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Morphological analysis of pits formed on Al 2024-T3 in chloride aqueous solution

Silva, JWJ; Bustamante, A. G.; Codaro, E. N.; Nakazato, R. Z.; Hein, LRO
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 356-365
ENG
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It has been used a new image analysis method, based on segmentation by shape parameters, for pits morphology examination from Al 2024 aluminum-copper alloy in chloride aqueous solution. Corrosion behavior of this alloys in naturally aerated 3.5% NaCl solution has been investigated through open circuit potential measurements. Afterwards, pits have been characterized by image analysis taking density and size measurements right from corroded surfaces. Morphological investigation has been conducted for profiles, cut orthogonally from mean surface planes, and observed through light microscopy. Image analysis data could demonstrate that pits are wider than deep, evoluting for conical, quasi-conical or irregular shapes. Most pits have presented a quasi-conical morphology, but the wider ones have evoluted to an irregular shape influenced by sub-surface microstructure. Image analysis based on shape segmentation could enhance the differences on morphological behavior. (C) 2004 Elsevier B.V. All rights reserved.

Studies on the interaction between humic substances and conducting polymers for sensor application

Venancio, Everaldo C.; Consolin Filho, Nelson; Constantino, Carlos J. L.; Martin-Neto, Ladislau; Mattoso, Luiz H. C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 24-30
ENG
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The interaction between humic substances and poly(o-ethoxyaniline) (POEA), a conducting polymer, was investigated for both solution and self-assembled films. The results have shown that the humic substances induce a doping of POEA by protonation, as indicated by UV-Vis and Raman spectroscopies. The atomic force microscopy (AFM) studies on the self-assembled films have shown that the average roughness of the polymer film has increased after exposing it to humic substances (fulvic and humic acids), consistent with the interaction between POEA and humic substances. However, this change in morphology is reversible by washing the films with water in agreement with the electrical data allowing using this system in sensor applications. Here, the sensor formed by an array of different sensing units was able to detect and distinguish humic substances in aqueous solution, as shown by multivariate analysis (principal component analysis). The motivation to detect humic substance comes due to its importance in terms of quality control of water or soil. ©2005 Sociedade Brasileira de Química.

Immersion enthalpy variation of surface-modified mineral activated carbon in lead (II) aqueous solution adsorption: the relation between immersion enthalpy and adsorption capacity

Giraldo,L.; Moreno-Piraján,J.C.
Fonte: Fundação Editora da Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP Publicador: Fundação Editora da Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
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An activated carbon was obtained by chemical activation with phosphoric acid, CM, from a mineral carbon. Afterwards, the carbon was modified with 2 and 5 molL-1, CMox2 and CMox5 nitric acid solutions to increase the surface acid group contents. Immersion enthalpy at pH 4 values and Pb2+ adsorption isotherms were determined by immersing activated carbons in aqueous solution. The surface area values of the adsorbents and total pore volume were approximately 560 m².g-1 and 0.36 cm³g-1, respectively. As regards chemical characteristics, activated carbons had higher acid sites content, 0.92-2.42 meq g-1, than basic sites, 0.63-0.12 meq g-1. pH values were between 7.4 and 4.5 at the point of zero charge, pH PZC. The adsorbed quantity of Pb2+ and the immersion enthalpy in solution of different pH values for CM activated carbon showed that the values are the highest for pH 4, 15.7 mgg-1 and 27.6 Jg-1 respectively. Pb2+ adsorption isotherms and immersion enthalpy were determined for modified activated carbons and the highest values were obtained for the activated carbon that showed the highest content of total acid sites on the surface.

