Chain Precursor Research Articles

Trends of polyfluoroalkyl compounds in marine biota and in humans

Environmental context Polyfluoroalkyl compounds are used in a variety of industrial and consumer applications, including polymer production and for surface treatment of textiles and paper. Research over the last 10 years has shown that these compounds are ubiquitous environmental contaminants – they are extremely persistent, show toxic effects and accumulate in the food chain. We evaluate global, temporal and spatial trends of these important emerging contaminants. Abstract This review gives an overview of existing knowledge of polyfluoroalkyl compounds (PFCs) in humans and in marine biota. Temporal trends and spatial distribution of PFCs were globally compared in humans, marine mammals, seabirds and fish. In general, PFC concentrations in the environment have increased significantly from the beginning of the production up to the 1990s. After the phase-out of perfluorooctane sulfonyl fluoride (POSF) production starting in 2000, PFC concentrations in humans generally decreased. In marine biota no clear temporal trends were observed. The temporal trends depended on the species, their trophic levels and the geographical locations. PFC patterns in humans and in marine wildlife species were compared regarding perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), their shorter and longer chain homologues (C4–C15) and precursor compounds. Finally knowledge gaps were identified and recommendations for future work were presented.

The PCA and LDA analysis on the differential expression of proteins in breast cancer.

Breast cancer is a leading cause of mortality in women. In Malaysia, it is the most common cancer to affect women. The most common form of breast cancer is infiltrating ductal carcinoma (IDC). A proteomic approach was undertaken to identify protein profile changes between cancerous and normal breast tissues from 18 patients. Two protein extracts; aqueous soluble and membrane associated protein extracts were studied. Thirty four differentially expressed proteins were identified. The intensities of the proteins were used as variables in PCA and reduced data of six principal components (PC) were subjected to LDA in order to evaluate the potential of these proteins as collective biomarkers for breast cancer. The protein intensities of SEC13-like 1 (isoform b) and calreticulin contributed the most to the first PC while the protein intensities of fibrinogen beta chain precursor and ATP synthase D chain contributed the most to the second PC. Transthyretin precursor and apolipoprotein A-1 precursor contributed the most to the third PC. The results of LDA indicated good classification of samples into normal and cancerous types when the first 6 PCs were used as the variables. The percentage of correct classification was 91.7% for the originally grouped tissue samples and 88.9% for cross-validated samples.

The PCA and LDA Analysis on the Differential Expression of Proteins in Breast Cancer

Breast cancer is a leading cause of mortality in women. In Malaysia, it is the most common cancer to affect women. The most common form of breast cancer is infiltrating ductal carcinoma (IDC). A proteomic approach was undertaken to identify protein profile changes between cancerous and normal breast tissues from 18 patients. Two protein extracts; aqueous soluble and membrane associated protein extracts were studied. Thirty four differentially expressed proteins were identified. The intensities of the proteins were used as variables in PCA and reduced data of six principal components (PC) were subjected to LDA in order to evaluate the potential of these proteins as collective biomarkers for breast cancer. The protein intensities of SEC13-like 1 (isoform b) and calreticulin contributed the most to the first PC while the protein intensities of fibrinogen beta chain precursor and ATP synthase D chain contributed the most to the second PC. Transthyretin precursor and apolipoprotein A-1 precursor contributed the most to the third PC. The results of LDA indicated good classification of samples into normal and cancerous types when the first 6 PCs were used as the variables. The percentage of correct classification was 91.7% for the originally grouped tissue samples and 88.9% for cross-validated samples.

