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  • Biochemistry and Biotechnology  (2)
  • Cochlea  (2)
  • Phylogeny  (2)
  • Aluminosilicates  (1)
  • Amino acid sequences
  • 1990-1994  (7)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 39 (1994), S. 631-643 
    ISSN: 1432-1432
    Keywords: Fibronectin type III ; Bacteria ; Glycohydrolases ; Phylogeny ; Horizontal gene transfers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolutionary spread of 22 fibronectin type III (Fn3) sequences among a dozen bacterial enzymes has been traced by searching databases with the non-Fn3 parts of the enzyme sequences. Numerous homologues were found that lacked the Fn3 domains. In each case the related sequences were aligned, phylogenetic trees were constructed, and the occurrences of Fn3 units on the trees were noted. Comparison with phylogenetic trees prepared from the Fn3 segments themselves allowed inferences to be made about when the Fn3 units were shuffled into their present positions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 171 (1993), S. 725-734 
    ISSN: 1432-1351
    Keywords: Cochlea ; Echolocation ; Resonance ; Body temperature ; Pteronotus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cochlea of the mustached bat (Pteronotus parnellii) has sharp tuning characteristics and pronounced resonance within a narrow band near the second harmonic, constant frequency (CF2) component of the animal's biosonar signals. That fine frequency discrimination occurs within this narrow band is evident from Doppler-shift compensation, whereby bats in flight lower the frequency of emitted CF2s to maintain returning echoes within this band. This study examined various factors capable of producing shifts in both the cochlear resonance frequency (CRF) and CF2s emitted by stationary bats and bats actively Doppler-shift compensating on a pendulum. Each of three experimental factors shifted the CRF in a reversible manner. Changes in body temperature produced an average CRF shift of 39 ± 18 Hz/°C. The CRF increased with flight by 150 ± 100 Hz and returned to baseline values within 10 min after flight. Contralateral sound exposure produced smaller (100 ± 20 Hz), rapid shifts in the CRF, suggesting that a mechanism different from the temperature- and flight-related shifts was involved. Changes in the CRF induced by temperature and flight were accompanied by shifts in the emitted CF2 of stationary and moving bats. Coupled with a companion study of associated shifts in neural tuning, the concomitant changes in CRF and CF2 provide evidence of cochlear tuning lability in the mustached bat.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 171 (1993), S. 735-748 
    ISSN: 1432-1351
    Keywords: Cochlea ; Cochlear nucleus ; Inferior colliculus ; Tonotopy ; Pteronotus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Acoustic stimuli near 60 kHz elicit pronounced resonance in the cochlea of the mustached bat (Pteronotus parnellii parnellii). The cochlear resonance frequency (CRF) is near the second harmonic, constant frequency (CF2) component of the bat's biosonar signals. Within narrow bands where CF2 and third harmonic (CF3) echoes are maintained, the cochlea has sharp tuning characteristics that are conserved throughout the central auditory system. The purpose of this study was to examine the effects of temperature-related shifts in the CRF on the tuning properties of neurons in the cochlear nucleus and inferior colliculus. Eighty-two single and multi-unit recordings were characterizedin 6 awake bats with chronically implanted cochlear microphonic electrodes. As the CRF changed with body temperature, the tuning curves of neurons sharply tuned to frequencies near the CF2 and CF3 shifted with the CRF in every case, yielding a change in the unit's best frequency. The results show that cochlear tuning is labile in the mustached bat, and that this lability produces tonotopic shifts in the frequency response of central auditory neurons. Furthermore, results provide evidence of shifts in the frequency-to-place code within the sharply tuned CF2 and CF3 regions of the cochlea. In conjunction with the finding that biosonar emission frequency and the CRF shift concomitantly with temperature and flight, it is concluded that the adjustment of biosonar signals accommodates the shifts in cochlear and neural tuning that occur with active echolocation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 34 (1992), S. 175-184 
    ISSN: 1432-1432
    Keywords: Superoxide dismutase ; Phylogeny ; Evolutionary rates ; Horizontal gene transfers ; Molecular clock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phylogenetic trees were constructed for 25 Cu-Zn superoxide dismutases and 31 Mn/Fe superoxide dismutases. The latter set includes seven new sequences that we determined in an effort to make the two phylogenies equally representative. We analyzed all pairwise differences in each set in an attempt to estimate rates of change. As reported by others, the Cu-Zn enzyme has experienced significant changes in its evolutionary rate. In contrast, the clock for the Mn/Fe enzyme is ticking quite regularly. The comparison of these two independently evolved superoxide dismutases that catalyze the same reaction and occur together throughout much of the biological world suggests that adaptation to environmental stress is not the basis for the erratic rate of change observed in the Cu-Zn enzyme.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1151-1154 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 1141-1150 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Based on the well-known mechanism describing Michaelis-Menten kinetics, three rate expressions may be developed: the exact solution (Model 1), a rate equation resulting from the pseudo-steady-state assumption (Model 2), and Model 2 with the additional assumption that the amount of free substrate is approximately equal to the total amount of substrate (Model 3). Although Model 1 is the most precise, it must be integrated numerically and it requires three experimentally determined parameters. Models 2 and 3, however, are simpler and require only two parameters. Using dimensionless forms of the three models, we have evaluated the errors in the two simplified models relative to the exact solution using a wide range of parameter values. The choice of model for reactor design depends on the initial substrate to enzyme ratio (α0), and on the ratio of the Michaelis-Menten constant to the enzyme concentration (σ). Based on a 2% model error criteria, when α0 〉 15 or σ ≥ 100, Model 3 is adequate; if 5 〈 α0 〈 15, or if σ ≥ 10, then Model 2 may be used; and if α0 〈 5 and σ 〈 10, then the exact solution (Model 1) is required.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 883-886 
    ISSN: 0749-1581
    Keywords: Aluminum-27 ; Gallium-71 ; Aluminosilicates ; Aluminophosphates ; Aluminas ; Gallosilicates ; Gallophosphates ; Gallias ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A linear relationship has been found to exist between the aluminum-27 and gallium-71 NMR chemical shifts of a series of structurally analogous aluminum and gallium compounds having only oxygen in the first metal coordination spheres; δ71Ga = 2.83(δ27Al) - 4.50. This relationship allows the prediction of 71Ga chemical shifts for such gallium compounds from the 27Al values already known for their aluminum analogues, and also a greater understanding of observed 71Ga chemical shifts.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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