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  • 11
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2137-2158 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of monovalent (Na+) and divalent (Mg++) cations on the temperature and breadth of the helix-coil transition of phage DNA have been investigated. The experimental results confirm the findings of Dove and Davidson [J. Mol. Biol. 5, 467-478 (1962)] for the limiting cases of zero divalent ion concentration and saturating levels of divalent ion, and extend their findings to the intermediate region of Mg++ concentrations. A theory for the dependence of transition temperature on the ion concentrations is developed, utilizing the approach of Wyman [Adv. Protein Chem. 19, 223-286 (1964)], modified to account for electrostatic nonideality of the polyelectrolytes. The theory is in agreement with Manning's treatment of the experiments of Dove and Davidson [Biopolymers 11, 937-949, 951-955 (1972)] and is in fair agreement with experimental data over the entire range of ion concentrations. Further investigation of the structure and ion-binding properties of the denatured form will be required before a quantitative comparison between theory and experiment can be performed.
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  • 12
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 205-214 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Changes in Δν½, the nmr linewidth of 23Na, have been determined during titrations of helical DNA with polyamines (divalent putrescine and trivalent spermidine) and with inorganic cations (Mg2+ and Co(NH3)63+). In each case additions of a multivalent cation (Mz+) to a solution containing NaDNA and NaCl cause decreases in Δν½, which is a population-weighted average of contributions from nuclei in bound and free environments. Thus, the binding of Mz+ to DNA displaces sodium ions from regions where the quadrupolar relaxation of 23Na is relatively efficient. At a given extent of titration, the binding of a polyamine produces a smaller decrease in Δν½ than does the binding of an inorganic ion of the same valence. The concentration dependence of Δν½ during the course of a titration can be interpreted most simply as a two-state ion-exchange reaction by assuming that the binding of Mz does not alter RB, the average relaxation rate of sodium nuclei that remain bound. On the basis of this assumption, the initial linear portions of titration curves can be analyzed to determine upper bounds for r°, the number of sodium ions bound per DNA phosphate in the absence of any competing counterion. Analyzing the titration curves for the four multivalent competitors leads to a range of upper-bound estimates for r°: 0.5-0.8. The differences in these estimates could indicate that polyamines displace fewer sodium ions from DNA than do their smaller inorganic counterparts. Alternatively, the range in upper-bound estimates for r° could also reflect specific differences in the effects of the various multivalent cations on RB, if this relaxation rate does change during titration.
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  • 13
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 825-841 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The strand-separation transition of T7 DNA has been investigated by temperature shift and viscosity measurements in two formamide-water solvents. The strand-separation region is quite narrow, and follows directly at the end of the denaturation transition observed by absorbance. The kinetics of strand separation of T7 DNA are slow and complex in the strand-separation transition. Similarities and differences in the behavior of T2 and T7 DNA in strand separation are indicated and discussed. Briefly, the time course of strand separation and the conformational changes observed in the population undergoing strand separation are similar for the two molecules. However, the transition breadths and the interval between the helix-coil transition and the strand-separation transition differ markedly. Both DNA molecules exhibit hysteresis in the strand-separation region. For both molecules, it appears that strand separation involves the coupled denaturation and disentanglement of the two-stranded form found at the end of the helix-coil transition.
    Additional Material: 9 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 717-728 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sedimentation velocity runs as a function of temperature in the region of the alkaline helix-coil transition have enabled us to demonstrate the existence of stable two-stranded intermediates in the strand-separation process for T7 DNA. The strand-separation transition under these conditions has an intrinsic breadth of ∼1°C, and within this temperature range (Tm + 2°C 〈 T 〈 Tm + 3°C) the intermediate forms are progressively converted (as a function of temperature) to single-stranded DNA. Parallel characterizations of the strand-separation transition by viscosity and absorbance-renaturation studies in the alkaline solvent are entirely consistent with the sedimentation experiments. Comparison of the experimental mean sedimentation coefficient of the intermediate forms with theoretical predictions for branched structures suggests that in these molecules the two strands are connected at a single point, not centrally located with respect to the ends of the molecule.
    Additional Material: 7 Ill.
