Search

γ-Amide-e-caprolactones including 7-oxo-N-propyloxepane-4-carboxamide (NNCL), N-isopropyl-7-oxooxepane-4-carboxamide (NICL), N,N-diethyl-7-oxooxepane-4-carboxamide (DECL), and 5-(pyrrolidine-1-carb...

Eukaryotic RNA polymerase I (Pol I) transcribes ribosomal DNA and generates RNA for ribosome synthesis. Pol I accounts for the majority of cellular transcription activity and dysregulation of Pol I transcription leads to cancers and ribosomopathies. Despite extensive structural studies of yeast Pol I, structure of human Pol I remains unsolved. Here, we determined the structures of the human Pol I in the pre-translocation, post-translocation, and backtracked states at near-atomic resolution. The single-subunit peripheral stalk lacks contacts with the DNA-binding clamp and is more flexible than the two-subunit stalk in yeast Pol I. Compared to yeast Pol I, human Pol I possesses a more closed clamp, which makes more contacts with DNA and may support more efficient transcription in human cells. The Pol I structure in the post-cleavage backtracked state shows that the C-terminal zinc ribbon of RPA12 inserts into an open funnel and facilitates “dinucleotide cleavage” on mismatched DNA-RNA hybrid. Critical disease-associated mutations are mapped on Pol I regions that are involved in catalysis and complex organization. In summary, the structures provide new sights into human Pol I complex organization and efficient proofreading, consistent with requirement of efficient transcription of ribosomal DNA in human cells.

Extracellular matrix viscoelasticity is a crucial parameter for designing biomaterials in tissue regeneration. However, the precise control of viscoelastic properties for reproducing the mechanical environment that cells experience in vivo remains a challenge. Here, we developed a series of injectable, viscoelastic PEGylated poly (glycerol sebacate) (PEGS-OH) hydrogels crosslinked via click chemistry and investigated the role of viscoelasticity in developmental tissue regeneration. We found that, compared to 100% and 60% crosslink degrees, 80% crosslinked PEGS-OH with incomplete network slipping promoted a striking increase in the adhesion and differentiation of bone mesenchymal stem cells (BMSCs). Moreover, with PEG segments increasing, the elastic hydrogel turned into viscous state and regulated BMSCs differentiation from osteogenesis to adipogenesis. Further studies revealed that the crosslink degree- and PEG segment-induced BMSCs response was greatly relied on the mechanosensitive Piezo1 mechanism. With in vivo cartilago articularis and skull defect regeneration as models, tendencies from experiments in vitro were further confirmed. Our findings highlight a potential material-biological strategy to precisely regulate cell fate and ensuing tissue regeneration, and provide insight into the relevance of material viscoelasticity in the fate of stem cell differentiation.

Lipid membranes are found in most intracellular organelles, and their heterogeneities play an essential role in regulating the organelles’ biochemical functionalities. Here we report a Spectrum and Polarization Optical Tomography (SPOT) technique to study the subcellular lipidomics in live cells. Simply using one dye that universally stains the lipid membranes, SPOT can simultaneously resolve the membrane morphology, polarity, and phase from the three optical-dimensions of intensity, spectrum, and polarization, respectively. These high-throughput optical properties reveal lipid heterogeneities of ten subcellular compartments, at different developmental stages, and even within the same organelle. Furthermore, we obtain real-time monitoring of the multi-organelle interactive activities of cell division and successfully reveal their sophisticated lipid dynamics during the plasma membrane separation, tunneling nanotubules formation, and mitochondrial cristae dissociation. This work suggests research frontiers in correlating single-cell super-resolution lipidomics with multiplexed imaging of organelle interactome., Lipid membranes are heterogeneous and dynamically regulated in cells. Here the authors report a Spectrum and Polarisation Optical Tomography (SPOT) method where they use Nile Red dye to resolve membrane morphology, polarity and phase in cells.

