scholarly journals Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine

Molecules ◽  
2018 ◽  
Vol 23 (8) ◽  
pp. 2036 ◽  
Author(s):  
Edward Matthews ◽  
Rosaria Cercola ◽  
Caroline Dessent
Keyword(s):  
Electronic Spectroscopy ◽  
Excited State Lifetime ◽  
Wide Range ◽  
Spectral Profiles ◽  
Minor Form ◽  
Photochemical Properties ◽  
Gas Phase Spectroscopy ◽  
Density Shift ◽  
Ground State Molecule ◽  
Key Questions

Flavin chromophores play key roles in a wide range of photoactive proteins, but key questions exist in relation to their fundamental spectroscopic and photochemical properties. In this work, we report the first gas-phase spectroscopy study of protonated alloxazine (AL∙H+), a model flavin chromophore. Laser photodissociation is employed across a wide range (2.34–5.64 eV) to obtain the electronic spectrum and characterize the photofragmentation pathways. By comparison to TDDFT quantum chemical calculations, the spectrum is assigned to two AL∙H+ protomers; an N5 (dominant) and O4 (minor) form. The protomers have distinctly different spectral profiles in the region above 4.8 eV due to the presence of a strong electronic transition for the O4 protomer corresponding to an electron-density shift from the benzene to uracil moiety. AL∙H+ photoexcitation leads to fragmentation via loss of HCN and HNCO (along with small molecules such as CO2 and H2O), but the photofragmentation patterns differ dramatically from those observed upon collision excitation of the ground electronic state. This reveals that fragmentation is occurring during the excited state lifetime. Finally, our results show that the N5 protomer is associated primarily with HNCO loss while the O4 protomer is associated with HCN loss, indicating that the ring-opening dynamics are dependent on the location of protonation in the ground-state molecule.

scholarly journals Physiology, Biochemistry, and Applications of F420- and Fo-Dependent Redox Reactions

2016 ◽  
Vol 80 (2) ◽  
pp. 451-493 ◽  
Author(s):  
Chris Greening ◽  
F. Hafna Ahmed ◽  
A. Elaaf Mohamed ◽  
Brendon M. Lee ◽  
Gunjan Pandey ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Methanogenic Archaea ◽  
Content Type ◽  
Sulfate Reducing ◽  
Single Function ◽  
Wide Range ◽  
Domains Of Life ◽  
Photochemical Properties ◽  
Endogenous Metabolites ◽  
Dependent Processes

SUMMARY5-Deazaflavin cofactors enhance the metabolic flexibility of microorganisms by catalyzing a wide range of challenging enzymatic redox reactions. While structurally similar to riboflavin, 5-deazaflavins have distinctive and biologically useful electrochemical and photochemical properties as a result of the substitution of N-5 of the isoalloxazine ring for a carbon. 8-Hydroxy-5-deazaflavin (Fo) appears to be used for a single function: as a light-harvesting chromophore for DNA photolyases across the three domains of life. In contrast, its oligoglutamyl derivative F420is a taxonomically restricted but functionally versatile cofactor that facilitates many low-potential two-electron redox reactions. It serves as an essential catabolic cofactor in methanogenic, sulfate-reducing, and likely methanotrophic archaea. It also transforms a wide range of exogenous substrates and endogenous metabolites in aerobic actinobacteria, for example mycobacteria and streptomycetes. In this review, we discuss the physiological roles of F420in microorganisms and the biochemistry of the various oxidoreductases that mediate these roles. Particular focus is placed on the central roles of F420in methanogenic archaea in processes such as substrate oxidation, C1pathways, respiration, and oxygen detoxification. We also describe how two F420-dependent oxidoreductase superfamilies mediate many environmentally and medically important reactions in bacteria, including biosynthesis of tetracycline and pyrrolobenzodiazepine antibiotics by streptomycetes, activation of the prodrugs pretomanid and delamanid byMycobacterium tuberculosis, and degradation of environmental contaminants such as picrate, aflatoxin, and malachite green. The biosynthesis pathways of Foand F420are also detailed. We conclude by considering opportunities to exploit deazaflavin-dependent processes in tuberculosis treatment, methane mitigation, bioremediation, and industrial biocatalysis.

