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The predominant Veillonella spp. were isolated from the dorsum surface of the tongues of 11 healthy adults and identified to species level using rpoB sequencing because 16S ribosomal RNA sequence analysis does not reliably differentiate between all members of this genus. In all, 253 isolates were identified and the mean proportion (+/- SE) of Veillonella spp. per sample was 16.2 (+/- 3.6) with a range of 3.0% to 36.3% of the total anaerobic colony count. The predominant species were Veillonella atypica (10/11), Veillonella dispar (9/11) and Veillonella rogosae (8/11) because they were isolated from the majority of subjects. Veillonella parvula was isolated from only one subject while Veillonella dentocariosi and Veillonella montpelleriensis were not isolated from any subject.

INTRODUCTION Previously we have shown that reference and freshly isolated Treponema denticola cultures possess 5alpha-reductase (5alpha-R) and 3beta- and 17beta-hydroxysteroid dehydrogenase activity. A gene matching the 3-oxo-5alpha-steroid 4-dehydrogenase family protein (gene ID: 2739284; locus tag: TDE2697) has been identified in T. denticola ATCC 35405. The aim of the work presented here was to optimize assay conditions and determine steroid substrate specificities for the 5alpha-R activity of T. denticola ATCC 33520. METHODS 5alpha-R activity of cell-free preparations was assayed with radioactive steroid substrates. 5alpha-R-reduced products were identified using thin-layer chromatography and a radioisotope scanner. Assay conditions were optimized for co-factor, buffer and pH requirements. Apparent substrate specificities were determined for progesterone, 4-androstenedione, testosterone and corticosterone. The time-course for metabolism of radiolabelled progesterone and cholesterol substrates was investigated with anaerobic cultures. RESULTS The optimum pH for 5alpha-R was 5.5 and the preferred co-factor was NADPH. The order of the steroids with respect to their 5alpha-R substrate specificities was (in descending order): progesterone, 4-androstenedione, testosterone and corticosterone. There are at least two intermediates in the synthesis of 5alpha-dihydrocholesterol from cholesterol. CONCLUSION These results suggest that the 3-oxo-5alpha-steroid 4-dehydrogenase family protein gene of T. denticola codes for a functional protein that resembles mammalian 5alpha-R isoenzyme 2 with regard to co-factor requirement and pH optimum.

Electrical conductivity during the XPS of ∽100 nm thick films of poly(methyl methacrylate) (PMMA) on silicon was induced by heating to above 100°C. Rapid x-ray-induced depolymerization set in at about the same temperature. The electrical conductivity allowed acquisition of high-resolution core line and valence band spectra from s- and i-PMMA, free of differential charging effects. Within a time-scale of ∽25 min the depolymerization did not affect the appearance of the spectra. The presence of methoxy groups at the uppermost surface of the two heated samples was confirmed by angle-dependent XPS, with an indication of a higher surface concentration of such groups for the s-polymer. At ambient temperature the valence band spectra of the two stereoisomers were identical, but when heated to above 100°C a difference of ∽0.15 eV developed in the O 2s binding energies; this is interpreted as being due to preferential crystallization of the s-polymer. Copyright © 1999 John Wiley & Sons, Ltd.

Crystalline regions of poly(ethylene terephthalate) (PET) are associated with the trans glycol conformation of the polymer repeat unit. Amorphous regions are largely associated with the gauche conformation. We describe experiments which follow the development of trans conformers at the surface and in the bulk of amorphous PET films (∼150 nm thick) annealed above the glass transition temperature T g . X-ray photoelectron spectroscopy was used to probe the surface region to a depth of ∼5 nm and Fourier transform infrared spectroscopy (FTIR) to examine changes in the bulk. For PET samples annealed at 90°C no conformational change was observed either at the surface or in the bulk after 120 min. At 95 and 110 °C the gauche to trans conformational change was over in ∼30 min (surface) and >120 min (bulk) and ∼15 minutes (surface) and ∼30 min (bulk), respectively. Hence the surface rearranges faster than the bulk, consistent with increased mobility at the surface due to the polymer chains being less constrained. This is analogous with the phenomenon of surface premelting in crystalline solids. A comparison of reflection-absorption infrared spectroscopy and transmission FTIR data demonstrates the occurrence of molecular reorientation in the bulk in addition to conformational change.

The Scienta ESCA300 is a state-of-the-art x-ray photoelectron spectrometer with high intensity, and high energy and spatial resolution. This unique combination of features is made possible by the use of a high-power rotating anode x-ray source with monochromatization, high transmission and imaging electron optics and multichannel detector. We report on the performance of this instrument for conducting samples and as a microanalytical device

The rapid defluorination of fluoropolymer surfaces by their exposure to a hydrogen plasma excited by an inductively coupled RF field has been studied using ESCA. The results are interpreted in terms of a reaction/depth profile; the reaction is not uniform with depth leading to the formation of an approximately 20 A thick boundary layer of defluorinated material.