Quasi-elastic Light-scattering Studies Research Articles

Noncovalent polymers based on aromatic derivatives of β-cyclodextrin

6-Monotosyl-and 6-mononaphthyl derivatives of β-cyclodextrin have been synthesized, and their self-association abilities have been compared. The quasi-elastic light-scattering study revealed the occurrence of self-organization of mono-6-naphtyl-β-cyclodextrin in dilute aqueous solutions that is responsible for the formation of nanosized aggregates. It is suggested that the driving forces of self-organization are the combination of hydrophobic interactions between the aromatic group of one cyclodextrin molecule and the cavity of the neighboring macrocycle that lead to the formation of noncovalent polymers and hydrogen bonds between these polymers. The absence of intermolecular interactions in the case of mono-6-tosyl-β-cyclodextrin is apparently related to the discrepancy between sizes of the tosyl moiety and of the β-cyclodextrin cavity. The influence of concentration, temperature, pH of solution, and competing low-molecular-mass agents on the self-assembly and stability of supramolecular polymers has been studied.

'Artificial' myosin isozymes: preparation and characteristics.

Using precisely monitored proteolytic digestion conditions rabbit fast skeletal muscle myosin could be selectively modified in different ways. A myosin isozyme with a 20-kDa alkali light chain 1 (A1) could be obtained by digesting with papain in the presence of Ca2+. Under these conditions alkali light chain 2 (A2) was cleaved at Lys-17 and lost a 2.3-kDa N-terminal fragment including the strongly basic N terminus and about half of the characteristic (Ala-Pro) sequence. The Nbs2-[5,5' dithiobis(2-nitrobenzoic acid)-]light chain and A2 were left unmodified and less than 5% of the myosin heavy chain presented a break in the subfragment-2 region. EDTA and Ca2+ ATPase activities were unchanged. A myosin isozyme with an 18-kDa Nbs2-light chain was obtained by limited digestion with trypsin in the presence of Ca2+. The 18.9 leads to 18-kDa conversion was nearly 100% whereas less than 10% of the heavy chain was fragmented and only about 5% of A1 was converted to A1. The Nbs2-light chain was cleaved at Arg-7 preserving Ser-15 and consequently a phosphorylated modified myosin could be obtained. A quasi-elastic light-scattering study showed that this modified myosin in high-ionic-strength solutions exhibited physicochemical characteristics quite similar to those of unmodified myosin.

X-ray and Quasi-Elastic Light-Scattering Studies of Sodium Deoxycholate

ADVERTISEMENT RETURN TO ISSUEPREVCorrectionX-ray and Quasi-Elastic Light-Scattering Studies of Sodium DeoxycholateA. A. D'Archivio, L. Galantini, E. Giglio, and A. JoverCite this: Langmuir 1998, 14, 20, 5972Publication Date (Web):September 12, 1998Publication History Published online12 September 1998Published inissue 1 September 1998https://doi.org/10.1021/la9810105Copyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views184Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (8 KB) Get e-AlertsSUBJECTS:Sodium,X-rays Get e-Alerts

X-ray and Quasi-Elastic Light-Scattering Studies of Sodium Deoxycholate

Sodium and rubidium deoxycholate (NaDC and RbDC, respectively) fibers have been drawn near the gelation point by lowering the pH of aqueous micellar solutions. Their X-ray diffraction patterns show a very close resemblance and can be interpreted by means of similar unit cell parameters and helical structures, formed by trimers arranged in 8/1 helices. Because the structures of the resulting fibers are connected with those observed in crystals, the helix of the RbDC crystal has been chosen to construct the 8/1 helix of the fibers. Calculations of interatomic distances support the 8/1 helix that can be used as a structural model of the NaDC micellar aggregates, especially near the gelation point. The lowering of pH within a narrow range in NaDC aqueous solutions causes a remarkable increase of the apparent hydrodynamic radius (Rh) and of the average scattered intensity. The intensity strongly changes within 2 °C around the temperature of the sol−gel transition. A bimodal Rh distribution, corresponding to very small and very big aggregates, is observed. The dominant mechanism causing the decay of the intensity autocorrelation function seems to be the translational motion of the center of mass of the aggregates. The absence of an appreciable rotational contribution is ascribed to the formation of roughly isotropic aggregates with spheroidal shape. It is proposed that the isotropic big aggregate is formed by helices randomly coordinated around a solvated hydrogen ion or a cluster containing hydrogen ions and water molecules, and that a network of cross-links, due to polar forces, connects the big aggregates and is responsible for the gel formation.

