Increase In Hydrodynamic Size Research Articles

A step forward towards optimized iron–nickel bimetal oxide core–shell nanoparticles and their magnetic properties

The core–shell nanoparticles of Fe3O4 and NiO are synthesized under different reaction conditions and are characterized by UV–vis and fluorescence spectroscopy, DLS, SEM, EDX, XRD, VSM, and FTIR spectroscopy. These techniques evaluated optimal synthetic conditions for desired size, morphology, stability, and crystallinity of these core–shell nanoparticles. Increasing the concentration of salt for shell material (Fe3O4 or NiO) in core–shell NPs resulted in better coating and increase in hydrodynamic size from 227 nm to 531 nm for (Fe3O4)NiO, and 244 nm to 544 nm for (NiO)Fe3O4, whereas lower concentration and higher temperature (80 °C) for (Fe3O4)NiO and lower temperature (25 °C) for (NiO)Fe3O4, higher pH 13 and 11 for (Fe3O4)NiO and (NiO)Fe3O4 respectively, and fast (quick) addition of reactants produces homogenous small sized nanoparticles. Stability is generally attained at higher concentration, higher temperature (80 °C), higher pH (13 and 11 for (Fe3O4)NiO and (NiO)Fe3O4 respectively), and slow addition (10 min) of reactants. Fluorescence enhancement is observed for (Fe3O4)NiO core–shell NPs at high concentration, temperature, pH and slow addition of reactants, representing proper coating of NiO. For (NiO)Fe3O4 NPs, fluorescence quenching is observed at higher concentration, lower temperature, higher pH, and slow addition of reactants representing proper coating of Fe3O4. XRD depicted pure cubic crystalline nature of these core–shell nanoparticles without any impurity. The identified optimized conditions are useful for obtaining nanoparticles with desired properties for various applications including sensing and catalysis etc. Magnetic properties of pure and core–shell nanoparticles show ferrimagnetic behavior for Fe3O4 NPs and weak ferromagnetic or superparamagnetic behavior NiO NPs.

Humic Acid Alleviates the Toxicity of Nanoplastics towards Solanum lycopersicum

Nanoplastics (NPs) are emerging pollutants that contaminate agricultural produce. The present study investigates the impact of polystyrene (PS) and humic acid (HA) individually and in combination on the germination and growth of seeds of Solanum lycopersicum (tomato). Here we report the formation of eco-corona upon the interaction of PS with humic acid at 24 h with a significant increase in hydrodynamic size. Seed germination, plant growth, and chlorophyll content increased in the coronated PS. In addition, we report that the treatment of seeds with PS + HA resulted in the germination of 90% of seeds, while treatment with only PS resulted in the germination of only 65.8% of seeds. A quantitative analysis of chlorophyll (a, b, and a + b) revealed that HA-treated groups and PS + HA-treated groups showed significantly high chlorophyll (a, b, and a + b) contents of (PS: 3.48 mg g−1, 2.12 mg g−1, and 4.19 mg g−1, HA: 5.76 mg g−1, 3.88 mg g−1, and 6.41 mg g−1, PS + HA: 4.17 mg g−1, 3.23 mg g−1, and 6.58 mg g−1)respectively compared to PS treated groups. Similarly, ROS levels were comparatively low in HA and PS + HA-treated groups than in only-PS-treated groups. Furthermore, we observed a decline in the level of antioxidant enzyme (superoxide dismutase and catalase) activity in HA and PS + HA treated groups than that in only-PS treated groups. The results indicate that HA significantly reduces PS-induced toxicity and improves germination and growth of seeds of Solanum lycopersicum; the corresponding reduction in toxic effects may be due to eco-corona formation on the PS. We understand that eco-corona is a way to protect plants from xenobiotics concerning nanoplastics.

The Effect of Humic Acid and Polystyrene Fluorescence Nanoplastics on Solanum lycopersicum Environmental Behavior and Phytotoxicity.

