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  • Chemistry  (5,638)
  • Life and Medical Sciences  (255)
  • 1970-1974  (5,893)
  • 1965-1969
  • 1974  (5,893)
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Keywords
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  • 1970-1974  (5,893)
  • 1965-1969
Year
  • 1
    Electronic Resource
    Electronic Resource
    The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry in rabbits (1974)
    Springer
    Calcified tissue international 16 (1974), S. 145-152 
    Details
    ISSN: 1432-0827
    Keywords: EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02008220
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  • 2
    Electronic Resource
    Electronic Resource
    Studies in the basic mineralizing system, CaO-P2O5-H2O (1974)
    Springer
    Calcified tissue international 14 (1974), S. 3-14 
    Details
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Mineral ; Phase ; Chemistry ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des diagrammes de phase d'équilibre ont été déterminés pour le système CaO-P2O5-H2O en utilisant des techniques de synthèse hydrothermique au cours de variatio nsde température allant de 300–600° et 2 Kb H2O de pression. De l'hydroxyapatite bien cristallisé a été synthétisé et caractérisé. De faibles variations de paramètres de la maille cristalline, liées à la température de synthèse et composition globale du matériel initial, ont été déterminées. Des conditions chimiques précises sont nécessaires pour obtenir de l'apatite, en tant que seule phase solide en équilibre dans la solution. Les résultats de diagramme de phase d'équilibre sont comparés avec ceux obtenus dans des milieux synthétiques.
    Abstract: Zusammenfassung Es wurden Gleichgewichts-Phasendiagramme für das System CaO-P2O5-H2O bestimmt, indem hydrothermale Synthese-Techniken im Temperaturbereich von 300–600° und bei einem Druck von 2 Kb H2O verwendet wurden. Es wurde gut-kristallisiertes Hydroxyapatit erzeugt und charakterisiert. Es wurden geringe Unterschiede in den Parametern der Zelleinheiten festgestellt, welche von der angewandten Temperatur und der Zusammensetzung des Startmaterials abhingen. Es waren genaue chemische Bedingungen nötig, um Apatit als die einzige feste Phase im Gleichgewicht mit der Lösung zu erhalten. Die Resultate der Gleichgewichts-Phasendiagramme werden mit früheren Untersuchungen mit der Synthesetechnik verglichen.
    Notes: Abstract Equilibrium phase diagrams have been determined for the system CaO-P2O5-H2 using hydrothermal synthesis techniques in the temperature range 300–600° and 2 Kb H2O pressure. Well-crystallized hydroxyapatite has been produced and characterized. Small variations in unit cell parameters dependent on temperature of synthesis and bulk composition of the starting materials have been determined. Precise chemical conditions were required to obtain apatite as the only solid phase in equilibrium with solution. Equilibrium phase diagram results are compared with previous synthetic investigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02060279
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  • 3
    Electronic Resource
    Electronic Resource
    Fluorescence correlation spectroscopy. I. Conceptual basis and theory (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1-27 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a method for determining chemical kinetic constants and diffusion coefficients by measuring the rates of decay of spontaneous concentration fluctuations. The equilibrium of the system is not disturbed during the measurement. We measure the number of molecules of a specified type in a defined open volume as a function of time and compute the time course of the deviations from the thermodynamic mean concentration. The method is based on the principle that the rates of decay of spontaneous microscopic fluctuations are determined by the same phenomenological rate coefficients as those of macroscopic departures from equilibrium which result from external perturbations. Hence, an analysis of fluctuations yields the same chemical rate constants and diffusion coefficients as are measured by conventional procedures. In practice the number of the specified molecules is measured by a property such as absorbance or fluorescence which is specific and sensitive to chemical change. The sample volume is defined by a light beam which traverses the cell. As the molecules appear in or disappear from the light beam, either due to diffusion or chemical reaction, their concentration fluctuations give rise to corresponding fluctuations of the intensity of absorbed or emitted light. This paper presents the theory needed to derive chemical rate constants and diffusion coefficients from these fluctuations in light intensity. The theory is applied to three examples of general interest: pure diffusion in the absence of chemical reaction; the binding of a small rapidly diffusing ligand to a larger slowly diffusing macromolecule; and a unimolecular isomerization. The method should be especially useful in studying highly cooperative systems, relatively noncooperative systems with intermediate states closely spaced in free energy, small systems, and systems not readily subject to perturbations of state.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130102
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular mobility of polypeptides containing proline as determined by 13C magnetic resonance (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 97-114 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular conformations and dynamics of poly(L-prolyl), poly(hydroxyl-L-prolyl), poly(L-prolyl-glycyl), poly(hydroxyl-L-prolyl), and poly(glycyl-glycyl-L-prolyl-glycyl), in aqueous solution, have been studied using 13C pulse Fourier transform nmr spectroscopy. From a measurement of the intensities of major and minor resonances in the spectra of the copolypeptides, it was determined that 15-20% of the glycyl-prolyl and glycyl-hydroxyprolyl peptide bonds are cis. Effective rotational correlation times (τeff), obtained from measurements of spin-lattice relaxation times (T1) of individual backbone and side-chain carbons, demonstrated that backbone reorientation is approximately isotropic for the five polypeptides and is characterized by correlation times of ca. 0.3-0.6 nanoseconds as a result of rapid segmental motion. In a given polypeptide glycyl and pyrrolidine residues were found to have the same backbone correlation times, but backbone carbon τeff values did decrease as the glycyl content of the peptides increased. A semi-quantitative analysis of Cβ, Cγ, and Cδ correlation times suggests that rapid ring motion in both prolyl and hydroxyprolyl involves primarily Cγ and Cβ, with the prolyl ring being more mobile than the hydroxyprolyl ring.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130106
