Search

For amine, hydroxyl and carboxyl terminated initiators, the organobase 1,1,3,3-tetramethylguanidine (TMG) catalyzes the rapid polymerization to afford polypeptides with controllable molecular weights and dispersities.

Ionic cross-linked hydrogels with flexibility, self-recovery and conductivity have attracted extensive attention for the diverse applications in flexible and wearable sensors as ionic conductive hydrogels. However, the hydrogels need to trade off the ionic conductivity for the mechanical property due to the significant decrease in ionic bond strength at high salt concentration. It remains a challenge to find a feasible strategy to realize both excellent mechanical property and ionic conductivity in ionic cross-linked hydrogels. Herein, hydrogels with high extensibility, fatigue, toughness resistance and ionic conductivity are prepared by the incorporating of trivalent metal cations as cross-linker in one-pot reaction. The improved mechanical property of Al3+ cross-linked hydrogel can be attributed to the labile ligand substitution of Al3+ compared with that of Cr3+, resulting in the rapid self-recovery of ionic bonds. Meanwhile, the hydrogels exhibit a high ionic conductivity, sensibility and stability as strain sensors. The hydrogel sensors can detect the motion of multiple body parts and distinguish different electrical signals. Our study will unfold the crucial role of the metal cation-ligand interaction in the design of soft materials with excellent mechanical performance.

Defects in DNA repair frequently lead to neurodevelopmental and neurodegenerative diseases, underscoring the particular importance of DNA repair in long-lived post-mitotic neurons(1,2). The cellular genome is subjected to a constant barrage of endogenous DNA damage, but surprisingly little is known about the identity of the lesion(s) that accumulate in neurons and whether they accrue throughout the genome or at specific loci. Here we show that post-mitotic neurons accumulate unexpectedly high levels of DNA single-strand breaks (SSBs) at specific sites within the genome. Genome-wide mapping reveals that SSBs are located within enhancers at or near CpG dinucleotides and sites of DNA demethylation. These SSBs are repaired by PARP1 and XRCC1-dependent mechanisms. Notably, deficiencies in XRCC1-dependent short-patch repair increase DNA repair synthesis at neuronal enhancers, whereas defects in long-patch repair reduce synthesis. The high levels of SSB repair in neuronal enhancers are therefore likely to be sustained by both short-patch and long-patch processes. These data provide the first evidence of site- and cell-type-specific SSB repair, revealing unexpected levels of localized and continuous DNA breakage in neurons. In addition, they suggest an explanation for the neurodegenerative phenotypes that occur in patients with defective SSB repair.

The coupling of material systems at different length scales enables new ways to take advantage of the unique properties of nano-/macroscale materials. Here, the self-organization of assembled metallacages generated ultralong nanowires, followed by the formation of nanowire-based soft films with diameters up to 6.5 cm. In contrast to previous reports that mainly focused on the preparation of metallacage assemblies with dimensions on the nano-/micrometer scale, the preparation of centimeter assemblies can serve as the bridge between nanostructures and the macroscopic world.

Coordination-driven suprastructures have attracted much interest due to their unique properties. Among these structures, platinum-based architectures have been broadly studied due to their facile preparation. The resultant two- or three-dimensional (2D or 3D) systems have many advantages over their precursors, such as improved emission tuning, sensitivity as sensors, and capture and release of guests, and they have been applied in biomedical diagnosis as well as in catalysis. Herein, we review the recent related to platinum-based coordination-driven self-assembly (CDSA), and the text is organized to emphasizes both the synthesis of new metallacycles and metallacages and their various applications. We review the recent developments in the growing field of platinum-based, coordination-driven self-assembly, and bringing together the key results.

Modulation of the secondary structures of peptides gives rise to a range of natural peptide-based soft materials with outstanding mechanical properties. Here, we discuss detailed insights on how th...

