Vibronic transitions and quantum dynamics in molecular oligomers: a theoretical analysis with an application to aggregates of perylene bisimides.

Vibronic absorption spectra of molecular aggregates consisting of up to N = 9 monomer units are calculated employing methods of time-dependent quantum mechanics. Taking one vibrational degree of freedom for each monomer into account and treating one-exciton excited electronic states leads to a problem with N vibrations and N electronically coupled states. The demanding quantum propagation is carried out within the multiconfiguration time-depended Hartree method (MCTDH). Spectral features of and population transfer in the aggregates are analyzed as a function of the aggregate size and the strength of the electronic coupling. With a model for oligomers of perylene bisimides, it is shown how measured temperature-dependent absorption spectra correlate with the aggregate size. Furthermore, the exciton localization and dynamics in these aggregates are investigated.

Multiconfiguration time-dependent Hartree and classical dynamics studies of the photodissociation of HF and HCl molecules adsorbed on ice: extension to three dimensions.

The 3D photodissociation dynamics of HCl and HF molecules adsorbed on ice is studied by quantum and classical simulations. The quantum calculations are carried out with the multiconfiguration time-dependent Hartree (MCTDH) approach. Dynamical observables like angular distributions in the momentum space of the H fragments, absorption cross sections are computed. The results are compared with our previous 2D studies. As expected, less encapsulation of the H atom between the ice surface and the halogen atom is obtained in the 3D study, resulting in less pronounced interference structures in the photoabsorption cross sections and in a decrease of the classical rainbow peaks observed in the 2D scheme. Although the amplitudes of the oscillations corresponding to quantum interferences in the asymptotic angular distribution of the H fragment are different between the 2D and 3D results, the qualitative pattern of the oscillations is similar in the 2D and 3D approaches. In addition, a good agreement is observed for the angular distribution between the classical and the quantum calculations.

Multistate vibronic interactions in difluorobenzene radical cations. II. Quantum dynamical simulations.

The multistate vibronic dynamics in the X-D electronic states of all three difluorobenzene radical cations are investigated theoretically by an ab initio quantum dynamical approach. The vibronic coupling scheme and the ab initio values of the system parameters are adopted from Paper I [S. Faraji and H. Koppel, J. Chem. Phys. 129, 074310 (2008)]. Extensive calculations by wave-packet propagation have been performed with the aid of the multiconfiguration time-dependent Hartree method. Five coupled electronic potential energy surfaces and 10 (11 in the case of the orthoisomer) vibrational degrees of freedom have been included in these calculations. The nonadiabatic interactions lead to the restructuring of the photoelectron spectral envelopes. Ultrafast internal conversion processes within the electronic manifolds in question demonstrate the strength of the nonadiabatic coupling effects and complement the analogous findings for the electronic spectra. The internal conversion dynamics is characterized by a stepwise transfer of the electronic population to the lowest electronic state on a time scale of femtoseconds to picoseconds. A difference between the three isomers is found to be related to the weaker interaction between the sets of X-A and B-C-D states (with high-energy conical intersections) in the meta isomer, as compared to the other isomers. The implications of these findings for the qualitative understanding of the fluorescence dynamics of fluorinated benzene radical cations are discussed.

Anterior pituitary hormone responses to a kappa-opioid agonist in man.

The present study was designed to investigate pituitary hormone responses to a kappa-opiate receptor agonist in man. Normal men were given the racemic benzomorphan kappa-agonist MR 2033 or its levorotatory isomer MR 2034 iv. Plasma levels of PRL and GH markedly increased after injection of 3.5 micrograms/kg MR 2033 or 1.9 or 3.8 micrograms/kg MR 2034. These effects of MR 2033 were blocked by the opiate antagonist naloxone (10 mg), thereby demonstrating their mediation by opiate receptors. The kappa-agonist did not change plasma levels of LH and FSH. The secretion of TSH was significantly suppressed by MR 2033 and MR 2034, but this action was not antagonized by pretreatment with naloxone. The suppression of plasma TSH was, however, stereospecific since the (+)-isomer, MR 2035, did not affect TSH secretion. These data indicate that kappa-opiate receptors are located on neuronal pathways regulating GH, TSH, and PRL secretion. The pattern of pituitary responses elicited by the kappa-agonist differs from that of mu-opioid agonists, indicating differential endocrine functions for the endogenous agonists.

