Right Angle Light Scattering Research Articles

Reversible four-color electrochromism triggered by the electrochemical multi-step redox of Cr-based metallo-supramolecular polymers.

Four color electrochromism (yellow, magenta, blue, and navy) has been achieved in Cr(iii)-based metallo-supramolecular polymers (polyCr), which were synthesized by 1 : 1 complexation of Cr ions and 1,4-di[[2,2′:6′,2′′-terpyridin]-4′-yl]benzene (L). The polymer structure was determined by X-ray absorption fine structure (XAFS) measurement and X-ray photoelectron spectroscopy (XPS). The molecular weight of polyCr was calculated as 3.2 × 107 Da using right angle light scattering (RALS). The EXAFS fitting indicated that the bond distances of Cr–N are 2.020 Å and 2.208 Å. A film of polyCr shows multi-color electrochromism (EC) or absorption: a sharp peak at 380 nm at 0 V vs. Ag/Ag+ (yellow), a sharp peak at 510 nm and a broad peak at 800 nm at −0.6 V vs. Ag/Ag+ (magenta), a broad peak at 610 nm and between 700–900 nm at −1.2 V vs. Ag/Ag+ (blue), a broad peak between 450–900 nm at −1.8 V vs. Ag/Ag+ (navy). The transmittances change (ΔT), the switching times for coloring and bleaching (Tc, Tb) and the coloration efficiency (ηc, ηb): [ΔT, (Tc, Tb), (ηc, ηb)] were [39.2%, (5.56 s, 1.39 s), (169 cm2 C−1, 230 cm2 C−1)] at 510 nm between −0.6 and 0.2 V vs. Ag/Ag+, [67.0%, (6.93 s, 2.52 s), (138 cm2 C−1, 172 cm2 C−1)] at 610 nm between −1.2 and 0.2 V vs. Ag/Ag+, [86.1%, (6.80 s, 3.03 s), (167 cm2 C−1, 134 cm2 C−1)] at 780 nm between −1.8 and 0.2 V vs. Ag/Ag+, respectively, during the cycles. The durability experiment indicates that polyCr shows an EC property for at least 100 cycles.

Characterization of Inherent Particles and Mechanism of Thermal Stress Induced Particle Formation in HSV-2 Viral Vaccine Candidate.

Vaccine formulations may contain visible and/or subvisible particles, which can vary in both size and morphology. Extrinsic particles, which are particles not part of the product such as foreign contaminants, are generally considered undesirable and should be eliminated or controlled in injectable products. However, biological products, in particular vaccines, may also contain particles that are inherent to the product. Here we focus on the characterization of visible and subvisible particles in a live, replication-deficient viral vaccine candidate against HSV genital herpes in an early developmental stage. HSV-2 viral vaccine was characterized using a panel of analytical methods, including Fourier transform infrared spectroscopy (FTIR), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot, liquid chromatography-mass spectrometry (LC-MS), light microscopy, transmission electron microscopy (TEM), micro-flow imaging (MFI), dynamic light scattering (DLS), right angle light scattering (RALS), and intrinsic fluorescence. Particles in HSV-2 vaccine typically ranged from hundreds of nanometers to hundreds of micrometers in size and were determined to be inherent to the product. The infectious titer did not correlate with any trend in subvisible particle concentration and size distribution as shown by DLS, MFI, and TEM under stressed conditions. This suggested that particle changes in the submicron range were related to HSV-2 virion structure and had direct impact on biological activity. It was also observed that subvisible and visible particles could induce aggregation in the viral product. The temperature induced aggregation was observed by RALS, intrinsic fluorescence, and DLS. The increase of subvisible particle size with temperature could be fitted to a two-step thermokinetic model. Visible and subvisible particles were found to be inherent to the HSV-2 viral vaccine product. The mechanism of protein aggregation was discussed and a two-step thermokinetic aggregation profile was proposed. The approaches reported in this study may be applied to a variety of vaccines and other biological products, as a way to assess the consistency of the manufacturing process and identify key product quality attributes.