Correlation between Corrosion Potential and Pitting Potential for AISI 304L Austenitic Stainless Steel in 3.5% NaCl Aqueous Solution

Alonso-Falleiros,Neusa; Wolynec,Stephan
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2002 EN
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We investigated the effect of surface finish of two AISI 304L (UNS S30403) stainless steels on the corrosion potential (Ecorr) in 3.5% NaCl aqueous solution and its value was compared with the pitting potential (Ep) value and the type of anodic potentiodynamic curve obtained for determination of Ep in this solution. Five different surface finishes were examined. Ecorr and its standard deviation are strongly affected by the type of surface finish. Moreover, there are evidences of a linear correlation between Ecorr and Ep, as well as between the percentage of anodic curves with a well-defined pitting potential and the uncertainty in the determination of Ecorr.

Bioremediation of herbicide velpar K® in vitro in aqueous solution with application of EM-4 (effective microorganisms)

Ramos,Márcio Antônio Gomes; Yoshioka,Sergio Akinobu
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2012 EN
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This work assessed the bioremediation of herbicide Velpar K®, in vitro in aqueous solution, used against weeds in sugar cane in São Paulo state. The herbicide contained Hexazinone and Diuron. It was used the microbial inoculant denominated Effective Microorganisms (EM-4), pool of microorganisms from soil that contained lactic and photosynthetic bacteria, fungi, yeasts and actinomycetes for bioremediation. Results for the depth of cultivation on agar-agar inoculated with EM-4 showed the microorganisms growth in the concentrations between 0.2% and 1.0% of the Velpar K®in the gel. The analysis of high performance liquid chromatography (HPLC) showed that the EM-4 was effective for the bioremediation of the herbicide, which reached the values of 80% for diuron and 70% for hexazinone after 21 days in solution of 2:1 of Velpar K®/EM-4 ratio. These results could be useful for planning the bioremediation of contaminated areas with Velpar K®.

Changes in conformation of reduced cytochrome c in neutral aqueous solution.

Land, E J; Swallow, A J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/09/1976 EN
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In neutral aqueous solution, high concentrations of alcohols perturb cytochrome c in such a way that reduction by means of ionizing radiation results in the formation of abnormal conformers of ferrocytochrome c resembling those previously seen on reduction in alkaline solution. These relax to normal ferrocytochrome c in about 0.1 s.

Aggregation of ferrihaems. Dimerization and protolytic equilibria of protoferrihaem and deuteroferrihaem in aqueous solution

Brown, S. B.; Dean, T. C.; Jones, Peter
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1970 EN
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1. The absorption spectra of deutero- and proto-ferrihaem in aqueous solution at 25°C show marked changes with concentration and pH in the Soret band region. Quantitative studies of these phenomena imply that they are associated with ferrihaem dimerization and with protolytic equilibria involving monomeric (M) and dimeric (D) ferrihaem species according to the scheme: [Formula: see text] 2. For deuteroferrihaem we obtain K=1.9×10−2, pKa(M)=7.1, pKa(D)=7.4. Protoferrihaem has a much higher dimerization constant, K=4.5 and pKa(D)=7.5 (pKa(M) is not accessible). 3. Possible structural relationships between monomeric and dimeric ferrihaem species in solution are discussed in relation to recent work on the oxo-bridged nature of crystalline ferrihaem dimers.

γ-Irradiation of Thymine Dimers in Aqueous Solution

Deering, R. A.; Snipes, Wallace
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1968 EN
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Thymine dimers were irradiated in aqueous solution with 60Co γ-rays in N2 or O2. Thymine and unidentified non-UV-absorbing products appeared. The thymine was identified by spectrophotometry, chromatography, and ability to support the growth of Escherichia coli 15 T-. Residual dimer was determined by a UV-reversibility assay. The G-values for dimer breakage were approximately equal in N2 and O2. At low γ-doses, about two thymines were produced per dimer broken in N2, whereas only about one thymine appeared per dimer broken in O2. For dimer irradiated in frozen solution, the yield of thymine was at least 100 times less than in liquid.

