Raman spectroscopy mapping of changes in the organization and relative quantities of cell wall polymers in bast fiber cell walls of flax plants exposed to gravitropic stress.

Flax is an important fiber crop that is subject to lodging. In order to gain more information about the potential role of the bast fiber cell wall in the return to the vertical position, 6-week-old flax plants were subjected to a long-term (6 week) gravitropic stress by stem tilting in an experimental set-up that excluded autotropism. Stress induced significant morphometric changes (lumen surface, lumen diameter, and cell wall thickness and lumen surface/total fiber surface ratio) in pulling- and opposite-side fibers compared to control fibers. Changes in the relative amounts and spatial distribution of cell wall polymers in flax bast fibers were determined by Raman vibrational spectroscopy. Following spectra acquisition, datasets (control, pulling- and opposite sides) were analyzed by principal component analysis, PC score imaging, and Raman chemical cartography of significant chemical bonds. Our results show that gravitropic stress induces discrete but significant changes in the composition and/or spatial organization of cellulose, hemicelluloses and lignin within the cell walls of both pulling side and opposite side fibers.

To What Extent Can Micro- and Macroplastics Be Trapped in Sedimentary Particles? A Case Study Investigating Dredged Sediments.

Plastic wastes and their fragments (microplastics, MPs < 5 mm) represent a global, persistent, and ubiquitous threat to ecosystems. Their sources, transfers, and fates are still poorly understood, especially in rivers. To fill this gap, sediments were collected from two dredging disposal sites along the Aa River (France). Four pits were dug, and triplicate samples were obtained at four depths (down to 140 cm). The sediments were sieved to 5 mm to collect macroplastics (MaPs). MPs were separated from the sediment based on density using a NaI solution (1.6 g/mL). Suspected plastics were analyzed with Fourier transform infrared spectroscopy. The studied sediments were found to be widely contaminated with concentrations ranging from 0.97 to 77 MaPs/kg and from 0.78 to 2800 MPs/kg, which were 1-4 orders of magnitude lower than those in most polluted European riverbeds. The MaPs were principally polyethylene, polypropylene, polystyrene, and polyvinyl chloride films, whereas the MPs were mainly polyamide and polyester fibers. The plastic concentrations and features of the two sites, which were filled at two different times, differed. Several factors occurring before and after dredging operations may explain these discrepancies. Nevertheless, no relationships with the sediment features were noted, and thus, one major driving force could not be identified. At the site scale, more than 1 ton of plastic could be stored. In conclusion, this study highlights the importance of dredged sediments for past plastic pollution studies and global plastic budget estimations.

Investigation of secondary structure evolution of micellar casein powder upon aging by FTIR and SRCD: consequences on solubility.

BACKGROUND: Synchrotron radiation circular dichroism (SRCD) and Fourier transform infrared (FTIR) spectroscopy were used to examine the conformation evolution of micellar casein (MC) powder during storage and to determine whether the spectral changes could be related to their solubility evolution. RESULTS: A loss in intensity of SRCD spectra as a function of storage time has been observed. Quantification of secondary structures revealed losses of α-helix content during storage. Moreover, a redshift of the amide I band in the FTIR spectrum was demonstrated during the storage and was interpreted as a rearrangement of the secondary structure of the protein, which is in line with the SRCD results. The qualitative results obtained by FTIR clearly support the quantitative evolution of the secondary structure obtained by the analysis of SRCD spectra. Principal component analysis (PCA) of FTIR spectra permits a good separation of samples according to the storage time. PCA shows that the evolution of secondary structures and solubility loss are closely linked. CONCLUSION: With the quantitative data provided by SRCD spectra, it was established that, whatever the storage conditions, a unique curve exists between loss of α-helix content and loss in solubility, showing that loss of α-helix content is a marker of solubility loss for the MC powders studied. © 2017 Society of Chemical Industry.

A Cell Wall Proteome and Targeted Cell Wall Analyses Provide Novel Information on Hemicellulose Metabolism in Flax.

