Fast Depolymerization Research Articles

Fast Depolymerization of PET Bottle Mediated by Microwave Pre-Treatment and An Engineered PETase.

Invited for this month's cover is the groups of Prof. Minna Hakkarainen, Prof. István Furó and Assoc. Prof. Per-Olof Syrén at KTH Royal Institute of Technology. The image shows how microwave irradiation is an efficient pre-treatment method of polyethylene terephthalate (PET) for subsequent biocatalytic depolymerization. The Research Article itself is available at 10.1002/cssc.202300742.

Front Cover: Fast Depolymerization of PET Bottle Mediated by Microwave Pre‐Treatment and An Engineered PETase (ChemSusChem 18/2023)

Front Cover: Fast Depolymerization of PET Bottle Mediated by Microwave Pre‐Treatment and An Engineered PETase (ChemSusChem 18/2023)

Fast Depolymerization of PET Bottle Mediated by Microwave Pre-Treatment and An Engineered PETase.

Recycling plastics is the key to reaching a sustainable materials economy. Biocatalytic degradation of plastics shows great promise by allowing selective depolymerization of man-made materials into constituent building blocks under mild aqueous conditions. However, insoluble plastics have polymer chains that can reside in different conformations and show compact secondary structures that offer low accessibility for initiating the depolymerization reaction by enzymes. In this work, we overcome these shortcomings by microwave irradiation as a pre-treatment process to deliver powders of polyethylene terephthalate (PET) particles suitable for subsequent biotechnology-assisted plastic degradation by previously generated engineered enzymes. An optimized microwave step resulted in 1400 times higher integral of released terephthalic acid (TPA) from high-performance liquid chromatography (HPLC), compared to original untreated PET bottle. Biocatalytic plastic hydrolysis of substrates originating from PET bottles responded to 78 % yield conversion from 2 h microwave pretreatment and 1 h enzymatic reaction at 30 °C. The increase in activity stems from enhanced substrate accessibility from the microwave step, followed by the administration of designer enzymes capable of accommodating oligomers and shorter chains released in a productive conformation.

Radical adducts formation mechanism of CH3CO2∙ and CH3CO3∙ realized decomposition of chitosan by plasma catalyzed peracetic acid

High-molecular-weight chitosan has limited applications due to unsatisfactory solubility and hydrophilicity. Discharge plasma coupled with peracetic acid (PAA) oxidation (“plasma+PAA”) realized fast depolymerization of high-molecular-weight chitosan in this study. The molecular weight of chitosan rapidly declined to 81.1 kDa from initial 682.5 kDa within 60 s of “plasma+PAA” treatment, and its reaction rate constant was 12-fold higher than single plasma oxidation. Compared with 1O2, ∙CH3, CH3O2·, and O2∙−, CH3CO2∙ and CH3CO3∙ played decisive roles in the chitosan depolymerization in the plasma+PAA system through mechanisms of radical adduct formation. The attacks of CH3CO2∙ and CH3CO3∙ destroyed the β-(1,4) glycosidic bonds and hydrogen bonds of chitosan, leading to generation of low-molecular-weight chitosan; the main chain structure of chitosan was not changed during the depolymerization process. Furthermore, the generated low-molecular-weight chitosan exhibited greater antioxidant activities than original chitosan. Overall, this study revealed the radical adduct formation mechanisms of CH3CO2∙ and CH3CO3∙ for chitosan decomposition, providing an alternative for fast depolymerization of high-molecular-weight chitosan.

Profilin enhances cofilin induced actin dynamics.

