All living organisms consist mainly of protein molecules. Drug molecules (usually much smaller than proteins) act by interacting with proteins (e.g. membrane proteins), and the understanding of this interaction at the atomic scale is crucial to the development of more and better drugs. At present the determination of protein atomic structure is performed mainly by X-ray cyrstallography (which requires a three-dimensional crystal of protein), electron cryomicroscopy (a slow and difficult method usually requiring two dimensional crystals) and NMR, a new method most useful for small proteins, currently under development. The overwhelming majority of proteins solved so far have been solved by X-ray crystallography, however the preparation of protein crystals is a slow, tedious and poorly understood process involving trial-and-error adjustment of many parameters, which is often unsuccessful. Of the appromiately one million proteins in the human organism, only a small percentage have been solved, and there is thus a crucial need for new reapid methods for solving protein structures at atomic or near-atomic resolution which do not depend on crystallization.Our invention addresses this problem by developing a form of "serial crystallography." Instead of arranging the molecules in a three-dimensional periodic array (a crystal), we fire hydrated molecules in a molecular beam (at very low temperatures) across a high energy beam, which produces a scattering (diffraction) pattern. Molecules of the beam are first aligned so that each is identically oriented. The scattering pattern from each molecule is thus identical. Due to radiation sensitivity of proteins to electrons and X-ray beams, patterns are obtained from analysis of a number of molecules, each subjected to a "sub-critical" radiation dose, such that the features of each molecule are not destroyed.The advantage of our scheme over X-ray crystallography is that it is not necessary to form crystals. The advantage over cryomicroscopy of 2D crystals, while it involves much simpler and more rapid data aquisition and sample preparation than "single particle" electron microscope imaging of macromolecules in this ice films.
|Original language||English (US)|
|State||Published - Oct 17 2005|