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Sample records for partially irreversible inactivation

  1. Partially-irreversible sorption of formaldehyde in five polymers

    NASA Astrophysics Data System (ADS)

    Ye, Wei; Cox, Steven S.; Zhao, Xiaomin; Frazier, Charles E.; Little, John C.

    2014-12-01

    Due to its environmental ubiquity and concern over its potential toxicity, the mass-transfer characteristics of formaldehyde are of critical importance to indoor air quality research. Previous studies have suggested that formaldehyde mass transfer in polymer is partially irreversible. In this study, mechanisms that could cause the observed irreversibility were investigated. Polycarbonate and four other polymeric matrices were selected and subjected to formaldehyde sorption/desorption cycles. Mass transfer of formaldehyde was partially irreversible in all cases, and three potential mechanisms were evaluated. First, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis was used to investigate possible formaldehyde polymerization on polymer surfaces. ATR-FTIR showed no detectable paraformaldehyde or formaldehyde on the film surfaces that had been exposed to formaldehyde and air. ATR-FTIR did detect aliphatic acids suggesting oxidation had occurred on film surfaces as a result of exposure to formaldehyde. However, additional study suggested that air is not the primary cause for irreversibility. Second, statistical physics theory was tested as a possible explanation. According to this theory, reversible and irreversible sorption could be taking place simultaneously. The irreversible fraction should be constant during sorption and the fraction could be determined by performing a complete sorption/desorption test. The sorption/desorption data was consistent with this theory. Third, chemisorption was considered as another possible cause for irreversibility. Extraction/fluorimetry testing of post-sorption and post-desorption polymer films showed measurable quantities of formaldehyde suggesting that some of the chemisorbed formaldehyde was reversible at the higher extraction temperature. Further quantitative study on chemical reaction products is needed.

  2. Preventing Scars after Injury with Partial Irreversible Electroporation.

    PubMed

    Golberg, Alexander; Villiger, Martin; Khan, Saiqa; Quinn, Kyle P; Lo, William C Y; Bouma, Brett E; Mihm, Martin C; Austen, William G; Yarmush, Martin L

    2016-11-01

    Preventing the formation of hypertrophic scars, especially those that are a result of major trauma or burns, would have enormous impact in the fields of regenerative and trauma medicine. In this report, we introduce a noninvasive method to prevent scarring based on nonthermal partial irreversible electroporation. Contact burn injuries in rats were treated with varying treatment parameters to optimize the treatment protocol. Scar surface area and structural properties of the scar were assessed with histology and non-invasive, longitudinal imaging with polarization-sensitive optical coherence tomography. We found that partial irreversible electroporation using 200 pulses of 250 V and 70 μs duration, delivered at 3 Hz every 20 days during a total of five therapy sessions after the initial burn injury, resulted in a 57.9% reduction of the scar area compared with untreated scars and structural features approaching those of normal skin. Unlike humans, rats do not develop hypertrophic scars. Therefore, the use of a rat animal model is the limiting factor of this work.

  3. Penicillanic acid sulfone: nature of irreversible inactivation of RTEM beta-lactamase from Escherichia coli.

    PubMed

    Brenner, D G; Knowles, J R

    1984-11-20

    When penicillanic acid sulfone in large molar excess is incubated with the RTEM beta-lactamase, the enzyme becomes inactivated irreversibly. From studies of the consequential spectroscopic changes, from the use of specifically tritiated penicillanic acid sulfone, and from comparison by isoelectric focusing of the enzyme after inactivation by the sulfone and by clavulanic acid, the inactivated enzyme appears to be cross-linked by a beta-aminoacrylate fragment deriving from C-5, C-6, and C-7 of the original beta-lactam. Model studies on the behavior of alcoholic solutions of penicillanic acid sulfone in the presence of amines are entirely consistent with this interpretation.

  4. Lysine acetylation can generate highly charged enzymes with increased resistance toward irreversible inactivation

    PubMed Central

    Shaw, Bryan F.; Schneider, Gregory F.; Bilgiçer, Başar; Kaufman, George K.; Neveu, John M.; Lane, William S.; Whitelegge, Julian P.; Whitesides, George M.

    2008-01-01

    This paper reports that the acetylation of lysine ε-NH3 + groups of α-amylase—one of the most important hydrolytic enzymes used in industry—produces highly negatively charged variants that are enzymatically active, thermostable, and more resistant than the wild-type enzyme to irreversible inactivation on exposure to denaturing conditions (e.g., 1 h at 90°C in solutions containing 100-mM sodium dodecyl sulfate). Acetylation also protected the enzyme against irreversible inactivation by the neutral surfactant TRITON X-100 (polyethylene glycol p-(1,1,3,3-tetramethylbutyl)phenyl ether), but not by the cationic surfactant, dodecyltrimethylammonium bromide (DTAB). The increased resistance of acetylated α-amylase toward inactivation is attributed to the increased net negative charge of α-amylase that resulted from the acetylation of lysine ammonium groups (lysine ε-NH3 + → ε-NHCOCH3). Increases in the net negative charge of proteins can decrease the rate of unfolding by anionic surfactants, and can also decrease the rate of protein aggregation. The acetylation of lysine represents a simple, inexpensive method for stabilizing bacterial α-amylase against irreversible inactivation in the presence of the anionic and neutral surfactants that are commonly used in industrial applications. PMID:18451358

  5. Mildly Acidic pH Triggers an Irreversible Conformational Change in the Fusion Domain of Herpes Simplex Virus 1 Glycoprotein B and Inactivation of Viral Entry.

    PubMed

    Weed, Darin J; Pritchard, Suzanne M; Gonzalez, Floricel; Aguilar, Hector C; Nicola, Anthony V

    2017-03-01

    Herpes simplex virus (HSV) entry into a subset of cells requires endocytosis and endosomal low pH. Preexposure of isolated virions to mildly acidic pH of 5 to 6 partially inactivates HSV infectivity in an irreversible manner. Acid inactivation is a hallmark of viruses that enter via low-pH pathways; this occurs by pretriggering conformational changes essential for fusion. The target and mechanism(s) of low-pH inactivation of HSV are unclear. Here, low-pH-treated HSV-1 was defective in fusion activity and yet retained normal levels of attachment to cell surface heparan sulfate and binding to nectin-1 receptor. Low-pH-triggered conformational changes in gB reported to date are reversible, despite irreversible low-pH inactivation. gB conformational changes and their reversibility were measured by antigenic analysis with a panel of monoclonal antibodies and by detecting changes in oligomeric conformation. Three-hour treatment of HSV-1 virions with pH 5 or multiple sequential treatments at pH 5 followed by neutral pH caused an irreversible >2.5 log infectivity reduction. While changes in several gB antigenic sites were reversible, alteration of the H126 epitope was irreversible. gB oligomeric conformational change remained reversible under all conditions tested. Altogether, our results reveal that oligomeric alterations and fusion domain changes represent distinct conformational changes in gB, and the latter correlates with irreversible low-pH inactivation of HSV. We propose that conformational change in the gB fusion domain is important for activation of membrane fusion during viral entry and that in the absence of a host target membrane, this change results in irreversible inactivation of virions.IMPORTANCE HSV-1 is an important pathogen with a high seroprevalence throughout the human population. HSV infects cells via multiple pathways, including a low-pH route into epithelial cells, the primary portal into the host. HSV is inactivated by low-pH preexposure, and gB, a

  6. Pulsed electric field inactivation of diarrhoeagenic Bacillus cereus through irreversible electroporation.

    PubMed

    Rowan, N J; MacGregor, S J; Anderson, J G; Fouracre, R A; Farish, O

    2000-08-01

    The physical effects of high-intensity pulsed electric fields (PEF) on the inactivation of diarrhoeagenic Bacillus cereus cells suspended in 0.1% peptone water were examined by transmission electron microscopy (TEM). The levels of PEF-induced microbial cell death were determined by enumeration on tryptone soy yeast extract agar and Bacillus cereus-selective agar plates. Following exposure to lethal levels of PEF, TEM investigation revealed irreversible cell membrane rupture at a number of locations, with the apparent leakage of intracellular contents. This study provides a clearer understanding of the mechanism of PEF-induced cellular damage, information that is essential for the further optimization of this emerging food-processing technology.

  7. Peptides containing acylated C-terminal gem diamines: novel irreversible inactivators of the cysteine and serine proteinases.

    PubMed

    Gilmore, B F; Lynas, J F; Harriott, P; Healy, A; Walker, B

    2006-05-01

    This study reports on the synthesis of peptides containing C-terminal acylated gem-diamines and their utilization for the preparation of irreversible inactivators of the serine and cysteine proteinases. We have succeeded in obtaining an inhibitor Acetyl-Val-Pro-g-Val-CO-O-C(6)H(4)-NO(2) of neutrophil and pancreatic elastases that functions in a time-dependent manner, indicative of the action of an irreversible inactivator, functioning, most probably, through the formation of a long-lived acyl enzyme intermediate. In addition, we have demonstrated the irreversible inhibition of the cysteine proteinase bovine cathepsin B, by chloroacetyl and bromoacetyl derivatives of a dipeptide gem-diamine, Cbz-Phe-g-Ala-CO-CH(2)Hal (Hal = Br, Cl).

  8. Irreversible inactivation of macrophage and brain nitric oxide synthase by L-NG-methylarginine requires NADPH-dependent hydroxylation.

    PubMed

    Feldman, P L; Griffith, O W; Hong, H; Stuehr, D J

    1993-02-19

    L-NG-Methylarginine (NMA) is an established mechanism-based inactivator of murine macrophage nitric oxide synthase (mNOS). In this report, NMA is shown to irreversibly inhibit both mNOS (k(inact) = 0.08 min-1) and the recombinant constitutive brain NOS (bNOS). For both NOS isoforms, metabolism of NMA parallels that of the natural substrate L-arginine (ARG), in that it undergoes a regiospecific, NADPH-dependent hydroxylation to form L-NG-hydroxy-NG-methylarginine (NOHNMA). This intermediate then undergoes further NADPH-dependent oxidation to form L-citrulline (CIT). Authentic NOHNMA, synthesized from L-ornithine, irreversibly inhibited both mNOS (k(inact) = 0.10 min-1) and bNOS in an NADPH-dependent reaction. The conversion of either NMA or NOHNMA to CIT correlated with irreversible enzyme inactivation. Thus, the data suggest that enzyme inhibition occurs as a consequence of oxidative metabolism of the intermediate, NOHNMA. A unified mechanism is proposed that accounts for NO biosynthesis from ARG, for the inactivation of NOS by NMA and for the intermediacy of hydroxylated ARG or NMA derivatives in these processes.

  9. Reversible, partial inactivation of plant betaine aldehyde dehydrogenase by betaine aldehyde: mechanism and possible physiological implications.

    PubMed

    Zárate-Romero, Andrés; Murillo-Melo, Darío S; Mújica-Jiménez, Carlos; Montiel, Carmina; Muñoz-Clares, Rosario A

    2016-04-01

    In plants, the last step in the biosynthesis of the osmoprotectant glycine betaine (GB) is the NAD(+)-dependent oxidation of betaine aldehyde (BAL) catalysed by some aldehyde dehydrogenase (ALDH) 10 enzymes that exhibit betaine aldehyde dehydrogenase (BADH) activity. Given the irreversibility of the reaction, the short-term regulation of these enzymes is of great physiological relevance to avoid adverse decreases in the NAD(+):NADH ratio. In the present study, we report that the Spinacia oleracea BADH (SoBADH) is reversibly and partially inactivated by BAL in the absence of NAD(+)in a time- and concentration-dependent mode. Crystallographic evidence indicates that the non-essential Cys(450)(SoBADH numbering) forms a thiohemiacetal with BAL, totally blocking the productive binding of the aldehyde. It is of interest that, in contrast to Cys(450), the catalytic cysteine (Cys(291)) did not react with BAL in the absence of NAD(+) The trimethylammonium group of BAL binds in the same position in the inactivating or productive modes. Accordingly, BAL does not inactivate the C(450)SSoBADH mutant and the degree of inactivation of the A(441)I and A(441)C mutants corresponds to their very different abilities to bind the trimethylammonium group. Cys(450)and the neighbouring residues that participate in stabilizing the thiohemiacetal are strictly conserved in plant ALDH10 enzymes with proven or predicted BADH activity, suggesting that inactivation by BAL is their common feature. Under osmotic stress conditions, this novel partial and reversible covalent regulatory mechanism may contribute to preventing NAD(+)exhaustion, while still permitting the synthesis of high amounts of GB and avoiding the accumulation of the toxic BAL.

  10. Irreversible APC(Cdh1) Inactivation Underlies the Point of No Return for Cell-Cycle Entry.

    PubMed

    Cappell, Steven D; Chung, Mingyu; Jaimovich, Ariel; Spencer, Sabrina L; Meyer, Tobias

    2016-06-30

    Proliferating cells must cross a point of no return before they replicate their DNA and divide. This commitment decision plays a fundamental role in cancer and degenerative diseases and has been proposed to be mediated by phosphorylation of retinoblastoma (Rb) protein. Here, we show that inactivation of the anaphase-promoting complex/cyclosome (APC(Cdh1)) has the necessary characteristics to be the point of no return for cell-cycle entry. Our study shows that APC(Cdh1) inactivation is a rapid, bistable switch initiated shortly before the start of DNA replication by cyclin E/Cdk2 and made irreversible by Emi1. Exposure to stress between Rb phosphorylation and APC(Cdh1) inactivation, but not after APC(Cdh1) inactivation, reverted cells to a mitogen-sensitive quiescent state, from which they can later re-enter the cell cycle. Thus, APC(Cdh1) inactivation is the commitment point when cells lose the ability to return to quiescence and decide to progress through the cell cycle.

  11. Removal of the free cysteine residue reduces irreversible thermal inactivation of feruloyl esterase: evidence from circular dichroism and fluorescence spectra.

    PubMed

    Li, Jingjing; Zhang, Shuaibing; Yi, Zhuolin; Pei, Xiaoqiong; Wu, Zhongliu

    2015-08-01

    Feruloyl esterase A from Aspergillus niger (AnFaeA) contains three intramolecular disulfide bonds and one free cysteine at position 235. Saturated mutagenesis at Cys235 was carried out to produce five active mutants, all of which displayed unusual thermal inactivation patterns with the most residual activity achieved at 75°C, much higher than the parental AnFaeA. But their optimal reaction temperatures were lower than the parental AnFaeA. Extensive investigation into their free thiol and disulfide bond, circular dichroism spectra and fluorescence spectra revealed that the unfolding of the parental enzyme was irreversible on all the tested conditions, while that of the Cys235 mutants was reversible, and their ability to refold was highly dependent on the denaturing temperature. Mutants denatured at 75°C were able to efficiently reverse the unfolding to regain native structure during the cooling process. This study provided valid evidence that free cysteine substitutions can reduce irreversible thermal inactivation of proteins. © The Author 2015. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

  12. Irreversible inactivation of interleukin 2 in a pump-based delivery environment.

    PubMed Central

    Tzannis, S T; Hrushesky, W J; Wood, P A; Przybycien, T M

    1996-01-01

    The physical stability of pharmaceutical proteins in delivery environments is a critical determinant of biological potency and treatment efficacy, and yet it is often taken for granted. We studied both the bioactivity and physical stability of interleukin 2 upon delivery via continuous infusion. We found that the biological activity of the delivered protein was dramatically reduced by approximately 90% after a 24-hr infusion program. Only a portion of these losses could be attributed to direct protein deposition on the delivery surfaces. Analysis of delivered protein by size exclusion chromatography gave no indication of insulin-like, surface-induced aggregation phenomena. Examination of the secondary and tertiary structure of both adsorbed and delivered protein via Fourier-transform infrared spectroscopy, circular dichroism, and fluorescence spectroscopy indicated that transient surface association of interleukin 2 with the catheter tubing resulted in profound, irreversible structural changes that were responsible for the majority of the biological activity losses. PMID:8643597

  13. Irreversible inactivation of interleukin 2 in a pump-based delivery environment.

    PubMed

    Tzannis, S T; Hrushesky, W J; Wood, P A; Przybycien, T M

    1996-05-28

    The physical stability of pharmaceutical proteins in delivery environments is a critical determinant of biological potency and treatment efficacy, and yet it is often taken for granted. We studied both the bioactivity and physical stability of interleukin 2 upon delivery via continuous infusion. We found that the biological activity of the delivered protein was dramatically reduced by approximately 90% after a 24-hr infusion program. Only a portion of these losses could be attributed to direct protein deposition on the delivery surfaces. Analysis of delivered protein by size exclusion chromatography gave no indication of insulin-like, surface-induced aggregation phenomena. Examination of the secondary and tertiary structure of both adsorbed and delivered protein via Fourier-transform infrared spectroscopy, circular dichroism, and fluorescence spectroscopy indicated that transient surface association of interleukin 2 with the catheter tubing resulted in profound, irreversible structural changes that were responsible for the majority of the biological activity losses.

  14. Pilot Study to Assess Safety and Clinical Outcomes of Irreversible Electroporation for Partial Gland Ablation in Men with Prostate Cancer

    PubMed Central

    Murray, Katie S.; Ehdaie, Behfar; Musser, John; Mashni, Joseph; Srimathveeravalli, Govindarajan; Durack, Jeremy C.; Solomon, Stephen B.; Coleman, Jonathan A.

    2016-01-01

    Purpose Partial prostate gland ablation is a strategy to manage localized prostate cancer. Irreversible electroporation can ablate localized soft tissues. We sought to describe 30- and 90-day complications and intermediate-term functional outcomes in men undergoing prostate gland ablation using irreversible electroporation. Materials and Methods We reviewed the charts of 25 patients with prostate cancer who underwent prostate gland ablation using irreversible electroporation as a primary procedure and who were followed for at least 6 months. Results Median follow-up was 10.9 months. Grade 3 complications occurred in 2 patients including epididymitis (1) and urinary tract infection (1). Fourteen patients experienced grade ≤ 2 complications, mainly transient urinary symptoms, hematuria, and urinary tract infections. Of 25 patients, 4 (16%) had cancer in the zone of ablation on routine follow-up biopsy at 6 months. Of those with normal urinary function at baseline, 88% and 94% reported normal urinary function at 6 and 12 months after prostate gland ablation, respectively. By 12 months, only 1 patient with normal erectile function at baseline reported new difficulty with potency and only 2 patients (8%) required a pad for urinary incontinence. Conclusions Prostate gland ablation with irreversible electroporation is feasible and safe in selected men with localized prostate cancer. Intermediate-term urinary and erectile function outcomes appear reasonable. Irreversible electroporation is effective in ablation of tumor-bearing prostate tissue, as a majority of men had no evidence of residual cancer on biopsy 6 months after prostate gland ablation. PMID:27113966

  15. Irreversible conversion of the physical state of herpes simplex virus preceding inactivation by thermal or antibody treatment

    SciTech Connect

    Yanagi, K.

    1981-05-01

    The buoyant density characteristics of infectious particles of herpes simplex virus types 1 and 2 were studied by centrifugation in sucrose and cesium chloride density gradients with a high resolution and satisfactory infectivity recovery. It was shown that two populations of infectious virions differing in buoyant density coexisted, the difference being slight but definite. The ratio of heavy (H) to light (L) viral particles varied depending upon the solute used, the strains of virus, and the cell origin. Circumstances favoring degradation of viral infectivity tended to increase the H portion. Incubation at 37 degrees C largely converted L to H, and heating at 45 degrees C converted all virions to H without infectivity. The L to H conversion was irreversible, and no populations intermediate between L and H were clearly observed. Inactivation by UV light irradiation did not affect the density pattern. That H was not an artefact due to penetration of solutes, osmotic pressure, viral aggregation, or loss of the envelope was shown experimentally. A difference in the outer shape of particles between negatively stained L and H populations was demonstrated by electron microscopy. Both cell-released and cell-bound herpes simplex virus particles gave essentially the same result with respect to the above characteristics. The effect of limiting dilutions of antiserum was similar to that of mild thermal treatment, in that denser virions increased parallel to a decrease in less dense virions. Sensitization with early immunoglobulin G, composed mainly of complement-requiring neutralizing antibody, caused the density transition, and subsequent addition of complement resulted in a further increase in the buoyant density of the sensitized virions.

  16. Partial purification of the mu opioid receptor irreversibly labeled with (/sup 3/H)b-funaltrexamine

    SciTech Connect

    Liu-Chen, L.Y.; Phillips, C.A.; Tam, S.W.

    1986-03-01

    The mu opioid receptor in bovine striatal membranes was specifically and irreversibly labeled by incubation with 5 nM (/sup 3/H)..beta..-funaltrexamine (approx.-FNA) at 37/sup 0/C for 90 min in the presence of 100 mM NaCl. The specific and irreversible binding of (/sup 3/H)..beta..-FNA as defined by that blocked by 1 /sup +/M naloxone was about 60% of total irreversible binding. The specific irreversible binding was saturable, stereospecific, time-, temperature, and tissue-dependent. Mu opioid ligands were much more potent than delta or kappa ligands in inhibiting the specific irreversible labeling. SDS polyacrylamide gel electrophoresis of solubilized membranes in the presence of 2-mercaptoethanol yielded a major radiolabeled broad band of MW 68-97K daltons, characteristic of a glycoprotein band. This band was not observed in membranes labeled in the presence of excess unlabeled naloxone. The glycoprotein nature of the (/sup 3/H)..beta..-FNA-labeled opioid receptor was confirmed by its binding to a wheat germ agglutinin-Sepharose column and its elution with N-acetylglucosamine.

  17. Inactivation of arginine esterase E-I of Bitis gabonica venom by irreversible inhibitors including a water-soluble carbodiimide, a chloromethyl ketone and isatoic anhydride.

    PubMed

    Gravett, P S; Viljoen, C C; Oosthuizen, M M

    1991-01-01

    1. Esterase E-I from Bitis gabonica was inactivated with irreversible inhibitors which included studies with a water-soluble carbodiimide, an affinity labelling peptide and a mechanism-based inactivator. 2. The reaction with 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide was biphasic and the dominant part followed saturation kinetics. At pH 5.5 a rate constant of 0.4 min-1 for inactive enzyme formation was calculated and a dissociation constant (Ki) of 0.2 M for the enzyme-inhibitor complex. 3. Inactivation with D-Phe-Pro-Arg-chloromethyl ketone indicated a two-step mechanism, for which the reaction parameters at pH 8.0 were determined. The Ki value was 0.2 microM and the inactivation rate was 2.5 min-1. 4. With isatoic anhydride pseudo-first-order kinetics was observed. At pH 8.0 a rate constant of 0.9 min-1 and a Ki of 2.0 mM were obtained. The inactivation of the enzyme was found to be governed by a group in the enzyme showing a pK value of 7.3.

  18. Characterization of CM572, a Selective Irreversible Partial Agonist of the Sigma-2 Receptor with Antitumor Activity

    PubMed Central

    Nicholson, Hilary; Comeau, Anthony; Mesangeau, Christophe; McCurdy, Christopher R.

    2015-01-01

    The sigma-2 receptors are promising therapeutic targets because of their significant upregulation in tumor cells compared with normal tissue. Here, we characterize CM572 [3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)-6-isothiocyanatobenzo[d]oxazol-2(3H)-one] (sigma-1 Ki ≥ 10 µM, sigma-2 Ki = 14.6 ± 6.9 nM), a novel isothiocyanate derivative of the putative sigma-2 antagonist, SN79 [6-acetyl-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one]. CM572 bound irreversibly to sigma-2 receptors by virtue of the isothiocyanate moiety but not to sigma-1. Studies in human SK-N-SH neuroblastoma cells revealed that CM572 induced an immediate dose-dependent increase in cytosolic calcium concentration. A 24-hour treatment of SK-N-SH cells with CM572 induced dose-dependent cell death, with an EC50 = 7.6 ± 1.7 µM. This effect was sustained over 24 hours even after a 60-minute pretreatment with CM572, followed by extensive washing to remove ligand, indicating an irreversible effect consistent with the irreversible binding data. Western blot analysis revealed that CM572 also induced cleavage activation of proapoptotic BH3-interacting domain death agonist. These data suggest irreversible agonist-like activity. Low concentrations of CM572 that were minimally effective were able to attenuate significantly the calcium signal and cell death induced by the sigma-2 agonist CB-64D [(+)-1R,5R-(E)-8-benzylidene-5-(3-hydroxyphenyl)-2-methylmorphan-7-one]. CM572 was also cytotoxic against PANC-1 pancreatic and MCF-7 breast cancer cell lines. The cytotoxic activity of CM572 was selective for cancer cells over normal cells, being much less potent against primary human melanocytes and human mammary epithelial cells. Taken together, these data show that CM572 is a selective, irreversible sigma-2 receptor partial agonist. This novel irreversible ligand may further our understanding of the endogenous role of this receptor, in addition to having potential use in targeted

  19. Characterization of CM572, a Selective Irreversible Partial Agonist of the Sigma-2 Receptor with Antitumor Activity.

    PubMed

    Nicholson, Hilary; Comeau, Anthony; Mesangeau, Christophe; McCurdy, Christopher R; Bowen, Wayne D

    2015-08-01

    The sigma-2 receptors are promising therapeutic targets because of their significant upregulation in tumor cells compared with normal tissue. Here, we characterize CM572 [3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)-6-isothiocyanatobenzo[d]oxazol-2(3H)-one] (sigma-1 Ki ≥ 10 µM, sigma-2 Ki = 14.6 ± 6.9 nM), a novel isothiocyanate derivative of the putative sigma-2 antagonist, SN79 [6-acetyl-3-(4-(4-(4-fluorophenyl)piperazin-1-yl)butyl)benzo[d]oxazol-2(3H)-one]. CM572 bound irreversibly to sigma-2 receptors by virtue of the isothiocyanate moiety but not to sigma-1. Studies in human SK-N-SH neuroblastoma cells revealed that CM572 induced an immediate dose-dependent increase in cytosolic calcium concentration. A 24-hour treatment of SK-N-SH cells with CM572 induced dose-dependent cell death, with an EC50 = 7.6 ± 1.7 µM. This effect was sustained over 24 hours even after a 60-minute pretreatment with CM572, followed by extensive washing to remove ligand, indicating an irreversible effect consistent with the irreversible binding data. Western blot analysis revealed that CM572 also induced cleavage activation of proapoptotic BH3-interacting domain death agonist. These data suggest irreversible agonist-like activity. Low concentrations of CM572 that were minimally effective were able to attenuate significantly the calcium signal and cell death induced by the sigma-2 agonist CB-64D [(+)-1R,5R-(E)-8-benzylidene-5-(3-hydroxyphenyl)-2-methylmorphan-7-one]. CM572 was also cytotoxic against PANC-1 pancreatic and MCF-7 breast cancer cell lines. The cytotoxic activity of CM572 was selective for cancer cells over normal cells, being much less potent against primary human melanocytes and human mammary epithelial cells. Taken together, these data show that CM572 is a selective, irreversible sigma-2 receptor partial agonist. This novel irreversible ligand may further our understanding of the endogenous role of this receptor, in addition to having potential use in targeted

  20. Active site directed irreversible inactivation of brewers' yeast pyruvate decarboxylase by the conjugated substrate analogue (E)-4-(4-chlorophenyl)-2-oxo-3-butenoic acid: development of a suicide substrate.

    PubMed

    Kuo, D J; Jordan, F

    1983-08-02

    (E)-4-(4-Chlorophenyl)-2-oxo-3-butenoic acid (CPB) was found to irreversibly inactivate brewers' yeast pyruvate decarboxylase (PDC, EC 4.1.1.1) in a biphasic, sigmoidal manner, as is found for the kinetic behavior of substrate. An expression was derived for two-site irreversible inhibition of allosteric enzymes, and the kinetic behavior of CPB fit the expression for two-site binding. The calculated Ki's of 0.7 mM and 0.3 mM for CPB were assigned to the catalytic site and the regulatory site, respectively. The presence of pyruvic acid at high concentrations protected PDC from inactivation, whereas low concentrations of pyruvic acid accelerated inactivation by CPB. Pyruvamide, a known allosteric activator of PDC, was found to enhance inactivation by CPB. The results can be explained if pyruvamide binds only to a regulatory site, but CPB and pyruvic acid compete for both the regulatory and the catalytic centers. [1-14C]CPB was found to lose 14CO2 concurrently with the inactivation of the enzyme. Therefore, CPB was being turned over by PDC, in addition to inactivating it. CPB can be labeled a suicide-type inactivator for PDC.

  1. Partial hydrogenation induced interaction in a graphene-SiO2 interface: irreversible modulation of device characteristics.

    PubMed

    Iwasaki, Takuya; Muruganathan, Manoharan; Schmidt, Marek E; Mizuta, Hiroshi

    2017-01-26

    The transformation of systematic vacuum and hydrogen annealing effects in graphene devices on the SiO2 surface is reported based on experimental and van der Waals interaction corrected density functional theory (DFT) simulation results. Vacuum annealing removes p-type dopants and reduces charged impurity scattering in graphene. Moreover, it induces n-type doping into graphene, leading to the improvement of the electron mobility and conductivity in the electron transport regime, which are reversed by exposing to atmospheric environment. On the other hand, annealing in hydrogen/argon gas results in smaller n-type doping along with a decrease in the overall conductivity and carrier mobility. This degradation of the conductivity is irreversible even the graphene devices are exposed to ambience. This was clarified by DFT simulations: initially, silicon dangling bonds were partially terminated by hydrogen, subsequently, the remaining dangling bonds became active and the distance between the graphene and SiO2 surface decreased. Moreover, both annealing methods affect the graphene channel including the vicinity of the metal contacts, which plays an important role in asymmetric carrier transport.

  2. Interactions of peptide triazole thiols with Env gp120 induce irreversible breakdown and inactivation of HIV-1 virions

    PubMed Central

    2013-01-01

    Background We examined the underlying mechanism of action of the peptide triazole thiol, KR13 that has been shown previously to specifically bind gp120, block cell receptor site interactions and potently inhibit HIV-1 infectivity. Results KR13, the sulfhydryl blocked KR13b and its parent non-sulfhydryl peptide triazole, HNG156, induced gp120 shedding but only KR13 induced p24 capsid protein release. The resulting virion post virolysis had an altered morphology, contained no gp120, but retained gp41 that bound to neutralizing gp41 antibodies. Remarkably, HIV-1 p24 release by KR13 was inhibited by enfuvirtide, which blocks formation of the gp41 6-helix bundle during membrane fusion, while no inhibition of p24 release occurred for enfuvirtide-resistant virus. KR13 thus appears to induce structural changes in gp41 normally associated with membrane fusion and cell entry. The HIV-1 p24 release induced by KR13 was observed in several clades of HIV-1 as well as in fully infectious HIV-1 virions. Conclusions The antiviral activity of KR13 and its ability to inactivate virions prior to target cell engagement suggest that peptide triazole thiols could be highly effective in inhibiting HIV transmission across mucosal barriers and provide a novel probe to understand biochemical signals within envelope that are involved in membrane fusion. PMID:24330857

  3. Interactions of peptide triazole thiols with Env gp120 induce irreversible breakdown and inactivation of HIV-1 virions.

    PubMed

    Bastian, Arangassery Rosemary; Contarino, Mark; Bailey, Lauren D; Aneja, Rachna; Moreira, Diogo Rodrigo Magalhaes; Freedman, Kevin; McFadden, Karyn; Duffy, Caitlin; Emileh, Ali; Leslie, George; Jacobson, Jeffrey M; Hoxie, James A; Chaiken, Irwin

    2013-12-13

    We examined the underlying mechanism of action of the peptide triazole thiol, KR13 that has been shown previously to specifically bind gp120, block cell receptor site interactions and potently inhibit HIV-1 infectivity. KR13, the sulfhydryl blocked KR13b and its parent non-sulfhydryl peptide triazole, HNG156, induced gp120 shedding but only KR13 induced p24 capsid protein release. The resulting virion post virolysis had an altered morphology, contained no gp120, but retained gp41 that bound to neutralizing gp41 antibodies. Remarkably, HIV-1 p24 release by KR13 was inhibited by enfuvirtide, which blocks formation of the gp41 6-helix bundle during membrane fusion, while no inhibition of p24 release occurred for enfuvirtide-resistant virus. KR13 thus appears to induce structural changes in gp41 normally associated with membrane fusion and cell entry. The HIV-1 p24 release induced by KR13 was observed in several clades of HIV-1 as well as in fully infectious HIV-1 virions. The antiviral activity of KR13 and its ability to inactivate virions prior to target cell engagement suggest that peptide triazole thiols could be highly effective in inhibiting HIV transmission across mucosal barriers and provide a novel probe to understand biochemical signals within envelope that are involved in membrane fusion.

  4. Specific, irreversible inactivation of the epidermal growth factor receptor and erbB2, by a new class of tyrosine kinase inhibitor

    PubMed Central

    Fry, David W.; Bridges, Alexander J.; Denny, William A.; Doherty, Annette; Greis, Kenneth D.; Hicks, James L.; Hook, Kenneth E.; Keller, Paul R.; Leopold, Wilbur R.; Loo, Joseph A.; McNamara, Dennis J.; Nelson, James M.; Sherwood, Veronika; Smaill, Jeff B.; Trumpp-Kallmeyer, Susanne; Dobrusin, Ellen M.

    1998-01-01

    A class of high-affinity inhibitors is disclosed that selectively target and irreversibly inactivate the epidermal growth factor receptor tyrosine kinase through specific, covalent modification of a cysteine residue present in the ATP binding pocket. A series of experiments employing MS, molecular modeling, site-directed mutagenesis, and 14C-labeling studies in viable cells unequivocally demonstrate that these compounds selectively bind to the catalytic domain of the epidermal growth factor receptor with a 1:1 stoichiometry and alkylate Cys-773. While the compounds are essentially nonreactive in solution, they are subject to rapid nucleophilic attack by this particular amino acid when bound in the ATP pocket. The molecular orientation and positioning of the acrylamide group in these inhibitors in relation to Cys-773 entirely support these results as determined from docking experiments in a homology-built molecular model of the ATP site. Evidence is also presented to indicate that the compounds interact in an analogous fashion with erbB2 but have no activity against the other receptor tyrosine kinases or intracellular tyrosine kinases that were tested in this study. Finally, a direct comparison between 6-acrylamido-4-anilinoquinazoline and an equally potent but reversible analog shows that the irreversible inhibitor has far superior in vivo antitumor activity in a human epidermoid carcinoma xenograft model with no overt toxicity at therapeutically active doses. The activity profile for this compound is prototypical of a generation of tyrosine kinase inhibitors with great promise for therapeutic significance in the treatment of proliferative disease. PMID:9751783

  5. (±)-(1S,2R,5S)-5-Amino-2-fluorocyclohex-3-ene Carboxylic Acid. A Potent GABA Aminotransferase Inactivator that Irreversibly Inhibits through an Elimination-Aromatization Pathway†

    PubMed Central

    Wang, Zhiyong; Yuan, Hai; Nikolic, Dejan; Van Breemen, Richard B.; Silverman, Richard B.

    2008-01-01

    Inhibition of γ-aminobutyric acid aminotransferase (GABA-AT) raises the concentration of GABA, an inhibitory neurotransmitter in human brain, which could have therapeutic applications for a variety of neurological diseases including epilepsy. Based on studies of several previously synthesized conformationally-restricted GABA-AT inhibitors, (±)- (1S,2R,5S)-5-amino-2-fluorocyclohex-3-ene carboxylic acid (12) was designed as a mechanismbased inactivator. This compound was shown to irreversibly inhibit GABA-AT; substrate protects the enzyme from inactivation. Mechanistic experiments demonstrated the loss of one fluoride ion per active site during inactivation and the formation of N-m-carboxyphenylpyridoxamine 5′-phosphate (26), the same product generated by inactivation of GABA-AT by gabaculine (8). An elimination-aromatization mechanism is proposed to account for these results. PMID:17128990

  6. Pharmacokinetics and Disposition of the Thiouracil Derivative PF-06282999, an Orally Bioavailable, Irreversible Inactivator of Myeloperoxidase Enzyme, Across Animals and Humans.

    PubMed

    Dong, Jennifer Q; Varma, Manthena V; Wolford, Angela; Ryder, Tim; Di, Li; Feng, Bo; Terra, Steven G; Sagawa, Kazuko; Kalgutkar, Amit S

    2016-02-01

    The thiouracil derivative PF-06282999 [2-(6-(5-chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide] is an irreversible inactivator of myeloperoxidase and is currently in clinical trials for the potential treatment of cardiovascular diseases. Concerns over idiosyncratic toxicity arising from bioactivation of the thiouracil motif to reactive species in the liver have been largely mitigated through the physicochemical (molecular weight, lipophilicity, and topological polar surface area) characteristics of PF-06282999, which generally favor elimination via nonmetabolic routes. To test this hypothesis, pharmacokinetics and disposition studies were initiated with PF-06282999 using animals and in vitro assays, with the ultimate goal of predicting human pharmacokinetics and elimination mechanisms. Consistent with its physicochemical properties, PF-06282999 was resistant to metabolic turnover from liver microsomes and hepatocytes from animals and humans and was devoid of cytochrome P450 inhibition. In vitro transport studies suggested moderate intestinal permeability and minimal transporter-mediated hepatobiliary disposition. PF-06282999 demonstrated moderate plasma protein binding across all of the species. Pharmacokinetics in preclinical species characterized by low to moderate plasma clearances, good oral bioavailability at 3- to 5-mg/kg doses, and renal clearance as the projected major clearance mechanism in humans. Human pharmacokinetic predictions using single-species scaling of dog and/or monkey pharmacokinetics were consistent with the parameters observed in the first-in-human study, conducted in healthy volunteers at a dose range of 20-200 mg PF-06282999. In summary, disposition characteristics of PF-06282999 were relatively similar across preclinical species and humans, with renal excretion of the unchanged parent emerging as the principal clearance mechanism in humans, which was anticipated based on its physicochemical properties and

  7. Partial X chromosome trisomy with functional disomy of Xp due to failure of X inactivation

    SciTech Connect

    Gustashaw, K.M.; Zurcher, V.; Dickerman, L.H.; Stallard, R.; Willard, H.F.

    1994-10-15

    A 5-month-old girl with mild phenotypic abnormalities, developmental delay, and seizures was found to have the de novo karyotype 46,XX,-13,+der(13)t(X;13)(p21.2;p11.1). The partial trisomy of Xp21.2 {yields} pter was confirmed with fluorescence in situ hybridization, using an X chromosome painting probe and several cosmid and YAC probes for Xp sequences. Replication banding showed that one of the structurally normal X chromosomes was late-replicating, but that the Xp segment of the der(13) was early-replicating in all cells examined. Since segments of the X chromosome separated from the X inactivation center in Xq13.2 cannot undergo X inactivation, the result is functional disomy of distal Xp. As the loss of short arm material from chromosome 13 is not considered to be clinically significant, the genomic imbalance of Xp expressed in this patient most likely accounts for her abnormal phenotype. 39 refs., 5 figs., 1 tab.

  8. An inactivated influenza D virus vaccine partially protects cattle from respiratory disease caused by homologous challenge.

    PubMed

    Hause, Ben M; Huntimer, Lucas; Falkenberg, Shollie; Henningson, Jamie; Lechtenberg, Kelly; Halbur, Tom

    2017-02-01

    Originally isolated from swine, the proposed influenza D virus has since been shown to be common in cattle. Inoculation of IDV to naïve calves resulted in mild respiratory disease histologically characterized by tracheitis. As several studies have associated the presence of IDV with acute bovine respiratory disease (BRD), we sought to investigate the efficacy of an inactivated IDV vaccine. Vaccinated calves seroconverted with hemagglutination inhibition titers 137-169 following two doses. Non-vaccinated calves challenged with a homologous virus exhibited signs of mild respiratory disease from days four to ten post challenge which was significantly different than negative controls at days five and nine post challenge. Peak viral shedding of approximately 5 TCID50/mL was measured in nasal and tracheal swabs and bronchoalveolar lavage fluids four to six days post challenge. Viral titers were significantly (P<0.05) decreased 1.4 TCID50/mL, 3.6 TCID50/mL and 5.0 TCID50/mL, respectively, in the aforementioned samples collected from vaccinated animals compared to non-vaccinated controls at peak shedding. Viral antigen was detected in the respiratory epithelium of the nasal turbinates and trachea by immunohistochemistry from all unvaccinated calves but in significantly fewer vaccinates. Inflammation characterized by neutrophils was observed in the nasal turbinate and trachea but not appreciably in lungs. Together these results support an etiologic role for IDV in BRD and demonstrate that partial protection is afforded by an inactivated vaccine. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Partially irreversible paresis of the deep peroneal nerve caused by osteocartilaginous exostosis of the fibula without affecting the tibialis anterior muscle.

    PubMed

    Paprottka, Felix Julian; Machens, Hans-Günther; Lohmeyer, Jörn Andreas

    2012-08-01

    Dysfunction of the lower limb's muscles can cause severe impairment and immobilisation of the patient. As one of the leg's major motor and sensory nerves, the deep peroneal nerve (synonym: deep fibular nerve) plays a very important role in muscle innervation in the lower extremities. We report the case of a 19-year-old female patient, who suffered from a brace-like exostosis 6-cm underneath her left fibular head causing a partially irreversible paresis of her deep peroneal nerve. This nerve damage resulted in complete atrophy of her extensor digitorum longus and extensor hallucis longus muscle, and in painful sensory disturbance at her left shin and first web space. The tibialis anterior muscle stayed intact because its motor branch left the deep peroneal nerve proximal to the nerve lesion. Diagnosis was first verified 6 years after the onset of symptoms by a magnetic resonance imaging (MRI) scan of her complete left lower leg. Subsequently, the patient was operated on in our clinic, where a neurolysis was performed and the 4-cm-long osteocartilaginous exostosis was removed. Paralysis was already irreversible but sensibility returned completely after neurolysis. The presented case shows that an osteocartilaginous exostosis can be the cause for partial deep peroneal nerve paresis. If this disorder is diagnosed at an early stage, nerve damage is reversible. Typical for an exostosis is its first appearance during the juvenile growth phase. Copyright © 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  10. Partial inactivation of Ankrd26 causes diabetes with enhanced insulin responsiveness of adipose tissue in mice

    PubMed Central

    Raciti, G. A.; Bera, T. K.; Gavrilova, O.; Pastan, I.

    2013-01-01

    Aims/hypothesis Ankyrin repeat domain 26 (ANKRD26) is a newly described gene located at 10p12 in humans, a locus identified with some forms of hereditary obesity. Previous studies showed that partial inactivation of Ankrd26 causes hyperphagia, obesity and gigantism in mice. We hypothesized that Ankrd26 mutant (MT) mice could develop diabetes and we sought to establish if the observed phenotype could be solely related to the development of obesity or could be caused by a direct action of Ankrd26 in peripheral tissues. Methods To test the hypothesis, a full metabolic characterization of the Ankrd26 MT mice under ad libutim feeding or placed under two different calorie restricted dietary regimens was completed. Results Highly obese Ankrd26 MT mice develop an unusual form of diabetes in which white adipose tissue (WAT) is insulin sensitive, while other tissues are insulin resistant. When obese MT mice were placed on a food-restricted diet their weight and glucose homeostasis returned to normal. Additionally, when young MT mice were placed on a pair-feeding diet with normal mice, they maintained a normal body weight but showed better glucose tolerance than normal mice, an increased responsiveness of WAT to insulin and enhanced phosphorylation of the insulin receptor. Conclusions/interpratation These findings show that the Ankrd26 protein has at least two functions in mice. One is to control the response of WAT to insulin and the other is to control appetite, which when mutated leads to hyperphagia and diabetes in an obesity-dependent manner. PMID:21842266

  11. Inactivation of Escherichia coli on blueberries using cold plasma with chemical augmentation inside a partial vacuum

    USDA-ARS?s Scientific Manuscript database

    Justification: The mechanism by which cold plasma inactivates pathogens is through the production of free reactive chemical species. Unfortunately, the most reactive chemical species have the shortest half-life. In a vacuum their half-life is believed to be prolonged. Additionally, these reactive sp...

  12. X inactivation in Rett syndrome: A preliminary study showing partial preferential inactivation of paternal X with the M27{beta} probe

    SciTech Connect

    Camus, P.; Abbadi, N.; Gilgenkrantz, S.

    1994-04-15

    Rett syndrome (RS) is a severe progressive neurological disorder occurring exclusively in females. Most cases are sporadic. The few familial cases (less than 1%) cannot be explained by a simple mode of inheritance. Several hypotheses have been proposed: X-linked male lethal mutation, maternal uniparental disomy, fresh mutation on the X chromosome, involvement of mitochondrial DNA and differential inactivation with metabolic interference of X-borne alleles. The authors have examined the pattern of X inactivation in 10 affected girls who were selected according to the clinical criteria previously described and accepted by the French Rett Scientific Committee. The X inactivation pattern was studied by analysis of methylation at the hypervariable locus DXS255 with the M27{beta} probe. The results show a more-or-less skewed inactivation of paternal X in 8 Rett females, and 2 cases of symmetrical inactivation. In control girls, inactivation was symmetrical cases and the maternal X has been preferentially inactivated in the other 2 cases. In no case was a total skewed inactivation observed. Though there was clear evidence for a preferential paternal X inactivation that was statistically significant further studies are necessary to establish a relationship between X inactivation pattern and Rett syndrome.

  13. Reversible Activation of Halophilic β-lactamase from Methanol-Induced Inactive Form: Contrast to Irreversible Inactivation of Non-Halophilic Counterpart.

    PubMed

    Tokunaga, Hiroko; Maeda, Junpei; Arakawa, Tsutomu; Tokunaga, Masao

    2017-06-01

    Effects of a water-miscible organic solvent, methanol, on the structure and activity of halophilic β-lactamase derived from Chromohalobacter sp.560 (HaBla), were investigated by means of circular dichroism (CD) measurement and enzymatic activity determination. Beta-lactamase activity was enhanced about 1.2-fold in the presence of 10-20% methanol. CD measurement of HaBla revealed different structures depending on the methanol concentration: native-like active form (Form I) in 10-20% methanol and methanol-induced inactive form at higher concentration (Form II in 40-60% and Form III in 75-80% methanol). Incubation of HaBla with 40% methanol led to the complete loss of activity within ~80 min accompanied by the formation of Form II, whose activity was recovered promptly up to ~80% of full activity upon dilution of the methanol concentration to 10%. In addition, when the protein concentration was sufficiently high (e.g., 0.7 mg/ml), HaBla activity of Form III in 75% methanol could be recovered in the same way (with slightly slower recovery rate), upon dilution of the methanol concentration. In contrast, non-halophilic β-lactamase from Escherichia coli K12 strain MG1655 (EcBla) was irreversibly denatured in the presence of 40% methanol. HaBla showed remarkable ability to renature from the methanol-induced inactive states.

  14. The disulfiram metabolites S-methyl-N,N-diethyldithiocarbamoyl sulfoxide and S-methyl-N,N-diethylthiocarbamoyl sulfone irreversibly inactivate betaine aldehyde dehydrogenase from Pseudomonas aeruginosa, both in vitro and in situ, and arrest bacterial growth.

    PubMed

    Zaldívar-Machorro, Víctor J; López-Ortiz, Manuel; Demare, Patricia; Regla, Ignacio; Muñoz-Clares, Rosario A

    2011-02-01

    Betaine aldehyde dehydrogenase from the human opportunistic pathogen Pseudomonas aeruginosa (PaBADH) catalyzes the irreversible, NAD(P)(+)-dependent oxidation of betaine aldehyde, producing glycine betaine, an osmoprotectant. PaBADH participates in the catabolism of choline and likely in the defense against the osmotic and oxidative stresses to which the bacterium is exposed when infecting human tissues. Given that choline or choline precursors are abundant in infected tissues, PaBADH is a potential drug target because its inhibition will lead to the build up of the toxic betaine aldehyde inside bacterial cells. We tested the thiol reagents, disulfiram (DSF) and five DSF metabolites-diethyldithiocarbamic acid (DDC), S-methyl-N,N-diethyldithiocarbamoyl sulfoxide (MeDDTC-SO) and sulfone (MeDDTC-SO(2)), and S-methyl-N,N-diethylthiocarbamoyl sulfoxide (MeDTC-SO) and sulfone (MeDTC-SO(2))-as inhibitors of PaBADH and P. aeruginosa growth. As in vitro PaBADH inhibitors, their order of potency was: MeDDTC-SO(2)>DSF>MeDTC-SO(2)>MeDDTC-SO>MeDTC-SO. DDC did not inactivate the enzyme. PaBADH inactivation by DSF metabolites (i) was not affected by NAD(P)(+), (ii) could not be reverted by dithiothreitol, and (iii) did not affect the quaternary structure of the enzyme. Of the DSF metabolites tested, MeDTC-SO(2) and MeDDTC-SO produced significant in situ PaBADH inactivation and arrest of P. aeruginosa growth in choline containing media, in which the expression of PaBADH is induced. They had no effect in media lacking choline, indicating that PaBADH is their main intracellular target, and that arrest of growth is due to accumulation of betaine aldehyde. The in vitro and in situ kinetics of enzyme inactivation by these two compounds were very similar, indicating no restriction on their uptake by the cells. MeDDTC-SO(2) and DSF have no inhibitory effects in situ, probably because their high reactivity towards intracellular nonessential thiols causes their depletion. Our results

  15. Irreversible cycle in linear irreversible thermodynamics

    NASA Astrophysics Data System (ADS)

    Wang, Xian-Zhi

    2010-10-01

    The reversible Carnot cycle in reversible thermodynamics is composed of two reversible heat exchange processes and two reversible adiabatic processes. We construct an irreversible cycle in linear irreversible thermodynamics by analogy with the reversible Carnot cycle. The irreversible cycle is composed of two linear irreversible heat exchange processes and two linear irreversible adiabatic processes. It is found that the Curzon-Alhborn efficiency can be attained if the power for each of the four linear irreversible processes reaches its maximum. The maximum efficiency is the Carnot efficiency. The strong coupling condition is prerequisite for the respective attainment of the Curzon-Alhborn efficiency and the Carnot efficiency.

