Polyion Hydrogels of Polymeric and Nanofibrous Carboxymethyl Cellulose and Chitosan: Mechanical Characteristics and Potential Use in Environmental Remediation.

Recently, cellulose and other biomass nanofibers (NFs) have been increasingly utilized in the design of sustainable materials for environmental, biomedical, and other applications. However, the past literature lacks a comparison of the macromolecular and nanofibrous states of biopolymers in various materials, and the advantages and limitations of using nanofibers (NF) instead of conventional polymers are poorly understood. To address this question, hydrogels based on interpolyelectrolyte complexes (IPECs) between carboxymethyl cellulose nanofibers (CMCNFs) and chitosan (CS) were prepared by ele+ctrostatic cross-linking and compared with the hydrogels of carboxymethyl cellulose (CMC) and CS biopolymers.

Multi-color polymer carbon dots synthesized from waste polyolefins through phenylenediamine-assisted hydrothermal processing.

The large accumulation and low recycling rates of polyolefin waste have posed a threat to the environment and human health. The shortage of chemical recycling methods for polyolefins strongly demands the development of new and sustainable treatment technologies for hydrocarbon plastics to improve their waste management. In this study, polyethylene (PE) and polypropylene (PP) were utilized for the preparation of multi-color polymer carbon dots (PCDs) via a two-step hydrothermal (HT) synthesis involving (i) thermo-oxidative degradation of polyolefins to precursors containing plentiful oxygen-based functional groups, and (ii) modification with phenylenediamine (PDA).

Functional upcycling of waste PET plastic to the hybrid magnetic microparticles adsorbent for cesium removal.

Accumulation of mismanaged plastic in the environment and the appearance of emerging plastic-derived pollutants such as microplastics strongly demand technologies for waste plastic utilization. In this study, polyethylene terephthalate (PET) from waste plastic bottles was directly utilized to prepare a matrix of an adsorbent for cesium (Cs) removal. The organic matrix of PET-derived oligomers obtained by aminolysis depolymerization was impregnated with bentonite clay and magnetite nanoparticles (FeO NPs), playing the roles as a major adsorptive medium for Cs removal and as a functional component to primarily provide efficient separation of the hybrid adsorbent from aqueous system, respectively.

Copper Ion Removal Using a Waste-Plastic-Derived Hydrogel Adsorbent Prepared via Microwave-Assisted PET Aminolysis.

Despite the tremendous progress in the development of functional materials from plastic waste to promote its recycling, only a few examples of hydrogel materials from plastic waste were reported. In this study, microwave-assisted depolymerization of waste PET plastic using polyamine was performed to prepare short aminophthalamide oligomers followed by chemically cross-linking into a hydrogel material. Catalyst-free microwave-assisted aminolysis of PET was completed within 30-40 s, demonstrating high efficiency of the depolymerization reaction.

Templating of catalytic gold and silver nanoparticles by waste plastic PET-derived hydrogel playing a dual role of a reductant and a matrix.

The progressive accumulation of discarded plastic in the environment demands further development of waste management of plastic waste and conversion technologies of such waste to value-added materials. Recently, the conversion of plastic waste to functional materials via chemical recycling has attracted considerable attention. In this report, plastic waste (PET) was utilized for the preparation of a hydrogel-based catalyst via a cross-linking reaction of PET-derived oligo(terephthalamide)s followed by the electroless metallization.

Reconstituted TAD-size chromatin fibers feature heterogeneous nucleosome clusters.

Large topologically associated domains (TADs) contain irregularly spaced nucleosome clutches, and interactions between such clutches are thought to aid the compaction of these domains. Here, we reconstituted TAD-sized chromatin fibers containing hundreds of nucleosomes on native source human and lambda-phage DNA and compared their mechanical properties at the single-molecule level with shorter '601' arrays with various nucleosome repeat lengths. Fluorescent imaging showed increased compaction upon saturation of the DNA with histones and increasing magnesium concentration.

DNA-Chitosan Hydrogels: Formation, Properties, and Functionalization with Catalytic Nanoparticles.

DNA-chitosan (DNA-CS) hydrogels were prepared on the basis of interpolyelectrolyte complexes (IPEC) in a co-assembled regime by charging of the polysaccharide in a DNA solution. In contrast to poorly controlled coacervates formed upon mixing of DNA and CS solutions, stable DNA-CS IPEC hydrogels are formed at near-stoichiometric ratios of DNA and chitosan ionogenic groups. Structure, stability, and ion absorption properties of such hydrogels depended strongly on the ratio between cationic (CS) and anionic (DNA) counterparts in hydrogels.

Fluorescent Nanoparticles Synthesized from DNA, RNA, and Nucleotides.

