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  • Polymer and Materials Science  (12)
  • Pseudogenes  (1)
  • 1980-1984  (13)
  • 1960-1964
  • 1950-1954
  • 1935-1939
  • 1920-1924
  • 1984  (13)
Collection
Keywords
Publisher
Years
  • 1980-1984  (13)
  • 1960-1964
  • 1950-1954
  • 1935-1939
  • 1920-1924
Year
  • 1
    Electronic Resource
    Electronic Resource
    Evolutionary constraints and the neutral theory (1984)
    Springer
    Journal of molecular evolution 21 (1984), S. 90-92 
    Details
    ISSN: 1432-1432
    Keywords: Neutral theory ; Codon usage ; Synonymous condons ; Pseudogenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The neutral theory of molecular evolution postulates that nucleotide substitutions inherently take place in DNA as a result of point mutations followed by random genetic drift. In the absence of selective constraints, the substitution rate reaches the maximum value set by the mutation rate. The rate in globin pseudogenes is about 5 × 10−9 substitutions per site per year in mammals. Rates slower than this indicate the presence of constraints imposed by negative (natural) selection, which rejects and discards deleterious mutations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02100633
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  • 2
    Electronic Resource
    Electronic Resource
    Computer building of β-helical polypeptide models (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 23-38 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general method is presented for computing the atomic coordinates of helices in which a dipeptide is the repeating unit. The method will generate both single- and double-stranded model helices having idealized bond lengths and angles, and any arbitrary, user-specified, pitch and number of residues per turn. The variation of inter- and intrastrand hydrogen bonds with pitch and number of residues per turn can thus be examined. An application of the method is the construction of a β-helix having pitch of 6.3 Å per turn and 4.85 residues per turn, a model which can pack nicely into the unit cell of crystals of cation-bound gramicidin A.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230104
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  • 3
    Electronic Resource
    Electronic Resource
    A peculiar temperature-dependent behavior of iodine species at the formation of chromophore between iodine and aqueous poly(vinyl alcohol) (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 749-755 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The blue colored complex between poly(vinyl alcohol) (PVA) and iodine was prepared at 5°C by mixing an aqueous solution of PVA with an aqueous ethanolic solution of iodine containing boric acid. The absorption spectrum of the system shows bands at 226 nm (A), 290 nm (B), 355 nm (C), and 650 nm (D). Their relative absorbances change largely depending on temperature. When the system is gradually warmed, the chromophoric band D decays and the intensity of band A increases. By lowering the temperature again to 5°C the concentration of chromophore increases. It was found that the decay and the re-formation of the chromophore are reversible in the temperature range 5 to 15°C. Above 15°C, contrarily, hysteresis effects are encountered for the re-formation. Thus, when the chromophore is re-formed at 5°C, the spectra shows an isosbestic point at 420 nm, between bands C and D. The dependence on temperature of bands B and C is quite independent from each other, which strongly indicates that the latter band should be assigned to another iodide species than the I-3 ion (band B) and the I- ion (band A). Based on these experimental data a new mechanism is proposed involving the complex ion I-3 · I2 which is supposed to be a precursor of the chromophoric pentaiodide ion I5-.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850411
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  • 4
    Electronic Resource
    Electronic Resource
    Syntheses of N-(4-substituted phenyl)isocitraconimides and reactivities in their radical copolymerizations with styrene (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 479-488 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Radical copolymerizations of isomeric N-(4-substituted phenyl)isocitraconimides 7a-f and 9a-f (M1) with styrene (ST) (M2) were performed at 60°C, using 2,2′-azoisobutyronitrile as initiator in tetrahydrofuran, in order to study the substitutent effect on the copolymerization parameters. From the results, the monomer reactivity rations were determined as r1 = 0,0,81 ≤ r2 = 1,76 in the 7/ST systems, and r1 = 0, 0,27 ≤ r2 ≤ 0,42 in the system 9/ST. It was found that the relative reactivities (1/r2) of 7 toward the polystyrly radical cannot be correlated by the polar-substituent constant (σ) but by the resonance-substituent constant (ER) in the modified Hammett equation: log(1/r2) = ρσ + γER. Furthermore, the monomer reactivity ratios considering the influence of the penultimate effect were also determined, and the substituent effect of 7 and 9 was studied according to the above equation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850306
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  • 5
    Electronic Resource
    Electronic Resource
    Ion transport through liquid membrane by cyclic octapeptides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 563-573 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cation transport through a chloroform liquid membrane by cyclic octapeptides - cyclo(Leu-Pro)4, cyclo(Phe-Pro)4, and cyclo[Lys(Z)-Pro]4 - was investigated. All of these cyclic octapeptides transported K+ and Ba2+, and the rate of cation transport was correlated with the ability to extract cations from the aqueous phase to the chloroform phase. Among them, cyclo (Leu-Pro)4 was the most efficient and transported K+ and Ba2+ selectively from other alkali and alkaline earth cations, respectively. The rate of K+ transport by cyclo(Leu-Pro)4 was about one-third as fast as that by dicyclohexyl 18-crown-6. Picrate anion transport against its concentration gradient was observed by cyclo(Leu-Pro)4, which is conjugated with the selective transport of K+. Complex formation in a liposome between cyclo(Leu-Pro)4 and Ba2+ was observed, but the binding constant was low.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230310