In eukaryotic cells, spatiotemporal control of actin dynamics is crucial to regulate essential functions. Cellular structure, behavior and response to stimuli are directly regulated by the economy of actin monomers within different cellular networks. This is obtained by tightly regulating the rates of polymerization, depolymerization, and regeneration of actin monomers. Unfortunately, treadmilling of actin alone cannot sustain the volume of polymerization necessary to maintain cellular functions, since the rate of subunit loss becomes prohibitive to generating a constant pool of polymerizable actin monomers. Faster depolymerization can be achieved by a) manipulating the number of filament ends, and b) increasing the availability of monomers. Combination of Profilin and Cofilin leads to a synergistic rise in ATP consumption during bulk actin polymerization. This presents us with two possibilities where either the monomer becomes limiting or the nucleotide. From pyrene-actin traces we concluded that presence of Cofilin and Profilin together suppresses the initial rate of polymerization of the filament but does not change the critical concentration. To observe the effect of this cocktail on individual filaments, we reconstituted actin filaments in vitro and measured rates of filament severing and monomer dissociation. Despite no evidence of binding to filament sides, Profilin enhances Cofilin mediated filament severing in a dose dependent manner. Addition of Profilin also accelerates Cofilin mediated subunit loss from the barbed end of filaments. Using wildtype and mutant variants of Cofilin we also demonstrate that Profilin's effect on monomer dissociation in presence of Cofilin is distinct from its effect on severing by Cofilin. We present macroscopic evidence of direct interplay between Cofilin and Profilin to enhance barbed end monomer dissociation at Profilin concentrations much lower than previously reported.

Molten salt-assisted valorization of waste PET plastics into nanostructured SnO2@terephthalic acid with excellent Li-ion storage performance

Polyethylene terephthalate (PET) is one of the most widely used plastic materials, and therefore, its clean, efficient and low-cost valorization into high-value materials is of substantial economic and environmental interest. Here, for the first time, the utilization of molten salts for the facile, scalable and fast depolymerization of PET into terephthalic acid (C8H6O4) is reported. It is asserted that the simple heat-treatment of PET in molten KCl-LiCl containing SnCl2 in air leads to the green preparation of nanocrystalline terephthalic acid embedded with SnO2 nanocrystals, with an excellent performance as the anode of lithium ion batteries (LIBs). The structural, morphological, thermal, surface, electrical and electrochemical characteristics of plastic-derived nanocomposites are evaluated by various techniques. The sample prepared at 500 °C (PDN-500) contains 28.3 wt% SnO2, and exhibits an enhanced bulk electrical conductivity of 447.3 S m−1, and an excellent Li-ion storage capacity of 498 mAh g-1 after 500 cycles, corresponding to 1657 mAh per gram of SnO2. This performance is accompanied by an enhanced lithium ions diffusion coefficient of 8.51 × 10−10 cm2 s−1 recorded after 300 cycles, and a capacitive storage contribution of above 42 %. The sustainability of the presented molten salt approach is discussed from two complementary points of view, in terms of the clean conversion of waste plastics into high-performance anode materials for LIBs, as well as the facile and scalable depolymerization of PET, reducing the waste plastics in our environment. This article proposes an efficient and green strategy for the valorization of waste plastics into nanostructured SnO2@terephthalic acid for energy storage applications.

Chemical recycling of multi-materials from glycol-modified poly(ethylene terephthalate)

Multi-materials, such as payment or access cards commonly in circulation, are non-recyclable. We show that the adoption of glycol-modified poly(ethylene terephthalate) (PET-G) as an alternative thermoplastic enables a transition from the current linear economy to a sustainable circular economy for these multi-materials. For the first time, we demonstrate the chemical recycling of PET-G. The system promotes effective depolymerization of both pure PET-G streams and PET-G multi-materials. Higher catalyst loading enables fast depolymerization kinetics and exceptional selectivity for mixed plastics under mild conditions, with up to 93% BHET conversion. Extending this process to multi-materials, less expensive and large-scale depolymerization is enabled with a low catalyst loading at higher temperature. Kilogram-scale depolymerization of over 300 complex multi-layered credit cards and the subsequent recovery of the metal components showed the high selectivity and tolerance of the system. The readily polymerizable isolated monomers confirmed the feasibility of the proposed circular economy.

Looking at LPMO reactions through the lens of the HRP/Amplex Red assay.