Iron absorption during the development of hexachlorobenzene-induced porphyria in rats.

The absorption of iron [59Fe-(FeSO4)] from jejunal loops was studied in rats after acute and subacute exposure to hexachlorobenzene (HCB). Female rats were given orally 100 mg HCB/kg body weight or fed a diet with 0, 500, 1,000, or 2,000 parts/10(6) HCB for 1 and 4 weeks. Male rats were fed on diets with 0 and 2,000 parts/10(6) HCB only. An increase in total urinary porphyrins and a decrease in the ratio of coproporphyrin to uroporphyrin in individual 24-h urine samples indicated different stages of porphyria in the rats at the time of determination of iron absorption. After acute oral administration of HCB, iron absorption decreased to about 70% of control values. After feeding the animals on HCB-containing diets, relative liver weight as well as total plasma protein increased depending on time and dose. The absorption of iron was not altered after 1 week of HCB exposure. After 4 weeks, the uptake of iron into the carcass decreased to less than 40% of control values, independently of dose and sex. The uptake of iron into the liver, expressed as percentage of the amount absorbed by the intestine, decreased significantly after 1 and 4 weeks of HCB feeding. No correlation could be observed between iron metabolism and urinary porphyrin excretion. The development of HCB-induced porphyria in rats is apparently not accelerated by an increased iron absorption.

Multimode Jahn-Teller and pseudo-Jahn-Teller interactions in the cyclopropane radical cation: complex vibronic spectra and nonradiative decay dynamics.

The complex vibronic spectra and the nonradiative decay dynamics of the cyclopropane radical cation (CP+) are simulated theoretically with the aid of a time-dependent wave packet propagation approach using the multireference time-dependent Hartree scheme. The theoretical results are compared with the experimental photoelectron spectrum of cyclopropane. The ground and first excited electronic states of CP+ are of X2E' and A2E'' type, respectively. Each of these degenerate electronic states undergoes Jahn-Teller (JT) splitting when the radical cation is distorted along the degenerate vibrational modes of e' symmetry. The JT split components of these two electronic states can also undergo pseudo-Jahn-Teller (PJT)-type crossings via the vibrational modes of e'', a1'' and a2'' symmetries. These lead to the possibility of multiple multidimensional conical intersections and highly nonadiabatic nuclear motions in these coupled manifolds of electronic states. In a previous publication [J. Phys. Chem. A 2004, 108, 2256], we investigated the JT interactions alone in the X2E' ground electronic manifold of CP+. In the present work, the JT interactions in the A2E'' electronic manifold are treated, and our previous work is extended by considering the coupling between the X2E' and A2E'' electronic states of CP+. The nuclear dynamics in this coupled manifold of two JT split doubly degenerate electronic states is simulated by considering fourteen active and most relevant vibrational degrees of freedom. The vibronic level spectra and the ultrafast nonradiative decay of the excited cationic states are examined and are related to the highly complex entanglement of electronic and nuclear degrees of freedom in this prototypical molecular system.

Classical and quantum studies of the photodissociation of a HX (X=Cl,F) molecule adsorbed on ice.

The photodissociation dynamics of a HX (X = Cl,F) molecule adsorbed on a hexagonal ice surface at T = 0 K is studied using time-dependent quantum wave packets and quasiclassical trajectories. The relevant potential energy surfaces are calculated using high-level ab initio methods. We present here two dimensional calculations for the dynamics of the hydrogen photofragment for both HCl and HF molecules. The purpose of this paper is to compare the photodissociation dynamics of the two molecules which are adsorbed on the ice surface with different equilibrium geometries. The total photodissociation cross section and the angular distribution are calculated. The comparison with classical trajectory calculations provides evidence for typical quantum effects and reveals rainbow structures.

