bluuebunny/crossref_metadata_2025 huggingface dataset:
Degree of Biomimicry of Artificial Spider Silk Spinning Assessed by NMR Spectroscopy
Authors: Otikovs Martins , Andersson Marlene , Jia Qiupin , Nordling Kerstin , Meng Qing , Andreas Loren B. , Pintacuda Guido , Johansson Jan , Rising Anna , Jaudzems Kristaps
Published: August 2017

Biomimetic spinning of artificial spider silk requires that the terminal domains of designed minispidroins undergo specific structural changes in concert with the β‐sheet conversion of the repetitive region. Herein, we combine solution and solid‐state NMR methods to probe domain‐specific structural changes in the NT2RepCT minispidroin, which allows us to assess the degree of biomimicry of artificial silk spinning. In addition, we show that the structural effects of post‐spinning procedures can be examined. By studying the impact of NT2RepCT fiber drying, we observed a reversible beta‐to‐alpha conversion. We think that this approach will be useful for guiding the optimization of artificial spider silk fibers.
Water absorption behavior and kinetics of glass fiber/waste cotton fabric hybrid composites
Authors: Bodur M. Safa , Englund Karl , Bakkal Mustafa
Published: August 2017

This study deals with the effect of water absorption on the physical and mechanical properties of the glass fiber/waste cotton fabric hybrid composites compared to the samples with maleic anhydride (MA) as coupling agent. Water absorption studies were performed for four different soaking times of 100, 250, 500, and 1000 h at room temperature. To clearly understand how long this type of composites can endure without any important loss of mechanical properties, tensile and impact tests were performed after 500 and 1000 h of water immersion time. Results showed that using MA can reduce water sorption values significantly from 5% to 1.5%. In addition, very limited variations in tensile properties were explored even after 1000 h of soaking time by the presence of MA. On the other hand, impact test results revealed that changes in impact strength values are very complex and different mechanisms play a role with respect to the hybrid formulations. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45506.
Sealing system activated by magnetic induction polymerization
Authors: Marques Fernanda Davi , Nele de Souza Marcio , Gomes de Souza Fernando
Published: August 2017

This work describes the one‐step production of glycerin based polyurethane/magnetite nanocomposites. The polymerization was performed in a nonaqueous dispersion containing the magnetic nanoparticles and the polar monomers under alternating magnetic field. Fourier transform infrared spectroscopy and crosslink degree tests were useful to conclude that the use of magnetic induction (∼3 min at 9300 W) produced results similar to the ones obtained by the conventional polymerization (∼3 h at 80 °C) in a fraction of the required time. A lost circulation fluid control test also was performed under magnetic induction heating and the system containing 5 wt % of the nanoparticles showed the highest reduction of the fluid flow rate. Scanning electron microscopy and probability density function tests of the best material allowed inferring that composite prepared by magnetic induction presents a non‐Gaussian distribution of the diameter, which is directly related to the observed sealing effect. These results showed that proposed polymer/polymerization system can be very useful to the sealing applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45549.
Construction of multilayer coatings for flame retardancy of ramie fabric using layer‐by‐layer assembly
Authors: Yan Hongqiang , Zhao Li , Fang Zhengping , Wang Hao
Published: August 2017

Complex multilayer coatings composed of α‐zirconium phosphate (ZrP), polyethylenimine (PEI), and ammonium polyphosphate (APP) were constructed via layer‐by‐layer assembly method for flame retardant ramie fabric. Bicomponent PEI/ZrP layers served as insulating barrier coating, and bicomponent PEI/APP layers served as intumescent coating. The flame retardancy of the coated ramie fabric was strongly dependent on the nature of the coatings and the layer‐by‐layer assembly patterns. The coated ramie fabric with inside PEI/ZrP layers and outside PEI/APP layers possessed the most uniform and consistent coating surface morphology, as well as the highest content of N and P elements, resulting in an excellent improvement in flame retardancy of ramie fabrics. When this kind of coated ramie fabric was heated, the inner PEI/ZrP layer effectively prevent oxygen and heat from penetrating into the substrate, and the outer PEI/APP layer exposed to air with good expansion during combustion. The synergistic effect was formed during the combustion process and could impart ramie fabrics with high flame retardancy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45556.
Enhanced gas separation performance of PSF membrane after modification to PSF/PDMS composite membrane in CO2/CH4 separation
Authors: Suleman Malik Shoaib , Lau K. K. , Yeong Y. F.
Published: August 2017

Asymmetric polysulfone (PSF) membrane was developed and modified to PSF/polydimethylsiloxane (PSF/PDMS) composite membrane by dip coating technique. Effect of PDMS coating time on membrane properties was examined by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, attenuated total reflectance‐Fourier transform infrared, and water contact angle. The increase in PDMS coating time resulted in a decrement in the thermal strength of PSF membrane. Surface contact angle values revealed that increase in PDMS coating time had increased the surface hydrophobicity in membranes. CO2/CH4 separation performance of membranes was evaluated, and an increase in CO2/CH4 ideal selectivity was observed with the increase of PDMS coating time. At feed pressure of 10 bar, the selectivity of PSF has increased up to 65% after dip coating with PDMS for 30 min. Modification of polymeric membrane into composite membrane provided a way forward towards the enhancement of gas separation performance in polymeric membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45650.
Stereogenic‐Only‐at‐Metal Asymmetric Catalysts
Authors: Zhang Lilu , Meggers Eric
Published: August 2017

