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PubMed2002

Stimulation and inhibition of fibril formation by a peptide in the presence of different concentrations of SDS.

Sodium dodecyl sulphate (SDS), a detergent that mimics some characteristics of biological membranes, has been found to affect significantly fibril formation by a peptide from human complement receptor 1. In aqueous solution the peptide is unfolded but slowly aggregates to form fibrils. In sub-micellar concentrations of SDS the peptide is initially alpha-helical but converts rapidly to a beta-sheet structure and large quantities of fibrils form. In SDS above the critical micellar concentration the peptide adopts a stable alpha-helical structure and no fibrils are observed. These findings demonstrate the sensitivity of fibril formation to solution conditions and suggest a possible role for membrane components in amyloid fibril formation in living systems.

Circular Dichroism↗
PubMed2003

Effects of salinity, pH and temperature on the re-establishment of bioluminescence and copper or SDS toxicity in the marine dinoflagellate Pyrocystis lunula using bioluminescence as an endpoint.

Pyrocystis lunula is a unicellular, marine, photoautotrophic, bioluminescent dinoflagellate. This organism is used in the Lumitox bioassay with inhibition of bioluminescence re-establishment as the endpoint. Experiments determined if acute changes in pH, salinity, or temperature had an effect on the organisms' ability to re-establish bioluminescence, or on the bioassay's potential to detect sodium dodecyl sulfate (SDS) and copper toxicity. The re-establishment of bioluminescence itself was not very sensitive to changes in pH within the pH 6-10 range, though reducing pH from 8 to levels below 6 decreased this capacity. Increasing the pH had little effect on Cu or SDS toxicity, but decreasing the pH below 7 virtually eliminated the toxicity of either compound in the bioassay. Lowering the salinity from 33 to 27 per thousandth or less resulted in a substantial decrease in re-establishment of bioluminescence, while increasing the salinity to 43 or 48 per thousandth resulted in a small decline. Salinity had little influence on the bioassay's quantification of Cu toxicity, while the data showed a weak negative relationship between SDS toxicity and salinity. Re-establishment of bioluminescence showed a direct dependence on temperature, but only at 10 degrees C did temperature have an obvious effect on the toxicity of Cu in this bioassay.

Animals↗
PubMed2002

Regional cerebral blood flow in deficit/nondeficit types of schizophrenia according to SDS criteria.

A relationship between "hypofrontality" and a negative form of schizophrenia is commonly found. The Schedule for the Deficit Syndrome (SDS) provides specific criteria for assessing the presence of negative symptoms, their duration and whether the symptoms are primary or secondary. The purpose of our study was to compare the regional cerebral blood flow (rCBF) at rest, in 62 deficit and nondeficit schizophrenic patients, according to the SDS criteria (French version). The deficit patients in our population were comparable to those described in the literature (stability of their negative symptoms with time, poor premorbid adjustment, duration of the illness, age at the first episode, etc.). No difference was found in the locoregional perfusion with respect to the DSM-III-R type of schizophrenia, the sex or the type of treatment received. The patients with a deficit form of schizophrenia showed a significant bilateral reduction in single photon emission computed tomography (SPECT) perfusion in the right frontodorsolateral cortex (P=.0105) and the left frontodorsolateral cortex (P=.0004) compared with the nondeficit schizophrenic patients. The contribution of SDS seems to be helpful in distinguishing between significant cerebral characteristics in deficit schizophrenics, as defined by Carpenter. These results suggest a decrease in prefrontal perfusion at rest, which corresponds with neuropsychological data.

Adult↗
PubMed1999

Acid-base properties and solubility of pindolol, diazepam and chlordiazepoxide in SDS micelles.