The impacts of nanoplastics (100 nm) on terrestrial systems are unclear at this time. Due to the utilization of sewage sludge, plastic particles are likely to accumulate in these systems. The current research investigates how Solanum lycopersicum seed germination and growth are affected by fluorescence polystyrene (Flu-PS), humic acid (HA), and a Flu-PS+HA combination (tomato). Following 24 h of interaction between Flu-PS and HA, our report details the development of an eco-corona with a significant increase in hydrodynamic size. Plant growth, seed germination, and chlorophyll content were all enhanced by the eco-coronated Flu-PS.Additionally, we discover that seeds treated with Flu-PS+HA demonstrated a germination rate of 90%, compared to just 65.8% for seeds treated with Flu-PS alone. Chlorophyll (a, b, and a + b) content measurements indicated that HA-treated groups and Flu-PS+HA-treated groups had considerably higher levels of chlorophyll (a, b, and a + b) than Flu-PS-treated groups (Flu-PS: 3.18 mg g-1, 2.12 mg g-1, and 3.89 mg g-1, HA: 5.96 mg g-1, 4.28 mg g-1, and 6.36 mg g-1, and Flu-PS+HA: 4.17 mg g-1, 3.01 mg g-1, and 6.08 mg g-1, respectively). In a similar manner, the HA and Flu-PS+HA treatment groups showed lower ROS levels than the Flu-PS treatment groups. In addition, we discovered that the activity of the antioxidant enzymes superoxide dismutase and catalase was lower in the groups treated with HA and Flu-PS+HA than in the groups solely treated with Flu-PS. The results demonstrated that HA significantly lessens the toxicity caused by Flu-PS, while also promoting the germination and growth of Solanum lycopersicum seeds. The related decrease in toxic effects may be ascribed to the establishment of an eco-corona on the Flu-PS. We think that the use of eco-coronas is a technique for safeguarding plants against xenobiotics such as nanoplastics.

Loading of hydrophobic drug silymarin in pluronic and reverse pluronic mixed micelles

In the presented work, pure pluronic and mixed micelles of normal pluronics (F108, F127, P85 and P84) with reverse pluronic (10R5) have been studied to enhance the solubilization of the hydrophobic drug silymarin (SLY) at different % w/v proportions (4:1, 2.5, 1:4 and 5). Solubilization capacity of SLY in the mixed micelles was found to be higher than pure pluronic micelles. Drug solubilization parameters including drug loading efficiency (DL), partition coefficient (P) and Gibbs free energy of solubilization (ΔG◦) were calculated. SLY loaded mixed micellar formulation of P84:10R5 (4:1% w/v) showed maximum solubility and drug loading efficiency as compared to other mixed micellar formulations. The cmc of pure as well as mixed micellar systems has been evaluated using fluorescence measurements. The locus of SLY in these micelles was evaluated by micropolarity measurements. After solubilization, increase in hydrodynamic size evidenced by DLS measurements confirmed the solubilization of SLY in the mixed micelles. In vitro drug release study was also performed for mixed micellar formulations with maximum SLY solubilization, and it was found to exhibit sustained release drug behavior. Different kinetics models were also applied and the best fitted model for the optimum SLY loaded mixed micellar formulation was found to be the Korsmeyer-Peppas model. To investigate the anti-oxidative potential of SLY drug and SLY loaded mixed micellar formulation of P84:10R5 (4:1% w/v),1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH·) scavenging, ferrous ions (Fe2+) chelating activities, total reducing ability determination by Fe3+ to Fe2+ transformation method, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging and nitric oxide assay were undertaken. The SLY loaded mixed micellar formulation of P84:10R5 (4:1% w/v) exhibited appreciably enhanced anti-oxidative activity as compared to SLY alone.

Iron Oxide Nanoparticle Coatings Dictate Cell Outcomes Despite the Influence of Protein Coronas.

