Action Of Sodium Dodecyl Sulfate Research Articles

Improvement in the thermal conductivity and stability of rare-earth metal oxide nanofluids using the stabilizing action of nano CaCO3 in comparison with the stabilizing action of sodium dodecyl sulphate

The stabilizing action of inorganic CaCO3 nanoparticles to increase the thermal conductivity of nanofluids containing nanoparticles of yttrium oxide (Y2O3), zirconium oxide (ZrO2), and yttria-stabilized zirconia (YSZ) prepared from their respective micron size metal oxide precursor through gel combustion method is reported in this work. The nanoparticles obtained through the gel-combustion method after calcination yield nano-size rare earth metal oxide particles. The morphology and composition of the constituents’ nanoparticles thus prepared were explored through XRD, FESEM with EDX, and elemental mapping analysis to confirm the purity and the particle sizes. Thermal conductivities of the nanofluids prepared using the above-mentioned nanoparticles were found to be superior to that of the base fluid, but their stabilities were lesser. Commercially available stabilizers like sodium dodecyl sulphate (SDS) were used to improve the stability but their addition reduces the thermal conductivity of the nanofluids. The nano-CaCO3 particle as a stabilizer provides better stability than SDS was reported. The stability of all the nanofluids was evaluated through the results obtained from zeta potential measurements and the mixture with the highest stability was evaluated. Based on the visual inspection and through UV–vis spectral measurements, the settling ability of the nanoparticles present in the nanofluid was also evaluated. Remarkably, Y2O3 + CaCO3 suspended nanofluid exhibits a commendable thermal conductivity of 29.18 % higher than the base fluid. Such fluids possessing higher stability with good thermal conductivity can be effectively utilized in heat exchanger applications.

Improvement on bioleaching interfacial behavior between Bacillus mucilaginosus and vanadium-bearing shale by surfactant additive

Effects of surfactant SDS (Sodium Dodecyl Sulfate) on bacterial metabolism and vanadium leaching effect by Bacillus mucilaginosus (B. mucilaginosus) were explored. The results indicated that the bacteria adsorption dissolution effect and the organic acid dissolution effect could extract 29.12% and 35.21% of vanadium, respectively, which were 9.70% and 6.27% higher than those without SDS. SDS significantly enhanced the bacteria adsorption dissolution effect and the organic acid dissolution effect of B. mucilaginosus on vanadium-bearing shale, and the bacteria adsorption dissolution effect to improve the vanadium leaching efficiency was more remarkable. When the bioleaching time began to enter the bacteria stable growth phase and the stable pH phase, the EPS (Extracellular Polymeric Substances) concentration decreased by 73.1 mg/L and 68.2 mg/L under the action of SDS, respectively. However, the bacteria’s adsorbance on the mineral surface increased by 0.07 × 109 cells/mL and 0.13 × 109 cells/mL, respectively. The improvement on the bacteria adsorption dissolution effect with SDS was then revealed. SDS decreased the secretion of EPS, reduced the bacterial agglomeration, increased the adsorption capacity of bacteria, and thereby strengthened the dissolution effect. Furthermore, it was found that the H+ concentration in the leachate increased by 1.36 × 10−5 mol/L and 4.33 × 10−5 mol/L, respectively. The enhancement on the organic acid dissolution effect with SDS was also achieved. The increase of the organic carboxylic acid metabolites was beneficial to further remove the hydroxyl groups in the vanadium-bearing muscovite crystal lattice, and strengthen the destruction of the basic structure of silicon-oxygen tetrahedron and aluminum-oxygen octahedron, resulting in the release of vanadium.

Extraction of High-Purity Native State Gutta-Percha from Enzymatic Hydrolyzed Eucommia ulmoides Pericarps by Ultrasound Treatment and Surfactant Aqueous Phase Dispersion