Chirality is an essential feature of asymmetric catalysts. This review summarizes asymmetric catalysts that derive their chirality exclusively from stereogenic metal centers. Reported chiral‐at‐metal catalysts can be divided into two classes, namely, inert metal complexes, in which the metal fulfills a purely structural role, so catalysis is mediated entirely through the ligand sphere, and reactive metal complexes. The latter are particularly appealing because structural simplicity (only achiral ligands) is combined with the prospect of particularly effective asymmetric induction (direct contact of the substrate with the chiral metal center). Challenges and solutions for the design of such reactive stereogenic‐only‐at‐metal asymmetric catalysts are discussed.
Stable morphological–physiological and neural protein expression changes in rat bone marrow mesenchymal stem cells treated with electromagnetic field and nitric oxide
Authors: Haghighat Nazanin , Abdolmaleki Parviz , Behmanesh Mehrdad , Satari Mohammad
Published: August 2017

As an external physical factor, electromagnetic field (EMF) may influence cellular processes and nitric oxide (NO) by serving as a secondary messenger molecule in intracellular signaling cascades. Effects of these factors were evaluated simultaneously on viability, morphology, and variation of calcium ion content, and neural protein marker expression in rat bone marrow mesenchymal stem cells (BMSCs). The mesenchymal stem cells were isolated from rat bone marrow and cultured. Deta‐NO as a donor molecule of NO was added to cell culture medium after several passages. These cells were also exposed by retinoic acid (RA, a molecule inducing cell differentiation) and EMF (50 Hz and 20 mT). Despite the effect observed with low concentration of NO, the high concentration of NO in the presence of EMF decreased cell viability and changed cell morphology. EMF increased entry of calcium ion into the cell. Effect of RA on cell death and morphology changes also intensified in the presence of NO and EMF. BMSCs maintained their proliferative state and continued to remain as a stem cell in low concentration of NO. The decrease of cell viability, and increase in number and length of cell neurites and percentage of cells expressing Map2 marker can be a sign of progression for cell neuronal differentiation treated by high concentration of NO with EMF. Bioelectromagnetics. 38:592–601, 2017. © 2017 Wiley Periodicals, Inc.
Evolution of peroxisomes illustrates symbiogenesis
Authors: Speijer Dave
Published: August 2017

Recently, the group of McBride reported a stunning observation regarding peroxisome biogenesis: newly born peroxisomes are hybrids of mitochondrial and ER‐derived pre‐peroxisomes. What was stunning? Studies performed with the yeast Saccharomyces cerevisiae had convincingly shown that peroxisomes are ER‐derived, without indications for mitochondrial involvement. However, the recent finding using fibroblasts dovetails nicely with a mechanism inferred to be driving the eukaryotic invention of peroxisomes: reduction of mitochondrial reactive oxygen species (ROS) generation associated with fatty acid (FA) oxidation. This not only explains the mitochondrial involvement, but also its apparent absence in yeast. The latest results allow a reconstruction of the evolution of the yeast's highly derived metabolism and its limitations as a model organism in this instance. As I review here, peroxisomes are eukaryotic inventions reflecting mutual host endosymbiont adaptations: this is predicted by symbiogenetic theory, which states that the defining eukaryotic characteristics evolved as a result of mutual adaptations of two merging prokaryotes.

See also the video abstract here: https://youtu.be/HtyKhQ3DSxg
Single‐cell Hi‐C bridges microscopy and genome‐wide sequencing approaches to study 3D chromatin organization
Authors: Ulianov Sergey V. , Tachibana‐Konwalski Kikue , Razin Sergey V.
Published: August 2017

Recent years have witnessed an explosion of the single‐cell biochemical toolbox including chromosome conformation capture (3C)‐based methods that provide novel insights into chromatin spatial organization in individual cells. The observations made with these techniques revealed that topologically associating domains emerge from cell population averages and do not exist as static structures in individual cells. Stochastic nature of the genome folding is likely to be biologically relevant and may reflect the ability of chromatin fibers to adopt a number of alternative configurations, some of which could be transiently stabilized and serve regulatory purposes. Single‐cell Hi‐C approaches provide an opportunity to analyze chromatin folding in rare cell types such as stem cells, tumor progenitors, oocytes, and totipotent cells, contributing to a deeper understanding of basic mechanisms in development and disease. Here, we review key findings of single‐cell Hi‐C and discuss possible biological reasons and consequences of the inferred dynamic chromatin spatial organization.
Overproduction of L‐tryptophan via simultaneous feed of glucose and anthranilic acid from recombinant Escherichia coli W3110: Kinetic modeling and process scale‐up
Authors: Jing Keju , Tang Yuanwei , Yao Chuanyi , del Rio‐Chanona Ehecatl A. , Ling Xueping , Zhang Dongda
Published: August 2017

L‐tryptophan is an essential amino acid widely used in food and pharmaceutical industries. However, its production via Escherichia coli fermentation suffers severely from both low glucose conversion efficiency and acetic acid inhibition, and to date effective process control methods have rarely been explored to facilitate its industrial scale production. To resolve these challenges, in the current research an engineered strain of E. coli was used to overproduce L‐tryptophan. To achieve this, a novel dynamic control strategy which incorporates an optimized anthranilic acid feeding into a dissolved oxygen‐stat (DO‐stat) glucose feeding framework was proposed for the first time. Three original contributions were observed. Firstly, compared to previous DO control methods, the current strategy was able to inhibit completely the production of acetic acid, and its glucose to L‐tryptophan yield reached 0.211 g/g, 62.3% higher than the previously reported. Secondly, a rigorous kinetic model was constructed to simulate the underlying biochemical process and identify the effect of anthranilic acid on both glucose conversion and L‐tryptophan synthesis. Finally, a thorough investigation was conducted to testify the capability of both the kinetic model and the novel control strategy for process scale‐up. It was found that the model possesses great predictive power, and the presented strategy achieved the highest glucose to L‐tryptophan yield (0.224 g/g) ever reported in large scale processes, which approaches the theoretical maximum yield of 0.227 g/g. This research, therefore, paves the way to significantly enhance the profitability of the investigated bioprocess.
Mechanisms of nitrous oxide (N2O) formation and reduction in denitrifying biofilms
Authors: Sabba Fabrizio , Picioreanu Cristian , Nerenberg Robert
Published: August 2017

