Water-soluble titanocene complexes with sulfur-containing aminoacids: synthesis, spectroscopic, electrochemical and Ti(IV)–transferrin interaction studies

Three new water soluble titanocene–aminoacid complexes have been synthesized via the reaction of Cp₂TiCl₂ and two equivalents of aminoacid (L) in methanol, affording [Cp₂TiL₂]Cl₂, L=L-cysteine (2), D-penicillamine (3) and L-methionine (4). These complexes have been characterized by ¹H, IR and UV-Vis spectroscopies, elemental analysis and cyclic voltammetry. Kinetic studies of ligand hydrolysis have been monitored at low pH using UV-Vis and ¹H NMR spectroscopies to assess their stability in aqueous solution. At low pH, aminoacid ligands are lost one order of magnitude faster than cyclopentadienyl. However, at physiological pH, in Tris buffer solution, the complexes decompose rapidly to form an insoluble titanium compound. The affinity of these complexes to apo-transferrin was also investigated to elucidate how the ancillary aminoacid ligands affect the titanium intake by apo-transferrin.Electronic Supplementary Material Supplementary material is available for this article at     

Ab initio model studies of copper binding to peptides containing a His–His sequence: relevance to the β-amyloid peptide of Alzheimer’s disease

Two of the defining hallmarks of Alzheimer’s disease (AD) are deposits of the β-amyloid peptide, Aβ, and the generation of reactive oxygen species, both of which may be due to the Aβ peptide coordinating metal ions. The Cu²⁺ concentrations in cores of senile plaques are significantly elevated in AD patients. Experimental results indicate that Aβ1–42 in particular has a very high affinity for Cu²⁺, and that His13 and His14 are the two most firmly established ligands in the coordination sphere of the copper ion. Quantum chemical calculations using the unrestricted B3LYP hybrid density functional method with the 6–31G(d) basis set were performed for geometries, zero point energies and thermochemistry. The effects of solvation were accommodated using the CPCM method. The enthalpies were calculated with the 6–311+G(2df,2p) basis set. Calculations show that when Cu(H₂O)₄²⁺ combines with the model compound 1 (3-(1H-imidazol-5-yl)-N-[2-(1H-imidazol-5-yl)ethyl] propanamide) in the aqueous phase, the most stable binding site involves the Nπ atoms of His13 and His14 as well as the carbonyl of the intervening backbone amide group. These structures are fairly rigid and the implications for conformational changes to the Aβ backbone are discussed. In solution at pH=7, Cu²⁺ promotes the deprotonation and involvement in the binding of the backbone amide nitrogen in a β-sheet like structure. This geometry does not induce strain in the peptide backbone, making it the most likely representation of that portion of the Cu²⁺–Aβ complex monomer in aqueous solution.     

Photosynthesis and carbon metabolism in plantain (Musa AAB) plantlets growing in temporary immersion bioreactors and during ex vitro acclimatization

Summary The photosynthetic capacity changes and the main enzymatic systems related to carbon metabolism were investigated during the in vitro culture of plantain shoots (Musa AAB cv. CEMSA 3/4) in temporary immersion bioreactors (TIB) and their subsequent acclimatization. The maximal rate of photosynthesis (Pn), transpiration, and the activity of the carbon metabolism enzymes phosphoenolpyruvate carboxylase (PEPC), acid invertase (AI), pyruvate kinase (PK) and sucrose phosphate synthase (SPS) were measured every 7 d during the 21 d of elongation in TIB, and the following 42 d of acclimatization. Sucrose content in the liquid medium and in the leaves was also determined. The most significant changes in plant growth were observed during acclimatization. During the in vitro stage photosynthesis was limited (4–6 μmol CO₂m⁻²s⁻¹); the photosynthetic rate however increases rapidly and significantly as soon as in vitro culture is over during acclimatization. PEPC activity increased during the whole evaluation period. The highest levels were achieved around days 42 and 56. PK and SPS activities were optimal during the first weeks in acclimatization (28–35 d), while AI increased at the beginning of the elongation phase (7 d), and later at the end of the acclimatization (49–63 d). The relationships between morphological parameters, photosynthetic capacity of the plantlets and the carbon metabolism enzymes during both phases of the culture are discussed.     

Controversies on the origin of life.

Different viewpoints, many with deep philosophical and historical roots, have shaped the scientific study of the origin of life. Some of these argue that primeval life was based on simple anaerobic microorganisms able to use a wide inventory of abiotic organic materials (i.e. a heterotrophic origin), whereas others invoke a more sophisticated organization, one that thrived on simple inorganic molecules (i.e. an autotrophic origin). While many scientists assume that life started as a self-replicative molecule, the first gene, a primitive self-catalytic metabolic network has also been proposed as a starting point. Even the emergence of the cell itself is a contentious issue: did boundaries and compartments appear early or late during life's origin? Starting with a recent definition of life, based on concepts of autonomy and open-ended evolution, it is proposed here that, firstly, organic molecules self-organized in a primordial metabolism located inside protocells. The flow of matter and energy across those early molecular systems allowed the generation of more ordered states, forming the cradle of the first genetic records. Thus, the origin of life was a process initiated within ecologically interconnected autonomous compartments that evolved into cells with hereditary and true Darwinian evolutionary capabilities. In other words, the individual existence of life preceded its historical-collective dimension.     

