Structural investigation of supported Cun clusters under vacuum and ambient air conditions using EXAFS spectroscopy

Structural analysis of deposited nanoclusters using extended X-ray absorption fine structure (EXAFS) spectroscopy.

Size-dependent Auger spectra and two-hole Coulomb interaction of small supported Cu-clusters

Auger (L3M4,5M4,5) and X-ray photoionization spectra (2p, 3d) of mass-selected CuN-clusters supported by a thin natural silica layer are presented in the size range N = 8-55 atoms per cluster. The Auger spectra of all clusters are shifted to a lower kinetic energy with respect to the spectrum of the bulk. Furthermore the Auger energy decreases systematically with decreasing cluster size. The binding energies of the 2p and 3d valence states are higher than the corresponding bulk values. Using the energy of the Auger main line, the corresponding core hole peak and the centroid of the self-convoluted 3d valence band the on-site Coulomb interaction energy Udd of the two-hole final state as a function of cluster size has been determined.

Spin and orbital magnetic moments of free nanoparticles

The determination of spin and orbital magnetic moments from the free atom to the bulk phase is an intriguing challenge for nanoscience, in particular, since most magnetic recording materials are based on nanostructures. We present temperature-dependent x-ray magnetic circular dichroism measurements of free Co clusters (N=8-22) from which the intrinsic spin and orbital magnetic moments of noninteracting magnetic nanoparticles have been deduced. An exceptionally strong enhancement of the orbital moment is verified for free magnetic clusters which is 4-6 times larger than the bulk value. Our temperature-dependent measurements reveal that the spin orientation along the external magnetic field is nearly saturated at ~20 K and 7 T, while the orbital orientation is clearly not.

Inner-shell photoionization spectroscopy on deposited metal clusters using soft x-ray synchrotron radiation: an experimental setup

Exploration of mass-selected clusters by soft x-ray synchrotron radiation is well suited to receive element specific information on clusters in contact with a support and to systematically follow the evolution of size-dependent electronic and geometrical properties from the smallest clusters toward the bulk. Here we describe an experimental setup, which combines cluster synthesis, mass selection, soft landing, ultrahigh vacuum transfer, and photoionization experiments such as x-ray photoelectron spectroscopy, x-ray absorption, and Auger electron spectroscopy. First spectroscopic results and experimental conditions are briefly discussed for Cu(19) deposited onto the natural oxide layer of a Si-wafer surface.

Core-hole screening as a probe for a metal-to-nonmetal transition in lead clusters

Metal clusters serve as model systems to study basic problems of electronic correlation. Vacuum ultraviolet light from the free-electron laser FLASH ionizes 5d electrons from mass-separated negatively charged clusters, thus transiently leading to core-ionized neutral systems. Shielding of the core hole affects the electron binding energy. From the strong deviation from expectations of the metallic droplet and jellium models we conclude on reduced electronic shielding once the cluster size falls below about 20 atoms. This suggests a metal-to-nonmetal transition, in agreement with previous local density approximation calculations.

Spatio-temporal coherence of free electron laser pulses in the soft x-ray regime

The temporal coherence properties of soft x-ray free electron laser pulses at FLASH are measured at 23.9 nm by interfering two time-delayed partial beams directly on a CCD camera. The partial beams are obtained by wave front beam splitting in an autocorrelator operating at photon energies from h nu = 30 to 200 eV. At zero delay a visibility of (0.63+/- 0.04) is measured. The delay of one partial beam reveals a coherence time of 6 fs at 23.9 nm. The visibility further displays a non-monotonic decay, which can be rationalized by the presence of multiple pulse structure.

Dynamic force distribution during level walking under the feet of patients with chronic ankle instability

OBJECTIVES

To examine changes in the pattern of force transfer between the foot and the floor associated with chronically sprained ankles by measuring the peak forces and their timing under several regions of the feet during level walking.

METHODS

Twelve young male subjects (mean (SD) age 21 (2) years) with recurrent ankle sprains were studied. Seven of them had unilateral and bilateral chronic instability and laxity, and five had bilateral instability. Twelve healthy men (without orthopaedic or medical disease) served as a control group. Subjects walked at their own pace along a 7 m walkway, which included a Mini-EMED pressure distribution measuring system. The variables measured were relative peak force (fraction of body weight) and relative timing (fraction of stance time). These variables were measured under six regions of interest in each foot print: heel, midfoot, medial, central, and lateral forefoot, and toes.

RESULTS

(a) A significant delay to the time of peak force under the central and lateral forefoot and toes in subjects with chronic ankle instability. (b) A significant decrease in the relative forces under the heel and toes and an increase in the relative forces under the midfoot and lateral forefoot in subjects with chronic ankle instability. (c) In the patients with unilateral instability, there were no significant differences in any of the variables between the injured and non-injured foot.

