| | 4 | Author
| Peter Zipper | Requires cookie* | | | Title
| Small-Angle X-Ray Scattering Studies on the X-Ray Induced Aggregation of Malate Synthase Computer Simulations and Models  | | | | Abstract
| Malate synthase undergoes an X-ray induced aggregation which can be monitored in situ by small-angle X-ray scattering; the analysis o f scattering curves, taken at subsequent stages o f aggregation, has led to the establishment of a tentative model for an aggregation in two dimensions (Zipper and Durchschlag (1980) Rad. and Environm. Biophys., in press). This model was checked by comparison o f appropriate theoretical curves with the experi mental curves. The theoretical scattering curves for this comparison were obtained by weighted averaging over the scattering curves calculated for various species o f hypothetical aggregates. Based on the approximation o f the unaggregated enzyme particle by an oblate cylinder, the aggregates were assumed to be composed of 2, 3, 4 or 6 of such cylinders, associated side-by-side in one and later on in two linear rows. The weight fractions o f the species were chosen so, that an optimum fit of the experimental mean radii o f gyration and mean degrees o f aggregation was achieved. The distance distribution functions calculated for the model are very similar to the functions derived from the scattering experiment. Cross-section Guinier plots o f the scattering curves of the model reveal the occurrence o f one and later on o f two pseudo cross-section factors similar to those observed in the experimental scattering curves. The pseudo thickness factor of the model of the unaggregated particle is found to be retained in the model curves for all stages of aggregation. From these results it can be concluded that the model for the aggregation process is essentially consistent with the scattering behaviour of the aggregating enzyme. Small differences between the theoretical and experimental curves may be explained by the idealizations o f the model. The comparison of theoretical curves for alternative models, assuming aggregation in three dimen sions, suggests that these models are unlikely, though small amounts o f three-dimensional aggregates cannot be ruled out completely. | | | |
Reference
| Z. Naturforsch. 35c, 890—901 (1980); received November 12 1979/July 14 1980 | | | |
Published
| 1980 | | | |
Keywords
| Malate Synthase, Small-Angle X-Ray Scattering, X-Ray Induced Aggregation, Computer Simula tions, Models for the Aggregation Process | | | |
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| ZNC-1980-35c-0890 | | | | Volume
| 35 | |
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