Dynamic Light Scattering Experiment Research Articles

Sizing Particles in Gases by an Advanced Optical Procedure

Several types of sensors capable of detecting fumes are commercially available. A well-established procedure for sizing particles suspended in liquid solvent is called Dynamic Light Scattering (DLS) and is based on assessing the diffusion coefficient of the particles from the fluctuations of the scattered light recorded in the scattered light intensity time series. This work highlights the difficulties encountered in an attempt to use DLS for sizing particles suspended in air and the particular, narrow experimental conditions chosen in designing and setting such a DLS experiment. The experimental setup was tested on combustion gases and the results of the preliminary experiment are presented in detail. The results stand as a proof of concept for using DLS in sizing particle in gases and in designing a sensor for fumes detection that can indicate the average size of the particles over an extended range.

In Vitro Targeting of NL2 Peptide Bounded on Poly L-DOPA Coated Graphene Quantum Dot.

Chemotherapy using drug delivery systems (DDS) can target cancer cells selectively and without affecting normal cells. In this paper, NL2 peptide as a tumor targeted peptide was bonded on the surface of poly 3,4-Dihydroxy-L-phenylalanine (Poly L-DOPA) graphene quantum dots (GQD), which was imprinted by Doxorubicin (DOX). The synthesized nanocomposite was characterized by Fourier-transform infrared spectroscopy (FTIR) and particle size was determined by dynamic light scattering (DLS) and Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). DOX release from synthesized nano-composite was investigated spectrophotometrically. Also, the toxicity and selectivity of NL2-GQD-NC on SK-BR-3 cell line were evaluated. FTIR and DLS experiment confirm the successful synthesis of Poly L-DOPA coated graphene quantum dots and their uniform particles. In vitro studies have shown that NL2-GQD-NC attached more to SK-BR-3 cells than NL2-free nanocomposites (GQD-NC). After attaching the cells could be imaged due to the presence of GQD particles and DOX release was accomplished in the tumor cells.

Synthesis and characterization of a novel thermally stable water dispersible polyurethane and its magnetic nanocomposites

In this work, a novel water dispersible polyurethane (WDPU) was synthesized from the reaction of hydroxyl-terminated polybutadiene (HTPB), 2,2 bis(hydroxymethyl) propionic acid (DMPA), and 1,5-naphthalene diisocyanate (NDI) and its magnetic nanocomposites were prepared by incorporation of modified Fe3O4 by 3-aminopropyltriethoxysilane (Fe3O4@APTS) nanoparticles (0.5, 1.5, and 3 wt%) via in situ polymerization method. Use of NDI as a high melting point diisocyanate by having the rigid naphthalene structure imparts physical strength as well as thermal stability to the resulted polyurethane. The synthesized WDPU based on NDI was characterized by using Fourier transform infrared spectroscopy (FTIR) technique. In addition, the morphology, mechanical, and magnetic features of the prepared polyurethane nanocomposites were investigated by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), magnetic force microscopy (MFM), thermogravimetry analysis (TGA), dynamic mechanical thermal analysis (DMTA), and vibrating sample magnetometer (VSM) methods, respectively. Data from DLS experiment showed that the average particles size of the WDPU nanocomposites increased by increasing the nanoparticle contents in comparison with bare WDPU. AFM and MFM analyses indicated that the magnetic nanoparticles (MNPs) were well dispersed in the polyurethane matrices via the formation of covalent bonding between the functionalized magnetic nanoparticles and polymer chains. TGA results demonstrated that adding MNPs increased the temperature of the thermal degradation of the polyurethane nanocomposite. VSM analysis showed that the super paramagnetic behavior of the prepared nanocomposites depended on the Fe3O4@APTS nanoparticle content, as well.