Herbivore arthropods benefit from vectoring plant viruses

Plants infected with pathogens often attract the pathogens’ vectors, but it is not clear if this is advantageous to the vectors. We therefore quantified the direct and indirect (through the host plant) effects of a pathogen on its vector. A positive direct effect of the plant‐pathogenic Tomato spotted wilt virus on its thrips vector (Frankliniella occidentalis) was found, but the main effect was indirect; juvenile survival and developmental rate of thrips was lower on pepper plants that were damaged by virus‐free thrips than on unattacked plants, but such negative effects were absent on plants that were damaged and inoculated by infected thrips or were mechanically inoculated with the virus. Hence, potential vectors benefit from attacking plants with virus because virus‐infected plants are of higher quality for the vector's offspring. We propose that plant pathogens in general have evolved mechanisms to overcome plant defences against their vectors, thus promoting pathogen spread.     

High concentrations of d-pinitol or d-chiro-inositol inhibit the biosynthesis of raffinose family oligosaccharides in maturing smooth tare (Vicia tetrasperma [L.] Schreb.) seeds

In the present study we have investigated the effect of exogenous cyclitols on accumulation of their galactosides and raffinose family oligosaccharides (RFOs) in maturing smooth tare (Vicia tetrasperma [L.] Schreb) seeds. Feeding d-pinitol to pods of smooth tare increased the amount of free d-pinitol and its galactosides: galactopinitol A, galactopinitol B, di- and trigalactopinitol A in seeds. Similarly, feeding d-chiro-inositol, which does not occur naturally in Vicia seeds, resulted in the transport of this cyclitol in the seed, and caused accumulation of high levels of d-chiro-inositol galactosides (fagopyritol B1, B2 and B3). Accumulation of both cyclitols and their galactosides drastically reduced accumulation of verbascose and, to a lesser extent, stachyose and di-galactosyl- myo-inositol. Feeding d-chiro-inositol also decreased accumulation of di- and tri-galactosyl pinitols, naturally occurring in seeds. Inhibition of RFOs accumulation by elevated levels of free cyclitols indicates competition between biosynthesis of both types galactosides, and similarity of both biosynthetic pathways in smooth tare seeds.     

Microbial encrustations from the Middle Oxfordian-earliest Kimmeridgian lithofacies in the Prebetic Zone (Betic Cordillera, southern Spain): characterization, distribution and controlling factors

Two main types of microbial encrustation were identified in Middle Oxfordian to lowermost Kimmeridgian deposits in the Prebetic Zone (southern Spain), showing existing relationships between skeletal content, fabric and morphology of these organosedimentary structures. Laminated planar and concentric encrustations relate to peloidal fabrics (mainly constituted of microbes = microbial laminated fabrics s. str. and microbial oncoids s. str.), as well as to dense microbial fabrics periodically colonized by encrusting foraminifera (microbial laminated fabrics with nubeculariids and microbial oncoids with nubeculariids). Sedimentation rates, substrate stability and grain size, as well as illumination, influenced microbial growth pattern as major controlling factors in low-energy conditions, and forced palaeogeographic and stratigraphic patterns of distribution. Significant encrustation was identified in terrigenous-poor lithofacies from the middle (Transversarium-Bifurcatus zones) to the outer (Transversarium-Bimammatum zones) shelf in the Prebetic Zone. Rare-to-absent encrustation characterized terrigenous-rich deposits (Bimammatum and Planula zones) in the area.     

Historical Ecology on Sandoy, Faroe Islands: Palaeoenvironmental and Archaeological Perspectives

We present palaeoenvironmental, geomorphological, archaeological, and place-name data which allow a holistic assessment of the history of landscape change on Sandoy, Faroe Islands, especially in terms of the changes that occurred in response to the colonization of the island by humans. In contrast to other situations in the North Atlantic region, there is considerable continuity in the patterns and processes of landscape evolution across the initial settlement horizon. Many of the characteristic features of post-settlement North Atlantic landscapes—absence of trees, widespread blanket mires, high rates of soil erosion—were already in place when the first people arrived. Although human impact on Sandoy appears to have been light, conversely, the unusual environment forced major alterations of the subsistence economy imported by the colonists. Settlement-era archaeological records suggest that, from the start, patterns of resource use differed substantially from the regional norm, and these differences became amplified over time as the Faroese economy created a locally sustainable cultural landscape.