A critical issue in nanomedicine is to understand the complex dynamics that dictate the interactions of nanoparticles (NPs) with their biological milieu. The most exposed part of a nanoparticle is its surface coating, which comes into contact with the biological medium and adsorbs proteins, forming what is known as a protein corona (PC). It is assumed that this PC mainly dictates the nanoparticle-cell interactions. As such, we set out to analyze how different coatings on iron oxide nanoparticles (MNPs) affect the composition of the PC that forms on top of them, and how these newly formed coronas influence the uptake of MNPs by macrophages and tumor cells, their subcellular location upon internalization, and their intracellular degradation. We found that different superficial charges of the coatings did not affect the PC composition, with an enrichment in proteins with affinity for divalent ions regardless of the type of coating. The iron oxide core of the MNP might become exposed to the biological medium, influencing the proteins that constitute the PCs. The presence of enzymes with hydrolase activity in the PC could explain the degradation of the coatings when they come into contact with the biological media. In terms of MNP internalization by cells, coatings mainly determine the endocytic pathways used, especially in terms of receptor-mediated endocytosis. However, the increase in hydrodynamic size provoked by the formation of the associated corona drives uptake mechanisms like macropinocytosis. Once inside the cells, the PC protected the NPs in their intracellular transit to lysosomes, where they were fully degraded. This understanding of how coatings and PCs influence different cellular processes will help design improved NPs for biomedical applications, taking into account the influence of the coating and corona on the biology of the NPs.

Peroxynitrite-Mediated Structural Changes in Histone H2A: Biochemical and Biophysical Analysis.

Peroxynitrite, a nitrating and oxidizing agent, is formed by the interaction between nitric oxide and superoxide radicals. H2A histone is a basic nucleoprotein and is one of the major core histones responsible for packaging DNA. It has been shown that they are highly sensitive to oxidizing and nitrating agents. Nitration of tyrosine residues in proteins by peroxynitrite is regarded as a marker of nitrosative damage. The dityrosine bond, an oxidative covalent cross-link between two tyrosines in protein, is increasingly identified as a marker of oxidative stress, aging and neurodegerative diseases. Peroxinitrite-mediated nitration and dinitration in H2A histone was assessed by various biophysical techniques. The data presented in this study showed that the dityrosine content was found to be elevated in H2A histone modified with peroxynitrite. The formation of dityrosine showed a decrease in fluorescence intensity, generation of a new peak in FT-IR, increase in hydrodynamic size, and loss of secondary and tertiary structure of H2A resulting in a partially folded structure. We report that H2A may undergo conformational and structural changes under nitrosative and oxidative stress from the deleterious effects of peroxynitrite.

Site-Specific PEGylation of Anti-Mesothelin Recombinant Immunotoxins Increases Half-life and Antitumor Activity.

Recombinant immunotoxins (RIT) are chimeric proteins containing an Fv that binds to tumor cells, fused to a fragment of Pseudomonas exotoxin (PE) that kills the cell. Their efficacy is limited by their short half-life in the circulation. Chemical modification with polyethylene glycol (PEG) is a well-established method to extend the half-lives of biologics. Our goal was to engineer RITs with an increase in half-life and high cytotoxic activity. We introduced single cysteines at different locations in five anti-mesothelin RITs and employed site-specific PEGylation to conjugate them to 20-kDa PEG. Because our previous PEGylation method using β-mercaptoethanol reduction gave poor yields of PEG-modified protein, we employed a new method using tris(2-carboxyethyl)phosphine to reduce the protein and could PEGylate RITs at approximately 90% efficiency. The new proteins retained 19% to 65% of cytotoxic activity. Although all proteins are modified with the same PEG, the radius of hydration varies from 5.2 to 7.1, showing PEG location has a large effect on protein shape. The RIT with the smallest radius of hydration has the highest cytotoxic activity. The PEGylated RITs have a 10- to 30-fold increase in half-life that is related to the increase in hydrodynamic size. Biodistribution experiments indicate that the long half-life is due to delayed uptake by the kidney. Antitumor experiments show that several PEG-RITs are much more active than unmodified RIT, and the PEG location greatly affects antitumor activity. We conclude that PEGylation is a useful approach to improve the half-life and antitumor activity of RITs.