Thermoresponsive hydrogel actuators have attracted tremendous interest due to their promising applications in artificial muscles, soft robotics, and flexible electronics. However, most of these materials are based on polymers with lower critical solution temperature (LCST), while those from upper critical solution temperature (UCST) are rare. Herein, we report a multiple-responsive UCST hydrogel actuator based on the complex of poly(acrylic acid) (PAAc) and poly(acrylamide) (PAAm). By applying a heterogeneous photopolymerization, a bilayer hydrogel was obtained, including a layer of the interpenetrating network (IPN) of PAAm/PAAc and a layer of a single network of PAAm. When cooled down below the UCST, the PAAm/PAAc layer contracted due to the hydrogen bonding of the two polymers while the PAAm layer stays in swelling state, driving the hydrogel to curl. By adjusting the composition of the two layers, the amplitude of actuation behavior could be regulated. By creating patterned IPN domains with photomasks, the hydrogel could deform into complex two-dimensional (2D) and three-dimensional (3D) shapes. An active motion was realized in both water and oil bath, thanks to the internal water exchange between the two layers. Interestingly, the hydrogel actuator is also responsive to urea and salts (Na2SO4, NaCl, NaSCN), due to that the strength of the hydrogen bonds in the IPN changes with the additives. Overall, the current study realized an anisotropic UCST transition by introducing asymmetrically distributed polymer-polymer hydrogen bonds, which would inspire new inventions of intelligent materials.

Ribozymes synthesize proteins in a highly regulated local environment to minimize side reactions caused by various competing species. In contrast, it is challenging to prepare synthetic polypeptides from the polymerization of N-carboxyanhydrides (NCAs) in the presence of water and impurities, which induce monomer degradations and chain terminations, respectively. Inspired by natural protein synthesis, we herein report the preparation of well-defined polypeptides in the presence of competing species, by using a water/dichloromethane biphasic system with macroinitiators anchored at the interface. The impurities are extracted into the aqueous phase in situ, and the localized macroinitiators allow for NCA polymerization at a rate which outpaces water-induced side reactions. Our polymerization strategy streamlines the process from amino acids toward high molecular weight polypeptides with low dispersity by circumventing the tedious NCA purification and the demands for air-free conditions, enabling low-cost, large-scale production of polypeptides that has potential to change the paradigm of polypeptide-based biomaterials.

Cooperative interactions and transitions are among the most important strategies utilized by biological systems to regulate a variety of physical and chemical processes. We report herein an auto-accelerated, rapid cooperative polymerization of N-carboxyanhydrides (NCAs) with initiators structurally as simple as linear aliphatic diamines for the synthesis of polypeptides. The polymerization initiated by diamines proceeds via the formation of "hinged" polypeptides, which are two blocks of helical chains connected head-to-head by the diamine molecules in the polymerization solution. The reactions follow a two-stage, cooperative polymerization kinetic; the cooperative interactions between the macrodipoles of the two hinged helical polypeptides dramatically accelerate the polymerization. Compared to the NCA polymerization initiated by the hexylamine (CH3(CH2)5NH2), the chain propagation rate of the NCA polymerization is increased by more than 600 times when initiated by its diamine analogue (1,6-diaminohexane, NH2(CH2)6NH2). This proximity-induced cooperative polymerization showcases the single helix as a remarkable cooperativity-enabling motif in synthetic chemistry.

Inspired by assemblies in the natural world, researchers have prepared diverse suprastructures with distinct spatial arrangements by artificial self-assembly, including micelles, vesicles, ribbons, films, fibers, and tubes. The field of assembly is undergoing a transition from single-component to multicomponent assembly and single-step to multistep processing. Control over the size, shape, and composition of these building blocks has enabled the formation of suprastructures with substantial structural diversity. More importantly, harnessing noncovalent interactions to create suprastructures in a controlled manner will lead to a better understanding of the formation of complex self-organized patterns. However, for the construction of multiscale self-assemblies with controllable shapes and functions, the selection of a suitable protocol remains challenging. Coordination-driven self-assembly provides a bottom-up approach to construct various metal-organic complexes (MOCs), which could be further used as building blocks with controllable shapes and sizes. Despite the tremendous progress made in the design of MOC-based supramolecular materials, most of these MOCs have dimensions of only several nanometers, and investigations of these structures rely on the characterization of their crystal structure. However, most of the functional suprastructures in living organisms have dimensions ranging from microns to centimeters and have the form of soft materials. Thus, obtaining MOC-based highly ordered materials of larger size remains a challenge. This Account focuses on our recent advances in the construction of soft suprastructure materials with MOCs. A series of functionalized MOCs were first constructed through coordination-driven self-assembly. Then, further self-assembly of the as-prepared MOCs gave rise to the formation of higher-order structures. By changing the functional groups in the acceptors and donors in the MOCs, different suprastructures, including nanospheres, nanodiamonds, nanorods, nanofibers, membranes, films, and gels, were prepared. These studies suggest that using MOCs as building blocks is a highly efficient strategy to achieve complex architectures and functional materials for the development of desired MOC-based soft materials with high precision and fidelity.

