Do formalin fixation and freeze‐thaw affect near‐infrared Raman spectroscopy of cartilaginous tissue? A preliminary ex vivo analysis of native human articular cartilage

Near‐infrared (NIR) Raman microprobe spectroscopy has been applied to the non‐invasive characterization of the biochemical structure of extracellular matrix in articular cartilage, a step forward along the path of in vivo diagnostic application of chondropathy. In most studies handling ex vivo cartilage specimens, formalin fixation or freeze‐thaw treatments have been applied in order to stabilize tissue and cell constituents prior to spectroscopic measurements. However, these pre‐processing manipulations might significantly affect certain target bands of the cartilage spectra, thus introducing biases in the characterizations, and potentially leading to data misinterpretation. In this study, we evaluated how formalin fixing and freeze‐thaw processes affect Raman spectra from human femur cartilage. Healthy cartilage specimens were fixed/stored either in a 10% neutral buffered formalin solution or in a deep freezer set at −80 °C. The results of this study show that formalin fixation significantly affects the NIR Raman spectra of cartilage specimens due to concurrent formalin absorption and water dehydration within both collagen and glycosaminoglycan macromolecules. Water dehydration was also confirmed in the amide I structure in the frozen‐thawed specimen, but to a much lesser extent. Furthermore, soaking the tissues in phosphate‐buffered saline solution minimized the storage‐induced Raman artifacts, but its immersion had limited effectiveness in formalin‐fixed specimens, predominantly due to an overlap of signals from the formalin liquid (i.e. emitting at 1046 and 1492 cm⁻¹). Therefore, to provide a highly accurate biochemical evaluation of extracellular matrix using NIR Raman spectroscopy, freeze‐thaw processes are more suitable for ex vivo samples of human cartilage than formalin fixation. Copyright © 2015 John Wiley & Sons, Ltd.     

Asymmetric transfer hydrogenation in aqueous media catalyzed by resin-supported peptide having a polyleucine tether

A resin-supported N-terminal prolyl peptide having a β-turn motif and a polyleucine tether has been developed for the organocatalytic asymmetric transfer hydrogenation under aqueous conditions. Polyleucine accelerated the reaction in a highly enantioselective manner by providing a hydrophobic microenvironment around the prolyl residue. The investigation of catalyst structures indicates that the l-form of polyleucine is essential for both reaction efficiency and enantioselectivity.     

Determination of rare-earth elements in a limestone geological standard reference material by ICP-MS following solvent extraction.

Rare-earth elements in a limestone geological standard (JLs-1) were determined by inductively coupled plasma mass spectroscopy (ICP-MS) using phosphoric acid 2-ethylhexyl ester solvent extraction, which had been established for seawater analysis. First, the limestone sample was divided into two fractions: acetic acid soluble (carbonate fraction) and insoluble (residue). A modification of the method was undertaken to achieve quantitative recovery. With this method most of the REEs in the carbonate fraction were quantitatively recovered, except for the heaviest three REEs (Tm, Tb and Lu). The reason for the poor recoveries of the three elements was investigated, but still remained unclear. The mass-spectroscopic interference of BaO with Eu made an accurate determination of both lighter REEs and Eu at the same time impossible. The precision of this method was better than 20%. The data adopted after analytical consideration were consistent with those previously reported.     

Enhanced absorption and fluorescence efficiency of silylethynyl-functionalized oligothiophenes and thieno[3,2-b]thiopahene

Silylethynyl-substituted oligothiophenes and thieno[3,2-b]thiophene were synthesized by the Sonogashira coupling reaction. The absorption and fluorescence maxima of these compounds shifted to longer wavelength, and they exhibited higher absorption coefficients and quantum yields than the corresponding unsubstituted molecules and tert-butylethynyl derivatives. From the DFT calculation, the energy band gap between HOMO and LUMO decreases by the introduction of a silicon atom. Thus, silyl groups can play important role in enhancing the quantum efficiency and decreasing the band-gap of chromophores. Hence, Silylethynyl group can serve as a highly efficient auxiliary for use in optical devices.     

