Depolymerization Agent Research Articles

Exploratory DSC investigation on the solvolytic depolymerization of PET in varied solvent systems and in the presence of model additives and contaminants

Solvolytic depolymerization of polyethylene terephthalate (PET) is a thermo-chemical recycling route that valorizes plastic waste by recovering monomers and chemicals that can be reused for the synthesis of new polymers. This study focuses on neutral hydrolysis due to the potential environmental and economic benefits of water as depolymerization agent compared to alternative organic solvents. High-pressure crucibles were used as batch reactors in differential scanning calorimetry (DSC) to perform real-time monitoring of the thermodynamic phenomena taking place during solvolytic depolymerization of PET in varied solvent systems. PET melting point depression was found to be the main identified phenomena, with PET melting point exhibiting a drop of almost 30 °C in water and 50 °C in monoalcohol solvents like methanol and ethanol. Moreover, PET only underwent significant depolymerization prior to melting in NaOH containing systems. Gas Chromatography and Mass Spectrometry were used to study the fate of model additives and contaminants under solvolytic conditions. The uncertainty concerning these foreign substances poses a challenge for the development of PET solvolytic technologies, and the methods here provided proved to be a fast-screening technique to quantify the conversion and identify potential degradation products of model additives like 2-(2-hydroxy-5-methylphenyl) benzotriazole UV-stabilizer, 1-(methylamino) anthraquinone dye, and model contaminant (R)-(+)-limonene under hydrothermal conditions.

Improving the Sustainability of Catalytic Glycolysis of Complex PET Waste through Bio-Solvolysis.

This work addresses a novel bio-solvolysis process for the treatment of complex poly(ethylene terephthalate) (PET) waste using a biobased monoethylene glycol (BioMEG) as a depolymerization agent in order to achieve a more sustainable chemical recycling process. Five difficult-to-recycle PET waste streams, including multilayer trays, coloured bottles and postconsumer textiles, were selected for the study. After characterization and conditioning of the samples, an evaluation of the proposed bio-solvolysis process was carried out by monitoring the reaction over time to determine the degree of PET conversion (91.3-97.1%) and bis(2-hydroxyethyl) terephthalate (BHET) monomer yield (71.5-76.3%). A monomer purification process, using activated carbon (AC), was also developed to remove the colour and to reduce the metal content of the solid. By applying this purification strategy, the whiteness (L*) of the BHET greatly increased from around 60 to over 95 (L* = 100 for pure white) and the Zn content was significantly reduced from around 200 to 2 mg/kg. The chemical structure of the purified monomers was analyzed via infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), and the composition of the samples was measured by proton nuclear magnetic resonance (1H-NMR), proving a high purity of the monomers with a BHET content up to 99.5% in mol.

Rapid chemical recycling of waste polyester plastics catalyzed by recyclable catalyst

Waste plastics are serious environmental threats due to their low degradability and low recycling rate. Rapid and efficient waste plastics recycling technologies are urgently demanded for a sustainable future. Herein, we report a rapid, closed-loop, and streamlined process to convert polyesters such as poly(ethylene terephthalate) (PET) back to its purified monomers. Using trifluoromethanesulfonic acid or metal triflates as the recyclable catalyst, polyesters such as PET can be completely depolymerized by simple carboxylic acids within 1 h. By coupling this acidolysis with a subsequent hydrogenolysis process, the consumed carboxylic acid was recovered and the closed-loop of PET depolymerization could be established. All catalysts and depolymerization agents are fully recycled while only PET and hydrogen are consumed.

Hydrothermal liquefaction of sewage sludge anaerobic digestate for bio-oil production: Screening the effects of temperature, residence time and KOH catalyst.

Due to sewage sludge being an abundant biobased resource, and with the number of biogas plants utilizing sewage sludge increasing, digested sewage sludge (DSS) is a promising feedstock for producing bio-oil. This study uses DSS from a biogas plant to produce bio-oil in a hydrothermal liquefaction process adjusting time from 2 to 6 hours, temperature from 280 to 380°C and the presence of a base as a depolymerization agent and potential catalyst. High conversion yields are obtained, with the maximum of 58 wt% on a dry, ash free basis and an energy recovery of up to 94%. The oils contain compounds with a potential for utilization as biofuels and building blocks, especially fatty acids as biodiesel feedstock and biobased phenols, glycols and aliphatic alcohols.