Synthesis and Properties of Polyurethane Elastomers with Castor Oil as Crosslinker

AbstractCastor oil–polyurethane elastomers were prepared by reacting poly (1,4‐butane diol) (Terathane 1400) with aliphatic 1,6‐hexamethylene diisocyanate. The prepolymers were chain‐extended with bifunctional precursor chains and/or with castor oil as a trifunctional crosslinker at stoichiometric ratios. These resulted in a series of crosslinked polyurethane elastomers with different structures of the hard segment. The properties of the material were measured by differential scanning calorimetry, thermogravimetric analysis, atomic force microscopy, as well as tensile properties measurements. The effect of stoichiometric balance (i.e., OH/NCO molar ratio) on the final properties was evaluated. The formation of hydrogen bonds was observed by Fourier transform infrared.spectroscopy The measured properties were found to be strongly influenced by the molar ratio of chain extenders to the diisocyanate component. The glass transition temperatures (Tg) for the polyurethanes with OHpolyol/NCO/OHchain extender having molar ratios of 1:2:1 and 1:4:3 were found to be −70 and −57 °C, respectively. The polyurethanes networks with a OH/NCO molar ratio of 1:2:1 had excellent mechanical properties, indicating that this is the optimum ratio to be used in castor oil polyurethane elastomer formulations. The objective of this work was to study the effect of the castor oil crosslinker on the morphology of the resulting crosslinked polyurethanes and to correlate the morphology with the properties of these bio‐based crosslinked polyurethanes.

A further investigation on a MALDI‐based method for evaluation of markers of renal damage

The validity of the urinary protein profile to characterize the pathological states of diabetic, nephropathic and diabetic-nephropathic patients was considered on the basis of previously obtained results by MALDI/MS, showing a different abundance ratio of the collagen alpha1 and alpha5 chain precursor fragments at m/z 1219 and 2049 and of the uromodulin precursor fragment at m/z 1912 observed in healthy subjects and patients; a larger number of subjects was examined and the obtained results were statistically evaluated. The p values related to the observed differences indicate that they are statistically significant when comparing all patients versus healthy controls, diabetic with normo or microalbuminuria versus nephropathic with advanced renal disease patients and diabetic with normo or microalbuminuria versus diabetic with advanced nephropathy patients. The scatter plot matrix gives evidence of the strict inverse relationship between the abundances of ions at m/z 1912 and 1219, the correlation coefficient being particularly high (r = 0.921, p < 0.001). The relationship between the true positive rate (sensitivity) and false positive rate (1-specificity) for every possible cutoff value in abundance of the considered ionic species was investigated through the receiver-operating characteristic (ROC) curve. The obtained data indicate that a good differentiation of nephropathic patients with advanced renal disease and diabetic patients with advanced nephropathy versus healthy subjects can be easily obtained by this approach.

Effect of Precursor Molar Mass on the 2H NMR Line Shapes of End-Linked PDMS Elastomers

A series of end-linked PDMS networks synthesized with different molar mass precursor chains is examined using 2H NMR spectroscopy. The resulting line shapes for networks in the undeformed state show clear differences with precursor chain molar mass. Furthermore, samples uniaxially extended to high extension ratio show a clear shoulder in the line shape and two characteristic splittings (two doublets). Comparison with spectra for deuterated free chains dissolved in an unlabeled network confirms that the inner doublet results from excluded volume interactions between segments whereas the outer doublet is due to more highly aligned chain segments from chains with conformations trapped by the cross-linking reaction.

Structure and properties of cross‐linked polyurethane copolymers

AbstractPolyurethane elastomers based on polyester diols and aromatic or aliphatic diisocyanates can be used as vibration dampers and isolation materials. Two series of cross‐linked polyurethanes with various hard segment structures and different amounts were prepared and thermomechanical properties of these materials were studied. Cross‐linked polyurethane copolymers composed of poly(ethylene adipate)diol as soft segment and 4,4′‐methylenebis(phenylisocyanate), 1,6‐hexamethylene diisocyanate, and diols glycerin, 1,4‐butanediol, and 1,6‐hexanediol as hard segments were synthesized by a two‐step process. The networks have been prepared by end‐linking a mixture of the bifunctional precursor chains with trifunctional cross‐linkers at off‐stoichiometric ratios. The results show that the cross‐link and the polyurethane hard segment interaction play a special role in the interconnected chain density and its magnitude is revealed by the mechanical properties. Of most importance, maximum stress, tensile modulus, and elongation at break increased significantly at the 22 wt % composition of hard segment content. Interchain cross‐linking improves thermal stability, which was measured by thermogravimetric analysis and differential scanning calorimetry. Cross‐linked polyurethane behaves as an elastomer and is useful for shock, noise, and vibration control. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:165–172, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20155

Biomarkers of Rejection: Are We Any Closer to the Philosopher’s Stone?

