Synthesis,characterization, antifungal and antibacterial activities evaluation of copper (II), zinc (II) and cadmium (II) chloride and bromide complexes with new (E)-1-(3,4-dimethoxybenzylidene)-4-methylthiosemicarbazone ligand

The reactions of Cu (II), Zn (II) and Cd (II) chloride or bromide with (E)-1-(3,4-dimethoxybenzylidene)-4-methylthiosemicarbazone (MTSVT) lead to the formation of new complexes. They were characterized by spectroscopic studies: IR, ¹H and ¹³C NMR. The crystal structures of the compounds [MTSVT] ( L ), [ZnBr₂(MTSVT)₂] ( 2 ), [CdCl₂(MTSVT)₂] ( 3 ) and [CdBr₂(MTSVT)₂^.H₂O] ( 4 ) were determined by X-ray diffraction. For complexes 2 – 4 , the ion is coordinated through the sulfur atom. All compounds were tested for their antifungal activity against human pathogenic fungi Candida albicans and Aspergillus fumigatus, and for their antibacterial activity against Gram (+) Bacillus subtilis and Enterococcus faecalis as well as against Gram (−) bacteria such as Paracoccus yeei and Acinetobacter baumanii. The results indicated that the metal complexes exhibited a marked enhancement in antibacterial activity compared with the parent Schiff base.     

Alkylation of γ-Azaproline Creates Conformationally Adaptable Proline Derivatives for pH-Responsive Collagen Triple Helices

C^γ-substituted proline derivatives are valuable tools for developing functionalized collagen peptides for biological and materials investigations, yet the stereochemistry at C^γ can produce undesired steric or stereoelectronic constraints. Alkylated γ-azaproline (γ-azPro) derivatives are proline mimetics that lack a stereogenic center at the γ-position of the ring and can thus utilize the invertibility of nitrogen to adapt their conformation. NMR spectroscopic analyses and DFT calculations highlighted how alkylated γ-azPro derivatives are conformationally dynamic and adopt conformational preferences through ring pucker flip along with nitrogen inversion. Lastly, incorporation of alkylated γ-azPro into collagen peptides produced functionalized pH-responsive triple helices with similar thermal stabilities, regardless of their placement in the Xaa or Yaa position within the characteristic Xaa-Yaa-Gly repeating unit of collagen peptides.     

Catalytic Mechanism of Fatty Acid Photodecarboxylase: On the Detection and Stability of the Initial Carbonyloxy Radical Intermediate

In fatty acid photodecarboxylase (FAP), light-induced formation of the primary radical product RCOO⋅ from fatty acid RCOO⁻ occurs in 300 ps, upon which CO₂ is released quasi-immediately. Based on the hypothesis that aliphatic RCOO⋅ (spectroscopically uncharacterized because unstable) absorbs in the red similarly to aromatic carbonyloxy radicals such as 2,6-dichlorobenzoyloxy radical (DCB⋅), much longer-lived linear RCOO⋅ has been suggested recently. We performed quantum chemical reaction pathway and spectral calculations. These calculations are in line with the experimental DCB⋅ decarboxylation dynamics and spectral properties and show that in contrast to DCB⋅, aliphatic RCOO⋅ radicals a) decarboxylate with a very low energetic barrier and on the timescale of a few ps and b) exhibit little red absorption. A time-resolved infrared spectroscopy experiment confirms very rapid, ≪300 ps RCOO⋅ decarboxylation in FAP. We argue that this property is required for the observed high quantum yield of hydrocarbons formation by FAP.     

Transitional Metal/Chalcogen Dependant Interactions of Hairpin DNA with Transition Metal Dichalcogenides,MX2

Owing to the attractive properties that transition metal dichalcogenides (TMDs) display, they have found recent application in the fabrication of biosensing devices. These devices involve the immobilization of a recognition element such as DNA onto the surface of TMDs. Therefore, it is imperative to examine the interactions between TMDs and DNA. Herein, we explore the effect of different transition metals (Mo and W) and chalcogens (S and Se) on the interactions between hairpin DNA and TMDs of both bulk and t‐BuLi exfoliated forms. We discovered that the interactions are strongly dependent on the metal/chalcogen composition in TMDs.     

