Presence Of Complexes Research Articles

Epicatechin an incredible tool to dissociate MDM2-p53 interaction for treatment of glioblastomas: a molecular docking and molecular dynamics simulation approach

Glioblastomas, aggressive tumors that arise from malignant transformation of astrocytes, account for 60% brain cancer cases. Current treatments including radiation and chemotherapy accompanied by surgeries result in an average survival increment of 15 months. New therapeutics based on molecular pathology and pathways demonstrate great scope. p53, a tumor-suppressor protein is downregulated by MDM2. In malignant conditions, MDM2 levels increase immensely due to genetic mutations, causing excessive p53 downregulation, thereby enhancing malignancy to extremities. Inhibition of MDM-2 to p53 interaction by potent inhibitors can be a potent therapy but the use of synthetic inhibitors poses many side effects. Natural dietary flavonoids like epicatechin possess high antioxidant and anti-carcinogenic properties. Molecular docking and MD simulation approaches were used to reveal the effectiveness of epicatechin in this regard, a high negative binding energy of -9.619 kcal/mol with Ki value of 82.34 nM and 6 hydrogen bonds with the leading residues responsible for MDM2 p53 interaction were noticed. MD simulation of 100 ns revealed that epicatechin continues to interact with the vital residues of MDM2 and p53 and occupies the hydrophobic p53-binding cleft in MDM2. Significant structural modifications in MDM2-p53 complex due to epicatechin interactions were observed. The increase in RMSD and Rg values of MDM2-p53 complex in presence of epicatechin provides evidence for the destabilization of complex. The extreme increase in RMSF values of p53 in turn indicates towards its reduced interaction with MDM2. Hence, epicatechin can promisingly treat adverse glioblastoma pathologies by inhibiting MDM2-p53 interactions, therefore exhaustive research is urgently demanded.

Synthesis, structure, polyphenol oxidase mimicking and bactericidal activity of a zinc-schiff base complex

Focusing on the important biological functions of metallo-enzymes and metallo-therapeutics in living world, this research work demonstrates the synthesis, crystal structure, supramolecular architecture, 4-methylcatechol oxidation and bactericidal activity of an interesting zinc-Schiff base complex, [Zn(HL)2Cl2] (1), [Schiff base (HL) = 2-(2-methoxybenzylideneamino)phenol]. Crystal structure analysis of the zinc-Schiff base reveals that zinc centre exists in a distorted tetrahedral geometry. The Schiff base adopts three donor centres, however it gets protonated to exist in a zwitter ionic form and behaves as a monodentate coordinator in 1. This zinc-Schiff base complex has been examined towards the bio-mimetic oxidation of 4-methylcatechol (4-MC) in methanol and portrays its good efficacy with good turnover number, 1.45 × 103 h−1. Electro-chemical study, electron paramagnetic resonance analysis and electrospray ionization mass spectrometry results for the zinc-Schiff base complex in presence of 4-MC ensures that the catalytic reaction undergoes through enzyme-substrate binding, and generation of radical in the course of catalysis drives the catalytic oxidation of 4-MC. Antibacterial study has also been performed against few clinical pathogens (Bacillus SP, Enterococcus, and E. coli). Scanning electron microscope and EDAX analysis for the pathogen with little dose of zinc complex confirms the destruction of bacterial cell membrane with 1.44% occurrence of zinc in the selected zone of inhibition area. This observation holds a great promise to develop future antibacterial agent.

Evaluation of dendronized gold nanoparticles as siRNAs carriers into cancer cells

Gene therapy is one of the most promising approaches for potential application in the treatment of diseases, ranging from cancer and heritable disorders to infectious diseases. Before nucleic acid molecules can reach their site of action inside target cells, they must overcome several obstacles. Thus, to fully exploit the therapeutic potential of nucleic acids, efficient delivery systems are required. We herein evaluated gold nanoparticles (AuNPs) covered with cationic carbosilane dendrons as siRNA delivery systems. Detailed analysis of formation of AuNP:siRNA complexes using circular dichroism, zeta-potential, zeta-size, electron microscopy and gel electrophoresis was performed. The stability of complexes in presence of heparin and RNase was evaluated. Internalization of AuNPs and their complexes with siRNAs into cancer cells was estimated by ultrastructure analysis and confocal microscopy. The cytotoxicity of dendrons, AuNPs and their complexes with siRNAs on 4 cancer cell lines (Caco-2, HeLa, U937 and THP-1) was estimated. We concluded that dendronization of AuNPs is a promising way to develop siRNA carriers for anticancer gene therapy.