Assemblies of functional small-sized molecules having 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl responsive to heat and pH in water and their water proton relaxivities

1,3,5-Triureabenzene derivatives carrying alkyl (C(n)) and poly(ethylene glycol) (Eg(m)) chains C(n)Eg(3) (1, 2, and 3, n = 6, 7, and 8, respectively) and C(n)N(X)Eg(m) (4 and 5, X = M (methyl), n = 6 and 8, respectively, m = 3; 6 and 7, X = T (2,2,6,6-tetramethylpiperidine-1-oxyl, TEMPO), n = 6, m = 3 and 6, respectively) were prepared. All compounds in aqueous solutions exhibited the lower critical solution temperature (LCST) phenomena unique for small-sized molecules and formed self-assemblies above the transition temperature, T(t), of the LCST. Only compound 3 formed a hydrogel with a minimum gelation concentration of 0.5 mM (0.05 wt %). In 1.0 mM aqueous solution, the T(t) values were determined to be in the range of 12-40 °C. In addition, the T(t) values for 4-7 containing tertiary amine also responded to the solution pH with high sensitivity. The LCST behaviors for all compounds were reversible in the cycles of warming and cooling. The water proton relaxivities, r(1), for 6 and 7 carrying TEMPO were altered below and above T(t) and were largely reduced by the formation of self-assemblies above T(t). Compound 6 showed r(1) values at 25 °C of 0.92 and 0.23 mM(-1) s(-1) at pH 7.0 and 6.0, respectively. In transmission electron microscopy (TEM) images, globular particles with polydispersity were observed, and their average hydrodynamic diameters (D(H)) were determined to be in the range of 2400-730 nm by dynamic light scattering. In the TEM and scanning electron microscopy images of a xerogel sample of 3, bundles of fibers with a diameter of ca. 10 nm and a network structure, respectively, were observed.     

PdPt Nanocubes: A High‐Performance Catalyst for Hydrolytic Dehydrogenation of Ammonia Borane

An effective way to improve the catalytic activity of metal‐based nanostructured materials is to control the size, shape, or composition. Here, the bimetallic PdPt nanoparticles (NPs) show significant dependency on the shape for catalytic hydrolysis of ammonia borane. The catalytic activity of PdPt cubic nanoparticles (cNPs) is found to be the best compared with the activities of spherical nanoparticles (sNPs) of Pd, Pt, and PdPt and cNPs of Pd under the same reaction conditions. The turnover frequency (50.02 min^?1) of PdPt cNPs for ammonia borane hydrolysis is among the values of the most active catalysts. This high catalytic performance of PdPt cNPs encourages the approach of shape and composition control for various catalytic applications.     

Emission and transient absorption measurements of substitution effects of C–C triple bonds on relaxation processes of the fluorescent state of naphthalenes

Photophysical and photochemical properties of naphthalenes substituted with trimethylsilylethynyl, tert-butylethynyl, and trimethylsilylbutadiynyl groups were investigated by measurement of fluorescence yields, lifetimes, and triplet absorption. Introducing trimethylsilylethynyl and tert-butylethynyl groups to the 1-position of the naphthalene skeleton substantially enhanced fluorescence and intersystem crossing (ISC). The rates of fluorescence of 2-substituted naphthalenes were low. The effect of ethynyl groups on the 1-substituted naphthalenes was rationalized in terms of an increase of the transition moment along the short axis of the naphthalene skeleton. Substitution of the trimethylsilylbutadiynyl group at the 1 or 2-position of the naphthalene skeleton caused a considerable decrease in the fluorescence yield (approximately 0.01) and an increase in the ISC yield (0.99).     

Palladium(0)‐Mediated Rapid Methylation and Fluoromethylation on Carbon Frameworks by Reacting Methyl and Fluoromethyl Iodide with Aryl and Alkenyl Boronic Acid Esters: Useful for the Synthesis of [11C]CH3?C‐ and [18F]FCH2?C‐Containing PET Tracers (PET=Positron Emission Tomography)

A new synthetic methodology for the rapid methylation and fluoromethylation on aryl and alkenyl frameworks by using methyl and fluoromethyl iodide with an organoboronic acid ester has been developed under the simple and mild conditions of [Pd₂(dba)₃]/P(o‐CH₃C₆H₄)₃/K₂CO₃ (dba= dibenzylideneacetone) in DMF at 60 °C for 5 min (see scheme). This boron protocol provides a firm chemical basis for the synthesis of ¹¹C‐ and ¹⁸F‐incorporated PET tracers.

     

Proton-neutron correlations in nuclei with N = 30

Structure of the nuclei with N = 30 and Z = 20–28 is investigated by the nuclear shell model within the proton-neutron configurations (1f_{$\text{7}\text{2}$})^z?20_p × (2p_{$\text{3}\text{2}$}, 2p_{$\text{case1}\text{2}$}, 1f_{$\text{case5}\text{2}$})²_n. Effective proton-neutron interactions determined by a least-squares fit to the observed spectra of N = 29 nuclei are adopted. Agreement of the calculated spectra with experimental spectra is satisfactory. Strong correlations between protons and neutrons break down the pairing scheme and lower the first J = 2 levels in doubly even nuclei, which is shown from the resultant wave functions. A relation between the shell model and collective rotational model is discussed concerning the calculated rotation-like spectrum of ⁵⁶Fe. Electromagnetic properties and spectroscopic factors of single-nucleon transfer reactions are calculated. They are in good agreement with experiments.