Low Molecular Weight Species Research Articles

Methyl‐DOPO—a new flame retardant for flexible polyurethane foam

AbstractFlexible polyurethane foams are widely used in many industrial applications, such as upholstered furniture and mattresses, automotive applications, etc. The chemical nature of the polyurethane, the low density, the high air permeability, and the open cell structure cause this material to be highly flammable. In this study, the influencing variables on the burning behavior of flexible polyurethane foams are investigated. Additionally the synthesis, formulation, characterization, and testing of a new phosphorus flame retardant (FR) methyl‐DOPO 9,10‐dihydro‐9‐oxa‐methylphosphaphenthrene‐10‐oxide in flexible polyurethane foam with low density is performed. The new FR shows an excellent flame retarding behavior by acting mainly in the gas phase. Here the vaporization of methyl‐DOPO occurs in the same temperature region as the depolymerization of the urethane and the bisubstituted urea groups during pyrolysis of the foam. Furthermore TG‐MS measurements revealed the release of high concentrations of low molecular weight species like HPO, CH3PO, or PO2 in the mentioned temperature region. These species are able to scavenge the H‐ and OH‐radicals in the radical chain reactions of the flame leading to a significant increase of the CO/CO2 ratio during cone calorimeter experiments. Copyright © 2010 John Wiley & Sons, Ltd.

Polyamides obtained by direct polycondesation of 4-[4-[9-[4-(4-aminophenoxy)-3-methyl-phenyl] fluoren-9-YL]-2-methyl-phenoxy]aniline with dicarboxylic acids based on a diphenyl-silane moiety

Polyamides (PAs) containing fluorene, oxy-ether, and diphenyl-silane moieties in the repeating unit were synthesized in > 85% yield by direct polycondesation between a diamine and four dicarboxylic acids. Alternatively, one PA was synthesized from an acid dichloride. The diamine 4-[4-[9-[4-(4-aminophenoxy)-3-methyl-phenyl]fluoren-9-yl]-2-methyl-phenoxy]aniline (3) was obtained from the corresponding dinitro compound, which was synthesized by nucleophilic aromatic halogen displacement from p-chloronitrobenzene and 9,9-bis (4-hydroxy-3-methyl-phenyl)fluorene (1). Monomers and polymers were characterized by FTIR and 1 H, 13 C, and 29 Si-NMR spectroscopy and the results were in agreement with the proposed structures. PAs showed inherent viscosity values between 0.14 and 0.43 dL/g, indicative of low molecular weight species, probably of oligomeric nature. The glass transition temperature (T g ) values were observed in the 188-211°C range by DSC analysis. Thermal decomposition temperature (TDT 10% ) values were above 400°C due to the presence of the aromatic rings in the diamine. All PAs showed good transparency in the visible region (>88% at 400 nm) due to the incorporation of the fluorene moiety.

Flame retardancy working mechanism of methyl‐DOPO and MPPP in flexible polyurethane foam

SUMMARYThe chemical nature of flexible polyurethane (flex PU) foams, the low density, the high air permeability and the open cell structure cause this material to be highly flammable. The new phosphorus flame‐retardant (FR) methyl‐DOPO (9, 10‐dihydro‐9‐oxa‐methylphosphaphenanthrene‐10‐oxide) is known to show an excellent flame retarding behavior in flex PU foam by acting mainly in the gas phase. In this study, the FR working mechanism of methyl‐DOPO and its ring‐opened analogue MPPP (methylphenoxyphenyl‐phosphinate) is investigated by TGA, TG–MS, FMVSS 302 and Cone Calorimeter measurements. Under TG–MS conditions comparable concentrations of low molecular weight species such as HPO, mathrmCH3PO or PO2 are released. These species are able to scavenge the H‐ and OH‐radicals in the radical chain reactions of the flame leading to a significant increase in the CO/CO2 ratio and the smoke density during cone calorimeter experiments. Finally, the flame retardancy of MPPP is determined to be less efficient in flex PU foam because of the higher vapor pressure compared with methyl‐DOPO. Here, the vaporization of methyl‐DOPO occurs in the same temperature region as the depolymerization of the urethane and the bisubstituted urea groups during pyrolysis of the foam leading to an optimal interaction. Copyright © 2010 John Wiley & Sons, Ltd.