Interaction and thermal stability of carboxymethyl cellulose on α-Fe2O3(001) surface: ReaxFF molecular dynamics simulations study

Reactive (ReaxFF) molecular dynamic simulations were performed to elucidate the nature of interaction between hematite and carboxymethyl cellulose (CMC) considering effect of moisture and temperature. Simulations showed that the presence of moisture prohibited CMC to interact directly with hematite surface. However, the moisture helps to disperse CMC along the hematite surface thus maximizing the interaction. In dry condition, it was found that the negatively charged oxygen present in the functional groups and in CMC backbone (–CH2OCH2–) take part to form chemical bond with the positively charged surface Fe. The bonding interaction with polymer back bone is a new finding from this simulation. The binding energy estimated as −56.2 kcal/mol clearly indicates chemisorption with bond length ∼2.00 Å. Upon heating up the complex in presence of atmospheric oxygen it was observed that CMC decomposed at high temperature rather than desorbed from the surface. This study clearly shows that CMC is a suitable binder for iron ore pelletization and will pave the way for more rationale design of organic binders.

A Simple and Efficient Method for Quantitative Synthesis of Cu (II) Complexes in Presence of SiO2: Structure Elucidation, DFT, Eukaryotic DNA, Antimicrobial and Potentiometric Studies

An effective methodology for the quantitative preparation of copper (II) complexes from benzaldehyde-[N-(3-Hydroxy-2-Naphthoyl)] Hydrazone (H2L) in existence of SiO2 as a catalyst which reduced reaction time and produced high yield was discussed. The formed complexes were elucidated by applying spectral, analytical and conformational methods. The octahedral configuration was proposed for Cu (II) complexes based on magnetic moments, electronic spectral and electron spin resonance (ESR). The DFT theory used to predict the optimized atomic-skeletons for all produced complexes. Also, biological activity measurements were performed to study the important of produced compounds. The association constants of ligand at various temperatures in 50% (v/v) DMSO/H2O, 0.05 M were calculated by applying potentiometric titration. Also, the stability constants of copper (II) compounds were calculated in DMSO/H2O as a mixed solvent at various temperatures.

DNA interaction and anticancer evaluation of new adenine complexes in presence of N, N-donors as secondary chelate

This article describes the synthesis and spectroscopic characterization of several Pd(II), Pt(II), Ag(I) and Rh(III) complexes with multi-dentate adenine (Had) as primary ligand and 2,2′-bipyridyl (bpy), 1,10-phenanthroline (phen) as secondary ligand. In the complexes, adenine coordinates bidentately through cyclic N7 and NH2 {[M(L)(Had)]Cl2 (M(II) = Pd, Pt; L = bpy, phen)}; cyclic N3 and deprotonated N9 {[Pd(ad)2] and [M(ad)Cl(H2O)] (M(II) = Pd, Pt)} or N1 & N7 in {dimeric [Ag(Had)(NO3)]2}, and monodentate through cyclic N3 {[Rh(Had)3(H2O)3]Cl3}. The main goal of this study is to prepare new low toxic and effective anticancer metal-based molecules. The in vitro anticancer activity against the human breast cancer (MDA-MB231) and human ovarian cancer (OVCAR-8) cell lines was tested using selected Pt(II) and Pt(II) mixed ligand, Had-phen and Had-bpy, complexes, which are rich N-donors, in comparison to cisplatin as a reference. Moreover, CT-DNA-binding properties of some complexes were studied using circular dichroism (CD) spectroscopy. Moreover, intercalative CT-DNA binding capability was indicated.

