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Here you will find a series of online tutorials to help you identify what you see in your crystallization drop, and what do to about it. Is it a hit worth optimizing, or should you keep screening? What is the best way to optimize a hit? Finally, take the quiz to see how well you do on drop phenomena identification.

Appearances can be deceiving!

Tutorial 1

Beauty is only skin deep as the saying goes. The first thing you should learn is that the appearance (also referred to as the habit or morphology) of your crystal is NOT what is important.


Types of precipitates

Tutorial 2
One of the most difficult things for beginners is to recognize promising precipitates and distinguish them from precipitiates that are not worth pursuing.

Between precipitates and crystals

Tutorial 3

Precipitates and crystals are relatively easy to recognize, but they are many other solid phases of protein that can occur in the drops. What do spherulites, oils, phase separation, and gels look like? 


Tutorial 4
Are needles better than plates? How do I get from long, thin crystals to big fat ones?


Tutorial 5
There are different kinds of seeding: macroseeding, microseeding, streak seeding, epitaxial seeding, cross-seeding, matrix microseeding. Here are some pictorial examples. Seeding is a powerful optimization tool and my personal favorite.

Ostwald ripening

Tutorial 6
In 1896 Ostwald described this phenomenon for small molecules and here are the references. The references are in German and very old, so they are probably hard to find.


Tutorial 7
When it comes to optimization, there are many options. You might want to do a grid screen around the initial hit in which you vary and fine-tune the protein concentration, pH, and precipitant concentration. Other options—and better ones—might be seeding or an additive screen around the hit.

Terese Bergfors

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