Visualizing intramolecular distortions as the origin of transverse magnetic anisotropy

The magnetic properties of metal–organic complexes are strongly influenced by conformational changes in the ligand. The flexibility of Fe-tetra-pyridyl-porphyrin molecules leads to different adsorption configurations on a Au(111) surface. By combining low-temperature scanning tunneling spectroscopy and atomic force microscopy, we resolve a correlation of the molecular configuration with different spin states and magnitudes of magnetic anisotropy. When the macrocycle exhibits a laterally undistorted saddle shape, the molecules lie in a S = 1 state with axial anisotropy arising from a square-planar ligand field. If the symmetry in the molecular ligand field is reduced by a lateral distortion of the molecule, we find a finite contribution of transverse anisotropy. Some of the distorted molecules lie in a S = 2 state, again exhibiting substantial transverse anisotropy

Electronic structure of an iron porphyrin derivative on Au(1 1 1)

Surface-bound porphyrins are promising candidates for molecular switches, electronics and spintronics. Here, we studied the structural and the electronic properties of Fe-tetra-pyridil-porphyrin adsorbed on Au(1 1 1) in the monolayer regime. We combined scanning tunneling microscopy/spectroscopy, ultraviolet photoemission, and two-photon photoemission to determine the energy levels of the frontier molecular orbitals. We also resolved an excitonic state with a binding energy of 420 meV, which allowed us to compare the electronic transport gap with the optical gap

Characterization of microsatellite loci in Leucorrhinia caudalis , a rare dragonfly endangered throughout Europe

Leucorrhinia caudalis is a rare dragonfly, threatened throughout Europe. It only survived in a single population in Switzerland in the 1980s. However, it recently spread and colonized new ponds. In order to be able to study contemporary migration in this species, eight new microsatellite markers were developed and tested on 24 individuals from six Swiss ponds. We detected three to eleven alleles per polymorphic locus and found observed and expected heterozygosities of 0.250 to 0.875 and 0.215 to 0.840, respectivel

Cost-Effective, Species-Specific Microsatellite Development for the Endangered Dwarf Bulrush (Typha minima) Using Next-Generation Sequencing Technology

The dwarf bulrush (Typha minima Funck ex Hoppe) is an endangered pioneer plant species of riparian flood plains. In Switzerland, only 3 natural populations remain, but reintroductions are planned. To identify suitable source populations for reintroductions, we developed 17 polymorphic microsatellite markers with perfect repeats using the 454 pyrosequencing technique and tested them on 20 individuals with low-cost M13 labeling. We detected 2 to 7 alleles per locus and found expected and observed heterozygosities of 0.05-0.76 and 0.07-1, respectively. The whole process was finished in less than 6 weeks and cost approximately USD 5000. Due to low costs and reduced expenditure of time, the use of next-generation sequencing techniques for microsatellite development represent a powerful tool for population genetic studies in nonmodel species, as we show in this first application of the approach to a plant species of conservation importanc

Development of microsatellite markers for the wetland grasshopper Stethophyma grossum

Stethophyma grossum is a threatened Eurosiberian grasshopper species. Since it is bound to wetlands, S. grossum is often used as indicator for extensive wet meadows. To study its movement capability and dispersal habitat in landscape genetic analyses, we developed ten polymorphic microsatellite markers, making use of next generation sequencing. Markers were tested on 75 individuals collected in five populations from Switzerland. We found four to 18 alleles per locus. Observed and expected heterozygosities varied between 0.215-0.893 and 0.397-0.831, respectively. One marker seems to be sex-chromosome X-linked and one showed high null allele frequencies, a phenomenon generally detected in microsatellite studies on grasshopper

Monitoring von Populationen der Helm-Azurjungfer Coenagrion mercuriale (Odonata: Coenagrionidae) : was taugen zwei Begehungen pro Saison?

