Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “data resolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed1991

Three-dimensional high-resolution volume rendering (HRVR) of computed tomography data: applications to otolaryngology-head and neck surgery.

Conventional computed tomographic display formats are not optimal for demonstrating three-dimensional anatomic relationships. In otolaryngology--head and neck surgery these critical relationships are often highly complex, and their complete understanding is essential to a successful surgical outcome. A new computer-generated image display format, high-resolution volume rendering (HRVR), facilities the understanding of these critical anatomic relationships by transforming conventional imaging data into clinically relevant 3-D images. Unlike many other 3-D reconstruction algorithms, HRVR suffers minimal data loss in the conversion process, which in turn provides for superior image resolution. This better allows the application of 3-D technology to small or complicated anatomic structures such as those frequently encountered in otolaryngology--head and neck surgery. Advances in computer-controlled manipulations that further enhance the evaluation of desired pathologic features have been achieved. This pilot study contains representative clinical cases chosen to illustrate the potential utility of HRVR in otolaryngology--head and neck surgery. The authors believe HRVR images will enhance the surgeon's understanding of the 3-D anatomic relationships that exist between critical pathologic features and surrounding vital structures.

Aged↗
PubMed2004

Crystallization and X-ray diffraction analyses of the outer membrane pyochelin receptor FptA from Pseudomonas aeruginosa.

FptA, the pyochelin outer membrane receptor from Pseudomonas aeruginosa, is a siderophore receptor involved in iron uptake when the bacterium grows under iron limitation. Two crystal forms of the FptA-pyochelin complex were obtained under different crystallization conditions. They belong to space groups P1 and P2(1)2(1)2(1) and data sets were collected for both crystal forms. The triclinic crystals diffract to 3.2 A resolution and the orthorhombic crystals show a 1.9 A resolution limit. A data set at the peak of the iron K edge was also collected at 3.1 A resolution.

Bacterial Outer Membrane Proteins↗
PubMed2005

Entropy minimization and spectral dissimilarity curve resolution technique applied to nuclear magnetic resonance data sets.

The use of entropy minimization and spectral dissimilarity is applied to three nuclear magnetic resonance (NMR) data sets. The data sets contain 2, 2, and 3 observables each. It was found that without any a priori information the sets of pure component spectra underlying the NMR spectroscopic observations could be extracted. These successful spectral resolutions suggest that a combined entropy minimization and spectral dissimilarity approach can be further developed for even larger NMR data sets containing a larger number of observables. Brief comparison to DECRA and PMF curve resolution results is also presented.

Journal Article↗
PubMed1996

The crystal structure of lipase II from Rhizopus niveus at 2.2 A resolution.

The crystal and molecular structure of Lipase II from Rhizopus niveus was analyzed using X-ray single crystal diffraction data at a resolution of 2.2 A. The structure was refined to an R-factor of 0.19 for all available data. This lipase was purified and crystallized as Lipase I, which contains two polypeptide chains combined through non-covalent interaction. However, during crystal growth, Lipase I was converted to Lipase II, which consists of a single polypeptide chain of 269 amino acid residues, by limited proteolysis. The structure of Lipase II shows a typical alpha/beta hydrolase fold containing the so-called nucleophilic elbow. The catalytic center of this enzyme is analogous to those of other neutral lipases and serine proteases. This catalytic center is sheltered by an alpha-helix lid, which appears in neutral lipases, opening the active site at the oil-water interface.

Amino Acid Sequence↗
PubMed2002

Long membrane helices and short loops predicted less accurately.

Low-resolution experiments suggest that most membrane helices span over 17-25 residues and that most loops between two helices are longer than 15 residues. Both constraints have been used explicitly in the development of prediction methods. Here, we compared the largest possible sequence-unique data sets from high- and low-resolution experiments. For the high-resolution data, we found that only half of the helices fall into the expected length interval and that half of the loops were shorter than 10 residues. We compared the accuracy of detecting short loops and long helices for 28 advanced and simple prediction methods: All methods predicted short loops less accurately than longer ones. In particular, loops shorter than 7 residues appeared to be very difficult to detect by current methods. Similarly, all methods tended to be more accurate for longer than for shorter helices. However, helices with more than 32 residues were predicted less accurately than all other helices. Our findings may suggest particular strategies for improving predictions of membrane helices.

Calcium-Transporting ATPases↗
PubMed2006

LAI inversion algorithm based on directional reflectance kernels.

