Multimeric Presentation of RGD Peptidomimetics Enhances Integrin Binding and Tumor Cell Uptake

The use of multimeric ligands is considered as a promising strategy to improve tumor targeting for diagnosis and therapy. Herein, tetrameric RGD (Arg-Gly-Asp) peptidomimetics were designed to target α_vβ₃ integrin-expressing tumor cells. These compounds were prepared by an oxime chemoselective assembly of cyclo(DKP-RGD) ligands and a cyclodecapeptide scaffold, which allows a tetrameric presentation. The resulting tetrameric RGD peptidomimetics were shown to improve α_vβ₃ integrin binding compared with the monomeric form. Interestingly, these compounds were also able to enhance tumor cell endocytosis in the same way as tetrameric RGD peptides. Altogether, the results show the potential of the tetrameric cyclo(DKP-RGD) ligands for in vivo imaging and drug delivery.     

Reaction of neptunyl ions with mycobactin S in nonaqueous medium

Addition of solutions of mycobactin S in acetone or methanol/acetone mixtures to solutions of NpO ₂ ²⁺ in the same solvent leads to the immediate reduction of neptunium/VI/ to neptunium/V/. Np/V/ interacts with the ionophore to form a yellow complex with a cation: ligand ratio of 21. The course of these reactions is followed by measurement of changes in characteristic optical absorption and by spectrophotometric titration within the range 700–1350 nm.     

Direct Synthesis of Carbamoyl Fluorides by CO2 Deoxyfluorination

Herein, a new concept for the direct synthesis of carbamoyl fluoride derivatives is disclosed. The developed method makes use of CO₂ as an inexpensive and abundant C₁ source; a variety of amines were successfully converted in the presence of a deoxyfluorinating reagent. The corresponding products were often obtained in excellent yields under mild reaction conditions (1 atm and room temperature). The reaction was easily scaled up, demonstrating the efficiency of the developed process.     

Thermal behaviour of melamine-modified urea–formaldehyde resins

Thermal behaviour of industrial UF resins modified by low level of melamine was followed by TG-DTA technique on the labsys ^TM instrument Setaram together with the ¹³C NMR analysis of resin structure and testing boards in current production at Estonian particleboard factory Pärnu Plaaditehas AS. DTA curve of UF resin which has been cocondensed during synthesis with even low level of melamine shows the shift of condensation exotherm and water evaporation endotherm to considerable higher temperatures. The effect of melamine monomer introduced to UF resin just before curing was compared. The effect of addition of urea as formaldehyde scavenger was studied.     

Speciation of Fe(II) and Fe(III) effect on CaCO3 crystallization

The present work was carried out to investigate separately the effect of Fe²⁺ and Fe³⁺ on the precipitation kinetics and the microstructure of CaCO₃. For this an experimental procedure was proposed. Precipitation tests were made by using the dissolved‐CO₂ degassing method. Both air and nitrogen were employed to strip the CO₂ from a Ca(HCO₃)₂ solution initially rich in this gas. At anoxic medium, it was shown that iron (II) prolongs the nucleation step and decelerates the crystalline growth rate. X‐ray diffraction analysis shows that its presence inhibits calcite and promotes aragonite variety. By using air, the reaction medium is rich in oxygen and iron (II) is rapidly oxidized. Seeing the higher solution pH (> 6.5), iron hydroxide forms before the onset of CaCO₃ precipitation and plays a role of seed permitting to initiate CaCO₃ nucleation. So, contrary to the observed effect of iron (II), the presence of iron (III) accelerates the precipitation rate of CaCO₃. As for iron (II), iron (III) inhibits calcite formation but favored the vaterite variety instead of the aragonite one.     

ON PSEUDOSYMMETRY TYPE HYPERSURFACES OF SEMI-EUCLIDEAN SPACES I

In this paper the authors investigate hypersurfaces M of a semi-Euclidean space Esn+1, n > 4, satisfying (aC + BR) ?H = LkQ(g, Hk), k = 1,2, 3. Using obtained results they show additional curvature properties of investigated hypersurfaces.     

Unprecedented stereoselective synthesis of 3-methylisoxazolidine-5-aryl-1,2,4-oxadiazoles via 1,3-dipolar cycloaddition and study of their in vitro antioxidant activity

The stereoselective 1,3-dipolar cycloaddition between allyl cyanide and a menthone-derived nitrone led to the desired isoxazolidine in good yield. Once the nitrile group transformed to an amidoxime group, the cyclocondensation of various aldehydes with chiral amidoxime led to unprecedented enantiopure 3-methylisoxazolidine-5-aryl-1,2,4-oxadiazoles. The menthone chiral auxiliary was then removed with acid hydrolysis. The new compounds were also screened for their in vitro antioxidant activity using DPPH and FRAP assays. Some of the compounds showed promising antioxidant activity.     

Electrochemical impedance probing of DNA hybridisation on oligonucleotide-functionalised polypyrrole

We report a new approach for detecting DNA hybridisation using non faradaic electrochemical impedance spectroscopy. The technique was applied to a system of DNA probes bearing amine groups that are immobilized by covalent grafting on a supporting polypyrrole matrix functionalised with activated ester groups.The kinetics of the attachment of the ss-DNA probe was monitored using the temporal evolution of the open circuit potential (OCP). This measurement allows the determination of the time necessary for the chemical reaction of ss-DNA probe into the polypyrrole backbone.The hybridisation reactions with the DNA complementary target and non complementary target were investigated by non faradaic electrochemical impedance spectroscopy. Results show a significant modification in the Nyquist plot upon addition of the complementary target whereas, in presence of the non complementary target, the Nyquist plot is not modified. The spectra, in the form of Nyquist plot, were analysed with the Randles circuit. The transfer charge resistance R₂ shows a linear variation versus the complementary target concentration. Sensitivity and detection limit (0.2 nM) were determined and detection limit was lower of one order of magnitude than that obtained with the same system and measuring variation of the oxidation current at constant potential.     

Kinetics and mechanism of the 1,3-dipolar cycloaddition of phenyl azides to methyl 3-pyrrolidinoacrylate

Kinetics of cycloadditions of phenyl azides to methyl 3-pyrrolidinoacrylate (2) produced Hammett ? = 2.2. An E_a of 13.5 kcal mole ^?1 and Δ S^* of ?37.4 cal.K^?l mole^?1 were calculated for the cycloaddition of p-O₂NC₆H₄N₃ to 2. The cycloadditions are concerted, non-synchronous, and are controlled by LUMO (azide) - HOMO (dipolarophile) interactions.     

Submanifolds and their k-planar number

IfM is a submanifold of ⁿ the normal plane together with a tangent at a pointx M span an affine plane which intersectsM, locally, in a curve called the normal section. This paper introduces, for each integerk, a parameter called(k) which depends on the curvature and torsion of these normal sections. Results are obtained showing how these parameters for a product submanifold depend on the value of this parameter for the factor submanifolds.The first author is supported by Uludag University in TURKEY