Broad Range Of Salt Concentrations Research Articles

Genomic analysis of vB_PaS-HSN4 bacteriophage and its antibacterial activity (in vivo and in vitro) against Pseudomonas aeruginosa isolated from burn

The most frequent infections caused by Pseudomonas aeruginosa are local infections in soft tissues, including burns. Today, phage use is considered a suitable alternative to cure infections caused by multi-drug-resistant (MDR) and extensively drug-resistant (XDR) bacteria. We investigated the potential of a novel phage (vB_PaS-HSN4) belonging to Caudoviricetes class, against XDR and MDR P. aeruginosa strains in vivo and in vitro. Its biological and genetic characteristics were investigated. The phage burst size and latent were 119 and 20 min, respectively. It could tolerate a broad range of salt concentrations, pH values, and temperatures. The combination with ciprofloxacin significantly enhanced biofilm removal after 24 h. The genome was dsDNA with a size of 44,534 bp and encoded 61 ORFs with 3 tRNA and 5 promoters. No virulence factor was observed in the phage genome. In the in vivo infection model, treatment with vB_PaS-HSN4 increased Galleria mellonella larvae survival (80%, 66%, and 60%) (MOI 100) and (60%, 40%, and 26%) (MOI 1) in the pre-treatment, co-treatment, and post-treatment experiments, respectively. Based on these characteristics, it can be considered for the cure of infections of burns caused by P. aeruginosa.

Macromolecular Crowding Promotes Re-entrant Liquid-Liquid Phase Separation of Human Serum Transferrin and Prevents Surface-Induced Fibrillation.

Protein aggregation and inactivation upon surface immobilization are major limiting factors for analytical applications in biotechnology-related fields. Protein immobilization on solid surfaces often requires multi-step surface passivation, which is time-consuming and inefficient. Herein, we have discovered that biomolecular condensates of biologically active human serum transferrin (Tf) can effectively prevent surface-induced fibrillation and preserve the native-like conformation of phase-separated Tf over a period of 30 days. It has been observed that macromolecular crowding promotes homotypic liquid-liquid phase separation (LLPS) of Tf through enthalpically driven multivalent hydrophobic interactions possibly via the involvement of its low-complexity domain (residues 3-20) containing hydrophobic amino acids. The present LLPS of Tf is a rare example of salt-mediated re-entrant phase separation in a broad range of salt concentrations (0-3 M) solely via the involvement of hydrophobic interactions. Notably, no liquid-to-solid-like phase transition has been observed over a period of 30 days, suggesting the intact conformational integrity of phase-separated Tf, as revealed from single droplet Raman, circular dichroism, and Fourier transform infrared spectroscopy measurements. More importantly, we discovered that the phase-separated condensates of Tf completely inhibit the surface-induced fibrillation of Tf, illustrating the protective role of these liquid-like condensates against denaturation and aggregation of biomolecules. The cell mimicking compact aqueous compartments of biomolecular condensates with a substantial amount of interfacial water preserve the structure and functionality of Tf. Our present study highlights an important functional aspect of biologically active protein condensates and may have wide-ranging implications in cell physiology and biotechnological applications.

Multi-Layered Bipolar Ionic Diode Working in Broad Range Ion Concentration.

Ion current rectification (ICR) is the ratio of ion current by forward bias to backward bias and is a critical indicator of diode performance. In previous studies, there have been many attempts to improve the performance of this ICR, but there is the intrinsic problem for geometric changes that induce ionic rectification due to fabrication problems. Additionally, the high ICR could be achieved in the narrow salt concentration range only. Here, we propose a multi-layered bipolar ionic diode based on an asymmetric nanochannel network membrane (NCNM), which is realized by soft lithography and self-assembly of homogenous-sized nanoparticles. Owing to the freely changeable geometry based on soft lithography, the ICR performance can be explored according to the variation of microchannel shape. The presented diode with multi-layered configuration shows strong ICR performance, and in a broad range of salt concentrations (0.1 mM~100 mM), steady ICR performance. It is interesting to note that when each anion-selective (AS) and cation-selective (CS) NCNM volume was similar to each optimized volume in a single-layered device, the maximum ICR was obtained. Multi-physics simulation, which reveals greater ionic concentration at the bipolar diode junction under forward bias and less depletion under backward in comparison to the single-layer scenario, supports this tendency as well. Additionally, under different frequencies and salt concentrations, a large-area hysteresis loop emerges, which indicates fascinating potential for electroosmotic pumps, memristors, biosensors, etc.