Key questions in zoo and aquarium studies: a study and revision guide

2021 ◽  
Keyword(s):  
Multiple Choice ◽  
Animal Behaviour ◽  
Multiple Choice Questions ◽  
Environmentally Conscious ◽  
Conservation Medicine ◽  
Wide Range ◽  
Conservation Breeding ◽  
Key Questions

Abstract This 229-paged book discussed the role of zoos in a modern, environmentally conscious society. It does this by offering the reader the opportunity to answer 600 multiple-choice questions on a wide range of topics including zoo history, enclosure design, aquarium management, animal behaviour and welfare, zoo research, conservation breeding, zoo visitor behaviour, conservation medicine, zoo legislation and many more.

scholarly journals Heat shock proteins and cancer: intracellular chaperones or extracellular signalling ligands?

2017 ◽  
Vol 373 (1738) ◽  
pp. 20160524 ◽  
Author(s):  
Stuart K. Calderwood
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Tumour Cells ◽  
Future Studies ◽  
Proteotoxic Stress ◽  
Wide Range ◽  
Window Of Vulnerability ◽  
Shock Proteins ◽  
Extracellular Signalling ◽  
Key Questions

Heat shock proteins (HSPs) are found at elevated concentrations in tumour cells, and this increase reflects the proteotoxic stress experienced by the cells due to expanding levels of the mutated oncoproteins that drive tumorigenesis. The protection of oncogenic proteins by HSPs offers a window of vulnerability in tumour metabolism that has been exploited using Hsp90-targeting drugs. Such compounds have been shown to cause inhibition and degradation of a wide range of proteins essential for oncogenesis. Recently, Hsp90 has also been shown to be secreted by tumour cells and to interact in autocrine or paracrine manners with the surfaces of adjacent cells, leading to increased growth and metastasis. Future studies will address a number of key questions associated with these findings, including the relative importance of intracellular versus extracellular HSPs in tumorigenesis, as well as overcoming potential problems with normal tissue toxicity associated with Hsp90 drugs. Targeting individual members of HSP families and inactivating extracellular HSPs may be desirable future approaches that offer increased selectivity in targeting HSPs in cancer. This article is part of the theme issue ‘Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective’.

Personal digital libraries: a self-archiving approach

2014 ◽  
Vol 63 (6/7) ◽  
pp. 436-451 ◽  
Author(s):  
Nikitas N. Karanikolas ◽  
Christos Skourlas
Keyword(s):  
Digital Libraries ◽  
Design Methodology ◽  
Low Cost ◽  
The Self ◽  
Information Process ◽  
Content Type ◽  
Wide Range ◽  
Software Product ◽  
Reduced Time ◽  
Key Questions

Purpose – The purpose of this paper is to examine personal digital libraries (PDL) as a self-archiving approach, mainly based on individuals’ activities. Literature presents a wide range of perceptions of the term PDL. The rationale of using PDL and the capabilities that PDL should offer are also discussed. The key questions we focus on are: “What are the critical features of PDL?” and “Are there technologies that enable the implementation/incorporation of such capabilities in a low cost software product?” Design/methodology/approach – We focus on “a user centred view of information process”, and examine how PDL could assist individuals to “create, seek, share and manage the life of information” (Foster et al., 2010). The capabilities that PDL should support, and the related technologies, are also discussed. Then, we describe experimentation with a prototype implemented to support/provide the mentioned capabilities. It is used to clarify our view for the creation of PDL. Finally, further discussion and conclusions are presented. Findings – The technology is mature enough for building up PDLs with the specified features/capabilities. Originality/value – A new perception of the term PDLs is presented. This perception tries to combine the self-archiving approach of information, based on a low-cost tool, and the user-centred approach to manage the “life of information”. This type of library is mainly used to cover personal needs. Users benefit from this type of PDL by personalised handling of information, reduced time to search and seek specific documents in their personal collections and less possibility for broken links or unavailable documents. We must also mention that new opportunities seem to appear for offering PDL as a service in the cloud.

