Ab initio modelling of the structure and redox behaviour of copper(I) bound to a His–His model peptide: relevance to the β-amyloid peptide of Alzheimer’s disease

A contributing factor to the pathology of Alzheimer's disease is the generation of reactive oxygen species, most probably a consequence of the beta-amyloid (Abeta) peptide coordinating copper ions. Experimental and theoretical results indicate that His13 and His14 are the two most firmly established ligands in the coordination sphere of Cu(II) bound to Abeta. Abeta1-42 is known to reduce Cu(II) to Cu(I). The Abeta-Cu(II) complex has been shown to catalytically generate H(2)O(2) from reducing agents and O(2). Cu(II) in the presence of Abeta has been reported to have a formal reduction potential of +0.72-0.77 V (vs. the standard hydrogen electrode). Quantum chemical calculations using the B3LYP hybrid density functional method with the 6-31G(d) basis set were performed to model the reduction of previously studied Cu(II) complexes representing the His13-His14 portion of Abeta (Raffa et al. in J. Biol. Inorg. Chem. 10:887-902, 2005). The effects of solvation were accommodated using the CPCM method. The most stable complex between Cu(I) and the model compound, 3-(5-imidazolyl)propionylhistamine (1) involves tricoordinated Cu(I) in a distorted-T geometry, with the Npi of both imidazoles as well as the oxygen of the backbone carbonyl bound to copper. This model would be the most likely representation of a Cu(I) binding site for a His-His peptide in aqueous solution. A variety of possible redox processes are discussed.     

Elucidating Relayed Proton Transfer through a His–Trp–His Triad of a Transmembrane Proton Channel by Solid-State NMR

Proton transfer through membrane-bound ion channels is mediated by both water and polar residues of proteins, but the detailed molecular mechanism is challenging to determine. The tetrameric influenza A and B virus M2 proteins form canonical proton channels that use an HxxxW motif for proton selectivity and gating. The BM2 channel also contains a second histidine (His), H27, equidistant from the gating tryptophan, which leads to a symmetric H¹⁹xxxW²³xxxH²⁷ motif. The proton-dissociation constants (pK_a's) of H19 in BM2 were found to be much lower than the pK_a's of H37 in AM2. To determine if the lower pK_a's result from H27-facilitated proton dissociation of H19, we have now investigated a H27A mutant of BM2 using solid-state NMR. ¹⁵N NMR spectra indicate that removal of the second histidine converted the protonation and tautomeric equilibria of H19 to be similar to the H37 behavior in AM2, indicating that the peripheral H27 is indeed the origin of the low pK_a's of H19 in wild-type BM2. Measured interhelical distances between W23 sidechains indicate that the pore constriction at W23 increases with the H19 tetrad charge but is independent of the H27A mutation. These results indicate that H27 both accelerates proton dissociation from H19 to increase the inward proton conductance and causes the small reverse conductance of BM2. The proton relay between H19 and H27 is likely mediated by the intervening gating tryptophan through cation–π interactions. This relayed proton transfer may exist in other ion channels and has implications for the design of imidazole-based synthetic proton channels.     

The Way to a Man's Heart Is through His Stomach: What about Horses?

Background

How do we bond to one another? While in some species, like humans, physical contact plays a role in the process of attachment, it has been suggested that tactile contact''s value may greatly differ according to the species considered. Nevertheless, grooming is often considered as a pleasurable experience for domestic animals, even though scientific data is lacking. On another hand, food seems to be involved in the creation of most relationships in a variety of species.

Methodology/Principal Findings

In this study, we used the horse training context to test the effects of food versus grooming during repeated human-horse interactions. The results reveal that food certainly holds a key role in the attachment process, while tactile contact was here clearly insufficient for bonding to occur.

Conclusion/Significance

This study raises important questions on the way tactile contact is perceived, and shows that large inter-species differences are to be expected.     