Leaf area index (LAI) is an important ecological and environmental parameter. A new LAI algorithm is developed using the principles of ground LAI measurements based on canopy gap fraction. First, the relationship between LAI and gap fraction at various zenith angles is derived from the definition of LAI. Then, the directional gap fraction is acquired from a remote sensing bidirectional reflectance distribution function (BRDF) product. This acquisition is obtained by using a kernel driven model and a large-scale directional gap fraction algorithm. The algorithm has been applied to estimate a LAI distribution in China in mid-July 2002. The ground data acquired from two field experiments in Changbai Mountain and Qilian Mountain were used to validate the algorithm. To resolve the scale discrepancy between high resolution ground observations and low resolution remote sensing data, two TM images with a resolution approaching the size of ground plots were used to relate the coarse resolution LAI map to ground measurements. First, an empirical relationship between the measured LAI and a vegetation index was established. Next, a high resolution LAI map was generated using the relationship. The LAI value of a low resolution pixel was calculated from the area-weighted sum of high resolution LAIs composing the low resolution pixel. The results of this comparison showed that the inversion algorithm has an accuracy of 82%. Factors that may influence the accuracy are also discussed in this paper.

Algorithms↗
PubMed1979

Low resolution models of self-assembled histone fibers from X-ray diffraction studies.

X-ray diffraction data from self-assembled histone fibers are presented for three systems: H4, H3-H4, and the four core histones H2A, H2B, H3 and H4. These data have been obtained under conditions of high ionic strength and high protein concentration which are thought to promote histone conformation similar to that found in intact chromatin. The low angle equatorial scattering (R less than .05 A-1) is analysed, and, with additional constraints imposed by electron microscopy data, four low resolution fibrillar models are derived. Two features common to all the possible models are a maximum outer diameter of approximately 60 A and a subfibril diameter of approximately 25 A. It is the interference of the protein subfibrils across a central region of low electron density - a 10 A "hole" - which gives rise to the characteristic diffraction peak at 36 A. Possible relationships of the models of the histone fibers to the structure of the histone component of chromatin are suggested.

Histones↗
PubMed1999

Structure of oxalate-substituted diferric mare lactoferrin at 2.7 A resolution.

Lactoferrin binds two Fe(3+) and two CO(2-)(3) ions with high affinity. It can also bind other metal ions and anions. In order to determine the perturbations in the environments of the binding sites in the N and C lobes and elsewhere in the protein, the crystal structure of oxalate-substituted diferric mare lactoferrin has been determined at 2.7 A resolution. The final model has a crystallographic R factor of 21.3% for all data in the resolution range 17.0-2.7 A. The substitution of an oxalate anion does not perturb the overall structure of the protein, but produces several significant changes at the metal-binding and anion-binding sites. The binding of the oxalate anion is symmetrical in both the N and C lobes, unlike in diferric dioxalate human lactoferrin, where the oxalate anion binds the metal ion symmetrically in the C lobe and asymmetrically in the N lobe.

Animals↗
PubMed1990

X-ray crystal structure of the bovine alpha-chymotrypsin/eglin c complex at 2.6 A resolution.

The crystal structure of the molecular complex formed by bovine alpha-chymotrypsin and the recombinant serine proteinase inhibitor eglin c from Hirudo medicinalis has been solved using monoclinic crystals of the complex, reported previously. Four circle diffractometer data at 3.0 A resolution were employed to determine the structure by molecular replacement techniques. Bovine alpha-chymotrypsin alone was used as the search model; it allowed us to correctly orient and translate the enzyme in the unit cell and to obtain sufficient electron density for positioning the eglin c molecule. After independent rigid body refinement of the two complex components, the molecular model yielded a crystallographic R factor of 0.39. Five iterative cycles of restrained crystallographic refinement and model building were conducted, gradually increasing resolution. The current R factor at 2.6 A resolution (diffractometer data) is 0.18. The model includes 56 solvent molecules. Eglin c binds to bovine alpha-chymotrypsin in a manner consistent with other known serine proteinase/inhibitor complex structures. The reactive site loop shows the expected conformation for productive binding and is in tight contact with bovine alpha-chymotrypsin between subsites P3 and P'2; Leu 451 acts as the P1 residue, located in the primary specificity S1 site of the enzyme. Hydrogen bonds equivalent to those observed in complexes of trypsin(ogen) with the pancreatic basic- and secretory-inhibitors are found around the scissile peptide bond.

Animals↗
PubMed1995

Preliminary X-ray diffraction analysis of crystals of tomato aspermy virus (TAV).

Tomato aspermy virus (TAV) is a member of the T = 3 cucumovirus group, and the chrysanthemum strain (C-TAV) has been crystallized in a form suitable for X-ray structural analysis. The crystals, which grow in 14-17% ethanol at pH 8.5, are of orthorhombic space group I222 with unit cell dimensions of a = 295.1 A, b = 320.5 A, and c = 383.6 A. There are two T = 3 virus particles in the unit cell, which means that they must be centered at 0,0,0 and 1/2, 1/2, 1/2 with icosahedral 222 symmetry elements coincident with crystallographic symmetry operators. The asymmetric unit of the crystals, therefore, contains one quarter of a virus particle, or 45 capsid subunits. Native diffraction data to 4 A resolution have been collected using synchrotron radiation, though data appear to be present beyond that resolution.