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  • 16
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Closed-form expression have been derived for the polyelectrolyte contribution to the colligative properties of solutions containing rodlike polyions in the presence of excess added salt. The derivations are based on: the conventional Poisson-Boltzmann equation for cylindrical symmetry; the thermodynamics of the cell model developed by Marcus [J. Chem. Phys. 23, 1057-1068 (1955)]; and an equation derived from the cylindrical Poisson-Boltzmann cell model by Anderson and Record [Biophys. Chem. 11, 353-360 (1980)]. Subject to the inherent limitations of the Poisson-Boltzmann approximation [Fixman (1979) J. Chem. Phys. 70, 4995-5005], the resulting expressions are nevertheless applicable outside the “limit of infinite dilution.” They conform over a range of salt concentrations to the limiting laws deduced by Manning from the hypothesis of counterion condensation [J. Chem. Phys. 51, 924-933 (1969)]. This hypothesis is found to be compatible with the Poisson-Boltzmann cell model but is not required in the derivation of the thermodynamic coefficients presented here. It is demonstrated that the magnitude of the polyion axial charge density plays a critical role in determining the low-salt limiting forms of the colligative properties obtained from the Poisson-Boltzmann equation, in close analogy with Manning's model.
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  • 17
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1249-1265 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In solutions containing DNA and cations of more than one type, the competitive interactions of these cations with DNA can be modeled as an ion exchange process that can be described quantitatively by means of the theoretical approach reported in this paper. Under conditions of experimental interest the radial distribution function of each type of counterion is calculated from the results of canonical Monte Carlo (MC) simulations using the primitive model for DNA (having a helical charge distribution) and for the electrolyte ions. These ions consist of monovalent coions, monovalent counterions intended to represent Na+, and counterions of a second type designated Mz+, having variable size and charge (z ≥ 1). The competitive association of these counterions with DNA is described in terms of D, a parameter analogous to an ion exchange equilibrium quotient. Values of D are calculated from the results of our MC simulations and compared with corresponding predictions of the Poisson-Boltzmann (PB) cell model and with results inferred from analyses of previously published nmr measurements. Over typical experimental concentration ranges (0.02M 〈 [Na+] 〈 0.20M, 0.001 〈 [Mz+] 〈 0.160M), DMC and DPB both are predicted to be relatively independent of the bulk ion concentrations. For various specifications of the size and charge of the competing cation (Mz+), DMC and DPB exhibit similar trends, although the MC simulations consistently predict that the cations bearing a higher charge density than that of Na+ are somewhat stronger competitors than indicated by the PB calculations. For monovalent and divalent competitors of varying radii, theoretical predictions of D are compared with values obtained by fitting nmr measurements. If the hard-sphere radii specified in the simulations are the (hydrated) ionic radii determined from conductance measurements, then the MC predictions and the corresponding nmr results are in reasonable agreement for various monovalent competitors and for a divalent polyamine, but not for Ca2+ and Mg2+.
    Additional Material: 5 Ill.
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  • 18
    ISSN: 1040-0397
    Keywords: Electrochemical quartz crystal microbalance ; Cyclic voltammetry ; Copper electrodeposition ; Copper electrodissolution ; Silver electrodeposition ; Silver electrodissolution ; Gold/quartz electrode ; Microweighing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The design and characteristics of a stationary, compact holder for an electrochemical quartz crystal microbalance (EQCM) are presented. A Au/quartz crystal oscillator is vertically mounted in a polytetrafluoroethylene body of the holder. The crystal is sealed with an O-ring and is easily accessible for change. The performance of the holder was tested under cyclic voltammetry (CV) conditions with the Ag+ /Ag and Cu+ /Cu electrodeposition/electrodissolution processes. Frequency changes due to mass changes of the Au/quartz electrode were correlated with CV parameters. The holder was calibrated for a 5 MHz crystal oscillator by means of CV anodic stripping of silver. The mass sensitivity was 19.5 ± 0.1 ng Hz-1 cm-2. The concentration sensitivity was 14.2 ± 0.2 μM Hz-1 cm-2 at a potential scan rate of 0.01 V s-1 and 23.7 ± 0.3 μM Hz-1 cm-2 at a scan rate of 0.02 V s-1 for a potential of scan reversal which was 250 mV more negative than the electrodeposition peak potential.
