Laser Light Scattering Study on Aggregation of Cellulose Diacetate in Acetone

We have investigated the properties of cellulose diacetate in solution by using laser light scattering. The cellulose diacetate molecules can form micelles and micellar clusters in acetone besides the individual chains. As the concentration increases, the average hydrodynamic radius （Rh） linearly increases, whereas the ratio of gyration radius to hydrodynamic radins 〈Rg〉/〈Rh〉 linearly decreases. It indicates that the micelles associate and form micellar clusters due to the intermolecular interactions.

On-chip classification of micro-particles using laser light scattering and machine learning

The rapid detection of microparticles exhibits a broad range of applications in the field of science and technology. The proposed method differentiates and identifies the 2 μm and 5 μm sized particles using a laser light scattering. The detection method is based on measuring forward light scattering from the particles and then classifying the acquired data using support vector machines. The device is composed of a microfluidic chip linked with photosensors and a laser device using optical fiber. Connecting the photosensors and laser device using optical fibers makes the device more diminutive in size and portable. The prepared sample containing microspheres was passed through the channel, and the surrounding photosensors measured the scattered light. The time-domain features were evaluated from the acquired scattered light, and then the SVM classifier was trained to distinguish the particle’s data. The real-time detection of the particles was performed with an overall classification accuracy of 96.06%. The optimum conditions were evaluated to detect the particles with a minimum concentration of 0.2 μg/m L. The developed system is anticipated to be helpful in developing rapid testing devices for detecting pathogens ranging between 2 μm to 10 μm.

LIGHT-SCATTERING STUDY OF POLYELECTROLYTE HOLLOW CAPSULES

Silver halide (AgX) microcrystal was used as template to synthesize hollow polyelectrolyte capsules. These hollow capsules were characterized by laser light scattering (LLS) used to measure the size of the capsules in solution. The ratio of hydrodynamic radius (R h ) from dynamic LLS to the radius of gyration (Rg) from static LLS is almost unity, revealing that the entities are hollow in solution. The results suggest that the LLS method can be regarded as a good complement to the confocal laser scanning microscopy (CLSM) method for the characterization of small hollow capsules, and it possesses the advantage of not needing fluorescence labeling.

Measurement of the Average Molecular Weight of Cotton Cellulose Crosslinked by a Polycarboxylic Acid at Different pH Using Multiple Angle Light Scattering Photometer in a DMAc/LiCl Solvent System

Durable press finishing of cotton fabrics with polycarboxylic acid increases fabric wrinkle-resistance at the expense of its mechanical strength. Severe tensile strength loss is the major disadvantage for wrinkle resistant cotton fabrics.Tensile strength loss of cotton fabric crosslinked by a polycarboxylic acid can be attributed to depolymerization and crosslink of cellulose molecules. Measurement of the molecular weight of cotton fabric before and after crosslinked by polycarboxylic acids can offer a possibility of direct understanding of the depolymerization. In this research, amultiple angle laser light scattering photometer was used todetermine the absolute molecular weight of cotton fabric treated with BTCA at different pH and then hydrolyzed with 0. 5 M NaOH solution at 50℃ for 144 h. The results indicate that average molecular weights of cotton fabric treated with polycarboxylic acids at different pH are almost the same.

Kinetics of Coil-to-Globule Transition of DansyI-Labeled Poly（N-isopropyl- acrylamide） Chains in Aqueous Solution

The coil-to-globule transition of thermally sensitive linear poly（N-isopropylacrylamide） （PNIPAM） labeled with dansyl group is induced by 1.54 μm laser pulses （widths10 ns）. The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino- l-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, Tfast≈0.1 ms, which can be attributed to the nucleation and formation of some ＂pearls＂ （locally contracting segments） on the chain, and tslow≈0.5 ms, which is related to the merging and coarsening of the ＂pearls＂.Tfast is independent of the PNIPAM chain length over a wide range （Mw=2.8× 10^6-4.2 × 10^7 g/mol）. On the other hand, Tslow only slightly increases with the chain length.