Characterization of suberinic acids from birch outer bark as bio-based adhesive in wood composites

Huge amounts of synthetic binders and polymers are used for the production of wood-based composites which are toxic to humans during the production and exploitation of products because of the risk of harmful vapor emissions. The bio-based society requires new value chains for the production of bio-based materials. Suberinic acids (SA) have a high potential to replace synthetic binders and polymers due to the unique structure. In this study, hydrolytic depolymerization of birch outer bark in alkaline environment was carried out. To evaluate the adhesive properties, the chemical composition and structure were analyzed using chemical and instrumental methods. To set independent variables for the design of experiments (DOE), the following preliminary parameters were investigated: filtered and unfiltered SA; impact of the depolymerization agent; the fractional composition of the raw material. Based on the obtained results, DOE with three independent variables (depolymerization time, pH after acidification, alkali concentration) was used for the selection of optimal depolymerization parameters. It has been concluded that, with increasing concentration of KOH in the depolymerization solution and the reaction time, suberin is depolymerized to a higher extent and thus there is a higher amount of monomeric SA, monosaccharides and polyphenolic compounds in the resulting adhesive, which positively affects the physico-mechanical properties of the obtained particleboards. These substances together form cross-linked structures that provides not only the mechanical strength but also water resistance of the resulting particleboards. The optimal SA-based adhesive was improved by increasing the KOH concentration to 4%, acidifying to the pH 3 and reducing the reaction time to 0.5 h. The obtained particleboards' properties (modulus of rupture – 19.0 N mm−2, modulus of elasticity – 2604 N mm−2, thickness swelling – 14.3% and internal bonding – 2.25 N mm−2) meet the requirements of the particleboard standard EN 312 type P3. Still, this is an experimental work and the hot-pressing parameters must be decreased to consider the possibility to introduce the adhesive in the large-scale industry.

Progressing Ultragreen, Energy-Efficient Biobased Depolymerization of Poly(ethylene terephthalate) via Microwave-Assisted Green Deep Eutectic Solvent and Enzymatic Treatment.

Effective interfacing of energy-efficient and biobased technologies presents an all-green route to achieving continuous circular production, utilization, and reproduction of plastics. Here, we show combined ultragreen chemical and biocatalytic depolymerization of polyethylene terephthalate (PET) using deep eutectic solvent (DES)-based low-energy microwave (MW) treatment followed by enzymatic hydrolysis. DESs are emerging as attractive sustainable catalysts due to their low toxicity, biodegradability, and unique biological compatibility. A green DES with triplet composition of choline chloride, glycerol, and urea was selected for PET depolymerization under MW irradiation without the use of additional depolymerization agents. Treatment conditions were studied using Box-Behnken design (BBD) with respect to MW irradiation time, MW power, and volume of DES. Under the optimized conditions of 20 mL DES volume, 260 W MW power, and 3 min MW time, a significant increase in the carbonyl index and PET percentage weight loss was observed. The combined MW-assisted DES depolymerization and enzymatic hydrolysis of the treated PET residue using LCC variant ICCG resulted in a total monomer conversion of ≈16% (w/w) in the form of terephthalic acid, mono-(2-hydroxyethyl) terephthalate, and bis-(2-hydroxyethyl) terephthalate. Such high monomer conversion in comparison to enzymatically hydrolyzed virgin PET (1.56% (w/w)) could be attributed to the recognized depolymerization effect of the selected DES MW treatment process. Hence, MW-assisted DES technology proved itself as an efficient process for boosting the biodepolymerization of PET in an ultrafast and eco-friendly manner.

