Dynamic light scattering on liquid-like polyelectrolyte solutions: correlation spectroscopy on dilute solutions of virus particles at very low ionic strength

2007 ◽  
pp. 76-80 ◽  
Author(s):  
S. F. Schulz ◽  
E. E. Maier ◽  
R. Krause ◽  
R. Weber
Keyword(s):  
Light Scattering ◽  
Ionic Strength ◽  
Dynamic Light Scattering ◽  
Correlation Spectroscopy ◽  
Dilute Solutions ◽  
Virus Particles ◽  
Polyelectrolyte Solutions ◽  
Low Ionic Strength

Dynamic Properties of Entangled Wormlike Micelles: Sodium Laurylethersulfate at High Ionic Strength-(II)

2001 ◽  
Vol 215 (7) ◽  
Author(s):  
S.F. Clancy ◽  
J.G. Fuller ◽  
T. Scheidt ◽  
H.H. Paradies
Keyword(s):  
Light Scattering ◽  
Ionic Strength ◽  
Dynamic Light Scattering ◽  
Dynamic Properties ◽  
High Ionic Strength ◽  
Wormlike Micelles ◽  
Dilute Solutions ◽  
Volume Fractions ◽  
Low Salt ◽  
Viscous Behaviour

We report on the viscous behaviour of long and flexible wormlike micelles at volume fractions between Ø = 0.05–0.14 comprised of sodium laurylethersulfate (SLES) in 0.15–0.5 M NaCl equivalent of SLES concentrations between 20–50 mM at temperatures ranging from 25 °C to 45 °C by means of static and dynamic light scattering and rheology, which is an extension of previous experiments on dilute/semi-dilute solutions of SLES micelles at much lower surfactant concentrations in the presence of low salt concentrations (Clancy and Paradies, Z. Phys. Chem.

scholarly journals The effect of heavy chain phosphorylation and solution conditions on the assembly of Acanthamoeba myosin-II.

1989 ◽  
Vol 109 (4) ◽  
pp. 1529-1535 ◽  
Author(s):  
J H Sinard ◽  
T D Pollard
Keyword(s):  
Light Scattering ◽  
Ionic Strength ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Critical Concentration ◽  
Myosin Ii ◽  
Acidic Ph ◽  
Thick Filaments ◽  
Low Ionic Strength

At low ionic strength, Acanthamoeba myosin-II polymerizes into bipolar minifilaments, consisting of eight molecules, that scatter about three times as much light as monomers. With this light scattering assay, we show that the critical concentration for assembly in 50-mM KCl is less than 5 nM. Phosphorylation of the myosin heavy chain over the range of 0.7 to 3.7 P per molecule has no effect on its KCl dependent assembly properties: the structure of the filaments, the extent of assembly, and the critical concentration for assembly are the same. Sucrose at a concentration above a few percent inhibits polymerization. Millimolar concentrations of MgCl2 induce the lateral aggregation of fully formed minifilaments into thick filaments. Compared with dephosphorylated minifilaments, minifilaments of phosphorylated myosin have a lower tendency to aggregate laterally and require higher concentrations of MgCl2 for maximal light scattering. Acidic pH also induces lateral aggregation, whereas basic pH leads to depolymerization of the myosin-II minifilaments. Under polymerizing conditions, millimolar concentrations of ATP only slightly decrease the light scattering of either phosphorylated or dephosphorylated myosin-II. Barring further modulation of assembly by unknown proteins, both phosphorylated and dephosphorylated myosin-II are expected to be in the form of minifilaments under the ionic conditions existing within Acanthamoeba.