  16. Specific labeling and partial inactivation of cytochrome oxidase by fluorescein mercuric acetate.

    PubMed

    Stonehuerner, J; O'Brien, P; Kendrick, L; Hall, J; Millett, F

    1985-09-25

    Addition of 1 eq of fluorescein mercuric acetate (FMA) to beef heart cytochrome oxidase was found to inhibit the steady-state electron transfer activity by 50%, but further additions up to 10 eq had no additional effect on activity. The partial inhibition caused by FMA is thus similar to that observed with other mercury compounds (Mann, A. J., and Auer, H. E. (1980) J. Biol. Chem. 255, 454-458). The fluorescence of FMA was quenched by a factor of 10 upon binding to cytochrome oxidase, consistent with the involvement of a sulfhydryl group. However, addition of mercuric chloride to FMA-cytochrome oxidase resulted in an increase in fluorescence, suggesting that FMA was displaced from the high affinity binding site. Cytochrome c binding to FMA-cytochrome oxidase resulted in a 10% decrease in the fluorescence, possibly caused by Forster energy transfer from FMA to the cytochrome c heme. The binding site for FMA in cytochrome oxidase was investigated by carrying out sodium dodecyl sulfate gel electrophoresis under progressively milder dissociation conditions. When FMA-cytochrome oxidase was dissociated with 3% sodium dodecyl sulfate and 6 M urea, FMA was predominantly bound to subunit II following electrophoresis. However, when the dissociation was carried out at 4 degrees C in the absence of urea with progressively smaller amounts of lithium dodecyl sulfate, the labeling of subunit II decreased and that of subunit I increased. These experiments demonstrate that mercury compounds bind to a high affinity site on cytochrome oxidase, possibly located in subunit I, but then migrate to subunit II under the normal sodium dodecyl sulfate gel electrophoresis conditions. A definitive assignment of the high affinity binding site in the native enzyme cannot be made, however, because it is possible that mercury compounds can migrate from one sulfhydryl to another under even the mildest electrophoresis conditions.

  17. Efficacy of orally administered prednisolone versus partial endodontic treatment on pain reduction in emergency care of acute irreversible pulpitis of mandibular molars: study protocol for a randomized controlled trial.

    PubMed

    Kérourédan, Olivia; Jallon, Léonard; Perez, Paul; Germain, Christine; Péli, Jean-François; Oriez, Dominique; Fricain, Jean-Christophe; Arrivé, Elise; Devillard, Raphaël

    2017-03-28

    Irreversible pulpitis is a highly painful inflammatory condition of the dental pulp which represents a common dental emergency. Recommended care is partial endodontic treatment. The dental literature reports major difficulties in achieving adequate analgesia to perform this emergency treatment, especially in the case of mandibular molars. In current practice, short-course, orally administered corticotherapy is used for the management of oral pain of inflammatory origin. The efficacy of intraosseous local steroid injections for irreversible pulpitis in mandibular molars has already been demonstrated but resulted in local comorbidities. Oral administration of short-course prednisolone is simple and safe but its efficacy to manage pain caused by irreversible pulpitis has not yet been demonstrated. This trial aims to evaluate the noninferiority of short-course, orally administered corticotherapy versus partial endodontic treatment for the emergency care of irreversible pulpitis in mandibular molars. This study is a noninferiority, open-label, randomized controlled clinical trial conducted at the Bordeaux University Hospital. One hundred and twenty subjects will be randomized in two 1:1 parallel arms: the intervention arm will receive one oral dose of prednisolone (1 mg/kg) during the emergency visit, followed by one morning dose each day for 3 days and the reference arm will receive partial endodontic treatment. Both groups will receive planned complete endodontic treatment 72 h after enrollment. The primary outcome is the proportion of patients with pain intensity below 5 on a Numeric Scale 24 h after the emergency visit. Secondary outcomes include comfort during care, the number of injected anesthetic cartridges when performing complete endodontic treatment, the number of antalgic drugs and the number of patients coming back for consultation after 72 h. This randomized trial will assess the ability of short-term corticotherapy to reduce pain in irreversible

  18. Examination of the Human Cytochrome P4503A4 Induction Potential of PF-06282999, an Irreversible Myeloperoxidase Inactivator: Integration of Preclinical, In Silico, and Biomarker Methodologies in the Prediction of the Clinical Outcome.

    PubMed

    Dong, Jennifer Q; Gosset, James R; Fahmi, Odette A; Lin, Zhiwu; Chabot, Jeffrey R; Terra, Steven G; Le, Vu; Chidsey, Kristin; Nouri, Parya; Kim, Albert; Buckbinder, Leonard; Kalgutkar, Amit S

    2017-05-01

    The propensity for CYP3A4 induction by 2-(6-(5-chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide (PF-06282999), an irreversible inactivator of myeloperoxidase, was examined in the present study. Studies using human hepatocytes revealed moderate increases in CYP3A4 mRNA and midazolam-1'-hydroxylase activity in a PF-06282999 dose-dependent fashion. At the highest tested concentration of 300 μM, PF-06282999 caused maximal induction in CYP3A4 mRNA and enzyme activity ranging from 56% to 86% and 47% t0 72%, respectively, of rifampicin response across the three hepatocyte donor pools. In a clinical drug-drug interaction (DDI) study, the mean midazolam Cmax and area under the curve (AUC) values following 14-day treatment with PF-06282999 decreased in a dose-dependent fashion with a maximum decrease in midazolam AUC0-inf and Cmax of ∼57.2% and 41.1% observed at the 500 mg twice daily dose. The moderate impact on midazolam pharmacokinetics at the 500 mg twice daily dose of PF-06282999 was also reflected in statistically significant changes in plasma 4β-hydroxycholesterol/cholesterol and urinary 6β-hydroxycortisol/cortisol ratios. Changes in plasma and urinary CYP3A4 biomarkers did not reach statistical significance at the 125 mg three times daily dose of PF-06282999, despite a modest decrease in midazolam systemic exposure. Predicted DDI magnitude based on the in vitro induction parameters and simulated pharmacokinetics of perpetrator (PF-06282999) and victim (midazolam) using the Simcyp (Simcyp Ltd., Sheffield, United Kingdom) population-based simulator were in reasonable agreement with the observed clinical data. Since the magnitude of the 4β-hydroxycholesterol or 6β-hydroxycortisol ratio change was generally smaller than the magnitude of the midazolam AUC change with PF-06282999, a pharmacokinetic interaction study with midazolam ultimately proved important for assessment of DDI via CYP3A4 induction. Copyright © 2017 by The American

  19. Differences in dopamine receptor reserve for N-n-propylnorapomorphine enantiomers: single unit recording studies after partial inactivation of receptors by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline.

    PubMed

    Cox, R F; Waszczak, B L

    1989-01-01

    Previous studies with (S)-(+)-N-n-propylnorapomorphine (NPA), an enantiomer of the potent dopaminergic agonist (R)-(-)-NPA, showed that this compound had a complex pharmacological profile. For example, (S)-(+)NPA had weak dopaminergic agonist potency, in that it could slow and ultimately stop firing of substantia nigra and ventral tegmental area dopamine neurons. However, antagonist properties were also evident inasmuch as immediate pretreatment with a low dose of (S)-(+)-NPA caused a significant rightward shift of the (R)-(-)-NPA dose-response curve. This dual agonist-antagonist nature of (S)-(+)-NPA suggested a low intrinsic efficacy for (S)-(+)-NPA. To test this hypothesis, we conducted dose-response studies for the inhibition of rat substantia nigra dopamine cell firing by (R)-(-)- and (S)-(+)-NPA 1 day after partial irreversible dopamine receptor inactivation with 6 mg/kg N-ethoxycarbonyl-2-ethoxy-1-2-dihydroquinoline (EEDQ) in an ethanol vehicle. This degree of inactivation resulted in a significant, parallel, rightward shift of the (R)-(-)-NPA dose-response curve relative to ethanol-treated control rats, with no loss of maximal response. After pretreatment with the same dose of EEDQ, however, the maximal response to (S)-(+)-NPA was reduced by 22% with no shift on the dose axis. The dose-response curves for control and EEDQ-treated groups were subjected to Furchgott analysis to determine per cent response versus fractional occupancy relationships for each drug. A steep hyperbolic relationship was revealed for (R)-(-)-NPA. Fifty per cent and maximal (greater than 95%) inhibitions of cell firing occurred at 3.5% and approximately 32% receptor occupancies, respectively. Hence, for (R)-(-)-NPA there is about a 68% receptor reserve in this model. The same analysis for (S)-(+)-NPA yielded an occupancy versus response plot that was more shallow and linear. Half-maximal effects occurred at 66% occupancy and the maximal response (96% inhibition) required 94% occupancy

  20. The inactivation of the sortilin gene leads to a partial disruption of prosaposin trafficking to the lysosomes

    SciTech Connect

    Zeng, Jibin; Racicott, Jesse; Morales, Carlos R.

    2009-11-01

    Lysosomes are intracellular organelles which contain enzymes and activator proteins involved in the digestion and recycling of a variety of cellular and extracellular substances. We have identified a novel sorting receptor, sortilin, which is involved in the lysosomal trafficking of the sphingolipid activator proteins, prosaposin and GM{sub 2}AP, and the soluble hydrolases cathepsin D, cathepsin H, and acid sphingomyelinase. Sortilin belongs to a growing family of receptors with homology to the yeast Vps10 protein, which acts as a lysosomal sorting receptor for carboxypeptidase Y. In this study we examined the effects of the sortilin gene inactivation in mice. The inactivation of this gene did not yield any noticeable lysosomal pathology. To determine the existence of an alternative receptor complementing the sorting function of sortilin, we quantified the concentration of prosaposin in the lysosomes of the nonciliated epithelial cells lining the efferent ducts. These cells were chosen because they express sortilin and have a large number of lysosomes containing prosaposin. In addition, the nonciliated cells are known to endocytose luminal prosaposin that is synthesized and secreted by Sertoli cells into the seminiferous luminal fluids. Consequently, the nonciliated cells are capable of targeting both exogenous and endogenous prosaposin to the lysosomes. Using electron microscope immunogold labeling and quantitative analysis, our results demonstrate that inactivation of the sortilin gene produces a significant decrease of prosaposin in the lysosomes. When luminal prosaposin was excluded from the efferent ducts, the level of prosaposin in lysosomes was even lower in the mutant mice. Nonetheless, a significant amount of prosaposin continues to reach the lysosomal compartment. These results strongly suggest the existence of an alternative receptor that complements the function of sortilin and explains the lack of lysosomal storage disorders in the sortilin

  1. Ribosome-inactivating proteins

    PubMed Central

    Walsh, Matthew J; Dodd, Jennifer E; Hautbergue, Guillaume M

    2013-01-01

    Ribosome-inactivating proteins (RIPs) were first isolated over a century ago and have been shown to be catalytic toxins that irreversibly inactivate protein synthesis. Elucidation of atomic structures and molecular mechanism has revealed these proteins to be a diverse group subdivided into two classes. RIPs have been shown to exhibit RNA N-glycosidase activity and depurinate the 28S rRNA of the eukaryotic 60S ribosomal subunit. In this review, we compare archetypal RIP family members with other potent toxins that abolish protein synthesis: the fungal ribotoxins which directly cleave the 28S rRNA and the newly discovered Burkholderia lethal factor 1 (BLF1). BLF1 presents additional challenges to the current classification system since, like the ribotoxins, it does not possess RNA N-glycosidase activity but does irreversibly inactivate ribosomes. We further discuss whether the RIP classification should be broadened to include toxins achieving irreversible ribosome inactivation with similar turnovers to RIPs, but through different enzymatic mechanisms. PMID:24071927

  2. Potentiality, irreversibility, and death.

    PubMed

    Lizza, John P

    2005-02-01

    There has been growing concern about whether individuals who satisfy neurological criteria for death or who become non-heart-beating organ donors are really dead. This concern has focused on the issue of the potential for recovery that these individuals may still have and whether their conditions are irreversible. In this article I examine the concepts of potentiality and irreversibility that have been invoked in the discussions of the definition of death and non-heart-beating organ donation. I initially focus on the recent challenge by D. Alan Shewmon to accepting any neurological criterion of death. I argue that Shewmon relies on a problematic and unrealistic concept of potentiality, and that a better, more realistic concept of potentiality is consistent with accepting a neurological criterion for death. I then turn to an analysis of how the concept of irreversibility has been used in discussion of non-heart-beating organ donation. Similarly, I argue that some participants in this discussion have invoked a problematic and unrealistic concept of irreversibility. I then propose an alternative, more realistic account of irreversibility that explains how "irreversibility" should be understood in the definition and criteria of death.

  3. Structural Analysis of Mammalian Cytochrome P450 2B4 Covalently Bound to the Mechanism-Based Inactivator tert-Butylphenylacetylene: Insight into Partial Enzymatic Activity†‡

    PubMed Central

    Gay, Sean C.; Zhang, Haoming; Wilderman, P. Ross; Roberts, Arthur G.; Liu, Tong; Li, Sheng; Lin, Hsia-lien; Zhang, Qinghai; Woods, Virgil L.; Stout, C. David; Hollenberg, Paul F.; Halpert, James R.

    2011-01-01

    A combined structural and computational analysis of rabbit cytochrome P450 2B4 covalently bound to the mechanism-based inactivator tert-butylphenylacetylene (tBPA) has yielded insight into how the enzyme retains partial activity. Since conjugation to tBPA modifies a highly conserved active site residue, the residual activity of tBPA-labeled 2B4 observed in previous studies was puzzling. Here we describe the first crystal structures of a modified mammalian P450, which show an oxygenated metabolite of tBPA conjugated to Thr 302 of helix I. These results are consistent with previous studies that identified Thr 302 as the site of conjugation. In each structure, the core of 2B4 remains unchanged, but the arrangement of plastic regions differs. This results in one structure that is compact and closed. In this conformation, tBPA points toward helix B′, making a 31° angle with the heme plane. This conformation is in agreement with previously performed in silico experiments. However, dimerization of 2B4 in the other structure, which is caused by movement of the B/C loop and helices F through G, alters the position of tBPA. In this case, tBPA lies almost parallel to the heme plane due to the presence of helix F′ of the opposite monomer entering the active site to stabilize the dimer. However, docking experiments using this open form show that tBPA is able to rotate upward to give testosterone and 7-ethoxy-4-trifluoromethylcoumarin access to the heme, which could explain the previously observed partial activity. PMID:21510666

  4. Partial inactivation of GABAA receptors containing the α5 subunit affects the development of adult-born dentate gyrus granule cells.

    PubMed

    Deprez, Francine; Vogt, Fabia; Floriou-Servou, Amalia; Lafourcade, Carlos; Rudolph, Uwe; Tyagarajan, Shiva K; Fritschy, Jean-Marc

    2016-09-01

    Alterations of neuronal activity due to changes in GABAA receptors (GABAA R) mediating tonic inhibition influence different hippocampal functions. Gabra5-null mice and α5 subunit((H105R)) knock-in mice exhibit signs of hippocampal dysfunction, but are capable of improved performance in several learning and memory tasks. Accordingly, alleviating abnormal GABAergic tonic inhibition in the hippocampal formation by selective α5-GABAA R modulators represents a possible therapeutic approach for several intellectual deficit disorders. Adult neurogenesis in the dentate gyrus is an important facet of hippocampal plasticity; it is regulated by tonic GABAergic transmission, as shown by deficits in proliferation, migration and dendritic development of adult-born neurons in Gabra4-null mice. Here, we investigated the contribution of α5-GABAA Rs to granule cell development, using retroviral vectors expressing eGFP for labeling precursor cells in the subgranular zone. Global α5-GABAA R knockout (α5-KO) mice showed no alterations in migration and morphological development of eGFP-positive granule cells. However, upregulation of α1 subunit-immunoreactivity was observed in the hippocampal formation and cerebral cortex. In contrast, partial gene inactivation in α5-heterozygous (α5-het) mice, as well as single-cell deletion of Gabra5 in newborn granule cells from α5-floxed mice, caused severe alterations of migration and dendrite development. In α5-het mice, retrovirally mediated overexpression of Cdk5 resulted in normal migration and dendritic branching, suggesting that Cdk5 cooperates with α5-GABAA Rs to regulate neuronal development. These results show that minor imbalance of α5-GABAA R-mediated transmission may have major consequences for neuronal plasticity; and call for caution upon chronic therapeutic use of negative allosteric modulators acting at these receptors. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  5. Effects of pulsed electric fields on inactivation and metabolic activity of Lactobacillus plantarum in model beer.

    PubMed

    Ulmer, H M; Heinz, V; Gänzle, M G; Knorr, D; Vogel, R F

    2002-01-01

    Inactivation and sublethal injury of Lactobacillus plantarum at different pulsed electric field (PEF) strengths and total energy inputs were investigated to differentiate reversible and irreversible impacts on cell functionality. Lactobacillus plantarum was treated with PEF in model beer (MB) to determine critical values of field strength and energy input for cell inactivation. Below critical values, metabolic activity and membrane integrity were initially reduced without loss of viability. Above critical values, however, irreversible cell damage occurred. Presence of nisin or hop extract, during PEF treatment, resulted in an additional reduction of cell viability by 1;5 log cycles. Also, addition of the hop extract resulted in an additional two log cycles of sublethal injury. Partial reversibility of membrane damage was observed using propidium iodide (PI) uptake and staining. Inoculated MB containing hops was stored after PEF to evaluate the efficacy of such treatment for beer preservation. Cells were inactivated only above critical values of 13 kV x cm(-1) and 64 kJ x kg(-1); below these values cell damage was reversible. Storage experiments revealed that surviving cells were killed after 15 h storage in MB containing hops. Both reversible and irreversible cell damage due to PEF treatment was detected, depending on specific treatment conditions. The combination of PEF and hop addition is a promising nonthermal method of preservation for beer.

  6. Irreversibility time scale.

    PubMed

    Gallavotti, G

    2006-06-01

    Entropy creation rate is introduced for a system interacting with thermostats (i.e., for a system subject to internal conservative forces interacting with "external" thermostats via conservative forces) and a fluctuation theorem for it is proved. As an application, a time scale is introduced, to be interpreted as the time over which irreversibility becomes manifest in a process leading from an initial to a final stationary state of a mechanical system in a general nonequilibrium context. The time scale is evaluated in a few examples, including the classical Joule-Thompson process (gas expansion in a vacuum).

  7. Removal of sodium channel inactivation in squid giant axons by n- bromoacetamide

    PubMed Central

    1978-01-01

    The group-specific protein reagents, N-bromacetamide (NBA) and N- bromosuccinimide (NBS), modify sodium channel gating when perfused inside squid axons. The normal fast inactivation of sodium channels is irreversibly destroyed by 1 mM NBA or NBS near neutral pH. NBA apparently exhibits an all-or-none destruction of the inactivation process at the single channel level in a manner similar to internal perfusion of Pronase. Despite the complete removal of inactivation by NBA, the voltage-dependent activation of sodium channels remains unaltered as determined by (a) sodium current turn-on kinetics, (b) sodium tail current kinetics, (c) voltage dependence of steady-state activation, and (d) sensitivity of sodium channels to external calcium concentration. NBA and NBS, which can cleave peptide bonds only at tryptophan, tyrosine, or histidine residues and can oxidize sulfur- containing amino acids, were directly compared with regard to effects on sodium inactivation to several other reagents exhibiting overlapping protein reactivity spectra. N-acetylimidazole, a tyrosine-specific reagent, was the only other compound examined capable of partially mimicking NBA. Our results are consistent with recent models of sodium inactivation and support the involvement of a tyrosine residue in the inactivation gating structure of the sodium channel. PMID:650167

  8. Human 5-HT7 receptor-induced inactivation of forskolin-stimulated adenylate cyclase by risperidone, 9-OH-risperidone and other "inactivating antagonists".

    PubMed

    Toohey, Nicole; Klein, Michael T; Knight, Jessica; Smith, Carol; Teitler, Milt

    2009-09-01

    We have previously reported on the unusual human 5-hydroxytryptamine(7) (h5-HT(7)) receptor-inactivating properties of risperidone, 9-OH-risperidone, bromocriptine, methiothepin, metergoline, and lisuride. Inactivation was defined as the inability of 10 microM 5-HT to stimulate cAMP accumulation after brief exposure and thorough removal of the drugs from HEK293 cells expressing h5-HT(7) receptors. Herein we report that brief exposure of the h5-HT(7) receptor-expressing cells to inactivating drugs, followed by removal of the drugs, results in potent and efficacious irreversible inhibition of forskolin-stimulated adenylate cyclase activity. Pretreatment, followed by removal of the inactivating drugs inhibited 10 microM forskolin-stimulated adenylate cyclase activity with potencies similar to the drugs' affinities for the h5-HT(7) receptor. The actions of the inactivating drugs were pertussis toxin-insensitive, indicating the lack of G(i) in their mechanism(s) of action. Methiothepin and bromocriptine maximally inhibited 10 microM forskolin-stimulated adenylate cyclase, whereas the other drugs produced partial inhibition, indicating the drugs are inducing slightly different inactive conformations of the h5-HT(7) receptor. Maximal effects of these inactivating drugs occurred within 15 to 30 min of exposure of the cells to the drugs. A G(s)-mediated inhibition of forskolin-stimulated activity has never been reported. The inactivating antagonists seem to induce a stable conformation of the h5-HT(7) receptor, which induces an altered state of G(s), which, in turn, inhibits forskolin-mediated stimulation of adenylate cyclase. These and previous observations indicate that the inactivating antagonists represent a unique class of drugs and may reveal GPCR regulatory mechanisms previously unknown. These drugs may produce innovative approaches to the development of therapeutic drugs.

  9. Partial protection of seasonal trivalent inactivated vaccine against novel pandemic influenza A/H1N1 2009: case-control study in Mexico City

    PubMed Central

    Garcia-Garcia, Lourdes; Valdespino-Gómez, Jose Luis; Lazcano-Ponce, Eduardo; Jimenez-Corona, Aida; Higuera-Iglesias, Anjarath; Cruz-Hervert, Pablo; Cano-Arellano, Bulmaro; Garcia-Anaya, Antonio; Ferreira-Guerrero, Elizabeth; Baez-Saldaña, Renata; Ferreyra-Reyes, Leticia; Ponce-de-León-Rosales, Samuel; Alpuche-Aranda, Celia; Rodriguez-López, Mario Henry; Perez-Padilla, Rogelio; Hernandez-Avila, Mauricio

    2009-01-01

    Objective To evaluate the association of 2008-9 seasonal trivalent inactivated vaccine with cases of influenza A/H1N1 during the epidemic in Mexico. Design Frequency matched case-control study. Setting Specialty hospital in Mexico City, March to May 2009. Participants 60 patients with laboratory confirmed influenza A/H1N1 and 180 controls with other diseases (not influenza-like illness or pneumonia) living in Mexico City or the State of Mexico and matched for age and socioeconomic status. Main outcome measures Odds ratio and effectiveness of trivalent inactivated vaccine against influenza A/H1N1. Results Cases were more likely than controls to be admitted to hospital, undergo invasive mechanical ventilation, and die. Controls were more likely than cases to have chronic conditions that conferred a higher risk of influenza related complications. In the multivariate model, influenza A/H1N1 was independently associated with trivalent inactivated vaccine (odds ratio 0.27, 95% confidence interval 0.11 to 0.66) and underlying conditions (0.15, 0.08 to 0.30). Vaccine effectiveness was 73% (95% confidence interval 34% to 89%). None of the eight vaccinated cases died. Conclusions Preliminary evidence suggests some protection from the 2008-9 trivalent inactivated vaccine against pandemic influenza A/H1N1 2009, particularly severe forms of the disease, diagnosed in a specialty hospital during the influenza epidemic in Mexico City. PMID:19808768

  10. Partial protection of seasonal trivalent inactivated vaccine against novel pandemic influenza A/H1N1 2009: case-control study in Mexico City.

    PubMed

    Garcia-Garcia, Lourdes; Valdespino-Gómez, Jose Luis; Lazcano-Ponce, Eduardo; Jimenez-Corona, Aida; Higuera-Iglesias, Anjarath; Cruz-Hervert, Pablo; Cano-Arellano, Bulmaro; Garcia-Anaya, Antonio; Ferreira-Guerrero, Elizabeth; Baez-Saldaña, Renata; Ferreyra-Reyes, Leticia; Ponce-de-León-Rosales, Samuel; Alpuche-Aranda, Celia; Rodriguez-López, Mario Henry; Perez-Padilla, Rogelio; Hernandez-Avila, Mauricio

    2009-10-06

    To evaluate the association of 2008-9 seasonal trivalent inactivated vaccine with cases of influenza A/H1N1 during the epidemic in Mexico. Frequency matched case-control study. Specialty hospital in Mexico City, March to May 2009. 60 patients with laboratory confirmed influenza A/H1N1 and 180 controls with other diseases (not influenza-like illness or pneumonia) living in Mexico City or the State of Mexico and matched for age and socioeconomic status. Odds ratio and effectiveness of trivalent inactivated vaccine against influenza A/H1N1. Cases were more likely than controls to be admitted to hospital, undergo invasive mechanical ventilation, and die. Controls were more likely than cases to have chronic conditions that conferred a higher risk of influenza related complications. In the multivariate model, influenza A/H1N1 was independently associated with trivalent inactivated vaccine (odds ratio 0.27, 95% confidence interval 0.11 to 0.66) and underlying conditions (0.15, 0.08 to 0.30). Vaccine effectiveness was 73% (95% confidence interval 34% to 89%). None of the eight vaccinated cases died. Preliminary evidence suggests some protection from the 2008-9 trivalent inactivated vaccine against pandemic influenza A/H1N1 2009, particularly severe forms of the disease, diagnosed in a specialty hospital during the influenza epidemic in Mexico City.

  11. Mechanistic insights into cyclooxygenase irreversible inactivation by aspirin.

    PubMed

    Tosco, Paolo; Lazzarato, Loretta

    2009-06-01

    A mechanistic hypothesis for the acetylation of cyclooxygenase (COX) by aspirin is proposed on the basis of a QM/MM study. This mechanism is consistent with previous experimental findings by other investigators. Ser 530 appears to be acetylated under intramolecular general base catalysis provided by the carboxylate moiety of aspirin, while Tyr 385 plays a crucial role in orienting and polarizing the acetyl group.

  12. From instability to irreversibility

    PubMed Central

    Elskens, Y.; Prigogine, I.

    1986-01-01

    A canonical procedure transforming the unitary evolution group Ut in a contracting semigroup Wt for phase-space ensembles has been developed for Kolmogorov dynamical systems in a series of recent papers. This paper investigates the physical meaning of this transformation. We stress that, for sufficiently unstable dynamical systems in which phase-space points are identified with an arbitrary but finite precision, one must take into account the undiscernibility of trajectories having the same asymptotic behavior in the future. The fundamental objects of our description are thus bundles of converging trajectories. We show that such an ensemble, corresponding to initial conditions whose support has finite measure, is then represented by a distribution function (called a Boltzmann ensemble) that evolves to equilibrium under the action of a markovian semigroup. The usual Gibbs-Koopman ensembles satisfying the Liouville equation are recovered as a singular limit. This work validates Boltzmann's intuition for a class of unstable dynamical systems and appears as a step toward the derivation of equations exhibiting irreversibility at a microscopic level. PMID:16593741

  13. Intrinsically irreversible heat engine

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1984-01-01

    A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. the second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat.

  14. Intrinsically irreversible heat engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1984-01-01

    A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. The second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat.

  15. Intrinsically irreversible heat engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1984-12-25

    A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. The second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat. 11 figs.

  16. Chemical studies on the inactivation of Escherichia coli RTEM beta-lactamase by clavulanic acid.

    PubMed

    Charnas, R L; Fisher, J; Knowles, J R

    1978-05-30

    Incubation of clavulanic acid with the beta-lactamase from Escherichia coli RTEM leads to enzyme-catalyzed depletion of clavulanic acid, to transient inhibition, and to irreversible inactivation of the enzyme. Both the transiently inhibited and the irreversibly inactivated species show a marked increase in the absorbance at 281 nm that is proportional to the decrease in enzyme activity. Hydroxylamine treatment of irreversibly inactivated enzyme restores about one-third of the catalytic activity, with a concomitant decrease in absorbance at 281 nm. Polyacrylamide isoelectric focusing of the irreversibly inactivated enzyme shows three bands of approximately equal intensity, different from native enzyme. Upon hydroxylamine treatment, one of the three bands disappears and now focuses identically with native enzyme. It is evident that the irreversible inactivation of enzyme by an excess of clavulanic acid generates three products, one of which can be reactivated by hydroxylamine.

  17. Origin of irreversibility of cell cycle start in budding yeast.

    PubMed

    Charvin, Gilles; Oikonomou, Catherine; Siggia, Eric D; Cross, Frederick R

    2010-01-19

    Budding yeast cells irreversibly commit to a new division cycle at a regulatory transition called Start. This essential decision-making step involves the activation of the SBF/MBF transcription factors. SBF/MBF promote expression of the G1 cyclins encoded by CLN1 and CLN2. Cln1,2 can activate their own expression by inactivating the Whi5 repressor of SBF/MBF. The resulting transcriptional positive feedback provides an appealing, but as yet unproven, candidate for generating irreversibility of Start. Here, we investigate the logic of the Start regulatory module by quantitative single-cell time-lapse microscopy, using strains in which expression of key regulators is efficiently controlled by changes of inducers in a microfluidic chamber. We show that Start activation is ultrasensitive to G1 cyclin. In the absence of CLN1,2-dependent positive feedback, we observe that Start transit is reversible, due to reactivation of the Whi5 transcriptional repressor. Introduction of the positive feedback loop makes Whi5 inactivation and Start activation irreversible, which therefore guarantees unidirectional entry into S phase. A simple mathematical model to describe G1 cyclin turn on at Start, entirely constrained by empirically measured parameters, shows that the experimentally measured ultrasensitivity and transcriptional positive feedback are necessary and sufficient dynamical characteristics to make the Start transition a bistable and irreversible switch. Our study thus demonstrates that Start irreversibility is a property that arises from the architecture of the system (Whi5/SBF/Cln2 loop), rather than the consequence of the regulation of a single component (e.g., irreversible protein degradation).

  18. Selective inactivation of parvulin-like peptidyl-prolyl cis/trans isomerases by juglone.

    PubMed

    Hennig, L; Christner, C; Kipping, M; Schelbert, B; Rücknagel, K P; Grabley, S; Küllertz, G; Fischer, G

    1998-04-28

    In contrast to FK506 binding proteins and cyclophilins, the parvulin family of peptidyl-prolyl cis/trans isomerases (PPIases; E.C. 5.2.1.8) cannot be inhibited by either FK506 or cyclosporin A. We have found that juglone, 5-hydroxy-1,4-naphthoquinone, irreversibly inhibits the enzymatic activity of several parvulins, like the E. coli parvulin, the yeast Ess1/Ptf1, and human Pin1, in a specific manner, thus allowing selective inactivation of these enzymes in the presence of other PPIases. The mode of action was studied by analyzing the inactivation kinetics and the nature of products of the reaction of E. coli parvulin and its Cys69Ala variant with juglone. For all parvulins investigated, complete inactivation was obtained by a slow process that is characterized by pseudo-first-order rate constants in the range of 5.3 x 10(-)4 to 4. 5 x 10(-)3 s-1. The inactivated parvulin contains two juglone molecules that are covalently bound to the side chains of Cys41 and Cys69 because of a Michael addition of the thiol groups to juglone. Redox reactions did not contribute to the inactivation process. Because thiol group modification was shown to proceed 5-fold faster than the rate of enzyme inactivation, it was considered as a necessary but not sufficient condition for inactivation. When measured by far-UV circular dichroism (CD), the rate of structural alterations following thiol group modification parallels exactly the rate of inactivation. Thus, partial unfolding of the active site of the parvulins was thought to be the cause of the deterioration of PPIase activity.

  19. Cell wall as a target for bacteria inactivation by pulsed electric fields

    PubMed Central

    Pillet, Flavien; Formosa-Dague, Cécile; Baaziz, Houda; Dague, Etienne; Rols, Marie-Pierre

    2016-01-01

    The integrity and morphology of bacteria is sustained by the cell wall, the target of the main microbial inactivation processes. One promising approach to inactivation is based on the use of pulsed electric fields (PEF). The current dogma is that irreversible cell membrane electro-permeabilisation causes the death of the bacteria. However, the actual effect on the cell-wall architecture has been poorly explored. Here we combine atomic force microscopy and electron microscopy to study the cell-wall organization of living Bacillus pumilus bacteria at the nanoscale. For vegetative bacteria, exposure to PEF led to structural disorganization correlated with morphological and mechanical alterations of the cell wall. For spores, PEF exposure led to the partial destruction of coat protein nanostructures, associated with internal alterations of cortex and core. Our findings reveal for the first time that the cell wall and coat architecture are directly involved in the electro-eradication of bacteria. PMID:26830154

  20. Cyanide inactivation of hydrogenase from Azotobacter vinelandii.

    PubMed Central

    Seefeldt, L C; Arp, D J

    1989-01-01

    The effects of cyanide on membrane-associated and purified hydrogenase from Azotobacter vinelandii were characterized. Inactivation of hydrogenase by cyanide was dependent on the activity (oxidation) state of the enzyme. Active (reduced) hydrogenase showed no inactivation when treated with cyanide over several hours. Treatment of reversibly inactive (oxidized) states of both membrane-associated and purified hydrogenase, however, resulted in a time-dependent, irreversible loss of hydrogenase activity. The rate of cyanide inactivation was dependent on the cyanide concentration and was an apparent first-order process for purified enzyme (bimolecular rate constant, 23.1 M-1 min-1 for CN-). The rate of inactivation decreased with decreasing pH. [14C]cyanide remained associated with cyanide-inactivated hydrogenase after gel filtration chromatography, with a stoichiometry of 1.7 mol of cyanide bound per mol of inactive enzyme. The presence of saturating concentrations of CO had no effect on the rate or extent of cyanide inactivation of hydrogenases. The results indicate that cyanide can cause a time-dependent, irreversible inactivation of hydrogenase in the oxidized, activatable state but has no effect when hydrogenase is in the reduced, active state. PMID:2656648

  1. Cyanide inactivation of hydrogenase from Azotobacter vinelandii

    SciTech Connect

    Seefeldt, L.C.; Arp, D.J. )

    1989-06-01

    The effects of cyanide on membrane-associated and purified hydrogenase from Azotobacter vinelandii were characterized. Inactivation of hydrogenase by cyanide was dependent on the activity (oxidation) state of the enzyme. Active (reduced) hydrogenase showed no inactivation when treated with cyanide over several hours. Treatment of reversibly inactive (oxidized) states of both membrane-associated and purified hydrogenase, however, resulted in a time-dependent, irreversible loss of hydrogenase activity. The rate of cyanide inactivation was dependent on the cyanide concentration and was an apparent first-order process for purified enzyme (bimolecular rate constant, 23.1 M{sup {minus}1} min{sup {minus}1} for CN{sup {minus}}). The rate of inactivation decreased with decreasing pH. ({sup 14}C)cyanide remained associated with cyanide-inactivated hydrogenase after gel filtration chromatography, with a stoichiometry of 1.7 mol of cyanide bound per mol of inactive enzyme. The presence of saturating concentrations of CO had no effect on the rate or extent of cyanide inactivation of hydrogenases. The results indicate that cyanide can cause a time-dependent, irreversible inactivation of hydrogenase in the oxidized, activatable state but has no effect when hydrogenase is in the reduced, active state.

  2. Irreversible thermal denaturation of Torpedo californica acetylcholinesterase.

    PubMed Central

    Kreimer, D. I.; Shnyrov, V. L.; Villar, E.; Silman, I.; Weiner, L.

    1995-01-01

    Thermal denaturation of Torpedo californica acetylcholinesterase, a disulfide-linked homodimer with 537 amino acids in each subunit, was studied by differential scanning calorimetry. It displays a single calorimetric peak that is completely irreversible, the shape and temperature maximum depending on the scan rate. Thus, thermal denaturation of acetylcholinesterase is an irreversible process, under kinetic control, which is described well by the two-state kinetic scheme N-->D, with activation energy 131 +/- 8 kcal/mol. Analysis of the kinetics of denaturation in the thermal transition temperature range, by monitoring loss of enzymic activity, yields activation energy of 121 +/- 20 kcal/mol, similar to the value obtained by differential scanning calorimetry. Thermally denatured acetylcholinesterase displays spectroscopic characteristics typical of a molten globule state, similar to those of partially unfolded enzyme obtained by modification with thiol-specific reagents. Evidence is presented that the partially unfolded states produced by the two different treatments are thermodynamically favored relative to the native state. PMID:8563632

  3. Inactivation of promoter 1B of APC causes partial gene silencing: evidence for a significant role of the promoter in regulation and causative of familial adenomatous polyposis

    PubMed Central

    Rohlin, A; Engwall, Y; Fritzell, K; Göransson, K; Bergsten, A; Einbeigi, Z; Nilbert, M; Karlsson, P; Björk, J; Nordling, M

    2011-01-01

    Familial adenomatous polyposis (FAP) is caused by germline mutations in the adenomatous polyposis coli (APC) gene. Two promoters, 1A and 1B, have been recognized in APC, and 1B is thought to have a minor role in the regulation of the gene. We have identified a novel deletion encompassing half of this promoter in the largest family (Family 1) of the Swedish Polyposis Registry. The mutation leads to an imbalance in allele-specific expression of APC, and transcription from promoter 1B was highly impaired in both normal colorectal mucosa and blood from mutation carriers. To establish the significance of promoter 1B in normal colorectal mucosa (from controls), expression levels of specific transcripts from each of the promoters, 1A and 1B, were examined, and the expression from 1B was significantly higher compared with 1A. Significant amounts of transcripts generated from promoter 1B were also determined in a panel of 20 various normal tissues examined. In FAP-related tumors, the APC germline mutation is proposed to dictate the second hit. Mutations leaving two or three out of seven 20-amino-acid repeats in the central domain of APC intact seem to be required for tumorigenesis. We examined adenomas from mutation carriers in Family 1 for second hits in the entire gene without any findings, however, loss of the residual expression of the deleterious allele was observed. Three major conclusions of significant importance in relation to the function of APC can be drawn from this study; (i) germline inactivation of promoter 1B is disease causing in FAP; (ii) expression of transcripts from promoter 1B is generated at considerable higher levels compared with 1A, demonstrating a hitherto unknown importance of 1B; (iii) adenoma formation in FAP, caused by impaired function of promoter 1B, does not require homozygous inactivation of APC allowing for alternative genetic models as basis for adenoma formation. PMID:21643010

  4. Kinetic studies on the inactivation of Escherichia coli RTEM beta-lactamase by clavulanic acid.

    PubMed

    Fisher, J; Charnas, R L; Knowles, J R

    1978-05-30

    The kinetic details of the irreversible inactivation of the Escherichia coli RTEM beta-lactamase by clavulanic acid have been elucidated. Clavulanate is destroyed by the enzyme and simultaneously inhibits it by producing two catalytically inactive forms. One of these is transiently stable and decomposes to free enzyme (k = 3.8 X 10(-3) S-1), while the other corresponds to an irreversibly inactivated form. The transient complex is formed from the Michaelis complex at a rate (k approximately 3 X 10(-2) S-1) which is some threefold faster than the rate of formation of the irreversibly inactivated complex. The transient complex is, therefore, the principle enzyme form present after short time periods. In the presence of excess clavulanate, however, all the enzyme accumulates into the irreversibly inactivated form. The number of clavulanate turnovers that occur prior to complete enzyme inactivation is 115.

  5. Thrombin generation, ProC(®)Global, prothrombin time and activated partial thromboplastin time in thawed plasma stored for seven days and after methylene blue/light pathogen inactivation.

    PubMed

    Thiele, Thomas; Hron, Gregor; Kellner, Sarah; Wasner, Christina; Westphal, Antje; Warkentin, Theodore E; Greinacher, Andreas; Selleng, Kathleen

    2016-01-01

    Methylene blue pathogen inactivation and storage of thawed plasma both lead to changes in the activity of several clotting factors. We investigated how this translates into a global loss of thrombin generation potential and alterations in the protein C pathway. Fifty apheresis plasma samples were thawed and each divided into three subunits. One subunit was stored for 7 days at 4 °C, one was stored for 7 days at 22 °C and one was stored at 4 °C after methylene blue/light treatment. Thrombin generation parameters, ProC(®)Global-NR, prothrombin time and activated partial thromboplastin time were assessed on days 0 and 7. The velocity of thrombin generation increased significantly after methylene blue treatment (increased thrombin generation rate; time to peak decreased) and decreased after storage (decreased thrombin generation rate and peak thrombin; increased lag time and time to peak). The endogenous thrombin generation potential remained stable after methylene blue treatment and storage at 4 °C. Methylene blue treatment and 7 days of storage at 4 °C activated the protein C pathway, whereas storage at room temperature and storage after methylene blue treatment decreased the functional capacity of the protein C pathway. Prothrombin time and activated partial thromboplastin time showed only modest alterations. The global clotting capacity of thawed plasma is maintained at 4 °C for 7 days and directly after methylene blue treatment of thawed plasma. Thrombin generation and ProC(®)Global are useful tools for investigating the impact of pathogen inactivation and storage on the clotting capacity of therapeutic plasma preparations.

  6. Intrinsically irreversible thermoacoustic heat engine

    SciTech Connect

    Wheatley, J.; Hofler, T.; Swift, G.W.; Migliori, A.

    1983-07-01

    Certain thermoacoustic effects are described which form the basis for a heat engine that is intrinsically irreversible in the sense that it requires thermal lags for its operation. After discussing several acoustical heating and cooling effects, including the behavior of a new structure called a ''thermoacoustic couple,'' we discuss structures that can be placed in acoustically resonant tubes to produce both substantial heat pumping effects and, for restricted heat inputs, large temperature differences. The results are analyzed quantitatively using a second-order thermoacoustic theory based on the work of Rott. The qualities of the acoustic engine are generalized to describe a class of intrinsically irreversible heat engines of which the present acoustic engine is a special case. Finally the results of analysis of several idealized intrinsically irreversible engines are presented. These suggest that the efficiency of such engines may be determined primarily by geometry or configuration rather than by temperature.

  7. Drought stress and carbon assimilation in a warming climate: Reversible and irreversible impacts.

    PubMed

    Feller, Urs

    2016-09-20

    Global change is characterized by increased CO2 concentration in the atmosphere, increasing average temperature and more frequent extreme events including drought periods, heat waves and flooding. Especially the impacts of drought and of elevated temperature on carbon assimilation are considered in this review. Effects of extreme events on the subcellular level as well as on the whole plant level may be reversible, partially reversible or irreversible. The photosynthetically active biomass depends on the number and the size of mature leaves and the photosynthetic activity in this biomass during stress and subsequent recovery phases. The total area of active leaves is determined by leaf expansion and senescence, while net photosynthesis per leaf area is primarily influenced by stomatal opening (stomatal conductance), mesophyll conductance, activity of the photosynthetic apparatus (light absorption and electron transport, activity of the Calvin cycle) and CO2 release by decarboxylation reactions (photorespiration, dark respiration). Water status, stomatal opening and leaf temperature represent a "magic triangle" of three strongly interacting parameters. The response of stomata to altered environmental conditions is important for stomatal limitations. Rubisco protein is quite thermotolerant, but the enzyme becomes at elevated temperature more rapidly inactivated (decarbamylation, reversible effect) and must be reactivated by Rubisco activase (carbamylation of a lysine residue). Rubisco activase is present under two forms (encoded by separate genes or products of alternative splicing of the pre-mRNA from one gene) and is very thermosensitive. Rubisco activase was identified as a key protein for photosynthesis at elevated temperature (non-stomatal limitation). During a moderate heat stress Rubisco activase is reversibly inactivated, but during a more severe stress (higher temperature and/or longer exposure) the protein is irreversibly inactivated, insolubilized and

  8. Irreversible Nek2 kinase inhibitors with cellular activity

    PubMed Central

    Henise, Jeffrey C.; Taunton, Jack

    2013-01-01

    A structure-based approach was used to design irreversible, cysteine-targeted inhibitors of the human centrosomal kinase, Nek2. Potent inhibition of Nek2 kinase activity in biochemical and cell-based assays required a noncatalytic cysteine residue (Cys22), located near the glycine-rich loop in a subset of human kinases. Elaboration of an oxindole scaffold led to our most selective compound, oxindole propynamide 16 (JH295). Propynamide 16 irreversibly inhibited cellular Nek2 without affecting the mitotic kinases, Cdk1, Aurora B, or Plk1. Moreover, 16 did not perturb bipolar spindle assembly or the spindle assembly checkpoint. To our knowledge, 16 is the first small molecule shown to inactivate Nek2 kinase activity in cells. PMID:21627121

  9. Comments to Irreversibility in Thermodynamics

    NASA Technical Reports Server (NTRS)

    Zak, M.

    1995-01-01

    The problem of irreversibility in thermodynamics was revisited and analyzed on the microscopic, stochastic, and macroscopic levels of description. It was demonstrated that Newtonian dynamics can be represented in the Reynolds form, a new phenomenological force with non-Lipschitz properties was introduced, and additional non- Lipschitz thermodynamical forces were incorporated into macroscopic models of transport phenomena.

  10. Tumor Ablation with Irreversible Electroporation

    PubMed Central

    Al-Sakere, Bassim; André, Franck; Bernat, Claire; Connault, Elisabeth; Opolon, Paule; Davalos, Rafael V.; Rubinsky, Boris; Mir, Lluis M.

    2007-01-01

    We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 µs at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%), in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation. PMID:17989772

  11. Reversible simulation of irreversible computation

    NASA Astrophysics Data System (ADS)

    Li, Ming; Tromp, John; Vitányi, Paul

    1998-09-01

    Computer computations are generally irreversible while the laws of physics are reversible. This mismatch is penalized by among other things generating excess thermic entropy in the computation. Computing performance has improved to the extent that efficiency degrades unless all algorithms are executed reversibly, for example by a universal reversible simulation of irreversible computations. All known reversible simulations are either space hungry or time hungry. The leanest method was proposed by Bennett and can be analyzed using a simple ‘reversible’ pebble game. The reachable reversible simulation instantaneous descriptions (pebble configurations) of such pebble games are characterized completely. As a corollary we obtain the reversible simulation by Bennett and, moreover, show that it is a space-optimal pebble game. We also introduce irreversible steps and give a theorem on the tradeoff between the number of allowed irreversible steps and the memory gain in the pebble game. In this resource-bounded setting the limited erasing needs to be performed at precise instants during the simulation. The reversible simulation can be modified so that it is applicable also when the simulated computation time is unknown.

  12. Angiotensin-Converting Enzyme 2 Metabolizes and Partially Inactivates Pyr-Apelin-13 and Apelin-17: Physiological Effects in the Cardiovascular System.

    PubMed

    Wang, Wang; McKinnie, Shaun M K; Farhan, Maikel; Paul, Manish; McDonald, Tyler; McLean, Brent; Llorens-Cortes, Catherine; Hazra, Saugata; Murray, Allan G; Vederas, John C; Oudit, Gavin Y

    2016-08-01

    Apelin peptides mediate beneficial effects on the cardiovascular system and are being targeted as potential new drugs. However, apelin peptides have extremely short biological half-lives, and improved understanding of apelin peptide metabolism may lead to the discovery of biologically stable analogues with therapeutic potential. We examined the ability of angiotensin-converting enzyme 2 (ACE2) to cleave and inactivate pyr-apelin 13 and apelin 17, the dominant apelin peptides. Computer-assisted modeling shows a conserved binding of pyr-apelin 13 and apelin 17 to the ACE2 catalytic site. In ACE2 knockout mice, hypotensive action of pyr-apelin 13 and apelin 17 was potentiated, with a corresponding greater elevation in plasma apelin levels. Similarly, pharmacological inhibition of ACE2 potentiated the vasodepressor action of apelin peptides. Biochemical analysis confirmed that recombinant human ACE2 can cleave pyr-apelin 13 and apelin 17 efficiently, and apelin peptides are degraded slower in ACE2-deficient plasma. The biological relevance of ACE2-mediated proteolytic processing of apelin peptides was further supported by the reduced potency of pyr-apelin 12 and apelin 16 on the activation of signaling pathways and nitric oxide production from endothelial cells. Importantly, although pyr-apelin 13 and apelin 17 rescued contractile function in a myocardial ischemia-reperfusion model, ACE2 cleavage products, pyr-apelin 12 and 16, were devoid of these cardioprotective effects. We designed and synthesized active apelin analogues that were resistant to ACE2-mediated degradation, thereby confirming that stable apelin analogues can be designed as potential drugs. We conclude that ACE2 represents a major negative regulator of apelin action in the vasculature and heart. © 2016 American Heart Association, Inc.

