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Oryx8 is driven by a PC, which is connected to a stepper motor drive box
(MCC). This is connected to 8 motorized syringes (1 large and 7 small) mounted
at the back of the two chassis, and to the XYZV Plate Loader, which has a moving
table and two arms.

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Small volumes are dispensed by the left-hand
arm, using the seven small (100
µl)
motorized syringes.
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Small volumes are dispensed from a two-bore or seven-bore
microtip.
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Stock solutions do not come into contact with
the motorized syringes, which are filled with degassed pure water - this avoids
the need for flushing out the syringes when the stock solutions are
changed.
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The manual syringes on the front panel are used
to refill the motorized syringes, to remove air bubbles, and to load stock
solutions.
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Large volumes, including oil for microbatch
experiments are
dispensed by the right-hand arm using the large (10 ml) motorized syringe. A 1 ml disposable tip is used for this.
2. What it does
a. Sitting Drop Crystallization
Oryx can rapidly dispense the droplets into trays such as
Crystal Clear, Cryschem, Greiner or
Corning
plates for sitting drop crystallization.
One channel of a 2-bore microtip is loaded
with protein at the start of the experiment, then, for each well, reservoir
solution is picked up with the other bore and transferred to the droplet. Protein is dispensed at the same time as the
reservoir solution and mixed by stirring.
Multi-drop plates can be dispensed to with differing
proportions of protein or up to three different protein variants. A
sliding evaporation shield covers and protects the drops during the time
that it takes to dispense the experiment
b. Microbatch screening
Oryx8 is used for screening (finding new
crystallization conditions) using the microbatch
crystallization method. Here
droplets are dispensed into plastic plates and covered with oil to prevent
evaporation. We generally dispense
0.2 to 2 µl into the bottom of each well. In order to dispense these very small
droplets accurately, a special proprietary microtip
is used.
Oryx has an extra liquid handling channel that can be used
to cover microbatch droplets with oil immediately after dispensing. This prevents the microtip
from coming into contact with the oil, which would significantly reduce
accuracy. (This is the reason that Oryx
is more accurate than IMPAX for dispensing microbatch experiments.)
Typically 96 premixed solutions can be combined with protein for
screening. These solutions are placed on the right-hand side of the Plate
Loader. A two-channel microtip is used to mix the solutions with protein. One
channel is loaded with the correct amount of protein at the start of the
experiment. The other channel is used to pick up 0.1 to 1 µl of the first
screening solution and transfer it to the first well of the VB plate. It is
dispensed and mixed with 0.1 to 1 µl of protein from the other channel.
Oil is immediately dispensed by the second arm to cover and protect the drop. The
microtip is then rinsed. This is repeated for all
96 solutions. It takes about 5 minutes for the user to set up a screening
experiment, and 50 minutes to dispense a screen with 96 solutions.
c. Microbatch optimization
A sophisticated “spreadsheet” environment is provided for
designing and carrying out optimization experiments. The stock solutions are shown on the
left. Each cell represents one
well. The user can input concentrations
simply by double-clicking on a well.
By defining the wells at opposite corners of a block, and
selecting “interpolate”, the user can rapidly define 2D grids. A similar routine automatically generates a
multi-dimensional multivariate experimental design. Here the conditions are based on the
conditions in a single well – the user chooses the total amount of variation
that he would like for each variable as a percentage. See our research report “Practical
Experimental Design Techniques” for more details.
The branches of the 7-channel microtip act as
reservoirs for protein, precipitant, pH buffer solutions and additives. These
are loaded using the lower row of valves and the disposable syringes. Solutions
are dispensed using the motorized gas-tight syringes, which contain water.
Exactly the right amount of protein is loaded by sucking it into one bore of
the microtip. It is kept separate from the water
already in the bore by a small air bubble. Solutions are dispensed from all
bores simultaneously. 96 wells can be dispensed in around 15 minutes. As with screening, oil is dispensed by Oryx onto each droplet immediately
after it is dispensed.
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