Fundamental formulae for wave-energy conversion.

The time-average wave power that is absorbed from an incident wave by means of a wave-energy conversion (WEC) unit, or by an array of WEC units-i.e. oscillating immersed bodies and/or oscillating water columns (OWCs)-may be mathematically expressed in terms of the WEC units' complex oscillation amplitudes, or in terms of the generated outgoing (diffracted plus radiated) waves, or alternatively, in terms of the radiated waves alone. Following recent controversy, the corresponding three optional expressions are derived, compared and discussed in this paper. They all provide the correct time-average absorbed power. However, only the first-mentioned expression is applicable to quantify the instantaneous absorbed wave power and the associated reactive power. In this connection, new formulae are derived that relate the 'added-mass' matrix, as well as a couple of additional reactive radiation-parameter matrices, to the difference between kinetic energy and potential energy in the water surrounding the immersed oscillating WEC array. Further, a complex collective oscillation amplitude is introduced, which makes it possible to derive, by a very simple algebraic method, various simple expressions for the maximum time-average wave power that may be absorbed by the WEC array. The real-valued time-average absorbed power is illustrated as an axisymmetric paraboloid defined on the complex collective-amplitude plane. This is a simple illustration of the so-called 'fundamental theorem for wave power'. Finally, the paper also presents a new derivation that extends a recently published result on the direction-average maximum absorbed wave power to cases where the WEC array's radiation damping matrix may be singular and where the WEC array may contain OWCs in addition to oscillating bodies

Status 1983 Of The Norwegian Wave-Power Buoy Project

Several official assessments of wave-power plants in Norway show decreasing figures for the estimated cost of wave energy. The latest updating seems to confirm some of the points in our own assessment of a phase-controlled power-buoy plant, where we estimate the energy cost to be roughly 0.6 kr/kWh (5 pence/kWh) which has prospects to be reduced to 0.3 kr/kWh (3 p/kWh) in the future. This cost would be competitive on national energy supply markets. Among many different assessed wave-energy devices the phase-controlled power buoy is outstanding in having a rather low investment of energy, materials and money in relation to the produced energy per year. On the other hand, relatively much labour is required to construct and maintain the plant. Since the device contains some critical moving parts, more development work and full scale testing in the sea are required in order to obtain acceptable lifetime and reliability. Such a development program should be started as soon as possible. The program may result in knowledge on how to design a reliable device. Our project has been pursued with design work to a stage where the next step is to construct a full-scale test buoy. However, since funds for such work are not yet available, our research team now continues its work another aspect of wave power, i.a. work on mini- power devices and on phase-control of oscillating water columns

Roles of Trm9- and ALKBH8-like proteins in the formation of modified wobble uridines in Arabidopsis tRNA

Uridine at the wobble position of tRNA is usually modified, and modification is required for accurate and efficient protein translation. In eukaryotes, wobble uridines are modified into 5-methoxycarbonylmethyluridine (mcm5U), 5-carbamoylmethyluridine (ncm5U) or derivatives thereof. Here, we demonstrate, both by in vitro and in vivo studies, that the Arabidopsis thaliana methyltransferase AT1G31600, denoted by us AtTRM9, is responsible for the final step in mcm5U formation, thus representing a functional homologue of the Saccharomyces cerevisiae Trm9 protein. We also show that the enzymatic activity of AtTRM9 depends on either one of two closely related proteins, AtTRM112a and AtTRM112b. Moreover, we demonstrate that AT1G36310, denoted AtALKBH8, is required for hydroxylation of mcm5U to (S)-mchm5U in tRNAGlyUCC, and has a function similar to the mammalian dioxygenase ALKBH8. Interestingly, atalkbh8 mutant plants displayed strongly increased levels of mcm5U, and also of mcm5Um, its 2′-O-ribose methylated derivative. This suggests that accumulated mcm5U is prone to further ribose methylation by a non-specialized mechanism, and may challenge the notion that the existence of mcm5U- and mcm5Um-containing forms of the selenocysteine-specific tRNASec in mammals reflects an important regulatory process. The present study reveals a role in for several hitherto uncharacterized Arabidopsis proteins in the formation of modified wobble uridines

Fine tuning Exo2, a small molecule inhibitor of secretion and retrograde trafficking pathways in mammalian cells

