McDonald Group

The original McDonald group page got lost, looking for the backups. In the meantime, here are some interesting images and links.

 ~~~ Nanolithography ~~~
 These are a couple 3x3 micron confocal microscopy images taken of fluorescently labeled crosses.  The crosses are made with a palladium coated atomic force microscopy tip which is scanned, in presence of a solution phase reducing agent, across the carbamate functionalized surface at high pressure.  We have other lithography schemes besides this one, but in all the mechanism is a Pd catalyzed reaction of organic or organometallic functional groups.  It works without electrical current.
 

         (3x3 microns)




Apparently we're only the second group to do this in this particular way in the world.  Most scanning probe methods involve either electrical current or displacement of surface species.

Since we don't use electrical current, we can do this on non-conductive substrates (like silane derivatized glass used above).

You can see evidence of the hysteresis of piezotubes in the big cross (right).  During writing, the tip starts in the center of each cross, it writes the lower right arm first, comes back (2 passes), and writes the second line, this time making 4 total passes.  It then makes 6 total passes over the upper left line, and 8 over the upper right.  Done with this cross, the tip is moved across the sample by inertial translation and another cross is started.

We have also attached biotin and streptavidin coated gold nanoparticles to such lines.  We have another scheme which could be used to place functional groups of many different kinds on the terminus of a surface assembly.

Genealogy Links

Here is a link to my maps showing worldwide distribution of Y chromosome and Mitochondrial DNA haplogroups. Click on the thumbnail.
Haplogroup Maps

And here is my Javascript based TMRCA calculator that runs in Web browsers.

To visit the Clan Donald USA DNA project, go here.