Modifying LnHPDO3A Chelates for Improved T1 and CEST MRI Applications

The new ligand HPDO3MA [(R,R,R,R)-10-(2-hydroxypropyl)-α,α′,α′′-trimethyl-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid] was designed to combine and optimize the chemical properties of the macrocyclic ligands HPDO3A and DOTMA. The presence of the methyl groups on the acetic pendant arms of HPDO3A is expected to rigidify the structure of the ligand and favor an increase of the kinetic inertness of the Ln complexes. ¹H NMR spectra of Eu(HPDO3MA) displayed the presence of two pairs of diastereoisomers: SAP (square antiprismatic) and TSAP (twisted square antiprismatic) isomers (56 and 44 %, respectively). In addition, ¹H and ¹⁷O relaxometric NMR studies of Gd(HPDO3MA) showed approximately a 10 % increase in relaxivity and a faster water exchange rate with respect to Gd(HPDO3A). Moreover, a detailed chemical exchange saturation transfer (CEST) characterization of Yb(HPDO3MA) displayed a sensitivity about two times larger than that of Yb(HPDO3A) both in phantom and in cell labeling experiments. Finally, the kinetic inertness of Yb(HPDO3MA) was measured to be twice as high as that of Yb(HPDO3A), with a dissociation half-life at physiological pH of about 2500 years.     

Quaternary ammonium compounds in roots and leaves of Capparis spinosa L. from Saudi Arabia and Italy: investigation by HPLC-MS and 1H NMR

Capparis spinosa L. is a perennial plant typical of the Mediterranean flora and a multipurpose plant used for curing various human ailments. Quaternary ammonium compounds (QACs), as constituents of Capparaceae, play important roles in protecting against abiotic stress. Aim of this work was to determine QACs in root and leaves of caper from two proveniences. The presence of stachydrine, choline, glycine betaine and homo-stachydrine has been confirmed by high resolution MS, while ¹H NMR was applied to quantify the main QACs in the aqueous extracts. Stachydrine was quantified at 20.2 mg/g and 32.3 mg/g on dry leaves from South of Italy and Saudi Arabia, respectively, while a minor content was in dry roots (from 10.4 to 12.5 mg/g). Choline was considerably lower both in leaves and roots (from 0.3 to 1.2 mg/g). To our knowledge, this is the first report on the determination of QACs both in root and leaves of C. spinosa.     

A novel statistical linearization solution for randomly excited coupled bending-torsional beams resting on non-linear supports

A novel statistical linearization technique is developed for computing stationary response statistics of randomly excited coupled bending-torsional beams resting on non-linear elastic supports. The key point of the proposed technique consists in representing the non-linear coupled response in terms of constrained linear modes. The resulting set of non-linear equations governing the modal amplitudes is then replaced by an equivalent linear one via a classical statistical error minimization procedure, which provides algebraic non-linear equations for the second-order statistics of the beam response, readily solved by a simple iterative scheme. Data from Monte Carlo simulations, generated by a pertinent boundary integral method in conjunction with a Newmark numerical integration scheme, are used as benchmark solutions to check accuracy and reliability of the proposed statistical linearization technique.

     

A finite-element-based coarse-grained model for global protein vibration

Meccanica - Protein mechanical vibrations play a pivotal role in biological activity. In particular, low-frequency (terahertz) modes are related to protein conformational changes, which represent...     

A Reader’s Comment on: “Hysteresis Model of Unconscious-Conscious Interconnection: Exploring Dynamics on m-Adic Trees”

p-Adic Numbers, Ultrametric Analysis and Applications - This comment is aimed to point out that the recent work due to H. Kim, J-Y. Moon, G. A. Mashour and U. Lee ([22]), in which the clinical and...     

To Sandwich Technetium: Highly Functionalized Bis-Arene Complexes [99mTc(η6-arene)2]+ Directly from Water and [99mTcO4]−

The labeling of (bio)molecules with metallic radionuclides such as ^99mTc demands conjugated, multidentate chelators. However, this is not always necessary since phenyl rings can directly serve as integrated, organometallic ligands. Bis-arene sandwich complexes are generally prepared by the Fischer–Hafner reaction. In extension of this, we show that [^99mTc(η⁶-C₆R₆)₂]⁺-type complexes are directly accessible from water and [^99mTcO₄]⁻, even using arenes incompatible with Fischer–Hafner conditions. To unambiguously confirm the nature of these unprecedented ^99mTc complexes, their rhenium homologous have been prepared by substituting naphthalene ligands in [Re(η⁶-C₁₀H₈)₂]⁺ with the corresponding phenyl groups. The ease with which highly stable [^99mTc(η⁶-C₆R₆)₂]⁺ complexes are formed under standard labeling conditions enables a multitude of new potential imaging agents based on commercial pharmaceuticals or lead structures.     

Maltodextrin as stabilizer for emulsion polymerization: Adsorption and grafting behavior

Emulsion polymerization of the three-monomer system butyl acrylate–styrene–methacrylic acid was performed in batch using a commercial maltodextrin derived from starch degradation as stabilizer. Stable latexes with narrow particle size distributions were obtained in all examined cases. A method was developed to analyze and quantify the partitioning of the maltodextrin between the continuous phase (supernatant) and the particle phase. Significant differences between the polysaccharides adsorbed onto particles with or without emulsion polymerization reaction were observed. The possible reactions of maltodextrin in presence of a radical initiator were studied in aqueous phase, thus confirming maltodextrin degradation. The formation of copolymers involving the original monomers and the stabilizer according to two different reactive pathways was also confirmed. In terms of adsorbed maltodextrin, two different contributions were observed: maltodextrin physically adsorbed and maltodextrin chemically grafted and/or physically incorporated into the polymer.     

Mechanosensitive membrane probes: push-pull papillons

ABSTRACT

Design, synthesis and evaluation of push-pull N,N′-diphenyl-dihydrodibenzo[a,c]phenazines are reported. Consistent with theoretical predictions, donors and acceptors attached to the bent mechanophore are shown to shift absorption maxima to either red or blue, depending on their positioning in the chromophore. Redshifted excitation of push-pull fluorophores is reflected in redshifted emission of both bent and planar excited states. The intensity ratios of the dual emission in more and less polar solvents imply that excited-state (ES) planarization decelerates with increasing fluorophore macrodipole, presumably due to attraction between the wings of closed papillons. ES planarization of highly polarisable papillons is not observed in lipid bilayer membranes. All push-pull papillon amphiphiles excel with aggregation-induced emission (AIE) from bent ES as micelles in water and mechanosensitivity in viscous solvents. They are not solvatochromic and only weakly fluorescent (QY < 4%).     

Singularity Formation in Fractional Burgers’ Equations

The formation of singularities in finite time in nonlocal Burgers’ equations, with time-fractional derivative, is studied in detail. The occurrence of finite-time singularity is proved, revealing the underlying mechanism, and precise estimates on the blowup time are provided. The employment of the present equation to model a problem arising in job market is also analyzed.