Dear Joy - microcrystalline in most cases would be birefringent - this is difficult to observe these days in our plastic boxed crystallization world with colours everywhere.
But if you really want to know you can pipette the droplet onto a glass coverslip and dim the room lights. Set the polarizers _exactly_ to extinction. Then you can see if the precipitate glows. Of course it could be a cubic space group crystal which I heard does not show BR. And it could be micro-spherulites which are indeed quasicrystalline - these are strongly bireringent - maybe _too_ strongly is the clue here! If any get to a reasonable size then you can see a X-like pattern in the centre of these since they appear to be ordered in spherical shells of unfolded protein. One other clue can be the density - most protein crystals are not far off the droplet density. So if the precipitate settles strongly into a circle at the bottom of the droplet then I would say this is a bad sign :( Hope this helps. regards Martyn Symmons EBI, Hinxton, Cambs. UK --- On Thu, 10/6/10, joybeiyang <[email protected]> wrote: From: joybeiyang <[email protected]> Subject: [ccp4bb] How to distinguish microcrystalline, quasicystalline and precipitation? To: [email protected] Date: Thursday, 10 June, 2010, 7:06 #yiv1007907758 BLOCKQUOTE { MARGIN-TOP:0px;MARGIN-BOTTOM:0px;MARGIN-LEFT:2em;} #yiv1007907758 OL { MARGIN-TOP:0px;MARGIN-BOTTOM:0px;} #yiv1007907758 UL { MARGIN-TOP:0px;MARGIN-BOTTOM:0px;} Hi everyone, I am preparing a "crystallization manual" for our group, however, I found that it is very difficult to distinguish microcrystalline, quasicrystalline and precipitation, especially when the precipitation was shiny, like the grit on the beach. Is there a way to distinguish the three? Comments and suggestions will be greatly appreciated! Joy
