Mihaela Matache

Spectroscopic investigations of the binding interaction of a new indanedione derivative with human and bovine serum albumins.

Binding of a newly synthesized indanedione derivative, 2-(2-hydroxy-3-ethoxybenzylidene)-1,3-indanedione (HEBID), to human and bovine serum albumins (HSA and BSA), under simulated physiological conditions was monitored by fluorescence spectroscopy. The binding parameters (binding constants and number of binding sites) and quenching constants were determined according to literature models. The quenching mechanism was assigned to a Förster non-radiative energy transfer due to the HEBID-SA complex formation. A slightly increased affinity of HEBID for HSA was found, while the number of binding sites is approximately one for both albumins. The molecular distance between donor (albumin) and acceptor (HEBID) and the energy transfer efficiency were estimated, in the view of Förster’s theory. The effect of HEBID on the protein conformation was investigated using circular dichroism and synchronous fluorescence spectroscopies. The results revealed partial unfolding in the albumins upon interaction, as well as changes in the local polarity around the tryptophan residues.

1,3,4-Oxadiazoles as luminescent materials for organic light emitting diodes via cross-coupling reactions

Highly efficient materials for the fabrication of OLEDs have been extensively investigated in terms of properties and convenient synthetic procedures. 2,5-Diaryl-1,3,4-oxadiazoles were found to display suitable structural features in order to act as good electron-transporters, and numerous research groups have focused on the synthesis of various small-molecules and polymers bearing this heterocyclic moiety. Characterisation of their optical and electronic properties indicated the oxadiazole derivatives as good candidates for the fabrication of electroluminescent devices. Chemical synthesis of compounds containing a variety of heterocyclic cores and functional organic groups has witnessed a tremendous evolution concomitant with the development of metal-catalysed cross-coupling reactions. This new approach to create molecular diversity was also observed in the field of oxadiazoles, in an attempt to prepare complex molecules whose structural particularities were able to furnish the properties required for the fabrication of functional materials. Herein, we describe a collection of literature studies that refer to 1,3,4-oxadiazole-based small-molecules and polymers that have found applications as materials for OLEDs, combined with their synthetic accesibility involving, as key step(s), cross-coupling reactions.

Protein-Inorganic Array Construction: Design and Synthesis of the Building Blocks

Herein we describe the design and synthesis of the first series of di-functional ligands for the directed construction of inorganic-protein frameworks. The synthesized ligands are composed of a metal-ion binding moiety (terpyridine-based) conjugated to an epoxysuccinyl peptide, known to covalently bind active cysteine proteases through the active-site cysteine. We explore and optimize two different conjugation chemistries between the di-functionalized metal-ion ligand and the epoxysuccinyl-containing peptide moiety: peptide-bond formation (with limited success) and Cu(I)-catalysed click chemistry (with good results). Further, the complexation of the synthesized ligands with Fe(II) and Ni(II) ions is investigated: the di-functional ligands are confirmed to behave similarly to the parent terpyridine. As designed, the peptidic moiety does not interfere with the complexation reaction, in spite of the presence of two triazole rings that result from the click reaction. ES-MS together with NMR and UV/Vis studies establish the structure, the stoichiometry of the complexation reactions, as well as the conditions under which chemically sensitive peptide-containing polypyridine ligands can undergo the self-assembly process. These results establish the versatility of our approach and open the way to the synthesis of di-functional ligands containing more elaborated polypyridine ligands as well as affinity labels for different enzyme families. As such, this paper is the first step towards the construction of robust supramolecular species that cover a size-regime and organization level previously unexplored.

Glycine Fluoromethylketones as SENP‐Specific Activity Based Probes

We report here the synthesis and biochemical properties of a new peptidyl activity‐based probe 1 for SUMO proteases, SENPs. The activity‐based probe has at its C terminus a glycine‐derived fluoromethylketone moiety as a reactive group designed to target the active‐site cysteine of SENPs. Based on a study of the interactions between SENPs and SUMOs, we introduced further design elements that allow the activity‐based probe to selectively target SENPs at low micromolar to high nanomolar concentrations. Moreover, 1 out‐competes SUMO1 from the reversible SUMO1–SENP1 complex, thus suggesting that 1 and SUMO1 share a common binding site on SENP1.