The small molecule 4-hydroxy-3-methoxybenzaldehyde (5,6,7,8-tetrahydro[1]benzothieno[2,3- d]pyrimidin-4-yl)hydrazone (Exo2) stimulates morphological changes at the mammalian Golgi and trans-Golgi network that are virtually indistinguishable from those induced by brefeldin A. Both brefeldin A and Exo2 protect cells from intoxication by Shiga(-like) toxins by acting on other targets that operate at the early endosome, but do so at the cost of high toxicity to target cells. The advantage of Exo2 is that it is much more amenable to chemical modification and here we report a range of Exo2 analogues produced by modifying the tetrahydrobenzothienopyrimidine core, the vanillin moiety and the hydrazone bond that links these two. These compounds were examined for the morphological changes they stimulated at the Golgi stack, the trans Golgi network and the transferrin receptor-positive early endosomes and this activity correlated with their inherent toxicity towards the protein manufacturing ability of the cell and their protective effect against toxin challenge. We have developed derivatives that can separate organelle morphology, target specificity, innate toxicity and toxin protection. Our results provide unique compounds with low toxicity and enhanced specificity to unpick the complexity of membrane trafficking networks

Schizosaccharomyces pombe Ofd2 Is a Nuclear 2-Oxoglutarate and Iron Dependent Dioxygenase Interacting with Histones

2-oxoglutarate (2OG) dependent dioxygenases are ubiquitous iron containing enzymes that couple substrate oxidation to the conversion of 2OG to succinate and carbon dioxide. They participate in a wide range of biological processes including collagen biosynthesis, fatty acid metabolism, hypoxic sensing and demethylation of nucleic acids and histones. Although substantial progress has been made in elucidating their function, the role of many 2OG dioxygenases remains enigmatic. Here we have studied the 2OG and iron (Fe(II)) dependent dioxygenase Ofd2 in Schizosaccharomyces pombe, a member of the AlkB subfamily of dioxygenases. We show that decarboxylation of 2OG by recombinant Ofd2 is dependent on Fe(II) and a histidine residue predicted to be involved in Fe(II) coordination. The decarboxylase activity of Ofd2 is stimulated by histones, and H2A has the strongest effect. Ofd2 interacts with all four core histones, however, only very weakly with H4. Our results define a new subclass of AlkB proteins interacting with histones, which also might comprise some of the human AlkB homologs with unknown function

Recognition and processing of a new repertoire of DNA substrates by human 3-methyladenine DNA glycosylase (AAG)

The human 3-methyladenine DNA glycosylase (AAG) recognizes and excises a broad range of purines damaged by alkylation and oxidative damage, including 3-methyladenine, 7-methylguanine, hypoxanthine (Hx), and 1,N[superscript 6]-ethenoadenine (εA). The crystal structures of AAG bound to εA have provided insights into the structural basis for substrate recognition, base excision, and exclusion of normal purines and pyrimidines from its substrate recognition pocket. In this study, we explore the substrate specificity of full-length and truncated Δ80AAG on a library of oligonucleotides containing structurally diverse base modifications. Substrate binding and base excision kinetics of AAG with 13 damaged oligonucleotides were examined. We found that AAG bound to a wide variety of purine and pyrimidine lesions but excised only a few of them. Single-turnover excision kinetics showed that in addition to the well-known εA and Hx substrates, 1-methylguanine (m1G) was also excised efficiently by AAG. Thus, along with εA and ethanoadenine (EA), m1G is another substrate that is shared between AAG and the direct repair protein AlkB. In addition, we found that both the full-length and truncated AAG excised 1,N[superscript 2]-ethenoguanine (1,N[superscript 2]-εG), albeit weakly, from duplex DNA. Uracil was excised from both single- and double-stranded DNA, but only by full-length AAG, indicating that the N-terminus of AAG may influence glycosylase activity for some substrates. Although AAG has been primarily shown to act on double-stranded DNA, AAG excised both εA and Hx from single-stranded DNA, suggesting the possible significance of repair of these frequent lesions in single-stranded DNA transiently generated during replication and transcription.United States. National Institutes of Health (grant ES05355)United States. National Institutes of Health (grant CA75576)United States. National Institutes of Health (grant CA55042)United States. National Institutes of Health (grant ES02109)United States. National Institutes of Health (grant T32-ES007020)United States. National Institutes of Health (grant CA80024)United States. National Institutes of Health (grant CA26731

Incorporation of oxygen into the succinate co-product of iron(II) and 2-oxoglutarate dependent oxygenases from bacteria, plants and humans.

The ferrous iron and 2-oxoglutarate (2OG) dependent oxygenases catalyse two electron oxidation reactions by coupling the oxidation of substrate to the oxidative decarboxylation of 2OG, giving succinate and carbon dioxide coproducts. The evidence available on the level of incorporation of one atom from dioxygen into succinate is inconclusive. Here, we demonstrate that five members of the 2OG oxygenase family, AlkB from&nbsp;Escherichia coli, anthocyanidin synthase and flavonol synthase from&nbsp;Arabidopsis thaliana, and prolyl hydroxylase domain enzyme 2 and factor inhibiting hypoxia-inducible factor-1 from&nbsp;Homo sapiens&nbsp;all incorporate a single oxygen atom, almost exclusively derived from dioxygen, into the succinate co-product.<br /

