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The x-ray structure of a short-chain dehydrogenase, the bacterial holo 3 alpha,20 beta-hydroxysteroid dehydrogenase (EC 1.1.1.53), is described at 2.6 A resolution. This enzyme is active as a tetramer and crystallizes with four identical subunits in the asymmetric unit. It has the alpha/beta fold characteristic of the dinucleotide binding region. The fold of the rest of the subunit, the quaternary structure, and the nature of the cofactor-enzyme interactions are, however, significantly different from those observed in the long-chain dehydrogenases. The architecture of the postulated active site is consistent with the observed stereospecificity of the enzyme and the fact that the tetramer is the active form. There is only one cofactor and one substrate-binding site per subunit; the specificity for both 3 alpha- and 20 beta-ends of the steroid results from the binding of the steroid in two orientations near the same cofactor at the same catalytic site.

The title compound crystallizes in space groupP212121 with lattice constantsa=16.253(3),b=17.107(3), andc=8.486(2) A. The A ring has 1α,2β-half-chair conformation. The calculated steric energy of a 6α-methyl-17α-ester progesterone molecule is lower by about 4 kJ/mol for the normal A-ring conformation. The progesterone side chain has typical conformation for 17α-ester steroids; the C(16)-C(17)-C(20)-O(20) torsion angle is −24.9(4)°.

The crystal structure of a synthetic analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D -Hyi)-] ([L-Val1, L-Val5]meso-valinomycin), C60H102N6O18, has been determined. Crystals grown from petroleum ether are orthorhombic, space group P2(1)2(1)2(1), with cell parameters a = 16.41(1), b = 18.76(1), c = 25.86(1) A, and Z = 4. The atomic coordinates for nonhydrogen atoms, except those of terminal carbons on one side chain, were refined in the anisotropic thermal motion approximation. The coordinate parameters of the H atoms were incorporated into the structure factor calculations at geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.074 and 0.083, respectively. The crystal structure of the molecule is asymmetric and adopts a conformation with four 4----1 type and one 6----1 type intramolecular hydrogen bonds between amide nitrogens and carbonyl oxygens. Valinomycin binds potassium more than 100 times strongly than the D,L stereoisomeric analogue, as a result of a different spatial orientation of potentially interacting carbonyl groups.

Direct x-ray analysis has been used to determine the crystal structure of [D-Hyi2, L-Hyi4]meso-valinomycin (cyclo[-D-Val-D-Hyi-L-Val-L-Hyi-(D-Val-L-Hyi-L-Val-D-+ ++Hyi)2-], C60H102N6O18), which crystallized from acetone with two solvent molecules. The crystals are trigonal, space group P32, number of molecules per unit cell Z = 3, cell parameters a = b = 15.2085 (8) A, c = 29.3250 (9) A, gamma = 120 degrees. The standard (R) and weighted (Rw) reliability factors after refinement of the atomic coordinates for C, N, and O atoms in the anisotropic thermal motion approximation, allowing for isotropic H atom contributions, were 0.070 and 0.082, respectively. The molecule adopts a distorted bracelet structure which is stabilized by six N-H ... O = C 4----1 type intramolecular hydrogen bonds. The side chains predominantly occupy external pseudoaxial positions relative to the cylindrical axis of the molecule. In contrast to meso-valinomycin, only four of the six Val carbonyl oxygen atoms are directed inwards to form a coordination centre for the molecule, and the carbonyl oxygen atoms of residues D-Val1 and L-Val3 are twisted outward and point away from the centre of the molecule. Although the analogue has a partially formed ion-binding center, it is inaccessible because the hydrophobic isopropyl groups of the D-Hyi2 and L-Hyi4 residues screen the molecular cavity on both sides.

C27H40O4, Mr = 428.6, orthorhombic, P2(1)2(1)2(1), a = 9.821(3), b = 25.766(6), c = 9.802(3) A, V = 2480(2) A3, Z = 4, Dx = 1.15 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 0.70 cm-1, F(000) = 936, T = 295 K, final R = 0.063 for 2778 observed reflections. The A ring assumes a normal 1 alpha,2 beta-half-chair conformation. The progesterone side chain has a conformation typical of 17 alpha-ester steroids; the C(16)-C(17)-C(20)-O(20) torsion angle is -17.9(5) degrees.