Ectopic expression of GhIQD14 (cotton IQ67 domain-containing protein 14) causes twisted organ and modulates secondary wall formation in Arabidopsis

In plants, although KNOX genes are known to regulate secondary cell wall (SCW) formation, their protein-regulating mechanisms remain largely unknown. Here, we showed that GhKNL1, which regulates SCW formation and fiber development in cotton, could interact with an IQ67 domain containing protein (GhIQD14) in yeast. Confocal observation showed that GhIQD14 was localized to the microtubules. In Arabidopsis, ectopic expression of GhIQD14 caused hypocotyls to be sensitive to microtubule depolymerization agent, organ twisting of seedlings, trichomes, rosette leaves, and capsules, as well as severely irregular xylem vessels and thicker interfascicular fiber cell walls in the inflorescence stem. Furthermore, we found that GhIQD14 interacted with AtKNAT7 in vivo, and instantaneous co-expression of GhIQD14 and AtKNAT7 in tobacco showed that GhIQD14 weakened the distribution of AtKNAT7 in the nucleus, bringing it into the microtubules, thus affecting the SCW formation related genes expression. Our results suggested that GhIQD14 might be involved in the morphological development and SCW formation in cotton.

Multidimensional profiling of drug-treated cells by Imaging Mass Cytometry.

In pharmaceutical research, high‐content screening is an integral part of lead candidate development. Measuring drug response in vitro by examining over 40 parameters, including biomarkers, signaling molecules, cell morphological changes, proliferation indices, and toxicity in a single sample, could significantly enhance discovery of new therapeutics. As a proof of concept, we present here a workflow for multidimensional Imaging Mass Cytometry™ (IMC™) and data processing with open source computational tools. CellProfiler was used to identify single cells through establishing cellular boundaries, followed by histoCAT™ (histology topography cytometry analysis toolbox) for extracting single‐cell quantitative information visualized as t‐SNE plots and heatmaps. Human breast cancer‐derived cell lines SKBR3, HCC1143, and MCF‐7 were screened for expression of cellular markers to generate digital images with a resolution comparable to conventional fluorescence microscopy. Predicted pharmacodynamic effects were measured in MCF‐7 cells dosed with three target‐specific compounds: growth stimulatory EGF, microtubule depolymerization agent nocodazole, and genotoxic chemotherapeutic drug etoposide. We show strong pairwise correlation between nuclear markers pHistone3S28, Ki‐67, and p4E‐BP1T37/T46 in classified mitotic cells and anticorrelation with cell surface markers. Our study demonstrates that IMC data expand the number of measured parameters in single cells and brings higher‐dimension analysis to the field of cell‐based screening in early lead compound discovery.

ESLICARBAZEPINE ACETATE IS ANTIEPILEPTOGENIC IN THE LATRUNCULIN A MOUSE MODEL OF PARTIAL SEIZURES

Although there are many drugs available which have powerful anticonvulsant activity, there is still a high unmet need for antiepileptogenic compounds that prevent the development of chronic epilepsy. Eslicarbazepine acetate (ESL) is a once‐daily (QD) antiepileptic drug (AED) that is converted extensively to eslicarbazepine (a voltage‐gated sodium channel and T‐type calcium channel blocker) after oral administration.1 ESL is a potent anticonvulsant in animal models. Latrunculin A is an actin depolymerization agent that promotes neurotransmitter release in hippocampal synapses and induces multiple action potential firing and increases action potential duration. Latrunculin A hippocampal microperfusion in freely moving mice induces acute epileptic seizures, followed by the occurrence of chronic sporadic spontaneous seizures, in association with changes in extracellular concentrations of excitatory and inhibitory amino acids.2 We have examined ESL for its potential antiepileptogenic activity in preventing the development of chronic partial seizures induced by latrunculin A microperfusion in the mouse hippocampus.Hippocampi of freely‐moving C57BL/6J male mice were continuously perfused with latrunculin A (8 μg/ml, 1 μl/min, 8h/day) for 72 hours. Sham animals received injections of artificial CSF. Forty‐eight‐hours after intrahippocampal latrunculin A infusion, mice were administered either vehicle, 75 mg/kg or 150 mg/kg ESL p.o. once‐daily for three consecutive days. CSF‐infused mice received vehicle. Body temperature and home‐cage locomotor behaviour were assessed four weeks after the end of ESL treatment. Cortical EEG monitoring by telemetry was performed once per week after the end of ESL treatment over a period of six weeks. Data is presented as means ± standard error of the mean (SEM). Data was analyzed using One‐ or Two‐way ANOVA followed by Holm‐Sidak's multiple comparisons test, as appropriate; planned comparison were performed between sham or vehicle (control) and ESL treated groups.Latrunculin A microperfusion in the mouse hippocampus induced electrographic seizures and discharges in the mouse. EEG monitoring showed that transitory ESL treatment within the epileptogenic period caused a sustained significant decrease in the frequency (42 and 74% decrease for 75 and 150 mg/kg ESL versus vehicle at week 4, respectively; 62 and 72% decrease for 75 and 150 mg/kg ESL versus vehicle at week 6, respectively) of epileptiform discharges. There were no significant differences between the two doses of ESL used. Latrunculin A microperfusion and transitory ESL treatment induced no changes in body temperature and locomotor activity, as assessed on week 4 after latrunculin A administration.Transitory oral ESL treatment attenuated sporadic spontaneous electrographic seizures and discharges induced by latrunculin A microperfusion in the mouse hippocampus, supporting a possible anti‐epileptogenic effect of ESL.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Functional role for stable microtubules in lens fiber cell elongation