Impacts of salt concentration on nucleate pool boiling of NaCl solution

Salt solution pool boiling is of great significance in thermal engineering equipment, such as boilers and heat exchangers. Few researchers have been able to draw on systematic research into the impacts of salt concentration on boiling heat transfer coefficients. This experimental work is aimed to understand the role of dissolved salts on pool boiling performance, which is affected by surface wettability and bubble dynamics. Pool boiling experiment was conducted within a broad range of salt concentration. The results show two different tendencies for the two heating surfaces. The heat transfer coefficient is enhanced in the pin–fin heating surface while deteriorated in the bare heating surface as the salt concentration increased. It is indicated that salt solution promotes bubble diameter and nucleate density for ∼13% and 9%, respectively, by strengthening the hydrophobicity of the pin–fin heating surface. Hence, the boiling heat transfer is strengthened.

Heat flows in rock cracks naturally optimize salt compositions for ribozymes.

Catalytic nucleic acids, such as ribozymes, are central to a variety of origin-of-life scenarios. Typically, they require elevated magnesium concentrations for folding and activity, but their function can be inhibited by high concentrations of monovalent salts. Here we show that geologically plausible high-sodium, low-magnesium solutions derived from leaching basalt (rock and remelted glass) inhibit ribozyme catalysis, but that this activity can be rescued by selective magnesium up-concentration by heat flow across rock fissures. In contrast to up-concentration by dehydration or freezing, this system is so far from equilibrium that it can actively alter the Mg:Na salt ratio to an extent that enables key ribozyme activities, such as self-replication and RNA extension, in otherwise challenging solution conditions. The principle demonstrated here is applicable to a broad range of salt concentrations and compositions, and, as such, highly relevant to various origin-of-life scenarios.

Covalent organic framework nanofluidic membrane as a platform for highly sensitive bionic thermosensation

Thermal sensation, which is the conversion of a temperature stimulus into a biological response, is the basis of the fundamental physiological processes that occur ubiquitously in all organisms from bacteria to mammals. Significant efforts have been devoted to fabricating artificial membranes that can mimic the delicate functions of nature; however, the design of a bionic thermometer remains in its infancy. Herein, we report a nanofluidic membrane based on an ionic covalent organic framework (COF) that is capable of intelligently monitoring temperature variations and expressing it in the form of continuous potential differences. The high density of the charged sites present in the sub-nanochannels renders superior permselectivity to the resulting nanofluidic system, leading to a high thermosensation sensitivity of 1.27 mV K−1, thereby outperforming any known natural system. The potential applicability of the developed system is illustrated by its excellent tolerance toward a broad range of salt concentrations, wide working temperatures, synchronous response to temperature stimulation, and long-term ultrastability. Therefore, our study pioneers a way to explore COFs for mimicking the sophisticated signaling system observed in the nature.

Molecular Level Differences in Ionic Solvation and Transport Behavior in Ethylene Oxide-Based Homopolymer and Block Copolymer Electrolytes.