The X-ray crystal structure of 4-methoxy-4-cholesten-3-one, C28H46O2, has been determined. Final agreement factors wereR=0.057 andR w =0.057 for 2912 reflections. TheA ring has a sofa-half-chair conformation, and the C4 side chain is turned under the steroid skeleton. The cholesterol side chain is fully extended, with agauche, trans conformation of the terminal C26 and C27 methyl groups.

Crystal structures of Norwalk virus polymerase bound to an RNA primer-template duplex and either the natural substrate CTP or the inhibitor 5-nitrocytidine triphosphate have been determined to 1.8A resolution. These structures reveal a closed conformation of the polymerase that differs significantly from previously determined open structures of calicivirus and picornavirus polymerases. These closed complexes are trapped immediately prior to the nucleotidyl transfer reaction, with the triphosphate group of the nucleotide bound to two manganese ions at the active site, poised for reaction to the 3'-hydroxyl group of the RNA primer. The positioning of the 5-nitrocytidine triphosphate nitro group between the alpha-phosphate and the 3'-hydroxyl group of the primer suggests a novel, general approach for the design of antiviral compounds mimicking natural nucleosides and nucleotides.

The structure of the title compound was determined by X-rays:M r =319.4,P212121,a=7.753(3),b=10.566(8),c=20.997(10) A,Z=4 andD x =1.171 M gm−3. FinalR=0.042 (R w =0.041) for 1814 unique reflections. The water molecule is the hydrogen donor to O3 and O17 and an hydrogen acceptor from the O17 hydroxyl group.

The crystal structure of 18-cyanoprogesterone was determined by X-ray diffraction methods:P212121a=7.436(2),b=11.322(2),c=22.642(2) A. The structure was solved usingShelx-86. Final conventionalR=0.054.Rw=0.051 for 1841 reflections. TheA ring has an intermediate sofa-half-chair conformation with asymmetry parameters ΔCs/1=11.0, ΔC23,4=14.9. The steroid skeleton exhibits a flattening of theA ring relative to the rest of the molecule. The progesterone side chain has a typical conformation, and the C16-C17-C20-O20 torsion angle is −19.0(6)°.

The crystal and molecular structure of 21-fluoro-4,9(ll)-pregnadiene-3,20-dion-17a-yl acetate has been determined by X-ray diffraction methods;P212121,a=15.827(4),b=16.912(4),c=7.513(2) A,Z=4;R=0.062, (R w =0.065) for 2028 unique observed reflections. The progesterone side chain has an unusual conformation; the C16-C17-C20-O20 torsion angle is 173.1(4)°. Molecular mechanics calculations suggest that this conformation may be cuased by 17α-acetoxy substituent and the additional double bond between C9 and C11.

The structure of the title compound, C21H30O3, was determined by X-rays.Mr=330.5, orthorhombic,P212121,a=8.4451(9),b=10.7074(8),c=20.1525(40) A,V=1822(8) A3,Z=4,Dx=1.205 mg m−3. CuKα radiation (1.54184 A),μ(CuKα)=5.85 cm−1,F(000)=720. FinalR=0.054Rw=0.049 for 1774 unique reflections. The structure was solved usingMultan. TheA ring adopts an intermediate sofa-half-chair conformation and is bent toward theα face of the steroid skeleton. RingsB andC have typical chair conformations, and theD ring has a slightly distorted half-chair conformation. The progesterone side chain has a typical conformation, and the C16-C17-C20-O20 torsion angle is −17.9°. An intermolecular hydrogen bond is formed between the hydroxyl group and the progesterone side chain.

The crystal structure of 4-thioethyl-4-cholesten-3-one, C29H48OS, has been determined by X-ray methods. The compound is orthorhombic:P212121,a=7.787(2),b=12.586(4),c=27.960(6) A,V=2740(3) A3,M r =444.8,Z=4,D x =1.08 Mg m−3, CuKα radiation (λ=1.5418 A),μ=11.2 cm−1,F(000)=984. FinalR=0.073 andR w =0.057 for 1562 reflections. A comparison with other 4-substituted 4-en-3-ore steroids suggests that theA ring conformation and its relative orientation can be influenced by the thioethyl substituent. The C4 side chain is turned under the steroid skeleton. The cholesterol side chain is fully extended, with atrans, +gauche conformation of the terminal C26 and C27 methyl groups.