Nitrous oxide (N2O) is a potent greenhouse gas that can be formed in wastewater treatment processes by ammonium oxidizing and denitrifying microorganisms. While N2O emissions from suspended growth systems have been extensively studied, and some recent studies have addressed emissions from nitrifying biofilms, much less is known about N2O emissions from denitrifying biofilm processes. This research used modeling to evaluate the mechanisms of N2O formation and reduction in denitrifying biofilms. The kinetic model included formation and consumption of key denitrification species, including nitrate (), nitrite (), nitric oxide (NO), and N2O. The model showed that, in presence of excess of electron donor, denitrifying biofilms have two distinct layers of activity: an outer layer where there is net production of N2O and an inner layer where there is net consumption. The presence of oxygen (O2) had an important effect on N2O emission from suspended growth systems, but a smaller effect on biofilm systems. The effects of and O2 differed significantly based on the biofilm thickness. Overall, the effects of biofilm thickness and bulk substrate concentrations on N2O emissions are complex and not always intuitive. A key mechanism for denitrifying biofilms is the diffusion of N2O and other intermediates from one zone of the biofilm to another. This leads to zones of N2O formation or consumption transformations that would not exist in suspended growth systems.
In situ preservation of the inferior parathyroid gland during central neck dissection for papillary thyroid carcinoma
Authors: Wang J B , Wu K , Shi L H , Sun Y Y , Li F B , Xie L
Published: August 2017

Background

Postoperative hypocalcaemia due to dysfunction of the parathyroid glands is the most common complication after total thyroidectomy plus central neck dissection (CND). There is a lack of surgical techniques described to help preserve the inferior parathyroid gland in situ during CND. The objective of this study was to introduce the ‘TBP layer’ (layer of thymus–blood vessel–inferior parathyroid gland) concept for preserving the inferior parathyroid gland in situ during CND, and to evaluate its effectiveness.

Methods

The study group included patients with primary papillary thyroid cancer who underwent total thyroidectomy with CND using the new surgical concept between January and December 2014. The control group included sex- and age-matched patients who underwent conventional total thyroidectomy with CND between January 2012 and December 2013. The proportion of inferior parathyroid glands preserved in situ and postoperative hypoparathyroidism rates in the two groups were compared.

Results

There were 181 patients in the study group and 306 in the control group. There were no significant differences between the groups in tumour size, multifocality, extrathyroidal extension, and number of harvested and metastatic central lymph nodes. The rate of inferior parathyroid gland preservation in situ was significantly improved from 37·9 to 76·3 per cent on the left side (P < 0·001), and from 52·0 to 77·9 per cent on the right side (P < 0·001), in the study group compared with the control group. The incidence of transient hypoparathyroidism decreased significantly from 35·0 to 7·2 per cent (P < 0·001).

Conclusion

Applying the proposed surgical concept improved the rate of inferior parathyroid gland preservation in situ and decreased the incidence of transient postoperative hypoparathyroidism.
Pancreatoduodenectomy with portal vein resection for distal cholangiocarcinoma
Authors: Maeta T , Ebata T , Hayashi E , Kawahara T , Mizuno S , Matsumoto N , Ohta S , Nagino M , Aoba T , Kaneoka Y , Arai T , Shimizu Y , Kiriyama M , Sakamoto E , Miyake H , Takara D , Shirai K , Ohira S , Morofuji N , Akutagawa A , Yamaguchi R , Takano M , Yamamoto H , Inoue M , Asaba Y , Watanabe T , Hashimoto M , Kawai S , Ikuta K , Matsubara H , Kato K , Kondo S
Published: August 2017

Background

Little is known about the value of portal vein (PV) resection in distal cholangiocarcinoma. The aim of this study was to evaluate the clinical significance of PV resection in distal cholangiocarcinoma.

Methods

Patients who underwent pancreatoduodenectomy (PD) for distal cholangiocarcinoma between 2001 and 2010 at one of 31 hospitals in Japan were reviewed retrospectively with special attention to PV resection. Short- and long-term outcomes were evaluated.

Results

In the study interval, 453 consecutive patients with distal cholangiocarcinoma underwent PD, of whom 31 (6·8 per cent) had combined PV resection. The duration of surgery (510 versus 427 min; P = 0·005) and incidence of blood transfusion (48 versus 30·7 per cent; P = 0·042) were greater in patients who had PV resection than in those who did not. Postoperative morbidity and mortality were no different in the two groups. Several indices of tumour progression, including high T classification, lymphatic invasion, perineural invasion, pancreatic invasion and lymph node metastasis, were more common in patients who had PV resection. Consequently, the incidence of R1/2 resection was higher in this group (32 versus 11·8 per cent; P = 0·004). Survival among the 31 patients with PV resection was worse than that for the 422 patients without PV resection (15 versus 42·4 per cent at 5 years; P < 0·001). Multivariable analyses revealed that age, blood loss, histological grade, perineural invasion, pancreatic invasion, lymph node metastasis and surgical margin were independent risk factors for overall survival. PV resection was not an independent risk factor.