Size-exclusion chromatography of ultrahigh molecular weight methylcellulose ethers and hydroxypropyl methylcellulose ethers for reliable molecular weight distribution characterization

Size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering (MALLS) and differential refractive index (DRI) detectors was employed for determination of the molecular weight distributions (MWD) of methylcellulose ethers (MC) and hydroxypropyl methylcellulose ethers (HPMC) having weight-average molecular weights (Mw) ranging from 20 to more than 1,000kg/mol. In comparison to previous work involving right-angle light scattering (RALS) and a viscometer for MWD characterization of MC and HPMC, MALLS yields more reliable molecular weight for materials having weight-average molecular weights (Mw) exceeding about 300kg/mol. A non-ideal SEC separation was observed for cellulose ethers with Mw>800kg/mol, and was manifested by upward divergence of logM vs. elution volume (EV) at larger elution volume at typical SEC flow rate such as 1.0mL/min. As such, the number-average molecular weight (Mn) determined for the sample was erroneously large and polydispersity (Mw/Mn) was erroneously small. This non-ideality resulting in the late elution of high molecular weight chains could be due to the elongation of polymer chains when experimental conditions yield Deborah numbers (De) exceeding 0.5. Non-idealities were eliminated when sufficiently low flow rates were used. Thus, using carefully selected experimental conditions, SEC coupled with MALLS and DRI can provide reliable MWD characterization of MC and HPMC covering the entire ranges of compositions and molecular weights of commercial interest.

Synthesis of poly(2‐methoxyethyl acrylate) by single electron transfer—Degenerative transfer living radical polymerization catalyzed by Na2S2O4 in water

AbstractLiving radical polymerization of 2‐methoxyethyl acrylate (MEA) was achieved by single‐electron‐transfer/degenerative transfer mediated living radical polymerization (SET‐DTLRP) in water catalyzed by sodium dithionate. The poly(2‐methoxyethyl acrylate) is an amphiphilic polymer with a hydrophobic part (polyethylene chain) and a mildly hydrophilic tail. The plots of number‐average molecular weight versus conversion and ln{[M]0/[M]} versus time are linear, indicating a controlled polymerization. This method leads to the preparation of α,ω‐di(iodo) poly(2‐methoxyethyl acrylate)s (α,ω‐di(iodo)PMEA) macroinitiators that can be further functionalized. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right‐angle light scattering (RALLS), a differential viscometer (DV) and refractive index (RI). The method studied in this work represents a possible route to prepare well‐tailored macromolecules made of 2‐methoxyethyl acrylate (biocompatible material) in an environmentally friendly reaction medium. To the best of our knowledge there is no previous report dealing with the synthesis of PMEA by any LRP approach in aqueous medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4454–4463, 2009

Light scattering sensing detection of pathogens based on the molecular recognition of immunoglobulin with cell wall-associated protein A

In this contribution, we report a rapid optical detection method of pathogens using Staphylococcus aureus ( S. aureus) as the model analyte based on the molecular recognition of immunoglobulin with cell wall-associated Protein A (SpA). It was found that the molecular recognition of human immunoglobulin (IgG) with protein A on the cell wall of S. aureus on glass slide sensing area could result in strong surface enhanced light scattering (SELS) signals, and the SELS intensity (Δ I) increases proportionally with the concentration of S. aureus over the range of 2.5 × 10 5–1.0 × 10 8 CFU mL −1 with right angle light scattering (RALS) signals detection mode. In order to identify the solid support based molecular recognition between IgG with SpA, we also employed water-soluble CdS quantum dots (CdS-QDs) as a fluorescent marker for IgG by immobilizing the IgG onto the surfaces of CdS-QDs through covalent binding in order to generate recognition probes for SpA on the cell wall of S. aureus. Consequently, the fluorescent method also showed that the detection for pathogens with solid supports is reliable based on the molecular recognition of IgG with SpA.

