The participation of crown ethers in the initiation of group-transfer polymerisation

Summary The use of crown ethers in conjunction with alkali metal salts, as catalysts in group-transfer polymerization, is discussed.     

Validation of MERIS LAI and FAPAR products for winter wheat-sown test fields in North-East Bulgaria

Progress in deriving land surface biophysical parameters in a spatially explicit manner using remotely sensed data has greatly enhanced our ability to model ecosystem processes and monitor crop development. A multitude of satellite sensors and algorithms have been used to generate ready-to-use maps of various biophysical parameters. Validation of these products for different vegetation types is needed to assess their reliability and consistency. While most of the current satellite biophysical products have spatial resolution of one kilometre, a recent effort utilizing data from the Medium Resolution Imaging Spectrometer (MERIS) provided leaf area index (LAI), Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), and other canopy parameters in a resolution as fine as 300 m over the European continent. This resolution would be more appropriate for application at the regional scale, particularly for crop monitoring. This higher-resolution MERIS product has been evaluated in a limited number of studies to date. This article aims to validate LAI and FAPAR from the MERIS 10-day composite BioPar BP-10 product over winter wheat fields in northeast Bulgaria. The ground measurements of LAI and FAPAR were up-scaled and 30 m resolution reference raster layers were created using empirical relationships with Landsat TM (RMSE = 0.06 and RMSE = 0.22 for FAPAR and LAI, respectively). MERIS FAPAR and LAI were found to have significant correlation with FAPAR and LAI from the reference raster layers (R² = 0.84 and R² = 0.78, respectively). When MERIS Green LAI was calculated (incorporating the fraction of vegetation and brown vegetation cover from the BioPar BP-10 product), better correspondence with LAI values from the reference raster layer was achieved, with RMSE and bias reduced by 30–35%. The results from this study confirm the findings of previous validations showing that MERIS Green LAI tends to overestimate LAI values lower than 1. As a conclusion of the study, the BioPar BP-10 product was found to provide reliable estimates of FAPAR and acceptably accurate estimates of LAI for winter wheat crops in North-East Bulgaria.     

Nanostructured biofilms and biocrystals

The design, the physical properties and the implementation of nanostructured protein biofilms and nanostructured biocrystals are here summarized from ab initio considerations. Particular emphasis is placed on those being developed in our Institute having unique properties useful in a wide range of applications.     

Highly-ordered supportless three-dimensional nanowire networks with tunable complexity and interwire connectivity for device integration

The fabrication of three-dimensional assemblies consisting of large quantities of nanowires is of great technological importance for various applications including (electro-)catalysis, sensitive sensing, and improvement of electronic devices. Because the spatial distribution of the nanostructured material can strongly influence the properties, architectural design is required in order to use assembled nanowires to their full potential. In addition, special effort has to be dedicated to the development of efficient methods that allow precise control over structural parameters of the nanoscale building blocks as a means of tuning their characteristics. This paper reports the direct synthesis of highly ordered large-area nanowire networks by a method based on hard templates using electrodeposition within nanochannels of ion track-etched polymer membranes. Control over the complexity of the networks and the dimensions of the integrated nanostructures are achieved by a modified template fabrication. The networks possess high surface area and excellent transport properties, turning them into a promising electrocatalyst material as demonstrated by cyclic voltammetry studies on platinum nanowire networks catalyzing methanol oxidation. Our method opens up a new general route for interconnecting nanowires to stable macroscopic network structures of very high integration level that allow easy handling of nanowires while maintaining their connectivity.     

