Pore-size control of chitin nanofibrous composite membrane using metal-organic frameworks.

Herein, environmentally benign chitin nanofiber (ChNF) membranes were fabricated by regulating suspension behavior. The introduction of zeolitic imidazole frameworks (ZIF-8) into the composite membranes led to the domain formation of ChNF derived by coordinative interaction, resulting in pore size-tunable membranes. Based on the rheological, morphological, and structural characterizations, the driving force of pore-size control was studied in the aqueous suspension of ChNF and ZIF-8 according to the relative concentration. At critical concentration, the 30-ChNF membrane presents superior water permeance (40 LMH h-1) while maintaining a high rejection rate (>80% for all organic dyes). Moreover, the molecular size cut-off of the composite membranes for dyes can be controlled in the range of less than 1 nm to 2 nm. The experimental results provide a simple strategy for the preparation of pore tunable ChNF membranes using MOF with high mechanical strength, good durability, high flux, dye rejection, and antifouling ability.

Syndecan Transmembrane Domain Specifically Regulates Downstream Signaling Events of the Transmembrane Receptor Cytoplasmic Domain.

Despite the known importance of the transmembrane domain (TMD) of syndecan receptors in cell adhesion and signaling, the molecular basis for syndecan TMD function remains unknown. Using in vivo invertebrate models, we found that mammalian syndecan-2 rescued both the guidance defects in C. elegans hermaphrodite-specific neurons and the impaired development of the midline axons of Drosophila caused by the loss of endogenous syndecan. These compensatory effects, however, were reduced significantly when syndecan-2 dimerization-defective TMD mutants were introduced. To further investigate the role of the TMD, we generated a chimera, 2eTPC, comprising the TMD of syndecan-2 linked to the cytoplasmic domain of platelet-derived growth factor receptor (PDGFR). This chimera exhibited SDS-resistant dimer formation that was lost in the corresponding dimerization-defective syndecan-2 TMD mutant, 2eT(GL)PC. Moreover, 2eTPC specifically enhanced Tyr 579 and Tyr 857 phosphorylation in the PDGFR cytoplasmic domain, while the TMD mutant failed to support such phosphorylation. Finally, 2eTPC, but not 2eT(GL)PC, induced phosphorylation of Src and PI3 kinase (known downstream effectors of Tyr 579 phosphorylation) and promoted Src-mediated migration of NIH3T3 cells. Taken together, these data suggest that the TMD of a syndecan-2 specifically regulates receptor cytoplasmic domain function and subsequent downstream signaling events controlling cell behavior.

Robust Nanocellulose/Metal-Organic Framework Aerogel Composites: Superior Performance for Static and Continuous Disposal of Chemical Warfare Agent Simulants.

Environment-friendly and robust nanocellulose/metal-organic framework aerogel composites were prepared for effective detoxification of chemical warfare agent simulants both in static and dynamic continuous flow systems. For this, we fabricated a durable porous composite of the UiO-66 catalyst and TEMPO-oxidized cellulose nanofibers (TOCN) to examine as a detoxification filter. Even with over 50 wt % UiO-66, the obtained cellulose aerogel composites exhibited high stability without leaking of UiO-66 for 4 weeks under an aqueous state. The cellulose aerogel composite with 54 wt % UiO-66 showed a quite high surface area (483 m2 g-1) despite the presence of TOCN, which caused fast degradation of methyl paraoxon (MPO), a nerve agent simulant, with a 0.7 min half-life in an aqueous solution with N-ethylmorpholine buffer. This aerogel composite was then examined as the detoxification filter in the continuous flow system under a 7.2 mL h-1 flow rate, which surprisingly decomposed 53.7 g of MPO within 1 h with 1 m2 of the effective area.

Chk2-p53 and JNK in irradiation-induced cell death of hematopoietic progenitors and differentiated cells in Drosophila larval lymph gland.