Studies on the parameters controlling the stability of the TET peptidase superstructure from Pyrococcus horikoshii revealed a crucial role of pH and catalytic metals in the oligomerization process

The TET proteases from Pyrococcus horikoshii are metallopeptidases that form large dodecameric particles with high thermal stability. The influence of various physico-chemical parameters on PhTET3 quaternary structure was investigated. Analytical ultracentrifugation and biochemical analyses showed that the PhTET3 quaternary structure and enzymatic activity are maintained in high salt and that the complex is stable under extreme acidic conditions. Under basic pH conditions the complex disassembled into a low molecular weight species that was identified as folded dimer. Metal analyses showed that the purified enzyme only contains two equivalent of zinc per monomer, corresponding to the metal ions responsible for catalytic activity. When these metals were removed by EDTA treatment, the complex dissociated into the same dimeric species as those observed at high pH. Dodecameric TET particles were obtained from the metal free dimers when 2 mM of divalent ions were added to the protein samples. Most of the dimers remained assembled at high temperature. Thus, we have shown that dimers are the building units in the TET oligomerization pathway and that the active site metals are essential in this process.

Inhibition of Bak Activation by VDAC2 Is Dependent on the Bak Transmembrane Anchor

Bax and Bak are pro-apoptotic factors that are required for cell death by the mitochondrial or intrinsic pathway. Bax is found in an inactive state in the cytosol and upon activation is targeted to the mitochondrial outer membrane where it releases cytochrome c and other factors that cause caspase activation. Although Bak functions in the same way as Bax, it is constitutively localized to the mitochondrial outer membrane. In the membrane, Bak activation is inhibited by the voltage-dependent anion channel isoform 2 (VDAC2) by an unknown mechanism. Using blue native gel electrophoresis, we show that in healthy cells endogenous inactive Bak exists in a 400-kDa complex that is dependent on the presence of VDAC2. Activation of Bak is concomitant with its release from the 400-kDa complex and the formation of lower molecular weight species. Furthermore, substitution of the Bak transmembrane anchor with that of the mitochondrial outer membrane tail-anchored protein hFis1 prevents association of Bak with the VDAC2 complex and increases the sensitivity of cells to an apoptotic stimulus. Our results suggest that VDAC2 interacts with the hydrophobic tail of Bak to sequester it in an inactive state in the mitochondrial outer membrane, thereby raising the stimulation threshold necessary for permeabilization of the mitochondrial outer membrane and cell death.

Multiple C-terminal tail Ca2+/CaMs regulate CaV1.2 function but do not mediate channel dimerization

Interactions between voltage-gated calcium channels (Ca(V)s) and calmodulin (CaM) modulate Ca(V) function. In this study, we report the structure of a Ca(2+)/CaM Ca(V)1.2 C-terminal tail complex that contains two PreIQ helices bridged by two Ca(2+)/CaMs and two Ca(2+)/CaM-IQ domain complexes. Sedimentation equilibrium experiments establish that the complex has a 2:1 Ca(2+)/CaM:C-terminal tail stoichiometry and does not form higher order assemblies. Moreover, subunit-counting experiments demonstrate that in live cell membranes Ca(V)1.2s are monomers. Thus, contrary to previous proposals, the crystallographic dimer lacks physiological relevance. Isothermal titration calorimetry and biochemical experiments show that the two Ca(2+)/CaMs in the complex have different properties. Ca(2+)/CaM bound to the PreIQ C-region is labile, whereas Ca(2+)/CaM bound to the IQ domain is not. Furthermore, neither of lobes of apo-CaM interacts strongly with the PreIQ domain. Electrophysiological studies indicate that the PreIQ C-region has a role in calcium-dependent facilitation. Together, the data show that two Ca(2+)/CaMs can bind the Ca(V)1.2 tail simultaneously and indicate a functional role for Ca(2+)/CaM at the C-region site.

