Watershed – A Humidity Controlled Workstation For Protein Crystallography

Watershed™ is a humidity controlled workstation for protein crystallography. It prevents drop dehydration during crystals harvesting helping you obtain the best possible diffraction.

Watershed is already used at several facilities including:

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Product Information

Watershed™ will simplify your crystal mounting allowing you to get the best possible diffraction which in turn allows you to optimize your crystal harvesting and post-growth treatment protocols. Additional benefits of using Watershed™ are:

  • Increase drop working times and prevent dried out drops
  • Reduce protein precipitation and degradation
  • Harvest more crystals from each drop
  • Reduce crystal non-isomorphism
  • Used controlled dehydration to improve diffraction
  • Use with cover slips, glass slides, crystallization plates, or your home X-ray source

Watershed™ provides a controlled humidity environment for a wide range of common sample preparation tasks, including:

  • Separating crystals from each other, from precipitate, and from protein skins that may form over crystallization drops
  • Soaking crystals in solutions containing cryoprotectants, heavy atoms or ligands
  • Harvesting crystals from drops onto X-ray sample mounts
  • Blotting or wicking away excess liquid from crystals to reduce background X-ray scatter and increase sample cooling rates during plunge cooling
  • Placing crystals in MiTeGen’s MicroRT capillaries or glass capillaries for room temperature data collection
  • Adjusting the hydration of crystals to a desired relative humidity, which may be different from their as-grown relative humidity, to modify protein structure or optimize diffraction properties

The Watershed system consists of:

Control Unit

Water tank

Humidified Enclosure Workstation

Positionable Nozzle Workstation

Other components include an air pressure regulator, connection accessories, tubing, tubing union, cover slips, a cryovial and GFCI power cord

The Humidified Chamber Workstation accepts drops on 18 or 22 mm cover slips or on standard microscope slides. Crystals can be harvested and manipulated within the workstation using standard crystal loops, goniometer bases, and magnetic wands, while being observed from above using a long-working distance stereo microscope.  Once mounted, the sample can be transferred to a cryovial containing humid air, and the sample + cryovial can then be removed and transported to, e.g., a cryocooling setup. The humidified chamber workstation provides controllable relative humidities between 50% and >90% RH.

The Directed Nozzle Workstation can be used with crystals in multiwell crystallization plates to provide a humidified air flow directed at a well being examined.  This workstation can also be used with a laboratory X-ray source to controllably vary the hydration of a crystal during diffraction data collection. The directed nozzle workstation provides controllable relative humidities between 50% and >90% RH.


Watershed mixes high-humidity, room-temperature air (generated by bubbling dry air through room temperature water) with dry air to obtain an air stream with a desired relative humidity.

Relative Humidity Range:  72% to >90% RH

Water content of the compressed air supply affects the lowest achievable humidity. 72% RH tested with 23°C water and 6% RH air source.

Water tank capacity:  2.5 gallons / 10 liters


Power source:  110-125 VAC, 50-60 Hz, preferably with GFCI protection

Source of dry air or nitrogen at a pressure of 25 psi

Distilled or deionized water

Control unit:

Dimensions:  5.3 (H) x 14.0 (W) x 10.0 (D) inches / 135 x 357 x 255 mm

Weight:  11.5 lbs / 5.2 kg

Water Tank:

Dimensions:  10.2 (H) x 14.0 (W) x 9.3 (D) inches / 260 x 357 x 235 mm

Weight:  5.0 lbs / 2.3 kg empty; 26 lbs / 11.8 kg full

Humidified Enclosure Workstation:

Dimensions:  2.6 (H) x 4.5 (W) x 2.2 (D) inches / 66 x 115 x 55 mm

Accepts two 18 mm or 22 mm round cover slips or one 25 x 75 mm microscope slide

Required microscope working distance:  1.8 inches / 45 mm minimum

Positionable Nozzle Workstation:

Magnetic base diameter:  2 inches / 54 mm

Positionable tubing length:  19 inches / 500 mm

The Watershed System was developed in collaboration with Prof. Douglas Juers (Whitman College).

Read the MiTeGen Watershed User Manual to learn more

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