Crystallization↗
PubMed1988

Crystallization and preliminary X-ray investigation reveals that tumor necrosis factor is a compact trimer furnished with 3-fold symmetry.

Crystals of recombinant human tumor necrosis factor produced by Escherichia coli have been obtained under different conditions. Crystals suitable for X-ray studies are produced by a vapor diffusion technique using sodium phosphate as both precipitant and buffer at pH 6.5. The crystals belong to the cubic space group, P2(1)3 with unit cell dimensions a = b = c = 95.7 A (1 A = 0.1 nm). Preliminary photography reveals that the crystals are moderately stable to X-rays and diffract to at least 3 A resolution. The diffraction data for native crystals have been collected on a diffractometer at 3 A resolution. Another crystal form, which appeared in a solution containing sodium phosphate at pH 8.0, has the trigonal space group P3 with unit cell dimensions a = b = 63.8 A and c = 54.4 A, and produces measurable reflections to a resolution of 3 A. Hexagonal crystals also have been obtained by the use of polyethylene glycol as precipitant in the range pH 7.6 to 8.0; however, the crystals are fragile and unstable to X-rays. Conservation of 3-fold symmetry in the different crystal forms obtained could reflect the ability of tumor necrosis factor molecules to form trimers in solution and probably the nature of binding of the molecules to cellular receptors.

Cloning, Molecular↗
PubMed1990

Analysis of meteorological and radiological data for selected fallout episodes.

The Weather Service Nuclear Support Office has analyzed the meteorological and radiological data collected for the following atmospheric nuclear tests: TRINITY; EASY of the Tumbler-Snapper series; ANNIE, NANCY, BADGER, SIMON, and HARRY of the Upshot-Knothole series; BEE and ZUCCHINI of the Teapot series; BOLTZMANN and SMOKY of the Plumbbob series; and SMALL BOY of the Dominic II series. These tests were chosen as having the greatest impact on nearby downwind populated locations, contributing approximately 80% of the collective estimated exposure. This report describes the methods of analysis used in deriving fallout-pattern contours and estimated fallout arrival times. Inconsistencies in the radiological data and their resolution are discussed. The methods of estimating fallout arrival times from the meteorological data are described. Comparisons of fallout patterns resulting from these analyses with earlier analyses show insignificant differences in the areas covered or people exposed.

Environmental Exposure↗
PubMed2006

Ultrahigh-resolution study of protein atomic displacement parameters at cryotemperatures obtained with a helium cryostat.

Two X-ray data sets for a complex of human aldose reductase (h-AR) with the inhibitor IDD 594 and the cofactor NADP(+) were collected from two different parts of the same crystal to a resolution of 0.81 A at 15 and 60 K using cold helium gas as cryogen. The contribution of temperature to the atomic B values was estimated by comparison of the independently refined models. It was found that although being slightly different for different kinds of atoms, the differences (deltaB) in the isotropic equivalents B of atomic displacement parameters (ADPs) were approximately constant (about 1.7 A(2)) for well ordered atoms as the temperature was increased from 15 to 60 K. The mean value of this difference varied according to the number of non-H atoms covalently bound to the parent atom. Atoms having a B value of higher than 8 A(2) at 15 K showed much larger deviations of deltaB from the average value, which might reflect partial occupancy of atomic sites. An analysis of the anisotropy of ADPs for individual atoms revealed an increase in the isotropy of ADPs with the increase of the temperature from 15 to 60 K. In a separate experiment, a 0.93 A resolution data set was collected from a different crystal of the same complex at 100 K using cold nitrogen as a cryogen. The effects of various errors on the atomic B values were estimated by comparison of the refined models and the temperature-dependent component was inferred. It was found that both decreasing the data redundancy and increasing the resolution cutoff led to an approximately constant increase in atomic B values for well ordered atoms.

Aldehyde Reductase↗
PubMed2001

Detection of alkali metal ions in DNA crystals using state-of-the-art X-ray diffraction experiments.

The observation of light metal ions in nucleic acids crystals is generally a fortuitous event. Sodium ions in particular are notoriously difficult to detect because their X-ray scattering contributions are virtually identical to those of water and Na(+.)O distances are only slightly shorter than strong hydrogen bonds between well-ordered water molecules. We demonstrate here that replacement of Na(+) by K(+), Rb(+) or Cs(+) and precise measurements of anomalous differences in intensities provide a particularly sensitive method for detecting alkali metal ion-binding sites in nucleic acid crystals. Not only can alkali metal ions be readily located in such structures, but the presence of Rb(+) or Cs(+) also allows structure determination by the single wavelength anomalous diffraction technique. Besides allowing identification of high occupancy binding sites, the combination of high resolution and anomalous diffraction data established here can also pinpoint binding sites that feature only partial occupancy. Conversely, high resolution of the data alone does not necessarily allow differentiation between water and partially ordered metal ions, as demonstrated with the crystal structure of a DNA duplex determined to a resolution of 0.6 A.