International audience; Polycyclic aromatic hydrocarbons (PAHs) continue to attract increasing interest with respect to their applications as luminescent materials. The ordered structure of the metal−organic complex facilitates the selective integration of PAHs that can be tuned to function cooperatively. Here, a unique highly twisted anthracene-based organoplatinum metallacycle was prepared via coordination-driven self-assembly. Single-crystal X-ray diffraction analysis revealed that the metallacycle was twisted through the cooperation of strong π···π stacking interactions and steric hindrance between two anthracene-based ligands. Notably, the intramolecular twist and aggregation behavior introduced restrictions to the conformational change of anthracenes, which resulted in increased emission intensity of the metallacycle in solution. The emission behaviors and suprastructures based on the highly twisted metallacycle can be modulated by the introduction of different solvents. This study demonstrates that this metallacycle with highly twisted structure is a promising candidate for sensing and bioimaging applications.

Objective: Integrin alpha 7 (ITGA7), a potential glioma stem cell marker, regulates several other stem cell markers including CD133 and Nestin in several cancers, meanwhile its high expression is related to poor prognosis in multiple solid tumor patients. However, few studies report correlation of ITGA7 with prognosis in astrocytoma patients. Hence, this study aimed to determine the astrocytoma-tissue ITGA7, CD133 and Nestin expressions to explore their relationship and clinical value for astrocytoma management. Methods: Totally, 124 patients with primary astrocytoma were included. Their tumor tissue ITGA7, CD133 and Nestin expressions were determined by immunohistochemical (IHC) assay and scored by intensity and density ranging from 0-12 points. Besides, their clinical features (such as world health organization (WHO) grade, isocitrate dehydrogenase (IDH) mutation, and adjuvant therapy etc.) were collected, also their overall survival (OS) were analyzed by follow-up data. Results: The mean IHC scores for ITGA7, CD133 and Nestin were 4.9±2.5, 2.1±2.6 and 5.8±2.6, respectively. Moreover, ITGA7 high expression correlated with absence of IDH mutation (P=0.004), advanced WHO grade (P=0.001) and shorter OS (P=0.005). Besides, ITGA7 positively correlated with CD133 (P=0.001) and Nestin (P=0.001) expressions. Regarding CD133 and Nestin, their high expression also correlated with increased WHO grade and shorter OS. Furthermore, multivariant Cox’s regression analysis displayed that only CD133 high expression (P=0.021) could independently predict reduced OS, while ITGA7 or Nestin high expression could not. Conclusion: ITGA7, CD133 and Nestin are intercorrelated, also their high expressions associate with deteriorating disease conditions and poor prognosis in astrocytoma patients.

International audience; Despite rapid progress in recent years, it has remained challenging to prepare well-defined metal–organic complex-based suprastructures. As a result, the physicochemical mechanisms leading to their geometrical complexity remain perplexing. Here, a porphyrin-based metallacage was used as a building block to construct octahedra via self-assembly, and the mechanism for the evolution of the metallacages into octahedra was disclosed by both experiments and theoretical simulations.

