Multicenter Evaluation of a Chromogenic Substrate Method for Photometric Determination of Prothrombin Time

A multicenter study of a chromogenic substrate method for photometric determination of prothrombin time was conducted in order to evaluate its clinical application. Seven laboratories pailicipaled in the study using a total of 742 plasma samples from 417 patients on oral anticoagulant therapy, 261 healthy subjects and 64 patients with different diseases especially of the liver as well as 30 patients with hereditary deficiency of coagulation factors II, V, VII, X. The chromogenic PT method was compared to a standardized coagulometric PT assay which uses the same sensitive human placenta thromboplastin calibrated against international reference preparations. A high correlation of the prothrombin ratio values of the chromogenic and the coagulometric assay was obtained in 402 plasma samples (r = 0.940; y = 1.02x − 0.1). The study showed that the chromogenic PT reagent is sensitive to deficiency of the coagulation factors of the extrinsic pathway but not affected by heparin up to 1 IU/ml because of the heparin antagonist added. The precision (coefficient of variation) of the photometric method ranged between 0.6 and 3% (intraassay CV) and between 1.4 and 5.8 (interassay CV). The International Sensitivity Index (ISI) obtained for the used lot was 1.09. The therapeutical range in percentage activity for patients in a stable phase of an anticoagulant therapy was found to be from 15 to 27 percent of normal. The results of the clinical evaluation proved the good comparability of the new chromogenic PT test with coagulometric methods, its high factor sensitivity, good reproducibility and easy performance.

Potential energy surface of HDO up to 25,000 cm-1

A new spectroscopically determined potential energy surface (PES) for HD(16)O is presented. This surface is constructed by adjusting the high accuracy ab initio PES of Polyansky et al. [Science 299, 539 (2003)] by fitting to both published experimental data and our still unpublished data. This refinement used experimentally derived term values up to 25,000 cm(-1) and with J< or =8: a data set of 3478 energy levels once some levels with ambiguous assignment is excluded. To improve the extrapolation properties of the empirical PES, the restraint that the resulting PESs remain close to the ab initio surface was imposed. The new HDO_07 PES reproduces the experimental data, including high J levels not included in the fit, with a root mean square error of 0.035 cm(-1). Predictions for rotation-vibration term values up to J=12 are made.

A dispersed fluorescence andab initioinvestigation of the X̃B12 and ÃA12 electronic states of the PH2 molecule

In this work, the X2B1 and A2A1 electronic states of the phosphino (PH2) free radical have been studied by dispersed fluorescence and ab initio methods. PH2 molecules were produced in a molecular free-jet apparatus by laser vaporizing a silicon rod in the presence of phosphine (PH3) gas diluted in helium. The laser-induced fluorescence, from the excited A2A1 electronic state down to the ground electronic state, was dispersed and analyzed. Ten (upsilon1upsilon2upsilon3) vibrationally excited levels of the ground electronic state, with upsilon1 < or = 2, upsilon2 < or = 6, and upsilon3 = 0, have been observed. Ab initio potential-energy surfaces for the X2B1 and A2A1 electronic states have been calculated at 210 points. These two states correlate with a 2Pi(u) state at linearity and they interact by the Renner-Teller coupling and spin-orbit coupling. Using the ab initio potential-energy surfaces with our RENNER computer program system, the vibronic structure and relative intensities of the A2A1 --> X2B1 emission band system have been calculated in order to corroborate the experimental assignments.

