Age-related differences in foraging behavior of Montagu's harrier<Emphasis Type="Italic"> Circus pygargus</Emphasis> males in south-east Poland

The hunting behaviour and habitat use of second-calendar-year males (subadult) and grey (adult) males of Montagu's harrier Circus pygargus were compared in south-east Poland. Subadult males performed cruising flights less frequently than did adult males. In contrast, subadult males more frequently soared thermals and were harassed more often by other birds. Overall, adult males were more frequently engaged in hunting activities than subadult males. Additionally, adult males were more successful in trapping prey than were subadult males. Only 7% (n=92) of trapping attempts by subadult males were successful, compared with 17% (n=126) by grey males. Both adult and subadult males tried to catch prey flushed by foxes Vulpes vulpes. Subadult males were seen begging and pirating from prey-carrying raptors. Communicated by M.E. dos Santos     

To the problem of biologically active conformation of enkephalin

Summary A semi-rigid structural analog of [Leu⁵] enkephalin, possessing the azo-bridge between Tyr¹ and Phe⁴ residues, was synthesized, along with two other linear enkephalin analogs: [4′-amino Phe⁴] enkephalin and [4′hydroxyphenyl/-azo Phe⁴] enkephalin. The results of the determination of the analgesic activity of the synthesized compounds suggest that the biologically active conformation of the enkephalin molecule should be such that both aromatic rings, Tyr¹ and Phe⁴, are situated in close proximity.     

On the taste of stereoisomeric cyclic dipeptides containing a proline residue

An investigation of the taste character and intensity of sixproline-containing cylic dipeptides demonstrates that thesecompounds are differentiated largley on the basis of their chemicalconfiguration. ^x/ Permanent address: Technical University, 80–952 Gdask,Poland     

Voltammetry as a virtual potentiometric sensor in modelling of a metal-ligand system and refinement of stability constants. Part 4. An electrochemical study of NiII complexes with methylene diphosphonic acid

The Ni(II)-MDP-OH system (MDP=methylene diphosphonic acid) and stability constants of complexes formed at ionic strength 0.15M at 298K were established by direct current polarography (DCP) and glass electrode potentiometry (GEP). The final M-L-OH model could only be arrived to by employing recent concept of virtual potentiometry (VP). VP-data were generated from non-equilibrium and dynamic DC polarographic technique. The VP and GEP data were refined simultaneously by software dedicated to potentiometric studies of metal complexes. Species distribution diagrams that were generated for different experimental conditions employed in this work assisted in making the final choice regarding the metal-ligand model. The model established contains ML, ML(2), ML(OH) and ML(OH)(2) with stability constants, as logbeta, 7.94+/-0.02, 13.75+/-0.02, 12.04 (fixed value), and 16.75+/-0.05, respectively. It has been demonstrated that virtual potential must be used in modelling operations (predictions of species formed) when a polarographic signal decreases significantly due to the formation of polarographically inactive species (or formation of inert complexes). The linear free energy relationships that included stability constant logK(1) for Ni(II)-MDP established in this work together with other available data were used to predict logK(1) values for Sm(III) and Ho(III) with MDP. The logK(1) values for Sm(III)-MDP and Ho(III)-MDP were estimated to be 9.65+/-0.10 and 9.85+/-0.10, respectively.     

Directional surface plasmon-coupled emission from a 3 nm green fluorescent protein monolayer

High-sensitivity detection schemes are of great interest for a number of applications. Unfortunately, such schemes are usually high-cost. We demonstrate a low-cost approach to a high-sensitivity detection scheme based on surface plasmon-coupled emission (SPCE). The SPCE of a monomolecular layer of green fluorescent protein (GFP) is reported here. The protein was electrostatically attached to a thin, SiO(2)-protected silver film deposited on a quartz substrate. The visible, directional emission of GFP was observed at a sharp, well-defined angle of 47.5 degrees from the normal to the coupling prism, and the spectrum corresponded to that of GFP. The SPCE resulting from the reverse Kretschmann configuration showed a 12-fold enhancement over the free space fluorescence. The directional emission was 97% p-polarized. The directionality and high polarization can be coupled with the intrinsic spectral resolution of SPCE to be used in the design miniaturized spectrofluorometers. The observation of SPCE in the visible region of the spectrum from a monolayer of protein opens up new possibilities in protein-based sensing.     