The process of tissue morphogenesis, especially for tissues reliant on the establishment of a specific cytoarchitecture for their functionality, depends a balanced interplay between cytoskeletal elements and their interactions with cell adhesion molecules. The microtubule cytoskeleton, which has many roles in the cell, is a determinant of directional cell migration, a process that underlies many aspects of development. We investigated the role of microtubules in development of the lens, a tissue where cell elongation underlies morphogenesis. Our studies with the microtubule depolymerizing agent nocodazole revealed an essential function for the acetylated population of stable microtubules in the elongation of lens fiber cells, which was linked to their regulation of the activation state of myosin. Suppressing myosin activation with the inhibitor blebbistatin could attenuate the loss of acetylated microtubules by nocodazole and rescue the effect of this microtubule depolymerization agent on both fiber cell elongation and lens integrity. Our results also suggest that acetylated microtubules impact lens morphogenesis through their interaction with N-cadherin junctions, with which they specifically associate in the region where lens fiber cell elongate. Disruption of the stable microtubule network increased N-cadherin junctional organization along lateral borders of differentiating lens fiber cells, which was prevented by suppression of myosin activity. These results reveal a role for the stable microtubule population in lens fiber cell elongation, acting in tandem with N-cadherin cell-cell junctions and the actomyosin network, giving insight into the cooperative role these systems play in tissue morphogenesis.

Design, synthesis and biological evaluation of 4-anilinoquinoline derivatives as novel potent tubulin depolymerization agents

A series of novel 4-anilinoquinoline derivatives were synthesized and evaluated for their antiproliferative activities. Among them, 14h exhibited the most potent cytotoxic activity with IC50 values ranging from 1.5 to 3.9 nM against all tested cancer cell lines, and showed promising efficacy in multidrug resistant cancer cells. Flow cytometry assay, immune-fluorescence staining, microtubule dynamics assays and competition assays with EBI identified that 14h was a novel tubulin depolymerization agent by binding to the colchicine site. Importantly, in vivo efficacy evaluation of HCT116 xenograft model, 14h showed efficient antitumor activity without significant loss in body weight. All the results indicated that 14h could be a promising candidate for the treatment of cancer.

Structural Insights into the Inhibition of Tubulin by the Antitumor Agent 4β-(1,2,4-triazol-3-ylthio)-4-deoxypodophyllotoxin.