Assembling for transcription initiation Eukaryotic transcription initiation by RNA polymerase II (Pol II) requires the assembly of a preinitiation complex (PIC) on core promoters. The binding of TATA box–binding protein (TBP) to the TATA box promoter has been thought to be a general rule in PIC assembly and transcription initiation. However, most coding genes lack a TATA box, and nearly all Pol II–mediated gene transcription requires the TBP-containing multisubunit complex transcription factor IID (TFIID). Chen et al. determined the structures of human TFIID-based PIC in sequential assembly states and revealed that TFIID supports distinct PIC assembly on TATA-containing and TATA-lacking promoters. The finding resolves the long-standing mystery of how one set of general transcription machinery initiates transcription on diverse promoters. Science , this issue p. eaba8490

Nanomicelles, by virtue of their prominent biocompatibility, degradability, and ability to solubilize hydrophobic drugs, have been widely used as the most effective delivery platform for anticancer drugs. However, undesirable drug-loading capacity, unfeasible modification, poor in vivo stability, and intratumoral penetration remain to be addressed. Herein, we introduce a novel core/shell PEGylated poly(glycerol sebacate) (PEGS)/hydroxyapatite (HA) hybrid nanomicelle based on a unique triblock PEGS substrate with functional carboxyls in terminals and free hydroxyls as pendant groups. The hydrophobic doxorubicin (DOX) can be controllably encapsulated in the core of nanomicelles via hydrogen bonding, and ensuing in situ mineralization of HA occurs as a shell layer with the electrostatic effect between the carboxylate radical (COO-) and calcium ion (Ca2+). Through optimizing the coordination of PEGS nanomicelles and HA mineralization, 20-30 nm spherical nanoparticles can be formed with considerable drug loading (0.38 mg DOX/1 mg nanoparticles) and a sensitive pH-responsive release (about 50% release amount at pH 5.6 while

Architecture of human BAF complex The SWI/SNF family chromatin remodelers regulate chromatin and transcription. The protein complexes BAF and PBAF are mammalian SWI/SNF remodelers that play essential functions in diverse developmental and physiological processes. He et al. determined the structure of the human BAF complex, which contains three modules that bind the nucleosome on the top, bottom, and side, making this nucleosome-recognition pattern distinct from other chromatin remodelers. Mutations in BAF that are frequently associated with human cancer cluster into a nucleosome-interacting region. This structure provides a framework for understanding the BAF-mediated chromatin remodeling mechanism and its dysregulation in cancer. Science , this issue p. 875

Localization of recombinant human bone morphogenetic protein-2 (rhBMP-2) with continuous and effective osteogenic stimulation is still a great challenge in the field of bone regeneration. To achieve this aim, rhBMP-2 was tethered on chondroitin sulfate (CS)-functionalized calcium phosphate cement (CPC) scaffolds through specific noncovalent interactions. CS, one of the core glycosaminoglycans, was covalently conjugated onto CPC scaffolds with the assistance of polydopamine (PDA) and further immobilized rhBMP-2 in a biomimetic form. The CPC-PDA-CS scaffolds not only controlled the release kinetics and presentation state of rhBMP-2 but also effectively increased the expression levels of bone morphogenetic protein receptors (BMPRs) and enhanced the recognitions of the remaining rhBMP-2 to BMPRs. Strikingly, the rhBMP-2-loaded CPC-PDA-CS significantly promoted the cellular surface translocation of BMPRs (especially BMPR-IA). In vivo studies demonstrated that, compared with the rhBMP-2 upon CPC and CPC-PDA, the rhBMP-2 upon CPC-PDA-CS exhibited sustained release and induced high quality and more ectopic bone formation. Collectively, these results suggest that rhBMP-2 can be localized within CS-functionalized CPC scaffolds and exert continuous, long-term, and effective osteogenic stimulation. Thus, this work could provide new avenues in mimicking bone extracellular matrix microenvironment and localizing growth factor activity for enhanced bone regeneration. Statement of Significance A bioinspired chondroitin sulfate (CS)-functionalized calcium phosphate cement (CPC) platform was developed to tether recombinant human bone morphogenetic protein-2 (rhBMP-2), which could exhibit continuous, long-term, and effective osteogenic stimulation in bone tissue engineering. Compared with rhBMP-2-loaded CPC, the rhBMP-2-loaded CPC-polydopamine-CS scaffolds induced higher expression of bone morphogenetic protein receptors (BMPRs), greater cellular surface translocation of bone morphogenetic protein receptor-IA, higher binding affinity of BMPRs/rhBMP-2, and thus higher activation of the drosophila gene mothers against decapentaplegic protein-1/5/8 (Smad1/5/8) and extracellular-regulated protein kinases-1/2 (ERK1/2) signaling. This work can provide new guidelines for the design of BMP-2-based bioactive materials for bone regeneration.