Calculating Absorption Shifts for Retinal Proteins: Computational Challenges

Rhodopsins can modulate the optical properties of their chromophores over a wide range of wavelengths. The mechanism for this spectral tuning is based on the response of the retinal chromophore to external stress and the interaction with the charged, polar, and polarizable amino acids of the protein environment and is connected to its large change in dipole moment upon excitation, its large electronic polarizability, and its structural flexibility. In this work, we investigate the accuracy of computational approaches for modeling changes in absorption energies with respect to changes in geometry and applied external electric fields. We illustrate the high sensitivity of absorption energies on the ground-state structure of retinal, which varies significantly with the computational method used for geometry optimization. The response to external fields, in particular to point charges which model the protein environment in combined quantum mechanical/molecular mechanical (QM/MM) applications, is a crucial feature, which is not properly represented by previously used methods, such as time-dependent density functional theory (TDDFT), complete active space self-consistent field (CASSCF), and Hartree-Fock (HF) or semiempirical configuration interaction singles (CIS). This is discussed in detail for bacteriorhodopsin (bR), a protein which blue-shifts retinal gas-phase excitation energy by about 0.5 eV. As a result of this study, we propose a procedure which combines structure optimization or molecular dynamics simulation using DFT methods with a semiempirical or ab initio multireference configuration interaction treatment of the excitation energies. Using a conventional QM/MM point charge representation of the protein environment, we obtain an absorption energy for bR of 2.34 eV. This result is already close to the experimental value of 2.18 eV, even without considering the effects of protein polarization, differential dispersion, and conformational sampling.

Fibrillation power, an alternative method of ECG spectral analysis for prediction of countershock success in a porcine model of ventricular fibrillation

BACKGROUND

Noninvasive prediction of defibrillation success after cardiac arrest and cardiopulmonary resuscitation (CPR) may help in determining the optimal time for a countershock, and thus increase the chance for survival.

METHODS

In a porcine model (n=25) of prolonged cardiac arrest, advanced cardiac life support was provided by administration of two or three doses of either vasopressin or epinephrine after 3 or 8 min of basic life support. After 4 min of ventricular fibrillation and 18 min of life support, defibrillation was attempted. The denoised power spectral density of 10 s intervals of the ventricular fibrillation electrocardiogram (ECG) was estimated from averaged and smoothed Fourier transforms. We have eliminated the spectral contribution of artifacts from manual chest compressions and provide a definition for the contribution of ventricular fibrillation to the power spectral density. This contribution is quantified and termed "fibrillation power".

RESULTS

We tested fibrillation power and two established methods in their discrimination of survivors (n=16) vs. non-survivors (n=9) in the last minute before the countershock. A fibrillation power > or =79 dB predicted successful defibrillation with sensitivity, specificity, positive predictive value and negative predictive value of 98%, 98%, 99% and 97% while a mean fibrillation frequency > or =7.7 Hz was predictive with 85%, 83%, 90% and 77% and a mean amplitude > or =0.49 mV was predictive with 95%, 90%, 94% and 91%.

CONCLUSIONS

We suggest that fibrillation power is an alternative source of information on the status of a fibrillating heart and that it may match the established mean frequency and amplitude analysis of ECG in predicting successful countershock during CPR.

Investigations on antimycobacterial activity of some Ethiopian medicinal plants

Fifteen crude extracts prepared from seven Ethiopian medicinal plants used to treat various infectious diseases were assessed for their ability to inhibit the growth of Mycobacterium tuberculosis. A preliminary screening of the crude extracts against M. tuberculosis typus humanus (ATCC 27294) was done by dilution assay using Löwenstein-Jensen medium. None of the tested extracts except the acetone fraction obtained from the stem bark of Combretum molle (R. Br. ex G. Don.) Engl & Diels (Combretaceae) showed significant inhibitory action against this strain. The acetone fraction of the stem bark of C. molle caused complete inhibition at concentrations higher than 1 mg/mL. Phytochemical analysis of the bioactive fraction led to the isolation of a major tannin and two oleanane-type pentacyclic triterpene glycosides. The tannin was identified as the ellagitannin, punicalagin, whilst the saponins were characterized as arjunglucoside (also called 4-epi-sericoside) and sericoside. All the pure compounds were further tested against the ATCC strain. Punicalagin was found to inhibit totally growth of the ATCC and also of a patient strain, which was fully sensitive to the standard antituberculosis drugs, at concentrations higher than 600 microg/mL and 1.2 mg/mL, respectively. On the other hand, the saponins failed to show any action on the ATCC strain. It appears that our findings are the first report of tannins exhibiting antimycobacterial activity.