The colchicine domain is widely recognized as the binding site of microtubule depolymerization agents for anticancer drug design. Almost all of the drugs targeting the colchicine domain have been confirmed to bind to the tubulin β-subunit. Here we studied a crystal structure (2.3 Å) of the complex between tubulin and 4β-(1,2,4-triazol-3-ylthio)-4-deoxypodophyllotoxin (compound 1S) with superior antitumor activity, which was designed on the basis of the colchicine domain and synthesized in our previous work. A distinct binding model of the colchicine domain was found in the complexes of tubulin with compound 1S. From a comparison of the crystal structures of tubulin-compound 1S and tubulin-colchicine complexes, the side chains of the T7 loop of β-tubulin flip outward and the T5 loop of α-tubulin changes its conformation. It has been shown that the β-subunit T7 loop reversibly participates in resistance to straightening that opposes microtubule assembly by flipping in and out. Together with the biochemical results from compound 1S, the structural data highlight the main contributors in the α-subunits and the colchicine domain β-subunits: the dual-target binding sites in the α-T7 loop and β-H7-T7 loop of tubulin. Compound 1S can synchronously bind to αβ-tubulin. The structures also highlight common features for the design and development of novel potent microtubule destabilizing agents.

Enzyme-Based Strategies for Structuring Foods for Improved Functionality.

Enzyme technologies can be used to create food dispersions with novel functional attributes using structural design principles. Enzymes that utilize food-grade proteins and/or polysaccharides as substrates have gained recent interest among food scientists. The utilization of enzymes for structuring foods is an ecologically and economically viable alternative to the utilization of chemical cross-linking and depolymerization agents. This review highlights recent progress in the use of enzymes to modify food structures, particularly the interfacial and/or bulk properties of food dispersions with special emphasis on commercially available enzymes. Cross-linking enzymes such as transglutaminase and laccase promote the formation of intra- and intermolecular bonds between biopolymers to improve stability and functionality, whereas various degrading enzymes such as proteases alter the native conformation of proteins, leading to self-assembly of hierarchically ordered colloids. Results of this bio-inspired approach show that rational use of structure-affecting enzymes may enable food manufacturers to produce food dispersions with improved physical, functional, textural, and optical properties.

Calcineurin/NFAT Activation-Dependence of Leptin Synthesis and Vascular Growth in Response to Mechanical Stretch.

Background and Aims: Hypertension and obesity are important risk factors of cardiovascular disease. They are both associated with high leptin levels and have been shown to promote vascular hypertrophy, through the RhoA/ROCK and ERK1/2 phosphorylation. Calcineurin/NFAT activation also induces vascular hypertrophy by upregulating various genes. This study aimed to decipher whether a crosstalk exists between the RhoA/ROCK pathway, Ca2+/calcineurin/NFAT pathway, and ERK1/2 phosphorylation in the process of mechanical stretch-induced vascular smooth muscle cell (VSMC) hypertrophy and leptin synthesis.Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch and exogenous leptin (3.1 nM) on VSMC hypertrophy and leptin synthesis. Results showed that stretching the RPV significantly upregulated leptin secretion, mRNA, and protein expression, which were inhibited by the calcium channel blocker nifedipine (10 μM), the selective calcineurin inhibitor FK506 (1 nM), and the ERK1/2 inhibitor PD98059 (1 μM). The transcription inhibitor actinomycin D (0.1 μM) and the translation inhibitor cycloheximide (1 mM) significantly decreased stretch-induced leptin protein expression. Mechanical stretch or leptin caused an increase in wet weight changes and protein synthesis, considered as hypertrophic markers, while they were inhibited by FK506 (0.1 nM; 1 nM). In addition, stretch or exogenous leptin significantly increased calcineurin activity and MCIP1 expression whereas leptin induced NFAT nuclear translocation in VSMCs. Moreover, in response to stretch or exogenous leptin, the Rho inhibitor C3 exoenzyme (30 ng/mL), the ROCK inhibitor Y-27632 (10 μM), and the actin depolymerization agents Latrunculin B (50 nM) and cytochalasin D (1 μM) reduced calcineurin activation and NFAT nuclear translocation. ERK1/2 phosphorylation was inhibited by FK506 and C3.Conclusions: Mechanical stretch-induced VSMC hypertrophy and leptin synthesis and secretion are mediated by Ca2+/calcineurin/NFAT activation. RhoA/ROCK and ERK1/2 activation are critical for mechanical stretch-induced calcineurin activation.