Green and Cost Effective Synthesis of Fluorescent Carbon Quantum Dots for Dopamine Detection

Carbon quantum dots (CQDs) due to its high fluorescent output is evolving as novel sensing material and is considered as future building blocks for nano sensing devices. Hence, in this investigation we report microwave assisted preparation and multi sensing application of CQDs. The microwave derived CQDs are characterized by Dynamic Light Scattering (DLS) experiment and Fourier Infrared spectra (FTIR) to investigate the size distribution and chemical purity respectively. Fluorescent emission spectra recorded at varying pH shows varying fluorescence emission intensities. Further, emission spectra recorded at different temperatures shows that fluorescence emission of CQDs greatly depends on temperature. Therefore, we demonstrate the pH and temperature sensing characteristics of CQDs by fluorescence quenching behaviour. In addition, the interaction and sensing behaviour of CQDs for dopamine is also presented in this work with a detection limit of 0.2mM. The steady state and time-resolved methods have been employed in fluorescence quenching methods for sensing dopamine through CQDs at room temperature. The bimolecular quenching rate constants for different concentration have been measured. The interaction between CQDs and dopamine indicates fluorescence quenching method is an elegant process for detecting dopamine through CQDs.

Conjugated polymers with carbazole, fluorene, and ethylene dioxythiophene in the main chain and a pendant cyano group: Synthesis, photophysical, and electrochemical studies

ABSTRACTSix new conjugated polymers comprising of carbazole, fluorene, and ethylene dioxythiophene (EDOT) moieties along the backbone with a pendant cyano group attached to the ethylene moiety have been designed and synthesized via Sonogashira coupling polymerization reaction. Optical and electrochemical characterizations have shown that the energy band gaps lie within the range of 2.35–2.44 eV. Additionally, the presence of carbazole and EDOT makes these polymers better hole transporting materials, which is reflected from their low oxidation potential peaks (0.55–1.11 V) in cyclic voltammograms. Furthermore, the aggregation enhanced emission (AEE) phenomenon resulted in a 2.6‐fold increase in fluorescence intensity in a 90:10 THF/water mixture in comparison to pristine THF. The AEE properties were further verified by DLS (dynamic light scattering) experiment and SEM (scanning electron microscopy) studies. Polymers in solution as well as in polystyrene matrix emit in the green region (quantum yield in solution state Φf =41–43%) with CIE values (0.25–0.36, 0.52–0.57). Excellent thermal stability is observed for the new polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2774–2784

Investigation on Structural, Surface Morphological and Dielectric Properties of Zn-doped SnO2 Nanoparticles

Zinc doped Tin oxide (SnO2) nanoparticles were prepared by co-precipitation method. The average crystallite size of pure and Zn-doped SnO2 nanoparticles was calculated from the X-ray diffraction (XRD) pattern. The FT-IR spectrum indicated the strong presence of SnO2 nanoparticles. The morphology and the particle size were studied using the scanning electron microscope (SEM) and transmission electron microscope (TEM). The particle size of the Zn-doped SnO2nanoparticles was also analyzed, using the Dynamic Light Scattering (DLS) experiment. The optical properties were studied by the UV–Visible absorption spectrum. The dielectric properties of Zn-doped SnO2 nanoparticles were studied at different frequencies and temperatures. The ac conductivity of Zn-doped SnO2 nanoparticles was also studied.

Analysis of Structure, Surface Morphology, Optical and Electrical Properties of Copper Nanoparticles

Copper (Cu) nanoparticles were prepared by chemical reduction method. The synthesized Cu nanoparticles were characterized with different techniques such as powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) spectrum, Transmission electron microscopy (TEM), UV-Visible spectrum and the dielectric properties of the prepared nanoparticles. The X-ray diffraction (XRD) analysis was used to study the structure and crystallite size of Cu nanoparticles. The morphology and the size of the Cu nanoparticles were characterized using Scanning Electron Microscopy and Transmission Electron Microscopy (SEM and TEM). The elemental composition of Cu nanoparticles was analyzed by Energy Dispersive X-ray (EDX) spectrum. The particle size of the Cu nanoparticles was also analyzed, using the Dynamic Light Scattering (DLS) experiment. The optical properties were studied using the UV-Visible spectrum in the wavelength range of 550 - 900 nm. The dielectric properties of Cu nanoparticles were studied at room temperature.

