Structural and conformational changes on chitosan after green heterogeneous synthesis of phenyl derivatives.

Four aromatic acid compounds: benzoic acid (Bz), 4-hydroxyphenylpropionic acid (HPPA), gallic acid (GA) and 4-aminobenzoic acid (PABA) were covalently bonded to chitosan in order to improve water solubility at neutral pH. The synthesis was performed via a radical redox reaction in heterogeneous phase by employing ascorbic acid and hydrogen peroxide (AA/H2O2) as radical initiators in ethanol. The analysis of chemical structure and conformational changes on acetylated chitosan was also the focus of this research. Grafted samples exhibited as high as 0.46 M degree of substitution (MS) and excellent solubility in water at neutral pH. Results showed a correlation between the disruption of C3-C5 (O3…O5) hydrogen bonds with increasing solubility in grafted samples. Spectroscopic techniques such as FT-IR and 1H and 13C NMR showed modifications in both glucosamine and N-Acetyl-glucosamine units by ester and amide linkage at C2, C3 and C6 position, respectively. Finally, loss of crystalline structure of 2-helical conformation of chitosan after grafting was observed by XRD and correlated with 13C CP-MAS-NMR analyses.

Polystyrene Macroporous Magnetic Nanocomposites Synthesized through Deep Eutectic Solvent-in-Oil High Internal Phase Emulsions and Fe3O4 Nanoparticles for Oil Sorption.

In this work, we report a nonaqueous one-step method to synthesize polystyrene macroporous magnetic nanocomposites through high internal phase emulsions (HIPEs) formulated with the deep eutectic solvent (DES) composed of urea:choline chloride (U:ChCl, in a 2:1 molar ratio) as the internal phase and co-stabilized with mixtures of Span 60 surfactant and non-functionalized magnetite nanoparticles (Fe3O4 NPs). The porous structure and the magnetic and lipophilic properties of the nanocomposite materials were easily tailored by varying the amount of Fe3O4 NPs (0, 2, 5 and 10 wt %) and the surfactant Span 60 (0, 5, 10, and 20 wt %) used in the precursor emulsion. The resultant nanocomposite polyHIPEs exhibit high sorption capacity toward different oils (hexane, gasoline, and vegetable oil) due to their high porosity, interconnectivity, and hydrophobic surface. It was observed that the oil sorption capacity was improved when the amount of surfactant decreased and Fe3O4 NPs increased in HIPE formulation. Therefore, polyHIPE formulated with 5 and 10 wt % Span 60 and Fe3O4 NPs, respectively, showed the highest oil sorption capacities of 4.151, 3.556, and 3.266 g g-1 for gasoline, hexane, and vegetable oil, respectively. In addition, the magnetic monoliths were reused for more than ten sorption/desorption cycles without losing their oil sorption capacity.

Epigenetic Deregulation of the Histone Methyltransferase KMT5B Contributes to Malignant Transformation in Glioblastoma.

Glioblastoma multiforme (GBM) is the most common and aggressive type of brain tumor in adulthood. Epigenetic mechanisms are known to play a key role in GBM although the involvement of histone methyltransferase KMT5B and its mark H4K20me2 has remained largely unexplored. The present study shows that DNA hypermethylation and loss of DNA hydroxymethylation is associated with KMT5B downregulation and genome-wide reduction of H4K20me2 levels in a set of human GBM samples and cell lines as compared with non-tumoral specimens. Ectopic overexpression of KMT5B induced tumor suppressor-like features in vitro and in a mouse tumor xenograft model, as well as changes in the expression of several glioblastoma-related genes. H4K20me2 enrichment was found immediately upstream of the promoter regions of a subset of deregulated genes, thus suggesting a possible role for KMT5B in GBM through the epigenetic modulation of key target cancer genes.

Epigenetic downregulation of TET3 reduces genome-wide 5hmC levels and promotes glioblastoma tumorigenesis.