DSC study of silicas with immobilized polysiloxane layer of different architecture

Core–shell structured nanocomposites of polydimethylsiloxane with different polymerization degree (PMS100 and PMS50) and polymethylphenylsiloxane (PMPS4) immobilized onto fumed silica nanoparticles were studied by means of differential scanning calorimetry. The polysiloxanes were attached to the particles’ surface using thermally stimulated binding and modification in the presence of depolymerization activator—dimethyl carbonate (DMC). Single- and multi-stage processes were applied in order to obtain a different architecture of polymeric layer on the silica nanoparticles surface. The effect of polysiloxane/DMC ratio on phase transitions of obtained polymeric layers was evaluated. The grafting of polydimethylsiloxane at the presence of chain scissor resulted in cross-linking of the attached polymeric layers. When using a multi-step modification with PMPS, a dense cross-linked layer was formed on the silica surface. Unlike the samples obtained by one-step modification with different polymer content, for which the amount of polymer attached to silica surface changes the parameters of the relaxation process in polymeric layer, for composites synthesized using multi-stage modification, a greater influence has the length of the oligomer introduced on first stage. The best results were achieved for composite with PMPS when using on the first stage of modification the PMPS/DMC mixture with low content of depolymerization agent (oligomers with long chain, respectively). A notable increase in the mobility of the polymeric layer was detected due to the formation of isotactic macromolecular chains.

Mechanical stretch-induced vascular hypertrophy occurs through modulation of leptin synthesis-mediated ROS formation and GATA-4 nuclear translocation

Background: Obesity and hypertension are associated with increased leptin production contributing to cardiovascular remodeling. Mechanisms involving mechanical stretch-induced leptin production and the cross talk between signaling pathways leading to vascular remodeling have not been fully elucidated.Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch on leptin protein expression in vascular smooth muscle cells (VSMCs). Moreover, the involvement of reactive oxygen species (ROS), the RhoA/ROCK pathway, actin cytoskeleton dynamics and the transcriptional factor GATA-4 activation in mechanical stretch-induced vascular remodeling were investigated. Stretching the RPV for 1 or 24 h significantly increased leptin protein level and ROS formation in VSMCs, which was prevented by 1 h pretreatment with the ROCK inhibitor Y-27632 and the actin cytoskeleton depolymerization agent cytochalasin D. Moreover, Western blotting and immunohistochemistry revealed that mechanical stretch or treatment with 3.1 nmol/L leptin for 24 h significantly increased actin polymerization, as reflected by an increase in the F-actin to G-actin ratio. Increases in blood vessels’ wet weight and [3H]-leucine incorporation following a 24 h treatment with conditioned media from cultured stretched RPVs indicated RPV hypertrophy. This effect was prevented by 1 h pretreatment with anti-leptin antibody, indicating leptin’s crucial role in promoting VSMC hypertrophy. As an index of GATA-4 activation, GATA-4 nuclear translocation was assessed by immunohistochemistry method. Pretreating VSMC with leptin for 1 h significantly activated GATA-4 nuclear translocation, which was potently attenuated by the NADPH oxidase inhibitor apocynin, Y-27632, and cytochalasin D.Conclusion: Our results demonstrate that ROS formation, RhoA/ROCK pathway, and GATA-4 activation play a pivotal role in mechanical stretch-induced leptin synthesis leading to VSMC remodeling.

Phosphorylation of eIF4GII and 4E-BP1 in response to nocodazole treatment: A reappraisal of translation initiation during mitosis