In the recent decade, Poly (glycerol sebacate) (PGS) has received tremendous attention in versatile biomedical fields because of its superior elasticity, excellent biocompatibility, and biodegradability. Conventionally, PGS comprised of glycerol and sebacic acid is prepared via a two-step polymerization, where synthesis parameters such as curing time and temperature, and feeding ratio of the reagents can be readily tailored to improve the performance for the ultimate use. However, such tweaks are no longer able to catch the high demand of intended biomedical applications. As such, a series of modification strategies and construction modalities have been developed to extend traditional PGS with a wider range of physicochemical, mechanical, and biological properties for unmet biomedical needs. Herein, we present a comprehensive literature review of these advanced modification approaches ranging from hydrophilization, functionalization, and mechanical reinforcement. Moreover, various PGS-related constructions used in biomedical applications are highlighted, including hard tissue engineering, soft tissue engineering, and drug delivery and device design. From the perspective of potential clinical use, challenges and limitations of current PGS-based biomaterials, and their future development are also discussed in this review.

The influence of the water-to-binder ratio and compressive stress on the waterproofing effect of graphene oxide/isobutyltriethoxysilane (GS) composite emulsion on cement-based materials was investigated. The results show that GS combines with calcium silicate hydrate to form a hydrophobic film, which prevents the intrusion of external water and carbon dioxide. In addition, after undergoing self-condensation, silanol reacts with calcium hydroxide to generate calcium silicate hydrate gel, which improves the microstructure of cement-based materials. Furthermore, the increase in the water-to-binder ratio and stress ratio leads to the expansion and connection of the pore structure of cement-based materials, resulting in an increase in the capillary water absorption coefficient. Meanwhile, the higher porosity is conducive to the penetration of the emulsion in cement-based materials and the formation of a waterproof layer. Thus, the waterproofing effect of GS composite emulsion on the specimen was improved.

Foamed concrete has several attractive properties such as low unit weight, high thermal conductivity and good sound insulation as well as being compatible with most building materials. However, the process of forming foamed concrete can also lead to a porous structure within the concrete, leading to increased water absorption and structural defects. This study aimed to investigate the use of silane-based emulsion to reduce the water absorption of foamed concrete. Four types of silane emulsion were synthesized and coated onto the surface of foamed concrete. The hydrophobic performance improved at a temperature of −20 °C, when the waterproof layer was the thickest. The freezing time of water drops on the surface of the concrete was delayed by up to 157% compared to the uncoated control. The silane-based emulsion significantly improved the anti-icing property of the concrete, and they endowed the concrete with superhydrophobicity, creating a self-cleaning effect. These findings show that foamed concrete coated with silane-based emulsion can be used in a broader array of applications and environments.

In this study, high-sensitively colorimetric detection of mercury ions was developed according to the surface plasmon resonance of modified gold nanoparticles. While in a citrate buffer solution, the selected modifier Bismuthiol II can cause gold nanoparticles to aggregate. Gold nanoparticles with a spherical shape and average diameter of about 13 nm were prepared. While mercury ions can inhibit gold nanoparticle aggregation, after the addition of mercury ions, the color of the gold nanoparticles solution changes from light violet to red with a hypochromatic shift at the absorption peak. By collecting the UV-Vis spectrum of the solution after the reaction, the characteristic bands are selected to build a partial least squares model. Both the 0.9477 correlation coefficient with a 0.0986 mg/L standard deviation for the calibration set, and 0.9274 correlation coefficient with a 0.1020 mg/L standard deviation for the prediction set were obtained via a partial least squares model.

