Radical reduction of aromatic azides to amines with tributylgermanium hydride

[reaction: see text] Aromatic azides are inert toward tributylgermanium hydride under thermal conditions in the absence and in the presence of a radical initiator but in the presence of catalytic amounts of benzenethiol undergo fast reaction, yielding reduced anilines and 2-germylated derivatives in high overall yields.     

On Neumann boundary control problem for ill-posed strongly nonlinear elliptic equation with p-Laplace operator and $$L^1$$L1-type of nonlinearity

Ricerche di Matematica - In this paper we study an optimal control problem for the mixed Dirichlet–Neumann boundary value problem for the strongly non-linear elliptic equation with p-Laplace...     

Microfluidic biofunctionalisation protocols to form multi‐valent interactions for cell rolling and phenotype modification investigations

In this study, we propose a fast, simple method to biofunctionalise microfluidic systems for cellomic investigations based on micro‐fluidic protocols. Many available processes either require expensive and time‐consuming protocols or are incompatible with the fabrication of microfluidic systems. Our method differs from the existing since it is applicable to an assembled system, uses few microlitres of reagents and it is based on the use of microbeads. The microbeads have specific surface moieties to link the biomolecules and couple cell receptors. Furthermore, the microbeads serve as arm spacer and offer the benefit of the multi‐valent interaction. Microfluidics was adapted together with topology and biochemistry surface modifications to offer the microenvironment for cellomic studies. Based on this principle, we exploit the streptavidin–biotin interaction to couple antibodies to the biofunctionalised microfluidic environment within 5 h using 200 μL of reagents and biomolecules. We selected the antibodies able to form complexes with the MHC class I (MHC‐I) molecules present on the cell membrane and involved in the immune surveillance. To test the microfluidic system, tumour cell lines (RMA) were rolled across the coupled antibodies to recognise and strip MHC‐I molecules. As result, we show that cell rolling performed inside a microfluidic chamber functionalised with beads and the opportune antibody facilitate the removal of MHC class I molecules. We showed that the level of median fluorescent intensity of the MHC‐I molecules is 300 for cells treated in a not biofunctionalised surface. It decreased to 275 for cells treated in a flat biofunctionalised surface and to 250 for cells treated on a surface where biofunctionalised microbeads were immobilised. The cells with reduced expression of MHC‐I molecules showed, after cytotoxicity tests, susceptibility 3.5 times higher than normal cells.     

Synthesis and characterization of a colloidal novel folic acid?C??-cyclodextrin conjugate for targeted drug delivery

A novel folic acid?C??-cyclodextrin (??-CD) conjugate was synthesized and preliminarily characterized by ¹H NMR, ESI-MS, and MALDI-MS. ¹H NMR shows the presence of ??- and ??-conjugates which are generated by ??-CD linkage in turn with both carboxylic functions of folic acid. Moreover ROESY evidences supramolecular interactions between the benzene ring of the folic acid and the ??-CD cavity. DOSY suggests that ethylenediamine derived ??-CD?Cfolic acid forms a colloidal dispersion difficult to purify from free folic acid. An analysis of self-diffusion coefficient (D_s) of the three species (??-, ??-conjugates, and free folic acid) and relaxation times (T₁ and T₂) is reported to tentatively explain the colloidal behaviour of the new species in an aqueous solution.     

Toggling bistable atoms via mechanical switching of bond angle

We reversibly switch the state of a bistable atom by direct mechanical manipulation of bond angle using a dynamic force microscope. Individual buckled dimers at the Si(100) surface are flipped via the formation of a single covalent bond, actuating the smallest conceivable in-plane toggle switch (two atoms) via chemical force alone. The response of a given dimer to a flip event depends critically on both the local and nonlocal environment of the target atom-an important consideration for future atomic scale fabrication strategies.     

A three-factor Doehlert matrix design in optimising the determination of octadecyltrimethylammonium bromide by cation-exchange chromatography with suppressed conductivity detection

A simple and effective chromatographic method with suppressed conductivity detection was developed and validated to determine dissolved samples of octadecyltrimethylammonium bromide (C₁₈H₃₇N⁺Me₃Br⁻, ODTAB) for purity testing. A response surface methodology generated with a Doehlert matrix design was applied to optimize the chromatographic and detection conditions in ion-exchange chromatography (IEC) with conductivity detection in the chemical suppression mode. A three-factor Doehlert design was performed to fit a second-order model and jointly optimize the peak intensity and shorten analysis time through a global desirability function. Regenerant flow rate, volume fraction of acetonitrile in the acidic eluent and its flow rate were studied at seven, five and three levels, respectively. The optimized separation and detection conditions were accomplished by using a cation-exchange column eluted at 0.5 mL min⁻¹ with an isocratic mobile phase composed of CH₃CN and 25 mN H₂SO₄, 82/18 (v/v). Chemical suppression of ionic conductivity was performed by 100 mN tetrabutylammonium hydroxide (TBAOH) as a regenerant at a flow-rate of 4.0 mL min⁻¹. Remarkably good agreement was found between predicted and experimental values of signal intensity and chromatographic retention. With the developed method, a linear calibration curve of ODTA⁺ as bromide salt from 5 to 1000 ppm was obtained using hexadecyltrimethylammonium bromide as internal standard. The estimated limit of detection was 0.3 ppm (S/N = 3). The effectiveness of electrochemically suppressed conductivity detection of ODTA⁺ was also demonstrated, thus making easier the whole detection operation and instrumental needs as well.     

Harnessing the ortho‐Directing Ability of the Azetidine Ring for the Regioselective and Exhaustive Functionalization of Arenes

This work demonstrates how the directing ability of the azetidine ring could be useful for regioselective ortho‐C?H functionalization of aryl compounds. Robust polar organometallic (lithiated) intermediates are involved in this synthetic strategy. The reagent n‐hexyllithium emerged as a safer, yet still effective, basic reagent for the hydrogen/lithium permutation relative to the widely used reagent nBuLi. Two different reaction protocols were discovered for regioselective lithiation at the ortho positions adjacent to the azetidine ring, which served as a toolbox when other competing directing groups were installed on the aromatic ring. The coordinating ability of the azetidine nitrogen atom, as well as the involvement of dynamic phenomena related to the preferential conformations of 2‐arylazetidine derivatives, were recognized to be responsible for the observed reactivity and regioselectivity. A site‐selective functionalization of the aromatic ring was achieved for aryl azetidines with either coordinatively competent groups (e.g. methoxy) or inductively electron‐withdrawing substituents (e.g. chlorine and fluorine). By fine‐tuning the reaction conditions, regioselective introduction of several substituents on the aromatic ring could be realized. Several substitution patterns were accomplished, which included 1,2,3‐trisubstitution, 1,2,3,4‐tetrasubstitution, and 1,2,3,4,5‐pentasubstitution, up to the exhaustive substitution of the aromatic ring.     

Minima of some non convex non coercive problems

We give here an existence result of minimizers for a class of one dimensional integrals of the Calculus of Variations with non convex, non coercive integrands.This work was performed as part of a national research project supported by M.U.R.S.T. (40%).Authors are members of G.N.A.F.A., C.N.R.     

Problemi quasi ellittici nel semispazio

This paper is concerned with quasi elliptic boundary value problems in a half space. They are investigated within suitable Sobolev weight spaces which have been studied by the author in [12].