This review describes the emerging field of waveguide quantum electrodynamics concerned with the interaction of photons propagating in a waveguide with localized quantum emitters. The collective ...emitter-photon interactions can lead to both enhanced and suppressed coupling compared to the case of independent emitters. Here the focus is on guided photons and ordered emitter arrays, manifesting superradiant and subradiant states, bound photon states, and quantum correlations with promising quantum information applications. Recent groundbreaking experiments performed with different quantum platforms, including cold atoms, superconducting qubits, semiconductor quantum dots, and quantum solid-state defects, are highlighted. The review also provides a comprehensive introduction to theoretical techniques to study the interactions and dynamics of these emitters and the photons in the waveguide.
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Mo- and W-dichalcogenide compounds have a two-dimensional monolayer form that differs from graphene in an important respect: it can potentially have more than one crystal structure. Some of these ...monolayers exhibit tantalizing hints of a poorly understood structural metal-to-insulator transition with the possibility of long metastable lifetimes. If controllable, such a transition could bring an exciting new application space to monolayer materials beyond graphene. Here we discover that mechanical deformations provide a route to switching thermodynamic stability between a semiconducting and a metallic crystal structure in these monolayer materials. Based on state-of-the-art density functional and hybrid Hartree-Fock/density functional calculations including vibrational energy corrections, we discover that MoTe2 is an excellent candidate phase change material. We identify a range from 0.3 to 3% for the tensile strains required to transform MoTe2 under uniaxial conditions at room temperature. The potential for mechanical phase transitions is predicted for all six studied compounds.
Selective alkylation of pyrazoles could solve a challenge in chemistry and streamline synthesis of important molecules. Here we report catalyst‐controlled pyrazole alkylation by a cyclic two‐enzyme ...cascade. In this enzymatic system, a promiscuous enzyme uses haloalkanes as precursors to generate non‐natural analogs of the common cosubstrate S‐adenosyl‐l‐methionine. A second engineered enzyme transfers the alkyl group in highly selective C−N bond formations to the pyrazole substrate. The cosubstrate is recycled and only used in catalytic amounts. Key is a computational enzyme‐library design tool that converted a promiscuous methyltransferase into a small enzyme family of pyrazole‐alkylating enzymes in one round of mutagenesis and screening. With this enzymatic system, pyrazole alkylation (methylation, ethylation, propylation) was achieved with unprecedented regioselectivity (>99 %), regiodivergence, and in a first example on preparative scale.
Biological alkylation is highly selective, yet it depends on complex leaving groups. Now, promiscuous and engineered enzymes achieve selective enzymatic alkylation using simple haloalkanes.
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Dynamic control of conductivity and optical properties via atomic structure changes is of technological importance in information storage. Energy consumption considerations provide a driving force ...towards employing thin materials in devices. Monolayer transition metal dichalcogenides are nearly atomically thin materials that can exist in multiple crystal structures, each with distinct electrical properties. By developing new density functional-based methods, we discover that electrostatic gating device configurations have the potential to drive structural semiconductor-to-semimetal phase transitions in some monolayer transition metal dichalcogenides. Here we show that the semiconductor-to-semimetal phase transition in monolayer MoTe2 can be driven by a gate voltage of several volts with appropriate choice of dielectric. We find that the transition gate voltage can be reduced arbitrarily by alloying, for example, for Mo(x)W(1-x)Te2 monolayers. Our findings identify a new physical mechanism, not existing in bulk materials, to dynamically control structural phase transitions in two-dimensional materials, enabling potential applications in phase-change electronic devices.
