Shaunivan Labiuk

Cyclo-linopeptide K butanol disolvate monohydrate.

The title compound, C56H83N9O11S·2C4H10O·H2O, is a butanol–water solvate of the cyclolinopeptide cyclo(Metsulfone1-Leu2–Ile3–Pro4–Pro5–Phe6–Phe7–Val8–Ile9) (henceforth referred to as CLP-K) which was isolated from flax oil. All the amino acid residues are in an l configuration based on the CORN rule. The cyclic nonapeptide exhibits eight trans peptide bonds and one cis peptide bond observed between the two proline residues. The conformation is stabilized by an α- and a β-turn, each containing an N—H⋯O hydrogen bond between the carbonyl group O atom of the first residue and the amide group H atom of the fourth (α-turn) and the third residue (β-turn), repectively. In the crystal, the components of the structure are linked by intermolecular N—H⋯O and O—H⋯O hydrogen bonds into a two-dimensional network parallel to (001). The –C(H2)OH group of one of the butanol solvent molecules is disordered over two sets of sites with refined occupancies of 0.863 (4) and 0.137 (4).

Gamma and Ultraviolet Radiation Cause DNA Crosslinking in the Presence of Metal Ions at High pH

M‐DNA is a novel duplex conformation in which metal ions such as Co2+, Ni2+ or Zn2+ replace the imino protons of every base pair. An ethidium fluorescence assay was used to estimate lesions in M‐DNA induced by γ‐ and UV radiation. General damage to DNA was assessed from the loss of ethidium fluorescence after irradiation of calf thymus DNA. Crosslinks were measured from the return of ethidium fluorescence after a heating and cooling step. Strand breaks were estimated from the loss of fluorescence in covalently closed circular plasmid DNA after a heating and cooling step. For the Co2+ form of M‐DNA, γ‐radiation caused the very efficient formation of crosslinks which was not observed with B‐DNA nor with the Ni2+ or Zn2+ forms of M‐DNA. The crosslinks occurred in both A–T and G–C base pairs but did not form in the presence of a free radical scavenger. Crosslinks induced by UV radiation also formed at a faster rate in the Co2+, Ni2+ and Zn2+ forms of M‐DNA compared to B‐DNA; crosslinking occurred in all DNA but was more prominent in AT‐rich sequences and was not inhibited by a free radical scavenger. Therefore, the presence of certain metal ions may lead to large increases in the formation of radiation‐induced crosslinks in DNA.

Cyclo­linopeptide B methanol tris­olvate

The title compound, C56H83N9O9S·3CH3OH, is a methanol trisolvate of the cyclolinopeptide cyclo(Met1—Leu2—Ile3—Pro4—Pro5—Phe6—Phe7—Val8—Ile9) (henceforth referred to as CLP-B), which was isolated from flaxseed oil. All the amino acid residues are in an l-configuration based on the CORN rule. The cyclic nonapeptide exhibits eight trans peptide bonds and one cis peptide bond observed between the two proline residues. The conformation is stabilized by an α-turn and two consecutive β-turns each containing a N—H⋯O hydrogen bond between the carbonyl group O atom of the first residue and the amide group H atom of the fourth (α-turn) or the third residue (β-turns), repectively. In the crystal, the components of the structure are linked by N—H⋯O and O—H⋯O hydrogen bonds into chains parallel to the a axis.

Jel44 monoclonal Fab fragment specific for HPr of the phosphoenolpyruvate:sugar phosphotransferase system of Escherichia coli and the complex of Jel44 Fab fragment with HPr: preparation, crystallization and preliminary crystallographic analysis.

Jel44 is a mouse monoclonal antibody specific for the histidine-containing phosphocarrier protein (HPr), a component of a sugar-transport system in Escherichia coli. Because Jel44 binding to HPr is dependent upon ionic strength and the enthalpic and entropic contributions do not vary over the temperature range 277-310 K, the complex is of great interest. A single crystal of the Jel44 Fab fragment was obtained and diffracted X-rays to a maximum resolution of 4.6 A on an in-house X-ray source. The crystal belongs to space group P2(1), with unit-cell parameters a = 68.6, b = 67.7, c = 105.5 A, beta = 96 degrees. Although crystals of the complex of Jel44 Fab fragment with HPr could not be fully characterized owing to suspected crystal twinning, it was encouraging that they diffracted X-rays to 2.5 A on an in-house X-ray source. It is thus foreseen that improvement of crystal quality will allow the complete solution of this novel structure.

The State of the Canadian Macromolecular Crystallography Facility

The Canadian Macromolecular Crystallography Facility (CMCF) at the Canadian Light Source consists of two macromolecular crystallography beamlines for structure determination using x-ray diffraction. The equipment at the CMCF beamlines have undergone or will undergo changes and improvements to better meet the needs of the most challenging experiments users may present. Among these improvements are: 1) Automounter improvements; 2) Better goniometry on 08ID-1 with the addition of a Huber air-bearing goniometer; 3) Added beam size capabilities on 08ID-1 with the addition of a multiple beam defining aperture holder; 4) XAFS capability on 08B1-1; 5) Improved low energy S-SAD data collection with the addition of a Helium path; 6) Improvements to the data collection and data management software; 7) A vacuum path for scattering experiments with detector distances up to 1 m; 8) A comprehensive beamline upgrade project on the 08ID-1 beamline; and 9) Service crystallography services.

Future developments for macromolecular crystallography at the CLS

The Canadian Macromolecular Crystallography Facility (CMCF) at the Canadian Light Source (CLS) is a suite of fully automated beamlines, 08ID-1 and 08B1-1 [1]. It serves over 60 Canadian groups plus academic and commercial users in the US. Besides remote data collection, we offer Mail-In service where data are collected by CMCF staff. Beamline 08B1-1 has been in operation since 2011 and beamline 08ID-1 since 2006. When beamline 08ID-1 was designed, over 10 years ago, small crystals were defined as having sizes of 50-100 μm. Today, the most challenging experiments require more intense X-ray beams that can be focused to accommodate much smaller crystal sizes of less than 5 μm with flux on the order of 10^11 photons/s. To reach these stringent parameters, a new more powerful source of X-rays will be required, which will be provided by a longer small-gap in-vacuum undulator (SGU). To accommodate the higher power levels and to focus X-rays to a smaller focal spot with a high degree of spatial and temporal stability, the existing X-ray optical elements need to be upgraded. The remaining components of the project include a 5-axis alignment table for improving alignment of small samples with the microbeam, a high-efficiency robotic sample-changer and a single-photon X-ray detector. Several options for the new design will be discussed. These developments are consistent with the current direction of structural biology research at the CLS [2]. Since 2006 over 225 (240) papers and 400 (444) PDB deposits reported data collected at beamline 08ID-1. Parentheses indicate the total number for the CMCF. Many of these have been published in very high impact journals such as N. Engl. J. Med., Nature, Cell, Science, PNAS, among others (http://cmcf.lightsource.ca/publications/).