N-lauroyl Sarcosine Research Articles

Inhibition of Pitting of Type 304L Stainless Steel by N‐Lauroylsarcosine

The resistance of Type 304L SS to localized corrosion by aqueous chloride solutions is increased by addition of N‐lauroylsarcosine (NLS). The effects of N‐lauroylsarcosine concentration, chloride concentration, pH, and metal surface prepassivation on the efficiency of pitting inhibition were investigated. Linear current scan and potentiodynamic polarization methods were used to determine the pitting potentials. The electrode capacitance depends on NLS concentration,pH, and buffer content of the solution. Distinct changes in the NLS concentration dependence of the breakdown potential and capacitance occur near the critical micelle concentration of NLS. The results suggest that NLS is strongly adsorbed onto the electrode surface with the possibility that it forms a hemimicellar structure above a certain critical concentration. An inhibition effect in is obtained with NLS concentration as low as . The inhibitor efficiency depends on pH and increases with more efficient solution mass transfer. Possible mechanisms for the inhibition effects are discussed.

Mechanisms of activation and secretion of a cell-associated precursor of an exocellular protease of Pseudomonas aeruginosa 34362A.

An inactive precursor to the active exocellular protease 1 of Pseudomonas aeruginosa is cell-associated and located primarily in the periplasmic space. We have studied factors that bring about activation of the precursor in vitro in order to shed some light on the process of its activation and secretion in vivo. A variety of diverse procedures were shown to effect irreversible activation. Several mild non-enzymatic procedures were effective, such as dialysis of an ammonium sulfate precipitate against neutral buffers, gel filtration (Sephadex G-100), and ion-exchange chromatography (DEAE-cellulose). Activation also resulted following treatment with anionic detergents (sodium dodecyl sulfate, N-lauroyl sarcosine) and deoxycholate. Limited exposure to any of several proteases with different specificities also resulted in activation. The kinetics of detergent-catalyzed activation reveals a long lag followed by rapid activation, suggesting at least a two-stage process. The precursor and the mature protease 1 have indistinguishable molecular masses (33 kDa), as measured by sodium dodecyl sulfate/polyacrylamide gel electrophoresis of these proteins purified by immunoabsorbance chromatography under denaturing conditions. Further, both precursor and protease have identical N-terminal alanine. Our results suggest that it is improbable that activation is the result of proteolytic processing of the precursor itself, but rather that it may involve the removal of a non-covalently associated inhibitor molecule. Hydrophobic interaction chromatography on octyl-Sepharose revealed that activation was accompanied by a significant change in the hydrophobicity, pointing to a significant change in the conformation of the precursor and the mature protease. A mutant has been studied which accumulates activatable precursor in the periplasm but releases no active enzyme into the culture medium, supporting the hypothesis that secretion through the inner and outer membranes proceed by different mechanisms. Comparison of outer membranes of protease-secreting strains (34362A and PAKS 1) and a protease-negative mutant (PAKS 18) which accumulates precursor has shown that there is a change in the outer membrane protein profile in the latter.

Effects of detergents and divalent cations on the functioning of cell envelopes of Escherichia coli in the early stages of infection with bacteriophage .PHI.X174.

Effects of detergents and divalent cations (Ca2+, Mg2+) on intact cells and envelope fraction I of Escherichia coli were examined by measuring the eclipse kinetics of bacteriophage ϕX174 and by polyacrylamide gel electrophoresis of cell envelope proteins. Cell envelopes having receptor activity to convert ϕX174 to eclipsed particles (eclipsing activity) were destroyed by cationic detergent cetyl trimethyl ammonium bromide (CTAB) and anionic detergent N-lauroyl sarcosine sodium salt (Sarkosyl), but were not destroyed by many nonionic detergents, such as Triton X-100, Pluronic PI03, Brij 58, Tween 20 and Tween 80 in the presence of divalent cations. However, nonionic detergent Span 80 caused the disruption of cell envelopes in the presence of a low concentration (1 mm) of divalent cations, but not in the presence of a higher concentration (5 mm) of divalent cations. Divalent cations were shown to stabilize the cell envelope structure and to protect the cell envelopes from solubilization by detergents.

Purification and partial characterization of the major outer membrane protein of Chlamydia trachomatis.

Elementary bodies (EB) of Chlamydia trachomatis serotypes C, E, and L2 were extrinsically radioiodinated, and whole-cell lysates of these serotypes were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Autoradiography of the polypeptide profiles identified a major surface protein with an apparent subunit molecular weight of 39,500 that was common to each C. trachomatis serotype. The abilities of nonionic (Triton X-100), dipolar ionic (Zwittergent TM-314), mild (sodium deoxycholate and sodium N-lauroyl sarcosine), and strongly anionic (SDS) detergents to extract this protein from intact EB of the L2 serotype were investigated by SDS-PAGE analysis of the soluble and insoluble fractions obtained after each detergent treatment. Only SDS readily extracted this protein from intact EB. Sarkosyl treatment selectively solubilized the majority of other EB proteins, leaving the 39,500-dalton protein associated with the Sarkosyl-insoluble fraction. Ultrastructural studies of the Sarkosyl-insoluble EB pellet showed it to consist of empty EB particles possessing an apparently intact outer membrane. No structural evidence for a peptidoglycan-like cell wall was found. Morphologically these chlamydial outer membrane complexes (COMC) resembled intact chlamydial EB outer membranes. The 39,500-dalton outer membrane protein was quantitatively extracted from COMC by treating them with 2% SDS at 60 degrees C. This protein accounted for 61% of the total COMC-associated protein, and its extraction resulted in a concomitant loss of the COMC membrane structure and morphology. The soluble extract obtained from SDS-treated COMC was adsorbed to a hydroxylapatite column and eluted with a linear sodium phosphate gradient. The 39,500-dalton protein was eluted from the column as a single peak at a phosphate concentration of approximately 0.3 M. The eluted protein was nearly homogeneous by SDS-PAGE and appeared free of contaminating carbohydrate, glycolipid, and nucleic acid. Hyperimmune mouse antiserum prepared against the 39,500-dalton protein from serotype L2 reacted with C. trachomatis serotypes Ba, E, D, K, L1, L2, and L3 by indirect immunofluorescence with EB but failed to react with serotypes A, B, C, F, G, H, I, and J, with the C. trachomatis mouse pneumonitis strain, or with the C. psittaci feline pneumonitis, guinea pig inclusion conjunctivitis, or 6BC strains. Thus, the 39,500-dalton major outer membrane protein is a serogroup antigen of C. trachomatis organisms.