Diffraction data have been collected from a crystal of Thermotoga maritima mannitol dehydrogenase at the Canadian Light Source. The crystal diffracted to 3.3 A resolution and belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 83.43, b = 120.61, c = 145.76 A. The structure is likely to be solved by molecular replacement.

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).

Recent additions to the Canadian Macromolecular Crystallography Facility have expanded the capabilities of its bending magnet beamline. It is now possible to perform x-ray absorption spectroscopy (XAS) on crystals. A wide range of biologically relevant metals can be further studied, supplementing diffraction data. XAS can be used to determine if metalloproteins are photoreducing during diffraction data collection. The geometries of metal complexes can also be inferred with near-edge and EXAFS data, often more accurately than crystallography. CMCF-BM can be employed to do the abovementioned techniques on powder and solution samples that contain a metal of interest. One XAS-based technique that shows promise is single crystal plane polarized EXAFS. This technique combines crystallographic data with the findings from XAS to yield a high resolution three dimensional atomic model. More recently a number of the procedural steps required for the acquisition of XAS-based data have been automated in the MxDC software suite. These changes to data collection make it easier for users new to these disciplines to run the XAS-based experiments. By having the necessary equipment to do XAS at a protein crystallography facility, researchers who may not have had the opportunity delve into the field of XAS now can do so with minimal risk in terms of materials, funds and time.

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/).

The Canadian Macromolecular Crystallography Facility (CMCF) operates two crystallography beamlines, 08ID-1 and 08B1-1 (http://cmcf.lightsource.ca), at the Canadian Light Source (CLS). Normal access is through a traditional peer review process but commercial access is also welcome. Users apply for beamtime against their active proposals and may collect data in person or via remote access (Remote Control or Mail-In). Remote Control allows users to control the beamlines remotely from home institutions. Additionally, users with the highest peer review scores have the option of Mail-In beamtime, where data are collected by CMCF staff according to investigators' instructions. This method has proven very effective for several reasons. Data are collected by trained personnel experienced with the beamlines, resulting in high quality data. Travel expenses are eliminated. Data are collected around regular user shifts using the most appropriate beamline, reducing wasted beamtime and providing flexibility. The process is made extremely efficient when integrated with MxLIVE, the CMCF Laboratory Information Management System, since images can be viewed and output files downloaded almost immediately after data have been collected for the user. Four Mail-In shifts per week are typically supported during normal operations. In 2013 alone, over 430 datasets were collected for more than 20 investigators across Canada. At least 12 peer-reviewed articles appeared in 2013 containing Mail-In data, many in high-impact journals. Several of these results will be discussed.

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.

The type two secretion system is a large, trans-envelope apparatus that secretes toxins across the outer membrane of many Gram-negative bacteria. In Aeromonas hydrophila, ExeA interacts with peptidoglycan and forms a heteromultimeric complex with ExeB that is required for assembly of the ExeD secretin of the secretion system in the outer membrane. While the peptidoglycan-ExeAB (PG-AB) complex is required for ExeD assembly, the assembly mechanism remains unresolved. We analyzed protein-protein interactions to address the hypothesis that ExeD assembly in the outer membrane requires direct interaction with the PG-AB complex. Yeast and bacterial two hybrid analyses demonstrated an interaction between the periplasmic domains of ExeB and ExeD. Two-codon insertion mutagenesis of exeD disrupted lipase secretion, and immunoblotting of whole cells demonstrated significantly reduced secretin in mutant cells. Mapping of the two-codon insertions and deletion analysis showed that the ExeB-ExeD interaction involves the N0 and N1 subdomains of ExeD. Rotational anisotropy using the purified periplasmic domains of ExeB and ExeD determined that the apparent dissociation constant of the interaction is 1.19±0.16 µM. These results contribute important support for a putative mechanism by which the PG-AB complex facilitates assembly of ExeD through direct interaction between ExeB and ExeD. Furthermore, our results provide novel insight into the assembly function of ExeB that may contribute to elucidating the role of homologous proteins in secretion of toxins from other Gram negative pathogens.

