PubMed · 7980926
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N G Kruchinina, P M Gresshoff. 1994. Detergent affects silver sequencing.. https://pubmed.ncbi.nlm.nih.gov/7980926/
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Effects of time-releasing toilet bowl sanitizers and their main constituents, detergents, on immunological fecal occult blood tests were examined. Six kinds of toilet sanitizers and 19 kinds of detergents were included. Patients' fecal samples and hemoglobin solutions were measured by means of quantitative immunological fecal occult blood tests after being mixed with sanitizer or detergent solutions. Marked reduction in hemoglobin concentration or antigenicity was observed after the addition of sanitizers or detergents at a final concentration of 0.5 g/l. Most of these inhibitory reactions were dose dependent. In contrast with the immunological method, the chemical method using o-tolidine and guaiac were not affected by the detergents tested. In sampling feces for immunological fecal occult blood tests, contact of samples with sanitizer solutions should be avoided.
Investigation of the membrane-embedded mannitol permease of Escherichia coli (EIImtl) steady-state tryptophan fluorescence was hampered by fluorescent impurities arising from detergents and other sources during the isolation. The signals from these impurities could not be distinguished from tryptophan fluorescence on the basis of lifetimes or emission spectra. Consequently, a tryptophan-minus mutant of EIImtl, EIImtl(Trp-), was constructed to address this problem. The findings were that the fluorescent impurities, present in the detergents and/or arising from the action of the detergents on plastic vials and tubing used during the isolation procedure, accumulate in enzyme solutions to levels comparable to the signal from the tryptophan residues in the protein. The high affinity of these impurities for EIImtl makes them impossible to remove by dialysis, by reconstitution of the protein with pure phospholipids, or by detergent exchange when the protein is immobilized on a resin. A procedure was developed to completely remove all fluorescent impurities from the nonionic polyethylene glycol-based detergent, decylpenta(ethylene glycol) (C10E5). This detergent and modified isolation procedures yield EIImtl(Trp-) and single tryptophan mutants in which the impurities no longer interfere with the tryptophan emission signal. The methodologies presented in this paper might make it possible to study the fluorescence of tryptophan residues in other membrane proteins without the interference of impurities with similar fluorescence properties.
The mechanisms governing the interaction of equimolecular mixtures of Triton X-100 (Tx-100) and sodium dodecyl sulfate (SDS) with phosphatidylcholine liposomes were investigated. Permeability alterations were determined as a change in 5(6)-carboxyfluorescein released from the interior of vesicles and bilayer solubilization as a decrease in the static light-scattered by liposome suspensions. At subsolubilizing level, a maximum bilayer/water partitioning of surfactant mixture was reached at 30% CF release, which correlated with the increased presence of SDS in the bilayers. However, transition stages between 70% CF release and 100% light-scattering corresponded to the increased presence of Tx-100 in these structures. These findings may be correlated with the reduced deleterious effects caused by this mixture in different tissues versus pure SDS, given that the presence of Tx-100 may modulate the level of SDS partitioning in the human stratum corneum. At subsolubilizing level, the mixture showed higher affinity with bilayers than those reported for single components, whereas at solubilizing level this affinity was slightly lower and higher than those reported for Tx-100 and SDS respectively. A direct relationship was established in the initial interaction steps between the growth of vesicles, the leakage of entrapped CF and the effective molar ratio of surfactant to phospholipid in bilayers (Re). This dependence was also detected during solubilization, where the decrease in the vesicle size and in the scattered light of the system depended on the Re parameter and hence on the bilayer composition. The fact that the free surfactant concentration at subsolubilizing and solubilizing levels showed respectively lower and similar values than the critical micelle concentration (c.m.c.) of the surfactant mixture indicates that permeability alterations and solubilization were determined respectively by the action of surfactant monomer and by the formation of mixed micelles. This finding supports the generally admitted assumption, for single surfactants, that the concentration of free surfactant must reach the c.m.c. for solubilization to occur and highlights the influence of the negative synergism of this surfactant mixture on the free surfactant concentration needed to saturate or solubilize liposomes.