Ts. Yoon et al., Mosaic spread analysis of Canadian advanced protein crystallization experiment on the Russian space station, Mir, J CRYST GR, 232(1-4), 2001, pp. 520-535
Protein crystallization experiments were performed on the Russian space sta
tion, Mir, using liquid-liquid interface diffusion. The technique was activ
ated in orbit by the sliding together of two half-wells containing protein
and precipitant fluids, respectively. Imperfections in protein crystals wer
e analyzed from rocking curve measurements of the diffracted intensities us
ing synchrotron radiation. Data were collected on microgravity and earth-gr
own crystals, and 10 different protein pairs were compared. To avoid bias,
a double-blind protocol was used throughout the data analysis. Rocking curv
es for individual reflections were analyzed in terms of crystal domains, ea
ch fitted by a three-dimensional Gaussian profile. The results of Gaussian
analysis were consistent with domain segregation corresponding to spatially
different regions of the protein crystal exhibiting distinct mosaic spread
s. When crystals were grown in microgravity the domain mosaic spreads were
consistent with five of 10 different proteins exhibiting fewer imperfection
s, three other proteins showed no significant difference while a remaining
two proteins displayed a greater number of apparent imperfections. Ground (
earth-grown) controls were also conducted on protein samples flown to asses
s protein stability as a function of solution storage time prior to protein
crystal growth (PCG) activation in microgravity. Protein samples were stor
ed in ground controls at concentrations used to initiate crystallization, a
nd aliquots were analyzed after a 30-day period by dynamic light scattering
. Polydispersity estimates indicated that prolonged storage induced heterog
eneity in all protein samples. Stable aggregates were present, and they wer
e concentration independent, as shown by resistance to protein sample dilut
ion. A PCG growth model is proposed that takes into account large scale agg
regation or self-impurities present during crystal growth and predicts doma
in segregation. Trapping or rejection of self-impurities using this model c
an qualitatively explain differences in domain mosaic spreads observed as a
function of gravitational environment. (C) 2001 Elsevier Science B.V. All
rights reserved.