Vanillin,a potential agent to prevent biofouling of reverse osmosis membrane

Reverse osmosis (RO) membrane systems are widely used in water purification plants. Reduction in plant performance due to biofilm formation over the membrane is an inherent problem. As quorum sensing (QS) mechanisms of microorganisms have been reported to be involved in the formation of biofilm, ways are sought for quorum quenching (QQ) and thereby prevention of biofilm formation. In this study using a chemostat culture run for seven days in a CDC reactor it was found that a natural QQ compound, vanillin considerably suppressed bacterial biofilm formation on RO membrane. There was 97% reduction in biofilm surface coverage, when grown in the presence of vanillin. Similarly, the average thickness, total biomass and the total protein content of the biofilm that formed in the presence of vanillin were significantly less than that of the control. However vanillin had no effect on 1-day old pre-formed biofilm.     

In vitro, Candida albicans releases the immune modulator adenosine and a second, high-molecular weight agent that blocks neutrophil killing.

We previously described a lyophilized supernatant from germinated Candida albicans that blocks human neutrophil (PMN) O2- production and degranulation stimulated by several PMN agonists but does not block stimulation by PMA. In studies to further characterize this Candida hyphal inhibitory product (CHIP), we noted several physicochemical parallels with the purine nucleoside adenosine (Ado). A Sephadex G-10 semipurified fraction of CHIP had an absorption peak near 260 nm, an apparent m.w. of less than 400, and was resistant to boiling and proteases. Maximally effective doses of CHIP (100 micrograms/ml) and Ado (100 microM) blocked 0.1 microM FMLP-stimulated O2- production by 76.8 +/- 4.1 and 81.7 +/- 4.8%, respectively. Ado deaminase, known to inactivate Ado, reversed inhibition by both Ado and CHIP. Results were comparable for the effect of CHIP and Ado on FMLP-stimulated beta-glucuronidase and lactoferrin release. Activation of the respiratory burst by opsonized C. albicans yeast was also inhibited by CHIP and Ado, but the extent of inhibition was less than for FMLP. At yeast:PMN ratios of 4:1, 10:1, and 40:1, CHIP inhibited O2- by -3.8%, 14.3%, and 12.8%, respectively; Ado blocked production by 32.9%, 24.2%, and 11.5%, respectively. The effect of CHIP and Ado on Candida killing by PMN was compared using two viability assays in each of four experiments. Ado (100 microM) had no effect on killing, although CHIP (100 micrograms/ml) inhibited killing in the MTT assay at 15 and 45 min by 81.6 +/- 6.3 and 24.7 +/- 6.2%, respectively; as assayed by CFU, CHIP inhibited killing by 34.1 +/- 6.2 and 10.3 +/- 2.5%, respectively. The ability of CHIP to inhibit killing was not affected by adding Ado deaminase, providing additional evidence that an Ado-like effect by CHIP is not essential for killing inhibition. Killing of opsonized Streptococcus pneumoniae was also inhibited in a concentration-dependent manner. Reverse-phase HPLC of the semipurified fraction revealed a peak, eluting identically to authentic Ado, which was eliminated by adding Ado deaminase. Ado content of the G-10 fraction was sufficient to account fully for the FMLP-inhibitory activity. The antikilling activity was resistant to boiling and proteases but was eliminated by mild periodation. Fractions eluting from a Sephadex CL6B column between 0.8 and 2.0 x 10(6) m.w. had increased sp. act. for killing inhibition. Sp. act. increased as carbohydrate content increased, but killing inhibition by various Candida cell wall constituents was absent to modest compared to inhibition induced by CHIP.(ABSTRACT TRUNCATED AT 400 WORDS)     

NAC functions as a modulator of SRP during the early steps of protein targeting to the endoplasmic reticulum