Loss of 5-hydroxymethylcytosine (5hmC) has been associated with mutations of the ten-eleven translocation (TET) enzymes in several types of cancer. However, tumors with wild-type TET genes can also display low 5hmC levels, suggesting that other mechanisms involved in gene regulation might be implicated in the decline of this epigenetic mark. Here we show that DNA hypermethylation and loss of DNA hydroxymethylation, as well as a marked reduction of activating histone marks in the TET3 gene, impair TET3 expression and lead to a genome-wide reduction in 5hmC levels in glioma samples and cancer cell lines. Epigenetic drugs increased expression of TET3 in glioblastoma cells and ectopic overexpression of TET3 impaired in vitro cell growth and markedly reduced tumor formation in immunodeficient mice models. TET3 overexpression partially restored the genome-wide patterns of 5hmC characteristic of control brain samples in glioblastoma cell lines, while elevated TET3 mRNA levels were correlated with better prognosis in glioma samples. Our results suggest that epigenetic repression of TET3 might promote glioblastoma tumorigenesis through the genome-wide alteration of 5hmC.

Oil-in-eutectic mixture HIPEs co-stabilized with surfactant and nanohydroxyapatite: ring-opening polymerization for nanocomposite scaffold synthesis.

Mixtures of a nonionic surfactant and non-functionalized nanohydroxyapatite (NHA) enhanced the stability of oil-in-eutectic mixture high internal phase emulsions (HIPEs). Upon ring opening polymerization of the eutectic mixture composed of l-lactide and ε-caprolactone, biodegradable polyHIPEs with specific cavity sizes and selective interfacial functionalization with NHA are produced.

Chromatin regulation by Histone H4 acetylation at Lysine 16 during cell death and differentiation in the myeloid compartment.

Histone H4 acetylation at Lysine 16 (H4K16ac) is a key epigenetic mark involved in gene regulation, DNA repair and chromatin remodeling, and though it is known to be essential for embryonic development, its role during adult life is still poorly understood. Here we show that this lysine is massively hyperacetylated in peripheral neutrophils. Genome-wide mapping of H4K16ac in terminally differentiated blood cells, along with functional experiments, supported a role for this histone post-translational modification in the regulation of cell differentiation and apoptosis in the hematopoietic system. Furthermore, in neutrophils, H4K16ac was enriched at specific DNA repeats. These DNA regions presented an accessible chromatin conformation and were associated with the cleavage sites that generate the 50 kb DNA fragments during the first stages of programmed cell death. Our results thus suggest that H4K16ac plays a dual role in myeloid cells as it not only regulates differentiation and apoptosis, but it also exhibits a non-canonical structural role in poising chromatin for cleavage at an early stage of neutrophil cell death.

Epigenetic dysregulation of TET2 in human glioblastoma.

Ten-eleven translocation (TET) enzymes are frequently deregulated in cancer, but the underlying molecular mechanisms are still poorly understood. Here we report that TET2 shows frequent epigenetic alterations in human glioblastoma including DNA hypermethylation and hypo-hydroxymethylation, as well as loss of histone acetylation. Ectopic overexpression of TET2 regulated neural differentiation in glioblastoma cell lines and impaired tumor growth. Our results suggest that epigenetic dysregulation of TET2 plays a role in human glioblastoma.

Loss of 5hmC identifies a new type of aberrant DNA hypermethylation in glioma.

Aberrant DNA hypermethylation is a hallmark of cancer although the underlying molecular mechanisms are still poorly understood. To study the possible role of 5-hydroxymethylcytosine (5hmC) in this process we analyzed the global and locus-specific genome-wide levels of 5hmC and 5-methylcytosine (5mC) in human primary samples from 12 non-tumoral brains and 53 gliomas. We found that the levels of 5hmC identified in non-tumoral samples were significantly reduced in gliomas. Strikingly, hypo-hydroxymethylation at 4627 (9.3%) CpG sites was associated with aberrant DNA hypermethylation and was strongly enriched in CpG island shores. The DNA regions containing these CpG sites were enriched in H3K4me2 and presented a different genuine chromatin signature to that characteristic of the genes classically aberrantly hypermethylated in cancer. As this 5mC gain is inversely correlated with loss of 5hmC and has not been identified with classical sodium bisulfite-based technologies, we conclude that our data identifies a novel 5hmC-dependent type of aberrant DNA hypermethylation in glioma.

Deep-Eutectic Solvents as MWCNT Delivery Vehicles in the Synthesis of Functional Poly(HIPE) Nanocomposites for Applications as Selective Sorbents.

