bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Yield Expression of Pea Thioredoxin m and Assessment of Its Efficiency in Chloroplast Fructose-1,6-Bisphosphatase Activation
Authors: Jaramillo J. L. , Chueca A. , Jacquot J. P. , Hermoso R. , Lazaro J. J. , Sahrawy M. , Gorge J. L. 
Published: July 2002

Abstract
A cDNA clone encoding pea (Pisum sativum L.) chloroplast thioredoxin (Trx) m and its transit peptide were isolated from a pea cDNA library. Its deduced amino acid sequence showed 70% homology with spinach (Spinacia oleracea L.) Trx m and 25% homology with Trx f from pea and spinach. After subcloning in the Ndel-BamHI sites of pET-12a, the recombinant supplied 20 mg Trx m/L Escherichia coli culture. This protein had 108 amino acids and was 12,000 D, which is identical to the pea leaf native protein. Unlike pea Trx f, pea Trx m showed a hyperbolic saturation of pea chloroplast fructose-1,6-bisphosphatase (FBPase), with a Trx m/FBPase molar saturation ratio of about 60, compared with 4 for the Trx f/FBPase quotient. Cross-experiments have shown the ability of pea Trx m to activate the spinach chloroplast FBPase, results that are in contrast with those in spinach found by P. Schurmann, K. Maeda, and A. Tsugita ([1981] Eur J Biochem 116: 37–45), who did not find Trx m efficiency in FBPase activation. This higher efficiency of pea Trx m could be related to the presence of four basic residues (arginine-37, lysine-70, arginine-74, and lysine-97) flanking the regulatory cluster; spinach Trx m lacks the positive charge corresponding to lysine-70 of pea Trx m. This has been confirmed by K70E mutagenesis of pea Trx m, which leads to a 50% decrease in FBPase activation.
Antisense Inhibition of the Photosystem I Antenna Protein Lhca4 in Arabidopsis thaliana
Authors: Zhang H. , Goodman H. M. , Jansson S. 
Published: July 2002

Abstract
The function of Lhca4, a gene encoding the photosystem I type IV chlorophyll a/b-binding protein complex in Arabidopsis, was investigated using antisense technology. Lhca4 protein was reduced in a number of mutant lines and abolished in one. The inhibition of protein was not correlated with the inhibition of mRNA. No depletion of Lhca1 was observed, but the low-temperature fluorescence emission spectrum was drastically altered in the mutants. The emission maximum was blue-shifted by 6 nm, showing that chlorophyll molecules bound to Lhca4 are responsible for most of the long-wavelength fluorescence emission. Some mutants also showed an unexplainable delay in flowering time and an increase in seed weight.
An Arabidopsis VPS45p Homolog Implicated in Protein Transport to the Vacuole1
Authors: Bassham Diane C. , Raikhel Natasha V. 
Published: July 2002

Abstract
The Sec1p family of proteins is required for vesicle-mediated protein trafficking between various organelles of the endomembrane system. This family includes Vps45p, which is required for transport to the vacuole in yeast (Saccharomyces cerevisiae). We have isolated a cDNA encoding a VPS45 homolog from Arabidopsis thaliana (AtVPS45). The cDNA is able to complement both the temperature-sensitive growth defect and the vacuolar-targeting defect of a yeast vps45 mutant, indicating that the two proteins are functionally related. AtVPS45p is a peripheral membrane protein that associates with microsomal membranes. Sucrose-density gradient fractionation demonstrated that AtVPS45p co-fractionates with AtELP, a potential vacuolar protein sorting receptor, implying that they may reside on the same membrane populations. These results indicate that AtVPS45p is likely to function in the transport of proteins to the vacuole in plants.
Overexpression of Iron Superoxide Dismutase in Transformed Poplar Modifies the Regulation of Photosynthesis at Low CO2Partial Pressures or Following Exposure to the Prooxidant Herbicide Methyl Viologen1
Authors: Arisi Ana-Carolina M. , Cornic Gabriel , Jouanin Lise , Foyer Christine H. 
Published: July 2002