  13. Benzene-Induced Uncoupling of Naphthalene Dioxygenase Activity and Enzyme Inactivation by Production of Hydrogen Peroxide

    PubMed Central

    Lee, Kyoung

    1999-01-01

    Naphthalene dioxygenase (NDO) is a multicomponent enzyme system that oxidizes naphthalene to (+)-cis-(1R,2S)-1,2-dihydroxy-1,2-dihydronaphthalene with consumption of O2 and two electrons from NAD(P)H. In the presence of benzene, NADH oxidation and O2 utilization were partially uncoupled from substrate oxidation. Approximately 40 to 50% of the consumed O2 was detected as hydrogen peroxide. The rate of benzene-dependent O2 consumption decreased with time, but it was partially increased by the addition of catalase in the course of the O2 consumption by NDO. Detailed experiments showed that the total amount of O2 consumed and the rate of benzene-induced O2 consumption increased in the presence of hydrogen peroxide-scavenging agents, and further addition of the terminal oxygenase component (ISPNAP) of NDO. Kinetic studies showed that ISPNAP was irreversibly inactivated in the reaction that contained benzene, but the inactivation was relieved to a high degree in the presence of catalase and partially relieved in the presence of 0.1 mM ferrous ion. Benzene- and naphthalene-reacted ISPNAP gave almost identical visible absorption spectra. In addition, hydrogen peroxide added at a range of 0.1 to 0.6 mM to the reaction mixtures inactivated the reduced ISPNAP containing mononuclear iron. These results show that hydrogen peroxide released during the uncoupling reaction acts both as an inhibitor of benzene-dependent O2 consumption and as an inactivator of ISPNAP. It is proposed that the irreversible inactivation of ISPNAP occurs by a Fenton-type reaction which forms a strong oxidizing agent, hydroxyl radicals (·OH), from the reaction of hydrogen peroxide with ferrous mononuclear iron at the active site. Furthermore, when [14C]benzene was used as the substrate, cis-benzene 1,2-dihydrodiol formed by NDO was detected. This result shows that NDO also couples a trace amount of benzene to both O2 consumption and NADH oxidation. PMID:10217759

  14. Ecological optimization for generalized irreversible Carnot refrigerators

    NASA Astrophysics Data System (ADS)

    Chen, Lingen; Xiaoqin, Zhu; Sun, Fengrui; Wu, Chih

    2005-01-01

    The optimal ecological performance of a Newton's law generalized irreversible Carnot refrigerator with the losses of heat resistance, heat leakage and internal irreversibility is derived by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the refrigerator. Numerical examples are given to show the effects of heat leakage and internal irreversibility on the optimal performance of generalized irreversible refrigerators.

  15. Stochastic approach to irreversible thermodynamics

    NASA Astrophysics Data System (ADS)

    Nicolis, Grégoire; De Decker, Yannick

    2017-10-01

    An extension of classical irreversible thermodynamics pioneered by Ilya Prigogine is developed, in which fluctuations of macroscopic observables accounting for microscopic-scale processes are incorporated. The contribution of the fluctuations to the entropy production is derived from a generalized entropy balance equation and expressed in terms of the fluctuating variables, via an extended local equilibrium Ansatz and in terms of the probability distributions of these variables. The approach is illustrated on reactive systems involving linear and nonlinear steps, and the role of the distance from equilibrium and of the nonlinearities is assessed.

  16. Irreversible evolution of quantum chaos

    NASA Astrophysics Data System (ADS)

    Ugulava, A.; Chotorlishvili, L.; Nickoladze, K.

    2005-05-01

    The pendulum is the simplest system having all the basic properties inherent in dynamic stochastic systems. In the present paper we investigate the pendulum with the aim to reveal the properties of a quantum analogue of dynamic stochasticity or, in other words, to obtain the basic properties of quantum chaos. It is shown that a periodic perturbation of the quantum pendulum (similarly to the classical one) in the neighborhood of the separatrix can bring about irreversible phenomena. As a result of recurrent passages between degenerate states, the system gets self-chaotized and passes from the pure state to the mixed one. Chaotization involves the states, the branch points of whose levels participate in a slow “drift” of the system along the Mathieu characteristics this “drift” being caused by a slowly changing variable field. Recurrent relations are obtained for populations of levels participating in the irreversible evolution process. It is shown that the entropy of the system first grows and, after reaching the equilibrium state, acquires a constant value.

  17. Peroxynitrite induces destruction of the tetrahydrobiopterin and heme in endothelial nitric oxide synthase: transition from reversible to irreversible enzyme inhibition.

    PubMed

    Chen, Weiguo; Druhan, Lawrence J; Chen, Chun-An; Hemann, Craig; Chen, Yeong-Renn; Berka, Vladimir; Tsai, Ah-Lim; Zweier, Jay L

    2010-04-13

    Endothelial nitric oxide synthase (eNOS) is an important regulator of vascular and cardiac function. Peroxynitrite (ONOO(-)) inactivates eNOS, but questions remain regarding the mechanisms of this process. It has been reported that inactivation is due to oxidation of the eNOS zinc-thiolate cluster, rather than the cofactor tetrahydrobiopterin (BH(4)); however, this remains highly controversial. Therefore, we investigated the mechanisms of ONOO(-)-induced eNOS dysfunction and their dose dependence. Exposure of human eNOS to ONOO(-) resulted in a dose-dependent loss of activity with a marked destabilization of the eNOS dimer. HPLC analysis indicated that both free and eNOS-bound BH(4) were oxidized during exposure to ONOO(-); however, full oxidation of protein-bound biopterin required higher ONOO(-) levels. Additionally, ONOO(-) triggered changes in the UV/visible spectrum and heme content of the enzyme. Preincubation of eNOS with BH(4) decreased dimer destabilization and heme alteration. Addition of BH(4) to the ONOO(-)-destabilized eNOS dimer only partially rescued enzyme function. In contrast to ONOO(-) treatment, incubation with the zinc chelator TPEN with removal of enzyme-bound zinc did not change the eNOS activity or stability of the SDS-resistant eNOS dimer, demonstrating that the dimer stabilization induced by BH(4) does not require zinc occupancy of the zinc-thiolate cluster. While ONOO(-) treatment was observed to induce loss of Zn binding, this cannot account for the loss of enzyme activity. Therefore, ONOO(-)-induced eNOS inactivation is primarily due to oxidation of BH(4) and irreversible destruction of the heme/heme center.

  18. Haloperidol-based irreversible inhibitors of the HIV-1 and HIV-2 proteases.

    PubMed

    De Voss, J J; Sui, Z; DeCamp, D L; Salto, R; Babé, L M; Craik, C S; Ortiz de Montellano, P R

    1994-03-04

    The proteases expressed by the HIV-1 and HIV-2 viruses process the polyproteins encoded by the viral genomes into the mature proteins required for virion replication and assembly. Eight analogs of haloperidol have been synthesized that cause time-dependent inactivation of the HIV-1 protease and, in six cases, HIV-2 protease. The IC50 values for the analogues are comparable to that of haloperidol itself. Enzyme inactivation is due to the presence of an epoxide in two of the analogues and carbonyl-conjugated double or triple bonds in the others. Irreversible inactivation is confirmed by the failure to recover activity when one of the inhibitors is removed from the medium. At pH 8.0, the agents inactivate the HIV-1 protease 4-80 times more rapidly than the HIV-2 protease. Faster inactivation of the HIV-1 protease is consistent with alkylation of cysteine residues because the HIV-1 protease has four such residues whereas the HIV-2 protease has none. Inactivation of the HIV-2 protease requires modification of non-cysteine residues. The similarities in the rates of inactivation of the HIV-2 protease by six agents that have intrinsically different reactivities toward nucleophiles suggest that the rate-limiting step in the inactivation process is not the alkylation reaction itself. At least five of the agents inhibit polyprotein processing in an ex vivo cell assay system, but they are also toxic to the cells.

  19. Inactivation of human myeloperoxidase by hydrogen peroxide☆

    PubMed Central

    Paumann-Page, Martina; Furtmüller, Paul G.; Hofbauer, Stefan; Paton, Louise N.; Obinger, Christian; Kettle, Anthony J.

    2013-01-01

    Human myeloperoxidase (MPO) uses hydrogen peroxide generated by the oxidative burst of neutrophils to produce an array of antimicrobial oxidants. During this process MPO is irreversibly inactivated. This study focused on the unknown role of hydrogen peroxide in this process. When treated with low concentrations of H2O2 in the absence of reducing substrates, there was a rapid loss of up to 35% of its peroxidase activity. Inactivation is proposed to occur via oxidation reactions of Compound I with the prosthetic group or amino acid residues. At higher concentrations hydrogen peroxide acts as a suicide substrate with a rate constant of inactivation of 3.9 × 10−3 s−1. Treatment of MPO with high H2O2 concentrations resulted in complete inactivation, Compound III formation, destruction of the heme groups, release of their iron, and detachment of the small polypeptide chain of MPO. Ten of the protein’s methionine residues were oxidized and the thermal stability of the protein decreased. Inactivation by high concentrations of H2O2 is proposed to occur via the generation of reactive oxidants when H2O2 reacts with Compound III. These mechanisms of inactivation may occur inside neutrophil phagosomes when reducing substrates for MPO become limiting and could be exploited when designing pharmacological inhibitors. PMID:24035742

  20. Lyapunov decay in quantum irreversibility.

    PubMed

    García-Mata, Ignacio; Roncaglia, Augusto J; Wisniacki, Diego A

    2016-06-13

    The Loschmidt echo--also known as fidelity--is a very useful tool to study irreversibility in quantum mechanics due to perturbations or imperfections. Many different regimes, as a function of time and strength of the perturbation, have been identified. For chaotic systems, there is a range of perturbation strengths where the decay of the Loschmidt echo is perturbation independent, and given by the classical Lyapunov exponent. But observation of the Lyapunov decay depends strongly on the type of initial state upon which an average is carried out. This dependence can be removed by averaging the fidelity over the Haar measure, and the Lyapunov regime is recovered, as has been shown for quantum maps. In this work, we introduce an analogous quantity for systems with infinite dimensional Hilbert space, in particular the quantum stadium billiard, and we show clearly the universality of the Lyapunov regime.

  1. Lyapunov decay in quantum irreversibility

    PubMed Central

    Roncaglia, Augusto J.; Wisniacki, Diego A.

    2016-01-01

    The Loschmidt echo—also known as fidelity—is a very useful tool to study irreversibility in quantum mechanics due to perturbations or imperfections. Many different regimes, as a function of time and strength of the perturbation, have been identified. For chaotic systems, there is a range of perturbation strengths where the decay of the Loschmidt echo is perturbation independent, and given by the classical Lyapunov exponent. But observation of the Lyapunov decay depends strongly on the type of initial state upon which an average is carried out. This dependence can be removed by averaging the fidelity over the Haar measure, and the Lyapunov regime is recovered, as has been shown for quantum maps. In this work, we introduce an analogous quantity for systems with infinite dimensional Hilbert space, in particular the quantum stadium billiard, and we show clearly the universality of the Lyapunov regime. PMID:27140966

  2. Inactivation of ribosomes by an inhibitor of protein synthesis from Salmonella enteritidis.

    PubMed

    Brigotti, M; Nanetti, A; Montanaro, L; Sperti, S

    1993-01-01

    Sonic extracts of Salmonella enteritidis contain a factor which inhibits protein synthesis in cell-free systems by irreversibly inactivating ribosomes. The extent of the inactivation of ribosomes depends on the system used to assay protein synthesis, natural mRNA translation being more strongly inhibited than poly(U) translation. The inhibitory power of the Salmonella factor is destroyed by trypsin and by 5% mercaptoethanol. Placental RNase inhibitor is unable to protect ribosomes from inactivation.

  3. Irreversible inhibition of delta 5-3-oxosteroid isomerase by 2-substituted progesterones.

    PubMed Central

    Penning, T M

    1985-01-01

    2 alpha-Cyanoprogesterone (I) and 2-hydroxymethyleneprogesterone (II) were synthesized and screened as irreversible active-site-directed inhibitors of the delta 5-3-oxosteroid isomerase (EC 5.3.3.1) from Pseudomonas testosteroni. Both compounds were found to inhibit the purified bacterial enzyme in a time-dependent manner. In either case the inactivated enzyme could be dialysed without return of activity, indicating that a stable covalent bond had formed between the inhibitor and the enzyme. Inactivation mediated by compounds (I) and (II) followed pseudo-first-order kinetics, and at higher inhibitor concentrations saturation was observed. The competitive inhibitor 17 beta-oestradiol offered protection against the inactivation mediated by both compounds, and initial-rate studies indicated that compounds (I) and (II) can also act as competitive inhibitors yielding Ki values identical with those generated during inactivation experiments. 2 alpha-Cyanoprogesterone (I) and 2-hydroxymethyleneprogesterone (II) thus appear to be active-site-directed. To compare the reactivity of these 2-substituted progesterones with other irreversible inhibitors of the isomerase, 3 beta-spiro-oxiranyl-5 alpha-pregnan-20 beta-ol (III) was synthesized as the C21 analogue of 3 beta-spiro-oxiranyl-5 alpha-androstan-17 beta-ol, which is a potent inactivator of the isomerase [Pollack, Kayser & Bevins (1979) Biochem. Biophys. Res. Commun. 91, 783-790]. Comparison of the bimolecular rate constants for inactivation (k+3/Ki) mediated by compounds (I)-(III) indicated the following order of reactivity: (III) greater than (II) greater than (I). 2-Mercaptoethanol offers complete protection against the inactivation of the isomerase mediated by 2 alpha-cyanoprogesterone (I). Under the conditions of inactivation compound (I) appears to be completely stable, and no evidence could be obtained for enolate ion formation in the presence or absence of enzyme. It is suggested that cyanoprogesterone inactivates

  4. Beta-lactamase inactivation by mechanism-based reagents.

    PubMed

    Fisher, J; Belasco, J G; Charnas, R L; Khosla, S; Knowles, J R

    1980-05-16

    The mechanistic pathway followed by the E. coli RTEM beta-lactamase has been studied with a view to clarifying the mode of action of a number of recently discovered inactivators of the enzyme. There is clear evidence that the beta-lactamase-catalysed hydrolysis of the 7-alpha-methoxycephem, cefoxitin, proceeds via an acyl-enzyme intermediate. An analysis of the inactivation reactions of all the known beta-lactam derivatives that result in irreversible loss of enzyme activity permits the identification of three structural features required for a beta-lactamase inactivator. The application of these principles suggests a new group of mechanism-based inactivators of the enzyme: the sulphones of N-acyl derivatives of 6-beta-aminopenicillanic acid that are themselves poor substrates for the enzyme. These sulphones are powerful inactivators of the beta-lactamase.

  5. Trypsin inactivation by intact Hymenolepis diminuta (Cestoda): some characteristics of the inactivated enzyme.

    PubMed

    Schroeder, L L; Pappas, P W; Means, G E

    1981-06-01

    In the presence of intact Hymenolepis diminuta, trypsin was inactivated; intact worms had no apparent effect on subtilisin, pepsin, or papain. Inactivation of trypsin was demonstrable using azoalbumin as a substrate, but the inactivated enzyme retained full catalytic activity against benzoyl-DL-arginine-p-nitroanilide, p-tosyl-L-arginine methyl ester (low molecular weight synthetic trypsin substrates) and p-nitro-p-guanidinobenzoate (an active site titrant). Inactivation was not reversible under conditions of heating, freezing and thawing, or prolonged dialysis of the enzyme. Analyses of inactivated 3H-trypsin by cationic and SDS-polyacrylamide gel electrophoresis, and gel chromatography failed to indicate the presence of a high molecular weight trypsin inhibitor associated with the inactivated enzyme; no low molecular weight, dissociable inhibitor was demonstrable following thermal denaturation of the inactivated enzyme. Analyses of trypsin after incubation in the presence of pulse-labeled worms also failed to demonstrate the presence of any inhibitor of worm origin associated with the inactivated enzyme. The data suggest that inactivation is the result of a small structural or conformational change in the enzyme molecule, a change which partially (rather than totally) inactivates the enzyme towards protein substrates.

  6. A Perspective on the Kinetics of Covalent and Irreversible Inhibition.

    PubMed

    Strelow, John M

    2017-01-01

    The clinical and commercial success of covalent drugs has prompted a renewed and more deliberate pursuit of covalent and irreversible mechanisms within drug discovery. A covalent mechanism can produce potent inhibition in a biochemical, cellular, or in vivo setting. In many cases, teams choose to focus on the consequences of the covalent event, defined by an IC50 value. In a biochemical assay, the IC50 may simply reflect the target protein concentration in the assay. What has received less attention is the importance of the rate of covalent modification, defined by kinact/KI. The kinact/KI is a rate constant describing the efficiency of covalent bond formation resulting from the potency (KI) of the first reversible binding event and the maximum potential rate (kinact) of inactivation. In this perspective, it is proposed that the kinact/KI should be employed as a critical parameter to identify covalent inhibitors, interpret structure-activity relationships (SARs), translate activity from biochemical assays to the cell, and more accurately define selectivity. It is also proposed that a physiologically relevant kinact/KI and an (unbound) AUC generated from a pharmacokinetic profile reflecting direct exposure of the inhibitor to the target protein are two critical determinants of in vivo covalent occupancy. A simple equation is presented to define this relationship and improve the interpretation of covalent and irreversible kinetics.

  7. Ribosome-inactivating proteins: potent poisons and molecular tools.

    PubMed

    Walsh, Matthew J; Dodd, Jennifer E; Hautbergue, Guillaume M

    2013-11-15

    Ribosome-inactivating proteins (RIPs) were first isolated over a century ago and have been shown to be catalytic toxins that irreversibly inactivate protein synthesis. Elucidation of atomic structures and molecular mechanism has revealed these proteins to be a diverse group subdivided into two classes. RIPs have been shown to exhibit RNA N-glycosidase activity and depurinate the 28S rRNA of the eukaryotic 60S ribosomal subunit. In this review, we compare archetypal RIP family members with other potent toxins that abolish protein synthesis: the fungal ribotoxins which directly cleave the 28S rRNA and the newly discovered Burkholderia lethal factor 1 (BLF1). BLF1 presents additional challenges to the current classification system since, like the ribotoxins, it does not possess RNA N-glycosidase activity but does irreversibly inactivate ribosomes. We further discuss whether the RIP classification should be broadened to include toxins achieving irreversible ribosome inactivation with similar turnovers to RIPs, but through different enzymatic mechanisms.

  8. Optimization of an irreversible Stirling regenerative cycle

    NASA Astrophysics Data System (ADS)

    Aragón-González, G.; Cano-Bianco, M.; León-Galicia, A.; Rivera-Camacho, J. M.

    2015-01-01

    In this work a Stirling regenerative cycle with some irreversibilities is analyzed. The analyzed irreversibilities are located at the heat exchangers. They receive a finite amount of heat and heat leakage occurs between both reservoirs. Using this model, power and the efficiency at maximum power are obtained. Some optimal design parameters for the exchanger heat areas and thermal conductances are presented. The relation between the power, efficiency and the results obtained are shown graphically.

  9. Inactivation of Caliciviruses

    PubMed Central

    Nims, Raymond; Plavsic, Mark

    2013-01-01

    The Caliciviridae family of viruses contains clinically important human and animal pathogens, as well as vesivirus 2117, a known contaminant of biopharmaceutical manufacturing processes employing Chinese hamster cells. An extensive literature exists for inactivation of various animal caliciviruses, especially feline calicivirus and murine norovirus. The caliciviruses are susceptible to wet heat inactivation at temperatures in excess of 60 °C with contact times of 30 min or greater, to UV-C inactivation at fluence ≥30 mJ/cm2, to high pressure processing >200 MPa for >5 min at 4 °C, and to certain photodynamic inactivation approaches. The enteric caliciviruses (e.g.; noroviruses) display resistance to inactivation by low pH, while the non-enteric species (e.g.; feline calicivirus) are much more susceptible. The caliciviruses are inactivated by a variety of chemicals, including alcohols, oxidizing agents, aldehydes, and β-propiolactone. As with inactivation of viruses in general, inactivation of caliciviruses by the various approaches may be matrix-, temperature-, and/or contact time-dependent. The susceptibilities of the caliciviruses to the various physical and chemical inactivation approaches are generally similar to those displayed by other small, non-enveloped viruses, with the exception that the parvoviruses and circoviruses may require higher temperatures for inactivation, while these families appear to be more susceptible to UV-C inactivation than are the caliciviruses. PMID:24276023

  10. Blueberry polyphenol oxidase: Characterization and the kinetics of thermal and high pressure activation and inactivation.

    PubMed

    Terefe, Netsanet Shiferaw; Delon, Antoine; Buckow, Roman; Versteeg, Cornelis

    2015-12-01

    Partially purified blueberry polyphenol oxidase (PPO) in Mcllvaine buffer (pH=3.6, typical pH of blueberry juice) was subjected to processing at isothermal-isobaric conditions at temperatures from 30 to 80 °C and pressure from 0.1 to 700 MPa. High pressure processing at 30-50 °C at all pressures studied caused irreversible PPO activity increase with a maximum of 6.1 fold increase at 500 MPa and 30 °C. Treatments at mild pressure-mild temperature conditions (0.1-400 MPa, 60 °C) also caused up to 3 fold PPO activity increase. Initial activity increase followed by a decrease occurred at relatively high pressure-mild temperature (400-600 MPa, 60 °C) and mild pressure-high temperature (0.1-400 MPa, 70-80 °C) combinations. At temperatures higher than 76 °C, monotonic decrease in PPO activity occurred at 0.1 MPa and pressures higher than 500 MPa. The activation/inactivation kinetics of the enzyme was successfully modelled assuming consecutive reactions in series with activation followed by inactivation.

  11. Photosensitized oxidation and inactivation of pyocyanin, a virulence factor of Pseudomonas aeruginosa.

    PubMed

    Reszka, Krzysztof J; Denning, Gerene M; Britigan, Bradley E

    2006-01-01

    Pyocyanin (PyO-) (1-hydroxy-5-methylphenazine) is a cytotoxic compound secreted by Pseudomonas aeruginosa, an omnipresent bacterium and a human pathogen. We report that visible light illumination in the presence of rose bengal, or riboflavin, in aerated solutions (pH 7.0-7.2) induces irreversible loss of the pigment's characteristic absorption band at 690 nm, indicating its oxidation. This photobleaching was paralleled by generation of a multiline Electron Paramagnetic Resonance (EPR) spectrum attributed to a PyO(-)-derived radical. The reaction was dependent on the presence of air, sensitizers and light, was inhibited by sodium azide and was unaffected by ethanol. This suggests that PyO- was oxidized largely via singlet oxygen and that hydroxyl radicals were not involved. The photochemically modified pigment was less efficient in oxidizing NAD(P)H and generated less superoxide (by approximately 50%) than the intact PyO-, indicating its partial inactivation. 1-Methoxy-5-methylphenazine, a PyO- analog in which the -O- moiety was replaced by the methoxy group (-OMe), was resistant to oxidation, suggesting that oxidation of PyO- involves its phenolate moiety. These results also suggest that photosensitization could be a potentially useful method for inactivation of PyO- and, possibly, detoxification of superficial wounds (skin, eye) infected with P. aeruginosa.

  12. Polyomavirus inactivation - a review.

    PubMed

    Nims, Raymond W; Plavsic, Mark

    2013-03-01

    Polyomavirus inactivation has been studied since the 1950s when it became apparent that certain polio vaccines were contaminated with SV40. Relatively high temperatures (≥70 °C) are required to effect thermal inactivation of the polyomaviruses. The chemical inactivants that are effective (β-propiolactone, ethanol, sodium hydroxide, and formaldehyde) are those that have displayed efficacy for other small, non-enveloped viruses, such as the circoviruses. Low pH inactivation can be effective, especially at pH at or below 3 and at higher temperatures. Polyomaviruses are more resistant to UV-C irradiation than are other small non-enveloped viruses such as the parvoviruses and caliciviruses. The efficacy of photodynamic inactivation of polyomaviruses is very much dye-dependent, with toluidine blue, acridine orange, and methylene blue dyes being effective photosensitizers. Ionizing radiation can be effective, depending on the conditions employed and the inactivation matrix. Inactivation of the oncogenic properties of the polyomaviruses may require higher doses of inactivant than those required to inactivate infectivity. While the polyomaviruses are considered to be highly resistant to inactivation, the degree of resistance is dependent upon the specific approach under consideration. For certain approaches, such as UV-C and gamma-irradiation, the polyomaviruses appear to be more resistant than other small non-enveloped viruses. Copyright © 2012 The International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved.

  13. N-Alkoxyheterocycles As Irreversible Photooxidants†

    PubMed Central

    Wosinska, Zofia M.; Stump, Faye L.; Ranjan, Rajeev; Lorance, Edward D.; Finley, GeNita N.; Patel, Priya P.; Khawaja, Muzamil A.; Odom, Katie L.; Kramer, Wolfgang H.; Gould, Ian R.

    2015-01-01

    Irreversible photooxidation based on N–O bond fragmentation is demonstrated for N-methoxyheterocycles in both the singlet and triplet excited state manifolds. The energetic requirements for bond fragmentation are studied in detail. Bond fragmentation in the excited singlet manifold is possible for ππ* singlet states with energies significantly larger than the N–O bond dissociation energy of ca 55 kcal mol−1. For the nπ* triplet states, N–O bond fragmentation does not occur in the excited state for orbital overlap and energetic reasons. Irreversible photooxidation occurs in the singlet states by bond fragmentation followed by electron transfer. Irreversible photooxidation occurs in the triplet states via bimolecular electron transfer to the donor followed by bond fragmentation. Using these two sensitization schemes, donors can be irreversibly oxidized with oxidation potentials ranging from ca 1.6–2.2 V vs SCE. The corresponding N-ethylheterocycles are characterized as conventional reversible photooxidants in their triplet states. The utility of these sensitizers is demonstrated by irreversibly generating the guanosine radical cation in buffered aqueous solution. PMID:24354634

  14. Designing Irreversible Inhibitors--Worth the Effort?

    PubMed

    González-Bello, Concepción

    2016-01-05

    Despite the unquestionable success of numerous irreversible drugs that are currently in clinical use, such as acetylsalicylic acid (Aspirin) and penicillin, the number of such approved drugs is much lower than that of noncovalent drugs. Over the years, the potential off-target effects of these types of compounds have been the primary concern that has hampered their development. However, their remarkable advantages over noncovalent drugs and a better analysis of the risks have decreased the widespread skepticism surrounding them. The design of irreversible inhibitors is a challenge, particularly considering that in some cases their efficacy is due to complex and unexpected mechanisms of action. In this review the main advantages of irreversible inhibition are summarized, and the complexity of certain covalent modification mechanisms is highlighted with selected examples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Lanford's Theorem and the Emergence of Irreversibility

    NASA Astrophysics Data System (ADS)

    Uffink, Jos; Valente, Giovanni

    2015-04-01

    It has been a longstanding problem to show how the irreversible behaviour of macroscopic systems can be reconciled with the time-reversal invariance of these same systems when considered from a microscopic point of view. A result by Lanford (Dynamical systems, theory and applications, 1975, Asterisque 40:117-137, 1976, Physica 106A:70-76, 1981) shows that, under certain conditions, the famous Boltzmann equation, describing the irreversible behaviour of a dilute gas, can be obtained from the time-reversal invariant Hamiltonian equations of motion for the hard spheres model. Here, we examine how and in what sense Lanford's theorem succeeds in deriving this remarkable result. Many authors have expressed different views on the question which of the ingredients in Lanford's theorem is responsible for the emergence of irreversibility. We claim that these interpretations miss the target. In fact, we argue that there is no time-asymmetric ingredient at all.

  16. Transiently Produced Hypochlorite Is Responsible for the Irreversible Inhibition of Chlorite Dismutase

    PubMed Central

    2014-01-01

    Chlorite dismutases (Clds) are heme b-containing prokaryotic oxidoreductases that catalyze the reduction of chlorite to chloride with the concomitant release of molecular oxygen. Over time, they are irreversibly inactivated. To elucidate the mechanism of inactivation and investigate the role of the postulated intermediate hypochlorite, the pentameric chlorite dismutase of “Candidatus Nitrospira defluvii” (NdCld) and two variants (having the conserved distal arginine 173 exchanged with alanine and lysine) were recombinantly produced in Escherichia coli. Exchange of the distal arginine boosts the extent of irreversible inactivation. In the presence of the hypochlorite traps methionine, monochlorodimedone, and 2-[6-(4-aminophenoxy)-3-oxo-3H-xanthen-9-yl]benzoic acid, the extent of chlorite degradation and release of molecular oxygen is significantly increased, whereas heme bleaching and oxidative modifications of the protein are suppressed. Among other modifications, hypochlorite-mediated formation of chlorinated tyrosines is demonstrated by mass spectrometry. The data obtained were analyzed with respect to the proposed reaction mechanism for chlorite degradation and its dependence on pH. We discuss the role of distal Arg173 by keeping hypochlorite in the reaction sphere for O–O bond formation. PMID:24754261

  17. Efficiency of Rectification: Reversible vs. Irreversible Regimes

    NASA Astrophysics Data System (ADS)

    Sokolov, I. M.

    2002-11-01

    Both man-made locomotive devices and molecular motors use gears to transform a reciprocating motion into a directed one. One of the most common gears is a rectifier, a mechanically irreversible appliance. The maximal energetic efficiency of an isothermic gear is bounded by unity, as a consequence of the Second Law. However, approaching this ideal efficiency does not imply approaching reversibility. We discuss what properties of a rectifier mostly influence the transduction efficiency and show that an appliance which locks under backward force is just the one which can approach the ideal efficiency either in the reversible or in the irreversible regime.

  18. A Case of SSRI Induced Irreversible Parkinsonism

    PubMed Central

    Khan, Shahbaj A; Azad, Sudip

    2015-01-01

    Serotonin specific reuptake inhibitors (SSRI) are widely used antidepressants for variety of clinical conditions and have found popularity. They are sometimes associated with extrapyramidal side effects including Parkinsonism. We report a case of generalized anxiety disorder on treatment with SSRI (fluoxetine / sertraline) who developed irreversible Parkinsonism. SSRI are known to cause reversible or irreversible motor disturbances through pathophysiological changes in basal ganglion motor system by altering the dopamine receptors postsynaptically. Clinician should keep risk benefit ratio in mind and change of antidepressant of different class may be considered. Case is reported to alert physicians to possibility of motor system damage while treating with SSRI. PMID:25859504

  19. Studies on the mechanism of activation and inactivation of pyruvate,phosphate dikinase. A possible regulatory role for the enzyme in the C4 dicarboxylic acid pathway of photosynthesis

    PubMed Central

    Hatch, M. D.; Slack, C. R.

    1969-01-01

    1. The activity of pyruvate,Pi dikinase in leaves of maize and Amaranthus palmeri rapidly falls on transferring illuminated plants to darkness. Illumination of dark-treated plants results in an immediate rapid increase in activity of the enzyme, the final activity reached being dependent on the intensity of the incident light. 2. Activation of the enzyme in extracts of dark-treated maize leaves after gel filtration on Sephadex G-25 requires a thiol and Pi. The Pi requirement for activation can be replaced by arsenate. Activation of the enzyme is inhibited by AMP and GMP and possibly also by ADP and ATP. Activation of the enzyme after gel filtration on Sephadex G-200 also requires a heat-labile component that is excluded by Sephadex G-25. 3. The active enzyme isolated from illuminated leaves is inactivated by ADP in the presence of a thiol, the rate of inactivation being very much faster in air than in an oxygen-free atmosphere. Reactivation of the ADP-inactivated enzyme requires a thiol, Pi and a component excluded by Sephadex G-25 but considerably retarded by Sephadex G-200. 4. The active enzyme is rapidly and irreversibly inactivated in the absence of a thiol. Inactivation is accelerated by both sodium diethyldithiocarbamate and tetraethylthiuram disulphide, and the enzyme inactivated by these reagents is completely reactivated by incubation with dithiothreitol. This reactivation does not require Pi. The inactive enzyme from dark-treated leaves is stabilized by diethyldithiocarbamate and can be partially activated by dithiothreitol alone; complete reactivation requires both dithiothreitol and Pi. 5. The enzyme activity is markedly inhibited by the thiol reagents p-chloromercuribenzoate, γ-(p-arsenophenyl)-n-butyrate and an equimolar mixture of arsenite and 2,3-dimercaptopropan-1-ol. 6. The processes of activation and inactivation observed in vitro are discussed in relation to the regulation of pyruvate,Pi dikinase activity in the leaf. PMID:5821721

  20. Markov Chain Monte Carlo and Irreversibility

    NASA Astrophysics Data System (ADS)

    Ottobre, Michela

    2016-06-01

    Markov Chain Monte Carlo (MCMC) methods are statistical methods designed to sample from a given measure π by constructing a Markov chain that has π as invariant measure and that converges to π. Most MCMC algorithms make use of chains that satisfy the detailed balance condition with respect to π; such chains are therefore reversible. On the other hand, recent work [18, 21, 28, 29] has stressed several advantages of using irreversible processes for sampling. Roughly speaking, irreversible diffusions converge to equilibrium faster (and lead to smaller asymptotic variance as well). In this paper we discuss some of the recent progress in the study of nonreversible MCMC methods. In particular: i) we explain some of the difficulties that arise in the analysis of nonreversible processes and we discuss some analytical methods to approach the study of continuous-time irreversible diffusions; ii) most of the rigorous results on irreversible diffusions are available for continuous-time processes; however, for computational purposes one needs to discretize such dynamics. It is well known that the resulting discretized chain will not, in general, retain all the good properties of the process that it is obtained from. In particular, if we want to preserve the invariance of the target measure, the chain might no longer be reversible. Therefore iii) we conclude by presenting an MCMC algorithm, the SOL-HMC algorithm [23], which results from a nonreversible discretization of a nonreversible dynamics.

  1. Absorption media for irreversibly gettering thionyl chloride

    DOEpatents

    Buffleben, George; Goods, Steven H.; Shepodd, Timothy; Wheeler, David R.; Whinnery, Jr., LeRoy

    2002-01-01

    Thionyl chloride is a hazardous and reactive chemical used as the liquid cathode in commercial primary batteries. Contrary to previous thinking, ASZM-TEDA.RTM. carbon (Calgon Corporation) reversibly absorbs thionyl chloride. Thus, several candidate materials were examined as irreversible getters for thionyl chloride. The capacity, rate and effect of temperature were also explored. A wide variety of likely materials were investigated through screening experiments focusing on the degree of heat generated by the reaction as well as the material absorption capacity and irreversibility, in order to help narrow the group of possible getter choices. More thorough, quantitative measurements were performed on promising materials. The best performing getter was a mixture of ZnO and ASZM-TEDA.RTM. carbon. In this example, the ZnO reacts with thionyl chloride to form ZnCl.sub.2 and SO.sub.2. The SO.sub.2 is then irreversibly gettered by ASZM-TEDA.RTM. carbon. This combination of ZnO and carbon has a high capacity, is irreversible and functions effectively above -20.degree. C.

  2. Ultrafast irreversible phototautomerization of o-nitrobenzaldehyde.

    PubMed

    Migani, Annapaola; Leyva, Verónica; Feixas, Ferran; Schmierer, Thomas; Gilch, Peter; Corral, Inés; González, Leticia; Blancafort, Lluís

    2011-06-14

    o-Nitrobenzaldehyde is photolabile because of an irreversible phototautomerization, whereas comparable aromatic compounds function as photoprotectors because the tautomerization is reversible. In this experimental and theoretical study we track down the cause of this difference to the electronic changes that occur during the tautomerization. This journal is © The Royal Society of Chemistry 2011

  3. Pilot Decision-Making in Irreversible Emergencies

    ERIC Educational Resources Information Center

    Winter, Scott R.

    2013-01-01

    The purpose of this study was to determine if a reflexive learning treatment utilizing select case studies could enhance the decision-making of pilots who encounter an irreversible emergency. Participants, who consisted of members of the subject university's professional pilot program, were divided into either a control or experimental group and…

  4. Mechanisms of irreversible decoherence in solids

    NASA Astrophysics Data System (ADS)

    Domínguez, F. D.; Zamar, R. C.; Segnorile, H. H.; González, C. E.

    2017-06-01

    Refocalization sequences in nuclear magnetic resonance (NMR) can in principle reverse the coherent evolution under the secular dipolar Hamiltonian of a closed system. We use this experimental strategy to study the effect of irreversible decoherence on the signal amplitude attenuation in a single-crystal hydrated salt where the nuclear spin system consists of the set of hydration water proton spins having a strong coupling within each pair and a much weaker coupling with other pairs. We study the experimental response of attenuation times with temperature, crystal orientation with respect to the external magnetic field, and rf pulse amplitudes. We find that the observed attenuation of the refocalized signals can be explained by two independent mechanisms: (a) evolution under the nonsecular terms of the reversion Hamiltonian, and (b) an intrinsic mechanism having the attributes of irreversible decoherence induced by the coupling with a quantum environment. To characterize (a) we compare the experimental data with the numerical calculation of the refocalized NMR signal of an artificial, closed spin system. To describe (b) we use a model of the irreversible adiabatic decoherence of spin pairs coupled with a phonon bath which allows evaluating an upper bound for the decoherence times. This model accounts for both the observed dependence of the decoherence times on the eigenvalues of the spin-environment Hamiltonian, and the independence from the sample temperature. This result, then, supports the adiabatic decoherence induced by the dipole-phonon coupling as the explanation for the observed irreversible decay of reverted NMR signals in solids.

  5. Pilot Decision-Making in Irreversible Emergencies

    ERIC Educational Resources Information Center

    Winter, Scott R.

    2013-01-01

    The purpose of this study was to determine if a reflexive learning treatment utilizing select case studies could enhance the decision-making of pilots who encounter an irreversible emergency. Participants, who consisted of members of the subject university's professional pilot program, were divided into either a control or experimental group and…

  6. A new microscopic level of irreversibility

    SciTech Connect

    Prigogine, I.

    1987-01-01

    In this paper, the non-exponential decay is analyzed with the help of simple computer experiments performed by T. Petrosky, simulating classical radiation damping. The non-exponential decay is studied and shown to depend on the preparation of the system. However, whatever the initial preparation, the system reaches the decay predicted by classical radiation theory after a short time we call the Zeno's time. The similitude of Petrosky's results with computer experiments for the approach to equilibrium in many-body systems is emphasized. However, while there one deals with times which are multiple of the relaxation time, the irreversibility manifest in radiation theory occurs always over a much shorter time scale, the Zeno's time. In atomic systems, this would be a time order of 10/sup /minus/18/ seconds. These results are of great interest for the understanding of the microscopic mechanism of radiation. Let us consider a charged oscillator. In a first stage, this oscillator has to produce the field oscillators to which it may transfer energy through the usual resonance mechanism. Radiation appears therefore as a kind of non linear autocatalytic process, involving a self-organization mechanism. The behavior during the Zeno period can be explained easily in terms of subdynamics as introduced by the Brussel's group. We see that there is no transition from reversibility to irreversibility. Irreversible processes start at the very moment at which the system is prepared. It is important to stress that an unstable particle is itself the result of irreversible processes. As a result, an unstable particle (or an excited atomic state) can no more be described in terms of wave functions, as irreversible processes are not included in Schroedinger's equation. 14 refs., 3 figs.

  7. Metabolically Labile Fumarate Esters Impart Kinetic Selectivity to Irreversible Inhibitors.

    PubMed

    Zaro, Balyn W; Whitby, Landon R; Lum, Kenneth M; Cravatt, Benjamin F

    2016-12-14

    Electrophilic small molecules are an important class of chemical probes and drugs that produce biological effects by irreversibly modifying proteins. Examples of electrophilic drugs include covalent kinase inhibitors that are used to treat cancer and the multiple sclerosis drug dimethyl fumarate. Optimized covalent drugs typically inactivate their protein targets rapidly in cells, but ensuing time-dependent, off-target protein modification can erode selectivity and diminish the utility of reactive small molecules as chemical probes and therapeutics. Here, we describe an approach to confer kinetic selectivity to electrophilic drugs. We show that an analogue of the covalent Bruton's tyrosine kinase (BTK) inhibitor Ibrutinib bearing a fumarate ester electrophile is vulnerable to enzymatic metabolism on a time-scale that preserves rapid and sustained BTK inhibition, while thwarting more slowly accumulating off-target reactivity in cell and animal models. These findings demonstrate that metabolically labile electrophilic groups can endow covalent drugs with kinetic selectivity to enable perturbation of proteins and biochemical pathways with greater precision.

  8. Irreversible inhibition of human cathepsins B, L, S and K by hypervalent tellurium compounds.

    PubMed

    Cunha, Rodrigo L O R; Gouvêa, Iuri E; Feitosa, Geovana P V; Alves, Márcio F M; Brömme, Dieter; Comasseto, João V; Tersariol, Ivarne L S; Juliano, Luiz

    2009-11-01

    The inhibition of human cysteine cathepsins B, L, S and K was evaluated by a set of hypervalent tellurium compounds (telluranes) comprising both organic and inorganic derivatives. All telluranes studied showed a time- and concentration-dependent irreversible inhibition of the cathepsins, and their second-order inactivation rate constants were determined. The organic derivatives were potent inhibitors of the cathepsins and clear specificities were detected, which were parallel to their known substrate specificities. In all cases, the activity of the tellurane-inhibited cathepsins was recovered by treatment of the inactivated enzymes with reducing agents. The maximum stoichiometry of the reaction between cysteine residues and telluranes were also determined. The presented data indicate that it is possible to design organic compounds with a tellurium(IV) moiety as a novel warhead that covalently modifies the catalytic cysteine, and which also form strong interactions with subsites of cathepsins B, L, S and K, resulting in more specific inhibition.

  9. Inequivalent models of irreversible dimer filling: ``Transition state'' dependence

    NASA Astrophysics Data System (ADS)

    Nord, R. S.; Evans, J. W.

    1990-12-01

    Irreversible adsorption of diatomics on crystalline surfaces is sometimes modeled as random dimer filling of adjacent pairs of sites on a lattice. We note that this process can be implemented in two distinct ways: (i) randomly pick adjacent pairs of sites, jj', and fill jj' only if both are empty (horizontal transition state); or (ii) randomly pick a single site, j, and if j and at least one neighbor are empty, then fill j and a randomly chosen empty neighbor (vertical transition state). Here it is instructive to consider processes which also include competitive random monomer filling of single sites. We find that although saturation (partial) coverages differ little between the models for pure dimer filling, there is a significant difference for comparable monomer and dimer filling rates. We present exact results for saturation coverage behavior for a linear lattice, and estimates for a square lattice. Ramifications for simple models of CO oxidation on surfaces are indicated.

  10. Maximum power, ecological function and efficiency of an irreversible Carnot cycle: a cost and effectiveness optimization

    NASA Astrophysics Data System (ADS)

    Aragón-González, G.; Canales-Palma, A.; León-Galicia, A.; Morales-Gómez, J. R.

    2008-12-01

    In this work we include, for the Carnot cycle, irreversibilities of linear finite rate of heat transferences between the heat engine and its reservoirs, heat leak between the reservoirs and internal dissipations of the working fluid. A first optimization of the power output, the efficiency and ecological function of an irreversible Carnot cycle, with respect to: internal temperature ratio, time ratio for the heat exchange and the allocation ratio of the heat exchangers; is performed. For the second and third optimizations, the optimum values for the time ratio and internal temperature ratio are substituted into the equation of power and, then, the optimizations with respect to the cost and effectiveness ratio of the heat exchangers are performed. Finally, a criterion of partial optimization for the class of irreversible Carnot engines is herein presented.

  11. Uncertainty Quantification in Irreversible Electroporation Simulations

    PubMed Central

    Labarbera, Nicholas

    2017-01-01

    One recent area of cancer research is irreversible electroporation (IRE). Irreversible electroporation is a minimally invasive procedure where needle electrodes are inserted into the body to ablate tumor cells with electricity. The aim of this paper is to investigate how uncertainty in tissue and tumor conductivity propagate into final ablation predictions used for treatment planning. Two dimensional simulations were performed for a circular tumor surrounded by healthy tissue, and electroporated from two monopolar electrodes. The conductivity values were treated as random variables whose distributions were taken from published literature on the average and standard deviation of liver tissue and liver tumors. Three different Monte Carlo setups were simulated each at three different voltages. Average and standard deviation data was reported for a multitude of electrical field properties experienced by the tumor. Plots showing the variability in the electrical field distribution throughout the tumor are also presented.

  12. Substituted isatoic anhydrides: selective inactivators of trypsin-like serine proteases.

    PubMed

    Gelb, M H; Abeles, R H

    1986-04-01

    Derivatives of isatoic anhydride were prepared and tested as inhibitors of serine proteases. A number of isatoic anhydrides with positively charged substituents irreversibly inactivated several trypsin-like enzymes and preferentially inactivated trypsin over chymotrypsin. Further selectivity was obtained by introduction of an aromatic group on the N-1 position of isatoic anhydride. 7-(Aminomethyl)-1-benzylisatoic anhydride was prepared and was a selective inactivator of thrombin; thus it is possible to prepare derivatives of isatoic anhydride that are highly enzyme selective without attaching peptide recognition structures.

  13. Irreversible enzyme inhibition kinetics and drug-drug interactions.

    PubMed

    Mohutsky, Michael; Hall, Stephen D

    2014-01-01

    This chapter describes the types of irreversible inhibition of drug-metabolizing enzymes and the methods commonly employed to quantify the irreversible inhibition and subsequently predict the extent and time course of clinically important drug-drug interactions.

  14. Multiscale multifractal time irreversibility analysis of stock markets

    NASA Astrophysics Data System (ADS)

    Jiang, Chenguang; Shang, Pengjian; Shi, Wenbin

    2016-11-01

    Time irreversibility is one of the most important properties of nonstationary time series. Complex time series often demonstrate even multiscale time irreversibility, such that not only the original but also coarse-grained time series are asymmetric over a wide range of scales. We study the multiscale time irreversibility of time series. In this paper, we develop a method called multiscale multifractal time irreversibility analysis (MMRA), which allows us to extend the description of time irreversibility to include the dependence on the segment size and statistical moments. We test the effectiveness of MMRA in detecting multifractality and time irreversibility of time series generated from delayed Henon map and binomial multifractal model. Then we employ our method to the time irreversibility analysis of stock markets in different regions. We find that the emerging market has higher multifractality degree and time irreversibility compared with developed markets. In this sense, the MMRA method may provide new angles in assessing the evolution stage of stock markets.

  15. Meiotic sex chromosome inactivation.

    PubMed

    Turner, James M A

    2007-05-01

    X chromosome inactivation is most commonly studied in the context of female mammalian development, where it performs an essential role in dosage compensation. However, another form of X-inactivation takes place in the male, during spermatogenesis, as germ cells enter meiosis. This second form of X-inactivation, called meiotic sex chromosome inactivation (MSCI) has emerged as a novel paradigm for studying the epigenetic regulation of gene expression. New studies have revealed that MSCI is a special example of a more general mechanism called meiotic silencing of unsynapsed chromatin (MSUC), which silences chromosomes that fail to pair with their homologous partners and, in doing so, may protect against aneuploidy in subsequent generations. Furthermore, failure in MSCI is emerging as an important etiological factor in meiotic sterility.

  16. Capsid Functions of Inactivated Human Picornaviruses and Feline Calicivirus

    PubMed Central

    Nuanualsuwan, Suphachai; Cliver, Dean O.

    2003-01-01

    The exceptional stability of enteric viruses probably resides in their capsids. The capsid functions of inactivated human picornaviruses and feline calicivirus (FCV) were determined. Viruses were inactivated by UV, hypochlorite, high temperature (72°C), and physiological temperature (37°C), all of which are pertinent to transmission via food and water. Poliovirus (PV) and hepatitis A virus (HAV) are transmissible via water and food, and FCV is the best available surrogate for the Norwalk-like viruses, which are leading causes of food-borne and waterborne disease in the United States. The capsids of all 37°C-inactivated viruses still protected the viral RNA against RNase, even in the presence of proteinase K, which contrasted with findings with viruses inactivated at 72°C. The loss of ability of the virus to attach to homologous cell receptors was universal, regardless of virus type and inactivation method, except for UV-inactivated HAV, and so virus inactivation was almost always accompanied by the loss of virus attachment. Inactivated HAV and FCV were captured by homologous antibodies. However, inactivated PV type 1 (PV-1) was not captured by homologous antibody and 37°C-inactivated PV-1 was only partially captured. The epitopes on the capsids of HAV and FCV are evidently discrete from the receptor attachment sites, unlike those of PV-1. These findings indicate that the primary target of UV, hypochlorite, and 72°C inactivation is the capsid and that the target of thermal inactivation (37°C versus 72°C) is temperature dependent. PMID:12514015

  17. Irreversible photoinhibition of photosystem II is caused by exposure of Synechocystis cells to strong light for a prolonged period.

