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In this work the behavior of NaDC as a function of solution pH in presence of Tween 40 has been studied. The pH results were modelled in terms of carboxylate soap solution theory by Lucassen and its generalized form by Kralchevsky et al. The results reveal that the composition of the NaDC solution in terms of various soaps changes as a function of Tween 40 concentration. In general, Tween 40 has almost no effect on the alkanoic acid HZ formation, but hinders the formation of acid soap (HZ)2(MZ)1 depending upon Tween 40 concentration. However, neutral soap MZ formation is favoured at very high concentrations of Tween 40. The influence of Tween 40 on the composition of NaDC solution has been attributed to the ability of the former to show enhanced hydrogen bonding. The presence of different precipitates is well correlated with the surface tension variation and micelles are formed prior to HZ precipitation. The study is expected to provide useful insights to understand the correlation between precipitation and micellization of bile salts and is expected to help in devising methods to enhance their biological functioning in presence of neutral amphiphiles like Tween 40 commonly encountered in delivery systems or food stuffs etc.

Plants of the Celastraceae family produce various dihydro- β -agarofuran sesquiterpene pyridine alkaloids. Two dihydro- β -agarofuran sesquitepene pyridine alkaloids (1,2) apart from four known compounds euojaponin C (3), wilforine (4), austronine (5) and O 9 -benzoyl- O 9 -deacetylevonine (6), were isolated from the ripe seeds of Euonymus hamiltonianus . Their chemical structures were elucidated mainly by analysis of NMR and MS spectral data. All compounds were evaluated for insecticidal activity.

Oscillating reactions often employed to mimic and understand complex dynamics in biological systems are known to be affected in aggregated host environments. The dynamic evolution of the oscillatory Belousov–Zhabotinsky (BZ) reaction upon addition of increasing amounts of anionic (sodium dodecylbenzenesulfonate; SDBS), cationic (hexadecyltrimethylammonium bromide; CTAB), nonionic (polyoxyethylene(20) cetyl ether; Brij58), and binary mixtures (CTAB + Brij58 and SDBS + Brij58) of surfactants was monitored using potentiometry at 25 and 35°C under stirred batch conditions. The experimental results reveal that the oscillatory parameters of the Ce(IV)-catalyzed BZ reaction are significantly altered depending on the concentration and nature of restricted micellar host environments. In the presence of ionic surfactants, it is proposed that the evolution of the oscillatory BZ system may be due to atypical proficiency (related to hydrophobic and electrostatic interactions) of such organized self-assemblies to affect the reactivity by selectively confiscating some key reacting species. However, the response of the BZ system to nonionic Brij58 was attributed to the reaction among the alcoholic functional groups of the surfactant with some vital species of the BZ reaction. Moreover, the nonionic + ionic binary surfactant systems exhibited behaviors representative of both the constitutive single surfactant systems.

Mixed micellization and mixed monolayer formation of two bile salts namely sodium cholate (NaC) and sodium deoxycholate (NaDC), in the presence of sodium chloride (NaCl) and three hydrophobic salts including sodium acetate (NaAc), sodium butanoate (NaBu) and sodium hexanoate (NaHx) in 10 mM phosphate buffer (pH 6.5) at 37 °C were investigated by means of surface tension measurements. The experimental results were utilized to evaluate various parameters like critical micellar concentration (CMC), micellar and monolayer interaction parameter (β and β σ), micellar and monolayer mole fractions (X and Z), activity coefficients of two bile salts in mixed micelles and monolayer (f and f (σ)), surface excess (Γmax) and minimum surface area per molecule of bile salt (A min). Mixed micelles and mixed monolayer were found to show slight non-ideality and both these phenomena have been found to be affected differently in the presence of various additive salts with NaHx showing larger effects. Higher efficiency of NaHx in affecting both phenomena has been attributed to its appreciable hydrophobicity and surface activity, thus showing stronger interactions with bile salt molecules.