C27H40O7, M(r) = 476.61, monoclinic, P2(1), a = 17.440 (5), b = 13.267 (1), c = 12.168 (2) A, beta = 110.49 (8) degrees, V = 2637.3 (9) A3, Z = 4, Dx = 1.20 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 7.04 cm-1, F(000) = 1032, T = 293 K, R = 0.048, wR = 0.068 for 5590 observed reflections with (Fo)2 > 2 sigma [(Fo)2]. The structure contains two crystallographically independent molecules in the asymmetric unit that have almost identical geometry. Rings A, B and C have chair conformations and the D ring assumes a half-chair conformation in both molecules. The progesterone side chain has a conformation typical for other 17 alpha-ester steroids; the C(16)--C(17)--C(20--O(20) torsion angles are -18.2 (5) and -15.0 (4) degrees for the first and the second molecule respectively.

C 27 H 44 O cristallise dans P2 1 2 1 2 1 avec a=11,109, b=11,213, c=19,104 A, Z=4; affinement jusqu'a R=0,069. Les cycles A et C possedent une conformation chaise, tandis que les cycles B et D ont une conformation demi-chaise. La chaine cholesterol est tout a fait etendue avec une conformation gauche, trans des carbones C 26 et C 27 terminaux des groupes methyl

C 27 H 44 O cristallise dans P2 1 2 1 2 1 avec a=10,326, b=10,460, c=22,331 A, Z=4; affinement jusqu'a R=0,060. Le cycle A se trouve dans une conformation chaine deformee, le cycle B dans une conformation moyenne soja=demi chaise, les cycles C et D possedent respectivement des conformations chaine et enveloppe. Dans la chaine cholesterol, totalement etendue, les carbones terminaux C 26 et C 27 des groupes methyl sont dans une conformation-gauche, trans

C24H30O4, Mr = 382.5, orthorhombic, P2(1)2(1)2(1), a = 13.091 (2), b = 19.711 (1), c = 8.242 (1) A, V = 2126.7 (5) A3, Z = 4, Dx = 1.195 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu(Cu K alpha) = 0.56 mm-1, F(000) = 824, T = 295 K. Final R = 0.045 for 2446 unique reflections. The planar A ring is bent relative to the rest of the steroid skeleton. The B ring has a typical chair conformation and the C and D rings assume 13 beta,14 alpha-half-chair and 13 beta-envelope conformations, respectively. The conformation of the progesterone side chain is similar to the conformation observed in other 17 alpha-ester pregnanes: C16-C17-C20-O20 torsion angle -27.4 (3) degrees.

The Canadian Macromolecular Crystallography Facility (CMCF) 08ID-1 beamline at the Canadian Light Source (CLS) is in the later stages of commissioning. The photon source is a small-gap in-vacuum undulator (SGU), which was designed in-house with a support structure and vacuum chamber from RMP of Italy. The undulator magnets were shimmed at the CLS and the SGU was installed in the 2.9 GeV storage ring. The storage ring has had currents up to 300 mA safely injected and stored since its first light in the diagnostic beamline in December of 2003. At these storage ring currents, the 7th harmonic of the SGU will yield a photon flux on the sample at the endstation on the order of ∼ 5 × 10 12 at 12 keV. The overall design of the beamline includes white beam slits, indirectly cryo-cooled first crystal of the DCM and sagittally focusing second crystal, and vertically focussing ULE mirror. The endstation of the beamline is innovative and robust, and was manufactured by ACCEL according to CLS specifications. The beamline controls, are being developed based on EPICS, and complemented with a user-friendly interface. The scientific goal of the 08ID-1 beamline is to operate a protein crystallography MAD beamline suitable for studying small crystals and crystals with large unit cells.

The crystal structure of a Ca(2+)-binding domain (dVI) of rat m-calpain has been determined at 2.3 A resolution, both with and without bound Ca2+. The structures reveal a unique fold incorporating five EF-hand motifs per monomer, three of which bind calcium at physiological calcium concentrations, with one showing a novel EF-hand coordination pattern. This investigation gives us a first view of the calcium-induced conformational changes, and consequently an insight into the mechanism of calcium induced activation in calpain. The crystal structures reveal a dVI homodimer which provides a preliminary model for the subunit dimerization in calpain.