On the unphysical impact of complex absorbing potentials on the Hamiltonian and its remedy.

The introduction of complex absorbing potentials as numerical tools to stabilize or increase the efficiency of calculations based on wave-packet propagation or on eigenvalue problems has the drawback of causing a modification of the Hamilton operator of the problem. In this work the consequences of such a modification are analyzed and the corrections required in order to properly describe the original physical process are derived. As an example, the decay of excited molecular states is considered: it is shown that the standard time-independent expression for the decay spectrum loses its validity when a complex absorbing potential is introduced in the nuclear Hamilton operator of the problem. To remedy the situation, a new, very stable formula is derived and tested on relevant model studies. Numerical examples are discussed.

Multiconfiguration time-dependent Hartree method applied to molecular dissociation on surfaces: H2 + Pt(111).

Four-dimensional quantum dynamics calculations are performed on the dissociative chemisorption of H(2) on Pt(111) using the multiconfiguration time-dependent Hartree method. The aim of this work is to study the performance of the multiconfiguration time-dependent Hartree method for a gas-surface reaction by comparison with the standard time-dependent wave-packet propagation method. The initial-state resolved dissociation probability of H(2) is calculated within two four-dimensional models. The first four-dimensional model treats explicitly the rotational motion of the molecule and the H(2) dissociation is studied above two different sites of the Pt(111). For this model, only a potential-energy surface of general form was available. This potential was refitted to a sum of product form to allow efficient calculations with the multiconfiguration time-dependent Hartree method. The second model focuses on the description of the center-of-mass motion parallel to the surface, the rotational motion of the molecule being frozen. These four-dimensional quantum dynamics calculations yield important insights which can help with performing full six-dimensional calculations on H(2) dissociating on Pt(111). The multiconfiguration time-dependent Hartree method is shown to be particularly efficient for computing initial-state selective dissociation probabilities for the system studied, with a good accuracy and a reduced amount of memory and computational time when compared to the standard time-dependent wave-packet method.

Wave packet study of the UV photodissociation of the Ar2HBr complex.

The photodissociation dynamics of the Ar2HBr van der Waals molecule is studied using the multiconfiguration time-dependent Hartree method. Standard Jacobian coordinates are used to describe the molecule. Two four-dimensional calculations are carried out where the rotation of the Ar2 molecule and, in addition, either the vibration of Ar2-Br or that of Ar2 are frozen. The time-evolution of the probability density in the different modes and the calculation of the dissociative flux show that the dissociating hydrogen atom preferentially moves out of the plane defined by Ar2 and Br. A comprehensive study of the cage effect in the process is presented.

One-point recalibration of heterogeneous enzyme immunoassays with non-linear calibration curves.

We have investigated one-point recalibration of heterogeneous enzyme immunoassays involving nonlinear calibration curves. By using a factor determined from a single standard we updated calibration curves obtained earlier by means of multiple-point determination. The prerequisite for this method is a reproducible working procedure, i.e., as ensured by a fully mechanized system. In our investigations with Enzymun-Test system ES 600 (Boehringer Mannheim) we determined alpha 1-fetoprotein, carcinoembryonic antigen, digoxin, ferritin, thyroxin-binding globulin, triiodothyronine, and thyroxin in human serum pools over a period of two weeks with both full calibration and one-point recalibration. Comparisons of the results thereby obtained show that the means of the concentrations and the CVs for the alternative calibration procedures differed negligibly, even if we used reagents exposed to different temperatures for different periods of time. With the one-point recalibration procedure presented here, therefore, one can considerably reduce the time and effort spent on calibration.

Diagnosis of porphyrias by ion-pair high-performance liquid chromatography.

