## Abstract

By use of digital autocorrelation and fast Fourier methods, dynamic light-scattering studies of in vitro reconstituted muscle F-actin were made over a wide range of concentrations. 0.01-2 mg ml F-actin. Measurements of correlation function [g^{1}(t)]^{2} showed that a transition from a dilute to a semidilute regime for the Brownian motions of filaments occurred at around 0.3 mg ml F-actin. Beyond this concentration, profiles of successively measured [g^{1}(t)]^{2} showed very poor reproducibility. This resulted from the existence of very slow components, which could not be measured with a high statistical accuracy even for a measuring time of 3600 s/run. On the other hand, subtraction of these components automatically by an electronic circuit, [g^{-1}(t)]^{2}, or by computer processing, [g^{1}(t)]^{2}, resulted in a fairly good reproducibility of the profies, The decay c of [g^{-1}(t)]^{2} (and [g^{-1}(t)]^{2}) were very similar to those of [g^{1}(t)]^{2} for dilute solutions. A theoret which could account for the above situation. The time sequence {n(t,T)} of photoelectron counts at a sampling time T of light scattered from semidilute solutions of F-actin was stored on magnetic tapes, and both power spectra S̄(f) and correlation functions [g^{-1}(t)]^{2} were computed by taking the ensemble average over many short records with duration 1024T. Since both S̄(f and [g^{-1}(t)]^{2} lacked frequency components lower than 1 (2048T) Hz. their profiles were highly reproducible. An of S̄(f) confirmed our earlier results which had shown an apparent contradiction to later results by a correlation method. A comparison of S̄(f) and [g^{-1}(t)]^{2} based on the same {n(t,T)} clarified the reasons why the bandwidth Γ of S̄( differed from the bandwidth \ ̄gG of [g^{1}(t)]^{2} and [g^{-1}(t)]^{2}. The temperature dependence of Γ suggested that F-actin flexible and that the flexibility parameter would change with temperature.

Original language | English |
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Pages (from-to) | 1-21 |

Number of pages | 21 |

Journal | Biophysical Chemistry |

Volume | 20 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - 1984 |

## Keywords

- Dynamic light scattering
- F-Actin
- Fast Fourier method
- Filament flexibility
- Semidilute solution

## ASJC Scopus subject areas

- Biochemistry
- Biophysics
- Physical and Theoretical Chemistry