Temperature dependence of the primary electron transfer in photosynthetic reaction centers from Rhodobacter sphaeroides

The primary electron transfer (ET) in reaction centers (RC) of Rhodobacter sphaeroides is investigated as a function of temperature with femtosecond time resolution. For temperatures from 300 to 25 K the ET to the bacteriopheophytin is characterized by a biphasic time dependence. The two time constants of τ1=3.5±0.4 ps and τ2=1.2±0.3 ps at T=300 K decrease continously with temperature to values of τ1=1.4±0.3 ps and τ2=0.3±0.15 ps at 25 K. The experimental results indicate that the ET is not thermally activated and that the same ET mechanisms are active at room and low temperatures. All observations are readily rationalized by a two-step ET model with the monomeric bacteriochlorophyll as a real electron carrier

Baseline cerebral oximetry values in cardiac and vascular surgery patients: a prospective observational study

<p>Abstract</p> <p>Aim</p> <p>This study was conducted to evaluate baseline INVOS values and identify factors influencing preoperative baseline INVOS values in carotid endarterectomy and cardiac surgery patients.</p> <p>Methods</p> <p>This is a prospective observational study on 157 patients (100 cardiac surgery patients, 57 carotid endarterectomy patients). Data were collected on factors potentially related to baseline INVOS values. Data were analyzed with student's t-test, Chi-square, Pearson's correlation or Linear Regression as appropriate.</p> <p>Results</p> <p>100 cardiac surgery patients and 57 carotid surgery patients enrolled. Compared to cardiac surgery, carotid endarterectomy patients were older (71.05 ± 8.69 vs. 65.72 ± 11.04, P < 0.001), with higher baseline INVOS (P < 0.007) and greater stroke frequency (P < 0.002). Diabetes and high cholesterol were more common in cardiac surgery patients. Right side INVOS values were strongly correlated with left-side values in carotid (r = 0.772, P < 0.0001) and cardiac surgery patients (r = 0.697, P < 0.0001). Diabetes and high cholesterol were associated with significantly (P < 0.001) lower INVOS and smoking was associated with higher INVOS values in carotid, but not in cardiac surgery patients. Age, sex, CVA history, Hypertension, CAD, Asthma, carotid stenosis side and surgery side were not related to INVOS. Multivariate analysis showed that diabetes is strongly associated with lower baseline INVOS values bilaterally (P < 0.001) and explained 36.4% of observed baseline INVOS variability in carotid (but not cardiac) surgery.</p> <p>Conclusion</p> <p>Compared to cardiac surgery, carotid endarterectomy patients are older, with higher baseline INVOS values and greater stroke frequency. Diabetes and high cholesterol are associated with lower baseline INVOS values in carotid surgery. Right and left side INVOS values are strongly correlated in both patient groups.</p

TbMP42 is a structure-sensitive ribonuclease that likely follows a metal ion catalysis mechanism

RNA editing in African trypanosomes is characterized by a uridylate-specific insertion and/or deletion reaction that generates functional mitochondrial transcripts. The process is catalyzed by a multi-enzyme complex, the editosome, which consists of approximately 20 proteins. While for some of the polypeptides a contribution to the editing reaction can be deduced from their domain structure, the involvement of other proteins remains elusive. TbMP42, is a component of the editosome that is characterized by two C2H2-type zinc-finger domains and a putative oligosaccharide/oligonucleotide-binding fold. Recombinant TbMP42 has been shown to possess endo/exoribonuclease activity in vitro; however, the protein lacks canonical nuclease motifs. Using a set of synthetic gRNA/pre-mRNA substrate RNAs, we demonstrate that TbMP42 acts as a topology-dependent ribonuclease that is sensitive to base stacking. We further show that the chelation of Zn2+ cations is inhibitory to the enzyme activity and that the chemical modification of amino acids known to coordinate Zn2+ inactivates rTbMP42. Together, the data are suggestive of a Zn2+-dependent metal ion catalysis mechanism for the ribonucleolytic activity of rTbMP42

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

Psychologische Experimente: Planen und Durchführen

This seminar taught the student how to plan experiments, how to program experiments with python and how to analyse them statistically with SPSS

Adult age differences in the benefit of syntactic and semantic constraints for sentence processing

Verbal working memory-intensive sentence processing declines with age. This might reflect older adults’ difficulties with reducing the memory load by grouping single words into multiword chunks. Here we used a serial order task emphasizing syntactic and semantic relations. We evaluated the extent to which older compared with younger adults may differentially use linguistic constraints during sentence processing to cope with verbal working memory limitations. Probing syntactic–semantic interactions, age differences were hypothesized to be confined to the use of syntactic constraints and to be accompanied by an increased reliance on semantic information. Two experiments varying in verbal working memory demands were conducted: the sequence length was increased from eight items in Experiment 1 to 11 items in Experiment 2. We found the use of syntactic constraints to be compromised with aging, while the benefit of semantic information for sentence processing was comparable across age groups. Hence, we suggest that semantic information processing may become relatively more important for successful sentence processing with advancing adult age, possibly inducing a syntactic-to-semantic-processing strategy shift

Modeling stand water budgets of mixed temperate broad-leaved forest stands by considering variations in species specific drought response.

