A large-scale purification procedure has been developed to isolate the membrane-bound bc(1) complex of Paracoccus denitrificans. From the purified complex, a water-soluble fragment has been... Show moreA large-scale purification procedure has been developed to isolate the membrane-bound bc(1) complex of Paracoccus denitrificans. From the purified complex, a water-soluble fragment has been isolated. The fragment comprising residues 50-190 contains the Rieske [2Fe-2S] cluster and has an optical spectrum which is typical of such a cluster. The EPR spectrum of the cluster in the bc(1) complex differs slightly from the spectrum of the water-soluble fragment. Differences in the g values and linewidths of the resonances can be attributed to the absence of bound quinone in the water-soluble fragment. Signals from the cysteines and histidines that coordinate to the [2Fe-2S] cluster could be identified in the H-1 NMR spectrum of the fragment in solution. (C) 1998 Elsevier Science S.A. All rights reserved. Show less
Expressions for the surface tension σ, Tolman length δ, and for the rigidity constants kk and k̄k̄ of a curved liquid-vapor interface in mean field approximation are presented. The local free... Show moreExpressions for the surface tension σ, Tolman length δ, and for the rigidity constants kk and k̄k̄ of a curved liquid-vapor interface in mean field approximation are presented. The local free energy comes from the Carnahan-Starling equation of state in mean field, and the usual square gradient term is replaced with a more general, integral nonlocal term. The surface tension and the Tolman length are calculated numerically, and the behavior as the critical temperature is approached is discussed; this behavior is compared with results from a molecular dynamics simulation. Two appendices are included; the first presents derivations of alternative expressions for σ and δ, and the second gives an analytical calculation of the value of δ at the critical point. The Tolman length is found to be negative and approximately 0.2 molecular diameters in magnitude for all temperatures investigated. It is also found to approach a constant value of −0.20263 molecular diameters at the critical point, in agreement with previous results. Show less
The mechanism of sound production in the collared dove Streptopelia decaocto was studied to test the validity of the 'whistle' model and to analyze the role of vocal tract resonances. In this study... Show moreThe mechanism of sound production in the collared dove Streptopelia decaocto was studied to test the validity of the 'whistle' model and to analyze the role of vocal tract resonances. In this study, the vocalizations of six male adult doves were recorded both in normal air and in a mixture of 80 % helium and 20 % oxygen (heliox). Depending on the way in which the syrinx operates, the spectral structure of the vocalizations is expected to show specific changes in heliox. The effects of heliox differed substantially depending on the type of vocal element. Except for a significant decrease in amplitude, unmodulated elements, i.e. elements with a constant frequency, were relatively unaffected by heliox. In contrast, modulated elements, i.e. elements with an abrupt increase in frequency, showed a gradual increase in frequency with increasing helium concentration. This specific increase in frequency stopped when the modulation frequency was 1.5 times the base frequency, even when the helium concentration was increased further. In some individuals, a frequency band of half the base frequency was also observed. In general, the proportion of modulated elements also showed a significant decrease. The lack of change in the fundamental frequency of the unmodulated elements and in the base frequency of the modulated elements indicates that these vocalizations are not produced like a whistle. It is more likely that they are the result of vibration of the syringeal membranes. Generally, vocal tract resonances do not play an active role in the modification of vocalizations, although they might enhance the fundamental frequency passively. The results suggest that the almost pure tonal vocalizations are produced as such in the syrinx and undergo limited modification when passing through the vocal tract. The effect of heliox on the modulation frequency suggests (1) that different sound-producing mechanisms may underlie different types of vocalizations, and (2) that resonance properties of the vocal system may be involved in the production or modification of the modulation frequency. Show less
Gaucher disease is a lysosomal storage disease characterized by storage of glucocerebroside due to lysosomal glucocerebrosidase deficiency. Increased urinary excretion of sialyloligosaccharides and... Show moreGaucher disease is a lysosomal storage disease characterized by storage of glucocerebroside due to lysosomal glucocerebrosidase deficiency. Increased urinary excretion of sialyloligosaccharides and mannosylglycoasparagines has been described for two patients with the infantile form of the disease, probably as a consequence of obstruction of lysosomal functioning due to the glycolipid accumulation in lysosomes. By thin‐layer chromatography, we found increased urinary oligosaccharide excretion in a series of adult non‐neuronopathic patients. Oligosaccharide patterns were comparable between patients and also with the pattern observed in infantile Gaucher disease. Composition was analysed by methanolysis and gas chromatography. Mannose and N‐acetylglucosamine are the main carbohydrates in all oligosaccharide bands. A statistically significant correlation was found between oligosaccharide excretion and the severity of the disease expressed as severity score index. Patients treated with enzyme replacement therapy showed a reduction up to 65% of the original oligosaccharide excretion after 1 year of treatment, comparable with the reduction in spleen volume. Show less
In this report we present data about the effect of the Rhizobium NodZ enzyme on zebrafish development. We injected zebrafish embryos with a plasmid expressing NodZ protein, and we confirmed that... Show moreIn this report we present data about the effect of the Rhizobium NodZ enzyme on zebrafish development. We injected zebrafish embryos with a plasmid expressing NodZ protein, and we confirmed that the enzyme is active and has chitin oligosaccharide fucosyltransferase (NodZ) activity in vitro. In addition, the embryos injected with the NodZ-expressing plasmid, but not with a control plasmid, showed malformations or bends in the tail, and in some cases shunted tail structures and fused somites. These results clearly indicate that the likely substrates for this enzyme, chitin oligosaccharides and free N-glycans, have essential functions during early vertebrate embryogenesis. Show less
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