Yes,You Can? A Speaker’s Potency to Act upon His Words Orchestrates Early Neural Responses to Message-Level Meaning

Evidence is accruing that, in comprehending language, the human brain rapidly integrates a wealth of information sources–including the reader or hearer’s knowledge about the world and even his/her current mood. However, little is known to date about how language processing in the brain is affected by the hearer’s knowledge about the speaker. Here, we investigated the impact of social attributions to the speaker by measuring event-related brain potentials while participants watched videos of three speakers uttering true or false statements pertaining to politics or general knowledge: a top political decision maker (the German Federal Minister of Finance at the time of the experiment), a well-known media personality and an unidentifiable control speaker. False versus true statements engendered an N400 - late positivity response, with the N400 (150–450 ms) constituting the earliest observable response to message-level meaning. Crucially, however, the N400 was modulated by the combination of speaker and message: for false versus true political statements, an N400 effect was only observable for the politician, but not for either of the other two speakers; for false versus true general knowledge statements, an N400 was engendered by all three speakers. We interpret this result as demonstrating that the neurophysiological response to message-level meaning is immediately influenced by the social status of the speaker and whether he/she has the power to bring about the state of affairs described.     

Michael Ruse and His Fifteen Years of Booknotes – For Better or for Worse

In this paper I trace Michael Ruse's Booknotes from the first volumeof Biology and Philosophy in 1986 to the present. I deal withboth the style and the content of these booknotes. Ruse paid specialattention to authors outside of the traditional English axis as wellas to feminist writers. He complained that too much attention wasbeing paid to certain topics (e.g., evolutionary ethics, evolutionaryepistemology, the species problem and reduction) while other, moreimportant topics were all but ignored (e.g., natural selection,population genetics, levels of selection and extraterrestrial life).He also dealt with the Darwin Industry. Creationism, his love-haterelationships with several authors and his undiluted love of CharlesDickens.     

Zinc to cadmium replacement in the A. thaliana SUPERMAN Cys₂ His₂ zinc finger induces structural rearrangements of typical DNA base determinant positions

Among heavy metals, whose toxicity cause a steadily increasing of environmental pollution, cadmium is of special concern due to its relatively high mobility in soils and potential toxicity at low concentrations. Given their ubiquitous role, zinc fingers domains have been proposed as mediators for the toxic and carcinogenic effects exerted by xenobiotic metals. To verify the structural effects of zinc replacement by cadmium in zinc fingers, we have determined the high resolution structure of the single Cys₂His₂ zinc finger of the Arabidopsis thaliana SUPERMAN protein (SUP37) complexed to the cadmium ion by means of UV–vis and NMR techniques. SUP37 is able to bind Cd(II), though with a dissociation constant higher than that measured for Zn(II). Cd‐SUP37 retains the ββα fold but experiences a global structural rearrangement affecting both the relative orientation of the secondary structure elements and the position of side chains involved in DNA recognition: among them Ser17 side chain, which we show to be essential for DNA binding, experiences the largest displacement. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 801‐810, 2011.     

How to quantify plant tolerance to loss of biomass?

In some plant species the whole shoot is occasionally removed, as a result of specialist herbivory, grazing, mowing, or other causes. The plant can adapt to defoliation by allocating more to tolerance and less to growth and defense. Plant tolerance to defoliation (TOL1) is typically measured as the ratio between the average dry weight of a group of damaged plants and a control group of undamaged plants, both measured some time after recovery. We develop a model to clarify what TOL1 actually measures. We advocate keeping regrowth (REG2) and shoot–root ratio, both elements of TOL1, separate in the analysis. Based on a resource trade‐off, exotic Jacobaea vulgaris plants from populations in the USA (no specialist herbivory) are expected to grow faster and be less tolerant than native Dutch populations (with specialist herbivory). Indeed Dutch plants had both a significantly larger fraction biomass in roots and faster regrowth (REG2), while US plants attained the highest weight in the control without defoliation. Using key‐factor analysis, we illustrate how growth rates, regrowth, and shoot–root ratio each contribute to final biomass (plant fitness). Our proposed method gives more insight in the mechanisms that underly plant tolerance against defoliation and how tolerance contributes to fitness.     

New methods to approach immunotherapy of cancer – and strategies of tumours to avoid elimination

Owing to the intense effort of numerous investigators, the number of tumour antigens potentially of use for clinical immunotherapy continues to increase. At the same time, further strategies employed by tumour cells to avoid destruction by the immune system are being uncovered. A combined onslaught to target tumour cells and prevent their “escape” will be required for successful immunotherapy. Progress in this area was the subject of a meeting supported by the European Cancer Research Consortium “EUCAPS”, which was held in London in February 2000. This conference was the second of a series, the first of which was summarised previously in this journal [Pawelec G et al. (1999) Cancer Immunol Immunother 48: 214]. Received: 14 March 2000 / Accepted: 30 March 2000     