Experimentally-generated (nanoLC-MS/MS) proteomic analyses of four different flax organs/tissues (inner-stem, outer-stem, leaves and roots) enriched in proteins from 3 different sub-compartments (soluble-, membrane-, and cell wall-proteins) was combined with publically available data on flax seed and whole-stem proteins to generate a flax protein database containing 2996 nonredundant total proteins. Subsequent multiple analyses (MapMan, CAZy, WallProtDB and expert curation) of this database were then used to identify a flax cell wall proteome consisting of 456 nonredundant proteins localized in the cell wall and/or associated with cell wall biosynthesis, remodeling and other cell wall related processes. Examination of the proteins present in different flax organs/tissues provided a detailed overview of cell wall metabolism and highlighted the importance of hemicellulose and pectin remodeling in stem tissues. Phylogenetic analyses of proteins in the cell wall proteome revealed an important paralogy in the class IIIA xyloglucan endo-transglycosylase/hydrolase (XTH) family associated with xyloglucan endo-hydrolase activity.Immunolocalisation, FT-IR microspectroscopy, and enzymatic fingerprinting indicated that flax fiber primary/S1 cell walls contained xyloglucans with typical substituted side chains as well as glucuronoxylans in much lower quantities. These results suggest a likely central role of xyloglucans and endotransglucosylase/hydrolase activity in flax fiber formation and cell wall remodeling processes.

Investigation of new alkali bismuth oxosulfates and oxophosphates with original topologies of oxo-centered units.

Two new alkali bismuth oxosulfates, [Bi12O15]Li2(SO4)4 (I) and [Bi7K2O8]K(SO4)4 (II), have been synthesized by heating a mixture of Bi2O3, CuSO45H2O, and A2CO3 (A = Li, K), and characterized by single crystal XRD, transmission electron microscopy, and multiphoton SHG and IR spectroscopy. In the above formula the [BixOy] subunits denote the 3D-porous (I) or 1D-columnar (II) polycationic host-lattice formed of edge-sharing OBi4 or O(Bi,K)4 oxocenterd tetrahedra. The SO4(2-) groups and alkali ions are arranged into channels in the interstices leading to original opened crystal structures for these two first reported alkali oxo-bismuth sulfates. The strong adaptability of the oxocentered framework is demonstrated by the possibility of preparing single crystals of [Bi8.73K0.27O8]K1.54(PO4)4 (III) whose crystal structure is similar to those of II with disorder between OBi4 and O(Bi3,K) tetrahedra and different channel occupancy due to the aliovalent replacement of SO4(2-) for PO4(3-).

Inhomogeneous distribution in methanol/acetone mixture: vibrational and NMR spectroscopy analysis.

The main aim of this paper is to quantify the inhomogeneous distribution of the components of acetone/methanol mixture and to give detailed insight into the interplay between the dipole-dipole and hydrogen bonding interactions inducing this inhomogeneity. To this end, we used the concept of infrared excess molar absorption of a given vibrational mode as an observable which contains all the information on the collective interactions in the mixture. Indeed, the changes in the infrared excess molar absorption may be associated with the inhomogeneous distribution (clustering, self-association, or high-density domains) of the components and consequently with the interaction between the two components of the mixture. The results show that acetone molecules are not homogeneously distributed in the mixture, particularly in the mole fraction range of acetone between 0.05 and 0.55. The spectral signature of this inhomogeneity is associated with the appearance of a shoulder in the C═O and C-C stretching vibrational profiles of acetone. This inhomogeneity is driven by the prevalence of the dipole-dipole interactions over those of hydrogen bonding between acetone and methanol molecules. The inhomogeneous distribution of methanol molecules is found to occur in the mole fraction range of acetone between 0.55 and 1. In this case, the hydrogen bond interactions between methanol molecules prevail over those between methanol and acetone. However, the extent of this inhomogeneity is small compared with that of acetone in the low mole fraction range. The spectral signature of this inhomogeneity is not visible in the O-H stretching vibrational mode; however, a second peak appears as a shoulder of the C-O stretching vibrational mode in this range of acetone mole fraction.