CONCLUSIONS

In patients with chronic ankle instability, there is a slowing down of weight transfer from heel strike to toe off, a reduced impact at the beginning and end of the stance phase, and a lateral shift of body weight.

Photon-induced thermal desorption of CO from small metal-carbonyl clusters

Thermal CO desorption from photoexcited free metal-carbonyl clusters has been resolved in real time using two-color pump-probe photoelectron spectroscopy. Sequential energy dissipation steps between the initial photoexcitation and the final desorption event, e.g., electron relaxation and thermalization, have been resolved for Au2(CO)(-) and Pt2(CO)5-. The desorption rates for the two clusters differ considerably due to the different numbers of vibrational degrees of freedom. The unimolecular CO-desorption thresholds of Au2(CO)(-) and Pt2(CO)5- have been approximated by means of a statistical Rice-Ramsperger-Kassel calculation using the experimentally derived desorption rate constants.

Global analysis of differential gene expression after transformation with the v-H-ras oncogene in a murine tumor model

Mouse PB-3c mast cells stably transfected with the v-H-ras oncogene induce tumor formation in vivo when implanted into mice. Such tumor cells are characterized by an autocrine IL-3 loop. DNA microarrays allow simultaneous transcript imaging of several thousand genes and the technique was applied in this tumor model to analyse gene expression following malignant transformation. Using three independent tumor lines derived from the same precursor the expression of about 400 out of 11 000 genes was modulated in each tumor. A subset of only 75 genes (0.68%) is shared and up- or downregulated in all three lines. A significant portion of this gene pool possesses functions related to tumorigenesis such as cell adhesion, signaling or transcriptional regulation. Apart from a number of expressed sequence tags (EST's) we find downregulation of four interferon-inducible genes in the tumor lines. Finally, when we extrapolate our data to the complete mouse genome, we estimate that about 500 genes are differentially expressed in tumor cells compared to the precursor cell PB-3c.

Transcript imaging of the development of human T helper cells using oligonucleotide arrays

Many pathological processes, including those causing allergies and autoimmune diseases, are associated with the presence of specialized subsets of T helper cells at the site of inflammation. Understanding the genetic program that controls the functional properties of T helper type 1 (Th1) versus T helper type 2 (Th2) cells may provide insight into the pathophysiology of inflammatory diseases. We compared the gene-expression profiles of human Th1 and Th2 cells using high-density oligonucleotide arrays with the capacity to display transcript levels of 6,000 human genes. Here we analyse the data sets derived from five independent experiments using statistical algorithms. This approach resulted in the identification of 215 differentially expressed genes, encoding proteins involved in transcriptional regulation, apoptosis, proteolysis, and cell adhesion and migration. A subset of these genes was further upregulated by exposure of differentiated Th1 cells to interleukin-12 (IL-12), as confirmed by kinetic PCR analysis, indicating that IL-12 modulates the effector functions of Th1 cells in the absence of antigenic stimulation. Functional assays and in vivo expression of selected genes have validated the biological relevance of our study. Our results provide new insight into the transcriptional program controlling the functional diversity of subsets of T helper cells.

Ultrafast hot-electron dynamics observed in Pt( -)(3) using time-resolved photoelectron spectroscopy

Time-resolved two-photon photoelectron spectra have been measured for free Pt( -)(3) using femtosecond pulses of 1.5 eV photon energy in a pump-probe configuration. The time-dependent photoelectron distribution reveals a lifetime of optically excited states of less than 70 fs. Such an unexpected fast electron relaxation in Pt( -)(3) suggests the existence of inelastic electron-electron scattering processes in a triatomic cluster which result in a lifetime similar to those of bulk metals.

High yield fermentation and purification of Tendamistat disulphide analogues secreted by Streptomyces lividans

In our studies of structure-function correlation of polypeptides we used Tendamistat (TM), an alpha-amylase-inhibitor of Streptomyces tendae, as a model to investigate the influence of different mutants on the expression and secretion of the protein. In addition, we examined the influence of replacing the two disulphide-bridges that stabilize the two-loop structure of the whole protein. The single mutants C27S, C27T, C45A, the double mutants C11A/C27A, C11A/C27S, C11A/C27T, C11A/C27L, C45/C73A and the fourfold mutant C11A/C27A/C45A/C73A were prepared. The mutated TM gene was expressed in S. lividans TK 24, which secretes the active form of the inhibitor into the culture medium. Compared with the wild-type, the double-mutated TM derivatives show an increase in secreted protein by a factor of two to ten. In contrast, the single-mutated inhibitor analogues show the reverse effect. In order to examine the influence of temperature and culture media on the production of protein derivative we used the most unstable C11A analogue. Our expression studies at 10, 19, 28 and 37 degrees C established 19 degrees C as the optimal temperature for production of the protein derivatives. The correlation between the stability and secretion of TM is discussed in the context of our knowledge of protein translocation in bacteria. Based on these experiments we optimized the fermentation parameters, isolated TM analogous on a large scale, and verified them.

