Artübergreifende Bestimmung von Parametern des Primärwurzelwachstums durch raum-zeitlich hochaufgelöste Bildsequenzanalyse unter besonderer Berücksichtigung der Variation der externen Nährstoffverfügbarkeit

Im Rahmen dieser Arbeit wurde das Primärwurzelwachstum vier verschiedener Arten (Arabidopsis, Nicotiana, Solanum und Zea) genau analysiert. Dabei konnte eine sehr hohe räumliche und zeitliche Auflösung erzielt werden, die bisher in dieser Kombination nicht erreicht wurde. Dies wurde durch die Anwendung einer innovativen Bildsequenzanalyse (DISP-Methode) möglich. Um die genannte Methode auf sehr kleinen Wurzeln (Durchmesser < 0,3 mm) anwenden zu können, wurde ein ‚Mikrorhizotron’-Aufbau konstruiert, mit dem die notwendige raum-zeitliche Auflösung erreicht wurde. In interdisziplinärer Zusammenarbeit wurde die Verfolgung der Wurzelspitze im Bildbereich zur kontinuierlichen Wurzelbeobachtung über mehrere Tage entwickelt und Optimierungen im Bereich des Auswertungsverfahrens eingeführt. Durch die Anwendung der weiterentwickelten DISP-Methode konnte eine Vielzahl neuer Erkenntnisse gewonnen werden. Invarianten des Wachstums: Die vergleichende Analyse der Wachstumsmuster hat ergeben, dass das Maximum der relativen elementaren Wuchsrate ( REGRmax), der Abstand der REGRmax von der Wurzelspitze, die REGR-Halbwertsbreite und die Länge der Wachstumszone sich bei den vier untersuchten Arten auf die gleiche Weise proportional zur Geschwindigkeit der Spitze (VSpitze) verhalten. Es konnte auch gezeigt werden, dass die oben genannten Wachstumsparameter sowie VSpitze in linearer Weise vom Wurzeldurchmesser abhängen. Die untersuchten Arten weisen keinen diurnalen Rhythmus des Wurzelwachstums auf. An Maiswurzeln konnte bei Versuchen unter konstanten sowie rasch veränderten Umgebungsbedingungen gezeigt werden, dass die Symmetrie der relativen Wuchsratenverteilung vom externen Nährstoffangebot abhängt. Auch die Wachstumsleistung der Primärwurzelspitze wird durch die umgebende Nährstoffkonzentration beeinflusst. Je höher die Konzentration ist, desto schneller nimmt die Wachstumsleistung ab. Erstmals konnte die dynamische Reaktion der Primärwurzeln auf rasche Variation der Nährstoffverfügbarkeit mit hoher raum-zeitlicher Auflösung untersucht werden. Bei der dynamischen Reaktion der Wurzel auf die veränderten Bedingungen werden fast ausschließlich REGRmax und VSpitze variiert. Das Ausmaß der Wachstumsveränderung ist geringer abhängig von der veränderten Osmolarität als von der Nährstoffkonzentration– sowohl von der Ausgangskonzentration als auch von der absoluten Veränderung. Dies legt einen Zusammenhang der Wachstumsreaktion mit der Nährstoffaufnahme nahe. Durch den Einsatz einer stabil transformierten Arabidopsis-Linie mit einem labilen Reportergen-Konstrukt konnte die Dynamik des G2/M-Übergangs (und damit der Zellteilungsaktivität) in vivo ohne externe Behandlung untersucht werden. Für die Zellteilungsaktivität und Meristemlänge wurde mit dieser Methode eine lineare Abhängigkeit von der Spitzengeschwindigkeit der Wurzel festgestellt

Quantifying the influence of yellow fluorescent protein photoconversion on acceptor photobleaching-based fluorescence resonance energy transfer measurements

Fluorescence resonance energy transfer (FRET) efficiency measurements based on acceptor photobleaching of yellow fluorescent protein (YFP) are affected by the fact that bleaching of YFP produces a fluorescent species that is detectable in cyan fluorescent protein (CFP) image channels. The presented quantitative measurement of this conversion makes it possible to correct the obtained FRET signal to increase the accuracy of intensity based CFP/YFP FRET measurements. The described method can additionally be used to compare samples with very different fluorescence levels

Ohmic vs. conventional heating : Influence of moderate electric fields on properties of egg white protein gels

The present study investigates properties of heat-induced, self-standing gels of globular proteins. Native egg white protein (EWP) with 9,8 wt% protein and 0,395 wt% NaCl content was adjusted to pH = 7,0 and heated from 25 to 85 °C via Ohmic heating (OH) and conventional heating (COV) with respective come-up times (CUT, 240 and 1200 s) and holding times (HOLD, 30 and 900 s). Gels heated under OH showed lower denaturation levels and less water holding capacity. When HOLD was short, the firmness of OH gels exceeded COV gel firmness but deceeded at long HOLD. Similarly, at short HOLD OH samples presented higher hydrophobic interactions whereas at long HOLD COV gels showed more hydrophobic interactions. This correlated with changes of intermolecular beta-sheet structures which increased with HOLD at COV but decreased or remained unchanged during OH. Furthermore, as an SDS-PAGE revealed the main EWP, ovalbumin, did not fully denature when heated via OH, this lead to the assumption that the oscillatory electric field partially interferes the complete denaturation and development of intermolecular beta-sheet structures and hydrophobic interactions during thermal gelation of this protein. Scanning electron microscopy also showed deviances in network structures between OH and COV as COV gels exhibited a denser and OH gels a more open and porous network structure

Influence of oil content and droplet size of an oil-in-water emulsion on heat development in an Ohmic heating process