Lytic polysaccharide monooxygenases (LPMOs) are unique redox enzymes capable of disrupting the crystalline surfaces of industry-relevant recalcitrant polysaccharides, such as chitin and cellulose. Historically, LPMOs were thought to be slow enzymes relying on O2 as the co-substrate, but it is now clear that these enzymes prefer H2O2, allowing for fast depolymerization of polysaccharides through a peroxygenase reaction. Thus, quantifying H2O2 in LPMO reaction set-ups is of a great interest. The horseradish peroxidase (HRP)/Amplex Red (AR) assay is one of the most popular and accessible tools for measuring hydrogen peroxide. This assay has been used in various types of biological and biochemical studies, including LPMO research, but suffers from pitfalls that need to be accounted for. In this Chapter, we discuss this method and its use for assessing the often rate-limiting in situ formation of H2O2 in LPMO reactions. We show that, after accounting for multiple potential side reactions, quantitative data on H2O2 production obtained with the HRP/Amplex Red assay provide useful clues for understanding the catalytic activity of LPMOs, including the impact of reductants and transition metal ions.

Modeling microtubule dynamic instability: Microtubule growth, shortening and pause

Microtubules (MTs) are protein polymers found in all eukaryotic cells. They are crucial for normal cell development, providing structural support for the cell and aiding in the transportation of proteins and organelles. In order to perform these functions, MTs go through periods of relatively slow polymerization (growth) and very fast depolymerization (shortening), where the switch from growth to shortening is called a catastrophe and the switch from shortening to growth is called a rescue. Although MT dynamic instability has traditionally been described solely in terms of growth and shortening, MTs have been shown to pause for extended periods of time, however the reason for pausing is not well understood. Here, we present a new mathematical model to describe MT dynamics in terms of growth, shortening, and pausing. Typically, MT dynamics are defined by four key parameters which include the MT growth rate, shortening rate, frequency of catastrophe, and the frequency of rescue. We derive a mathematical expression for the catastrophe frequency in the presence of pausing, as well as expressions to describe the total time that MTs spend in a state of growth and pause. In addition to exploring MT dynamics in a control-like setting, we explore the implicit effect of stabilizing MT associated proteins (MAPs) and stabilizing and destabilizing chemotherapeutic drugs that target MTs on MT dynamics through variations in model parameters.

Application Progress of Modified Chitosan and Its Composite Biomaterials for Bone Tissue Engineering.

In recent years, bone tissue engineering (BTE), as a multidisciplinary field, has shown considerable promise in replacing traditional treatment modalities (i.e., autografts, allografts, and xenografts). Since bone is such a complex and dynamic structure, the construction of bone tissue composite materials has become an attractive strategy to guide bone growth and regeneration. Chitosan and its derivatives have been promising vehicles for BTE owing to their unique physical and chemical properties. With intrinsic physicochemical characteristics and closeness to the extracellular matrix of bones, chitosan-based composite scaffolds have been proved to be a promising candidate for providing successful bone regeneration and defect repair capacity. Advances in chitosan-based scaffolds for BTE have produced efficient and efficacious bio-properties via material structural design and different modifications. Efforts have been put into the modification of chitosan to overcome its limitations, including insolubility in water, faster depolymerization in the body, and blood incompatibility. Herein, we discuss the various modification methods of chitosan that expand its fields of application, which would pave the way for future applied research in biomedical innovation and regenerative medicine.

Cationic polymerization of high‐molecular‐weight phthalaldehyde‐butanal copolymer

ABSTRACTLow ceiling temperature polyaldehydes are of interest for transient materials because the temperature of depolymerization can be at or below room temperature. There is interest in expanding the number of aldehydes which can be copolymerized so as to change the vapor pressure and other properties of the depolymerized products. Although fast depolymerization has been achieved with polyaldehydes, the rate of monomer evaporation after depolymerization can be controlled by incorporating lower molecular weight monomers into the polymer. High vapor pressure aliphatic aldehydes have been copolymerized with low vapor pressure and high reactivity phthalaldehyde to create stable, high molecular weight polymers with high vapor pressure. A method for measuring the depolymerization time by quartz crystal microbalance has been developed. The copolymer of phthalaldehyde and butanal improves the evaporation time for the polymer by a factor of 11. The onset of thermal decomposition of the copolymer was increased from 107 °C for the phthalaldehyde homopolymer to 141 °C for the copolymer. The tensile strength of the copolymer was 0.8–1.6 GPa. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46921.