The effect of sodium dodecyl sulphate (SDS) on the acid-base properties and on the solubility of a beta-blocker (pindolol) and of two benzodiazepines (diazepam and chlordiazepoxide) has been assessed. The study was performed by potentiometric and spectrophotometric determinations of the acidity constants and by spectrophotometric evaluation of the solubilities of the pharmaceutical drugs in aqueous solution and in solutions to which was added SDS with concentrations below and above the critical micelle concentration (cmc), at 25 degrees C and at an ionic strength 0.1 M (NaCl). The effect of the organized assemblies on the pKa values was quantified by the application of two theoretical models that differ in the inclusion of ionic exchange between positively charged species in solution. These models have allowed the determination of the binding constants for drug/micelle and yielded values in good agreement with those obtained by the solubility method, and in addition provide a more detailed picture of the effect of drug charge on its partition. The results can be taken to evidence different interaction modes of the drugs with the SDS micelles.

Adrenergic beta-Antagonists↗
PubMed1990

Comparison of SDS-PAGE protein patterns with other typing methods for investigating the epidemiology of 'Klebsiella aerogenes'.

Twenty-four cultures comprising 20 clinical isolates of 'Klebsiella aerogenes' from two hospitals, a reference strain of 'K. aerogenes' and the type strains of three other Klebsiella species, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into 12 protein types. Comparison with established typing methods indicated that the level of discrimination of SDS-PAGE was similar to that achieved with conventional typing methods but the strains were grouped differently. Protein typing subdivided five serotype K3 isolates that could also be distinguished by phage typing. Conversely, three strains of protein type 11 were clearly distinguishable by both serotyping and phage typing. We conclude that high-resolution SDS-PAGE of proteins provides an effective adjunct to other methods for typing isolates of 'K. aerogenes'.

Bacterial Proteins↗
PubMed1990

Numerical analysis of SDS-PAGE protein patterns of Serratia marcescens: a comparison with other typing methods.

Twenty-five cultures comprising 18 clinical isolates of Serratia marcescens from two hospitals, the type strain of S. marcescens, two reference strains of S. marinorubra, the type or a reference strain of three other Serratia species and a reference strain of undetermined species, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into eight protein types. Comparison with O-serotyping indicated that the level of discrimination by SDS-PAGE was similar. As with O-serotyping, a secondary scheme, such as phage typing, is necessary to differentiate strains of the same protein type. We conclude that high-resolution SDS-PAGE of proteins provides an effective adjunct to other methods for typing isolates of S. marcescens.

Bacterial Proteins↗
PubMed1990

Investigation of a pseudo-outbreak of 'Pseudomonas thomasii' in a special-care baby unit by numerical analysis of SDS-PAGE protein patterns.

Forty-two cultures of pseudomonas comprising 28 clinical isolates from a pseudo-outbreak on a Special-Care Baby Unit and 14 reference strains, including 9 type strains, of various Pseudomonas species, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis for a numerical analysis which divided the strains into 9 phenons. Two of the 28 clinical isolates were identified by biochemical tests as P. pickettii and their identification was confirmed by SDS-PAGE as they fell in the same phenon as the type strain of the species. The remaining 26 isolates, which could not be identified on phenotypic tests, fell in the same phenon as three reference strains of 'P. thomasii'. The protein patterns provided the first clear evidence that P. pickettii and 'P. thomasii' were separate taxa and that the 'outbreak' was polymicrobial in origin, in line with the probable aqueous source of contamination. We conclude that high-resolution SDS-PAGE of proteins provides an effective method of identifying and differentiating pseudomonads, especially where this cannot be done adequately using conventional biochemical tests.

Bacterial Proteins↗
PubMed1996

Characterization of SDS--PAGE-separated proteins by matrix-assisted laser desorption/ionization mass spectrometry.

A new strategy to characterize SDS--PAGE-separated proteins with MALDI MS is described. The proteins, electroblotted onto nitrocellulose after SDS--PAGE separation and stained with reversible Ponceau S dye, are readily recovered by dissolving the membrane in matrix solutions prepared with acetone. The resulting mixtures are amenable to direct MALDI MS analysis, which provides a rapid and accurate means of measuring the molecular weights of SDS--PAGE-separated proteins and of peptides that result from CNBr digestion of proteins on the nitrocellulose membrane. Compared with the traditional elution method, this procedure provides more efficient detection of proteins and peptides, especially the higher molecular weight proteins from the membrane. As little as 3.5 pmol of lysozyme and 15 pmol of bovine albumin loaded onto a gel can be detected using this method. The detection sensitivity is higher than or comparable to that of the traditional Coomassie Brilliant Blue staining procedure.

