QSAR Modeling of Toxicity of Quaternary Ammonium Compounds to Chlorella pyrenoidosa Using 2D and 3D Descriptors

To investigate the relationships between structures and toxicities of 13 quaternary ammonium compounds （QACs） to Chlorella pyrenoidosa, 2D- and 3D-QSAR models were built. The 2D-QSAR model included two parameters： averaged polarizability （a） and total connectivity （Tcon）. Furthermore, 3D-QSAR models were proposed by using comparative molecular field analysis （CoMFA） and molecular similarity index analysis （CoMSIA）. All these models were robust and predictive. To our interest, 3D-QSAR model suggested that the hydrophobieity of substituents was the dominating factor for the toxicities, electrostatic effect was the secondly important, and steric field gave the least contribution. Comparatively, the predictive ability of 3D-QSAR model is slightly more advantageous than that of 2D-QSAR. They can be used complementally in the toxicity description of this kind of compounds.

Current State and Development of Quaternary Ammonium Compounds Disinfectants in China

Quaternary ammonium compound are a class of broad-spectrum,high-efficiency and low-toxicity bactericide,which are widely used in daily life and industrial sterilization.Herein,the current state of domestic quaternary ammonium disinfectant products was summarized,as well as those new products developed and studied,and the development trend was also predicted.

The antimicrobial activities of a series of bis-quaternary ammonium compounds

A series of bis-quaternary ammonium compounds（bis-QACs） N,N＇-hevamethylenebis（1-alkyl-4-carbamoyl pyridinium bromide）（4BCAP-6,n）（alkyl chain length,n=8,10,12,14,16 and 18） were synthesized and characterized.Their surface tensions,critical micelle concentrations（CMC）,and antimicrobial activities were evaluated.4BCAP-6,10 exhibited the strongest antimicrobial activities except for that against Proteus vulgari.The activities of 4BCAP-6.n against Escherichia coli zk126 were not significantly influenced by temperature.pH and initial bacteria concentration.These results indicate that bis-QACs exhibit high antimicrobial activity regardless of the environmental conditions.

OXIDATION OF α-METHYL OR α-METHYLENE GROUPS IN CARBONYL COMPOUNDS WITH AMMONIUM CHLOROCHROMATE

This paper reports a new method for oxidizing the α-methyl or α-methylene groups in carbonyl compounds into 1,2-dicarbonyl compounds by ammonium chlorochromate(ACC).

Antibacterial Activity of Polymeric Quaternary Ammonium Compounds Tuned by Incorporating Hydrophilic co-Monomer

Copolymers of quaternary ammonium monomer（QAM） and hydrophilic co-monomer were successfully synthesized by free radical polymerization. It was discovered that the hydrophilic co-monomers with poor antibac- terial activity significantly enhanced the activity of QAM substituted with a long alkyl chain[i.e., N,N-dimethyl-N-dodecyl methacrylate ammonium bromide（DMAEMA-DB）]. When a suitable molar ratio of DMAEMA-DB to co-monomer was selected, the activity of the copolymers was up to 123 times that of the homopolymer of DMAEMA-DB against S. aureus, and 282 times that of it against E. colt. But unlike DMAEMA-DB, the co-monomers might weaken the activity of QAM substituted with a short alkyl chain[i.e., N,N-dimethyl-N-butyl methacrylate ammonium bromide（DMAEMA-BB）]. Moreover, it was found that copolymers of DMAEMA-DB were much more biocidal than those of DMAEMA-BB. Therefore, it could be speculated that the long alkyl chain plays an important role in the antibacterial activity, and that the hydrophilie co-monomers are beneficial to polymeric guaternary ammonium compounds（PQACs） to exert the positive effect of the long alkyl chain to the greatest degree.