Application of Arrhenius law to DP and zero-span tensile strength measurements taken on iron gall ink impregnated papers: relevance of artificial ageing protocols

Iron gall inks (IGI) were largely used for writing until the nineteenth century. Under certain circumstances, they provoke a substantial degradation of their cellulosic support. It was shown in a previous works that combination of oxygen and iron largely impacts cellulose chain breaking occurring in acidic conditions (pH 3–4). The present study aims to study the kinetic of this degradation. It assesses the validity of Arrhenius law between 20 and 90 °C taking advantage of the fast depolymerization of IGI impregnated papers at room temperature and using two complementary tools: DP measurements and zero-span tensile strength. The first one is sensitive enough to measure degradation at its very beginning, while the second is more appropriate for advanced stage of degradation. Similar activation energies (97 ± 2 kJ mol−1) were found via DP and zero-span measurements, and reaction rates of IGI impregnated papers were 1–2 orders of magnitude above available data related to lignin-free acidic papers. These observations suggest a dominant hydrolytic mechanism that involves directly or indirectly oxygen and iron.

CaMKII prevents spontaneous acrosomal exocytosis in sperm through induction of actin polymerization

In order to interact with the egg and undergo acrosomal exocytosis or the acrosome reaction (AR), mammalian spermatozoa must undergo a series of biochemical changes in the female reproductive tract, collectively called capacitation. We showed that F-actin is formed during sperm capacitation and fast depolymerization occurs prior to the AR. We hypothesized that F-actin protects the sperm from undergoing spontaneous-AR (sAR) which decreases fertilization rate. We show that activation of the actin-severing protein gelsolin induces a significant increase in sAR. Moreover, inhibition of CaMKII or PLD during sperm capacitation, caused an increase in sAR and inhibition of F-actin formation. Spermine, which leads to PLD activation, was able to reverse the effects of CaMKII inhibition on sAR-increase and F-actin-decrease. Furthermore, the increase in sAR and the decrease in F-actin caused by the inactivation of the PLD-pathway, were reversed by activation of CaMKII using H2O2 or by inhibiting protein phosphatase 1 which enhance the phosphorylation and oxidation states of CaMKII. These results indicate that two distinct pathways lead to F-actin formation in the sperm capacitation process which prevents the occurrence of sAR.

Microwave-assisted fast conversion of lignin model compounds and organosolv lignin over methyltrioxorhenium in ionic liquids

Fast depolymerization of β-O-4 model compounds and organosolv lignin to aromatic chemicals over methyltrioxorhenium in ionic liquids without oxidant/reducing agent under microwave irradiation is developed.

Preparation of 5-Hydroxymethylfurfural from Cellulose via Fast Depolymerization and Consecutively Catalytic Conversion

The conversion of cellulose to 5-hydroxymethylfurfural (HMF) has been investigated by a one-pot consecutive reaction. At first, cellulose was depolymerised into glucose via a fast degradation of cellulose in molten ZnCl2 in the presence of hydrochloric acid, and the yield of glucose is 75% in 120 s at reaction temperature of 95 °C. Then, DMSO was used as solvent and different kinds of metal chloride were added as catalysts, and the conversion was carried out continuously at 110–130 °C for 0.5–4 h. The yield of HMF was 53% when CrCl3 were used as catalyst. The one-pot two steps conversion was carried out at atmosphere pressure, and it is a simple route to prepare HMF from lignocellulosic feedstock on a large scale.

Novel macrothiols for the synthesis of a structurally comprehensive dendritic library using thiol–ene click chemistry

