Biology Reference
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Fig. 4. Determination of the contact area between a crystallization trial and its support-
ing vessel by application of oil. (a) Large contact area: a crystallization drop dispensed
onto the floor of a vial and then covered by a layer of oil; the drop spreads out and flattens
over the floor of the container. (b) Small contact area: the result of dispensing by the nor-
mal microbatch procedure (shown in Fig. 1); a rounded drop with only a small part of it
touching the floor. (c) “Containerless crystallization”: a crystallization drop is suspended
between two oils of different densities; the drop floats at the interface thereby not touch-
ing the container walls.
grown by procedure (a), where the drop has the largest contact area
with its vessel (Blow et al ., 1994; Chayen, 1996). Nucleation is not
totally eliminated by procedure (c) and surprisingly, the difference
between the number of crystals grown by the normal microbatch pro-
cedure (b) and the containerless situation (c) was not marked. The num-
ber of crystals in the containerless procedure was merely 10% less than
the number obtained by normal microbatch dispensing. This indicates
that the interface between the two oils also acts as a surface but with
somewhat reduced nucleation properties compared with that of a solid
material. A simpler way to conduct such “containerless crystallization”
is by replacing the bottom layer with a layer of Vaseline above which
the low density oil is dispensed (Chayen, Saridakis, 2002). A kit for
such experiments is available from Molecular Dimension (Cat. no.
MD1-12ROWORLD).
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