Single electron transfer–degenerative chain transfer living radical polymerization of N‐butyl acrylate catalyzed by Na2S2O4 in water media

AbstractLiving radical polymerization of n‐butyl acrylate was achieved by single electron transfer/degenerative‐chain transfer mediated living radical polymerization in water catalyzed by sodium dithionate. The plots of number–average molecular weight versus conversion and ln[M]0/[M] versus time are linear, indicating a controlled polymerization. This methodology leads to the preparation of α,ω‐di(iodo) poly (butyl acrylate) (α,ω‐di(iodo)PBA) macroinitiators. The influence of polymerization degree ([monomer]/[initiator]), amount of catalyst, concentration of suspending agents and temperature were studied. The molecular weight distributions were determined using a combination of three detectors (TriSEC): right‐angle light scattering (RALLS), a differential viscometer (DV), and refractive index (RI). The methodology studied in this work represents a possible route to prepare well‐tailored macromolecules made of butyl acrylate in an environmental friendly reaction medium. Moreover, such materials can be subsequently functionalized leading to the formation of different block copolymers of composition ABA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2809–2825, 2006

Characterization of suspension poly(vinyl chloride) resins and narrow polystyrene standards by size exclusion chromatography with multiple detectors: Online right angle laser-light scattering and differential viscometric detectors

This work reports the utilization of a multi-detector size chromatography for the characterization of poly(vinyl chloride) (PVC) resins prepared by suspension polymerization in the range of temperatures between 21 and 75 °C. The chromatography equipment offers the possibility of analyzing the samples in terms of their absolute molecular mass using a combination of three detectors (TriSEC): right angle light scattering (RALLS), a differential viscometer (DV) and refractive index (RI). The PVC resins were fully characterized concerning the molecular weight distribution (MWD), its dependence with intrinsic viscosity ( η) and molecular sizes (radius of gyration, R g and hydrodynamic radius, R h). Additionally, it is also presented the characterization of polystyrene narrow standards serving as reference polymers. It is possible to find in the literature several methodologies concerning the breaking of typical aggregates presented in PVC solutions. The most suitable for the experiments were chosen, adapted and analysed by light scattering. It was observed that the application of the TriSEC to study PVC solutions was effective and it was concluded that this is an important tool for the polymer characterization, opening the possibility of running experiments avoiding the need of fractionation of the polydisperse PVC in order to obtain the Mark–Houwink–Sakurada (MHS) constants, or the utilization of MHS, that are quite diverse in literature.

Studies on hyperbranched polyurethane by multidetector size exclusion chromatography

Hyperbranched polyurethane (HP) and its linear analog (LPU) were studied by size exclusion chromatography (SEC), utilizing a combination of refractive index (RI), right angle light scattering (RALLS), and differential viscosity (DV) detectors. The relationships between retention volume (Ve), intrinsic viscosity (η), radius of gyration (Rg), and the molecular structure were investigated. It was shown that the hyperbranched polyurethane had lower Ve, η, and Rg than its linear analog when they had the same molecular weight. The branching parameter g and g′ were calculated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2445–2450, 2002

Characterization of star-block copolymers having PS-b-PI arms via SEC/RI/RALLS/DV

Poly (styrene-b-isoprene) (PS-b-PI) star-block copolymers were studied by triple detector size exclusion chromatography (SEC 3 ), utilizing a combination of refractive index (RI), right angle light scattering (RALLS), and differential viscosity (DV) detectors. The relationships between the number of arms, the composition, and molecular size of the star polymers were investigated. The effect of the number of arms of the star polymer on elution behavior was established and compared to a linear polystyrene calibration curve. It was found that universal calibration was valid for star polymers having up to 32 arms The branching parameters (g and g') were calculated from intrinsic viscosity and radius of gyration data. The results indicate that, in addition to molecular weight determinations, much useful conformational information on star-block copolymers can be obtained from SEC 3 . The technique is an especially useful tool for characterizing branched copolymers, which are difficult to characterize by conventional SEC.

Periodic formation of nascent lamellae is driven by changes in the stable F-actin pool of polymorphonuclear neutrophils after stimulation with chemotactic peptide and cross-linking of CD18 or CD61.

