Folding and association of oligomeric enzymes

The spontaneous structure formation of oligomeric enzymes consists of the consecutive ‘folding’ and association of the constituent polypeptide chains. Whether catalytic function is an intrinsic property of the folded monomers may be determined using kinetic reconstitution experiments. It is shown that full activity requires association; the correct assembly of subunits depends on their proper folding. The native structure is determined as the kinetically accessible state of lowest free energy.     

Meister

A mobile remote sensing system is presented for measuring the concentration of gaseous pollutants in ambient air and in directed effluent streams. MEISTER is based on Fourier-Transform-Infrared-Spectroscopy (FTIS), which is predestinated for a simultaneous analysis of a large number of atmospheric gases. The Kayser-Threde Double-Pendulum interferometer K300 and the Multicomponent Air Pollution Software (MAPS) of the Fraunhofer Institute of Atmospheric Environmental Research, which is based on radiative transfer modeling and least square fit procedures, enable a concentration determination under almost all meteorological conditions. CO, CO₂, NO, N₂O, CH₄, H₂O and HCl concentrations have been determined in good agreement with results from conventionalin situ sensors. NO₂, SO₂, NH₃, HCHO and hydrocarbons have been successfully detected provided their concentrations were high enough.     

A prospective cytogenetic study of third-trimester placentae in small-for-date but otherwise normal newborns

Data in the literature suggest that confined placental mosaicism might be associated with intrauterine growth retardation. However, this association may be coincidental and due to bias of ascertainment. We therefore started a prospective study based on the cytogenetic evaluation of placentae derived from growth-retarded newborns. We further minimized possible bias by excluding those small-for-date infants displaying findings which already could explain intrauterine growth retardation (mothers who are smokers, multiple pregnancies, gestosis, dysmorphic infants). In a collection of 71 small-for-gestational age newborns, we did not see a single case of true confined placental mosaicism.     

Assessment of Bacterial Degradation of Aromatic Hydrocarbons in the Environment by Analysis of Stable Carbon Isotope Fractionation

¹³C/¹²C stable carbon isotope fractionation was used to assess biodegradation in contaminated aquifers with toluene as a model compound. Different strains of anaerobic bacteria (Thauera aromatica, Geobacter metallireducens, and the sulfate-reducing strain TRM1) showed consistent ¹³C/¹²C carbon isotope fractionation with fractionation factors between C = 1.0017 and 1.0018. In contrast, three cultures of aerobic organisms, using different mono- and dioxygenase enzyme systems to initiate toluene degradation, showed variable isotope fractionation factors of C = 1.0027 (Pseudomonasputida strain mt-2), C = 1.0011 (Ralstonia picketii), andC = 1.0004 (Pseudomonas putida strain F1). The great variability of isotope fractionation between different aerobic bacterial strains suggests that interpretation of isotope data in oxic habitats can only be qualitative. A soil column was run as a model system for contaminated aquifers with toluene as the carbon source and sulfate as the electron acceptor and samples were taken at different ports along the column. Microbial toluene degradation was calculated based on the ¹³C/¹²C isotope fractionation factors of the batch culture experiments together with the observed ¹³C/¹²C isotope shifts of the residual toluene fractions. The calculated percentage of biodegradation, B, correlated well with the decreasing toluene concentrations at the sampling ports and indicated the increasing extent of biodegradation along the column. The theoretical toluene concentrations as calculated based on the isotope values matched the measured concentrations at the different sampling ports indicating that the Rayleigh equation can be used to calculate biodegradation in quasi closed systems based on measured isotope shifts. A similar attempt was performed to assess toluene degradation in a contaminated, anoxic aquifer. A transect of groundwater wells was monitored along the main direction of the groundwater flow and revealed decreasing concentrations accompanied with an increase in the ¹³C/¹²C stable carbon isotope ratio of the residual toluene. Calculation of the extent of biodegradation based on the isotope values and laboratory derived isotope fractionation factors showed that the residual toluene was degraded to more than 99% by microbial activity. Calculation of the theoretical residual toluene concentrations based on the measured isotope values described the strongly decreasing concentrations along the plume. Other aromatic hydrocarbons like benzene and naphthalene which were analysed in the same course also showed decreasing concentrations along the groundwater flow path accompanied by increasing ¹³C values indicating biodegradation.     

Is unexplained third trimester intrauterine death of fetuses with gastroschisis caused by umbilical cord compression due to acute extra-abdominal bowel dilatation?

We report on a case of gastroschisis in which sudden dilatation of extra-abdominal bowel at 34+1 weeks was followed by an unusual umbilical flow velocity waveform (diastolic notching). The condition was associated with normal umbilical Doppler indices, brain sparing effect and a non-reactive cardiotocograph (CTG). Findings at postnatal surgery strongly suggested severe cord compression by the herniated dilated bowel. The significance of notching in the umbilical artery waveform is discussed, as is the potential importance of this sign in the prepartum management of fetuses with gastroschisis. Copyright © 2002 John Wiley & Sons, Ltd.