The recent development of undulator in-vacuum technology has allowed intermediate energy storage rings, such the Canadian Light Source (CLS), to build high brilliance protein crystallography beamlines. The Canadian Macromolecular Crystallography Facility (CMCF) beamline 08ID-1 is the first small period (20 mm) hybrid small-gap in-vacuum undulator (SGU) to be employed at the CLS as a source of high harmonic, high brightness radiation (6.5 – 18 keV). The SGU was assembled and shimmed at the CLS Magnetic Mapping Facility. It is installed in the upstream part of straight section 8 of the CLS ring and chicaned inboard by 0.75 mrad. The downstream half of this section is reserved for future development. To achieve a maximum undulator field (B0) in conjunction with low sensitivity to radiation damage, a hybrid layout for the undulator is used with Sm2Co17 permanent magnets sandwiched between Vanadium Permendur ferromagnetic poles. To date, operations in the 6.5 – 18 keV energy range have been achieved using the 3rd to 9th harmonics, with gap sizes of 5.9 – 8.6 mm. Gaps smaller than 5.9 mm are not being used since in the 5.0 – 5.9 mm range the rms phase errors are larger than 2.5° and lower harmonics at larger gaps are being used instead. The goal of the present study is to measure the output spectrum for various gap sizes and compare these with theoretical expectations calculated from the magnetic characteristics of the undulator measured at the CLS Magnetic Mapping Facility. The 08ID-1 beamline now has several years of successful operation as a highly competitive, high brilliance beamline.

In this review we summarize some aspects of the enantiopreference of the lipase from Candida rugosa following structural analysis of complexes of this lipase with two enantiomers of an analog of a tetrahedral intermediate in the hydrolysis of simple esters. The analysis of the molecular basis of the enantiomeric differentiation suggests that these results can be generalized to a large class of lipases and esterases. We also summarize our experiments on identification of the key regions in the lipases from Geotrichum candidum lipase responsible for differentiation between fatty acyl chains.Key words: lipases, stereoselectivity, three-dimensional structure, conformational rearrangement.

Candida rugosa lipase belongs to a large lipase/esterase family of evolutionarily related hydrolytic enzymes identified on the basis of their amino acid homology (Krejci et al., 1991; Gentry et al., 1991; Cygler et al., 1993). Other members of this family include acetyl- and butyrylcholinesterases, carboxylesterases, cholesterol esterases, etc. The catalytic apparatus of these enzymes is composed of a Ser-His-Glu/Asp triad. Apart from the hydrolytic enzymes there are also other proteins with domains that clearly belong to this family but are devoid of the hydrolytic activity, eg. neurotactin, thyroglobulin, etc. The amino acid identity within this family varies from ∼16%, for distantly related proteins, to 97% and a number of subfamilies are clearly distinguishable (Cygler et al., 1993). To date, the crystal structures of three of these proteins have been determined: Torpedo californica acetylcholinesterase (AChE, Sussman et al., 1991), Geotrichum candidum lipase (GCL, Schrag et al., 1991) and Candida rugosa lipase (CRL, Grochulski et al., 1993). These three enzymes display great similarities in their three-dimensional structures and provide prototypic models for other members of this large family. They belong to the α/β hydrolase fold superfamily (Ollis et al., 1992). The two lipases, which share ∼40% sequence identity, have also more similar structures. Approximately 90% of their Ca atoms superimpose with a root-mean-square (rms) deviation of 1.4A. Comparison of GCL and TcAChE (∼25% identity) shows that ∼75% of their Ca atoms can be superimposed with a 1.9A rms, including the catalytic apparatus composed of a Ser-His-Glu triad. Yet despite their significant structural similarity TcAChE and GCL/CRL hydrolyze very different substrates. While the lipases break down water insoluble triglycerides, the acetylcholinesterase hydrolyzes the water soluble neurotransmitter, acetylcholine.