Novel AlkB Dioxygenases—Alternative Models for In Silico and In Vivo Studies

Background: ALKBH proteins, the homologs of Escherichia coli AlkB dioxygenase, constitute a direct, single-protein repair system, protecting cellular DNA and RNA against the cytotoxic and mutagenic activity of alkylating agents, chemicals significantly contributing to tumor formation and used in cancer therapy. In silico analysis and in vivo studies have shown the existence of AlkB homologs in almost all organisms. Nine AlkB homologs (ALKBH1–8 and FTO) have been identified in humans. High ALKBH levels have been found to encourage tumor development, questioning the use of alkylating agents in chemotherapy. The aim of this work was to assign biological significance to multiple AlkB homologs by characterizing their activity in the repair of nucleic acids in prokaryotes and their subcellular localization in eukaryotes. Methodology and Findings: Bioinformatic analysis of protein sequence databases identified 1943 AlkB sequences with eight new AlkB subfamilies. Since Cyanobacteria and Arabidopsis thaliana contain multiple AlkB homologs, they were selected as model organisms for in vivo research. Using E. coli alkB2 mutant and plasmids expressing cyanobacterial AlkBs, we studied the repair of methyl methanesulfonate (MMS) and chloroacetaldehyde (CAA) induced lesions in ssDNA, ssRNA, and genomic DNA. On the basis of GFP fusions, we investigated the subcellular localization of ALKBHs in A. thaliana and established its mostly nucleo-cytoplasmic distribution. Some of the ALKBH proteins were found to change their localization upon MMS treatment. Conclusions: Our in vivo studies showed highly specific activity of cyanobacterial AlkB proteins towards lesions and nucleic acid type. Subcellular localization and translocation of ALKBHs in A. thaliana indicates a possible role for these proteins in the repair of alkyl lesions. We hypothesize that the multiplicity of ALKBHs is due to their involvement in the metabolism of nucleo-protein complexes; we find their repair by ALKBH proteins to be economical and effective alternative to degradation and de novo synthesis

Flavin-Induced Oligomerization in Escherichia coli Adaptive Response Protein AidB

The process known as “adaptive response” allows Escherichia coli to respond to small doses of DNA-methylating agents by upregulating the expression of four proteins. While the role of three of these proteins in mitigating DNA damage is well understood, the function of AidB is less clear. Although AidB is a flavoprotein, no catalytic role has been established for the bound cofactor. Here we investigate the possibility that flavin plays a structural role in the assembly of the AidB tetramer. We report the generation and biophysical characterization of deflavinated AidB and of an AidB mutant that has greatly reduced affinity for flavin adenine dinucleotide (FAD). Using fluorescence quenching and analytical ultracentrifugation, we find that apo AidB has a high affinity for FAD, as indicated by an apparent dissociation constant of 402.1 ± 35.1 nM, and that binding of substoichiometric amounts of FAD triggers a transition in the AidB oligomeric state. In particular, deflavinated AidB is dimeric, whereas the addition of FAD yields a tetramer. We further investigate the dimerization and tetramerization interfaces of AidB by determining a 2.8 Å resolution crystal structure in space group P32 that contains three intact tetramers in the asymmetric unit. Taken together, our findings provide strong evidence that FAD plays a structural role in the formation of tetrameric AidB.National Institutes of Health (U.S.) (grant R01-GM0272663)National Institutes of Health (U.S.) (grant P30-ES002109)National Science Foundation (U.S.) (grant MCB-0543833

The protein that binds to DNA base J in trypanosomatids has features of a thymidine hydroxylase

© 2007 The Author et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The definitive version was published in Nucleic Acids Research 35 (2007): 2107-2115, doi:10.1093/nar/gkm049.Trypanosomatids contain an unusual DNA base J (ß-D-glucosylhydroxymethyluracil), which replaces a fraction of thymine in telomeric and other DNA repeats. To determine the function of base J, we have searched for enzymes that catalyze J biosynthesis. We present evidence that a protein that binds to J in DNA, the J-binding protein 1 (JBP1), may also catalyze the first step in J biosynthesis, the conversion of thymine in DNA into hydroxymethyluracil. We show that JBP1 belongs to the family of Fe2+ and 2-oxoglutarate-dependent dioxygenases and that replacement of conserved residues putatively involved in Fe2+ and 2-oxoglutarate-binding inactivates the ability of JBP1 to contribute to J synthesis without affecting its ability to bind to J-DNA. We propose that JBP1 is a thymidine hydroxylase responsible for the local amplification of J inserted by JBP2, another putative thymidine hydroxylase.This work was funded by a grant from the Netherlands Organization for Scientific Research and Chemical Sciences (NWO-CW) to P.B., NIH grant A1063523 to R.S. and NIH grant GM063584 to R.P.H