Biological Synthesis of Colloidal Gold Nanoprisms Using <i>Penicillium citrinum</i> MTCC9999

This report provides for the first time rapid novel environment friendly cell surface based synthesis of stable gold nanoprisms at room temperature using Penicillium citrinum MTCC9999 biomass. The UV-Visible spectral scan of dispersed gold nanoparticles (GNPs) solution showed absorption maxima at 540 nm due to surface plasma resonance (SPR) of gold nanoparticles. Typical Transmission Electron Microscopic (TEM) images showed that most of them were prism (55%) shaped with a diameter ranging from 20 - 40 nm. These results obtained from TEM correlated well with the data obtained from Dynamic Light Scattering (DLS) experiment. Average zeta potential of GNPs was -20 mV suggesting some biomolecules capped the nanoparticles imparting a net negative charge over it. FTIR analysis also showed that protein molecules were involved in stabilization.

Purification, crystallization and preliminary X-ray diffraction studies of the ATP-binding subunit of an ABC transporter fromGeobacillus kaustophilus

ATP-binding cassette (ABC) transporters, also known as traffic ATPases, form a large family of integral membrane proteins responsible for the translocation of a variety of chemically diverse substrates across the lipid bilayers of cellular membranes of both prokaryotes and eukaryotes by the hydrolysis of ATP. The ATP-binding subunit of an ABC transporter from Geobacillus kaustophilus, a homodimeric enzyme, was overexpressed in Escherichia coli and purified. Crystals were obtained using the microbatch-under-oil method at 291 K. X-ray diffraction data to 1.6 Å resolution were collected on SPring-8 beamline BL26B1. The crystals belonged to the orthorhombic space group I222, with unit-cell parameters a=54.94, b=78.63, c=112.96 Å. Assuming the presence of a dimer in the asymmetric unit gave a crystal volume per protein weight (VM) of 2.32 Å3 Da(-1) and a solvent content of 47%; this was consistent with the results of a dynamic light-scattering experiment, which showed a dimeric state of the protein in solution. Molecular-replacement trials using the crystal structure of HisP from the Salmonella typhimurium ATP-binding subunit of an ABC transporter as a search model did not provide a satisfactory solution, indicating that the two ATP-binding subunits of ABC transporters have substantially different structures.

Dynamic Origin and Thermally Induced Evolution of New Self‐Assembled Aggregates from an Amphiphilic Comb‐Like Graft Copolymer: A Multiscale and Multimorphological Procedure