A trypsin-activated CrylA(a) protein from Bacillus thuringiensis has been purified and crystallized. Crystals belong to orthorhombic space group P2(1)2(1)2(1), with cell dimensions a = 53.3, b = 111.3 and c = 154.7 A. The crystals diffract to at least 2.2 angstrum resolution and are suitable for X-ray structural analysis. They contain a single molecule in the asymmetric unit.

The structures of Candida rugosa lipase-inhibitor complexes demonstrate that the scissile fatty acyl chain is bound in a narrow, hydrophobic tunnel which is unique among lipases studied to date. Modeling of triglyceride binding suggests that the bound lipid must adopt a "tuning fork" conformation. The complexes, analogs of tetrahedral intermediates of the acylation and deacylation steps of the reaction pathway, localize the components of the oxyanion hole and define the stereochemistry of ester hydrolysis. Comparison with other lipases suggests that the positioning of the scissile fatty acyl chain and ester bond and the stereochemistry of hydrolysis are the same in all lipases which share the alpha/beta-hydrolase fold.

The crystal structure of a synthetic analogue of valinomycin, cyclo[-(D-Val-L-Hyi-L-Val-D-Hyi)2-] (octa-meso-valinomycin) (I) (C40H68N4O12.1.5.C4H8O2, M(r) = 937.01 + 88.10), has been determined. Crystals grown from dioxane are monoclinic, space group P2(1)/a, with cell parameters a = 21.487 (8), b = 16.836 (5), c = 16.089 (4) A, beta = 111.70 (4), and Z = 4. The atomic coordinates for nonhydrogen atoms were refined in the anisotropic thermal motion approximation. H atom positions were included in the structure factor calculations at their geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.11 and 0.13, respectively. The conformation of the depsipeptide crystallized from dioxane is different from that crystallized from chloroform (II). The molecule adopts a rectangular shape with two type IV beta-turns containing a hydrogen bond and possesses pseudorotational symmetry. The side chains are located on the molecular periphery. The orientation of the carbonyl groups of the molecule is not conducive for efficient metal-ion coordination and in the observed conformation cannot behave as an ionophore. In the crystal the molecules form infinite chains parallel to the c axis, and are stabilized by two intermolecular hydrogen bonds that are shorter and have better geometry than the intramolecular hydrogen bonds. A phi/psi plot for dodecadepsipeptides with a (DLLD)3 sequence has well-defined areas for Val and Hyi residues only in cases when the crystals have been grown from nonpolar or medium-polar solvents. The phi/psi plot for octadepsipeptides crystallized from chloroform (II) shows this behavior also.(ABSTRACT TRUNCATED AT 250 WORDS)

C24H30O4, Mr = 382.5, orthorhombic, P2(1)2(1)2(1), a = 13.091 (2), b = 19.711 (1), c = 8.242 (1) A, V = 2126.7 (5) A3, Z = 4, Dx = 1.195 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu(Cu K alpha) = 0.56 mm-1, F(000) = 824, T = 295 K. Final R = 0.045 for 2446 unique reflections. The planar A ring is bent relative to the rest of the steroid skeleton. The B ring has a typical chair conformation and the C and D rings assume 13 beta,14 alpha-half-chair and 13 beta-envelope conformations, respectively. The conformation of the progesterone side chain is similar to the conformation observed in other 17 alpha-ester pregnanes: C16-C17-C20-O20 torsion angle -27.4 (3) degrees.

C22H30O2 (1), Mr = 326.47, orthorhombic, P2(1)2(1)2(1), a = 9.662 (3), b = 23.32 (7), c = 8.167 (2) A, V = 1840.3 (4) A3, Z = 4, Dx = 1.178 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 5.34 cm-1, F(000) = 712, T = 293 K, R = 0.035, wR = 0.044, S = 1.954 for 2147 unique observed reflections with Fo greater than 2 sigma(Fo). Rings B and C have chair conformations, the A ring assumes an intermediate sofa-half-chair conformation, and the D ring is in the half-chair conformation. The progesterone side chain has the same conformation as observed in 81 steroids; the C16-C17-C20-O20 torsion angle is -18.9 (3) degrees; the C4-C5-C6-C6M torsion angle is -48.6 degrees.

