bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolism of Methanol in Plant Cells. Carbon-13 Nuclear Magnetic Resonance Studies
Authors: Gout Elizabeth , Aubert Serge , Bligny Richard , Rébeillé Fabrice , Nonomura Arthur R. , Benson Andrew A. , Douce Roland 
Published: July 2002

Abstract
Using 13C-NMR, we demonstrate that [13C]methanol readily entered sycamore (Acer pseudoplatanus L.) cells to be slowly metabolized to [3-13C]serine, [13CH3]methionine, and [13CH3]phosphatidylcholine. We conclude that the assimilation of [13C]methanol occurs through the formation of 13CH3H4Pte-glutamate (Glu)n and S-adenosyl-methionine, because feeding plant cells with [3-13CH3]serine, the direct precursor of13CH2H4Pte-Glun, can perfectly mimic [13CH3]methanol for folate-mediated single-carbon metabolism. On the other hand, the metabolism of [13C]methanol in plant cells revealed assimilation of label into a new cellular product that was identified as [13CH3]methyl-β-d-glucopyranoside. The de novo synthesis of methyl-β-d-glucopyranoside induced by methanol did not require the formation of13CH3H4Pte-Glun and was very likely catalyzed by a “transglycosylation” process.
Regulation of High-Affinity Nitrate Transporter Genes and High-Affinity Nitrate Influx by Nitrogen Pools in Roots of Barley
Authors: Vidmar Joseph John , Zhuo Degen , Siddiqi M. Yaeesh , Schjoerring Jan K. , Touraine Bruno , Glass Anthony D.M. 
Published: July 2002

Abstract
To investigate the regulation of HvNRT2, genes that encode high-affinity NO3 − transporters in barley (Hordeum vulgare) roots, seedlings were treated with 10 mm NO3 − in the presence or absence of amino acids (aspartate, asparagine, glutamate [Glu], and glutamine [Gln]), NH4 +, and/or inhibitors of N assimilation. Although all amino acids decreased high-affinity13NO3 − influx andHvNRT2 transcript abundance, there was substantial interconversion of administered amino acids, making it impossible to determine which amino acid(s) were responsible for the observed effects. To clarify the role of individual amino acids, plants were separately treated with tungstate, methionine sulfoximine, or azaserine (inhibitors of nitrate reductase, Gln synthetase, and Glu synthase, respectively). Tungstate increased the HvNRT2 transcript by 20% to 30% and decreased NO3 − influx by 50%, indicating that NO3 − itself does not regulate transcript abundance, but may exert post-transcriptional effects. Experiments with methionine sulfoximine suggested that NH4 + may down-regulate HvNRT2gene expression and high-affinity NO3 − influx by effects operating at the transcriptional and post-transcriptional levels. Azaserine decreased HvNRT2 transcript levels and NO3 − influx by 97% and 95%, respectively, while decreasing Glu and increasing Gln levels. This suggests that Gln (and not Glu) is responsible for down-regulating HvNRT2expression, although it does not preclude a contributory effect of other amino acids.
Molecular Characterization of CYP73A9 andCYP82A1 P450 Genes Involved in Plant Defense in Pea
Authors: Whitbred Joy M. , Schuler Mary A. 
Published: July 2002

Abstract
Cytochrome P450 monooxygenases (P450s) mediate a wide range of oxidative reactions involved in the biosynthesis of phenylpropanoids, terpenes, and alkaloids. Two pea (Pisum sativum) P450 cDNAs (CYP73A9v1, encoding trans-cinnamic acid hydroxylase [t-CAH] in the core phenylpropanoid pathway, and CYP82A1v1, possibly encoding an activity in a late branch of the phenylpropanoid pathway) have previously been described. Of three CYP73A9 genes now isolated, theCYP73A9v1 gene is full-length with two introns at positions conserved in other t-CAH genes, and theCYP73A9v2 and CYP73A9v3 gene fragments are 5′-truncated and lack introns. The full-lengthCYP82A1v2 gene contains a single intron at an alternate position. Nucleotide searches of the CYP73A9v1 andCYP82A1v2 promoters have indicated that the regulatory sequences for these early and late phenylpropanoid transcripts are substantially different. The P-, L-, and H-boxes identified in white light-, ultraviolet light-, and elicitor-induced footprints in early phenylpropanoid promoters (phenylalanine ammonia lyase [PAL], 4-coumarate coenzyme A:ligase [4-CL], and chalcone synthase [CHS]) are conserved in the t-CAH promoter and are absent from the CYP82A1v2 promoter. Both promoters contain TCA motifs identified in stress-responsive promoters, box IV elements identified in elicitor-responsive PAL andCHS promoters, and spatially conserved wound-response elements potentially coordinating regulation of these wound-responsive promoters.
Overexpression of Auxin-Binding Protein Enhances the Sensitivity of Guard Cells to Auxin
Authors: Bauly James M. , Sealy Ian M. , Macdonald Heather , Brearley Jane , Dröge Swenja , Hillmer Stefan , Robinson David G. , Venis Michael A. , Blatt Michael R. , Lazarus Colin M. , Napier Richard M. 
Published: July 2002