Ubiquitous on Earth, DNA and other nucleic acids are being increasingly considered as promising biomass resources. Due to their unique chemical structure, which is different from that of more common carbohydrate biomass polymers, materials based on nucleic acids may exhibit new, attractive characteristics. In this study, fluorescent nanoparticles (biodots) were prepared by a hydrothermal (HT) method from various nucleic acids (DNA, RNA, nucleotides, and nucleosides) to establish the relationship between the structure of precursors and fluorescent properties of biodots and to optimize conditions for preparation of the most fluorescent product.

Metal Ions Sensing by Biodots Prepared from DNA, RNA, and Nucleotides.

Nucleic acids that exhibit a high affinity toward noble and transition metal ions have attracted growing attention in the fields of metal ion sensing, toxic metal ion removal, and the construction of functional metal nanostructures. In this study, fluorescent nanoparticles (biodots) were synthesized from DNA, RNA, and RNA nucleotides (AMP, GMP, UMP, and CMP) using a hydrothermal (HT) method, in order to study their metal ion sensing characteristics. The fluorescent properties of biodots differ markedly between those prepared from purine and pyrimidine nucleobases.

Adsorptive Removal of Heavy Metal Ions, Organic Dyes, and Pharmaceuticals by DNA-Chitosan Hydrogels.

DNA-chitosan (DNA-CS) hydrogel was prepared by in situ complexation between oppositely charged DNA and chitosan polyelectrolytes via electrostatic cross-linking to study its adsorption characteristics. The DNA-chitosan hydrogel matrix contains (i) cationic (NH) and anionic (PO) sites for electrostatic binding with ionic species, (ii) -OH and -NH groups and heteroaromatic DNA nucleobases for chelation of heavy metal ions, and (iii) DNA double-helix for recognition and binding to small organic molecules of various structures and polarities. DNA-CS hydrogels efficiently bind with Hg, Pb, Cd, and Cu metal cations of significant environmental concern.

Internal Motion of Chromatin Fibers Is Governed by Dynamics of Uncompressed Linker Strands.

Chromatin compaction and internal motion are fundamental aspects of gene expression regulation. Here, we have investigated chromatin fibers comprising recombinant histone octamers reconstituted with double-stranded bacteriophage T4-DNA. The size of the fibers approaches the typical size of genomic topologically associated domains.

Compaction and self-association of megabase-sized chromatin are induced by anionic protein crowding.

Highly compacted chromatin, a complex of DNA with cationic histone proteins, is found in the nucleus of eukaryotic cells in an environment with a high concentration of macromolecular species, many of which possess a negative charge. In the majority of previous studies, however, these crowding conditions were experimentally modelled using neutral synthetic macromolecules such as polyethylene glycol (PEG). Despite the importance of the crowding agent charge in the condensation process of chromatin, to the best of our knowledge, the behavior of chromatin under conditions of anionic protein crowding has not been studied.

Encapsulation of Long Genomic DNA into a Confinement of a Polyelectrolyte Microcapsule: A Single-Molecule Insight.

Encapsulation of nucleic acids is an important technology in gene delivery, construction of "artificial cells", genome protection, and other fields. However, although there have been a number of protocols reported for encapsulation of short or oligomeric DNAs, encapsulation of genome-sized DNA containing hundreds of kilobase pairs is challenging because the length of such DNA is much longer compared to the size of a typical microcapsule. Here, we report a protocol for encapsulation of a ca.

Amino Acid Sequence of Oligopeptide Causes Marked Difference in DNA Compaction and Transcription.

Compaction of T4 phage DNA (166 kbp) by short oligopeptide octamers composed of two types of amino acids, four cationic lysine (K), and four polar nonionic serine (S) having different sequence order was studied by single-molecule fluorescent microscopy. We found that efficient DNA compaction by oligopeptide octamers depends on the geometrical match between phosphate groups of DNA and cationic amines. The amino acid sequence order in octamers dramatically affects the mechanism of DNA compaction, which changes from a discrete all-or-nothing coil-globule transition induced by a less efficient (KS) octamer to a continuous compaction transition induced by a (KS) octamer with a stronger DNA-binding character.

Hybrid porous magnetic bentonite-chitosan beads for selective removal of radioactive cesium in water.

Easy-to-obtain magnetic bentonite-chitosan hybrid beads (Bn-CTS) were prepared by immobilizing bentonite within a porous structure of chitosan beads to achieve a hybrid adsorption effect for the removal of cesium ion (Cs) from water. The hybrid adsorbent, which had a porous structure and abundant binding sites contributed by both chitosan and bentonite, ensured superb adsorption characteristics. The paramagnetic character of the beads enabled their facile separation for recycling.

Efficient prevention of nanomaterials transport in the porous media by treatment with polyelectrolytes.