Translation mechanisms at different stages of the cell cycle have been studied for many years, resulting in the dogma that translation rates are slowed during mitosis, with cap-independent translation mechanisms favored to give expression of key regulatory proteins. However, such cell culture studies involve synchronization using harsh methods, which may in themselves stress cells and affect protein synthesis rates. One such commonly used chemical is the microtubule de-polymerization agent, nocodazole, which arrests cells in mitosis and has been used to demonstrate that translation rates are strongly reduced (down to 30% of that of asynchronous cells). Using synchronized HeLa cells released from a double thymidine block (G1/S boundary) or the Cdk1 inhibitor, RO3306 (G2/M boundary), we have systematically re-addressed this dogma. Using FACS analysis and pulse labeling of proteins with labeled methionine, we now show that translation rates do not slow as cells enter mitosis. This study is complemented by studies employing confocal microscopy, which show enrichment of translation initiation factors at the microtubule organizing centers, mitotic spindle, and midbody structure during the final steps of cytokinesis, suggesting that translation is maintained during mitosis. Furthermore, we show that inhibition of translation in response to extended times of exposure to nocodazole reflects increased eIF2α phosphorylation, disaggregation of polysomes, and hyperphosphorylation of selected initiation factors, including novel Cdk1-dependent N-terminal phosphorylation of eIF4GII. Our work suggests that effects on translation in nocodazole-arrested cells might be related to those of the treatment used to synchronize cells rather than cell cycle status.

Stimulation of biogenic methane generation in coal samples following chemical treatment with potassium permanganate

Bioconversion of coal to methane has many economic and environmental advantages over more conventional processes. This study summarizes data on the stimulation of generation of methane from a subbituminous coal treated with potassium permanganate (KMnO4) as a depolymerization agent. The general bioavailability of the soluble coal-derived components is also evaluated by the aerobic production of CO2. Of the total coal carbon, 5.4% was solubilized into the aqueous phase. Based on aerobic and anaerobic bioassay, 27.7% of the soluble carbon was used as substrate by microorganism to produce carbon dioxide (CO2), and 3.2% was used to produce methane (CH4). The methane accumulated rapidly and peaked at day 40 with 93.4μmol CH4/g coal. A small fraction of the soluble carbon (143.0μmol CH4/g coal) was designated as volatile and was removed by sparging with nitrogen gas. This fraction was shown to have a significant impact on gas generation. The findings of this study provide the basis for a better understanding of the underlying processes involved in the rate-limiting step of coal solubilization; moreover, they provide evidence of the significant potential for the in situ/ex situ enhancement of biogenic natural gas production in depleted hydrocarbon reserves such as coal. The aerobic and anaerobic bioassays may be useful to evaluate sites for field applications intended to enhance methane production processes.

Contribution of the Actin Cytoskeleton to the Viscoelastic Characteristics of Inwardly Remodeled Arterioles

In hypertension, one of the most important structural changes in the vasculature is the inward remodeling of arterioles, which is characterized by a reduction in passive luminal diameter. In arterioles, prolonged exposure to vasoconstrictor agonists or the reducing agent Dithiothreitol (DTT) induces inward remodeling. Therefore, we hypothesized that DTT induces inward remodeling via prolonged vasoconstriction and remodeling of the actin cytoskeleton. In rat cremaster isolated arterioles, acute exposure to DTT induced a concentration‐dependent constriction. A 4‐hour exposure to 200μM DTT caused prolonged vasoconstriction and induced an 11±4% reduction in passive diameter, with an increase in media‐to‐lumen ratio from 0.14±0.01 to 0.20±0.02. All this was inhibited in the presence of Cytochalasin‐D (500nM). Passive pressure‐diameter curves were obtained for control and remodeled arterioles before and after a 1‐hour incubation with the actin depolymerization agent Mycalolide‐B (2μM). The elasticity of control arterioles was not affected by Mycalolide‐B, but was increased by 21% in remodeled arterioles. These results indicate that DTT induces inward remodeling via prolonged vasoconstriction and that the change in viscoelastic characteristics of inwardly remodeled arterioles, namely increased stiffness, is partially dependent on the F‐actin components of the cytoskeleton. NIH HL‐088105 to LAM