Quasi Elastic Light Scattering Study on Solutions of Linear Flexible Polyelectrolytes at Low Ionic Strengths

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuasi Elastic Light Scattering Study on Solutions of Linear Flexible Polyelectrolytes at Low Ionic StrengthsRoy G. Smits, Maxim E. Kuil, and Michel MandelCite this: Macromolecules 1994, 27, 20, 5599–5608Publication Date (Print):September 1, 1994Publication History Published online1 May 2002Published inissue 1 September 1994https://doi.org/10.1021/ma00098a013RIGHTS & PERMISSIONSArticle Views125Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Influence of polydispersity on protein crystallization: a quasi-elastic light-scattering study applied to α-amylase

The early stages of the crystallization process of porcine pancreatic alpha-amylase were investigated by quasi-elastic light scattering. It is shown that at 288 and 293 K the diffusion coefficient does not monotonically change with increasing protein concentration but passes through a maximum at 10 mg ml(-1). In supersaturated solutions, prior to nucleation, the protein is strictly monodisperse. Nucleation induces the formation of aggregates and a polydispersity of, for example, 18% for an initial supersaturation C/C(e) = 5.8. Monodispersity is restored after the nuclei have grown and partially consumed the solute. On the other hand, polydispersity increases up to 20% at 298 K if the protein concentration decreases to 3-4 mg ml(-1), values at which the solutions are under-saturated. When the protein concentration exceeds 5-6 mg ml(-1) the protein becomes monodisperse again. These results, confirmed by those of another system we are studying (bovine pancreatic trypsin inhibitor), are at variance with the statements that supersaturation is always at the origin of aggregation and polydispersity, and that in undersaturated solutions the diffusion coefficient should remain constant for obtaining crystals once the solutions are supersaturated.

Synthesis and physicochemical properties of bolaamphiphiles from dimeric acid

The physicochemical behaviour of bolaamphiphile derivatives with an anionic, a cationic, or a non-ionic polar group and their mixtures is studied mainly by surface tension measurements, quasi-elastic light-scattering studies, 1H NMR spectroscopy, and surface monolayers. Bolaamphiphiles are synthesized by classical methods from a non-expensive mixture of α,ω-dicarboxylic acids, obtained by thermal Diels–Alder type cyclization of methyl 10-E,12-E linoleate, obtained from tall oil. The anionic and cationic bolaamphiphiles synthesized are water soluble and form stable monolayers when they are compressed. The anionic and the cationic bolaamphiphiles with an iodide atom as counter-anion show a behaviour between liquid-condensed and liquid-expanded. The other synthesized cationic bolaamphiphiles and the (1:1) mixtures of anionic–cationic bolaamphiphiles behave as liquid-condensed.

Structure of zwitterionic surfactant micelles: micellar size and intermicellar interactions

An elastic and quasielastic light-scattering study of micelles made of zwitterionic phosphobetaine surfactants dissolved in water has provided their size and information about intermicellar interactions, as a function of surfactant molecular structure. Attention was focused on the influence of the length of the intercharge polymethylene bridge linking the two opposite electrical charges of the zwitterionic headgroup. The micelles are small, the size of most of them allowing a spherical shape

Quasi-elastic and total intensity light-scattering studies of mucin glycoproteins and cartilage proteoglycans

Quasi-elastic and total intensity light-scattering studies of mucin glycoproteins and cartilage proteoglycans

Quasi-elastic laser light-scattering studies of size and dispersity of secretory vesicles and neurosecretosomes isolated from vertebrate neurohypophyses

