Biological and Chemical Investigation of Cultured Cyanobacteria

Cyanobacteria have been used as a source of natural products for drug development. Previous studies have demonstrated that compounds with cytotoxic activity are widely distributed in cyanobacteria and that the chemical classes of the cytotoxic compounds are diverse. Several compounds derived from cyanobacteria are approved by FDA or under clinical evaluations for cancer treatment, validating that these organisms have great potential as a source for anticancer drugs or drug leads. In this study, over 300 cyanobacteria strains were cultured, harvested, and extracted. A total of 306 cyanobacterial extracts were evaluated for both cytotoxicity using a set of cancer cells (HT-29, MCF-7, NCI-H460, and SF268 as well as a cancer cell panel consisting of 12 different cancer cells) and inhibition of 20S proteasome, an established target for cancer treatment. Of the 306 screened extracts, nine displayed cytotoxicity and seven showed inhibition of 20S proteasome. Five of these bioactive cyanobacterial strains, Fischerella sp. (SAG 46.79), Westiellopsis sp. (SAG 20.93), Fischerella muscicola (UTEX LB1829), Nostoc sp. (UIC 10047), and Oscillatoria sp. (UIC 10109), were selected for chemical investigation. Activity-guided fractionation led to the isolation of 22 compounds. Structures of these isolated compounds were elucidated using a variety of spectroscopic analyses and 9 of 22 were found to be novel compounds. Most of these compounds showed moderate to strong cytotoxicity and/or 20S proteasome inhibition. It has been shown that cyanobacteria have a great potential as a source for discovery of anticancer lead compounds, and the results of this study also support this. We believe that continued efforts on the chemical and biological evaluation of these organisms will provide a great opportunity for the discovery of new anticancer lead compounds

Thermodynamic Studies of the Solvent Effects in Chromatography on Molecularly Imprinted Polymers. 3. Nature of the Organic Mobile Phase

Experimental isotherm data of the Fmoc-tryptophan (Fmoc-Trp) enantiomers were measured by frontal analysis on a Fmoc-l-Trp imprinted polymer, using different organic mobile phases, in a wide concentration range. The nonlinear regression of the data and the independent calculation of the affinity energy distributions of the two enantiomers allowed the selection of the isotherm model and the determination of the isotherm parameters. The organic solvents studied were acetonitrile (MeCN), methylene chloride, chloroform, and tetrahydrofuran (THF), all in the presence of the same concentration of acetic acid, used as an organic modifier. It was found that the highest overall affinity and enantiomeric selectivity were obtained in MeCN, which is also the solvent used in the polymerization. In the other solvents, the overall affinity decreases with increasing hydrogen-bonding ability of the solvents but not the enantiomer selectivity. In MeCN, three types of adsorption sites coexist for the two enantiomers on the MIP. The highest energy sites for Fmoc-l-Trp in MeCN are inactive in CH2Cl2, CHCl3, and THF, and only two types of sites were identified in these solvents. Increasing the acetic acid concentration from 0.2 to 0.9 M causes a large decrease in the association constant of the highest energy sites in CH2Cl2, CHCl3, and THF but not in MeCN. The overall affinity of Fmoc-l-trp in CH2Cl2, CHCl3, and THF is dominated by adsorption on the lowest energy sites, the most abundant ones. In contrast, in MeCN, the overall affinity of Fmoc-l-Trp is dominated by adsorption on the highest energy sites, the least abundant sites. In CH2Cl2, CHCl3, and THF, the number of each type of sites increases with decreasing hydrogen-bonding ability of the solvents while the association constant of the corresponding sites does not change significantly

An Orthogonal Approach to Multifunctional Molecularly Imprinted Polymers

An “orthogonal” approach to molecularly imprinted polymers has been demonstrated using a crown ether derived monomer that does not exhibit cross-reactivity with other functional monomers. This strategy provides multiple functional groups in the binding site of molecularly imprinted polymers (MIPs) without unproductive interactions between functional monomers. The orthogonal functional group system was shown to act cooperatively in MIPs to bind a template with higher selectivity than any of the individual functional monomers alone