Summary Easy regenerability of core components such as electrode and electrolyte is highly required in advanced electrochemical devices. This work reports a reliable, regenerable, and stretchable hydrogel electrolyte based on ionic bonds between polyacrylic acid (PAA) and polyallylamine (PAH). PAA-PAH electrolyte (1M LiCl addition) exhibits high ionic conductivity (0.050 S·cm-1) and excellent mechanical property (fracture strain of 1,688%). Notably, the electrolyte can be regenerated to any desired shape under mild conditions and remains 96% and 90% of the initial ionic conductivity after the first and second regeneration, respectively. PAA-PAH/LiCl-based supercapacitor exhibits nearly 100% capacitance retention upon rolling, stretching, and 5,000 charge-discharge cycles, whereas the regenerated device holds 97.6% capacitance of the initial device and 90.9% after 5,000 cycles. This low-cost, high-efficiency, and regenerable hydrogel electrolyte reveals very promising use in solid-state/flexible supercapacitors and possibly becomes a standard commercial hydrogel electrolyte for sustainable electrochemical energy devices., Graphical Abstract, Highlights • Highly reliable PAA-PAH/LiCl electrolyte for flexible supercapacitor is developed • PAA-PAH/LiCl hydrogel electrolyte can be easily regenerated under mild conditions • Regenerated hydrogel shows high retention of ionic conductivity and extensibility • Regenerated device reserves >90% capacitance and durability of the original one, Energy Materials; Materials Science; Polymer Chemistry

A novel shape memory hydrogel with photo-adaptable permanent shape has been developed on the basis of alginate–Ca2+ coordination and the host–guest interaction between α-cyclodextrin and azobenzene. The reversible nature of alginate–Ca2+ confers the hydrogel with functions such as shape memory and shape recovery, and the light-responsive transition of azobenzene could be applied to generate a new permanent shape by tuning the host–guest complexation via UV light.

In this work, a versatile and simple strategy for building self-healing hydrogels with tunable mechanical properties and shape memory behavior is reported. A commercially available small molecule with three amino groups, diethylenetriamine (DETA), is applied to crosslink poly (acrylic acid) (PAAc) chains via ionic bonding, and the complexes of the PAAc chains with DETA form hydrophobic microdomains in the hydrogel network. The cooperation of ionic bonding and hydrophobic interactions drastically improves the mechanical properties, which can be modulated by adjusting the molar ratio of PAAc to DETA. Due to the physical interaction of the crosslinks, the hydrogels can self-heal rapidly in ambient conditions. The thermal responsiveness of the physical microdomain crosslinks endow the hydrogels with shape memory behavior. It is hoped that this novel strategy will provide new opportunities for the design of high-strength hydrogels with variable functionalities for a wide range of applications, such as artificial muscle and skin. A versatile and simple strategy for building self-healing hydrogels with tunable mechanical properties and shape memory behavior has been developed using diethylenetriamine to crosslink polyacrylic acid chains. Hydrophobic domains form in the network in addition to ionic bonds between the amino and carboxylic acid groups. The combination of ionic bonds and hydrophobic interactions not only provides self-healing ability but also drastically improves the strength.

Virus-like particles are a significant class of biomaterials composed of coat polymers and DNA that assemble into different shapes with a variety of sizes from tens to hundreds of nanometers. In this work, a novel system of virus-like hierarchical nanostructures has been developed by the combination of poly(ethylene glycol)-poly(L-lysine) block copolymers with the poly(benzyl ether) dendron-DNA hybrids. Because of the unique topological structure of polyelectrolytes, the dimension of assemblies could be switched from 1D nanorods to 2D nanosheets to 3D vesicles via varying the molar ratio of two components. Morphologies of the vesicles were characterized by transmission electron microscopy.

A novel electrode material, three-dimensional (3D) hierarchical Ni(PO3)2 nanosheet arrays, is explored via a rational topotactic strategy combining hydrothermal growth with subsequent phosphorylation treatment. The as-synthesized Ni(PO3)2 nanosheet arrays self-supported on activated carbon cloth (Ni(PO3)2@ACC) exhibit superior electrochemical capacitive behaviors to a Ni(OH)2 analogue with similar structural characteristics. The areal and mass specific capacitances of the arrays are as high as 4.43 F cm−2 at a current density of 2 mA cm−2 and 2237 F g−1 at ∼1 A g−1, respectively, which is comparable to the best reported results for Ni-based and Me-POx battery-type electrodes. Furthermore, even at a high rate of 10 mA cm−2, the arrays maintain ∼90% charge retention after 2000 cycles, suggesting their robust stability and their very promising applications for energy storage.