In the past several decades, the self-assembly of block copolymers in selective solvents has attracted extensive interest due to the formation of various aggregates including spherical and cylindrical micelles, vesicles, tubes, helices, toroids, and other complex forms. Research has been focused on aggregates with spherical, flowerlike, tubular or sheet-like superstructures, obtained through the hierarchical self-assembly of Janus micelles or Janus nanoparticles, owning to their formation mechanisms and potential applications in biomedical materials and new nanodevices. The self-assembled aggregates can also be constructed from amphiphilic comb-like graft copolymers in water or organic solvents. Despite that many interesting aggregates including petal-like micelles, spindle-like micelles, wormlike micelles, chiral helices, and so on, are obtained by the change of structural and environmental parameters, in most cases conventional spherical micelles and vesicles are observed. In comparison with block copolymers, self-assembled aggregates of amphiphilic comb-like graft copolymers reveal the morphological characteristics of obviously low diversity and complexity. Considering the shape plays a crucial role in determining physical and chemical properties of aggregates, the controlled fabrication and switch of morphologies have been paid a great attention, which has been implemented by regulating the conditions, such as solvent, pH, redox, and so on. Typically, crystallization is an important factor utilized to control the self-assembly of semicrystalline block copolymers consisting of the crystallizable block and amorphous block, which has been actively researched recently. Inspired by this specific class of copolymer, we have designed an amphiphilic comb-like graft copolymer consisting of poly(p-dioxanone) (PPDO) as a crystallizable hydrophobic side chain and poly(vinyl alcohol) (PVA) as a hydrophilic main chain, and found that this copolymer presented an unique self-assembled behavior. In fact, recently we reported a “star anise”-like nanoaggregate from a PPDO-based branched alternating multi-block copolymer. Herein, by directly dispersing this PPDO-based amphiphilic comb-like graft copolymer into water, more complex and regular aggregates with a well-defined snowflake-like superstructure was obtained, and their origin involving a dynamically disorder–order change from nanoto submicroscale was visualized. Moreover, the aggregates showed thermally induced multimorphological evolution from a snowflake-like to cluster-like structure. As an original and significant work, this superstructure enriches the self-assembled morphology of amphiphiles, especially comb-like macromolecules. Furthermore, the direct water phase self-assembled strategy of PPDO-based amphiphilic copolymers and temperature-adjusted morphological change could provide a new idea to construct complex multimorphological and multiscale objects. The precursors of the copolymers were synthesized through ring-opening polymerization and the acylation, respectively. The copolymers were prepared in DMSO by a coupling reaction between carboxyl groups presenting on PPDO chain-end and hydroxyl groups of PVA (Scheme 1). The information of the molecular structure of copolymers is listed in the Supporting Information, Table S1. The self-assembly was achieved by adding PVA500-g5.6%PPDO15 to water at room temperature, heating the system to homogenous phase (to erase the thermal history), and aging it at 25 8C. Tests of dynamic light scattering (DLS) indicated the presence of monodispersed and stable particles with 791 nm of intensity-averaged hydrodynamic diameter ( ) and a polydispersity index (PDI) of 0.053 (Figure 1a, their and PDI after 7 days was shown in the Supporting Information, Figure S1). Transmission electron microscopy (TEM) images revealed well-defined snowflakelike aggregates having about 260 nm of average thickness, 530 nm of average width, and 620 nm of average length, respectively (marked by short arrows in Figure 1band 1c). For monodisperse spherical aggregates, they have same diffusion coefficient in every direction, and their size from CONTIN analysis is independent of scattering angles. Conversely, for the anisotropic or polydisperse aggregates, the results of DLS are dependent of scattering angles. By multi-angle DLS experiment, we found that the diameter and apparent [a] G. Wu, Dr. S.-C. Chen, Dr. X.-L. Wang, Dr. K.-K. Yang, Prof. Y.-Z. Wang National Engineering Laboratory of Eco-Friendly Polymeric Materials (Sichuan) State Key Laboratory of Polymer Materials Engineering College of Chemistry, Sichuan University 29 Wangjiang Road, Chengdu 610064 (P.R. China) Fax: (+86)28-85410259 E-mail : chensichong@scu.edu.cn yzwang@scu.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201103961.

Effect of Sodium Salicylate on the Properties of Gemini Surfactant Solutions

AbstractIn this paper, the effect of sodium salicylate on the solution properties of a gemini surfactant, butylidene‐α, ω‐bis (cetyl dimethyl ammonium bromide), was investigated through absorbance and dynamic light scattering (DLS) measurement, transmission electron microscope (TEM) observation, and rheology measurement. The DLS experiment showed that the average size of aggregates increases with the addition of sodium salicylate. The TEM experiment showed that the addition of sodium salicylate causes the change of the size and shape of aggregate. With the increase of the concentration of sodium salicylate, the viscosity of the gemini surfactant solution reaches a maximum value and the flow pattern of the gemini surfactant solution also undergoes a great change with a transition from a Newtonian fluid to a non‐Newtonian fluid.