Ionizing radiation (IR) induces DNA double-strand breaks that activate the DNA damage response (DDR), which leads to cell cycle arrest, senescence, or apoptotic cell death. Understanding the DDR of stem cells is critical to tissue homeostasis and the survival of the organism. Drosophila hematopoiesis serves as a model system for sensing stress and environmental changes; however, their response to DNA damage remains largely unexplored. The Drosophila lymph gland is the larval hematopoietic organ, where stem-like progenitors proliferate and differentiate into mature blood cells called hemocytes. We found that apoptotic cell death was induced in progenitors and hemocytes after 40 Gy irradiation, with progenitors showing more resistance to IR-induced cell death compared to hemocytes at a lower dose. Furthermore, we found that Drosophila ATM (tefu), Chk2 (lok), p53, and reaper were necessary for IR-induced cell death in the progenitors. Notably, IR-induced cell death in mature hemocytes required tefu, Drosophila JNK (bsk), and reaper, but not lok or p53. In summary, we found that DNA damage induces apoptotic cell death in the late third instar larval lymph gland and identified lok/p53-dependent and -independent cell death pathways in progenitors and mature hemocytes, respectively.

In-situ synthesis of carbon dot at cellulose nanofiber for durable water treatment membrane with high selectivity.

In this work, carbon dot (CD) was in-situ synthesized and attached to cellulose nanofiber (CNF) via hydrothermal process. The in-situ synthesized CD uniformly enveloped the CNF surface by means of amide bonding, without significant changes of the chemical structure of CNF. The prepared CD@CNF composite showed rough and bumpy morphology. The attached CD increased the interaction between the fibers and enhanced the thermal stability and the dimensional stability in aqueous solution. CD@CNF showed excellent performance as a dye-rejection membrane with high-water flux (∼32 LMH bar-1) and high rejection rate (∼99.8 %), as well as the selective removal of cationic dye. This study suggests a novel synthesizing method of durable CNF membrane by envelopment of CD for effective water treatment.

Ionizing radiation reduces larval brain size by inducing premature differentiation of Drosophila neural stem cells.

DNA damaging agents, such as ionizing radiation (IR), induce cell cycle arrest, senescence, differentiation, or cell death of stem cells, which may affect tissue homeostasis. The specific response of stem cells upon irradiation seems to vary depending on the cell type and their developmental stages. Drosophila larval brain contains neural stem cells called neuroblasts (NBs) and maintaining an appropriate number of NBs is critical to maintain brain size. Irradiation of larvae at early larval stage results in microcephaly, whereas the DNA damage response of NBs that could explain this small brain size is not clearly understood. We observed that the irradiation of larvae in the second instar retarded brain growth, accompanied by fewer NBs. The IR-induced microcephaly does not seem to result from apoptosis since the irradiated larval brain was not stained with activated Caspase nor was the microcephaly affected by the ectopic expression of the apoptosis inhibitor. When analyzed for the percentage of mitotic cells, irradiated NBs recovered their proliferative potential within 6 h post-irradiation after transient cell cycle arrest. However, IR eventually reduced the proliferation of NBs at later time points and induced the premature differentiation of NBs. In summary, IR-induced microcephaly occurs by NB loss due to premature differentiation, rather than apoptotic cell death.

Role of p53 isoforms in the DNA damage response during Drosophila oogenesis.

The tumor suppressor p53 is involved in the DNA damage response and induces cell cycle arrest or apoptosis upon DNA damage. Drosophila p53 encodes two isoforms, p53A and p53B, that induce apoptosis in somatic cells. To investigate the roles of Drosophila p53 isoforms in female germline cells, the DNA damage response was analyzed in the adult ovary. Early oogenesis was sensitive to irradiation and lok-, p53-, and hid-dependent cell death occurred rapidly after both low- and high-dose irradiation. Both p53 isoforms were responsible for this cell death. On the other hand, delayed cell death in mid-oogenesis was induced at a low level only after high-dose irradiation in a p53-independent manner. The daily egg production, which did not change after low-dose irradiation, was severely reduced after high-dose irradiation in p53 mutant females due to the loss of germline stem cells. When the p53A or p53B isoform was expressed in the germline cells in the p53 mutant females at levels that do not affect normal oogenesis, p53A, but not p53B, restored the fertility of the irradiated female. In summary, moderate expression of p53A is critical to maintain the function of germline stem cells during normal oogenesis as well as after high-dose irradiation.

Structural control of cellulose nanofibrous composite membrane with metal organic framework (ZIF-8) for highly selective removal of cationic dye.

Highly durable cellulose nanofibrous composite membranes were prepared by in-situ growing of zeolitic imidazolate frameworks (ZIF-8) as spacers in the presence of TEMPO oxidized cellulose nanofibers (TOCN) as their anchoring points. The obtained composite membranes showed three-dimensionally networked nanofibers with ZIF-8 to generate porous structures, which gave high durability without critical compaction of the membrane under pressure (1∼3 bar). The 20 µm thick ZIF-8/TOCN membrane showed most superior water flux (84 Lm-2 h-1 bar-1) without critical flux drop for 24 h operation. Interestingly, the composite membrane exhibited highly selective removal of cationic dyes in the presence of anionic dyes due to strong interaction through negatively charged TOCN networks. The experimental results in the study reveal a novel strategy for durable cellulose nanofibrous membrane via introduction of metal organic frameworks for highly selective filtration.

