Carboxyl End Research Articles

Pyrolysis mechanism of Poly(lactic acid) for giving lactide under the catalysis of tin

In order to obtain the mechanisms of the pyrolysis reaction that poly (lactic acid) (PLA) gives lactide in the presence of Sn, the four types of low molecular weight PLAs (L-PLA) with different end-groups were prepared, including HO-L-PLA-COOH, R-L-PLA-OH, R-L-PLA-COOH, and R-L-PLA-R, and depolymerized by thermogravimetry at different heating rates. As for the pyrolysis reactions of the L-PLAs, their activation energy (Ea) were estimated by the several isoconversional model-free methods and their kinetic models were also explored by the Malek method. The random degradation behavior of L-PLAs was determined by the plots of ln{−ln[1−(1−w)0.5]}vs. 1/T for experimental data from TG for L-PLAs and model reactions. The experimental results showed that the Ea values and the possible kinetic models for the pyrolysis reactions of the L-PLAs were different due to the different end-groups and thereof the mechanisms for the pyrolysis reactions of PLA that give lactide were proposed under the catalysis of Sn. The pyrolysis reactions of R-L-PLA-OH and R-L-PLA-R trend to be controlled by a single kinetic model. The pyrolysis reactions of HO-L-PLA-COOH and R-L-PLA-COOH are more complex and controlled by not less than two kinetic processes. The pyrolysis reaction of PLA selectively produces lactide through the unzipping and intramolecular transesterification reactions, including the backbiting reaction caused by the Sn-carboxylate and Sn-alkoxide chain ends, which are directly formed from the hydroxyl and carboxyl end-groups of PLA, and the lactide selective elimination at the random position of the polymeric backbone.

Development of a Tetravalent Anti-GPA33/Anti-CD3 Bispecific Antibody for Colorectal Cancers.

Despite progress in the treatment of colorectal cancer, curing metastatic colorectal cancer remains a major unmet medical need worldwide. Here, we describe a T-cell-engaging bispecific antibody (T-BsAb) to redirect polyclonal cytotoxic T cells to eradicate colorectal cancer. A33, a murine antibody specific for GPA33, was humanized to huA33 and reformatted to huA33-BsAb, based on a novel IgG(L)-scFv platform by linking the anti-CD3 huOKT3 scFv to the carboxyl end of the light chain. This T-BsAb was stably expressed in CHO cells and purified as a stable monomer by HPLC, retaining immunoreactivity by FACS through 30 days of incubation at 37°C. In vitro, it induced activation and expansion of unstimulated T cells and elicited potent T-cell-dependent cell-mediated cytotoxicity against colon and gastric cancer cells in an antigen-specific manner. In vivo, huA33-BsAb inhibited the colon and gastric cancer xenografts, in both subcutaneous and intraperitoneal tumor models. More importantly, both microsatellite instable and microsatellite stable colorectal cancer were effectively eliminated by huA33-BsAb. These preclinical results provide further support for the use of IgG(L)-scFv platform to build BsAb, and especially one targeting GPA33 for colorectal cancer. These preclinical results also support further development of huA33-BsAb as a potential immunotherapeutic. Mol Cancer Ther; 17(10); 2164-75. ©2018 AACR.

Synthesis and kinetics of photochromic carboxy-substituted dithizonatophenylmercury(II)

With the aim of improving water-solubility and providing anchor points for follow-up reactions, the well-known intensely colored green analytical reagent, dithizone (H2Dz), was functionalized by two carboxylic acid substituents. Similarly, sulfacetamide and sulfonyl substituents were also employed, but its dithizone products decomposed in aqueous medium. The crystal structure of the nitroformazan carboxylic acid intermediate is reported. Its bent conformation is maintained by intramolecular hydrogen-bonding. Together with the two added dithizone carboxylate end groups the three spatially removed points are now available for complexation, eg. with phenylmercury(II) moieties. As opposed to the otherwise single-metal PhHgHDz(COOH)2 complex, added heavy mercury atoms in PhHgHDz(COOHgPh)2 inhibit photochromism in the tri-metallic complex. Kinetic studies of the photochromic return reaction of PhHgHDz(COOH)2 show the reaction rate to be linearly dependant on concentration and exponentially dependant on temperature, with rate constant of 0.0084 s−1 at 0 °C, i.e. four times faster than observed for the unsubstituted complex, PhHgHDz.

