Effects of citral on Aspergillus flavus spores by quasi-elastic light scattering and multiplex microanalysis techniques

Litsea cubeba (Lour.) Pers. is a kind of medicinal plantin China. The first report about the antibacterial and anti-phlogistic function of Litsea cubeba (Lour.) Pers. and itsoil appeared in the Zhong Yao Da Ci Dian [1]. Since 1980s,many studies showed that Litsea cubeba oil had wideantibacterial and antifungal activity [2–4]. The antibioticfunctions of Litsea cubeba oil are attributable mainly tocitral [5–7], which amounts to 60%–80% of the essentialoil [8]. Pattnaik [9] reported that…     

Application of constrained regularization analysis to low-angle quasi-elastic light scattering

A constrained regularization procedure has been applied to a low-angle quasi-elastic light scattering system in order to determine particle size distributions. The conditions under which this procedure may be successfully applied to low-angle photon correlation spectroscopy have been characterized. Acquisition of photon count data over a short time period, relative to the long exponential decay constants of correlation functions obtained at low forward angles, resulted in particle size distributions which were stable with regard to peak width and weighted mean particle radius. Irrespective of the number of photon counts obtained, peak resolution and position on the particle size scale were not optimized unless anomalies in the correlation function due to transient increases in the mean photon counting rate were removed from the photon count data prior to autocorrelation. When such measures were taken, reasonable size distributions were obtained for well characterized protein standards and for liposomal suspensions.     

Quasi-elastic light scattering of Artemia ribosomes sedimented in a CsCl density gradient

It is impossible to measure the diffusion coefficient of macromolecules directly and accurately by quasi—elastic light scattering, when aggregates cannot be eliminated from the solutions to be investigated. Nevertheless, a simple method can be applied to overcome this problem in many cases. Aggregates are separated from the monomeric macromolecules by rate-zonal sedimentation in a CsCl density gradient in a transparent centrifugation tube; the monomers are then located by laser light scattering intensity measurements; photon correlation spectroscopy of the scattered light finally yields their diffusion coefficient. The viscosity of aqueous CsCl solutions at different temperatures and concentrations allows a good separation by centrifugation and a low uncertainty in the reduction of the measured diffusion coefficient to standard conditions.The application of the method to eukaryotic large ribosomal subunits is described as an example.     

Properties of pancreatic zymogen granules studied by quasi-elastic light scattering

Physico-chemical properties of isolated zymogen granules of the mouse pancreas were studied by means of quasi-elastic light scattering. The average diameter of the granules in 0.3 M sucrose was found to be 1.1 ± 0.1 μm from the correlation time of intensity fluctuation of the scattered light. The average diameter altered depending on the osmolality of the medium in a manner that the alteration was smaller than that expected from the van't Hoff relation. Aggregation of the granules induced by the increase of Ca²⁺ concentration or the decrease of pH in the medium was also detected. The aggregation started at a critical level of 1 mM CaCl₂ or at pH 5.4.     

Quasi-elastic light scattering study of salt induced conformational transitions of chromatin subunit

The translational diffusion coefficient D_T of monodisperse solutions of 146 base pairs (bp) core particles was studied by the quasi-elastic light scattering technique. When the salinity was raised a change of D_T from 1.9 × 10^?7 cm² s^?1 to 3.2 × 10^?7 cm² s^?1 was detected at about 2 mM NaCl, followed by a smooth decrease of D_T beyond 0.6 M NaCl. The measurements of particle concentration and scattering vector effects on the D_T showed that the influence of interactions between particles can be disregarded. The interaction between particles and counterions is also discussed and does not appear to be the origin of the actual changes in D_T. These transitions of D_T are hence related to changes of shape and size of the particles. It is shown that the single transition at low salinity corresponds to a conformational change while the variation of D_T at high salinity can be interpreted by a destabilization of the edifice. In different regions of salinities, the observed values of D_T can lead to reasonable hydrodynamic models.     

Microscope laser light scattering spectroscopy of single biological cells

A microscope laser light scattering setup was developed, allowing us to do intensity autocorrelation spectroscopy on the light scattered from a volume as small as (2 μm)³. This non-invasive technique makes cytoplasmic studies possible inside single live biological cells. The effect of osmotic swelling and shrinking on the diffusion coefficient of hemoglobin inside intact red blood cells is shown as an illustrative example of the applicability and sensitivity of this new experimental method.     