DRP1 Inhibition Rescues Mitochondrial Integrity and Excessive Apoptosis in CS-A Disease Cell Models

Cockayne syndrome group A (CS-A) is a rare recessive progeroid disorder characterized by sun sensitivity and neurodevelopmental abnormalities. Cells derived from CS-A patients present as pathological hallmarks excessive oxidative stress, mitochondrial fragmentation and apoptosis associated with hyperactivation of the mitochondrial fission dynamin related protein 1 (DRP1). In this study, by using human cell models we further investigated the interplay between DRP1 and CSA and we determined whether pharmacological or genetic inhibition of DRP1 affects disease progression. Both reactive oxygen and nitrogen species are in excess in CS-A cells and when the mitochondrial translocation of DRP1 is inhibited a reduction of these species is observed together with a recovery of mitochondrial integrity and a significant decrease of apoptosis. This study indicates that the CSA-driven modulation of DRP1 pathway is key to control mitochondrial homeostasis and apoptosis and suggests DRP1 as a potential target in the treatment of CS patients.     

Effect of Sample Solubilized Aliquot Volume and Concentration on Hydroperoxide Detection in PUFA-Rich Fish Oil

The objective of this work was to study the effect of sample oil concentration and volume on hydroperoxide determination in n-3 PUFA-rich sardine-anchovy oil. Oil samples were stored at??20°C, 6 d, air-free (T1); and 20°C, 2 d in air (T2). Significant differences between storage conditions were observed on hydroperoxide concentration. High reproducibility was obtained even in sample concentrations as low as 5 mg oil/mL of propan-1-ol. A high correlation was observed between the modified ferrous oxidation-xylenol orange method (FOX2) and AOAC peroxide value analysis methods, although FOX2 was faster, more sensitive, and precise when analyzing small hydroperoxide concentrations.     

Atomic force microscopy of protein films and crystals

A customized atomic force microscopy (AFM) instrument optimized for imaging protein crystals in solution is described. The device was tested on crystals and Langmuir-Blodgett (LB) films of two proteins with quite different molecular weights. This approach enables the periodicity and morphology of crystals to be studied in their mother liquid, thereby preserving the native periodic protein crystal structure, which is typically destroyed by drying. Moreover, the instrument appears to distinguish protein crystals from salt crystals, which under the optical microscope are frequently quite similar, the difference between them often being revealed only during x-ray analysis. AFM estimates of the packing, order, and morphology of the given single proteins appear quite similar in the LB thin film and in the crystals, which means that routine crystal measurements can be performed at high resolution. The AFM consists of a custom-built measuring head and a homemade flexible SPM controller which can drive the head for contact, noncontact and spectroscopy modes, thus providing the user with a high degree of customization for crystal measurement.     

Concentrations and patterns of organochlorine pesticides and PCBs in Mediterranean monk seals (Monachus monachus) from Western Sahara and Greece

Blubber from Mediterranean monk seals (Monachus monachus) from the Western Sahara coast (Atlantic), sampled during 1996-1999, and from the Greek coast (Mediterranean), sampled during 1995-1999, was analyzed for organochlorine pollutants (OCs). In both populations, no significant difference was found between sexes. In the Atlantic population, mature females presented greater percentages of higher chlorinated PCB (polychlorinated biphenyl) congeners in relation to total PCBs (sum of 25 congeners) than pups, indicating a differential transfer of PCB congeners through lactation. In the Mediterranean, the reduced sample size of adult individuals precluded proper statistical investigation of age-related variation. Significant differences in concentrations and pollutant patterns were found between populations. Thus, Mediterranean individuals presented significantly higher levels of HCB (hexachlorobenzene), tPCB, and DDTs (dichlorodiphenyltrichloroethane) concentrations and DDE/tDDT and tDDT/tPCB ratios than their counterparts from the Atlantic. Moreover, the relative proportion of different congeners in relation to the total PCB load (congener/tPCB) was also different between the two areas. The 100*tDDT/tPCB ratio in Atlantic seals was 38.46, which indicates a predominance of industrial inputs over those associated with agriculture. Conversely, in the Mediterranean seal population, the 100*tDDT/tPCB ratio was 177.1, denoting a proportionally higher contribution of pollutants of agricultural origin.