Hyaluronan: the absence of amide–carboxylate hydrogen bonds and the chain conformation in aqueous solution are incompatible with stable secondary and tertiary structure models

Blundell, Charles D.; Deangelis, Paul L.; Almond, Andrew
Fonte: Portland Press Ltd. Publicador: Portland Press Ltd.
Tipo: Artigo de Revista Científica
EN
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Contradictory descriptions for the aqueous solution conformation of the glycosaminoglycan hyaluronan (HA) exist in the literature. According to hydrodynamic and simulation data, HA molecules are stiffened by a rapidly interchanging network of transient hydrogen bonds at the local level and do not significantly associate at the global level. In marked contrast, models derived from NMR data suggest that the secondary structure involves persistent hydrogen bonds and that strong associations between chains can occur to form vast stable tertiary structures. These models require an extended 2-fold helical conformation of the HA chain and specific hydrogen bonds between amide and carboxylate groups. To test these descriptions, we have used 15N-labelled oligosaccharides and high-field NMR to measure pertinent properties of the acetamido group. The amide proton chemical shift perturbation and carboxylate group pKa value are inconsistent with a highly populated hydrogen bond between the amide and carboxylate groups. Amide proton temperature coefficients and chemical exchange rates confirm this conclusion. Comparison of oligomer properties with polymeric HA indicates that there is no discernible difference in amide proton environment between the centre of octasaccharides and the polymer...

Stability of a Trivalent Recombinant Protein Vaccine Formulation Against Botulinum Neurotoxin during Storage in Aqueous Solution

Vessely, Christina; Estey, Tia; Randolph, Theodore W.; Henderson, Ian; Cooper, Julianne; Nayar, Rajiv; Braun, LaToya Jones; Carpenter, John F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/2009 EN
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The adsorption of recombinant botulinum neurotoxin (BoNT) protein-derived vaccine antigens to aluminum salt adjuvants has been previously studied for the development of a trivalent vaccine against the neurotoxins1. The current paper describes an investigation of the stability of recombinant BoNT antigens adsorbed to aluminum salt adjuvants during storage in aqueous solution. Both chemical and physical changes occurred during storage. Phosphate groups in the buffer exchanged with hydroxyl groups on the adjuvant surface. The resulting changes in solution pH and adjuvant surface chemistry promoted more favorable electrostatic interaction between the BoNT proteins and the surface, possibly increasing the affinity of the proteins for the surface during storage. Fluorescence and UV spectroscopy suggested changes to protein structure during storage, whereas differential scanning calorimetry showed changes to thermal processes related to protein conformation and/or surface adsorption. The consequence of the chemical and physical changes to the proteins was a decrease in the ability to desorb protein from the adjuvant surface during storage. Overall, the results of this study emphasize the utility of a thorough characterization of the interactions between protein antigens and aluminum salt adjuvants.

Conformational Heterogeneity of a Leucine Enkephalin Analog in Aqueous Solution and SDS Micelles: Comparison of Time-Resolved FRET and Molecular Dynamics Simulations

Unruh, Jay R.; Kuczera, Krzysztof; Johnson, Carey K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 29/10/2009 EN
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We have undertaken time-resolved Förster resonance energy transfer (FRET) and molecular dynamics simulations to analyze conformations and conformational heterogeneity of an analog of leucine enkephalin in solution and in the presence of SDS micelles. Enkephalins are opioid pentapeptides that interact with opioid receptors in the central nervous system. We used time-correlated single-photon counting to detect energy transfer between the N-terminal tyrosine and a tryptophan residue substituted for phenylalanine at the 4 position. FRET from Tyr to Trp was measured over a temperature range from 5°C to 55°C in aqueous solution. By taking into account Tyr rotamer interconversion rates measured previously, we determined average distances between Tyr and Trp for the two populated rotameric conformations of Tyr. Molecular dynamics simulations (100 ns) support this analysis and indicate extensive conformational heterogeneity. The simulations also predict that the FRET orientational factor is correlated with the Tyr-Trp separation. Failure to account for the correlation between orientation and distance results in errors that appear to be largely offset in YGGWL by a weighting bias inherent in the R−6 dependence of the energy-transfer rate. The Tyr lifetimes decrease upon titration of the peptides with SDS...

