Disinfection of upper gastrointestinal fibreoptic endoscopy equipment: an evaluation of a cetrimide chlorhexidine solution and glutaraldehyde. (1/196)

There is little information available on the bacteriological contamination of upper gastrointestinal fibreoptic endoscopes during routine use and the effects of 'disinfecting solutions'. A bacteriological evaluation was therefore made of cleaning an endoscope and its ancillary equipment with (1) water, (2) an aqueous solution of 1% cetrimide with 0.1% chlorhexidine, and (3) activated aqueous 2% glutaraldehyde. All equipment, but particularly the endoscope itself, was found to be heavily contaminated after use with a wide variety of organisms of which 53% were Gram positive. Cleaning the endoscope and ancillary equipment with water and the cetrimide/chlorhexidine solution alone or in combination was inadequate to produce disinfection but immersion in glutaraldehyde for two minutes consistently produced sterile cultures with our sampling technique. A rapid and simple method for disinfection of endoscopic equipment is therefore recommended and we think this is especially suitable for busy endoscopy units.  (+info)

CTAB-mediated enrichment for active forms of novel dimeric maxizymes. (2/196)

We demonstrated previously that shortened forms of (stem II-deleted) hammerhead ribozymes with low intrinsic activity form very active dimers with a common stem II (very active short ribozymes capable of forming dimers were designated maxizymes). As a result of such a dimeric structure, heterodimeric maxizymes are potentially capable of cleaving a substrate at two different sites simultaneously. In this case, active heterodimers are in equilibrium with inactive homodimers. Longer forms of common stem II can lead to enrichment of the active heterodimers in vitro. In this study, we investigated whether the cationic detergent CTAB, which is known to enhance strand displacement of nucleic acids, might inhibit the dimerization of maxizymes. Significantly, under all conditions examined, CTAB instead enhanced the activity of a variety of maxizymes, with the extent of enhancement depending on the conditions. The activity of our least stable, least active maxizyme was enhanced 100-fold by CTAB. The strand displacement activity of CTAB thus appears to enhance the conversion of alternative conformations of inactive maxizymes, with intra- and inter-molecular hydrogen bonds, to active forms. Thus, our smallest maxizyme can also be considered a potential candidate for a gene-inactivating agent in vivo, in view of the fact that various facilitators of strand displacement reactions are known to exist in vivo (indeed, a separate experiment in cell culture supported the conclusion that our smallest maxizyme is a good gene-inactivating agent). Although activities of ribozymes in vitro do not necessarily reflect their activities in vivo, our findings suggest that the activity of ribozymes in vivo can be better estimated by running ribozyme kinetics in the presence of CTAB in vitro.  (+info)

Optimised sample preparation of synovial fluid for detection of Chlamydia trachomatis DNA by polymerase chain reaction. (3/196)

OBJECTIVE: To optimise sample preparation of synovial fluid for Chlamydia trachomatis (CT) specific polymerase chain reaction (PCR). METHODS: Serial dilutions of purified CT elementary bodies in synovial fluid were prepared. The synovial fluid pellet was processed by eight different methods of sample preparation. Then samples were analysed by CT specific PCR. The sensitivity of PCR was the basis of ranking of the eight different methods. RESULTS: Highest sensitivity was achieved by methods including an additional step of DNA isolation. Additional extraction of protein and polysaccharides by cetyltrimethylammonium bromide (CTAB) increased sensitivity. Addition of hyaluronidase did not increase sensitivity of QIAEX-DNA extraction but was necessary, however, before phenol-chloroform-DNA extraction. CONCLUSIONS: The method of synovial fluid sample preparation significantly influences the sensitivity of subsequent PCR. Additional DNA isolation and extraction of PCR inhibitors by CTAB led to higher sensitivity.  (+info)

DNA conformational dynamics in the presence of catanionic mixtures. (4/196)

DNA conformational behavior in the presence of non-stoichiometric mixtures of two oppositely charged surfactants, cetyltrimethylammonium bromide and sodium octyl sulfate, was directly visualized in an aqueous solution with the use of a fluorescence microscopy technique. It was found that in the presence of cationic-rich catanionic mixtures, DNA molecules exhibit a conformational transition from elongated coil to compact globule states. Moreover, if the catanionic mixtures form positively charged vesicles, DNA is adsorbed onto the surface of the vesicles in a collapsed globular form. When anionic-rich catanionic mixtures are present in the solution, no change in the DNA conformational behavior was detected. Cryogenic transmission electron microscopy, as well as measurements of translational diffusion coefficients of individual DNA chains, supported our optical microscopy observations.  (+info)

