The vital role that nitrogenase plays in sustaining life is examined from a biomolecular perspective. Nitrogen fixation is shown to occur in lightning and the Haber-Bosch process.
High‐efficiency electromagnetic (EM) functional materials are the core building block of high‐performance EM absorbers and devices, and they are indispensable in various fields ranging from ...industrial manufacture to daily life, or even from national defense security to space exploration. Searching for high‐efficiency EM functional materials and realizing high‐performance EM devices remain great challenges. Herein, a simple solution‐process is developed to rapidly grow gram‐scale organic–inorganic (MAPbX3, X = Cl, Br, I) perovskite microcrystals. They exhibit excellent EM response in multi bands covering microwaves, visible light, and X‐rays. Among them, outstanding microwave absorption performance with multiple absorption bands can be achieved, and their intrinsic EM properties can be tuned by adjusting polar group. An ultra‐wideband bandpass filter with high suppression level of −71.8 dB in the stopband in the GHz band, self‐powered photodetectors with tunable broadband or narrowband photoresponse in the visible‐light band, and a self‐powered X‐ray detector with high sensitivity of 3560 µC Gyair−1 cm−2 in the X‐ray band are designed and realized by precisely regulating the physical features of perovskite and designing a novel planar device structure. These findings open a door toward developing high‐efficiency EM functional materials for realizing high‐performance EM absorbers and devices.
A facile one‐step solution processing method is developed to rapidly prepare gram‐scale MAPbX3 microcrystals. Utilizing its intrinsic electromagnetic (EM) properties, a series of EM devices is designed and fabricated, which can be applied in the fields of ultra‐wideband bandpass filters and multi‐band photodetection covering X‐rays, UV, visible light, and microwaves.
We proposed a reductive elimination/oxidative addition (re/oa) mechanism for reduction of N2 to 2NH3 by nitrogenase, based on identification of a freeze-trapped intermediate of the α-70Val→Ile MoFe ...protein as the Janus intermediate that stores four reducing equivalents on FeMo-co as two Fe–H–Fe bridging hydrides (denoted E4(4H)). The mechanism postulates that obligatory re of the hydrides as H2 drives reduction of N2 to a state (denoted E4(2N2H)) with a moiety at the diazene (HNNH) reduction level bound to the catalytic FeMo-co. EPR/ENDOR/photophysical measurements on wild type (WT) MoFe protein now establish this mechanism. They show that a state freeze-trapped during N2 reduction by WT MoFe is the same Janus intermediate, thereby establishing the α-70Val→Ile intermediate as a reliable guide to mechanism. Monitoring the Janus state in WT MoFe during N2 reduction under mixed-isotope condition, H2O buffer/D2, and the converse, establishes that the bridging hydrides/deuterides do not exchange with solvent during enzymatic turnover, thereby solving longstanding puzzles. Relaxation of E4(2N2H) to the WT resting-state is shown to occur via oa of H2 and release of N2 to form Janus, followed by sequential release of two H2, demonstrating the kinetic reversibility of the re/oa equilibrium. Relative populations of E4(2N2H)/E4(4H) freeze-trapped during WT turnover furthermore show that the reversible re/oa equilibrium between E4(4H) + N2 and E4(2N2H) + H2 is ∼ thermoneutral (Δ re G 0 ∼ −2 kcal/mol), whereas, by itself, hydrogenation of N2(g) is highly endergonic. These findings demonstrate that (i) re/oa accounts for the historical Key Constraints on mechanism, (ii) that Janus is central to N2 reduction by WT enzyme, which (iii) indeed occurs via the re/oa mechanism. Thus, emerges a picture of the central mechanistic steps by which nitrogenase carries out one of the most challenging chemical transformations in biology.
During HIV-1 infection, antibodies are generated against the region of the viral gp120 envelope glycoprotein that binds CD4, the primary receptor for HIV-1. Among these antibodies, VRC01 achieves ...broad neutralization of diverse viral strains. We determined the crystal structure of VRC01 in complex with a human immunodeficiency virus HIV-1 gp120 core. VRC01 partially mimics CD4 interaction with gp120. A shift from the CD4-defined orientation, however, focuses VRC01 onto the vulnerable site of initial CD4 attachment, allowing it to overcome the glycan and conformational masking that diminishes the neutralization potency of most CD4-binding-site antibodies. To achieve this recognition, VRC01 contacts gp120 mainly through immunoglobulin V-gene regions substantially altered from their genomic precursors. Partial receptor mimicry and extensive affinity maturation thus facilitate neutralization of HIV-1 by natural human antibodies.
Competitive interactions drive critical ecological processes in plant communities. Yet, how competitive interactions are influenced by polyploidy that has a widespread incidence in plants remains ...largely unknown.
To evaluate the hypothesis of competitive asymmetry between polyploids and diploids, we competed tetraploid and diploid plants of perennial herbaceous Chrysanthemum indicum L. (Asteraceae) at different relative frequencies under contrasting soil water contents. We quantified the interaction intensity between competing plants of the same (intraploidy) and different ploidy levels (interploidy), and measured functional traits related to gas exchange and plant water use to understand the underlying mechanisms.
The stronger competitive effect of tetraploids on diploids than that of diploids on tetraploids provided evidence for the competitive asymmetry. As a stronger competitor, tetraploids were limited more by individuals of their own than by diploids. Such competitive asymmetry was not only maintained under reduced soil water content, but also translated into higher above‐ground biomass of tetraploids. Tetraploids showed more resource‐acquisitive traits than diploids under high soil water content and more resource‐conservative traits under reduced soil water content. As such, the higher trait plasticity in tetraploids than diploids likely explained the competitive asymmetry.