Responsive porphyrinoid nanoparticles: development and applications

2011 ◽  
Vol 15 (05n06) ◽  
pp. 338-349 ◽  
Author(s):  
Amit Aggarwal ◽  
Meroz Qureshy ◽  
Jason Johnson ◽  
James D. Batteas ◽  
Charles Michael Drain ◽  
...  
Keyword(s):  
Self Assembly ◽  
Environmental Changes ◽  
Chemical Properties ◽  
Photonic Devices ◽  
Inorganic Nanoparticles ◽  
Synthetic Methods ◽  
Wide Range ◽  
Photochemical Properties ◽  
Increasing Demand ◽  
Organic Nanomaterials

The economy of space and materials and the continuously increasing demand for advanced functionalities for diverse technologies requires the development of new synthetic methods. Many nanomaterials have enhanced photophysical and photochemical properties in solutions and/or on surfaces, while others have enhanced chemical properties, compared to the atomic, molecular, or bulk phases. Nanomaterials have a wide range of applications in catalysis, sensors, photonic devices, drug delivery, and as therapeutics for treatment of a variety of diseases. Inorganic nanoparticles are widely studied, but the formation of organic nanomaterials via supramolecular chemistry is more recent, and porphyrinoids are at the forefront of this research because of their optical, chemical, and structural properties. The formation of nanoscaled materials via self-assembly and/or self-organization of molecular subunits is an attractive approach because of reduced energy requirements, simpler molecular subunits, and the material can be adaptive to environmental changes. The presence of biocompatible groups such as peptides, carbohydrates, polyglycols and mixtures of these on the periphery of the porphyrin macrocycle may make nanoparticles suitable for therapeutics. This perspective focuses on responsive, non-crystalline porphyrinoid nanomaterials that are less than about 100 nm in all dimensions and used for catalytic or therapeutic applications.

scholarly journals SYNTHESIS OF MONOMERS BASED ON 6-HYDROXYAURONE AND INVESTIGATION ITS PHOTOCHEMICAL PROPERTIES

2020 ◽  
Vol 86 (4) ◽  
pp. 118-125
Author(s):  
Oksana Kharchenko ◽  
Vitaliy Smokal ◽  
Oksana Krupka
Keyword(s):  
1H Nmr Spectroscopy ◽  
Irradiation Time ◽  
Photophysical Properties ◽  
Slope Angle ◽  
Molecular Engineering ◽  
Vis Spectroscopy ◽  
Wide Range ◽  
Properties Of Materials ◽  
Photochemical Properties ◽  
Optical Properties Of Materials

In particular, as an important class of organic heterocyclic dyes, aurones exhibit unique photochemical and photophysical properties, which render them useful in a variety of applications, such as fluorescent labels and probes in biology and medicine. Despite of the wide range of applications, the photochemical properties of the aurone class remain less well known. The backbone of aurone molecule has excellent planarity and from the viewpoint of molecular engineering, molecular planarity plays an important role in tuning nonlinear optical properties of materials. Therefore, this work is aimed to the synthesis of new derivatives based on 6-hydroxyaurone and study their photochemical properties. Novel monomers based on (2Z)-2-benzylidene)-6-hydroxy-1-benzofuran-3 (2H)-one with different withdrawing substituents in the benzylidene moiety were synthesized by acylation of the hydroxy group by methacryloil chloride. The polymerization was carried out in 10% solutions of the monomers in dimethylformamide, 2,2ˊ-azobisisobutyronitrile was used as the initiator The structure of the synthesized compounds was proved by 1H NMR spectroscopy. The study of the photochemical properties of synthesized polymers was performed by UV VIS spectroscopy. New polymers with auron moiety have been shown ability to photoinduced Z-E-isomerization. The rate constants of Z-E-photoisomerization were determined by slope angle tangent of dependence ln(D/D0) on the irradiation time. The half-reaction periods for E-isomers of auronecontaining polymers were calculated.

Money Talks

2017 ◽  
Keyword(s):  
Social Relationships ◽  
Social Relations ◽  
First Century ◽  
Social Meaning ◽  
Payment Systems ◽  
Social Foundations ◽  
Wide Range ◽  
Financing And Investment ◽  
The Impact ◽  
Key Questions

The world of money is being transformed as households and organizations face changing economies, and new currencies and payment systems like Bitcoin and Apple Pay gain ground. What is money, and how do we make sense of it? This is the first book to offer a wide range of alternative and unexpected explanations of how social relations, emotions, moral concerns, and institutions shape how we create, mark, and use money. The book proposes fresh explanations for money's origins, uses, effects, and future. It explores five key questions: How do social relationships, emotions, and morals shape how people account for and use their money? How do corporations infuse social meaning into their financing and investment practices? What are the historical, political, and social foundations of currencies? When does money become contested, and are there things money shouldn't buy? What is the impact of the new twenty-first-century currencies on our social relations? At a time of growing concern over financial inequality, this book overturns conventional views about money by revealing its profound social potential.