Abstract
To explore the role of auxin-binding protein (ABP1) in planta, a number of transgenic tobacco (Nicotiana tabacum) lines were generated. The wild-type KDEL endoplasmic reticulum targeting signal was mutated to HDEL, another common retention sequence in plants, and to KEQL or KDELGL to compromise its activity. The auxin-binding kinetics of these forms of ABP1 were found to be similar to those of ABP1 purified from maize (Zea mays). To test for a physiological response mediated by auxin, intact guard cells of the transgenic plants were impaled with double-barreled microelectrodes, and auxin-dependent changes in K+ currents were recorded under voltage clamp. Exogenous auxin affected inwardly and outwardly rectifying K+ currents in a dose-dependent manner. Auxin sensitivity was markedly enhanced in all plants overexpressing ABP1, irrespective of the form present. Immunogold electron microscopy was used to investigate the localization of ABP1 in the transgenic plants. All forms were detected in the endoplasmic reticulum and the KEQL and KDELGL forms passed further across the Golgi stacks than KDEL and HDEL forms. However, neither electron microscopy nor silver-enhanced immunogold epipolarization microscopy revealed differences in cell surface ABP1 abundance for any of the plants, including control plants, which indicated that overexpression of ABP1 alone was sufficient to confer increased sensitivity to added auxin. Jones et al. ([1998] Science 282: 1114–1117) found increased cell expansion in transgenic plants overexpressing wild-type ABP1. Single cell recordings extend this observation, with the demonstration that the auxin sensitivity of guard cell K+ currents is mediated, at least in part, by ABP1.
Trienoic Fatty Acids Are Required to Maintain Chloroplast Function at Low Temperatures
Authors: Routaboul Jean-Marc , Fischer Steven F. , Browse John 
Published: July 2002

Abstract
The chloroplast membranes of all higher plants contain very high proportions of trienoic fatty acids. To investigate how these lipid structures are important in photosynthesis, we have generated a triple mutant line of Arabidopsis that contains negligible levels of trienoic fatty acids. For mutant plants grown at 22°C, photosynthetic fluorescence parameters were indistinguishable from wild type at 25°C. Lowering the measurement temperature led to a small decrease in photosynthetic quantum yield, ΦII, in the mutant relative to wild-type controls. These and other results indicate that low temperature has only a small effect on photosynthesis in the short term. However, long-term growth of plants at 4°C resulted in decreases in fluorescence parameters, chlorophyll content, and thylakoid membrane content in triple-mutant plants relative to wild type. Comparisons among different mutant lines indicated that these detrimental effects of growth at 4°C are strongly correlated with trienoic fatty acid content with levels of 16:3 + 18:3, approximately one-third of wild type being sufficient to sustain normal photosynthetic function. In total, our results indicate that trienoic fatty acids are important to ensure the correct biogenesis and maintenance of chloroplasts during growth of plants at low temperatures.
Study of the Role of Antimicrobial Glucosinolate-Derived Isothiocyanates in Resistance of Arabidopsis to Microbial Pathogens
Authors: Tierens Koenraad F.M.-J. , Thomma Bart P.H.J. , Brouwer Margreet , Schmidt Jürgen , Kistner Katherine , Porzel Andrea , Mauch-Mani Brigitte , Cammue Bruno P.A. , Broekaert Willem F. 
Published: July 2002