Biomarkers of Rejection: Are We Any Closer to the Philosopher’s Stone?

Cycloate, an inhibitor of fatty acid elongase, modulates the metabolism of very‐long‐side‐chain alkylresorcinols in rye seedlings

Cycloate inhibits the biosynthesis of very-long-chain fatty acids, the essential constituents of plant waxes and suberin. Fatty acids also serve as precursors of aliphatic carbon chains in resorcinolic lipids, which play a fundamental role in the plant defence system against fungal pathogens. In this study, the effect of cycloate on the biosynthesis of 5-n-alkylresorcinols in rye seedlings (Secale cereale L.) grown under various light and thermal conditions was examined. The content of alkylresorcinols biosynthesised in rye was generally increased by the herbicide in both green and etiolated plants. The presence of cycloate also affected patterns of alkylresorcinol homologues in plants grown at 15 and 22 degrees C; very-long-side-chain compounds were less abundant, whereas both short-chain saturated and unsaturated homologues were generally accumulated. No cycloate-related effects caused by homologue pattern modifications were observed at elevated temperature. This study extends present understanding of the mode of action of thiocarbamate herbicides. Cycloate markedly affected the biosynthesis of very-long-side-chain resorcinolic lipids in rye seedlings, confirming the existence of parallels in both fatty acid and alkylresorcinol biosynthetic pathways. The observed cycloate-driven accumulation of 5-n-alkylresorcinols may improve the resistance of cereals to infections caused by microbial pathogens.

Identification of novel immunodominant epididymal sperm proteins using combinatorial approach

Functionally immature spermatozoa leave the testis mature during epididymal transit. This process of maturation involves either addition of new proteins or modification of existing proteins onto the sperm domains that are responsible for domain-specific functions. Epididymal proteins are preferred targets for immunocontraception. In an attempt to identify epididymis-specific sperm proteins, we used a novel combinatorial approach comprising subtractive immunization (SI) followed by proteomics. Following SI, sera of mice were used for immunoproteomics, which led to the identification of 30 proteins, of which four proteins namely sperm head protein 1, sperm flagella protein 2 (SFP2), SFP3, and SFP4 are being reported for the first time on sperm. Another group of four proteins namely collagen alpha-2 (I) chain precursor, homeodomain-interacting protein kinase 1, GTP-binding protein Rab1, and ubiquinol cytochrome c reductase core protein II although reported earlier in testis are being reported for the first time in epididymal sperm. Furthermore, seven out of these eight novel proteins could be validated using peptide ELISA. These data are a useful repository, which could be exploited to develop targets for post-testicular immunocontraception or biomarkers for infertility diagnosis and management.

Mass transfer model of nanoparticle-facilitated contaminant transport in saturated porous media

A one-dimensional model has been evaluated for transport of hydrophobic contaminants, such as polycyclic aromatic hydrocarbon (PAH) compounds, facilitated by synthetic amphiphilic polyurethane (APU) nanoparticles in porous media. APU particles synthesized from poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains have been shown to enhance the desorption rate and mobility of phenanthrene (PHEN) in soil. A reversible process governed by attachment and detachment rates was considered to describe the PMUA binding in soil in addition to PMUA transport through advection and dispersion. Ultimately, an irreversible second-order PMUA attachment rate in which the fractional soil saturation capacity with PMUA was a rate control was found to be adequate to describe the retention of PMUA particles. A γ-distributed site model (GS) was used to describe the spectrum of physical/chemical constraints for PHEN transfer from solid to aqueous phases. Instantaneous equilibrium was assumed for PMUA–PHEN interactions. The coupled model for PMUA and PHEN behavior successfully described the enhanced elution profile of PHEN by PMUA. Sensitivity analysis was performed to analyze the significance of model parameters on model predictions. The adjustable parameter α in the γ-distribution shapes the contaminant desorption distribution profile as well as elution and breakthrough curves. Model simulations show the use of PMUA can be also expected to improve the release rate of PHEN in soils with higher organic carbon content. The percentage removal of PHEN mass over time is shown to be influenced by the concentration of PMUA added and this information can be used to optimize cost and time require to accomplish a desired remediation goal.