Abstract: This modeling study used recent observations at a temperate broad-leaved forest in Central Germany to calculate water balances of a Fagus sylvatica monoculture and mixed stands of F. sylvatica, Tilia spp., Acer spp., Carpinus betulus, Fraxinus excelsior and Quercus robur. To simulate soil water flow the modeling framework Expert-N was applied which combines models that describe the physiological and hydrological processes of the plant-soil system including models of evapotranspiration (Penman-Monteith equation), interception (revised Gash model) and soil water flow (Richards equation). Measurements of rainfall partitioning, volumetric soil water content, evapotranspiration and tree transpiration provided reliable data for the parameterization and the calibration of the model for three stands of different diversity levels. They allowed to include species specific physiological (transpiration rates, response to dry soil water conditions) and structural (leaf area dynamics) characteristics. During the 3-year long observation period 2005-2007 the mean yearly precipitation was 652 mm, the simulated mean yearly interception loss of the three observed forest stands was between 219 and 272 mm, the transpiration accounted for 197-225 mm, the forest floor evaporation for 96-104 mm. the drainage for 16-60 mm and the runoff for 13-50 mm. The calculations of the water balance were sensitive to the species composition of the forest and showed differences of rainfall interception and root water uptake between the stands. The applied stand-level model was able to simulate the water dynamics of the monospecific and mixed forest stands. It was shown that differences in drought tolerance of tree species can have a strong impact on the simulated soil water extraction during periods when available soil water is low

Age-related decline in sentence processing: Deriving corpus-linguistic hypotheses from psycholinguistic data

Healthy aging is associated with language changes. We here advocate the position that a strong determinant of such changes may be alterations in the underlying processing systems. Age-related processing differences of language information such as syntactic structure or semantic content might entail changes observed in corpus research. That is specifically because information on, for example, syntactic structure and semantic content can facilitate language processing (Bonhage et al. 2014) and thereby determine language use as observed in corpora. It has previously been suggested that older adults’ syntactic but not semantic information processing may be compromised (Radvansky & Dijkstra 2007). Therefore, our research has examined whether the abilities to process syntactic structure and semantic content undergo differential changes during healthy aging. We expected a decreased benefit of information on syntactic structure but an enhanced benefit of semantic content on language processing in older compared to younger adults. To this end, in an experimental setting, we manipulated the availability of syntactic structure and semantic content (Table 1). That is, syntactic information was only available in sentences but not in word lists whereas semantic content was only available in real word sentences or real word lists but not in pseudoword sentences or pseudoword lists. Participants had to remember sentences or lists for a subsequent comprehension task. In total, 53 healthy, younger (mean age: 26 years; SD: 3 years) and 53 healthy, older adults (mean age: 65 years; SD: 3 years) participated in this study. No participant suffered from any neurological disorders according to self-report. The age groups were matched upon their level of education (i.e., minimum of 13 years). We assessed whether the availability of syntactic structure or semantic content would differentially facilitate younger compared to older adults’ language comprehension. The results showed that the availability of syntactic structure was less beneficial for older than younger adults. In contrast, the benefit of semantic content was comparable across age groups. In sum, this means that healthy aging compromises the processing of syntactic structure, but spares the processing of semantic content. Our findings may thus suggest that semantic information processing may become relatively more important for successful language processing with advancing adult age, possibly inducing a syntactic-to-semantic-processing strategy shift. These clear-cut psycholinguistic changes in language processing generate strong hypotheses for corpus- linguistic research: Older adults’ disadvantage in the processing of syntactic information may decrease the complexity of their sentence production, while semantic processing and production remain unchanged. We propose to test these hypotheses by an interdisciplinary approach combining methodology from natural language processing and psycholinguistics

Age differences in the use of syntactic and semantic associations during sentence processing

While sentence processing remains generally well preserved with increasing adult age, difficulties arise when sentence processing taxes verbal working memory. Such difficulties may be related to age differences in the use of syntactic and/or semantic associations to reduce the memory load (Stine-Morrow & Payne 2016). Both syntactic and semantic associations enable the grouping of single words into larger units (Bonhage et al. 2014). Therefore, in this behavioral study, we varied the availability of syntactic and semantic associations. Syntactic associations were made available in sentences, which were contrasted to word lists; semantic associations were made available in meaningful sentences and lists, which were contrasted to pseudoword sentences and lists (Table 1). We evaluated the extent to which older compared to younger adults may differentially use the availability of syntactic or semantic associations to cope with verbal working memory limitations. Eased by the availability of syntactic or semantic associations, participants judged whether the serial order of two words from either sentence or list matched the order in which they were previously encountered. Varying the level of verbal working memory demands, two experiments were conducted. In experiment 1, 8-word stimuli were used; in experiment 2, 11-word stimuli were used, increasing verbal working memory demands. 27 younger (mean age: 26 years) and 26 older adults (mean age: 66 years) participated in experiment 1. Similarly, 26 younger (mean age: 25 years) and 27 older adults (mean age: 64 years) participated in experiment 2. While the effective use of syntactic associations was expected to decrease with age, the use of semantic associations was hypothesized to be enhanced for older compared to younger adults (Stine-Morrow & Payne 2016). The results showed that, only when verbal working memory demands were high (i.e., in experiment 2 when using longer stimuli), the use of syntactic regularities was indeed compromised at old age (experiment 2, sentence structure x age group interaction, F(1,51) = 9.88, p .05). In light of the reduced use of syntactic associations, our findings may suggest that semantic information processing may become relatively more important for successful sentence processing with advancing adult age, possibly inducing a syntactic-to-semantic-processing strategy shift