This article analyzes redistribution layer (RDL) technologies needed for 2.5-dimensional (2.5-D) die integration on thin glass interposers and developed using low-cost processes. The design, fabrication, and characterization of a four-metal layer RDL buildup required for wide input/output (I/O) routing at 40-μm bump pitch and a two-metal layer RDL buildup fabricated directly on glass for high-speed, off-package signaling are described. Such RDL technologies are targeted at 2.5-D glass interposer packages to achieve up to 1 Tb/s die-to-die bandwidth and off-interposer data rates > 400 Gb/s, driven by consumer demand of online services for mobile devices. Advanced packaging architectures including 2.5-D and 3-D interposers require fine-line lithography beyond the capabilities of current organic package substrates. High electrical loss and high cost are characteristic of silicon interposers fabricated using back-end-of-line (BEOL) processes that can achieve RDL wiring densities required for 2.5-D die integration. Organic interposers with high wiring densities have also been demonstrated using a single-sided, thin-film process. This article goes beyond silicon and organic interposers in demonstrating fine-pitch RDL on glass interposers fabricated by low-cost, double-side, and panel-scalable processes. The high modulus and smooth surface of glass help to achieve lithographic pitch close to that of silicon. Furthermore, the low permittivity and low loss tangent of glass reduce dielectric losses, thus improving high-speed signal propagation. A semiadditive process flow and projection excimer laser ablation were used to fabricate four-metal layer (2 + 0 + 2) fine-pitch RDL and two-metal layer RDL directly on glass. A minimum of 3 μm lithography and 20 μm microvia pitch was achieved. High-frequency characterization of these RDL structures demonstrated single-ended insertion losses of −0.097 dB/mm at f = 1 GHz and differential insertion losses of −0.05 dB/mm at f = 14 GHz.

A quantum dot (QD) is a semiconductor nanocrystal with a radius that is less than or equal to the exciton Bohr radius. As a new type of fluorescent marker, it shows great potential in biological and medical fields due to its unique tunable optical properties, such as a broad excitation spectrum, narrow emission spectra, tunable emission wavelength, and negligible photo-bleaching. Detection technology based upon this marker is simple, quick to use, sensitive, stable, and exhibits high throughput. The aim of this study was to examine the optical properties and surface modifications of QD in aquaculture pollution detection to assess potential applicability.

This paper describes the design, fabrication, and characterization of a two-metal layer RDL structure at 40 um pitch on thin glass interposers. Such an RDL structure is targeted at 2.5D glass interposer packages to achieve up to 1 TB/s die-to-die bandwidth and off-interposer data rates greater than 400 Gb/s, driven by consumer demand of online services for mobile devices. Advanced packaging architectures including 2.5D and 3D interposers require fine line lithography beyond the capabilities of current organic package substrates. Although silicon interposers fabricated using back-end-of-line processes can achieve these RDL wiring densities, they suffer from high electrical loss and high cost. Organic interposers with high wiring densities have also been demonstrated recently using a single sided thin film process. This paper goes beyond silicon and organic interposers in demonstrating fine pitch RDL on glass interposers fabricated by low cost, double sided, and panel-scalable processes. The high modulus and smooth surface of glass helps to achieve lithographic pitch close to that of silicon. Furthermore, the low loss tangent of glass helps in reducing dielectric losses, thus improving high-speed signal propagation. A semi-additive process flow and projection excimer laser ablation was used to fabricate two-metal layer RDL structures and bare glass RDL layers. A minimum of 3 um lithography and 20 um mico-via pitch was achieved. High-frequency characterization of these RDL structures demonstrated single-ended insertion losses of −0.097 dB/mm at f = 1 GHz and differential insertion losses of −0.05 dB/mm at f = 14 GHz.

