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Calcium citrate also a relatively low solubility (~15 mM in the cold), and its solubility decreases as the temperature goes up.  Thus, getting calcium citrate crystals is a possibility if both components are at a relatively high concentration.  However, sodium citrate alone is soluble up to ~1.4 M at least, depending on the pH.
 
Calcium citrate also a relatively low solubility (~15 mM in the cold), and its solubility decreases as the temperature goes up.  Thus, getting calcium citrate crystals is a possibility if both components are at a relatively high concentration.  However, sodium citrate alone is soluble up to ~1.4 M at least, depending on the pH.
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A list of conditions from commercial screens, where people obtained crystals that turned out to be from salt, is at [[Conditions prone to salt crystallization]]. This should not be taken to mean that these conditions ''always'' produce salt crystals, but they apparently sometimes do.
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==What if I have a membrane protein?==
 
Most nonionic detergents do not form crystals in aqueous solution.  Check the published phase diagrams to be sure.  In fact, few of the alkyl glycoside detergents (like octyl glucoside and dodecyl maltoside) crystallize if the sugar group is a beta anomer, even in organic solvents.  This is one of the reasons why they are so difficult to purify by recrystallization.  Under some extreme conditions, nonionic detergents can form liquid crystals, but these are rare.
 
Most nonionic detergents do not form crystals in aqueous solution.  Check the published phase diagrams to be sure.  In fact, few of the alkyl glycoside detergents (like octyl glucoside and dodecyl maltoside) crystallize if the sugar group is a beta anomer, even in organic solvents.  This is one of the reasons why they are so difficult to purify by recrystallization.  Under some extreme conditions, nonionic detergents can form liquid crystals, but these are rare.
  
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