Guidelines for
experiments involving heavy atom compounds
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The compounds
typically used for making heavy atom derivatives are inherently
toxic because of their heavy metal content (Pb, U, Pt, Hg, Se,
Br, etc.). However, in most cases the quantities, forms, and
means of containment of the samples brought to CHESS are such
that the CHESS Safety Committee deems the experiment to be
non-hazardous. The following criteria are used to determine the
classification of an experiment:
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Form: |
Already incorporated in crystals,
the crystals being mounted in capillaries, frozen, or contained
in small hanging drops, wells or vials; or in solution in small
hanging drops, wells, or vials. "Small" means less than 1ml.
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Total quantity: |
No more than 1/50 the LD50 for a
50kg animal or 0.01millimoles if the LD50 is not available.
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Manipulations: |
Limited to transfer of crystals
in and out of solutions, and transfer of small amounts of
solution from one container to another. |
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Form: |
In solution or dry
in closed containers. Dry form is only acceptable when solutions
are unstable and absolutely must be made fresh.
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Total quantity: |
Between 1/50 and 1/2
the LD-50 for a 50 kg. animal, or between 0.01 and 0.25
millimoles if the LD-50 is not available.
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Manipulations: |
Mixing/dilution of
solutions, transfer of crystals into and out of solutions. |
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Quantities greater than those given in the "hazardous" category.
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All crystals, solutions, and dry
samples containing heavy atom compounds should be transported
into and out of CHESS in double-sealed containers.
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In the
case of non-hazardous experiments, spilled samples may be
cleaned up with tissues or paper towels and the affected area
washed with soap and water. In the unlikely case of spillage of
multiple samples, notification of the CHESS operator to
supervise cleanup is recommended.
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In the case of hazardous
experiments, heavy atom solutions are to be kept in a designated
location, which will normally be Room 172 Wilson for A1 or F2
users, and the prep area of the BL-3 facility for F1 users. The
work area in this location will be clearly demarcated by the
experimenters, and their solutions and affected glassware and
equipment should not be used by anyone else. It is recommended
to cover the workbench in this area with absorbent material
(e.g. paper towels) to absorb spills. For larger volumes of
solution, pans on the benchtop to contain spills are
appropriate. Small spills may be cleaned up with tissues or
paper towels and soap and water, as for the non-hazardous
situation. In the event of larger spills, notification of the
CHESS operator to supervise cleanup is required. Crystals
containing heavy atoms, and small amounts of heavy atom
solution, may then be transported to the experimental stations,
preferably in covered containers. Dry heavy atom compounds
should remain sealed until dissolved, and be opened only in the
fume hood. Handling of hazardous material should be done by
experienced experimenters only.
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In all cases, experimenters are
responsible for following the CHESS safety guidelines and
keeping experimental areas clean and neat, and for the prompt
and complete removal of their solutions, affected glassware, and
utensils at the end of their time at CHESS.
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CHESS Safety Committee, June, 1994 |
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