[Identity and physicochemical properties of 1-(4-chlorophenyl)-4-morpholino-imidazolin-2-one, AWD 131-138]

The structure of the anticonvulsant 1-(4-chlorophenyl)-4-(4-morpholinyl)-2,5-dihydro-1H-imidazolin-2-one (Code: AWD 131-138, CAS-No.: 188116-07-6) was proved by IR, UV, 1H NMR, 13C NMR and mass spectra. AWD 131-138 is practically insoluble in a neutral aqueous medium at 20 degrees C (S approximately 0.08 g/l). The solubility of the substance in 0.1 N HCl is about 2.7 g/l. In DMF, AWD 131-138 is sparingly soluble (S approximately 28.5 g/l). The pKa-value is about 2.5. The partition coefficients P = COctanol/Cwater at 37 degrees C range from 0.7 at pH approximately 1 to about 20 at pH > or = 6.

BN-Doped Fullerenes: An NICS Characterization

Heterofullerenes C(58)(BN), C(54)(BN)(3), C(48)(BN)(6), and C(12)(BN)(24) and their hexaanions as well as the C(58)(BN) dimer have been investigated by ab initio calculations. On the basis of the computed nucleus independent chemical shifts (NICS) at the cage center and also at the center of individual rings, BN-doped fullerenes C(58)(BN), C(54)(BN)(3), and C(48)(BN)(6) are slightly more aromatic than C(60), whereas the corresponding hexaanions are significantly less aromatic than C(60)(6)(-). The predicted NICS values may be useful for the identification of the heterofullerenes through their endohedral (3)He NMR chemical shifts. Compared to C(60), the dimerization of C(58)(BN) is calculated to be more exothermic by 16 kcal/mol.

Superelectrophilic tetrakis(carbonyl)palladium(II)- and -platinum(II) undecafluorodiantimonate(V), [Pd(CO)4][Sb(2)F(11)]2 and [Pt(CO)4][Sb(2)F(11)]2: syntheses, physical and spectroscopic properties, their crystal, molecular, and extended structures, and density functional calculations: an experimental, computational, and comparative study

The salts [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, are prepared by reductive carbonylation of Pd[Pd(SO(3)F)(6)], Pt(SO(3)F)(4) or PtF(6) in liquid SbF(5), or HF-SbF(5). The resulting moisture-sensitive, colorless solids are thermally stable up to 140 degrees C (M = Pd) or 200 degrees C (M = Pt). Their thermal decompositions are studied by differential scanning calorimetry (DSC). Single crystals of both salts are suitable for an X-ray diffraction study at 180 K. Both isostructural salts crystallize in the monoclinic space group P2(1)/c (No. 14). The unit cell volume of [Pt(CO)(4)][Sb(2)F(11)](2) is smaller than that of [Pd(CO)(4)][Sb(2)F(11)](2) by about 0.4%. The cations [M(CO)(4)](2+), M = Pd, Pt, are square planar with only very slight angular and out-of-plane deviations from D(4)(h)() symmetry. The interatomic distances and bond angles for both cations are essentially identical. The [Sb(2)F(11)](-) anions in [M(CO)(4)][Sb(2)F(11)](2,) M = Pd, Pt, are not symmetry-related, and both pairs differ in their Sb-F-Sb bridge angles and their dihedral angles. There are in each salt four to five secondary interionic C- -F contacts per CO group. Of these, two contacts per CO group are significantly shorter than the sum of the van der Waals radii by 0.58 - 0.37 A. In addition, structural, and spectroscopic details of recently synthesized [Rh(CO)(4)][Al(2)Cl(7)] are reported. The cations [Rh(CO)(4)](+) and [M(CO)(4)](2+), M = Pd, Pt, are characterized by IR and Raman spectroscopy. Of the 16 vibrational modes (13 observable, 3 inactive) 10 (Pd, Pt) or 9 (Rh), respectively, are found experimentally. The vibrational assignments are supported by DFT calculations, which provide in addition to band positions also intensities of IR bands and Raman signals as well as internal force constants for the cations. (13)C NMR measurements complete the characterization of the square planar metal carbonyl cations. The extensive characterization of [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, reported here, allows a comparison to linear and octahedral [M(CO)(n)()][Sb(2)F(11)](2) salts [M = Hg (n = 2); Fe, Ru, Os (n = 6)] and their derivatives, which permit a deeper understanding of M-CO bonding in the solid state for superelectrophilic cations with [Sb(2)F(11)](-) or [SbF(6)](-) as anions.