Schutzmassnahmen für bedrohte Kleinlibellenarten werden für die Erfolgskontrolle oft von einem minimalen Monitoring mit zwei Begehungen pro Jahr begleitet. Dabei wird die Anzahl Imagines erfasst. Wir haben untersucht, ob ein solches Minimalmonitoring eine vertrauenswürdige Schätzung der Bestandesgrössen erlaubt. Dazu wurden zwei Datensätze, die im Jahr 2009 in denselben Populationen der Helm-Azurjungfer Coenagrion mercuriale erhoben wurden, miteinander verglichen. Der eine Datensatz umfasste ein Minimalmonitoring mit zwei Begehungen pro Jahr. Für den anderen Datensatz wurde während der Fortpflanzungsperiode jeder Tag mit guten Wetterbedingungen für Erhebungen genutzt, um so eine verlässliche Schätzung der Populationsgrössen zu erhalten. Die statistische Auswertung zeigte eine gute Übereinstimmung der beiden Methoden. Daraus folgern wir, dass auch mit einem Minimalmonitoring von zwei Begehungen pro Jahr Bestandesgrössen adäquat geschätzt werden können – ein Ergebnis, das wahrscheinlich auch auf andere Kleinlibellenarten übertragbar ist

Correlation of vibrational excitations and electronic structure with submolecular resolution

The detection of vibrational excitations of individual molecules on surfaces by scanning tunneling spectroscopy does not obey strict selection rules but rather propensity rules. The experimental verification of these excitations is challenging because it requires the independent variation of specific parameters, such as the electronic structure, while keeping the vibrational modes the same. Here, we make use of the versatile self-assembled structures of Fe-tetra-pyridyl-porphyrin molecules on a Au(111) surface. These molecules exhibit different energy-level alignments of the frontier molecular orbitals, thus allowing the correlation of the electronic structure and detection of vibrations. We identify up to seven vibrational modes in the tunneling spectra of the molecules in some of the arrangements, whereas we observe none in other structures. We find that the presence of vibrational excitations and their distribution along the molecule correlate with the observation of energetically low-lying molecular states. This correlation allows the explanation of the different numbers of vibrational signatures for molecules embedded within different structures as well as the bias asymmetry of the vibrational intensities within an individual molecule. Our observations are in agreement with the resonant enhancement of vibrations by the virtual excitation of electronic states

Microsatellites reveal substantial among-population genetic differentiation and strong inbreeding in the relict fern Dryopteris aemula

Background and Aims A previous study detected no allozyme diversity in Iberian populations of the buckler-fern Dryopteris aemula. The use of a more sensitive marker, such as microsatellites, was thus needed to reveal the genetic diversity, breeding system and spatial genetic structure of this species in natural populations. Methods Eight microsatellite loci for D. aemula were developed and their cross-amplification with other ferns was tested. Five polymorphic loci were used to characterize the amount and distribution of genetic diversity of D. aemula in three populations from the Iberian Peninsula and one population from the Azores. Key Results Most microsatellite markers developed were transferable to taxa close to D. aemula. Overall genetic variation was low (HT = 0·447), but was higher in the Azorean population than in the Iberian populations of this species. Among-population genetic differentiation was high (FST = 0·520). All loci strongly departed from Hardy-Weinberg equilibrium. In the population where genetic structure was studied, no spatial autocorrelation was found in any distance class. Conclusions The higher genetic diversity observed in the Azorean population studied suggested a possible refugium in this region from which mainland Europe has been recolonized after the Pleistocene glaciations. High among-population genetic differentiation indicated restricted gene flow (i.e. lack of spore exchange) across the highly fragmented area occupied by D. aemula. The deviations from Hardy-Weinberg equilibrium reflected strong inbreeding in D. aemula, a trait rarely observed in homosporous ferns. The absence of spatial genetic structure indicated effective spore dispersal over short distances. Additionally, the cross-amplification of some D. aemula microsatellites makes them suitable for use in other Dryopteris tax