Introduction

2019 ◽  
pp. 1-14
Author(s):  
Paul Dragos Aligica ◽  
Peter J. Boettke ◽  
Vlad Tarko
Keyword(s):  
Public Goods ◽  
Public Administration ◽  
Classical Liberalism ◽  
Public Governance ◽  
Welfare Policies ◽  
Classical Liberal ◽  
Wide Range ◽  
Systematic Framework ◽  
Key Questions

The introduction sets up the stage for the rest of the book by asking a series of key questions: Does classical liberalism entail a systematic framework of principles regarding public governance? If so, what are its broad recommendations and how does this perspective differ from other, more well-known perspectives on public administration? Classical liberalism accepts a wide range of collective arrangements and activities ranging from certain types of regulation to the provision of specific public goods and even to specific welfare policies. As such, the question arises, within the range of government activities accepted as legitimate, or at least not entirely beyond the pale, what are the particular classical-liberal views on the instruments and procedures of the administration of collective affairs? What kind of doctrine of governance and public administration does classical liberalism inspire? Is it possible to reconstruct or piece together such a position using the existing literature and practice?

scholarly journals Coumarins into Polyurethanes for Smart and Functional Materials

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 630 ◽  
Author(s):  
José María Cuevas ◽  
Rubén Seoane-Rivero ◽  
Rodrigo Navarro ◽  
Ángel Marcos-Fernández
Keyword(s):  
Smart Materials ◽  
Scientific Community ◽  
Functional Materials ◽  
Wide Range ◽  
Photochemical Properties ◽  
Natural And Synthetic

Polyurethanes are of undoubted interest for the scientific community and the industry. Their outstanding versatility from tailor-made structures turns them into major polymers for use in a wide range of different applications. As with other polymers, new, emerging molecules and monomers with specific attributes can provide new functions and capabilities to polyurethanes. Natural and synthetic coumarin and its derivatives are characterised by interesting biological, photophysical and photochemical properties. Then, the polyurethanes can exploit those features of many coumarins which are present in their composition to achieve new functions and performances. This article reviews the developments in the proper use of the special properties of coumarins in polyurethanes to produce functional and smart materials that can be suitable for new specific applications.

Polly wants a Doha deal: what does the trade community think?

2011 ◽  
Vol 10 (4) ◽  
pp. 551-555 ◽  
Author(s):  
PATRICK MESSERLIN ◽  
ERIK VAN DER MAREL
Keyword(s):  
Latin America ◽  
International Institutions ◽  
Think Tanks ◽  
List Type ◽  
Type Number ◽  
Doha Round ◽  
Wide Range ◽  
The Usa ◽  
Open Discussion ◽  
Key Questions

After ten years of negotiations, the Doha ‘Round is on the verge of collapse. At this difficult juncture, it is interesting to get a sense of the mood and thinking of the trade community on three key questions1:1.How serious is the situation?2.What are the causes of the current stalemate?3.What are the best solution(s)Two recent fora give an opportunity to analyze the answers of 71 observers to these questions at a crucial time, namely the month preceding the collapse of expectations that Doha might be completed by the end of 2011 (from April 1 to May 2, 2011). The CUTS Trade Forum (2011) triggered by Jagdish Bhagwati's op.ed. ‘Polly Wants a Doha Deal’ offered an open discussion forum where the 57 self-selected respondents could make their remarks with no pre-established format. The VoxEU (2011) e-book ‘Why World Leaders Must Resist the False Promise of a Doha Delay’ gathered short chapters written by 14 authors chosen by the e-book editors and willing to contribute. The respondents (all of them with a long experience in trade matters) include academics (25), former and current negotiators (9), lawyers (4), journalists (3), business (3), national civil servants (2) and trade policy experts (25 in total, of whom six are working in international institutions and nine in think tanks). Participants came from all continents: Africa (1), Asia (6), Europe (23), North America (15), Latin America (6), with a few countries particularly well represented (11 from the USA, 4 from Canada, 3 from Australia). The 17 respondents based in Geneva represent a wide range of nationalities.

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