Block copolymer electrolytes (BCE) such as polystyrene-block-poly(ethylene oxide) (SEO) blended with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and composed of mechanically robust insulating and rubbery conducting nanodomains are promising solid-state electrolytes for Li batteries. Here, we compare ionic solvation, association, distribution, and conductivity in SEO-LiTFSI BCEs and their homopolymer PEO-LiTFSI analogs toward a fundamental understanding of the maximum in conductivity and transport mechanisms as a function of salt concentration. Ionic conductivity measurements reveal that SEO-LiTFSI and PEO-LiTFSI exhibit similar behaviors up to a Li/EO ratio of 1/12, where roughly half of the available solvation sites in the system are filled, and conductivity is maximized. As the Li/EO ratios increase to 1/5 the conductivity, of the PEO-LiTFSI drops nearly 3-fold, while the conductivity of SEO-LiTFSI remains constant. FTIR spectroscopy reveals that additional Li cations in the homopolymer electrolyte are complexed by additional EO units when the Li/EO ratio exceeds 1/12, while in the BCE, the proportion of complexed and uncomplexed EO units remains constant; Raman spectroscopy data at the same concentrations show that Li cations in the SEO-LiTFSI samples tend to coordinate more to their counteranions. Atomistic-scale molecular dynamics simulations corroborate these results and further show that associated ions tend to segregate to the SEO-LiTFSI domain interfaces. The opportunity for "excess" salt to be sequestered at BCE interfaces results in the retention of an optimum ratio of uncompleted and complexed PEO solvation sites in the middle of the conductive nanodomains of the BCE and maximized conductivity over a broad range of salt concentrations.

Taxonomic and functional profiling of nitrifying biofilms in freshwater, brackish and marine RAS biofilters

In recirculating aquaculture systems (RAS), the crucial step of eliminating toxic N compounds like ammonia and nitrite is mediated via nitrifying microorganisms and takes place in biofilters. In this study, analyses of microorganisms colonizing biocarriers of nine moving-bed biofilters of three different RAS operated with freshwater, brackish or marine process water uncovered site specific communities. Illumina-based amplicon sequencing of the V4-region of the 16S rRNA gene revealed a high microbial diversity with 1000–2500 species-level operational taxonomic units (OTUs) in all biofilters with the highest diversity in the brackish RAS. Proteobacteria, Bacteriodetes, Plantomycetes, Chloroflexi and Nitrospirae represented the most abundant phyla. 76 out of 674 known genera occurred in all nine biofilters and were defined as core-taxa, including nitrifying bacteria (Nitrosomonas and Nitrospira) as well as members of the (heterotrophic) genera Planctomyces, Blastopirellula, Nannocystis and Lewinella. Nitrifying communities composed of different, closely related and so far uncultured members of Nitrosomonas and Nitrospira were identified, strongly indicating that several potentially novel ammonia and nitrite oxidizing species are present in RAS biofilters. Relatives of known comammox Nitrospira were detected in the brackish biofilters, revealing 94–99 % identity of the 16S rRNA gene sequence to Ns. inopinata. Salinity tolerance tests with biocarriers derived from biofilters of the three distinct RAS showed an unexpected broad physiological flexibility with regard to salinity. Nitrification performance of freshwater nitrifiers was drastically reduced with increasing salinity and nearly completely inhibited at 15 PSU, while the brackish and marine nitrifiers showed a high resistance and maintained nitrification activity in a broad range of salt concentrations. This data can help to improve the nitrification process in RAS with changing salinity of the process water.

Packing Polydisperse Colloids into Crystals: When Charge-Dispersity Matters.

MonteCarlo simulations, fully constrained by experimental parameters, are found to agree well with a measured phase diagram of aqueous dispersions of nanoparticles with a moderate size polydispersity over a broad range of salt concentrations, c_{s}, and volume fractions, ϕ. Upon increasing ϕ, the colloids freeze first into coexisting compact solids then into a body centered cubic phase (bcc) before they melt into a glass forming liquid. The surprising stability of the bcc solid at high ϕ and c_{s} is explained by the interaction (charge) polydispersity and vibrational entropy.

Self-, co-organisation behaviour and encapsulation efficiency of waterborne polyurethane pre-polymers

Polyurethane-prepolymers are the precursor for waterborne polyurethane coating applications. The physical–chemical behavior of the pre-polymers are worth thorough investigation, since they will largely influence the final properties of coating products [1–3]. In this paper, we experimentally studied the self-, co-organization characteristics and encapsulation efficiency of a polyurethane pre-polymer in aqueous electrolyte environment, by means of light scattering and small angle X-ray scattering. Due to the amphiphilic nature, pre-polymers are expected to form micelles in water. Systematic studies were conducted on dispersions at different pre-polymer concentrations and salt concentrations. Our experiments show that the micelles have a radius of about 10 nm and are stable over a broad range of salt concentrations; only at high salt, 100 mM NaCl, we observe the onset of colloidal instability. Moreover, we find that the amphiphilic pre-polymers are able to encapsulate hydrophobic counterparts, forming particles with radii of about 130 nm. The threshold ratio of hydrophilic over hydrophobic pre-polymers to form stable dispersion is found to be 5:1.