Quasi-elastic laser light-scattering studies of size and dispersity of secretory vesicles and neurosecretosomes isolated from vertebrate neurohypophyses

Quasi-elastic light-scattering studies of the assembly properties of microtubules

Quasi-elastic light-scattering studies of the assembly properties of microtubules

Relaxation phenomena near the sol‐gel transition

AbstractNear the sol‐gel transition, relaxation phenomena exhibit a form of critical slowing down that is manifest in a variety of microscopic and macroscopic dynamical phenomena. For example, quasielastic light scattering studies (QELS) of the relaxation of thermally induced density fluctuations in critical silica sol‐gels reveal a self‐similar dynamics wherein decay processes occur on all time scales (fractal time), and average decay times diverge. Likewise, time‐ and frequency‐dependent viscoelastic phenomena of critical gels are described by power laws and both the viscosity and recoverable equilibrium creep compliance diverge. These unusual relaxation phenomena appear to be associated with the connectivity divergence that occurs at the sol‐gel transition. Light scattering studies of this sol‐gel transition reveal fractal clusters whose size diverges as a power law, in reasonable accord with the predictions of percolation theory. Based on these structural observations, we have developed a scaling description of the dynamics that relies on a length‐scale‐dependent viscosity and the geometrical self‐similarity of the sol‐gel transition. When percolation exponents are used in these expressions, a good description of the viscoelastic phenomena and the relaxation of density fluctuations near the gel point is obtained. Finally, it is shown that the dynamic scaling treatment of the viscoelastic properties can be summarized in a Time‐Cure Superposition principle, which predicts certain universal axes for frequency‐ or time‐dependent properties near the gel point.

Elastic and quasielastic light-scattering studies of the aggregation phenomena in water solutions of polystyrene particles.

We report measurements on the aggregation processes in a colloidal solution of polystyrene particles performed by elastic (intensity) and quasielastic light scattering. In order to observe the different kinetics of aggregation of the system, reversible flocculation, and the slow and the fast irreversible coagulation, the experiment was made varying the concentration of a simple electrolyte (NaCl) in the 0.01--3 mol/liter range. Intensity data give direct information that aggregated clusters are built with fractal structure and different kinetics; in the slow regime the aggregation process is reaction limited, whereas in the raft regime we have a diffusion-limited cluster-cluster aggregation. Dynamical data, showing well-defined scaling behavior in the measured mean linewidth, confirm such a picture and give a rough estimate of the cluster dimension. Experimental results are consistent with the Derjaguin-Landau-Verwey-Overbeek theory on colloidal stability [Derjaguin and Landau, Acta Phys. Chim. Debricina 14, 633 (1941); Verwey and Overbeek, Theory of the Stability of Lyophobic Colloids (Elsevier, Amsterdam, 1948)].

Interactive data-acquisition and evaluation system for quasielastic light scattering

A photoelectron-counting system has been constructed for all kinds of quasielastic light-scattering studies. The system consists of two parts, a data-acquisition unit, based upon a 16-bit microprocessor with additional hardware and software, and an evaluation unit, which can be any minicomputer, provided it has a parallel input port. The sample time resolution of the data-acquisition system is 500 ns at a data width of 4 bits, 1 μs at 8 bits, and 50 μs at 16 bits. The storage size is 2 Mbyte or more. The system also controls and remotes the measurement, as it is necessary for electrophoretic experiments or for time-resolved investigations. It is possible to store the raw data on a file. The evaluation either leads to a power spectrum or performs an autocorrelation function, with the time-critical parts written in assembly language.

Solution properties of xanthan. Light scattering and viscometry on dilute and moderately concentrated solutions

Elastic and quasi-elastic light-scattering, viscometric and rheological studies are given for solutions of the microbial polysaccharide Xanthomonas campestris (xanthan) in aqueous 0.62N NaCl for polymer concentrations from 0.03 to 2.2 g kg −1. The observed negative ∂ ln[η] ∂ ln T is interpreted as a decrease of the persistence length with increasing T. The behaviour in moderately concentrated solutions (2<[ η] c<25) reveals intermolecular association, leading to gel formation in the extreme case. The effect of the association on the viscometric and light-scattering data is discussed. It is concluded that the early stages of association involve structure with the chain axes nearly parallel, but that larger, particulate-like structures develop with increasing c, eventually leading to gel formation under certain conditions.