Well-defined nanostructures were constructed by self-assembling hexamethylenediamine-functionalized tetrachloroperylene bisimides (compound A) in water/acetone. These structures could further reversibly transform into fluorescent vesicles by adding and removing water-soluble pillar[5]arene.

Cubic metallacages were arranged into multidimensional (one-, two-, and three-dimensional) suprastructures via multistep assembly. Four new shape-controllable, hybrid metallacages with modified substituents and tunable electronic properties were prepared using dicarboxylate ligands with various substituents (sodium sulfonate, nitro, methoxyl, and amine), tetra-(4-pyridylphenyl) ethylene, and cis-(PEt3)2Pt(OTf)2. The as-prepared metallacages were used as building blocks for further assembly. Diverse suprastructures with tunable emissions (λmax from 451 to 519 nm) and various substituents (−SO3Na, −NO2, −OCH3, and −NH2) were prepared depending on the substituents and solvents used.

Background This study aimed to evaluate the predictive value of presurgical factors for psychiatric disorders (PD) in refractory temporal lobe epilepsy and mesial temporal sclerosis (TLE-MTS) patients underwent cortico-amygdalohippocampectomy (CAH). Methods A total of 98 refractory TLE-MTS patients underwent CAH were consecutively enrolled in this cohort study. Several presurgical factors were recorded, such as married status, employment status, highest education, disease duration, family history of epilepsy, and disorganized VEEG background activity. Results There were 17 (17.3%) refractory TLE-MTS patients occurring PD after CAH, including 8 (8.2%) mood disorders, 7 (7.1%) anxiety disorders, 8 (8.2%) psychoses, and 1 (1.0%) interictal dysphoric disorder. Employed status correlated with low PD occurrence, while disease duration and asymmetric VEEG background activity positively correlated with PD occurrence. Multivariate logistic analysis revealed employed status (P = 0.009) could independently predict lower PD occurrence, while highest education (P = 0.027), disease duration (P = 0.028), seizure frequencies (P = 0.015), and asymmetric VEEG background activity (P = 0.034) could independently predict higher PD occurrence. Receiver operating characteristic curve showed combination of these five factors (area under curve (AUC) = 0.871, 95%CI: 0.783-0.960) disclosed a great predictive value of PD occurrence. The sensitivity and specificity were 70.6% and 92.6% at the best cutoff point. In addition, the percentage of PD was increased with higher Engel classification (P = 0.003). Conclusion Employed status, highest education, disease duration, seizure frequencies, and asymmetric VEEG background activity correlate with PD occurrence independently in epileptic patients.

Genomic and chromosomal changes occur with a high rate in the germline and preimplantation embryos. To study such changes directly in the germline of mammals requires access to material as well as single cell genomics. Recent improvements in embryology and single-cell DNA amplification make it possible to study the genomic changes directly in human oocytes, sperm, and preimplantation embryos. This is particularly important for the study of chromosome segregation directly in human oocytes and preimplantation embryos. Here, we present a practical approach how to obtain high quality DNA sequences and genotypes from single cells, using manual handling of the material that makes it possible to detect genomic changes in meiosis and mitosis spanning the entire range from single nucleotide changes to whole chromosome aneuploidies.