Rapid and label-free classification of pathogens based on light scattering,reduced power spectral features and support vector machine

The rapid identification of pathogens is crucial in controlling the food quality and safety.The proposed system for the rapid and label-free identification of pathogens is based on the principle of laser scattering from the bacterial microbes.The clinical prototype consists of three parts:the laser beam,photodetectors,and the data acquisition system.The bacterial testing sample was mixed with 10 mL distilled water and placed inside the machine chamber.When the bacterial microbes pass by the laser beam,the scattering of light occurs due to variation in size,shape,and morphology.Due to this reason,different types of pathogens show their unique light scattering patterns.The photo-detectors were arranged at the surroundings of the sample at different angles to collect the scattered light.The photodetectors convert the scattered light intensity into a voltage waveform.The waveform features were acquired by using the power spectral characteristics,and the dimensionality of extracted features was reduced by applying minimal-redundancy-maximal-relevance criterion(mRMR).A support vector machine(SVM)classifier was developed by training the selected power spectral features for the classification of three different bacterial microbes.The resulting average identification accuracies of E.faecalis,E.coli and S.aureus were 99%,87%,and 94%,respectively.The ove rall experimental results yield a higher accuracy of 93.6%,indicating that the proposed device has the potential for label-free identification of pathogens with simplicity,rapidity,and cost-effectiveness.

Real-Time Observation of Pyoverdine Dissolving Ferric Hydroxide

Pyoverdine is one of the siderphores excreted by Pseudomonas aeruginosa that can help microbe to uptake iron in vitro. To determine the effect of pyoverdine chelating with iron, we purified the free pyoverdine and applied the dynamic laser light scattering （DLS） to detect the interaction between the pyoverdine and ferric hydroxide. The real-time DLS data analysis indicated that pyoverdine can directly combine with Fe（OH）3 to form complexes and these substances are gradually degraded by themselves then completely disappeared. In our experiment, we have demonstrated that pyoverdine may not only chelate ferric ion but also availably dissolve ferric hydroxide which assists bacteria to survive in iron-deficient environments.

A SLOW RELAXATION MODE OF POLYMER CHAINS IN A SEMIDILUTE SOLUTION

Dust-free semidilute and concentrated polystyrene(PS)solutions in different solvents were prepared by slow evaporation and in situ anionic polymerization,which removes the effects of troublesome artifacts such as dust contamination and concentration gradient.The dynamics was reexamined by a combination of static and dynamic laser light scattering.In benzene and toluene(good solvents for PS),only one fast diffusive mode of polymer chains can be observed when the concentration(c)is up to 20%,which is attribut...

Study on Molecular Chain Morphology of Konjac Glucomannan

The long-range structure of konjac glucomannan(KGM)is studied by using laser light scatter(LLS), gel permeation chromatography(GPC)and method of viscosidity. The weight-average molecular weight(Mw), root-mean-square ratio of gyration[(S2)1/2], second viral coefficient(A2)and multi-dispersion coefficient(Mw/Mn)are 1.04×106, 105. 0±0. 9 nm,(-1. 59±0.28)×10-3 mol ml g-2 and 1.015±0.003, respectively. Mark-Houwink equation is established as [η] = 5. 96×10-2Mw0.73 and the molecular chain parameters are as follows: ML=982. 82 nm-1, Lp = 27. 93 nm, d = 0. 74 nm, h = 0. 26 nm, L = l 054.11 nm. Further more molecular chain morphology of KGM is studied by using atom force microscope(AFM)and transmission electronic microscope(TEM), and the result shows that the KGM molecular is an extending semi-flexible linear chain without branch. Therefore, the image of molecular chain morphology confirms the deduction drawn by Mark-Houwink equation and molecular chain parameters.

Preparation of true solutions of monomeric amyloidogenic protein/peptide:A critical prerequisite for aggregation kinetic study

Our dynamic laser light scattering(LLS) study shows that the current widely used protocols of dissolving amyloidogenic protein/peptide do not really result in a true solution;namely,there always exist a trace amount of interchain aggregates,which greatly affect the association kinetics,partially explaining why different kinetics were reported even for a solution with identical protein and solvent.Recently,using a combination of the conventional dissolution procedure and our newly developed ultra-filtration method,we have developed a novel protocol to prepare a true solution of amyloidogenic protein/peptide without any interchain aggregates.The resultant solutions remain in their monomeric state for at least one week,which is vitally important for further study of the very initial stage of the interchain association under the physiological conditions because more and more evidence suggests that it is those small oligomers rather than large fabric aggregates that are cytotoxic.In addition,this study shows that combining static and dynamic LLS can lead to more physical and microscopic information about the protein association instead of only the size distribution.