Contamination of soil by engineered nanomaterials (ENM) is an emergent environmental problem that urges the development of robust treatment protocols to prevent ENM transport through soil. We developed a method for efficient entrapment and retention of ENM in solid porous media of quartz sand with grain size of 300-500 μm used as a simple model of soil and studied the transport properties of multi-walled carbon nanotubes, fullerenes, silica and gold nanoparticles through the sand-packed column by UV-vis and fluorescent spectroscopy. The treatment of ENM-contaminated porous media with a mixture of oppositely charged polyelectrolytes, cationic poly(diallyldimethylammonium chloride) and anionic poly(acrylic acid) sodium salt, dissolved in NaCl solution followed by dilution in the column results in strong electrostatic interaction between the polyelectrolytes and a formation of inter-polyelectrolyte complexes (IPEC) that induce flocculation of ENM and adsorption to the surface of sand.

Compaction of Single-Molecule Megabase-Long Chromatin under the Influence of Macromolecular Crowding.

The megabase-sized length of chromatin is highly relevant to the state of chromatin in vivo, where it is subject to a highly crowded environment and is organized in topologically associating domains of similar dimension. We developed an in vitro experimental chromatin model system reconstituted from T4 DNA (approximately 166 kbp) and histone octamers and studied the monomolecular compaction of this megabase-sized chromatin fiber under the influence of macromolecular crowding. We used single-molecule fluorescence microscopy and observed compaction in aqueous solutions containing poly(ethylene glycol) in the presence of monovalent (Na and K) and divalent (Mg) cations.

Single-molecule compaction of megabase-long chromatin molecules by multivalent cations.

To gain insight into the conformational properties and compaction of megabase-long chromatin molecules, we reconstituted chromatin from T4 phage DNA (165 kb) and recombinant human histone octamers (HO). The unimolecular compaction, induced by divalent Mg2+ or tetravalent spermine4+ cations, studied by single-molecule fluorescence microscopy (FM) and dynamic light scattering (DLS) techniques, resulted in the formation of 250-400 nm chromatin condensates. The compaction on this scale of DNA size is comparable to that of chromatin topologically associated domains (TAD) in vivo.

Novel highly porous magnetic hydrogel beads composed of chitosan and sodium citrate: an effective adsorbent for the removal of heavy metals from aqueous solutions.

This research focuses on the removal of heavy metal ions from aqueous solutions using magnetic chitosan hydrogel beads as a potential sorbent. Highly porous magnetic chitosan hydrogel (PMCH) beads were prepared by a combination of in situ co-precipitation and sodium citrate cross-linking. Fourier transform infrared spectroscopy indicated that the high sorption efficiency of metal cations is attributable to the hydroxyl, amino, and carboxyl groups in PMCH beads.

Photoinduced Fusion of Lipid Bilayer Membranes.

We have developed a novel system for photocontrol of the fusion of lipid vesicles through the use of a photosensitive surfactant containing an azobenzene moiety (AzoTAB). Real-time microscopic observations clarified a change in both the surface area and internal volume of vesicles during fusion. We also determined the optimal cholesterol concentrations and temperature for inducing fusion.

Divalent cation shrinks DNA but inhibits its compaction with trivalent cation.

Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA.

DNA conformational behavior and compaction in biomimetic systems: Toward better understanding of DNA packaging in cell.

In a living cell, long genomic DNA is strongly compacted and exists in the environment characterized by a dense macromolecular crowding, high concentrations of mono- and divalent cations, and confinement of ca. 10μm size surrounded by a phospholipid membrane. Experimental modelling of such complex biological system is challenging but important to understand spatiotemporal dynamics and functions of the DNA in cell.

Enzymatic synthesis of 2'-ara and 2'-deoxy analogues of c-di-GMP.

The substrate specificity of recombinant full-length diguanylate cyclase (DGC) of Thermotoga maritima with mutant allosteric site was investigated. It has been originally shown that the enzyme could use GTP closest analogues - 2'-deoxyguanosine-5'-triphosphate (dGTP) and 9-β-D-arabinofuranosyl-guanine-5'-triphosphate (araGTP) as the substrates. The first demonstrations of an enzymatic synthesis of bis-(3'-5')-cyclic dimeric deoxyguanosine monophosphate (c-di-dGMP) and the previously unknown bis-(3'-5')-cyclic dimeric araguanosine monophosphate (c-di-araGMP) using DGC of T.

Uptake of aromatic compounds by DNA: Toward the environmental application of DNA for cleaning water.

Hypothesis: Although the interaction of DNA with various types of intercalating chemicals, such as planar polycyclic aromatic compounds, has been extensively investigated over the past several decades, little is known about the relationship between the structure of a DNA binder and its affinity for DNA. The use of DNA as an adsorbent for environmental cleaning purposes requires information on its affinity for organic chemicals with different structures.

Experiment: In the present study we investigated the binding of DNA to aromatic chemicals with various structures and charges by three methods: binding of organic chemicals to DNA followed by removal by precipitation with cationic nanoparticles (1) or a cationic surfactant (2), and absorption of organic chemicals by a DNA hydrogel (3).