Poly (glycerol sebacate) (PGS), a tough elastomer, has been widely explored in tissue engineering due to the desirable mechanical properties and biocompatibility. However, the complex curing procedure (high temperature and vacuum) and limited hydrophilicity (∼90° of wetting angle) greatly impede its functionalities. To address these challenges, a urethane-based low-temperature setting, PEGylated PGS bioelastomer was developed with and without solvent. By simultaneously tailoring PEG and hexamethylene diisocyanate (HDI) contents, the elastomers X-P-mUs (X referred to the PEG content and m referred to HDI content) with a broad ranging mechanical properties and customized hydrophilicity were constructed. The X-P-mUs synthesized exhibited adjustable tensile Young’s modulus, ultimate tensile strength and elongation at break in the range of 1.0 MPa–14.2 MPa, 0.3 MPa–7.6 MPa and 53.6%–272.8%, with the water contact angle varying from 28.6° to 71.5°, respectively. Accordingly, these elastomers showed favorable biocompatibility in vitro and mild host response in vivo. Furthermore, the potential applications of X-P-mU elastomers prepared with solvent-base and solvent-free techniques in biomedical fields were investigated. The results showed that these X-P-mU elastomers with high molding capacity at mild temperature could be easily fabricated into various shapes, used as reinforcement for fragile materials, and controllable delivery of drugs and proteins with excellent bioactivity, demonstrating that the X-P-mU elastomers could be tailored as potential building blocks for diverse applications in biomedical research. Statement of Significance Poly(glycerol sebacate) (PGS), a tough biodegradable elastomer, has received great attentions in biomedical field. But the complex curing procedure and limited hydrophilicity greatly hamper its functionality. Herein, a urethane-based low-temperature setting, PEGylated PGS (PEGS-U) bioelastomer with highly-customized mechanical properties, hydrophilicity and biodegradability was first explored. The synthesized PEGS-U showed favorable biocompatibility both in vitro and in vivo. Furthermore, the PEGS-U elastomer could be easily fabricated into various shapes, used as reinforcement for fragile materials, and controllable delivery of drugs and proteins with excellent bioactivity. This versatile, user-tunable bioelastomers should be a promising biomaterials for biomedical applications.

This study investigates the colorimetric reaction between dithizone and mercury in aqueous media which generate the orange Hg-dithizone complexes extracted by chloroform. Then combining with spectral analysis, the UV-vis spectral data of the complexes are obtained to build a forecast model. By means of the multiple linear regression model with SG smoothing method, RPD (Residual Predictive Deviation) of 3.2461 is reached with the detection limit of 0.1129 ug/L. This colorimetric method was found to be rapid, simple and sensitive for the detection of mercury in aqueous medium.

This paper presents a comprehensive study on the fundamental factors that impact the scalability of organic interposers to 40µm area array bump pitch, leading to the design and fabrication of ultra-thin and low CTE organic interposers at 40µm pitch. Silicon interposers were the first substrates used for 2.5D integration of logic and memory ICs at close proximity. However, the high cost and electrical loss of wafer back end of line (BEOL) silicon interposers has fueled the need for fine-pitch organic interposers. Organic substrates face two primary challenges in achieving finer I/O pitch: layer-to-layer mis-registration during copper-polymer re-distribution layer (RDL) fabrication due to the thermo-mechanical stability issue of organic laminate cores, and warpage during chip assembly on thin core substrates. This paper studies these two fundamental factors by finite element modeling (FEM) and experimental characterization, resulting in RDL design guidelines for low mis-registration and warpage. Reducing the copper thickness in each layer as well as the thickness of the polymer dielectric to below 10µm, resulted in significant reduction in CTE mismatch-induced stresses at different interfaces. The modeling-based design was verified by fabrication of a multi-layer RDL stack on 100µm thin low coefficient of thermal expansion (CTE) organic cores with ultra-thin build-up layers to achieve a bump pitch of 40µm. The assembly of chips on the thin organic interposer was optimized to minimize the warpage, leading to the demonstration of two-chip 2.5D organic interposers.