Equilibrium Structure and Spectroscopic Constants of Difluorovinylidene: An ab Initio Study

Highly correlated ab initio calculations with large basis sets are reported for difluorovinylidene, F(2)CC. Based on CCSD(T)/aug-cc-pVQZ results and taking core correlation effects properly into account, a reliable theoretical equilibrium geometry is derived: r(e)(CC) = 134.74(10) pm, r(e)(CF) = 131.00(10) pm, and angle(e)(FCC) = 123.23(10) degrees. The error bars are estimated from analogous comparative calculations on the equilibrium structures of the CF(2), C(2), and C(3) species. Correlated harmonic [CCSD(T)/aug-cc-pVQZ] and anharmonic [CCSD(T)/TZ2Pf] force fields provide theoretical values for the fundamental vibrational wavenumbers which are in excellent agreement with those measured previously in an argon matrix. Many spectroscopic constants of F(2)CC are predicted. In addition, the energy of F(2)CC relative to difluoroethyne (FCCF) and the barrier to isomerization from F(2)CC to FCCF have been reinvestigated by means of the present high-level ab initio calculations. Copyright 2001 Academic Press.

Molecular-dynamics simulation of the beta domain of metallothionein with a semi-empirical treatment of the metal core

The three-metal-containing beta domain of rat liver metallothionein-2 in aqueous solution was simulated with different metal contents. The Cd(3), the CdZn(2), and the Zn(3) variant were investigated using a conventional molecular dynamics simulation, as well as a simulation with a semi-empirical quantum-chemical description (MNDO and MNDO/d) of the metal core embedded in a classical environment. For the purely classical simulations, the standard GROMOS96 force-field parameters were used, and parameters were estimated for cadmium. The results of both kinds of simulations were compared to each other and to the corresponding experimental X-ray crystallographic and NMR solution data. The purely classical simulations were found to produce a too compact metal cluster with partially incorrect geometries, which affected the enfolding protein backbone structure. The inclusion of MNDO/d for the treatment of the metal cluster improved the results to give correct cluster geometries and an overall protein structure in agreement with the experiment. The metal cluster and the cysteine residues bound to it are structurally stable, while the irregular polypeptide backbone loops between the cysteines exhibit a considerable flexibility. MNDO without extension to d orbitals failed to maintain the structure of the metal core.

Syntheses, molecular structures, and vibrational spectra of chloropentacarbonylrhodium(III) and -iridium(III) undecafluorodiantimonate(V), [Rh(CO)5Cl][Sb2F11]2 and [Ir(CO)5Cl][Sb2F11]2: an experimental and density functional study