A dynamic sandwich assay on magnetic beads for selective detection of single-nucleotide mutations at room temperature

Single-nucleotide mutation (SNM) has proven to be associated with a variety of human diseases. Development of reliable methods for the detection of SNM is crucial for molecular diagnosis and personalized medicine. The sandwich assays are widely used tools for detecting nucleic acid biomarkers due to their low cost and rapid signaling. However, the poor hybridization specificity of signal probe at room temperature hampers the discrimination of mutant and wild type. Here, we demonstrate a dynamic sandwich assay on magnetic beads for SNM detection based on the transient binding between signal probe and target. By taking the advantage of mismatch sensitive thermodynamics of transient DNA binding, the dynamic sandwich assay exhibits high discrimination factor for mutant with a broad range of salt concentration at room temperature. The beads used in this assay serve as a tool for separation, and might be helpful to enhance SNM selectivity. Flexible design of signal probe and facile magnetic separation allow multiple-mode downstream analysis including colorimetric detection and isothermal amplification. With this method, BRAF mutations in the genomic DNA extracted from cancer cell lines were tested, allowing sensitive detection of SNM at very low abundances (0.1–0.5% mutant/wild type).

Dielectric Relaxation Behavior of a Poly(ethylene carbonate)‐Lithium Bis‐(trifluoromethanesulfonyl) Imide Electrolyte

A new class of polymer electrolytes, consisting of poly(ethylene carbonate) (PEC) and metal salts, is expected to find application in all‐solid‐state batteries because of its excellent performance as an electrolyte. To study the ion‐conductive mechanism in PEC‐based electrolytes, broadband dielectric spectroscopy is used to analyze the correlation between dielectric relaxation and ionic conduction in PEC‐lithium bis‐(trifluoromethanesulfonyl) imide electrolytes over a broad range of salt concentration (0–150 mol%) at 40 °C. The PEC system has two relaxation modes, α and β, associated respectively with the segmental motion and the local motion of PEC chains. The conductivity increases exponentially with increasing salt concentration, while the α relaxation frequency (fα) decreases with increasing strength (Δεα) at low salt concentrations, whereas in contrast fα increases with Δεα being saturated at high salt concentrations above 10 mol%. It is believed that the mobility of PEC segment at high concentration is enhanced by two factors. The first is that intermolecular interactions decrease, given the existence of many ion pairs and aggregated ions around saturated PEC domains where the dissociated ions are highly concentrated. The second is that intramolecular interactions between CO and CH2 are lowered by the ion–dipole interaction. image

Ionic Conduction and Dielectric Relaxation in Poly(ethylene carbonate)-Li Salt Electrolytes