Characterization of the size distribution of unilamellar vesicles by gel filtration, quasi-elastic light scattering and electron microscopy

The size and size distribution of unilamellar phospholipid vesicles present in unsonicated phosphatidic acid and mixed phosphatidic acid/phosphatidylcholine dispersions were determined by gel filtration, quasi-elastic light scattering and freeze-fracture electron microscopy. The vesiculation in these dispersions was induced by a transient increase in pH as described previously (Hauser, H. and Gains, N. (1982) Proc. Natl. Acad. Sci. USA 79, 1683–1687). The resulting phospholipid dispersions are heterogeneous consisting of small unilamellar vesicles (average radius r < 50 nm) and large unilamellar vesicles (average r ranging from about 50 to 500 nm). The smallest vesicles with r = 11 ± 2 nm are observed with dispersions of pure phosphatidic acid, the population of these vesicles amounting to about 80% of the total lipid. With increasing phosphatidylcholine content the radius of the small unilamellar vesicles increases and at the same time the population of small unilamellar vesicles decreases. The average radius of small unilamellar vesicles present in phosphatidic acid/phosphatidylcholine dispersions (mole ratio, 1:1) is 17.5 ± 2 nm, the population of these vesicles amounting to about 70% of the total lipid. By a combination of gel filtration, quasi-elastic light scattering and freeze-fracture electron microscopy it was possible to characterize the large unilamellar vesicles. This population is heterogeneous with its mean radius also increasing with increasing phosphatidylcholine content. After separating the large unilamellar vesicles from small unilamellar vesicles on Sepharose 4B it can be shown by quasi-elastic light scattering that in pure phosphatidic acid dispersions 80–90% of the large unilamellar vesicle population consist of vesicles with a mean radius of 170 nm. In mixed phosphatidic acid/phosphatidylcholine dispersions this radius increases to about 265 nm as the phosphatidylcholine content is raised to 90 mol%.     

Determination of phase transition temperatures of lipids by light scattering

Various techniques have been proposed to specify the phase transition temperatures of surfactant molecules. The work reported herein deals with a new general method of T(c) determination based on the optical properties' modifications of aqueous surfactant solutions when the phase transitions occur in the phospholipid membrane. The shape alteration of supramolecular systems induced by the phase transition was correlated with the refraction and absorption coefficients of their aqueous dispersion. The mean count rate (average number of photons detected per second) measured with a Zetasizer Nano-S model ZEN1600 Dynamic Light Scattering Instrument, is representative of an emerging macroscopic phenomenon, but not directly size dependent and has been adapted to our expectations. Changes in the measured scattering intensity reflect changes in the optical properties of the material during temperature variations. Thus, this method allowed to specify the phase transition temperature of many natural or synthetic surfactants independently of their polar head or hydrophobic part.     

A quasi-elastic light scattering study of smooth muscle myosin in the presence of ATP.

We have investigated the hydrodynamic properties of turkey gizzard smooth muscle myosin in solution using quasi-elastic light scattering (QELS). The effects of ionic strength (0.05-0.5 M KCl) and light chain phosphorylation on the conformational transition of myosin were examined in the presence of ATP at 20 degrees C. Cumulant analysis and light scattering models were used to describe the myosin system in solution. A nonlinear least squares fitting procedure was used to determine the model that best fits the data. The conformational transition of the myosin monomer from a folded form to an extended form was clearly demonstrated in a salt concentration range of 0.15-0.3 M KCl. Light chain phosphorylation regulates the transition and promotes unfolding of the myosin. These results agree with the findings obtained using sedimentation velocity and electron microscopy (Onishi and Wakabayashi, 1982; Trybus et al., 1982; Trybus and Lowey, 1984). In addition, we present evidence for polymeric myosin coexisting with the two monomeric myosin species over a salt concentration range from 0.05 to 0.5 M KCl. The size of the polymeric myosin varied with salt concentration. This observation supports the hypothesis that, in solution, a dynamic equilibrium exists between the two conformations of myosin monomer and filaments.     

Structure of 7S seed globulin from Phaseolus vulgaris L. in solution

The structure of the 7S globulin from Phaseoulus vulgaris L in dilatue solutions has been studied by small angle X-ray scattering (SAXS), by quasi-elastic light scattering (Q ELS), by circular dichroism spectroscopy (c.d.), and by precise density measurements. The molar mass, the radius of gyration, the volume, the maximum dimension and the diffusion coefficient were determined as M = 1.45 × 10⁵ g mol⁻¹, R_G = 4.05 nm, V = 300- nm³, L = 13.0 nm and D_20,w⁰ = 4.5 × 10⁻⁷ cm² s⁻¹, respectively. The molecule has an asymmetrical shape with the dimensions 12.5 × 12.5 × 3.75 nm. The secondary structure of the 7S globulin is characterized by a small portion of -helical structure (14%) and a marked content of β-structure (18%).     