We report an alternative green strategy based on deep-eutectic solvents (DES) to deliver multiwalled carbon nanotubes (MWCNTs) for a bottom-up approach that allows for the selective interfacial functionalization of nonaqueous poly(high internal phase emulsions), poly(HIPEs). The formation and polymerization of methacrylic and styrenic HIPEs were possible through stabilization with nitrogen doped carbon nanotube (CNX) and surfactant mixtures using a urea-choline chloride DES as a delivering phase. Subtle changes in CNX concentration (less than 0.2 wt % to the internal phase) produced important changes in the macroporous monolith functionalization, which in turn led to increased monolith hydrophobicity and pore openness. These materials displayed great oleophilicity with water contact angles as high as 140° making them apt for biodiesel, diesel, and gasoline fuel sorption applications. Overall, styrene divinylbenzene (StDvB) based poly(HIPEs) showed hydrophobicity and fuel sorption capacities as high as 4.8 (g/g). Pore hierarchy, namely pore openness, regulated sorption capacity, and sorption times where greater openness resulted in faster sorption and increased sorption capacity. Monoliths were subject to 20 sorption-desorption cycles demonstrating recyclability and stable sorption capacity. Finally, CNX/surfactant hybrids made it possible to reduce surfactant requirements for successful HIPE formation and stabilization during polymerization. All poly(HIPEs) retained acceptable conversion as a function of CNX loading nearing 90% or better with thermal stability as high as 283 °C.

Age-associated hydroxymethylation in human bone-marrow mesenchymal stem cells.

BACKGROUND: Age-associated changes in genomic DNA methylation have been primarily attributed to 5-methylcytosine (5mC). However, the recent discovery of 5-hydroxymethylcytosine (5hmC) suggests that this epigenetic mark might also play a role in the process. METHODS: Here, we analyzed the genome-wide profile of 5hmc in mesenchymal stem cells (MSCs) obtained from bone-marrow donors, aged 2-89 years. RESULTS: We identified 10,685 frequently hydroxymethylated CpG sites in MSCs that were, as in other cell types, significantly associated with low density CpG regions, introns, the histone posttranslational modification H3k4me1 and enhancers. Study of the age-associated changes to 5hmC identified 785 hyper- and 846 hypo-hydroxymethylated CpG sites in the MSCs obtained from older individuals. CONCLUSIONS: DNA hyper-hydroxymethylation in the advanced-age group was associated with loss of 5mC, which suggests that, at specific CpG sites, this epigenetic modification might play a role in DNA methylation changes during lifetime. Since bone-marrow MSCs have many clinical applications, and the fact that the epigenomic alterations in this cell type associated with aging identified in this study could have associated functional effects, the age of donors should be taken into account in clinical settings.

The Impact of External Factors on the Epigenome: In Utero and over Lifetime.

Epigenetic marks change during fetal development, adult life, and aging. Some changes play an important role in the establishment and regulation of gene programs, but others seem to occur without any apparent physiological role. An important future challenge in the field of epigenetics will be to describe how the environment affects both of these types of epigenetic change and to learn if interaction between them can determine healthy and disease phenotypes during lifetime. Here we discuss how chemical and physical environmental stressors, diet, life habits, and pharmacological treatments can affect the epigenome during lifetime and the possible impact of these epigenetic changes on pathophysiological processes.

Synthesis of Biodegradable Macroporous Poly(l-lactide)/Poly(ε-caprolactone) Blend Using Oil-in-Eutectic-Mixture High-Internal-Phase Emulsions as Template.

We have demonstrated that l-lactide (LLA) forms a eutectic mixture with ε-caprolactone (CL) in a 30:70 mol ratio with a melting point of -19 °C. Taking advantage of the liquid nature and polarity at the LLA-CL eutectic mixture, we have formulated oil-in-eutectic-mixture high-internal-phase emulsions (HIPEs) by stepwise addition of the oil phase (tetradecane) into the continuous phase (mixture of surfactant and LLA-CL eutectic mixture) at room temperature and under stirring. The oil-in-LLA-CL-eutectic-mixture HIPEs were polymerized in the presence of both the organocatalysts 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and methanesulfonic acid (MSA) and the initiator benzyl alcohol (BnOH) at 37 °C and without the addition of any extra reagent or solvent in one single pot. The catalytic selectivities of DBU and MSA for the ring-opening polymerizations of LLA and CL, respectively, allowed the synthesis of macroporous poly(l-lactide)/poly(ε-caprolactone) blend materials. The resulting materials exhibited a macroporous morphology that resembled that of the HIPE internal-phase droplets used as templates. These materials proved effective as oil absorbents for oil/water separation with not only a noticeable performance, similar to that of conventional sorbents in terms of both selectivity and recyclability, but also unprecedented safe disposability, certainly of interest for applications in the cleanup of industrial oily wastewaters and oil spills, thanks to the biodegradable features of both poly(ε-caprolactone) and poly(l-lactide).