Herein, a method of ultrasound treatment combined with surfactant aqueous phase dispersion was proposed for the extraction of high-purity gutta-percha in its native state from enzymatic hydrolyzed Eucommia ulmoides pericarps. Firstly, the plant tissues wrapped around gutta-percha were destructed through enzymatic hydrolysis, then the plant tissues debris still attached to gutta-percha were further stripped off by ultrasound. Finally, under the “amphiphilic” action of sodium dodecyl sulfate (SDS), the entangled gutta-percha was untwined, allowing the residual plant tissue debris to be released and precipitated, thus high purity gutta-percha was obtained. The process parameters were optimized through single factor and response surface experiments. The optimal parameters for ultrasonic treatment were displayed as follows: frequency of 40 kHz, power of 320 W, time of 7.3 h, temperature of 50 °C, and material-to-liquid ratio of 1:70 g/mL, and for the aqueous phase dispersion of surfactant were SDS concentration 1.7%, temperature 80 °C, stirring speed 1200 rpm, solid-to-liquid ratio 1:60 g/mL, and time 60 h. Under optimal conditions, the purity of gutta-percha reached 95.4 ± 0.31% and its weight average molecular weight (Mw) was 20.85 × 104. Moreover, the obtained gutta-percha maintained its native filamentous form. The obtained products were characterized by IR, NMR, XRD, TGA, DSC, and tensile experiments, which showed that the obtained product was gutta-percha and maintained the natural α- and β- crystal structure. The proposed method overcomes the disadvantages of the traditional organic solvent method, which has great environmental pollution and destroys the gutta-percha structure. This is also the first reported method to obtain high purity gutta-percha while maintaining its native state.

Combined Action of Sodium Dodecyl Sulfate, Tween-85 and Oil on Duckweed (Lemna Minor)

Surfactants (surfactants) are found in large quantities in industrial and domestic wastewater. Along with them, there are also oil products. In a certain concentration, they have a depressing effect on aquatic organisms. In recent decades, along with physicochemical methods for assessing the quality of water bodies, biodiagnostics - biotesting and bioindication - has been actively used. Depending on a number of factors, the effect of the combined action of substances on the test organism can be additive, antagonistic, or synergistic. Biotesting in combination with a multifactorial experiment makes it possible to identify the final effect and the nature of the combined toxic effect of pollutants. The study investigated the isolated and combined effect of oil and some surfactants on the duckweed. The criterion for the influence of pollutants was the growth dynamics of fronds of this aquatic plant. During biotesting, the most widely used anionic detergent, sodium dodecyl sulfate (SDS), was used. In addition, we studied the effect of the nonionic surfactant Tween-85 on this test object. The toxicity of the effect of certain substances on the duckweed was assessed, and this made it possible to calculate the concentrations that cause a certain toxic effect. Then a full two-factor experiment was carried out with the combined action of two pairs of substances: oil - SDS, oil - Tween-85. Regression equations for two pairs of substances are compiled. The action of the investigated compounds is interdependent. The nature of the combined toxic effect turned out to be less than additive.

Curing of some Antibiotic Resistance by the Action of Sodium Dodecyl Sulphate and Ethidium bromide in Pseudomonas aeruginosa Isolated from urine of human, cow meat and horses wound

Thirty seven isolates of Pseudomonas aeruginosa Twenty-two isolates were collected from urine in Al-Diywania teaching hospital, eleven isolates from cow meat and four isolates from wound horses. They were identified using the Vitek 2, for detecting characteristics of the biochemical tests and morphological appearance. All isolates resisted to Nalidixic acid, Oxacillin ,Vancomycin, Ampicillin, and Ciprofloxacin , while show sensitive to Kanamycin and Tetracycline. The minimum inhibitory concentrations (MICs) of two curing agents, sodium dodecyl sulphate (SDS) and ethidium bromide, used in this study were determined and the results indicated that the curing percentage and efficiency of each curing agent was determined. From treatment with 700 μg/ml ethidium bromide, it was observed that no cured cells were obtained for all antibiotics used and obtained for all antibiotics used by SDS at a concentration of (1, 0.9, 0.8)% (W/V) where had no effect on plasmid curing and bacterial cells complete lysis, the isolates appeared sensitive to (0.5,0.6 and 0.7)% concentration of SDS were Nalidixic acid 10mg was (35.1, 94.5 and 100) %, Vancomycin 30mg ( 59.4, 86.4 and 100) %, Kanamycin 30mg was (97.2, 100,100)% and Tetracycline 30mg was (75.6, 100 and 100)% respectively , no there sensitivity for each Oxacillin 30mg , Ciprofloxacin 5mg and Ampicillin 10mg.

Draft Genome Sequence of the Deep-Sea Bacterium Moritella sp. JT01 and Identification of Biotechnologically Relevant Genes.