Conclusion

PV invasion in distal cholangiocarcinoma is associated with locally advanced disease and several negative prognostic factors. Survival for patients who have PV resection is poor even after curative resection.
Meta-analysis of the costs of carotid artery stenting and carotid endarterectomy
Authors: de Vries E E , Baldew V G M , den Ruijter H M , de Borst G J
Published: August 2017

Background

Carotid artery stenting (CAS) is currently associated with an increased risk of 30-day stroke compared with carotid endarterectomy (CEA), whereas both interventions seem equally durable beyond the periprocedural period. Although the clinical outcomes continue to be scrutinized, there are few data summarizing the costs of both techniques.

Methods

A systematic search was conducted in MEDLINE, Embase and Cochrane databases in August 2016 identifying articles comparing the costs or cost-effectiveness of CAS and CEA in patients with carotid artery stenosis. Combined overall effect sizes were calculated using random-effects models. The in-hospital costs were specified to gain insight into the main heads of expenditure associated with both procedures.

Results

The literature search identified 617 unique articles, of which five RCTs and 12 cohort studies were eligible for analysis. Costs of the index hospital admission were similar for CAS and CEA. Costs of the procedure itself were 51 per cent higher for CAS, mainly driven by the higher costs of devices and supplies, but were balanced by higher postprocedural costs of CEA. Long-term cost analysis revealed no difference in costs or quality of life after 1 year of follow-up.

Conclusion

Hospitalization and long-term costs of CAS and CEA appear similar. Economic considerations should not influence the choice of stenting or surgery in patients with carotid artery stenosis being considered for revascularization.
Highly Enantioselective Production of Chiral Secondary Alcohols Using Lactobacillus paracasei BD101 as a New Whole Cell Biocatalyst and Evaluation of Their Antimicrobial Effects
Authors: Yılmaz Durmuşhan , Şahin Engin , Dertli Enes
Published: August 2017

Chiral secondary alcohols are valuable intermediates for many important enantiopure pharmaceuticals and biologically active molecules. In this work, we studied asymmetric reduction of aromatic ketones to produce the corresponding chiral secondary alcohols using lactic acid bacteria (LAB) as new biocatalysts. Seven LAB strains were screened for their ability to reduce acetophenones to their corresponding alcohols. Among these strains, Lactobacillus paracasei BD101 was found to be the most successful at reducing the ketones to the corresponding alcohols. The reaction conditions were further systematically optimized for this strain and high enantioselectivity (99%) and very good yields were obtained. These secondary alcohols were further tested for their antimicrobial activities against important pathogens and significant levels of antimicrobial activities were observed although these activities were altered depending on the secondary alcohols as well as their enantiomeric properties. The current methodology demonstrates a promising and alternative green approach for the synthesis of chiral secondary alcohols of biological importance in a cheap, mild, and environmentally useful process.
Antifungal Activity of the Lipophilic Antioxidant Ferrostatin‐1
Authors: Horwath Michael C. , Bell‐Horwath Tiffany R. , Lescano Victor , Krishnan Karthik , Merino Edward J. , Deepe George S.
Published: August 2017

Ferrostatin‐1 (Fer‐1) is a lipophilic antioxidant that effectively blocks ferroptosis, a distinct non‐apoptotic form of cell death caused by lipid peroxidation. During many infections, both pathogens and host cells are subjected to oxidative stress, but the occurrence of ferroptosis had not been investigated. We examined ferroptosis in macrophages infected with the pathogenic yeast Histoplasma capsulatum. Unexpectedly, Fer‐1 not only reduced the death of macrophages infected in vitro, but inhibited the growth of H. capsulatum and related species Paracoccidioides lutzii and Blastomyces dermatitidis at concentrations under 10 μm. Other antioxidant ferroptosis inhibitors, including liproxstatin‐1, did not prevent fungal growth or reduce macrophage death. Structural analysis revealed a potential similarity of Fer‐1 to inhibitors of fungal sterol synthesis, and ergosterol content of H. capsulatum decreased more than twofold after incubation with Fer‐1. Strikingly, additional Fer‐1 analogues with slight differences from Fer‐1 had limited impact on fungal growth. In conclusion, the ferroptosis inhibitor Fer‐1 has unexpected antifungal potency distinct from its antiferroptotic activity.
The combination of miR‐122 overexpression and Let‐7f silencing induces hepatic differentiation of adipose tissue‐derived stem cells
Authors: Davoodian Nahid , Lotfi Abbas S. , Soleimani Masoud , Ghaneialvar Hori
Published: August 2017

Human adipose tissue‐derived stem cells (hADSCs) have been considered as a promising source for cell therapy of liver diseases due to their accessibility, abundance, and expression of hepatocyte markers. Currently, the important role of certain microRNAs (miRNAs) has been reported during hepatic differentiation of stem cells. However, the combination effect of miRNAs on hepatic differentiation of these cells needs to be more investigated. The present study seeks to determine whether the combination of miRNAs can enhance hepatic differentiation of hADSCs in the absence of any other stimulation. First, lentiviral transduction was used to overexpress miR‐122 and silence d
let‐7f in hADSCs for up to 21 days. Then, hepatic functionality was evaluated by analyzing specific hepatocyte genes and biochemical markers at different time points of differentiation induction. Stable miR‐122 overexpression and let‐7f silencing together in hADSCs resulted in increased expression of hepatocyte markers including ALB, AFP, CK18, CK19, and HNF4a. In addition, urea and albumin production, immunocytochemistry, and glycogen staining confirmed that the treated cells differentiated toward hepatocyte‐like cells. Therefore, our findings demonstrate the possibility of using microRNAs to induce hADSCs into functional hepatocyte‐like cells.
Absorption of CO2 with Amino Acid‐Based Ionic Liquids and Corresponding Amino Acid Precursors
Authors: Guzmán Javier , Ortega-Guevara Christian , de León Roberto García , Martínez-Palou Rafael
Published: August 2017