Ligand directed synthesis of a unprecedented tetragonalbipyramidal copper (II) complex and its antibacterial activity and catalytic role in oxidative dimerisation of 2‐aminophenol

In pursuit of the significant contribution of copper ion in different biological processes, this research work describes the synthesis, X‐ray structure, Hirshfeld surface analysis, oxidative dimerization of 2‐aminophenol and antibacterial activity of a newly designed copper (II)‐Schiff base complex, [Cu(L)2] (1), [Schiff base (HL) = 2‐(2‐methoxybenzylideneamino)phenol]. X‐ray structural analysis of 1 reveals that the Cu (II) complex crystallizes in a cubic crystal system with Ia‐3d space group. The Cu (II) centre adopts an unprecedented tetragonal bipyramidal geometry in its crystalline phase. The Schiff base behaves as a tridentate chelator and forms an innermetallic chelate of first order with Cu (II) ion. The copper (II) complex has been tested in the bio‐mimics of phenaxozinone synthase activity in acetonitrile and exhibits good catalytic activity as evident from high turnover number, 536.4 h−1. Electrochemical analysis exhibits the appearance of two additional peaks at −0.15 and 0.46 V for Cu (II) complex in presence of 2‐AP and suggests the development of AP−/AP•− and AP•−/IQ redox couples in solution, respectively. The presence of iminobenzosemiquinone radical at g = 2.057 in the reaction mixture was confirmed by electron paramagnetic resonance and may be considered the driving force for the oxidative dimerisation of 2‐AP. The existence of a peak at m/z 624.81 for Cu (II) complex in presence of 2‐AP in electrospray ionization mass spectrum ensures that the catalytic oxidation proceeds through enzyme‐substrate adduct formation. The copper (II) complex exhibits potential antibacterial properties against few pathogenic bacterial species like Staphylococcus aureus, Enterococcus and Klebsiella pneumonia and scanning electron microscope studies consolidates that destruction of bacterial cell membrane accounts on the development of antibacterial activity.

Oxidative dimerisation of 2-aminophenol by a copper(II) complex: Synthesis, non-covalent interactions and bio-mimics of phenoxazinone synthase activity

This research study aims to overview the synthesis, structural characterization, long range crystalline architectures and bio-inspired oxidative catalysis of a mononuclear copper(II) complex, [Cu(Phen)2(H2O)](NO3)2 (1);[phen = 1,10-phenanthroline]. Single crystal X-ray diffraction study reveals that copper complex crystallizes in C2/c space group and Cu(II) centre exists in a highly distorted trigonalbipyramidal geometry. A close look at supramolecular architecture for this copper(II) complex indicates that oxygen atoms of nitrate ions and H atoms from phenanthroline ligand lead to intermolecular H-bonded 3D crystalline architecture in solid state. Noteworthy O ⋯ π interactions are also operative in between nitrate-O and centroids of ligands to provide additional stability in 3D architecture. Hirshfeld surface analysis further corresponds to the active participation of intermolecular H⋯O bonding and anion ⋯ π interactions. This copper complex has been tested as a bio-inspired catalyst towards oxidative coupling of 2-AP in methanol medium and the catalytic efficiency, kcat/KM(h−1) is found excellent, 1.007 × 107, towards the aerobic oxidation of 2-aminophenol (2-AP). The copper(II) complex in presence of 2-AP exhibits two new additional peaks at −0.13 and 0.49 V which correspond to AP−/AP•− and AP•−/IQ redox couple and suggests the generation of radical as a driving force for the oxidative coupling of 2-AP. Electrospray ionization mass spectrometry of the reaction mixture suggests that the course of oxidative cyclisation proceeds through enzyme-substrate adduct formation during this course of catalysis.

