Question

In preparing protein sample for crystal structure : (a) Why is it necessary to use large amount of crystallisation solutions for the vapour diffusion experiment ? (b) Give reason why sitting drop format may be used for the experiment .(c) Explain why it will not be necessary to make selenium derivatives of enzyme used for the crystal trials .

Answer 1

In preparing protein sample for crystal structure,

(a) the common technique is to use vapor diffusion experiment, wherein, large volumes of crystallization solutions are used so that slow formation of crystals occurs and we get large crystal size for good crystal structure. Lower volumes would give smaller and faster crystals not suitable for the experiment.

(b) Sitting drop format allows for neuclear growth of crystal formation which results in larger size crystals and thus are most preferred way.

(c) Selenium derrivatisation was used earlier for low resolution data sets, since the advancement of methods, the derrivatization are no more a necessary step for enzymes used for crystal trials.