Correlated Exciton Transport in Rydberg-Dressed-Atom Spin Chains.

We investigate the transport of excitations through a chain of atoms with nonlocal dissipation introduced through coupling to additional short-lived states. The system is described by an effective spin-1/2 model where the ratio of the exchange interaction strength to the reservoir coupling strength determines the type of transport, including coherent exciton motion, incoherent hopping, and a regime in which an emergent length scale leads to a preferred hopping distance far beyond nearest neighbors. For multiple impurities, the dissipation gives rise to strong nearest-neighbor correlations and entanglement. These results highlight the importance of nontrivial dissipation, correlations, and many-body effects in recent experiments on the dipole-mediated transport of Rydberg excitations.

Full counting statistics of laser excited Rydberg aggregates in a one-dimensional geometry.

We experimentally study the full counting statistics of few-body Rydberg aggregates excited from a quasi-one-dimensional atomic gas. We measure asymmetric excitation spectra and increased second and third order statistical moments of the Rydberg number distribution, from which we determine the average aggregate size. Estimating rates for different excitation processes we conclude that the aggregates grow sequentially around an initial grain. Direct comparison with numerical simulations confirms this conclusion and reveals the presence of liquidlike spatial correlations. Our findings demonstrate the importance of dephasing in strongly correlated Rydberg gases and introduce a way to study spatial correlations in interacting many-body quantum systems without imaging.

Observing the dynamics of dipole-mediated energy transport by interaction-enhanced imaging.

Electronically highly excited (Rydberg) atoms experience quantum state-changing interactions similar to Förster processes found in complex molecules, offering a model system to study the nature of dipole-mediated energy transport under the influence of a controlled environment. We demonstrate a nondestructive imaging method to monitor the migration of electronic excitations with high time and spatial resolution, using electromagnetically induced transparency on a background gas acting as an amplifier. The continuous spatial projection of the electronic quantum state under observation determines the many-body dynamics of the energy transport.

Spontaneous avalanche ionization of a strongly blockaded Rydberg gas.

We report the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. Under continuous laser coupling we create a Rydberg ensemble in the strong blockade regime, which at longer times undergoes an ionization avalanche. By combining optical imaging and ion detection, we access the full information on the dynamical evolution of the system, including the rapid increase in the number of ions and a sudden depletion of the Rydberg and ground state densities. Rydberg-Rydberg interactions are observed to strongly affect the dynamics of plasma formation. Using a coupled rate-equation model to describe our data, we extract the average energy of electrons trapped in the plasma, and an effective cross section for ionizing collisions between Rydberg atoms and atoms in low-lying states. Our results suggest that the initial correlations of the Rydberg ensemble should persist through the avalanche. This would provide the means to overcome disorder-induced heating, and offer a route to enter new strongly coupled regimes.

Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons.

We observe individual dark-state polaritons as they propagate through an ultracold atomic gas involving Rydberg states coupled via an electromagnetically induced transparency resonance. Strong long-range interactions between Rydberg excitations give rise to a blockade between polaritons, resulting in large optical nonlinearities and modified polariton number statistics. By combining optical imaging and high-fidelity detection of the Rydberg polaritons we investigate both aspects of this coupled atom-light system. We map out the full nonlinear optical response as a function of atomic density and follow the temporal evolution of polaritons through the atomic cloud. In the blockade regime, the statistical fluctuations of the polariton number drop well below the quantum noise limit. The low level of fluctuations indicates that photon correlations modified by the strong interactions have a significant backaction on the Rydberg atom statistics.

Interaction enhanced imaging of individual Rydberg atoms in dense gases.

We propose a new all-optical method to image individual Rydberg atoms embedded within dense gases of ground state atoms. The scheme exploits interaction-induced shifts on highly polarizable excited states of probe atoms, which can be spatially resolved via an electromagnetically induced transparency resonance. Using a realistic model, we show that it is possible to image individual Rydberg atoms with enhanced sensitivity and high resolution despite photon-shot noise and atomic density fluctuations. This new imaging scheme could be extended to other impurities such as ions, and is ideally suited to equilibrium and dynamical studies of complex many-body phenomena involving strongly interacting particles. As an example we study blockade effects and correlations in the distribution of Rydberg atoms optically excited from a dense gas.

Coherent population trapping with controlled interparticle interactions.