New Insight into Modeling Non-Covalently Imprinted Polymers

Three series of polymers were carefully formulated with increasing amounts of template while keeping the polymer components constant. The number of binding sites (N) and the number average association constant (Kn) were calculated for each polymer in a series, using equations adapted from the literature describing molecularly imprinted polymers (MIPs). The trends of N and Kn for each series of polymers, which were graphed versus percent template, suggest multiple functional monomers in the binding sites of noncovalent MIPs. This new insight has implications for understanding the underlying mechanisms for the formation of binding sites in the MIPs studied

Influence of Perfluorooctanoic Acid on the Transport and Deposition Behaviors of Bacteria in Quartz Sand

The significance of perfluorooctanoic acid (PFOA) on the transport and deposition behaviors of bacteria (Gram-negative <i>Escherichia coli</i> and Gram-positive <i>Bacillus subtilis</i>) in quartz sand is examined in both NaCl and CaCl₂ solutions at pH 5.6 by comparing both breakthrough curves and retained profiles with PFOA in solutions versus those without PFOA. All test conditions are found to be highly unfavorable for cell deposition regardless of the presence of PFOA; however, 7%–46% cell deposition is observed depending on the conditions. The cell deposition may be attributed to micro- or nanoscale roughness and/or to chemical heterogeneity of the sand surface. The results show that, under all examined conditions, PFOA in suspensions increases cell transport and decreases cell deposition in porous media regardless of cell type, presence or absence of extracellular polymeric substances, ionic strength, and ion valence. We find that the additional repulsion between bacteria and quartz sand caused by both acid–base interaction and steric repulsion as well as the competition for deposition sites on quartz sand surfaces by PFOA are responsible for the enhanced transport and decreased deposition of bacteria with PFOA in solutions

Effect of Carbon Nanotubes on the Transport and Retention of Bacteria in Saturated Porous Media

This study investigated the influence of carbon nanotubes (CNTs) on the transport and retention behaviors of bacteria (E. coli) in packed porous media at both low and high ionic strength in NaCl and CaCl2 solutions. At low ionic strengths (5 mM NaCl and 0.3 mM CaCl2), both breakthrough curves and retained profiles of bacteria with CNTs (both 5 and 10 mg L–1) were equivalent to those without CNTs, indicating the presence of CNTs did not affect the transport and retention of E. coli at low ionic strengths. The results were supported by those from cell characterization tests (i.e., viability, surface properties, sizes), which showed no significant difference between with and without CNTs. In contrast, breakthrough curves of bacteria with CNTs were lower than those without CNTs at high ionic strengths (25 mM NaCl and 1.2 mM CaCl2), suggesting that the presence of CNTs decreased cell transport at high ionic strengths. The enhanced bacterial deposition in the presence of CNTs was mainly observed at segments near the column inlet, leading to much steeper retained profiles relative to those without CNTs. Additional transport experiments conducted with sand columns predeposited with CNTs revealed that the codeposition of bacteria with CNTs, as well as the deposition of the cell–CNTs cluster formed in cell suspension due to cell bridging effect, largely contributed to the increased deposition of bacteria at high ionic strengths in porous media

Chemical Kinetics of Nanoparticles in the Emulsion State during Phase-Transfer Synthesis

The creation of waterborne nanoparticles (NPs) is one of the main topics in environmental science as an area of ecofriendly research. Phase-transfer synthesis, an emulsion/solvent evaporation method, facilitates the generation of the NPs using immiscible oil and water phases in a biphasic combination. Chemical interactions of the two phases by synthesis conditions or parameters determine different chemical intermediate states of the emulsions, resulting in various sizes or shapes of the NPs. However, a molecular-level understanding and chemical origin of the emulsion have not been elucidated in detail. In this work, we study the chemical kinetics of the nanoparticles in the emulsion state during synthesis as a function of surfactant concentration. Surfactant-covered gold nanoparticles (AuNPs) with ca. 20 nm size are transferred at a medium surfactant concentration, enough to cover the AuNP and stabilize it in the water phase. However, sub-2 nm-sized AuNPs are produced at a high surfactant concentration beyond the critical micelle concentration of the surfactant. AuNPs surrounded by CTAB micelles with a hemisphere contact are not formed, facilitating chemical interactions between solvent molecules of the oil phase and the water phase to crack the AuNPs. Based on our time-dependent UV–vis absorption and confocal microscope experiments and real-time in situ X-ray scattering analyses, we observed that the intermediate states in the chemical and structural states determine the colloidal conformation. This work provides insight into the chemical mechanism with a structural variation of two components in water and oil phases. Therefore, the current finding can promote the phase-transfer synthesis, which would motivate the community to create ideal NPs

