Analysis of type I and IV collagens by FT-IR spectroscopy and imaging for a molecular investigation of skeletal muscle connective tissue

Many muscular diseases result from abnormal organization of connective tissue and/or collagen network formation. Only a few molecular imaging techniques are able to analyze this collagen network by differentiating collagen types. In this study, FT-IR spectroscopy was used to analyze type I and IV collagens, the most important compounds of which are perimysium and endomysium, respectively. Secondary structure of collagen types was determined by curve-fitting the 1,700–1,480 cm⁻¹ spectral interval. Type I collagen could be differentiated from type IV by its higher amounts of triple helix and α-helix, but lower amounts of β-sheets (P < 0.01). FT-IR imaging was then used to determine structural features of perimysium and endomysium collagen network in bovine Flexor carpi radialis muscle. Secondary structure of proteins contained in perimysium and endomysium was found to be very close to type I and IV collagens, respectively. FT-IR spectroscopy and imaging are thus analytical tools that might be used for investigating biodistribution and assembly of collagen types in connective tissues. Figure Visible (left) and full spectral FT-IR (right) images of skeletal muscle tissue section (16 μm) exhibiting a vertical arrangement of fibers. + and × in FT-IR image show selected positions to obtain FT-IR spectra of perimysium and endomysium, respectively     

Synthesis, structural studies, theoretical calculations, and linear and nonlinear optical properties of terpyridyl lanthanide complexes: new evidence for the contribution of f electrons to the NLO activity

The synthesis and structural, photophysical, and second-order nonlinear optical (NLO) properties of a novel lanthanide terpyridyl-like complex family LLn(NO(3))(3) (Ln = La, Gd, Dy, Yb, and Y) are reported. The isostructural character of this series in solution and in the solid state has been established on the basis of X-ray diffraction analysis in the cases of yttrium and gadolinium complexes, theoretical optimization of geometry (DFT), and NMR spectroscopy. The absorption, emission, and solvatochromic properties of the free terpyridyl-like ligand L were thoroughly investigated, and the twist intramolecular charge transfer (TICT) character of the lowest energy transition was confirmed by theoretical calculation (TDDFT and CIS). The similar ionochromic effect of the different lanthanide ions was evidenced by the similar UV-visible spectra of the complete family of complexes. On the other hand, the quadratic hyperpolarizability coefficient beta, measured by the harmonic light scattering (HLS) technique, is clearly dependent on the nature of the metal, and a careful examination of the particular case of yttrium unambiguously confirms the contribution of metal f electrons to the NLO activity.     

2D supramolecular assemblies of benzene-1,3,5-triyl-tribenzoic acid: temperature-induced phase transformations and hierarchical organization with macrocyclic molecules

Two-dimensional supramolecular honeycomb networks with cavities of an internal diameter of 2.95 nm were formed by the self-assembly of 4,4',4' '-benzene-1,3,5-triyl-tribenzoic acid (BTA) on a Ag(111) surface at room temperature. Annealing to higher temperatures resulted in two sequential phase transformations into closer-packed supramolecular arrangements. The phase transformations are associated with stepwise deprotonation of the carboxylic acid groups. The voids of the honeycomb network of BTA have a suitable size for the construction of hierarchical structures with guest molecules. Single molecules of the macrocyclic compound mt-33 were successfully confined inside 2D nanocavities of the honeycomb networks and released when the phase was transformed to the close-packed structure.     

Shallow water equations for power law and Bingham fluids

In this note,we provide a consistant thin layer theory for power law and Bingham incompressible fluids flowing down an inclined plane under the effect of gravity.The derivation of such equations is based on formal asymptotic expansions of solutions of Cauchy momentum equations in the shallow water scaling and in the neighbourhood of steady solutions so that we can close the average equations on the fluid height h and the total discharge rate q.     

Ground state of the quasi-1D correlated electronic system BaVS3

In this paper we review the salient features of the different instabilities exhibited by the quasi-1D system BaVS₃ and show that there is a subtle interplay between the different phases stabilized. The analysis of the Peierls instability shows that the mobile dz² electrons are more localized than calculated because of their strong correlation with the localized e(t_2g) electrons. The complex AF magnetic structure of BaVS₃ incorporates the magnetization of the e(t_2g) electrons with the Peierls pairing of the dz² electrons into magnetic singlets. Finally, we propose that the zig-zag disorder remaining after an incomplete orthorhombic phase transition could change the sign of the magnetic coupling and thus help to stabilize the canted ferromagnetism observed in non stoichiometric BaVS_3−δ and Sr and Ba substituted compounds.     