АПРОБАЦІЯ КАРТИ СКРИНІНГ-КОНТРОЛЮ БІОГЕОМЕТРИЧНОГО ПРОФІЛЮ ПОСТАВИ ДІТЕЙ ДОШКІЛЬНОГО ВІКУ В ПРОЦЕСІ ФІЗИЧНОЇ РЕАБІЛІТАЦІЇ

Мета. Розробити та апробувати карту візуального скринінгу біогеометричного профілю постави дітей 5–6 років у процесі фізичної реабілітації. Методи. У процесі дослідження використанометод аналізу науково-методичної літератури, соціологічні методи (анкетування, опитування), методи кваліметрії та методи математичної статистики. Основним методом дослідження обрано педагогічний експеримент. Констатувальний етап передбачав отримання інформації про стан біогеометричного профілю постави дітей 5–6 років (n=76) у процесі фізичної реабілітації. Результати. Науково обґрунтована та апробована карта скринінг-контролю стану біогеометричного профілю постави дітей 5–6 років у процесі фізичної реабілітації, в умовах закладів дошкільної освіти, для своєчасної профілактики та корекції її порушень. Розроблена карта дає можливість розділити дітей з функціональними порушеннями постави за такими рівнями стану їх біогеометричного профілю постави:високий, вище за середній, середній та низький. Використання розробленої технології контролю стану біогеометричного профілю постави дітей 5–6 років у процесі фізичної реабілітації дозволило розподілити дітей з різними типами порушення постави за рівнями стану біогеометричного профілю. Отримані результати дослідження являлись підґрунтям для розробки комплексів фізичних вправ окремо для кожного типу постави на різних періодах фізичної реабілітації з урахуванням рівнів стану біогеометричного профілю постави дітей 5–6 років. Висновок. За рівнем стану біогеометричного профілю у 10,53% обстежених дітей зафіксовано низький рівень стану біогеометричного профілю постави за наявності комбінованих порушень постави у фронтальній і сагітальній площинах, у 19,74% зареєстровано вище за середній рівеньстану біогеометричного профілю постави за наявності такого порушення останньої, як сутула спина.Ключові слова: контроль, біогеометричний профіль постави, діти старшого дошкільного віку,фізична реабілітація.

Direct Synthesis of Rhenium and Technetium-99m Metallosurfactants by a Transmetallation Reaction of Lipophilic Groups: Potential Applications in the Radiolabeling of Liposomes.

A new zinc dithiocarbamate functionalized with palmitoyl groups is described as a useful tool for the preparation of metallosurfactants through a transmetallation reaction with the transition metals rhenium and technetium. An amphiphilic rhenium complex is synthesized by a transmetallation reaction with the zinc complex in presence of the polar phosphine sodium triphenylphosphine trisulfonate, which leads to a rhenium complex with a lipophilic dithiocarbamate and a polar phosphine ligand. The study of this rhenium complex has shown that it self-aggregates, leading to the formation of aggregates that have been analyzed by dynamic light scattering and cryotransmission electron microscopy (cryo-TEM). In addition, this amphiphilic rhenium complex is incorporated into soy phosphatidylcholine liposomes, whether liposomes are prepared by mixing phospholipid and the rhenium complex or by the incorporation of the rhenium complex into preformed liposomes. The one-pot reaction of the radiocompound [99mTc(H2O)3(CO)3]+ with the above-mentioned zinc dithiocarbamate, the phosphine sodium triphenylphosphine trisulfonate and the phospholipid soy phosphatidylcholine, leads to liposomes labeled with a Tc-99m homologous complex of the rhenium complex, in accordance with the high-performance liquid chromatography (HPLC) data.

Ion-Pair Formation of [CoIII(pn)2(Cl)(L)2+····· I−] by Aqueous-Organic Solvent Medium Enhanced Photoreduction: A Perspective Regression Analysis

