Effect of hydrophobicity and size of the ligands on the intercalative binding interactions of some metallo-surfactants containing π-conjugated systems with yeast tRNA.

The intercalative yeast t-RNA binding behavior of some metallo-surfactant complexes, Co(ip)2(TA)2](ClO4)3 (1) and [Co(dpq)2(TA)2](ClO4)3 (2) where TA = Tetradecylamine (Myristylamine), ip = imidazo[4,5-f][1,10]phenanthroline and dpq = dipyrido[3,2-d:2'-3'-f]quinoxaline containing π-conjugated systems (both below and above critical micelle concentration) have been investigated by means of absorption spectral titration, competitive binding, circular dichroism, cyclic voltammetry, and viscometry measurements. Absorption spectral titration results implicate yeast tRNA has significant effects on the binding behaviors of two surfactant complexes via intercalative mode showed a significant absorption band of hypochromicity with red shift. The intrinsic binding constant values below and above CMC were determined as Kb = 6.12 × 105 M-1, 2.31 × 106 M-1, for complex (1) and 7.23 × 105 M-1, 3.57 × 106 M-1, for complex (2). In both sets of complexes (1) and (2), the complexes bind more strongly to yeast tRNA in the above critical micelle concentration can be hydrophobic and confirm intercalation. Competitive displacement studies confirmed that complexes bind to yeast tRNA via intercalative mode. Cyclic voltammetry studies suggest the increasing amounts of yeast tRNA, the cathodic potential Epc for the two complexes shows a positive shift in peak potential indicated the process of binding via intercalation. These observations were further validated by CD, and hydrodynamic measurements. All these studies suggesting that a surfactant complex binds to yeast tRNA appear to be mainly intercalative because of hydrophobicity due to extending aromaticity of the π system of the ligand and planarity of the complex has a significant effect on tRNA binding affinity increasing in the order of complexes containing ligands ip < dpq.Communicated by Ramaswamy H. Sarma.

Metallo-Surfactant assisted silver nanoparticles: A new approach for the colorimetric detection of amino acids.

In this study, we report a new class of metallo-surfactant assisted silver nanoparticle produced by reduction process via AgNO3 solution and extract of Turnera Subulata (TS) in aqueous which act as reducing and metallo-surfactant [Co(ip)2(C12H25NH2)2](ClO4)3 (ip = imidazo[4,5-f][1,10]phenanthroline) act as stabilizing agent. In this study the silver nanoparticles produced using Turnera Subulata extract has showed yellowish brown color formation and an absorption peak at 421 nm signaling the biosynthesis of silver nanoparticles. The presence of functional groups in the plant extracts were identified by FTIR analysis. In addition, the effects of ratio, changing the concentration of the metallo surfactant, TS plant leave extract, metal precursors, and pH of the medium have been investigated on the scale of the Ag nanoparticles. Spherical shaped, crystalline in nature and ∼50 nm sized particles were recorded using TEM and DLS analysis. Furthermore, the mechanistic insights into cysteine and dopa detection by silver nanoparticles were investigated using HR-TEM analysis. This induces aggregation in stable silver nanoparticles owing to selective and strong interaction of -SH group of cysteine with silver nanoparticle surface. The biogenic Ag NPs are found to be highly sensitive to amino acids of dopa and cysteine with the diagnosis maximum for both amino acids as low as 0.9 µM (dopa) and 1 µM (cysteine) under optimized conditions.

'On and Off' intercalative binding behaviour of double chain surfactant cobalt(III) complex containing 2, 2'-bipyridyl ligand in ß-Cyclodextrin: A detail approach on Host-guest inclusion of surfactant cobalt(III) complex and CT-DNA binding in micro-heterogeneous medium.

The binding interaction of surfactant cobalt(III) complex, cis-[Co(bpy)2(HA)2](ClO4)3, in which bpy is 2,2-bipyridine and HA is hexadecylamine or cetylamnine with DNA was through intercalative mode via the long aliphatic chains present in the ligands. The binding was investigated by various techniques, electronic absorption, fluorescence spectroscopy, circular dichroism (CD), cyclic voltametry (CV) and viscosimetry measurements. The spectroscopic studies together with cyclic voltammetry and viscosity experiments support that the surfactant cobalt(III) complex binds to calf thymus DNA by intercalation through the aliphatic chain present in the complex into the base pairs of DNA. The presence of bipyridine ligand with larger π-frame work may also enhance intercalation. UV-vis., spectrum showed 4 nm bathochromic shift of the absorption band at 352 nm along with significant hypochromicity for the absorption band of the complex. The intrinsic binding constants(at below and above CMC are Kb = 2.41 × 105M-1, Kb = 3.12 × 106M-1 respectively) is more in keeping with intercalators and suggests this binding mode. The viscosity measurements showed that the surfactant cobalt(III) complex-DNA interaction can be hydrophobic and confirm intercalation. Moreover, the complex induced detectable changes in the CD spectrum of CT-DNA. Competitive binding study with ethidium bromide (EB) shows that the surfactant complex exhibits the ability to displace the DNA-bound EB indicating that the complex binds to DNA in strong competition with EB for the intercalative binding site. Also, CV results confirm this mode because, with increasing the CT-DNA concentration, shift to higher potential was observed. Besides the effect of binding of surfactant cobalt(III) complex to DNA in presence of ß-cyclodextrin has also studied. This binding of the surfactant cobalt(III) complex in presence of ß-cyclodextrin medium has been prevented (at below and above CMC are Kb = 5.45 × 104M-1, Kb = 6.92 × 105M-1 respectively) due to the incorporation of the aliphatic chains into the cavity of ß-cyclodextrin. In presence of ß-cyclodextrin the binding occur through surface and (or) groove binding can be attributed to the inclusion of the long aliphatic chain that is present in one of the ligands into cyclodextrin.