A comparative study for CO2 absorption among amino acids (AAs) and ionic liquids (ILs) containing tetramethylammonium [TMA] and tetrabutylphosphonium [TBP] as cations and the corresponding deprotonated amino acid as anions, namely, [TMA][AA] and [TBP][AA], is reported. Amino acids show an excellent performance for CO2 capture, better than the corresponding [TMA][AA], but AAs are less efficient than [TBP][AA]. In addition, [TBP][AA] present faster kinetics of absorption than the corresponding AA. [TBP][lysinate] exhibits the highest CO2 absorption capacity. A novel and fast method with low energy demand for microwave‐assisted regeneration of the absorbents from the CO2‐saturated solution is also described for the first time.
Two‐Dimensional Titanium Carbide MXene as a Capacitor‐Type Electrode for Rechargeable Aqueous Li‐Ion and Na‐Ion Capacitor Batteries
Authors: Zhu Kai , Zhang Hongyu , Ye Ke , Zhao Wenbin , Yan Jun , Cheng Kui , Wang Guiling , Yang Baofeng , Cao Dianxue
Published: August 2017

To bridge the gap of the alkali‐metal‐ion (Li or Na) batteries and supercapacitors, hybrid devices called capacitor batteries are being designed, which are adaptive for large‐scale energy‐storage systems. Two‐dimensional transition‐metal carbide materials (MXene) with high electronic conductivities have become capable electrode materials for supercapacitors. Herein, Ti3C2Tx synthesized by selectively etching the Al layer from the Ti3AlC2 presents a remarkable electrochemical performance as an electrode material for the supercapacitor with Li2SO4 or Na2SO4 aqueous electrolyte. It displays a capacitance of 243 F g−1 at a low current density of 100 mA g−1 with a capacitance retention of 95 % in the Li2SO4 electrolyte, and a capacitance of 150 F g−1 at a low current density of 200 mA g−1 with a capacitance retention of 95 % in the Na2SO4 electrolyte, which shows its potential application for capacitor batteries. Moreover, the LiMn2O4//Ti3C2Tx Li‐ion capacitor battery and MnO2//Ti3C2Tx Na‐ion capacitor battery are designed and assembled for the first time. Such rechargeable aqueous capacitor batteries display capable capacities, remarkable rate abilities, and excellent cycling performances, which further demonstrates that Ti3C2Tx is an outstanding capacitor‐type electrode material for capacitor batteries.
Solvent‐Induced Cadmium(II) Metal‐Organic Frameworks with Adjustable Guest‐Evacuated Porosity: Application in the Controllable Assembly of MOF‐Derived Porous Carbon Materials for Supercapacitors
Authors: Yue Man‐Li , Jiang Yi‐Fan , Zhang Lin , Yu Cheng‐Yan , Zou Kang‐Yu , Li Zuo‐Xi
Published: August 2017

In this work, five new cadmium metal‐organic frameworks (Cd‐MOFs 1–5) have been synthesized from solvothermal reactions of Cd(NO3)2⋅4 H2O with isophthalic acid and 1,4‐bis(imidazol‐1‐yl)‐benzene under different solvent systems of CH3OH, C2H5OH, (CH3)2CHOH, DMF, and N‐methyl‐2‐pyrrolidone (NMP), respectively. Cd‐MOF 1 shows a 3D diamondoid framework with 1D rhombic and hexagonal channels, and the porosity is 12.9 %. Cd‐MOF 2 exhibits a 2D (4,4) layer with a 1D parallelogram channel and porosity of 23.6 %. Cd‐MOF 3 has an 8‐connected dense network with the Schäfli symbol of [424⋅64] based on the Cd6 cluster. Cd‐MOFs 4–5 are isomorphous, and display an absolutely double‐bridging 2D (4,4) layer with 1D tetragonal channels and porosities of 29.2 and 28.2 %, which are occupied by DMF and NMP molecules, respectively. Followed by the calcination‐thermolysis procedure, Cd‐MOFs 1–5 are employed as precursors to prepare MOF‐derived porous carbon materials (labeled as PC‐me, PC‐eth, PC‐ipr, PC‐dmf and PC‐nmp), which have the BET specific surface area of 23, 51, 10, 122, and 96 m2 g−1, respectively. The results demonstrate that the specific surface area of PCs is tuned by the porosity of Cd‐MOFs, where the later is highly dependent on the solvent. Thereby, the specific surface area of PCs could be adjusted by the solvent used in the synthese of MOF precusors. Significantly, PCs have been further activated by KOH to obtain activated carbon materials (APCs), which possess even higher specific surface area and larger porosity. After a series of characterization and electrochemical investigations, the APC‐dmf electrode exhibits the best porous properties and largest specific capacitances (153 F g−1 at 5 mV s−1 and 156 F g−1 at 0.5 Ag−1). Meanwhile, the APC‐dmf electrode shows excellent cycling stability (ca. 84.2 % after 5000 cycles at 1 Ag−1), which can be applied as a suitable electrode material for supercapacitors.
Buildup of Redox‐Responsive Hybrid from Polyoxometalate and Redox‐Active Conducting Oligomer: Its Self‐Assemblies with Controllable Morphologies
Authors: She Shan , Huang Zehuan , Yin Panchao , Bayaguud Aruuhan , Jia Hongli , Huang Yichao , Wei Yen , Wei Yongge
Published: August 2017