Unexpected formation of N-(1-(2-aryl-hydrazono)isoindolin-2-yl)benzamides and their conversion into 1,2-(bis-1,3,4-oxadiazol-2-yl)benzenes.

Reaction between ortho-phthalaldehyde and various aroylhydrazines unexpectedly yields N-(1-(2-aryl-hydrazono)isoindolin-2-yl)benzamides as major products along with the predictable 1,2-bis-aroylhydrazones. NMR investigation of the major reaction products indicate the presence of a mixture of geometrical isomers, in various ratios. Single crystal X-ray diffraction confirms the proposed structure and indicates a Z configuration of the C═N double bond substitutents. Optimization of the condensation reaction conditions enabled quantitative isolation of the cyclic isomer. Oxidation of the isomers with bis(trifluoroacetoxy)iodobenzene (PIFA) leads to rapid formation of new highly fluorescent 1,2-bis(5-aryl-1,3,4-oxadiazol-2-yl)benzenes.

Seasonal variation in trace metals concentrations in the Ialomita River, Romania

Sampling streams for metals is an important aspect of water-quality monitoring. Using ICP-AES the concentration of some microelements in the Ialomiţa River (Romania) were determined. In order to grasp the different phases of the river regime, samples were collected from its water–sediment interface at seven locations along the river, during three campaigns: during snow melting periods in the mountain zones (April), the period of reduced flow and high water temperature (August) and the period of high precipitations (November). HNO3 was added to the samples for fixation. Cadmium and copper appear accidentally; lead was detected only in samples collected in the vicinity of roads; the MAC (maximum admitted concentration) for surface waters is exceeded for nickel and chromium in samples collected in April and respectively in April and November; zinc concentrations were usually above the MAC; molybdenum concentration was above the set reference value, especially for samples collected in April and November. Possible explanations are given for the presence of the investigated microelements along the river.

Metal Ion Mediated Self-Assembly Directed Formation of Protein Arrays

Self-assembled inorganic-protein arrays with well-defined and controllable size and structure were obtained through the Fe(II) complexation of protein-conjugated terpyridine units (ligand). The atom-level control of the ligand is obtained through residue-specific conjugation between the complexing unit (terpy) containing an activity-based probe and a corresponding active enzyme (papain). The Fe(II)-based self-assembly performed on this unique building block (ligand) leads to chemical species of unprecedented constitution. The first example presented herein opens the way to a shape and size regime usually reserved to polymers.

Kinetics of exothermal decomposition of some ketone-2,4-dinitrophenylhydrazones

In this study, the thermal stability and exothermal decomposition of some ketone-2,4-dinitrophenylhydrazones have investigated using the DSC technique. The synthesized and purified crystalline solids are thermally stable and start to decompose after melting. Non-isothermal DSC curves, recorded at several heating rates, were used to evaluate the melting properties and the kinetics of thermal decomposition. The isoconversional and model-fitting methods were applied to determine the activation parameters from the common analysis of multiple curves measured at different heating rates. Based on the results of the model—free method, a kinetic model was derived, and the kinetic parameters were obtained by means of a multivariate nonlinear regression. The results are discussed in relation to the effect of the ketone structure.

A general solid phase method for the synthesis of sequence independent peptidyl-fluoromethyl ketones.

We present here a new, general, solid phase strategy for the synthesis of sequence independent peptidyl-fluoromethyl ketones using standard Fmoc peptide chemistry. Our method is based on the synthesis of bifunctional linkers which allows the incorporation of amino acid fluoromethyl ketone unit at the C-terminal end of peptide sequences. Application of this approach for the synthesis of activity based probes for SENPs is also described.

Hyperaccummulation: A Key to Heavy Metal Bioremediation

As environmental issues become more and more stringent, the biotechnological approaches to maintain clean environments are receiving increasing attention. Heavy metal pollution is of great concern as it ultimately forces heavy metals into the food chain leading to serious ecological and health problems. Removal of excess heavy metals from contaminated sites could be achieved by means of organisms that bioaccumulate heavy metals without developing toxicity symptoms, features that are characteristic to hyperaccumulating plants. This review focuses on the applicability of hyperaccumulation phenomenon to heavy metal bioremediation as well as on the possibility to extend the hyperaccumulation concept to organisms other than plants.