Oncometabolic Nuclear Reprogramming of Cancer Stemness.

By impairing histone demethylation and locking cells into a reprogramming-prone state, oncometabolites can partially mimic the process of induced pluripotent stem cell generation. Using a systems biology approach, combining mathematical modeling, computation, and proof-of-concept studies with live cells, we found that an oncometabolite-driven pathological version of nuclear reprogramming increases the speed and efficiency of dedifferentiating committed epithelial cells into stem-like states with only a minimal core of stemness transcription factors. Our biomathematical model, which introduces nucleosome modification and epigenetic regulation of cell differentiation genes to account for the direct effects of oncometabolites on nuclear reprogramming, demonstrates that oncometabolites markedly lower the "energy barriers" separating non-stem and stem cell attractors, diminishes the average time of nuclear reprogramming, and increases the size of the basin of attraction of the macrostate occupied by stem cells. These findings establish the concept of oncometabolic nuclear reprogramming of stemness as a bona fide metabolo-epigenetic mechanism for generation of cancer stem-like cells.

H3K4me1 marks DNA regions hypomethylated during aging in human stem and differentiated cells.

In differentiated cells, aging is associated with hypermethylation of DNA regions enriched in repressive histone post-translational modifications. However, the chromatin marks associated with changes in DNA methylation in adult stem cells during lifetime are still largely unknown. Here, DNA methylation profiling of mesenchymal stem cells (MSCs) obtained from individuals aged 2 to 92 yr identified 18,735 hypermethylated and 45,407 hypomethylated CpG sites associated with aging. As in differentiated cells, hypermethylated sequences were enriched in chromatin repressive marks. Most importantly, hypomethylated CpG sites were strongly enriched in the active chromatin mark H3K4me1 in stem and differentiated cells, suggesting this is a cell type-independent chromatin signature of DNA hypomethylation during aging. Analysis of scedasticity showed that interindividual variability of DNA methylation increased during aging in MSCs and differentiated cells, providing a new avenue for the identification of DNA methylation changes over time. DNA methylation profiling of genetically identical individuals showed that both the tendency of DNA methylation changes and scedasticity depended on nongenetic as well as genetic factors. Our results indicate that the dynamics of DNA methylation during aging depend on a complex mixture of factors that include the DNA sequence, cell type, and chromatin context involved and that, depending on the locus, the changes can be modulated by genetic and/or external factors.

Structural insights into the binding of uranyl with human serum protein apotransferrin structure and spectra of protein-uranyl interactions.

Ab initio quantum mechanical computational studies for the structure and IR spectra of the uranyl complex with human serum apotransferrin (TF) protein are carried out to model uranyl intake into the human cell through endocytosis and formation of a coordination complex with the protein binding sites. The computed IR spectra and structure of the uranyl-protein complex facilitate interpretation of the observed spectra and confirm the primary binding sites of the transferrin protein with the uranyl ion. Our computed equilibrium geometry and the IR spectra of the uranyl-TF complex reveal that uranyl ion is bound to two tyrosines, one aspartate group, and one carbonate ion. Our IR spectra indicate that histidine is not involved in binding to uranyl with transferrin protein. Our computations reveal a short, strong hydrogen bond, which could play an important role in the stabilization and formation of the uranyl-TF complex. Computed Laplacian charge plots indicate high chemical reactivity on this complex as both an electrophile and a nucleophile, facilitating binding to different receptors and thus entry into a number of target organs and the blood-brain barrier. The Mulliken charge density plots and the three-dimensional charge density plots suggest a donor-acceptor mechanism in the complex formation.

Loop entropy and cytochrome c stability.

