Untersuchung chiraler Moleküle mittels Breitbandrotationsspektroskopie

Natural essential oils are complex mixtures containing several compounds of structural similarity. They are well known for their wide range of applications in different areas, from medicine to cosmetics. One of the conventional methods for their quantitative analysis is gas chromatography (GC). Despite the numerous advantages of GC as an analytical tool, some aspects such as structure determination cannot be addressed with it. Another technique which is applicable to the volatile essential oil components is rotational spectroscopy. It is a powerful method for the structure determination not only of the respective compounds, but also of their different isomers and conformers. Rotational spectroscopy thus complements the information obtained with GC, which is necessary for a comprehensive study on the molecular systems of interest. In the first part of this thesis, some of the main constituents of peppermint and thyme oils were analyzed with rotational spectroscopy. Structure determination of several oil components including menthol, thymol, linalool, and pulegone was performed. The internal dynamics of trans-thymol-B, linalool, pulegone, and menthyl acetate, resulting from the internal rotation of their methyl groups were studied. The conformational landscape of menthyl acetate was characterized both experimentally and computationally. All these key points help to better understand the functionality of the chemical substances discussed here, and their mode of interaction in our body. Additionally, a semi-quantitative analysis of thyme oil was performed. The results were compared to the GC study for benchmarking purposes, showing a good agreement. Many of the essential oil constituents are chiral. Chirality is of utmost importance in the biological context. There is a high demand for reliable methods for a detailed characterization of chiral molecules. Recent developments in rotational spectroscopy have enabled the exploration of molecules in a chirality-sensitive way by applying the microwave three-wave mixing (M3WM) technique. The M3WM makes use of the advantages of rotational spectroscopy such as conformer selectivity and mixture compatibility. It was successfully applied in the scope of this thesis to differentiate between the enantiomers of some essential oil constituents. The M3WM was recently extended to allow coherent population transfer (CPT) of the enantiomers to rotational states of choice. This approach is discussed in the second part of the present work. It may pave the way for enantioseparation in future experiments. Finally, M3WM and CPT were combined in the experiment to manipulate the chiral conformers of a molecule, which has no stereogenic center (cyclohexylmethanol). Such a procedure significantly widens the range of molecular systems available for chiral analysis with rotational spectroscopy.Natürliche ätherische Öle sind komplexe Gemische, die mehrere strukturell ähnliche Komponenten beinhalten. Sie sind bekannt für ihr breites Anwendungsspektrum in verschiedenen Bereichen, von Medizin bis Kosmetik. Eine der konventionellen Methoden für deren quantitative Analyse ist die Gaschromatographie (GC). Trotz zahlreicher Vorteile der GC als eines analytischen Werkzeugs, können einige Aspekte wie z.B. Strukturbestimmung nicht damit erfasst werden. Eine andere Methode, die auf flüchtige Ölkomponenten anwendbar ist, ist die Rotationsspektroskopie. Dies ist eine leistungsfähige Methode, um nicht nur die Struktur der zu untersuchenden Komponenten, sondern auch die Strukturen ihrer Konformere und Isomere zu bestimmen. Somit ergänzt die Rotationsspektroskopie die mit GC gewonnene Information, was für eine umfassende Studie an dem zu untersuchenden Molekülsystem notwendig ist. Im ersten Teil dieser Dissertation wurden einige der Hauptbestandteile von Pfefferminz- und Thymianöl mittels Rotationsspektroskopie analysiert. So wurde die Strukturbestimmung mehrerer Komponenten wie Menthol, Thymol, Linalool und Pulegon durchgeführt. Außerdem wurde die interne Dynamik von trans-Thymol-B, Linalool, Pulegon und auch Menthylacetat, die von der internen Rotation ihrer Methylgruppen hervorgerufen wird, erforscht. Die Konformationslandschaft von Menhylacetat wurde sowohl experimentell, als auch mittels quanten-chemischer Methoden charakterisiert. Alle diese Schlüsselaspekte tragen zu einem besseren Verständnis der Funktionalität der hier diskutierten Komponenten, sowie ihrer Wechselwirkung in unserem Körper bei. Zusätzlich wurde eine semiquantitative Analyse des Thymianöls, durchgeführt. Die Ergebnisse wurden für Benchmarking-Zwecke mit der GC-Analyse verglichen und zeigen eine gute Übereinstimmung. Viele Komponenten ätherischer Öle sind chiral. Chiralität ist von herausragender Bedeutung im biologischen Zusammenhang. Deshalb besteht ein großer Bedarf nach zuverlässigen Methoden für eine detaillierte Charakterisierung chiraler Moleküle. Neuste Entwicklungen in der Rotationsspektroskopie ermöglichen es, sich mit den Molekülen unter Anwendung des Mikrowellen Drei-Wellen Mischens (M3WM) chiralitätssensitiv auseinanderzusetzen. Das M3WM macht sich die Vorteile der Rotationsspektroskopie wie Konformerenselektivität und ihre Anwendbarkeit auf komplexe Gemische zunutze. Sie wurde erfolgreich im Rahmen dieser Dissertation angewendet, um zwischen den Enantiomeren von molekularen Bestandteilen ätherischer Öle zu unterscheiden. Das M3WM wurde vor Kurzem erweitert, um einen kohärenten Populationstransfer (CPT) von Enantiomeren in ausgewählte Rotationsenergieniveaus zu ermöglichen. Dieser Ansatz ist im zweiten Teil der vorliegenden Arbeit diskutiert. Er könnte den Weg für eine Enantiomerentrennung in zukünftigen Experimenten ebnen. Schlussendlich wurden M3WM und CPT kombiniert, um chirale Konformere eines Moleküls ohne stereogenes Zentrum (Chyclohexylmethanol) zu manipulieren. Dieser Vorgang erweitert erheblich das Sortiment an molekularen Systemen, die für die chirale Analyse mittels Rotationsspektroskopie verfügbar sind

