In-house phasing with iodide soaks

Fast iodide-SAD phasing for high-throughput membrane protein structure determination

We describe a fast, easy, and potentially universal method for the de novo solution of the crystal structures of membrane proteins via iodide-single-wavelength anomalous diffraction (I-SAD). The potential universality of the method is based on a common feature of membrane proteins-the availability at the hydrophobic-hydrophilic interface of positively charged amino acid residues with which iodi...

MAD phasing with krypton.

Experiments demonstrating the feasibility of Kr-edge MAD on frozen crystals as a routine method for structure determination are reported. Approximately 50% of protein crystals can be successfully derivatized by pressurization with the noble gases xenon or krypton. While Xe has produced many useful derivatives for MIR phasing over the last several years, the Xe edges (K edge = 34.6 keV, L(I) = 5...

Away from the edge: SAD phasing from the sulfur anomalous signal measured in-house with chromium radiation.

Anomalous scattering with soft X-ray radiation opens new possibilities in phasing for macromolecular crystallography. Anomalous scattering from S atoms collected on an in-house chromium radiation source (lambda = 2.29 A) was used to phase the X-ray diffraction data of thaumatin (22 kDa) and trypsin (24 kDa) crystals. The contribution to the anomalous term, Deltaf" = 1.14 e(-), from sulfur for C...

Advances in experimental phasing

Triiodide derivatization in protein crystallography.

Methods for producing protein derivatives using cryosoak techniques with triiodide solutions are described. The methods have been tested using six different proteins. SAD/SIRAS phasing was attempted for each protein using data measured with conventional Cu Kalpha X-ray equipment and synchrotron radiation. Refinement of all six derivative structures showed that iodine is able to bind as I(-) (as...