Abstract
Chloroplast-targeted overexpression of an Fe superoxide dismutase (SOD) from Arabidopsis thaliana resulted in substantially increased foliar SOD activities. Ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase activities were similar in the leaves from all of the lines, but dehydroascorbate reductase activity was increased in the leaves of the FeSOD transformants relative to untransformed controls. Foliar H2O2, ascorbate, and glutathione contents were comparable in all lines of plants. Irradiance-dependent changes in net CO2 assimilation and chlorophyll a fluorescence quenching parameters were similar in all lines both in air (21% O2) and at low (1%) O2. CO2-response curves for photosynthesis showed similar net CO2-exchange characteristics in all lines. In contrast, values of photochemical quenching declined in leaves from untransformed controls at intercellular CO2 (Ci) values below 200 μL L−1 but remained constant with decreasing Ci in leaves of FeSOD transformants. When the O2 concentration was decreased from 21 to 1%, the effect of FeSOD overexpression on photochemical quenching at limiting Ci was abolished. At high light (1000 μmol m−2s−1) a progressive decrease in the ratio of variable (Fv) to maximal (Fm) fluorescence was observed with decreasing temperature. At 6oC the high-light-induced decrease in theFv/Fm ratio was partially prevented by low O2 but values were comparable in all lines. Methyl viologen caused decreasedFv/Fm ratios, but this was less marked in the FeSOD transformants than in the untransformed controls. These observations suggest that the rate of superoxide dismutation limits flux through the Mehler-peroxidase cycle in certain conditions.
Cloning and Characterization ofTPE4A, a Thiol-Protease Gene Induced during Ovary Senescence and Seed Germination in Pea1
Authors: Cercós Manuel , Santamarı́a Salvador , Carbonell Juan 
Published: July 2002

AbstractA cDNA clone encoding a thiol-protease (TPE4A) was isolated from senescent ovaries of pea (Pisum sativum) by reverse transcriptase-polymerase chain reaction. The deduced amino acid sequence of TPE4A has the conserved catalytic amino acids of papain. It is very similar to VSCYSPROA, a thiol-protease induced during seed germination in common vetch. TPE4A mRNA levels increase during the senescence of unpollinated pea ovaries and are totally suppressed by treatment with gibberellic acid. In situ hybridization indicated thatTPE4A mRNA distribution in senescent pea ovaries is different from that of previously reported thiol-proteases induced during senescence, suggesting the involvement of different proteases in the mobilization of proteins from senescent pea ovaries.TPE4A is also induced during the germination of pea seeds, indicating that a single protease gene can be induced during two different physiological processes, senescence and germination, both of which require protein mobilization.
A Gene Encoding the Cytokinin Enzyme ZeatinO-Xylosyltransferase of Phaseolus vulgaris1
Authors: Martin Ruth C. , Mok Machteld C. , Mok David W.S. 
Published: July 2002

Abstract
Zeatin is the most active and ubiquitous form of the naturally occurring cytokinins. Glycosyl conjugates of zeatin are found in many plant tissues and are considered important for storage and protection against degradative enzymes. Two enzymes catalyzing the formation of O-glycosyl derivatives of zeatin have been characterized,O-glucosyltransferase andO-xylosyltransferase, occurring in seeds of lima bean (Phaseolus lunatus) and bean (Phaseolus vulgaris), respectively. Recently, the ZOG1 gene (zeatinO-glucosyltansferase) was isolated from P. lunatis (Martin et al., 1999). Based on the ZOG1 sequence, the ZOX1 gene (zeatinO-xylosyltransferase) was cloned from P. vulgaris. ZOX1contains an open reading frame of 1362 bp that codes for a 454-amino acid peptide of 51 kD. The recombinant protein has properties identical to the native enzyme: it catalyzes O-xylosylzeatin formation with UDP-Xyl as a glycosyl donor but does not recognize UDP-Glucose as a substrate. The ZOX1 andZOG1 genes exhibit 93% identity at the nucleotide level and 90% similarity at the amino acid level. Neither gene contains introns. These zeatin-specific genes and their promoters will be useful for studies of the regulation of active versus storage forms of cytokinins. Comparison of sequences encoding similar enzymes with distinct substrate specificity may lead to identification of epitopes specific to cytokinin and glycosyl donor molecules.
Cambial-Region-Specific Expression of the Agrobacterium iaa Genes in Transgenic Aspen Visualized by a LinkeduidA Reporter Gene
Authors: Tuominen Hannele , Puech Laurence , Regan Sharon , Fink Siegfried , Olsson Olof , Sundberg Björn 
Published: July 2002