C22H30O2 (1), Mr = 326.47, orthorhombic, P2(1)2(1)2(1), a = 9.662 (3), b = 23.32 (7), c = 8.167 (2) A, V = 1840.3 (4) A3, Z = 4, Dx = 1.178 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 5.34 cm-1, F(000) = 712, T = 293 K, R = 0.035, wR = 0.044, S = 1.954 for 2147 unique observed reflections with Fo greater than 2 sigma(Fo). Rings B and C have chair conformations, the A ring assumes an intermediate sofa-half-chair conformation, and the D ring is in the half-chair conformation. The progesterone side chain has the same conformation as observed in 81 steroids; the C16-C17-C20-O20 torsion angle is -18.9 (3) degrees; the C4-C5-C6-C6M torsion angle is -48.6 degrees.

The Canadian Macromolecular Crystallography Facility has more than sixty participating protein crystallographers, located across Canada, will eventually consist of three beamlines; two insertion devices beamlines and one bending magnet beamline [1]. The first insertion device beamline (08ID-1) was intended to be a highly efficient and flexible, capable of satisfying the requirements of the most challenging and diverse crystallographic experiments, i.e. physically small crystals with large unit cell dimensions. The recently funded bending magnet 08B1 beamline has been designed to be dedicated to highthroughput data collection capable of being accessed remotely. The third, an undulator based 08ID-2 beamline, is envisioned to have micro-focusing capabilities with some restrictions in energy range. The CMCF 08ID-1 beamline has been built and is now being commissioned. The beamline is illuminated by a small-gap in-vacuum hybrid undulator (SGU), located in the upstream half of the straight section, and chicaned inboard by 0.75 mrad. The downstream half of this section is reserved for the 08ID-2 beamline SGU. The overall design of the beamline contains white beam slits (WBS), a double crystal monochromator (DCM) equipped with an indirectly cryocooled first crystal and a sagittally-focusing second crystal followed by a vertically focussing mirror (VFM). The beamline is completed with an innovative and very robust endstation, including the MarMosaic225 CCD X-ray detector. Most of the beamline components were manufactured by ACCEL Instruments GmbH (Germany). The beamline controls, similarly for the CLS facility, are being developed based on the EPICS platform. The beamline is equipped with a Rontek Spectrometer System (XFLASH 101A) for carrying out X-ray absorption near edge structure spectroscopy (XANES) for multiwavelength anomalous diffraction (MAD) experiments, and X-ray fluorescence (XRF) for the detection of metal atoms in protein derivative crystals. The beamline will be equipped with a robotic cryogenic sample changer that is based on the SSRL design (SAM). At the meeting we will present recent results of experiments performed at the CMCF 08ID-1 beamline. The CLS is supported by NSERC, NRC, CIHR and the University of Saskatchewan..

The crystal structure of progesterone hydroquinone monohydrate was determined by means of X-ray diffraction methods:Mr=442.6, orthorhombic,P212121,a=14.680(2),b=22.725(3),c=7.334(1) A,Va=2446.6(6) A3,Z=4,Dx=1.190 M gm−3, MoKα radiation\(\left( {\bar \lambda = 0.7107{\AA}} \right)\),μ(MoKα)=0.75 cm−1,F(000)=948. The structure was solved usingMultan;R=0.059,Rw=0.059 for 2736 reflections. This progesterone molecule has the most flattenedA ring, relative to the rest of the skeleton, of all progesterone molecules studied so far. Steroid, hydroquinone, and water molecules form, by means of hydrogen bonds, two parallel chains connected with each other by hydrogen bonds.

The X-ray crystal structure of 6β-acetoxyprogesterone, C23H32O4, has been determined. This compound crystallizes in space groupP212121 witha=13.195(3),b=15.035(4),c=10.705(3) A,V=2139.8(9) A3,Mr=372.5,Z=4,Dx=1.156g cm−3; MoKα radiation (λ=0.7107 A),μ=0.72 cm−1,F(000)=808;R=0.069, andRw=0.052 for 1292 reflections. RingA adopts a normal 1α,2β-half-chair conformation. The side chain is typical for a 20-ketosteroid conformation.