    PubMed

    Allakhverdiev, Suleyman I; Tsvetkova, Nelly; Mohanty, Prasanna; Szalontai, Balász; Moon, Byoung Yong; Debreczeny, Mónika; Murata, Norio

    2005-07-15

    Irreversible photoinhibition of photosystem II (PSII) occurred when Synechocystis sp. PCC 6803 cells were exposed to very strong light for a prolonged period. When wild-type cells were illuminated at 20 degrees C for 2 h with light at an intensity of 2,500 micromol photons m(-2) s(-1), the oxygen-evolving activity of PSII was almost entirely and irreversibly lost, whereas the photochemical reaction center in PSII was inactivated only reversibly. The extent of irreversible photoinhibition was enhanced at lower temperatures and by the genetically engineered rigidification of membrane lipids. Western and Northern blotting demonstrated that, after cells had undergone irreversible photoinhibition, the precursor to D1 protein in PSII was synthesized but not processed properly. These observations may suggest that exposure of Synechocystis cells to strong light results in the irreversible photoinhibition of the oxygen-evolving activity of PSII via impairment of the processing of pre-D1 and that this effect of strong light is enhanced by the rigidification of membrane lipids.

  18. The connection between logical and thermodynamic irreversibility

    NASA Astrophysics Data System (ADS)

    Ladyman, James; Presnell, Stuart; Short, Anthony J.; Groisman, Berry

    There has recently been a good deal of controversy about Landauer's Principle, which is often stated as follows: the erasure of one bit of information in a computational device is necessarily accompanied by a generation of kT ln 2 heat. This is often generalised to the claim that any logically irreversible operation cannot be implemented in a thermodynamically reversible way. Norton [2005. Eaters of the lotus: Landauer's principle and the return of Maxwell's demon. Studies in History and Philosophy of Modern Physics, 36, 375-411] and Maroney [2005. The (absence of a) relationship between thermodynamic and logical reversibility. Studies in History and Philosophy of Modern Physics, 36, 355-374] both argue that Landauer's Principle has not been shown to hold in general, and Maroney offers a method that he claims instantiates the operation Reset in a thermodynamically reversible way. In this paper we defend the qualitative form of Landauer's Principle, and clarify its quantitative consequences (assuming the second law of thermodynamics). We analyse in detail what it means for a physical system to implement a logical transformation L, and we make this precise by defining the notion of an L-machine. Then we show that logical irreversibility of L implies thermodynamic irreversibility of every corresponding L-machine. We do this in two ways. First, by assuming the phenomenological validity of the Kelvin statement of the second law, and second, by using information-theoretic reasoning. We illustrate our results with the example of the logical transformation 'Reset', and thereby recover the quantitative form of Landauer's Principle.

  19. Irreversible translation arrest in the reperfused brain

    PubMed Central

    DeGracia, Donald J; Hu, Bingren R

    2012-01-01

    Irreversible translation arrest occurs in reperfused neurons that will die by delayed neuronal death. It is now recognized that suppression of protein synthesis is a general response of eukaryotic cells to exogenous stressors. Indeed, stress-induced translation arrest can be viewed as a component of cell stress responses, and consists of initiation, maintenance, and termination phases that work in concert with stress-induced transcriptional mechanisms. Within this framework, we review translation arrest in reperfused neurons. This framework provides a basis to recognize that phosphorylation of the alpha subunit of eukaryotic initiation factor 2 is the initiator of translation arrest, and a key marker indicating activation of neuronal stress responses. However, eIF2 alpha phosphorylation is reversible. Other phases of stress-induced translation arrest appear to contribute to irreversible translation arrest specifically in ischemic vulnerable neuron populations. We detail two lines of evidence supporting this view. First, ischemia, as a stress stimulus, induces irreversible co-translational protein misfolding and aggregation after 4 to 6 h of reperfusion, trapping protein synthesis machinery into functionally inactive protein aggregates. Second, ischemia and reperfusion leads to modifications of stress granules (SGs) that sequester functionally inactive 48S preinitiation complexes to maintain translation arrest. At later reperfusion durations, these mechanisms may converge such that SGs become sequestered in protein aggregates. These mechanisms result in elimination of functionally active ribosomes and preclude recovery of protein synthesis in selectively vulnerable neurons. Thus, recognizing translation arrest as a component of endogenous cellular stress response pathways will aid in making sense of the complexities of postischemic translation arrest. PMID:16926841

  20. Inactivated pepsin inhibits neutrophil activation by Fcgamma-receptor-dependent and independent stimuli.

    PubMed

    Kustiawan, Iwan; Derksen, Ninotska; Rispens, Theo

    2016-08-01

    Pepsin is widely used to produce F(ab')2 fragments of immunoglobulin G (IgG). In many cases, at least part of the pepsin will remain present in the F(ab')2 preparation, albeit in (irreversibly) inactivated form. Here we report on a potent immunomodulatory effect of irreversibly inactivated pepsin on activated human neutrophils. Degranulation, induced by coated IgG or via cytochalasin B/N-formyl-Met-Leu-Phe, was measured by quantifying elastase release, and was found to be inhibited in a dose-dependent manner by inactivated pepsin. Since a number of intravenous immunoglobulin (IVIg) products are also treated by limited digestion with pepsin, we investigated if pepsin would be present in quantities large enough to inhibit neutrophil activation. The amounts of pepsin detected in three different pepsin-treated IVIg products were found to be too low to induce an effect, at least in an in vitro setting.

  1. Chaos and irreversibility in simple model systems.

    PubMed

    Hoover, Wm. G.; Posch, Harald A.

    1998-06-01

    The multifractal link between chaotic time-reversible mechanics and thermodynamic irreversibility is illustrated for three simple chaotic model systems: the Baker Map, the Galton Board, and many-body color conductivity. By scaling time, or the momenta, or the driving forces, it can be shown that the dissipative nature of the three thermostated model systems has analogs in conservative Hamiltonian and Lagrangian mechanics. Links between the microscopic nonequilibrium Lyapunov spectra and macroscopic thermodynamic dissipation are also pointed out. (c) 1998 American Institute of Physics.

  2. Irreversibility for All Bound Entangled States

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Horodecki, Michał; Horodecki, Ryszard; Synak-Radtke, Barbara

    2005-11-01

    We derive a new inequality for entanglement for a mixed four-partite state. Employing this inequality, we present a one-shot lower bound for entanglement cost and prove that entanglement cost is strictly larger than zero for any entangled state. We demonstrate that irreversibility occurs in the process of formation for all nondistillable entangled states. In this way we solve a long standing problem of how “real” is entanglement of bound entangled states. Using the new inequality we also prove the impossibility of local cloning of a known entangled state.

  3. Ascorbate-induced oxidative inactivation of Zn2+-glycerophosphocholine cholinephosphodiesterase.

    PubMed

    Sok, D E

    1998-03-01

    Zn2+-glycerophosphocholine cholinephosphodiesterase, responsible for the conversion of glycerophosphocholine into glycerol and phosphocholine, was inactivated during incubation with ascorbic acid at 38 degrees C. The inclusion of copper ions or Fe2+ accelerated the ascorbate-induced inactivation, with Cu2+ or Cu+ being much more effective than Fe2+, suggestive of ascorbate-mediated oxidation. Dehydroascorbic acid had no effect on the phosphodiesterase, but H2O2 inactivated the enzyme in a concentration-dependent manner. Also, the enzyme was inactivated partially by a superoxide anion-generating system but not an HOCl generator. In support of involvement of H2O2 in the ascorbate action, catalase and superoxide dismutase expressed a complete and a partial protection, respectively. However, hydroxy radical scavengers such as mannitol, benzoate, or dimethyl sulfoxide were incapable of preventing the ascorbate action, excluding the participation of extraneous .OH. Although p-nitrophenylphosphocholine exhibited a modest protection against the ascorbate action, a remarkable protection was expressed by amino acids, especially by histidine. In addition, imidazole, an electron donor, showed a partial protection. Separately, when Cu2+-induced inactivation of the phosphodiesterase was compared with the ascorbate-mediated one, the protection and pH studies indicate that the mechanism for the ascorbate action is different from that for the Cu2+ action. Here, it is proposed that Zn2+-glycerophosphocholine cholinephosphodiesterase is one of brain membrane proteins susceptible to oxidative inactivation.

  4. Kinetics of combined pressure-temperature inactivation of avocado polyphenoloxidase.

    PubMed

    Weemaes, C A; Ludikhuyze, L R; Van den Broeck, I; Hendrickx, M E

    1998-11-05

    Irreversible combined pressure-temperature inactivation of the food quality related enzyme polyphenoloxidase was investigated. Inactivation rate constants (k) were obtained for about one hundred combinations of constant pressure (0.1-900 MPa) and temperature (25-77.5 degrees C). According to the Eyring and Arrhenius equation, activation volumes and activation energies, respectively, representing pressure and temperature dependence of the inactivation rate constant, were calculated for all temperatures and pressures studied. In this way, temperature and pressure dependence of activation volume and activation energy, respectively, could be considered. Moreover, for the first time, a mathematical model describing the inactivation rate constant of a food quality-related enzyme as a function of pressure and temperature is formulated. Such pressure-temperature inactivation models for food quality-related aspects (e.g., the spoilage enzyme polyphenoloxidase) form the engineering basis for design, evaluation, and optimization of new preservation processes based on the combined effect of temperature and pressure. Furthermore, the generated methodology can be used to develop analogous kinetic models for microbiological aspects, which are needed from a safety and legislative point of view, and other quality aspects, e.g., nutritional factors, with a view of optimal quality and consumer acceptance. Copyright 1998 John Wiley & Sons, Inc.

  5. Inactivation of Anopheles gambiae Glutathione Transferase ε2 by Epiphyllocoumarin

    PubMed Central

    Marimo, Patience; Hayeshi, Rose; Mukanganyama, Stanley

    2016-01-01

    Glutathione transferases (GSTs) are part of a major family of detoxifying enzymes that can catalyze the reductive dehydrochlorination of dichlorodiphenyltrichloroethane (DDT). The delta and epsilon classes of insect GSTs have been implicated in conferring resistance to this insecticide. In this study, the inactivation of Anopheles gambiae GSTε2 by epiphyllocoumarin (Tral 1) was investigated. Recombinant AgGSTε2 was expressed in Escherichia coli cells containing a pET3a-AGSTε2 plasmid and purified by affinity chromatography. Tral 1 was shown to inactivate GSTε2 both in a time-dependent manner and in a concentration-dependent manner. The half-life of GSTε2 in the presence of 25 μM ethacrynic acid (ETA) was 22 minutes and with Tral 1 was 30 minutes, indicating that Tral 1 was not as efficient as ETA as an inactivator. The inactivation parameters kinact and KI were found to be 0.020 ± 0.001 min−1 and 7.5 ± 2.1 μM, respectively, after 90 minutes of incubation. Inactivation of GSTε2 by Tral 1 implies that Tral 1 covalently binds to this enzyme in vitro and would be expected to exhibit time-dependent effects on the enzyme in vivo. Tral 1, therefore, would produce irreversible effects when used together with dichlorodiphenyltrichloroethane (DDT) in malaria control programmes where resistance is mediated by GSTs. PMID:26925266

  6. Structure of suicide-inactivated. beta. -hydroxydecanoyl-thioester dehydrase

    SciTech Connect

    Schwab, J.M.; Ho, C.K.; Li, W.B.; Townsend, C.A.; Salituro, G.M.

    1986-05-01

    ..beta..-Hydroxydecanoylthioester dehydrase, the key enzyme in biosynthesis of unsaturated fatty acids under anaerobic conditions, equilibrates thioesters of (R)-3-hydroxydecanoic acid, E-2-decenoic acid, and Z-3-decenoic acid. Dehydrase is irreversibly inactivated by the N-acetylcysteamine thioester of 3-decynoic acid (3-decynoyl-NAC), via dehydrase-catalyzed isomerization to 2,3-decadienoyl-NAC. To probe the relationship between normal catalysis and suicide inactivation, the structure of the inactivated enzyme has been studied. 3-(2-/sup 13/C)Decynoyl-NAC was synthesized and incubated with dehydrase. /sup 13/C NMR showed that attack of 2,3-decadienoyl-NAC by the active site histidine gives 3-histidinyl-3-decenoyl-NAC, which slowly rearranges to the more stable ..delta../sup 2/ isomer. Model histidine-allene adducts have been made and characterized. Analysis of NMR data show that the C=C configuration of the decenoyl moiety of enzyme-bound inactivator is E. The suggestion that the mechanism of dehydrase inactivation parallels its normal mechanism of action is supported these findings.

  7. Probabilistic Gompertz model of irreversible growth.

    PubMed

    Bardos, D C

    2005-05-01

    Characterizing organism growth within populations requires the application of well-studied individual size-at-age models, such as the deterministic Gompertz model, to populations of individuals whose characteristics, corresponding to model parameters, may be highly variable. A natural approach is to assign probability distributions to one or more model parameters. In some contexts, size-at-age data may be absent due to difficulties in ageing individuals, but size-increment data may instead be available (e.g., from tag-recapture experiments). A preliminary transformation to a size-increment model is then required. Gompertz models developed along the above lines have recently been applied to strongly heterogeneous abalone tag-recapture data. Although useful in modelling the early growth stages, these models yield size-increment distributions that allow negative growth, which is inappropriate in the case of mollusc shells and other accumulated biological structures (e.g., vertebrae) where growth is irreversible. Here we develop probabilistic Gompertz models where this difficulty is resolved by conditioning parameter distributions on size, allowing application to irreversible growth data. In the case of abalone growth, introduction of a growth-limiting biological length scale is then shown to yield realistic length-increment distributions.

  8. Irreversibility-inversions in 2D turbulence

    NASA Astrophysics Data System (ADS)

    Bragg, Andrew; de Lillo, Filippo; Boffetta, Guido

    2016-11-01

    We consider a recent theoretical prediction that for inertial particles in 2D turbulence, the nature of the irreversibility of their pair dispersion inverts when the particle inertia exceeds a certain value. In particular, when the particle Stokes number, St , is below a certain value, the forward-in-time (FIT) dispersion should be faster than the backward-in-time (BIT) dispersion, but for St above this value, this should invert so that BIT becomes faster than FIT dispersion. This non-trivial behavior arises because of the competition between two physically distinct irreversibility mechanisms that operate in different regimes of St . In 3D turbulence, both mechanisms act to produce faster BIT than FIT dispersion, but in 2D, the two mechanisms have opposite effects because of the inverse energy cascade in the turbulent velocity field. We supplement the qualitative argument given by Bragg et al. by deriving quantitative predictions of this effect in the short-time dispersion limit. These predictions are then confirmed by results of inertial particle dispersion in a direct numerical simulation of 2D turbulence.

  9. Magnetic Irreversibility in VO2/Ni Bilayers

    NASA Astrophysics Data System (ADS)

    de La Venta, Jose; Lauzier, Josh; Sutton, Logan

    The temperature dependence of the coercivity and magnetization of VO2/Ni bilayers was studied. VO2 exhibits a well-known Structural Phase Transition (SPT) at 330-340 K, from a low temperature monoclinic (M) to a high temperature rutile (R) structure. The SPT of VO2 induces an inverse magnetoelastic effect that strongly modifies the coercivity and magnetization of the Ni films. In addition, the growth conditions allow tuning of the magnetic properties. Ni films deposited on top of VO2 (M) show an irreversible change in the coercivity after the first cycle through the high temperature phase, with a corresponding change in the surface morphology of VO2. On the other hand, the Ni films grown on top of VO2 (R) do not show this irreversibility. These results indicate that properties of magnetic films are strongly affected by the strain induced by materials that undergo SPT and that it is possible to control the magnetic properties by tuning the growth conditions.

  10. Irreversible heavy chain transfer to chondroitin.

    PubMed

    Lauer, Mark E; Hascall, Vincent C; Green, Dixy E; DeAngelis, Paul L; Calabro, Anthony

    2014-10-17

    We have recently demonstrated that the transfer of heavy chains (HCs) from inter-α-inhibitor, via the enzyme TSG-6 (tumor necrosis factor-stimulated gene 6), to hyaluronan (HA) oligosaccharides is an irreversible event in which subsequent swapping of HCs between HA molecules does not occur. We now describe our results of HC transfer experiments to chondroitin sulfate A, chemically desulfated chondroitin, chemoenzymatically synthesized chondroitin, unsulfated heparosan, heparan sulfate, and alginate. Of these potential HC acceptors, only chemically desulfated chondroitin and chemoenzymatically synthesized chondroitin were HC acceptors. The kinetics of HC transfer to chondroitin was similar to HA. At earlier time points, HCs were more widely distributed among the different sizes of chondroitin chains. As time progressed, the HCs migrated to lower molecular weight chains of chondroitin. Our interpretation is that TSG-6 swaps the HCs from the larger, reversible sites on chondroitin chains, which function as HC acceptors, onto smaller chondroitin chains, which function as irreversible HC acceptors. HCs transferred to smaller chondroitin chains were unable to be swapped off the smaller chondroitin chains and transferred to HA. HCs transferred to high molecular weight HA were unable to be swapped onto chondroitin. We also present data that although chondroitin was a HC acceptor, HA was the preferred acceptor when chondroitin and HA were in the same reaction mixture.

  11. Kv4 channels exhibit modulation of closed-state inactivation in inside-out patches.

    PubMed Central

    Beck, E J; Covarrubias, M

    2001-01-01

    The mechanisms of inactivation gating of the neuronal somatodendritic A-type K(+) current and the cardiac I(to) were investigated in Xenopus oocyte macropatches expressing Kv4.1 and Kv4.3 channels. Upon membrane patch excision (inside-out), Kv4.1 channels undergo time-dependent acceleration of macroscopic inactivation accompanied by a parallel partial current rundown. These changes are readily reversible by patch cramming, suggesting the influence of modulatory cytoplasmic factors. The consequences of these perturbations were investigated in detail to gain insights into the biophysical basis and mechanisms of inactivation gating. Accelerated inactivation at positive voltages (0 to +110 mV) is mainly the result of reducing the time constant of slow inactivation and the relative weight of the slow component of inactivation. Concomitantly, the time constants of closed-state inactivation at negative membrane potentials (-90 to -50 mV) are substantially decreased in inside-out patches. Deactivation is moderately accelerated, and recovery from inactivation and the peak G--V curve exhibit little or no change. In agreement with more favorable closed-state inactivation in inside-out patches, the steady-state inactivation curve exhibits a hyperpolarizing shift of approximately 10 mV. Closed-state inactivation was similarly enhanced in Kv4.3. An allosteric model that assumes significant closed-state inactivation at all relevant voltages can explain Kv4 inactivation gating and the modulatory changes. PMID:11463631

  12. Nucleation of a new phase on a surface that is changing irreversibly with time.

    PubMed

    Sear, Richard P

    2014-02-01

    Nucleation of a new phase almost always starts at a surface. This surface is almost always assumed not to change with time. However, surfaces can roughen, partially dissolve, and change chemically with time. Each of these irreversible changes will change the nucleation rate at the surface, resulting in a time-dependent nucleation rate. Here we use a simple model to show that partial surface dissolution can qualitatively change the nucleation process in a way that is testable in experiment. The changing surface means that the nucleation rate is increasing with time. There is an initial period during which no nucleation occurs, followed by relatively rapid nucleation.

  13. Competitive irreversible random one-, two-, three-, . . . point adsorption on two-dimensional lattices

    NASA Astrophysics Data System (ADS)

    Evans, J. W.; Nord, R. S.

    1985-02-01

    An analytic treatment of competitive, irreversible (immobile) random one-, two-, three-, . . . point adsorption (or monomer, dimer, trimer, . . . filling) on infinite, uniform two-dimensional lattices is provided by applying previously developed truncation schemes to the hierarchial form of the appropriate master equations. The behavior of these processes for two competing species is displayed by plotting families of ``filling trajectories'' in the partial-coverage plane for various ratios of adsorption rates. The time or coverage dependence of various subconfiguration probabilities can also be analyzed. For processes where no one-point (monomer) adsorption occurs, the lattice cannot fill completely; accurate estimates of the total (and partial) saturation coverages can be obtained.

  14. Suppression of α-Amylase inactivation in the presence of ethanol: Application of a two-step model.

    PubMed

    Calabrese, Vincent T; Minns, Jason W; Khan, Arshad

    2016-09-01

    A number of years ago we reported a two-step inactivation mechanism for α-amylase (enzyme) on the basis of theoretical and experimental studies in aqueous solutions. In the first step the metal (Ca(2+) ) ion dissociates reversibly from the enzyme followed by an irreversible thermal inactivation of the apoenzyme. In this study we report inactivation of the enzyme in the presence of ethanol-water solutions. We noticed that as the concentration of ethanol in the aqueous solution is increased, the thermal inactivation of the enzyme is suppressed with almost no inactivation (in 1 h, 30°C) when 50% alcohol is present in the solution. These results are explained by the two-step inactivation model. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1271-1275, 2016. © 2016 American Institute of Chemical Engineers.

  15. Partial agonism: mechanisms based on ligand-receptor interactions and on stimulus-response coupling.

    PubMed

    Pliska, V

    1999-01-01

    Substances eliciting, at very high concentrations, a lower maximal response of a particular biological system than a defined standard, are defined as partial agonists. The convention rests on the definition of a standard substance that achieves a 'full' maximal response; partial agonism being, therefore, relative. Various mechanisms lie behind this phenomenon: 1. Receptor-related mechanisms: the agonist-receptor complex exists in several conformational states from which only one, or only a few, activate the cell signaling pathway. This may occur when the receptor itself, or the agonist, exists in multiple states (e.g., in the form of enantiomers or stereoisomers), or when the agonist-receptor complex changes its conformation (receptor switch: two-state model of receptor activation). Furthermore, a steric hindrance by a 'wrong-way binding' of a part of the agonist's molecules may prevent the full 'correct' occupancy of receptors. 2. Mechanisms based on the efficacy of the stimulus-response coupling. The efficacy is then proportional to the sum of probabilities that receptors in individual states activate the cell-signaling pathway. Doses (concentrations) eliciting the half maximal response (EC50), or similar response sensitivity parameters, are not included in the definition of partial agonism. However, tight correlations exist between maximal response and EC50 in many, but not all, generic groups of agonistically acting substances. These relationships are frequently linear; intercepts and slopes of these 'E, KE plots' are characteristic for individual, putative mechanisms. Dose-response curves of partial agonists are akin to those obtained for a response to a full agonist after a stepwise partial inactivation of receptors by an irreversible inhibitor. Also, the E, KE plots obtained in these instances are similar to those of partial agonists. The receptor reserve, rather vaguely defined in early reports, is therefore closely linked to the phenomenon of partial

  16. Mechanisms of inactivation of lipoxygenases by phenidone and BW755C.

    PubMed

    Cucurou, C; Battioni, J P; Thang, D C; Nam, N H; Mansuy, D

    1991-09-17

    Inhibition of soybean lipoxygenase (L-1) and potato 5-lipoxygenase (5-PLO) by the pyrazoline derivatives phenidone and BW755C only occurs after oxidation of these compounds by the peroxidase-like activity of the lipoxygenases. There is a clear relationship between this oxidation and the irreversible inactivation of L-1. The final product of phenidone oxidation by L-1, 4,5-didehydrophenidone, is not responsible of this inactivation, but the species derived from a one-electron oxidation of phenidone plays a key role in L-1 inactivation. In the absence of O2, inactivation of 1 mol of L-1 occurs after the oxidation of 34 mol of phenidone and the covalent binding of 0.8 mol of phenidone-derived metabolite(s) to L-1. In the presence of O2, inactivation of 1 mol of L-1 occurs already after oxidation of 11 mol of phenidone and only involves the covalent binding of 0.4 mol of phenidone-derived metabolite(s) to L-1. A mechanism is proposed for L-1 inactivation by phenidone, which involves the irreversible binding of a phenidone metabolite to the protein and the oxidation of an L-1 amino acid residue (in the presence of O2).

  17. Inactivation of rabies virus.

    PubMed

    Wu, Guanghui; Selden, David; Fooks, Anthony R; Banyard, Ashley

    2017-05-01

    Rabies virus is a notifiable pathogen that must be handled in high containment facilities where national and international guidelines apply. For the effective inactivation of rabies virus, a number of reagents were tested. Virkon S (1%) solution caused more than 4log reduction of rabies virus in culture medium supplemented with 10% foetal calf serum within 1min. Isopropyl alcohol (70%) treatment resulted in >3log reduction of rabies virus within 20s when applied at a ratio of 19:1, making it a suitable agent for surface decontamination whereas 70% ethanol was ineffective. Rabies virus (from 10(2.33) to 10(3)ffu/ml) was also inactivated when cell cultures were fixed with 3% or 4% paraformaldehyde for 30min. Regardless of inactivation procedure, when taking inactivated virus preparations out of a biological containment envelope, proof of inocuity must be demonstrated to cover any possible error/deviation from procedure. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

  18. Exergetic sustainability evaluation of irreversible Carnot refrigerator

    NASA Astrophysics Data System (ADS)

    Açıkkalp, Emin

    2015-10-01

    Purpose of this paper is to assess irreversible refrigeration cycle by using exergetic sustainability index. In literature, there is no application of exergetic sustainability index for the refrigerators and, indeed, this index has not been derived for refrigerators. In this study, exergetic sustainability indicator is presented for the refrigeration cycle and its relationships with other thermodynamics parameters including COP, exergy efficiency, cooling load, exergy destruction, ecological function and work input are investigated. Calculations are conducted for endoreversible and reversible cycles and then results obtained from the ecological function are compared. It is found that exergy efficiency, exergetic sustainable index reduce 47.595% and 59.689% and rising at the COP is 99.888% is obtained for endoreversible cycle. Similarly, exergy efficiency and exergetic sustainability index reduce 90.163% and 93.711% and rising of the COP is equal to 99.362%.

  19. Geroconversion: irreversible step to cellular senescence

    PubMed Central

    Blagosklonny, Mikhail V

    2014-01-01

    Cellular senescence happens in 2 steps: cell cycle arrest followed, or sometimes preceded, by gerogenic conversion (geroconversion). Geroconvesrion is a form of growth, a futile growth during cell cycle arrest. It converts reversible arrest to irreversible senescence. Geroconversion is driven by growth-promoting, mitogen-/nutrient-sensing pathways such as mTOR. Geroconversion leads to hyper-secretory, hypertrophic and pro-inflammatory cellular phenotypes, hyperfunctions and malfunctions. On organismal level, geroconversion leads to age-related diseases and death. Rapamycin, a gerosuppressant, extends life span in diverse species from yeast to mammals. Stress–and oncogene-induced accelerated senescence, replicative senescence in vitro and life-long cellular aging in vivo all can be described by 2-step model. PMID:25483060

  20. Irreversible electroporation: state of the art.

    PubMed

    Wagstaff, Peter Gk; Buijs, Mara; van den Bos, Willemien; de Bruin, Daniel M; Zondervan, Patricia J; de la Rosette, Jean Jmch; Laguna Pes, M Pilar

    2016-01-01

    The field of focal ablative therapy for the treatment of cancer is characterized by abundance of thermal ablative techniques that provide a minimally invasive treatment option in selected tumors. However, the unselective destruction inflicted by thermal ablation modalities can result in damage to vital structures in the vicinity of the tumor. Furthermore, the efficacy of thermal ablation intensity can be impaired due to thermal sink caused by large blood vessels in the proximity of the tumor. Irreversible electroporation (IRE) is a novel ablation modality based on the principle of electroporation or electropermeabilization, in which electric pulses are used to create nanoscale defects in the cell membrane. In theory, IRE has the potential of overcoming the aforementioned limitations of thermal ablation techniques. This review provides a description of the principle of IRE, combined with an overview of in vivo research performed to date in the liver, pancreas, kidney, and prostate.

  1. Performance of an irreversible quantum Carnot engine with spin 12.

    PubMed

    Wu, Feng; Chen, Lingen; Wu, Shuang; Sun, Fengrui; Wu, Chih

    2006-06-07

    The purpose of this paper is to investigate the effect of quantum properties of the working medium on the performance of an irreversible Carnot cycle with spin 12. The optimal relationship between the dimensionless power output P* versus the efficiency eta for the irreversible quantum Carnot engine with heat leakage and other irreversible losses is derived. Especially, the performances of the engine at low temperature limit and at high temperature limit are discussed.

  2. Calcium-binding parameter of Bacillus amyloliquefaciens alpha-amylase determined by inactivation kinetics.

    PubMed Central

    Tanaka, Atsushi; Hoshino, Eiichi

    2002-01-01

    The irreversible thermal inactivation and the thermodynamics of calcium ion binding of Bacillus amyloliquefaciens alpha-amylase in the absence of substrates were studied. The enzyme inactivation on heating was apparently followed by first-order kinetics. The enzyme was stabilized with an increased concentration of calcium ion and thus the inactivation was highly dependent on the state of calcium binding. The activation parameter for the inactivation suggests an unfolding of the enzyme protein upon heating. Values of both the activation enthalpy and entropy were increased with a higher calcium ion concentration. An inactivation kinetic model is based on the assumption of a two-stage unfolding transition in which the bivalent ion dissociation occurs in the first step followed by the secondary structural unfolding. This simple kinetic model provides both a qualitative and quantitative interpretation of calcium ion binding to the enzyme and its effect on the inactivation properties. The specific approximations of the kinetic model were strictly followed in the analysis to calculate the apparent inactivation rate at each calcium ion concentration in terms of the calcium-binding parameters. The enthalpy and entropy changes for the calcium ion binding were calculated to be -149 kJ/mol and -360 J.mol(-1).K(-1) respectively and these values suggest a strong enthalpic affinity for the bivalent ion binding to the enzyme protein. The thermodynamical interpretation attempts to provide clear relations between the terms of an apparent inactivation rate and the calcium binding. PMID:12049626

  3. Heat-induced Irreversible Denaturation of the Camelid Single Domain VHH Antibody Is Governed by Chemical Modifications

    PubMed Central

    Akazawa-Ogawa, Yoko; Takashima, Mizuki; Lee, Young-Ho; Ikegami, Takahisa; Goto, Yuji; Uegaki, Koichi; Hagihara, Yoshihisa

    2014-01-01

    The variable domain of camelid heavy chain antibody (VHH) is highly heat-resistant and is therefore ideal for many applications. Although understanding the process of heat-induced irreversible denaturation is essential to improve the efficacy of VHH, its inactivation mechanism remains unclear. Here, we showed that chemical modifications predominantly governed the irreversible denaturation of VHH at high temperatures. After heat treatment, the activity of VHH was dependent only on the incubation time at 90 °C and was insensitive to the number of heating (90 °C)-cooling (20 °C) cycles, indicating a negligible role for folding/unfolding intermediates on permanent denaturation. The residual activity was independent of concentration; therefore, VHH lost its activity in a unimolecular manner, not by aggregation. A VHH mutant lacking Asn, which is susceptible to chemical modifications, had significantly higher heat resistance than did the wild-type protein, indicating the importance of chemical modifications to VHH denaturation. PMID:24739391

  4. Mesoscopic systems: classical irreversibility and quantum coherence.

    PubMed

    Barbara, Bernard

    2012-09-28

    Mesoscopic physics is a sub-discipline of condensed-matter physics that focuses on the properties of solids in a size range intermediate between bulk matter and individual atoms. In particular, it is characteristic of a domain where a certain number of interacting objects can easily be tuned between classical and quantum regimes, thus enabling studies at the border of the two. In magnetism, such a tuning was first realized with large-spin magnetic molecules called single-molecule magnets (SMMs) with archetype Mn(12)-ac. In general, the mesoscopic scale can be relatively large (e.g. micrometre-sized superconducting circuits), but, in magnetism, it is much smaller and can reach the atomic scale with rare earth (RE) ions. In all cases, it is shown how quantum relaxation can drastically reduce classical irreversibility. Taking the example of mesoscopic spin systems, the origin of irreversibility is discussed on the basis of the Landau-Zener model. A classical counterpart of this model is described enabling, in particular, intuitive understanding of most aspects of quantum spin dynamics. The spin dynamics of mesoscopic spin systems (SMM or RE systems) becomes coherent if they are well isolated. The study of the damping of their Rabi oscillations gives access to most relevant decoherence mechanisms by different environmental baths, including the electromagnetic bath of microwave excitation. This type of decoherence, clearly seen with spin systems, is easily recovered in quantum simulations. It is also observed with other types of qubits such as a single spin in a quantum dot or a superconducting loop, despite the presence of other competitive decoherence mechanisms. As in the molecular magnet V(15), the leading decoherence terms of superconducting qubits seem to be associated with a non-Markovian channel in which short-living entanglements with distributions of two-level systems (nuclear spins, impurity spins and/or charges) leading to 1/f noise induce τ(1)-like

  5. Monte Carlo simulations of the short time dynamics of a first-order irreversible phase transition

    NASA Astrophysics Data System (ADS)

    Albano, Ezequiel V.

    2001-09-01

    The ZGB model (Ziff-Gulari-Barshad, Phys. Rev. Lett. 56 (1986) 2553) for the catalytic oxidation of carbon monoxide has a single parameter given by the normalized partial pressure of CO molecules ( PCO). For PCO⩾ PCOCoex≃0.52583 the surface of the catalyst becomes irreversibly covered by CO molecules and the system cannot escape from this state. However, for PCO slightly below PCOCoex the system reaches an active stationary state. So, just at PCOCoex a sharp first-order irreversible phase transition is observed. It is shown that a study of the short time dynamics of the ZGB model allows to obtain a fairly accurate evaluation of the upper spinodal point given by PCOUsp≃0.52675(5). This figure is in excellent agreement with extensive simulations performed using the constant coverage ensemble.

  6. Enterovirus inactivation in soil.

    PubMed Central

    Yeager, J G; O'Brien, R T

    1979-01-01

    The inactivation of radioactively labeled poliovirus type 1 and coxsackievirus B 1 in soils saturated with surface water, groundwater, and septic tank liquor was directly proportional to temperature. Virus persistence was also related to soil type and the liquid amendment in which viruses were suspended. At 37 degrees C, no infectivity was recovered from saturated soil after 12 days; at 4 degrees C, viruses persisted for at least 180 days. No infectivity was recovered from dried soil regardless of temperature, soil type, or liquid amendment. Additional experiments showed that evaporation of soil water was largely responsible for the decreased recovery of infectivity from drying soil. Increased rates of virus inactivation at low soil moisture levels were also demonstrated. PMID:44178

  7. Hydrazine inactivates bacillus spores

    NASA Technical Reports Server (NTRS)

    Schubert, Wayne; Plett, G. A.; Yavrouian, A. H.; Barengoltz, J.

    2005-01-01

    Planetary Protection places requirements on the maximum number of viable bacterial spores that may be delivered by a spacecraft to another solar system body. Therefore, for such space missions, the spores that may be found in hydrazine are of concern. A proposed change in processing procedures that eliminated a 0.2 um filtration step propmpted this study to ensure microbial contamination issue existed, especially since no information was found in the literature to substantiate bacterial spore inactivation by hydrazine.

  8. Thermal Inactivation of Viruses

    DTIC Science & Technology

    1977-10-01

    Hammon. 1966. Studies on Japanese B encephalitis virus vaccines from tissue culture. VI. Development of a hamster kidney tissue culture inactivated... tissue culture passage, storage, temperature and drying on viability of SE polyoma virus. Exper. Biol. and Hed. Proc. of the Soc. for Exper. Biol...studies of heated tissue suspensions containing foot- and-mouth disease virus. Amer. J. Vet. Res. 20:510-521. Dupre’, M. V., and M. Frobisher. 1966

  9. Inactivation and covalent modification of CTP synthetase by thiourea dioxide.

    PubMed Central

    Robertson, J. G.; Sparvero, L. J.; Villafranca, J. J.

    1992-01-01

    Thiourea dioxide was used in chemical modification studies to identify functionally important amino acids in Escherichia coli CTP synthetase. Incubation at pH 8.0 in the absence of substrates led to rapid, time dependent, and irreversible inactivation of the enzyme. The second-order rate constant for inactivation was 0.18 M-1 s-1. Inactivation also occurred in the absence of oxygen and in the presence of catalase, thereby ruling out mixed-function oxidation/reduction as the mode of amino acid modification. Saturating concentrations of the substrates ATP and UTP, and the allosteric activator GTP prevented inactivation by thiourea dioxide, whereas saturating concentrations of glutamine (a substrate) did not. The concentration dependence of nucleotide protection revealed cooperative behavior with respect to individual nucleotides and with respect to various combinations of nucleotides. Mixtures of nucleotides afforded greater protection against inactivation than single nucleotides alone, and a combination of the substrates ATP and UTP provided the most protection. The Hill coefficient for nucleotide protection was approximately 2 for ATP, UTP, and GTP. In the presence of 1:1 ratios of ATP:UTP, ATP:GTP, and UTP:GTP, the Hill coefficient was approximately 4 in each case. Fluorescence and circular dichroism measurements indicated that modification by thiourea dioxide causes detectable changes in the structure of the protein. Modification with [14C]thiourea dioxide demonstrated that complete inactivation correlates with incorporation of 3 mol of [14C]thiourea dioxide per mole of CTP synthetase monomer. The specificity of thiourea dioxide for lysine residues indicates that one or more lysines are most likely involved in CTP synthetase activity. The data further indicate that nucleotide binding prevents access to these functionally important residues. PMID:1303749

  10. Greenland's pronounced glacier retreat not irreversible

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-02-01

    In recent decades, the combined forces of climate warming and short-term variability have forced the massive glaciers that blanket Greenland into retreat, with some scientists worrying that deglaciation could become irreversible. The short history of detailed glacier observations, however, makes pinning the ice loss to either short-term dynamics or long-term change difficult. Research by Young et al. detailing the effects of two bouts of sudden and temporary cooling during an otherwise warm phase in Greenland's climate history could help answer that question by showing just how heavy a hand short-term variability can have in dictating glacier dynamics. Along the western edge of Greenland the massive Jakobshavn Isbræ glacier reaches out to the coast, its outflow dropping icebergs into Baffin Bay during the summer months. Flanking the glacier's tongue are the Tasiussaq and Marrait moraines—piles of rock marking the glacier's former extent. Researchers suspected the moraines were tied to two periods of abrupt cooling that hit Greenland 9300 and 8200 years ago, and that association was reinforced by the authors' radiocarbon and beryllium isotope analyses of the area surrounding the moraines. Beryllium-10 forms when cosmic radiation travels through the atmosphere and strikes the Earth's surface, with surface rock concentrations indicating how long it has been ice-free.

  11. Combustion irreversibilities: Numerical simulation and analysis

    NASA Astrophysics Data System (ADS)

    Silva, Valter; Rouboa, Abel

    2012-08-01

    An exergy analysis was performed considering the combustion of methane and agro-industrial residues produced in Portugal (forest residues and vines pruning). Regarding that the irreversibilities of a thermodynamic process are path dependent, the combustion process was considering as resulting from different hypothetical paths each one characterized by four main sub-processes: reactant mixing, fuel oxidation, internal thermal energy exchange (heat transfer), and product mixing. The exergetic efficiency was computed using a zero dimensional model developed by using a Visual Basic home code. It was concluded that the exergy losses were mainly due to the internal thermal energy exchange sub-process. The exergy losses from this sub-process are higher when the reactants are preheated up to the ignition temperature without previous fuel oxidation. On the other hand, the global exergy destruction can be minored increasing the pressure, the reactants temperature and the oxygen content on the oxidant stream. This methodology allows the identification of the phenomena and processes that have larger exergy losses, the understanding of why these losses occur and how the exergy changes with the parameters associated to each system which is crucial to implement the syngas combustion from biomass products as a competitive technology.

  12. Simulations of kinetically irreversible protein aggregate structure.

    PubMed Central

    Patro, S Y; Przybycien, T M

    1994-01-01

    We have simulated the structure of kinetically irreversible protein aggregates in two-dimensional space using a lattice-based Monte-Carlo routine. Our model specifically accounts for the intermolecular interactions between hydrophobic and hydrophilic protein surfaces and a polar solvent. The simulations provide information about the aggregate density, the types of inter-monomer contacts and solvent content within the aggregates, the type and extent of solvent exposed perimeter, and the short- and long-range order all as a function of (i) the extent of monomer hydrophobic surface area and its distribution on the model protein surface and (ii) the magnitude of the hydrophobic-hydrophobic contact energy. An increase in the extent of monomer hydrophobic surface area resulted in increased aggregate densities with concomitant decreased system free energies. These effects are accompanied by increases in the number of hydrophobic-hydrophobic contacts and decreases in the solvent-exposed hydrophobic surface area of the aggregates. Grouping monomer hydrophobic surfaces in a single contiguous stretch resulted in lower aggregate densities and lower short range order. More favorable hydrophobic-hydrophobic contact energies produced structures with higher densities but the number of unfavorable protein-protein contacts was also observed to increase; greater configurational entropy produced the opposite effect. Properties predicted by our model are in good qualitative agreement with available experimental observations. Images FIGURE 6 FIGURE 13 PMID:8061184

  13. Reversible and irreversible aggregation of magnetic liposomes.

    PubMed

    García-Jimeno, Sonia; Estelrich, Joan; Callejas-Fernández, José; Roldán-Vargas, Sándalo

    2017-10-12

    Understanding stabilization and aggregation in magnetic nanoparticle systems is crucial to optimizing the functionality of these systems in real physiological applications. Here we address this problem for a specific, yet representative, system. We present an experimental and analytical study on the aggregation of superparamagnetic liposomes in suspension in the presence of a controllable external magnetic field. We study the aggregation kinetics and report an intermediate time power law evolution and a long time stationary value for the average aggregate diffusion coefficient, both depending on the magnetic field intensity. We then show that the long time aggregate structure is fractal with a fractal dimension that decreases upon increasing the magnetic field intensity. By scaling arguments we also establish an analytical relation between the aggregate fractal dimension and the power law exponent controlling the aggregation kinetics. This relation is indeed independent on the magnetic field intensity. Despite the superparamagnetic character of our particles, we further prove the existence of a population of surviving aggregates able to maintain their integrity after switching off the external magnetic field. Finally, we suggest a schematic interaction scenario to rationalize the observed coexistence between reversible and irreversible aggregation.

  14. Irreversible thermodynamics of creep in crystalline solids

    NASA Astrophysics Data System (ADS)

    Mishin, Y.; Warren, J. A.; Sekerka, R. F.; Boettinger, W. J.

    2013-11-01

    We develop an irreversible thermodynamics framework for the description of creep deformation in crystalline solids by mechanisms that involve vacancy diffusion and lattice site generation and annihilation. The material undergoing the creep deformation is treated as a nonhydrostatically stressed multicomponent solid medium with nonconserved lattice sites and inhomogeneities handled by employing gradient thermodynamics. Phase fields describe microstructure evolution, which gives rise to redistribution of vacancy sinks and sources in the material during the creep process. We derive a general expression for the entropy production rate and use it to identify of the relevant fluxes and driving forces and to formulate phenomenological relations among them taking into account symmetry properties of the material. As a simple application, we analyze a one-dimensional model of a bicrystal in which the grain boundary acts as a sink and source of vacancies. The kinetic equations of the model describe a creep deformation process accompanied by grain boundary migration and relative rigid translations of the grains. They also demonstrate the effect of grain boundary migration induced by a vacancy concentration gradient across the boundary.

  15. Irreversible electroporation on the small intestine

    PubMed Central

    Phillips, M A; Narayan, R; Padath, T; Rubinsky, B

    2012-01-01

    Background: Non-thermal irreversible electroporation (NTIRE) has recently been conceived as a new minimally invasive ablation method, using microsecond electric fields to produce nanoscale defects in the cell membrane bilayer and induce cell death while keeping all other molecules, including the extracellular matrix, intact. Here, we present the first in vivo study that examines the effects of NTIRE on the small intestine, an organ whose collateral damage is of particular concern in the anticipated use of NTIRE for treatment of abdominal cancers. Methods: A typical NTIRE electrical protocol was applied directly to the rat small intestine and histological analysis was used to examine the effect of NTIRE over time. Results: The application of NTIRE led to complete cell ablation in the targeted tissue, but the animal did not show any physiological effects of the procedure and the intestine showed signs of recovery, developing an epithelial layer 3 days post treatment and regenerating its distinct layers within a week. Conclusion: Our results indicate that this novel procedure can be used for abdominal cancer treatment while minimising collateral damage to adjacent tissues because of the unique ability of the NTIRE ablation method to target the cell membrane. PMID:22223084

  16. Guinea pig ductus arteriosus. II - Irreversible closure after birth.

    NASA Technical Reports Server (NTRS)

    Fay, F. S.; Cooke, P. H.

    1972-01-01

    To investigate the mechanism underlying irreversibility of ductal closure after birth, studies were undertaken to determine the exact time course for the onset of irreversible closure of the guinea pig ductus arteriosus. Parallel studies of the reactivity of ductal smooth muscle to oxygen and studies of the postpartum cellular changes within the vessel were also carried out.

  17. Formation of Irreversible H-bonds in Cellulose Materials

    Treesearch

    Umesh P. Agarwal; Sally A. Ralph; Rick S. Reiner; Nicole M. Stark

    2015-01-01

    Understanding of formation of irreversible Hbonds in cellulose is important in a number of fields. For example, fields as diverse as pulp and paper and enzymatic saccharification of cellulose are affected. In the present investigation, the phenomenon of formation of irreversible H-bonds is studied in a variety of celluloses and under two different drying conditions....

  18. Guinea pig ductus arteriosus. II - Irreversible closure after birth.

    NASA Technical Reports Server (NTRS)

    Fay, F. S.; Cooke, P. H.

    1972-01-01

    To investigate the mechanism underlying irreversibility of ductal closure after birth, studies were undertaken to determine the exact time course for the onset of irreversible closure of the guinea pig ductus arteriosus. Parallel studies of the reactivity of ductal smooth muscle to oxygen and studies of the postpartum cellular changes within the vessel were also carried out.

  19. The Anesthetic Efficacy of the Intraosseous Injection in Irreversible Pulpitis.

    DTIC Science & Technology

    1995-01-01

    The purpose of this study was to evaluate the anesthetic efficacy of an intraosseous injection in teeth diagnosed with irreversible pulpitis . Fifty...one healthy human subjects with symptomatic maxillary or mandibular posterior teeth diagnosed with irreversible pulpitis were used in this study. The

  20. Identification of new peptide amides as selective cathepsin L inhibitors: the first step towards selective irreversible inhibitors?

    PubMed

    Torkar, Ana; Lenarčič, Brigita; Lah, Tamara; Dive, Vincent; Devel, Laurent

    2013-05-15

    A small library of peptide amides was designed to profile the cathepsin L active site. Within the cathepsin family of cysteine proteases, the first round of selection was on cathepsin L and cathepsin B, and then selected hits were further evaluated for binding to cathepsin K and cathepsin S. Five highly selective sequences with submicromolar affinities towards cathepsin L were identified. An acyloxymethyl ketone warhead was then attached to these sequences. Although these original irreversible inhibitors inactivate cathepsin L, it appears that the nature of the warhead drastically impact the selectivity profile of the resulting covalent inhibitors.

  1. Irreversible thermodynamic analysis and application for molecular heat engines

    NASA Astrophysics Data System (ADS)

    Lucia, Umberto; Açıkkalp, Emin

    2017-09-01

    Is there a link between the macroscopic approach to irreversibility and microscopic behaviour of the systems? Consumption of free energy keeps the system away from a stable equilibrium. Entropy generation results from the redistribution of energy, momentum, mass and charge. This concept represents the essence of the thermodynamic approach to irreversibility. Irreversibility is the result of the interaction between systems and their environment. The aim of this paper is to determine lost works in a molecular engine and compare results with macro (classical) heat engines. Firstly, irreversible thermodynamics are reviewed for macro and molecular cycles. Secondly, irreversible thermodynamics approaches are applied for a quantum heat engine with -1/2 spin system. Finally, lost works are determined for considered system and results show that macro and molecular heat engines obey same limitations. Moreover, a quantum thermodynamic approach is suggested in order to explain the results previously obtained from an atomic viewpoint.

  2. Recent advances in the uses and applications of ribosome-inactivating proteins from plants.

    PubMed

    Girbés, T; Ferreras, J M; Iglesias, R; Citores, L; De Torre, C; Carbajales, M L; Jiménez, P; De Benito, F M; Muñoz, R

    1996-06-01

    Plant ribosome-inactivating proteins (RIPs) are inhibitors present in all parts of plants that irreversibly inactivate eukaryotic ribosomes, thus impairing protein synthesis. RIPs are enzymes with N-glycosidase activity on the large rRNA. Their powerful inhibitory activity has been made use of advantageously to construct conjugates with suitable carriers targeted to altered specific cells. RIPs may be used to inhibit replication of both animal and plant viruses. The introduction of genes coding for RIPs into the genome of plants leads to an increase in resistance towards fungal pathogens and viruses. RIPs are important tools for the treatment of cancer and AIDS and for the protection of crop production.

