Biomedical subjects

L Picton

Publications and source records attributed to L Picton.

6 recordsLinked to original sources

PubMed2005

Flax (Linum usitatissimum) seed cake: a potential source of high molecular weight arabinoxylans?

Water-soluble polysaccharides were extracted from flaxseed cake and analyzed. Two groups were separated by anion-exchange chromatography. The first one (nonretained) was the major fraction (83%) and possessed a high molecular weight (HMW) arabinoxylan (56%) with an Ara/Xyl ratio of 0.32 and an M(w) of 846 000. This polymer was accompanied by a smaller galactoglucan (44%), with an M(w) of 6.5 x 10(4). The latter group (17%), retained by the gel, was further described as a HMW pectin heterogeneous group, with, respectively, 3.1 x 10(5) and 1.3 x 10(5). Despite the presence of HMW arabinoxylans, the investigation of rheological flow sweep at the concentration of 2% (w/v) has shown a slight shear thinning behavior with a small zero-rate viscosity at 9.6 Pa.s.

Chromatography, Ion Exchange↗

PubMed2005

Structural investigations of the neutral polysaccharide of Linum usitatissimum L. seeds mucilage.

The heterogeneity of the purified water-soluble neutral fraction coming from the mucilage extract of the yellow flaxseed was investigated. After fractionation by size-exclusion chromatography, the analyse of the neutral monosaccharides composition showed a mixture of three major families of polymers. They were all identified as arabinoxylans with a constant A/X ratio of 0.24, but varying in their galactose and fucose residues in the side chains. Furthermore, the molecular weight (M(w)) analysis acquired by multi-angle laser light scattered, revealed the association of two high M(w) polymers [5.7x10(6) (11.1%) and 9.3x10(5) (42.4%) g mol(-1)] with a smaller one [3.2x10(5) g mol(-1) (45.3%)].

Adhesives↗

PubMed2002

Associative pullulan gels and their interaction with biological active substances.

This paper studies the synthesis and properties of anionic and/or amphiphilic pullulan microparticles crosslinked with epichlorohydrine or with sodium trimethaphosphate. The polysaccharide gels were physicochemically characterized and their interaction with enzymes (lysozyme) was studied with the aim to appreciate the performances for separation/purification/immobilization of the enzymes or controlled release drug systems.

Cross-Linking Reagents↗

PubMed2001

Aggregation of amphiphilic pullulan derivatives evidenced by on-line flow field flow fractionation/multi-angle laser light scattering.

Size-exclusion chromatography (SEC) is a useful steric separation technique for the analysis of water-soluble polysaccharides in aqueous solution. However, in the case of amphiphilic derivatives, the usefulness is limited because of interactions between hydrophobic segments and the stationary phase. Alkyl-bearing pullulans differing from the extent and the length of alkyl groups were characterized using flow-field flow fractionation with on-line coupling multi-angle laser light scattering (F4/MALLS). Comparison of SEC and F4 is presented and the interest of F4 in the field of amphiphilic derivatives is demonstrated.

Glucans↗

PubMedDate not supplied

Hypothesis: hyperstructures regulate bacterial structure and the cell cycle.

A myriad different constituents or elements (genes, proteins, lipids, ions, small molecules etc.) participate in numerous physico-chemical processes to create bacteria that can adapt to their environments to survive, grow and, via the cell cycle, reproduce. We explore the possibility that it is too difficult to explain cell cycle progression in terms of these elements and that an intermediate level of explanation is needed. This level is that of hyperstructures. A hyperstructure is large, has usually one particular function, and contains many elements. Non-equilibrium, or even dissipative, hyperstructures that, for example, assemble to transport and metabolize nutrients may comprise membrane domains of transporters plus cytoplasmic metabolons plus the genes that encode the hyperstructure's enzymes. The processes involved in the putative formation of hyperstructures include: metabolite-induced changes to protein affinities that result in metabolon formation, lipid-organizing forces that result in lateral and transverse asymmetries, post-translational modifications, equilibration of water structures that may alter distributions of other molecules, transertion, ion currents, emission of electromagnetic radiation and long range mechanical vibrations. Equilibrium hyperstructures may also exist such as topological arrays of DNA in the form of cholesteric liquid crystals. We present here the beginning of a picture of the bacterial cell in which hyperstructures form to maximize efficiency and in which the properties of hyperstructures drive the cell cycle.

Bacteria↗

PubMedDate not supplied

Contributions of intermolecular interactions between constitutive arabinoxylans to the flaxseeds mucilage properties.

The main fraction (about 75%) of the mucilage extracted from seeds of Linum usitatissimum which consists of arabino-xylans (AX) has been studied in dilute and semidilute regimes by SEC/MALLS analysis and rheology, respectively. It has been found that AX contains 3 populations of about 5 000 000 g mol(-1) (less than 10%), 1 000 000 g mol(-1) (about 40%), and 200 000 g mol(-1) (about 50%). We have also observed a great retention of polymer during the filtration procedure, which is much pronounced as the AX concentration increases. This evidences the presence of large aggregates in the solution. The retention can be greatly diminished if the filtration is conducted under higher temperature. Aggregation could result from the establishment of intermolecular associations via hydrogen bonds. This hypothesis seems to be confirmed by the two higher populations in molar masses which present a random coil conformation consistent with a low degree of branching. Rheological measurements, conducted at 20 g L(-1), have confirmed the association tendency leading to pseudo gels behavior. Viscoelastic properties have been evidenced by time-temperature master curves of dynamic spectra. Such master curves have also been established with addition of chaotropic (i.e., KSCN) and lyotropic (i.e., NaCl) salts. It has been shown that intermolecular associations are greatly diminished under chaotropic salts influence. This has been also confirmed by SEC/MALLS analysis. These results point out the role of hydrogen bonds in the organization of the AX system.

Flax↗