Electrophoresis, Polyacrylamide Gel↗
PubMed2000

SDS-stable complex formation between native apolipoprotein E3 and beta-amyloid peptides.

Extracellular senile plaques composed predominantly of fibrillar amyloid-beta (Abeta) are a major neuropathological feature of Alzheimer's disease (AD). Genetic evidence and in vivo studies suggest that apolipoprotein E (apoE) may contribute to amyloid clearance and/or deposition. In vitro studies demonstrate that native apoE2 and E3 form an SDS-stable complex with Abeta(1-40), while apoE4 forms little such complex. Our current work extends these observations by presenting evidence that apoE3 also binds to Abeta(1-42) and with less avidity to modified species of the peptide found in senile plaque cores. These modified peptides include a form that originates at residue 3-Glu as pyroglutamyl and another with isomerization at the 1-Asp and 7-Asp positions. In addition, we used binding reactions between apoE3 and various Abeta fragments, as well as binding reactions with apoE3 and Abeta(1-40) plus Abeta fragments as competitors, to identify the domain(s) of Abeta involved in the formation of an SDS-stable complex with apoE3. Residues 13-28 of Abeta appear to be necessary, while complex formation is further enhanced by the presence of residues at the C-terminus of the peptide. These results contribute to our understanding of the biochemical basis for the SDS-stable apoE3/Abeta complex and support the hypothesis that Abeta can be transported in vivo complexed with apoE. This complex may then be cleared from the interstitial space by apoE receptors in the brain or become part of an extracellular amyloid deposit.

Amino Acid Substitution↗
PubMed2005

Toward defining the human parotid gland salivary proteome and peptidome: identification and characterization using 2D SDS-PAGE, ultrafiltration, HPLC, and mass spectrometry.

Saliva plays many biological roles, from lubrication and digestion to regulating bacterial and leukocyte adhesion. To understand the functions of individual components and families of molecules, it is important to identify as many salivary proteins as possible. Toward this goal, we used a proteomic approach as the first step in a global analysis of this important body fluid. We collected parotid saliva as the ductal secretion from three human donors and separated the protein components by two-dimensional SDS-polyacrylamide gel electrophoresis (2D SDS-PAGE). Proteins in gel spots were identified by peptide mass fingerprinting, and the results were confirmed by tandem mass spectrometry of selected peptides. Complementing this approach we used ultrafiltration to prepare a low-molecular-weight fraction of parotid saliva, which was analyzed directly or after reversed phase high-performance liquid chromatography separation by using mass spectrometric approaches. MS analyses of 2D SDS-PAGE spots revealed known components of saliva, including cystatins, histatins, lysozyme, and isoforms and/or fragments of alpha-amylase, albumin, and proline-rich proteins. We also discovered novel proteins, such as several isoforms of Zn-alpha-2-glycoprotein and secretory actin-binding protein. MS analyses of the ultrafiltrate showed that the low-molecular-weight fraction of parotid saliva was peptide-rich, with novel fragments of proline-rich proteins and histatins in abundance. Experiments using Candida albicans as the test organism showed that at least one of the novel peptides had antifungal activity. Our results show that saliva is a rich source of proteins and peptides that are potential diagnostic and therapeutic targets.

Adult↗
PubMed2006

Conformational properties of the SDS-bound state of alpha-synuclein probed by limited proteolysis: unexpected rigidity of the acidic C-terminal tail.

