Neutron Scattering Studies of the E. coli Ribosome

Abstract

INTRODUCTION
It is obvious from the reports so far presented in this volume that increasing effort is being applied to understanding the three-dimensional structure of the ribosome. About a year ago it was suggested that the quaternary structure of the ribosome could be studied by the technique of low-angle scattering of thermal neutrons in solution (Engelman and Moore 1972). We would like to take this opportunity to report on the progress made over the last year towards bringing this proposal to fruition. In so doing, we will discuss some recent results on the global distribution of RNA and protein in the 50S ribosomal subunit of E. coli.

Background Information
To understand why neutron scattering is useful in this context, it is necessary to review some facts about how neutrons are generated and how they interact with matter (Schoenborn and Nunes 1972; Bacon 1962). At present, the only practical thermal neutron sources for the work under consideration are nuclear reactors. High energy neutrons are produced in abundance by fission in the reactor core. Some neutrons escape from the core and enter a surrounding blanket of material called the moderator, where they lose kinetic energy by collision events, rapidly reaching equilibrium with the moderator substance. These “thermalized” neutrons can be tapped from the reactor by the simple expedient of cutting a hole in the radiation shielding surrounding the reactor and providing a thin window in the moderator container through which the neutrons can pass.

The neutrons in the moderator region of the...