We investigate coherent population trapping in a strongly interacting ultracold Rydberg gas. Despite the strong van der Waals interactions and interparticle correlations, we observe the persistence of a resonance with subnatural linewidth at the single-particle resonance frequency as we tune the interaction strength. This narrow resonance cannot be understood within a mean-field description of the strong Rydberg-Rydberg interactions. Instead, a many-body density matrix approach, accounting for the dynamics of interparticle correlations, is shown to reproduce the observed spectral features.

Radical scavenging and anti-inflammatory properties of STW 5 (Iberogast) and its components.

A combination of ethanolic extracts from nine medicinal plants is successfully used in STW 5 (Iberogast((R))) for treatment of gastrointestinal disorders. To elucidate possible modes of action, the focus of this study is on antioxidant properties of the phytomedicine STW 5. In fact, functional gastrointestinal diseases, such as non-ulcer dyspepsia (NUD) and irritable bowel syndrome, are often initiated by or correlated to inflammatory processes, where oxidants such as reactive oxygen species (ROS) play a crucial role. Prominent in vivo sources of ROS generation are represented by the enzymes xanthine oxidase (XOD) or myeloperoxidase (MPO). Applying these enzymes in models in vitro, we show that STW 5 and its components possess strong antioxidant activities. Depending on the model investigated, even pro-oxidant activities of single components of STW 5 could be observed. Interestingly, these effects were absent in STW 5, indicating cooperation between the components. Moreover, if one of the component extracts of STW 5 is omitted, the antioxidant activity is reduced. Thus we conclude that all the single extracts combined in STW 5 are of importance for the therapeutic effect, working in concert. The component of STW 5 performing best in vitro differed with the model investigated, respectively, with ROS and ROS generators. In the XOD system, the extracts of lemon balm leaf and peppermint leaf showed the best antioxidant result, whereas concerning MPO driven chlorination reactions, bitter candy tuft extract was the most efficient antioxidant. Best protection against peroxynitrite induced oxidation of methionine like sulfur-compounds exhibited the STW 5 components lemon balm leaf, Matricaria flower and peppermint leaf.

Vitamin C, vitamin E and flavonoids.

All inflammatory processes include oxygen-activating processes where reactive oxygen species are produced. Intrinsic radical scavenging systems or compounds administered with food warrant metabolic control within certain limits. Antioxidants, which in many cases are free radical scavengers or quenchers of activated states, comprise a vast number of classes of organic molecules including most prominently the phenolics. In this report, mechanisms of protection from oxidative damage by the antioxidants vitamin C and E and flavonoids, as present in most plant extracts used as natural drugs, are summarized. For this purpose the principle of oxygen activation during representative disease processes and the protective actions of antioxidants are outlined in short.

Chlorite-hemoprotein interaction as key role for the pharmacological activity of the chlorite-based drug WF10.

WF10 is a chlorite-based drug that modulates macrophages functional states and can be safely administered to humans. WF10 potentially modulates disease-related up-regulation of immune responses both in vitro and in vivo. Thus immune response is influenced in a way that inappropriate inflammatory reactions are downregulated. The molecular mechanisms involved are not completely understood. Biochemical data suggest the reaction of chlorite with hemoproteins as the central step in the activation process of the drug. Thereby a chlorinating agent is generated, resulting in the oxidation of reduced sulfur-containing molecules and in the conversion of amino residues into more or less stable chloramines. The most prominent chloramine in vivo is taurine chloramine. Taurine chloramine is a long-lived molecule with immunomodulatory properties. For instance, taurine chloramine inhibits the generation of macrophage inflammatory mediators such as nitric oxide, prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). This study on the biochemical mechanism of WF10 gives evidence that hemoprotein dependent chlorination of taurine is not only observed in vitro but also very likely in vivo. To characterize the oxidant, generated during heme activation, different methods were used: Chemiluminescence, EPR-spectroscopy, UV/VIS-spectroscopy, gas (GC) and size exclusion chromatography. In summary, the results indicate as the first products of hemoprotein catalyzed chlorite activation a chloroxygen-species (probably HOCl/OCl-) and a ferryl-oxygen species at the hemoprotein active site in analogy to the known peroxidase (compound I and II) intermediates. Moreover, hydrogen peroxide and chlorite seem to react in a similar way with heme centers. It is proposed that WF10 represents an "inactive" transport form of potentially active chlorine. Reactivity of the latter is restricted unless heme moieties in proteins or enzymes activate the "transport form" to perform reactions in analogy to peroxidases (i.e. myeloperoxidase-catalyzed formation of HOCl/OCl-).

