Structural organisation of the type IV secretion systems

Type IV secretion (T4S) systems are large dynamic nanomachines that transport DNAs and/or proteins through the membranes of bacteria. Because of their complexity and multi-protein organisation, T4S systems have been extremely challenging to study structurally. However in the past five years significant milestones have been achieved by X-ray crystallography and cryo-electron microscopy. This review describes some of the more recent advances: the structures of some of the protein components of the T4S systems and the complete core complex structure that was determined using electron microscopy

4D electron imaging: principles and perspectives

In this perspective we highlight developments and concepts in the field of 4D electron imaging. With spatial and temporal resolutions reaching the picometer and femtosecond, respectively, the field is now embracing ultrafast electron diffraction, crystallography and microscopy. Here, we overview the principles involved in the direct visualization of structural dynamics with applications in chemistry, materials science and biology. The examples include the studies of complex isolated chemical reactions, phase transitions and cellular structures. We conclude with an outlook on the potential of the approach and with some questions that may define new frontiers of research

Characterization of Aptamer-Protein Complexes by X-ray Crystallography and Alternative Approaches

Aptamers are oligonucleotide ligands, either RNA or ssDNA, selected for high-affinity binding to molecular targets, such as small organic molecules, proteins or whole microorganisms. While reports of new aptamers are numerous, characterization of their specific interaction is often restricted to the affinity of binding (KD). Over the years, crystal structures of aptamer-protein complexes have only scarcely become available. Here we describe some relevant technical issues about the process of crystallizing aptamer-protein complexes and highlight some biochemical details on the molecular basis of selected aptamer-protein interactions. In addition, alternative experimental and computational approaches are discussed to study aptamer-protein interactions.

Study for identification of Beneficial Uses of Space (BUS) (phase 2). Volume 1: Executive summary

A study was conducted to analyze the benefits to the world which can be realized from space manufacturing processes. The study envisaged the use of the space shuttle and manned space stations for the purpose. For each proposed operation a data base and rationale were established for those processes or portions of processes which would be improved by performance in the orbital environment. The four experiments which were recommended for the initial investigation are identified. The procedures for conducting the weightless manufacturing processes are outline

Crystallography and Nobel Prizes: On the 2011 Nobel Prize in Chemistry, awarded to Dan Shechtman

La cristal·lografia té una gran presència en els premis Nobel; així doncs, 48 guardonats estan estretament vinculats a la cristal·lografia. El Premi Nobel de Química 2011 va ser concedit a Dan Shechtman pel descobriment dels quasicristalls. A part del mèrit científic del descobriment, el Premi és un reconeixement al treball de Dan Shechtman, ja que les seves idees van ser rebutjades inicialment per la comunitat científica internacional. Finalment la raó es va imposar, amb el suport d'arguments que van venir per camins insospitats i aparentment sense cap relació, com ara l'estudi dels mosaics presents en edificacions àrabs i també del concepte de tessel·lació. També hi van contribuir conceptes més pròpiament cristal·logràfics com les macles i les estructures modulades. L'any 1992 la Unió Internacional de Cristal·lografia va modificar la definició de cristall per tal d'incloure-hi els quasicristalls.Crystallography has a considerable presence among Nobel Prize laureates. Indeed, 48 of them have close links to crystallography. The 2011 Nobel Prize in Chemistry was awarded to Dan Shechtman for his discovery of quasicrystals. In addition to the scientific merit of the work, the Prize is a personal recognition of Dan Shechtman, whose ideas were initially rejected by the international scientific community. Yet, reason prevailed in the end, supported by arguments that arrived from seemingly unrelated directions, such as the study of Arab building tiles and the mathematical concept of tessellation. Concepts of a more crystallographic nature, such as twinned crystals and modulated and incommensurate crystal structures, also played an important role. Finally, in 1992, the International Union of Crystallography modified the definition of “crystal” to include quasicrystals

Structure determination techniques flex their muscles

A historical challenge: Gas-phase electron diffraction and single-crystal X-ray diffraction are both established techniques, but they were both pushed to their limits by the challenge posed by the highly flexible tetranitromethane molecule. New approaches had to be developed for the structure of the molecule to be elucidated