Framework nitrogen atoms of carbon nitride (C3N4) can coordinate with and activate metal sites for catalysis. In this study, C3N4 was employed to harvest visible light and activate Co2+ sites, ...without the use of additional ligands, in photochemical CO2 reduction. Photocatalysts containing single Co2+ sites on C3N4 were prepared by a simple deposition method and demonstrated excellent activity and product selectivity toward CO formation. A turnover number of more than 200 was obtained for CO production using the synthesized photocatalyst under visible-light irradiation. Inactive cobalt oxides formed at relatively high cobalt loadings but did not alter product selectivity. Further studies with X-ray absorption spectroscopy confirmed the presence of single Co2+ sites on C3N4 and their important role in achieving selective CO2 reduction.
A
bstract
A Standard Model extension with two Majorana neutrinos can explain the measured neutrino masses and mixings, and also account for the matter-antimatter asymmetry in a region of parameter ...space that could be testable in future experiments. The testability of the model relies to some extent on its minimality. In this paper we address the possibility that the model might be extended by extra generic new physics which we parametrize in terms of a low-energy effective theory. We consider the effects of the operators of the lowest dimensionality,
d
= 5, and evaluate the upper bounds on the coefficients so that the predictions of the minimal model are robust. One of the operators gives a new production mechanism for the heavy neutrinos at LHC via higgs decays. The higgs can decay to a pair of such neutrinos that, being long-lived, leave a powerful signal of two displaced vertices. We estimate the LHC reach to this process.
Synthetic polymers have been used as a molecular platform to develop host-defense antimicrobial peptide (AMP) mimetics which are effective in killing drug-resistant bacteria. In this topical review, ...we will discuss the AMP-mimetic design and chemical optimization strategies as well as the biological and biophysical implications of AMP mimicry by synthetic polymers. Traditionally, synthetic polymers have been used as a chemical means to replicate the chemical functionalities and physicochemical properties of AMPs (e.g., cationic charge, hydrophobicity) to recapitulate their mode of action. However, we propose a new perception that AMP-mimetic polymers are an inherently bioactive platform as whole molecules, which mimic more than the side chain functionalities of AMPs. The tunable nature and chemical simplicity of synthetic random polymers facilitate the development of potent, cost-effective, broad-spectrum antimicrobials. The polymer-based approach offers the potential for many antimicrobial applications to be used directly in solution or attached to surfaces to fight against drug-resistant bacteria.
We synthesized cationic random amphiphilic copolymers by radical copolymerization of methacrylate monomers with cationic or hydrophobic groups and evaluated their antimicrobial and hemolytic ...activities. The nature of the hydrophobic groups, and polymer composition and length were systematically varied to investigate how structural parameters affect polymer activity. This allowed us to obtain the optimal composition of polymers suitable to act as non‐toxic antimicrobials as well as non‐selective polymeric biocides. The antimicrobial activity depends sigmoidally on the mole fraction of hydrophobic groups (fHB). The hemolytic activity increases as fHB increases and levels off at high values of fHB, especially for the high‐molecular‐weight polymers. Plots of HC50 values versus the number of hydrophobic side chains in a polymer chain for each polymer series showed a good correlation and linear relationship in the log–log plots. We also developed a theoretical model to analyze the hemolytic activity of polymers and demonstrated that the hemolytic activity can be described as a balance of membrane binding of polymers through partitioning of hydrophobic side chains into lipid layers and the hydrophobic collapsing of polymer chains. The study on the membrane binding of dye‐labeled polymers to large, unilamellar vesicles showed that the hydrophobicity of polymers enhances their binding to lipid bilayers and induces collapse of the polymer chain in solution, reducing the apparent affinity of polymers for the membranes.
The antimicrobial and hemolytic activities of cationic polymethacrylate derivatives are driven by the total hydrophobicity of polymers (see picture). Polymer hydrophobicity results in collapse of the polymer chain in solution, causing a turnover of hemolytic activity. This effect also limits the efficacy and selectivity of synthetic polymers towards bacteria relative to erythrocytes.
Single‐source precursor syntheses have been devised for the preparation of structurally similar graphitic carbon dots (CDs), with (g‐N‐CD) and without (g‐CD) core nitrogen doping for artificial ...photosynthesis. An order of magnitude improvement has been realized in the rate of solar (AM1.5G) H2 evolution using g‐N‐CD (7950 μmolH2 (gCD)−1 h−1) compared to undoped CDs. All graphitized CDs show significantly enhanced light absorption compared to amorphous CDs (a‐CD) yet undoped g‐CD display limited photosensitizer ability due to low extraction of photogenerated charges. Transient absorption spectroscopy showed that nitrogen doping in g‐N‐CD increases the efficiency of hole scavenging by the electron donor and thereby significantly extends the lifetime of the photogenerated electrons. Thus, nitrogen doping allows the high absorption coefficient of graphitic CDs to be translated into high charge extraction for efficient photocatalysis.
Carbon dots are investigated for solar H2 production and a number of critical structure–activity relationships are determined for the first time. Nitrogen‐doping of the core structure is established as a strategy to enhance charge‐transfer reactions in graphitic carbons dots, which also demonstrate strong light absorption.