Influence of Bentonite Particles on Representative Gram Negative and Gram Positive Bacterial Deposition in Porous Media

The significance of clay particles on the transport and deposition kinetics of bacteria in irregular quartz sand was examined by direct comparison of both breakthrough curves and retained profiles with clay particles in bacteria suspension versus those without clay particles. Two representative cell types, Gram-negative strain <i>E. coli</i> DH5α and Gram-positive strain <i>Bacillus subtilis</i> were utilized to systematically determine the influence of clay particles (bentonite) on cell transport behavior. Packed column experiments for both cell types were conducted in both NaCl (5 and 25 mM ionic strengths) and CaCl₂ (5 mM ionic strength) solutions at pH 6.0. The breakthrough plateaus with bentonite in solutions (30 mg L^–1 and 50 mg L^–1) were lower than those without bentonite for both cell types under all examined conditions, indicating that bentonite in solutions decreased cell transport in porous media regardless of cell types (Gram-negative or Gram-positive) and solution chemistry (ionic strength and ion valence). The enhanced cell deposition with bentonite particles was mainly observed at segments near to column inlet, retained profiles for both cell types with bentonite particles were therefore steeper relative to those without bentonite. The increased cell deposition with bentonite observed in NaCl solutions was attributed to the codeposition of bacteria with bentonite particles whereas, in addition to codeposition of bacteria with bentonite, the bacteria–bentonite–bacteria cluster formed in suspensions also contributed to the increased deposition of bacteria with bentonite in CaCl₂ solution

Drivers of COVID-19 protest across localities in Israel: a machine-learning approach

Anti-government protests emerged globally in response to COVID-19 countermeasures. What are the key drivers of these pandemic-related protests, and to what extent do they differ from the drivers of non-COVID protests? We examine these questions in the context of Israel, which faced a growing political crisis at the start of the pandemic, effectively blurring the distinction between different causes of protest. Our data features 1,922 protests across 189 Israeli localities for the period between March and July 2022. Using a machine learning approach, we find that all protests, regardless of whether they were directly related to the pandemic or not, were motivated by the same set of key indicators – albeit with the ranking of drivers for COVID-related protests inverted for non-COVID protests. Local infection rates and government responses were more pronounced for the former, whereas differences in residential and commercial property taxes, access to affordable housing, quality of education and demography were among the most important drivers for the latter. Our analysis underscores the role that local governments played in managing the pandemic, and demonstrates that variation in socioeconomic conditions had an important effect on the incidence of protests across Israel.</p

Evaluating the Transport of <i>Bacillus subtilis</i> Spores as a Potential Surrogate for <i>Cryptosporidium parvum</i> Oocysts

The U.S. Environmental Protection Agency has recommended the use of aerobic spores as an indicator for <i>Cryptosporidium</i> oocysts when determining groundwater under the direct influence of surface water. Surface properties, interaction energies, transport, retention, and release behavior of <i>B. subtilis</i> spores were measured over a range of physicochemical conditions, and compared with reported information for <i>C. parvum</i> oocysts. Interaction energy calculations predicted a much larger energy barrier and a shallower secondary minimum for spores than oocysts when the solution ionic strength (IS) equaled 0.1, 1, and 10 mM, and no energy barrier when the IS = 100 mM. Spores and oocysts exhibited similar trends of increasing retention with IS and decreasing Darcy water velocity (<i>q</i>_<i>w</i>), and the predicted setback distance to achieve a six log removal was always larger for spores than oocysts. However, low levels of observed spore and oocyst release significantly influenced the predicted setback distance, especially when the fraction of reversibly retained microbes (<i>F</i>_rev) was high. An estimate for <i>F</i>_rev was obtained from large release pulses of spore and oocyst when the IS was reduced to deionized water. The value of <i>F</i>_rev always increased with <i>q</i>_w, whereas an opposition trend for <i>F</i>_rev with IS was observed for spores (decreasing) and oocysts (increasing)