Expanding functions of lipoprotein receptors

Lipoprotein receptors are evolutionarily ancient proteins that are expressed on the surface of many cell types. Beginning with the appearance of the first primitive multicellular organisms, several structurally and functionally distinct families of lipoprotein receptors evolved. Originally, these cell surface proteins were thought to merely mediate the traffic of lipids and nutrients between cells and, in some cases, by functioning as scavenger receptors, remove other kinds of macromolecules, such as proteases and protease inhibitors from the extracellular space and the cell surface. Over the last decade, this picture has fundamentally changed. We now appreciate that many of these receptors are not mere cargo transporters; they are deeply embedded in the machinery by which cells communicate with each other. By physically interacting and coevolving with fundamental signaling pathways, lipoprotein receptors have occupied essential and surprisingly diverse functions that are indispensable for integrating the complex web of cellular signal input during development and in differentiated tissues.

VGD and MLD-motifs containing heterodimeric disintegrin viplebedin-2 from Vipera lebetina snake venom

We have previously demonstrated that the fibrinolytic enzyme lebetase is synthesized with disintegrin-like domain that is cleaved posttranslationally (Siigur et al., 1996). Now we isolated a heterodimeric disintegrin viplebedin-2 containing this disintegrin-like part from Vipera lebetina venom using size-exclusion chromatography on Sephadex G-100 sf and HPLC on C18 column. The molecular masses of viplebedin-2 and tryptic peptides from both chains of viplebedin-2 were determined by MALDI-TOF mass spectrometry. Using cDNA library of the venom gland of a single V. lebetina turanica snake the viplebedin-2 coding cDNAs were cloned and sequenced. Viplebedin-2 chains are synthesized from two different genes. One chain, containing VGD sequence in disintegrin loop, is synthesized as a disintegrin-like part of the PII-type metalloprotease, lebetase. The other chain, containing MLD sequence in disintegrin loop, is synthesized from the gene without metalloproteinase domain. Two polyadenylation signal sequences have been found in MLD sequence coding chain precursor cDNAs. Viplebedin-2 dose-dependently inhibited adhesion of platelets to immobilized collagen and inhibited collagen-induced platelet aggregation.

Visualizing phase separation in polystyrene/polystyrene homo‐IPNs via sulfonation

AbstractBACKGROUND: Polystyrene/polystyrene (PS/PS) interpenetrating polymer networks (IPNs) represent ideal homo‐IPNs. Whether phase separation occurs in this system has been a long‐standing problem, which is closely related to the self‐organization mechanism in IPN formation and is important to the exploration of new polymer morphologies and properties by topological isomerism.RESULTS: A series of bead samples of PS/PS sequential IPNs with the same nominal divinylbenzene contents were synthesized by suspension polymerization, followed by sulfonation. Scanning electron micrographs and energy‐dispersive X‐ray mapping show unique distinctive topography on both surfaces and fractured surfaces and large heterogeneity in sulfonation of the PS/PS IPN beads, which for the first time provide visual evidence for dual‐phase continuity in PS/PS IPNs.CONCLUSION: The phase separation behavior is proposed to be due to hydrodynamic screening, architectural asymmetry and excluded volume interactions between network I and the precursor chains of network II. This is considered to represent pure IPN effects in sequential formation and may shed light on the general constitution mechanism and molecular design of IPN materials. Copyright © 2009 Society of Chemical Industry