Sequential Extraction of Late Exponentials (SELE): A technique for deconvolving multimodal correlation curves in Dynamic Light Scattering

MRS Advances ◽  
2020 ◽  
Vol 5 (17) ◽  
pp. 865-880 ◽  
Author(s):  
Preethi L Chandran
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Sequential Extraction ◽  
Time Scales ◽  
Scattered Light ◽  
Correlation Spectroscopy ◽  
Least Square ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Correlation Curve

Abstract:In techniques such as Dynamic Light Scattering (DLS), Fluorescence Correlation Spectroscopy, and image mining, motion is tracked by the autocorrelation of a signal over logarithmic time scales. For instance the tracking signal in DLS is the scattered light intensity; it remains correlated at time scales where scant changes in the arrangement of the scattering particles occur, but decays exponentially at the time scales of their diffusion. When there are multiple time scales of motion (for instance due to scatterers of different sizes), the correlation curve has more than one exponential fall. Extracting the decay constants or hydrodynamic sizes due to each exponential fall in a multi-species field correlation curve becomes an ill-conditioned mathematical problem. We describe a new algorithm to invert a multi-modal correlation curve by Sequential Extraction of the Late Exponentials (SELE). The idea is that while the inversion of a multi-exponential equation may be ill posed, that of a single exponential is not. So we fit data windows towards to base of the correlation curve to extract the largest contribution species, remove the species contribution from the correlation curve, and repeat the process with the remnant curve. The single exponent can be robustly fitted by least-square minimization with initial guesses generated by an adapted cumutant technique (power-series) that includes stretch coefficients (measure of sample dispersity). The proposed algorithm resolves particle sizes separated by 3X, and is reliable against fluctuations in the correlation curve and to localized regions of suboptimal data. The algorithm can be used to track particle dynamics in solution in multi-species problems such as self-assembly.

scholarly journals The mechanism of assembly of Acanthamoeba myosin-II minifilaments: minifilaments assemble by three successive dimerization steps.

1989 ◽  
Vol 109 (4) ◽  
pp. 1537-1547 ◽  
Author(s):  
J H Sinard ◽  
W F Stafford ◽  
T D Pollard
Keyword(s):  
Electron Microscopy ◽  
Light Scattering ◽  
Ionic Strength ◽  
Analytical Ultracentrifugation ◽  
Myosin Ii ◽  
Alkaline Ph ◽  
Predominant Species ◽  
Assembly Mechanism ◽  
Rapid Equilibrium ◽  
Low Ionic Strength

We used 90 degrees light scattering, analytical ultracentrifugation, and electron microscopy to deduce that Acanthamoeba myosin-II minifilaments, composed of eight molecules each, assemble by a novel mechanism consisting of three successive dimerization steps rather than by the addition of monomers or parallel dimers to a nucleus. Above 200 mM KCl, Acanthamoeba myosin-II is monomeric. At low ionic strength (less than 100 mM KCl), myosin-II polymerizes into bipolar minifilaments. Between 100 and 200 mM KCl, plots of light scattering vs. myosin concentration all extrapolate to the origin but have slopes which decrease with increasing KCl. This indicates that structures intermediate in size between monomers and full length minifilaments are formed, and that the critical concentrations for assembly of these structures is very low. Analytical ultracentrifugation has confirmed that intermediate structures exist at these salt concentrations, and that they are in rapid equilibrium with each other. We believe these structures represent assembly intermediates and have used equilibrium analytical ultracentrifugation and electron microscopy to identify them. Polymerization begins with the formation of antiparallel dimers, with the two tails overlapping by approximately 15 nm. Two antiparallel dimers then associated with a 15-nm stagger to form an antiparallel tetramer. Finally, two tetramers associate with a 30-nm stagger to form the completed minifilament. At very low ionic strengths, the last step in the assembly mechanism is largely reversed and antiparallel tetramers are the predominant species. Alkaline pH, which can also induce minifilament disassembly, produces the same assembly intermediates as are found for salt induced disassembly.

scholarly journals Optical detection of gadolinium(iii) ions via quantum dot aggregation

RSC Advances ◽  
2017 ◽  
Vol 7 (40) ◽  
pp. 24730-24735 ◽  
Author(s):  
Steven D. Quinn ◽  
Steven W. Magennis
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Quantum Dot ◽  
Fluorescence Correlation Spectroscopy ◽  
Correlation Spectroscopy ◽  
Trivalent Metal ◽  
Fluorescence Correlation ◽  
Trivalent Metal Ions ◽  
Cdte Quantum Dot ◽  
Fluorescence Dynamic

CdTe quantum dot aggregation induced by trivalent metal ions is followed using fluorescence, dynamic light scattering and fluorescence correlation spectroscopy.

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