Deep-sea bacteria can produce various biotechnologically relevant enzymes due to their adaptations to high pressures and low temperatures. To identify such enzymes, we have sequenced the genome of the polycaprolactone-degrading bacterium Moritella sp. JT01, isolated from sediment samples from Japan Trench (6957m depth), using a Illumina HiSeq2000 sequencer (12.1 million paired-end reads) and CLC Genomics Workbench (version 6.5.1) for the assembly, resulting in a 4.83-Mb genome (42 scaffolds). The genome was annotated using Rapid Annotation using Subsystem Technology (RAST), Protein Homology/analogY Recognition Engine V 2.0 (PHYRE2), and BLAST2Go, revealing 4439 protein coding sequences and 101 RNAs. Gene products with industrial relevance, such as lipases (three) and esterases (four), were identified and are related to bacterium's ability to degrade polycaprolactone. The annotation revealed proteins related to deep-sea survival, such as cold-shock proteins (six) and desaturases (three). The presence of secondary metabolite biosynthetic gene clusters suggests that this bacterium could produce nonribosomal peptides, polyunsaturated fatty acids, and bacteriocins. To demonstrate the potential of this genome, a lipase was cloned an introduced into Escherichia coli. The lipase was purified and characterized, showing activity over a wide temperature range (over 50% at 20-60°C) and pH range (over 80% at pH6.3 to 9). This enzyme has tolerance to the surfactant action of sodium dodecyl sulfate and shows 30% increased activity when subjected to a working pressure of 200MPa. The genomic characterization of Moritella sp. JT01 reveals traits associated with survival in the deep-sea and their potential uses in biotechnology, as exemplified by the characterized lipase.

Processability and mechanical properties of bioplastics produced from decoloured bloodmeal

AbstractBloodmeal is a protein‐rich coproduct of the meat industry and can be converted into a thermoplastic. A solution of peracetic acid can be used to degrade colored compounds in bloodmeal, yielding a light yellow material. This causes an increase in β‐sheets in the protein's secondary structure, but the addition of sodium dodecyl sulfate (SDS) and triethylene glycol (TEG) reduced α‐helical and β‐sheet content, thereby increasing random coils. Without SDS, chains were less capable of folding into these structures, preventing sufficient intermolecular interactions and chain entanglement, leading to low specific mechanical energy input (SME) during extrusion, and poor consolidation. The whiteness of molded samples showed no correlation with SME during extrusion or the degree of consolidation after extrusion; however, they were observed to have a higher level of whiteness with increasing TEG content and should be considered as a secondary process not directly linked to extrusion. Increasing the amount of water during extrusion increased the Young's modulus (E) by facilitating formation of new interactions, while increasing TEG decreased E as a result of plasticization. The action of SDS on destabilizing electrostatic and hydrophobic interactions was beneficial to extrusion, although it had no further effect during injection molding. TEG had virtually no effect on tensile strength, although it was required for flow and facilitated the formation of strong interactions after water had been evaporated during conditioning.

STATE OF THE ANTIOXIDANT SYSTEM OF RAPANA VENOSA (VALENCIENNES, 1846) UNDER ACTION OF ANIONIC DETERGENT

The antioxidant system in the ctenidium, hepatopancreas and nephridia of gastropod Rapana venosa under stress caused by an anionic detergent – sodium dodecyl sulfate were studied. The experimental animals were kept for 3, 24 and 72 hours in aquariums with sea water with addition of sodium dodecyl sulfate in concentration of 5 and 20, the maximum permissible concentration (MPC). We determined the total antioxidant activity (TAA) and the content of reduced glutathione (GSH). The degree of oxidative damage to biopolymers was evaluated by the level of malondialdehyde (MDA). It was shown that the MDA content under the action of sodium dodecyl sulfate increased only in ctenidium after 72 hours from the start of the experiment. The index remained unchanged in the hepatopancreas and nephridia. The level of GSH in the shellfish ctenidium increased in presence of sodium dodecyl sulfate in all periods of observation. The hepatopancreas GSH level was not changed, and in nephridia GSH level increased only after three days of observation. TAA decreased in the ctenidium within the first 3 hours of observation, and in hepatopancreas and nephridia only after 72 hours at the maximum concentration of the detergent. In the other terms of the experiment at all concentrations of sodium dodecyl sulfate TAA in the tested bodies remained at the control level. It is concluded that the antioxidant system is resistant to sodium dodecyl sulfate and has a great adaptive capacity.

