Hoarfrost crystals

I like how these ice crystals on my car this morning had symmetry resembling full hexagonal or truncated snowflakes.

Comments on Tangle Proteins Building Set

I recently purchased a Tangle Proteins Building Set from Educational Innovations and just put together the first model in the set: the third IgG-binding domain from Streptococcal Protein G.  The pieces in the primary chain were hard to wrestle together. My assembly tactics ranged from dish soap to sandpaper to leather gloves to simple "elbow grease",  and the pieces eventually came together.  The clear lengths of plastic used to make hydrogen bonds should have probably been just a smidge longer.  The directions in the book had issues, too.  It was difficult to tell from the photographs where one structural element ended and the other began.  I have experienced similar difficulties in displaying the seams between LEGO bricks on my Exploring the Nanoworld with LEGO Bricks website (they are also brightly colored plastic pieces).  On the LEGO site, we have had to sometimes color the seams between the bricks with permanent markers to emphasize them.  The  first model also has an error in the instructions: only 12 red helix pieces were given in the list for the primary sequence, yet everywhere else in the instructions 14 red pieces are required.  Despite all these challenges, I think this little protein model is pretty cool when finally assembled. It features an alpha helix and a beta pleated sheet, and this inorganic materials chemist can appreciate the fact that, as others have said, the hydrogen bonds and other secondary interactions between various parts of the primary chain  really direct the structure of the entire molecule.  Two other models are also described, but this inorganic materials chemist would love to eventually see some metal binding sites (e.g. a heme group) added.

Elephant's Toothpaste in a Pumpkin (catalytic decompostion of hydrogen peroxide within dishsoap creates a foam)

ORIGINALLY POSTED 5-1-12:

Doing the "Elephant's Toothpaste" reaction inside a carved pumpkin (a plastic pumpkin works too). The foam oozes from the mouth and eye holes of the pumpkin, resulting in a totally gross demonstration! ABOVE: The foam is just beginning to ooze out. BELOW: At the end of the demo (left) and photographs of another run (middle and right). Aqueous potassium iodide was used as the catalyst. Special thanks to Kathleen Shanks from the Institute for Chemical Education for helpful advice.

This demonstration is based on an article published in Chem 13 News. We do not have the article information, but we would be happy to post it if anyone finds the reference.

UPDATE 11-18-13:

Here is a picture of the pumpkin that we have used for years of shows.  We tell the audience that the pumpkin is green because it does not feel very well.  The lid has been recently redesigned: 1) it is clear so that the demonstrator can monitor the initial progress of the reaction, and 2) the "stem" of the pumpkin is a wooden dowel that is long enough for the demonstrator to use to hold the lid down without discomfort from the exothermic reaction.