Abstract
The level of indole-3-acetic acid (IAA) was locally modified in cambial tissues of transgenic aspen (Populus tremula L. × Populus tremuloides Michx.). We also demonstrate the use of a linked reporter gene to visualize the expression of theiaa genes. The rate-limiting bacterial IAA-biosynthetic gene iaaM and the reporter gene for β-glucuronidase (GUS), uidA, were each fused to the cambial-region-specific Agrobacterium rhizogenes rolCpromoter and linked on the same T-DNA. In situ hybridization of theiaaM gene confirmed that histochemical analysis of GUS activity could be used to predict iaaM gene expression. Moreover, quantitative fluorometric analysis of GUS activity allowed estimation of the level of de novo production of IAA in transgenic lines carrying a single-copy insert of the iaaM,uidA T-DNA. Microscale analysis of the IAA concentration across the cambial region tissues showed an increase in IAA concentration of about 35% to 40% in the two transgenic lines, but no changes in the radial distribution pattern of IAA compared with wild-type plants. This increase did not result in any changes in the developmental pattern of cambial derivatives or the cambial growth rate, which emphasizes the importance of the radial distribution pattern of IAA in controlling the development of secondary xylem, and suggests that a moderate increase in IAA concentration does not necessarily stimulate growth.
Production of Fatty Acid Components of Meadowfoam Oil in Somatic Soybean Embryos
Authors: Cahoon Edgar B. , Marillia Elizabeth-France , Stecca Kevin L. , Hall Sarah E. , Taylor David C. , Kinney Anthony J. 
Published: July 2002

Abstract
The seed oil of meadowfoam (Limnanthes alba) and other Limnanthes spp. is enriched in the unusual fatty acid Δ5-eicosenoic acid (20:1Δ5). This fatty acid has physical and chemical properties that make the seed oil of these plants useful for a number of industrial applications. An expressed sequence tag approach was used to identify cDNAs for enzymes involved in the biosynthesis of 20:1Δ5). By random sequencing of a library prepared from developing Limnanthes douglasii seeds, a class of cDNAs was identified that encode a homolog of acyl-coenzyme A (CoA) desaturases found in animals, fungi, and cyanobacteria. Expression of a cDNA for the L. douglasii acyl-CoA desaturase homolog in somatic soybean (Glycine max) embryos behind a strong seed-specific promoter resulted in the accumulation of Δ5-hexadecenoic acid to amounts of 2% to 3% (w/w) of the total fatty acids of single embryos. Δ5-Octadecenoic acid and 20:1Δ5also composed &lt;1% (w/w) each of the total fatty acids of these embryos. In addition, cDNAs were identified from the L. douglasii expressed sequence tags that encode a homolog of fatty acid elongase 1 (FAE1), a β-ketoacyl-CoA synthase that catalyzes the initial step of very long-chain fatty acid synthesis. Expression of the L. douglassi FAE1 homolog in somatic soybean embryos was accompanied by the accumulation of C20and C22 fatty acids, principally as eicosanoic acid, to amounts of 18% (w/w) of the total fatty acids of single embryos. To partially reconstruct the biosynthetic pathway of 20:1Δ5in transgenic plant tissues, cDNAs for the L. douglasii acyl-CoA desaturase and FAE1 were co-expressed in somatic soybean embryos. In the resulting transgenic embryos, 20:1Δ5 and Δ5-docosenoic acid composed up to 12% of the total fatty acids.
Identification and Analysis of a Gene from Calendula officinalis Encoding a Fatty Acid Conjugase
Authors: Qiu Xiao , Reed Darwin W. , Hong Haiping , MacKenzie Samuel L. , Covello Patrick S. 
Published: July 2002

Abstract
Two homologous cDNAs, CoFad2 andCoFac2, were isolated from a Calendula officinalis developing seed by a polymerase chain reaction-based cloning strategy. Both sequences share similarity to FAD2 desaturases and FAD2-related enzymes. In C. officinalis plants CoFad2 was expressed in all tissues tested, whereas CoFac2 expression was specific to developing seeds. Expression of CoFad2 cDNA in yeast (Saccharomyces cerevisiae) indicated it encodes a Δ12 desaturase that introduces a double bond at the 12 position of 16:1(9Z) and 18:1(9Z). Expression ofCoFac2 in yeast revealed that the encoded enzyme acts as a fatty acid conjugase converting 18:2(9Z, 12Z) to calendic acid 18:3(8E, 10E, 12Z). The enzyme also has weak activity on the mono-unsaturates 16:1(9Z) and 18:1(9Z) producing compounds with the properties of 8,10 conjugated dienes.
β-Alanine Betaine Synthesis in the Plumbaginaceae. Purification and Characterization of a Trifunctional,S-Adenosyl-l-Methionine-DependentN-Methyltransferase from Limonium latifoliumLeaves
Authors: Rathinasabapathi Bala , Fouad Walid M. , Sigua Celia A. 
Published: July 2002