In the last decades, the fabrication of ordered nano- and microporous structures has attracted increasing interest due to their specific properties and multiple possible applications in electronics, as templates or in the biological field. The development of such materials has been favored by the introduction of the simple breath-figure templating method in the 1990’s. In order to fully exploit the potential of these porous materials, the use of advanced functional molecules as precursors is essential. One suitable class of molecules is the well-defined linear-dendritic hybrids (LD hybrids) family. The structural variations, multiple end-groups and possible amphiphilicity of these molecules are significant advantages that could lead to highly sophisticated functional materials with potential usage in biology. Therefore, this project was directed towards the synthesis of advanced LD hybrids and the evaluation of their ability to form ordered functional porous films.A degradation and toxicity study was initially conducted on polyester-based 2,2-bis(methylol)propionic acid (bis-MPA) dendrimers under physiological conditions to support the potential usage of these molecules for biological purposes. The materials were found to undergo a relatively fast depolymerization process at pH 7.5. Moreover, the initial dendrimer and its decomposition products were proven to be non-toxic for immune competent cells, allowing for the utilization of these molecules for biological applications.A linear-dendritic-linear hybrid library was successfully synthesized from biocompatible poly(ethylene glycol) (PEG), poly(e-caprolactone) (PCL) and bis-MPA building blocks using a combination of ring-opening polymerization (ROP)and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The materials, consisting of one long PEG block connected to the focal point of the dendron and several PCL arms attached at its periphery, were used to construct ordered porous films using the breath figure method. The polymeric architecture strongly affected the ordering of the films with a more regular morphology obtained from a more flexible polymer. Changing the semi-crystalline PCL to amorphous polylactide (PLA) also permitted the formation of porous arrays. Interestingly, films obtained from inverted structures possessing one long PCL block and several short PEG chains, also presented a regular morphology. Moreover they could be activated to exhibit multiple surface hydroxyl groups.To increase the number of orthogonal synthetic methodologies available for the preparation of advanced macromolecules, high molecular weight dendritic macrothiols were synthesized. These molecules were efficiently coupled to a number of core molecules via thiol-ene coupling, generating a comprehensive library of dendritic materials. This approach represents an attractive alternative to the commonly used, but potentially toxic, CuAAC.Exploiting the obtained results, a final LD hybrid was synthesized from atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) derivatives and thiol-ene coupling (TEC) with macrothiols. This macromolecule was successfully utilized to form functional ordered porous arrays and the availability of peripheral alkyne functional groups was demonstrated by efficient coupling with fluorescent Rhodamine-B. The HEMA-backbone allowed for the introduction of cross-linkable azide groups that were used to significantly improve the thermal stability of the films from 50 °C to 200 °C. These materials have the potential to be used in applications such as catalysis, in medicine and as sensors.

Patronin Regulates the Microtubule Network by Protecting Microtubule Minus Ends

Tubulin assembles into microtubule polymers that have distinct plus and minus ends. Most microtubule plus ends in living cells are dynamic; the transitions between growth and shrinkage are regulated by assembly-promoting and destabilizing proteins. In contrast, minus ends are generally not dynamic, suggesting their stabilization by some unknown protein. Here, we have identified Patronin (also known as ssp4) as a protein that stabilizes microtubule minus ends in Drosophila S2 cells. In the absence of Patronin, minus ends lose subunits through the actions of the Kinesin-13 microtubule depolymerase, leading to a sparse interphase microtubule array and short, disorganized mitotic spindles. In vitro, the selective binding of purified Patronin to microtubule minus ends is sufficient to protect them against Kinesin-13-induced depolymerization. We propose that Patronin caps and stabilizes microtubule minus ends, an activity that serves a critical role in the organization of the microtubule cytoskeleton.

CYTO 2010—Overview of the XXV ISAC Congress Proceedings Issue of Cytometry Part A