This study displays an easy preparation of high-performance electrocatalyst from cellulose nanocrystals for oxygen reduction reaction (ORR) that occurs at cathode of fuel cells. Through a direct pyrolysis of cellulose nanocrystals and urea, porous nitrogen-doped carbon nanosheets (NCN) are successfully synthesized without involving any catalysts or post treatments. As-prepared NCN displays very high specific surface area (∼1362.36 m 2 g −1 ), large pore volume (∼3.36 cm 3 g −1 ) and high graphitic-/pyridinic-N proportion (∼80% in total N content). This metal-free material demonstrates a superior catalytic performance in terms of a comparable electrocatalytic activity, a better tolerance to the methanol crossover effect and an improved long-term durability toward ORR in the alkaline media when compared with the commercial Pt/C catalyst. Interestingly, the addition of FeCl 3 catalyst to the reaction system does not benefit ORR activity of the resultant material; the replacement of urea by NH 3 gas brings about much poorer material features of morphology, structure and catalytic activity. It is suggested that urea is irreplaceable during this catalyst-free synthesis of nitrogen-doped nanocarbons while cellulose nanocrystal is an unique choice for preparing high performance ORR electrocatalyst. The study herein contributes a very promising Pt-alternative cathode catalyst and also a facile and practical preparation of advanced carbon materials.

Genomic and chromosomal changes occur with a high rate in the germline and preimplantation embryos. To study such changes directly in the germline of mammals requires access to material as well as single cell genomics. Recent improvements in embryology and single-cell DNA amplification make it possible to study the genomic changes directly in human oocytes, sperm, and preimplantation embryos. This is particularly important for the study of chromosome segregation directly in human oocytes and preimplantation embryos. Here, we present a practical approach how to obtain high quality DNA sequences and genotypes from single cells, using manual handling of the material that makes it possible to detect genomic changes in meiosis and mitosis spanning the entire range from single nucleotide changes to whole chromosome aneuploidies.

Synthetic polypeptides from the ring-opening polymerization of N-carboxyanhydrides (NCAs) are one of the most important biomaterials. The unique features of these synthetic polypeptides, including their chemical diversity of side chains and their ability to form secondary structures, enable their broad applications in the field of gene delivery, drug delivery, bio-imaging, tissue engineering, and antimicrobials. In this review article, we summarize the recent advances in the design of polypeptide-based supramolecular structures, including complexes with nucleic acids, micelles, vesicles, hybrid nanoparticles, and hydrogels. We also highlight the progress in the chemical design of functional polypeptides, which plays a crucial role to manipulate their assembly behaviours and optimize their biomedical performances. Finally, we conclude the review by discussing the future opportunities in this field, including further studies on the secondary structures and cost-effective synthesis of polypeptide materials.

SUMMARY Transcription of highly expressed genes has been shown to occur in stochastic bursts. But the origin of such ubiquitous phenomenon has not been understood. Here, we present the mechanism in bacteria. We developed a high-throughput, in vitro, single-molecule assay to follow transcription on individual DNA templates in real time. We showed that positive supercoiling buildup on a DNA segment by transcription slows down transcription elongation and eventually stops transcription initiation. Transcription can be resumed upon gyrase binding to the DNA segment. Furthermore, using single-cell mRNA counting fluorescence in situ hybridization (FISH), we found that duty cycles of transcriptional bursting depend on the intracellular gyrase concentration. Together, these findings prove that transcriptional bursting of highly expressed genes in bacteria is primarily caused by reversible gyrase dissociation from and rebinding to a DNA segment, changing the supercoiling level of the segment.