Short Communication: Genetic diversity of the IGF2 gene as a source of genetic marker for halal authentication

Hamdani AD, Madihah, Suryohastari RB, Virgianti DP, Putrie RFW. 2018. Genetic diversity of the IGF2 gene as a source of genetic marker for halal authentication. Nusantara Bioscience 10: 203-209. The main issue of halal authenticity is the availability of reliable and rapid analytical methods to identify animal species in raw and processed food. The two most popular procedures for identifying the source of the meat are protein-based and DNA-based methods, including mass spectroscopy (MS) using a peptide marker or PCR based DNA marker, respectively. This study aims to investigate the genetic diversity of insulin-like growth factor 2 (IGF2) gene, mainly from porcine (Sus scrofa) and bovine (Bos taurus) as a source of genetic marker for halal authentication by in-silico analysis using bioinformatic tools. Multiple sequence alignment and phylogenetic tree construction of IGF2 protein sequences from representative species of mammals, birds, and fishes showed the paraphyletic relationship between the IGF2 protein of S. scrofa and B. taurus. Protein structure analysis revealed differences in helical structures near the carboxyl end of the protein, while gene analysis showed different number of exon and motifs. By in-silico analysis, we have designed a peptide marker from amino acids at position of 93-107 (S. scrofa) and 93-112 (B. taurus) from peptide preptin region that resulted in different pattern of mass spectrum between the two species. We have also identified two DNA markers that can be detected by PCR using two primers sets designed from the IGF2 transcript sequences, to examine the presence of porcine in the sample. Thus, this study provides new genetic predictive markers, derived from the IGF2 gene, to identify the source of meat for halal authentication.

Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs—Part 2: Dynamic Mechanical Analysis

Thermo-reversible supramolecular networks from polyisoprene-block-polystyrene-block-polyisoprene (ISI) triblock copolymers with short, functionalized polyisoprene (PI) blocks were investigated. Functional groups along the PI blocks were hydroxyl groups, ester groups with a carboxylic end-group (-O-CO-CH2-CH2-COOH), and urethane groups with an amine end-group—synthesized from various types of diamines—(-O-CO-NH-R-NH2). Dynamic mechanical analysis (DMA) was performed at temperatures above Tg of polystyrene (PS) to investigate the influence of the different functional groups, the molecular weight, and the composition of the triblock copolymers on the materials’ properties. Furthermore, comparisons to DMA results of diblock copolymers, modified in the same way, will be presented. Arising reversible and irreversible processes observed during DMA experiments will be compared to results from temperature-dependent Fourier transform infrared (FTIR) spectroscopy. For the elaborated systems, the transition from reversible, hydrogen-bonded to permanently cross-linked networks was observed at around 150 °C.

Preparation, characterization and in vitro anticancer activity of paclitaxel conjugated magnetic nanoparticles

In this study, magnetic nanoparticles (MNPs) coated with L-aspartic acid (F-Asp NPs) were synthesized through a co-precipitation method and conjugated with paclitaxel (PTX) (F-Asp-PTX NPs) by esterification reaction between the carboxylic acid end groups on MNPs surface and the hydroxyl groups of the PTX and studied its cytotoxic effect in vitro. The successful conjugating of PTX onto the nanoparticles (NPs) was confirmed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and transmission electron microscopy (TEM) techniques. The results showed that the average size was 46.11 ± 7.8 (mean ± SD (n = 25)) nm. The cytotoxicity of void of PTX and F-Asp-PTX NPs were compared to each other by MTT assay of the treated MCF-7 cell line. The F-Asp-PTX NPs showed pH-dependent drug release behavior. These studies specify that F-Asp-PTX NPs have a very remarkable anticancer effect, for breast cancer cell line.

Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs-Part 1: Synthesis and Characterization.

The combination of controlled anionic polymerization and subsequent introduction of hydrogen bonding groups was established to form thermo-reversible, supramolecular networks. Several polyisoprene-block-polystyrene-block-polyisoprene (ISI) copolymers—with polystyrene (PS) as the main block, and consequently giving the decisive material characteristics—were synthesized. The novel modification approach to post-functionalize the polyisoprene (PI) end-blocks and to introduce different motifs, which are able to form self-complementary hydrogen bonds, was attained. In the first step, hydroxylation was accomplished using 9-borabicyclo[3.3.1]nonane. Starting from the hydroxylated polymer, esterification with succinic anhydride was implemented to form an ester group with carboxylic end-group (-O-CO-CH2-CH2-COOH). In a second approach, 1,1’-carbonyldiimidazole was used as coupling agent to introduce various types of diamines (diethylenetriamine, triethylentetramine, and 2,6-diaminopyridine) to prepare urethane groups with amine end-group (-O-CO-NH-R-NH2). 1H NMR spectroscopy was used to confirm the successful synthesis and to calculate the degree of functionalization Df. Differential scanning calorimetry (DSC) showed a difference of the glass transition temperature Tg between unfunctionalized and functionalized block copolymers, but no greater influence between the different types of modification, and thus, on the Tg of the PS block. In temperature dependent FTIR spectroscopy, reversible processes were observed.

Ferrocene-terminated dendrimer functionalized graphene oxide layered sensor toward highly sensitive evaluation of Di(2-ethylhexyl) phthalate in liquor samples

We demonstrate the use of a dendrimer functionalized graphene oxide (GO) to fabricate a novel sensitive ferrocene-terminated poly(amine) ester dendrimer (Fc-AED)-GO modified glassy carbon electrodes (Fc-AED/GO/GCE) for direct quantification of Di(2-ethylhexyl) phthalate (DEHP) in liquor sample. GO sheets were grafted on the Fc-AED molecules by the esterification reaction between carboxylic end group in Fc-AED and hydroxyl group on GO sheets so as to form Fc-AED-GO composites. Construction of electrochemical sensors using the structure of nanosized dendrimer can provide compact matrix for the incorporation of GO to improve the adhesion of GO on electrode, which would be more possible for the design of sensor to improve the film forming performance and then increase the electrochemical activity of the electrode. Additionally, it can directly use the redox probe of ferrcene to sense the content variation of analyte. The GO also provides a larger surface area to facilitate deposition of Fc-AED redox probe resulting in the increased current response of the modified sensor. The modified sensor exhibites a wide linear response to DEHP and a low detection limit of 0.06 μM with higher sensitivity, good selectivity, and a better reproducibility promising to be a useful tool in the DEHP evaluation. The outstanding performance of the developed sensor could be attributed to the synergistic effect of Fc-AED and GO. Possible redox mechanism of DEHP on Fc-AED/GO/GCE are proposed based on experimental results.

Molecular Level Structure of Biodegradable Poly(Delta-Valerolactone) Obtained in the Presence of Boric Acid.

