Influence of Chlorides of Mono- and Divalent Metals on the Oligomeric Composition of Lysozyme Crystallization Solutions and Further Crystal Growth

The influence of the precipitant type (LiCl, NaCl, KCl, NiCl 2 , and CuCl 2 ) on the formation of oligomers (dimers and octamers) in lysozyme crystallization solutions at two protein concentrations has been investigated by small-angle X-ray scattering (SAXS). The same solutions have been used to grow crystals in order to reveal the influence of the oligomeric composition on the crystal growth. The data obtained in this and previous studies on the influence of precipitant concentration yield an inversely proportional dependence of the total content of octamers and dimers on the cation atomic number, which is in agreement with the increase in the ion activity in the lyotropic series for Li + , Na + , and K + and the increase in the ionic radius for Li + , Na + , K + , Ni 2+ , and Cu 2+ . It is shown that a decrease in the protein concentration in a crystallization solution leads to a decrease in octamer volume fraction at an invariable volume fraction of dimers and reduces the probability of crystal formation.