Isaac Lea's Palaeosauropus (= “Sauropus”) primaevus: A Review of His Discovery

In 1849, Isaac Lea named Sauropus primaevus for footprints from Mount Carbon, Pennsylvania, USA, then the oldest fossil vertebrate footprints reported. In 1902, O. P. Hay constructed a new ichnogenus Palaeosauropus for this ichnospecies. Palaeosauropus has been one of the most frequently reported Mississippian footprint ichnogenera in North America and remains a valid ichnotaxon. The holotype of Palaeosauropus (= “Sauropus”) primaevus (referred to as P. primaevus), consisting of a single manus/pes pair, is described and illustrated in Lea (1853) Lea, I. 1853. On the fossil foot-marks in the Red Sandstones of Pottsville, Schuylkill County, Penna. Transactions of the American Philosophical Society, 10(new series): 307–315.  [Google Scholar] and is housed at the Academy of Natural Sciences in Philadelphia, Pennsylvania (ANS9752). Lea's large specimen of P. primaevus (approximately 86 cm by 53 cm), that included a trackway of six manus/pes pairs, described and illustrated in 1853 and 1855, was a combination of ANS9752 and a second specimen represented by a plaster cast housed at the National Museum of Natural History (USNM487148). Historical documents and examination of the Mauch Chunk Formation at Mount Carbon, Pennsylvania, enabled the identification of Lea's tracksite, originally reported to be a few hundred feet (about 75 m) from the former Mount Carbon Hotel. Our forensic evidence indicates the type locality for P. primaevus is approximately 90 m south from the southwest corner of Centre and Main Streets in Mount Carbon, Pennsylvania, with geographical coordinates of N 40° 40' 25.7”, W 76° 11' 14.9”. The type locality is within the middle member of the Mauch Chunk Formation, a fluvial sequence of late Mississippian (Visean) Age.     

May TLR4 Asp299Gly and IL17 His161Arg polymorphism be associated with progression of primary measles infection to subacute sclerosing panencephalitis?

SSPE is a progressive neurological disorder of children. Only some of the children who are infected with measles virus develop SSPE, which supports individual variation. TLR-2 and TLR-4 play an important role in innate immunity by recognizing envelope proteins of MV. Another important cytokine that plays an important role in orchestrating innate immune function is IL-17. The purpose of our study is to elucidate whether the TLR2, TLR4, IL17F and IL17A gene polymorphisms are susceptibility genes for the development of SSPE.     

How to determine the susceptibility of Meligethes aeneus to neonicotinoids?

Three different bioassays were used to determine the susceptibility to the neonicotinoid Biscaya^® of oilseed rape pollen beetles collected from fields in Bavaria. The one in which the test substance was applied to the inner wall of glass tubes is recommended for future studies on pollen beetles because it is not dependent on the availability of plant material and provides precise information on the amount of insecticide required per unit area.     

Use of liposomes as membrane models to evaluate the contribution of drug–membrane interactions to antioxidant properties of etodolac

Abstract

This work stresses the need to combine antioxidant assays and drug–membrane interaction studies to describe more accurately the antioxidant profile of non-steroidal anti-inflammatory drugs (NSAIDs). Different experiments performed in liposomes and aqueous solution were compared and used to evaluate the protective effect of etodolac in lipid peroxidation. Lipid peroxidation was induced by the peroxyl radical (ROO?) derived from 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and hydroxyl radical (HO?) generated by the Fenton reaction and was assessed by the fluorescence intensity decay of three fluorescence probes with distinct lipophilic properties – fluorescein; hexadecanoyl aminofluorescein (HDAF) and diphenylhexatriene propionic acid (DPHPA). Membrane fluidity changes due to lipid peroxidation were also evaluated by steady-state anisotropy measurements. Interactions of etodolac with lipid bilayers were evaluated by membrane zeta-potential measurements. Results indicate a drug location near the membrane surface and show that etodolac can scavenge the radicals studied but to a variable extent, depending on the assayed media and reactive species. The use of different probes and liposomes as membrane mimetic systems allowed us to conclude that membrane lipoperoxidation is not only related to the scavenging characteristics of the antioxidants, but also to their ability to interact with lipid bilayers.     