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  • 6
    Electronic Resource
    Electronic Resource
    Blends of poly(ethylene terephthalate) and a polyarylate before and after transesterification (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1629-1638 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of poly(ethylene terephthalate) (PET) and a copolyester of bisphenol A-terephthaloylisophthaloyl (PAr) (2:1:1) have been studied both before and after transesterification. The physical blends exhibit phase separation in their amorphous states: a pure PET phase and a mixed PAr-rich phase. In spite of this phase separation, PET crystallinity in blends, normalized to PET fraction, surprisingly goes through a maximum at 25% PAr content. The transesterfied copolymers are noncrystallizable and exhibit a single Tg between those of starting polymers, PET and PAr.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290517
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of ethylene-1-butene copolymer by differential scanning calorimetry and 13C-NMR spectroscopy (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 3161-3170 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two kinds of ethylene-1-butene copolymers that were produced by the different procedures, that is, the slurry and the high-pressure polymerizations, were characterized by differential scanning calorimetry (DSC) and carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy. The melting points of both copolymers were found to be different in spite of the same 1-butene content. It was deduced that this phenomenon depended upon the subtly different chain structures between these two copolymers from the tetrad monomer sequence analysis by 13C-NMR method. In addition, the behavior of the composition fractionation by temperature rising elution technique was also considered to be affected by the chain structures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070291018
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  • 8
    Electronic Resource
    Electronic Resource
    Rejection of phenolic derivatives in aqueous solution by an interpolymer anionic composite reverse osmosis membrane (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 2929-2936 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Reverse osmosis separation for 23 phenollic derivatives was examined by an anionic charged composite membrane. The solute permeation was carried out in single-solute aqueous solution (200 mg/L) under applied pressure of 3.92-7.85 MPa at 25°C. The correlation between the solute rejection and polar parameters for phenolic derivatives has been investigated. For p-alkylphenols, the solute rejection increased with molecular weight and/or molecular branching. In undissociated state, the rejection of phenolic derivatives was closely related with the Taft's number and the Hammett's number of substituents. Also rejections of phenolic derivatives depended upon the pH value of feed soultion and the polar effect of substituted groups. For example, rejections of aminophenols showed the minimum value at a certain pH value and on either side of the minimum point, the rejection of aminophenol increased. From these facts, the main factors in reverse osmosis serparation by an anionic composite membrane were discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290920
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  • 9
    Electronic Resource
    Electronic Resource
    Casting properties of Ni-Ti shape memory alloy (1984)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 427-434 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A Ni-45 wt % Ti (Ni-50 at % Ti) alloy was cast into molds of magnesia and silica investments by use of a dental argon-arc pressure casting machine with a copper crucible. The castings exhibited shape memory properties. The shape recovery process was sharper in the specimens cast in magnesia investment molds than in those cast in silica (phosphate-bonded) investment molds. The latter casting had a hard region of the periphery, suggesting that shape recovery process may be affected by reaction of molten metal with silica. Furthermore, the alloy possessed the adequate mechanical properties for consideration as crown-and-bridge prostheses.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820180410
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  • 10
    Electronic Resource
    Electronic Resource
    Catalysis of enantiomeric ester hydrolysis in polymer domains: Catalytic effects of N-decanoyl-histidine and of dipeptide derivatives containing a histidyl residue (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 407-417 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The catalytic activities of N-decanoyl-L-histidine and its methyl ester and of dipeptide derivatives containing an L-histidine residue toward the stereoselective hydrolysis of enantiomeric substrates have been studied at pH 7.30 (in 0.01M Bis-tris buffer) and 25°C in the presence of poly(ethyleneimine) derivatives. The dipeptide catalyst revealed greatest stereoselectivity in a quaternized poly(ethyleneimine) derivative. A comparison of catalytic effects on both the rate constants and stereoselectivities of N-decanoyl-L-histidine and its methyl ester elucidates the cooperative effects of carboxyl groups in the polymer domains. The structure of the substrates influenced both the rate constants and stereoselectivities in polymer domains.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170220212
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