issue of Cytometry Part A presents the second occasionon which a call has been issued to encourage authors to sub-mit their best work to the Journal for publication in a specialCongress Proceedings Issue of Cytometry. The incentive forsubmission was that accepted papers would be guaranteed anoral presentation at the XXV ISAC Congress in Seattle—CYTO 2010. The manuscripts submitted for the call werereviewed via the normal Cytometry Part A review process andthen by a second level of review by the Congress OrganizingCommittee. The outcome of this strict peer-review processwas that nine papers were accepted for the Proceedings Issueof Cytometry Part A. The research articles provide excellentexamples of some of the latest trends in the field of cytometryand we highlight them here in this editorial review. The topicsof the accepted papers range from application of 12-color flowcytometry through characterization of new probes and investi-gation of cytoskeleton elements to analysis of nuclear structurefrom histopathology images.Modern polychromatic flow cytometry can providehigher resolution approaches for the dissection and identifica-tion of cell subpopulations (1,2). In this issue, the paper byAutissier et al. (page 410) describes how 12-color flow cytome-try can be used for studying the phenotypes of lymphocyte,monocyte, and dendritic cell subsets. The authors developed asingle flow cytometry panel that allows for simultaneousdetection of the lymphocyte and monocyte cell populationsand all known DC subsets. Studying these crucial subpopula-tions of the immune system in one single panel may give abroader view of the immune response during HIV infectionand can be used for monitoring AIDS pathogenesis.Polychromatic cytometry has become increasingly impor-tant in slide-based applications with the drive to increase thenumber of measurable fluorochromes for multiparametricanalysis. New fluorochromes have been introduced where thefluorescent dyes possess different optical characteristicsincluding spectral range, lifetime signatures, and improvedphotostability (3–5). The special feature of slide-based cyto-metry is that analyzed fields can be revisited, providing a basisfor the application of sequential photobleaching of fluoro-chromes next to very photostable dyes to increase the numberof parameters captured. In this issue, Wessels et al. (page 420)analyzed the newly available NorthernLights secondary anti-bodies for use in slide-based cytometry and microscopy. Theypointed out that since the NorthernLights are bright, resistantto photobleaching, stable in alcohols and xylene, these dyesare promising candidates for use with most laser- and HBO/XBA-based fluorescence microscopy techniques. It is antici-pated that combination of NorthernLights with laser scanningcytometry could provide a better methodology for analysis oftumor dissemination to bone marrow and lymph node (6).The other group of fluorescent probes aims to stain cellorganelles with high specificity. Development of fluorescent,organelle-targeted probes has been driven by an interest in dis-covering new probes that excite and emit in the visible spec-

The effects of detergents on the polymerization properties of actin

Effects of some detergents-most frequently used in membrane raft studies-on the polymerization properties of actin were examined under in vitro and in vivo conditions, for protein and cellular investigations, respectively. Under in vitro conditions the polymerization rates were measured with pyrene-labeled actin. We found that polymerization rate depended on the detergent concentration by following either biphasic characteristics or only decreasing tendency. The strongest effects were observed at relatively low detergent concentrations. SDS-PAGE electrophoresis and dynamic light-scattering measurements provided further evidences for the size distribution of actin filaments formed under the influence of detergents. Comparing the polymerization rates measured in the presence of different detergents to those obtained with various magnesium and KCl concentrations showed that detergents may influence the actin polymerization at three levels by modifying: (i) the monomer-monomer interaction, (ii) the local ionic strength, and (iii) the affinity of actin for various cations. In vivo studies on NIH 3T3MDR1 cells using TRITC-phalloidin detected fast depolymerization of large extent around the critical micellar concentrations of the detergents. We concluded that microdomain insolubility observed in the presence of detergents is hardly to be the result of the stabilization of the submembrane actin cytoskeleton merely; rather inter-lipid and lipid-protein interactions are also involved within the detergent-resistant membranes.

Soluble and Thermally Stable Polysulfones Prepared by the Regiospecific and Alternating Radical Copolymerization of 2,4-Hexadiene with Sulfur Dioxide

We synthesized the alternating copolymers of 1,3-diene monomers with sulfur dioxide (SO2) as a new class of thermally stable polymers by the radical copolymerization process and the subsequent hydrogenation. The copolymerizations of 2,4-hexadiene (HD), 1,3-butadiene (BD), and isoprene (IP) with SO2 were carried out at −78 to 0 °C in toluene in the presence of tert-butyl hydroperoxide, which acts as one component in the redox initiating system in combination with SO2. The resulting poly(diene-alt-SO2)s were found to consist of highly controlled repeating units, that is, an alternating and 1,4-regiospecific repeating structure. Poly(HD-alt-SO2) was soluble in several organic solvents, such as chloroform, nitromethane, tetrahydrofuran, acetone, and dimethyl sulfoxide. In contrast, poly(IP-alt-SO2) was soluble only in dimethyl sulfoxide, whereas poly(BD-alt-SO2) was insoluble in all of the solvents. The poly(diene-alt-SO2)s readily degraded upon heating because of the expected fast depolymerization. We have d...