Synthetic Inositol Phosphoglycans Related to GPI Lack Insulin-Mimetic Activity

Insulin signaling has been suggested, at least in part, to be affected by an insulin-mimetic species of low molecular weight. These inositol phosphoglycans (IPGs) are generated upon growth hormone/cytokine stimulation and control the activity of a multitude of insulin effector enzymes. The minimal structural requirements of IPGs for insulin-mimetic action have been debated. Two types of IPGs were suggested, and the IPG-A type resembles the core glycan of glycosylphosphatidylinositol (GPI)-anchors. In fact, purified GPI-anchors of lower eukaryotic origin have been shown to influence glucose homeostasis. To elucidate active IPGs, a collection of synthetic IPGs designed on the basis of previous reports of activity were tested for their insulin-mimetic activity. In vitro and ex vivo assays in rodent adipose tissue as well as in vivo analyses in mice were employed to test the synthetic IPGs. None of the IPGs we tested mimic insulin actions as determined by PKB/Akt phosphorylation and quantification of glucose transport and lipogenesis. Furthermore, none of the IPGs had any effect in in vivo insulin tolerance assays. In stark contrast to previous claims, we conclude that neither of the compounds tested is insulin-mimetic.

Analytical Characterization of Sediment Formed in Soy Oil-Based B20 Biodiesel

Abstract A thick, gel-like precipitate, which separated from a B20 blend, has been characterized using a variety of analytical techniques. The sediment formed in a blend of soy-based fatty acid methyl ester (FAME) and ultra low sulfur diesel (ULSD), which had been stored under ASTM D4625 conditions without the presence of antioxidant. Analysis indicates that the majority of the sediment consists of a wide variety of polar oxygenated compounds. These vary considerably in molecular weight. The lower molecular weight species arise due to oxidative cleavage of the methyl esters. Also present are free fatty acids formed due to hydrolysis of FAME. The highest molecular weight compounds are oxidized FAME that have not undergone cleavage and oligomers of the oxidized FAME. Monoglycerides and steryl glucosides are not significant components in this sediment. The sediment does contain some diesel fuel, intact FAME, and impurities, which are inherent to the FAME. A proposed scenario for the formation of this type of sediment is as follows: As free radical formation, oxidation, and hydrolysis occur in unsaturated methyl esters, there are numerous polar organic compounds formed. These vary widely in molecular weight and include carboxylic acids, alcohols, aldehydes, and ketones, as well as compounds containing combinations of these functional groups. All of these reaction products undergo aggregation due to their polarity differences with the bulk matrix. Included in these aggregates are the trace components present as impurities in the FAME, such as water, glycerol, glycerides, plant sterols, and steryl glucosides. Eventually, a level of thermodynamic instability is reached and phase separation occurs. While the aggregates and sediment contain significant polar functionality, they still maintain a very high degree of alkyl and olefinic character. As a result, intact FAME and diesel fuel components have a certain degree of solubility in the aggregated mixture and make up part of the precipitated sediment.

Buffer-Dependent Fragmentation of a Humanized Full-Length Monoclonal Antibody

During storage stability studies of a monoclonal antibody (mAb) it was determined that the primary route of degradation involved fragmentation into lower molecular weight species. The fragmentation was characterized with size-exclusion high performance liquid chromatography (SE-HPLC), SDS-PAGE, and matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry. Fragmentation proceeded via hydrolysis, likely catalyzed by trace metal ions, of a peptide bond in the hinge region of the mAb's heavy chain, which produced two prominent low molecular weight species during storage: a single, free Fab fragment and a Fab + Fc fragment. The fragmentation is observed in phosphate-buffered solutions at two ionic strengths but not in histidine-buffered solutions at identical ionic strengths. Chaotrope-induced and thermally induced unfolding studies of the mAb indicated differences in the unfolding pathways between the two buffer solutions. The folding intermediate observed during chaotrope-induced unfolding was further characterized by intrinsic fluorescence quenching, which suggested that a small portion of the molecule is resistant to chaotrope-induced unfolding in histidine buffer systems. The thermally induced unfolding indicates a reduction in cooperativity of the unfolding process in the presence of histidine relative to phosphate. A relationship between the histidine-induced effects on unfolding pathway and the relative resistance to fragmentation is suggested.

Creep behavior of high density polyethylene after aging in contact with different oil derivates

AbstractThe creep behavior of a high density polyethylene (HDPE), currently used as raw material for pipe manufacture, was evaluated before and after exposure to oil derivates using transient rheometry. The creep behavior of the original HDPE was satisfactorily described using a generalized Kelvin‐Voigt model based on two retardation times. The values of these critical times were quite different from each other, indicating a large distribution of macromolecular weight. The aging procedure was performed by immersing the polymer in two model fluids chosen to discriminate and understand the action of aromatic and paraffinic fractions of fuel derivatives (white oil, gas‐oil). The batch operation was also carried out at two different temperatures to investigate the thermal activation of plausible degrading mechanisms. In the case of the aging performed in the paraffinic fluid, the polymer compliance continuously increased with the immersion duration. This behavior was attributed to a plasticization induced by the diffusion of the liquid in the polymer matrix. The same phenomenon was observed in the early stage of the HDPE aging carried out with the aromatic fluid. However, for longer aging times, the extraction of low molecular weight species produced the stiffening of the thermoplastic. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