Quasielastic light-scattering study of the movement of particles in gels.

Quasielastic light-scattering study of the movement of particles in gels.

Quasielastic Light-Scattering Study on Changes in Sizes of Native White Membranes after Addition of Retinal

Aqueous suspensions of native white membranes from Halobacterium halobium, strain JW2N, have been studied by quasielastic light scattering. The intensity autocorrelation functions of polarized scattered light from suspensions of white membranes themselves and of white membranes after reconstitution with retinal were measured at various K(2), K being the magnitude of the scattering vector. The first cumulant or the average decay rate of the correlation function was obtained by a cumulant expansion method. The first cumulant for the white membranes increased after retinal was added to the suspension. The first cumulants obtained before and after the addition of retinal were almost independent of pH in the range 7 to 11, and of temperature in the range 15 degrees to 40 degrees C after T/eta scaling, eta being the solvent viscosity. This suggests that photocycling in reconstituted membranes, induced by the probe laser-beam, did not cause any detectable change in spectra, and that the membrane flexibility, if present, was independent of the above conditions, so that the spectral changes after the addition of retinal could be attributed mostly to the changes in the sizes of the membranes. A theoretical formulation for the first cumulant for a rigid disk-like scatterer (Fujime, S. and K. Kubota, 1985, Biophys. Chem., 23:1-13.) was applied to the analysis of the spectra. The results suggest that the radii of the membrane patches decreased by several percent after the addition of retinal.

Quasielastic light-scattering study of semiflexible polymers. Poly(γ-benzyl L-glutamate) in dimethylformamide

Etude en solution diluee pour examiner l'influence de la flexibilite sur le spectre de diffusion de la lumiere

General Discussion III Evening Session, December 7, 1983

HepatologyVolume 4, Issue S2 p. 180S-190S ArticleFree Access General Discussion III Evening Session, December 7, 1983 First published: September/October 1984 https://doi.org/10.1002/hep.1840040835Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References 1 Bellocq AM, Biais J, Clin B, et al. Three-dimensional phase diagram of the brine-toluene-butarol-sodium dodecyl sulfate system. J Colloid Interface Sci 1980; 74: 311– 321. 2 Duane WC, Adler RD, Bennion LJ, et al. Determination of bile acid pool size in man: a simplified method with advantages of increased precision, shortened analysis and decreased isotope. J Lipid Res 1975; 16: 155– 158. 3 Duane WC. Taurocholate- and taurochenodeoxycholate-lecithin micelles: the equilibrium of bile salt between aqueous phase and micelle. Biochem Biophys Res Commun 1977; 74: 223– 229. 4 Mazer NA, Benedek GB, Carey MC. Quasielastic light-scattering studies of aqueous biliary lipid systems. Mixed micelle formation in bile salt-lecithin solutions. Biochemistry 1980; 19: 601– 615. 5 Borgstrom B. Equilibrium of taurodeoxycholate between mixed micellar and aqueous phases: effect of amphiphile. Lipids 1978; 13: 187– 189. 6 Mazer NA, Schurtenberger P, Carey MC, et al. Quasielastic light scattering studies of native hepatic bile from the dog: comparison with the aggregative behavior of model biliary lipid systems. Biochemistry 1984 (in press). 7 Ammon HV, Walter LG. Determination of monomer concentration of conjugated bile acids in micellar solutions. Anal Chem 1982; 54: 2079– 2082. 8 Small DM, Bourges MC. Lyotropic paracrystalline phases obtained with ternary and quaternary systems of amphiphilic substances in water: studies on aqueous systems of lecithin, bile salts and cholesterol. Molec Cryst 1966; 1: 541– 561. 9 Brown MF, Seelig J. Influence of cholesterol on the polar region of phosphatidylcholine and phosphatidylethanolamine bilayers. Biochemistry 1978; 17: 381– 384. 10 Smith IC. The Ayerst Award Lecture 1978. Organization and dynamics of membrane lipids as determined by magnetic resonance spectroscopy. Can J Biochem 1979; 57: 1– 14. 11 Igimi H, Carey MC. pH-solubility relations of chenodeoxycholic and ursodeoxycholic acids: physical-chemical basis for dissimilar solution and membrane phenomena. J Lipid Res 1980; 21: 72– 89. 12 Armstrong MJ, Carey MC. The hydrophilic-hydrophobic balance of bile salts: inverse correlation between reverse-phase high performance liquid chromatographic mobilities and micellar cholesterol-solubilizing capacities. J Lipid Res 1982; 23: 70– 80. 13 Wolpers C. Morphologie der Gallensteine. Leber Magen Darm 1974; 4: 43– 57. Citing Literature Volume4, IssueS2September/October 1984Pages 180S-190S ReferencesRelatedInformation