Reduction of CoIII centre in CoIII(pn)2(Cl)(L)2+ with reference to solvent medium and structure of the complex via ion pair charge transfer (IPCT) paves way for the novel reaction mechanism route. In this work, we prepared, characterized and photoinduced the complexes CoIII(pn)2(Cl)(L)2+ (where L = RC6H4NH2, R = m-OMe, p-F and H) in the presence of iodide ion. Quantum yield for 254 nm excitation of CoIII(pn)2(Cl)(L)2+(where L = RC6H4NH2, R = m-OMe, p-F and H) in water-1,4-dioxane mixtures (Diox = 0, 5, 10, 15, 20, 25, and 30% (v/v)) were also derived for all the complexes in presence of added iodide ion, in which CoIII was reduced via [CoIII(pn)2(Cl)(L)2+….. I-] ion-pair formation. The photoinduced state is ion-pair charge transfer transition state and the quantum efficiency is solvent reliant and they are non-reactive. That is, change in ΦCo(II) is dependable with observed increase in xDiox of the mixed solvent medium. Correlation analysis using empirical parameters εr, Y, ET N and DNN provides a model to understand the solvent medium participation and interaction. This work gains an insight into the role of aqueous-organic solvent medium in CoIII(pn)2(Cl)(L)2+ photoreduction, which may be of great significance in developing novel approaches in the field of high performance catalysis

In silico assessment of human Calprotectin subunits (S100A8/A9) in presence of sodium and calcium ions using Molecular Dynamics simulation approach.

Calprotectin is a heterodimeric protein complex which consists of two subunits including S100A8 and S100A9. This protein has a major role in different inflammatory disease and various types of cancers. In current study we aimed to evaluate the structural and thermodynamic changes of the subunits and the complex in presence of sodium and calcium ions using molecular dynamics (MD) simulation. Therefore, the residue interaction network (RIN) was visualized in Cytoscape program. In next step, to measure the binding free energy, the potential of mean force (PMF) method was performed. Finally, the molecular mechanics Poisson-Boltzmann surface area (MMPBSA) method was applied as an effective tool to calculate the molecular model affinities. The MD simulation results of the subunits represented their structural changes in presence of Ca2+. Moreover, the RIN and Hydrogen bond analysis demonstrated that cluster interactions between Calprotectin subunits in presence of Ca2+ were greater in comparison with Na+. Our findings indicated that the binding free energy of the subunits in presence of Ca2+ was significantly greater than Na+. The results revealed that Ca2+ has the ability to induce structural changes in subunits in comparison with Na+ which lead to create stronger interactions between. Hence, studying the physical characteristics of the human proteins could be considered as a powerful tool in theranostics and drug design purposes.

Pyridylbenzimidazole‐Based Gold(III) Complexes: Lysozyme Metalation, DNA Binding Studies, and Biological Activity

The lysozyme binding affinity of new Au(III) complexes, bearing pyridylbenzimidazole ligands, was investigated by ESI‐MS and UV/Vis. Metalation of lysozyme happened mainly by {Au}n+, {AuCl}0/n+ and {AuCl2}n+/–. The appendage sulfonate group of pyridylbenzimidazole ligand system played a role in determining the products of interaction of HEWL with Au(III) complexes. The hydrophilic sulfonate group inhibited the ligand cleavage via the participation in several coulombic and H‐bond interactions giving several AuLn+ containing adduct peaks (L = 1‐[(pyridin‐2‐yl) benzimidazole]‐propyl‐sulfonic acid). The stability of the complexes in presence of ascorbic acid was examined by UV/Vis and 13C NMR. To recognize if His15 side‐chain is the metalation site of HEWL, the interactions between the complexes and imidazole, as a simple model of histidine, were investigated by 1H and 13C NMR. The DNA binding studies of the complexes were reported. For this class of Au(III) complexes, it is preferred to decorate the pyridylbenzimidazole system with ethyl group rather than sulfonate and phthalimido group to have a complex with interesting antifungal activity against Candida albicans and Cryptococcus neoformans var. grubii. Au(III) complex, having sulfonate group, is noncytotoxic to non‐malignant cells (human embryonic kidney cells (HEK293)), shows negligible hemoglobin release and is safe to the normal cells if applicable.