Sucrose in Aqueous Solution Revisited: 1. Molecular Dynamics Simulations and Direct and Indirect Dipolar Coupling Analysis

Xia, Junchao; Case, David A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Although the crystal structure of the disaccharide sucrose was solved more than 30 years ago, its conformational distribution in aqueous solution is still a matter of debate. We report here a variety of molecular dynamics simulations (mostly of 100 ns) using the GLYCAM06 force field and various water models, paying particular attention to comparisons to NMR measurements of residual dipolar couplings and electron-mediated spin-spin couplings. We focus on the glycosidic linkage conformation, the puckering phase angle of the fructose ring, and intramolecular hydrogen bonds between the two sugars. Our results show that sucrose is indeed a dynamic molecule, but the that crystal conformation is qualitatively the dominant one in dilute solution. A second conformational basin, populated in many force fields, is probably over-stabilized in the calculations.

In situ wet-cell TEM observation of gold nanoparticle motion in an aqueous solution

Chen, Xin; Wen, Jianguo
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 29/10/2012 EN
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In situ wet-cell transmission electron microscopy (TEM) technology enables direct observation of nanomaterials in a fully hydrated environment with high spatial and temporal resolution, which can be used to address a wide range of scientific problems. In this paper, the motions of approximately 5-nm sized gold nanoparticles in an aqueous solution are studied using the wet-cell TEM technology. It is observed that gold nanoparticles can be either in a single particle or cluster forms, and dynamic displacement and rotation motions are observed for both forms in the solution. Under electron beam irradiation, nanoparticles in some clusters gradually fused together; sometimes they also showed dramatic growth behavior. Mechanisms for the motion and growth of the particles/clusters are discussed.

Development of Wood Apple Shell (Feronia acidissima) Powder Biosorbent and Its Application for the Removal of Cd(II) from Aqueous Solution

Suresh, Ch.; Reddy, D. Harikisore Kumar; Harinath, Yapati; Naik, B. Ramesh; Seshaiah, K.; Reddy, Annareddy V. Ramana
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
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A biosorbent was prepared by using wood apple shell (WAS) powder and studied its application for the removal of Cd(II) from aqueous solution by a batch method. The biosorbent was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and elemental analysis. WAS is principally made up of lignin and cellulose, containing functional groups such as alcoholic, ketonic, and carboxylic groups which can be involved in complexation reactions with Cd(II). The effect of experimental parameters like initial pH, contact time, metal ion concentration, and sorbent dose on adsorption was investigated. The optimum pH for biosorption of Cd(II) onto WAS was found to be pH 5.0 and the quantitative removal of Cd(II) ions was achieved in 30 min. The kinetic study showed that the biosorption process followed the pseudo-second-order rate. Experimental data were analyzed by Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. Desorption studies were carried out using HCl solution.

Efficient removal of Eriochrome black-T from aqueous solution using NiFe2O4 magnetic nanoparticles

Moeinpour, Farid; Alimoradi, Asma; Kazemi, Maryam
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 27/08/2014 EN
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The magnetic NiFe2O4 nanoparticles have been synthesized and used as adsorbents for removal of an azo dye, Eriochrome black-T (EBT) from aqueous solution. The NiFe2O4 nanoparticles were characterized by scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). The adsorption studies were carried out under various parameters, such as pH, adsorbent dosage, contact time and initial dye concentration. The experimental results show that the percentage of adsorption increases with an increase in the adsorbent dosage. The maximum adsorption occurred at the pH value of 6.0. The equilibrium uptake was increased with an increase in the initial dye concentration in solution. Adsorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm equations. The best fit was obtained by the Langmuir model with high correlation coefficients (R2 = 0.9733) with a maximum monolayer adsorption capacity of 47.0 m g/g.