Most bacterial glycoproteins identified to date are virulence factors of pathogenic bacteria, i.e. adhesins and invasins. However, the impact of protein glycosylation on the major human pathogen Staphylococcus aureus remains incompletely understood. To study protein glycosylation in staphylococci, we analyzed lysostaphin lysates of methicillin-resistant Staphylococcus aureus (MRSA) strains by SDS-PAGE and subsequent periodic acid-Schiff’s staining. We detected four (>300, ∼250, ∼165, and ∼120 kDa) and two (>300 and ∼175 kDa) glycosylated surface proteins with strain COL and strain 1061, respectively. The ∼250, ∼165, and ∼175 kDa proteins were identified as plasmin-sensitive protein (Pls) by mass spectrometry. Previously, Pls has been demonstrated to be a virulence factor in a mouse septic arthritis model. The pls gene is encoded by the staphylococcal cassette chromosome (SCC)mec type I in MRSA that also encodes the methicillin resistance-conferring mecA and further genes. In a search for glycosyltransferases, we identified two open reading frames encoded downstream of pls on the SCCmec element, which we termed gtfC and gtfD. Expression and deletion analysis revealed that both gtfC and gtfD mediate glycosylation of Pls. Additionally, the recently reported glycosyltransferases SdgA and SdgB are involved in Pls glycosylation. Glycosylation occurs at serine residues in the Pls SD-repeat region and modifying carbohydrates are N-acetylhexosaminyl residues. Functional characterization revealed that Pls can confer increased biofilm formation, which seems to involve two distinct mechanisms. The first mechanism depends on glycosylation of the SD-repeat region by GtfC/GtfD and probably also involves eDNA, while the second seems to be independent of glycosylation as well as eDNA and may involve the centrally located G5 domains. Other previously known Pls properties are not related to the sugar modifications. In conclusion, Pls is a glycoprotein and Pls glycosyl residues can stimulate biofilm formation. Thus, sugar modifications may represent promising new targets for novel therapeutic or prophylactic measures against life-threatening S. aureus infections., Author Summary Staphylococcus aureus is a serious pathogen that causes life-threatening infections due to its ability to attach to surfaces, form biofilms, and persist inside the host. One of previously identified virulence factors in S. aureus pathogenesis is the plasmin-sensitive surface protein Pls. We here identified Pls as a posttranslationally modified glycoprotein and characterized the domain within Pls that becomes glycosylated as well as the modifying sugars. Moreover, we found that the glycosyltransferases GtfC and GtfD carry out the glycosylation reactions. In a search for a role for the modifying sugars, we found that Pls can stimulate biofilm formation apparently via two distinct mechanisms, one being dependent on glycosylation by GtfC and GtfD the other being independent of glycosylation as well as eDNA. Moreover, we found that none of the already known Pls functions is mediated by the sugar moieties. Thus, we conclude that GtfC/GtfD-glycosylated Pls may contribute to MRSA pathogenicity via stimulation of biofilm formation and may serve as future target to combat or prevent infections with this serious pathogen.

Solubilization and co-solubilization of triphenyls (TPs) viz., triphenylphosphine (TPP), triphenylphosphineoxide (TPPO), triphenylamine (TPA) and triphenylmethanol (TPM) were studied in various single and binary surfactant systems at 25 °C using UV-visible spectroscopy and HPLC. The solubilization capacities of different micelles towards TPs were found to be a function of the nature and structure of solubilizates, locus of solubilization, size of micelles and the nature of interactions between the solubilizate and micelles. The effect of surfactant mixing on the solubilization of TPs was evaluated using the Regular Solution Approach (RSA). The solubility enhancement of TPs within mixed micelles relative to that observed in single surfactant systems was explained in light of the structural micellar changes associated with the mixing of ionic and non-ionic surfactants. Moreover, kinetics of oxidation of TPP by hydrogen peroxide investigated in these surfactant systems was found to be sensitive to the nature of micelle and the locus of solubilization of TPP within the micelles.