Barium↗
PubMed1996

Commutator filter: a novel technique for the identification of structures producing significant susceptibility inhomogeneities and its application to functional MRI.

A robust postprocessing method to detect regions of magnetic field change is presented. High resolution gradient echo data is acquired to create a complex baseline image. From this image, two low resolution images are obtained by applying a low pass filter on the magnitude image and the complex image, respectively. Subtraction of the magnitude of the filtered complex image from the filtered magnitude image gives a new image called a commutator image in which regions of susceptibility-induced field variation are greatly enhanced. Results on phantoms and applications to visualize paramagnetic venous blood vessels in the human brain are presented. The use of this technique on a 3D gradient echo data set represents a new approach to obtain an MR venogram. The application of this method to blood oxygenation level dependent (BOLD) functional brain MR imaging is demonstrated and the important role susceptibility plays in this model is verified.

Algorithms↗
PubMed1991

A multisolution method of phase determination by combined maximization of entropy and likelihood. V. The use of likelihood as a discriminator of phase sets produced by the SAYTAN program for a small protein.

The use of a likelihood criterion associated with maximum-entropy (ME) extrapolation for selecting phase sets as part of a new multisolution phasing strategy, already applied to solving small crystal structures from single-crystal data [Gilmore, Bricogne & Bannister (1990). Acta Cryst. A46, 297-308] and X-ray powder diffraction data [Gilmore, Henderson & Bricogne (1991). Acta Cryst. A47, 830-841], has been tested on the small protein avian pancreatic polypeptide (APP) with 301 non-H atoms in the asymmetric unit in space group C2. A collection of 50 phase sets for APP were provided by Woolfson & Yao. They had been generated from random starting phases by the SAYTAN procedure [Woolfson & Yao (1990). Acta Cryst. A46, 409-413] using data to a resolution of 0.98 A. Six of these had an unweighted mean absolute phase error, mean value of magnitude of delta phi, of less than 50 degrees, the remainder having phase errors of 60 degrees or more. However, none of the conventional figures of merit were able to identify these preferred sets. Each phase set was subjected to our standard procedure of entropy maximization and of evaluation of the log-likelihood gain resulting from the associated ME extrapolation. With only a small subset of data (to 2 A resolution), the likelihood criterion identified unambiguously the phase sets with mean value of magnitude of delta phi less than 50 degrees. In contrast, conventional figures of merit showed no such ability.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic Polypeptide↗
PubMed2004

Two- and three-dimensional ultrasound in the development of a needle-free injection system.

Ultrasound was used to assess a needle-free injection device for both intradermal and subcutaneous injections. The aim of this study was, first, to differentiate intradermal from subcutaneous injections, both in vivo and in vitro using 2D ultrasound, and second, to quantify the amount of injectate that actually arrives within the dermis or subcutaneous tissues using volume measurements derived from high-resolution 3D ultrasound data sets, using a freehand system (Stradx), developed by the Cambridge University Departments of Engineering and Radiology. For the in vitro study the devices were filled with dye and injected into a pig preparation. The injection site was examined with high-resolution ultrasound and subsequently dissected to locate the injected dye with respect to the dermis. For the in vivo study, 8 volunteers received needle-free injections of normal saline. High-resolution 2D images and 3D data sets were obtained of the injected sites. Proprioceptive information for the 3D data sets was produced using an optically tracked freehand system. Segmentation of the 3D data sets gave an estimation of the volume of injected material (injectate) within the dermis. The results demonstrated that 2D ultrasound could identify the location of the injectate in the in vitro experiments and successfully distinguished an intradermal from a subcutaneous injection. In the in vivo study, 2D ultrasound clearly demonstrated the injectate location within the volunteers' dermis but was less able to demonstrate the dispersion of injectate within the subcutaneous tissues.

Animals↗
PubMed1974

Direct determination of the lamellar structure of peripheral nerve myelin at moderate resolution (7A).

Low-angle X-ray diffraction patterns have been recorded from normal nerve and nerve swollen in glycerol solutions. The new X-ray data have a resolution of 7 A. Direct methods of structure analysis which include deconvolution of the auto-correlation function and sampling theorem reconstructions have been used in the interpretation of the X-ray data. Phases have been assigned to the first 12 orders of diffraction from normal nerve. Fourier syntheses at a resolution of 7 A are described and an absolute electron density scale is derived. A possible molecular interpretation of the electron density profile is given.

Animals↗