MRI Relaxivity Changes of the Magnetic Nanoparticles Induced by Different Amino Acid Coatings.

In this study, we analysed the physico-chemical properties of positively charged magnetic fluids consisting of magnetic nanoparticles (MNPs) functionalised by different amino acids (AAs): glycine (Gly), lysine (Lys) and tryptophan (Trp), and the influence of AA–MNP complexes on the MRI relaxivity. We found that the AA coating affects the size of dispersed particles and isoelectric point, as well as the zeta potential of AA–MNPs differently, depending on the AA selected. Moreover, we showed that a change in hydrodynamic diameter results in a change to the relaxivity of AA–MNP complexes. On the one hand, we observed a decrease in the relaxivity values, r1 and r2, with an increase in hydrodynamic diameter (the relaxivity of r1 and r2 were comparable with commercially available contrast agents); on the other hand, we observed an increase in r2* value with an increase in hydrodynamic size. These findings provide an interesting preliminary look at the impact of AA coating on the relaxivity properties of AA–MNP complexes, with a specific application in molecular contrast imaging originating from magnetic nanoparticles and magnetic resonance techniques.

Fabricating mono-dispersed Fe3O4-SiO2 core-shell particles with help of triboelectrification

For years, it has been widely held that triboelectrification is not the sought-after technique to develop innovative materials with enhanced functionalities. In this study, we tried to break such a traditional concept and find its ever-expanding roles in material science. In our strategy, triboelectrification brought adequate charge to particles, so as to achieve their mono-dispersity in solutions. Following this strategy, the synthesis of mono-dispersed Fe3O4-SiO2 core-shell particles involved two-stage triboelectrification treatment. In the first-stage treatment, positive triboelectric charges on Fe3O4 cores ensured their uniform SiO2 coating and well-defined core-shell structure. In the second-stage treatment, positive triboelectric charges on Fe3O4-SiO2 core-shell particles guaranteed their mono-dispersity for further biological use. The Zeta potential of these triboelectrically-treated Fe3O4-SiO2 core-shell particles still maintained at ca. +55 mV after standing for two months, and their conglomeration was negligible owing to their limited increase in hydrodynamic size. Besides, their excellent linearity between relaxivities and iron concentration, and their virtually unchanged r2/r1 ratio within two months manifested that triboelectrification can be a promising technique in fabricating advanced materials.

Effect of hydrodynamic size on colloidal stability and lifetime of Mn-Zn magnetic fluids

For transformer cooling applications, magnetic particles need to be dispersed in carrier fluids with high colloidal stability for a long period without significant degradation. However, stability of the suspension, especially the long term colloidal stability is a crucial factor for the applications in power transformers because aggregation of particles could cause clogging of micro-channels in transformers. In this article, we have reported effect of hydrodynamic size on the colloidal stability of Mn1-xZnxFe2O4 (MZ) nanoparticles (NPs)–based magnetic fluids. Lifetime of fluids has been determined from the increase in hydrodynamic size of magnetic NPs due to aggregation. Colloidal stability of fluids decreases with increase in the polydispersity of fluids caused by the enhanced dipole interactions between NPs resulting in the aggregation of NPs in chain-like structures.