NLRX1 regulates TNF-α-induced mitochondria-lysosomal crosstalk to maintain the invasive and metastatic potential of breast cancer cells

An increased level of proinflammatory cytokines, including TNF-α in tumor microenvironment regulates the bioenergetic capacity, immune evasion and survival of cancer cells. Emerging evidences suggest that mitochondrial immune signaling proteins modulates mitochondrial bioenergetic capacity, in addition to the regulation of innate immune response. The optimal oxidative phosphorylation (OxPhos) capacity is required for the maintenance of functional lysosomes and autophagy flux. NLRX1, a mitochondrial NOD family receptor protein, regulates mitochondrial function during apoptosis and tissue injury. However, its role in regulation of mitochondrial and lysosomal function to modulate autophagy flux during inflammatory conditions is not understood. In the current study, we investigated the role of NLRX1 in modulating TNF-α induced autophagy flux and mitochondrial turnover and its implication in regulating the invasive and metastatic capability of breast cancer cells. Expression analyses of clinical breast cancer samples and meta-analysis of multiple public databases revealed that NLRX1 expression is significantly increased in basal-like and metastatic breast carcinoma as compared to non-basal-like and primary breast cancer. Depletion of NLRX1 expression in triple-negative breast cancer cells, altered the organization and activity of OxPhos complexes in presence of TNF-α. NLRX1 depletion further impaired lysosomal function and hence the turnover of damaged mitochondria through mitophagy in presence of TNF-α. Importantly, loss of NLRX1 decreased OxPhos-dependent cell proliferation and migration ability of triple-negative breast cancer cells in presence of TNF-α. These evidences suggest an essential role of NLRX1 in maintaining the crosstalk of mitochondrial metabolism and lysosomal function to regulate invasion and metastasis capability of breast cancer cells.

Multiscale cyclic dynamics in light harvesting complex in presence of vibrations and noise

Starting from the many-body Schr\"odinger equation, we derive a new type of Lindblad Master equations describing a cyclic exciton/electron dynamics in the light harvesting complex and the reaction center. These equations resemble the Master equations for the electric current in mesoscopic systems, and they go beyond the single-exciton description by accounting for the multi-exciton states accumulated in the antenna, as well as the charge-separation, fluorescence and photo-absorption. Although these effects take place on very different timescales, their inclusion is necessary for a consistent description of the exciton dynamics. Our approach reproduces both coherent and incoherent dynamics of exciton motion along the antenna in the presence of vibrational modes and noise. We applied our results to evaluate energy (exciton) and fluorescent currents as a function of sunlight intensity.

Expansion of Tumor-Infiltrating Lymphocytes from Melanoma Tumors.

Autologous, in vitro-expanded tumor-infiltrating lymphocytes (TIL) have been successfully used for treatment of melanoma patients. Expansion of TIL from tumors is usually performed in two steps. The details of the procedure differ between different laboratories, but the general concept remains the same. In the first step, small fragments of a tumor are placed in culture medium containing one or more T cell stimulating growth factors. Here the most common protocol using interleukin (IL)-2 is described. The length of the first step is flexible to allow generation of enough cell to start the second step of the procedure. The second step is a so-called rapid expansion protocol (REP) where harvested TIL from the first step are induced to massive proliferation via triggering of their T cell receptor (TCR) complex in presence of an excess of feeder cells and, again, T cell stimulating growth factors. This second expansion step is usually around 2weeks in length. Here will be described a REP that uses soluble anti-CD3 antibodies for TCR triggering, irradiated peripheral blood mononuclear cells (PBMC) as feeder cells, and IL-2 as the T cell growth factor. Furthermore, the described protocol utilizes gas-permeable cell culture flasks that yield large number of cells similar to conventional bioreactors but using standard laboratory equipment.

Cherenkov Radiation‐Mediated In Situ Excitation of Discrete Luminescent Lanthanide Complexes

AbstractLanthanide luminescence, while ideal for in vivo applications owing to sharp emission bands within the optical window, requires high‐intensity, short‐wavelength excitation of small organic “antenna” chromophores in the vicinity of the lanthanide complex to access excited f‐orbital states through intersystem crossing. Herein, we explored Cherenkov radiation of the radioisotopes 18F and 89Zr as an in situ source of antenna excitation. The effective inter‐ and intramolecular excitation of the terbium(III) complexes of a macrocylic polyaminocarboxylate ligand (hydration number (q)=0, quantum yield (φ)=47 %) as well as its analogue functionalized to append an intramolecular Cherenkov excitation source (q=0.07, φ=63 %) was achieved. Using conventional small‐animal fluorescence imaging equipment, we have determined a detection limit of 2.5 nmol of Tb(III) complex in presence of 10 μCi of 18F or 89Zr. Our system is the first demonstration of the optical imaging of discrete luminescent lanthanide complexes without external short‐wave excitation.

