Transient magnetic gratings on the nanometer scale.

Laser-driven non-local electron dynamics in ultrathin magnetic samples on a sub-10 nm length scale is a key process in ultrafast magnetism. However, the experimental access has been challenging due to the nanoscopic and femtosecond nature of such transport processes. Here, we present a scattering-based experiment relying on a laser-induced electro- and magneto-optical grating in a Co/Pd ferromagnetic multilayer as a new technique to investigate non-local magnetization dynamics on nanometer length and femtosecond timescales. We induce a spatially modulated excitation pattern using tailored Al near-field masks with varying periodicities on a nanometer length scale and measure the first four diffraction orders in an x-ray scattering experiment with magnetic circular dichroism contrast at the free-electron laser facility FERMI, Trieste. The design of the periodic excitation mask leads to a strongly enhanced and characteristic transient scattering response allowing for sub-wavelength in-plane sensitivity for magnetic structures. In conjunction with scattering simulations, the experiment allows us to infer that a potential ultrafast lateral expansion of the initially excited regions of the magnetic film mediated by hot-electron transport and spin transport remains confined to below three nanometers.

Induction of a host-specific chromatin-associated glycopolypeptide by human cytomegalovirus.

Analysis of chromatin preparations from [3H]glucosamine-labelled human foreskin fibroblasts revealed that a chromatin-associated glycopolypeptide with the approximate mol. wt. 130 000 (130K) is induced in response to either infection with human cytomegalovirus (HCMV) or serum treatment. Comparative limited proteolysis suggested that the [3H]glucosamine-labelled 130K polypeptides induced by these different stimuli were not identical. This observation was in contrast to results obtained by immunoprecipitation with antisera raised against the 130K glycopolypeptide from serum-induced cells which favoured a relatedness to the 130K polypeptide from virus-infected cultures. Two-dimensional separation by isoelectric focusing and SDS-polyacrylamide gel electrophoresis subsequently showed that the 130K glycopolypeptide from serum-induced cells consists of two components, one of which is identical to the single component observed in samples from HCMV-infected cultures. Experiments on the effect of glycosylation inhibitors on DNA replication in HCMV-infected as well as in serum-induced cells support the view that the host-specific chromatin-associated glycopolypeptide may be involved in DNA replication in infected cells.

Effect of 2-deoxy-D-glucose on cytomegalovirus-induced DNA synthesis in human fibroblasts.

2-Deoxy-D-glucose (dGlc) was found to selectively inhibit virus DNA synthesis in human embryonic lung cells infected with human cytomegalovirus (HCMV). The effective concentration of dGlc was approx. 10-fold higher in culture medium containing glucose instead of sodium pyruvate. This inhibitory action of dGlc was fully reversible following replacement of the inhibitor medium by fresh medium after a 48 h treatment of infected cells. Virus DNA synthesis could be selectively inhibited by addition of dGlc even after initiation of HCMV DNA replication. In contrast, virus DNA synthesis in herpes simplex virus-infected cells was insensitive to dGlc. The drug was found to deplete HCMV-infected cells of uridine triphosphate and caused a progressive reduction of uridine incorporation into RNA. To substantiate a possible interference by dGlc with the expression and/or function of virus-induced, chromatin-associated factors essential for virus DNA replication, DNA synthesis of chromatin preparations from dGlc-treated, HCMV-infected cells was analysed. In contrast to preparations of untreated or phosphonoacetic acid (PAA)-treated, HCMV-infected cells, those of dGlc-treated cells lacked significant in vitro DNA-synthesizing activity; virus DNA was not synthesized by these preparations. Tunicamycin in the presence of low concentrations of dimethyl sulphoxide was also found to be effective in abolishing HCMV-induced DNA replication. It is thus suggested that dGlc interferes with the function of an 'early' chromatin-associated glycoprotein essential for virus DNA synthesis.

Actin distribution and synthesis in human fibroblasts infected by cytomegalovirus.

"Early functions" of human cytomegalovirus were found to induce a loss of microfilaments as revealed by indirect immunofluorescence and by the use of fluorescent phalloidin. Actin synthesis in infected cultures, on the other hand, appeared to be largely unchanged as estimated from the specific radioactivity of cytoplasmic actin.

Microtubular reaction in human fibroblasts infected by cytomegalovirus. Brief report.

By the use of indirect immunofluorescence it is shown that "early" functions of human cytomegalovirus induce a loss of microtubuli in human foreskin fibroblasts within 12 hours postinfection (p.i.) which persists until about 60 hours p.i. At later times p.i. microtubular structures are eventually reestablished. Following depression during the initial 48 hours p.i. tubulin synthesis in infected cells is significantly enhanced during the initial 48 hours p.i. tubulin synthesis in infected cells is significantly enhanced during the late phase of the infectious cycle suggesting that the mechanisms regulating tubulin synthesis are not impaired.