Bulk shear-mode contribution to thermally generated capillary waves on a room-temperature ionic-liquid surface

In the present work, we show that the autocorrelation function of the capillary-wave displacement is expressed by the sum of the ordinary oscillator and the bulk shear-mode terms. The former is expressed by a simple damped oscillator form or a sum of exponentially damping functions depending on the extent of damping. The latter is also written by superposition of exponentially damping modes, and an analytically exact formulation is obtained. We performed surface dynamic light-scattering experiment for the surface of an ionic liquid, 1-butyl- 3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, and compared the experimental autocorrelation function with the theoretical one. We observed for the first time the bulk shear-mode contribution, and confirmed that the experimental data is well explained by the theoretical autocorrelation function.

Purification, crystallization and preliminary crystallographic study of the putative enolase MJ0232 from the hyperthermophilic archaeonMethanococcus jannaschii

Enolase is a glycolytic enzyme that catalyzes the interconversion of phosphoenolpyruvate and 2-phosphoglycerate. In order to gain insight into the biological significance of the oligomeric state of this enzyme, the putative enolase MJ0232 from the hyperthermophilic archaeon Methanococcus jannaschii was cloned, overexpressed and purified. Crystals were obtained by the oil-microbatch method at 291 K using PEG 4000 as a precipitant. A native data set was collected to 1.85 A resolution. The crystal belonged to the tetragonal space group I4, with unit-cell parameters a = 148.8, c = 91.2 A. An initial model was obtained by molecular replacement, which revealed an octameric subunit association (a tetramer of dimers). This result is consistent with that from a dynamic light-scattering experiment, suggesting biological relevance of the octameric state of MJ0232 in solution.

Separation and characterization of the colored material from sugarcane molasses

The colored material (X) was effectively separated from sugarcane molasses using reversed-phase chromatography. Characterization of the molecular structure of sample X was performed using infrared absorption (IR) spectrometry, mass spectrometry (MS), and dynamic light scattering (DLS). The IR spectrum was similar to that of commercial humic acid, and the MS analysis showed that the sample possessed relatively small heterogeneous molecules with molecular masses around 234, 446, 657, 868, and 1079 Da. On the other hand, X sample showed an inhibitory activity toward the cysteine proteinase papain. Furthermore, the inhibitory (G-1) and weak inhibitory (G-2) fractions were separated from sample X using gel permeation chromatography. Samples G-1 and G-2 inhibited papain partial-noncompetitively and had the inhibition constants of 5.01 × 10 −5 and 1.08 × 10 −3 M, respectively. Interestingly, in the DLS experiment, the Stokes radius of sample G-1 was ∼2 nm, about twice one of sample G-2.

Purification, crystallization and preliminary X-ray diffraction studies of a putative UDP-N-acetyl-D-mannosamine dehydrogenase fromPyrococcus horikoshiiOT3

A putative UDP-N-acetyl-D-mannosamine dehydrogenase from Pyrococcus horikoshii OT3, an essential enzyme for polysaccharide biosynthesis, has been overexpressed in Escherichia coli and purified. Crystals were obtained using the oil-microbatch method at 291 K. A native data set extending to 1.8 A resolution has been collected and processed in space group P2(1). Assuming the presence of a dimer in the asymmetric unit, the V(M) value is calculated to be 2.3 A3 Da(-1), which is consistent with the result of a dynamic light-scattering experiment that shows a dimeric state of the protein in solution.

Quantitative comparison between dynamic structure factors obtained experimentally and those calculated with Doi-Onuki theory

This paper reports results of quantitative comparison between dynamic structure factors obtained experimentally and those calculated by using the Doi and Onuki (DO) theory for semidilute polymer solutions. The authors obtained the dynamic structure factors with dynamic light scattering (DLS) experiment while the dynamic structure factors were calculated by using DO theory with osmotic compressibility, viscoelastic relaxation function, and friction coefficient which are obtained independently of DLS experiment. Calculated dynamic structure factors agree with experimental ones well and can express the q-dependent fast modes and the q-insensitive slow mode which experimental ones show. The authors estimated the characteristic parameters, interdiffusion coefficient and cooperative diffusion coefficient, from experimental and calculated results by using the procedure proposed by Einaga and Fujita [Polymer 40, 565 (1999)]. The estimated parameters for the DLS experiment agree with those for the calculation. These agreements in dynamic structure factors and the parameters indicate that DO theory can describe well the relaxation processes of semidilute polymer solutions.