Polymer electrolytes such as poly(ethylene oxide) (PEO)-metal salt complexes have attracted much attention as ion-conductive soft materials for novel battery systems, because of their safety compared with liquid electrolytes, their flexibility and their lightweight. However, the conductivity of typical PEO-based electrolytes is limited to approximately 10-5 S/cm at room temperature, and it is extremely difficult to enhance the lithium (cation) transference number. We believe that the development of novel polymers without PEO chains is one solution for improving the conductivity. So we consider polycarbonates that can be obtained by the alternating copolymerization of carbon dioxide with epoxides and comprise novel polymer candidates for electrolytes. Following the first report of the CO2/epoxide copolymer by Tsuruta et al., there has been considerable development of highly active catalysts for effective polymerization. This copolymer is a remarkable macromolecule because it utilizes CO2as a raw material and has excellent properties; it is biodegradable, easily processed and colored, and has high transparency and low oxygen permeability. We have focused on the chemical structure of the copolymer, which has one alternating carbonate group (-O-(C=O)-O-) in each repeating unit of the main chain. The carbonate group has a large dipole moment, and it can dissolve many types of salts. Carbonate-based organic solvents, such as dimethyl carbonate, are used as the electrolyte solution in Li-ion batteries because of their high dielectric constant. Therefore, we think that the carbonate group can provide a suitable structure for the polymer framework. In this study, we report on the use of poly(ethylene carbonate) (PEC) as a matrix for novel ion-conductive polymer electrolytes [1]. We found that the addition of small amount of TiO2 nano-particulates to the PEC-based electrolytes can enhance lithium transference numbers, t +, which are measured using an electrochemical combination method of DC polarization and AC impedance measurements for Li│electrolyte│Li cells. Moreover, we undertook lithium-7 and fluoride-19 NMR spectroscopic and pulsed field gradient (pfg) diffusion measurements on these electrolytes. The values of self-diffusion coefficients of the lithium cation (D Li) and the estimated t + values for PEC-LiFSI-TiO2 were more than 10-7 cm2/s and 0.8 at 60 oC. The Li-ion conductivities (σ at 60 oC × t + estimated from the electrochemical method) of samples PEO20LiFSI, PEC0.53LiFSI and PEC0.53LiFSI-TiO2 (1 wt%) were calculated to be 5.6×10-5, 2.2×10-4 and 4.3×10-4S/cm, which are superior as a structure to polyether as an electrolyte for flexible batteries. On the other hand, there are no detailed information on the ion-conductive behavior of PEC-based electrolytes. So, we used broadband dielectric spectroscopy (BDS) measurement for the investigation of correlation between ionic conduction and dielectric relaxation behavior over the broad range of salt concentration. We measured BDS data and analyzed dielectric spectra using the Havriliak-Negami functions. Fig. 1 shows salt concentration dependence of relaxation peak for PEC-LiTFSI electrolytes at 40 oC. A strong peak indicates α relaxation derived from segmental motion of PEC main chains. As the salt concentration increased, the α relaxation peak shifted to the high frequency region with increasing the peak area, which is opposite to the behavior of typical PEO-based electrolytes (the peak shifts to the lower frequencies) [2]. This means that the PEC-LiTFSI electrolytes show good conductivities at high salt concentrations because of the fast segmental motion with local ion-rich structures. [1] Y. Tominaga et al.,Chem. Commun., 50,4448 (2014). [2] T. Furukawa et al., Electrochim. Acta, 57,139 (2011). Acknowledgment: This work was financially supported by a Grant-in-Aid for Scientific Research (B) of JSPS KAKENHI (25288095), Japan. Fig.1 Salt concentration dependence of relaxation peaks for PEC-LiTFSI at 40 oC. Figure 1

고검화도 폴리비닐알콜 필름에서의 이색성 유기염료의 염착 특성

Abstract: Dyeing of a poly(vinyl alcohol) (PVA) film with a high degree hydrolysis (>98%) using Direct Black 22, adichroic organic dye, was investigated under various conditions (dye concentration, salt (Na 2 SO 4 ) concentration, andtemperature). This process could correctly be analyzed using the Freundlich isotherm ( C film =K F C soln1/n ) based on the poremodel. The Freundlich exponent 1/n appeared to be constant over a broad range of salt concentrations, but the Freun-dlich constant K F assumed the maximum value for [Na 2 SO 4 ]=~0.010 M. However, this value was 10 times greater thanthat under the no-salt conditions. Analysis of the adsorption kinetics revealed that only the early stage of dyeing was fol-lowed second-order, with an activation energy of 50.2 kJ/mol. However, gradual deviation from the second-orderoccurred with an increase in the dyeing time. These results indicated that the surfaces of the inner pores in the PVA filmare dyed through multilayer adsorption, which is accompanied by complicated kinetics.Keywords: poly(vinyl alcohol), dichroic dye, dyeing, Freundlich's isotherm, pore model, the second-order kinetics