  3. Irreversible Electroporation in a Swine Lung Model

    SciTech Connect

    Dupuy, Damian E.; Aswad, Bassam; Ng, Thomas

    2011-04-15

    Purpose: This study was designed to evaluate the safety and tissue effects of IRE in a swine lung model. Methods: This study was approved by the institutional animal care committee. Nine anesthetized domestic swine underwent 15 percutaneous irreversible electroporation (IRE) lesion creations (6 with bipolar and 3 with 3-4 monopolar electrodes) under fluoroscopic guidance and with pancuronium neuromuscular blockade and EKG gating. IRE electrodes were placed into the central and middle third of the right mid and lower lobes in all animals. Postprocedure PA and lateral chest radiographs were obtained to evaluate for pneumothorax. Three animals were sacrificed at 2 weeks and six at 4 weeks. Animals underwent high-resolution CT scanning and PA and lateral radiographs 1 h before sacrifice. The treated lungs were removed en bloc, perfused with formalin, and sectioned. Gross pathologic and microscopic changes after standard hematoxylin and eosin staining were analyzed within the areas of IRE lesion creation. Results: No significant adverse events were identified. CT showed focal areas of spiculated high density ranging in greatest diameter from 1.1-2.2 cm. On gross inspection of the sectioned lung, focal areas of tan discoloration and increased density were palpated in the areas of IRE. Histological analysis revealed focal areas of diffuse alveolar damage with fibrosis and inflammatory infiltration that respected the boundaries of the interlobular septae. No pathological difference could be discerned between the 2- and 4-week time points. The bronchioles and blood vessels within the areas of IRE were intact and did not show signs of tissue injury. Conclusion: IRE creates focal areas of diffuse alveolar damage without creating damage to the bronchioles or blood vessels. Short-term safety in a swine model appears to be satisfactory.

  4. Irreversible Sorption of Contaminants During Ferrihydrite Transformation

    SciTech Connect

    Anderson, H.L.; Arthur, S.E.; Brady, P.V.; Cygan, R.T.; Nagy, K.L.; Westrich, H.R.

    1999-05-19

    A better understanding of the fraction of contaminants irreversibly sorbed by minerals is necessary to effectively quantify bioavailability. Ferrihydrite, a poorly crystalline iron oxide, is a natural sink for sorbed contaminants. Contaminants may be sorbed/occluded as ferrihydrite precipitates in natural waters or as it ages and transforms to more crystalline iron oxides such as goethite or hematite. Laboratory studies indicate that Cd, Co, Cr, Cu, Ni, Np, Pb, Sr, U, and Zn are irreversibly sorbed to some extent during the aging and transformation of synthetic ferrihydrite. Barium, Ra and Sr are known to sorb on ferrihydrite in the pH range of 6 to 10 and sorb more strongly at pH values above its zero point of charge (pH> 8). We will review recent literature on metal retardation, including our laboratory and modeling investigation of Ba (as an analogue for Ra) and Sr adsorption/resorption, during ferrihydrite transformation to more crystalline iron oxides. Four ferrihydrite suspensions were aged at pH 12 and 50 °C with or without Ba in 0.01 M KN03 for 68 h or in 0.17 M KN03 for 3424 h. Two ferrihydrite suspensions were aged with and without Sr at pH 8 in 0.1 M KN03 at 70°C. Barium or Sr sorption, or resorption, was measured by periodically centrifuging suspension subsamples, filtering, and analyzing the filtrate for Ba or Sr. Solid subsamples were extracted with 0.2 M ammonium oxalate (pH 3 in the dark) and with 6 M HCl to determine the Fe and Ba or Sr attributed to ferrihydrite (or adsorbed on the goethite/hematite stiace) and the total Fe and Ba or Sr content, respectively. Barium or Sr occluded in goethite/hematite was determined by the difference between the total Ba or Sr and the oxalate extractable Ba or Sr. The percent transformation of ferrihydrite to goethite/hematite was estimated from the ratio of oxalate and HC1 extractable Fe. All Ba was retained in the precipitates for at least 20 h. Resorption of Ba reached a maximum of 7 to 8% of the Ba2+ added

  5. Inactivation and reactivation of B. megatherium phage.

    PubMed

    NORTHROP, J H

    1955-11-20

    Preparation of Reversibly Inactivated (R.I.) Phage.- If B. megatherium phage (of any type, or in any stage of purification) is suspended in dilute salt solutions at pH 5-6, it is completely inactivated; i.e., it does not form plaques, or give rise to more phage when mixed with a sensitive organism (Northrop, 1954). The inactivation occurs when the phage is added to the dilute salt solution. If a suspension of the inactive phage in pH 7 peptone is titrated to pH 5 and allowed to stand, the activity gradually returns. The inactivation is therefore reversible. Properties of R.I. Phage.- The R.I. phage is adsorbed by sensitive cells at about the same rate as the active phage. It kills the cells, but no active phage is produced. The R.I. phage therefore has the properties of phage "ghosts" (Herriott, 1951) or of colicines (Gratia, 1925), or phage inactivated by ultraviolet light (Luria, 1947). The R.I. phage is sedimented in the centrifuge at the same rate as active phage. It is therefore about the same size as the active phage. The R.I. phage is most stable in pH 7, 5 per cent peptone, and may be kept in this solution for weeks at 0 degrees C. The rate of digestion of R.I. phage by trypsin, chymotrypsin, or desoxyribonuclease is about the same as that of active phage (Northrop, 1955 a). Effect of Various Substances on the Formation of R.I. Phage.- There is an equilibrium between R.I. phage and active phage. The R.I. form is the stable one in dilute salt solution, pH 5 to 6.5 and at low temperature (<20 degrees C.). At pH >6.5, in dilute salt solution, the R.I. phage changes to the active form. The cycle, active right harpoon over left harpoon inactive phage, may be repeated many times at 0 degrees C. by changing the pH of the solution back and forth between pH 7 and pH 6. Irreversible inactivation is caused by distilled water, some heavy metals, concentrated urea or quanidine solutions, and by l-arginine. Reversible inactivation is prevented by all salts tested (except

  6. Kinetics and thermodynamics of irreversible inhibition of matrix metalloproteinase 2 by a Co(III) Schiff base complex

    PubMed Central

    Harney, Allison S.; Sole, Laura B.

    2012-01-01

    Cobalt(III) Schiff base complexes have been used as potent inhibitors of protein function through the coordination to histidine residues essential for activity. The kinetics and thermodynamics of the binding mechanism of Co(acacen)(NH3)2Cl [Co(acacen); where H2acacen is bis(acetylacetone)ethylenediimine] enzyme inhibition has been examined through the inactivation of matrix metalloproteinase 2 (MMP-2) protease activity. Co(acacen) is an irreversible inhibitor that exhibits time- and concentration-dependent inactivation of MMP-2. Co(acacen) inhibition of MMP-2 is temperature-dependent, with the inactivation increasing with temperature. Examination of the formation of the transition state for the MMP-2/Co(acacen) complex was determined to have a positive entropy component indicative of greater disorder in the MMP-2/Co(acacen) complex than in the reactants. With further insight into the mechanism of Co(acacen) complexes, Co(III) Schiff base complex protein inactivators can be designed to include features regulating activity and protein specificity. This approach is widely applicable to protein targets that have been identified to have clinical significance, including matrix metalloproteinases. The mechanistic information elucidated here further emphasizes the versatility and utility of Co(III) Schiff base complexes as customizable protein inhibitors. PMID:22729838

  7. Inactivation of biofilm bacteria.

    PubMed Central

    LeChevallier, M W; Cawthon, C D; Lee, R G

    1988-01-01

    The current project was developed to examine inactivation of biofilm bacteria and to characterize the interaction of biocides with pipe surfaces. Unattached bacteria were quite susceptible to the variety of disinfectants tested. Viable bacterial counts were reduced 99% by exposure to 0.08 mg of hypochlorous acid (pH 7.0) per liter (1 to 2 degrees C) for 1 min. For monochloramine, 94 mg/liter was required to kill 99% of the bacteria within 1 min. These results were consistent with those found by other investigators. Biofilm bacteria grown on the surfaces of granular activated carbon particles, metal coupons, or glass microscope slides were 150 to more than 3,000 times more resistant to hypochlorous acid (free chlorine, pH 7.0) than were unattached cells. In contrast, resistance of biofilm bacteria to monochloramine disinfection ranged from 2- to 100-fold more than that of unattached cells. The results suggested that, relative to inactivation of unattached bacteria, monochloramine was better able to penetrate and kill biofilm bacteria than free chlorine. For free chlorine, the data indicated that transport of the disinfectant into the biofilm was a major rate-limiting factor. Because of this phenomenon, increasing the level of free chlorine did not increase disinfection efficiency. Experiments where equal weights of disinfectants were used suggested that the greater penetrating power of monochloramine compensated for its limited disinfection activity. These studies showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria. The research provides important insights into strategies for control of biofilm bacteria. Images PMID:2849380

  8. Suicide inactivation of catechol 2,3-dioxygenase from Pseudomonas putida mt-2 by 3-halocatechols

    SciTech Connect

    Bartels, I.; Knackmuss, H.J.; Reineke, W.

    1984-03-01

    The inactivation of catechol 2,3-dioxygenase from Pseudomonas putida mt-2 by 3-chloro- and 3-fluorocatechol and the iron-chelating agent Tiron (catechol-3,5-disulfonate) was studied. Whereas inactivation by Tiron is an oxygen-independent and mostly reversible process, inactivation by the 3-halocatechols was only observed in the presence of oxygen and was largely irreversible. The rate constants for inactivation (K/sub 2/) were 1.62 x 10/sup -3/ sec/sup -1/ for 3-chlorocatechol and 2.38 x 10/sup -3/ sec/sup -1/ for 3-fluorocatechol. The inhibitor constants (K/sub i/) were 23 ..mu..M for 3-chlorocatechol and 17 ..mu..M for 3-fluorocatechol. The kinetic data for 3-fluorocatechol could only be obtained in the presence of 2-mercaptoethanol. Besides inactivated enzyme, some 2-hydroxyhexa-2,4-dienoic acid as the actual suicide product of meta-cleavage. A side product of 3-fluorocatechol cleavage is a yellow compound with the spectral characteristics of a 2-hydroxy-6-oxohexa-2,4-dienoci acid indicating 1,6-cleavage. Rates of inactivation by 3-fluorocatechol were reduced in the presence of superoxide dismutase, catalase, formate, and mannitol, which implies that superoxide anion, hydrogen peroxide, and hydroxyl radical exhibit additional inactivation. 64 references.

  9. Hierarchical Variational Principles of Irreversible Processes in Thermal Disturbance

    NASA Astrophysics Data System (ADS)

    Nakano, H.

    1997-09-01

    Quantum variational principles of irreversible processes in the linear response theory which have been developed by the present author and his coworker taking the electric conduction as an example are generalized to the transport phenomena in thermal disturbance, where the fluctuation-dissipation law is manifested. By contracting the information, the principle presented at the dynamical stage which concerns no irreversibility is converted into those at the more coarse grained stages, which concerns irreversibility. The conversion takes place from the dynamical to kinetic stage and next from the kinetic to hydrothermodynamical stage.

  10. Irreversibility transition of colloidal polycrystals under cyclic deformation

    PubMed Central

    Jana, Pritam Kumar; Alava, Mikko J.; Zapperi, Stefano

    2017-01-01

    Cyclically loaded disordered particle systems, such as granular packings and amorphous media, display a non-equilibrium phase transition towards irreversibility. Here, we investigate numerically the cyclic deformation of a colloidal polycrystal with impurities and reveal a transition to irreversible behavior driven by the displacement of dislocations. At the phase transition we observe enhanced particle diffusion, system size effects and broadly distributed strain bursts. In addition to provide an analogy between the deformation of amorphous and polycrystalline materials, our results allow to reinterpret Zener pinning of grain boundaries as a way to prevent the onset of irreversible crystal ordering. PMID:28358018

  11. Irreversible formation of intermediate BSA oligomers requires and induces conformational changes.

    PubMed

    Vaiana, S M; Emanuele, A; Palma-Vittorelli, M B; Palma, M U

    2004-06-01

    Understanding the relation between protein conformational changes and aggregation, and the physical mechanisms leading to such processes, is of primary importance, due to its direct relation to a vast class of severe pathologies. Growing evidence also suggests that oligomeric intermediates, which may occur early in the aggregation pathway, can be themselves pathogenic. The possible cytotoxicity of oligomers of non-disease-associated proteins adds generality to such suggestion and to the interest of studies of oligomer formation. Here we study the early stages of aggregation of Bovine Serum Albumin (BSA), a non pathogenic protein which has proved to be a useful model system. Dynamic light scattering and circular dichroism measurements in kinetic experiments following step-wise temperature rises, show that the "intermediate" form, which initiates large-scale aggregation, is the result of structural and conformational changes and concurrent formation of oligomers, of average size in the range of 100-200 A. Two distinct thresholds are observed. Beyond the first one oligomerization starts and causes partial irreversibility of conformational changes. Beyond the second threshold, additional secondary structural changes occurring in proteins being recruited progress on the same time scale of oligomerization. The concurrent behavior causes a mutual stabilization of oligomerization, and of structural and conformational changes, evidenced by a progressive increase of their irreversibility. This process interaction appears to be pivotal in producing irreversible oligomers. Copyright 2004 Wiley-Liss, Inc.

  12. Fourteen. beta. -(bromoacetamido)morphine irreversibly labels. mu. opioid receptors in rat brain membranes

    SciTech Connect

    Bidlack, J.M.; Frey, D.K.; Seyed-Mozaffari, A.; Archer, S. )

    1989-05-16

    The binding properties of 14{beta}-(bromoacetamido)morphine (BAM) and the ability of BAM to irreversibly inhibit opioid binding to rat brain membranes were examined to characterize the affinity and selectivity of BAM as an irreversible affinity ligand for opioid receptors. BAM had the same receptor selectivity as morphine, with a 3-5-fold decrease in affinity for the different types of opioid receptors. When brain membranes were incubated with BAM, followed by extensive washing, opioid binding was restored to control levels. However, when membranes were incubated with dithiothreitol (DTT), followed by BAM, and subsequently washed, 90% of the 0.25 nM ({sup 3}H)(D-Ala{sup 2},(Me)Phe{sup 4},Gly(ol){sup 5})enkephalin (DAGO) binding was irreversibly inhibited as a result of the specific alkylation of a sulfhydryl group at the {mu} binding site. This inhibition was dependent on the concentrations of both DTT and BAM. The {mu} receptor specificity of BAM alkylation was demonstrated by the ability of BAM alkylated membranes to still bind the {delta}-selective peptide ({sup 3}H)(D-penicillamine{sup 2},D-penicillamine{sup 5})enkephalin (DPDPE) and (-)-({sup 3}H)bremazocine in the presence of {mu} and {delta} blockers, selective for {kappa} binding sites. Morphine and naloxone partially protected the binding site from alkylation with BAM, while ligands that did not bind to the {mu}s site did not afford protection. These studies have demonstrated that when a disulfide bond at or near {mu} opioid binding sites was reduced, BAM could then alkylate this site, resulting in the specific irreversible labeling of {mu} opioid receptors.

  13. Experiments with an intrinsically irreversible acoustic heat engine

    SciTech Connect

    Wheatley, J.; Hofler, T.; Swift, G.W.; Migliori, A.

    1983-02-14

    The general qualities of a type of thermodynamic engine that depends intrinsically for its operation on irreversible processes are set forth and demonstrated experimentally in the context of a thermoacoustic heat-pumping engine.

  14. Ecological optimization of an irreversible harmonic oscillators Carnot heat engine

    NASA Astrophysics Data System (ADS)

    Liu, Xiaowei; Chen, Lingen; Wu, Feng; Sun, Fengrui

    2009-12-01

    A model of an irreversible quantum Carnot heat engine with heat resistance, internal irreversibility and heat leakage and many non-interacting harmonic oscillators is established in this paper. Based on the quantum master equation and semi-group approach, equations of some important performance parameters, such as power output, efficiency, exergy loss rate and ecological function for the irreversible quantum Carnot heat engine are derived. The optimal ecological performance of the heat engine in the classical limit is analyzed with numerical examples. Effects of internal irreversibility and heat leakage on the ecological performance are discussed. A performance comparison of the quantum heat engine under maximum ecological function and maximum power conditions is also performed.

  15. Irreversible adsorption/desorption of PAHs in sediment/water

    SciTech Connect

    Fu, G.; Kan, A.T.; Tomson, M.B.

    1996-10-01

    Successive adsorption isotherm of phenanthrene on soil corresponds to a constant partition of phenanthrene between the bulk solution and solid phase. This shows that the hydrophobic reaction is a dominant mechanism in adsorption process. However, desorption of PAHs appears irreversibility. Cyclic and multiple adsorption and desorption experiments indicated that there is an irreversibly adsorbed intrinsic capacity in the interaction of PAHs (naphthalene and phenanthrene) and soil in aqueous solution. This irreversible fraction for PAHs (naphthalene and phenanthrene) is about 1000-5000 {mu}g/g normalized on the basis of soil organic carbon. The desorption of PAHs from soil appears biphasic when the total adsorbed capacity is greater than the intrinsic irreversibly adsorbed value. In phase, the partitioning coefficient of desorption of PAHs is similar to that of adsorption. However, the other mechanism may be responsible to control the release of PAHs in phase 2.

  16. Gibbs Paradox Revisited from the Fluctuation Theorem with Absolute Irreversibility

    NASA Astrophysics Data System (ADS)

    Murashita, Yûto; Ueda, Masahito

    2017-02-01

    The inclusion of the factor ln (1 /N !) in the thermodynamic entropy proposed by Gibbs is shown to be equivalent to the validity of the fluctuation theorem with absolute irreversibility for gas mixing.

  17. Irreversibility and dissipation in finite-state automata

    NASA Astrophysics Data System (ADS)

    Ganesh, Natesh; Anderson, Neal G.

    2013-12-01

    Irreversibility and dissipation in finite-state automata (FSA) are considered from a physical-information-theoretic perspective. A quantitative measure for the computational irreversibility of finite automata is introduced, and a fundamental lower bound on the average energy dissipated per state transition is obtained and expressed in terms of FSA irreversibility. The irreversibility measure and energy bound are germane to any realization of a deterministic automaton that faithfully registers abstract FSA states in distinguishable states of a physical system coupled to a thermal environment, and that evolves via a sequence of interactions with an external system holding a physical instantiation of a random input string. The central result, which is shown to follow from quantum dynamics and entropic inequalities alone, can be regarded as a generalization of Landauer's Principle applicable to FSAs and tailorable to specified automata. Application to a simple FSA is illustrated.

  18. Microscopic reversibility and macroscopic irreversibility: A lattice gas model

    NASA Astrophysics Data System (ADS)

    Pérez-Cárdenas, Fernando C.; Resca, Lorenzo; Pegg, Ian L.

    2016-09-01

    We present coarse-grained descriptions and computations of the time evolution of a lattice gas system of indistinguishable particles, whose microscopic laws of motion are exactly reversible, in order to investigate how or what kind of macroscopically irreversible behavior may eventually arise. With increasing coarse-graining and number of particles, relative fluctuations of entropy rapidly decrease and apparently irreversible behavior unfolds. Although that behavior becomes typical in those limits and within a certain range, it is never absolutely irreversible for any individual system with specific initial conditions. Irreversible behavior may arise in various ways. We illustrate one possibility by replacing detailed integer occupation numbers at lattice sites with particle probability densities that evolve diffusively.

  19. Inactivation of pectin methylesterase by immobilized trypsins from cunner fish and bovine pancreas.

    PubMed

    Li, Dan; Matos, Madyu; Simpson, Benjamin K

    2013-01-01

    Immobilized cunner fish trypsin was used to inactivate pectin methylesterase (PME). The effects of different reaction conditions (e.g., incubation time, PME concentration, and temperature) on PME inactivation and kinetics of inactivation were investigated. Temperature, incubation time, and PME concentration significantly affected the extent of PME inactivation. Generally, higher temperature, longer incubation time, and low PME concentration caused more PME inactivation. The immobilized fish trypsin had higher capacity to inactivate PME than immobilized bovine trypsin. The inactivation efficiency of the immobilized fish trypsin was about 20% higher than that of its bovine counterpart. However, PME inactivated by both trypsins regained partial activity during storage at 4°C, with immobilized fish trypsin-treated PME regaining more of its original activity than the immobilized bovine trypsin-treated PME. Heat-denatured PME was hydrolyzed more extensively by immobilized fish trypsin than by its bovine counterpart. The rate constants increased, whereas the D-values decreased with temperature for both immobilized fish and bovine trypsins. The inactivation rate constants of immobilized fish trypsin at all the temperatures investigated (i.e., 15-35°C) were higher than those of immobilized bovine trypsin. Furthermore, the activation energy (Ea ) of PME inactivation by immobilized fish trypsin was lower than that of immobilized bovine trypsin.

  20. Ultrarapid delayed rectifier current inactivation in human atrial myocytes: properties and consequences.

    PubMed

    Feng, J; Xu, D; Wang, Z; Nattel, S

    1998-11-01

    The ultrarapid delayed rectifier current (IK,ur) plays a significant role in human atrial repolarization and is generally believed to show little rate dependence because of slow and partial inactivation. This study was designed to evaluate in detail the properties and consequences of IK,ur inactivation in isolated human atrial myocytes. IK,ur inactivated with a biexponential time course and a half-inactivation voltage of -7.5 +/- 0.6 mV (mean +/- SE), with complete inactivation during 50-s pulses to voltages positive to +10 mV (37 degreesC). Recovery from inactivation proceeded slowly, with time constants of 0.42 +/- 0.06 and 7.9 +/- 0.9 s at -80 mV (37 degreesC). Substantial frequency dependence was observed at 37 degreesC over a clinically relevant range of frequencies. Inactivation was faster and occurred at more positive voltages at 37 degreesC compared with room temperature. The voltage and time dependencies of Kv1.5 inactivation were studied in Xenopus oocytes to avoid overlapping currents and strongly resembled those of IK,ur in native myocytes. We conclude that, while IK,ur inactivation is slow, it is extensive, and slow recovery from inactivation confers important frequency dependence with significant consequences for understanding the role of IK,ur in human atrial repolarization.

  1. Extended irreversible thermodynamics and the quality of temperature and pressure

    NASA Astrophysics Data System (ADS)

    Bhalekar, Anil A.

    1999-08-01

    It is reiterated that without a Gibbs-Duhem equation no thermodynamic description ofirreversible and reversible processes exists. It is shown with the help of Gibbs-Duhem equation of extended irreversible thermodynamics that the physical contents of intensive quantities, the temperature and the pressure, do not change in going from reversible to irreversible processes. This confirms well with the earlier demonstrations of Eu and Garcia-Colin.

  2. Optimization of Irreversible Cogeneration Systems under Alternative Performance Criteria

    NASA Astrophysics Data System (ADS)

    Atmaca, M.; Gumus, M.; Inan, A. T.; Yilmaz, T.

    2009-10-01

    In this study, an exergy optimization has been performed for a cogeneration plant consisting of an irreversible Carnot heat engine. In the analysis, different objective functions have been defined based on alternative performance criteria and the optimum values of the design parameters of a cogeneration cycle were determined for different criteria. In this context, the effects of irreversibilities on the exergetic performance are investigated, and the results are discussed.

  3. Neuroprotective effects of allopregnenolone on hippocampal irreversible neurotoxicity in vitro.

    PubMed

    Frank, C; Sagratella, S

    2000-10-01

    1. The effects of allopregnenolone, a neurosteroid, endowed with GABAmimetic properties, were tested towards two models of irreversible hippocampal neurotoxicity: i) the irreversible depression produced by hypoxia on the CA1 evoked field potentials in rat hippocampal slices, and ii) glutamate-induced irreversible changes in intracellular calcium concentration in primary hippocampal cell coltures. 2. In control conditions during the reoxygenation period after the application of 15 min of hypoxia, the CA1 evoked field potentials were irreversibly suppressed in almost the 50% of the experiments. In the remaining experiments there were a significative (p<0.01) irreversible reduction of the magnitude of the CA1 population spike with respect with the pre-hypoxia values. Allopregnenolone (50-75 microM) perfused 30 min before, during and 30 min after hypoxia produced a significative (p<0.05) decrease both in the hypoxia-induced irreversible suppression of the CA1 PS and both in the irreversible decrease of the CA1 PS at the end of reoxygenation. 3. The exposition of the primary hippocampal cultured cells to glutamate 0.5 mM for 10 min was followed by a sustained elevation of [Ca2+]i, that persisted at 70-80% of maximal increase for the rest of the experiment (60 min). When a pretreatment with 10-50 microM allopregnanolone preceded Glu 0.5 mM application, [Ca2+]i increased to a maximal value during the glutamate application, after which a fast decrease to 50% was observed, followed by a slow recovery within about 30 min. 4. The results showed that the neurosteroid allopregnenolone, endowed with GABAmimetic properties, ameliorated the functional correlates of irreversible hippocampal neurotoxicity.

  4. Irreversible pulpitis and achieving profound anesthesia: Complexities and managements

    PubMed Central

    Modaresi, Jalil; Davoudi, Amin; Badrian, Hamid; Sabzian, Roya

    2016-01-01

    Dental pain management is one of the most critical aspects of modern dentistry. Irreversible pulpitis and further root canal therapy might cause an untolerated pain to the patients. The improvements in anesthetic agents and techniques were one of the advantages of studying nerve biology and stimulation. This article tried to overview of the nerve activities in inflammatory environments or induced pain. Furthermore, the proper advises, and supplementary techniques were reviewed for better pain management of irreversible pulpitis. PMID:26957681

  5. Recovery of prostacyclin synthesis in vascular smooth muscle cells following self-inactivation and requirement for growth factors

    SciTech Connect

    Bailey, J.M.; Hla, T.T.; Pash, J.M.

    1986-05-01

    The cyclooxygenase enzyme system is a prime example of a metabolic pathway that is regulated by self inactivation. This is believed to occur in part via the irreversible reaction of the endoperoxide intermediate species with the cyclooxygenase enzyme. This inactivation and recovery of activity is similar to the inactivation observed with aspirin which irreversibly acetylates the enzyme. Self inactivation was studied in cultured rat and bovine aorta smooth muscle cells. The production of the prostanoid PGI2 was demonstrated by incubation of a monolayer of cells with 12 ..mu..M C-14 labeled arachidonic acid. Products were analyzed by thin layer chromatography and identified by their comigration with authentic standards and confirmed by gas chromatography/mass spectrometry. Preincubation of the cells for 10 minutes with arachidonic acid at concentrations as low as 1 ..mu..g/mL inactivated the cells to a second challenge with radiolabeled arachidonic acid. Recovery from self inactivation took place over a three hour time period and was similar to the recovery observed with aspirin pretreatment. Recovery was inhibited by addition of 10 ..mu..g/mL cycloheximide to the medium indicating that it involves synthesis of cyclooxygenase protein. Epidermal growth factor was identified as a serum factor responsible for the rapid recovery of cyclooxygenase activity in rat and bovine aorta smooth muscle cells.

  6. The incidence of mechanical allodynia in patients with irreversible pulpitis.

    PubMed

    Owatz, Christopher B; Khan, Asma A; Schindler, William G; Schwartz, Scott A; Keiser, Karl; Hargreaves, Kenneth M

    2007-05-01

    The mechanisms of odontogenic pain are complex and incompletely understood. Cases of irreversible pulpitis are thought to represent a localized inflammatory response to bacterial challenge in dental pulp tissue. The presenting symptoms are classically defined by exaggerated painful episodes to thermal stimuli that may linger after cessation of the stimulus. However, the associated incidence of mechanical allodynia, defined as reduced mechanical pain threshold to masticatory forces, has not been characterized. This study evaluated pain intensity ratings and the presence of mechanical allodynia reported by 993 consecutive dental patients presenting for tooth extraction in a community health center. After clinical and radiographic examinations, the pulpal/periradicular diagnostic categories were normal pulp/normal periradicular (n=792 patients), irreversible pulpitis/normal periradicular (n=86), or irreversible pulpitis/acute periradicular periodontitis (n=115). The rank order for the mean values of pain intensity ratings was irreversible pulpitis/acute periradicular periodontitis > irreversible pulpitis/normal periradicular > normal/normal (p<0.05 for all comparisons). The incidence of mechanical allodynia in patients presenting with irreversible pulpitis was 57.2%, indicating that periradicular mechanical allodynia contributes to early stages of odontogenic pain because of inflammation of vital pulpal tissue.

  7. Inactivation of Microorganisms

    NASA Astrophysics Data System (ADS)

    Alzamora, Stella Maris; Guerrero, Sandra N.; Schenk, Marcela; Raffellini, Silvia; López-Malo, Aurelio

    Minimal processing techniques for food preservation allow better retention of product flavor, texture, color, and nutrient content than comparable conventional treatments. A wide range of novel alternative physical factors have been intensely investigated in the last two decades. These physical factors can cause inactivation of microorganisms at ambient or sublethal temperatures (e.g., high hydrostatic pressure, pulsed electric fields, ultrasound, pulsed light, and ultraviolet light). These technologies have been reported to reduce microorganism population in foods while avoiding the deleterious effects of severe heating on quality. Among technologies, high-energy ultrasound (i.e., intensities higher than 1 W/cm2, frequencies between 18 and 100 kHz) has attracted considerable interest for food preservation applications (Mason et al., 1996; Povey and Mason, 1998).

  8. Long-term hydroxytamoxifen treatment of an MCF-7-derived breast cancer cell line irreversibly inhibits the expression of estrogenic genes through chromatin remodeling.

    PubMed

    Badia, E; Duchesne, M J; Semlali, A; Fuentes, M; Giamarchi, C; Richard-Foy, H; Nicolas, J C; Pons, M

    2000-08-01

    Antiestrogen resistance is frequently observed in patients after longterm treatment with tamoxifen, a nonsteroidal antiestrogen widely used for endocrine therapy of breast cancer. In vitro studies in resistant cells showed that the expression of natural estrogen-responsive genes is frequently altered. Using MVLN cells, an MCF-7-derived cell model, we previously demonstrated that 4-hydroxytamoxifen (OHT) treatment irreversibly inactivated an estrogen-regulated chimeric luciferase response by a direct effect of the drug and not through a cell selection process (E. Badia et al., Cancer Res., 54: 5860-5866, 1994). In the present study, we present tamoxifen-resistant but still estrogen-dependent clones isolated after long-term treatment of MVLN cells with OHT and show that progesterone receptor (PR) expression was irreversibly decreased in some of these clones, whereas the PRA:PRB ratio of residual PR remained unchanged. The irreversible inactivation of both chimeric luciferase gene and PR gene expression was associated with the disappearance of DNase 1-hypersensitive sites. In the case of the chimeric gene, at least one of these sites was close to the estrogen responsive element. Genomic sequencing analysis of a clone with very low PR content did not reveal any methylation on CpG dinucleotides or any mutation in the PR gene promoter region. In all of the resistant clones tested and independently of their PR content, estrogen receptor expression was only lowered by half and remained functional, whereas pS2 expression was not modified. We also observed that the residual luciferase activity level (1-2%) of the MVLN clones, the luciferase expression of which had been irreversibly inactivated, was raised 4-fold by trichostatin A treatment. We conclude that long-term OHT treatment may modify the chromatin structure and thus could contribute to differentially silencing natural target genes.

  9. [Mechanisms for protecting nitrogenase from inactivation by oxygen].

    PubMed

    Soto-Urzúa, L; Baca, B E

    2001-01-01

    The biological fixation of dinitrogen is the most important way to access of N to organisms, this process requires a fairly high proportion of the ATP; which is generated in the course of respiratory electron transport reactions with O2 as electron acceptor. The Nitrogenase enzyme complex (the nitrogen. fixing enzyme) is sensitive to O2, that irreversible inactivates the enzyme. Diazotrophs must employ mechanisms which, on the other hand, permit the supply of O2 required for energy regeneration and protect Nase from the deleterious effect of O2. They have developed several strategies for limiting O2 access to Nase: 1).--It could avoid O2 and live in environments which are permanently anaerobic, 2).--Alternatively, it could generate a physical barrier around its Nase and in this way prevent O2 from diffusing to the enzyme, 3).--The microorganism could, by its metabolism, reduce the concentration of O2 within the vicinity of Nasa, 4).--They could modify its Nasa in such manner as to render it resistant to inactivation by O2 (conformational protection). 5).--Finally, the microorganism could simply balance Nasa inactivation with the synthesis of new enzyme. In this article we examine the antipathy between Nasa and O2, particularly with strict aerobic and photosynthetic microorganisms.

  10. Comparative thermal inactivation analysis of Aspergillus oryzae and Thiellavia terrestris cutinase: Role of glycosylation.

    PubMed

    Shirke, Abhijit N; Su, An; Jones, J Andrew; Butterfoss, Glenn L; Koffas, Mattheos A G; Kim, Jin Ryoun; Gross, Richard A

    2017-01-01

    Cutinase thermostability is important so that the enzymes can function above the glass transition of what are often rigid polymer substrates. A detailed thermal inactivation analysis was performed for two well-characterized cutinases, Aspergillus oryzae Cutinase (AoC) and Thiellavia terrestris Cutinase (TtC). Both AoC and TtC are prone to thermal aggregation upon unfolding at high temperature, which was found to be a major reason for irreversible loss of enzyme activity. Our study demonstrates that glycosylation stabilizes TtC expressed in Pichia pastoris by inhibiting its thermal aggregation. Based on the comparative thermal inactivation analyses of non-glycosylated AoC, glycosylated (TtC-G), and non-glycosylated TtC (TtC-NG), a unified model for thermal inactivation is proposed that accounts for thermal aggregation and may be applicable to other cutinase homologues. Inspired by glycosylated TtC, we successfully employed glycosylation site engineering to inhibit AoC thermal aggregation. Indeed, the inhibition of thermal aggregation by AoC glycosylation was greater than that achieved by conventional use of trehalose under a typical condition. Collectively, this study demonstrates the excellent potential of implementing glycosylation site engineering for thermal aggregation inhibition, which is one of the most common reasons for the irreversible thermal inactivation of cutinases and many proteins. Biotechnol. Bioeng. 2017;114: 63-73. © 2016 Wiley Periodicals, Inc.

  11. Thermal stability of Artemia HGPRT: effect of substrates on inactivation kinetics.

    PubMed

    Montero, C; Llorente, P; Argomaniz, L; Menendez, M

    1996-06-01

    Hypoxanthine-guanine phosphoribosyltransferase (HGPRT, E.C.2.4.2.8) from Artemia cysts exhibits maximum activity at 70 degrees C. Its thermal stability has been examined following enzymatic activity as a function of temperature. Cold-induced renaturation experiments of samples heated at increasing temperatures showed that reversibility of thermal inactivation depends on the incubation time and final temperature. Prolonged incubation of the thermoinactivated enzyme at 0 degree C did not afford any further increase of the catalytic activity at 37 degrees C. The complex substrate PRPP:Mg protects HGPRT from thermal inactivation. However, incubations with hypoxanthine rendered a less thermostable enzyme at any temperature tested. The irreversible inactivation of HGPRT proceeds in two exponential steps. The analysis of the apparent rate constants for the fast and the slow phases, lambda 1 and lambda 2 as per the Lumry and Eyring model suggests the existence of more than three states in the thermal denaturation pathway of the free enzyme. In the presence of PRPP:Mg the irreversible process follows a single exponential and proceeds very slowly below 70 degrees C. PRPP:Mg also protects the enzyme from inactivation by NEM and pCMB, suggesting that -SH groups may be in the vicinity of the active site.

  12. Attribution of irreversible loss to anthropogenic climate change

    NASA Astrophysics Data System (ADS)

    Huggel, Christian; Bresch, David; Hansen, Gerrit; James, Rachel; Mechler, Reinhard; Stone, Dáithí; Wallimann-Helmer, Ivo

    2016-04-01

    The Paris Agreement (2015) under the UNFCCC has anchored loss and damage in a separate article which specifies that understanding and support should be enhanced in areas addressing loss and damage such as early warning, preparedness, insurance and resilience. Irreversible loss is a special category under loss and damage but there is still missing clarity over what irreversible loss actually includes. Many negative impacts of climate change may be handled or mitigated by existing risk management, reduction and absorption approaches. Irreversible loss, however, is thought to be insufficiently addressed by risk management. Therefore, countries potentially or actually affected by irreversible loss are calling for other measures such as compensation, which however is highly contested in international climate policy. In Paris (2015) a decision was adopted that loss and damage as defined in the respective article of the agreement does not involve compensation and liability. Nevertheless, it is likely that some sort of mechanism will eventually need to come into play for irreversible loss due to anthropogenic climate change, which might involve compensation, other forms of non-monetary reparation, or transformation. Furthermore, climate litigation has increasingly been attempted to address negative effects of climate change. In this context, attribution is important to understand the drivers of change, what counts as irreversible loss due to climate change, and, possibly, who or what is responsible. Here we approach this issue by applying a detection and attribution perspective on irreversible loss. We first analyze detected climate change impacts as assessed in the IPCC Fifth Assessment Report. We distinguish between irreversible loss in physical, biological and human systems, and accordingly identify the following candidates of irreversible loss in these systems: loss of glaciers and ice sheets, loss of subsurface ice (permafrost) and related loss of lake systems; loss

  13. [Nourseothricin (streptothricin) inactivated by plasmid pIE 636-encoded acetyltransferase: detection of N-acetyl-beta-lysine in the inactivated product].

    PubMed

    Seltmann, G

    1985-12-01

    Nourseothricin (streptothricin) can be inactivated by an acetyl transferase synthesized by E. coli strains containing plasmid pIE 636. Nourseothricin inactivated in the presence of 14C-acetyl-coenzyme A was purified and submitted to partial acidic hydrolysis. By electrophoresis of the hydrolysate a 14C-containing substance moving only slowly towards the cathode could be isolated. This substance after complete hydrolysis yields only unlabelled beta-lysine.

  14. Complement-inactivating Proteinase(s) from Clostridium histolyticum1

    PubMed Central

    Goldlust, Marvin B.; Luzzati, Alma; Levine, Lawrence

    1968-01-01

    A proteinase fraction inhibiting the hemolytic activity of guinea pig complement was obtained from supernatant fluids of Clostridium histolyticum cultures and purified 150- to 350-fold by ammonium sulfate precipitation, Sephadex G-75 gel filtration, and diethylaminoethyl cellulose chromatography. An assay was developed based on the inactivation of hemolytic complement. Partially purified anticomplementary preparations were active against casein and were capable of “solubilizing” Escherichia coli endotoxin. Two components were found by differential heat inactivation, with complement and casein as substrates, but only one of these components was active against endotoxin. The more heat-stable activity, showing 50% inactivation at about 47 C, was characterized as to pH and ionic strength optima and sensitivity to reagents such as cysteine, β-mercaptoethanol, ethylenediaminetetraacetate, and heavy metals. PMID:5724966

  15. Irreversible stimulation of adenylate cyclase activity of fat cell membranes of phosphoramidate and phosphonate analogs of GTP.

    PubMed

    Cuatrecasas, P; Bennett, V; Jacobs, S

    1975-01-01

    The ability of 5'-guanylylimidodiphosphate (Gpp(NH)p) to stimulate irreversibly the adenylate cyclease activity of fat cell membranes has been studied by preincubating the membranes with this or related analogs followed by assaying after thoroughly washing the membranes. Activation can occur in a simple Tris-HCl buffer, in the absence of added divalent cations and in the presence of EDTA. Dithiothreitol enhances the apparent degree of activation, perhaps by stabilization. The importance of utilizing optimal conditions for stabilizing enzyme activity, and of measuring the simultaneous changes in the control enzyme, is illustrated. The organomercurial, p-aminophenylmercuric acetate, inhibits profoundly the activity of the native as well as the Gpp(NH)p-stimulated adenylate cyclase, but in both cases subsequent exposure to dithiothreitol restores fully the original enzyme activity. However, the mercurial-inactivated enzyme does not react with Gpp(NP)p, as evidenced by the subsequent restoration of only the control enzyme activity upon exposure to dithiothreitol. Thus, reaction with Gpp(NH)p requires intact sulfhydryl groups, but the activated state is not irreversibly destroyed by the inactivation caused by sulfhydryl blockade. GTP and, less effectively, GDP and ATP inhibit activation by Gpp(NH)p, but interpretations are complicated by the facts that this inhibition is overcome with time and that GTP and ATP can protect potently from spontaneous inactivation. These two nucleotides can be used in the Gpp(NH)p preincubation to stabilize the enzyme. The Gpp(NH)p-activated enzyme cannot be reversed spontaneously during prolonged incubation at 30 degrees C in the absence or presence of GTP, ATP, MgCl2, glycine, dithiothreitol, NaF or EDTA. The strong nucleophile, neutral hydroxylamine, decreases the Gpp(NH)p-activated enzyme activity and no subsequent activation is detected upon re-exposure to the nucleotide.

  16. INACTIVATION OF SEXUAL AGGLUTINATION IN HANSENULA WINGEI AND SACCHAROMYCES KLUYVERI BY DISULFIDE-CLEAVING AGENTS.

    PubMed

    TAYLOR, N W

    1964-10-01

    Taylor, Neil W. (Northern Regional Research Laboratory, Peoria, Ill.). Inactivation of sexual agglutination in Hansenula wingei and Saccharomyces kluyveri by disulfide-cleaving agents. J. Bacteriol. 88:929-936. 1964.-Mating types of both Hansenula wingei and Saccharomyces kluyveri can be activated to produce uniformly strong sexual agglutination by treatments with various solvents, such as 8 m LiBr. The strongly agglutinative mating-type preparations were irreversibly inactivated for sexual agglutination by various chemical treatments. Type 5 of H. wingei was inactivated by disulfide-cleaving reagents, but type 21 of H. wingei was not. Type 3 of S. kluyveri was more sensitive than type 26 of S. kluyveri to inactivation by disulfide-cleaving reagents. Comparison of sensitivities to these and other treatments, plus a moderately strong cross-agglutination between type 3 and type 21, indicated that the sexually agglutinative elements on type 3 are similar to type 5, and those of type 21 are similar to those of type 26. Inactivation-rate experiments showed a loss of agglutinative ability according to a sigmoid decrement with time for both types 5 and 21. The apparent extent of inactivation depended markedly on agglutination test conditions. Results of these experiments were interpreted to indicate tentatively, first, that the agglutinative elements of both types of a species are proteins and, second, that several agglutinating linkages are formed between any two cells in sexual agglutination.

  17. Cyclooxygenase inactivation kinetics during reaction of prostaglandin H synthase-1 with peroxide.

    PubMed

    Wu, Gang; Kulmacz, Richard J; Tsai, Ah-Lim

    2003-11-25

    The peroxidase and cyclooxygenase activities of prostaglandin H synthase-1 (PGHS-1) both become irreversibly inactivated during reaction with peroxide. Sequential stopped-flow absorbance measurements with a chromogenic peroxidase cosubstrate previously were used to evaluate the kinetics of peroxidase inactivation during reaction of PGHS-1 with peroxide [Wu, G., et al. (1999) J. Biol. Chem. 274, 9231-7]. This approach has now been adapted to use a chromogenic cyclooxygenase substrate to analyze the detailed kinetics of cyclooxygenase inactivation during reaction of PGHS-1 with several hydroperoxides. In the absence of added reducing cosubstrates, which maximizes the levels of oxidized enzyme intermediates expected to lead to inactivation, cyclooxygenase activity was lost as fast as, or somewhat faster than, peroxidase activity. Cyclooxygenase inactivation kinetics appeared to be sensitive to the structure of the peroxide used. The addition of reducing cosubstrate during reaction of PGHS-1 with peroxide protected the peroxidase activity to a much greater degree than the cyclooxygenase activity. The results suggest a new concept of PGHS inactivation: that distinct damage can occur at the two active sites during side reactions of Intermediate II, which forms during reaction of PGHS with peroxide and which contains two oxidants, a ferryl heme in the peroxidase site, and a tyrosyl free radical in the cyclooxygenase site.

  18. Imperatorin is a mechanism-based inactivator of CYP2B6.

    PubMed

    Zheng, Liwei; Cao, Jiaojiao; Lu, Dan; Ji, Lin; Peng, Ying; Zheng, Jiang

    2015-01-01

    Imperatorin (IMP) is the major active ingredient in many common medicinal herbs. We examined the irreversible inhibitory effect of IMP on CYP2B6. IMP produced a time- and concentration-dependent inactivation of CYP2B6. About 70% of activity of CYP2B6 was suppressed after its incubation with 1.5 μM IMP for 9 minutes. KI and kinact were found to be 0.498 μM and 0.079 min(-1), respectively. The loss of CYP2B6 activity required the presence of NADPH. Glutathione and catalase/superoxide dismutase showed little protection against the IMP-induced enzyme inactivation. Ticlopidine, a substrate of CYP2B6, showed protection of the enzyme against the inactivation induced by IMP. The estimated partition ratio of the inactivation was approximately 4. Additionally, a γ-ketoenal intermediate was identified in microsomal incubations with IMP. CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 were found to be involved in bioactivation of IMP. In conclusion, IMP is a mechanism-based inactivator of CYP2B6. The formation of γ-ketoenal intermediate may account for the enzyme inactivation.

  19. INACTIVATION OF SEXUAL AGGLUTINATION IN HANSENULA WINGEI AND SACCHAROMYCES KLUYVERI BY DISULFIDE-CLEAVING AGENTS

    PubMed Central

    Taylor, Neil W.

    1964-01-01

    Taylor, Neil W. (Northern Regional Research Laboratory, Peoria, Ill.). Inactivation of sexual agglutination in Hansenula wingei and Saccharomyces kluyveri by disulfide-cleaving agents. J. Bacteriol. 88:929–936. 1964.—Mating types of both Hansenula wingei and Saccharomyces kluyveri can be activated to produce uniformly strong sexual agglutination by treatments with various solvents, such as 8 m LiBr. The strongly agglutinative mating-type preparations were irreversibly inactivated for sexual agglutination by various chemical treatments. Type 5 of H. wingei was inactivated by disulfide-cleaving reagents, but type 21 of H. wingei was not. Type 3 of S. kluyveri was more sensitive than type 26 of S. kluyveri to inactivation by disulfide-cleaving reagents. Comparison of sensitivities to these and other treatments, plus a moderately strong cross-agglutination between type 3 and type 21, indicated that the sexually agglutinative elements on type 3 are similar to type 5, and those of type 21 are similar to those of type 26. Inactivation-rate experiments showed a loss of agglutinative ability according to a sigmoid decrement with time for both types 5 and 21. The apparent extent of inactivation depended markedly on agglutination test conditions. Results of these experiments were interpreted to indicate tentatively, first, that the agglutinative elements of both types of a species are proteins and, second, that several agglutinating linkages are formed between any two cells in sexual agglutination. PMID:14219056

  20. The Gauss-Eyring model: A new thermodynamic model for biochemical and microbial inactivation kinetics.

    PubMed

    Mastwijk, H C; Timmermans, R A H; Van Boekel, M A J S

    2017-12-15

    A new primary model has been developed, using Gaussian distributed populations and Eyrings rate constant for the transition state, to describe inactivation kinetics of enzymes and micro-organisms subjected to heat and chemical treatment. The inactivation of both enzymes and micro-organisms could be associated with the irreversible transition to an inactivated state, as suggested by the Lumry-Eyring model for protein denaturation and enzyme inactivation. The characteristic inactivation model parameters, standard activation enthalpy and entropy, are directly related to the reference temperature and Z-value commonly used for kinetic analysis in food microbiology. An essential feature of the kinetic model is that its parameters, and hence the transition temperature, are treated as stochastic variables. The characteristic line shape of the primary model is the log-normal distribution. The performance of the model was validated, using literature data for enzyme and microbial inactivation over a wide range of temperature and pH. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Irreversible climate change due to carbon dioxide emissions.

    PubMed

    Solomon, Susan; Plattner, Gian-Kasper; Knutti, Reto; Friedlingstein, Pierre

    2009-02-10

    The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450-600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the "dust bowl" era and inexorable sea level rise. Thermal expansion of the warming ocean provides a conservative lower limit to irreversible global average sea level rise of at least 0.4-1.0 m if 21st century CO(2) concentrations exceed 600 ppmv and 0.6-1.9 m for peak CO(2) concentrations exceeding approximately 1,000 ppmv. Additional contributions from glaciers and ice sheet contributions to future sea level rise are uncertain but may equal or exceed several meters over the next millennium or longer.