A redox‐responsive hybrid of polyoxometalate and conducting oligomer including its self‐assemblies with controllable morphologies are reported. To this end, a hybrid molecule, containing a Lindqvist hexamolybdate as the polar head group and N,N′‐bis(4′‐amino‐2,6‐dimethylphenyl)‐1,4‐quinonediimine as the redox‐responsive and aggregating group, is prepared. This hybrid exhibits redox‐responsive behavior with controllable assembling morphological transition from spherical vesicles to short cylindrical vesicles. Besides, the hybrid‐based self‐assemblies are transferred to the surface, thus the surface wettability can be well‐tuned owing to the morphological transitions of the self‐assemblies. By marrying conducting materials with polyoxometalate chemistry, this research opens a new horizon of polyoxometalate‐based self‐assembled systems with potential applications in functional materials.
Mechanistic Insight into the Binding of Multivalent Pyrrolidines to α‐Mannosidases
Authors: Mirabella Stefania , D'Adamio Giampiero , Matassini Camilla , Goti Andrea , Delgado Sandra , Gimeno Ana , Robina Inmaculada , Moreno‐Vargas Antonio J. , Šesták Sergej , Jiménez‐Barbero Jesús , Cardona Francesca
Published: August 2017

Novel pyrrolidine‐based multivalent iminosugars, synthesized by a CuAAC approach, have shown remarkable multivalent effects towards jack bean α‐mannosidase and a Golgi α‐mannosidase from Drosophila melanogaster, as well as a good selectivity with respect to a lysosomal α‐mannosidase, which is important for anticancer applications. STD NMR and molecular modeling studies supported a multivalent mechanism with specific interactions of the bioactive iminosugars with Jack bean α‐mannosidase. TEM studies suggested a binding mode that involves the formation of aggregates, which result from the intermolecular cross‐linked network of interactions between the multivalent inhibitors and two or more dimers of JBMan heterodimeric subunits.
Elucidation of Dual Magnetic Relaxation Processes in Dinuclear Dysprosium(III) Phthalocyaninato Triple‐Decker Single‐Molecule Magnets Depending on the Octacoordination Geometry
Authors: Katoh Keiichi , Aizawa Yu , Morita Takaumi , Breedlove Brian K. , Yamashita Masahiro
Published: August 2017

When applying single‐molecule magnets (SMMs) to spintronic devices, control of the quantum tunneling of the magnetization (QTM) as well as a spin‐lattice interactions are important. Attempts have been made to use not only coordination geometry but also magnetic interactions between SMMs as an exchange bias. In this manuscript, dinuclear dysprosium(III) (DyIII) SMMs with the same octacoordination geometry undergo dual magnetic relaxation processes at low temperature. In the dinuclear DyIIIphthalocyaninato (Pc2−) triple‐decker type complex [(Pc)Dy(ooPc)Dy(Pc)] (1) (ooPc2−=2,3,9,10,16,17,23,24‐octakis(octyloxy)phthalocyaninato) with a square‐antiprismatic (SAP) geometry, the ground state is divided by the Zeeman effect, and level intersection occurs when a magnetic field is applied. Due to the ground state properties of1, since the Zeeman diagram where the levels intersect in anHdcof 2500 Oe, two kinds of QTM and direct processes occur. However, dinuclear DyIII‐Pc systems withC4geometry, which have a twist angle (ϕ) of less than 45° do not undergo dual magnetic relaxation processes. From magnetic field and temperature dependences, the dual magnetic relaxation processes were clarified.
Bonding in Heavier Group 14 Zero‐Valent Complexes—A Combined Maximum Probability Domain and Valence Bond Theory Approach
Authors: Turek Jan , Braïda Benoît , De Proft Frank
Published: August 2017

The bonding in heavier Group 14 zero‐valent complexes of a general formula L2E (E=Si–Pb; L=phosphine,N‐heterocyclic and acyclic carbene, cyclic tetrylene and carbon monoxide) is probed by combining valence bond (VB) theory and maximum probability domain (MPD) approaches. All studied complexes are initially evaluated on the basis of the structural parameters and the shape of frontier orbitals revealing a bent structural motif and the presence of two lone pairs at the central E atom. For the VB calculations three resonance structures are suggested, representing the “ylidone”, “ylidene” and “bent allene” structures, respectively. The influence of both ligands and central atoms on the bonding situation is clearly expressed in different weights of the resonance structures for the particular complexes. In general, the bonding in the studied E0compounds, the tetrylones, is best described as a resonating combination of “ylidone” and “ylidene” structures with a minor contribution of the “bent allene” structure. Moreover, the VB calculations allow for a straightforward assessment of the π‐backbonding (E→L) stabilization energy. The validity of the suggested resonance model is further confirmed by the complementary MPD calculations focusing on the E lone pair region as well as the E–L bonding region. Likewise, the MPD method reveals a strong influence of the σ‐donating and π‐accepting properties of the ligand. In particular, either one single domain or two symmetrical domains are found in the lone pair region of the central atom, supporting the predominance of either the “ylidene” or “ylidone” structures having one or two lone pairs at the central atom, respectively. Furthermore, the calculated average populations in the lone pair MPDs correlate very well with the natural bond orbital (NBO) populations, and can be related to the average number of electrons that is backdonated to the ligands.
Prussian Blue‐Derived Synthesis of Hollow Porous Iron Pyrite Nanoparticles as Platinum‐Free Counter Electrodes for Highly Efficient Dye‐Sensitized Solar Cells
Authors: Chen Jeffrey E. , Fan Miao‐Syuan , Chen Yen‐Lin , Deng Yu‐Heng , Kim Jung Ho , Alamri Hatem R. , Alothman Zeid A. , Yamauchi Yusuke , Ho Kuo‐Chuan , Wu Kevin C.‐W.
Published: August 2017