Ion-pair reversed-phase high-performance liquid chromatography together with fluorescence detection is useful in the analysis of urinary porphyrin carboxylic acids. The sensitive and quantitative detection facilitates the clinical diagnosis of porphyrias. The method described permits the detection of porphyrins down to 0.1 ng directly from urine without laborious sample pre-treatment. A linear response curve was obtained from 0.2 up to 200 ng for coproporphyrin I. The within-assay correlation coefficients ranged from 2.5 to 10.1%. Recovery experiments gave an accuracy of 89-109%. The rapidity and simplicity of the method allows its application to the routine analysis of urinary porphyrins in the clinical laboratory.

Analysis of free stool porphyrins by high-performance liquid chromatography.

The determination of stool porphyrins is necessary for the diagnosis of some porphyrias in clinical laboratories. Quantitative methods for the analysis of faeces for porphyrins are unpleasant and difficult to perform. An extraction and ion-pair reversed-phase high-performance liquid chromatographic procedure is described for the separation and determination of individual free stool porphyrins. The within-assay coefficients of variation range from 2 to 6%. A linear response curve is observed between 38 and 380 nmol/g for coproporphyrin I in dry stool The method can be applied to the routine analysis of free stool porphyrins in the clinical laboratory.

Improved separation and detection of free porphyrins by high-performance liquid chromatography.

Porphyrins were separated using ion-pair reversed-phase high-performance liquid chromatography. The eluents were aqueous potassium phosphate buffer and tetrabutylammonium phosphate in methanol. The influences of pH value and ionic strength of the phosphate buffer and molarity of the ion-pair reagent in methanol were investigated to improve separation and detection. A linear response curve was obtained from 0.38 to 7.64 pmol for coproporphyrin I. The detection limits were determined to be 0.12 pmol for coproporphyrin I and 0.22 pmol for uroporphyrin I.

Na+-Li+ countertransport in human erythrocytes--effects of hypokalaemia, oral contraceptives and antihypertensive medication.

PIP: A series of experiments were conducted to analyze the sodium-lithium countertransport in subjects with hypertension, chronic hypokalemia, and those taking oral contraceptives (OCs). A significantly higher transport rate was observed in hypertensive subjects than in normotensive controls. An elevated sodium-lithium transport rate was also observed in normotensive women on OCs compared to women not on hormonal medication. Patients with chronic hypokalemia showed the highest values of all. No significant correlation between age and transport values was found in any of the groups. These results have been confirmed in other studies. It is concluded that antihypertensive medication does not correct the underlying pathophysiologic changes of the cell membrane. The results suggest that regulation of the sodium-lithium countertransport by the renin-aldosterone system seems possible.^ieng

High-performance liquid chromatographic determination of hormonal peptides and their fluorenylmethoxycarbonyl derivatives.

Reference methods for the quantitation of peptide and protein hormones in blood are urgently needed and high-performance liquid chromatography (HPLC) is potentially applicable. Owing to the low concentrations of these substances in body fluids, very low detection limits have to be achieved. This can be done on the one hand by reducing the diameter of the separation column and increasing the number of theoretical plates, and on the other by derivatization. Angiotensin II was chosen as a model compound. Reduction of the inner diameter from 4 to 2 mm increased the peak height by a factor of 3.4 (theoretical value 4.0). The peptide was derivatized with 9-fluorenyl methylchloroformate in lithium carbonate-sodium hydrogencarbonate or sodium borate buffer at different pH values. The precision (coefficient of variation) was 10.4%, the linear range 1:40 (r = 0.998) and the detection limit 500 fmol of derivative on-column. The volume injected was 2 microliter. However, this is not sufficiently sensitive for the quantitation of most peptide hormones using an acceptable maximum specimen volume of 5 ml of serum or plasma.

Effects of a kappa-opioid agonist on adrenocorticotropic and diuretic function in man.