States of Aggregation and Phase Transformation Behavior of Metallosurfactant Complexes by Hexacyanoferrate(II): Thermodynamic and Kinetic Investigation of ETR in Ionic Liquids and Liposome Vesicles.

Electronic absorption spectroscopy was used to study the ETR of surfactant-cobalt(III) complexes containing imidazo[4,5-f][1,10]phenanthroline, dipyrido[3,2-d:2'-3'-f]quinoxaline and dipyrido[3,2-a:2',4'-c](6,7,8,9-tetrahydro)phenazine ligands by using ferrocyanide ions in unilamellar vesicles of dipalmitoylphosphotidylcholine (DPPC) and 1-butyl-3-methylimidazolium bromide ((BMIM)Br), at different temperatures under pseudo-first-order conditions using an excess of the reductant. The reactions were found to be second-order and the electron transfer is postulated as occurring in the outer sphere. The rate constant for the electron transfer reactions was found to increase with increasing concentrations of ionic liquids. Besides these, the effects of surfactant complex ions on liposome vesicles in these same reactions have also been studied on the basis of hydrophobicity. We observed that, below the phase transition temperature, there is an increasing amount of surfactant-cobalt(III) complexes expelled from the interior of the vesicle membrane through hydrophobic effects, while above the phase transition temperature, the surfactant-cobalt(III) complexes are expelled from the interior to the exterior surface of the vesicle. Kinetic data and activation parameters are interpreted in respect of an outer-sphere electron transfer mechanism. By assuming the existence of an outer-sphere mechanism, the results have been clarified based on the presence of hydrophobicity, and the size of the ligand increases from an ip to dpqc ligand and the reactants become oppositely charged. In all these media, the ΔS# values are recognized as negative in their direction in all the concentrations of complexes employed, indicative of a more ordered structure of the transition state. This is compatible with a model in which these complexes and [Fe(CN)6]4- ions bind to the DPPC in the transition state. Thus, the results have been interpreted based on the self-aggregation, hydrophobicity, charge densities of the co-ligand and the reactants with opposite charges.

SARS-CoV-2 and other pathogens in municipal wastewater, landfill leachate, and solid waste: A review about virus surveillance, infectivity, and inactivation.

This review discusses the techniques available for detecting and inactivating of pathogens in municipal wastewater, landfill leachate, and solid waste. In view of the current COVID-19 pandemic, SARS-CoV-2 is being given special attention, with a thorough examination of all possible transmission pathways linked to the selected waste matrices. Despite the lack of works focused on landfill leachate, a systematic review method, based on cluster analysis, allows to analyze the available papers devoted to sewage sludge and wastewater, allowing to focalize the work on technologies able to detect and treat pathogens. In this work, great attention is also devoted to infectivity and transmission mechanisms of SARS-CoV-2. Moreover, the literature analysis shows that sewage sludge and landfill leachate seem to have a remote chance to act as a virus transmission route (pollution-to-human transmission) due to improper collection and treatment of municipal wastewater and solid waste. However due to the incertitude about virus infectivity, these possibilities cannot be excluded and need further investigation. As a conclusion, this paper shows that additional research is required not only on the coronavirus-specific disinfection, but also the regular surveillance or monitoring of viral loads in sewage sludge, wastewater, and landfill leachate. The disinfection strategies need to be optimized in terms of dosage and potential adverse impacts like antimicrobial resistance, among many other factors. Finally, the presence of SARS-CoV-2 and other pathogenic microorganisms in sewage sludge, wastewater, and landfill leachate can hamper the possibility to ensure safe water and public health in economically marginalized countries and hinder the realization of the United Nations' sustainable development goals (SDGs).

Indirect impact of COVID-19 on environment: A brief study in Indian context.

Worldwide spread of COVID-19 in a quite short time has brought a dramatic decrease in industrial activities, road traffic and tourism. Restricted human interaction with nature during this crisis time has appeared as a blessing for nature and environment. Reports from all over the world are indicating that after the outbreak of COVID-19, environmental conditions including air quality and water quality in rivers are improving and wildlife is blooming. India has always been a hub of pollution with huge population, heavy traffics and polluting industries leading to high air quality index (AQI) values in all major cities. But after declaration of lockdown due to COVID-19, quality of air has started to improve and all other environmental parameters such as water quality in rivers have started giving a positive sign towards restoring. This paper provides evidence-based insight into improvement of air quality and environment during pre and post lockdown of this pandemic situation. An attempt has been made to visualize the improvement in the air quality using tools like satellite images of Indian atmosphere, results of onsite real-time monitoring at specific locations (Ghaziabad-highest polluting city of India) and Air quality index (AQI) calculated by central pollution control board of India.