QUantitative Cross-Polarization at magic-angle spinning frequency of about 20 kHz

We study the QUantitative Cross-Polarization (QU-CP) method proposed by Hou et al. (Chem. Phys. Lett. 421 (2006) 356) under the moderate MAS speed of 23 kHz, re-examining its two building blocks, namely, the CP polarization transfer from (1)H to (13)C, and the thermal equalization of the (13)C magnetizations. We show that the nuclear-integrated cross-polarization (NI-CP) scheme is conveniently used for (1)H-(13)C polarization transfer, because of its simplicity, robustness to rf-mismatch, and compatibility with fast sample spinning. In the mixing part, in addition to dipolar-assisted rotational-resonance (DARR) recoupling, we examine the Phase-Alternated Recoupling Irradiation Schemes (PARIS and PARIS(xy)), and Second-order Hamiltonian among Analogous Nuclei Generated by Hetero-nuclear Assistance Irradiation (SHANGHAI) sequences, and show that SHANGHAI gives the best performances in equalizing the (13)C magnetizations.     

Structure determination from powder diffraction data and thermal behaviour of layered lead nitrate oxalate hydrate, Pb2(NO3)2(C2O4).2H2O

The mixed lead nitrate oxalate, Pb₂(NO₃)₂(C₂O₄).2H₂O, has been obtained in a polycrystalline form in the course of a study on precursors of nanocrystalline PZT-type oxides. Its crystal structure has been solved from powder diffraction data collected using a monochromatic radiation from a conventional X-ray source. The symmetry is monoclinic, space group P2₁/c (No. 14), the cell dimensions are a=10.623(2) Å, b=7.9559(9) Å, c=6.1932(5) Å, β=104.49(1)° and Z=4. The structure consists of a stacking of complex double sheets parallel to (1 0 0), forming layers held together by hydrogen bonds. The sheets result from the condensation of PbO₁₀ polyhedra, in which the oxalate and nitrate groups, as well as water molecules, play a major role. The structure is discussed in terms of Pb---O distances, polyhedra shape and lead coordination, with emphasis on the dimensional polymerisation role of water molecules. The thermal behaviour of this layered compound is carefully described from temperature-dependent powder diffraction and thermogravimetric measurements. The enthalpy, Δ_rH=232(3) kJ mol⁻¹, and entropy, Δ_rS=532(8) J K⁻¹ mol⁻¹, of the dehydration reaction have been determined. The high value of Δ_rH demonstrates that the water molecules are strongly bonded in the structure. The complex decomposition proceeds through the crystallisation and decomposition of Pb(NO₃)₂(C₂O₄) into Pb(NO₃)₂ and PbC₂O₄, and, finally, various lead oxides.     

Influence of ultrashort laser pulse duration on the X-ray emission spectrum of plasma produced in cluster target

Line emission spectrum of a laser plasma produced in an argon cluster jet target was measured on the n ¹ P1?1¹ S ₀ (n=5–9) transitions of the helium-like Ar XVII ion for a pulse duration varying from 45 fs to 1.1 ps and a constant fluence of ～10⁵ J/cm². The independent modeling of the relative intensities of the transitions from the n=5,..., 10 levels, as well as of the 2¹ P ₁? 1² S ₀ and 2³ P ₁?1² S ₀ lines and dielectronic satellites indicates that the electron temperature is anomalously low and that the electron density in emitting plasma increases with shortening the laser pulse. The excitation from the ground state by a small fraction of hot electrons is expected to be the main channel of populating the Ar XVII levels.     

Rational interpolation through the optimal attachment of poles to the interpolating polynomial

After recalling some pitfalls of polynomial interpolation (in particular, slopes limited by Markov's inequality) and rational interpolation (e.g., unattainable points, poles in the interpolation interval, erratic behavior of the error for small numbers of nodes), we suggest an alternative for the case when the function to be interpolated is known everywhere, not just at the nodes. The method consists in replacing the interpolating polynomial with a rational interpolant whose poles are all prescribed, written in its barycentric form as in [4], and optimizing the placement of the poles in such a way as to minimize a chosen norm of the error. This revised version was published online in June 2006 with corrections to the Cover Date.