An investigation of the effect of ammonium sulfate addition on compound fertilizer granulation

We investigated the effect of small amounts of ammonium sulfate （NH4）2SO4 on compound fertilizer granulation. We examined the following raw materials： humic acid, ammonium chloride, urea, potassium chloride, and monoammonium phosphate. The mass ratio of organic matter, nitrogen, phosphorus, and potassium was typically 22：17：7：2. In the absence of （NH4）2SO4, the granulation rate of the compound fertilizer was low, and increased significantly following the addition of 1–2% （NH4）2SO4. We suggested the following physical and chemical processes as potential mechanisms： （NH4）2SO4 promoted the conversion of yellow flue gas desulfurization gypsum into gypsum whiskers; （NH4）2SO4 interacted with humic acid and urea to generate a new complex; urea sulfate was formed under acidic conditions. The combined effect of the above physical and chemical processes was an increase both in the rate of interactions between the materials and in system viscosity, which has the end result of increasing the granulation rate.

Toxicity of the disinfectant benzalkonium chloride(C_(14))towards cyanobacterium Microcystis results from its impact on the photosynthetic apparatus and cell metabolism

Quaternary ammonium compounds(QACs)are commonly used in a variety of consumer and commercial products,typically as a component of disinfectants.During the COVID-19 pandemic,QACs became one of the primary agents utilized to inactivate the SARS CoV-2 virus on surfaces.However,the ecotoxicological effects of QACs upon aquatic organisms have not been fully assessed.In this study,we examined the effects of a widely used QAC(benzalkonium chloride-C_(14),BAC-14)on two toxigenic Microcystis strains and one non-toxigenic freshwater Microcystis strain and carried out an analysis focused on primary,adaptive and compensatory stress responses at apical(growth and photosynthesis)and metabolic levels.This analysis revealed that the two toxic Microcystis strains were more tolerant than the non-toxic strain,with 96 hr-EC_(50)values of 0.70,0.76,and 0.38 mg/L BAC-14 for toxigenic M.aeruginosa FACHB-905,toxigenic M.aeruginosa FACHB-469,and non-toxigenic M.wesenbergii FACHB-908,respectively.The photosynthetic activities of the Microcystis,assessed via F_(v)/F_(m) values,were significantly suppressed under 0.4 mg/L BAC-14.Furthermore,this analysis revealed that BAC-14 altered 14,12,and 8 metabolic pathways in M.aeruginosa FACHB-905,M.aeruginosa FACHB-469,and M.wesenbergii FACHB-908,respectively.It is noteworthy that BAC-14 enhanced the level of extracellular microcystin production in the toxigenic Microcystis strains,although cell growth was not significantly affected.Collectively,these data show that BAC-14 disrupted the physiological and metabolic status of Microcystis cells and stimulated the production and release of microcystin,which could result in damage to aquatic systems.

Theoretical and experimental researches on a PCF-based SPR sensor

A photonic crystal fiber based surface plasmon resonance(PCF-SPR)sensor is simulated by finite element method and experimentally realized.The calculations show that there is an obvious loss peak in the vicinity of 1.2μm while the PCF of LMA-8 is used as a sensor.The suspension of silver nanoparticle mixed with hexadecyl trimethyl ammonium bromide (CTAB)is inhaled into the PCF to form a metal film which can be stimulated to generate plasmon in the experiment.A spectrometer is utilized to detect the continuous broadband transmission spectrum from the PCF.The experimental results verify the loss peak.Compared with the theoretical calculations,the offset of loss peak about 40 nm can be acceptable, because the uniformity of the metal coating is difficult to guarantee and the film thickness is difficult to control.

Recyclable, non-leaching antimicrobial magnetic nanoparticles

Pathogenic bacterial contaminations in water cause serious or even lethal threats.Strategies that effectively kill bacteria without causing environmental contamination are urgently needed in a wide range of applications.We prepared recyclable antimicrobial magnetic nanoparticles,Fe304@P(St-coAcQAC),through surfactant-free seeded emulsion polymerization involving a polymerizable,hydrophobic quaternary ammonium compound(QAC).Fe304 particles were first synthesized by a solvothermal reaction,followed by functionalization with a methacrylic silane(MPS),and then copolymerized with a QAC-containing acrylic monomer(AcQAC),leading to Fe304@P(St-co-AcQAC) nanoparticles.As confirmed by antibacterial assays,these Fe304@P(St-co-AcQAC) nanoparticles exhibited strong antimicrobial action against both Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli,without leaching out any bactericidal agent.An additional benefit of antimicrobial magnetic particles is that they can be easily recycled while maintaining excellent antimicrobial efficacy.