Measurements on monodisperse preparations of the filamentous virus Xf give 17.3 +/- 0.6 s-1 for its rotational diffusion coefficient in 1 mM sodium phosphate, pH 7.5 at 20 degrees C and (2.53 +/- 0.06) X 10(-8) cm2 s-1 for its translational diffusion coefficient in 0.15 M NaCl and 0.015 M sodium phosphate, pH 7, at 25 degrees C. These coefficients yield a length of 980 +/- 30 nm and a diameter of 7.2 +/- 1.5 nm for the virus in solution when used to solve simultaneously the two Broersma equations for the diffusion of rigid rods.
The Hall coefficient of plastically bent n-type Ge is measured between 77 and 280 OK.
SynopsisDynamic light scattering experiments were performed on solutions of the bacteriophages T7 and T4B in order to obtain the rotational diffusion coefficients of these phages. Correlation functions were determined from the depolarized intensity scattered in the forward direction. The apparatus used in this study is described in detail. Particular attention is paid to the minimalization of the depolarized intensity due to double scattering. If double scattering cannot he neglected, the correlation function of the depolarized field is the sum of the correlation functions resulting from single and double scattering. It is shown that by correcting for double scattering, it is then possible to obtain the rotational diffusion coefficient of the macromolecules. Although the optical anisotropy of both T4R (retracted fihers) and T7 is very small, the experimental conditions could be chosen in such a way that no depolarized scattering due to double scattering was observed. The measured rotational diffusion coefficients for T4B and T7 are D R~,~ = 258 f 12 and 4528 f 100 sec-', respectively. These values compare very well with those obtained by electric birefringence experiments.
Expressions are derived for specified magnetoresistance and magneto-conductivity coefficients for n-type Ge with an array of parallel dislocations. The obtained equations are compared with measurements a t 77 O K on plastically bent n-type Ge. From the results we conclude that the electron mobility is not reduced by the dislocations for Ndw. <2 x lo7 cm-2.The observed anisotropies in the conductivity can be attributed to the inhomogeneous distribution of the dislocations.Es werden Ausdrucke fur bestimmte Magnetowiderstands-und Magnetoleitfiihigkeitakoeffizienten von n-leitendem Ge mit einer Anordnung paralleler Versetzungen abgeleitet. Die erhaltenen Gleichungen werden mit MeSergebnissen an plastisch gebogenem, n-leitendem Ge bei 77 O K verglichen. Aus den Ergebnissen wird geschlossen, da13 die Elektronenbeweglichkeit durch die Versetzungen nicht verkleinert wird, solange N&,l. < 2 x lo7 cm-2 ist. Beobachtete Anisotropien der Leitfiihigkeit konnen der inhomogenen Verteilung der Versetzungen zugeschrieben werden.
' calculated the molecular weights of the "slow" and "fast" forms of the bacteriophage T2L by applying the Svedberg relation between the sedimentation and diffusion coefficients. They used a diffusion coefficient determined by quasielastic light scattering techniques and found that the calculated molecular weight of the "fast" form (tail fibers folded back) was 1.22 times that of the "slow" form (tail fibers stretched). They attributed this anomalous result to thermodynamic or hydrodynamic nonideality.It is possible however to explain the anomaly in another way. It is doubtful whether the application of standard formulas to the results of quasielastic light scattering yields the correct translational diffusion coefficient in the case of lollipop-shaped particles like the T-even bacteriophages. Such particles consist of an ellipsoidal head and a rodlike tail. As almost all the mass of such particles is packed in the head, we assume that the light is scattered by the head only. The hydrodynamic center of the particles is positioned a t a distance ro from the center of the head towards the tail. Recently we calculated2 the correlation function of the light scattered by lollipop-shaped particles, taking into account not only the distance ro, but also the optical anisotropy and the nonzero dimensions of the head. In the case of T-even phages, the latter two factors may, however, be neglected to a first approximation.It can be shown2 that the first-order correlation function of the field scattered from lollipop-shaped particles can be written as( 1) where ro is the distance between the hydrodynamic and scattering centers, q is the magnitude of the scattering vector, DT is the translational diffusion coefficient, DR is the rotational diffusion coefficient, and Bf are coefficients depending on the product qro (and in principle also on the anisotropy and dimensions of the particles). I=OThis correlation function can be characterized by Koppel's method3 of cumulants as -where A = x&.
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