Globally, about 2 million people are diagnosed with lung cancer annually, making it the most common type of cancer in the world. In addition, lung cancer is the leading cause of cancer death among both men and women, accounting for ~25% of all cancer deaths in the United States and ~19% of cancer deaths worldwide. Although tobacco smoking is the most common cause of lung cancer, it is estimated that 10-25% of all patients diagnosed with lung cancer worldwide are never smokers, with higher proportions in Asians and women. Compared to former and current smokers with lung cancer, lung cancers in never smokers tend to present at an earlier age and more frequently have adenocarcinoma histology. Although a few risk factors are known to contribute to the etiology of lung cancer in never smokers, a large fraction of cancer cases cannot be explained by established environmental and genetic risk factors, highlighting the need for research in this area. One promising approach to identify the etiological factors involved in lung tumorigenesis in never smokers is based on the study of the “mutational signatures” that the exogenous and endogenous processes leave on the tumor tissue and surrounding areas. Somatic mutations accumulate throughout individuals’ lifetime, as a result of the balance between DNA damage and DNA repair. Mutational sources can change over time and mutational signatures can provide information on the tumor evolutionary trajectory, tracking activities of mutational processes. We designed “Sherlock-Lung” to identify mutational signatures in lung cancers from never smokers and order them based on their clonal and subclonal localization to have an insight on the factors involved in the initiation of the tumors. Prevention and treatment strategies are likely to be more effective when targeting the tumor initiating factors rather than those responsible for the tumor progression. Here, we present the Sherlock-Lung study design, which includes a combination of lung cancer cases from populations highly exposed to lung cancer risk factors and populations with unknown exposures. We also present preliminary data from this study and what we have learned from whole genome sequencing analysis of the mutational landscape of lung cancers from smokers and nonsmokers and from different histological subtypes. For example, although the mutational signature associated with tobacco smoking is largely clonal in all lung cancers from smokers, consistent with an initiating role of tobacco smoking in lung tumorigenesis, the mutational signatures distribution varies across histological subtypes. Moreover, the frequency of mutations in major cancer driver genes varies dramatically between smokers and never smokers, and mutational signatures distribution appears to differ between tumors with and without specific driver genes. In never smokers, without the dominant mutational source of tobacco smoking, other signatures emerged, e.g., that associated with reactive oxygen species. Although this approach has already revealed important information on the etiological processes involved in tumorigenesis of lung cancer and other cancer types, there is a growing list of open questions and challenges that need to be addressed. In population studies, careful exposure assessment to identify and validate new mutational signatures and the inclusion of study subjects from different geographical locations and ethnicities are critical. Citation Format: Maria Teresa Landi, Tongwu Zhang, Montserrat Garcia-Closas, Yohan Bossé, Jianxin Shi, Bin Zhu, Qing Lan, Nathaniel Rothman, Jiyeon Choi, Neil E. Caporaso, Wei Zhao, Chongyi Chen, Eytan Ruppin, Jennifer Rosenbaum, Dmitry Gordenin, Sai Yendamuri, Chris Amos, Paul Brennan, David C. Christiani, Geoff Liu, Bonnie Gould Rothberg, Matthew Schabath, Han Liang, Ludmil Alexandrov, David Wedge, Stephen Chanock. Sherlock-Lung: Tracing lung cancer mutational processes in never smokers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr SY26-02.

Amphiphilic rod–coil dendritic–linear block copolymers PEG(Gm)-b-PMPCS (where m is the number of dendron generation, and m = 1, 2, 3) composed of a semirigid Percec-type dendron with hydrophilic poly(ethylene glycol) (PEG) tails and a rod-like mesogen-jacketed liquid crystalline polymer, poly{2,5-bis[(4′-methoxy-phenyl)oxycarbonyl]styrene} (PMPCS), were successfully prepared. The self-assembled structures undergo a transition from vesicles through large compound vesicles (LCVs) to short cylindrical micelles with increasing dendron generation. PEG(G2)-b-PMPCS forms stable LCVs with porous surfaces of a narrow size distribution in a mixed solvent of tetrahydrofuran and water. The formation mechanism of the supramolecular structure with nano- and microsized scales is studied through changing the rate of water addition. It is composed of two steps: morphological transformation and vesicles fusion or differentiation. Vesicles are precursors for LCVs regardless of what the initial morphology is. However, the fi...

Radio coverage directly affects the network connectivity, which is the foundational issue to ensure the normal operation of the network. Many efforts have been made to estimate the radio coverage of sensor nodes. The existing approaches (often RSSI measurement-based), however, suffer from heavy measurement cost and are not well suitable for the large-scale densely deployed WSNs. NRC-Map, a novel algorithm is put forward for sensor nodes radio coverage mapping. The algorithm is based on the RSSI values collected by the neighbor nodes. According to the spatial relationship, neighbor nodes are mapping to several overlapped sectors. By use of the least squares fitting method, a log-distance path loss model is established for each sector. Then, the max radius of each sector is computed according to the path loss model and the given signal attenuation threshold. Finally, all the sectors are overlapped to estimate the node radio coverage. Experimental results show that the method is simple and effectively improve the prediction accuracy of the sensor node radio coverage.