Abstract
β-Alanine (β–Ala) betaine is an osmoprotective compound accumulated by most members of the highly stress-tolerant family Plumbaginaceae. Its potential role in plant tolerance to salinity and hypoxia makes its synthetic pathway an interesting target for metabolic engineering. In the Plumbaginaceae, β-Ala betaine is synthesized byS-adenosyl-l-methionine-dependentN-methylation of β-Ala via N-methyl β-Ala and N,N-dimethyl β-Ala. It was not known how many N-methyltransferases (NMTases) participate in the three N-methylations of β-Ala. An NMTase was purified about 1,890-fold, from Limonium latifolium leaves, using a protocol consisting of polyethylene glycol precipitation, heat treatment, anion-exchange chromatography, gel filtration, native polyacrylamide gel electrophoresis, and two substrate affinity chromatography steps. The purified NMTase was trifunctional, methylating β-Ala, N-methyl β-Ala, andN,N-dimethyl β-Ala. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses indicated that the native NMTase is a dimer of 43-kD subunits. The NMTase had an apparentK m of 45 μm S-adenosyl-l-methionine and substrate inhibition was observed above 200 μm. The apparentK m values for the methyl acceptor substrates were 5.3, 5.7, and 5.9 mm for β-Ala,N-methyl β-Ala, and N,N-dimethyl β-Ala, respectively. The NMTase had an isoelectric point of 5.15 and was reversibly inhibited by the thiol reagentp-hydroxymercuribenzoic acid.
Extension and Simplification of Salukvadze’s Solution to the Deterministic Nonhomogeneous LQR Problem
Authors: Hampton R. D. , Knospe C. R. , Townsend M. A. 
Published: July 2002

AbstractIn a previous paper (Hampton, R. D., et al., 1996, “A Practical Solution to the Deterministic Nonhomogeneous LQR Problem,” ASME Journal of Dynamic Systems, Measurement, and Control, Vol. 118, pp. 354–360.) the authors presented a solution to the nonhomogeneous linear-quadratic-regulator (LQR) problem, for the case of known, deterministic, persistent (“non-dwindling”) disturbances. The authors used variational calculus and state-transition-matrix methods to produce an optimal matric solution, for bounded determinist forcing terms. A restricted version of this problem (treating dwindling disturbances) was evidently first investigated by Salukvadze, M. E., 1962, “Analytic Design of Regulators (Constant Disturbance),” Automation and Remote Control, Vol. 22, No. 10, Mar., pp. 1147–1155, using a differential-equations approach. The present paper uses Salukvadze’s approach to extend his work to the case of non-dwindling disturbances, with cross-weightings between state- and control vectors, and pursues the solution to the same form reported previously in Hampton et al.
Heat Transfer and Pressure Drop Characteristics of Laminar Flow
Through a Circular Tube With Longitudinal Strip Inserts Under Uniform Wall Heat
Flux
Authors: Saha S. K. , Langille P. 
Published: July 2002

Abstract
Heat transfer and pressure drop characteristics in a circular tube fitted with full-length strip, short-length strip, and regularly spaced strip elements connected by thin circular rods have been investigated experimentally. The strips have been rectangular, square and crossed in cross-section with different aspect ratio. Laminar flow of water and other viscous liquids was considered. The rod diameter and length of the strip-rod assembly and the length of the strips were varied. Isothermal friction factor data has been generated. The heat transfer test section was heated electrically imposing axially and circumferentially constant wall heat flux (UWHF) boundary condition. Reynolds number, Prandtl number, strip length, strip ratio, space ratio, and rod-diameter govern the characteristics. Smaller rod-diameter in the strip-rod assembly or “pinching” of the strips in place rather than connecting the strip elements by rods performs better thermohydraulically. Short-length strips (upto a limited fraction of the test section tube length) perform better than the full-length strip. The friction factor correlation and the correlation for Nusselt number under UWHF condition for full-length strip have been modified to make them suitable for short-length strip as well as regularly-spaced strip elements. Thermal entrance length in the correlations is represented by Graetz number. Friction factor and Nusselt number correlations for short-length strips as well as regularly-spaced strip elements, in the limit, reduce to their full-length counterparts.
Three-Dimensional Finite Element Analysis of the Cold Expansion of
Fastener Holes in Two Aluminum Alloys
Authors: Kang Jidong , Johnson W. Steven , Clark David A. 
Published: July 2002

