Run 17 Protein Crystal Screening (PCS) Proposals

The LCLS Protein Crystal Screening (PCS) program aims to enable increased access to LCLS beamtime for biological structure determination by making use of short, 6-hour runs to screen the quality of different sample preparations or potentially collect a full data set under good running conditions. To enable measurements within such a short time frame and maximize efficiency and the chances of success, these studies must be carried out with limited instrumentation flexibility to minimize the time impact of setup changes. Schedule constraints are unpredictable and no guarantees can be made that any of the mentioned experimental setups will be available for PCS in any given run. Please contact Mark Hunter (mhunter2@slac.stanford.edu) for additional information and guidance.

PCS at CXI

PCS experiments at CXI will be carried out using the standard CXI configuration, using the refocused X-ray beam from the 1 μm focus as a parasitic measurement to a primary experiment, depending on scheduling constraints and at the discretion of LCLS. Sample delivery will be via the gas dynamic virtual nozzle (GDVN) liquid jet system and fixed targets in vacuum. User-supplied sample delivery systems or modifications to the existing system are allowable only if they are compatible with the existing systems and can be exchanged with the other systems used for PCS beamtime within a time frame compatible with 12-hour parasitic runs and rapid turnaround between groups. Decisions on using alternative sample delivery systems are entirely at the discretion of the LCLS facility.

PCS at MFX

PCS experiments at atmospheric pressure are expected to be available. The home of such experiments is now the MFX instrument with multiple options likely to be available, including a goniometer system, allowing scanning of fixed-mounted crystals, and a liquid jet system compatible with various types of jets. These systems can also be modified in principle for use of a variety of atmospheric pressure sample delivery systems. User-supplied systems may also be available. The availability of all these systems will depend on scheduling constraints and is entirely at the discretion of LCLS.

Other Experimental Geometries or Capabilities

Time-resolved studies and spectroscopy are currently not within the scope of PCS beam time.

Proposal Review and Beamtime Award

These PCS proposals will be reviewed by the PRP BIO-C panel separately from the regular proposals. It is desirable to shorten the period between PCS proposal submission and beam time allocation to maximize flexibility and the ability to be reactive to novel samples or ideas. LCLS will aim to pre-allocate blocks of beamtime on CXI and/or MFX based on the overall demand. The expected amount of beamtime is approximately 10-12 shifts in every LCLS run. Proposals will be awarded beam time by LCLS based on the scientific recommendation of the Proposal Review Panel and other technical considerations by LCLS, including sample readiness, technical feasibility and scheduling constraints. A minimum 2 months notice will be given to the selected user groups to allow for appropriate preparation.

Overlap with Regular LCLS Proposals

There is no restriction with regards to possible overlap or redundancy with regular LCLS proposals. Submission of PCS proposals similar or related to regular LCLS proposals are encouraged and will not adversely impact the rankings of either types of proposals. Regular LCLS proposals that do not receive beamtime may be considered for PCS if deemed suitable.

Proposal Format

PCS proposals follow a similar format as regular proposals. They must be submitted separately.

PCS proposals are evaluated on the impact, originality, need for LCLS, scientific risk, prior results, as well as technical feasibility.

LCLS PCS proposals should be submitted through the User Portal

Provide a descriptive title of your proposed experiment that you would be willing to be made public if awarded beam time.

The proposal text is limited to 2 pages in PDF format. Pages should have at least 1 inch margins and not less than 10 pt font. It should include the following information:

• Experimental Team: In a table, list the names, institution, email address of PIs and collaborators who would participate in the proposed experiment (e.g., sample prep, theory, data collection, data analysis). This section could also briefly mention directly-relevant previous work done by the team members.
• Scientific Case: Briefly explain the background and significance of your experiment. In particular, why is LCLS required for this experiment? Itemize the specific aims and particular questions you want to answer. Focus on the specific experiment and avoid broad discussions in general terms.
• Experimental Procedure: If the PCS proposal is related to one or more regular LCLS proposals that have been submitted or already received beam time, state this in the proposal. Tell us if you plan or have carried out supporting experiments at other facilities. Have simulations of the experiment been performed? What are the anticipated data rates? Provide a beam time plan, indicating what could be accomplished in less than 6 hours of beam time. Describe any additional equipment you plan to bring to LCLS for the experiment. We strongly recommend that you contact LCLS Scientist Mark Hunter (mhunter2@slac.stanford.edu) before proposal submission to discuss capabilities, to identify possible problems in integrating external equipment with LCLS instrumentation and to determine possible solutions.
• Technical Feasibility: Proposals must contain sufficient information for LCLS to review the proposal for technical feasibility. This information should include:
  • Equipment
    • Which elements of the proposed instrument do you require for the proposal?
    • What additional equipment is needed, including detector, sample delivery/environment, temperature, pressure, etc.?
    • How do you plan to provide/organize the additional equipment?
  • Experimental Protocol 
    • Describe the experimental geometry.
    • Calculate the expected signal rate/background.
    • Describe samples and concentrations, sample preparation and storage.
    • Describe local facilities that may be required.