Alpha-synuclein (alpha-syn) is a "natively unfolded" protein constituting the major component of intracellular inclusions in several neurodegenerative disorders. Here, we describe proteolysis experiments conducted on human alpha-syn in the presence of SDS micelles. Our aim was to unravel molecular features of micelle-bound alpha-syn using the limited proteolysis approach. The nonspecific proteases thermolysin and proteinase K, as well as the Glu-specific V8-protease, were used as proteolytic probes. While alpha-syn at neutral pH is easily degraded to a variety of relatively small fragments, in the presence of 10 mM SDS the proteolysis of the protein is rather selective. Complementary fragments 1-111 and 112-140, 1-113 and 114-140, and 1-123 and 124-140 are obtained when thermolysin, proteinase K, and V8 protease, respectively, are used. These results are in line with a conformational model of alpha-syn in which it acquires a folded helical structure in the N-terminal region in its membrane-bound state. At the same time, they indicate that the C-terminal portion of the molecule is rather rigid, as seen in its relative resistance to extensive proteolytic degradation. It is likely that, under the specific experimental conditions of proteolysis in the presence of SDS, the negatively charged C-terminal region can be rigidified by binding a calcium ion, as shown before with intact alpha-syn. In this study, some evidence of calcium binding properties of isolated C-terminal fragments 112-140, 114-140, and 124-140 was obtained by mass spectrometry measurements, since molecular masses for calcium-loaded fragments were obtained. Our results indicate that the C-terminal portion of the membrane-bound alpha-syn is quite rigid and structured, at variance from current models of the membrane-bound protein deduced mostly from NMR. Considering that the aggregation process of alpha-syn is modulated by its C-terminal tail, the results of this study may provide useful insights into the behavior of alpha-syn in a membrane-mimetic environment.

Amino Acid Sequence↗
PubMed2001

Use of SDS micelles to stabilize a ternary intermediate in the reaction of ferrioxamine B and 1,10-phenanthroline.

Spectrophotometric measurements of the reaction of ferrioxamine B (FeHDFB(+)) with 1,10-phenanthroline (phen) reveal the presence of a ternary intermediate complex in both aqueous solution and an aqueous solution of 0.16 M sodium dodecyl sulfate (SDS). The stoichiometry of the intermediate is Fe(H(2)DFB)(phen)(2+) on the basis of a Schwarzenbach analysis of spectrophotometric data obtained at variable pH and phen concentrations. The ternary complex formation constant for the reaction FeHDFB(+) + H(+) + phen right arrow over left arrow Fe(H(2)DFB)(phen)(2+) is log K = 6.96 in aqueous solution and log K = 8.64 in aqueous 0.16 M SDS. The enhanced stability of Fe(H(2)DFB)(phen)(2+) in micellar solution was analyzed in terms of the pseudophase ion-exchange (PPIE) model of micellar reactions. The association constants for the binding of each reactant to the micellar pseudophase were measured by ultrafiltration. According to PPIE model calculations, the enhanced stability of Fe(H(2)DFB)(phen)(2+) in micellar SDS arises from a proximity effect created by the high local concentrations of reactants in the micellar pseudophase. The calculations also indicate that an inhibitory medium or compartmentalization effect is operative since the observed micellar enhancement is much smaller than predicted by the PPIE model. The micellar stabilization of the Fe(H(2)DFB)(phen)(2+) intermediate and the overall conversion of FeHDFB(+) to Fe(phen)(3)(2+) are discussed as a possible model system for siderophore iron release in microbial organisms.

Cell Membrane↗
PubMed2005

Shape and position of 4-aminophthalimide (4-AP) time-resolved emission spectra (TRES) versus sodium dodecyl sulfate sds concentration in micellar solutions: the partitioning of 4-AP in the micellar phase and in water surrounding the micelles.