Proteomics Analysis of Epithelial Cells Reprogrammed in Cell-free Extract

The functional reprogramming of a differentiated cell to a pluripotent state presents potential beneficial applications in regenerative medicine. We report here the proteomic profile of 293T epithelial cells reprogrammed to a pluripotent state using undifferentiated embryonal carcinoma (NCCIT) cellular extracts. 293T cells were reversibly permeabilized with streptolysin O, incubated in an extract of NCCIT cells or a control extract of 293T cells for 1 h, resealed with CaCl(2), and cultured. OCT4 and SOX2 gene expression were up-regulated in NCCIT extract-treated cells relative to control cells, whereas there was no alteration in DNMT3B gene expression. Thirty percent of NCCIT extract-treated cells were positive for SSEA-4, and karyotyping confirmed their 293T origin, excluding the possibility of contamination from NCCIT cells. Two-dimensional PAGE revealed approximately 400 protein spots for each cell type studied. At least 10 protein spots in the proteome of NCCIT extract-treated cells had an expression profile similar to that of NCCIT and remained unaltered in control cells. Using tandem mass spectrometry, we identified these proteins, which include 78-kDa glucose-regulated protein precursor and tropomyosin alpha-3 chain. This investigation provides the first evidence that proteins are altered in a specific manner in NCCIT extract-treated cells. This is the first report on the proteomic characterization of the nuclear reprogramming process.

Low molecular weight proteins in urines from healthy subjects as well as diabetic, nephropathic and diabetic‐nephropathic patients: a MALDI study

Urine samples from healthy subjects as well as diabetic, nephropathic and diabetic-nephropathic patients were analyzed by matrix assisted laser desorption/ionization (MALDI) mass spectrometry in order to establish evidence of some possible differences in the peptide profile related to the pathological states. Multivariate analysis suggested the possibility of a distinction among the considered groups of patients. Some differences have been found, in particular, in the relative abundances of three ions at m/z 1912, 1219 and 2049. For these reasons, further investigation was carried out by MALDI/TOF/TOF to determine the sequence of these peptides and, consequently, to individuate their possible origin. By this approach, the peptide at m/z 1912 was found to originate from uromodulin, and its lower expression in the case of nephropathy can be well related to the pathological condition. Ions at m/z 2049 and 1219 originate from the collagen alpha-1(I) chain precursor and from the collagen alpha-5 (IV) chain precursor, respectively, and, also in this case, their different expressions can be related to the pathologies under investigation. The obtained data seem to indicate that urine is an interesting biological fluid to investigate on the peptide profile and to obtain, consequently, information on the dismetabolism activated by specific pathologies.

Understanding the molecular basis of plant growth promotional effect of Pseudomonas fluorescens on rice through protein profiling.

BackgroundPlant Growth Promoting Rhizobacteria (PGPR), Pseudomonas fluorescens strain KH-1 was found to exhibit plant growth promotional activity in rice under both in-vitro and in-vivo conditions. But the mechanism underlying such promotional activity of P. fluorescens is not yet understood clearly. In this study, efforts were made to elucidate the molecular responses of rice plants to P. fluorescens treatment through protein profiling. Two-dimensional polyacrylamide gel electrophoresis strategy was adopted to identify the PGPR responsive proteins and the differentially expressed proteins were analyzed by mass spectrometry.ResultsPriming of P. fluorescens, 23 different proteins found to be differentially expressed in rice leaf sheaths and MS analysis revealed the differential expression of some important proteins namely putative p23 co-chaperone, Thioredoxin h- rice, Ribulose-bisphosphate carboxylase large chain precursor, Nucleotide diPhosphate kinase, Proteosome sub unit protein and putative glutathione S-transferase protein.ConclusionFunctional analyses of the differential proteins were reported to be directly or indirectly involved in growth promotion in plants. Thus, this study confirms the primary role of PGPR strain KH-1 in rice plant growth promotion.