Adaptive estimation for stochastic damping Hamiltonian systems under partial observation

The paper considers a process $Z_t=(X_t,Y_t)$ where $X_t$ is the position of a particle and $Y_t$ its velocity, driven by a hypoelliptic bi-dimensional stochastic differential equation. Under adequate conditions, the process is stationary and geometrically $\beta$-mixing. In this context, we propose an adaptive non-parametric kernel estimator of the stationary density $p$ of $Z$, based on $n$ discrete time observations with time step $\delta$. Two observation schemes are considered: in the first one, $Z$ is the observed process, in the second one, only $X$ is measured. Estimators are proposed in both settings and upper risk bounds of the mean integrated squared error (MISE) are proved and discussed in each case, the second one being more difficult than the first one. We propose a data driven bandwidth selection procedure based on the Goldenshluger and Lespki (2011) method. In both cases of complete and partial observations, we can prove a bound on the MISE asserting the adaptivity of the estimator. In practice, we take advantage of a very recent improvement of the Goldenshluger and Lespki (2011) method provided by Lacour et al. (2016), which is computationally efficient and easy to calibrate. We obtain convincing simulation results in both observation contexts.     

Biorecognition on Graphene: Physical,Covalent, and Affinity Immobilization Methods Exhibiting Dramatic Differences

The preparation of biorecognition layers on the surface of a sensing platform is a very crucial step for the development of sensitive and selective biosensors. Different protocols have been used thus far for the immobilization of biomolecules onto various electrode surfaces. In this work, we investigate how the protocol followed for the immobilization of a DNA aptamer affects the performance of the fabricated thrombin aptasensor. Specifically, the differences in selectivity and optimum amount of immobilized aptamer of the fabricated aptasensors adopting either physical, covalent, or affinity immobilization were compared. It was discovered that while all three methods of immobilization uniformly show a similar optimum amount of immobilized aptamer, physical, and covalent immobilization methods exhibit higher selectivity than affinity immobilization. Hence, it is believed that our findings are very important in order to optimize and improve the performance of graphene‐based aptasensors.     

MLCT excited states in Ru(II) complexes: Reactivity and related two-photon absorption applications in the near-infrared spectral range

This short review provides a concise summary of the current state of research on the population by two-photon absorption of the triplet metal-to-ligand ³MLCT excited state of ruthenium(II) complexes. Several effective and potential applications of this nonlinear optics phenomenon (optical power limiting in the near infrared, biological imagery and photodynamic therapy, PDT) and related linear effects will also be presented.     

Effect of microemulsion component purity on the chromatographic figures of merit in chiral microemulsion electrokinetic chromatography

Numerous combinations of one-, two-, and three-chiral-component microemulsions have been previously prepared in our group, using N-dodecoxycarbonylvaline (DDCV), 2-hexanol, and ethyl acetate, dibutyl tartrate, or diethyl tartrate. A few results of the various formulations investigated suggested the possible presence of minor impurities in one or more components of the microemulsion. In this study, the purity of the current lots of R- and S-surfactant were measured, as was the subsequent effect of minor impurities on the relevant chromatographic figures of merit (CFOMs) that describe a chiral separation, i.e., efficiency, enantioselectivity, retention, migration window (elution range), and resolution. Two related methods are proposed for correcting enantioselectivities measured in the presence of chiral impurities in the chiral microemulsion.     

Synthesis of Polycyclic Aromatic Hydrocarbon‐Based Nanovehicles Equipped with Triptycene Wheels

Two new nanovehicles that have extended aromatic platforms as the cargo zones have been obtained. Two strategies were considered for the formation of the perylene core from two naphthalene precursors. The first was based on a Scholl‐type reaction involving an oxidant, and the second used a brominated derivative to perform a homocoupling reaction. The first strategy failed under diverse coupling conditions in the presence of several strong oxidants. Nevertheless, the use of CoF₃ in trifluoroacetic acid triggered a dimerization reaction between two ester groups of one molecule and the naphthalene unit of another, thereby surprisingly yielding a ten‐membered carbon macrocycle. The second strategy encountered a lack of reactivity of the substrate under several homocoupling conditions. The dimerization was not easily performed but Ullmann‐type conditions ultimately gave the expected product. The low yield and low solubility of the product encouraged us to modify our initial design. The synthesis of a new chassis that incorporated additional tert‐butyl groups improved the solubility of the molecules and also prevented overcyclization of the aromatic platform by blocking these positions. Some p‐phenylene spacers were also intercalated between the iodine and perylene centers to increase the reactivity of the halide towards coupling reactions. Two new chassis were obtained by Scholl‐type oxidative coupling using FeCl₃ as the oxidant. The introduction of four triptycene wheels allowed the formation of the two corresponding nanovehicles.