Escherichia coli TEM1 beta-lactamase in CTAB reverse micelles: exchange/diffusion-limited catalysis. (5/196)

We report kinetic data of penicillin hydrolysis catalyzed by beta-lactamase entrapped in reverse micelles formed with cetyl trimethylammonium bromide (CTAB), n-octane, hexanol and aqueous buffer. The K(cat) of this diffusion-limited reaction can be improved in aqueous buffer by a factor of 1.1-1.2 just by increasing the phosphate buffer concentration from 50 to 100 mM. In reverse micelles, increasing the buffer concentration has little effect on K(cat) when the size of the empty micelle is below the size of the protein. However, in larger micelles, the effect is enhanced and the K(cat) improves several fold, changing the form of the curve of K(cat) versus Wo from bell-shaped to almost hyperbolic. The results indicate that micellar exchange and internal diffusion may limit the reaction in reverse micelles and provide further evidence that the form of the curve depends on other factors besides the relationship between the size of the enzyme and that of the empty reverse micelle.  (+info)

Models for enzyme superactivity in aqueous solutions of surfactants. (6/196)

Theoretical models are developed here for enzymic activity in the presence of direct micellar aggregates. An approach similar to that of Bru et al. [Bru, Sanchez-Ferrer and Garcia-Carmona (1989) Biochem. J. 259, 355-361] for reverse micelles has been adopted. The system is considered to consist of three pseudo-phases: free water, bound water and surfactant tails. The substrate concentration in each pseudo-phase is related to the total substrate concentration in the reaction medium. In the absence of interactions between the enzyme and the micelles, the model predicts either monotonically increasing or monotonically decreasing trends in the calculated reaction rate as a function of surfactant concentration. With enzyme-micelle interactions included in the formulation (by introducing an equilibrium relation between the enzyme confined in the free water and in the bound water pseudo-phases, and by allowing for different catalytic behaviours for the two forms), the calculated reaction rate can exhibit a bell-shaped dependence on surfactant concentration. The effect of the partition of enzyme and substrate is described, as is that of enzyme efficiency in the various pseudo-phases.  (+info)

Second harmonic generation of glucose oxidase at the air/water interface. (7/196)

We present a study of the adsorption of the glucose oxidase enzyme (GOx) at the air/water interface, using the nonlinear optical technique of surface second harmonic generation (SSHG). Resonant SSHG experiments were achieved by probing the pi-pi* transition of the flavin adenine dinucleotide (FAD) chromophores embedded in the GOx protein. Because of the subsequent resonance enhancement of the signal, the second harmonic (SH) wave arising from the GOx entities adsorbed at the interface was detectable for protein bulk aqueous concentrations as low as 70 nM. The protein adsorption was followed, and, at high GOx coverage, a change in the orientation of the FAD chromophore was observed, indicating either a rearrangement or a reorientation of the protein at the interface. Inasmuch as GOx is negatively charged at the biological pH of 7, its interactions with charged surfactants were also investigated. As expected, spreading positively charged surfactants onto a partial protein monolayer was found to increase the GOx surface concentration, whereas in the case of negatively charged surfactants, the GOx surface concentration decreased until the SH signal went back to the pure buffer solution response level. With the increasing GOx surface concentration, the rearrangement or reorientation of the protein was also observed.  (+info)

A method for preparing genomic DNA that restrains branch migration of Holliday junctions. (8/196)

The Holliday junction is a central intermediate in genetic recombination. This four-stranded DNA structure is capable of spontaneous branch migration, and is lost during standard DNA extraction protocols. In order to isolate and characterize recombination intermediates that contain Holliday junctions, we have developed a rapid protocol that restrains branch migration of four-way DNA junctions. The cationic detergent hex-adecyltrimethylammonium bromide is used to lyse cells and precipitate DNA. Manipulations are performed in the presence of the cations hexamine cobalt(III) or magnesium, which stabilize Holliday junctions in a stacked-X configuration that branch migrates very slowly. This protocol was evaluated using a sensitive assay for spontaneous branch migration, and was shown to preserve both artificial Holliday junctions and meiotic recombination intermediates containing four-way junctions.  (+info)