Synthesis. These results elucidate the nature and magnitude of species interactions between polyploid and diploid plants under changing environments and the underlying mechanisms, and provide important insights into the prevalence and persistence of polyploid plants under a changing climate.
These results elucidate the nature and magnitude of species interactions between polyploid and diploid plants under changing environments and the underlying mechanisms, and provide important insights into the prevalence and persistence of polyploid plants under a changing climate.
The development of an effective AIDS vaccine has been challenging because of viral genetic diversity and the difficulty of generating broadly neutralizing antibodies (bnAbs). We engineered ...trispecific antibodies (Abs) that allow a single molecule to interact with three independent HIV-1 envelope determinants: the CD4 binding site, the membrane-proximal external region (MPER), and the V1V2 glycan site. Trispecific Abs exhibited higher potency and breadth than any previously described single bnAb, showed pharmacokinetics similar to those of human bnAbs, and conferred complete immunity against a mixture of simian-human immunodeficiency viruses (SHIVs) in nonhuman primates, in contrast to single bnAbs. Trispecific Abs thus constitute a platform to engage multiple therapeutic targets through a single protein, and they may be applicable for treatment of diverse diseases, including infections, cancer, and autoimmunity.
A new three‐dimensional (3D) framework, Ni(btzip)(H2btzip)⋅2 DMF⋅2 H2O (1) (H2btzip=4,6‐bis(triazol‐1‐yl)isophthalic acid) as an acidic heterogeneous catalyst was constructed by the reaction of ...nickel wire and a triazolyl‐carboxyl linker. Framework 1 possesses intersected 2D channels decorated by free COOH groups and uncoordinated triazolyl N atoms, leading to not only high CO2 and C2H6 adsorption capacity but also significant selective capture for CO2 and C2H6 over CH4 and CO in 273–333 K. Moreover, 1 reveals chemical stability toward water. Grand Canonical Monte Carlo simulations confirmed the multiple CO2‐ and C2H6‐philic sites. As a result of the presence of accessible Brønsted acidic COOH groups in the channels, the activated framework demonstrates highly efficient catalytic activity in the cycloaddition reaction of CO2 with propylene oxide/4‐chloromethyl‐1,3‐dioxolan‐2‐one/3‐butoxy‐1,2‐epoxypropane into cyclic carbonates.
Through employing a triazolyl‐carboxyl linker, a stable porous Ni metal–organic framework (MOF) was constructed, which contains free carboxyl groups in channels and reveals not only high CO2 and C2H6 loadings but also significant selective capture for CO2 and C2H6 over CH4 and CO, as well as highly efficient catalytic activity in the cycloaddition reaction of CO2 with epoxides. The multi‐point framework–CO2/C2H6 interactions were confirmed by Grand Canonical Monte Carlo simulations (see scheme).
Progesterone is required for the establishment and maintenance of mammalian pregnancy and widely used for conservative treatment of luteal phase deficiency in clinics. However, there are limited ...solid evidences available for the optimal timing and dose of progesterone therapy, especially for the possible adverse effects on implantation and decidualization when progesterone is administrated empirically. In our study, mouse models were used to examine effects of excess progesterone on embryo implantation and decidualization. Our data indicate that excess progesterone is not only harmful for mouse implantation, but also impairs mouse decidualization. In excess progesterone-treated mice, the impaired LIF/STAT3 pathway and dysregulated endoplasmic reticulum stress may lead to the inhibition of embryo implantation and decidualization. It is possible that the decrease in birth weight of excess progesterone-treated mice is due to a compromised embryo implantation and decidualization. Furthermore, excess progesterone compromises in vitro decidualization of human endometrial stromal cells.
Cross-reactive neutralizing antibodies (NAbs) are found in the sera of many HIV-1-infected individuals, but the virologic basis of their neutralization remains poorly understood. We used knowledge of ...HIV-1 envelope structure to develop antigenically resurfaced glycoproteins specific for the structurally conserved site of initial CD4 receptor binding. These probes were used to identify sera with NAbs to the CD4-binding site (CD4bs) and to isolate individual B cells from such an HIV-1-infected donor. By expressing immunoglobulin genes from individual cells, we identified three monoclonal antibodies, including a pair of somatic variants that neutralized over 90% of circulating HIV-1 isolates. Exceptionally broad HIV-1 neutralization can be achieved with individual antibodies targeted to the functionally conserved CD4bs of glycoprotein 120, an important insight for future HIV-1 vaccine design.
Risk Factors and Preventions of Breast Cancer Sun, Yi-Sheng; Zhao, Zhao; Yang, Zhang-Nv ...
International journal of biological sciences,
01/2017, Letnik:
13, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Breast cancer is the second leading cause of cancer deaths among women. The development of breast cancer is a multi-step process involving multiple cell types, and its prevention remains challenging ...in the world. Early diagnosis of breast cancer is one of the best approaches to prevent this disease. In some developed countries, the 5-year relative survival rate of breast cancer patients is above 80% due to early prevention. In the recent decade, great progress has been made in the understanding of breast cancer as well as in the development of preventative methods. The pathogenesis and tumor drug-resistant mechanisms are revealed by discovering breast cancer stem cells, and many genes are found related to breast cancer. Currently, people have more drug options for the chemoprevention of breast cancer, while biological prevention has been recently developed to improve patients' quality of life. In this review, we will summarize key studies of pathogenesis, related genes, risk factors and preventative methods on breast cancer over the past years. These findings represent a small step in the long fight against breast cancer.
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