The loop entropy model proposes that loop closure in a protein becomes entropically more costly as the length of the loop increases. A model protein, cytochrome c, is composed of four loops connecting five helices surrounding a heme-containing core. To test the loop entropy model a series of mutant proteins are constructed with (Gly)n or (Thr)n segments (n = 4-20) inserted between Gly23 and Gly24 of omega loop A of a pseudo wild-type reference protein. Scanning calorimetry shows that protein stability decreases as n increases in the (Gly)n or (Thr)n segment. The dependence of stability on loop length is analyzed with the loop entropy model. Fitting to the model gives a quantitative description of stability differences for the mutant proteins, but with a smaller power-dependence of the probability of loop closure (c-value) than expected from polymer theory. A possible explanation for the discrepancy is that thermodynamically unfavorable loop entropy is partially offset by interactions between the inserted homopolymer and flanking heteropolymer portions of the unfolded protein. The interactions may involve molecular crowding that favors coalescence of the heteropolymer at the insert site and thus closure of the homopolymer loops, possibly as an aspect of the folding code. This may allow use of loop insert mutants to assess the strength of the heteropolymer-encoded folding signals that facilitate loop closure at the insert site.

Effect of beginning recombinant erythropoietin treatment within the first week of life, among very-low-birth-weight neonates, on "early" and "late" erythrocyte transfusions: a meta-analysis.

OBJECTIVES: Erythrocyte transfusions to neonates can be categorized as "early" if given during the first 3 weeks of life and "late" if given thereafter. We used a meta-analysis to determine whether recombinant erythropoietin (rEpo) administration to very-low-birth-weight (VLBW, <1500 g) neonates, beginning in the first week of life, reduces either "early" or "late" transfusions. STUDY DESIGN AND METHODS: Studies that used a randomized, placebo-controlled, double-masked design were deemed acceptable. We identified 12 acceptable, relevant, clinical trials. Additional data not provided in the publications were obtained from two of the authors. RESULTS: The acceptable studies involved an aggregate of 561 rEpo and 529 placebo recipients. If rEpo was begun in the first week of life, the summary odds ratio (OR) for receiving any transfusion ("early" or "late") was 0.52, 95% confidence interval (CI): 0.34 to 0.79 (p=0.001). The OR for receiving an "early" transfusion was 0.54 (95% CI: 0.25 to 1.15; p=0.055), and the OR for receiving a "late" transfusion was 0.56 (95% CI: 0.37 to 0.83; p=0.036). Heterogeneity among studies was too great to estimate the effect of rEpo on the number of transfusions received or the volume of blood transfused (p<0.001 for the Q-test statistic). Subgroup analysis suggested that when rEpo is begun in the first week of life, neonates 1000 to 1500 g and >29 weeks are more likely to completely avoid transfusion than are extremely low-birth-weight (ELBW, <1000 g) neonates. No dose-response relationship was apparent between rEpo dose or iron dose and transfusion. No difference was apparent depending on whether the rEpo was given subcutaneously vs intravenously. CONCLUSION: If rEpo is begun in the first week of life, a moderate reduction can be expected (p=0.001) in the proportion of VLBW neonates transfused. Reduction is less significant in "early" transfusion (p=0.055) than in "late" transfusion (p=0.036). Such treatment is not likely to eliminate transfusions among ELBW neonates completely.

Tolerance of a sterile isotonic electrolyte solution containing select recombinant growth factors in neonates recovering from necrotizing enterocolitis.

OBJECTIVE: To assess the tolerance of a sterile isotonic electrolyte solution containing select recombinant growth factors enterally administered in neonates who were NPO because of necrotizing enterocolitis (NEC). STUDY DESIGN: A phase I trial was accomplished among 30 neonates. Patients received 5, 10, or 20 mL enterally of the study solution/kg/day divided into every 3-hour dosing, for 3 days prior to when feedings of milk were to resume. The occurrence of emesis, gastric residuals, diarrhea, bloody stools, abdominal distention, skin rashes and death were sought. RESULTS: Gestational ages ranged from 25.2 to 41.1 weeks. A total of 16 neonates had Stage IA NEC, six Stage IB, and eight Stage IIA. The solution was well tolerated in all 30; none developed diarrhea, guaiac positive or bloody stools, or abdominal distention. Administration of the solution was not prematurely discontinued in any infant. Two neonates died secondary to late-onset sepsis remote from the study period. CONCLUSIONS: Enteral administration of a sterile isotonic electrolyte solution containing select recombinant growth factors was well tolerated by neonates with NEC.

Remoción de As mediante el método RAOS en Los Pereyra, provincia de Tucumán, Argentina

Describe el comportamiento del método RAOS (Remoción de Arsénico por Oxidación Solar) para la remoción del arsénico de aguas de consumo humano en regiones rurales de la prov. de Tucumán