Although kappa-opiate receptors represent an important fraction of the total opiate receptor capacity in human brain their endocrine function is unknown. We determined the effects of a kappa-opiate receptor agonist on the secretion of vasopressin, ACTH and cortisol and on diuresis. The racemic benzomorphan kappa agonist MR 2033 or its opiate active (-)-isomer, MR 2034, inhibited the release of cortisol and ACTH in 12 trials in a naloxone reversible manner; plasma levels of vasopressin were not altered. The (+)-isomer, MR 2035, did not affect the secretion of cortisol or ACTH. Surprisingly, in five other subjects large increases were observed in vasopressin, ACTH and cortisol following the kappa-agonist, which were probably elicited indirectly by aversive effects of the opioid. The subjects in whom vasopressin release was not altered by MR 2033 and MR 2034 displayed large decreases in urine osmolality which were not antagonized by naloxone. The opiate inactive (+)-isomer, MR 2035, caused no diuretic response. Subjects in whom vasopressin release was stimulated did not show decreases in urine osmolality indicating that vasopressin is capable of antagonizing the diuretic action of the kappa-agonist. Our data show that a kappa-agonist inhibits secretion of cortisol and ACTH by acting at stereospecific opiate receptors and elicits diuresis by acting at stereospecific, but naloxone-insensitive non-classical opioid receptors. These data support the concept that different types of kappa-receptors can be distinguished in man.

Seminal oestrogens in the boar: origin and functions in the sow.

The boar produces considerable amounts of oestrogens in the Leydig-cells also occurring in semen. Very high oestrogen concentrations are measurable in the fluid of the tubuli, which contribute the main part of seminal oestrogens. Additionally, the accessory sex glands add 22% of the unconjugated oestrogens and 12% of conjugated oestrogens to the ejaculate. Concentrations vary considerably according to season and individuals. So far a maximum of 15.3 micrograms was measured in one ejaculate. Infusion of oestrogens (simulation of the oestrogen content of an ejaculate) at oestrus through a catheter into the uterus lumen leads to an increase of the myometrial contraction-frequency for 3 h. Additionally "inseminations" with oestradiol-17 beta (Oe 2), oestrone (Oe 1), and oestrone-sulfate (Oe 1-S) (naturally occurring in the ejaculate) in 10-micrograms amounts at oestrus may lead to an increase of PGF2 alpha concentrations in the uterine veins within a few minutes. This increase may be found after "insemination" with each of the three steroids but not after saline. A parallel rise of the "inseminated" oestrogen is measurable in the uterine vein plasma and may reach concentrations up to several thousand pg/ml. This rise also leads to significantly increased concentrations in peripheral plasma for about 30 min after the "insemination" of Oe 2 (increase of Oe 2 and Oe 1-S) and Oe 1 (Oe 1 and Oe 1-S). Consequences of seminal oestrogens for sperm transport and the timing of ovulation are discussed.

[Formaldehyde sediment in incubators following disinfection]. / Formaldehydrückstände in Inkubatoren nach der Desinfektion.

Measurements in incubators revealed the presence of formaldehyde concentrations involving a health risk for premature and normal newborns kept and cared for in incubators. Prior to measurements, the incubators had been disinfected by means of formaldehyde vapours in an "Aseptor" disinfecting cabinet (Drägerwerk AG, Lübeck) and then ventilated in strict adherence to operating instructions. The elevated formaldehyde concentrations found had been due to residues of paraformaldehyde and urotropin on the surfaces of the disinfected apparatus, liberating formaldehyde by hydrolysis depending on temperature and relative humidity. There should be a basic reconsideration of the present practice of incubator disinfection. From experiments with activated-carbon filters in incubators it would seem that there is a chance of reducing such formaldehyde concentrations.

Characterization of the two-phase systems in airlift tower-loop bioreactors during the cultivation of E. coli.

During the cultivation of E. coli in an airlift tower-loop bioreactor, the following properties were measured: transverse profiles of Sauter bubble diameter, d(S); local relative gas holdup, E(G); bubble rise velocity, u(BS); local mean velocity, u turbulence intensity, u'; macrotime scale, T(EL); dissipation time scale, tau(E); power spectrum, E(n); and energy dissipation spectrum D(n) at different distances from the aerator. The influence, distance from the aerator, absence and/or presnece of cells, and batch and/or continuous-culture operation on the behavior of the two-phase system are discussed on the basis of these properties.