Time-resolved emission spectra (TRES) of 4-aminophthalimide (4-AP) dissolved in water solutions of sodium dodecyl sulfate (SDS) for three surfactant concentrations (0.05, 0.15, and 0.45 M) have been determined. The fraction of 4-AP dissolved in the water phase surrounding the micelles has been shown to increase with decreasing concentration of the surfactant. To obtain TRES of 4-AP present exclusively in micelles, a method of subtraction of the contribution of the emission originating from 4-AP present in the water phase surrounding the micelles from the total emission of the probe dissolved in SDS solution has been proposed. The consequences of failing to take into account the partitioning of 4-AP between the water and micellar phases are illustrated by some exemplary TRES results, taken before and after the subtraction of the emission originating from 4-AP present in the water phase. Together with the time of appearance and presence of isoemissive points in the time-resolved area-normalized emission spectra (TRANES), these results have shown a clear dependence of the rate and character of the 4-AP TRES changes on the SDS concentration. In connection with our earlier results and literature data, it has been concluded that the concentration of the water solubilized in micelles is the main factor determining the rate and character of these changes.

Chemical Phenomena↗
PubMed2006

Effect of added poly(oxyethylene)dodecyl ether on the phase and rheological behavior of wormlike micelles in aqueous SDS solutions.

Upon the addition of a short EO chain nonionic surfactant, poly(oxyethylene) dodecyl ether (C12EOn), to dilute micellar solution of sodium dodecyl sulfate (SDS) above a particular concentration, a sharp increase in viscosity occurs and a highly viscoelastic micellar solution is formed. The oscillatory-shear rheological behavior of the viscoselastic solutions can be described by the Maxwell model at low shear frequency and combined Maxwell-Rouse model at high shear frequency. This property is typical of wormlike micelles entangled to form a transient network. It is found that when C12EO4 in the mixed system is replaced by C12EO3 the micellar growth occurs more effectively. However, with the further decrease in EO chain length, phase separation occurs before a viscoelastic solution is formed. As a result, the maximum zero-shear viscosity is observed at an appropriate mixing fraction of surfactant in the SDS-C12EO3 system. We also investigated the micellar growth in the mixed surfactant systems by means of small-angle X-ray scattering (SAXS). It was found from the SAXS data that the one-dimensional growth of micelles was obtained in all the SDS-C12EOn (n=0-4) aqueous solutions. In a short EO chain C12EOn system, the micelles grow faster at a low mixing fraction of nonionic surfactant.

Journal Article↗
PubMed2005

Mixed micelles formed by SDS and a bolaamphiphile with carbohydrate headgroups.

The formation of micelles in aqueous mixtures of a carbohydrate-based bolaamphiphile and sodium dodecyl sulfate (SDS) is investigated by surface tension and small-angle neutron scattering. The obtained values of critical micelle concentration (CMC) are analyzed within the framework of regular solution theory. Synergetic interactions between the bolaamphiphile and SDS are observed (parameter beta is negative; a minimum in the plot CMC vs composition). SANS data are collected for mixtures containing protonated and deuterated SDS. This gives us the possibility to conclude that mixed micelles with a homogeneous distribution of surfactant molecules within the micelle are formed. The shape of the micelles is found to be slightly oblate.

Journal Article↗
PubMed2006

On-line concentration of microheterogeneous proteins by capillary electrophoresis using SDS and PEO as additives.

In this paper, we describe a method for analyzing large-volume protein samples using capillary electrophoresis in conjunction with laser-induced fluorescence detection (CE-LIF). To improve the stacking and separation efficiencies of proteins, we added either 0.01% sodium dodecyl sulfate (SDS) or 0.01% poly(ethylene oxide) (PEO) to the Tris-borate solutions (pH 10.0) used to prepare the protein samples. After injection of the large-volume samples (ca. 1.0 microL, 0.1 microM), the proteins migrate against the electroosmotic flow (EOF) and enter the PEO zone; this process causes them to slow and stack at the boundary between the PEO and sample zones. As a result, the limits of detection (LODs) at a signal-to-noise (S/N) of 3 for most proteins are sub-nM to several nM. For instance, the LOD (S/N = 3) for alpha-lactalbumin is 0.48 nM, which is an 84-fold sensitivity enhancement over the traditional method. By applying a short plug of 0.2% SDS prior to sample injection, a greater number of peaks, representing the microheterogeneity of the proteins, were resolved and the stacking efficiency of the proteins increased slightly. This method allowed us to detect 12 peaks when injecting a large volume of sample containing six model proteins (0.1 microM). We also analyzed the microheterogeneities of the proteins by using CE with UV-Vis absorption detection when injecting a large volume of sample containing six model proteins (1.0 microM) in the presence of a 1.0% SDS plug. The practical method is validated by the detection of human serum albumin in a urine sample, obtained from a healthy female, without sample pretreatment; its concentration was 0.18 microM. We further demonstrate the capability of this method to detect low amounts of proteins through the detection of 45 nM hemoglobin after injecting ca. 1.0 microL of ultradilute lysed red blood cells. The experimental results indicate that our proposed method has great potential for use in diagnosis and proteomics applications.