The structure of the title compound, C19H26O2·H2O, was determined by X-rays.Mr=304.4, space groupP21,a=10.3113(6),b=10.3978(21),c=7.8710(9) A, γ=89.527(9)°,Vc=844(1) A3,Z=2,Dx=1.194 Mg m−3. CuKα radiation\(\left( {\bar \lambda = 1.54184{\AA}} \right)\),μ(CuKα)=5.9 cm−,F(000)=332. FinalR factor=0.046 (Rw=0.047) for 1002 unique reflections. The structure was solved usingMultan. The water molecule is the hydrogen donor to O(3) and a hydrogen acceptor from the O(17) hydroxyl group. RingA is rather flat relative to the rest of the steroid backbone and the O(3)-plane distance is 1.99 A.

The crystal structure of 17β-hydroxy-4-pregnen-20-yn-3-one, C21H28O2, was determined by means of X-ray diffraction methods.Mr=312.5, space groupP21,a=6.493(1),b=21.065(3),c=6.478(1) A,β=105.97(1)°,Vc=851.9(3) A3,Z=2,Dx=1.22 Mg m−3, CuKα radiation (λ=1.54184 A),μ(CuKα)=5.5 cm−1,F(000)=340. The structure was solved withMultan; final conventionalR=0.032 (Rw=0.032) for 1803 reflections. The molecule studied (I) has an overall conformation almost identical to 19-norethindrone (II), although ringA of molecule (I) is slightly more bent toward theα direction of the steroid skeleton in comparison with molecule (II).

The crystal structure of 17α-methyltestosterone hemihydrate, C20H30O2·1/2H2O, has been determined:M r =312.5, space groupP21212121,a=6.374(2),b=12.807(2),c=43.398(5)A,V c =3543(2)A3,Z=8,D x =1.172 mg−3, CuKα radiation ( $$\bar \lambda $$ = 1.54184 A),μ(CuKα)=5.5 cm−1,F(000)=1376. The structure was solved usingMultan. The final conventionalR=0.053 (R w =0.052) for 3634 reflections. The structure contains two crystallographically independent molecules in the asymmetric part of the unit cell that have almost identical geometry.

The crystal and molecular structure of 9α, 11β-dichloro-4-pregnene-3,20-dione, C21H28O2C12, has been determined:Mr=383.4,P31,a=7.358(2),c=30.137(20) A,Vc=1413(2)A3,Z=3,Dx=1.35 g cm−3, λ(MoKα)=0.71073A,μ=3.6 cm−1,F(000)=612,T≈80K,R=0.060,Rw=0.052 for 2376 unique observed reflections. The steroid skeleton exhibits a flattening of theA ring relative to the rest of the molecule caused by halogen substituents. The title compound has a very high relative binding affinity for the rabbit uterine progesterone receptor. The high binding affinity may result from the flattening of theA ring relative to the rest of the steroid skeleton.

The crystal and molecular structure of 3α,12β-dihydroxy-2β-morpholino-5α-pregnan-20-one, C25H41O4N, has been determined:M r =419.6,P21,a=13.5778(8),b=14.4340(8),c=5.8943(5) A,β=94.32(1)°,V c =1151.9(3) A3,Z=2,D x =1.21 g cm−3, $$\bar \lambda $$ (CuKα) = 1.5418 A, μ=5.6 cm−1,F(000)=460,R=0.039,R w =0.040 for 2421 unique observed reflections. All six-membered rings have chair conformations, and theD ring has a 13β-envelope conformation. The progesterone side chain has an unusual conformation, and the C16-C17-C20-O20 torsion angle, which defines the conformation, is −152.6(3)°. The unusual conformation seems to be forced by the intramolecular hydrogen bond between the hydroxyl group at C12 and the O20 atom from the side-chain.

The crystal and molecular structure of the equimolar molecular complex of semicarbazide with nitric acid has been determinated by X-ray diffraction method. The crystals are orthorhombic, space group P2t2t2t with cell parameters a = 12.85(1), b = 8.62(1), c = 4.76(3)A and four formal molecules per unit cell. The structure was solved by direct methods and refined by full-matrix least-squares to the final R = 0,161 for 414 visually estimated intensities collected on a Weissenberg camera. In the crystals both the semicarbazide and nitric acid molecules exist in ionic form [H2NCO NHNH3 +·NO3 −] and intermolecular hydrogen bonds are formed.