In this study, low molecular weight poly(δ-valerolactone) (PVL) was synthesized through bulk-ring openings polymerization of δ-valerolactone with boric acid (B(OH)3) as a catalyst and benzyl alcohol (BnOH) as an initiator. The resulting homopolymer was characterized with the aid of nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques to gain further understanding of its molecular structure. The electrospray ionization mass spectrometry (ESI-MS) spectra of poly(δ-valerolactone) showed the presence of two types of homopolyester chains—one terminated by benzyl ester and hydroxyl end groups and one with carboxyl and hydroxyl end groups. Additionally, a small amount of cyclic PVL oligomers was identified. To confirm the structure of PVL oligomers obtained, fragmentation of sodium adducts of individual polyester molecules terminated by various end groups was explored in ESI-MSn by using collision induced dissociation (CID) techniques. The ESI-MSn analyses were conducted both in positive- and negative ion mode. The comparison of the fragmentation spectra obtained with proposed respective theoretical fragmentation pathways allowed the structure of the obtained oligomers to be established at the molecular level. Additionally, using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), it was proven that regardless of the degree of oligomerization, the resulting PVL samples were a mixture of two types of linear PVL oligomers differing in end groups and containing just a small amount of cyclic oligomers that tended to be not visible at higher molar masses.

In vivo lipid 'tag and track' approach shows acyl editing of plastid lipids and chloroplast import of phosphatidylglycerol precursors in Arabidopsis thaliana.

In plant lipid metabolism, the synthesis of many intermediates or end products often appears overdetermined with multiple synthesis pathways acting in parallel. Lipid metabolism is also dynamic with interorganelle transport, turnover, and remodeling of lipids. To explore this complexity invivo, we developed an invivo lipid 'tag and track' method. Essentially, we probed the lipid metabolism in Arabidopsis thaliana by expressing a coding sequence for a fatty acid desaturase from Physcomitrella patens (Δ6D). This enzyme places a double bond after the 6th carbon from the carboxyl end of an acyl group attached to phosphatidylcholine at its sn-2 glyceryl position providing a subtle, but easily trackable modification of the glycerolipid. Phosphatidylcholine is a central intermediate in plant lipid metabolism as it is modified and converted to precursors for other lipids throughout the plant cell. Taking advantage of the exclusive location of Δ6D in the endoplasmic reticulum (ER) and its known substrate specificity for one of the two acyl groups on phosphatidylcholine, we were able to 'tag and track' the distribution of lipids within multiple compartments and their remodeling in transgenic lines of different genetic backgrounds. Key findings were the presence of ER-derived precursors in plastid phosphatidylglycerol and prevalent acyl editing of thylakoid lipids derived from multiple pathways. We expect that this 'tag and track' method will serve as a tool to address several unresolved aspects of plant lipid metabolism, such as the nature and interaction of different subcellular glycerolipid pools during plant development or in response to adverse conditions.

Adapting to oxygen: 3-Hydroxyanthrinilate 3,4-dioxygenase employs loop dynamics to accommodate two substrates with disparate polarities

3-Hydroxyanthranilate 3,4-dioxygenase (HAO) is an iron-dependent protein that activates O2 and inserts both oxygen atoms into 3-hydroxyanthranilate (3-HAA). An intriguing question is how HAO can rapidly bind O2, even though local O2 concentrations and diffusion rates are relatively low. Here, a close inspection of the HAO structures revealed that substrate- and inhibitor-bound structures exhibit a closed conformation with three hydrophobic loop regions moving toward the catalytic iron center, whereas the ligand-free structure is open. We hypothesized that these loop movements enhance O2 binding to the binary complex of HAO and 3-HAA. We found that the carboxyl end of 3-HAA triggers changes in two loop regions and that the third loop movement appears to be driven by an H-bond interaction between Asn27 and Ile142 Mutational analyses revealed that N27A, I142A, and I142P variants cannot form a closed conformation, and steady-state kinetic assays indicated that these variants have a substantially higher Km for O2 than WT HAO. This observation suggested enhanced hydrophobicity at the iron center resulting from the concerted loop movements after the binding of the primary substrate, which is hydrophilic. Given that O2 is nonpolar, the increased hydrophobicity at the iron center of the binary complex appears to be essential for rapid O2 binding and activation, explaining the reason for the 3-HAA-induced loop movements. Because substrate binding-induced open-to-closed conformational changes are common, the results reported here may help further our understanding of how oxygen is enriched in nonheme iron-dependent dioxygenases.