Impact of sodium dodecyl sulphate on the dissolution of poorly soluble drug into biorelevant medium from drug-surfactant discs

The purpose was to elucidate the mechanism of action of sodium dodecyl sulphate (SDS) on drug dissolution from discs under physiologically relevant conditions. The effect of incorporating SDS (4-30%, w/w) and drug into discs on the dissolution constant and solubility were evaluated for the poorly soluble drugs griseofulvin and felodipine in a biorelevant dissolution medium (BDM). Dissolution constants from dissolution profiles of drug discs with and without SDS were measured using miniaturized rotating disc dissolution. Solid state changes were investigated by X-ray diffraction. Solubility was determined using HPLC-UV. The interaction between micelles in BDM and SDS was investigated by isothermal titration calorimetry and dynamic light scattering. Isothermal titration calorimetry showed that SDS formed mixed micelles with bile salt:phospholipid (BS:PC) micelles in BDM. Dynamic light scattering showed that the addition of SDS made the BS:PC micelles grow up to 2.5 times in volume. As a function of SDS addition, the dissolution constant showed an apparent exponential increase, while drug solubility showed a weak linear dependence. The pronounced effect on dissolution constant with SDS in the discs is not caused by an increased surface area as SDS dissolves, micelles in the bulk medium or changes in the solid state properties of the drugs. The proposed mechanism involves a high local concentration of SDS at the solid-liquid interface as SDS dissolves and this solubilizes the drug. The improved solubility at the solid-liquid interface provided a much steeper concentration gradient resulted in a faster dissolution. The total amount of SDS in the discs only gave a minor increase in total surfactant concentration in the dissolution medium and did therefore not to any large extent affect the drug solubility in the bulk.

Rotational diffusion of bovine serum albumin denaturated by sodium dodecylsulfate, According to data from tryptophan fluorescence

The rotational diffusion of bovine serum albumin (BSA) molecules in solutions with different concentrations of the anionic detergent sodium dodecylsulfate (SDS) at different pH values is investigated, yielding information on the denaturation of BSA under the action of SDS. It is found from the increased degree of polarization in the tryptophan fluorescence of BSA and the registered parameters for the rotational diffusion of BSA molecules that the denaturation of BSA under the action of SDS at pH values less than the isoelectric point (pI) of BSA (4–9) is a two-stage process. It is shown that the first stage of BSA denaturation common for all pH values is the decondensation of BSA globules, while the second stage of BSA denaturation at pH greater than the pI of BSA is the unfolding of the protein’s amino acid chain. It is concluded that the denaturation of BSA under the action of SDS proceeds more deeply at pH values greater than the pI of BSA.

Polarized fluorescence in the study of rotational diffusion of human albumin during denaturation under the action of SDS

Polarized tryptophan fluorescence of human serum albumin (HSA) was analyzed to determine the parameters of rotational diffusion (rotational relaxation time, rotational diffusion coefficient, and the effective Einstein radius) of HSA molecules during denaturation under the action of sodium dodecyl sulfate (SDS). Two stages of HSA denaturation under the action of SDS were shown: (1) loosening of protein globules and (2) unfolding of the amino-acid chain of the protein. HSA denaturation under the action of SDS is a two-stage process at pH values lower than the pI of HAS but passes through stage 1 only at pH values higher than the pI.

Fluorescence of tryptophan in the denaturation of human serum albumin under the action of sodium dodecyl sulfate

Tryptophan fluorescence of human serum albumin (HSA) when sodium dodecyl sulfate (SDS) was added to a solution of the protein was studied at various pH values, which allowed us to get an idea about the mechanism of the denaturation of HSA under the action of SDS. The two-stage quenching of tryptophan fluorescence of HSA as the concentration of SDS increased was evidence of the two-stage character of denaturation. The first stage involved loosening of protein globules, and the second one was the complete uncoiling of the amino acid protein chain. At solution pH higher than the isoelectric point of the protein (pI 4.7), denaturation stopped at the first stage. At pH values below pI of the protein, the denaturation of the protein under the action of SDS was more effective and deep (involved both stages).