Laser light scattering measurements on vitreous and rooster comb hyaluronic acids

Molecular weights and translational diffusion coefficients have been measured for rooster comb and vitreous hyaluronic acid (HA) at pH 7.2 and 11. The results indicate that the molecular weight, second virial coefficient and translational diffusion coefficient for vitreous HA can be reversibly decreased by increasing the solution pH from 7.2 to 11, whereas the physical properties of rooster comb HA are independent of pH studied. In addition, it is reported that the second virial coefficient for vitreous HA is negative, suggesting intermolecular interactions exist in solution at both neutral and alkaline pH as opposed to rooster comb HA which exhibits a positive second vitrial coefficient associated with decreasing molecular weights may be related to the accessibility and number of hydrogen bond forming groups. Differences in the dependence of molecular weight on pH between vitreous and rooster comb HA may be due to differences in the number of intramolecular interactions per molecule. These studies indicate that molecules of low molecular weight HA are able to form higher molecular weight complexes and differences in the organization of the polysaccharide chains may contribute to the differences in molecular weight of HAs isolated from various tissues.     

Quantitation of phospholipid vesicles and their cholesterol content in human bile by quasi-elastic light scattering

The proportion of biliary cholesterol carried by phospholipid vesicles may be an important determinant of the lithogenicity of bile. The distribution of biliary cholesterol between vesicles and other aggregational forms is often determined by gel filtration under standard conditions. The aim of this study was to measure the proportion of biliary cholesterol in vesicles in native unprocessed bile and to compare it with values obtained by chromatography. A modified quasi-elastic light-scattering method was used to measure vesicular cholesterol in whole bile. It was suitable only for lightly pigmented biles with a relatively monodisperse population of vesicles. In ten human biles examined, the proportion of cholesterol in vesicles by gel filtration was 40 +/- 8.1% (mean +/- S.D.) by chemical measurement, and 38 +/- 7.2% by [3H]cholesterol estimation. Quasi-elastic light-scattering measurements of these biles produced vesicular cholesterol values of 36 +/- 9.4%. Chromatography may affect lipid particles in bile. Nevertheless, it provides a relatively accurate measurement of biliary cholesterol in vesicles.     

Insight into molecular imprinting in precipitation polymerization systems using solution NMR and dynamic light scattering

Molecular imprinting is a powerful synthetic technique for generating template-defined binding sites in cross-linked polymers. One scientific challenge in molecular imprinting research is to understand the intermolecular interactions leading to molecular complexation and the process of binding site formation during polymerization. In this work, we present a novel method for studying the molecular imprinting process in precipitation polymerization systems. This method employs solution (1) H NMR and dynamic light scattering (DLS) to investigate the association of template molecules with colloidal particles and the dynamic process of particle growth. Under precipitation polymerization conditions, the colloidal particles formed did not interfere with NMR signals from the soluble components, allowing unreacted monomers and free template to be easily quantified. To examine the process of particle nucleation and growth, DLS was used to measure the hydrodynamic particle size at different reaction times. To corroborate the interpretation of the NMR and DLS results, imprinted nanoparticles were collected at different reaction times and their binding characteristics were evaluated using radioligand-binding analysis. Our experimental results provide new insights into the molecular imprinting process that will be useful in the development of new imprinted nanoparticles.     

A study of the diffusion of compact particles in polymer solutions using quasi-elastic light scattering

This paper describes an investigation, using quasi-elastic light scattering, of the diffusion of polystyrene spheres through solutions of dextran. The diffusion coefficient, D, of the spheres is shown to vary inversely with the volume fraction, φ, of dextran according to $\text{D =}\text{D}{}_0\text{(1 + νφ + κφ}{}^2\text{)}$. Changes in the molecular weight of dextran are shown to reflect changes in the macromolecular shape parameter, ν, and the interaction parameter, κ. This result differs from previous studies which suggested an $\text{exp}\text{(?}\text{B}\text{φ}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$ dependence and no molecular weight dependence [8].     

Viscoelastic and light scattering studies on thermally induced sol to gel phase transition in fish myosin solutions

Viscoelastic (VE) and dynamic light scattering (DLS) analyses of fish (white croaker) myosin solutions were performed at myosin concentrations of 30 mg/mL for VE and 0.1 mg/mL for DLS at 0.6M KCl and pH 7.0 to clarify thermally induced gelation. The hydrodynamic radius R(h) considerably decreased around 30-35 degrees C. The shear modulus G was constant below 25 degrees C and increased by incubating the sample at 30 degrees C. G further increased as the temperature of the incubated sample decreased. The curves of G vs T for different time courses showed a sharp peak around 35 degrees C and a moderate peak around 60 degrees C in the heating process, while a stepwise increase in G was observed around 30 degrees C in the cooling process when the temperature was elevated to not more than 60 degrees C. No distinct stepwise change was observed once the temperature of the sample exceeded 60 degrees C. The absolute value of G strongly depended on the maximum elevated temperature and the incubation time at that temperature. The corresponding behavior of the viscosity eta was observed for each time course. Based on these results, the mechanism of thermally induced gelation of myosin solutions is discussed in view of S-S bridge formation in the head and tail portions and unwinding/rewinding of coiled-coil alpha-helices in the tail portion.     