  2. Irreversible climate change due to carbon dioxide emissions

    PubMed Central

    Solomon, Susan; Plattner, Gian-Kasper; Knutti, Reto; Friedlingstein, Pierre

    2009-01-01

    The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450–600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the “dust bowl” era and inexorable sea level rise. Thermal expansion of the warming ocean provides a conservative lower limit to irreversible global average sea level rise of at least 0.4–1.0 m if 21st century CO2 concentrations exceed 600 ppmv and 0.6–1.9 m for peak CO2 concentrations exceeding ≈1,000 ppmv. Additional contributions from glaciers and ice sheet contributions to future sea level rise are uncertain but may equal or exceed several meters over the next millennium or longer. PMID:19179281

  3. A criterion to maximize the irreversible efficiency in heat engines

    NASA Astrophysics Data System (ADS)

    Aragón-González, G.; Canales-Palma, A.; León-Galicia, A.; Musharrafie-Martínez, M.

    2003-02-01

    The purpose of this work is to obtain a more precise calculation of the effective limits to the efficiency, of several cyclic heat engines. This calculation is based, first, on the equations describing the irreversible efficiency, and second, on a method which results from a general criterion to maximize this efficiency, applicable to several heat engines. With this method, we apply the criterion to maximize efficiencies; establish lower and upper bounds, corresponding to the efficiencies of Curzon-Ahlborn-like and Carnot-like heat engines; and, finally, find analytical or numerical expressions for the efficiencies etame and etamax. etamax is the maximum irreversible efficiency; etame is the efficiency in which the irreversible efficiency achieves its maximum, in a similar way to the Curzon-Ahlborn efficiency (maximum work or power). The method was applied to a Brayton cycle, presenting internal dissipations of the working fluid and irreversibilities due to the finite-rate heat transfer between the heat engine and its reservoirs. Also, we applied this method to a Carnot cycle including the irreversibilities of a finite-rate heat transfer between the heat engine and its reservoirs, heat leak between the reservoirs, and internal dissipations of the working fluid. The results obtained for the Brayton cycle are more general and useful than those in the relevant literature.

  4. Reversible and irreversible protein glutathionylation: biological and clinical aspects

    PubMed Central

    Cooper, Arthur J L.; Pinto, John T.; Callery, Patrick S.

    2011-01-01

    Introduction Depending in part on the glutathione to glutathione disulfide ratio, reversible protein glutathionylation to a mixed disulfide may occur. Reversible glutathionylation is important in protecting proteins against oxidative stress, guiding correct protein folding, regulating protein activity, and modulating proteins critical to redox signaling. The potential also exists for irreversible protein glutathionylation via Michael addition of an -SH group to a dehydroalanyl residue, resulting in formation of a stable, non-reducible thioether linkage. Areas covered This article reviews factors contributing to reversible and irreversible protein glutathionylation and their biomedical implications. It also examines the possibility that certain drugs such as busulfan may be toxic by promoting irreversible glutathionylation. The reader will gain an appreciation of the protective nature and control of function resulting from reversible protein glutathionylation. The reader is also introduced to the recently identified phenomenon of irreversible protein glutathionylation and its possible deleterious effects. Expert opinion The process of reversible protein glutathionylation is now well established but these findings need to be substantiated at the tissue and organ levels, and also with disease state. That being said, irreversible protein glutathionylation can also occur and this has implications in disease and aging. Toxicologists should consider this when evaluating the possible side effects of certain drugs such as busulfan that may generate a glutathionylating species in vivo. PMID:21557709

  5. CHLORINE INACTIVATION OF BACILLUS ENDOSPORES

    EPA Science Inventory

    The possibility of a bioterrorism event resulting in the release of Bacillus anthracis endospores into a drinking water distribution system necessitates research into means by which these endospores can be inactivated. This study was designed to determine the chlorine resistance...

  6. Free radical inactivation of pepsin

    NASA Astrophysics Data System (ADS)

    Josimović, Lj; Ruvarac, I.; Janković, I.; Jovanović, S. V.

    1994-06-01

    Alkylperoxy radicals containing one, two or three chlorine atoms, CO -2, O 2 - were reacted with pepsin in aqueous solutions. It was found that only Cl 3COO and CO -2 inactive pepsin, attacking preferentially the disulfide bridge. Transient spectra obtained upon completion of the Cl 3COO + pepsin reaction at pH 5 indicate that 20% of initially produced Cl 3COO radicals oxidizes tryptophan residues, and 40% disulfide bridges. The inactivation induced by the Cl 3COO radical increases at lower pH, and the maximal inactivation, Gin = 5.8, was observed at pH 1.5. The inactivation of pepsin by CO -2 radicals depends on the absorbed dose. The maximal inactivation, Gin = 4.5, was determined in the dose range from 38 to 53 Gy.

  7. CHLORINE INACTIVATION OF BACILLUS ENDOSPORES

    EPA Science Inventory

    The possibility of a bioterrorism event resulting in the release of Bacillus anthracis endospores into a drinking water distribution system necessitates research into means by which these endospores can be inactivated. This study was designed to determine the chlorine resistance...

  8. Influenza Vaccine, Inactivated or Recombinant

    MedlinePlus

    ... die from flu, and many more are hospitalized.Flu vaccine can:keep you from getting flu, make flu ... inactivated or recombinant influenza vaccine?A dose of flu vaccine is recommended every flu season. Children 6 months ...

  9. 3-Nitropropionate, the toxic substance of Indigofera, is a suicide inactivator of succinate dehydrogenase

    PubMed Central

    Alston, Theodore A.; Mela, Leena; Bright, Harold J.

    1977-01-01

    We have shown that 3-nitropropionate, an isoelectronic analogue of succinate, is a suicide inactivator of succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1] as follows. (i) When rat liver mitochondria oxidize succinate in the presence of 3-nitropropionate carbanion, the rate of O2 consumption decreases exponentially to a zero value. This pattern is duplicated by subsequent additions of mitochondria. The dependence of the apparent first-order rate constant for enzyme inhibition, as well as the number of enzyme turnovers completed before inhibition, on the concentrations of 3-nitropropionate carbanion and succinate are those expected for an active site-directed and irreversible inhibitor. (ii) The inactivated enzyme is not resuscitated by centrifugation and washing of the mitochondria, in contrast to malonate-treated enzyme, and malonate protects against irreversible, inhibition. (iii) The inhibitor species is 3-nitropropionate carbanion and no external nucleophile is required for inhibition. (iv) The respiratory rates, respiratory control ratios, and ADP/O ratios obtained with NAD-linked substrates are unaffected by 3-nitropropionate carbanion. These results show that 3-nitropropionate carbanion is a highly specific, time-dependent, and irreversible inhibitor of succinate dehydrogenase. By analogy with the reaction of nitroethane with D-amino acid oxidase, the data are consistent with the hypothesis that the carbanionic inhibitor forms a covalent N-5 adduct with the active site flavin. However, the precise mechanism of inactivation, as well as mechanistic extrapolations to the oxidation of succinate, must await the elucidation of the structure of the modified enzyme. We can now explain the toxicity of plants such as Indigofera endecaphylla for mammals and fowl as being due to the irreversible blockage of the Krebs cycle by 3-nitropropionate carbanion. PMID:269430

  10. 3-Nitropropionate, the toxic substance of Indigofera, is a suicide inactivator of succinate dehydrogenase.

    PubMed

    Alston, T A; Mela, L; Bright, H J

    1977-09-01

    We have shown that 3-nitropropionate, an isoelectronic analogue of succinate, is a suicide inactivator of succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1] as follows. (i) When rat liver mitochondria oxidize succinate in the presence of 3-nitropropionate carbanion, the rate of O(2) consumption decreases exponentially to a zero value. This pattern is duplicated by subsequent additions of mitochondria. The dependence of the apparent first-order rate constant for enzyme inhibition, as well as the number of enzyme turnovers completed before inhibition, on the concentrations of 3-nitropropionate carbanion and succinate are those expected for an active site-directed and irreversible inhibitor. (ii) The inactivated enzyme is not resuscitated by centrifugation and washing of the mitochondria, in contrast to malonate-treated enzyme, and malonate protects against irreversible, inhibition. (iii) The inhibitor species is 3-nitropropionate carbanion and no external nucleophile is required for inhibition. (iv) The respiratory rates, respiratory control ratios, and ADP/O ratios obtained with NAD-linked substrates are unaffected by 3-nitropropionate carbanion. These results show that 3-nitropropionate carbanion is a highly specific, time-dependent, and irreversible inhibitor of succinate dehydrogenase. By analogy with the reaction of nitroethane with D-amino acid oxidase, the data are consistent with the hypothesis that the carbanionic inhibitor forms a covalent N-5 adduct with the active site flavin. However, the precise mechanism of inactivation, as well as mechanistic extrapolations to the oxidation of succinate, must await the elucidation of the structure of the modified enzyme. We can now explain the toxicity of plants such as Indigofera endecaphylla for mammals and fowl as being due to the irreversible blockage of the Krebs cycle by 3-nitropropionate carbanion.

  11. Slow inactivation in human cardiac sodium channels.

    PubMed Central

    Richmond, J E; Featherstone, D E; Hartmann, H A; Ruben, P C

    1998-01-01

    The available pool of sodium channels, and thus cell excitability, is regulated by both fast and slow inactivation. In cardiac tissue, the requirement for sustained firing of long-duration action potentials suggests that slow inactivation in cardiac sodium channels may differ from slow inactivation in skeletal muscle sodium channels. To test this hypothesis, we used the macropatch technique to characterize slow inactivation in human cardiac sodium channels heterologously expressed in Xenopus oocytes. Slow inactivation was isolated from fast inactivation kinetically (by selectively recovering channels from fast inactivation before measurement of slow inactivation) and structurally (by modification of fast inactivation by mutation of IFM1488QQQ). Time constants of slow inactivation in cardiac sodium channels were larger than previously reported for skeletal muscle sodium channels. In addition, steady-state slow inactivation was only 40% complete in cardiac sodium channels, compared to 80% in skeletal muscle channels. These results suggest that cardiac sodium channel slow inactivation is adapted for the sustained depolarizations found in normally functioning cardiac tissue. Complete slow inactivation in the fast inactivation modified IFM1488QQQ cardiac channel mutant suggests that this impairment of slow inactivation may result from an interaction between fast and slow inactivation. PMID:9635748

  12. Irreversibility analysis in the process of solar distillation

    NASA Astrophysics Data System (ADS)

    Chávez, S.; Terres, H.; Lizardi, A.; López, R.; Lara, A.

    2017-01-01

    In this work an irreversibility analysis for the thermal process of solar distillation of three different substances is presented, for which it employs a solar still of a slope where three experimental tests with 5.5 L of brine, river water and MgCl2 were performed. Temperature data principally in the glass cover, absorber plate, fluid, environment and the incident solar radiation on the device were obtained. With measurements of temperature, solar radiation and exergetic balance, irreversibilities are found on the device. The results show that the highest values of irreversibilities are concentrated in the absorber plate with an average of 321 W, 342 W and 276 W, followed by the cover glass with an average of 75.8 W, 80.4 W and 86.7 W and finally the fluid with 15.3 W, 15.9 W and 16 W, for 5.5 L of brine, river water and MgCl2.

  13. Irreversible fouling during multicycle microfiltration of wastewater effluent.

    PubMed

    Shan, Huifeng; Neufeld, Ronald D

    2007-12-01

    This study focused on irreversible fouling during microfiltration of primary and secondary effluents from municipal wastewater treatment plants. Flow resistances were calculated from the sum of clean membrane resistances, resultant cake layer resistances, and consequent irreversible fouling resistances. Results from a dead-end cell experimental system showed that the accumulated cake resistance was dominating for microfiltration of primary/secondary effluents. Suspended solids in the primary and secondary effluents had a similar compressibility index, n, with a value of approximately 0.5, indicating that they were moderately compressible particles. The value of irreversible resistance is dependent on the intensity of membrane cleaning; however, for a given membrane cleaning strategy, this value steadily increased and reached a maximum after approximately 6 cycles of filtration and cleaning. This study provided an explanation for the significant drop of throughput flux in the early application of membrane processes, and a plateau flux approached correspondingly.

  14. Mitochondrial aconitase reaction with nitric oxide, S-nitrosoglutathione, and peroxynitrite: mechanisms and relative contributions to aconitase inactivation.

    PubMed

    Tórtora, Verónica; Quijano, Celia; Freeman, Bruce; Radi, Rafael; Castro, Laura

    2007-04-01

    Using highly purified recombinant mitochondrial aconitase, we determined the kinetics and mechanisms of inactivation mediated by nitric oxide (*NO), nitrosoglutathione (GSNO), and peroxynitrite (ONOO(-)). High *NO concentrations are required to inhibit resting aconitase. Brief *NO exposures led to a reversible inhibition competitive with isocitrate (K(I)=35 microM). Subsequently, an irreversible inactivation (0.65 M(-1) s(-1)) was observed. Irreversible inactivation was mediated by GSNO also, both in the absence and in the presence of substrates (0.23 M(-1) s(-1)). Peroxynitrite reacted with the [4Fe-4S] cluster, yielding the inactive [3Fe-4S] enzyme (1.1 x 10(5) M(-1) s(-1)). Carbon dioxide enhanced ONOO(-)-dependent inactivation via reaction of CO(3)*(-) with the [4Fe-4S] cluster (3 x 10(8) M(-1) s(-1)). Peroxynitrite also induced m-aconitase tyrosine nitration but this reaction did not contribute to enzyme inactivation. Computational modeling of aconitase inactivation by O(2)*(-) and *NO revealed that, when NO is produced and readily consumed, measuring the amount of active aconitase remains a sensitive method to detect variations in O(2)*(-) production in cells but, when cells are exposed to high concentrations of NO, aconitase inactivation does not exclusively reflect changes in rates of O(2)*(-) production. In the latter case, extents of aconitase inactivation reflect the formation of secondary reactive species, specifically ONOO(-) and CO(3)*(-), which also mediate m-aconitase tyrosine nitration, a footprint of reactive *NO-derived species.

  15. Human PIEZO1: Removing Inactivation

    PubMed Central

    Bae, Chilman; Gottlieb, Philip A.; Sachs, Frederick

    2013-01-01

    PIEZO1 is an inactivating eukaryotic cation-selective mechanosensitive ion channel. Two sites have been located in the channel that when individually mutated lead to xerocytotic anemia by slowing inactivation. By introducing mutations at two sites, one associated with xerocytosis and the other artificial, we were able to remove inactivation. The double mutant (DhPIEZO1) has a substitution of arginine for methionine (M2225R) and lysine for arginine (R2456K). The loss of inactivation was accompanied by ∼30-mmHg shift of the activation curve to lower pressures and slower rates of deactivation. The slope sensitivity of gating was the same for wild-type and mutants, indicating that the dimensional changes between the closed and open state are unaffected by the mutations. The unitary channel conductance was unchanged by mutations, so these sites are not associated with pore. DhPIEZO1 was reversibly inhibited by the peptide GsMTx4 that acted as a gating modifier. The channel kinetics were solved using complex stimulus waveforms and the data fit to a three-state loop in detailed balance. The reaction had two pressure-dependent rates, closed to open and inactivated to closed. Pressure sensitivity of the opening rate with no sensitivity of the closing rate means that the energy barrier between them is located near the open state. Mutant cycle analysis of inactivation showed that the two sites interacted strongly, even though they are postulated to be on opposite sides of the membrane. PMID:23972840

  16. Oxidative inactivation of paraoxonase1, an antioxidant protein and its effect on antioxidant action.

    PubMed

    Nguyen, Su Duy; Sok, Dai-Eun

    2003-12-01

    Paraoxonase1 (PON1), one of antioxidant proteins to protect low density lipoprotein (LDL) from the oxidation, is known to lose its activity in the oxidative environment. Here, we attempted to elucidate the possible mechanisms for the oxidative inactivation of PON1, and to examine the capability of hydroxyl radicals-inactivated PON1 to prevent against LDL oxidation. Of various oxidative systems, the ascorbate/Cu2+ system was the most potent in inactivating the purified PON1 (PON1) as well as HDL-bound PON1 (HDL-PON1). In contrast to a limited inactivation by Fe2+ (2.0 microM), the inclusion of Cu2+ (0.1-1.0 microM) remarkably enhanced the inactivation of PON1 in the presence of ascorbate (0.5mM). A similar result was also obtained with the inactivation of HDL-PON1. The inactivation of PON1 by ascorbate/Cu2+ was pevented by catalase, but not general hydroxyl radical scavengers, supporting inactivation. In addition, Cu2+ alone inactivated PON1, either soluble or HDL-bound, by different mechanisms, concentration-dependent. Separately, there was a reverse relationship between the inactivation of PON1 and its preventive action against LDL oxidation during Cu2+-induced oxidation of LDL. Noteworthy, ascorbate/Cu2+-inactivated PON1, which was charaterized by the partial loss of histidine residues, expressed a lower protection against Cu2+-induced LDL oxidation, compared to native PON1. Based on these results, it is proposed that metal-catalyzed oxidation may be a primary factor to cause the decrease of HDL-associated PON1 activity under oxidative stress, and radicals-induced inactivation of PON1 may lead to the decrease in its antioxidant action against LDL oxidation.

  17. Entanglement irreversibility from quantum discord and quantum deficit.

    PubMed

    Cornelio, Marcio F; de Oliveira, Marcos C; Fanchini, Felipe F

    2011-07-08

    We relate the problem of irreversibility of entanglement with the recently defined measures of quantum correlation--quantum discord and one-way quantum deficit. We show that the entanglement of formation is always strictly larger than the coherent information and the entanglement cost is also larger in most cases. We prove irreversibility of entanglement under local operations and classical communication for a family of entangled states. This family is a generalization of the maximally correlated states for which we also give an analytic expression for the distillable entanglement, the relative entropy of entanglement, the distillable secret key, and the quantum discord.

  18. Mechanism-based inhibitors for the inactivation of the bacterial phosphotriesterase.

    PubMed

    Hong, S B; Mullins, L S; Shim, H; Raushel, F M

    1997-07-22

    1-Bromovinyl (I), Z-2-bromovinyl (II), 1,2-dibromoethyl (III), and a series of 4-(halomethyl)-2-nitrophenyl (IVa-c) diethyl phosphate esters were examined as substrates and mechanism-based inhibitors for the bacterial phosphotriesterase. All of these compounds were found to act as substrates for the enzyme. Inhibitor I rapidly inactivated the enzyme within 1 min, giving a partition ratio of 230. The newly formed covalent adduct with inhibitor I was susceptible to hydrolysis at elevated values of pH and dissociation by NH2OH. Azide was not able to protect the enzyme from inactivation with inhibitor I, implying that the reactive species was not released into solution prior to the inactivation event. The reactive species was proposed to be either an acyl bromide or a ketene intermediate formed by the enzymatic hydrolysis of inhibitor I. Compounds II and III were shown to be relatively poor substrates of phosphotriesterase and they did not induce any significant inactivation of the enzyme. The inhibitor, 4-(bromomethyl)-2-nitrophenyl diethyl phosphate (IVa), was found to irreversibly inactivate the enzyme with a KI = 7.9 mM and kinact = 1. 2 min-1 at pH 9.0. There was no effect on the rate of inactivation upon the addition of the exogenous nucleophiles, azide, and NH2OH. The species responsible for the covalent modification of the enzyme by IVa was most likely a quinone methide formed by the elimination of bromide from the phenolic intermediate. NMR experiments demonstrated that the quinone methide did not accumulate in solution. The chloro (IVb) and fluoro (IVc) analogues did not inactivate the enzyme. These results suggest that the elimination of the halide ion from the phenolic intermediate largely determines the partition ratio for inactivation.

  19. Partial Tonsillectomy.

    PubMed

    Wong, Kevin; Levi, Jessica R

    2017-03-01

    Evaluate the content and readability of health information regarding partial tonsillectomy. A web search was performed using the term partial tonsillectomy in Google, Yahoo!, and Bing. The first 50 websites from each search were evaluated using HONcode standards for quality and content. Readability was assessed using the Flesch-Kincaid Grade Level (FKGL), Flesch Reading Ease, Gunning-Fog Index, Coleman-Liau Index, Automated Readability Index, and SMOG score. The Freeman-Halton extension of Fisher's exact test was used to compare categorical differences between engines. Less than half of the websites mentioned patient eligibility criteria (43.3%), referenced peer-reviewed literature (43.3%), or provided a procedure description (46.7%). Twenty-two websites (14.7%) were unrelated to partial tonsillectomy, and over half contained advertisements (52%). These finding were consistent across search engines and search terms. The mean FKGL was 11.6 ± 0.11, Gunning-Fog Index was 15.1 ± 0.13, Coleman-Liau Index was 14.6 ± 0.11, ARI was 12.9 ± 0.13, and SMOG grade was 14.0 ± 0.1. All readability levels exceeded the abilities of the average American adult. Current online information regarding partial tonsillectomy may not provide adequate information and may be written at a level too difficult for the average adult reader.

  20. Inactivation of urease by catechol: Kinetics and structure.

    PubMed

    Mazzei, Luca; Cianci, Michele; Musiani, Francesco; Lente, Gábor; Palombo, Marta; Ciurli, Stefano

    2017-01-01

    Urease is a Ni(II)-containing enzyme that catalyzes the hydrolysis of urea to yield ammonia and carbamate at a rate 10(15) times higher than the uncatalyzed reaction. Urease is a virulence factor of several human pathogens, in addition to decreasing the efficiency of soil organic nitrogen fertilization. Therefore, efficient urease inhibitors are actively sought. In this study, we describe a molecular characterization of the interaction between urease from Sporosarcina pasteurii (SPU) and Canavalia ensiformis (jack bean, JBU) with catechol, a model polyphenol. In particular, catechol irreversibly inactivates both SPU and JBU with a complex radical-based autocatalytic multistep mechanism. The crystal structure of the SPU-catechol complex, determined at 1.50Å resolution, reveals the structural details of the enzyme inhibition.

  1. Ribosome-Inactivating Proteins: From Plant Defense to Tumor Attack

    PubMed Central

    de Virgilio, Maddalena; Lombardi, Alessio; Caliandro, Rocco; Fabbrini, Maria Serena

    2010-01-01

    Ribosome-inactivating proteins (RIPs) are EC3.2.32.22 N-glycosidases that recognize a universally conserved stem-loop structure in 23S/25S/28S rRNA, depurinating a single adenine (A4324 in rat) and irreversibly blocking protein translation, leading finally to cell death of intoxicated mammalian cells. Ricin, the plant RIP prototype that comprises a catalytic A subunit linked to a galactose-binding lectin B subunit to allow cell surface binding and toxin entry in most mammalian cells, shows a potency in the picomolar range. The most promising way to exploit plant RIPs as weapons against cancer cells is either by designing molecules in which the toxic domains are linked to selective tumor targeting domains or directly delivered as suicide genes for cancer gene therapy. Here, we will provide a comprehensive picture of plant RIPs and discuss successful designs and features of chimeric molecules having therapeutic potential. PMID:22069572

  2. Dimensional accuracy of 2 irreversible hydrocolloid alternative impression materials with immediate and delayed pouring.

    PubMed

    Nassar, Usama; Hussein, Bayan; Oko, Andrea; Carey, Jason P; Flores-Mir, Carlos

    2012-01-01

    To assess dimensional accuracy and stability of 2 irreversible hydrocolloid alternative impression materials with immediate and delayed pouring. Two alternative impression materials, AlgiNot FS and Position Penta Quick, were compared with a traditional irreversible hydrocolloid, Jeltrate Plus antimicrobial alginate. Impressions were made of a metal model with 4 cylinders of known dimensions, with pouring performed immediately or after 4 hours of storage. A digital micrometer was used to measure cylinder diameter on the model and the poured casts. Dimensional changes were analyzed according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 19 (2004 version) (α=0.05). There were significant differences among the 3 materials, between the 2 pour times and as a function of storage time (multivariate analysis of variance, p<0.001). One-way analysis of variance revealed no significant differences between the 2 alternative impression materials, but changes for these materials differed significantly from those for the traditional impression material for immediate (p<0.05) and 4-hour (p<0.001) pouring. Linear dimensional changes for the 2 substitute materials were within the limits of the ANSI/ADA specification. With immediate pouring, both alternative impression materials exhibited minimal dimensional changes, which were maintained or reduced with 4-hour pouring. For both pouring times, these changes were less than 0.5%. The minimal dimensional changes observed with these irreversible hydrocolloid alternative impression materials after 4 hours of storage may save chairside time and help to produce accurate results for procedures such as partial denture framework, surgical guides, and pediatric and orthodontic devices.

  3. Cellular inactivation by ultrasound.

    PubMed

    Li, G C; Hahn, G M; Tolmach, L J

    1977-05-12

    The lethal effect of ultrasound (US) on mammalian cells has received relatively little attention. Understandably, potential genetic aspects of US have been of prime concern to physicians who use US as a diagnostic tool; at the average power densities involved (<1 W cm(-2)) little, if any cell killing is to be expected. There have been sporadic attempts to use higher intensities ( approximately 1 W cm(-2)) as a treatment modality in cancer therapy, but those experiments seem to have been based on inadequate cellular studies. The effects of US usually were evaluated in terms of morphological criteria rather than on quantitative determination of the loss of viability as measured by colony formation. There are few reports of the effects of US on survival of mammalian cells, and none specifically examine hyperthermic interaction. With the increased interest in hyperthermia for tumour therapy, attention has been directed towards the use of ultrasound to achieve tumour heating. In preliminary experiments in which US was used to heat the EMT6 sarcoma and KHJJ carcinoma in mice, we found a high percentage of tumour cures with short (approximately 30 min) treatments at temperatures (43-44 degrees C) where in vitro results of hyperthermia-induced cell killing would not have led to a prediction of any cures. We therefore initiated an investigation of the effects of US on survival of Chinese hamster cells to see if direct cell killing by US could explain our in vivo results, or, as in the case of radiofrequency (RF) electromagnetic heating, we would be forced to invoke host response(8). In particular, we examined the thermal and non-thermal components of cellular inactivation by US. We report here that there is a definite non-thermal cytotoxic effect of US. Its relative contribution to cell killing is a highly nonlinear function of the temperature of the cellular milieu. The survival curves show clearly that, beyond an initial threshold, small changes in temperature and/or US

  4. The plasma membrane Ca2+ pump mutant lysine591 --> arginine retains some activity, but is still inactivated by fluorescein isothiocyanate.

    PubMed Central

    Adamo, H P; Filoteo, A G; Penniston, J T

    1996-01-01

    Inactivation of the wild-type human plasma membrane Ca2+ pump (isoform 4b) by fluorescein isothiocyanate is accompanied by covalent modification of Lys591. The mutation of Lys591 to arginine reduced the Ca2+ transport activity to 35% of the wild-type, and diminished the amount of acylphosphate formed from ATP by a corresponding amount. When this mutant was treated with fluorescein isothiocyanate; the enzyme was still irreversibly inactivated, even though no reactive residue was available at position 591. The results show that, although Ca2+ pump function is sensitive to the residue at position 591, Lys591 is not essential for enzyme activity. They also demonstrate that irreversible inhibition of the plasma membrane Ca2+ pump by fluorescein isothiocyanate does not require the covalent modification of Lys591. This indicates that fluorescein isothiocyanate reacts with lysine residues at other positions in addition to Lys591. PMID:8694784

  5. When an Adiabatic Irreversible Expansion or Compression Becomes Reversible

    ERIC Educational Resources Information Center

    Anacleto, Joaquim; Ferreira, J. M.; Soares, A. A.

    2009-01-01

    This paper aims to contribute to a better understanding of the concepts of a "reversible process" and "entropy". For this purpose, an adiabatic irreversible expansion or compression is analysed, by considering that an ideal gas is expanded (compressed), from an initial pressure P[subscript i] to a final pressure P[subscript f], by being placed in…

  6. Pressure-Volume Integral Expressions for Work in Irreversible Processes

    ERIC Educational Resources Information Center

    Gislason, Eric A.; Craig, Norman C.

    2007-01-01

    Different formulations of thermodynamic work "w" as a pressure-volume integral are examined for a piston moving against a gas in an irreversible process. Proper expressions are obtained using the instantaneous pressure of the gas on the piston as the integrand and also using certain external pressures as the integrand. There are two common yet…

  7. Irreversible visual sensing of humidity using a cholesteric liquid crystal.

    PubMed

    Saha, Abhijit; Tanaka, Yoko; Han, Yang; Bastiaansen, Cees M W; Broer, Dirk J; Sijbesma, Rint P

    2012-05-14

    Irreversible optical sensing of humidity by a doped cholesteric liquid crystal is achieved by using a thin film of nematic host E7 with a binaphthylorthosilicate ester as dopant (guest). The film changes its color from blue (to green to orange to red) to colorless when exposed to humidity as the dopant is hydrolyzed. This journal is © The Royal Society of Chemistry 2012

  8. Irreversible electroporation: evolution of a laboratory technique in interventional oncology.

    PubMed

    Deipolyi, Amy R; Golberg, Alexander; Yarmush, Martin L; Arellano, Ronald S; Oklu, Rahmi

    2014-01-01

    Electroporation involves applying electric field pulses to cells, leading to the alteration or destruction of cell membranes. Irreversible electroporation (IRE) creates permanent defects in cell membranes and induces cell death. By directly targeting IRE to tumors, percutaneous nonthermal ablation is possible. The history of IRE, evolution of concepts, theory, biological applications, and clinical data regarding its safety and efficacy are discussed.

  9. Irreversible electroporation: evolution of a laboratory technique in interventional oncology

    PubMed Central

    Deipolyi, Amy R.; Golberg, Alexander; Yarmush, Martin L.; Arellano, Ronald S.; Oklu, Rahmi

    2014-01-01

    Electroporation involves applying electric field pulses to cells, leading to the alteration or destruction of cell membranes. Irreversible electroporation (IRE) creates permanent defects in cell membranes and induces cell death. By directly targeting IRE to tumors, percutaneous nonthermal ablation is possible. The history of IRE, evolution of concepts, theory, biological applications, and clinical data regarding its safety and efficacy are discussed. PMID:24412820

  10. When an Adiabatic Irreversible Expansion or Compression Becomes Reversible

    ERIC Educational Resources Information Center

    Anacleto, Joaquim; Ferreira, J. M.; Soares, A. A.

    2009-01-01

    This paper aims to contribute to a better understanding of the concepts of a "reversible process" and "entropy". For this purpose, an adiabatic irreversible expansion or compression is analysed, by considering that an ideal gas is expanded (compressed), from an initial pressure P[subscript i] to a final pressure P[subscript f], by being placed in…

  11. Reactivation strategies by unfolding/refolding of chymotrypsin derivatives after inactivation by organic solvents.

    PubMed

    Soler, G; Bastida, A; Blanco, R M; Fernández-Lafuente, R; Guisán, J M

    1997-04-25

    Immobilized enzyme derivatives, in organic media at neutral pH and moderate temperatures, should be mainly and perhaps uniquely inactivated by promotion of conformational changes on their 3D structure. Subsequent irreversible inactivation mechanisms (intermolecular aggregations, chemical modifications, thiol-disulfide exchanges) are thus impossible. However, simple reincubation in aqueous medium of enzymes previously inactivated by solvents usually yields significant but slow and incomplete reactivations. Disruption of incorrect protein structures by denaturing agents (urea, guanidine) is proposed as a new strategy to get rapid, complete and technologically feasible reactivations. By using multipoint immobilized chymotrypsin derivatives, we have evaluated the possibility of unfolding and further refolding of native (non-inactivated) derivatives by different denaturing conditions. After unfolding in 8 M guanidine, derivatives were quickly and completely refolded up to 100% of catalytic activity in 10 minutes. Besides, successive cycles of unfolding and refolding could be exactly reproduced. Finally we checked the possibility to reactivate chymotrypsin derivatives inactivated by dioxane. Simple reincubations in aqueous media yielded a poor reactivation even after 24 hours. However, unfolding in 8 M guanidine enabled complete reactivation in less than 2 hours. From this point of view, by working under 'chemically inert conditions' (moderate pH and temperatures), fully dispersed covalently immobilized enzyme derivatives seem to behave as almost everlasting catalysts despite the very deleterious effect of organic media.

  12. Human PIEZO1: removing inactivation.

    PubMed

    Bae, Chilman; Gottlieb, Philip A; Sachs, Frederick

    2013-08-20

    PIEZO1 is an inactivating eukaryotic cation-selective mechanosensitive ion channel. Two sites have been located in the channel that when individually mutated lead to xerocytotic anemia by slowing inactivation. By introducing mutations at two sites, one associated with xerocytosis and the other artificial, we were able to remove inactivation. The double mutant (DhPIEZO1) has a substitution of arginine for methionine (M2225R) and lysine for arginine (R2456K). The loss of inactivation was accompanied by ∼30-mmHg shift of the activation curve to lower pressures and slower rates of deactivation. The slope sensitivity of gating was the same for wild-type and mutants, indicating that the dimensional changes between the closed and open state are unaffected by the mutations. The unitary channel conductance was unchanged by mutations, so these sites are not associated with pore. DhPIEZO1 was reversibly inhibited by the peptide GsMTx4 that acted as a gating modifier. The channel kinetics were solved using complex stimulus waveforms and the data fit to a three-state loop in detailed balance. The reaction had two pressure-dependent rates, closed to open and inactivated to closed. Pressure sensitivity of the opening rate with no sensitivity of the closing rate means that the energy barrier between them is located near the open state. Mutant cycle analysis of inactivation showed that the two sites interacted strongly, even though they are postulated to be on opposite sides of the membrane. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  13. 1,6-Cyclophellitol Cyclosulfates: A New Class of Irreversible Glycosidase Inhibitor.

    PubMed

    Artola, Marta; Wu, Liang; Ferraz, Maria J; Kuo, Chi-Lin; Raich, Lluís; Breen, Imogen Z; Offen, Wendy A; Codée, Jeroen D C; van der Marel, Gijsbert A; Rovira, Carme; Aerts, Johannes M F G; Davies, Gideon J; Overkleeft, Herman S

    2017-07-26

    The essential biological roles played by glycosidases, coupled to the diverse therapeutic benefits of pharmacologically targeting these enzymes, provide considerable motivation for the development of new inhibitor classes. Cyclophellitol epoxides and aziridines are recently established covalent glycosidase inactivators. Inspired by the application of cyclic sulfates as electrophilic equivalents of epoxides in organic synthesis, we sought to test whether cyclophellitol cyclosulfates would similarly act as irreversible glycosidase inhibitors. Here we present the synthesis, conformational analysis, and application of novel 1,6-cyclophellitol cyclosulfates. We show that 1,6-epi-cyclophellitol cyclosulfate (α-cyclosulfate) is a rapidly reacting α-glucosidase inhibitor whose (4)C1 chair conformation matches that adopted by α-glucosidase Michaelis complexes. The 1,6-cyclophellitol cyclosulfate (β-cyclosulfate) reacts more slowly, likely reflecting its conformational restrictions. Selective glycosidase inhibitors are invaluable as mechanistic probes and therapeutic agents, and we propose cyclophellitol cyclosulfates as a valuable new class of carbohydrate mimetics for application in these directions.

  14. 1,6-Cyclophellitol Cyclosulfates: A New Class of Irreversible Glycosidase Inhibitor

    PubMed Central

    2017-01-01

    The essential biological roles played by glycosidases, coupled to the diverse therapeutic benefits of pharmacologically targeting these enzymes, provide considerable motivation for the development of new inhibitor classes. Cyclophellitol epoxides and aziridines are recently established covalent glycosidase inactivators. Inspired by the application of cyclic sulfates as electrophilic equivalents of epoxides in organic synthesis, we sought to test whether cyclophellitol cyclosulfates would similarly act as irreversible glycosidase inhibitors. Here we present the synthesis, conformational analysis, and application of novel 1,6-cyclophellitol cyclosulfates. We show that 1,6-epi-cyclophellitol cyclosulfate (α-cyclosulfate) is a rapidly reacting α-glucosidase inhibitor whose 4C1 chair conformation matches that adopted by α-glucosidase Michaelis complexes. The 1,6-cyclophellitol cyclosulfate (β-cyclosulfate) reacts more slowly, likely reflecting its conformational restrictions. Selective glycosidase inhibitors are invaluable as mechanistic probes and therapeutic agents, and we propose cyclophellitol cyclosulfates as a valuable new class of carbohydrate mimetics for application in these directions. PMID:28776021

  15. The inactivating K+ current in GH3 pituitary cells and its modification by chemical reagents.

    PubMed Central

    Oxford, G S; Wagoner, P K

    1989-01-01

    1. Whole-cell and single-channel recording techniques were applied to the study of the permeability and gating of inactivating K+ channels from clonal pituitary cells. 2. The cation selectivity sequence (measured from reversal potentials) for the channels underlying the inactivating K+ current was Tl+ greater than K+ greater than Rb+ greater than NH4+. The conductance sequence (determined from current amplitudes) was K+ = Tl+ greater than Rb+ greater than NH4+. 3. The inactivating current (IK(i] which was blocked by 4-aminopyridine (4-AP), activated at voltages more positive than -40 mV and half-inactivated at that voltage. Inactivation proceeded as the sum of two exponentials with mean time constants of 21 and 82 ms. Deactivation followed a single-exponential time course. 4. Recovery from inactivation was slow, voltage dependent and multi-exponential, taking more than 50 s near the cell's resting potential. 5. The magnitudes of outward current and of slope conductance increased as the concentration of external K+ was increased. 6. On-cell and outside-out membrane patches revealed minicurrents with gating and pharmacological properties identical to whole-cell currents. Single channels with inactivating characteristics, while rarely observed, had an average slope conductance of 6-8 pS. 7. Intracellular application of the disulphonic stilbene derivative, SITS, and the protein-modifying reagent, N-bromoacetamide (NBA), at concentrations of 0.2-1 mM for several tens of minutes dramatically slowed the decay (inactivation) of K+ currents and caused coincident increases in the magnitude of outward IK(i). 8. Extracellular application of NBA at much lower concentrations (1-100 microM) and much shorter exposure times (1-30 s) also slowed inactivation. This effect was reversible for brief applications at low doses, but became irreversible after longer exposures. 9. Both internal and external NBA shifted the steady-state inactivation-voltage relation by +10 mV and reduced

  16. Inactivated smallpox vaccine. A comparison of inactivation methods

    PubMed Central

    Turner, G. S.; Squires, E. J.; Murray, H. G. S.

    1970-01-01

    Vaccines were prepared from a single pool of high-titred vaccinia virus and inactivated by six methods, namely heat, formalin, hydroxylamine, β-propiolactone, ultraviolet irradiation, and visible light and methylene blue. Large doses of the vaccines were required to protect mice against intracerebral challenge. Differences in protection were not attributable to the method of their inactivation. The vaccines also induced similar degrees of skin immunity in rabbits which showed no severe dermal reactions when challenged with either homologous killed vaccine or live virus. The virus-neutralizing, haemagglutinin-inhibiting and complement fixing antibody responses to the vaccines differed; heat-inactivation preserved these antigens least well and β-propiolactone apparently the best. In both rabbits and mice there was little association between the different antibody responses to each vaccine or between the degrees of antibody response and the protection they induced. The relation of these findings to pox-virus immunity and the use of inactivated smallpox vaccine in man is discussed. PMID:4988047

  17. The intrinsically disordered domain of the antitoxin Phd chaperones the toxin Doc against irreversible inactivation and misfolding.

    PubMed

    De Gieter, Steven; Konijnenberg, Albert; Talavera, Ariel; Butterer, Annika; Haesaerts, Sarah; De Greve, Henri; Sobott, Frank; Loris, Remy; Garcia-Pino, Abel

    2014-12-05

    The toxin Doc from the phd/doc toxin-antitoxin module targets the cellular translation machinery and is inhibited by its antitoxin partner Phd. Here we show that Phd also functions as a chaperone, keeping Doc in an active, correctly folded conformation. In the absence of Phd, Doc exists in a relatively expanded state that is prone to dimerization through domain swapping with its active site loop acting as hinge region. The domain-swapped dimer is not capable of arresting protein synthesis in vitro, whereas the Doc monomer is. Upon binding to Phd, Doc becomes more compact and is secured in its monomeric state with a neutralized active site.

  18. Indomethacin inactivates gastric peroxidase to induce reactive-oxygen-mediated gastric mucosal injury and curcumin protects it by preventing peroxidase inactivation and scavenging reactive oxygen.

    PubMed

    Chattopadhyay, Ishita; Bandyopadhyay, Uday; Biswas, Kaushik; Maity, Pallab; Banerjee, Ranajit K

    2006-04-15

    We have investigated the mechanism of indomethacin-induced gastric ulcer caused by reactive oxygen species (ROS) and the gastroprotective effect of curcumin thereon. Curcumin dose-dependently blocks indomethacin-induced gastric lesions, showing 82% protection at 25 mg/kg. Indomethacin-induced oxidative damage by ROS as shown by increased lipid peroxidation and thiol depletion is almost completely blocked by curcumin. Indomethacin causes nearly fivefold increase in hydroxyl radical (()OH) and significant inactivation of gastric mucosal peroxidase to elevate endogenous H(2)O(2) and H(2)O(2)-derived ()OH, which is prevented by curcumin. In vitro studies indicate that indomethacin inactivates peroxidase irreversibly only in presence of H(2)O(2) by acting as a suicidal substrate. 5,5-Dimethyl-pyrroline-N-oxide (DMPO) protects the peroxidase, indicating involvement of indomethacin radical in the inactivation. Indomethacin radical was also detected in the peroxidase-indomethacin-H(2)O(2) system as DMPO adduct (a(N) = 15 G, a(beta)(H) = 16 G) by electron spin resonance spectroscopy. Curcumin protects the peroxidase in a concentration-dependent manner and consumes H(2)O(2) for its oxidation as a suitable substrate of the peroxidase, thereby blocking indomethacin oxidation. Curcumin can also scavenge ()OH in vitro. We suggest that curcumin protects gastric damage by efficient removal of H(2)O(2) and H(2)O(2) -derived ()OH by preventing peroxidase inactivation by indomethacin.

  19. Kinetic and structural characterization of caspase-3 and caspase-8 inhibition by a novel class of irreversible inhibitors

    SciTech Connect

    Wang, Zhigang; Watt, William; Brooks, Nathan A.; Harris, Melissa S.; Urban, Jan; Boatman, Douglas; McMillan, Michael; Kahn, Michael; Heinrikson, Robert L.; Finzel, Barry C.; Wittwer, Arthur J.; Blinn, James; Kamtekar, Satwik; Tomasselli, Alfredo G.

    2010-09-17

    Because of their central role in programmed cell death, the caspases are attractive targets for developing new therapeutics against cancer and autoimmunity, myocardial infarction and ischemic damage, and neurodegenerative diseases. We chose to target caspase-3, an executioner caspase, and caspase-8, an initiator caspase, based on the vast amount of information linking their functions to diseases. Through a structure-based drug design approach, a number of novel {beta}-strand peptidomimetic compounds were synthesized. Kinetic studies of caspase-3 and caspase-8 inhibition were carried out with these urazole ring-containing irreversible peptidomimetics and a known irreversible caspase inhibitor, Z-VAD-fmk. Using a stopped-flow fluorescence assay, we were able to determine individual kinetic parameters of caspase-3 and caspase-8 inhibition by these inhibitors. Z-VAD-fmk and the peptidomimetic inhibitors inhibit caspase-3 and caspase-8 via a three-step kinetic mechanism. Inhibition of both caspase-3 and caspase-8 by Z-VAD-fmk and of caspase-3 by the peptidomimetic inhibitors proceeds via two rapid equilibrium steps followed by a relatively fast inactivation step. However, caspase-8 inhibition by the peptidomimetics goes through a rapid equilibrium step, a slow-binding reversible step, and an extremely slow inactivation step. The crystal structures of inhibitor complexes of caspases-3 and -8 validate the design of the inhibitors by illustrating in detail how they mimic peptide substrates. One of the caspase-8 structures also shows binding at a secondary, allosteric site, providing a possible route to the development of noncovalent small molecule modulators of caspase activity.

  20. Irreversible antagonism of 5HT2c receptors by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ).

    PubMed

    Ni, Y G; Camacho, N; Miledi, R

    1997-03-18

    To determine if N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), a carboxyl group activating agent, can inactivate 5HT2c receptors, we have examined the effects of EEDQ on 5HT2c receptor-mediated responses to 5-hydroxytryptamine (5HT) in Xenopus oocytes, and on the binding of [3H]5HT to 5HT2c receptors in transfected HeLa cells. In oocytes expressing rat 5HT2c receptors, EEDQ inhibited the 5HT2c receptor-mediated Cl- currents; and the response did not recover more than 24 h after removal of the EEDQ. To see if this effect of EEDQ was on the receptor itself, the binding of 5HT to 5HT2c receptors was studied in transfected HeLa cells. EEDQ decreased the specific binding of [3H]5HT to 5HT2c receptors. At approximately 22 degrees C, incubating the membranes with 2 x 10(-4) M EEDQ for 1 h caused a 40% decrease in the Bmax, without changing the K(d). At 37 degrees C, the same treatment with EEDQ blocked [3H]5HT binding completely. Half-maximal inhibition occurred at 5 microM EEDQ at both temperatures, and washing for 1.5 h did not restore the binding, suggesting that the inactivation of 5HT2c receptor binding was practically irreversible. Results from both systems showed clearly that EEDQ is an irreversible antagonist of 5HT2c receptors and therefore can be used for many studies of this receptor.

  1. BNNT-mediated irreversible electroporatio: its potential on cancer cells

    SciTech Connect

    Vittoria Raffa, Cristina Riggio, Michael W. Smith, Kevin C. Jordan, Wei Cao, Alfred Cuschieri

    2012-10-01

    Tissue ablation, i.e., the destruction of undesirable tissues, has become an important minimally invasive technique alternative to resection surgery for the treatment of tumours. Several methods for tissue ablation are based on thermal techniques using cold, e.g. cryosurgery [1] or heat, e.g. radiofrequency [2] or high-intensity focused ultrasound [3] or nanoparticle-mediated irradiation [4]. Alternatively, irreversible electroporation (IRE) has been proposed as non thermal technique for minimally invasive tissue ablation based on the use of electrical pulses. When the electric field is applied to a cell, a change in transmembrane potential is induced, which can cause biochemical and physiological changes of the cell. When the threshold value of the transmembrane potential is exceeded, the cell membrane becomes permeable, thus allowing entrance of molecules that otherwise cannot cross the membrane [5]. A further increase in the electric field intensity may cause irreversible membrane permeabilization and cell death. These pulses create irreversible defects (pores) in the cell membrane lipid bilayer, causing cell death through loss of cell homeostasis [6]. This is desirable in tumour ablation in order to produce large cell death, without the use of cytostatic drugs. A study of Davalos, Mir and Rubinsky showed that IRE can ablate substantial volumes of tissue without inducing a thermal effect and therefore serve as an independent and new tissue ablation modality; this opened the way to the use of IRE in surgery [7]. Their finding was subsequently confirmed in studies on cells [8], small animal models [9] and in large animal models in the liver [10] and the heart [11]. The most important finding in these papers is that irreversible electroporation produces precisely delineated ablation zones with cell scale resolution between ablated and non-ablated areas, without zones in which the extent of damage changes gradually as during thermal ablation. Furthermore, it is

  2. A dielectric barrier discharge terminally inactivates RNase A by oxidizing sulfur-containing amino acids and breaking structural disulfide bonds

    NASA Astrophysics Data System (ADS)

    Lackmann, J.-W.; Baldus, S.; Steinborn, E.; Edengeiser, E.; Kogelheide, F.; Langklotz, S.; Schneider, S.; Leichert, L. I. O.; Benedikt, J.; Awakowicz, P.; Bandow, J. E.

    2015-12-01

    RNases are among the most stable proteins in nature. They even refold spontaneously after heat inactivation, regaining full activity. Due to their stability and universal presence, they often pose a problem when experimenting with RNA. We investigated the capabilities of nonthermal atmospheric-pressure plasmas to inactivate RNase A and studied the inactivation mechanism on a molecular level. While prolonged heating above 90 °C is required for heat inactivating RNase A, direct plasma treatment with a dielectric barrier discharge (DBD) source caused permanent inactivation within minutes. Circular dichroism spectroscopy showed that DBD-treated RNase A unfolds rapidly. Raman spectroscopy indicated methionine modifications and formation of sulfonic acid. A mass spectrometry-based analysis of the protein modifications that occur during plasma treatment over time revealed that methionine sulfoxide formation coincides with protein inactivation. Chemical reduction of methionine sulfoxides partially restored RNase A activity confirming that sulfoxidation is causal and sufficient for RNase A inactivation. Continued plasma exposure led to over-oxidation of structural disulfide bonds. Using antibodies, disulfide bond over-oxidation was shown to be a general protein inactivation mechanism of the DBD. The antibody’s heavy and light chains linked by disulfide bonds dissociated after plasma exposure. Based on their ability to inactivate proteins by oxidation of sulfur-containing amino acids and over-oxidation of disulfide bonds, DBD devices present a viable option for inactivating undesired or hazardous proteins on heat or solvent-sensitive surfaces.