Tissue-Specific Expression of Fucosylated Glycosphingolipid Species in Rat Prostate

Analysis of fucosylated glycoconjugates in rat prostate by lectin blotting with Aleuria aurantia lectin revealed that the tissue contained characteristic low-molecular weight species (prostatic fucosylated glycoconjugates, PFGs). PFGs were detected almost exclusively in the ventral lobe of the prostate among rat tissues examined, and showed an apparent positive androgen dependency, that is, the content of PFGs decreased after castration and then slowly recovered upon androgen replacement. PFGs were resistant to solubilization with Triton X-100, but could be extracted with chloroform-methanol. Treatment of the crude PFG preparation with endoglycoceramidase resulted in the complete disappearance of PFGs. PFGs were also susceptible to alpha1,3/4-L-fucosidase but not to peptide-N-glycosidase F. Prostate-specific expression of PFGs was confirmed by thin layer chromatography and subsequent blot analysis. These results suggest that PFGs are fucosylated glycosphingolipid species specifically expressed in the rat ventral prostate, and that PFG expression is associated with some androgen-regulated processes in the tissue.

Distribution of adiponectin multimeric forms in Chinese women with polycystic ovary syndrome and their relation to insulin resistance

Adiponectin, an abundant adipokine with insulin-sensitizing properties, exists in different multimeric forms, including low-molecular weight, medium-molecular weight, and high-molecular weight (HMW) species. Alterations in the distribution of adiponectin multimers and the relationship between adiponectin multimers and insulin resistance (IR) in women with polycystic ovary syndrome (PCOS) remain unclear. The objective of this study was to compare adiponectin multimerization status and estimate insulin sensitivity in Chinese women with PCOS compared with age- and body mass index (BMI)-matched controls. Cross-sectional study involving 64 Chinese women with PCOS and 59 normal women. Circulating total adiponectin and its multimeric forms were determined by ELISA, and IR was estimated using the homeostasis model assessment IR index (HOMA-IR). After controlling for BMI status, levels of both total and HMW adiponectin were significantly lower in women with PCOS compared with normal women (P<0.05). Furthermore, HMW adiponectin provided a stronger contribution to models predicting IR than total adiponectin. Lastly, decreased HMW adiponectin was associated with increased HOMA-IR in both normal and PCOS women, and this association was independent of both overall adiposity and visceral adiposity. Levels of both total and HMW adiponectin were decreased in Chinese women with PCOS compared with normal control women, and the differences in HMW adiponectin persisted after controlling for BMI. Furthermore, HMW adiponectin is a stronger predictor of IR than total adiponectin in both women with PCOS and normal women.

Separation and characterization of aggregated species of amyloid-beta peptides

We have investigated the use of isoelectric focusing and immunodetection for the separation of low molecular weight species of amyloid-beta (Abeta) peptides from their aggregates. From solutions of Abeta(1-40) or Abeta(1-42) monomeric peptides, low molecular weight material appeared at a pI value of ca. 5, while the presence of aggregates was detected as bands, observed at a pI of 6-6.5. The formation of Abeta aggregates (protofibrils) was verified by a sandwich ELISA, employing the protofibril conformation-selective antibody mAb158. In order to study the aggregation behavior when using a mixture of the monomers, we utilized the IEF separation combined with Western blot using two polyclonal antisera, selective for Abeta(1-40) and Abeta(1-42), respectively. We conclude that both monomers were incorporated in the aggregates. In a further study of the mixed aggregates, we used the protofibril conformation-selective antibody mAb158 for immunoprecipitation, followed by nanoelectrospray mass spectrometry (IP-MS). This showed that the Abeta(1-42) peptide is incorporated in the aggregate in a significantly larger proportion than its relative presence in the original monomer composition. IP-MS with mAb158 was also performed, and compared to IP-MS with the Abeta-selective antibody mAb1C3, where a monomeric Abeta(1-16) peptide was added to the protofibril preparation. Abeta(1-16) is known for its poor aggregation propensity, and acted therefore as a selectivity marker. The results obtained confirmed the protofibril conformation selectivity of mAb158.