Prodrugs are cunning derivatives of therapeutic agents designed to improve the pharmacokinetics profile of the drug. Within a prodrug, pharmacological activity of the drug is masked and is recovered ...within the human body upon bioconversion of the prodrug, a process that is typically mediated by enzymes. This concept is highly successful and a significant fraction of marketed therapeutic formulations is based on prodrugs. An advanced subset of prodrugs can be engineered such as to achieve site-specific bioconversion of the prodrug – to comprise the highly advantageous “enzyme prodrug therapy”, EPT. Design of prodrugs for EPT is similar to the prodrugs in general medicinal use in that the pharmacological activity of the drug is masked, but differs significantly in that site-specific bioconversion is a prime consideration, and the enzymes typically used for EPT are non-mammalian and/or with low systemic abundance in the human body. This review focuses on the design of prodrugs for EPT in terms of the choice of an enzyme and the corresponding prodrug for bioconversion. We also discuss the recent success of “self immolative linkers” which significantly empower and diversify the prodrug design, and present methodologies for the design of prodrugs with extended blood residence time. The review aims to be of specific interest for medicinal chemists, biomedical engineers, and pharmaceutical scientists.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Polymer films and coatings are among the popular and most successful tools to modulate surface properties of biomaterials, specifically tissue responses and fouling behavior. Over the past decade, a ...novel opportunity has been widely investigated, namely utility of surface coatings in surface-mediated drug delivery. In these applications, deposited polymer films act as both a coating to modulate surface properties and a reservoir for active therapeutic cargo. The field has recently accelerated beyond the proof-of-concept reports toward delivering practical solutions and established technologies for biomedical applications. This review briefly summarizes the recent successes of polymer thin films, specifically those constructed by sequential polymer deposition technique, in surface-mediated drug delivery.
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Biological drugs generated via recombinant techniques are uniquely positioned due to their high potency and high selectivity of action. The major drawback of this class of therapeutics, however, is ...their poor stability upon oral administration and during subsequent circulation. As a result, biological drugs have very low bioavailability and short therapeutic half-lives. Fortunately, tools of chemistry and biotechnology have been developed into an elaborate arsenal, which can be applied to improve the pharmacokinetics of biological drugs. Depot-type release systems are available to achieve sustained release of drugs over time. Conjugation to synthetic or biological polymers affords long circulating formulations. Administration of biological drugs through non-parenteral routes shows excellent performance and the first products have reached the market. This Review presents the main accomplishments in this field and illustrates the materials and methods behind existing and upcoming successful formulations and delivery strategies for biological drugs.
Evolution and Future of Earth's Nitrogen Cycle Canfield, Donald E; Glazer, Alexander N; Falkowski, Paul G
Science (American Association for the Advancement of Science),
10/2010, Volume:
330, Issue:
6001
Journal Article
Peer reviewed
Atmospheric reactions and slow geological processes controlled Earth's earliest nitrogen cycle, and by approximately 2.7 billion years ago, a linked suite of microbial processes evolved to form the ...modern nitrogen cycle with robust natural feedbacks and controls. Over the past century, however, the development of new agricultural practices to satisfy a growing global demand for food has drastically disrupted the nitrogen cycle. This has led to extensive eutrophication of fresh waters and coastal zones as well as increased inventories of the potent greenhouse gas nitrous oxide (N₂O). Microbial processes will ultimately restore balance to the nitrogen cycle, but the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated.
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In oxygenic photosynthetic systems, the cytochrome
b
6
f
(Cyt
b
6
f
) complex (plastoquinol:plastocyanin oxidoreductase) is a heart of the hub that provides connectivity between photosystems (PS) II ...and I. In this review, the structure and function of the Cyt
b
6
f
complex are briefly outlined, being focused on the mechanisms of a bifurcated (two-electron) oxidation of plastoquinol (PQH
2
). In plant chloroplasts, under a wide range of experimental conditions (pH and temperature), a diffusion of PQH
2
from PSII to the Cyt
b
6
f
does not limit the intersystem electron transport. The overall rate of PQH
2
turnover is determined mainly by the first step of the bifurcated oxidation of PQH
2
at the catalytic site Q
o
, i.e., the reaction of electron transfer from PQH
2
to the Fe
2
S
2
cluster of the high-potential Rieske iron–sulfur protein (ISP). This point has been supported by the quantum chemical analysis of PQH
2
oxidation within the framework of a model system including the Fe
2
S
2
cluster of the ISP and surrounding amino acids, the low-potential heme
b
6
L
, Glu78 and 2,3,5-trimethylbenzoquinol (the tail-less analog of PQH
2
). Other structure–function relationships and mechanisms of electron transport regulation of oxygenic photosynthesis associated with the Cyt
b
6
f
complex are briefly outlined: pH-dependent control of the intersystem electron transport and the regulatory balance between the operation of linear and cyclic electron transfer chains.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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