Influenza D virus M2 protein exhibits ion channel activity in Xenopus laevis oocytes

BackgroundA new type of influenza virus, known as type D, has recently been identified in cattle and pigs. Influenza D virus infection in cattle is typically asymptomatic; however, its infection in swine can result in clinical disease. Swine can also be infected with all other types of influenza viruses, namely A, B, and C. Consequently, swine can serve as a “mixing vessel” for highly pathogenic influenza viruses, including those with zoonotic potential. Currently, the only antiviral drug available targets influenza M2 protein ion channel is not completely effective. Thus, it is necessary to develop an M2 ion channel blocker capable of suppressing the induction of resistance to the genetic shift. To provide a basis for developing novel ion channel-blocking compounds, we investigated the properties of influenza D virus M2 protein (DM2) as a drug target.ResultsTo test the ion channel activity of DM2, the DNA corresponding to DM2 with cMyc-tag conjugated to its carboxyl end was cloned into the shuttle vector pNCB1. The mRNA of the DM2–cMyc gene was synthesized and injected into Xenopus oocytes. The translation products of DM2–cMyc mRNA were confirmed by immunofluorescence and mass spectrometry analyses. The DM2–cMyc mRNA-injected oocytes were subjected to the two-electrode voltage-clamp (TEVC) method, and the induced inward current was observed. The midpoint (Vmid) values in Boltzmann modeling for oocytes injected with DM2–cMyc RNA or a buffer were −152 and −200 mV, respectively. Assuming the same expression level in the Xenopus oocytes, DM2 without tag and influenza C virus M2 protein (CM2) were subjected to the TEVC method. DM2 exhibited ion channel activity under the condition that CM2 ion channel activity was reproduced. The gating voltages represented by Vmid for CM2 and DM2 were –141 and –146 mV, respectively. The reversal potentials observed in ND96 for CM2 and DM2 were −21 and −22 mV, respectively. Compared with intact DM2, DM2 variants with mutation in the YxxxK motif, namely Y72A and K76A DM2, showed lower Vmid values while showing no change in reversal potential.ConclusionThe M2 protein from newly isolated influenza D virus showed ion channel activity similar to that of CM2. The gating voltage was shown to be affected by the YxxxK motif and by the hydrophobicity and bulkiness of the carboxyl end of the molecule.

Enhancement of NLO Properties in OBO Fluorophores Derived from Carbazole–Coumarin Chalcones Containing Carboxylic Acid at the N-Alykl Terminal End

The nonlinear optical (NLO) properties of carbazole–coumarin-based chalcones and their OBO complexes of D−π–A and D−π–A−π–D types with carbazole as donor substituted with N-alykl chain at the 9 position with carboxylic acid end group are studied in detail. These dyes exhibit good emission solvatochromism. The NLO properties of dyes 5–8 were studied by two methods, namely, solvatochromic and computational method. The linear polarizability (α), hyperpolarizability (β), and second-order hyperpolarizability (γ) of dyes 5–8 were studied by time-dependent density-functional theory computational method using five different range-separated functionals, namely, CAM-B3LYP, HISSbPBE, HSEH1PBE, wB97, and wB97X, with triple ζ basis set 6-311++G(d,p). The correlation between the NLO properties is well established with the geometry of the dyes by understanding the enhancement of hyperpolarizability, second-order hyperpolarizability, and two-photon absorption (TPA) properties of complexed and uncomplexed carbazole–coumar...

