Updated 2011-10-17

MacCHESS automounter

MacCHESS has an ALS-style crystal automounters available at beamlines A1 and F1. The F1 automounter is a BAM-1 model with pneumatic actuators, while the automounter at A1 is a BAM-2 with a 3-axis Cartesian robot. Both accept Uni-pucks and ALS pin bases with 18 mm pins. The F1 automounter also accepts the earlier ALS pucks. See "required equipment" for more details.

• Making arrangements for use
• Use
• Trial kit
• Required equipment
• Laser sensors
• Recent Developments

Automounters are intended to help maximize throughput at synchrotron beam lines where heavy shielding and safety interlocks slow manual access to the experiment. A sizable number of crystals (64 in our setup) can be stored in the hutch, accessed randomly, mounted and dismounted; all without entering the hutch.

Making arrangements for use

If you wish to use the MacCHESS automounter, please specify this when you apply for beam time. Automounter requests may affect scheduling, since we may want to schedule equipment setup by our technical staff during weekday working hours and schedule automounter users consecutively.

If you need to borrow a trial kit from MacCHESS, allow enough time for us to ship the kit and for you to familiarize yourself with the equipment. See below for more details.

Some other facilities use elaborate database tracking, which requires advance registration of every crystal. MacCHESS does not have this, so advance database registration of your crystals is not required nor available.

If your crystals or reagents are hazardous, advance notification is required, as for all other MacCHESS experiments.

Use of equipment at MacCHESS

If you wish to transfer crystals from vials to pucks at MacCHESS, we can provide Dewars and nitrogen. Be sure to allow for adequate time for such activity before your scheduled beam time.

MacCHESS personnel will set up the automounter and train you in its use.

Accomodation for automounter commands has been incorporated into the MacCHESS data collection software.

At present the software interface is not very sophisticated, but we will be improving it as we gain experience. Auto-centering of the crystal using the XREC routine is now possible in the MacCHESS crystal centering interface.

Sudhir Babu Pothineni, Tilo Strutz & Victor S. Lamzin (2006) Automated detection and centring of cryocooled protein crystals Acta Cryst. D62, 1358-1368.

The automounter does not interfere with manual mounting methods, and switching between automatic and manual mounting methods is no problem.

Trial Kit

MacCHESS has a trial kit consisting of seven (7) pucks stacked in a tower, all the tools necessary to handle the pucks, and an out-of-date instructional CD-ROM from Brookhaven. Pins and bases are not included.

Since MacCHESS has only one trial kit, we cannot guarantee that one will be available for you. Please request a trial kit at least a full week in advance to allow for shipping and to provide sufficient time to familarize yourself with the equipment and load the pucks. Also, please return the kit when you visit CHESS or in a timely manner afterwards. Regular users of automounters might consider purchasing their own equipment.

Required equipment: pins and pucks

The automounter requires the use of pins and bases with tight tolerances to ensure that they can be reproducibly accessed by the gripper. These products should work well:

Pin bases (also sometimes referred to as vial caps)

• Hampton Research HR4-779 - specifically designed for ALS. These are the ones I recommend. The shoulder-free base is more tolerant of slight misalignment of the automount gripper.
  HR4-904 - vials for HR4-779
  
• ALS lists another source of these bases, Vineburg Machining Inc.
  
• Hampton Research HR8-116 = "CrystalCap HT" (HighThroughput)*
  
• Mitegen Base B1*
  

• HR4-733 - CrystalCap Magnetic
  
• HR4-745 - CrystalCap Copper Magnetic
  
• Any style of base with plastic parts or vial threads.
  

The Hampton "CrystalCap Magnetic" is the most popular base on the market, so if you're not certain what you have, assume that it is not automounter-compatible.

Pins

No bent pins, no copper pins. Pin height should be consistent. Try Hampton 18 mm pins or Mitegen 19 mm pins. The MacCHESS automounter is similar to equipment in use on some beamlines at ALS, APS and Brookhaven. Our gripper is the ALS Mk II Gripper (with local modifications by Mike Cook), so information from ALS can be considered most relevant:
Brookhaven pin list
LBNL says:

The dimensions are fairly critical here, and the most important one from the automounter's standpoint is the distance from the inside mounting surface (which corresponds with the top of the goniometer magnetic mount) to the center of the crystal = 20.3mm ± 1mm.

Pucks

Sixteen (16) pins fit into a puck. In the automounter Dewar, the puck lid is held in place upside-down, as depicted below, with the crystals pointing up for access by the gripper. The pin bases are held in place on the puck lid magnetically.

When loading the pucks in your own lab, it may be easier to put the pins in the puck body crystal end down, and non-magnetic puck lids are provided in the trial kit for this purpose.

Up to four (4) pucks fit into the Dewar of the BAM-1 automounter at F1, so up to 64 pins may be accessed without manual reloading. The BAM-2 at A1 holds up to nine (9) pucks for a total of 144 without reloading.

Up to seven (7) pucks fit into a tower, which fits right into a Taylor-Wharton CP-100 travel Dewar. Store pins in the lower pucks first for best liquid nitrogen coverage. Note that the crystal end of the pins point towards the bottom for the same reason.

According to ALS, pucks and tools are available from Boyd Technologies.

SSRL, ALS and the SMB-CAT at APS collaborated on the Universal Puck Project to design a puck usable with both ALS and SSRL automounters. The puck lid is strongly magnetic, and the puck body has weak magnets inset for use with the SSRL robot. MacCHESS has a sample of the universal puck.

Laser sensors

The BAM-1 automounter has two laser sensors. One checks the goniometer position to guard against mounting while a base is already in place, and to check the success of mounting and unmounting. the other sensor is near the sample Dewar, to check whether the base was properly released in the Dewar. The software has an "override" checkbox to allow continued data collection should the sensors fail.

The BAM-2 automounter at A1 uses a laser sensor for the goniometer, and a Hall effect proximity sensor for the gripper.

Recent Developments

The MacCHESS automounter has reached a state of consistent mechanical reliability. The BAM-2 automounter for A1 is just about ready for use. Contact MacCHESS if you want to be the first guinea pig.

ALS-style Automounter resources at other synchrotron facilities:
Berkeley Center for Structural Biology
NSLS Protein Crystallography Research Resource

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