Salt effects on aggregation of O-carboxymethylchitosan in aqueous solution

Zhu, A.; Dai, S.; Li, L.; Zhao, F.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
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The effects of salt with different valences (NaCl, CaCl2 and CrCl3) on the aggregation of O-carboxylmethylchitosan (OCMCS) in dilute aqueous solution were investigated using viscometry, dynamic laser light scattering (DLS) and atomic force microscopy (AFM). With increasing OCMCS concentration beyond a critical aggregation concentration (cac) of ∼0.045 g/l, the aggregation of OCMCS appears in solution. The driving forces of the OCMCS aggregation are intermolecular hydrogen bond, hydrophobic interaction and electrostatic repulsion. The OCMCS aggregation behavior strongly depends on the valence of salt. When NaCl is added, the aggregate size increases with NaCl concentration. When CaCl2 or CrCl3 is added to a given OCMCS concentration, there exists a critical concentration each of Ca2+ and Cr3+. Before the critical concentration, the aggregates decrease in size with increasing salt concentration due to the intra-aggregate complexation; while after the critical concentration, the size of the aggregates increases with salt concentration due to the inter-aggregate complexation. Moreover, the effect of Cr3+ on the OCMCS aggregation is greater than that of Ca2+. The formation of the intra-aggregate complexation is found to be a kinetic process and the aggregate size decreases with time; the formation of the inter-aggregate complexation is also kinetic where the aggregate size increases with time. The aggregates dominated by the intra-aggregate complexation are small...

Infrared CD of deoxy oligonucleotides. Conformational studies of 5'd(GCGC)3', 5'd(CGCG)3', 5'd(CCGG)3', and 5'd(GGCC)3' in low and high salt aqueous solution.

Birke, S S; Moses, M; Kagalovsky, B; Jano, D; Gulotta, M; Diem, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1993 EN
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Infrared (vibrational) circular dichroism (VCD) spectra have been obtained for the self-complementary tetranucleotides, 5'd(CGCG)3', 5'd(GCGC)3', 5'd(CCGG)3', and 5'd(GGCC)3'. In buffered aqueous solution at low salt concentration, these tetramers exhibit spectra associated with right-handed polymers, although the spectra differ significantly for the four species. In high salt solution, a B-->Z transition occurs in 5'd(CGCG)3', while the other tetranucleotides appear only slightly altered. Temperature dependent studies of these oligonucleotides reveal a greater amount of thermal stability for the tetramers in low salt than for the high salt solutions. VCD intensities computed via the exciton formalism are compared with observed results.

Molecular rulers for measuring RNA structure: sites of crosslinking in chlorambucilyl-phenylalanyl-tRNAPhe (yeast) and chlorambucilyl-pentadecaprolyl-phenylalanyl-tRNAPhe (yeast) intramolecularly crosslinked in aqueous solution.

Wickstrom, E; Behlen, L S; Reuben, M A; Ainpour, P R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1981 EN
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Intramolecular crosslinking of yeast phenylalanine tRNA in aqueous solution with rigid, variable-length crosslinking reagents, which we call "molecular rulers," has given results in reasonable agreement with the crystal structure. Chlorambucilyl-[3H]phenylalanyl-tRNAPhe crosslinked intramolecularly at G-71 and A-73, whereas chlorambucilyl-pentadecaprolyl-[3H]phenylalanyl-tRNAPhe crosslinked at G-20 and Y-37. The pentadecaprolyl reagent was predicted to be 62 A long, including chlorambucil and phenylalanine; the sites that it reached are 60 A distant from the 3' OH (in the case of G-20) or 80 A distant (in the case of Y-37) in the crystal structure of tRNAPhe. The close agreement between the length of the reagent and the distance of G-20 from the 3' OH in the crystal structure illustrates the rigidity of the tRNAPhe molecule in the dihydrouridine loop region at the corner of the molecule. The apparent ability of the 62-A-long reagent to crosslink to a site, Y-37, that is 80 A distant from the 3' OH in the crystal structure appears to illustrate the flexibility of both the 3' A-C-C-A terminus and the anticodon stem and loop, with respect to the tRNA molecule. These observations demonstrate the utility of oligoproline-based crosslinking reagents as rigid...