Structural and Dynamics Characteristics of Acylphosphatase from Sulfolobus solfataricus in the Monomeric State and in the Initial Native-like Aggregates

It has previously been shown that the acylphosphatase from Sulfolobus solfataricus is capable of forming amyloid-like aggregates under conditions in which the native structure is maintained and via the transient formation of native-like aggregates. Based on the previously determined NMR structure of the native protein, showing a ferredoxin-like fold and the peculiar presence of an unstructured N-terminal segment, we show here, at a molecular level using NMR spectroscopy, that indeed S. solfataricus acylphosphatase remains in a native-like conformation when placed in aggregating conditions and that such a native-like structure persists when the protein forms the initial aggregates, at least within the low molecular weight species. The analysis carried out under different solution conditions, based on the measurement of the combined (1)H and (15)N chemical shifts and hydrogen/deuterium exchange rates, enabled the most significant conformational changes to be monitored upon transfer of the monomeric state into aggregating conditions and upon formation of the initial native-like aggregates. Important increases of the hydrogen/deuterium exchange rates throughout the native protein, accompanied by small and localized structural changes, in the monomeric protein were observed. The results also allow the identification of the intermolecular interaction regions within the native-like aggregates, that involve, in particular, the N-terminal unstructured segment, the apical region including strands S4 and S5 with the connecting loop, and the opposite active site.

Abstract LB-214: Identification of patients with adenomas or early- and late-stage colon carcinomas using nanoporous silica chips for protein profiling

Abstract With more than 600,000 deaths worldwide per year, Colorectal cancer (CRC) is the fifth most common form of cancer in the United States and the third leading cause of cancer-related death in the Western world. The survival rate in CRC patients is mainly influenced by the stage of the disease at the moment of diagnosis, with 5-year survival rates dropping from 95% in stage I to &amp;lt;5% in stage IV. It is widely accepted that the large majority of CRCs develop from adenomatous polyps. The so called “poly dwell time“, the average time required for the transformation of adenomatous polyps to localized cancer, is estimated to be about 10 years. These considerations point at the importance of and at the urgent need for new effective tests for the screening and monitoring of CRC onset and development. Unfortunately, the many progresses in the understanding of the malignant transformations and of the patho-genetic pathways leading to CRC onset did not result in the generation of reliable non-invasive tools for the better and earlier detection of CRC in the clinical practice. The Low Molecular Weight (LMW) region of the blood proteome provides an unprecedented opportunity for clinical diagnosis or prognosis, and for monitoring response to therapy. Proteins and peptides are degraded by proteases in the tumor stromal environment and shed into the circulation from leaky vessels. The LMW peptidome presents an attractive opportunity to capture pathological changes occurring in the tumor tissue and microenvironment. Thus far, the successful translation of this technology to routine clinical application has been limited due to: a) the large dynamic range of blood proteins limiting the detection of LMW, low abundance biomarkers; b) the rapid enzymatic alteration of the specimens due to endogenous and exogenous proteases. We developed a high-throughput, cheap, fast and reliable size-exclusion strategy based on nanoporous silica chips (NSC) for the isolation of LMW species from complex biological samples. In the NSC, pore sizes/structure and surface chemistries act as “processors” for the isolation, enrichment and stabilization of LMW species. In this work we demonstrated the identification of several circulating biomarkers able to significantly and specifically discriminate the patients according to the progression of the malignancy. This pilot study was conducted on the plasma obtained from 2 groups of patients. 1- 80 subjects (48 males and 32 females) with a median age of 68 years (range 38-85) presenting an adenocarcinoma (right colon, n=21; left colon, n=42; rectum, n=17) classified following the TNM staging system (stage IV, n=3; stage III, n=37; stage II, n=26 and stage I, n=14). 2- 29 subjects (14 males and 14 females) with median age of 66 years (range 41-80) presenting adenomatous polyps. Blood samples were obtained before any treatment. The Control group comprised 40 clean-colon healthy subjects. Unsupervised clustering showed a discriminative peptide signature that differentiates the adenoma and the carcinoma patients. We further used supervised PCA to identify specific patterns for early and late stages patients developing colorectal cancer. The surgical specimens, assessed in a standardized way, were reviewed by an independent pathologist, who was unaware of the patient's diagnosis and outcome. The histopathology findings were reported following the American Joint Committee on Cancer TNM (2002) as a confirmation of the diagnostic robustness of the NSCs. In conclusion, the analysis of the NSCs generated MALDI-MS plasma protein profiles showed a distinct pattern in late onset CRC patients with respect to early onset, adenomas and healthy subjects. Significant biomarkers for the early detection and for the assessment of cancer staging have been sequenced and identified using MALDI-MS/MS and LC-MS/MS. We envision that screenings based on the NSC technology may serve as a complement to histopathology, molecular imaging and other state of the art diagnostic techniques. In the future this approach may allow for the molecular stratification of patients, help in the selection of individualized therapeutic combinations that target the entire cancer-specific protein network, in the real-time assessment of therapeutic efficacy and toxicity, and in the rational modulation of therapy based on changes in the cancer protein network associated with prognosis and drug resistance. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-214.