On the peptide-antipeptide interactions in interleukin-1 receptor system

Interleukin-1 receptor antagonist (IL-1Ra) and vaccinia virus protein C10L share a VTXFYF motif, with X being Lys or Arg residue, respectively. Peptides of such sequence compete successfully with IL-1 for the cellular receptor. A pair of complementary peptides, based on the Siemion's hypothesis on the periodicity of the genetic code (QWLNIN and QWANIN), and another pair, in which, following the Root- Bernstein theory, Lys was used as complementary amino acid to Phe (QWLKIK and QWAKIK), were investigated for the peptide-antipeptide interactions using mass spectrometry (ESI-MS) and circular dichroism (CD) methods. The CD measurements indicated some conformational changes, more pronounced in the Siemion's pairs, however, no heterodimer formation was found by MS. In the region of IL-1 receptor situated close to the position of IL-1Ra in the IL-1Ra-receptor complex, a KQKL motif is present, suggesting a possibility of complementary recognition of the Root-Bernstein type in the IL-1 receptor. The biological activity of the complementary peptides is similar to that of the original ones. They efficiently compete with IL-1 and show moderate immunosuppressory activity in humoral and cellular immune response. The inhibition of the IL-1-IL-1 receptor interaction may result from the complementary peptides acting as mini-receptors with affinity for IL-1.     

Radiative decay engineering 4. Experimental studies of surface plasmon-coupled directional emission

Fluorescence is typically isotropic in space and collected with low efficiency. In this paper we describe surface plasmon-coupled emission (SPCE), which displays unique optical properties and can be collected with an efficiency near 50%. SPCE occurs for fluorophores within about 200 nm of a thin metallic film, in our case a 50-nm-thick silver film on a glass substrate. We show that fluorophore proximity to this film converts the normally isotropic emission into highly directional emission through the glass substrate at a well-defined angle from the normal axis. Depending on the thickness of the polyvinyl alcohol (PVA) film on the silver, the coupling efficiency of sulforhodamine 101 in PVA ranged from 30 to 49%. Directional SPCE was observed whether the fluorophore was excited directly or by the evanescent field due to the surface plasmon resonance. The emission is always polarized perpendicular to the plane of incidence, irrespective of the polarization of the incident light. The lifetimes are not substantially changed, indicating a mechanism somewhat different from that observed previously for the effects of silver particles on fluorophores. Remarkably, the directional emission shows intrinsic spectral resolution because the coupling angles depend on wavelength. The distances over which SPCE occurs, 10 to 200 nm, are useful because a large number of fluorophores can be localized within this volume. The emission of more distant fluorophores does not couple into the glass, allowing background suppression from biological samples. SPCE can be expected to become rapidly useful in a variety of analytical and medical sensing applications.     

Bioactive peptides: Conformational studies of [TYR4] cyclolinopeptide A

The solid state conformational analysis of [Tyr⁴] cyclolinopeptide A has been carried out by x-ray diffraction studies. The crystal structure of the monoclinic form, grown from a dioxane-water mixture [a = 9.849 (5) Å, b = 20.752 (4) Å, c = 16.728 (5) Å, β = 98.83 (3)°, space group P2₁, Z = 2], shows the presence of five intramolecular N-H? O?C hydrogen bonds, with formation of one C₁₇ ring structure, one α-turn (C₁₃), one inverse γ-turn (C₇), and two β-turns (C₁₀, one of type III and one of type 1). The Pro¹-Pro² peptide unit is cis (ω = 5°) all others are trans. The structure is almost superimposable with that of cyclolinopeptide A. The rms deviation for the atoms of the backbones is on the average 0.33 Å. © 1995 John Wiley & Sons, Inc.     

Quality Control of Genotypes Using Heritability Estimates of Gene Content at the Marker

Quality control filtering of single-nucleotide polymorphisms (SNPs) is a key step when analyzing genomic data. Here we present a practical method to identify low-quality SNPs, meaning markers whose genotypes are wrongly assigned for a large proportion of individuals, by estimating the heritability of gene content at each marker, where gene content is the number of copies of a particular reference allele in a genotype of an animal (0, 1, or 2). If there is no mutation at the marker, gene content has an additive heritability of 1 by construction. The method uses restricted maximum likelihood (REML) to estimate heritability of gene content at each SNP and also builds a likelihood-ratio test statistic to test for zero error variance in genotyping. As a by-product, estimates of the allele frequencies of markers at the base population are obtained. Using simulated data with 10% permutation error (4% actual error) in genotyping, the method had a specificity of 0.96 (4% of correct markers are rejected) and a sensitivity of 0.99 (1% of wrong markers are accepted) if markers with heritability lower than 0.975 are discarded. Checking of Mendelian errors resulted in a lower sensitivity (0.84) for the same simulation. The proposed method is further illustrated with a real data set with genotypes from 3534 animals genotyped for 50,433 markers from the Illumina PorcineSNP60 chip and a pedigree of 6473 individuals; those markers underwent very little quality control. A total of 4099 markers with P-values lower than 0.01 were discarded based on our method, with associated estimates of heritability as low as 0.12. Contrary to other techniques, our method uses all information in the population simultaneously, can be used in any population with markers and pedigree recordings, and is simple to implement using standard software for REML estimation. Scripts for its use are provided.