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Digitale Medien

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle (1992)

Fan, Shih-fang ; Dewey, M. M. ; Gaylinn, B. ; [weitere]

Springer

Journal of comparative physiology 162 (1992), S. 508-512

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ISSN: 1432-136X

Schlagwort(e): Crossbridge motions ; Dynamic light scattering ; Seasonal changes ; Muscle ; Thick filament ; Limulus polyphemus

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL〉1 (where K is the scattering vector), the average characteristic linewidth ( $$\bar \Gamma$$ ) increased with the addition of Ca2+ or with the depletion of ATP. The increase in the $$\bar \Gamma$$ with the addition of Ca2+ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca2+. The increase in $$\bar \Gamma$$ which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in $$\bar \Gamma$$ following the addition of Ca2+ was found to be seasonal, i.e., values of $$\bar \Gamma$$ obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in $$\bar \Gamma$$ was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in $$\bar \Gamma$$ developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca2+ per myosin molecule was 1 during the summer and 2 at other times.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00264810

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Digitale Medien

Calibration of an optical self-beating spectrometer by polystyrene latex spheres and confirmation of the stokes-einstein formula (1972)

Lee, S. P. ; Tscharnuter, W. ; Chu, B.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 10 (1972), S. 2453-2459

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ISSN: 0098-1273

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The Rayleigh linewidth Γ of light scattered by dilute aqueous solutions of polystyrene latex spheres has been measured by using time-dependent photocurrent signal correlation with a precision typically of 0.5-1% over a range of scattering angles θ. With independent measurements of the diffusion coefficient D from D = lim K → 0 (Γ/K2), the diameter of the sphere d by means of electron microscopy, and the hydrodynamic shear viscosity η, we have confirmed the Stokes-Einstein relation D = kT/3πηd to within 1% if we take into account the effect of polydispersity on our Rayleigh linewidth data. We also find that dEM = 907 ± 56 Å for sample LS-1132-B as reported by the Dow Chemical Company differs from our dSB = 847 (±1.6%) Å ≈ dEM = 851 (±2%) by about 7%, which is outside the limits of error of our experiments. The subscripts EM and SB denote electron microscope and self-beating, respectively, while K ≡ (4π/λ)sin(θ/2) is the magnitude of the momentum transfer vector.

Zusätzliches Material: 1 Ill.