Abstract
A three-dimensional finite element analysis is developed for the cold expansion process in two aluminum alloys, 2024-T351 and 7050-T7451. The entire cold working process including hole expansion, elastic recovery, and finish reaming is simulated. Both isotropic hardening and kinematic hardening models are considered in the numerical calculations. The results suggest that a three-dimensional nature exists in the residual stress fields surrounding the hole. There are significant differences in residual stresses at different sections through the thickness. However, residual stress at the surface is shown to remain the same for the different plastic hardening models after the hole has recovered and finish reaming has been performed. The reaming of the material around the hole has slight effect on the maximum value and distribution of residual stresses. A comparison has been drawn between the FEA of average through thickness strain and a previous experimental investigation of strain that utilized neutron diffraction and modified Sachs boring on a 7050 aluminum specimen containing a cold expanded hole. The different methods show very good agreement in the magnitude of strain as well as the general trend. The conclusions obtained here are beneficial to the understanding of the phenomenon of fatigue crack initiation and growth at the perimeter of cold worked holes.
Abstract: Mass microanalyzer using electron-beam guiding ion source
Authors: Takagi T. , Yamada I. , Kishi T. 
Published: July 2002

A new apparatus which performs microanalysis by analyzing ions evaporated from a specimen by the impact of a focused, scanned electron beam from an electron-optical column which includes a ring cathode and electrostatic lenses is described. A model is developed that involves four steps:
(1) Material is locally evaporated from a specimen by bombardment with electrons of energy about 10 keV.
(2) The evaporated atoms are ionized by inelastic collisions with both primary and secondary electrons near the point of impact of the electron beam.
(3) The ions are trapped in the potential well (∠0.1–1 eV) formed by the electron beam.
(4) The ions are accelerated through the electron-optical column toward the entrance slit of the mass spectrometer and are mass analyzed.
The model predicts that for a primary electron current Ie, the collected ion current Ii is equal to (2m/M) Ie or 4×10−8 A for N2 ions and Ie=1 mA. For high beam currents (1 mA), the spatial resolution of the system was demonstrated to be less than 1 mm. The ultimate spatial resolution of the system is estimated to be 1 μm with the removal of 44 atom layers from the specimen; this estimate is based on a minimum detectable ion current of 10−16 A and a collection angle of 10−2 rad.
Experimental results were obtained from a specimen of evaporated NaCl on stainless steel. The preliminary experiments demonstrate the possible use of this instrument for surface analysis and the theory indicates the technique could provide micron spatial resolution.
Dangling bonds and Schottky barriers
Authors: Sankey Otto F. , Allen Roland E. , Ren Shang-Fen , Dow John D. 
Published: July 2002

We review theoretical interpretations of Schottky barriers and Fermi-level pinning, which result when metals and other chemical species are deposited on semiconductor surfaces. Experiments indicate that these two phenomena are closely connected, so a theory of Schottky barriers must also explain Fermi-level pinning for submonolayer coverages of both metallic and nonmetallic species. Proposed mechanisms include the following: (a) Intrinsic surface states. For GaAs and several other materials, there are no intrinsic surface states within the band gap; GaP, e.g., does have surface states in the gap, but they are not at the correct energy to explain Schottky barrier formation. (b)
M e t a l-induced gap states. These states, which require a thick metal overlayer, cannot explain Fermi-level pinning at submonolayer metallic coverages. They also cannot explain why a single semiconductor (n-type InP) exhibits two distinct Schottky barrier heights. Furthermore, they cannot explain why the Schottky barrier persists when there is an oxide layer between semiconductor and metal. Metal-induced states can in principle give rise to Schottky barriers at defect-free interfaces, but they fail to explain much of the existing experimental data for III–V semiconductors and Si. (c) The classic Schottky model. This model is not in agreement with experiment for III–V and Group IV semiconductors, but does appear to account for the measurements involving nonreactive metals on GaSe−a layered material expected to be relatively free of defects. (d) The Spicer defect model. This phenomenological model, now supported by microscopic theoretical studies, appears to account for many of the observations regarding Schottky barrier and Fermi-level pinning. We review our theoretical investigations within the framework of the defect model, which provide a satisfactory explanation of the principal observations for both III–V and Group IV semiconductors. We conclude that the levels responsible for Schottky barriers and Fermi-level pinning arise from two sources: (1) bulk-derived deep levels (e.g., the deep donor level for the antisite defect AsGa, which persists when this defect is present at the surface, but which is shifted in energy), and (2) dangling-bond deep levels (which are also shifted in energy according to the environment of the dangling bond). Most of the observed Schottky barriers—for both III–V and Group IV semiconductors—are attributed to dangling bonds.