Thiol-maleimide poly(ethylene glycol) crosslinking of L-asparaginase subunits at recombinant cysteine residues introduced by mutagenesis

L-Asparaginase is an enzyme successfully being used in the treatment of acute lymphoblastic leukemia, acute myeloid leukemia, and non-Hodgkin’s lymphoma. However, some disadvantages still limit its full application potential, e.g., allergic reactions, pancreatitis, and blood clotting impairment. Therefore, much effort has been directed at improving its performance. A popular strategy is to randomly conjugate L-asparaginase with mono-methoxy polyethylene glycol, which became a commercial FDA approved formulation widely used in recent years. To improve this formulation by PEGylation, herein we performed cysteine-directed conjugation of the L-asparaginase subunits to prevent dissociation-induced loss of activity. The recombinant cysteine conjugation sites were introduced by mutagenesis at surface-exposed positions on the protein to avoid affecting the catalytic activity. Three conjugates were obtained using different linear PEGs of 1000, 2000, and 5000 g/mol, with physical properties ranging from a semi-solid gel to a fully soluble state. The soluble-conjugate exhibited higher catalytic activity than the non-conjugated mutant, and the same activity than the native enzyme. The cysteine-directed crosslinking of the L-asparaginase subunits produced a higher molecular weight conjugate compared to the native tetrameric enzyme. This strategy might improve L-asparaginase efficiency for leukemia treatment by reducing glomerular filtration due to the increase in hydrodynamic size thus extending half-live, while at the same time retaining full catalytic activity.

Influence of behaviors of magnetic particles in ferrofluids under alternating magnetic fields on harmonic responses

We describe the relationship between the excitation frequency dependence of harmonic signal intensity under alternating magnetic fields and the hydrodynamic size of magnetic particles in ferrofluids. The hydrodynamic size estimated from magnetic susceptibility increases with the increase in ion and particle concentrations in the ferrofluids. The excitation frequency dependence of the fifth-harmonic signal intensity exhibits a minimum point at a certain frequency. The frequency of the minimum point shifts to the lower-frequency range, and after reaching the minimum, it increases with the increase in ion and particle concentrations, reflecting the increase in hydrodynamic size owing to the aggregation of magnetic particles. These behaviors may be useful for applications in ion sensing by a magnetic technique.

Evaluation of antioxidants in protein formulation against oxidative stress using various biophysical methods

To evaluate the biophysical stability of protein against oxidative stress, hydrogen peroxide (H2O2) was used to induce non-site-specific protein oxidation. Various biophysical methods were utilized including RP-HPLC, DSC, DLS, and CD. Lysozyme was chosen as a model protein and three different antioxidants (ascorbic acid, N-acetyl-l-cysteine, and l-methionine) were selected to observe their effect. Significant increase in hydrodynamic size, decrease in α-helix propensity, and increase in β-sheet content evident with increasing H2O2 concentration and temperature suggested methionine residues as the most probable site of oxidation. Among the three anti-oxidants, methionine proved superior in suppressing protein oxidation with its increasing concentration. Methionine reacted with H2O2 to form methionine sulfoxide, which aided in decreasing the oxidant concentration to react with the protein. The hydrodynamic size of methionine containing protein was retained when incubated at 40°C after 14 days with unchanged transition temperature (Tm). In contrast, RP-HPLC revealed oxidation alterations when the same samples were stored at 40°C, highlighting the significant impact of temperature on kinetics. N-acetyl-l-cysteine and ascorbic acid were relatively less protective. Their hydrodynamic size was increased with decreasing Tm compared to the reference. In summary, methionine was a superior antioxidant, implicating a promising component in the protein formulation for suppressing oxidation.

Fine characterization of glucosylated human IgG by biochemical and biophysical methods

Nonenzymatic glycosylation of proteins finally generates advanced glycation end products (AGEs). The Schiff's base and Amadori adduct are stages of early glycation. AGE-modified IgG may undergo conformational alterations and the final entity of the process may be involved in the pathogenesis of Rheumatoid Arthritis (RA). In this study, glycation of human IgG was carried out with varying concentrations of glucose. Effect of incubation period on glycation of IgG has also been studied. Amadori adduct was detected by nitroblue tetrazolium (NBT) dye. The glucose mediated structural alterations in IgG were studied by UV, fluorescence, CD, FT-IR, DLS and DSC spectroscopy, and SDS-PAGE. Glycation-induced aggregation in AGE-IgG was reported in the form of binding of thioflavin T and congo red. Furthermore, AGE-modified IgG exhibited hyperchromicity, decrease of tryptophan fluorescence accompanied by increase in AGE specific fluorescence, loss of β-sheet, appearance of new peak in FT-IR, increase in hydrodynamic size and melting temperature. SDS-PAGE results showed decrease in the band intensity of glycosylated-IgG compared to native IgG. Glycation-induced modifications and aggregation of IgG might be important in the pathogenesis of RA.

