Subcellular localization and tissue specific expression of amidase 1 from Arabidopsis thaliana

Amidase 1 (AMI1) from Arabidopsis thaliana converts indole-3-acetamide (IAM), into indole-3-acetic acid (IAA). AMI1 is part of a small isogene family comprising seven members in A. thaliana encoding proteins which share a conserved glycine- and serine-rich amidase-signature. One member of this family has been characterized as an N-acylethanolamine-cleaving fatty acid amidohydrolase (FAAH) and two other members are part of the preprotein translocon of the outer envelope of chloroplasts (Toc complex) or mitochondria (Tom complex) and presumably lack enzymatic activity. Among the hitherto characterized proteins of this family, AMI1 is the only member with indole-3-acetamide hydrolase activity, and IAM is the preferred substrate while N-acylethanolamines and oleamide are not hydrolyzed significantly, thus suggesting a role of AMI1 in auxin biosynthesis. Whereas the enzymatic function of AMI1 has been determined in vitro, the subcellular localization of the enzyme remained unclear. By using different GFP-fusion constructs and an A. thaliana transient expression system, we show a cytoplasmic localization of AMI1. In addition, RT-PCR and anti-amidase antisera were used to examine tissue specific expression of AMI1 at the transcriptional and translational level, respectively. AMI1-expression is strongest in places of highest IAA content in the plant. Thus, it is concluded that AMI1 may be involved in de novo IAA synthesis in A. thaliana

Groundwater controls on colloidal transport in forest stream waters

Biogeochemical changes of whole catchments may, at least in part, be deduced from changes in streamwater composition. We hypothesized that there are seasonal variations of natural nanoparticles (NNP; 1–100 nm) and fine colloids (<300 nm) in stream water, which differ in origin depending on catchmentinflow parameters. To test this hypothesis, we assessed the annual dynamics of the elemental compositionof NNP and fine colloids in multiple water compartments, namely in stream water, above and belowcanopy precipitation, groundwater and lateral subsurface flow from the Conventwald catchment,Germany. In doing so, we monitored meteorological and hydrological parameters, total element loads,and analyzed element concentrations of org C, Al, Si, P, Ca, Mn and Fe by Asymmetric Flow Field FlowFractionation (AF4). The results showed that colloid element concentrations were < 5 mmol/L. Up to anaverage of 55% (Fe) of total element concentrations were not truly dissolved but bound to NNP and finecolloids. The colloid patterns showed seasonal variability with highest loads in winter. The presence ofgroundwater-derived colloidal Ca in stream water showed that groundwater mainly fed the streamsthroughout the whole year. Overall, the results showed that different water compartments vary in theNNP and fine colloidal composition making them a suitable tool to identify the streams NNP and fine colloidsources. Given the completeness of the dataset with respect to NNP and fine colloids in multiplewater compartments of a single forest watershed this study adds to the hitherto underexplored role ofNNP and fine colloids in natural forest watersheds

Ultrafast Melting of a Charge-Density Wave in the Mott Insulator 1T−TaS21T-TaS_2

Femtosecond time-resolved core-level photoemission spectroscopy with a free-electron laser is used to measure the atomic-site specific charge-order dynamics in the charge-density-wave/Mott insulator 1T-TaS2. After strong photoexcitation, a prompt loss of charge order and subsequent fast equilibration dynamics of the electron-lattice system are observed. On the time scale of electron-phonon thermalization, about 1 ps, the system is driven across a phase transition from a long-range charge ordered state to a quasi-equilibrium state with domain-like short-range charge and lattice order. The experiment opens the way to study the nonequilibrium dynamics of condensed matter systems with full elemental, chemical, and atomic site selectivity

Time-Resolved X-Ray Photoelectron Spectroscopy at FLASH

The technique of time-resolved pump–probe x-ray photoelectron spectroscopy using the free-electron laser in Hamburg (FLASH) is described in detail. Particular foci lie on the macrobunch resolving detection scheme, the role of vacuum space-charge effects and the synchronization of pump and probe lasers. In an exemplary case study, the complete Ta 4f core-level dynamics in the layered charge-density-wave (CDW) compound 1T-TaS2 in response to impulsive optical excitation is measured on the sub-picosecond to nanosecond timescale. The observed multi-component dynamics is related to the intrinsic melting and reformation of the CDW as well as to extrinsic pump-laser-induced vacuum space-charge effects