Biology Reference
In-Depth Information
Other Uses of Magnetic Orientation
Figures 1 and 2 show that the group of equivalent crystalline faces {110}
is directed perpendicularly to the line of sight. It must be emphasized that
a similar orientation is rather difficult to achieve by any other means. An
advantage of the orientation of the crystalline faces being perpendicular to
the line of sight is that the growth rate with time of this particular face can
be directly measured with precision. If the face is not perpendicular, we
need to know the angle of its inclination to the line of sight in order to cal-
culate the growth rate. The perpendicular orientation allows one to find
the growth rate directly from the images recorded, e.g. in a video tape or
in a recording medium through a CCD camera. Pusey (1993) developed a
computer-controlled microscopy system for following protein crystal face
growth rates for automatic recording — potentially useful in microgravity
experiments. If the magnetic orientation is combined, the system devel-
oped by Pusey could prove to be an excellent solution.
Other Possible Mechanisms Through Which
Homogeneous Magnetic Fields May
Contribute to Quality Improvement
The action of primary importance for a homogeneous magnetic field to
improve the quality of protein crystals, we believe, is the magnetic orien-
tation of sedimenting microcrystals as already discussed. However, there
are other possible actions. A strong, homogeneous magnetic field can
align the precrystalline structure, the formation of which we have studied
previously (Ataka, 1998), as long as such structure has magnetic
anisotropy. The postulated (but not yet fully proven) “gel-formation”
(Zhong
et al
., 2001) may be related to such precrystalline structure. If
such precrystalline structure aligns in response to a magnetic field then
suppression of convection and/or impurity diffusion take place, which
may also lead to quality improvement.
There is evidence that the crystal growth rate (and the crystal dissolu-
tion rate in undersaturated solutions) reduces in a strong, homogeneous
magnetic field. The evidence has been collected by observing the growth
Search WWH ::
Custom Search