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  • 19
    Publication Date: 2002-04-27
    Description: Little is known of how plant disease resistance (R) proteins recognize pathogens and activate plant defenses. Rcr3 is specifically required for the function of Cf-2, a Lycopersicon pimpinellifolium gene bred into cultivated tomato (Lycopersicon esculentum) for resistance to Cladosporium fulvum. Rcr3 encodes a secreted papain-like cysteine endoprotease. Genetic analysis shows Rcr3 is allelic to the L. pimpinellifolium Ne gene, which suppresses the Cf-2-dependent autonecrosis conditioned by its L. esculentum allele, ne (necrosis). Rcr3 alleles from these two species encode proteins that differ by only seven amino acids. Possible roles of Rcr3 in Cf-2-dependent defense and autonecrosis are discussed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kruger, Julia -- Thomas, Colwyn M -- Golstein, Catherine -- Dixon, Mark S -- Smoker, Matthew -- Tang, Saijun -- Mulder, Lonneke -- Jones, Jonathan D G -- New York, N.Y. -- Science. 2002 Apr 26;296(5568):744-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11976458" target="_blank"〉PubMed〈/a〉
    Keywords: Alleles ; Amino Acid Sequence ; Base Sequence ; Cladosporium/*physiology ; Cloning, Molecular ; Cysteine Endopeptidases/chemistry/*genetics/*metabolism ; Cysteine Proteinase Inhibitors/pharmacology ; Gene Expression Regulation, Plant ; *Genes, Plant ; Immunity, Innate ; Leucine/analogs & derivatives/pharmacology ; Lycopersicon esculentum/*enzymology/genetics/*microbiology/physiology ; Molecular Sequence Data ; Mutation ; Phenotype ; *Plant Diseases ; Plant Leaves/enzymology ; Plant Proteins/*metabolism ; Plants, Genetically Modified ; Promoter Regions, Genetic ; Recombinant Fusion Proteins/chemistry/metabolism ; Tobacco/genetics ; Transgenes
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 20
    Publication Date: 2011-11-01
    Description: A full description of the human proteome relies on the challenging task of detecting mature and changing forms of protein molecules in the body. Large-scale proteome analysis has routinely involved digesting intact proteins followed by inferred protein identification using mass spectrometry. This 'bottom-up' process affords a high number of identifications (not always unique to a single gene). However, complications arise from incomplete or ambiguous characterization of alternative splice forms, diverse modifications (for example, acetylation and methylation) and endogenous protein cleavages, especially when combinations of these create complex patterns of intact protein isoforms and species. 'Top-down' interrogation of whole proteins can overcome these problems for individual proteins, but has not been achieved on a proteome scale owing to the lack of intact protein fractionation methods that are well integrated with tandem mass spectrometry. Here we show, using a new four-dimensional separation system, identification of 1,043 gene products from human cells that are dispersed into more than 3,000 protein species created by post-translational modification (PTM), RNA splicing and proteolysis. The overall system produced greater than 20-fold increases in both separation power and proteome coverage, enabling the identification of proteins up to 105 kDa and those with up to 11 transmembrane helices. Many previously undetected isoforms of endogenous human proteins were mapped, including changes in multiply modified species in response to accelerated cellular ageing (senescence) induced by DNA damage. Integrated with the latest version of the Swiss-Prot database, the data provide precise correlations to individual genes and proof-of-concept for large-scale interrogation of whole protein molecules. The technology promises to improve the link between proteomics data and complex phenotypes in basic biology and disease research.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3237778/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3237778/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tran, John C -- Zamdborg, Leonid -- Ahlf, Dorothy R -- Lee, Ji Eun -- Catherman, Adam D -- Durbin, Kenneth R -- Tipton, Jeremiah D -- Vellaichamy, Adaikkalam -- Kellie, John F -- Li, Mingxi -- Wu, Cong -- Sweet, Steve M M -- Early, Bryan P -- Siuti, Nertila -- LeDuc, Richard D -- Compton, Philip D -- Thomas, Paul M -- Kelleher, Neil L -- F30 DA026672/DA/NIDA NIH HHS/ -- F30 DA026672-03/DA/NIDA NIH HHS/ -- GM 067193-08/GM/NIGMS NIH HHS/ -- P30 DA018310/DA/NIDA NIH HHS/ -- P30 DA018310-06/DA/NIDA NIH HHS/ -- P30DA 018310/DA/NIDA NIH HHS/ -- R01 GM067193/GM/NIGMS NIH HHS/ -- R01 GM067193-08/GM/NIGMS NIH HHS/ -- England -- Nature. 2011 Oct 30;480(7376):254-8. doi: 10.1038/nature10575.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, and the Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22037311" target="_blank"〉PubMed〈/a〉
    Keywords: Alternative Splicing ; Cell Aging/genetics ; Cell Line ; DNA Damage ; Databases, Protein ; HMGA1a Protein/analysis ; HMGA1b Protein/analysis ; HeLa Cells ; Humans ; Phenotype ; Protein Isoforms/*analysis/*chemistry ; Protein Processing, Post-Translational ; Proteolysis ; Proteome/*analysis/*chemistry ; Proteomics/instrumentation/*methods
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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