Notice of PROXIMA 1

First station for macromolecular crystallography at SOLEIL, proposed by a working groupe (17 members) representative of most French teams.
General purpose beamline optimised for MAD measurements (5-17.5 keV).
Main targets are:

• accurate and fast MAD measurements including: high orientational and positional beam stability plus fast, accurate and reproducible energy tuning ; fluorescence detection ; large area detector with short readout time.
• focus 50 x 50 mm
• automatization and user-friendliness including: alignment of diffractometer and wavelength selection; manipulation of normal and cryocooled crystals : setting, alignment, quality assessment ; data collection strategy and on-line data treatment; control at a distance.
• capability for storage of a large number of high resolution 2D images and on-line analysis.

A decisive advance in the life sciences has recently taken place with the advent of "large scale biology". Automation of sequencing techniques has been instrumental for decoding of the complete human genome, as well as that of many other organisms. The possibility to identify and systematically clone each and every gene of an organism, together with the determination of its state of transcription (transcriptome) and translation (proteome) in different tissues at any given time, now permits a broad study of biological function at a level that would have been inconceivable ten years ago. Knowing the presence of, and the interactions between, each one of these gene products at a given moment is essential for understanding the complex network of biological processes inside the living cell. In particular, comprehension of these phenomena at the molecular level requires detailed knowledge of the atomic structure of each component as well as that of the molecular associations in which it participates. Such knowledge allows, among other things, to envisage the development of molecules for therapeutic intervention in malfunctioning cells. The medical and pharmaceutical industries of tomorrow will depend increasingly on the availability of atomic resolution data of macromolecules participating at different stages of the cell cycle.
The construction of SOLEIL will endow France with a resource of first rank for the advancement of fundamental research in biology and its applications to the domains of medicine, pharmacology and food industry. It is thus indispensable that the number and performance of the beamlines destined for biology meet the level required to conduct biology on a large scale in the years to come.

A few years ago, the French structural biology was at the 4^th rank, behind the USA, the UK and Germany, at about the same level as Japan. The current importance of structural data for the community of biologists can be gauged by the quality and impact of publications relating to protein structures determined recently using synchrotron radiation. This has been quantified by an inquiry conducted with the French biocrystallography community : a total of 313 publications produced over the past three years (1998 – 2000) by 25 French laboratories had made direct use of synchrotron radiation. Moreover, their mean impact factor was 7.7, and for 17 of these publications, the impact factor was over 25 (Cell, Nature and Science).
Several factors must be taken into account in the growing demand for structure determination.

• The standardisation of crystallographic methodologies has placed structure determination more directly into the hands of the non-specialist. This is creating a major increase in the demand for structure determination, which must be resolved by the availability of beamlines in sufficient number, in combination with automations and the standardisation of crystallographic methodologies.
  
  
• The efficacy of recombinant technology for protein production in quantities sufficient for structural studies has improved considerably. These improvements now allow a systematic structural survey of all gene products from a wide variety of organisms, both prokaryotes and eukaryotes. As noted above, recent advances in crystallographic methodologies are pushing the limit on protein size for structure determination to a higher and higher molecular weight. The number of proteins that can, in practice, be studied by X-ray crystallography will correspondingly increase.
  
  
• The growing demand for structural results by industrial research in medicine, pharmacy and food products must be added to these factors. Such activities, either by company teams or in collaboration with academic groups, will certainly increase and spread. The launching of systematic structural analyses of the ensemble of proteins expressed by given organism, or of proteins having the same function in a series of different organisms, is currently under way in several concerted national and international programmes. In France, 11 laboratories are implicated in three structural genomics projects coordinated at Gif-Orsay, Strasbourg and Paris. The three projects are now under way and will expand following integration within an European initiative on structural genomics, accepted by the EU in 2001. Within the next few years, each of these projects will be producing tens of structures to be analysed using synchrotron radiation. This type of systematic effort will eventually extend to other, more technically difficult, classes of protein, such as membrane proteins, as experience in structural genomics technology accumulates.

A clear consensus has emerged for a minimum of two biocrystallography stations to be in operation when the first beamlines of SOLEIL become available to users in 2006. Emphasis was placed on the need to accommodate small crystals (10 – 50 mm), placing stringent requirements on the flux, beam properties and diffractometer design. Over a ten-year term, the number of stations available to the biocrystallography community should probably increase to five, all placed in the same sector of the storage ring.

The first station will be a versatile instrument covering a wide energy range (5-17.5 keV) for Multiple wavelength Anomalous Diffraction (MAD) and Single Anomalous diffraction (SAD) using a variety of anomalous scatterers.
The optics should provide a focus of nominal HxV fwhm 50 mm x 50 mm. Mirror/double crystal monochromator options will be considered, either separating or not focusing and monochromatisation. The crystal will be mounted on a EMBL-ESRF microdiffractometer including a video-microscope and beam visualisation. The detector should be state-of the art in terms of pixel size and number, dead-time and efficiency. Ancillary equipment include cryocooling, fluorescence detection for MAD analysis and automatic cryosample changer. Artificial intelligence will be pushed as far as possible, in collaboration with industry and other facilities, in order to provide control at a distance, extreme user-friendliness such as automated alignment , choice of wavelength, data collection protocols, data storage and analysis. Local computing and storage will be state-of- the art.
The safety level of the beamline will be P2.
The importance of sufficient manpower was underlined, and the necessity to provide an adequate scientific environment, either on site or close to SOLEIL, that will provide an autonomous scientific infrastructure to support in-house projects in structural biology. For the construction phase of PX1, requirements are 1 scientist beamline manager, 1 scientist/engineer (applications software), 1 engineer (system and real time programming), 2 technicians (resp. assembly and mechanics; automation and electronics).

SAC is in favor of the construction of the first bio-crystallography beamline on an in-vacuum undulator and reserves its opinion concerning a second beamline until a detailed study is presented at its April meeting.
The scientific case for a state of the art protein crystallography beamline is convincing. The French community is strong and needs equipment at the level of its future needs, as it is the case in other European countries. The evolution of SOLEIL to a 2.75 GeV energy machine is valuable for bio-crystallography. The idea to develop a full sector of the ring for bio-crystallography makes sense since it allows for efficient sharing of common facilities. A high degree of automation is mandatory for a high throughput beamline, which requires that the optical system be simple, robust and reliable.
SAC recommendations are :

• first focus on one MAD beamline on an undulator
  
  
• there should be a close connection between the community and the staff building the beamline; for example create a users group which can follow the beamline construction
  
  
• work on the optical design (ray tracing is needed). Numbers for the expected photon flux on the sample are needed. Consider undulators on a medium or short straight section of SOLEIL.
  
  
• consider focusing optics with one fixed focal point only since it seems risky to have two positions for the diffractometer. However, SAC is aware that, this way, the beamline will not be optimized both for small crystals and for crystals with very large unit cells: accurate flux calculations should enable to select the proper configuration during the APD phase.