Quasi-elastic light-scattering studies of aqueous biliary lipid systems. Cholesterol solubilization and precipitation in model bile solutions

We have employed quasi-elastic light-scattering methods to characterize micellar aggregates and microprecipitates formed in aqueous solutions containing sodium taurocholate (TC), egg lecithin (L), and cholesterol (Ch). Particle size and polydispersity were studied as functions of Ch mole fraction (XCh = 0-15%), L/TC molar ratio (0-1.6), temperature (5-85 degrees C), and total lipid concentration (3 and 10 g/dL in 0.15 M NaCl). For XCh values below the established solubilization limits (XChmax) [Carey, M. C., & Small, D. M. (1978) J. Clin. Invest. 61, 998], added Ch has little influence on the size of simple TC micelles (type 1 systems), on the coexistence of simple and mixed TC-L micelles (type 2 systems), or on the growth of "mixed disc" TC-L micelles (type 3 systems). For supersaturated systems (XCh/XChmax greater than 1), 10 g/dL type 1 systems (L/TC = 0) exist as metastable micellar solutions even at XCh/XChmax = 5.3. Metastability is decreased in type 2 systems (0 less than L/TC less than 0.6), and "labile" microprecipitation occurs when XCh/XChmax exceeds approximately 1.6. In 10 g/dL mixtures, the microprecipitates initially range in size from 500 to 20000 A and later coalesce to form a buoyant macroscopic precipitate phase. In 3 g/dL mixtures, the microprecipitates are smaller (200-400 A) and remain as a stable, noncoalesced microdispersion. Transmission electron microscopy of the microprecipitates formed at both concentrations indicates a globular noncrystalline structure, and lipid analysis reveals the presence of cholesterol and lecithin in a molar ratio (Ch/L) of approximately 2/1, suggesting that the microprecipitates represent a metastable cholesterol-rich liquid-crystalline phase. In supersaturated type 3 systems (0.6 less than L/TC less than 2.0), the precipitate phase is a lecithin-rich liquid-crystalline phase which likewise coalesces in a 10 g/dL system but forms stable vesicle (liposomal) structures (600-800 A radius) in 3 g/dL systems. In conjunction with these experimental data, we present a quantitative thermodynamic analysis of Ch solubilization in model bile systems from which rigorous deductions of the free energy and enthalpy change for solubilization of cholesterol monohydrate in type 1 and type 2 systems are obtained. In addition, we employ homogeneous nucleation theory to analyze the origin of the metastable/labile limit in supersaturated systems and to deduce the interfacial tension between microprecipitates and solution. On the basis of these experimental data and theoretical analyses, we offer new hypotheses on the structure and physiology of bile and the pathogenesis of Ch gallstones. In particular, it is suggested that the "stable" microprecipitates observed in 3 g/dL type 2 systems may provide a secondary vehicle (in addition to micelles) for cholesterol transport in supersaturated hepatic bile.