  3. Heat inactivation of enteric viruses in dewatered wastewater sludge.

    PubMed

    Ward, R L; Ashley, C S

    1978-12-01

    The effect of moisture content on the rates of heat inactivation of enteric viruses in wastewater sludge was determined. The protective effect of raw sludge on poliovirus previously observed (R. L. Ward, C. S. Ashley, and R. H. Moseley, Appl. Environ. Microbiol. 32:339--346, 1976) was found to be greatly enhanced in sludge dewatered by evaporation. Other enteroviruses responded in a similar fashion. This effect did not appear to be due merely to the state of dryness of the sludge samples because in humus-deficient soil, a relatively inert material, the rate of poliovirus inactivation by heat was not significantly altered through dewatering. Instead, this effect appeared to have been caused by protective substances in the sludge, such as detergents, which are concentrated through dewatering. As reported previously (R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol. 34:681-688, 1977; R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol 36:889--897, 1978) raw sludge is not protective of reovirus, but, instead, the ionic detergents in sludge cause the rate of heat inactivation of this virus to be accelerated. Dewatering of sludge, however, was found to partially reverse this virucidal effect. Evidence is presented indicating that this reversal is caused by an unidentified protective substance in sludge also concentrated through dewatering. Finally, it was shown that the effects of raw sludge on heat inactivation of poliovirus and reovirus are greatly reduced by composting, a result that correlated with the degradation of detergents.

  4. Skewed X inactivation in Lesch-Nyhan disease carrier females.

    PubMed

    Torres, Rosa J; Puig, Juan G

    2017-09-14

    X chromosome inactivation (XCI) ratios of normal females can range from a highly skewed ratio of 0:100 to a 50:50 ratio. In several X-linked disorders, female carriers present skewed X inactivation. Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency is an X-linked disorder. Males are affected and present with the complete Lesch-Nyhan disease (LND) or with a partial phenotype (Lesch-Nyhan variant, LNV). Female carriers are usually asymptomatic. The aim of the present study was to analyze the XCI pattern of HPRT-deficiency carrier females. As a group, 75% of HPRT-deficiency carrier females presented skewed XCI. Moreover, skewed XCI is significantly more frequent in LND carriers (83%) than in LNV (0-50%, depending on the phenotype severity). The ratios of the preferentially inactivated allele of carrier females were significantly higher than the ratios of the preferentially inactivated allele of noncarrier females (89.4±15, n=52 vs 65.2±12, n=52; P<0.0001). For carrier diagnosis, the presence of skewed XCI presents a sensitivity of 75% with a specificity of 85%. In LND families, the presence of skewed XCI is more sensitive for carrier diagnosis than in LNV families; however, we believe that this test is not accurate for carrier diagnostic purposes.Journal of Human Genetics advance online publication, 14 September 2017; doi:10.1038/jhg.2017.88.

  5. Inactivation of enveloped virus by laser-driven protein aggregation

    NASA Astrophysics Data System (ADS)

    Tsen, Shaw-Wei D.; Chapa, Travis; Beatty, Wandy; Tsen, Kong-Thon; Yu, Dong; Achilefu, Samuel

    2012-12-01

    Ultrafast lasers in the visible and near-infrared range have emerged as a potential new method for pathogen reduction of blood products and pharmaceuticals. However, the mechanism of enveloped virus inactivation by this method is unknown. We report the inactivation as well as the molecular and structural effects caused by visible (425 nm) femtosecond laser irradiation on murine cytomegalovirus (MCMV), an enveloped, double-stranded DNA virus. Our results show that laser irradiation (1) caused a 5-log reduction in MCMV titer, (2) did not cause significant changes to the global structure of MCMV virions including membrane and capsid, as assessed by electron microscopy, (3) produced no evidence of double-strand breaks or crosslinking in MCMV genomic DNA, and (4) caused selective aggregation of viral capsid and tegument proteins. We propose a model in which ultrafast laser irradiation induces partial unfolding of viral proteins by disrupting hydrogen bonds and/or hydrophobic interactions, leading to aggregation of closely associated viral proteins and inactivation of the virus. These results provide new insight into the inactivation of enveloped viruses by visible femtosecond lasers at the molecular level, and help pave the way for the development of a new ultrafast laser technology for pathogen reduction.

  6. Structural mechanism of C-type inactivation in K(+) channels.

    PubMed

    Cuello, Luis G; Jogini, Vishwanath; Cortes, D Marien; Perozo, Eduardo

    2010-07-08

    Interconversion between conductive and non-conductive forms of the K(+) channel selectivity filter underlies a variety of gating events, from flicker transitions (at the microsecond timescale) to C-type inactivation (millisecond to second timescale). Here we report the crystal structure of the Streptomyces lividans K(+) channel KcsA in its open-inactivated conformation and investigate the mechanism of C-type inactivation gating at the selectivity filter from channels 'trapped' in a series of partially open conformations. Five conformer classes were identified with openings ranging from 12 A in closed KcsA (Calpha-Calpha distances at Thr 112) to 32 A when fully open. They revealed a remarkable correlation between the degree of gate opening and the conformation and ion occupancy of the selectivity filter. We show that a gradual filter backbone reorientation leads first to a loss of the S2 ion binding site and a subsequent loss of the S3 binding site, presumably abrogating ion conduction. These structures indicate a molecular basis for C-type inactivation in K(+) channels.

  7. Inactivation of an astrovirus associated with poult enteritis mortality syndrome.

    PubMed

    Schultz-Cherry, S; King, D J; Koci, M D

    2001-01-01

    Outbreaks of poult enteritis mortality syndrome (PEMS) continue to cause financial losses to the turkey industry. Clinically, PEMS is defined by mortality profiles, diarrhea, flock unevenness, and immunosuppression. PEMS is a very difficult disease to control and prevent. Depopulation of PEMS-affected flocks and thorough cleaning of the contaminated housing have failed to prevent infection (disease) in subsequent flock placements. The relationship of PEMS to other enteric disease complexes of young turkeys is unknown, partly because the causative agent of PEMS remains unknown. Recently, we isolated a unique astrovirus strain from the thymus and intestines of PEMS-infected poults. This strain is molecularly and serologically distinct from the astrovirus that circulated in turkeys in the 1980s. Mammalian astroviruses are very resistant to inactivation. In these studies, we examined the stability of partially purified PEMS-associated astrovirus to inactivation with heat, laboratory disinfectants, and commercial disinfectants used in commercial turkey houses in an embryonated egg model system. Similar to mammalian astroviruses, the PEMS-associated astrovirus is resistant to inactivation by heat, acidification, detergent treatment, and treatment with phenolic, quaternary ammonium, or benzalkonium chloride-based products. Only treatment with formaldehyde, beta-propriolactone, or the peroxymonosulfate-based product Virkon S completely inactivated the astrovirus in the embryo model. These studies provide an alternate means to potentially control at least one virus associated with PEMS through the use of specific disinfectants.

  8. Structural mechanism of C-type inactivation in K+ channels

    PubMed Central

    Cuello, Luis G.; Jogini, Vishwanath; Cortes, D. Marien; Perozo, Eduardo

    2011-01-01

    Interconversion between conductive and non-conductive forms of the K+ channel selectivity filter underlies a variety of gating events, from flicker transitions (μs) to C-type inactivation (ms-s). Here, we report the crystal structure of the K+ channel KcsA in its Open-Inactivated conformation and investigate the mechanism of C-type inactivation gating at the selectivity filter from channels “trapped” in a series of partially open conformations. Five conformer classes were identified with openings ranging, from 12 Å in closed KcsA (Cα-Cα distances at T112) to 32 Å when fully open. They revealed a remarkable correlation between the degree of gate opening and the conformation and ion occupancy of the selectivity filter. We show that a gradual filter backbone reorientation leads first, to a loss of the S2 ion binding site and a subsequent loss of the S3 binding site, presumably abrogating ion conduction. These structures suggest a molecular basis for C-type inactivation in K+ channels. PMID:20613835

  9. CRYPTOSPORIDIUM LOG INACTIVATION CALCULATION METHODS

    EPA Science Inventory

    Appendix O of the Surface Water Treatment Rule (SWTR) Guidance Manual introduces the CeffT10 (i.e., reaction zone outlet C value and T10 time) method for calculating ozone CT value and Giardia and virus log inactivation. The LT2ESWTR Pre-proposal Draft Regulatory Language for St...

  10. CRYPTOSPORIDIUM LOG INACTIVATION CALCULATION METHODS

    EPA Science Inventory

    Appendix O of the Surface Water Treatment Rule (SWTR) Guidance Manual introduces the CeffT10 (i.e., reaction zone outlet C value and T10 time) method for calculating ozone CT value and Giardia and virus log inactivation. The LT2ESWTR Pre-proposal Draft Regulatory Language for St...

  11. Flux pinning characteristics and irreversibility line in high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Matsushita, T.; Ihara, N.; Kiuchi, M.

    1995-01-01

    The flux pinning properties in high temperature superconductors are strongly influenced by thermally activated flux motion. The scaling relation of the pinning force density and the irreversibility line in various high temperature superconductors are numerically analyzed in terms of the flux creep model. The effect of two factors, i.e., the flux pinning strength and the dimensionality of the material, on these properties are investigated. It is speculated that the irreversibility line in Bi-2212 superconductors is one order of magnitude smaller than that in Y-123, even if the flux pinning strength in Bi-2212 is improved up to the level of Y-123. It is concluded that these two factors are equally important in determination of the flux pinning characteristics at high temperatures.

  12. Irreversible adsorption of phenolic compounds by activated carbons

    SciTech Connect

    Grant, T.M.; King, C.J.

    1988-12-01

    Studies were undertaken to determine the reasons why phenolic sorbates can be difficult to remove and recover from activated carbons. The chemical properties of the sorbate and the adsorbent surface, and the influences of changes in the adsorption and desorption conditions were investigated. Comparison of isotherms established after different contact times or at different temperatures indicated that phenolic compounds react on carbon surfaces. The reaction rate is a strong function of temperature. Regeneration of carbons by leaching with acetone recovered at least as much phenol as did regeneration with other solvents or with displacers. The physiochemical properties of adsorbents influences irreversible uptakes. Sorbates differed markedly in their tendencies to undergo irreversible adsorption. 64 refs., 47 figs., 32 tabs.

  13. Reversible and Irreversible Time-Dependent Behavior of GRCop-84

    NASA Technical Reports Server (NTRS)

    Lerch, Bradley A.; Arnold, Steven M.; Ellis, David L.

    2017-01-01

    A series of mechanical tests were conducted on a high-conductivity copper alloy, GRCop-84, in order to understand the time dependent response of this material. Tensile, creep, and stress relaxation tests were performed over a wide range of temperatures, strain rates, and stress levels to excite various amounts of time-dependent behavior. At low applied stresses the deformation behavior was found to be fully reversible. Above a certain stress, termed the viscoelastic threshold, irreversible deformation was observed. At these higher stresses the deformation was observed to be viscoplastic. Both reversible and irreversible regions contained time dependent deformation. These experimental data are documented to enable characterization of constitutive models to aid in design of high temperature components.

  14. Elucidating the mechanism behind irreversible deformation of viral capsids.

    PubMed

    Arkhipov, Anton; Roos, Wouter H; Wuite, Gijs J L; Schulten, Klaus

    2009-10-07

    Atomic force microscopy has recently provided highly precise measurements of mechanical properties of various viruses. However, molecular details underlying viral mechanics remain unresolved. Here we report atomic force microscopy nanoindentation experiments on T=4 hepatitis B virus (HBV) capsids combined with coarse-grained molecular dynamics simulations, which permit interpretation of experimental results at the molecular level. The force response of the indented capsid recorded in simulations agrees with experimental observations. In both experiment and simulation, irreversible capsid deformation is observed for deep indentations. Simulations show the irreversibility to be due to local bending and shifting of capsid proteins, rather than their global rearrangement. These results emphasize the viability of large capsid deformations without significant changes of the mutual positions of HBV capsid proteins, in contrast to the stiffer capsids of other viruses, which exhibit more extensive contacts between their capsid proteins than seen in the case of HBV.

  15. Overcoming of energy barrier for irreversible magnetization in nanocomposite magnets

    NASA Astrophysics Data System (ADS)

    Li, Zhu-bai; Zhang, Ying; Shen, Bao-gen; Zhang, Ming; Hu, Feng-xia; Sun, Ji-rong

    2017-01-01

    The irreversible magnetization occurs mainly in hard grains in nanocomposite magnets, and the domain wall involves a little part of defect region in irreversible magnetization due to the self-interaction. The investigation on thermal activation shows that the defect region involved in domain wall becomes narrower due to the TiNb addition in Pr2Fe14B/α-Fe magnets. The defect region augments the energy density in the negative direction of domain wall to overcome the energy barrier of perfect hard region. The soft phase, exchange-coupled with defect region at hard grain outer-layer, promotes magnetization reversal in defect region by exchange coupling. While the defect region plays a role as a ladder to overcome the energy barrier, resulting in the decrease of coecivity more or less depending upon the width and anisotropy of defect region.

  16. Reversible and irreversible interactions between elastin and plasma lipoproteins.

    PubMed

    Winlove, C P; Parker, K H; Ewins, A R

    1985-03-08

    The interactions between radiolabeled, human plasma lipoproteins and elastin derived from bovine ligamentum nuchae were investigated using a washout technique. The interaction was characterised by Ki, a coefficient of irreversible binding, and Kr, the reversible partition coefficient. For both low-density lipoproteins (LDL) and high-density lipoproteins (HDL) the Ki values decreased as total lipoprotein concentration increased, suggesting that the binding is saturable, and were similar in magnitude to those measured by other workers using elastin derived from the human aorta. For both LDL and HDL the Kr values were independent of lipoprotein concentration in the range 0.1 microgram/ml-1.5 micrograms/ml. At a total protein concentration of 1.5 mg/ml in the incubation medium, the reversible interactions were comparable in magnitude to the irreversible.

  17. Thermoeconomic analysis of an irreversible Stirling heat pump cycle

    NASA Astrophysics Data System (ADS)

    Lucia, U.; Gervino, G.

    2006-03-01

    In this paper an analysis of the Stirling cycle in thermoeconomic terms is developed using the entropy generation. In the thermoeconomic optimization of an irreversible Stirling heat pump cycle the F function has been introduced to evaluate the optimum for the higher and lower sources temperature ratio in the cycle: this ratio represents the value which optimizes the cycle itself. The variation of the function F is proportional to the variation of the entropy generation, the maxima and minima of F has been evaluated in a previous paper without giving the physical foundation of the method. We investigate the groundwork of this approach: to study the upper and lower limits of F function allows to determine the cycle stability and the optimization conditions. The optimization consists in the best COP at the least cost. The principle of maximum variation for the entropy generation becomes the analytic foundation of the optimization method in the thermoeconomic analysis for an irreversible Stirling heat pump cycle.

  18. Prostaglandin E2 to diagnose between reversible and irreversible pulpitis.

    PubMed

    Petrini, M; Ferrante, M; Ciavarelli, L; Brunetti, L; Vacca, M; Spoto, G

    2012-01-01

    The aim of this work is to verify a correlation between the grade of inflammation and the concentration of PGE2 in human dental pulp. A total of 25 human dental pulps were examined by histological analysis and radioimmunologic dosage of PGE2. The pulps used in this experiment were from healthy and symptomatic teeth; the first ones were collected from teeth destined to be extracted for orthodontic reasons. An increase was observed of PGE2 in reversible pulpitis compared with healthy pulps and with the irreversible pulpitis and the clear decrease of these when NSAIDs are taken. This study demonstrates that PGE2 level is correlated to histological analysis thus allowing to distinguish symptomatic teeth in reversible and irreversible pulpitis.

  19. Irreversible sortase A-mediated ligation driven by diketopiperazine formation.

    PubMed

    Liu, Fa; Luo, Ethan Y; Flora, David B; Mezo, Adam R

    2014-01-17

    Sortase A (SrtA)-mediated ligation has emerged as an attractive tool in bioorganic chemistry attributing to the remarkable specificity of the ligation reaction and the physiological reaction conditions. However, the reversible nature of this reaction limits the efficiency of the ligation reaction and has become a significant constraint to its more widespread use. We report herein a novel set of SrtA substrates (LPETGG-isoacyl-Ser and LPETGG-isoacyl-Hse) that can be irreversibly ligated to N-terminal Gly-containing moieties via the deactivation of the SrtA-excised peptide fragment through diketopiperazine (DKP) formation. The convenience of the synthetic procedure and the stability of the substrates in the ligation buffer suggest that both LPETGG-isoacyl-Ser and LPETGG-isoacyl-Hse are valuable alternatives to existing irreversible SrtA substrate sequences.

  20. Aftereffect in rocks caused by preexisting irreversible deformations

    SciTech Connect

    Stavrogin, A.N.; Shirkes, O.A.

    1987-05-01

    In this paper, rock specimens cut as cores of a diameter of 30 mm, 80 mm in length, were subjected to irreversible deformation in a high hydrostatic pressure chamber according to Karman's procedure. The types of rocks investigated were white Koelga marble, non-burst-hazardous (NBH) sandstone from Donets Basin, limestone from Estonslanets deposit and brown coal from Shurab coal deposit. Marble specimens were subjected to the most extensive studies. The aftereffect curves are shown for each type of rock studied. Aftereffect deformations of rocks are basically creep flows occurring under the effect of residual stresses introduced into the rock material on the course of its irreversible deformation by a high hydrostatic pressure, according to the authors. The physical nature of the residual stresses in the rocks and the mechanism of their creation are examined at the level of structural elements (grains or crystals).

  1. INACTIVATION OF CRYPTOSPORIDIUM PARVUM OOCYSTS WITH OZONE

    EPA Science Inventory

    Ozone inactivation rates for Cryptosporidium parvum (C. parvum) oocysts were determined with an in-vitro excystation method based on excysted sporozoite counts. Results were consistent with published animal infectivity data for the same C. parvum strain. The inactivation kinetics...

  2. INACTIVATION OF CRYPTOSPORIDIUM PARVUM OOCYSTS WITH OZONE

    EPA Science Inventory

    Ozone inactivation rates for Cryptosporidium parvum (C. parvum) oocysts were determined with an in-vitro excystation method based on excysted sporozoite counts. Results were consistent with published animal infectivity data for the same C. parvum strain. The inactivation kinetics...

  3. Determination of Time Dependent Virus Inactivation Rates

    NASA Astrophysics Data System (ADS)

    Chrysikopoulos, C. V.; Vogler, E. T.

    2003-12-01

    A methodology is developed for estimating temporally variable virus inactivation rate coefficients from experimental virus inactivation data. The methodology consists of a technique for slope estimation of normalized virus inactivation data in conjunction with a resampling parameter estimation procedure. The slope estimation technique is based on a relatively flexible geostatistical method known as universal kriging. Drift coefficients are obtained by nonlinear fitting of bootstrap samples and the corresponding confidence intervals are obtained by bootstrap percentiles. The proposed methodology yields more accurate time dependent virus inactivation rate coefficients than those estimated by fitting virus inactivation data to a first-order inactivation model. The methodology is successfully applied to a set of poliovirus batch inactivation data. Furthermore, the importance of accurate inactivation rate coefficient determination on virus transport in water saturated porous media is demonstrated with model simulations.

  4. Variability of Irreversible Poleward Transport in the Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Olsen, Mark; Douglass, Anne; Newman, Paul; Nash, Eric; Witte, Jacquelyn; Ziemke, Jerry

    2011-01-01

    The ascent and descent of the Brewer-Dobson circulation plays a large role in determining the distributions of many constituents in the extratropical lower stratosphere. However, relatively fast, quasi-horizontal transport out of the tropics and polar regions also significantly contribute to determining these distributions. The tropical tape recorder signal assures that there must be outflow from the tropics into the extratropical lower stratosphere. The phase of the quasi-biennial oscillation (QBO) and state of the polar vortex are known to modulate the transport from the tropical and polar regions, respectively. In this study we examine multiple years of ozone distributions in the extratropical lower stratosphere observed by the Aura Microwave Limb Sounder (MLS) and the Aura High Resolution Dynamic Limb Sounder (HIRDLS). The distributions are compared with analyses of irreversible, meridional isentropic transport. We show that there is considerable year-to-year seasonal variability in the amount of irreversible transport from the tropics, which is related to both the phase of the QBO and the state of the polar vortex. The reversibility of the transport is consistent with the number of observed breaking waves. The variability of the atmospheric index of refraction in the lower stratosphere is shown to be significantly correlated with the wave breaking and amount of irreversible transport. Finally, we will show that the seasonal extratropical stratosphere to troposphere transport of ozone can be substantially modulated by the amount of irreversible meridional transport in the lower stratosphere and we investigate how observable these differences are in data of tropospheric ozone.

  5. Entropy production and irreversibility of dissipative trajectories in electric circuits

    NASA Astrophysics Data System (ADS)

    Chiang, K.-H.; Lee, C.-L.; Lai, P.-Y.; Chen, Y.-F.

    2017-01-01

    We experimentally examine the equivalence between the entropy production evaluated from irreversibility of trajectories and the physical dissipation in dissipative processes via electric resistor-capacitor (RC) circuits. The examinations are performed for two nonequilibrium steady states that are driven by an injected current and temperature difference, respectively. Such an equivalence demonstrates a parameter-free method to evaluate the entropy production of a system. The effects of configurational and temporal resolutions are also studied.

  6. The State of Irreversible Electroporation in Interventional Oncology

    PubMed Central

    Silk, Mikhail; Tahour, David; Srimathveeravalli, Govindarajan; Solomon, Stephen B.; Thornton, Raymond H.

    2014-01-01

    A new ablation modality, irreversible electroporation (IRE), has been of increasing interest in interventional radiology. Its nonthermal mechanism of action of killing tumor cells allows physicians the ability to ablate tumors in areas previously contraindicated for thermal ablation. This article reviews the current published clinical outcomes, imaging follow-up, and the current knowledge gaps in the procedure for patients treated with IRE. PMID:25053862

  7. Irreversibility and chaos: role of lubrication interactions in sheared suspensions.

    PubMed

    Metzger, Bloen; Pham, Phong; Butler, Jason E

    2013-05-01

    We investigate non-Brownian particles suspended in a periodic shear-flow using simulations. Following Metzger and Butler [Phys. Rev. E 82, 051406 (2010)], we show that the chaotic dynamics arising from lubrication interactions are too weak to generate an observable particle dispersion. The irreversibility observed in periodic flow is dominated by contact interactions. Nonetheless, we show that lubrication interactions must be included in the calculation to obtain results that agree with experiments.

  8. Entropy production and irreversibility of dissipative trajectories in electric circuits.

    PubMed

    Chiang, K-H; Lee, C-L; Lai, P-Y; Chen, Y-F

    2017-01-01

    We experimentally examine the equivalence between the entropy production evaluated from irreversibility of trajectories and the physical dissipation in dissipative processes via electric resistor-capacitor (RC) circuits. The examinations are performed for two nonequilibrium steady states that are driven by an injected current and temperature difference, respectively. Such an equivalence demonstrates a parameter-free method to evaluate the entropy production of a system. The effects of configurational and temporal resolutions are also studied.

  9. Spontaneous subtalar fusion: an irreversible complication of subtalar arthroereisis.

    PubMed

    Lui, Tun Hing

    2014-01-01

    Subtalar arthroereisis has been used for the treatment of symptomatic flexible flatfoot deformities in both pediatric and adult patients. Chronic sinus tarsi pain is the most common complication of this procedure and can be relieved by removal of the implant. We describe a case of spontaneous fusion of the subtalar joint after arthroereisis. This is an irreversible complication that should be described to the patient as a rare, but possible, outcome of arthroereisis of the subtalar joint.

  10. Irreversible Electroporation for Focal Ablation at the Porta Hepatis

    SciTech Connect

    Kasivisvanathan, Veeru; Thapar, Ankur Oskrochi, Youssof; Picard, John; Leen, Edward L. S.

    2012-12-15

    Patients with chemotherapy-refractory liver metastases who are not candidates for surgery may be treated with focal ablation techniques with established survival benefits. Irreversible electroporation is the newest of these and has the putative advantages of a nonthermal action, preventing damage to adjacent biliary structures and bowel. This report describes the use of irreversible electroporation in a 61-year-old man with a solitary chemoresistant liver metastasis unsuitable for radiofrequency ablation as a result of its proximity to the porta hepatis. At 3 months, tumor size was decreased on computed tomography from 28 Multiplication-Sign 19 to 20 Multiplication-Sign 17 mm, representing stable disease according to the response evaluation criteria in solid tumors. This corresponded to a decrease in tumor volume size from 5.25 to 3.16 cm{sup 3}. There were no early or late complications. Chemoresistant liver metastases in the proximity of the porta hepatis that are considered to be too high a risk for conventional surgery or thermal ablation may be considered for treatment by the novel ablation technique of irreversible electroporation.

  11. Irreversibility in energy processes: Non-dimensional quantification and balance

    NASA Astrophysics Data System (ADS)

    Pons, Michel

    2004-06-01

    The concept of thermodynamic efficiency (ratio of real cycle efficiency by Carnot efficiency) is well-known. The concept of numbers of entropy-production and of exergy-loss proposed by A. Bejan are also known, but rarely used. The present study firstly evidences that these two last numbers are actually identical, thus being a common number of irreversibility, independent of the method used for obtaining it. The study also evidences a non-dimensional irreversibility balance that applies to any energy conversion process. This balance correlates the thermodynamic efficiency of a whole process (which in most cases equals the exergetic efficiency) and the numbers of irreversibility of the different components or sub-processes involved in this process. Moreover, the basic additivity of entropy-productions and exergy-losses is maintained in this balance. This balance applies to the basic cycles (heat-engines, refrigerators, heat-pumps and heat-transformers), either work- or heat-powered. It also applies to more complex cycles (heat-powered cycles consuming electricity, four-temperature heat-powered cycles, cogeneration processes), thus giving a robust framework for analyzing these cycles.

  12. Irreversibility and complex network behavior of stream flow fluctuations

    NASA Astrophysics Data System (ADS)

    Serinaldi, Francesco; Kilsby, Chris G.

    2016-05-01

    Exploiting the duality between time series and networks, directed horizontal visibility graphs (DHVGs) are used to perform an unprecedented analysis of the dynamics of stream flow fluctuations with focus on time irreversibility and long range dependence. The analysis relies on a large quality-controlled data set consisting of 699 daily time series recorded in the continental United States (CONUS) that are not affected by human activity and primarily reflects meteorological conditions. DHVGs allow a clear visualization and quantification of time irreversibility of flow dynamics, which can be interpreted as a signature of nonlinearity, and long range dependence resulting from the interaction of atmospheric, surface and underground processes acting at multiple spatio-temporal scales. Irreversibility is explored by mapping the time series into ingoing, outgoing, and undirected graphs and comparing the corresponding degree distributions. Using surrogate data preserving up to the second order linear temporal dependence properties of the observed series, DHVGs highlight the additional complexity introduced by nonlinearity into flow fluctuation dynamics. We show that the degree distributions do not decay exponentially as expected, but tend to follow a subexponential behavior, even though sampling uncertainty does not allow a clear distinction between apparent or true power law decay. These results confirm that the complexity of stream flow dynamics goes beyond a linear representation involving for instance the combination of linear processes with short and long range dependence, and requires modeling strategies accounting for temporal asymmetry and nonlinearity.

  13. Anesthetic Efficacy in Irreversible Pulpitis: A Randomized Clinical Trial.

    PubMed

    Allegretti, Carlos E; Sampaio, Roberta M; Horliana, Anna C R T; Armonia, Paschoal L; Rocha, Rodney G; Tortamano, Isabel Peixoto

    2016-01-01

    Inferior alveolar nerve block has a high failure rate in the treatment of mandibular posterior teeth with irreversible pulpitis. The aim of this study was to compare the anesthetic efficacy of 4% articaine, 2% lidocaine and 2% mepivacaine, all in combination with 1:100,000 epinephrine, in patients with irreversible pulpitis of permanent mandibular molars during a pulpectomy procedure. Sixty-six volunteers from the Emergency Center of the School of Dentistry, University of São Paulo, randomly received 3.6 mL of local anesthetic as a conventional inferior alveolar nerve block (IANB). The subjective signal of lip numbness, pulpal anesthesia and absence of pain during the pulpectomy procedure were evaluated respectively, by questioning the patient, stimulation using an electric pulp tester and a verbal analogue scale. All patients reported the subjective signal of lip numbness. Regarding pulpal anesthesia success as measured with the pulp tester, the success rate was respectively 68.2% for mepivacaine, 63.6% for articaine and 63.6% for lidocaine. Regarding patients who reported no pain or mild pain during the pulpectomy, the success rate was, respectively 72.7% for mepivacaine, 63.6% for articaine and 54.5% for lidocaine. These differences were not statistically significant. Neither of the solutions resulted in 100% anesthetic success in patients with irreversible pulpitis of mandibular molars.

  14. Developing irreversible inhibitors of the protein kinase cysteinome

    PubMed Central

    Liu, Qingsong; Sabnis, Yogesh; Zhao, Zheng; Zhang, Tinghu; Buhrlage, Sara J.; Jones, Lyn H.; Gray, Nathanael S.

    2013-01-01

    Protein kinases are a large family of approximately 530 highly conserved enzymes that transfer a γ-phosphate group from ATP to a variety of amino acid residues such as tyrosine, serine and threonine which serves as a ubiquitous mechanism for cellular signal transduction. The clinical success of a number of kinase-directed drugs and the frequent observation of disease causing mutations in protein kinases suggest that a large number of kinases may represent therapeutically relevant targets. To-date the majority of clinical and preclinical kinase inhibitors are ATP-competitive, non-covalent inhibitors that achieve selectivity through recognition of unique features of particular protein kinases. Recently there has been renewed interest in the development of irreversible inhibitors that form covalent bonds with cysteine or other nucleophilic residues in the ATP-binding pocket. Irreversible kinase inhibitors have a number of potential advantages including prolonged pharmacodynamics, suitability for rational design, high potency and ability to validate pharmacological specificity through mutation of the reactive cysteine residue. Here we review recent efforts to develop cysteine-targeted irreversible protein kinase inhibitors and discuss their modes of recognizing the ATP-binding pocket and their biological activity profiles. In addition, we provided an informatics assessment of the potential ‘kinase-cysteinome’ and discuss strategies for the efficient development of new covalent inhibitors. PMID:23438744

  15. Irreversible gelation of wormlike micelle solutions under microfluidic flow

    NASA Astrophysics Data System (ADS)

    Cheung, Perry; Cardiel, Joshua; Dubash, Neville; Shen, Amy

    2010-11-01

    The formation of flow-induced gel-like structures in surfactant solutions containing wormlike micelles have previously been observed in macroscopic flow under applied shear in dilute solutions of cetyl-trimethylammonium bromide (CTAB) and sodium salicylate (NaSal). However, the observed gelation phase transition is short-lived once the applied flow is stopped and reversibly disappears. Recently, irreversible gelation was achieved by applying high shear and extensional flows within a packed bed of microbeads in a microfluidic device [1]. We present here a further investigation of the irreversible flow-induced gelation of dilute solutions of CTAB/NaSal in microfluidic devices with microfabricated arrays of microposts with varying post diameters and inter-post spacing. The onset of gelation at various surfactant concentrations and flow rates (both shear and extension rates) will be examined to determine the extent of this phenomenon. [4pt] [1] Vasudevan, M., et al., Irreversible nanogel formation in surfactant solutions by microporous flow. Nat Mater, 2010. 9(5): p. 436-441.

  16. The problematic role of 'irreversibility' in the definition of death.

    PubMed

    Hershenov, David

    2003-02-01

    Most definitions of death--whether cardiopulmonary, whole brain and brain stem, or just upper brain--include an irreversibility condition. Cessation of function is not enough to declare death. Irreversibility should be limited to an organism's ability to 'restart' itself after vital organs have ceased to function. However, this would mean that every hour people who cannot be revived without the intervention of medical personnel and their technology are coming back from the dead. However, the alternative of irreversibility being dependent upon technology will lead to even more counterintuitive results such as: some people are dead at a particular time and place, but others in more technologically advanced eras and locations are alive despite their being in identical physical states; in the future, millions of cryogeneically frozen human beings could spend centuries in a non-dead state because of the future technological breakthroughs; or large numbers of 'frozen' people are dead for aeons but coroners are not able to declare them so because they are unaware of what biological conditions science will never be able to reverse. So death should be defined only in non-relational biological terms, with a self-starting condition similar to that once advocated by Lawrence Becker.

  17. Thermodynamic performance optimization for an irreversible vacuum thermionic generator

    NASA Astrophysics Data System (ADS)

    Chen, Lingen; Ding, Zemin; Zhou, Junle; Wang, Wenhua; Sun, Fengrui

    2017-07-01

    Theoretical model of an irreversible vacuum thermionic generator considering external and internal finite rate heat transfer is established in this paper. By assuming radiative heat transfer processes, the general expressions of performance parameters are derived based on non-equilibrium thermodynamics and finite-time thermodynamics (FTT). The thermodynamic performances of the irreversible thermionic device are further analyzed and optimized by using the FTT theory with multiple optimization criteria such as power output, efficiency, ecological function, and efficient power. The influences of design parameters, such as output voltage, collector work function and heat reservoir temperature, on optimal performance are analyzed in detail by numerical calculations. By properly choosing the work function and output voltage, the thermionic generator can be tuned to operate in the optimal condition with maximum power or efficiency. By comparing the device performance at different design points, the optimal operation regions of power and efficiency of the irreversible thermionic generator are determined. The obtained results are of theoretical significance for the optimal design of practical solar-powered thermionic generators.

  18. Effective Chemical Inactivation of Ebola Virus

    PubMed Central

    Haddock, Elaine; Feldmann, Friederike

    2016-01-01

    Reliable inactivation of specimens before removal from high-level biocontainment is crucial for safe operation. To evaluate efficacy of methods of chemical inactivation, we compared in vitro and in vivo approaches using Ebola virus as a surrogate pathogen. Consequently, we have established parameters and protocols leading to reliable and effective inactivation. PMID:27070504

  19. Inactivation of jack bean urease by N-ethylmaleimide: pH dependence, reversibility and thiols influence.

    PubMed

    Kot, Mirosława; Bicz, Anna

    2008-08-01

    N-Ethylmaleimide (NEM) was studied as an inactivator of jack bean urease at 25 degrees C in 20 mM phosphate buffer, pHs 6.4, 7.4, and 8.3. The inactivation was investigated by incubation procedure in the absence of a substrate. It was found that NEM acted as a time and concentration dependent inactivator of urease. The dependence of urease residual activity on the incubation time showed that the activity decreased with time until the total loss of enzyme activity. The process followed a pseudo-first-order reaction. A monophasic loss of enzyme activity was observed at pH 7.4 and 8.4, while a biphasic reaction occurred at pH 6.4. Moreover, the alkaline pH promoted the inactivation. The presence of thiol-compounds, such as L-cysteine, glutathione or dithiothreitol (DTT), in the incubation mixture significantly slowed down the rate of inactivation. The interaction test showed that the decrease of inactivation was an effect of NEM-thiol interaction that lowered NEM concentration in the incubation mixture. The reactivation of NEM-blocked urease by DTT application and multidilution did not result in an effective activity regain. The applied DTT reacted with the remaining inactivator and could stop the progress of enzyme activity loss but did not cause the reactivation. This confirmed the irreversibility of inactivation. Similar results obtained at pH 6.4, 7.4 and 8.4 indicated that the mechanism of urease inactivation by NEM was pH-independent. However, the pH value significantly influenced the process rate.

  20. Lacosamide Inhibition of Nav1.7 Voltage-Gated Sodium Channels: Slow Binding to Fast-Inactivated States.

    PubMed

    Jo, Sooyeon; Bean, Bruce P

    2017-04-01

    Lacosamide is an antiseizure agent that targets voltage-dependent sodium channels. Previous experiments have suggested that lacosamide is unusual in binding selectively to the slow-inactivated state of sodium channels, in contrast to drugs like carbamazepine and phenytoin, which bind tightly to fast-inactivated states. Using heterologously expressed human Nav1.7 sodium channels, we examined the state-dependent effects of lacosamide. Lacosamide induced a reversible shift in the voltage dependence of fast inactivation studied with 100-millisecond prepulses, suggesting binding to fast-inactivated states. Using steady holding potentials, lacosamide block was very weak at -120 mV (3% inhibition by 100 µM lacosamide) but greatly enhanced at -80 mV (43% inhibition by 100 µM lacosamide), where there is partial fast inactivation but little or no slow inactivation. During long depolarizations, lacosamide slowly (over seconds) put channels into states that recovered availability slowly (hundreds of milliseconds) at -120 mV. This resembles enhancement of slow inactivation, but the effect was much more pronounced at -40 mV, where fast inactivation is complete, but slow inactivation is not, than at 0 mV, where slow inactivation is maximal, more consistent with slow binding to fast-inactivated states than selective binding to slow-inactivated states. Furthermore, inhibition by lacosamide was greatly reduced by pretreatment with 300 µM lidocaine or 300 µM carbamazepine, suggesting that lacosamide, lidocaine, and carbamazepine all bind to the same site. The results suggest that lacosamide binds to fast-inactivated states in a manner similar to other antiseizure agents but with slower kinetics of binding and unbinding.

  1. Secreted Metalloproteinase ADAMTS-3 Inactivates Reelin.

    PubMed

    Ogino, Himari; Hisanaga, Arisa; Kohno, Takao; Kondo, Yuta; Okumura, Kyoko; Kamei, Takana; Sato, Tempei; Asahara, Hiroshi; Tsuiji, Hitomi; Fukata, Masaki; Hattori, Mitsuharu

    2017-03-22

    The secreted glycoprotein Reelin regulates embryonic brain development and adult brain functions. It has been suggested that reduced Reelin activity contributes to the pathogenesis of several neuropsychiatric and neurodegenerative disorders, such as schizophrenia and Alzheimer's disease; however, noninvasive methods that can upregulate Reelin activity in vivo have yet to be developed. We previously found that the proteolytic cleavage of Reelin within Reelin repeat 3 (N-t site) abolishes Reelin activity in vitro, but it remains controversial as to whether this effect occurs in vivo Here we partially purified the enzyme that mediates the N-t cleavage of Reelin from the culture supernatant of cerebral cortical neurons. This enzyme was identified as a disintegrin and metalloproteinase with thrombospondin motifs-3 (ADAMTS-3). Recombinant ADAMTS-3 cleaved Reelin at the N-t site. ADAMTS-3 was expressed in excitatory neurons in the cerebral cortex and hippocampus. N-t cleavage of Reelin was markedly decreased in the embryonic cerebral cortex of ADAMTS-3 knock-out (KO) mice. Importantly, the amount of Dab1 and the phosphorylation level of Tau, which inversely correlate with Reelin activity, were significantly decreased in the cerebral cortex of ADAMTS-3 KO mice. Conditional KO mice, in which ADAMTS-3 was deficient only in the excitatory neurons of the forebrain, showed increased dendritic branching and elongation in the postnatal cerebral cortex. Our study shows that ADAMTS-3 is the major enzyme that cleaves and inactivates Reelin in the cerebral cortex and hippocampus. Therefore, inhibition of ADAMTS-3 may be an effective treatment for neuropsychiatric and neurodegenerative disorders.SIGNIFICANCE STATEMENT ADAMTS-3 was identified as the protease that cleaves and inactivates Reelin in the cerebral cortex and hippocampus. ADAMTS-3 was expressed in the excitatory neurons of the embryonic and postnatal cerebral cortex and hippocampus. Cleavage by ADAMTS-3 is the major

  2. Submicromolar concentrations of zinc irreversibly reduce a calcium-dependent potassium current in rat hippocampal neurons in vitro.

    PubMed

    Sim, J A; Cherubini, E

    1990-01-01

    The action of the endogenous divalent cation zinc on Ca2+ and Ca2(+)-dependent currents was studied in rat hippocampal CA1 and CA3 neurons in vitro, by means of a single electrode voltage clamp technique. Bath application of zinc (0.5-1 microM) produced a small membrane depolarization associated with an increase in synaptic noise and cell excitability and a depression of the afterhyperpolarization following a train of action potentials. The effects on the afterhyperpolarization, could not be reversed on washout. In voltage-clamped neurons, zinc induced a steady inward current and reduced, at resting membrane potential, the peak amplitude of the outward current underlying the afterhyperpolarization, IAHP. In caesium loaded neurons (in the presence of tetrodotoxin and tetraethylammonium), zinc reduced the slow inactivating Ca2+ current activated from a holding potential of -40 mV. Similar results were observed with nickel and cobalt at comparable concentrations, with Zn2+ greater than Ni2+ greater than Co2+, in their order of potency. In contrast to nickel and cobalt the effects of zinc did not reverse on washout. These results suggest that low concentrations of zinc enhance cell excitability by reducing IAHP. In addition, zinc reduces the slow inactivating voltage-dependent Ca2+ current. The irreversible effect of this metal ion is compatible with a toxic, intracellular site of action.

  3. Similarity of and differences between the mechanisms of thermal inactivation of β-galactosidases of different origins

    NASA Astrophysics Data System (ADS)

    Atyaksheva, L. F.; Pilipenko, O. S.; Chukhrai, E. S.; Poltorak, O. M.

    2008-05-01

    A comparative study of the thermal stabilities of five β-galactosidases of different origins in buffer solutions at pH of their highest activity was performed. The thermal inactivation of these enzymes was found to occur via different mechanisms. The thermal inactivation of four β-galactosidases followed the mechanism with intermediate stages not accompanied by catalytic activity loss. The dissociative mechanism of inactivation, including the reversible dissociation of the oligomeric enzyme and the irreversible dissociation of the monomeric enzyme, was observed for bacterial ( Escherichia coli) and yeast ( Kluyveromices fragilis) β-galactosidases. The kinetic parameters of dissociative thermal inactivation of these enzymes and the stability parameters of β-galactosidases studied were determined. The latter included the critical temperature of changes in the kinetic regime of inactivation, the smallest number of intermediate stages without catalytic activity loss, the temperature of the disappearance of the induction period of thermal inactivation, and induction period duration at the given temperature (40°C).

  4. Characterization of an AM404 analogue, N-(3-hydroxyphenyl)arachidonoylamide, as a substrate and inactivator of prostaglandin endoperoxide synthase.

    PubMed

    Turman, Melissa V; Kingsley, Philip J; Marnett, Lawrence J

    2009-12-29

    N-(4-Hydroxyphenyl)arachidonoylamide (AM404) is an inhibitor of endocannabinoid inactivation that has been used in cellular and animal studies. AM404 is a derivative of arachidonic acid and has been reported to inhibit arachidonate oxygenation by prostaglandin endoperoxide synthase-1 and -2 (PGHS-1 and -2, respectively). While examining the structural requirements for inhibition of PGHS, we discovered that the meta isomer of AM404, N-(3-hydroxyphenyl)arachidonoylamide (3-HPAA), is a substrate for purified PGHS. PGHS-2 efficiently oxygenated 3-HPAA to prostaglandin and hydroxyeicosatetraenoate products. No oxidation of the phenolamide moiety was observed. 3-HPAA appeared to be converted by PGHS-1 in a similar manner; however, conversion was less efficient than that by PGHS-2. PGHS-2 was selectively, dose-dependently, and irreversibly inactivated in the presence of 3-HPAA. Complete inactivation of PGHS-2 was achieved with 10 muM 3-HPAA. Preliminary characterization revealed that 3-HPAA inactivation did not result from covalent modification of PGHS-2 or damage to the heme moiety. These studies provide additional insight into the structural requirements for substrate metabolism and inactivation of PGHS and report the first metabolism-dependent, selective inactivator of PGHS-2.

  5. Characterization of an AM404 Analogue, N-(3-Hydroxyphenyl)arachidonoylamide, as a Substrate and Inactivator of Prostaglandin Endoperoxide Synthase†

    PubMed Central

    2009-01-01

    N-(4-Hydroxyphenyl)arachidonoylamide (AM404) is an inhibitor of endocannabinoid inactivation that has been used in cellular and animal studies. AM404 is a derivative of arachidonic acid and has been reported to inhibit arachidonate oxygenation by prostaglandin endoperoxide synthase-1 and -2 (PGHS-1 and -2, respectively). While examining the structural requirements for inhibition of PGHS, we discovered that the meta isomer of AM404, N-(3-hydroxyphenyl)arachidonoylamide (3-HPAA), is a substrate for purified PGHS. PGHS-2 efficiently oxygenated 3-HPAA to prostaglandin and hydroxyeicosatetraenoate products. No oxidation of the phenolamide moiety was observed. 3-HPAA appeared to be converted by PGHS-1 in a similar manner; however, conversion was less efficient than that by PGHS-2. PGHS-2 was selectively, dose-dependently, and irreversibly inactivated in the presence of 3-HPAA. Complete inactivation of PGHS-2 was achieved with 10 μM 3-HPAA. Preliminary characterization revealed that 3-HPAA inactivation did not result from covalent modification of PGHS-2 or damage to the heme moiety. These studies provide additional insight into the structural requirements for substrate metabolism and inactivation of PGHS and report the first metabolism-dependent, selective inactivator of PGHS-2. PMID:19928795

  6. Interface-mediated inactivation of pancreatic lipase by a water-reactive compound: 2-sulfobenzoic cyclic anhydride.

    PubMed

    Moulin, A; Fourneron, J D; Piéroni, G; Verger, R

    1989-07-25

    2-Sulfobenzoic cyclic anhydride (SBA) rapidly and selectively inactivates porcine pancreatic lipase (PPL) only when added during the hydrolysis of an emulsified ester such as tributyrin or dodecyl acetate. The present data suggest that the inactivation of PPL occurs preferentially at the oil/water interface and not in the aqueous phase, since colipase and bile salt were found to adversely affect the inhibition process. Moreover, it is shown that at a molar ratio of SBA to pure PPL of 1, 40% of the lipase activity was already irreversibly lost. Complete inactivation was observed at SBA to pure PPL molar ratios of 120. A 60% inactivation occurred when 0.5 mol of 3H-labeled SBA was attached per mole of PPL. The SBA-inactivated PPL competes for binding to the dodecyl acetate/water interface as efficiently as the native enzyme. Larger SBA concentrations are required when crude lipase preparations are used as well as with pure PPL in the presence of bile salts and colipase. Lipases were found to have variable sensitivities to SBA inactivation, depending on their origin. In the presence of bile salts and tributyrin at pH 6.0, human gastric lipase activity was not affected by the presence of a 10(6) molar excess of SBA.

  7. Inactivation of RTEM beta-lactamase from Escherichia coli by clavulanic acid and 9-deoxyclavulanic acid.

    PubMed

    Charnas, R L; Knowles, J R

    1981-05-26

    The interaction of the TEM-2 beta-lactamase with 9-deoxyclavulanic acid (3) and with both extensively labeled (2) and specifically labeled (1) clavulanic acid has been studied. The close similarity between 9-doexyclavulanate and clavulanate in kinetics, spectroscopic, and protein chemical terms show that the allyl alcohol group of clavulanate is irrelevant to its action as a beta-lactamase inactivator. Use of the radiolabeled samples of clavulanate shows that, of three irreversibly inactivated forms of the enzymes, two contain the whole clavulanate skeleton and the third only retains the carbon atoms of the original beta-lactam ring. These findings allow the complex interaction between clavulanic acid and the beta-lactamase to be defined more narrowly in chemical terms.

  8. An enzymatic mechanism for calcium current inactivation in dialysed Helix neurones.

    PubMed Central

    Chad, J E; Eckert, R

    1986-01-01

    'Wash-out' and inactivation of the Ca current were examined in dialysed, voltage-clamped neurones of Helix aspersa under conditions that isolate the Ca current virtually free of other currents. EGTA or other internal Ca2+ chelators were routinely omitted from the dialysate. The time-dependent loss, or wash-out, of Ca current was slowed by addition to the dialysing solution of agents, such as dibutyryl adenosine 3'-5'-cyclic monophosphate (dibutyryl cyclic AMP), Mg adenosine 5'-triphosphate (ATP) and the catalytic subunit of cyclic-AMP-dependent protein kinase, that promote protein phosphorylation and by EGTA. However, neither the phosphorylation-promoting agents nor internal EGTA prevented wash-out entirely, nor did they significantly restore previously 'washed-out' current. With phosphorylating agents in the dialysing solution, the irreversible development of wash-out was greatly reduced by introduction of leupeptin, an inhibitor of protease activity. Thus, the irreversible component of wash-out appears to result from a Ca-dependent proteolytic process. In the presence of leupeptin alone, Ca current amplitude continued to decline: however, the current could be largely or fully restored with addition of catalytic subunit, dibutyryl cyclic AMP, and Mg ATP to the dialysing solution. Thus, inhibition of proteolysis revealed a reversible component of wash-out that appears to result from dephosphorylation. During perfusion with leupeptin, Mg ATP, dibutyryl cyclic AMP and catalytic subunit the Ca current remained stable for up to several hours without addition of internal Ca2+ buffer. The rate of inactivation of the current that occurs during a depolarizing step showed only a very gradual decline during this time. Under these conditions, perfusion with calcineurin, a Ca-calmodulin-dependent phosphatase, caused a significant increase in the rate of Ca current inactivation. This inactivation was virtually eliminated by introduction of EGTA or by replacement of external Ca2

  9. Characterization of the Reversible Inactivation of Ankistrodesmus braunii Nitrate Reductase by Hydroxylamine.

    PubMed

    Balandin, T; Fernández, V M; Aparicio, P J

    1986-09-01

    The photoreversible nature of the regulation of nitrate reductase is one of the most interesting features of this enzyme. As well as other chemicals, NH(2)OH reversibly inactivates the reduced form of nitrate reductase from Ankistrodesmus braunii. From the partial activities of the enzyme, only terminal nitrate reductase is affected by NH(2)OH. To demonstrate that the terminal activity was readily inactivted by NH(2)OH, the necessary reductants of the terminal part of the enzyme had to be cleared of dithionite since this compound reacts chemically with NH(2)OH. Photoreduced flavins and electrochemically reduced methyl viologen sustain very effective inactivation of terminal nitrate reductase activity, even if the enzyme was previously deprived of its NADH-dehydrogenase activity. The early inhibition of nitrate reductase by NH(2)OH appears to be competitive versus NO(3) (-). Since NO(3) (-), as well as cyanate, carbamyl phosphate and azide (competitive inhibitors of nitrate reductase versus NO(3) (-)), protect the enzyme from NH(2)OH inactivation, it is suggested that NH(2)OH binds to the nitrate active site. The NH(2)OH-inactivated enzyme was photoreactivated in the presence of flavins, although slower than when the enzyme was previously inactivated with CN(-). NH(2)OH and NADH concentrations required for full inactivation of nitrate reductase appear to be low enough to potentially consider this inactivation process of physiological significance.