Snapshot polarized light scattering spectroscopy using spectrally-modulated polarimetry for early gastric cancer detection

Polarized light scattering spectroscopy (PLSS) is a promising optical technique developed for the detection of cancer, which extracts the single scattering light to infer morphological information of epithelial cells. However, traditional PLSS uses either a rotatable polarizer or two orthogonal polarizers to purify the single scattering light, which makes it complicated and challenged to build a PLSS endoscope. Herein, we propose a snapshot PLSS with a single optical path to directly get the single scattering light for the first time. The single scattering light is encoded using the spectrally - modulated polarimetry and decoded using the continuous slide iterative method. Both the polystyrene microsphere solutions and the ex vivo gastric cancer samples are used to verify the method. The experimental results of the snapshot PLSS are consistent well with that of the traditional PLSS. The proposed method has a potential for the building of snapshot PLSS endoscope systems in future.      

The onset of amelogenin nanosphere aggregation studied by small-angle X-ray scattering and dynamic light scattering

Proteins with predominantly hydrophobic character called amelogenins play a key role in the formation of the highly organized enamel tissue by forming nanospheres that interact with hydroxyapatite crystals. In the present investigation, we have studied the temperature and pH-dependent self-assembly of two recombinant mouse amelogenins, rM179 and rM166, the latter being an engineered version of the protein that lacks a 13 amino acid hydrophilic C-terminus. It has been postulated that this hydrophilic domain plays an important role in controlling the self-assembly behavior of rM179. By small-angle X-ray and neutron scattering, as well as by dynamic light scattering, we observed the onset of an aggregation of the rM179 protein nanospheres at pH 8. This behavior of the full-length recombinant protein is best explained by a core-shell model for the nanospheres, where hydrophilic and negatively charged side chains prevent the agglomeration of hydrophobic cores of the protein nanospheres at lower temperatures, while clusters consisting of several nanospheres start to form at elevated temperatures. In contrast, while capable of forming nanospheres, rM166 shows a very different aggregation behavior resulting in the formation of larger precipitates just above room temperature. These results, together with recent observations that rM179, unlike rM166, can regulate mineral organization in vitro, suggest that the aggregation of nanospheres of the full-length amelogenin rM179 is an important step in the self-assembly of the enamel matrix.     

Using resonance light scattering and UV/vis absorption spectroscopy to study the interaction between gliclazide and bovine serum albumin

At different temperatures (298, 310 and 318 K), the interaction between gliclazide and bovine serum albumin (BSA) was investigated using fluorescence quenching spectroscopy, resonance light scattering spectroscopy and UV/vis absorption spectroscopy. The first method studied changes in the fluorescence of BSA on addition of gliclazide, and the latter two methods studied the spectral change in gliclazide while BSA was being added. The results indicated that the quenching mechanism between BSA and gliclazide was static. The binding constant (K_a), number of binding sites (n), thermodynamic parameters, binding forces and Hill's coefficient were calculated at three temperatures. Values for the binding constant obtained using resonance light scattering and UV/vis absorption spectroscopy were much greater than those obtained from fluorescence quenching spectroscopy, indicating that methods monitoring gliclazide were more accurate and reasonable. In addition, the results suggest that other residues are involved in the reaction and the mode ‘point to surface’ existed in the interaction between BSA and gliclazide. Copyright © 2015 John Wiley & Sons, Ltd.     

Concomitant Raman spectroscopy and dynamic light scattering for characterization of therapeutic proteins at high concentrations

A Raman spectrometer and dynamic light scattering system were combined in a single platform (Raman–DLS) to provide concomitant higher order structural and hydrodynamic size data for therapeutic proteins at high concentration. As model therapeutic proteins, we studied human serum albumin (HSA) and intravenous immunoglobulin (IVIG). HSA concentration and temperature interval during heating did not affect the onset temperatures for conformation perturbation or aggregation. The impact of pH on thermal stability of HSA was tested at pHs 3, 5, and 8. Stability was the greatest at pH 8, but distinct unfolding and aggregation behaviors were observed at the different pHs. HSA structural transitions and aggregation kinetics were also studied in real time during isothermal incubations at pH 7. In a forced oxidation study, it was found that hydrogen peroxide (H₂O₂) treatment reduced the thermal stability of HSA. Finally, the structure and thermal stability of IVIG were studied, and a comprehensive characterization of heating-induced structural perturbations and aggregation was obtained. In conclusion, by providing comprehensive data on protein tertiary and secondary structures and hydrodynamic size during real-time heating or isothermal incubation experiments, the Raman–DLS system offers unique physical insights into the properties of high-concentration protein samples.