Thermo-chemical behaviour and chemical product formation from Polar seaweeds during intermediate pyrolysis

Fundamental analytical pyrolysis studies of biomass from Polar seaweeds, which exhibit a different biomass composition than terrestrial and micro-algae biomass were performed via thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass-spectrometry (Py-GC/MS). The main reason for this study is the adaptation of these species to very harsh environments making them an interesting source for thermo-chemical processing for bioenergy generation and production of biochemicals via intermediate pyrolysis. Several macroalgal species from the Arctic region Kongsfjorden, Spitsbergen/Norway (Prasiola crispa, Monostroma arcticum, Polysiphonia arctica, Devaleraea ramentacea, Odonthalia dentata, Phycodrys rubens, Sphacelaria plumosa) and from the Antarctic peninsula, Potter Cove King George Island (Gigartina skottsbergii, Plocamium cartilagineum, Myriogramme manginii, Hymencladiopsis crustigena, Kallymenia antarctica) were investigated under intermediate pyrolysis conditions. TGA of the Polar seaweeds revealed three stages of degradation representing dehydration, devolatilization and decomposition of carbonaceous solids. The maximum degradation temperatures Prasiola crispa were observed within the range of 220-320 C and are lower than typically obtained by terrestrial biomass, due to divergent polysaccharide compositions. Biochar residues accounted for 33-46% and ash contents of 27-45% were obtained. Identification of volatile products by Py-GC/MS revealed a complexity of generated chemical compounds and significant differences between the species. A widespread occurrence of aromatics (toluene, styrene, phenol and 4-methylphenol), acids (acetic acid, benzoic acid alkyl ester derivatives, 2-propenoic acid esters and octadecanoic acid octyl esters) in pyrolysates was detected. Ubiquitous furan-derived products included furfural and 5-methyl-2-furaldehyde. As a pyran-derived compound maltol was obtained by one red algal species (P. rubens) and the monosaccharide d-allose was detected in pyrolysates in one green algal (P. crispa). Further unique chemicals detected were dianhydromannitol from brown algae and isosorbide from green algae biomass. In contrast, the anhydrosugar levoglucosan and the triterpene squalene was detected in a large number of pyrolysates analysed. © 2013 Elsevier B.V. All rights reserved.

Detection of phosphatidylserine with a modified polar head group in human keratinocytes exposed to the radical generator AAPH

Phosphatidylserine (PS) is preferentially located in the inner leaflet of the cell membrane, and translocation of PS oxidized in fatty acyl chains to the outside of membrane has been reported as signaling to macrophage receptors to clear apoptotic cells. It was recently shown that PS can be oxidized in serine moiety of polar head-group. In the present work, a targeted lipidomic approach was applied to detecting OxPS modified at the polar head-group in keratinocytes that were exposed to the radical generator AAPH. Glycerophosphoacetic acid derivatives (GPAA) were found to be the major oxidation products of OxPS modified at the polar head-group during oxidation induced by AAPH-generated radicals, similarly to previous observations for the oxidation induced by OH radical. The neutral loss scan of 58Da and a novel precursor ion scan of m/z 137.1 (HOPO3CH2COOH) allowed the recognition of GPAA derivatives in the total lipid extracts obtained from HaCaT cells treated with AAPH. The positive identification of serine head group oxidation products in cells under controlled oxidative conditions opens new perspectives and justifies further studies in other cellular environments in order to understand fully the role of PS polar head-group oxidation in cell homeostasis and disease.

A hydrogen-bonded polar network in the core of the glucagon-like peptide-1 receptor is a fulcrum for biased agonism:lessons from class B crystal structuress

The glucagon-like peptide 1 (GLP-1) receptor is a class B G protein-coupled receptor (GPCR) that is a key target for treatments for type II diabetes and obesity. This receptor, like other class B GPCRs, displays biased agonism, though the physiologic significance of this is yet to be elucidated. Previous work has implicated R2.60190 , N3.43240 , Q7.49394 , and H6.52363 as key residues involved in peptide-mediated biased agonism, with R2.60190 , N3.43240 , and Q7.49394 predicted to form a polar interaction network. In this study, we used novel insight gained from recent crystal structures of the transmembrane domains of the glucagon and corticotropin releasing factor 1 (CRF1) receptors to develop improved models of the GLP-1 receptor that predict additional key molecular interactions with these amino acids. We have introduced E6.53364 A, N3.43240 Q, Q7.49493N, and N3.43240 Q/Q7.49 Q/Q7.49493N mutations to probe the role of predicted H-bonding and charge-charge interactions in driving cAMP, calcium, or extracellular signal-regulated kinase (ERK) signaling. A polar interaction between E6.53364 and R2.60190 was predicted to be important for GLP-1- and exendin-4-, but not oxyntomodulin-mediated cAMP formation and also ERK1/2 phosphorylation. In contrast, Q7.49394 , but not R2.60190 /E6.53364 was critical for calcium mobilization for all three peptides. Mutation of N3.43240 and Q7.49394 had differential effects on individual peptides, providing evidence for molecular differences in activation transition. Collectively, this work expands our understanding of peptide-mediated signaling from the GLP-1 receptor and the key role that the central polar network plays in these events.