single event (scattering on a single nucleus or single diffusive jump, respectively) and the cooperative combination (in space and time) of those events in solids. The history of neutron scattering is outlined with the development of neutron sources and neutron scattering instruments. All large scale neutron scattering facilities, based on research reactors or on neutron spallation sources, are nowadays operated as user facilities with the consequence that neutron scattering is not ‘big science’ like high energy particle physics, but the practise of neutron scattering is characterized by a large variety of small groups working on many different scientific problems. A brief summary of the remainder of the book covers the fundamentals of quasielastic neutron scattering and its application to different material systems.Less

Making the most of difficult crystals — beamline and detector optimization

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

The geometry of the crystallographic instrumentation is described with an emphasis on synchrotron radiation beamline setups in the hutch. The measurement principles of ‘signal to noise’ as well as ... More

The geometry of the crystallographic instrumentation is described with an emphasis on synchrotron radiation beamline setups in the hutch. The measurement principles of ‘signal to noise’ as well as random and systematic errors are described. The special case of microcrystals is described in detail including a short history of key developments. A brief resume of data for phasing is given and references to particular example apparatus is given. There is a growing number of opportunities for robotics, telepresence and automation and readers are referred to Facility websites. More specialized applications involving time‐resolved Laue, freeze trapping and neutron macromolecular crystallography are summarized. This chapter has had to be more indicative than detailed as the topic is large. The consultation of the example references given and wider literature is obviously important. Nevertheless, in the context of macromolecular crystallization and crystal perfection the chapter connects directly with the data collection requirements for structure determination and offers useful pointers in that direction in the various categories.Less

Introduction

Naomi E. Chayen, John R. Helliwell, and Edward H. Snell

in Macromolecular Crystallization and Crystal Perfection

Macromolecules are the machinery of life and their function is determined by their 3D structure. Visual observation with a light microscope is not possible as the sizes of macromolecules are well ... More

Macromolecules are the machinery of life and their function is determined by their 3D structure. Visual observation with a light microscope is not possible as the sizes of macromolecules are well below the wavelength of visible light. X‐rays and neutrons allow visualization but they cannot be focused, so diffraction techniques have to be used. An understanding of the three‐dimensional macromolecular structure gives us a deeper understanding of basic biological concepts and processes, and reveals the cause of diseases, helps rational pharmaceutical design and can lead to the design of macromolecules with novel properties. Visualizing these macromolecules is a complex ballet involving diverse but interrelated fields of endeavour. In this chapter we cover an introduction to crystallization and X‐ray and neutron diffraction techniques. We distinguish between long‐ and short‐range order and introduce the rest of the book.Less

Theory – the bare essentials

Erich H. Kisi and Christopher J. Howard

in Applications of Neutron Powder Diffraction

This chapter presents the properties of thermal neutrons. Their wavelength (from the de Broglie equation) is well suited to the investigation of condensed matter, i.e., to the study of liquids, ... More

This chapter presents the properties of thermal neutrons. Their wavelength (from the de Broglie equation) is well suited to the investigation of condensed matter, i.e., to the study of liquids, glasses (amorphous materials), and crystalline materials with varying degrees of order. That the neutrons carry magnetic moment also makes them well suited to the study of magnetic ordering. The theory of nuclear and magnetic scattering from individual atoms and from assemblies of atoms is presented, this leading to the definition of neutron scattering length and to the concepts of coherent and incoherent scattering. The focus then shifts to the direction and intensity of diffraction from crystalline materials (Bragg's law, structure factors), and to the description of this scattering when samples are presented in polycrystalline or powder form (Debye-Scherrer cones).Less

Basic instrumentation and experimental techniques

Erich H. Kisi and Christopher J. Howard

in Applications of Neutron Powder Diffraction

This chapter first gives the location of facilities for neutron powder diffraction. Constant wavelength (CW) and time-of-flight (TOF) diffractometers are introduced. The typical components ... More

This chapter first gives the location of facilities for neutron powder diffraction. Constant wavelength (CW) and time-of-flight (TOF) diffractometers are introduced. The typical components (monochromators, collimators, neutron detectors) are described in some detail and a comparison of CW with TOF instruments is presented. The chapter includes advice on planning and executing measurements by neutron powder diffraction, as well as detail on the important matter of sample environment, that is, the furnaces, cryostats, pressure cells, electrochemical cells, etc., that the experiments might involve. Sample preparation is also a matter that demands quite careful attention, so important considerations are presented.Less