The concept of Resilience is gaining an increasing importance in industrial systems, service networks and supply chains, as it extends traditional risk assessment methods by capturing both shortterm ...and long-term effects of accidents and disruptions. Resilience is, in fact, both a qualitative property and a performance indicator that measures the system's ability to survive disruptive events, and rapidly restore its functionality after the disruptive event has occurred. However, while literature about systems resilience is ample, comparatively scarce attention has been devoted to the evaluation of production systems resilience. As a contribution to fill this gap, in this paper a quantitative method for resilience estimation specifically aimed at manufacturing plants is developed. The method focuses on computing resilience of the manufacturing process, according to its structure, when resources are subjected to physical damage resulting from disruptive events such as sabotage, technical accidents or natural disasters. Overall, the paper allows to assess the economic loss and duration of production interruption in any kind of manufacturing plant when subjected to damage produced by the above causes. In particular, the method enables direct assessment of the initial capacity loss following a prescribed disruptive event, and explicit estimation of the time-dependent capacity recovery path based on the actual process structure and sequence of resources restoration tasks, also allowing the quantification of resulting economic losses. In the paper, after model development, an application example is provided to show model capabilities. Facility designers and emergency managers can use this model as a decision support tool for risk assessment, and to plan emergency actions and plant refurbishment aimed at resilience enhancement.
Antibiotic‐resistant bacteria ‘superbugs’ are an emerging threat to public health due to the decrease in effective antibiotics as well as the slowed pace of development of new antibiotics to replace ...those that become ineffective. The need for new antimicrobial agents is a well‐documented issue relating to world health. Tremendous efforts have been given to developing compounds that not only show high efficacy, but also those that are less susceptible to resistance development in the bacteria. However, the development of newer, stronger antibiotics which can overcome these acquired resistances is still a scientific challenge because a new mode of antimicrobial action is likely required. To that end, amphiphilic, cationic polymers have emerged as a promising candidate for further development as an antimicrobial agent with decreased potential for resistance development. These polymers are designed to mimic naturally occurring host‐defense antimicrobial peptides which act on bacterial cell walls or membranes. Antimicrobial‐peptide mimetic polymers display antibacterial activity against a broad spectrum of bacteria including drug‐resistant strains and are less susceptible to resistance development in bacteria. These polymers also showed selective activity to bacteria over mammalian cells. Antimicrobial polymers provide a new molecular framework for chemical modification and adaptation to tune their biological functions. The peptide‐mimetic design of antimicrobial polymers will be versatile, generating a new generation of antibiotics toward implementation of polymers in biomedical applications. WIREs Nanomed Nanobiotechnol 2013, 5:49–66. doi: 10.1002/wnan.1199
This article is categorized under:
Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease
Biology-Inspired Nanomaterials > Peptide-Based Structures
The seesaw path to leptonic CP violation Caputo, A.; Hernandez, P.; Kekic, M. ...
The European physical journal. C, Particles and fields,
04/2017, Letnik:
77, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Future experiments such as SHiP and high-intensity
e
+
e
-
colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below
M
Z
. We show that the measurement of the mixing to ...electrons and muons of one such state could establish the existence of CP violating phases in the neutrino mixing matrix, in the context of low-scale seesaw models. We quantify in the minimal model the CP reach of these future experiments, and demonstrate that CP violating phases in the mixing matrix could be established at 5
σ
CL in a very significant fraction of parameter space.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Venom mixtures from insects, reptiles, and mollusks have long been a source of bioactive peptides which often have alternative uses as therapeutics. While these molecules act in numerous capacities, ...there have been many venom components that act on the target cells through membrane disruptive mechanisms. These peptides have long been of interest as potential antimicrobial peptide platforms, but the inherent cytotoxicity of venom peptides often results in poor therapeutic potential. Despite this, efforts are ongoing to identify and characterize venom peptide which exhibit high antimicrobial activity with low cytotoxicity and modify these to further enhance the efficacy while reducing toxicity. One example is ponericin L1 from
Neoponera goeldii
which has been demonstrated to have good antimicrobial activity and low in vitro cytotoxicity. The L1 sequence was modified by uniformly replacing the native hydrophobic residues with either Leu, Ile, Phe, Ala, or Val. Spectroscopic and microbiological approaches were employed to investigate how the amino acid sequence changes impacted membrane interaction, secondary structure, and antimicrobial efficacy. The L1 derivatives showed varying degrees of bilayer interaction, in some cases driven by bilayer composition. Several of the variants exhibited enhanced antimicrobial activity compared to the parent strain, while others lost all activity. Interestingly, the variant containing Val lost all antimicrobial activity and ability to interact with bilayers. Taken together the results indicate that peptide secondary structure, amino acid composition, and hydrophobicity all play a role in peptide activity, although this is a delicate balance that can result in non-specific binding or complete loss of activity if specific amino acids are incorporated.
Graphic Abstract
As we are on the cusp of the "post-antibiotic" era due to rapid spread of drug resistant bacteria, there is an urgent need for new antimicrobials that are not susceptible to bacterial resistance ...mechanisms. In this review, we will discuss the recent development of "polymer therapeutics" with antimicrobial activity. Learning from host-defence peptides, we propose the biomimetic design of synthetic polymers to target bacterial cell membranes, which act by compromising the membrane integrity. The discussion is extended to the future challenges and opportunities of antimicrobial polymers for clinical applications.
Amphiphilic antimicrobial polymers show promising potential as polymer therapeutics to fight drug resistant bacteria and biofilms.
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