Cell motility and changes in cell shape are largely powered by actin polymerization and depolymerization. Eight to ten second periodic changes in human polymorphonuclear neutrophil (PMN) shape were detected by video-image analysis of PMN crawling on a surface and by right angle light scattering (RALS) in suspended PMN. However, sustained RALS oscillations in suspended PMN requires pre-treatment with an inhibitor of phosphatidylinositol 3-kinase or an activator of protein kinase C. Here, we show that cross-linking of the beta(2) (CD18) or beta(3) (CD61), but not beta(1) (CD 29) integrins in the presence of a low dose of formyl-Methionyl-Leucyl-Phenylalanine (fMLP) enables similar 8-s periodic RALS oscillations in suspended PMN in response to stimulation with two consecutive doses of chemoattractants. This effect did not appear to be due to increased surface expression of CD18 or CD61. RALS oscillations occurred in phase with 8-s oscillations in the stable F-actin pool and peaks in F-actin correlated with predominance of cells exhibiting a nascent lamella. Thus, simulation of surface attachment by CD18 and CD61 cross-linking after exposure to fMLP in suspended cells supports shape oscillations that are the result of actin-driven cyclic extension/retraction of nascent lamellae at the same frequency as the shape changes previously observed in crawling PMN.

On the Accuracy of Molecular Weight and Radius of Gyration Measured by Right-Angle Light Scattering with SEC-Viscometry

Abstract The use of a right-angle light scattering detector with a size exclusion chromatograph equipped with an online viscometer provides a convenient method of estimating polymer molecular weight distribution. The 90° scattered intensity provides an initial estimate of the molecular weight at each elution slice. This value is then improved using an estimate of the light-scattering asymmetry based on the measured intrinsic viscosity in order to determine the 0° scattering intensity required to obtain the true molecular weight. In addition, an estimate of the radius of gyration can be obtained. In this paper the accuracy of the method is examined for different linear polymers and also for branched polymers. In most cases molecular weights within 2% of the true values can be obtained up to 1 × 106 g/mol. Errors are about 5% for molecular weights of 2 × 106 g/mol and rapidly increase for higher molecular weights. The errors in the radius of gyration estimated using this method are higher (∼ 10%); however, ...

Flow cytometric assessment of cell viability: a multifaceted analysis

Flow cytometry offers the possibility to simultaneously analyze, on a cell by cell basis, different parameters related to cell viability i.e. cell size, morphology and incorporation of dyes. Different types of analysis: light absorption of unstained/stained cells, forward angle light scattering (FALS), right angle light scattering (RALS) or both, cell fluorescence based on dye retention or dye exclusion (due to erythrosin B, ethidium bromide, fluorescein diacetate, rhodamine 123) were tested and compared, with the classical Trypan blue exclusion test, for their effectiveness in the determination of cell viability. Two types of cells in monolayer cultures (L929, SIRC) and a freshly isolated suspension of mouse splenocytes were used. For each dye, the optimal dose, incubation time and conditions for analysis were determined. Viability indications by different techniques for the three type of cell line and their reliability as compared with Trypan blue were analyzed.

Saturation relations in mixtures of sucrose, dextrose, and levulose

Size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering (MALLS) and differential refractive index (DRI) detectors was employed for determination of the molecular weight distributions (MWD) of methylcellulose ethers (MC) and hydroxypropyl methylcellulose ethers (HPMC) having weight-average molecular weights (Mw) ranging from 20 to more than 1,000 kg/mol. In comparison to previous work involving right-angle light scattering (RALS) and a viscometer for MWD characterization of MC and HPMC, MALLS yields more reliable molecular weight for materials having weight-average molecular weights (Mw) exceeding about 300 kg/mol. A non-ideal SEC separation was observed for cellulose ethers with Mw > 800 kg/mol, and was manifested by upward divergence of log M vs. elution volume (EV) at larger elution volume at typical SEC flow rate such as 1.0 mL/min. As such, the number-average molecular weight (Mn) determined for the sample was erroneously large and polydispersity (Mw/Mn) was erroneously small. This non-ideality resulting in the late elution of high molecular weight chains could be due to the elongation of polymer chains when experimental conditions yield Deborah numbers (De) exceeding 0.5. Non-idealities were eliminated when sufficiently low flow rates were used. Thus, using carefully selected experimental conditions, SEC coupled with MALLS and DRI can provide reliable MWD characterization of MC and HPMC covering the entire ranges of compositions and molecular weights of commercial interest.