Abstract
Crude aqueous extracts from Arabidopsis leaves were subjected to chromatographic separations, after which the different fractions were monitored for antimicrobial activity using the fungus Neurospora crassa as a test organism. Two major fractions were obtained that appeared to have the same abundance in leaves from untreated plants versus leaves from plants challenge inoculated with the fungusAlternaria brassicicola. One of both major antimicrobial fractions was purified to homogeneity and identified by 1H nuclear magnetic resonance, gas chromatography/electron impact mass spectrometry, and gas chromatography/chemical ionization mass spectrometry as 4-methylsulphinylbutyl isothiocyanate (ITC). This compound has previously been described as a product of myrosinase-mediated breakdown of glucoraphanin, the predominant glucosinolate in Arabidopsis leaves. 4-Methylsulphinylbutyl ITC was found to be inhibitory to a wide range of fungi and bacteria, producing 50% growth inhibition in vitro at concentrations of 28 μm for the most sensitive organism tested (Pseudomonas syringae). A previously identified glucosinolate biosynthesis mutant, gsm1-1, was found to be largely deficient in either of the two major antimicrobial compounds, including 4-methylsulphinylbutyl ITC. The resistance ofgsm1-1 was compared with that of wild-type plants after challenge with the fungi A. brassicicola,Plectosphaerella cucumerina, Botrytis cinerea, Fusarium oxysporum, orPeronospora parasitica, or the bacteria Erwinia carotovora or P. syringae. Of the tested pathogens, only F. oxysporum was found to be significantly more aggressive on gsm1-1 than on wild-type plants. Taken together, our data suggest that glucosinolate-derived antimicrobial ITCs can play a role in the protection of Arabidopsis against particular pathogens.
The Maize MADS Box Gene ZmMADS3 Affects Node Number and Spikelet Development and Is Co-Expressed withZmMADS1 during Flower Development, in Egg Cells, and Early Embryogenesis
Authors: Heuer Sigrid , Hansen Susanne , Bantin Jörg , Brettschneider Reinhold , Kranz Erhard , Lörz Horst , Dresselhaus Thomas 
Published: July 2002

Abstract
MADS box genes represent a large gene family of transcription factors with essential functions during flower development and organ differentiation processes in plants. Addressing the question of whether MADS box genes are involved in the regulation of the fertilization process and early embryo development, we have isolated two novel MADS box cDNAs, ZmMADS1 and ZmMADS3, from cDNA libraries of maize (Zea mays) pollen and egg cells, respectively. The latter gene is allelic to ZAP1. Transcripts of both genes are detectable in egg cells and in in vivo zygotes of maize. ZmMADS1 is additionally expressed in synergids and in central and antipodal cells. During early somatic embryogenesis, ZmMADS1 expression is restricted to cells with the capacity to form somatic embryos, and to globular embryos at later stages. ZmMADS3 is detectable only by more sensitive reverse transcriptase-PCR analyses, but is likewise expressed in embryogenic cultures. Both genes are not expressed in nonembryogenic suspension cultures and in isolated immature and mature zygotic embryos. During flower development, ZmMADS1 andZmMADS3 are co-expressed in all ear spikelet organ primordia at intermediate stages. Among vegetative tissues,ZmMADS3 is expressed in stem nodes and displays a gradient with highest expression in the uppermost node. Transgenic maize plants ectopically expressing ZmMADS3are reduced in height due to a reduced number of nodes. Reduction of seed set and male sterility were observed in the plants. The latter was due to absence of anthers. Putative functions of the genes during reproductive and vegetative developmental processes are discussed.
Crystallization and preliminary X-ray studies on the molbindin ModG from Azotobacter vinelandii
Authors: Williams Clare E. M. , White Daniel J. , Delarbre Laure , Mitchenall Lesley A. , Pau Richard N. , Lawson David M. 
Published: July 2002

Crystals of the molbindin ModG (subunit Mr
= 14359 Da), a cytoplasmic molybdate-binding protein from Azotobacter vinelandii, were grown by vapour diffusion. Both apo and tungstate-bound forms were crystallized and X-ray data were collected at 100 K. Apo-ModG crystallizes in space group P6322, with unit-cell dimensions a = b = 90.62, c = 79.46 Å. Native data to a resolution of 2.5 Å were collected from a single crystal, which showed a marked improvement in diffraction quality after annealing. Data from a single-site gold derivative were also collected at 2.7 Å resolution. Crystals of the ligand-bound form of ModG belong to space group P321, with unit-cell parameters a = b = 50.57, c = 79.29 Å. X-ray data to a resolution of 2.0 Å were collected.
Purification, crystallization and preliminary crystallographic studies on the N-terminal fragment of human protein disulfide isomerase
Authors: Wang Xin-Quan , Gui Lu-Lu , Dai Yong , Wang Chih-Chen , Chang Wen-Rui , Liang Dong-Cai 
Published: July 2002