A study of matching fluid loss in a biomedical microwave tomography system

Effective imaging of human tissue with microwave tomography systems requires a matching fluid to reduce the wave reflections at the tissue boundary. Further, in order to match the idealized mathematical model used for imaging with the complicated physical measurement environment, loss must be added to the matching fluid. Both too little and too much loss result in low-quality images, but due to the nonlinear nature of the imaging problem, the exact nature of loss-to-image quality cannot be predicted a priori. Possible optimal loss levels include a single, highly sensitive value, or a broad range of acceptable losses. Herein, the authors outline a process of determining an appropriate level of loss inside the matching fluid and attempt to determine the bounds for which the images are the highest quality. Our biomedical microwave tomography system is designed for 2D limb imaging, operating from 0.8 to 1.2 GHz. Our matching fluid consists of deionized water with various levels of loss introduced by the addition of table salt. Using two homogeneous tissue-mimicking phantoms, and eight different matching fluids of varying salt concentrations, the authors introduce quantitative image quality metrics based on L-norms, mean values, and standard deviations to test the tomography system and assess image quality. Images are generated with a balanced multiplicative regularized contrast source inversion algorithm. The authors further generate images of a human forearm which may be analyzed qualitatively. The image metrics for the phantoms support the claim that the worst images occur at the extremes of high and low salt concentrations. Importantly, the image metrics show that there exists a broad range of salt concentrations that result in high-quality images, not a single optimal value. In particular, 2.5-4.5 g of table salt per liter of deionized water provide the best reconstruction quality for simple phantoms. The authors argue that qualitatively, the human forearm data provide the best images at approximately the same salt concentrations. There exists a relatively large-range of matching fluid losses (i.e., salt concentrations) that provide similar image quality. In particular, it is not necessary to spend time highly optimizing the level of loss in the matching fluid.

Screening and isolation of an organic solvent tolerant-protease from Bacillus sp. JER02: Activity optimization by response surface methodology

Abstract Organic solvent-tolerant enzymes are becoming increasingly popular in synthetic biotechnology, due to their industrially attractive advantages over the aqueous solvents. Screening of organic solvent-tolerant microorganisms is a promising strategy for identification of novel enzymes that are naturally tolerant toward organic solvents. Crude proteases which have been shown to be active at high temperatures, alkaline pH and broad range of salt concentrations, are favorite proteases for industrial applications. In this study, Bacillus sp. JER02 was isolated from Gehver hot spring in Jiroft, Iran, and grown in medium supplemented with cyclohexane (30%), toluene (10%). Protease activity in the presence of different concentrations of organic solvents showed that, this enzyme was activated about 10% and 30% in the presence of 5% isopropanol and 10% DMF, respectively. In addition, this enzyme retained more than 90% of its initial activity after 1 h pre-incubation with 40% organic solvent at room temperature. Moreover, response surface methodology was applied to optimize the assay constituents of Bacillus sp. JER02 protease. The best condition for protease activity was achieved in buffer containing 8 mM NaCl, 4 mM MgSO4, at 54 °C, and pH8. The statistical optimization by RSM resulted in 2.5 fold increase in protease activity by Bacillus sp. JER02.

The Effect of DNA CpG Methylation on the Dynamic Conformation of a Nucleosome

DNA methylation is an important epigenetic mark that is known to induce chromatin condensation and gene silencing. We used a time-domain fluorescence lifetime measurement to quantify the effects of DNA hypermethylation on the conformation and dynamics of a nucleosome. Nucleosomes reconstituted on an unmethylated and a methylated DNA both exhibit dynamic conformations under physiological conditions. The DNA end breathing motion and the H2A-H2B dimer destabilization dominate the dynamic behavior of nucleosomes at low to medium ionic strength. Extensive DNA CpG methylation, surprisingly, does not help to restrain the DNA breathing motion, but facilitates the formation of a more open nucleosome conformation. The presence of the divalent cation, Mg2+, essential for chromatin compaction, and the methyl donor molecule SAM, required for DNA methyltransferase reaction, facilitate the compaction of both types of nucleosomes. The difference between the unmethylated and the methylated nucleosome persists within a broad range of salt concentrations, but vanishes under high magnesium concentrations. Reduced DNA backbone rigidity due to the presence of methyl groups is believed to contribute to the observed structural and dynamic differences. The observation of this study suggests that DNA methylation alone does not compact chromatin at the nucleosomal level and provides molecular details to understand the regulatory role of DNA methylation in gene expression.