Structure and phase transitions of carbonaceous mesophase binary mixtures under uniaxial extensional flow

The Maier–Saupe model for binary mixtures of uniaxial discotic nematogens, formulated in previous studies [1], is extended to simulate the effect of uniaxial extensional flow on the phase behavior and structure. The rotational diffusivity of each disk-like component in the mixture of a high molecular weight (Mw) and a low molecular weight species, is derived based on: (i) a power law that relates molecular size to molecular weight and (ii) the excluded volume of binary disc-like molecules. The thermo-rheological phase diagram of a 50/50 mixture, given in terms of temperature ( T) and Deborah ( De) number show the existence of four T– De regions and six solutions: oblate (⊥, ∥), prolate (⊥, ∥) and scalene (⊥, ∥), where the symbols (⊥, ∥) indicate alignment of the tensor order ellipsoid with respect to the extension axis. It is found that, with increasing T, the higher molecular weight component exhibits weak deviations from the well-known pure species response to uniaxial extensional flow (uniaxial ⊥ nematic → biaxial nematic → uniaxial ∥ paranematic). In contrast, the low molar mass component is always uniaxial and the orientation of the oblate or prolate states is dictated by the coupling effects emanating from the high molar mass component. Analysis of the coupling effects reveals that the changes in conformation ( oblate ⇄ prolate ) and orientation ( ⊥ ⇄ ∥ ) is effected through changes in pairs of eigenvalues. At high temperature, extensional flow acting on an isotropic phase produces an oblate paranematic state in the high Mw species and a prolate paranematic state in the low Mw species. Finally we show that X-ray intensity calculations are able to detect the different regions of the thermo-rheological phase diagram characterized by the presence of oblate, prolate, scalene nematic and paranematic states.

An Arginine Stretch Limits ADAM10 Exit from the Endoplasmic Reticulum

A disintegrin and metalloproteinase 10 (ADAM10) is a type I transmembrane glycoprotein responsible for the ectodomain shedding of a number of proteins implicated in the pathogenesis of diseases ranging from cancer to Alzheimer Disease. ADAM10 is synthesized in an inactive form, which is proteolytically activated during its forward transport along the secretory pathway and at the plasma membrane. Therefore, modulation of its trafficking could provide a mechanism to finely tune its shedding activity. Here we report the identification of an endoplasmic reticulum (ER) retention motif within the ADAM10 intracellular C-terminal tail. Sequential deletion/mutagenesis analyses showed that an arginine-rich ((723)RRR) sequence was responsible for the retention of ADAM10 in the ER and its inefficient surface trafficking. Mutating the second arginine to alanine was sufficient to allow ER exit and surface expression in both heterologous cells and hippocampal neurons. As synapse-associated protein 97 (SAP97) binds ADAM10 at its cytoplasmic tail and facilitates forward ADAM10 trafficking in neurons, we tested whether SAP97 could modulate ER export. However, neither expression nor Ser-39 phosphorylation of SAP97 in heterologous cells or hippocampal neurons were sufficient to allow the ER exit of ADAM10, suggesting that other signaling pathways or alternative binding partners are responsible for ADAM10 ER exit. Together, these results identify a novel mechanism regulating the intracellular trafficking and membrane delivery of ADAM10.

