Biomedical subjects

H Szöke

Publications and source records attributed to H Szöke.

3 recordsLinked to original sources

PubMed2001

A simple inverse method for calculating electron-density maps.

Electron-density maps are generally prepared by Fourier transforming a set of complex structure factors. However, a map can also be obtained through a real-space reconstruction method. Starting from an empty unit cell, the map can be iteratively modified until it agrees with the given structure factors. In this paper, a simple method is described for preparing electron-density maps using this technique and two examples of its application are given.

Journal Article↗

PubMed2000

Capture and visualization of a catalytic RNA enzyme-product complex using crystal lattice trapping and X-ray holographic reconstruction.

We have determined the crystal structure of the enzyme-product complex of the hammerhead ribozyme by using a reinforced crystal lattice to trap the complex prior to dissociation and by employing X-ray holographic image reconstruction, a real-space electron density imaging and refinement procedure. Subsequent to catalysis, the cleavage site residue (C-17), together with its 2',3'-cyclic phosphate, adopts a conformation close to and approximately perpendicular to the Watson-Crick base-pairing faces of two highly conserved purines in the ribozyme's catalytic pocket (G-5 and A-6). We observe several interactions with functional groups on these residues that have been identified as critical for ribozyme activity by biochemical analyses but whose role has defied explanation in terms of previous structural analyses. These interactions may therefore be relevant to the hammerhead ribozyme reaction mechanism.

Crystallography↗

PubMed1995

Holographic methods in X-ray crystallography. IV. A fast algorithm and its application to macromolecular crystallography.

The holographic method makes use of partially modeled electron density and experimentally measured structure-factor amplitudes to recover electron density corresponding to the unmodeled part of a crystal structure. This paper describes a fast algorithm that makes it possible to apply the holographic method to sizable crystallographic problems. The algorithm uses positivity constraints on the electron density and can incorporate a 'target' electron density, making it similar to solvent flattening. The potential for applying the holographic method to macromolecular X-ray crystallography is assessed using both synthetic and experimental data.

Algorithms↗