We investigated the ring opening polymerization (ROP) of di- and tri-ethylene glycol monomethyl ether functionalized L-glutamate N-carboxyanhydrides (NCAs) using hexamethyldisilazane (HMDS) as primary initiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as co-initiator. The binary initiator system afforded a living ROP for these pegylated NCAs, and a series of homopolypeptides with controlled molecular weight (MW) and low polydispersity were obtained. We then systematically studied the helical content and clouding point (CP) dependence on polypeptide MW using circular dichroism (CD) spectroscopy and turbidity measurements, respectively. We found that the helical content of both homopolypeptides increased with MW, but the triethylene glycol functionalized poly-L-glutamate (poly-L-EG3Glu) intended to form more stable α-helical structure than diethylene glycol functionalized counterpart (poly-L-EG2Glu) at similar MW. Accordingly, the CP of poly-L-EG2Glu with known end group has strong dependence on its helical content, which is essentially determined by MW. Our results suggested that the thermal responsive properties of these unique pegylated poly-L-glutamates not only rely on their chemical structure but also on their secondary structures, which is different from conventional thermal responsive polymers.

Making an unbiased library Sequencing the genome of single cells gives insight into issues such as cell-to-cell heterogeneity and genome instability. Key to single-cell sequencing techniques are whole-genome amplification (WGA) methods that provide sufficient DNA for next-generation sequencing. Current WGA methods have been hampered by low accuracy and spatial resolution of gene copy numbers and by low amplification fidelity. Chen et al. report an improved single-cell WGA method, Linear Amplification via Transposon Insertion (LIANTI). The DNA is randomly fragmented by Tn5 transposition of a transposon that includes a T7 promoter, which allows linear amplification. The authors used the method to determine the spectrum of single-nucleotide variations in a single human cell after ultraviolet radiation. Science , this issue p. 189

We demonstrate that a tripeptide hydrogelator, Nap-FFG, can selectively self-assemble at the surface of platelets, thus inhibiting ADP-, collagen-, thrombin- and arachidonic acid (AA)-induced human platelet aggregations with the IC(50) values of 0.035 (41), 0.14 (162), 0.062 (68), and 0.13 mg/mL (148 μM), respectively. Other tripeptide hydrogelators with chemical structures of Nap-FFX (X = A, K, S, or E) could not or possessed less potencies to inhibit platelet aggregations. We observed higher amounts of Nap-FFG at the platelet surface by the techniques of LC-MS and confocal microscopy. We also observed self-assembled nanofibers around the platelet incubated with the Nap-FFG by cryo-TEM. The ζ potential of Nap-FFG treated platelets was a little bit more negative than that of untreated ones. The amount of Nap-FFG at the surface of NIH 3T3 cells was much less than that of platelets. These observations suggested that Nap-FFG could selectively self-assemble through unknown ligand-receptor interactions and form thin layers of hydrogels at the surface of platelets, thus preventing the aggregation of them. This study not only broadened the application and opened up a new door for biomedical applications of molecular hydrogels but also might provide a novel strategy to counteract infection diseases through selective surface-induced hydrogelations at pathogens, such as bacteria and virus.

A new type of hetero-grafted molecular bottlebrush with polypeptide as backbone was synthesized using graft-onto strategy. Poly(γ-propargyl-L-glutamate) (PPLG) as backbone was firstly synthesized via ring-opening polymerization (ROP) of γ-propargyl-L-glutamate (PLG) N-carboxyanhydride (NCA). Next, polystyrene-N3 (PS-N3) and monomethoxy poly(ethylene glycol)-N3 (mPEG-N3) as side chains were grafted onto the PPLG backbone using copper-catalyzed click reaction, which afforded good grafting density and efficiency. Two polypeptide bottlebrushes with PS-to-mPEG molar ratio at 70/30 and 30/70 were prepared. The self-assembly behaviors of these two polypeptide bottlebrushes were investigated using the cosolvent method, and their supramolecular structures were characterized using light scattering (LS) and electron microscopy.