Invited for the cover of this issue is the group of Kuo‐Chuan Ho and Kevin C.‐W. Wu at the National Taiwan University. The image depicts the hollow porous iron pyrite nanoparticles which are deposited on the conducting substrate as the counter electrode (CE) in a dye‐sensitized solar cell (DSSC). Iron pyrite, with a hollow porous structure, offers a high surface area for the reduction of the triiodide ions. The DSSC directly converts the sunlight into electric power, which could power the flashlight without pollution. It is expected that the DSSC will emerge as a new class of low cost energy conversion device. Read the full text of the article at 10.1002/chem.201702687.
Functionalized Base‐Stable Metal–Organic Frameworks for Selective CO2 Adsorption and Proton Conduction
Authors: He Tao , Zhang Yong‐Zheng , Wu Hao , Kong Xiang‐Jing , Liu Xiao‐Min , Xie Lin‐Hua , Dou Yibo , Li Jian‐Rong
Published: August 2017

Metal–organic frameworks (MOFs) have shown great potential for application in various fields, including CO2 capture and proton conduction. For promoting their practical applications, both optimization of a given property and enhancement of chemical stability are crucial. In this work, three base‐stable isostructural MOFs, [Ni8(OH)4(H2O)2(BDP‐X)6] (Ni–BDP‐X; H2BDP=1,4‐bis(4‐pyrazolyl)benzene, X=CHO, CN, COOH) with different functional groups, are designed, synthesized, and used in CO2 capture and proton conduction experiments. They possess face‐centered cubic topological structures with functional nanoscale cavities. Importantly, these MOFs are fairly stable to maintain their structures in boiling water and 4 M sodium hydroxide solution at room temperature. Functionalization endows them with tunable properties. In gas adsorption studies, these MOFs exhibit selective adsorption of CO2 over CH4 and N2, and in particular the introduction of COOH groups provides the highest selectivity. In addition, the COOH‐functionalized Ni–BDP exhibits a high proton conductivity of 2.22×10−3 S cm−1 at 80 °C and approximately 97 % relative humidity.
Mononuclear Ruthenium and Osmium Complexes with a Bicyclic Guanidinate Ligand: Synthesis and Catalytic Behavior in Olefin Isomerization Processes
Authors: Gámez‐Rivera Sebastián A. , Francos Javier , Borge Javier , Cadierno Victorio
Published: August 2017

The preparation of the first mononuclear RuII, RuIV, and OsII complexes containing the anion of the bicyclic guanidine 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine (Hhpp) as a chelating ligand, namely [RuX{κ2‐(N,N′)‐hpp}(η6‐arene)] [arene = p‐cymene, X = Cl (2a), Br (2b), I (2c); arene = C6Me6, X = Cl (7)], [RuCl{κ2‐(N,N′)‐hpp}(η3:η3‐C10H16)] (9; C10H16 = 2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl), and [OsCl{κ2‐(N,N′)‐hpp}(η6‐p‐cymene)] (11), is described. Compounds 2a–c, 7, 9, and 11 have been fully characterized by elemental analysis, HRMS, IR and NMR spectroscopy. In addition, the structure of 2a has been unequivocally confirmed by single‐crystal X‐ray diffraction methods. The catalytic behavior of these metal guanidinate complexes in the base‐free redox isomerization of allylic alcohols is explored, with the ruthenium(IV) derivative 9 showing the best performance (TOF up to 5940 h–1). All of the synthesized complexes have also proven to be active in the isomerization of the allylbenzene estragole into the industrially relevant 1‐propenylbenzene anethole, with a trans selectivity of up to 95 %.
The Thermodynamic Effects of Ligand Structure on the Molecular Recognition of Mono‐ and Biruthenium Polypyridyl Complexes with G‐Quadruplex DNA
Authors: Mikek Clinton G. , Machha Venkata R. , White Jake C. , Martin Logan R. , West Savannah J. , Butrin Arseniy , Shumaker Carmen , Gwin J. Cole , Alatrash Nagham , MacDonnell Frederick M. , Lewis Edwin A.
Published: August 2017

Isothermal titration calorimetry (ITC) and circular dichroism (CD) were used to study the thermodynamics of RPC·G‐quadruplex DNA (G4) complex formation. The ruthenium polypyridyl complexes (RPCs) were [Ru(phen)3]2+ (12+), [Ru(phen)2(dppz)]2+ (22+), [Ru(phen)2(tatpp)]2+ (32+), and [Ru(phen)2(tatpp)(phen)2Ru]4+ (44+), and target DNAs were c‐MYC NHE‐III1 promoter sequence mutants forming 1‐2‐1 and 1‐6‐1 G‐quadruplexes. Formation of the 2:1 RPC·G4 complexes is characterized by entropy driven RPC binding to the top and bottom of G‐tetrad faces. 12+ appears to bind very weakly or not at all to G4 DNA. 22+ having a dipyridophenazine group to stack on the top and bottom of the G4 core, exhibits an average Ka = 6.7 × 104 m–1. 32+, with a larger G4 interactive tetraazatetrapyridopentacene group, binds with significantly higher affinity, Ka = 1.1 × 106 m–1. 22+ and 32+ appear to bind independently of G4 folding topology and RPC conformation. The thermograms for the titration of G4 DNA with rac‐44+ are characterized by two binding modes exhibiting higher and lower affinity (Ka,1 = 3.6 × 107 m–1 and Ka,2 = 3.2 × 105 m–1). The two binding modes are attributed to preferential binding of one of the 44+ enantiomers (e.g. ΛΛ) over the other isomers (e.g. ΔΔ or ΔΛ). Tighter binding of the preferred 44+ enantiomer, in comparison to 32+, is due to additional favorable entropy for locating a second [(phen)2Ru–]2+ moiety in a G4 groove. Weaker binding of the disfavored 44+ isomers must be due to a poorer fit of these isomers with the G4 faces.
Radical‐Scavenging Antioxidant Cyclic Dipeptides and Silk Fibroin Biomaterials
Authors: Manchineella Shivaprasad , Voshavar Chandrashekhar , Govindaraju Thimmaiah
Published: August 2017

