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Hi!

I am not sure how much this may or may not help, but I used to demonstrate basics of crystallization using peas (well, anything small, regular, and round-ish) on various plates. Depending on your level of involvement you can make some pretty sophisticated experiments including mixing two sizes of 'molecules' to show fractional crystallization and crystal inclusion defects (better if they are same density - ball bearings of two sizes work best in my experience) and nucleation can be demonstrated using a saw-edged piece of cardboard.

If you use irregular objects (like beans rather than peas or if you really like pain then you can dry out some gummy bears and try it with those) you can demonstrate crystallization of proteins quite nicely. A 'nucleant' is almost a must to achieve regular patterns with those.

A bonus factor: this type of demo works very well on many levels, including showing your senior management why crystallization is hard.

Cheers,

Artem
www.harkerbio.com
'We will cheerfully attempt to crystallize whatever you send us. Bring money.'


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On Wed, Jan 4, 2017 at 11:45 AM, Nicolas FOOS <[log in to unmask]> wrote:

Dear Evette,

If I was is your situation (explaining nucleation and other concept). I will discuss in terms of energy.

I mean obtaining the initial nuclei is the "costly" step in terms of energy. To represent that, out the classical curve of energy, I will use a metaphoric representation such as jump over a barrier and run after.

With this analogy, it's possible to explain that the first step is difficult and the second more accessible. If the barrier is to high, it's impossible to continue and run. If you don't have any barrier it's easy to run and if you only have a small barrier is not to difficult to jump over and run. But It also allow you to explain that if you facilitate the apparition of the first "surface" thanks to appropriate method (seeding, dust...) you can help the first step (to continue with the barrier story, it like you have ladder to help, or the ability to decrease the size of the barrier.

For why the crystal and how, I will maybe use the example of orange pyramid in the food store. Orange are stable together because they have enough contact, because they have relatively homogeneous shape. If you mixed orange with water melon it's difficult to obtain nice pyramid.

For crystallization experiment which work, I have no Idea out of the one you already mentioned.


Hope this help.

Nicolas

Nicolas Foos
PhD
Structural Biology Group
European Synchrotron Radiation Facility (E.S.R.F)
71, avenue des Martyrs
CS 40220
38043 GRENOBLE Cedex 9
+33 (0)6 76 88 14 87
+33 (0)4 76 88 45 19
On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
Can anyone point to some especially useful resources to help explain to kids (pre-chemistry, ~age 10-12) how and why molecules crystallize? Maybe a good online movie or animation?  I am especially needing help with the concept of nucleation, and why nucleation is slower and then crystal growth faster once nuclei have formed.  I have been supervising some experiments growing sucrose crystals from supersaturated solutions, which have worked really well, but I am having more difficulty in explaining the underlying fundamental concepts in a way that is understandable to the kids.

Thanks!
Evette

Evette Radisky, PhD

Associate Professor of Cancer Biology

Mayo Clinic Cancer Center

Griffin Cancer Research Building

tel: 904-953-6372

fax: 904-953-0277