Poly-albumen: Bio-derived structural polymer from polymerized egg white

Bio-derived materials could play an important role in future sustainable green and health technologies. This work reports the synthesis of a unique egg white-based bio-derived material showing excellent stiffness and ductility by polymerizing it with primary amine-based chemical compounds to form strong covalent bonds. As shown by both experiments and theoretical simulations, the amine-based molecules introduce strong bonds between amine ends and carboxylic ends of albumen amino acids resulting in an elastic modulus of ∼4 GPa, a fracture strength of ∼2 MPa and a high ductility of 40%. The distributed and interconnected network of interfaces between the hard albumen and the soft amine compounds gives the structure its unique combination of high stiffness and plasticity. A range of in-situ local and bulk mechanical tests as well as molecular dynamics (MD) simulations, reveal a significant interfacial stretching during deformation and a micro-crack diversion leading to an increased in ductility and toughness. The structure also shows a self-stiffening behavior under dynamic loading and a strength-induced aging suggesting adaptive mechanical behavior. This egg white-derived material could also be developed for bio-compatible and bio-medical applications.

Hyperactivation of serine proteases by the Hofmeister effect

α-Chymotrypsin (CHT) is a serine protease that hydrolyzes peptide bonds at the carboxyl end of hydrophobic amino acids. It has been shown that the enzyme activity of CHT increases one order of magnitude in the presence of some types of amine compounds and inorganic ions. Here we show that hyperactivation occurs for several kinds of serine proteases in the presence of a kosmotrope. Among the eight model enzymes, the catalytic activities of four serine protease increased 1.3–30-fold by the addition of 1.5 M sodium sulfate. Enzyme kinetics and circular dichroism analyses revealed that the hyperactivation is caused by both increased kcat and decreased KM, which reflect stabilization of the active form of the enzyme and the affinity between the enzyme and hydrophobic substrate, respectively. These findings demonstrate the effectiveness of this simple method for enzyme activation without cost and contribute to our fundamental understanding of enzyme activity in solution.

Sulfonated Poly(Arylene Ether Sulfone) and Perfluorosulfonic Acid Composite Membranes Containing Perfluoropolyether Grafted Graphene Oxide for Polymer Electrolyte Membrane Fuel Cell Applications.

Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end group onto the surface of GO via ring opening reaction between the carboxylic acid group in poly(hexafluoropropylene oxide) and the epoxide groups in GO, using 4-dimethylaminopyridine as a base catalyst. Both SPAES and PFSA composite membranes containing PFPE-GO showed much improved mechanical strength and dimensional stability, compared to each linear SPAES and PFSA membrane, respectively. The enhanced mechanical strength and dimensional stability of composite membranes can be ascribed to the homogeneous dispersion of rigid conjugated carbon units in GO through the increased interfacial interactions between PFPE-GO and SPAES/PFSA matrices.

Supramolecular aggregates of linear and star-shaped polylactides with different number of hydroxyl or carboxyl end-groups

In this paper a set of linear and star-shaped polylactides (PLA's) containing a different number of -OH end-groups (1, 2, 4, 6 and 8) were synthesized. To compare the extent of interactions between different end-groups, the OH end-groups were transformed to COOH end-groups. To attain the proper conditions of this transformation, the conditions were optimized for the chosen model and then used for all synthesized polymers. The structure of synthesized polymers were confirmed by SEC-MALS, NMR and ATR FT-IR analyses. It was shown that PLA's architecture and number of OH and COOH groups in a single macromolecule have an influence on a viscosity of their solution due to their self-organization. For star-shaped PLA's containing higher than four number of COOH end-groups, it has been observed for the first time that the effect of intramolecular interactions exceeds intermolecular interactions what strongly affect their properties in diluted and concentrated solutions.

Solid-State Polymerization of Poly(Ethylene Furanoate) Biobased Polyester, II: An Efficient and Facile Method to Synthesize High Molecular Weight Polyester Appropriate for Food Packaging Applications.

