BL12-1

BL12-1 is designed for investigations of the most challenging macromolecular crystallography systems confronting scientists today, including cases where crystals can only be grown to a few microns in size, serial room temperature studies and time-resolved measurements. BL12-1 supports fully remote-access experiments using samples at cryogenic conditions in uni-pucks or cassettes, and samples at controlled humidity and elevated-temperature conditions using specialized SSRL plates. 

BL12-1 employs a 154-pole, 1-Tesla in-vacuum undulator, a flat side-deflecting Rh-coated Si mirror, and a liquid nitrogen-cooled double-crystal Si(111) monochromator with a 0.01% energy bandpass producing ~4x1012 p/s at 11 KeV. The full energy range extends from 6.2 to 18 keV. BL12-1 is also fitted with a multilayer monochromator with a ~1% energy bandpass that boosts the x-ray flux by a factor of ~40. Kirkpatrick-Baez (KB) optical mirrors are used for 18:1 horizontal and 12:1 vertical beam focusing. The vertical mirror polish is ~100 nrad RMS providing a vertical beam focus of 5 µm FWHM. BL12-1 has excellent performance at lower energies and is equipped with an Eiger2 XE 16M pixel array detector with a readout speed of up to 500 Hz detector which enables new modes of time-resolved and serial measurements, and ultra-high-redundancy MAD or SAD phasing. 

BL12-1 is also an effective gateway for the Linac Coherent Light Source (LCLS), providing a common platform for instrument R&D, pre-screening, and characterization of micro- to nano-sized crystalline samples prior to LCLS studies. BL12-1 has nearly identical goniometer-based equipment for fixed-target serial diffraction studies as the standard setup for the LCLS-MFX station as well as identical equipment for injector-based serial crystallography experiments.

Features

Bright X-ray Microbeams – X-ray microbeams (~5-15 µm) can be used to study very small microcrystals and in some cases, they can be used to select portions of larger crystals with improved diffraction of up to 0.5 Å resolution.

Remote Access Cryo-Crystallography - Users control and carry out their experiments at cryogenic temperatures and non-cryogenic temperatures and controlled humidity in real time from anywhere in the world. This is accomplished with a simple free app that runs on the user's remote computer which connects to a server running at SSRL.

Remote Access Controlled Humidity - Expanding on the mature remote access program for cryogenically cooled crystals using the Stanford Auto-Mounting robot, remote experiments using crystals at controlled and elevated temperature conditions or at controlled humidity and ambient temperature conditions are supported, including stepwise crystal dehydration experiments. For these experiments, crystals are shipped in specialized SSRL plates compatible with crystal growth, crystal storage and robotic sample mounting.
 

Expanded Energy Bandwidth Option - A multilayer monochromator option with a ~1% energy bandpass boosts the x-ray flux by a factor of ~40 to support fast flowing liquid injector data collection.
 

Large Unit Cells - Diffraction from very large unit cells (for example, viruses and large complexes) can be resolved with pixel array detectors (PADs). They have large detection areas and can be placed long distances from the sample, and they have excellent intrinsic resolving power with no pixel crosstalk.
 

Automated Screening - Samples are systematically mounted from a frozen cassette or an ambient temperature container using a robot and subsequently aligned, exposed, indexed, and assigned a score for overall diffraction quality.
 

High Speed X-ray Rastering - Low-dose X-rays are used to accurately locate microcrystals or other visually obscured crystals in loops and other mounts, or to identify areas of a crystal that have improved diffraction. A typical 400 µm diameter Mitogen Mesh can be fully scanned in 2 minutes using a beam and step size of only 10 µm.
 

Serial Fixed Target Crystallography- Multiple crystals are mounted in predetermined locations on a grid so that diffraction data can be collected from each crystal in rapid succession. SSRL grids or user-supplied grids that have fiducial markings can be used.
 

Serial Injector Crystallography - Serial injector experiments make use of multiple small crystals that are in solution.  Through a collaboration with the LCLS sample delivery group, multiple types of crystal injectors are supported including mixing injectors for time-resolved measurements.
 

MAD/SAD Phasing - Multi- and single wavelength anomalous diffraction (MAD and SAD, respectively) is used to solve the phase problem in structure determination.  Accurate heavy atom absorption edge spectra provide the most useful energies (f' and f") for MAD data collection.  High-speed ultra-redundant data collection can be used to obtain significant signal from weak anomalous scattering atoms such as sulfur.
 

Metal Identification – Excitation scans are useful to quickly determine the heavy element content in crystals.  The excitation scan measures the fluorescence counts from any element present in the sample with an absorption edge below the excitation energy. Excitation scans take less time than the MAD scans and thus are a faster way to determine the presence of a heavy atom derivative/ligand in the sample.

Source - 154-pole, 1-Tesla in-vacuum undulator.

See the Macromolecular Crystallography website for technical details.