Electrophoresis, Capillary↗
PubMed2005

Study of the adsorption of sodium dodecyl sulfate (SDS) at the air/water interface: targeting the sulfate headgroup using vibrational sum frequency spectroscopy.

The surface sensitive technique vibrational sum frequency spectroscopy (VSFS), has been used to study the adsorption behaviour of SDS to the liquid/vapour interface of aqueous solutions, specifically targeting the sulfate headgroup stretches. In the spectral region extending from 980 to 1850 cm(-1), only the vibrations due to the SO(3) group were detectable. The fitted amplitudes for the symmetric SO(3) stretch observed at 1070 cm(-1) for the polarization combinations ssp and ppp, were seen to follow the adsorption isotherm calculated from surface tension measurements. The orientation of the sulfate headgroup in the concentration range spanning from 1.0 mM to above the critical micellar concentration (c.m.c.) was observed to remain constant within experimental error, with the pseudo-C(3) axis close to the surface normal. Furthermore, the effect of increasing amounts of sodium chloride at SDS concentrations above c.m.c. was also studied, showing an increase of approximately 12% in the fitted amplitude for the symmetric SO(3) stretch when increasing the ionic strength from 0 to 300 mM NaCl. Interestingly, the orientation of the SDS headgroup was also observed to remain constant within this concentration range and identical to the case without NaCl.

Adsorption↗
PubMed2000

Improvement of Staphylococcus aureus-V8-protease hydrolysis of bovine haemoglobin by its adsorption on to a solid phase in the presence of SDS: peptide mapping and obtention of two haemopoietic peptides.

Hydrolysis of bovine haemoglobin by the V8 protease from Staphylococcus aureus (EC 3.4.21.19) was studied in the presence of SDS in a homogeneous-phase and in a solid-phase system. In both cases, hydrolyses were performed at 37 degrees C, in 50 mM phosphate buffer, pH 6.0, containing 0.1% SDS. Solid-phase hydrolyses were carried out with haemoglobin adsorbed on a negatively charged hydrophobic support, namely Amberlyst 15Wet (Rohm and Haas). The peptides were isolated from the hydrolysates by reverse-phase HPLC and analysed for their amino acid composition on a Waters Pico-Tag column, confirmed by second-order derivative spectrometry or by MS. A peptide map of the hydrolysates was drawn up, and numerous new cleavages in haemoglobin chains were observed, especially after Asp. This study showed that SDS permitted a dramatic improvement in the hydrolysis of whole haemoglobin by V8 protease in both homogeneous-phase and solid phase systems after adsorption of haemoglobin on to an anionic support. Moreover, in the heterogeneous phase, all the theoretical cleavage sites of V8 protease, Asp as well as Glu bonds, were hydrolysed, except for four sites which were resistant owing to strong interactions with the support. These results led to us obtain two haemopoietic peptides, namely peptide alpha (Leu(76)-Pro-Gly-Ala-Leu-Ser-Glu(82)) and peptide beta (Lys(94)-Leu-His-Val-Asp-Pro-Glu(100)). These active peptides have never before been prepared from bovine haemoglobin, and they may have great potentialities in biotechnology.

Adsorption↗