On the mechanism of SDS‐induced protein denaturation

To understand the mechanism of ionic detergent-induced protein denaturation, this study examines the action of sodium dodecyl sulfate on ferrocytochrome c conformation under neutral and strongly alkaline conditions. Equilibrium and stopped-flow kinetic results consistently suggest that tertiary structure unfolding in the submicellar and chain expansion in the micellar range of SDS concentrations are the two major and discrete events in the perturbation of protein structure. The nature of interaction between the detergent and the protein is predominantly hydrophobic in the submicellar and exclusively hydrophobic at micellar levels of SDS concentration. The observation that SDS also interacts with a highly denatured and negatively charged form of ferrocytochrome c suggests that the interaction is independent of structure, conformation, and ionization state of the protein. The expansion of the protein chain at micellar concentration of SDS is driven by coulombic repulsion between the protein-bound micelles, and the micelles and anionic amino acid side chains.

Mechanism of activation of cytochrome c peroxidase activity by cardiolipin

In this work, the actions of bovine heart cardiolipin, synthetic tetraoleyl cardiolipin, and a nonspecific anionic detergent sodium dodecyl sulfate (SDS) on cytochrome c (Cyt c) peroxidase activity recorded by chemiluminescence in the presence of luminol and on the Fe...S(Met80) bond whose presence was estimated by a weak absorption band amplitude with peak at 695-700 nm (A(695)) were compared. A strict concurrency between Fe...S(Met80) breaking (A(695)) and cytochrome peroxidase activity enhancement was shown to exist at cardiolipin/Cyt c and SDS/Cyt c molar ratios of 0 : 1 to 50 : 1 (by chemiluminescence). Nevertheless, when A(695) completely disappeared, Cyt c peroxidase activity under the action of cardiolipin was 20 times more than that under the action of SDS, and at low ligand/protein molar ratios (=4), SDS failed to activate peroxidase activity while cardiolipin enhanced Cyt c peroxidase activity 16-20-fold. A(695) did not change on Cyt c binding with liposomes consisting of tetraoleyl cardiolipin and phosphatidylcholine (1 : 10 : 10), while peroxidase activity was enhanced by a factor of 8. Breaking of 70% of the Fe...S(Met80) bonds resulted in only threefold enhancement of peroxidase activity. Cardiolipin-activated Cyt c peroxidase activity was reduced by high ionic strength solution (1 M KCl). The aggregated data suggest that cardiolipin activating action is caused, first, by a nonspecific effect of Fe...S(Met80) breaking as the result of conformational changes in the protein globule caused by the protein surface electrostatic recharging by an anionic amphiphilic molecule, and second, by a specific acceleration of the peroxidation reaction which is most likely due to enhanced heme accessibility for H(2)O(2) as a result of the hydrophobic interaction between cardiolipin and cytochrome.

A Lactobacillus acidophilus Strain of Human Gastrointestinal Microbiota Origin Elicits Killing of Enterovirulent Salmonella enterica Serovar Typhimurium by Triggering Lethal Bacterial Membrane Damage

The human gastrointestinal microbiota produces antagonistic activities against gastrointestinal bacterial pathogens. We undertook a study to investigate the mechanism(s) by which a Lactobacillus acidophilus strain of human microbiota origin antagonizes the gram-negative enteroinvasive pathogen Salmonella enterica serovar Typhimurium. We showed that the cell-free culture supernatant of L. acidophilus strain LB (LB-CFCS) induced the following effects in S. enterica SL1344: (i) a decrease in intracellular ATP that paralleled bacterial death, (ii) the release of lipopolysaccharide, (iii) permeabilization of the bacterial membrane, and (iv) an increase in the sensitivity of Salmonella to the lytic action of sodium dodecyl sulfate. Finally, we showed using two mutant strains of Salmonella, PhoP MS7953s and PmrA JKS1170, that the two-component regulatory systems PhoP-PhoQ and PmrA-PmrB that regulate the mechanisms of resistance to antibacterial agents in Salmonella did not influence the anti-Salmonella effect of LB-CFCS.

Lactic acid permeabilizes gram-negative bacteria by disrupting the outer membrane.

