Über die Aktivierung des Hemmstoffsystems vonHelianthus durch kurzfristige Belichtung

Zusammenfassung Hypokotylzylinder vonHelianthus annuus wurden mit Hilfe der Agar-Abfangmethode auf ihren Wirkstoffgehalt geprüft. Aus dunkel kultivierten Keimlingen wurde Wuchsstoff während 2–3 Std in Agar abgefangen, teils im Dunkeln, teils bei Belichtung mit etwa 600 Lux. Es konnten aber nur sehr geringe Wuchsstoffmengen erhalten werden, und zwar fast nur in den Dunkelversuchen. Wurde den Agarwürfeln aber eine IES-Vorlage gegeben, so erhöhte das im Dunkeln erhaltene Diffusat die Wuchsstoffkrümmungen im Hafertest, während das im Licht erhaltene sie herabsetzte.Aus diesen Versuchen kann auf eine Bildung oder Aktivierung eines Hemmstoffes oder aber auf eine Steigerung seiner Wanderungsfähigkeit geschlossen werden. Zur Auslösung dieses Effektes genügt bereits eine 2–3stündige Belichtung mit etwa 600 Lux.Mit 1 TextabbildungTeil einer Dissertation der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Hamburg.     

Increased backbone flexibility in threonine45-phosphorylated hirudin upon pH change.

Protein phosphorylation on serine/threonine side chains represents a major regulatory event in the posttranslational control of protein functionality, where it is thought to operate at the level of structural changes in the polypeptide chain. However, key questions about molecular aspects of phosphate ester induced conformational alterations remain open. Among these concerns are the radius of action of the phosphate ester group, its effective ionic state, and its interplay with distinct bonds of the polypeptide chain. Primarily to define short-range effects upon threonine phosphorylation, the native 65 amino acid protein hirudin, conformationally restrained by a proline flanking the pThr(45) site and three intramolecular disulfide bonds, was structurally characterized in both the phosphorylated and the unphosphorylated state in solution. Circular dichroism and hydrogen exchange experiments (MALDI-TOF) showed that structural changes were caused by Thr(45)-Pro(46) phosphorylation only when the phosphate ester group was in its dianionic state. The spatial arrangement of the amino acids, monitored by 1H NMR spectroscopy, appears to be affected within a radius of about 10 A around the pThr(45)-OgammaH, with phosphorylation resulting in a loss of structure and increased flexibility within a segment of at least seven amino acid residues. Thus, the transition from the monoanionic to the dianionic phosphate group over the pH range 5.2-8.5 represents a general phosphorylation-dependent conformational switch operating at physiological pH values.     

The ultrastructural delineation of cell growth and division processes using the avidin-biotin complex

A novel method for the study of the fate of cell envelope components during growth and division is described. Successive treatment of the budding yeast, Saccharomyces cerevisiae, with sodium periodate and biotin hydrazide results in the covalent attachment of biotin to an unidentified cell surface component(s), without concomitant interference with subsequent growth and/or division. Further treatment of the cells with ferritin-avidin conjugates (FAv) enables the localization of the position of biotinylated surface components. Electron microscopical analysis of the distribution of attached FAv on cells fixed immediately after biotinylation revealed an even distribution of the biotin sites over the entire surface (including buds and scars) of all cells in the population. Labeling of biotinylated cells following a defined growth period revealed a new cell subpopulation completely devoid of label. The absence of biotin sites on the majority of buds and newly formed scars which appeared on the biotinylated yeasts indicate that the labeled cell wall constituents are stationary and not transferred to the newly synthesized cell wall of the daughter cells. The selective interaction of the biotinylated parent cells with avidin or antibiotin antibodies may enable an affinity-based separation of successive generations from a mixed yeast cell population.     

The ‘Swallow Tail’ Appearance of the Healthy Nigrosome – A New Accurate Test of Parkinson's Disease: A Case-Control and Retrospective Cross-Sectional MRI Study at 3T

There is no well-established in vivo marker of nigral degeneration in Parkinson''s disease (PD). An ideal imaging marker would directly mirror the loss of substantia nigra dopaminergic neurones, which is most prominent in sub-regions called nigrosomes. High-resolution, iron-sensitive, magnetic resonance imaging (MRI) at 7T allows direct nigrosome-1 visualisation in healthy people but not in PD. Here, we investigated the feasibility of nigrosome-1 detection using 3T - susceptibility-weighted (SWI) MRI and the diagnostic accuracy that can be achieved for diagnosing PD in a clinical population. 114 high-resolution 3T – SWI-scans were reviewed consisting of a prospective case-control study in 19 subjects (10 PD, 9 controls) and a retrospective cross-sectional study in 95 consecutive patients undergoing routine clinical SWI-scans (>50 years, 9 PD, 81 non-PD, 5 non-diagnostic studies excluded). Two raters independently classified subjects into PD and non-PD according to absence or presence of nigrosome-1, followed by consensus reading. Diagnostic accuracy was assessed against clinical diagnosis as gold standard. Absolute inter- and intra-rater agreement was ≥94% (kappa≥0.82, p<0.001). In the prospective study 8/9 control and 8/10 PD; and in the retrospective study 77/81 non-PD and all 9 PD subjects were correctly classified. Diagnostic accuracy of the retrospective cohort was: sensitivity 100%, specificity 95%, NPV 1, PPV 0.69 and accuracy 96% which dropped to 91% when including non-diagnostic scans (‘intent to diagnose’). The healthy nigrosome-1 can be readily depicted on high-resolution 3T - SWI giving rise to a ‘swallow tail’ appearance of the dorsolateral substantia nigra, and this feature is lost in PD. Visual radiological assessment yielded a high diagnostic accuracy for PD vs. an unselected clinical control population. Assessing the substantia nigra on SWI for the typical ‘swallow tail’ appearance has potential to become a new and easy applicable 3T MRI diagnostic tool for nigral degeneration in PD.     

Enter exitrons

Exitrons are exon-like introns located within protein-coding exons. Removal or retention of exitrons through alternative splicing increases proteome complexity and thus adds to phenotypic diversity.     

Phospholipase a activity in commercial nucleases. Implications for membrane vesicle isolation

Phospholipase A activity was detected in commercial DNAases I and II and in RNAase preparations. The amount of phospholipase correlates inversely with the degree of nuclease purification. The assessment of the level of phospholipase in commercial nucleases is important in cases where enzymatic properties other than those of DNAases and RNAases are to be investigated and when these preparations are to be used in the isolation of biological membranes.