Identification of D-glucose-binding polypeptides which are components of the renal Na+-D-glucose cotransporter

D-Glucose-binding polypeptides in the Na+-D-glucose cotransporter from pig renal cortex were identified by affinity labeling with two D-glucose analogs, 10-N-(N-[4-azido-2-nitrophenyl]-beta-alanyl)amino-1-decyl-beta-D- glucopyranoside (NapADG) and 10-N-(bromoacetyl)amino-1-decyl-beta-D-glucopyranoside (BADG). During short-term incubation in the dark, NapADG and BADG are reversible inhibitors of Na+ gradient-dependent D-glucose uptake and Na+-dependent phlorizin binding with Ki values of about 40 and 400 microM, respectively. Irreversible inhibition of Na+-dependent phlorizin binding, which was prevented by D-glucose or phlorizin, was measured after a 1-h incubation with BADG. Both NapADG and BADG selectively labeled polypeptides with apparent molecular weights of 82,000, 75,000, 64,000, and 47,000. Since labeling of the Mr 82,000 and 75,000 polypeptides by both analogs was partially dependent on the presence of Na+ and was partially protected by D-glucose or phlorizin but not by L-glucose or D-mannose, these polypeptides are thought to be components of the renal Na+-D-glucose cotransporter which contain D-glucose-binding sites. For the Mr 64,000 and 47,000 polypeptides, Na+ dependence and D-glucose protection were not constantly observed. However, also, these polypeptides are thought to be components or proteolytic splitting products of the Na+-D-glucose cotransporter since we observed that three monoclonal antibodies showed cross-reaction with the BADG-labeled Mr 82,000, 64,000, and 47,000 polypeptides (K. Korn, A. Raszeja-Specht, S. Bernotat-Danielowski, and H. Koepsell, manuscript in preparation). When the BADG-labeled Mr 82,000 and 75,000 polypeptides were analyzed after two-dimensional separation by isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, three-labeled, D-glucose-protectable polypeptides with the respective molecular weights and isoelectric points of 82,000 and 5.6, 75,000 and 5.4, and 75,000 and 6.9 were distinguished. The data indicate that renal brush-border membranes contain several polypeptides which are components of the Na+-D-glucose cotransporter and contain D-glucose-binding sites.

Identification of the D-glucose binding polypeptide of the renal Na+-D-glucose cotransporter with a covalently binding D-glucose analog

The covalently binding D-glucose analog 10-N-(bromoacetyl)amino-1-decyl-beta-D-glucopyranoside (BADG) was synthesised and shown to be a high-affinity inhibitor of the renal Na+-D-glucose contransporter. From renal brush-border membranes a protein fraction was isolated, in which the concentration of Na+-dependent phlorizin binding sites per mg protein was enriched 7-fold. In labeling experiments with this protein fraction a polypeptide of Mr approximately 79000 was identified as containing the D-glucose binding site of the renal Na+-D-glucose cotransporter.

Do endocrines play an etiological role in diabetic and nondiabetic sexual dysfunctions?

Sexually dysfunctional diabetic and nondiabetic males were compared with a group of normal controls using different endocrinological, psychophysiological, and psychological parameters. One hundred male subjects participated in this study: 47 diabetics with sexual dysfunction (DD), 31 nondiabetics with sexual dysfunction (NDD), and 22 normal controls (C). They were evaluated by an internist (physical examination and medical history), a psychologist (psychological and sexual functioning tests), a psychiatrist (psychiatric history and mental status examination), a urologist (genitourinary physical examination), and an endocrine biochemist (evaluation of endocrine factors). Additionally, subjects were evaluated for nocturnal penile tumescence (NPT) during three nights in the sleep laboratory to obtain a differential diagnosis of impotence, that is, psychogenic vs. organic. Both sexually dysfunctional groups showed significant differences on several measures in the psychological and psychophysiological evaluations. There were also significant differences between these two groups and the control group. Plasma levels of total testosterone and serum levels of prolactin, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) showed no significant differences among the three groups, but there were some significant correlations between the endocrine and psychological measures. No significant correlations were found between the endocrine and psychophysiological measures.

Sensation seeking and psychopathology

A sample of 2,115 persons responded to an article in a popular magazine by taking the Sensation Seeking Scale (SSS) and supplying personal information by mail, including data about past treatment, hospitalization, and diagnosis of psychiatric disorders. Subjects falling into certain diagnostic categories were closely matched with controls from the same sample who reported no history, treatment, or diagnosis of disorder. SSS scores were not related to general psychopathology, unipolar depression, schizophrenia, or neurosis, but were found to be elevated in persons reporting a history of manic-depressive or sociopathic spectrum (including alcoholism and drug abuse) disorder.