Magnetite–polylactic acid nanoparticles by surface initiated organocatalysis ring opening polymerization

Organocatalysis by 4-N,N-dimethylaminopyridine was employed for ring opening polymerization of lactide initiated at magnetic nanoparticles covered by glycerol phosphate or ascorbic acid phosphate. The resulting magnetite–polylactic acid nanoparticles exhibit high colloidal stability in water and alcohol. Their morphology was investigated by transmission electron microscopy and the chemical structure was elucidated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The increase in mass after coating the nanoparticles was determined by thermogravimetric analysis, while dynamic light scattering revealed the increase in hydrodynamic size. Magnetic measurements revealed superparamagnetic behavior and high magnetization values. The magnetite–polylactic acid nanoparticles were further used for magnetic tagging of biotin.

Comparative pharmacokinetics of PAMAM-OH dendrimers and HPMA copolymers in ovarian tumor-bearing mice

The purpose of this study was to model data from a head to head comparison of the in vivo fate of hyper-branched PAMAM dendrimers with linear HPMA copolymers in order to understand the influence of molecular weight (MW), hydrodynamic size (Rh) and polymer architecture on biodistribution in tumor-bearing mice using compartmental pharmacokinetic analysis. Plasma concentration data was modeled by two-compartment analysis using Winnonlin® to obtain elimination clearance (E.CL) and plasma exposure (AUCplasma). Renal clearance (CLR) was calculated from urine data collected over 1 week. A plasma-tumor link model was fitted to experimental plasma and tumor data by varying the tumor extravasation (K4, K6) and elimination (K5) rate constants using multivariable constrained optimization solver in Matlab®. Tumor exposures (AUCtumor) were computed from area under the tumor concentration time profile curve by the linear trapezoidal method. Along with MW and Rh, polymer architecture was critical in affecting the blood and tumor pharmacokinetics of the PAMAM-OH dendrimers and HPMA copolymers. Elimination clearance decreased more rapidly with increase in hydrodynamic size for PAMAM-OH dendrimers as compared to HPMA copolymers. HPMA copolymers were eliminated renally to a higher extent than PAMAM-OH dendrimers. These results are suggestive of a difference in extravasation of polymers of varying architecture through the glomerular basement membrane. While the linear HPMA copolymers can potentially reptate through a pore smaller in size than their hydrodynamic radii in a random coil conformation, PAMAM dendrimers have to deform in order to permeate across the pores. With increase in molecular weight or generation, the deforming capacity of PAMAM-OH dendrimers is known to decrease, making it harder for higher generation PAMAM-OH dendrimers to sieve through the glomerulus as compared to HPMA copolymers of comparable molecular weights. PAMAM-OH dendrimer had greater tumor extravsation rate constants and higher tumor to plasma exposure ratios than HPMA copolymers of comparable molecular weights which indicated that in the size range studied, when in circulation, PAMAM-OH dendrimers had a higher affinity to accumulate in the tumor than the HPMA copolymers.