Cyclic dipeptide (CDP) based radical‐scavenging antioxidant molecules have been developed through structure–activity screening of rationally designed symmetric and asymmetric aromatic molecules. The antioxidant efficiencies of the designed CDPs were evaluated against the standard antioxidants ascorbic acid (natural) and butylated hydroxyanisole (a synthetic ingredient used in food, cosmetics, and medicine). Incorporation of the non‐proteinogenic aromatic amino acidl‐3,4‐dihydroxyphenylalanine (DOPA) into the structure bestowed the CDPs with superior antioxidant properties. Detailed colorimetric antioxidant studies demonstrated the potential radical‐scavenging properties of DOPA‐containing CDPs. The non‐cytotoxic nature of the antioxidant CDPs was established in murine adrenal PC12 cells. Antioxidant CDP‐incorporated silk fibroin (CDP/SF) electrospun biomaterial scaffolds were prepared from their respective solutions. The CDP/SF biomaterial scaffolds exhibited excellent radical‐scavenging properties highlighting their potential for therapeutic and tissue engineering applications. Overall, the present study highlights the radical‐scavenging properties of antioxidant CDPs both in their molecular form and in their electrospun biomaterial scaffolds.
Synthesis of Isotope‐Labeled Deoxynivalenol‐15‐O‐Glycosides
Authors: Weber Julia , Fruhmann Philipp , Hametner Christian , Schiessl Alois , Häubl Georg , Fröhlich Johannes , Mikula Hannes
Published: August 2017

A versatile and efficient protocol for the Schmidt glycosylation of 3‐acetyldeoxynivalenol (3‐ADON) and subsequent deprotection has been developed to gain access to deoxynivalenol‐15‐O‐glycosides in reasonable amounts for biological analysis and further investigations. By using this protocol with [13C6]glycosyl donors, we were able to prepare isotope‐labeled deoxynivalenol‐15‐O‐glycosides, which are pivotal to enabling accurate quantification of masked mycotoxins by LC–MS.
Recent trends in capillary electrophoresis for complex samples analysis: A review
Authors: Ramos‐Payán María , Ocaña‐Gonzalez Juan A. , Fernández‐Torres Rut M. , Llobera Andreu , Bello‐López Miguel Ángel
Published: August 2017

CE has been a continuously evolving analytical methodology since its first introduction in the 1980s of the last century. The development of new CE separation procedures, the coupling of these systems to more sensitive and versatile detection systems, and the advances in miniaturization technology have allowed the application of CE to the resolution of new and complex analytical problems, overcoming the traditional disadvantages associated with this method. In the present work, different recent trends in CE and their application to the determination of high complexity samples (as biological fluids, individual cells, etc.) will be reviewed: capillary modification by different types of coatings, microfluidic CE, and online microextraction CE. The main advantages and disadvantages of the different proposed approaches will be discussed with examples of most recent applications.
Quantifying weathering on variable rocks, an extension of geochemical mass balance: Critical zone and landscape evolution
Authors: Fisher Beth A. , Rendahl Aaron K. , Aufdenkampe Anthony K. , Yoo Kyungsoo
Published: August 2017

We present a statistical model of soil and rock weathering in deep profiles to expand the capacity to assess weathering to heterogeneous bedrock types, which are common at the Earth's surface. We developed the Weathering Trends (WT) model by extending the fractional mass change calculation (tau) of the geochemical mass balance model in two important ways. First, WT log transforms the elemental ratio data, to discern the log‐linear patterns that naturally develop from thermodynamic and kinetic laws of chemistry. Second, WT statistically fits log‐transformed element concentration ratio data – log(cj/ci), the only depth‐varying term in tau – as a function of depth to determine characteristic depths of transitions in weathering processes, along with confidence intervals. With no prior assumptions, WT estimates average parent material composition, average composition of the upper weathered zone and mean fractional mass change of each element over the entire weathering profile. WT displays the mean shape of weathering profiles of log‐transformed geochemical data bounded by calculated confidence intervals. We share the WT model code as an open‐source R package (https://github.com/fisherba/WeatheringTrends). The WT model was designed to interpret two 21 m cores from the Laurels Schist bedrock in the Christina River Basin Critical Zone Observatory in the Pennsylvania Piedmont, where our morphological and elemental data provided inconclusive estimates of bedrock depth. The WT model differentiated between rock variability and weathering to delineate the maximum extent of weathering at 12.3 m (CI 95% [9.2, 21.3]) in Ridge Well 1 and 7.2 m (CI 95% [4.3, 13.0]) in Interfluve Well 2. The water table was 5–8 m below fresh rock at Ridge Well 1, but at the same depth as fresh rock at the lower elevation interfluve. We assess statistical approaches to identify the best immobile element for use in WT and tau calculations. Copyright © 2017 John Wiley & Sons, Ltd.