Decrypting the H-NS-dependent regulatory cascade of acid stress resistance in Escherichia coli

<p>Abstract</p> <p>Background</p> <p>H-NS regulates the acid stress resistance. The present study aimed to characterize the H-NS-dependent cascade governing the acid stress resistance pathways and to define the interplay between the different regulators.</p> <p>Results</p> <p>We combined mutational, phenotypic and gene expression analyses, to unravel the regulatory hierarchy in acid resistance involving H-NS, RcsB-P/GadE complex, HdfR, CadC, AdiY regulators, and DNA-binding assays to separate direct effects from indirect ones. RcsB-P/GadE regulatory complex, the general direct regulator of glutamate-, arginine- and lysine-dependent acid resistance pathways plays a central role in the regulatory cascade. However, H-NS also directly controls specific regulators of these pathways (e.g. <it>cadC</it>) and genes involved in general stress resistance (<it>hdeAB, hdeD, dps, adiY</it>). Finally, we found that in addition to H-NS and RcsB, a third regulator, HdfR, inversely controls glutamate-dependent acid resistance pathway and motility.</p> <p>Conclusions</p> <p>H-NS lies near the top of the hierarchy orchestrating acid response centred on RcsB-P/GadE regulatory complex, the general direct regulator of glutamate-, arginine- and lysine-dependent acid resistance pathways.</p

A Scent of Peppermint—A Microwave Spectroscopy Analysis on the Composition of Peppermint Oil

Essential oils have a vast number of applications in different areas of our daily life. Detailed chiral analysis and structural characterization of their constituents remains an important subject in analytical chemistry. Here, we report on a broadband rotational spectroscopy study of peppermint oil in the frequency range 2–8 GHz. We focus on an unambiguous determination of the excess enantiomers of the oil constituents menthone and isomenthone in the oil by applying chiralitysensitive rotational spectroscopy, the so-called microwave three-wave mixing (M3WM) technique. Additionally, a new menthol conformer, not previously characterized, was experimentally observed, and the gas-phase structures of the two conformers of menthol and menthone were determined experimentally based on the assignment of their 13C-isotopologues in natural abundance.German Research Foundation (DFG) 328961117 SFB 1319 ELCHFundacion Alfonso Martin EscuderoMinisterio de Ciencia, Innovacion y Universidades - MCIN/AEI FJC2018-035709-

Disaster medicine: the caring contradiction

The nature of mankind is a concern for those in need. Disasters, both natural and manmade, have been with us since the beginning of recorded history but media coverage of them is a relatively new phenomenon. When these factors come together, there is great potential to both identify and serve the sick and injured. However, the mass media by its nature tends to enhance the humanistic aspect of rescue while minimizing the practical problems involved. We describe a recent scenario in Haiti that puts some of these complications into a practical perspective