Interaction of Lactoferrin and Lysozyme with Casein Micelles

On addition of lactoferrin (LF) to skim milk, the turbidity decreases. The basic protein binds to the caseins in the casein micelles, which is then followed by a (partial) disintegration of the casein micelles. The amount of LF initially binding to casein micelles follows a Langmuir adsorption isotherm. The kinetics of the binding of LF could be described by first-order kinetics and similarly the disintegration kinetics. The disintegration was, however, about 10 times slower than the initial adsorption, which allowed investigating both phenomena. Kinetic data were also obtained from turbidity measurements, and all data could be described with one equation. The disintegration of the casein micelles was further characterized by an activation energy of 52 kJ/mol. The initial increase in hydrodynamic size of the casein micelles could be accounted for by assuming that it would go as the cube root of the mass using the adsorption and disintegration kinetics as determined from gel electrophoresis. The results show that LF binds to casein micelles and that subsequently the casein micelles partly disintegrate. All micelles behave in a similar manner as average particle size decreases. Lysozyme also bound to the casein micelles, and this binding followed a Langmuir adsorption isotherm. However, lysozyme did not cause the disintegration of the casein micelles.

The need for stable, mono-dispersed, and biofunctional magnetic nanoparticles for one-step magnetic immunoassays

We have developed a magnetic immunoassay system (MIA) using magnetic nanoparticle markers for biomolecule detection. We have magnetically characterized multi-core magnetic nanoparticles (MNPs) containing single-domain crystals of Fe3O4 and CoFe2O4 with our system using a high temperature superconducting quantum interference device as detector. We use a Helmholtz coil to excite the MNPs and study the AC-susceptibility. The data is fit to a model and information about the particle size distribution of the MNP system is extracted. We observe high stability of the unfunctionalized MNPs. However, our MIA measurements require stable functionalized MNPs. We have found a significant increase in hydrodynamic size of the functionalized MNP systems in the course of just a few days caused by agglomeration behaviour. Separate measurements performed at Imego AB with their AC-Susceptometer, DynoMAG®, confirm these findings. Without stable, functionalized MNPs MIAs of this kind are impossible.

Lipophilic Diol Induced Micellization of Pluronic® F88 in Water

The presence of a lipophilic S104 (also known as C14diol) induces micellization in a highly hydrophilic ethylene oxide–propylene oxide–ethylene oxide triblock copolymer Pluronic® F88 [(EO)103(PO)39–(EO)103] in water. The dynamic light scattering (DLS) and small angle neutron scattering (SANS) reveal that F88 remains as molecularly dissolved at ambient temperature even at fairly high concentrations (5 wt% or more). However, the micellization is induced at lower concentration/temperature in the presence of S104. The scattering measurements indicated micellar growth, though no phase transition was observed. The addition of hydrophobic S104 increases the aggregation numbers of the micellar system, but does not show a considerable increase in hydrodynamic size. The micellar parameters for the copolymer in the presence of S104 are reported at 30 and 40°C. Hydrophobic S104 interacts with PPO blocks of F88, makes the decreasing CMT of F88, which may be the synergistic effect. Using intermolecular rotating-frame nuclear overhauser effect (ROE) profiles, the interactions between PPO methyl and S104 terminal methyl groups can be obviously observed.

Structural changes and aggregation of human influenza virus.

The pH-induced change in the structure and aggregation state of the PR-8 and X-31 strains of intact human influenza virus has been studied in vitro. Reducing the pH from 7.4 to 5.0 produces a large increase in the intensity of light scattered to low angles. A modest increase in the polydispersity parameter from cumulants fits to the dynamic light scattering correlograms accompanies the increase, as does a change in how that parameter varies with scattering angle. These trends imply that the virus particles are not uniform, even at pH 7.4, and tend to aggregate as pH is reduced. The scattering profiles (angular dependence of intensity) never match those of isolated, spherical particles of uniform size, but the deviations from that simple model remain modest at pH 7.4. At pH 5.0, scattering profiles calculated for aggregates of uniformly sized spheres come much closer to matching the experimental data than those computed for isolated particles. Although these observations indicate that acid-induced aggregation develops over a period of minutes to hours after acidification, a nearly instantaneous increase in hydrodynamic size is the first response of intact virus particles to lower pH.