Impact of surface functionalization on bacterial cytotoxicity of single-walled carbon nanotubes

The addition of surface functional groups to single-walled carbon nanotubes (SWNTs) is realized as an opportunity to achieve enhanced functionality in the intended application. At the same time, several functionalized SWNTs (fSWNTs), compared to SWNTs, have been shown to exhibit decreased cytotoxicity. Therefore, this unique class of emerging nanomaterials offers the potential enhancement of SWNT applications and potentially simultaneous reduction of their negative human health and environmental impacts depending on the specific functionalization. Here, the percent cell viability loss of Escherichia coli K12 resulting from the interaction with nine fSWNTs, n-propylamine, phenylhydrazine, hydroxyl, phenydicarboxy, phenyl, sulfonic acid, n-butyl, diphenylcyclopropyl, and hydrazine SWNT, is presented. The functional groups range in molecular size, chemical composition, and physicochemical properties. While physiochemical characteristics of the fSWNTs did not correlate, either singularly or in combination, with the observed trend in cell viability, results from combined light scattering techniques (both dynamic and static) elucidate that the percent loss of cell viability can be correlated to fSWNT aggregate size distribution, or dispersity, as well as morphology. Specifically, when the aggregate size polydispersity, quantified as the width of the distribution curve, and the aggregate compactness, quantified by the fractal dimension, are taken together, we find that highly compact and narrowly distributed aggregate size are characteristics of fSWNTs that result in reduced cytotoxicity. The results presented here suggest that surface functionalization has an indirect effect on the bacterial cytotoxicity of SWNTs through the impact on aggregation state, both dispersity and morphology.     

The Thermal Effects of Nucleation and Crystallization of KBr and KCL Solutions. III. The Heat of Crystallization and the Co-Precipitation of Lead Ions

Salt solutions saturated at 44° C and containing varying amounts of lead ions were allowed to cool to about 29°C in 5.5 h. The total heat, ΔH_t, evolved decreased to 2/3 of its highest value with the increase of Pb²⁺-concentration, while the amount of salt crystallized, W_c, decreased to nil. The distribution coefficient of Pb²⁺ between crystals and solution was 10.5 and 9.8 for KBr and KCl respectively. The high lead content improved the perfection of the crystals. The results are consistent with a two-stage mechanism of crystallization: heterogeneous nucleation by complex ions and growth of crystals by the addition of bloc nuclei.     

Particulate and THM Precursor Removal with Ferric Chloride

Pilot-scale experiments were performed to investigate the effectiveness of enhanced coagulation in removing particles and trihalomethane (THM) precursors from two surface source waters: California State Project water and Colorado River water. The removal of suspended particles and natural organic matter at various ferric chloride doses and coagulation pHs was assessed through source water and filter effluent measurements of turbidity, particle count, UV254, TOC, and THM formation potential. Overall, it was found that optimal removal of particles and THM precursors by enhanced coagulation with ferric chloride is obtained at high coagulant doses (>16 mg∕L) and low pH conditions. Generally, turbidity removal is more efficient and head loss is more moderate at ambient pH compared with pH 5.5. Additionally, filter effluent particle counts were found to be consistent with residual turbidity data. The removal of THM precursors by enhanced coagulation is significantly enhanced at pH 5.5 compared with ambient pH. The reduction in THM formation potential is consistent with the trends observed for the THM precursor removal data (i.e., UV254 and TOC data). Furthermore, specific UV absorbance was used to estimate the proportion of humic substances in the raw waters. Enhanced coagulation was found to be less effective for the source water with the lower specific UV absorbance.     

Targeted Modulation of Interferon Response-Related Genes with IFN-Alpha/Lambda Inhibition

Interferon (IFN) signaling resulting from external or internal inflammatory processes initiates the rapid release of cytokines and chemokines to target viral or bacterial invasion, as well as cancer and other diseases. Prolonged exposure to IFNs, or the overexpression of other cytokines, leads to immune exhaustion, enhancing inflammation and leading to the persistence of infection and promotion of disease. Hence, to control and stabilize an excessive immune response, approaches for the management of inflammation are required. The potential use of peptides as anti-inflammatory agents has been previously demonstrated. Our team discovered, and previously published, a 9-amino-acid cyclic peptide named ALOS4 which exhibits anti-cancer properties in vivo and in vitro. We suggested that the anti-cancer effect of ALOS4 arises from interaction with the immune system, possibly through the modulation of inflammatory processes. Here, we show that treatment with ALOS4 decreases basal cytokine levels in mice with chronic inflammation and prolongs the lifespan of mice with acute systemic inflammation induced by irradiation. We also show that pretreatment with ALOS4 reduces the expression of IFN alpha, IFN lambda, and selected interferon-response genes triggered by polyinosinic-polycytidylic acid (Poly I:C), a synthetic analog of viral double-stranded RNA, while upregulating the expression of other genes with antiviral activity. Hence, we conclude that ALOS4 does not prevent IFN signaling, but rather supports the antiviral response by upregulating the expression of interferon-response genes in an interferon-independent manner.     

High-photon-throughput snapshot colour imaging using a monochromatic digital camera and a pupil-domain diffuser

Colour RGB imaging with high throughput was achieved by a monochromatic digital camera with a dispersive diffuser at its pupil. An acquired snapshot monochromatic image was converted to colour coordinates through spectra, by resorting to digital processing with a compressed sensing-based algorithm of spectral imaging. Results of optical evaluation and calibration of an optical system and colour imaging experiments are reported.     

The Translocation of Na+ Ion Inside Human Thrombin Accounts for the Activation of the Enzyme

Thrombin is a member of the chymotrypsin family that splits the peptide bond next to arginine. The catalytic activity of thrombin is accelerated by Na⁺. Inspection of the crystal structure reveals an ion binding site 17 Å from the active-site, leading to ambiguous definition of its mode of rate-enhancement. During unbiased Molecular Dynamics simulations in the presence of Na⁺ ions, the Na⁺ ion was noticed to alternate between two locations: the crystal-structure site (adjacent to R221a and K224) and another site next to D189, very close to the binding and the active sites. There is a free passage between the two locations, and both sites can exchange ions with the bulk. When the ion is close to D189 it can assume position between the guanidino moiety of the product and the carboxylate of D189, thus weakening the protein-product interaction. This transient structure either ejects the Na⁺ ion out of the protein or releases the product from the enzyme. We propose that the enhancement of the catalysis by the ion is a reflection of its ability to destabilize the product-enzyme complex.     

The Privilege of Looking at the Molecular Details of Biochemical Reactions

The introducing the Laser-Induced-Proton-Pulse (1979) allowed to monitor, at real time, the response of multi equilibria systems to pulse protonation. The reaction was initiated by the excitation of “photo acid” that releases a proton in the sub-ns time-scale, offsetting all acid base equilibria. This method was used to study the interaction of the protons with water, dyes, membranes, and proteins. The complexity of the systems increased from the most basic properties of dynamics up to mapping the structure of proton collecting antenna on protein surfaces, monitoring the chemical activity of water inside proteins, studying the electro-neutral mechanism of proton ion exchange across bio-membranes and charting the trajectories of ions inside ionic channels. The analysis of these systems led to deeper understanding of the physical chemical properties of micro-environments like active sites and ionic channels, as well as a tool for advanced kinetic analysis of multi-equilibria systems.