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  • 5
    Electronic Resource
    Electronic Resource
    Comment on “rotational relaxation of macromolecules determined by dynamic light scattering” (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 237-238 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No. Abstract.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130117
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  • 6
    Electronic Resource
    Electronic Resource
    Flexibility of DNA (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 217-226 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for the flexibility of DNA is proposed that is based on discrete variations in the direction of propagation in going from one subunit to the next. Expansion of the local free energy in terms of the local bending gives a Gaussian distribution function. The assumption of the independence of local bends on neighbors lead to very simple formulae for the persistence length and the characteristic ratio. Emphasis, however, is placed on the application of the formulae for molecules of finite size where the persistence length and C∞ are not defined. The formulae are worked out for two models, which should serve as limits for the real physical situation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130115
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  • 7
    Electronic Resource
    Electronic Resource
    Dispersion effect on turbidimetric size measurement (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 735-743 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If dispersion effects are not taken into account, the dimensions of particles in suspension estimated from spectrophotometric data (slope of the log OD versus log λ plot) are too low. By measuring dispersion curves for the medium and for the suspension, a consistent estimate of the size of latex particles of different diameter is obtained from the OD data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130408
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  • 8
    Electronic Resource
    Electronic Resource
    13C nmr study of the helix-coil transition of poly-N5-(3-hydroxypropyl)-L-glutamine (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 765-768 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-coil transition of poly-N5-(3-hydroxypropyl)-L-glutamine in methanol-water solutions has been observed using 13C nuclear magnetic resonance. Two signals appear in the α-CH region in the course of the transition; this is in contrast with previous proton magnetic resonance experiments carried out on this polymer in the same solvent system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130411
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  • 9
    Electronic Resource
    Electronic Resource
    The V amylose-H2O system: Structural changes resulting from hydration (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 779-790 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray diffraction and stereochemical analyses were used to study the hydrated structure of the helical amylose polymorph having a fiber repeat spacing of 8 Å. Intensity calculations using computer models confirmed six as the number of residues per turn and supported the space group P212121. Both diffraction intensity and stereochemical methods indicate the suitability of residue G3 from the potassium acetate complex of cyclohexaamylose as opposed to residues with longer O(4)-O(1) vectors. Comparison of the present results with those obtained for V amylose dehydrate indicated no major conformational differences between the two helix skeletons. A net helical rotation of approximately 30° accompanied the hydrate-dehydrate transition and the rotational position in the hydrate allowed packing that was less close. Hydration water molecules were not located; noncarbohydrate peaks on the electron density maps were primarily due to Fourier series termination errors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130413
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  • 10
    Electronic Resource
    Electronic Resource
    A circular dichroism study of the primary structures of three crab satellite DNA's rich in A:T base pairs (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 843-852 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have measured the circular dichroism spectra and have obtained melting curves for samples of purified satellite DNA's from three species of crab, Cancer borealis, Gecarcinus lateralis, and Callinectes sapidus. Although all three satellite DNA's have the same density in neutral CsCl, their circular dichroism spectra and melting and reassociation characteristics are different, as are other properties of these DNA's. The circular dichroism spectra are analyzed to give estimates of nearest-neighbor frequencies. We estimate that about 90% of the Cancer borealis satellite DNA and over 80% of the Gecarcinus lateralis satellite DNA consist of d(AT)n:d(AT)n sequences, while the serially repeating unit of the Callinectes sapidus satellite DNA may not contain any extended d(AT)n:d(AT)n sequences. The results from the circular dichroism spectra for the Cancer borealis, Gecarcinus lateralis, and the Callinectes sapidus satellite DNA's are in agreement with base composition analyses, which give 2.4, 8, and 25% G+C, respectively, for these DNA's.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130417
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