Characterization of food waste-driven carbon dot focusing on chemical structural, electron relaxation behavior and Fe3+ selective sensing.

In the study, carbon dot (CD) with high fluorescence properties was obtained via one-step hydrothermal carbonization of food model and sandwich leftover, respectively. The data in the article represent the change of the chemical structure and PL properties of the food waste-driven carbon dot (FWCDs). In higher carbonization temperature, pyridinic N and graphitic N were increased while amino N and pyrrolic N was decreased. The lifetime was increased with the increase of temperature. The CD prepared from sandwich leftover showed the dependency of the emission on the exciting wavelength and excellent Fe3+ sensitivity without significant change of lifetime. It also had a pH-sensitive fluorescence feature and good stability in NaCl solutions. For more insight, please see Food waste-driven N-doped carbon dots: Applications for Fe3+ sensing and cell imaging Ahn et al., 2019.

Food waste-driven N-doped carbon dots: Applications for Fe3+ sensing and cell imaging.

We report highly fluorescent N-doped carbon dots (CDs) synthesized from food waste via one-step hydrothermal carbonization. To study the chemical transition of carbon dots from food wastes, the cat feed stocks driven from food waste were used as the waste model. In the model study, the core of the CDs was successfully self N-doped without extra pre- or post-treatments. The experimental results reveal that the nitrogen in the waste model played an important role in the formation of graphitic N and pyridinic N in the core and functional groups on the surface. Especially, high process temperature (≥180 °C) resulted in high quantum yield as 23% of the CDs from the waste model. To demonstrate the conversion of real food waste into CDs, the hamburger sandwich leftover was used as a precursor for CDs. The food waste driven CDs had similar chemical and fluorescent properties to that of the waste model, having quantum yield of 28%. This study exhibits the food waste driven carbon dots are excellent candidates for fluorescence probe to Fe3+ with high selectivity even under the interference of other metal, and for bio-imaging material with good cell viability over 80%.

Effect of ionized calcium on bacteria contamination in chicken carcass under slaughter process.

The purpose of this study was to determine the effect of ionized calcium on bacteria cross contamination on chicken carcass and meat during the slaughter process. Compared to the control group, colony of E. coli was not observed on medium containing 0.5% ionized calcium. Cross contamination of bacteria on carcass surface of fresh chicken was increased as the number of scalding was increased. Cross contamination of bacteria on carcass surface of fresh chicken was lower in the 0.5% ionized calcium scalding treatment group than that in the control group. Bacteria colony count on chicken meat surface after cooling water treatment was increased as the storage period was increased. Bacteria colony count was lower in the 0.5% ionized calcium treatment group than that in the control group.

Evaluation of the Microbiological Status of Raw Beef in Korea: Considering the Suitability of Aerobic Plate Count Guidelines.

This study was conducted to analyze the microbiological contamination status of raw beef distributed in Korea, and evaluate the suitability of current aerobic plate count (APC) guidelines. We analyzed five years (2010-2014) of microbiological monitoring data obtained from the Ministry of Food and Drug Safety and investigated the microbiological status of raw beef collected from meat packing centers and meat shops in the Seoul/Gyeonggi, Gangwon, and Chungcheong regions in August 2015. From 2010-2014, most raw beef (>94%) displayed APC levels of < 1.0 × 106 CFU/g. However, raw beef samples collected from all three regions in August 2015 had comparatively higher APC levels than those reported in previous years. To evaluate the relationship between the APC level and quality, changes in beef loin were evaluated during cold storage for 15 days at 4°C. On day 11, the mean APC level (4.7 × 106 CFU/g) conformed to current guidelines in Korea (1.0 × 107 CFU/g) and the pH value was 5.82. However, the sensory evaluation score for color and overall acceptability was under 3.0, meaning that the beef loin was not acceptable for eating. These results suggest that current APC guideline for raw beef should be lowered to 1.0 × 106 CFU/g to improve both the microbiological safety and palatability of raw beef.

Initiation of Drosophila chorion gene amplification requires Claspin and mus101, whereas Claspin, but not mus101, plays a major role during elongation.