Micelles of different surfactants are well known to affect chemical equilibria and reactivities by selectively sequestering the reagent substrates through electrostatic and hydrophobic interactions. In this article, the effects of micelles of various surfactants on different parameters of the Ce(IV)-catalyzed Belousov–Zhabotinsky (BZ) oscillatory reaction at 35°C in nonstirred closed conditions are studied by employing spectrophotometry and tensiometry. Surfactants used in this study are the cationics hexadecyltrimethylammonium bromide (CTAB) and pentamethylene-1,5-bis(N-hexadecyl-N,N-dimethylammonium)bromide gemini (Gemini), anionic sodium dodecylbenzene sulfonate (SDBS), and nonionic Brij58, whereas the binary surfactant systems used are cationic–nonionic CTAB+Brij58 and anionic–nonionic SDBS+Brij58. The results revealed that the induction period shows a definite variation with increasing concentration of different surfactants above their critical micelle concentration (cmc). The amplitudes of oscillation and absorbance maxima and minima are enhanced in the presence of micelles of CTAB and Gemini surfactants, whereas micelles of SDBS and Brij58 have almost no effect on the nature of the oscillations. However, mixed micelles of CTAB+Brij58 and SDBS+Brij58 binary mixtures show a quite different effect on the overall behavior of the oscillations. The enhanced effect of CTAB and Gemini surfactants on the overall nature of oscillations has been attributed to the positive charge on the surface of their micelles and to some extent on the presence of nitrogen in their head group. The effect of mixed binary micelles may be attributed to their synergistic nature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 659–668, 2010

While coagulase-negative staphylococci (CoNS), with their ability to form a thick, multilayered biofilm on foreign bodies, have been identified as the major cause of implant-associated infections, no data are available about biofilm formation by staphylococcal small-colony variants (SCVs). In the past years, a number of device-associated infections due to staphylococcal SCVs were described, among them, several pacemaker infections due to SCVs of CoNS auxotrophic to hemin. To test the characteristics of SCVs of CoNS, in particular, to study the ability of SCVs to form a biofilm on foreign bodies, we generated a stable mutant in electron transport by interrupting one of the hemin biosynthetic genes, hemB , in Staphylococcus epidermidis . In fact, this mutant displayed a stable SCV phenotype with tiny colonies showing strong adhesion to the agar surface. When the incubation time was extended to 48 h or a higher inoculum concentration was used, the mutant produced biofilm amounts on polystyrene similar to those produced by the parent strain. When grown under planktonic conditions, the mutant formed markedly larger cell clusters than the parental strain which were completely disintegrated by the specific β-1,6-hexosaminidase dispersin B but were resistant to trypsin treatment. In a dot blot assay, the mutant expressed larger amounts of polysaccharide intercellular adhesin (PIA) than the parent strain. In conclusion, interrupting a hemin biosynthetic gene in S. epidermidis resulted in an SCV phenotype. Markedly larger cell clusters and the ability of the hemB mutant to form a biofilm are related to the augmented expression of PIA.

New steroidal imidazolidinone derivatives (7-9) were synthesized after reacting steroidal thiosemicarbazones with oxalyl chloride in absolute ethanol. After characterization by spectral and analytical data, the interaction studies of compounds (7-9) with DNA were carried out by UV-vis, fluorescence spectroscopy, circular dichroism, molecular docking and gel electrophoresis. The compounds bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb; 2.31 × 10(4) M(-1), 2.57 × 10(4) M(-1) and 2.16 × 10(4) M(-1), respectively indicating the higher binding affinity of compound 8 towards DNA. Gel electrophoresis demonstrated that the compounds 7-9 show strong interaction during the cleavage activity with pBR322 DNA. The docking study suggested the intercalation of imidazolidinone moiety of steroid derivative in minor groove of DNA. During in vitro cytotoxicity, compounds 7-9 revealed potential toxicity against the different human cancer cells (MTT assay). Apoptotic degradation of DNA in presence of compounds 7-9 was analyzed by agarose gel electrophoresis and visualized by ethidium bromide staining (comet assay). FACS analysis shows that the compound 8 bring about cell cycle arrest at 7 μM concentration.