A fragment of human protein disulfide isomerase composed of the thioredoxin-like a and b domains (ab) has been expressed in Escherichia coli as a fusion protein with glutathione-S-transferase and purified after thrombin cleavage. Two forms of ab crystal were obtained with polyethylene glycol as precipitant and different additives at pH 7.5. The space group of form I is P41212 or P43212, with unit-cell dimensions a = 81.5, c = 259.7 Å. The space group of form II is P4122 or P4322, with unit-cell dimensions a = 82.7, c = 86.5 Å.
High‐resolution crystal structure of apolipoprotein(a) kringle IV type 7: Insights into ligand binding
Authors: Ye Qilu , Rahman Mona N. , Koschinsky Marlys L. , Jia Zongchao 
Published: July 2002

AbstractApolipoprotein(a) [apo(a)] consists of a series of tandemly repeated modules known as kringles that are commonly found in many proteins involved in the fibrinolytic and coagulation cascades, such as plasminogen and thrombin, respectively. Specifically, apo(a) contains multiple tandem repeats of domains similar to plasminogen kringle IV (designated as KIV1 to KIV10) followed by sequences similar to the kringle V and protease domains of plasminogen. The KIV domains of apo(a) differ with respect to their ability to bind lysine or lysine analogs. KIV10 represents the high‐affinity lysine‐binding site (LBS) of apo(a); a weak LBS is predicted in each of KIV5–KIV8 and has been directly demonstrated in KIV7. The present study describes the first crystal structure of apo(a) KIV7, refined to a resolution of 1.45 Å, representing the highest resolution for a kringle structure determined to date. A critical substitution of Tyr‐62 in KIV7 for the corresponding Phe‐62 residue in KIV10, in conjunction with the presence of Arg‐35 in KIV7, results in the formation of a unique network of hydrogen bonds and electrostatic interactions between key LBS residues (Arg‐35, Tyr‐62, Asp‐54) and a peripheral tyrosine residue (Tyr‐40). These interactions restrain the flexibility of key LBS residues (Arg‐35, Asp‐54) and, in turn, reduce their adaptability in accommodating lysine and its analogs. Steric hindrance involving Tyr‐62, as well as the elimination of critical ligand‐stabilizing interactions within the LBS are also consequences of this interaction network. Thus, these subtle yet critical structural features are responsible for the weak lysine‐binding affinity exhibited by KIV7 relative to that of KIV10.
Dynamics of green fluorescent protein mutant2 in solution, on spin‐coated glasses, and encapsulated in wet silica gels
Authors: Chirico Giuseppe , Cannone Fabio , Beretta Sabrina , Diaspro Alberto , Campanini Barbara , Bettati Stefano , Ruotolo Roberta , Mozzarelli Andrea 
Published: July 2002

AbstractSingle‐molecule experiments are performed by investigating spectroscopic properties of molecules either diffusing in and out of the observation volume or fixed in space by different immobilization procedures. To evaluate the effect of immobilization methods on the structural and dynamic properties of proteins, a highly fluorescent mutant of the green fluorescent protein, GFPmut2, was spectroscopically characterized in bulk solutions, dispersed on etched glasses, and encapsulated in wet, nanoporous silica gels. The emission spectrum, the fluorescence lifetimes, the anisotropy, and the rotational correlation time of GFPmut2, encapsulated in silica gels, are very similar to those obtained in solution. This finding indicates that the gel matrix does not alter the protein conformation and dynamics. In contrast, the fluorescence lifetimes of GFPmut2 on glasses are two‐to fourfold higher and the fluorescence anisotropy decays yield almost no phase shifts. This indicates that the interaction of the protein with the bare glass surface induces a significant structural perturbation and severely restricts the rotational motion. Single molecules of GFPmut2 on glasses or in silica gels, identified by confocal image analysis, show a significant stability to illumination with bleaching times of the order of 90 and 60 sec, respectively. Overall, these data indicate that silica gels represent an ideal matrix for following biologically relevant events at a single molecule level.
Thermal unfolding of ribonuclease A in phosphate at neutral pH: Deviations from the two–state model
Authors: Stelea Simona D. , Pancoska Petr , Benight Albert S. , Keiderling Timothy A. 
Published: July 2002