The effect of lactic acid on the outer membrane permeability of Escherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium was studied utilizing a fluorescent-probe uptake assay and sensitization to bacteriolysis. For control purposes, similar assays were performed with EDTA (a permeabilizer acting by chelation) and with hydrochloric acid, the latter at pH values corresponding to those yielded by lactic acid, and also in the presence of KCN. Already 5 mM (pH 4.0) lactic acid caused prominent permeabilization in each species, the effect in the fluorescence assay being stronger than that of EDTA or HCl. Similar results were obtained in the presence of KCN, except for P. aeruginosa, for which an increase in the effect of HCl was observed in the presence of KCN. The permeabilization by lactic and hydrochloric acid was partly abolished by MgCl(2). Lactic acid sensitized E. coli and serovar Typhimurium to the lytic action of sodium dodecyl sulfate (SDS) more efficiently than did HCl, whereas both acids sensitized P. aeruginosa to SDS and to Triton X-100. P. aeruginosa was effectively sensitized to lysozyme by lactic acid and by HCl. Considerable proportions of lipopolysaccharide were liberated from serovar Typhimurium by these acids; analysis of liberated material by electrophoresis and by fatty acid analysis showed that lactic acid was more active than EDTA or HCl in liberating lipopolysaccharide from the outer membrane. Thus, lactic acid, in addition to its antimicrobial property due to the lowering of the pH, also functions as a permeabilizer of the gram-negative bacterial outer membrane and may act as a potentiator of the effects of other antimicrobial substances.

A Novel Method for the On-Line Room-Temperature Hydrolysis of Hydrophobic Organic Phosphates Using a Cooperative Action of Sodium Dodecyl Sulfate, Acid and UV-Irradiation.

A Novel Method for the On-Line Room-Temperature Hydrolysis of Hydrophobic Organic Phosphates Using a Cooperative Action of Sodium Dodecyl Sulfate, Acid and UV-Irradiation.

Action on ileal smooth muscle of synthetic detergents and pardaxin.

Pardaxin (PX), a toxic and repellent substance isolated from the Red Sea flatfish, causes a sharp ball-like profile of drop of saline placed on a hydrophobic film to turn into a flattened one. This effect results with a decrease of the contact angle (theta) from 96 degrees to a maximum of 42 degrees at 10(-4) M of PX. The action of sodium dodecyl sulphate (SDS), a synthetic anionic detergent, benzalkonium chloride (BAC) cationic detergent and pardaxin (PX) a toxic protein with detergent properties, were studied in the ileal guinea-pig longitudinal smooth muscle preparation. SDS (4 X 10(-4) M) and PX (5 X 10(-6) M) diminished the muscle contractile response to field stimulation (0.1 Hz, 1 msec) and to acetylcholine (Ach) and to histamine and elicited a prolonged (4-6 min) TTX-insensitive muscle contraction. The dose dependence of muscle contraction to SDS and PX was found to be sigmoidal and occurred over a narrow range of concentrations. The SDS- but not PX-induced muscle contraction could be reduced by diphenhydramine (H1 antihistamine). BAC (10(-5)-10(-4) M) suppressed the muscle's contractile response to electrical stimulation (0.1 Hz, 1 msec), to Ach, histamine and 5-hydroxytryptamine but did not produce muscle contraction. PX at concentrations higher than 5 X 10(-6) M is a potent detergent and at this concentration shares several pharmacological similarities with SDS.

Stimulatory action of sodium dodecyl sulfate (SDS) on the lecithin-cholesterol acyltransferase reaction in human plasma.

Stimulatory action of sodium dodecyl sulfate (SDS) on the lecithin-cholesterol acyltransferase reaction in human plasma.

Zur Bestimmung der katalytischen Aktivität der Lipase mit 2,3-Dimercapto-1-propanol-tributyrat als Substrat

The two point test for the determination of lipase by Kurooka et al. (J. Biochem. Tokyo 81, 361-369 (1977)) was studied in detail. This procedure uses 2,3-dimercapto-1-propanol-tributyrate as substrate and Ellman's reagent as an acceptor for the released thiol groups. The time course of the enzymic hydrolysis of the substrate showed a pronounced lag phase, which can be influenced by sodium glycocholate. There is no proportionality between the quantity of added serum and the concentration of released thiol groups. Preincubation of the sample with the esterase inhibitor, phenylmethylsulphonylfluoride, as recommended by the authors, does not completely inhibit the serum esterase activity. The action of sodium dodecyl sulphate, which is included in the system, is not explained; in the continuous titrimetric test with triolein as substrate, it acts as a powerful lipase inhibitor. Using 104 serum samples, significant differences were found between the results from this method and those obtained by the titrimetric determination of lipase. Possible fundamental improvements of this test system, using thioesters as substrate, are discussed.