INTERNAL DYNAMICS AND CHIRAL ANALYSIS OF PULEGONE, USING MICROWAVE BROADBAND SPECTROSCOPY

Essential oils, such as peppermint or pennyroyal oil, are widely used in medicine, pharmacology and cosmetics. Their major constituents, terpenes, are mostly chiral molecules and thus may exhibit different biological functionality with respect to their enantiomers. Here, we present recent results on the enantiomers of pulegone, one of the components of the peppermint (textit{Mentha piperita L.}) and pennyroyal (textit{Mentha pulegium}) essential oils, using the microwave three-wave mixing (M3WM) technique.\_x000d_ M3WM relies on the fact that the scalar triple product of the dipole moment components $mu_{a}$, $mu_{b}$ and $mu_{c}$ differs in sign between the enantiomers. A loop of three dipole-allowed rotational transitions is required for the analysis of a chiral molecule. Since the recorded signal will be exactly out of phase for the two enantiomers, an unambiguous differentiation between them is possible, even in complex mixtures.\_x000d_ In addition to the chiral analysis of pulegone, its internal dynamics, resulting from the independent rotation of two of its three methyl groups, will be discussed. Moreover, a cluster of pulegone with one water molecule will be presented. _x000d

Physical Modeling of Coupled Water and Heat Flow Within a Borehole Heat Exchanger Array in the Vadose Zone

This thesis is focused on characterization of the heat transfer and water flow processes in a physical model of a borehole array in an unsaturated soil layer. The overall goal is to develop a dataset for validation of coupled thermo-hydraulic flow models used for simulating the efficiency of heat injection or extraction from soil-borehole thermal energy storage systems. The physical model consists of a layer of unsaturated silt compacted atop a layer of sand within an insulated, 0.53 m-tall, 0.6 m-diameter cylindrical tank. A water table was imposed at the top of the sand layer. Three steel "U"-tube pipes were inserted through the silt layer into the top of the sand layer to represent a triangular array of geothermal borehole heat exchangers, and several tests were performed with different heat exchanger spacings. Heated fluid was circulated through the steel pipes to inject heat into the unsaturated silt layer at a constant rate, during which time changes in volumetric water content and temperature were measured at different depths along the center of the silt layer using dielectric sensors. The thermal conductivity and specific heat of the silt were also monitored using a thermal probe at the center of the soil layer at mid-height. The temperature of the silt at different distances from the heat exchangers, the inlet and outlet temperatures of the fluid, as well as the temperature and relative humidity of the air at the soil surface were monitored. Regardless of the heat exchanger spacing, the temperature of the unsaturated silt layer was observed to increase to a relatively steady-state value after a short period of time. Dielectric sensor measurements initially show an increase in water content at all depths in the soil, indicating that that water is moving away from the heat exchangers, albeit at a slower rate than the heat flow process. Further, water was observed to condense at the soil surface, indicating that water vapor moved upward though the soil layer due to buoyancy. In the test with the smallest radial heat exchanger spacing of 80 mm, after the initial increase in water content, a sharp decrease in water content was observed. This indicates that water was driven from the center of the array into the surrounding soil, and that a convective cycle of water phase change did not occur for this small heat exchanger spacing. In the test with the greatest radial heat exchanger spacing of 300 mm, the soil in the center of the array did not experience a decrease in water content after the initial increase, which may indicate that a convective cycle was formed. In the case of the test with an intermediate heat exchanger spacing of 160 mm, an intermediate behavior was observed. In the tests, downward liquid water flow due to gravity could not be confirmed through evaluation of the water content data. This phenomenon, which is expected if a convective cycle of water phase change is observed in the array, may have been observed for longer testing times. The thermal conductivity measured using the thermal probe was observed to increase significantly during the heating process, and was observed to be a function of both the degree of saturation of the soil and the temperature. In the case of the smallest radial borehole heat exchanger spacing, the thermal conductivity of the soil inside of the array was observed to decrease as the water content decreased, while the thermal conductivity outside of the heat exchanger array was observed to increase with increasing radial location. This confirms that the borehole spacing can have an important effect on the long-term heat storage in the vadose zone, and that small spacings may lead to an increase in thermal energy transfer to the soil outside of the array. In the case of the largest radial borehole heat exchanger spacing, a stable increase in thermal conductivity of the soil within the array was observed. As expected, the heat storage in the unsaturated soil within

Improving Effective Surgical Delivery in Humanitarian Disasters: Lessons from Haiti

Kathryn Chu and colleagues describe the experiences of Médecins sans Frontières after the 2010 Haiti earthquake, and discuss how to improve delivery of surgery in humanitarian disasters