Biochemical activities of extracts from Hypericum perforatum L. 5th communication: dopamine-beta-hydroxylase-product quantification by HPLC and inhibition by hypericins and flavonoids.

Extracts from the herb "St. John's wort" (Hypericum perforatum L.) exhibit beneficial effects on patients suffering from mental depressions. Lack of catecholamine neurotransmitters may be one biochemical mechanism for this problem under discussion. It has been recently reported that alcoholic extracts from Hypericum perforatum inhibit dopamine-beta-hydroxylase (D-beta-H) with an I50 of 0.1 mumol/l on the basis of total hypericin content and with an I50 of 21 mumol/l with pure commercial hypericin. As test system polarographic determination of oxygen uptake with tyramine as a substrate analogue was used. In the present paper the quantification of the enzymatic activity and the potential influence of inhibitors are reported using dopamine as substrate and product (noradrenaline) quantification by HPLC. With this test system it could be shown that D-beta-H is strongly inhibited by pseudohypericin (I50 = approx. 3 mumol/l) and hypericin (I50 = approx. 5 mumol/l), whereas the I50-values of various flavonoids (quercitrin, isoquercitrin, hyperoside, rutin, quercetin, amentoflavone, kaempferol) are in the range of 50 mumol/l or higher.

Biochemical model reactions indicative of inflammatory processes. Activities of extracts from Fraxinus excelsior and Populus tremula.

All processes of oxygen activation include very reactive intermediates. Therefore, aerobic cells must cope with--and to some extent also adapt to--oxidative stress provoked for example by infections or intoxications, where these reactive intermediates accumulate. All inflammatory processes include such oxygen activating processes where reactive oxygen species (ROS) are produced. Dependent on the strength of these impact(s), several symptoms indicate the deviation from normal, steady-state metabolism. Intrinsic radical scavenging processes or compounds administered with food thus have to warrant metabolic control within certain limits. Antioxidants which in many cases are free radical scavengers or quenchers of activated states comprise a vast number of classes of organic molecules including phenolics as the most prominent ones. In this publication the activities of extracts from Fraxinus excelsior, Populus tremula and Solidago virgaurea as components of the drug Phytodolor and their mechanisms of protection from oxidative damage are summarized. In addition, new results on tyrosine nitration, a process characteristic for sites of inflammation, and its inhibition by these plant extracts, is reported.

Detection of the production of reactive oxygen species by neutrophils in whole blood: modulation by adamantanes and triggering by Fe(3+)-ions.

Using indicators for the production of reactive oxygen species (ROS) such as the a) OH-radical type (alpha-keto-gamma-methiolbutyric acid, KMB) or b) hypochlorous acid (1-amino-cyclopropyl-1-carboxylic acid, ACC) neutrophil activities can be both quantified and differentiated in whole blood via ethene production. Ethene is trapped in the head space of blood samples incubated in the presence of zymosan and the respective indicators, KMB or ACC. This procedure allows the detection of effects of aminoadamantanes (AAD) such as amantadine or memantine, compounds frequently used for the treatment of Morbus Parkinson and Morbus Alzheimer. In this report we describe the detection of OH.-type oxidants produced by isolated activated neutrophils and whole blood. Immunomodulatory activities of AAD are deduced from the following observations: AAD-stimulated ethene formation from (KMB) as an indicator for production of OH.-type reactive oxygen species by zymosan-stimulated neutrophils ("respiratory burst") is detectable with isolated neutrophils. In whole blood, however, this reaction is only measurable in the presence of Fe-EDTA-complex. Stimulating effects of AAD are observed within a concentration range between 10(-8) and 10(-4) M with a maximum at 1 microM. Ethene release from (ACC) as indicator for the myeloperoxidase reaction after degranulation is not stimulated by AAD but inhibited at concentrations higher than 100 microM. The presented results suggest that submicromolar concentrations of AAD only stimulate the respiratory burst and apparently not degranulation of zymosan-prestimulated polymorphonuclear neutrophils (PMN).

Biochemical activities of extracts from Hypericum perforatum L. 3rd Communication: modulation of peroxidase activity as a simple method for standardization.

Alcoholic extracts from the herb "St. John's wort" (Hypericum perforatum L.) are widely used to counteract depressive situations, where the question on the mainly active principle is still under discussion. Thus, standardization of the drug on the basis of dry matter has been chosen instead of the popular leading component, hypericin. Inhibition of myeloperoxidase-catalyzed dimerization of enkephalins by Hypericum extracts has recently been reported. This method is based on the separation and quantification of enkephalin dimers by HPLC. In order to simplify this assay myeloperoxidase could be substituted by the cheaper horseradish peroxidase and the enkephalins by the amino acid tyrosine without loss of significance. In this communication we represent a more rapid photometric method based on peroxidase-catalyzed indole acetic acid oxidation suitable for quick, simple and economic drug standardization.