Immobilization and Activity of Pepsin in Silicone Elastomers

Pepsin [EC, 3.4.23.1] from Porcine stomach mucosa was immobilized in silicone elastomers utilizing condensation-cure room temperature vulcanization (RTV) of silanol-terminated poly(dimethylsiloxane) (PDMS). Two network precursor chain molar masses were used in this investigation: in pepsin–silicone (A), M n ∼26,000 g mol−1 and in pepsin–silicone (B) M n ∼750 g mol−1. Tetraethyl orthosilicate (TEOS) was used as the cross-linking agent and dibutyltin dilaurate was used as the catalyst. The activity and stability of free pepsin and pepsin immobilized in PDMS were studied with respect to pH, temperature, cross-link density, solvents and storage time using a hemoglobin assay. A notable finding is that free pepsin has zero activity in neutral buffer solution (pH 7) after incubation for 5 h, while pepsin immobilized in the silicone elastomers was found to retain more than 70% of its maximum normalized activity. There was no marked improvement in the thermal stability of the PDMS immobilized pepsin when compared to free pepsin and all the three systems showed no activity at and above 70 °C. From the Lineweaver–Burk kinetic analyses, the apparent K m (g L−1 hemoglobin) for free pepsin was 4.5, for pepsin–silicone (A) was 5.1, and for pepsin–silicone (B) was 3.9, the V max (U/mg of pepsin) for free pepsin was 14,000, for pepsin–silicone (A) was 11,710, and for pepsin–silicone (B) was 8,510, respectively after incubation in buffer solution at pH 2 and 37 °C. The activity of the free and the PDMS immobilized pepsin in six different organic solvents was also studied. The pepsin retained high activity in non-polar solvents such as n-hexane, isooctane and toluene, but the enzyme performed poorly in methanol, ethanol and tetrahydrofuran. The degree of swelling of the pepsin immobilized silicone elastomers in these solvents had no impact on the activity of the pepsin. When stored at room temperature for time periods up to 6 months, pepsin immobilized in silicone elastomers was observed to retain its full activity. The results reported herein demonstrate that cross-linked PDMS is a promising support material for the immobilization of hydrolytic enzymes such as pepsin.

Large strain behaviour of nanostructured polyelectrolyte hydrogels

The mechanical properties of nanostructured polyelectrolyte hydrogels have been investigated targeting specifically the nonlinear deformation regime at large strains and the fracture properties. The hydrogels were synthesized using a thiol-ene cross-linking chemistry of polyacrylic acid precursor chains previously functionalized with double bonds. Some polymers were also grafted with C12 side chains able to form hydrophobic clusters in water. The large strain deformation of these nanostructured gels was tested in uniaxial compression by performing loading/unloading cycles at different strain rates and up to different maximum strains. All hydrogels displayed a pronounced strain hardening before fracture and a strain dependent hysteresis but the magnitude of these effects depended on the details of the composition. The most pronounced strain hardening was observed for the unmodified hydrogels in pure water while the largest hysteresis was found for the gels containing the highest concentration of nanoclusters. These dissipative processes barely influence the mechanical behaviour at small strains where the gel remains very elastic but become important at large strains and improve the resistance to fracture of the gels.

Synthesis of Lipid-α-End-Functionalized Chains by RAFT Polymerization. Stabilization of Lipid/Polymer Particle Assemblies

A functional dithioester including a phospholipid moiety (Lipid-DT) has been synthesized in a high yield (71% after purification) from a precursor chain transfer agent (CTA) and fully characterized. The RAFT polymerization of an acrylamide derivative, N-acryloylmorpholine (NAM), mediated by this Lipid-DT exhibits a prolonged induction period in comparison with a nonfunctional dithioester. This phenomenon is discussed in terms of steric shielding induced by the bulky lipid moiety of the CTA. Moreover, the lipid moiety located at the α-end of the chains has a strong influence on the size exclusion chromatography analyses in THF using a standard-based calibration, with the suspicion of a retention phenomenon. The well-defined structure of the lipid-end-functionalized polymer chains has been evidenced by MALDI−TOF mass spectrometry. Finally, these chains have been successfully incorporated into lipid/polymer particle assemblies (LipoParticles) that resulted in an improved stabilization in aqueous medium at re...