Computational study of binding of epothilone A to β-tubulin

Understanding the interactions of epothilones with β-tubulin is crucial for computer aided rational design of macrocyclic drugs based on epothilones and epothilone derivatives. Despite numerous structure-activity relationship investigations we still lack substantial knowledge about the binding mode of epothilones and their derivatives to β-tubulin. In this work, we reevaluated the electron crystallography structure of epothilone A/β-tubulin complex (PDB entry 1TVK) and proposed an alternative binding mode of epothilone A to β-tubulin that explains more experimental facts.     

The Possible Role of Polyamines to the Recalcitrance of “Kalamata” Olive Leafy Cuttings to Root

The objective of this study was to investigate the role of endogenous polyamines (PAs) (the sum of free plus soluble conjugate plus insoluble bound) on rooting potential of leafy cuttings of an easy, that is,“Arbequina” and a difficult-to-root olive cultivar, that is, “Kalamata”. Subsamples of cuttings were taken for PAs analysis before planting in the mist system and during the early phases of rhizogenesis (EPR). “Arbequina” exhibited higher initial free and total PA content than “Kalamata”. Spermidine (Spd) was the predominant PA observed in both cultivars. A low content of free putrescine (Put) and Spd was found in both cultivars, whereas spermine (Spm) was occasionally detected. “Arbequina” as well as “Kalamata” exhibited the highest free Put and free Spd in summer and Put was the predominant PA among the free PAs. “Arbequina” exhibited the highest individual and total PAs in spring, followed by those in summer and autumn. In contrast, “Kalamata” had the maximum PAs in summer and the lowest in autumn. Changes in the endogenous content of individual and total PAs during the EPR were also observed. Treatment of “Kalamata” cuttings in autumn with both indole-3-butyric acid (IBA) and Put increased rooting compared to IBA alone. Among the PAs administered, Put was the most effective, whereas Spd and Spm failed to promote rooting. PAs, especially in their free form, seem to be involved in the rooting process of olive cuttings; Put application enhanced the rooting response of the difficult-to-root “Kalamata” olive cultivar.     

Cobalt-chelated magnetic particles for one-step purification and immobilization of His6-tagged Escherichia coli γ-glutamyltranspeptidase

Cobalt-chelated magnetic (Fe₃O₄-AA-ANTA-Co^{2 +}) particles were prepared and one-step purification and immobilization of His₆-tagged Escherichia coli γ-glutamyltranspeptidase (His₆-EcGGT) using these particles were evaluated. The optimal conditions for the adsorption of His₆-EcGGT to Fe₃O₄-AA-ANTA-Co^{2 +} particles were found to be 24.7 U g^–1 adsorbent, pH 6.5, 300 mM NaCl and 30 min incubation at 4°C, while the elution solution was optimized to be 50 mM phosphate buffer (pH 6.5) containing 150 mM imidazole and 300 mM NaCl. The immobilized His₆-EcGGT was recycled five times without significant loss of GGT activity. The average yield rate for the synthesis l-theanine from glutamine and ethylamine reached 56.7%. These results indicate that one-step affinity purification and immobilization of His₆-EcGGT by Fe₃O₄-AA-ANTA-Co^{2 +} particles might serve as an effective process for industrial application.     

Binding of doxorubicin to cardiolipin as compared to other anionic phospholipids—An evaluation of electrostatic effects

The binding of doxorubicin to large unilamellar vesicles consisting of cardiolipin or other anionic phospholipids was analyzed in terms of the local drug concentration at the membrane surface, according to the Gouy-Chapman theory. The analysis suggests strong positive binding cooperativity. Part of the drug binds in the uncharged form. The affinity for cardiolipin and other anionic phospholipids is comparable. A binding level of 0.5 doxorubicin per lipid-phosphorus is reached when the local concentration of free doxorubicin monomer-equivalents at the membrane surface is about 0.2–0.7 mM. This contrasts with earlier findings indicating a 300–1000 fold higher affinity for cardiolipin. The present analysis provides an explanation for this apparent discrepancy.     

Application of Animal Modeling to Biodefense Research

The use of biological agents to attack enemies has substantial historical precedent,and includes documented attempts tocontaminate the wells andreservoirs of enemies withcadavers and animal carcasses;and attemptstoinfect Native Ameri-cans with smallpox via contaminated blankets offered as gifts.Awareness and concern over biological weapons has in-creased greatly as the technological sophistication required to produce related agents has become more global.That theuse of biological agents as a m…