Biochemical activities of extracts from Hypericum perforatum L. 4th Communication: influence of different cultivation methods.

Extracts from the herb "St. John's wort" (Hypericum perforatum L.), know since ancient times as medical plant, besides other activities such as wound healing, antighout, antirheumatic and diuretic properties, is used in the treatment of mild to moderate depression. Increasing application continuously makes cultivation under controlled conditions of Hypericum perforatum L. more important. This report shows the results of three-years cultivation experiments with Hypericum perforatum L. The findings indicate that N-fertilizing yields more plant material but results in a drug with less quantity of secondary metabolites. Important components of the drug were quantified by HPLC and their activities were analyzed with the aid of biochemical test systems. Narrowleaved and broadleaved varieties of Hypericum perforatum L. show differences both in activity and quality. In this experiments the most active extract was a methanolic extract derived from non-fertilized, broadleaved plants.

Modulation of the production of reactive oxygen species by pre-activated neutrophils by aminoadamantane derivatives.

Aminoadamantane derivatives (AAD) such as amantadine or memantine have been used for the treatment of Morbus Parkinson and Morbus Alzheimer. In this communication, we report on the immunomodulatory activities of AAD. Luminol-dependent chemiluminescence of zymosan-, N-formylmethionylleucylphenylalanine(FMLP)- or experimental Ca2+-ionophore(A 231879)-preactivated polymorphonuclear leukocytes (PMN) was strongly enhanced by submicromolar concentrations of AAD and inhibited at higher concentrations than 0.1 mM. Light emission by phorbol-12-myristate-acetate(PMA)-preactivated cells was not further stimulated but inhibited by the elevated concentrations, just as with the other, above-mentioned activators. Ethylene formation from alpha-keto-methylthiobutyrate (KMB) as an indicator for production of OH.-type reactive oxygen species by the NADPH-oxidase ("respiratory burst") was augmented by AAD and completely inhibited by superoxide dismutase. In contrast, ethylene release from 1-amino-cyclopropyl-l-carboxylic acid (ACC) as relatively specific indicator for the myeloperoxidase reaction after degranulation was not influenced by AAD. As documented by several model reactions, AAD per se did not act as scavengers or quenchers of activated oxygen species such as superoxide, OH.-radical, hydrogen peroxide or hypochlorite. Altogether, these results suggest that submicromolar concentrations of AAD upregulate the respiratory burst, but apparently not the degranulation of prestimulated polymorphonuclear leukocytes. At higher concentrations of AAD, both respiratory burst and degranulation are inhibited, however. These effects can also be shown in complete blood samples.

Gas chromatographic differentiation between myeloperoxidase activity and Fenton-type oxidants.

Several pathological situations are characterized by the production of reactive oxygen species (ROS), whereby different sources such as activated leukocytes and xanthine oxidase seem to be mainly responsible. The contribution of immigrating activated neutrophils to symptom development during inflammatory processes or after reperfusion of ischemic tissues is a matter of continuing discussion. We present a simple method for the differentiation between oxygen activating reactions in which neutrophil-derived myeloperoxidase is involved. The method is based on the gas chromatographic detection of ethylene, which is formed by the reaction of alpha-keto-gamma-methylthiobutyric acid (KMB) or 1-amino-cyclopropane-1-carboxylic acid (ACC) with ROS. In the presence of OH-radical-type oxidants, only KMB yields ethylene whereas ACC is fragmented by myeloperoxidase-derived species (OCl-, chloramines). The amounts of ethylene may be used as an indicator for the relative contribution of Fenton-type or myeloperoxidase-catalyzed reactions.

Stereospecific reduction of R(+)-thioctic acid by porcine heart lipoamide dehydrogenase/diaphorase.

R(+)-thioctic acid is the naturally occurring cofactor in alpha-ketoacid dehydrogenases. We show both photometrically by NADH+H+ oxidation and by HPLC product analysis that this enantiomer is rapidly reduced by NADH+H+ catalyzed by porcine heart lipoamide dehydrogenase/diaphorase. The racemate exhibits approximately 40% activity as compared to the R(+) form while the S(-) enantiomer photometrically shows little activity and yields no detectable reduced lipoic acid.