Nascent polypeptide-associated complex (NAC) was initially found to bind to any segment of the nascent chain except signal sequences. In this way, NAC is believed to prevent mistargeting due to binding of signal recognition particle (SRP) to signalless ribosome nascent chain complexes (RNCs). Here we revisit the interplay between NAC and SRP. NAC does not affect SRP function with respect to signalless RNCs; however, NAC does affect SRP function with respect to RNCs targeted to the endoplasmic reticulum (ER). First, early recruitment of SRP to RNCs containing a signal sequence within the ribosomal tunnel is NAC dependent. Second, NAC is able to directly and tightly bind to nascent signal sequences. Third, SRP initially displaces NAC from RNCs; however, when the signal sequence emerges further, trimeric NAC·RNC·SRP complexes form. Fourth, upon docking to the ER membrane NAC remains bound to RNCs, allowing NAC to shield cytosolically exposed nascent chain domains not only before but also during cotranslational translocation. The combined data indicate a functional interplay between NAC and SRP on ER-targeted RNCs, which is based on the ability of the two complexes to bind simultaneously to distinct segments of a single nascent chain.     

Movement of modulator in maize: a test of an hypothesis

A model of Modulator movement (Greenblatt 1968) from one chromosomal site to another requires that all movements produce potential twin mutations within the affected cell lineage. From this model the prediction would be that (1) untwinned red and untwinned light-variegated sectors within the pericarp of medium-variegated maize must occur in equal frequency even though partners become lost, during ear morphogenesis, to the final pericarp tissue, and that (2) among the backcross progeny of a homozygous P(rr)Mp individual mated with P(wr)/P(wr) pollen, red offspring and light-variegated offspring would occur in equal frequency. Both expectations have been realized and herein reported.     

Rational design of a pirinixic acid derivative that acts as subtype-selective PPARγ modulator

Peroxisome proliferator-activated receptor γ (PPARγ) is involved in glucose and lipid homeostasis. PPARγ agonists are in clinical use for the treatment of type 2 diabetes. Lately, a new class of selective PPARγ modulators (SPPARγMs) was developed, which are believed to show less side effects than full PPARγ agonists. We have previously shown that α-substitution of pirinixic acid, a moderate agonist of PPARα and PPARγ, leads to low micromolar active balanced dual agonists of PPARα and PPARγ. Herein we present modifications of pirinixic acid leading to subtype-selective PPARγ agonists and furthermore the development of a selective PPARγ modulator guided by molecular docking studies.     

Purification and structural analysis of the modulator of the glucocorticoid-receptor complex. Evidence that modulator is a novel phosphoglyceride

Modulator is the low molecular weight heat-stable inhibitor of glucocorticoid-receptor complex activation. We have purified modulator to apparent homogeneity from heated rat liver cytosol. This was accomplished using Sephadex G-15 gel filtration, Dowex 1 anion-exchange chromatography, and preparative silica high-performance liquid chromatography. The modulator preparation was judged to be homogeneous by analytical silica high-performance liquid chromatography, two-dimensional silica thin-layer chromatography, and proton nuclear magnetic resonance spectroscopy. The apparent concentration of modulator in rat liver cytosol is 6.5 microM. The purified modulator inhibits heat activation of the rat liver glucocorticoid-receptor complex and stabilizes the steroid binding ability of the unoccupied rat liver glucocorticoid receptor in a dose-dependent manner. At a concentration of 5-6.5 microM, modulator inhibits receptor activation and stabilizes the unoccupied receptor by 50%. At a concentration of 500-630 microM, sodium molybdate also inhibits receptor activation and stabilizes the unoccupied receptor by 50%. Thus, modulator appears to be the endogenous factor that exogenous sodium molybdate mimics in vitro. Chemical analysis of the purified modulator following two-dimensional silica thin-layer chromatography indicates that modulator is an aminophospholipid. Physical analysis of the purified modulator by infrared and nuclear magnetic resonance spectroscopy, as well as mass spectrometry, demonstrates that modulator is an ether aminophosphoglyceride.     

