Crystallization and preliminary X-ray diffraction studies of d(ACGTAGCTACGT)2:[actinomycin D, (echinomycin)2] and d(ACGTAGCTACGT)2: [actinomycin D, (triostin A)2] complexes

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0907444999016790.A DNA-multiple drug complex, d(ACGTAGCTACGT)2:[actinomycin D, (echinomycin)2] has been crystallized. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 85.6, b = 72.8, c = 56.6 Å, [beta] = 101.5° at 93 K and Z = 8. The crystal diffracted to 3.0 Å resolution along the DNA fiber axis and to 3.5 Å resolution in other directions. The Patterson maps indicate that all complexes in the crystal are oriented along their helical axes in the [10\bar 1] direction

A neutron diffraction study of bis(cyclopentadienyl)(methyl)(methylene)tantalum(V) at 15 K

This is the published version. Copyright 1988 by International Union of Crystallography.[Ta(C5H5)2(CH2)(CH3)], Mr = 340-206, monoclinic, Pljc, a = 6-492 (1), 6 = 11-539 (2), c= 15-174(2) A, P = 117-33 (2)°, V= 1009-8 (3) A3, Z = 4, Dx = 2-238 Mg m-3, neutrons, X = 1-1617(2) A, // = 0-2473 mm"1, F(000) = 122-68 fm. T= 15(0-5) K. The structure has been refined based on 2446 reflections to yield an unweighted R value based on F2 of 0-043. The molecule has approximate Cs point symmetry. All C—H bond distances have been determined with e.s.d.'s < 0-003 A. The mean C - H distance [ 1 - 091 (4) A] in the methyl group is slightly longer than that in the methylene group [1-081 (5) A], while therespective H-C-H angles are 107-8(3)° (methyl, mean value) and 112-3(2)° (methylene). The Ta-C methylene distance is 2-039 (1) A, corresponding to a full double bond, 0-229 (1) A shorter than the Ta-C methyl distance of 2-268 (1) A. The cyclopentadienyl rings have an envelope geometry and exhibit small systematic deviations of the C - C bond distances from the mean value of 1-419 A; by contrast, the ring C—H distances are equivalent, with a mean value of 1-084(1) A

A combined isotropic and multiple s-shell anisotropic scaling method for multiple data sets

This is the published version. Copyright 1992 International Union of Crystallography.A method to improve the scaling of multiple intensity data sets is presented. A general scaling function K(x, s), which uses the direction cosine of the diffraction vector (x) and (sin [theta])/[lambda] (s) as scaling parameters, is developed by combining an isotropic scaling function, K(s) = A exp (Bs2), and a multiple s-shell anisotropic scaling function, K(x)s = ([Sigma] [Sigma] cijxij)s. This combined scaling function can greatly reduce the systematic differences in intensities among multiple data sets measured independently. This scaling method for the multiple data sets consists of three steps. In the first step, the individual isotropic scaling functions, K(s), are determined by an indirect least-squares method. Then the weighted mean intensity, , is calculated by applying the K(s) to the individual data sets. In the second step, the data in each data set are divided equally into 20 thin shells of (sin [theta])/[lambda] (s). The anisotropic scaling functions, K(x)s, of each s shell are determined by using the weighted mean intensity, , obtained in the first step as the target quantity in a least-squares minimization, i.e. [Sigma] wi{i - K(x)s[K(s)Ii]}2. In the final step, the new weighted mean intensity, , is calculated by applying the combined scaling function, K(x, s) = K(s)K(x)s, to the individual data sets. The new multiple s-shell anisotropic scaling functions are determined using the new weighted mean intensity, , as the target quantity in another least-squares minimization. By repeating this procedure three to five times, the least-squares minimization will converge. The method was successfully used to scale and merge 27 sets of S-adenosylmethionine synthetase data into a single data set. It was also used to scale the isomorphous replacement data sets of the enzyme

A simple method of absorption and decay correction in intensities measured by area-detector X-ray diffractometer

This is the published version. Copyright 1987 International Union of Crystallography.A simple numerical method has been developed to correct for absorption and decay effects in the intensities measured by area-detector X-ray diffractometers. Application of this method improves not only the internal consistency of symmetry-equivalent reflections, but also the agreement between the two independent data sets

Isonicotinic acid

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0567740876006754.See article for abstract

An Error in Space Group P6(2)22 in International Tables for X-ray Crystallography

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0108767390002148.No abstract is available for this item

Neutron diffraction study of quinolinic acid recrystallized from D2O: evaluation of temperature and isotope effects in the structure

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0567740879008591.The structure of quinolinic acid recrystallized from D2 0 (2,3-pyridinedicarboxylic acid; C7H3D2N04 ) has been refined based on neutron diffraction data measured at four temperatures: 35, 80, 100 and 298 K. The principal temperature dependence in cell constants is observed for the b axis, which is perpendicular to the molecular planes. The refined thermal parameters have been extrapolated by a least-squares procedure, to yield values for T = 0 K which provide estimates of the combined effects of static disorder and zero-point motion. The D atom shifts toward the midpoint of the short intramolecular 0 - - - 0 hydrogen bond when the crystal is cooled, just as was found in an earlier study to occur for the H atom in the undeuterated material. At 100 and 298 K, the D atom is displaced significantly further from the bond midpoint than is the H atom at the same temperature. The magnitude of this isotope effect appears to be independent of temperature. The exchangeable protons in the crystal have not been completely replaced by D; refinement of the D scattering lengths indicates the presence of approximately 2-7% H attached to N(l) and 4-4% H in the short hydrogen bond.Research carried out at Brookhaven National Laboratory under contract with the US Department of Energy and supported by its Division of Basic Energy Sciences

The crystal and molecular structure of 1,1'-ferrocenedicarboxylic acid (triclinic modification): neutron and X-ray diffraction studies at 78 K and 298 K

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0567740879010906

A study of the charge density in putrescine diphosphate at 85 K

This is the publisher's version, also available electronically from http://scripts.iucr.org/cgi-bin/paper?S0567740879005082.See article for abstract