The goal of this study was to synthesize, through a facile strategy, high molecular weight poly(ethylene furanoate) (PEF), which could be applicable in food packaging applications. The efficient method to generate PEF with high molecular weight consists of carrying out a first solid-state polycondensation under vacuum for 6 h reaction time at 205 °C for the resulting polymer from two-step melt polycondensation process, which is catalyzed by tetrabutyl titanate (TBT). A remelting step was thereafter applied for 15 min at 250 °C for the obtained polyester. Thus, the PEF sample was ground into powder, and was then crystallized for 6 h at 170 °C. This polyester is then submitted to a second solid-state polycondensation (SSP) carried out at different reaction times (1, 2, 3.5, and 5 h) and temperatures 190, 200, and 205 °C, under vacuum. Ultimately, a significant increase in intrinsic viscosity is observed with only 5 h reaction time at 205 °C during the second SSP being needed to obtain very high molecular weight PEF polymer greater than 1 dL/g, which sufficient for manufacturing purposes. Intrinsic viscosity (IV), carboxyl end-group content (–COOH), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polyesters. Thanks to the post-polymerization process, DSC results showed that the melting temperatures of the prepared PEF samples were steadily enhanced in an obvious way as a function of reaction time and temperature increase. It was revealed, as was expected for all SSP samples, that the intrinsic viscosity and the average molecular weight of PEF polyester increased with increasing SSP time and temperature, whereas the number of carboxyl end-group concentration was decreased. A simple kinetic model was also developed and used to predict the time evolution of polyesters IV, as well as the carboxyl and hydroxyl end-groups of PEF during the SSP.

Accelerated ageing and hydrolytic stabilization of poly(lactic acid) (PLA) under humidity and temperature conditioning

The accelerated hygrothermal ageing of two commercial poly(lactic acid) grades, a semi-crystalline and an amorphous one, was studied in order to establish a baseline degradation mechanism and kinetics. In particular, the water uptake, the molecular weight, the carboxylic end groups concentration and the thermal properties were monitored during the course of humidity and temperature conditioning at 70 °C and 80% relative humidity (RH), revealing significant extent of chain scission. The effect of four commercial anti-hydrolysis agents of different composition was then examined in order to stabilize the two PLA grades. The additives comprised an epoxy-based chain extender, an aromatic carbodiimide, as well as an aromatic and an aliphatic polycarbodiimide. The epoxy-based additive did not exhibit any stabilizing effect, while the other three carbodiimide-based additives were found efficient as anti-hydrolysis agents at a concentration of 1% especially in the case of the amorphous grade.

Biophysical Investigation of Gastrointestinal Fatty Acid Binding Proteins (FABPs) with Fatty Acid Ethanolamides (FAEs)

Fatty acids are the precursors for lipids that make up cellular membranes and have significant roles in signal transduction pathways. In order for fatty acids to be shuttled inside the cytoplasm they bind to fatty acid binding proteins (FABPs). Much interest has been focused on a particular class of lipids known as the fatty acid ethanolamines (FAEs) due to the recent discovery that they are involved in regulating appetite, pain, and inflammation. In this present work, we explore the FAE interaction with the intestinal and liver fatty acid‐binding proteins (I‐ and L‐FABP) that are co‐expressed in the gastrointestinal system. Previously, a striking phenotypic divergence was observed in IFABP and LFABP knock out mice: IFABP−/− mice exhibited lean phenotype while the LFABP−/− mice exhibited obese phenotype after high fat diet. Our direct comparison will elucidate if IFABP and LFABP have distinct ligand preferences to the FAE ligands. Here, we adapt a fluorescence competition assay to characterize the affinity of the FAEs to I‐ and L‐FABP. From our preliminary work, we found that I‐FABP exhibits a lower Kd, i.e. tighter binding, to ligand in all cases examined. We also found that the functional group of the ligands has the most impact on binding affinity: specifically, we found the tightest protein binding for the ligand with the carboxyl end group followed by ligands with amide and then with glycerol ends. In addition, 2D 15N‐1H HSQC NMR was used to reveal significant backbone amide chemical shift changes in the presence of a subset of the ligands we investigated. Further analysis of the HSQC results is expected to identify the perturbed ligand‐binding locations.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.