The reactions of either bis(mu-chloro)tetracarbonyldirhodium(I), [Rh(CO)2(mu-Cl)]2, or chlorotricarbonyliridium(I), [Ir(CO)3Cl]n, in the conjugate Brønsted-Lewis superacid HF-SbF5 and in a CO atmosphere, produce [Rh(CO)5Cl][Sb2F11]2 or [Ir(CO)5Cl][Sb2F11]2, respectively. In these oxidative carbonylation reactions, antimony(V) fluoride functions as an oxidizing agent. The reduced product is identified as 6SbF3.5SbF5. [Rh(CO)5Cl][Sb2F11]2 is obtained in the form of single crystals. Crystal data: monoclinic, space group P2(1) (No. 4); a = 9.721(1), b = 12.602(1), c = 10.538(1) A; beta = 106.51(1) degrees; V = 1237.7(2) A3; Z = 2; T = 300 K; R1 [I > 3 sigma (I)] = 0.0367, wR2 = 0.0739. Single crystals of [Ir(CO)5Cl][Sb2F11]2 are produced in small amounts from a solution of mer-Ir(CO)3(SO3F)3 in magic acid, HSO3F-SbF5. The possible source of chlorine will be discussed. Crystal data for [Ir-(CO)5Cl][Sb2F11]2: monoclinic, space group P2(1) (No. 4); a = 9.686(2), b = 12.585(2), c = 10.499(2) A; beta = 106.59(2) degrees; V = 1226.5(4) A3; Z = 2; T = 294 K; R1[I > 3 sigma (I)] = 0.032, Rw = 0.031. The bond lengths and bond angles are nearly identical in the two isostructural salts; however, the cell volume of [Ir(CO)5Cl][Sb2F11]2 is slightly smaller than that of [Rh(CO)5Cl][Sb2F11]2. The cations (point group C4v) feature unusually long M-C bonds (M = Rh, Ir) and correspondingly short CO bonds, as well as high CO stretching wavenumbers and high CO stretching force constants. The [Sb2F11]- anions are not symmetry related, and their dihedral and bridge angles differ slightly in both salts. There are significant interionic contacts in [Ir(CO)5Cl][Sb2F11]2 exclusively of the C-F type (about 2 for each C atom of the five carbonyl groups) resulting in extended structures. The vibrational spectra for both [M(CO)5Cl]2+ cations (M = Rh, Ir) are assigned with the help of density functional calculations, which also provide intensities for IR and Raman bands. While [Rh(CO)5Cl]2+ is the first cationic carbonyl derivative of Rh(III), the vibrational and structural parameters for [Ir(CO)5Cl]2+ are compared to data for [Ir(CO)6]3+ and mer-Ir(CO)3(SO3F)3.

The Tetrakis(carbonyl)dioxoosmium(VI) Cation: trans-

The first carbonyl compound of a transition metal in the oxidation state +6 was obtained by reductive carbonylation of OsO(4) in SbF(5). Through the use of extensive IR, NMR, and UV/Vis spectroscopic studies as well as density functional calculations it was determined that the trans-[OsO(2)(CO)(4)](2+) cation adopts the octahedral structure shown in the picture with trans oxygen atoms.

Clonal relationship of Salmonella enterica serovar typhimurium phage type DT104 in Germany and Austria

A new epidemic clone of Salmonella enterica serovar Typhimurium designated definitive phage type (DT) 104 has been emerging since 1990 to become most common type among S. Typhimurium isolates in Germany and Austria. Molecular fingerprinting (PFGE-pattern, plasmid profiles, IS200 pattern, ribotype, ERIC-type, OMP and MLE patterns) revealed the majority of the DT104 isolates to have clonal identity; they were designated as type 1 (about 95%). Moreover, clonal type 1 of DT104 was found to occur in sensitive as well as in a range of multiply drug-resistant variants and in a variety of plasmid profile types (in particular with small cryptic plasmids in the range of 1.0 to 5.0 Md). Since the clonal type 1 of DT104 has been identified among isolates from other countries, too, including such from the United Kingdom, the United Arab Emirates, the Philippines, and the Netherlands, its pandemic spread in man indicates that the import/export of this pathogen continues. About 5% of the DT104 isolates have been identified as genetically diverse indicating the independent appearance of the same multiple drug resistance and phage pattern phenotype among different Salmonella ancestor strains.