Poly(imide‐amide)s and poly(imide‐ester)s obtained from N,N′‐(4,4′‐Me,R‐diphthaloyl)‐bis‐glycine acid dichloride (R = Me, Et): Synthesis, characterization, and thermal studies

AbstractPoly(imide‐amide)s (PIAs) and poly(imide‐ester)s (PIEs) containing two Si‐atoms in the repeating unit were synthesized from acid dichlorides and diamines and diphenols, respectively. The acid dichlorides were obtained from the dianhydrides, which reacted first with glycine and then with thionyl chloride. The dianhydrides were obtained from the tetramethyl derivatives, which were oxidized to the tetra acids and then the dianhydrides were obtained with acetic anhydride. PIAs were obtained in N,N‐dimethylacetamide solution at low temperature and the PIEs in a CHCl3 solution. Monomers and polymers were characterized by IR and 1H, 13C, and 29Si‐NMR spectroscopy and the results were in agreement with the proposed structures. The ηinh values were indicative of low molecular weight species and of oligomeric nature. The glass transition (Tg) and thermal decomposition temperatures (TDT) values of PIAs were higher than those of PIEs due to the presence of the aromatic rings of the diamine. The aliphatic groups bonded to the Si atom of the acid dichloride moiety promoted the decrease of the thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The pyrolytic degradation of wood-derived lignin from pulping process

Lignin is a key component in the biomass with a complex polymeric structure of the phenyl-C3 alkyl units. The kraft lignin from the wood pulping process is tested in TG-FTIR and Py-GC-MS. The samples are pyrolyzed in TGA coupled with FTIR from 30 to 900°C at the heating rate of 20 and 40K/min. The evolution of phenolic compounds in the initial pyrolysis stage of lignin is determined by FTIR, while the second stage is mainly attributed to the production of the low molecular weight species. A bench-scale fast pyrolysis unit is employed to investigate the effect of temperature on the product yield and composition. It is found that the guaiacol-type and syringol-type compounds as the primary products of lignin pyrolysis are predominant in bio-oil, acting as the significant precursors for the formation of the derivatives such as the phenol-, cresol- and catechol-types. A series of free-radical chain-reactions, concerning the cracking of different side-chain structures and the methoxy groups on aromatic ring, are proposed to demonstrate the formation pathways for the typical compounds in bio-oil by closely relating lignin structure to the pyrolytic mechanisms. The methoxy group (–OCH3) is suggested to work as an important source for the formation of the small volatile species (CO, CO2 and CH4) through the relevant free radical coupling reactions.

Interleukin-1α treatment of meniscal explants stimulates the production and release of aggrecanase-generated, GAG-substituted aggrecan products and also the release of pre-formed, aggrecanase-generated G1 and m-calpain-generated G1-G2

Pro-inflammatory cytokines induce meniscal matrix degradation and inhibition of endogenous repair mechanisms, but the pathogenic mechanisms behind this are mostly unknown. Therefore, we investigated details of interleukin-1 (IL-1alpha)-induced aggrecan turnover in mature meniscal tissue explants. Fibro-cartilagenous disks (3 mm diameter x 1 mm thickness) were isolated from the central, weight-bearing region of menisci from 2-year-old cattle. After 3 or 6 days of IL-1alpha-treatment, GAG loss (DMMB assay), biosynthetic activity ([(35)SO(4)]-sulfate and [(3)H]-proline incorporation), gene expression (quantitative RT-PCR) and the abundance (zymography, Western blot) of matrix-degrading enzymes and specific aggrecan products were determined. Meniscal fibrocartilage had a 4-fold lower GAG content (per wet weight) than adjacent articular cartilage, and expressed MMPs-1, -2, -3 and ADAMTS4 constitutively, whereas ADAMTS5 m-RNA was essentially undetectable. Significant IL-1 effects were a decrease in biosynthetic activity, an increase in GAG release and in the expression/abundance of MMP-2, MMP-3 and ADAMTS4. Fresh tissue contained aggrecan core protein products similar to those previously described for bovine articular cartilage of this age. IL-1 induced the release of aggrecanase-generated CS-substituted products including both high (>250 kDa) and low molecular weight (about 75 kDa) species. TIMP-3 (but not TIMP-1 and -2 or a broad spectrum MMP inhibitor) inhibited IL-1-dependent GAG loss. In addition, IL-1 induced the release of preformed pools of three known G1-bearing products. We conclude that aggrecanases are responsible for IL-1-stimulated GAG release from meniscal explants, and that IL-1 also stimulates release of G1-bearing products, by a process possibly involving hyaluronan fragmentation.