Evaluation of a diospyrin derivative as antileishmanial agent and potential modulator of ornithine decarboxylase of Leishmania donovani

World health organization has called for academic research and development of new chemotherapeutic strategies to overcome the emerging resistance and side effects exhibited by the drugs currently used against leishmaniasis. Diospyrin, a bis-naphthoquinone isolated from Diospyros montana Roxb., and its semi-synthetic derivatives, were reported for inhibitory activity against protozoan parasites including Leishmania. Presently, we have investigated the antileishmanial effect of a di-epoxide derivative of diospyrin (D17), both in vitro and in vivo. Further, the safety profile of D17 was established by testing its toxicity against normal macrophage cells (IC₅₀ ∼ 20.7 μM), and also against normal BALB/c mice in vivo. The compound showed enhanced activity (IC₅₀ ∼ 7.2 μM) as compared to diospyrin (IC₅₀ ∼ 12.6 μM) against Leishmania donovani promastigotes. Again, D17 was tested on L. donovani BHU1216 isolated from a sodium stibogluconate-unresponsive patient, and exhibited selective inhibition of the intracellular amastigotes (IC₅₀ ∼ 0.18 μM). Also, treatment of infected BALB/c mice with D17 at 2 mg/kg/day reduced the hepatic parasite load by about 38%. Subsequently, computational docking studies were undertaken on selected enzymes of trypanothione metabolism, viz. trypanothione reductase (TryR) and ornithine decarboxylase (ODC), followed by the enzyme kinetics, where D17 demonstrated non-competitive inhibition of the L. donovani ODC, but could not inhibit TryR.     

Beta-glucosidase: substrate, solvent, and viscosity variation as probes of the rate-limiting steps

The second-order rate constants (kcat/Km) for the beta-glucosidase-catalyzed hydrolysis of aryl beta-D-glucopyranosides show a bell-shaped dependence of pH. The pKas that characterize this dependence are 4.4 (delta Hion approximately equal to 0) and 6.7 (delta Hion approximately equal to 0). In D2O these pKas are increased by 0.5 (+/- 0.1) unit, but there is no solvent isotope effect on the pH-independent second-order rate constant. Nath and Rydon [Nath, R. L., & Rydon, H. N. (1954) Biochem. J. 57, 1-10] examined the kinetics of the beta-glucosidase-catalyzed hydrolysis of a series of substituted phenyl glucosides. We have extended this study to include glucosides with phenol leaving groups of pKa less than 7. Br?nsted plots for this extended series were nonlinear for both kcat/Km and kcat. Br?nsted coefficients for those compounds with leaving groups of pKa greater than 7 (for kcat/Km) or pKa greater than 8.5 (for kcat) were nearly equal to -1.0, indicating substantial negative charge buildup on the leaving group in the transition state. The nonlinearity indicates an intermediate in the reaction. This was confirmed by partitioning experiments in the presence of methanol as a competing glucose acceptor. A constant product ratio, [methyl glucoside]/[glucose], was found with aryl glucoside substrates varying over 16,000-fold in reactivity (V/K), indicative of a common intermediate. Viscosity variation (in sucrose-containing buffers) was used to probe the extent to which the beta-glucosidase reactions are diffusion-controlled.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phytochrome photoreversibility: Empirical test of the hypothesis that it varies as a consequence of pigment compartmentation

Phytochrome of oat (Avena sativa L., cv. Garry) coleoptile cells in the red-light-absorbing form, Pr, is diffusely distributed while after conversion to the far-red-light-absorbing form, Pfr, it is observed only in very small areas within the cell. Comparison of phytochrome photoversibility measurements to the distribution of the pigment within the cell indicates that the spectral assay is not influenced by the observed compartmentalization of the chromoprotein. However, the observed compartmentalization of phytochrome is correlated with a loss in spectrophotometrically detectable Pr.Abbreviations Pr red-absorbing form of phytochrome - Pfr farred-absorbing form of phytochrome - R red light - FR far-red light C.I.W.-D.P.B. Publication No. 622     

Cisplatin resistance and mechanism in a viral test system: SV40 isolates that resist inhibition by the antitumor drug have lost regulatory DNA

Isolates of SV40 that have enhanced ability to survive inhibition by the antitumor drug cisplatin were selected by serial drug challenge in vivo. These mutant viruses have acquired specific deletions within the repeated regulatory motif (GGGCGG)6 or GC box. This DNA element was shown previously to be a strong target of drug attack by cisplatin and other anticancer drugs in vitro and is an important viral and cellular DNA control sequence. Thus, drug resistance in this viral test system is dependent on the loss of important target DNA sequences. The results also indicate that drug efficacy may be related to the ability of certain anticancer drugs to attack regulatory DNA sequences containing strings of guanosines.