Tutorial 3: Oils, gels, spherulites, etc.

Not crystals but not precipitates either

Remember: click on any picture to get a magnified view.

 Oils.

These "oils" are actually liquid protein, highly concentrated, often as a result of a phase separation of the components in the crystallization mother liquor. (See phase separation below.) If you find oils in your drops, use them to streak seed new drops and crystals often grow.

 

 Oils.

This is my favorite example of an oil because the protein is red (it is a heme-binding protein). When this oil was used to streak-seed new drops, good crystals grew.

 

 Gels. (Gelatinous protein)

Transparent, irregular regions in the drop. You are very close to the right conditions. In this example, the large crystal in the center of the drop grew some weeks after the gel. Some of the gel is covering the right side of the crystal.

 

 Gels. (Gelatinous protein)

Another example of what gels look like, this time in a microbatch drop. Compare the difference between gels and precipitates. Gels are an improvement over precipitate.

 Spherulites.

I sometimes describe these as "asteroids" because they look like chunky rocks. Spherulites can be difficult to distinguish from oils unless you probe them with a whisker or needle. (Oils are liquidy, spherulites will be crunchy.) In practice, it doesn't really make any difference: treat the oils or spherulites in the same manner, i.e. streak seed into a new drop.

Tip from Dr. Madeleine Riess-Kautt, Paris, France: Crush the spherulite directly in the same drop. Crystals will sometimes grow.

 

 

 

 Phase separation.

Often appears as hundreds of small droplets inside the drop, as in this picture. This is the most common appearance. However, it can look like the "waves" as seen in this second picture.

 Phase separation.

In this example of a phase separation within the drop, a huge crystal that appeared some weeks after the occurence of the phase separation.

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