AbstractThe thermal denaturation of ribonuclease A (RNase A) in the presence of phosphate at neutral pH was studied by differential scanning calorimetry (DSC) and a combination of optical spectroscopic techniques to probe the existence of intermediate states. Fourier transform infrared (FTIR) spectra of the amide I′ band and far‐uv circular dichroism (CD) spectra were used to monitor changes in the secondary structure. Changes in the tertiary structure were monitored by near‐uv CD. Spectral bandshape changes with change in temperature were analyzed using factor analysis. The global unfolding curves obtained from DSC confirmed that structural changes occur in the molecule before the main thermal denaturation transition. The analysis of the far‐uv CD and FTIR spectra showed that these lower temperature–induced modifications occur in the secondary structure. No pretransition changes in the tertiary structure (near‐uv CD) were observed. The initial changes observed in far‐uv CD were attributed to the fraying of the helical segments, which would explain the loss of spectral intensity with almost no modification of spectral bandshape. Separate analyses of different regions of the FTIR amide I′ band indicate that, in addition to α‐helix, part of the pretransitional change also occurs in the β‐strands.
Measurements of Rotordynamic Coefficients of Hybrid Bearings With (a)
a Plugged Orifice, and (b) a Worn Land Surface
Authors: Laurant F. , Childs D. W. 
Published: July 2002

Abstract
Test results are presented for the rotordynamic coefficients of a hybrid bearing that is representative of bearings for liquid-rocket-engine turbopump applications. The bearing is tested in the following two degraded conditions: (a) one of five orifices plugged, and (b) a locally enlarged clearance to simulate a worn condition. Test data are presented at 24,600 rpm, with supply pressures of 4.0, 5.5, and 7.0 MPa, and eccentricity ratios from 0.1 to 0.5 in 0.1 increments. Overall, the results suggest that neither a single plugged orifice nor significant wear on the bearing land will “disable” a well-designed hybrid bearing. These results do not speak to multiple plugged orifices and are not an endorsement for operations without filters to prevent plugging orifices.
A New Flow Chamber for the Study of Shear Stress and Transmural Pressure Upon Cells Adhering to a Porous Biomaterial
Authors: Chotard-Ghodsnia Roxana , Drochon Agnès , Grebe Reinhard 
Published: July 2002

AbstractBiomaterials used in some biomedical devices are porous and exposed to normal and tangential flow of biofluids. To examine the influence of flow induced forces on the morphology and the biochemical responses of cells adhering to such biomaterials, a Hele-Shaw cell with a porous bottom wall was designed and characterized experimentally. Theoretical predictions for the flow in the chamber are provided and allow to quantify the shear stress and/or transmural pressure exerted on cells. It is thus possible to follow up continuously the shape changes of cells that are adherent on a permeable membrane used in bioreactors.
Regional, Directional, and Age-Dependent Properties of the Brain Undergoing Large Deformation
Authors: Prange Michael T. , Margulies Susan S. 
Published: July 2002

AbstractThe large strain mechanical properties of adult porcine gray and white matter brain tissues were measured in shear and confirmed in compression. Consistent with local neuroarchitecture, gray matter showed the least amount of anisotropy, and corpus callosum exhibited the greatest degree of anisotropy. Mean regional properties were significantly distinct, demonstrating that brain tissue is inhomogeneous. Fresh adult human brain tissue properties were slightly stiffer than adult porcine properties but considerably less stiff than the human autopsy data in the literature. Mixed porcine gray/white matter samples were obtained from animals at “infant” and “toddler” stages of neurological development, and shear properties compared to those in the adult. Only the infant properties were significantly different (stiffer) from the adult.
A Review of Purge Air Designs for Aeroengine-Based Optical Pyrometers
Authors: Kerr Clive I. , Ivey Paul C. 
Published: July 2002

Abstract
With the advent of "power by the hour" type agreements within the civil aeroengine market, the application of engine monitoring system data has reached the level of strategic use for informed decision making in not only the aftermarket but increasingly in the contract negotiation stage. One of the key cost drivers in these dollar-per-hour contracts for the OEMs to analyze is the life and maintenance requirements of the turbine blades leading ultimately to blade life management. Such life management of key components is of critical importance to ensure that the economic and technical risks to both service provider and customer are minimized. The optical pyrometer, through providing a direct temperature measurement of the turbine blades, is a primary input for providing a more realistic assessment of the component’s operating history associated with the use of life usage/remaining algorithms. However, the greatest concern with the in-service use of pyrometry is the issue of fouling since the pyrometer’s lens is exposed to the turbine environment. The level of optical contamination is usually minimized by introducing purge air, bled from the compressor, down the sight tube to prevent both the build-up of contaminants on the exposed system optics and particles in the gas stream from coming in contact with the lens. This paper provides a review of purge air designs and the key methodologies for engine designers to be acquainted with when seeking to integrate the use of optical pyrometry systems in new engine concepts.