BACKGROUND: Claspin and TopBP1 are checkpoint mediators that are required for the phosphorylation of Chk1 by ATR to maintain genomic stability. Here, we investigated the functions of Drosophila Claspin and mus101 (TopBP1 ortholog) during chorion (eggshell component) gene amplification, which occurs in follicle cells in the absence of global genomic DNA replication. RESULTS: Unlike Drosophila mei-41 (ATR ortholog) mutant embryos, Claspin and mus101 mutant embryos showed severe eggshell defects resulting from defects in chorion gene amplification. EdU (5-ethynyl-2'-deoxyuridine) incorporation assay during initiation and elongation stages revealed that Claspin and mus101 were required for initiation, while only Claspin had a major role in the efficient progression of the replication forks. Claspin proteins were enriched in the amplification foci both in the initiation and elongation stage-follicle cell nuclei in a mei-41-independent manner. The focal localization of ORC2, a component of the origin recognition complex, was not significantly affected in the Claspin mutant, whereas it was reduced in the mus101 mutant. CONCLUSIONS: Drosophila Claspin plays a major role in the initiation and elongation stages of chorion gene amplification by localizing to the amplification foci in a mei-41-independent manner. Drosophila mus101 is also involved in chorion gene amplification, mostly functioning in initiation, rather than elongation. Developmental Dynamics 246:466-474, 2016. © 2017 The Authors Developmental Dynamics published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Formation of cellulose-carbene complex via depolymerization in ILs: Dependence of IL types on kinetics, conformation and dispersity.

This study focused on the influence of anion type on the depolymerization and its effect on the molecular state, dynamics and dispersity of cellulose. GPC and the van Gurp-Palmen plot showed that molar mass was more significantly decreased by 1-butyl-3-methylimidazolium chloride ([C4C1Im][Cl]) comparing to 1-butyl-3-methylimidazolium acetate ([C4C1Im][OAc]). Acid-catalyzed hydrolysis of cellulose in IL was proved using base titration which was monitored by conductivity and pH value. On the contrary to the depolymerization case, [C4C1Im][OAc] solution needed more base to be neutralized than [C4C1Im][Cl] solution. The generated carbene was combined with reducing ends of cellulose, which was facilitated in low molar mass consisting of a large number of reducing ends. The formation of cellulose-carbene substitution caused steric hindrance of cellulose chain, thus resulting in increased segmental friction with high molecular density. The cellulose particle combined with carbene can be dispersed stably in aqueous media.

In Situ Formation of Autodispersing Cellulose Nanoparticles with Extreme Uniformity.

Autodispersing cellulose nanospheres with a uniform diameter of 20 nm were prepared via self-assembly of cellulose chains with controlled molar masses in an ionic liquid. To obtain nanospheres, cellulose was dissolved in 1-butyl-3-methylimidazolium chloride and then precipitated in deionized water. During dissolution, positive charges were induced at the reducing ends of cellulose by the reaction with the imidazolium. The reaction was more active when the molar mass was smaller than 100 kg·mol-1. As the molar mass decreased, the surface charge originating from the imidazolium increased, resulting in a stable dispersion in aqueous media. The increase of the surface charge also improved the crystallinity and the uniformity of the size dramatically.

Physical state of cellulose in BmimCl: dependence of molar mass on viscoelasticity and sol-gel transition.

In this work, we investigated the correlation between the molar mass and the rheological properties of cellulose/1-butyl-3-methylimidazolium chloride (BmimCl) solutions, and provided the depolymerization kinetics of cellulose in BmimCl. Gel permeation chromatography was used to track the change in molar mass and kinetics as a function of the dissolution time. The molar mass of cellulose in BmimCl decreased significantly as the dissolution time increased, following a zeroth order rate law. The decrease of inter-chain friction induced by depolymerization resulted in a lower viscosity, shorter relaxation time, and lower activation energy. The activation energies for flow were distinctly different above and below the critical molar mass, which indicates that the relaxation mechanisms were not identical above and below the critical molar mass. The transition behavior of liquid crystalline phase also changed at the critical molar mass, which strongly demonstrated the effect of chain length on the formation of cholesteric phase. The exponents of Mark-Houwink-Sakurada and the radius of gyration showed that cellulose in BmimCl existed as a Gaussian chain in a theta solvent.

Highly ordered cellulose II crystalline regenerated from cellulose hydrolyzed by 1-butyl-3-methylimidazolium chloride.