Keep Your Eyes Open: Challenges And Opportunities In Ophthalmic Therapeutics

The eyes are our windows to the world. Major ocular diseases, including cataracts, glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), dry eye syndrome and allergic conjunctivitis, can cause vision impairment and even blindness, which not only affect our daily life, but also have a significant socio-economic and psychological impact on our society. The prevalence of vision impairment was estimated to be 147 million people in 2010, and is projected to reach 191 million in the word in 2020 due to an increase in aging populations. The market for ophthalmic disease therapeutics is expected to reach $18.7 billion this year, and is predicted to grow steadily. Ophthalmic drug development has been in the forefront of therapeutic research partly because the eye is an accessible and immunologically isolated organ, which has the advantage of avoiding the complications of systemic drug delivery. With the recent advances in genetics, genomics and stem cell biology, the mechanisms of many ophthalmic diseases are being increasingly revealed. Accordingly, the field of ophthalmic therapeutics is facing unprecedented challenges and opportunities. Looking back in history, ophthalmic drug development has been driven by the scientific breakthroughs. For example, the discovery that vascular endothelial growth factor (VEGF) is a driving force of choroidal neovascularization in AMD has led to the successful development of anti-VEGF antibodies for wet AMD therapy. The discovery that prostaglandin mediates reduction in intraocular pressure (IOP) has led to the treatment of ocular hypertension in glaucoma using prostaglandin analogues. Research over the past decade has uncovered novel mechanisms for many ocular diseases, which will likely spawn new therapeutic solutions. But this field is not without challenges: (A) currently there is no cure for many ocular diseases, including dry AMD, DR and glaucoma; (B) current ophthalmic drug development is not based on the unique characteristics of ocular diseases, but mainly applies agents developed for non-ocular diseases to the eye; (C) most of the ocular diseases are multi-factorial diseases with both genetic and environmental (nutritional) risk factors, therefore many drugs only work for a subset of patients. For example, cyclosporine, acting as an immune-modulator for dry-eye disease, is only effective in about 15% of all patients; (D) ophthalmic drug delivery, especially to the posterior eye, remains a considerable challenge. These challenges present unique opportunities for researchers in the field of ophthalmology to further elucidate the mechanisms of and develop innovative therapeutics and delivery approaches for ocular diseases. Despite the challenges, significant progress has recently been made towards understanding the mechanisms of several ocular diseases, which may translate into future therapeutics. Dry AMD accounts for up to 90% of the AMD cases and is currently without cure. Polymorphisms in members of the complement system, especially complement factor H (CFH), have been associated with AMD. Moreover, CFH was recently shown to protect against oxidative stress-induced inflammation in animal model. Inhibitors of the complement system and the recombinant form of CFH are being tested preclinically for AMD treatment. Aβ amyloid, originally implicated in Alzheimer’s disease, was recently associated with pathogenesis of AMD. Anti-Aβ amyloid antibody has shown promise in animal models of AMD. Autophagy is currently being investigated for AMD involvement, and may represent a potential therapeutics for AMD (See review in this issue). Diabetic retinopathy is one of the leading causes of blindness in the working class. Besides laser photocoagulation and vitrectomy surgery, several therapeutic options, including protein kinase inhibitors, cyclooxygenase inhibitors, anti-VEGF and slow release steroid, are on clinical trials. Some of them may enter the market in the near future. As reviewed in this issue, pericytes and the angiopoietin (Ang)-Tie-2 signaling also play an important role in the development of DR, and may be potential therapeutic targets for DR. For glaucoma, the current mainstay for treatment is to lower IOP, therefore preventing further damage to the optic nerve. β-blocker, prostaglandin, carbonic anhydrase inhibitor, miotics, α-adrenergic agonist, or their combinations are routinely used for lowering IOP. Rho kinase inhibitors and actin depolymerization agents are currently tested in clinical trials for safely reducing IOP. Dominant mutations in the olfactomedin (OLF) domain of myocilin have been associated with several populations of familial glaucoma, and molecular studies suggest that the OLF domain of myocilin may be a bona fide target for future glaucoma therapeutics (reviewed in this issue). Looking into future, the explosion in basic research in ocular biology and disease will lead to revolutionarily innovative ophthalmic therapeutics. Numerous opportunities also present themselves to researchers working on medicinal chemistry, new biomaterials, and new delivery system (see reviews for these subjects in the issue). With the coordinated effort of all these groups, the future of ophthalmic therapeutics is bright.