The extracellular adherence protein (Eap), a broad-spectrum adhesin secreted by Staphylococcus aureus, was previously shown to curb acute inflammatory responses, presumably through its binding to endothelial cell (EC) ICAM-1. Examining the effect of Eap on endothelial function in more detail, we here show that, in addition, Eap functions as a potent angiostatic agent. Concomitant treatment of EC with purified Eap resulted in the complete blockage of the mitogenic and sprouting responses elicited by vascular endothelial growth factor (VEGF)165 or basic fibroblast growth factor (bFGF). Moreover, the induction of tissue factor and decay-accelerating factor were repressed by Eap, as determined by qRT-polymerase chain reaction (qRT-PCR), with a corresponding reduction in Egr-1 protein up-regulation seen. This angiostatic activity was accompanied by a corresponding inhibition in ERK1/2 phosphorylation, while activation of p38 was not affected. Inhibition occurred downstream of tyrosine kinase receptor activation, as comparable effects were seen on TPA-induced ERK1/2 phosphorylation. Similar to previously described angiostatic agents like angiopoietin-1 or the 16-kDa prolactin fragment, Eap blockage of the Ras/Raf/MEK/ERK cascade was localized by pull-down assay at the level of Ras activation. Eap's combined anti-inflammatory and antiangiogenic properties render this bacterial protein not only an important virulence factor during S. aureus infection but open new perspectives for therapeutic applications in pathological neovascularization.

The interaction of the antioxidant Rutin with the radical DPPH (2,2-diphenyl-1-picrylhydrazyl) in presence of cationic (CTAB, TTAB, DTAB), non-ionic (Brij78, Brij58, Brij35), anionic (SDS) and mixed surfactant systems (CTAB-Brij58, DTAB-Brij35, SDS-Brij35) has been followed by spectrophotometric and tensiometric methods to evaluate the DPPH radical scavenging activity (RSA) of Rutin in these model self-assembled structures. The results show that the solubilization capacity of various single surfactant systems for both DPPH as well as Rutin followed the order cationics > non-ionics > anionic. The radical scavenging activity of Rutin in the solubilized form was higher within ionic micelles than in non-ionic micelles. However, the antioxidant exhibited enhanced activity for the radical in mixed cationic-non-ionic micelles compared with any of the single component micelles. In contrast, anionic-non-ionic mixed micelles modulated the activity of Rutin in-between that seen for pure anionic and non-ionic micelles only.

Bergenin pentacetate (2), a peracetate derivative of biologically active lead compound Bergenin (1) isolated from Bergenia stracheyi was subjected to lipase catalyzed regioselective alcoholysis to obtain 3,4,10,11-tetracetate of Bergenin (3). The free hydroxyl group of 3 was derivatised using higher carboxylic acids to obtain acyl derivatives (4-7). These compounds synthesized via chemoenzymatic route were characterized using 1H NMR, 13C NMR and mass spectral data and evaluated for DPPH radical scavenging, antimicrobial and xanthine oxidase inhibitory activities. The studies revealed that biological activity of Bergenin can be optimized by selective modification of its structure.

A firmly adherent mass of slime plus organisms (biofilm) accumulates on the sides of culture tubes when some strains of coagulase-negative staphylococci are grown in a chemically-defined medium containing [14C]glucose. This mass was washed (to remove labelled medium) and then counted after adding scintillation fluid. Organisms from the liquid culture were also washed and counted to check that [14C]glucose had been utilised to label the bacteria. Nine strains were examined in this way, and the results were compared with those obtained with four older techniques for recognising slime production or adherent bacteria. The new method is quick, and has advantages of reproducibility and good discrimination between strains; there was a 15-fold difference in counts in the biofilm between slime-producing and non-producing strains respectively. With the new radiolabel assay, the effects of several antibacterial compounds on the build-up of the biofilm were investigated with four slime-producing strains. Tunicamycin, chloramphenicol and 5-fluorouracil, at levels below their minimum growth-inhibitory concentrations, each greatly diminished biofilm formation; several other drugs had less effect.

Slime isolated after growth of four strains of coagulase-negative staphylococci on chemically defined medium plus agar was rich in galactose. However, when sterile agar plates were extracted with saline, high-molecular-weight material with similar properties was obtained that also was galactose-rich. Most of the dry weight attributed to slime, and probably all the galactose, originated from agar. Slime isolated by gel and ion-exchange chromatography from liquid culture in the same medium contained glycerol phosphate, glucose (no galactose), glucosamine, alanine, uronate, an unidentified component, and protein. Separation of protein from carbohydrate was achieved by affinity chromatography. [14C]glucose in the medium labeled the carbohydrate polymer; [14C]amino acids chiefly labeled extracellular proteins. Slime from bacteria grown on medium solidified with silica gel or on dialysis membrane above an agar surface showed essentially the same composition and behavior after purification as the material isolated from liquid culture.