High-resolution dynamic light scattering using a software correlator with analog detection

In this article, a dynamic light scattering (DLS) experimental system with 12.5ns time resolution has been realized based on the use of a photomultiplier tube, a virtual digital storage oscilloscope module, and a personal computer. This experimental system is designed to work on analog detection, in which the photomultiplier output is used directly as an analog signal. Several tests about this system are carried out and the time resolution of this system is demonstrated theoretically and experimentally. From the data and the result, this system is feasible to execute the DLS experiment.

Purification, crystallization and preliminary X-ray crystallographic analysis of the archaeal phosphoglycerate mutase PH0037 from Pyrococcus horikoshii OT3.

Phosphoglycerate mutases catalyze the interconversion of 2-phosphoglycerate and 3-phosphoglycerate in glycolysis and gluconeogenesis pathways. The archaeal phosphoglycerate mutase PH0037 from Pyrococcus horikoshii OT3 has been overexpressed in Escherichia coli and purified. Crystals were obtained using the oil-microbatch method at 291 K. A native data set extending to a resolution of 2.2 angstroms has been collected and processed in space group R32. Assuming the presence of a dimer in the asymmetric unit, the V(M) value is calculated to be 3.0 angstroms3 Da(-1), consistent with the dynamic light-scattering experiment result, which shows a dimeric state of the protein in solution. Molecular-replacement trials using the crystal structure of Bacilllus stearothermophilus phosphoglycerate mutase as a search model did not provide a satisfactory solution, indicating substantially different structures of these two phophoglycerate mutases.

Expression and Characterization of Full-length Human Huntingtin, an Elongated HEAT Repeat Protein

Huntington disease is an inherited neurodegenerative disorder that is caused by expanded CAG trinucleotide repeats, resulting in a polyglutamine stretch of >37 on the N terminus of the protein huntingtin (htt). htt is a large (347 kDa), ubiquitously expressed protein. The precise functions of htt are not clear, but its importance is underscored by the embryonic lethal phenotype in htt knock-out mice. Despite the fact that the htt gene was cloned 13 years ago, little is known about the properties of the full-length protein. Here we report the expression and preliminary characterization of recombinant full-length wild-type human htt. Our results support a model of htt composed entirely of HEAT repeats that stack to form an elongated superhelix.

The expression and refolding of isotopically labeled recombinant Matrilysin for NMR studies

Matrilysin (MMP7) is the smallest member of matrix metalloproteinases (MMPs) family, which are collectively responsible for remodeling of connective tissue. MMP7 plays an essential role in cancer, innate immunity, and in inflammatory disorders, and has been justified as a novel drug target. Here, we report the gene synthesis, overexpression in Escherichia coli, purification and refolding of MMP7. The gene of Matrilysin was synthesized based on PCR method and overexpressed in E. coli in the form of inclusion bodies. The protein was subsequently purified and refolded to yield sufficient quantities for structural and functional studies. The purified protein was characterized by means of MALDI-TOF mass spectroscopy and dynamic light scattering (DLS) analysis. The MS data confirms the correctness of the primary sequence, while DLS experiment proves that the protein exists as a monomeric form. A significantly optimized protocol has been worked out to prepare 15N and/or 13C-labeled MMP7 in minimal medium with high yields for NMR studies. Under the various conditions optimized for the purification of MMP7, the yield of the purified protein is estimated to be 18–20 mg from 0.5 L of M9 minimal media. Finally, the 15N–1H HSQC spectrum of uniformly 15N-labeled MMP7 sample reveals that the protein is properly folded, and exists in a well-ordered structure.