This research focused on the preparation of highly ordered cellulose II crystalline by cellulose hydrolysis in ionic liquid, and the influence of molecular mobility on recrystallization of cellulose. The molar mass of cellulose was controlled by hydrolysis using 1-butyl-3-methylimidazolium chloride (BmimCl). The molecular mobility of cellulose dissolved in BmimCl was characterized by rheological properties. After characterization of cellulose solution and regeneration, change of molar mass and conversion to crystalline were monitored using gel-permeation chromatography and powder X-ray diffraction, respectively. The molar mass of the cellulose in BmimCl was remarkably decreased with an increase in duration time, resulting in better mobility and a lower conformational constraint below critical molar mass. The decrease in molar mass surprisingly increased the crystallinity up to ∼ 85%, suggesting a recrystallization rate dependence of the mobility. The correlation between the mobility and recrystallization rate represented quit different behavior above and below a critical molar mass, which strongly demonstrated to the effect of mobility on the conversion of amorphous state to crystalline structure.

High-dose irradiation induces cell cycle arrest, apoptosis, and developmental defects during Drosophila oogenesis.

Ionizing radiation (IR) treatment induces a DNA damage response, including cell cycle arrest, DNA repair, and apoptosis in metazoan somatic cells. Because little has been reported in germline cells, we performed a temporal analysis of the DNA damage response utilizing Drosophila oogenesis as a model system. Oogenesis in the adult Drosophila female begins with the generation of 16-cell cyst by four mitotic divisions of a cystoblast derived from the germline stem cells. We found that high-dose irradiation induced S and G2 arrests in these mitotically dividing germline cells in a grp/Chk1- and mnk/Chk2-dependent manner. However, the upstream kinase mei-41, Drosophila ATR ortholog, was required for the S-phase checkpoint but not for the G2 arrest. As in somatic cells, mnk/Chk2 and dp53 were required for the major cell death observed in early oogenesis when oocyte selection and meiotic recombination occurs. Similar to the unscheduled DNA double-strand breaks (DSBs) generated from defective repair during meiotic recombination, IR-induced DSBs produced developmental defects affecting the spherical morphology of meiotic chromosomes and dorsal-ventral patterning. Moreover, various morphological abnormalities in the ovary were detected after irradiation. Most of the IR-induced defects observed in oogenesis were reversible and were restored between 24 and 96 h after irradiation. These defects in oogenesis severely reduced daily egg production and the hatch rate of the embryos of irradiated female. In summary, irradiated germline cells induced DSBs, cell cycle arrest, apoptosis, and developmental defects resulting in reduction of egg production and defective embryogenesis.

Relationship between CES2 genetic variations and rifampicin metabolism.

OBJECTIVES: Rifampicin is known to be deacetylated in vivo, resulting in its metabolite 25-desacetyl rifampicin, but the enzyme metabolizing rifampicin and the association of this process with any genetic variation have not yet been elucidated. In this study, genetic variations of a surrogate enzyme, carboxylesterase 2 (CES2), and their association with the metabolism of this drug, were investigated. METHODS: Plasma concentrations of rifampicin and 25-desacetyl rifampicin were measured in 35 patients with tuberculosis receiving a first-line antituberculosis treatment. Direct PCR-based sequencing of the CES2 gene, covering all 12 exons, the 5'-untranslated region (UTR), the 3'-UTR and intronic and promoter regions, was performed. A dual luciferase reporter assay was carried out to assess whether variations in the promoter region affected the transcription of this gene. RESULTS: Ten variations were detected, of which two were in the candidate promoter region, five in introns and three in the 3'-UTR. One of the variations in the 3'-UTR was a novel variation. Genotypes at three closely linked variations (c.-2263A > G, c.269-965A > G and c.1612 + 136G > A) and c.1872*302_304delGAA were associated with significantly different plasma rifampicin concentrations. The mean plasma rifampicin concentration significantly increased with the number of risk alleles at the three closely linked variations, while the plasma concentration decreased along with an increase in the number of risk alleles at c.1872*302_304delGAA. When HepG2 cells were transfected with a luciferase reporter construct bearing the c.-2263G allele, luciferase activities were consistently decreased (by 5%-10%) compared with those harbouring the c.-2263A sequence. CONCLUSIONS: Variations in CES2, especially c.-2263A > G in the promoter region, may alter rifampicin metabolism by affecting expression of the gene.