Cherenkov Radiation-Mediated In Situ Excitation of Discrete Luminescent Lanthanide Complexes.

Lanthanide luminescence, while ideal for in vivo applications owing to sharp emission bands within the optical window, requires high-intensity, short-wavelength excitation of small organic "antenna" chromophores in the vicinity of the lanthanide complex to access excited f-orbital states through intersystem crossing. Herein, we explored Cherenkov radiation of the radioisotopes 18 F and 89 Zr as an in situ source of antenna excitation. The effective inter- and intramolecular excitation of the terbium(III) complexes of a macrocylic polyaminocarboxylate ligand (hydration number (q)=0, quantum yield (φ)=47 %) as well as its analogue functionalized to append an intramolecular Cherenkov excitation source (q=0.07, φ=63 %) was achieved. Using conventional small-animal fluorescence imaging equipment, we have determined a detection limit of 2.5 nmol of Tb(III) complex in presence of 10 μCi of 18 F or 89 Zr. Our system is the first demonstration of the optical imaging of discrete luminescent lanthanide complexes without external short-wave excitation.

Generic and Scalable Method for the Preparation of Monodispersed Metal Sulfide Nanocrystals with Tunable Optical Properties.

A rational synthetic method that produces monodisperse and air-stable metal sulfide colloidal quantum dots (CQDs) in organic nonpolar solvents using octyl dithiocarbamic acid (C8DTCA) as a sulfur source, is reported. The fast decomposition of metal-C8DTCA complexes in presence of primary amines is exploited to achieve this purpose. This novel technique is generic and can be applied to prepare diverse CQDs, like CdS, MnS, ZnS, SnS, and In2S3, including more useful and in-demand PbS CQDs and plasmonic nanocrystals of Cu2S. Based on several control reactions, it is postulated that the reaction involves the in situ formation of a metal-C8DTCA complex, which then reacts in situ with oleylamine at slightly elevated temperature to decompose into metal sulfide CQDs at a controlled rate, leading to the formation of the materials with good optical characteristics. Controlled sulfur precursor's reactivity and stoichiometric reaction between C8DTCA and metal salts affords high conversion yield and large-scale production of monodisperse CQDs. Tunable and desired crystal size could be achieved by controlling the precursor reactivity by changing the reaction temperature and reagent ratios. Finally, the photovoltaic devices fabricated from PbS CQDs displayed a power conversion efficiency of 4.64% that is comparable with the reported values of devices prepared with PbS CQDs synthesized by the standard methods.

Selective separation of α- and β-cyclodextrins by complexation/ultrafiltration using supra molecular host-guest interaction

This work is aimed at developing a new process to separate alpha-cyclodextrin (CD) from binary alpha-CD/beta-CD mixtures. To achieve this objective, a membrane process was designed with water as solvent and using the selective accommodation of a guest Igepal Co-890 (IG) within the beta-CD cavity. In the first part, host-guest inclusion study suggested the formation of IG(2)/beta-CD complex in presence of IG excess. Moreover, increasing IG/CD molar ratio to 1.5 leads to the complete complexation of beta-CD while alpha-CD remains free. The second part was devoted to the separation of alpha- and beta-CD using UF membranes (GH and GK from GE-Osmonics). The influence of parameters including membrane molecular weight cut-off (MWCO), transmembrane pressure (Delta P), IG/beta-CD and alpha-CD/beta-CD molar ratios, was investigated. MWCO, Delta P, IG/beta-CD and alpha-CD/beta-CD molar ratios respectively of 1000 Da, 2 bar, 1.5 and 11:89 are the optimized values to reach an alpha-CD separation factor as high as 38. The experimental data fits very well with predicted values calculated using the parameters found in the complexation study and rejection of single solutions indicating that selectivity predominantly originates from steric exclusion of species by membrane GH.