The influence of oil content and droplet size of oil-in-water emulsions on the heat development in an ohmic heating system was investigated. The setup was run with constant power or voltage. Emulsions consisted of sunflower oil (10–50 wt%), aqua dest. (90–50 wt%) and whey protein isolate (1.25/ 2.5/ 3.75/ 5.0 and 6.25 wt%) Two different droplet size distributions were produced, large (d0.5 ≈ 2.0 μm) and small (d0.5 ≈ 0.3 μm), for each oil mass fraction. The emulsions were ohmically heated from 10 to 80 °C at a constant power of 3.0 kW and constant voltage of 15 V/cm. The electrical conductivity decreased with an increasing oil content, resulting in longer or shorter heating time for constant voltage or constant power input, respectively. The droplet size only affected the heating process at the highest oil content. Industrial relevance Emulsions occur in a wide range of food products (e.g. sauces, dressings, desserts) and have properties giving structure to the food system. Ohmic heating is an emerging thermal process with improved (e.g. faster or less energy required) heating characteristics. The influence of physical changes due to different droplet sizes are of interest because these might also affect the heating characteristic. In addition, the direct comparison of two different process regulations (constant power and constant voltage) indicate which set up is expedient to a successful heating process. This study aims to identify the influence of emulsion-induced structural changes and process changes on the heating rates, which is of interest for the food industry and the related machine building industry

DGV flow field analysis and OH* chemiluminescence imaging in an industrial combustor operating under thermo-acoustic combustion oscillations

On the way towards a low emission combustion a possible solution seems to be the use of leaner fuel mixtures. But the main problem occurring at full power conditions are the thermo-acoustic combustion oscillations which can not be tolerated. In order to examine the reasons for that problem we applied two different measurement techniques – DGV and OH* imaging – to an industrial sized combustion chamber operating at atmospheric pressure conditions. For the DGV measurements in hot environments the biggest challenge is to overcome the strong background luminosity. Therefore we applied a self-developed pulse laser system with suitable DGV characteristics such as high power (~1mJ), narrow bandwidth (&lt;1MHz) and frequency stability (single-mode operation) together with a gated camera system. To record phase resolved measurements we extracted a trigger signal from the output of a piezo pressure transducer placed in front of the burner outlet. Another important aspect of applying the DGV technique is the addition of seeding particles to the flow. Therefore we used AlO-powder in a solid particle seeding generator which contains a sintered glass filter and a stirring device. Three light sheets were guided through small slits from the sidewalls into the measurement area. A cooled endoscope was mounted inside the combustor looking directly onto the burner head. With this arrangement we obtained all three velocity components for stationary conditions and for different phase angles during an oscillation cycle. The results show that under stationary conditions the flow field is nearly rotational symmetrically with a distinct recirculation zone. In contrast to the stationary flow the phase resolved measurements revealed a drastic change from a combustion with recirculation to a complete forward directed flow depending on the phase angle. In addition to this flow field measurements we recorded heat release images. The underlying principle of this technique is the use of the chemical excitation of the OH-radical as an indicator of the heat release. This is a simple imaging technique which uses only an intensified CCD-camera together with a wavelength filter permeable for OH* fluorescence. We examined the transition from stationary conditions to combustion oscillations with the help of those heat release images. During combustion oscillations the maximum of the heat release is connected to the development of a maximum velocity gradient between the recirculation zone and the outer swirled flow. The minimum of the heat release corresponds to a complete forward directed flow with a vanishing recirculation zone

Formation of amyloid fibrils from ovalbumin under Ohmic heating

Ohmic heating (OH) is an alternative sustainable heating technology that has demonstrated its potential to modify protein structures and aggregates. Furthermore, certain protein aggregates, namely amyloid fibrils (AF), are associated with an enhanced protein functionality, such as gelation. This study evaluates how Ohmic heating (OH) influences the formation of AF structures from ovalbumin source under two electric field strength levels, 8.5 to 10.5 and 24.0–31.0 V/cm, respectively. Hence, AF aggregate formation was assessed over holding times ranging from 30 to 1200 sunder various environmental conditions (3.45 and 67.95 mM NaCl, 80, 85 and 90 °C, pH = 7). AF were formed under all conditions. SDS-PAGE revealed that OH had a higher tendency to preserve native ovalbumin molecules. Furthermore, Congo Red and Thioflavin T stainings indicated that OH reduces the amount of AF structures. This finding was supported by FTIR measurements, which showed OH samples to contain lower amounts of beta-sheets. Field flow fractioning revealed smaller-sized aggregates or aggregate clusters occurred after OH treatment. In contrast, prolonged holding time or higher treatment temperatures increased ThT fluorescence, beta-sheet structures and aggregate as well as cluster sizes. Ionic strength was found to dominate the effects of electric field strength under different environmental conditions

Ohmic vs. conventional heating: Influence of moderate electric fields on properties of potato protein isolate gels

The influence of moderate electric fields (MEF) on thermally induced gelation and network structures of patatin enriched potato protein (PPI) was investigated. PPI solutions with 9 wt% protein (pH 7) and 25 mM NaCl were heated from 25 to 65 °C via OH (3–24 V/cm) or conventional heating (COV) at various come-up (240 s and 1200 s) and holding times (30 s and 600 s). Self-standing gels were produced but less proteins denatured when heated via OH. Further, SDS-PAGE and GPC measurements revealed more native patatin remaining after OH treatment. Scanning electron microscopy showed OH gels to have more gap-like structures and frayed areas than COV treated gels which resulted in lower water holding capacity. On molecular scale, less hydrophobic interactions were measured within the protein network and FTIR trials showed the MEF to affect beta-sheet structures. OH gels further showed lower rigidity and higher flexibility, thus, gelling functionality was affected via OH