Homopolymer Self-Assembly into Stable Nanoparticles: Concerted Action of Hydrophobic Association and Hydrogen Bonding in Thermoresponsive Poly(alkylacrylic acid)s

A new approach to polymer self-assembly was presented recently [M. Sedlák, Č. Koňák, J. Dybal, Macromolecules 2009, 2, 7430-7438 and 7439-7446.] (1, 2) where stable polymeric nanoparticles were formed from poly(ethylacrylic acid) homopolymers without any assembly triggering additives, simply by heating polymer solution under conditions of thermosensitivity to certain temperature. In the current Article, we present successful results on poly(propylacrylic acid), which is a more hydrophobic polymer. We also present results on a less hydrophobic polymer from this series, poly(methacrylic acid), from which nanoparticles cannot be formed. Comparison of results on all three polymers gives a solid physicochemical insight and supports the molecular mechanism of the self-assembly previously suggested: The solvent quality gradually worsens upon heating of a thermosensitive polymer solution, and polymer-polymer contacts are preferred over polymer-solvent contacts, which leads to the formation of polymer assemblies. The presence of a significant amount of charge on chains prevents macroscopic phase separation. Upon subsequent cooling to laboratory temperature, the assemblies (nanoparticles) should eventually dissolve; however, this is not the case due to the fact that polymer chains brought to a close proximity at elevated temperatures become hydrogen-bonded. In addition, hydrogen bonds strengthen upon cooling. Mainly carboxylic-carboxylate hydrogen bonds (COOH····COO(-)) are responsible for the irreversibility of the process and the stability of nanoparticles. Conclusions are supported by results from static and dynamic light scattering, FTIR spectroscopy, and cryo-TEM microscopy. Size of nanoparticles can be monitored during the growth and custom-tailored by tuning critical parameters, especially the degree of ionization, temperature, and time of heating. Nanoparticles are stable over long periods of time. They are stable in a broad range of salt concentrations, including physiological conditions, and possess a mild acceptable degree of polydispersity.

Assembly of Molten Transition Metal Salt–Surfactant in a Confined Space for the Synthesis of Mesoporous Metal Oxide-Rich Metal Oxide–Silica Thin Films

Uniform and homogeneous coating of mesoporous materials with an active (catalytically, photonic, electrical) nanostructure can be very useful for a number of applications. Understanding chemical reactions in a confined space is important in order to design new advanced materials. In this work, we demonstrate that an extensive amount (as high as 53 mol percent) of transition metal salts can be confined between silica walls and two surfactant domains (cetyltrimethylammonium bromide, CTAB, and lauryl ether, C12H25(OCH2CH2)10OH, C12EO10) as molten salts and then converted into sponge-like mesoporous silica–metal oxides by thermal annealing. This investigation has been carried out using two different salts, namely, zinc nitrate hexahydrate, [Zn(H2O)6](NO3)2, and cadmium nitrate tetrahydrate, [Cd(H2O)4](NO3)2, in a broad range of salt concentrations. The ZnO (or CdO) layers are as thin as about ∼1.6 nm and are homogenously coated as crystalline nano-islands over the silica pore walls.

Modeling protein binding and elution over a chromatographic surface probed by surface plasmon resonance

Surface plasmon resonance (SPR) spectroscopy is used as a scaled-down, analytical, pseudo-chromatography tool for analyzing protein binding and elution over an ion-exchange surface under cyclic sorption conditions. A micrometric-scale adsorption surface was produced by immobilizing a typical ion exchange ligand – diethylaminoethyl (DEAE) – onto commercially available planar gold sensor chip surfaces pre-derivatized with a self-assembled monolayer of 11-mercaptoundecanoic acid with known density. An explicit mathematical formulation is provided for the deconvolution and interpretation of the SPR sensorgrams. An adsorption rate model is proposed to describe the SPR sensorgrams for bovine serum albumin, used here as model protein, when the DEAE surface is subjected to a cyclic series of binding and elution steps. Overall, we demonstrate that the adsorption rate model is capable of quantitatively describing BSA binding and elution for protein titers from dilute conditions up to overloaded conditions and a broad range of salt concentrations.