Conductivity and Viscosity Measurements for Binary Lysozyme Chloride Aqueous Solution and Ternary Lysozyme-Salt-Water Solution

Buzatu, D.; Petrescu, E.; Buzatu, F. D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/03/2004
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We use the conductimetric method, adequate to electrolytes, to determine the lysozyme charge in lys-water and ternary lys-salt-water systems. We measured also the viscosities for the above binary and ternary systems in the same conditions at pH$=4.5$ and T$=298$ K, measurements that allow us to see any effect of viscosity on cations mobilities and implicitly on the lysozyme charge. The method is illustrated for the lysozyme chloride aqueous solution system at 25$^o$ C, using the data reported here for pH$=4.5$ at 0.15, 0.6, 0.8, 1., 1.5, 2., 2.5, 3., 3.5 mM (mg/mL) lysozyme chloride concentrations. The method was also applied to ternary lys-salt-water systems in the same conditions at pH$=4.5$ and T$=25^o$ C. Ternary conductivities are reported for a mean concentration 0.6 mM of lysozyme chloride in all systems and a mean concentration 0.01, 0.025, 0.05, 0.1, 0.175, 0.2, 0.5, 0.7, 0.9, 1.2, 1.3 and 1.4 M for NaCl; 0.005, 0.01, 0.05, 0.1, 0.175, 0.2, 0.5, 0.7, 0.9, 1.2, 1.3, 1.4 and 1.5 M for KCl; 0.005, 0.01, 0.05, 0.1, 0.175, 0.2, 0.5, 0.7, 1.2, 1.3, 1.4, 1.5, 1.6 and 1.7 M for NH$_4$Cl.; Comment: 6 figures

Molecular rulers for measuring RNA structure: sites of crosslinking in chlorambucilyl-phenylalanyl-tRNA^(Phe) (yeast) and chlorambucilyl-pentadecaprolyl-phenylalanyl-tRNA^(Phe) (yeast) intramolecularly crosslinked in aqueous solution

Wickstrom, Eric; Behlen, Linda S.; Reuben, Michael A.; Ainpour, Parviz R.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/04/1981
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Intramolecular crosslinking of yeast phenylalanine tRNA in aqueous solution with rigid, variable-length crosslinking reagents, which we call "molecular rulers," has given results in reasonable agreement with the crystal structure. Chlorambucilyl-[^(3)H]phenylalanyl-tRNA^(Phe) crosslinked intramolecularly at G-71 and A-73, whereas chlorambucilyl-pentadecaprolyl-[^(3)H]phenylalanyl-tRNA^(Phe) crosslinked at G-20 and Y-37. The pentadecaprolyl reagent was predicted to be 62 Å long, including chlorambucil and phenylalanine; the sites that it reached are 60 Å distant from the 3' OH (in the case of G-20) or 80 Å distant (in the case of Y-37) in the crystal structure of tRNA^(Phe). The close agreement between the length of the reagent and the distance of G-20 from the 3' OH in the crystal structure illustrates the rigidity of the tRNA^(Phe) molecule in the dihydrouridine loop region at the corner of the molecule. The apparent ability of the 62-Å-long reagent to crosslink to a site, Y-37, that is 80 Å distant from the 3' OH in the crystal structure appears to illustrate the flexibility of both the 3' A-C-C-A terminus and the anticodon stem and loop, with respect to the tRNA molecule. These observations demonstrate the utility of oligoproline-based crosslinking reagents as rigid...