To identify novel putative staphylococcal adhesins, lithium chloride extraction (an established method for selective surface molecule solubilization) was employed. N-terminal sequencing and functional assays identified a 42-kDa fibronectin-binding protein from Staphylococcus epidermidis as ornithine carbamoyltransferase (OCTase). However, OCTase was not recognizable extracellularly, and this fact together with the fact that LiCl induced DNA release and a decrease in viability suggests that LiCl extraction may not be the method of choice for selective surface molecule extraction from staphylococci.

Adhesion is a prerequisite for coagulase-negative staphylococci to cause invasive disease and may be mediated by adhesive host molecules adsorbed on implanted polymers. In this study, we can confirm previous observations demonstrating binding of Staphylococcus epidermidis to fibronectin (FN) adsorbed polymer surfaces. So far, the nature of FN-recognizing adhesin(s) in S. epidermidis remains elusive. Since teichoic acids (TA) have been shown to exert binding functions for extracellular matrix molecules in several Gram-positive species, we have purified wall TA of S. epidermidis laboratory strains KH11 and RP62A, as well as clinical isolate AB9. Using a polymethylmethacrylate (PMMA) coverslip adhesion assay, a microtitre plate assay and a particle agglutination assay, we found that purified TA significantly enhanced adhesion of S. epidermidis KH11 and RP62A to FN coated surfaces. Enhanced adhesion was dose-dependent and saturable. Preincubation, either of microorganisms or of FN coated surfaces, with TA promoted adhesion, while adhesion to TA-adsorbed PMMA was comparably low. This observation may suggest a potential role of cell wall carbohydrates as bridging molecules between microorganisms and immobilized FN in early steps of S. epidermidis pathogenesis.

In recent years, infections of implanted plastic devices by coagulase-negative staphylococci have become a major cause of septicaemia in human patients. The causal bacterial species is usually Staphylococcus epidermidis and these organisms grow as a biofilm adherent to a solid surface. Several methods have been introduced to assess the mass of adherent bacteria and the slimy matrix in which they are embedded. Some methods measure total biofilm, others measure the organisms or the slime alone. In vitro, the type of medium, the atmosphere during incubation, and the nature of the solid surface, affect the quantity of biofilm that is formed. In most studies on the chemistry of the slime, the material used was formed on complex media solidified with agar. Contamination by ingredients of the media or by agar may not always have been recognised. Recent work with chemically defined medium (liquid or solidified with silica gel) shows that the slime is a mixture of about 80% (w/w) teichoic acid and 20% protein. Growth as a biofilm may protect the staphylococci from antibiotics. At present, the greatest success in preventing infection has come from improved surgical techniques during the insertion of implants.

SUMMARY: Extracellular high-mol.-wt material was separated from liquid cultures of Staphylococcus epidermidis. This material contained protein c. 20% w/w and polysaccharide c. 80% w/w. The polysaccharide was isolated by gel and ion-exchange chromatography and contained glycerol phosphate, glucose, N-acetylglucosamine, and d-alanine. Cell-wall teichoic acid was isolated from strain RP-62A and had a similar composition.

Marked differences in both the production of slime and adherence by Staphylococcus epidermidis were observed when comparing four culture media. Slime isolated from a strain cultured in a chemically defined medium (HHW) in air was chemically indistinguishable from that formed in both HHW and synthetic dialysis fluid (SDF) in air with 5% CO2. The presence of a physiological level of CO2 during culture in tryptone soya broth (TSB) prevented production of slime. It was not possible to separate the constituents of slime from those of the culture medium in bacteria grown in TSB in air using DEAE cellulose. Slime production was notably poor in used peritoneal dialysis fluid (PUD). Adherent growth was marked in HHW and SDF but was poor in TSB and PUD when air with 5% CO2 was used. These findings emphasize the advantages in using chemically defined and biological fluids when studying slime production and adherence by S. epidermidis.

Summary. In a chemically defined medium in which the principal constituents were glucose, 18 amino acids, two purines and six vitamins, eight strains of coagulase-negative staphylococci grew as rapidly and heavily as in tryptic soy broth. Slime formation was slightly better in the defined medium than in tryptic soy broth.