The effect of motional averaging on the calculation of NMR-derived structural properties

The effect of motional averaging when relating structural properties inferred from nuclear magnetic resonance (NMR) experiments to molecular dynamics simulations of peptides is considered. In particular, the effect of changing populations of conformations, the extent of sampling, and the sampling frequency on the estimation of nuclear Overhauser effect (NOE) inter-proton distances, vicinal (3)J-coupling constants, and chemical shifts are investigated. The analysis is based on 50-ns simulations of a beta-heptapeptide in methanol at 298 K, 340 K, 350 K, and 360 K. This peptide undergoes reversible folding and samples a significant proportion of the available conformational space during the simulations, with at 298 K being predominantly folded and at 360 K being predominantly unfolded. The work highlights the fact that when motional averaging is included, NMR data has only limited capacity to distinguish between a single fully folded peptide conformation and various mixtures of folded and unfolded conformations. Proteins 1999;36:542-555.

Ab Initio Calculations and High-Resolution Spectroscopy of the Bending Pentad of SiH2D2 in the 10-16 µm Region

The SiH2D2 asymmetric top has nine vibrational modes, five of them forming a pentad strongly perturbed by Coriolis interactions. High-level ab initio calculations of SiH2D2 have been performed which yield numerous spectroscopic parameters related to the harmonic and anharmonic force fields. The bending pentad comprising nu4(A1), nu7(B1), nu5(A2), nu9(B2), and nu3(A1) has been studied by high-resolution Fourier transform spectroscopy; the region 600-1050 cm-1 has been investigated with a resolution of ca. 4 x 10(-3) cm-1. Raman BOXCARS spectroscopy has been used for the infrared inactive nu5 band. The Raman apparatus function was 0.0054 cm-1. Assignments of about 4000 transitions including all bands have been made, mostly employing ground state combination differences techniques, and a global fit has been performed. The fundamentals nu4 (681.624 cm-1), nu7 (742.640 cm-1), nu5 (842.381 cm-1), nu9 (859.750 cm-1), and nu3 (942.741 cm-1) are strongly coupled by A-, B-, and C-type Coriolis interactions, and ab initio predictions of these interaction parameters were used to set up a network of interactions that was refined by the experimental data. The global standard deviation for the entire body of data is 7.1 x 10(-4) cm-1. Satisfactory synthetic spectra which are very sensitive to relative signs of dipole moment derivatives and Coriolis interaction constants were obtained with the guidance of ab initio calculations. Finally, fair to good agreement of experimental and ab initio calculated molecular parameters was obtained. For the first time, a complete analysis of the pentad of SiH2D2 in the 10-16 µm region has been carried out. A full set of rovibrational parameters is given for these five interacting levels, including first and second order Coriolis interaction constants. Copyright 1998 Academic Press.

Equilibrium Structure and Spectroscopic Constants of Dichloroethyne: An ab Initio Study

High-level ab initio calculations with large basis sets are reported for dichloroethyne, ClCCCl. Based on CCSD(T)/cc-pVQZ results, an empirically corrected theoretical equilibrium geometry is derived: re(CC) = 1.2025(6) A and re(CCl) = 1.635(5) A. Correlated harmonic (CCSD(T)/cc-pVQZ) and anharmonic (MP2/TZ2Pf) force fields provide theoretical predictions for the fundamental vibrational wavenumbers and many other spectroscopic constants for the four most important isotopomers of dichloroethyne. Copyright 1997 Academic Press. Copyright 1997Academic Press

[Hypoplasia of the left heart ventricle--casuistic contribution to the development of this heart malformation]

The case report describes and compares an univentricular heart of a calf with hypoplasias of left ventricles of two further calves and a newborn moufflon. In all cases there is also stenosis of the aortic arch. The functional effects of the malformations are discussed. The hypothesis is proposed that an univentricular heart may be the extreme variant of hypoplasia of the left heart when there is an additional aortic stenosis.