  10. Characterization of the Reversible Inactivation of Ankistrodesmus braunii Nitrate Reductase by Hydroxylamine 1

    PubMed Central

    Balandin, Teresa; Fernández, Victor M.; Aparicio, Pedro J.

    1986-01-01

    The photoreversible nature of the regulation of nitrate reductase is one of the most interesting features of this enzyme. As well as other chemicals, NH2OH reversibly inactivates the reduced form of nitrate reductase from Ankistrodesmus braunii. From the partial activities of the enzyme, only terminal nitrate reductase is affected by NH2OH. To demonstrate that the terminal activity was readily inactivted by NH2OH, the necessary reductants of the terminal part of the enzyme had to be cleared of dithionite since this compound reacts chemically with NH2OH. Photoreduced flavins and electrochemically reduced methyl viologen sustain very effective inactivation of terminal nitrate reductase activity, even if the enzyme was previously deprived of its NADH-dehydrogenase activity. The early inhibition of nitrate reductase by NH2OH appears to be competitive versus NO3−. Since NO3−, as well as cyanate, carbamyl phosphate and azide (competitive inhibitors of nitrate reductase versus NO3−), protect the enzyme from NH2OH inactivation, it is suggested that NH2OH binds to the nitrate active site. The NH2OH-inactivated enzyme was photoreactivated in the presence of flavins, although slower than when the enzyme was previously inactivated with CN−. NH2OH and NADH concentrations required for full inactivation of nitrate reductase appear to be low enough to potentially consider this inactivation process of physiological significance. PMID:16665024

  11. Bacterial inactivation of the anticancer drug doxorubicin.

    PubMed

    Westman, Erin L; Canova, Marc J; Radhi, Inas J; Koteva, Kalinka; Kireeva, Inga; Waglechner, Nicholas; Wright, Gerard D

    2012-10-26

    Microbes are exposed to compounds produced by members of their ecological niche, including molecules with antibiotic or antineoplastic activities. As a result, even bacteria that do not produce such compounds can harbor the genetic machinery to inactivate or degrade these molecules. Here, we investigated environmental actinomycetes for their ability to inactivate doxorubicin, an aminoglycosylated anthracycline anticancer drug. One strain, Streptomyces WAC04685, inactivates doxorubicin via a deglycosylation mechanism. Activity-based purification of the enzymes responsible for drug inactivation identified the NADH dehydrogenase component of respiratory electron transport complex I, which was confirmed by gene inactivation studies. A mechanism where reduction of the quinone ring of the anthracycline by NADH dehydrogenase leads to deglycosylation is proposed. This work adds anticancer drug inactivation to the enzymatic inactivation portfolio of actinomycetes and offers possibilities for novel applications in drug detoxification. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Inactivation technology for pitch doubling lithography

    NASA Astrophysics Data System (ADS)

    Hatakeyama, Jun; Ohashi, Masaki; Ohsawa, Youichi; Katayama, Kazuhiro; Kawai, Yoshio

    2010-04-01

    We propose novel inactivation technologies which improve resolution. Base generators have been developed, which inactivate acid by thermal treatment or exposure. This thermal inactivation technology realizes simple litho-inactivation-litho-etch (LILE) process with good fidelity. After 1st patterning, acid is inactivated by amine released from the thermal base generator under low temperature baking of less than 150°C. Just adding one simple low temperature bake process, LILE has two advantages; i) keeping high throughput, and ii) avoidance of pattern deformation. 32nm line and space (l&s) pattern is successfully delineated. The inactivation technology has been expanded to frequency doubling patterning. Photo base generator (PBG) is used to inactivate acid generated by exposure. Acid concentration in both of low and high exposed area is precisely controlled by base generation efficiency of PBG. The dual tone resist successfully delineates 32.5nm l&s pattern using 65nm l&s mask patterns with single exposure.

  13. Cefoxitin inactivation by Bacteroides fragilis.

    PubMed

    Cuchural, G J; Tally, F P; Jacobus, N V; Marsh, P K; Mayhew, J W

    1983-12-01

    We have surveyed the susceptibility of 1,575 clinical isolates of the Bacteroides fragilis group of organisms to cefoxitin and eight other antimicrobial agents. Eleven isolates, 0.7% of the total, were highly cefoxitin resistant and had minimum inhibitory concentrations of greater than or equal to 64 micrograms/ml. These isolates were also resistant to other beta-lactam antibiotics. Of 11 isolates, 4 were able to inactivate cefoxitin in broth cultures, as measured by microbiological and high-pressure liquid chromatography assays. Two distinct patterns of cefoxitin breakdown products were detected by high-pressure liquid chromatography analysis. The beta-lactamase inhibitors clavulanic acid and sulbactam failed to show synergism with cefoxitin. These data demonstrate that members of the B. fragilis group have acquired a novel resistance mechanism enabling them to inactivate cefoxitin.

  14. Inactivation of allergens and toxins.

    PubMed

    Morandini, Piero

    2010-11-30

    Plants are replete with thousands of proteins and small molecules, many of which are species-specific, poisonous or dangerous. Over time humans have learned to avoid dangerous plants or inactivate many toxic components in food plants, but there is still room for ameliorating food crops (and plants in general) in terms of their allergens and toxins content, especially in their edible parts. Inactivation at the genetic rather than physical or chemical level has many advantages and classical genetic approaches have resulted in significant reduction of toxin content. The capacity, offered by genetic engineering, of turning off (inactivating) specific genes has opened up the possibility of altering the plant content in a far more precise manner than previously available. Different levels of intervention (genes coding for toxins/allergens or for enzymes, transporters or regulators involved in their metabolism) are possible and there are several tools for inactivating genes, both direct (using chemical and physical mutagens, insertion of transposons and other genetic elements) and indirect (antisense RNA, RNA interference, microRNA, eventually leading to gene silencing). Each level/strategy has specific advantages and disadvantages (speed, costs, selectivity, stability, reversibility, frequency of desired genotype and regulatory regime). Paradigmatic examples from classical and transgenic approaches are discussed to emphasize the need to revise the present regulatory process. Reducing the content of natural toxins is a trade-off process: the lesser the content of natural toxins, the higher the susceptibility of a plant to pests and therefore the stronger the need to protect plants. As a consequence, more specific pesticides like Bt are needed to substitute for general pesticides.

  15. Inactivation of Bacillus anthracis Spores

    PubMed Central

    Whitney, Ellen A. Spotts; Beatty, Mark E.; Taylor, Thomas H.; Weyant, Robbin; Sobel, Jeremy; Arduino, Matthew J.

    2003-01-01

    After the intentional release of Bacillus anthracis through the U.S. Postal Service in the fall of 2001, many environments were contaminated with B. anthracis spores, and frequent inquiries were made regarding the science of destroying these spores. We conducted a survey of the literature that had potential application to the inactivation of B. anthracis spores. This article provides a tabular summary of the results. PMID:12780999

  16. Hydrazine vapor inactivates Bacillus spores

    NASA Astrophysics Data System (ADS)

    Schubert, Wayne W.; Engler, Diane L.; Beaudet, Robert A.

    2016-05-01

    NASA policy restricts the total number of bacterial spores that can remain on a spacecraft traveling to any planetary body which might harbor life or have evidence of past life. Hydrazine, N2H4, is commonly used as a propellant on spacecraft. Hydrazine as a liquid is known to inactivate bacterial spores. We have now verified that hydrazine vapor also inactivates bacterial spores. After Bacillus atrophaeus ATCC 9372 spores deposited on stainless steel coupons were exposed to saturated hydrazine vapor in closed containers, the spores were recovered from the coupons, serially diluted, pour plated and the surviving bacterial colonies were counted. The exposure times required to reduce the spore population by a factor of ten, known as the D-value, were 4.70 ± 0.50 h at 25 °C and 2.85 ± 0.13 h at 35 °C. These inactivation rates are short enough to ensure that the bioburden of the surfaces and volumes would be negligible after prolonged exposure to hydrazine vapor. Thus, all the propellant tubing and internal tank surfaces exposed to hydrazine vapor do not contribute to the total spore count.

  17. Four-mode gating model of fast inactivation of sodium channel Nav1.2a.

    PubMed

    Huth, Tobias; Schmidtmayer, Johann; Alzheimer, Christian; Hansen, Ulf-Peter

    2008-10-01

    Basic principles of the gating mechanisms of neuronal sodium channels, especially the fast inactivation process, were revealed by a quantitative analysis of the effects of the chemically irreversible modifying agent chloramine T. The compound is known to enhance the open probability of sodium channels by interfering with the inactivation process. The key for the deduction of structure-function relationships was obtained from the analysis of single-channel patch-clamp data, especially the finding that chloramine T-induced modification of inactivation occurred in four steps. These steps were termed modes 1-4 (four-mode gating model), and their temporal sequence was always the same. The kinetic analysis of single-channel traces with an improved two-dimensional dwell-time fit revealed the possible mechanism related to each mode. Similarities to the kinetics of the sodium channel mutant F1489Q led to the assignment of modes 1 and 2 to transient defects in the locking of the inactivation particle (hinged lid). In the third mode, the hinged lid was unable to lock permanently. Finally, in mode 4, the apparent single-channel current was reduced, which could be explained by fast gating, presumably related to the selectivity filter.

  18. Factors limiting aliphatic chlorocarbon degradation by Nitrosomonas europaea: Cometabolic inactivation of ammonia monooxygenase and substrate specificity

    SciTech Connect

    Rasche, M.E.; Hyman, M.R.; Arp, D.J. )

    1991-10-01

    The soil nitrifying bacterium Nitrosomonas europaea is capable of degrading trichloroethylene (TCE) and other halogenated hydrocarbons. TCE cometabolism by N. europaea resulted in an irreversible loss of TCE biodegradative capacity, ammonia-oxidizing activity, and ammonia-dependent O{sub 2} uptake by the cells. Inactivation was not observed in the presence of allylthiourea, a specific inhibitor of enzyme ammonia monooxygenase, or under anaerobic conditions, indicating that the TCE-mediated inactivation required ammonia monooxygenase activity. When N. europaea cells were incubated with ({sup 14}C)TCE under conditions which allowed turnover of ammonia monooxygenase, a number of cellular proteins were covalently labeled with {sup 14}C. Treatment of cells with allylthiourea or acetylene prior to incubation with ({sup 14}C)TCE prevented incorporation of {sup 14}C into proteins. The ammonia-oxidizing activity of cells inactivated in the presence of TCE could be recovered through a process requiring de novo protein synthesis. In addition to TCE, a series of chlorinated methanes, ethanes, and other ethylenes were screened as substrates for ammonia monooxygenase and for their ability to inactivate the ammonia-oxidizing system of N. europaea. The chlorocarbons would be divided into three classes depending on their biodegradability and inactivating potential: (1) compounds which were not biodegradable by N. europaea and which had no toxic effect on the cells (2) compounds which were cooxidized by N. europaea and had little or no toxic effect on the cells; and (3) compounds which were cooxidized and produced a turnover-dependent inactivation of ammonia oxidation by N. europaea.

  19. Suicidal inactivation of methemoglobin by generation of thiyl radical: insight into NAC mediated protection in RBC.

    PubMed

    Balaji, S N; Trivedi, V

    2013-07-01

    N-acetyl-L-cysteine (NAC) improves antioxidant potentials of RBCs to provide protection against oxidative stress induced hemolysis. The antioxidant mechanism of NAC to reduce oxidative stress in RBC, studied through inactivation of pro-oxidant MetHb. NAC causes irreversible inactivation of the MetHb in an H2O2 dependent manner, and the inactivation follows the pseudo- first- order kinetics. The kinetic constants are ki = 8.5μM, kinact = 0.706 min(-1) and t1/2 = 0.9 min. Spectroscopic studies indicate that MetHb accepts NAC as a substrate and oxidizes through a single electron transfer mechanism to the NACox. The single e- oxidation product of NAC has been identified as the 5, 5'- dimethyl-1- pyrroline N- oxide (DMPO) adduct of the sulfur centered radical (a(N) = 15.2 G and a(H)=16.78 G). Binding studies indicate that NACox interacts at the heme moiety and NAC oxidation through MetHb is essential for NAC binding. Heme-NAC adduct dissociated from MetHb and identified (m/z 1011.19) as 2:1 ratio of NAC/heme in the adduct. TEMPO and PBN treatment reduces NAC binding to MetHb and protects against inactivation confirms the role of thiyl radical in the inactivation process. Furthermore, scavenging thiyl radicals by TEMPO abolish the protective effect of NAC in hemolysis. Current work highlights antioxidant mechanism of NAC through NAC thiyl radical generation, and MetHb inactivation to exhibit protection in RBC against oxidative stress induced hemolysis.

  20. Lagrangian view of time irreversibility of fluid turbulence

    NASA Astrophysics Data System (ADS)

    Xu, HaiTao; Pumir, Alain; Bodenschatz, Eberhard

    2016-01-01

    A turbulent flow is maintained by an external supply of kinetic energy, which is eventually dissipated into heat at steep velocity gradients. The scale at which energy is supplied greatly differs from the scale at which energy is dissipated, the more so as the turbulent intensity (the Reynolds number) is larger. The resulting energy flux over the range of scales, intermediate between energy injection and dissipation, acts as a source of time irreversibility. As it is now possible to follow accurately fluid particles in a turbulent flow field, both from laboratory experiments and from numerical simulations, a natural question arises: how do we detect time irreversibility from these Lagrangian data? Here we discuss recent results concerning this problem. For Lagrangian statistics involving more than one fluid particle, the distance between fluid particles introduces an intrinsic length scale into the problem. The evolution of quantities dependent on the relative motion between these fluid particles, including the kinetic energy in the relative motion, or the configuration of an initially isotropic structure can be related to the equal-time correlation functions of the velocity field, and is therefore sensitive to the energy flux through scales, hence to the irreversibility of the flow. In contrast, for singleparticle Lagrangian statistics, the most often studied velocity structure functions cannot distinguish the "arrow of time". Recent observations from experimental and numerical simulation data, however, show that the change of kinetic energy following the particle motion, is sensitive to time-reversal. We end the survey with a brief discussion of the implication of this line of work.

  1. Determining the complex modulus of alginate irreversible hydrocolloid dental material.

    PubMed

    King, Shalinie; See, Howard; Thomas, Graham; Swain, Michael

    2008-11-01

    The aim of the study is to investigate the visco-elastic response of an alginate irreversible hydrocolloid dental impression material during setting. A novel squeeze film Micro-Fourier Rheometer (MFR, GBC Scientific Equipment, Australia) was used to determine the complex modulus of an alginate irreversible hydrocolloid dental impression material (Algident, ISO 1563 Class A Type 1, Dentalfarm Australia Pty. Ltd.) during setting after mixing. Data was collected every 30s for 10 min in one study and every 10 min for a total of 60 min in another study. A high level of repeatability was observed. The results indicate that the MFR is capable of recording the complex shear modulus of alginate irreversible hydrocolloid for 60 min from the start of mixing and to simultaneously report the changing visco-elastic parameters at all frequencies between 1 Hz and 100 Hz. The storage modulus shows a dramatic increase to 370% of its starting value after 6 min and then reduces to 55% after 60 min. The loss modulus increases to a maximum of 175% of its starting value after 10 min and then reduces to 94% after 60 min. The MFR enables the changes in the complex modulus through the complete setting process to be followed. It is anticipated this approach may provide a better method to compare the visco-elastic properties of impression materials and assist with identification of optimum types for different clinical requirements. The high stiffness of the instrument and the use of band-limited pseudo-random noise as the input signal are the main advantages of this technique over conventional rheometers for determining the changes in alginate visco-elasticity.

  2. Advanced Caries Microbiota in Teeth with Irreversible Pulpitis.

    PubMed

    Rôças, Isabela N; Lima, Kenio C; Assunção, Isauremi V; Gomes, Patrícia N; Bracks, Igor V; Siqueira, José F

    2015-09-01

    Bacterial taxa in the forefront of caries biofilms are candidate pathogens for irreversible pulpitis and are possibly the first ones to invade the pulp and initiate endodontic infection. This study examined the microbiota of the most advanced layers of dentinal caries in teeth with irreversible pulpitis. DNA extracted from samples taken from deep dentinal caries associated with pulp exposures was analyzed for the presence and relative levels of 33 oral bacterial taxa by using reverse-capture checkerboard hybridization assay. Quantification of total bacteria, streptococci, and lactobacilli was also performed by using real-time quantitative polymerase chain reaction. Associations between the target bacterial taxa and clinical signs/symptoms were also evaluated. The most frequently detected taxa in the checkerboard assay were Atopobium genomospecies C1 (53%), Pseudoramibacter alactolyticus (37%), Streptococcus species (33%), Streptococcus mutans (33%), Parvimonas micra (13%), Fusobacterium nucleatum (13%), and Veillonella species (13%). Streptococcus species, Dialister invisus, and P. micra were significantly associated with throbbing pain, S. mutans with pain to percussion, and Lactobacillus with continuous pain (P < .05). Quantitative polymerase chain reaction revealed a mean total bacterial load of 1 × 10(8) (range, 2.05 × 10(5) to 4.5 × 10(8)) cell equivalents per milligram (wet weight) of dentin. Streptococci and lactobacilli were very prevalent but comprised only 0.09% and 2% of the whole bacterial population, respectively. Several bacterial taxa were found in advanced caries lesions in teeth with exposed pulps, and some of them were significantly associated with symptoms. A role for these taxa in the etiology of irreversible pulpitis is suspected. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  3. Testing time series irreversibility using complex network methods

    NASA Astrophysics Data System (ADS)

    Donges, Jonathan F.; Donner, Reik V.; Kurths, Jürgen

    2013-04-01

    The absence of time-reversal symmetry is a fundamental property of many nonlinear time series. Here, we propose a new set of statistical tests for time series irreversibility based on standard and horizontal visibility graphs. Specifically, we statistically compare the distributions of time-directed variants of the common complex network measures degree and local clustering coefficient. Our approach does not involve surrogate data and is applicable to relatively short time series. We demonstrate its performance for paradigmatic model systems with known time-reversal properties as well as for picking up signatures of nonlinearity in neuro-physiological data.

  4. On Irreversibility and Radiation in Classical Electrodynamics of Point Particles

    NASA Astrophysics Data System (ADS)

    Bauer, Gernot; Deckert, Dirk-André; Dürr, Detlef; Hinrichs, Günter

    2013-09-01

    The direct interaction theory of electromagnetism, also known as Wheeler-Feynman electrodynamics, is often misinterpreted and found unappealing because of its reference to the absorber and, more importantly, to the so-called absorber condition. Here we remark that the absorber condition is indeed questionable and presumably not relevant for the explanation of irreversible radiation phenomena in our universe. What is relevant and deserves further scrutiny is the emergent effective description of a source particle in an environment. We therefore rephrase what we consider the relevant calculation by Wheeler and Feynman and comment on the status of the theory.

  5. Irreversible shear-activated aggregation in non-Brownian suspensions.

    PubMed

    Guery, J; Bertrand, E; Rouzeau, C; Levitz, P; Weitz, D A; Bibette, J

    2006-05-19

    We have studied the effect of shear on the stability of suspensions made of non-Brownian solid particles. We demonstrate the existence of an irreversible transition where the solid particles aggregate at remarkably low volume fractions (phi approximately 0.1). This shear-induced aggregation is dramatic and exhibits a very sudden change in the viscosity, which increases sharply after a shear-dependent induction time. We show that this induction time is related exponentially to the shear rate, reflecting the importance of the hydrodynamic forces in reducing the repulsive energy barrier that prevents the particles from aggregating.

  6. Typical pure nonequilibrium steady states and irreversibility for quantum transport.

    PubMed

    Monnai, Takaaki; Yuasa, Kazuya

    2016-07-01

    It is known that each single typical pure state in an energy shell of a large isolated quantum system well represents a thermal equilibrium state of the system. We show that such typicality holds also for nonequilibrium steady states (NESS's). We consider a small quantum system coupled to multiple infinite reservoirs. In the long run, the total system reaches a unique NESS. We identify a large Hilbert space from which pure states of the system are to be sampled randomly and show that the typical pure states well describe the NESS. We also point out that the irreversible relaxation to the unique NESS is important to the typicality of the pure NESS's.

  7. Reversible and irreversible magnetoresistance of quasisingle domain permalloy microstructures

    NASA Astrophysics Data System (ADS)

    Steiner, M.; Pels, C.; Meier, G.

    2004-06-01

    Permalloy microstructures are investigated by magnetoresistance measurements at 2.0 K and by magnetic-force microscopy at room temperature. While the reversible anisotropic magnetoresistance is determined to be 2.4% at saturation fields of Bsat=1020 mT, the irreversible switching yields a resistance change of the order of 0.05% at 13 mT. By tilting the external magnetic field relative to the easy axis of the quasi single-domain microstructures insight in the reversal process is gained. Comparison with an analytical model provides evidence for magnetization reversal by curling.

  8. Intrinsic irreversibility limits the efficiency of multidimensional molecular motors

    NASA Astrophysics Data System (ADS)

    Jack, M. W.; Tumlin, C.

    2016-05-01

    We consider the efficiency limits of Brownian motors able to extract work from the temperature difference between reservoirs or from external thermodynamic forces. These systems can operate in a variety of modes, including as isothermal engines, heat engines, refrigerators, and heat pumps. We derive analytical results showing that certain classes of multidimensional Brownian motor, including the Smoluchowski-Feynman ratchet, are unable to attain perfect efficiency (Carnot efficiency for heat engines). This demonstrates the presence of intrinsic irreversibilities in their operating mechanism. We present numerical simulations showing that in some cases the loss process that limits efficiency is associated with vortices in the probability current.

  9. Intrinsic irreversibility limits the efficiency of multidimensional molecular motors.

    PubMed

    Jack, M W; Tumlin, C

    2016-05-01

    We consider the efficiency limits of Brownian motors able to extract work from the temperature difference between reservoirs or from external thermodynamic forces. These systems can operate in a variety of modes, including as isothermal engines, heat engines, refrigerators, and heat pumps. We derive analytical results showing that certain classes of multidimensional Brownian motor, including the Smoluchowski-Feynman ratchet, are unable to attain perfect efficiency (Carnot efficiency for heat engines). This demonstrates the presence of intrinsic irreversibilities in their operating mechanism. We present numerical simulations showing that in some cases the loss process that limits efficiency is associated with vortices in the probability current.

  10. Microscopic time-reversibility and macroscopic irreversibility: Still a paradox

    SciTech Connect

    Posch, H.A.; Dellago, Ch.; Hoover, W.G.; Kum, O. |

    1995-09-13

    Microscopic time reversibility and macroscopic irreversibility are a paradoxical combination. This was first observed by J. Loschmidt in 1876 and was explained, for conservative systems, by L. Boltzmann the following year. Both these features are also present in modern simulations of classic many-body systems in steady nonequilibrium states. We illustrate them here for the simplest possible models, a continuous one-dimensional model of field-driven diffusion, the so-called driven Lorentz gas or Galton Board, and an ergodic time reversible dissipative map.

  11. Irreversible electroporation of hepatocellular carcinoma: patient selection and perspectives

    PubMed Central

    Zimmerman, Asha; Grand, David; Charpentier, Kevin P

    2017-01-01

    Irreversible electroporation (IRE) is a novel form of tissue ablation that uses high-current electrical pulses to induce pore formation of the cell lipid bilayer, leading to cell death. The safety of IRE for ablation of hepatocellular carcinoma (HCC) has been established. Outcome data for ablation of HCC by IRE are limited, but early results are encouraging and suggest equivalency to the outcomes obtained for thermal ablation for appropriately selected, small (<3 cm) tumors. Long-term oncologic efficacy and histopathologic response data have not been published, and therefore, application of IRE for the treatment of HCC should still be viewed with caution. PMID:28331845

  12. The irreversibly comatose: respect for the subhuman in human life.

    PubMed

    Rolston, H

    1982-11-01

    In the case of the irreversibly comatose patient, though no personal consciousness remains, some moral duty is owed the remaining biological life. Such an ending to human life, if pathetic, is also both intelligible and meaningful in a biological and evolutionary perspective. By distinguishing between the human subjective life and the spontaneous objective life, we can recognize a naturalistic principle in medical ethics, contrary to a current tendency to defend purely humanistic norms. This principle has applications in clinical care in the definition of death, in the use of life support therapy, in distinguishing ordinary from extraordinary therapy, in evaluating euthanasia, and in the extent of appropriate medical intervention in terminal cases.

  13. Purification to homogeneity and partial amino acid sequence of a fragment which includes the methyl acceptor site of the human DNA repair protein for O6-methylguanine.

    PubMed

    Major, G N; Gardner, E J; Carne, A F; Lawley, P D

    1990-03-25

    DNA repair by O6-methylguanine-DNA methyltransferase (O6-MT) is accomplished by removal by the enzyme of the methyl group from premutagenic O6-methylguanine-DNA, thereby restoring native guanine in DNA. The methyl group is transferred to an acceptor site cysteine thiol group in the enzyme, which causes the irreversible inactivation of O6-MT. We detected a variety of different forms of the methylated, inactivated enzyme in crude extracts of human spleen of molecular weights higher and lower than the usually observed 21-24kDa for the human O6-MT. Several apparent fragments of the methylated form of the protein were purified to homogeneity following reaction of partially-purified extract enzyme with O6-[3H-CH3]methylguanine-DNA substrate. One of these fragments yielded amino acid sequence information spanning fifteen residues, which was identified as probably belonging to human methyltransferase by virtue of both its significant sequence homology to three procaryote forms of O6-MT encoded by the ada, ogt (both from E. coli) and dat (B. subtilis) genes, and sequence position of the radiolabelled methyl group which matched the position of the conserved procaryote methyl acceptor site cysteine residue. Statistical prediction of secondary structure indicated good homologies between the human fragment and corresponding regions of the constitutive form of O6-MT in procaryotes (ogt and dat gene products), but not with the inducible ada protein, indicating the possibility that we had obtained partial amino acid sequence for a non-inducible form of the human enzyme. The identity of the fragment sequence as belonging to human methyltransferase was more recently confirmed by comparison with cDNA-derived amino acid sequence from the cloned human O6-MT gene from HeLa cells (1). The two sequences compared well, with only three out of fifteen amino acids being different (and two of them by only one nucleotide in each codon).

  14. Separation and partial characterization of enzymes catalyzing delta-aminolevulinic acid formation in Synechocystis sp. PCC 6803.

    PubMed

    Rieble, S; Beale, S I

    1991-09-01

    Formation of the universal tetrapyrrole precursor, delta-aminolevulinic acid (ALA), from glutamate via the five-carbon pathway requires three enzymes: glutamyl-tRNA synthetase, glutamyl-tRNA reductase, and glutamate-1-semialdehyde (GSA) aminotransferase. All three enzymes were separated from extracts of the unicellular cyanobacterium Synechocystis sp. PCC 6803, and two of them, glutamyl-tRNA synthetase and GSA aminotransferase, were partially characterized. After an initial high speed centrifugation and differentiatial ammonium sulfate fractionation of cell extract, the enzymes were separated by successive affinity chromatography on Reactive Blue 2-Sepharose and 2',5'-ADP-agarose. All three enzyme fractions were required to reconstitute ALA formation from glutamate. The apparent native molecular masses of glutamyl-tRNA synthetase and GSA aminotransferase were determined by gel filtration chromatography to be 63 and 98 kDa, respectively. Neither glutamyl-tRNA synthetase nor GSA aminotransferase activity was affected by hemin concentrations up to 10 and 30 microM, respectively, and neither activity was affected by protochlorophyllide concentrations up to 2 microM. GSA aminotransferase was inhibited 50% by 0.5 microM gabaculine. The gabaculine inhibition was reversible for up to 1 h after its addition, if the gabaculine was removed by gel filtration before the enzyme was incubated with substrate. However, irreversible inactivation was obtained by preincubating the enzyme at 30 degrees C either for several hours with gabaculine alone or for a few minutes with both gabaculine and GSA. Neither pyridoxal phosphate nor pyridoxamine phosphate significantly affected the activity of GSA aminotransferase at physiologically relevant concentrations, and neither of these compounds reactivated the gabaculine-inactivated enzyme. It was noted that the presence of pyridoxamine phosphate in the ALA assay mixture produced a false positive color reaction even in the absence of enzyme.

  15. Bacteria, mould and yeast spore inactivation studies by scanning electron microscope observations.

    PubMed

    Rozali, Siti N M; Milani, Elham A; Deed, Rebecca C; Silva, Filipa V M

    2017-10-04

    the inner membrane, altering its permeability, and allowing in final stages the transfer of intracellular components to the outside. The spore destruction caused by thermal treatment was more severe than HPP, as HPP had less effect on the spore core. All injured spores have undergone irreversible volume and shape changes. While some of the leakage of spore contents is visible around the deformed but fully shaped spore, other spores exhibited large indentations and were completely deformed, apparently without any contents inside. This current study contributed to the understanding of spore inactivation by thermal and non-thermal processes. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Reductive inactivation of yeast glutathione reductase by Fe(II) and NADPH.

    PubMed

    Cardoso, Luciano A; Ferreira, Sérgio T; Hermes-Lima, Marcelo

    2008-11-01

    Glutathione reductase (GR) carries out the enzymatic reduction of glutathione disulfide (GSSG) to its reduced form (GSH) at the expense of the reducing power of NADPH. Previous studies have shown that GR from several species is progressively inactivated in the presence of NADPH, but that the mechanism of inactivation (especially in the presence of metals) has not been fully elucidated. We have investigated the involvement of iron ions in the inactivation of yeast (Saccharomyces cerevisiae) GR in the presence of NADPH. Even in the absence of added iron, inactivation of GR was partly blocked by the iron chelators, deferoxamine and ortho-phenanthroline, suggesting the involvement of trace amounts of contaminating iron in the mechanism of inhibition. Exogenously added antioxidants including ethanol, dimethylsulfoxide and 2-deoxyribose did not protect GR against NADPH-induced inactivation, whilst addition of exogenous Fe(II) (but not Fe(III)) potentiated the inactivation. Moreover, removal of oxygen from the medium led to increased inhibition of GR, whereas pre-incubation of the Fe(II)-containing medium for 30 min under normoxic conditions prior to the addition of GR abolished the enzyme inactivation by NADPH. Under these pre-incubation conditions, Fe(II) is fully oxidized to Fe(III) within 1 min. Furthermore, GR that had been previously inactivated in the presence of Fe(II) plus NADPH could be partially reactivated by treatment with ortho-phenanthroline and deferoxamine. In contrast, Fe(III) had no effect on GR reactivation. Together, these results indicate that yeast GR is inactivated by a reductive mechanism mediated by NADPH and Fe(II). According to this mechanism, GR is diverted from its normal redox cycling by the generation of an inactive reduced enzyme form in which both the FAD and thiol groups at the active site are likely in a reduced state.

  17. The inhaled glucocorticoid fluticasone propionate efficiently inactivates cytochrome P450 3A5, a predominant lung P450 enzyme

    PubMed Central

    Murai, Takahiro; Reilly, Christopher R.; Ward, Robert M.; Yost, Garold S.

    2010-01-01

    Inhaled glucocorticoid (GC) therapy is a vital part of the management of chronic asthma. GCs are metabolized by members of the cytochrome P450 3A family in both liver and lung, but the enzymes are differentially expressed. Selective inhibition of one or more P450 3A enzymes could substantially modify target and systemic concentrations of GCs. In this study, we have evaluated the mechanism-based inactivation of P450 3A4, 3A5 and 3A7 enzymes by GCs. Among the five major inhaled GCs approved for clinical use in the United States, fluticasone propionate (FLT) was the most potent mechanism-based inactivator of P450 3A5, the predominant P450 enzyme in the lung. FLT inactivated P450 3A5 in a time- and concentration-dependent manner with KI, kinact and partition ratio of 16 μM, 0.027 min-1 and 3, respectively. In contrast, FLT minimally inactivated P450 3A4 and did not inactivate 3A7, even with a concentration of 100 μM. The inactivation of P450 3A5 by FLT was irreversible because dialysis did not restore enzyme activity. In addition, the exogenous nucleophilic scavenger GSH did not attenuate inactivation. The prosthetic heme of P450 3A5 was not modified by FLT. The loss of P450 3A5 activity in lung cells could substantially decrease the metabolism of FLT, which would increase the effective FLT concentration at its target site, the respiratory epithelium. Also, inactivation of lung P450 3A5 could increase the absorption of inhaled FLT, which could lead to high systemic concentrations and adverse effects, such as life-threatening adrenal crises or cataracts that have been documented in children receiving high doses of inhaled GCs. PMID:20707410

  18. Critical behavior of an irreversible multiple-reaction process

    NASA Astrophysics Data System (ADS)

    Albano, Ezequiel V.

    1994-04-01

    A multiple-reaction irreversible surface reaction model (M-R) involving one monomer (A) and two different dimers (B 2 and C 2) is proposed and studied by means of Monte Carlo simulations. In the absence of the monomer species the M-R model reduces to the DD model (Maltz et al. Surf. Sci. 277 (1992) 414), while in the absence of one of the dimer species the M-R gives the ZGB model (Ziff et al. Phys. Rev. Lett. 56 (1986) 2553). The M-R model is suitable to investigate: on the one hand, the influence caused by the presence of H 2-traces (H 2 is C 2) on the catalytic oxidation of carbon monoxide, e.g. A + {1}/{2})B 2 → AB where A is CO, B 2 is O 2 and AB is CO 2, and on the other hand, the effect of CO-traces on the catalytic oxidation of hydrogen, e.g. ( {1}/{2})B 2 + C 2 → C 2B. Furthermore, the M-R model exhibits irreversible phase transitions (IPTs) between poisoned states with the surface saturated by adsorbed species and reactive regimes with production of both AB and C 2B. The critical points at which the first and second-order IPTs characteristic of the M-R take place are determined. Interesting theoretical possibilities which become opened when studying the observed critical behavior of the M-R model are discussed.

  19. Voter model with arbitrary degree dependence: clout, confidence and irreversibility

    NASA Astrophysics Data System (ADS)

    Fotouhi, Babak; Rabbat, Michael G.

    2014-03-01

    The voter model is widely used to model opinion dynamics in society. In this paper, we propose three modifications to incorporate heterogeneity into the model. We address the corresponding oversimplifications of the conventional voter model which are unrealistic. We first consider the voter model with popularity bias. The influence of each node on its neighbors depends on its degree. We find the consensus probabilities and expected consensus times for each of the states. We also find the fixation probability, which is the probability that a single node whose state differs from every other node imposes its state on the entire system. In addition, we find the expected fixation time. Then two other extensions to the model are proposed and the motivations behind them are discussed. The first one is confidence, where in addition to the states of neighbors, nodes take their own state into account at each update. We repeat the calculations for the augmented model and investigate the effects of adding confidence to the model. The second proposed extension is irreversibility, where one of the states is given the property that once nodes adopt it, they cannot switch back. This is motivated by applications where, agents take an irreversible action such as seeing a movie, purchasing a music album online, or buying a new product. The dynamics of densities, fixation times and consensus times are obtained.

  20. Carnot's cycle for small systems: irreversibility and cost of operations

    PubMed

    Sekimoto; Takagi; Hondou

    2000-12-01

    In the thermodynamic limit, the existence of a maximal efficiency of energy conversion attainable by a Carnot cycle consisting of quasistatic isothermal and adiabatic processes precludes the existence of a perpetual machine of the second kind, whose cycles yield positive work in an isothermal environment. We employ the recently developed framework of the energetics of stochastic processes (called "stochastic energetics") to reanalyze the Carnot cycle in detail, taking account of fluctuations, without taking the thermodynamic limit. We find that in this nonmacroscopic situation both processes of connection to and disconnection from heat baths and adiabatic processes that cause distortion of the energy distribution are sources of inevitable irreversibility within the cycle. Also, the so-called null-recurrence property of the cumulative efficiency of energy conversion over many cycles and the irreversible property of isolated, purely mechanical processes under external "macroscopic" operations are discussed in relation to the impossibility of a perpetual machine, or Maxwell's demon. This analysis may serve as the basis for the design and analysis of mesoscopic energy converters in the near future.

  1. Irreversible entropy model for damage diagnosis in resistors

    SciTech Connect

    Cuadras, Angel Crisóstomo, Javier; Ovejas, Victoria J.; Quilez, Marcos

    2015-10-28

    We propose a method to characterize electrical resistor damage based on entropy measurements. Irreversible entropy and the rate at which it is generated are more convenient parameters than resistance for describing damage because they are essentially positive in virtue of the second law of thermodynamics, whereas resistance may increase or decrease depending on the degradation mechanism. Commercial resistors were tested in order to characterize the damage induced by power surges. Resistors were biased with constant and pulsed voltage signals, leading to power dissipation in the range of 4–8 W, which is well above the 0.25 W nominal power to initiate failure. Entropy was inferred from the added power and temperature evolution. A model is proposed to understand the relationship among resistance, entropy, and damage. The power surge dissipates into heat (Joule effect) and damages the resistor. The results show a correlation between entropy generation rate and resistor failure. We conclude that damage can be conveniently assessed from irreversible entropy generation. Our results for resistors can be easily extrapolated to other systems or machines that can be modeled based on their resistance.

  2. Essays on oil price volatility and irreversible investment

    NASA Astrophysics Data System (ADS)

    Pastor, Daniel J.

    In chapter 1, we provide an extensive and systematic evaluation of the relative forecasting performance of several models for the volatility of daily spot crude oil prices. Empirical research over the past decades has uncovered significant gains in forecasting performance of Markov Switching GARCH models over GARCH models for the volatility of financial assets and crude oil futures. We find that, for spot oil price returns, non-switching models perform better in the short run, whereas switching models tend to do better at longer horizons. In chapter 2, I investigate the impact of volatility on firms' irreversible investment decisions using real options theory. Cost incurred in oil drilling is considered sunk cost, thus irreversible. I collect detailed data on onshore, development oil well drilling on the North Slope of Alaska from 2003 to 2014. Volatility is modeled by constructing GARCH, EGARCH, and GJR-GARCH forecasts based on monthly real oil prices, and realized volatility from 5-minute intraday returns of oil futures prices. Using a duration model, I show that oil price volatility generally has a negative relationship with the hazard rate of drilling an oil well both when aggregating all the fields, and in individual fields.

  3. MTA pulpotomy of human permanent molars with irreversible pulpitis.

    PubMed

    Eghbal, Mohammad Jafar; Asgary, Saeed; Baglue, Reza Ali; Parirokh, Masoud; Ghoddusi, Jamileh

    2009-04-01

    The histological success of mineral trioxide aggregate (MTA) pulpotomy for treatment of irreversible pulpitis in human teeth as an alternative treatment was investigated in this study. Fourteen molars which had to be extracted were selected from patients 16-28 years old. The selection criteria include carious pulp exposure with a history of lingering pain. After isolation, caries removal and pulp exposure, MTA was used in pulpotomy treatment. Patients were evaluated for pain after 24 h. Two patients were lost from this study. Twelve teeth were extracted after 2 months and were assessed histologically. Recall examinations confirmed that none of the patients experienced pain after pulpotomy. Histological observation revealed that all samples had dentin bridge formation completely and that the pulps were vital and free of inflammation. Although the results favour the use of MTA as a pulpotomy material, more studies with larger samples and a longer recall period are suggested to justify the use of MTA for treatment of irreversible pulpitis in human permanent teeth.

  4. Molecular control of irreversible bistability during trypanosome developmental commitment

    PubMed Central

    Domingo-Sananes, Maria Rosa; Szöőr, Balazs; Ferguson, Michael A.J.

    2015-01-01

    The life cycle of Trypanosoma brucei involves developmental transitions that allow survival, proliferation, and transmission of these parasites. One of these, the differentiation of growth-arrested stumpy forms in the mammalian blood into insect-stage procyclic forms, can be induced synchronously in vitro with cis-aconitate. Here, we show that this transition is an irreversible bistable switch, and we map the point of commitment to differentiation after exposure to cis-aconitate. This irreversibility implies that positive feedback mechanisms operate to allow commitment (i.e., the establishment of “memory” of exposure to the differentiation signal). Using the reversible translational inhibitor cycloheximide, we show that this signal memory requires new protein synthesis. We further performed stable isotope labeling by amino acids in cell culture to analyze synchronized parasite populations, establishing the protein and phosphorylation profile of parasites pre- and postcommitment, thereby defining the “commitment proteome.” Functional interrogation of this data set identified Nek-related kinase as the first-discovered protein kinase controlling the initiation of differentiation to procyclic forms. PMID:26483558

  5. Endovascular nonthermal irreversible electroporation: a finite element analysis.

    PubMed

    Maor, Elad; Rubinsky, Boris

    2010-03-01

    Tissue ablation finds an increasing use in modern medicine. Nonthermal irreversible electroporation (NTIRE) is a biophysical phenomenon and an emerging novel tissue ablation modality, in which electric fields are applied in a pulsed mode to produce nanoscale defects to the cell membrane phospholipid bilayer, in such a way that Joule heating is minimized and thermal damage to other molecules in the treated volume is reduced while the cells die. Here we present a two-dimensional transient finite element model to simulate the electric field and thermal damage to the arterial wall due to an endovascular NTIRE novel device. The electric field was used to calculate the Joule heating effect, and a transient solution of the temperature is presented using the Pennes bioheat equation. This is followed by a kinetic model of the thermal damage based on the Arrhenius formulation and calculation of the Henriques and Moritz thermal damage integral. The analysis shows that the endovascular application of 90, 100 mus pulses with a potential difference of 600 V can induce electric fields of 1000 V/cm and above across the entire arterial wall, which are sufficient for irreversible electroporation. The temperature in the arterial wall reached a maximum of 66.7 degrees C with a pulse frequency of 4 Hz. Thermal damage integral showed that this protocol will thermally damage less than 2% of the molecules around the electrodes. In conclusion, endovascular NTIRE is possible. Our study sets the theoretical basis for further preclinical and clinical trials with endovascular NTIRE.

  6. Strategies for discovering and derisking covalent, irreversible enzyme inhibitors

    PubMed Central

    Johnson, Douglas S; Weerapana, Eranthie; Cravatt, Benjamin F

    2010-01-01

    This article presents several covalent inhibitors, including examples of successful drugs, as well as highly selective, irreversible inhibitors of emerging therapeutic targets, such as fatty acid amide hydolase. Covalent inhibitors have many desirable features, including increased biochemical efficiency of target disruption, less sensitivity toward pharmacokinetic parameters and increased duration of action that outlasts the pharmacokinetics of the compound. Safety concerns that must be mitigated include lack of specificity and the potential immunogenicity of protein–inhibitor adduct(s). Particular attention will be given to recent technologies, such as activity-based protein profiling, which allow one to define the proteome-wide selectivity patterns for covalent inhibitors in vitro and in vivo. For instance, any covalent inhibitor can, in principle, be modified with a ‘clickable’ tag to generate an activity probe that is almost indistinguishable from the original agent. These probes can be applied to any living system across a broad dose range to fully inventory their on and off targets. The substantial number of drugs on the market today that act by a covalent mechanism belies historical prejudices against the development of irreversibly acting therapeutic small molecules. Emerging proteomic technologies offer a means to systematically discriminate safe (selective) versus deleterious (nonselective) covalent inhibitors and thus should inspire their future design and development. PMID:20640225

  7. Linear Dimensional Stability of Irreversible Hydrocolloid Materials Over Time.

    PubMed

    Garrofé, Analía B; Ferrari, Beatriz A; Picca, Mariana; Kaplan, Andrea E

    2015-12-01

    The aim of this study was to evaluate the linear dimensional stability of different irreversible hydrocolloid materials over time. A metal mold was designed with custom trays made of thermoplastic sheets (Sabilex, sheets 0.125 mm thick). Perforations were made in order to improve retention of the material. Five impressions were taken with each of the following: Kromopan 100 (LASCOD) [AlKr], which has dimensional stability of 100 hours, and Phase Plus (ZHERMACK) [AlPh], which has dimensional stability of 48 hours. Standardized digital photographs were taken at different time intervals (0, 15, 30, 45, 60, 120 minutes; 12, 24 and 96 hours), using an "ad-hoc" device. The images were analyzed with software (UTHSCSA Image Tool) by measuring the distance between intersection of the lines previously made at the top of the mold. The results were analyzed by ANOVA for repeated measures. Initial and final values were (mean and standard deviation): AlKr: 16.44 (0.22) and 16.34 (0.11), AlPh: 16.40 (0.06) and 16.18 (0.06). Statistical evaluation showed significant effect of material and time factors. Under the conditions in this study, time significantly affects the linear dimensional stability of irreversible hydrocolloid materials.

  8. Frequency spectroscopy of irreversible electrochemical nucleation kinetics on the nanoscale

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Chen, Chi; Arruda, Thomas M.; Jesse, Stephen; Ciucci, Francesco; Kalinin, Sergei V.

    2013-11-01

    An approach is developed for probing the thermodynamics and kinetics of irreversible electrochemical reactions on solid surfaces based on local frequency-voltage spectroscopy. For a model Li-ion conductor surface, two regimes for bias-controlled behavior are demonstrated and ascribed to the difference in the critical nucleus size. The electrostatic and electrochemical phenomena at the tip-surface junction are analyzed. These studies suggest an experimental pathway for exploring local electrochemical activity in solids.An approach is developed for probing the thermodynamics and kinetics of irreversible electrochemical reactions on solid surfaces based on local frequency-voltage spectroscopy. For a model Li-ion conductor surface, two regimes for bias-controlled behavior are demonstrated and ascribed to the difference in the critical nucleus size. The electrostatic and electrochemical phenomena at the tip-surface junction are analyzed. These studies suggest an experimental pathway for exploring local electrochemical activity in solids. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03953f

  9. From Maximum Entropy Models to Non-Stationarity and Irreversibility

    NASA Astrophysics Data System (ADS)

    Cofre, Rodrigo; Cessac, Bruno; Maldonado, Cesar

    The maximum entropy distribution can be obtained from a variational principle. This is important as a matter of principle and for the purpose of finding approximate solutions. One can exploit this fact to obtain relevant information about the underlying stochastic process. We report here in recent progress in three aspects to this approach.1- Biological systems are expected to show some degree of irreversibility in time. Based on the transfer matrix technique to find the spatio-temporal maximum entropy distribution, we build a framework to quantify the degree of irreversibility of any maximum entropy distribution.2- The maximum entropy solution is characterized by a functional called Gibbs free energy (solution of the variational principle). The Legendre transformation of this functional is the rate function, which controls the speed of convergence of empirical averages to their ergodic mean. We show how the correct description of this functional is determinant for a more rigorous characterization of first and higher order phase transitions.3- We assess the impact of a weak time-dependent external stimulus on the collective statistics of spiking neuronal networks. We show how to evaluate this impact on any higher order spatio-temporal correlation. RC supported by ERC advanced Grant ``Bridges'', BC: KEOPS ANR-CONICYT, Renvision and CM: CONICYT-FONDECYT No. 3140572.

  10. Influence of delayed pouring on irreversible hydrocolloid properties.

    PubMed

    Rodrigues, Stéfani Becker; Augusto, Carolina Rocha; Leitune, Vicente Castelo Branco; Samuel, Susana Maria Werner; Collares, Fabrício Mezzomo

    2012-01-01

    The aim of this study was to evaluate the physical properties of irreversible hydrocolloid materials poured immediately and after different storage periods. Four alginates were tested: Color Change (Cavex); Hydrogum (Zhermack); Hydrogum 5 (Zhermack); and Hydro Print Premium (Coltene). Their physical properties, including the recovery from deformation (n = 3), compressive strength (n = 3), and detail reproduction and gypsum compatibility (n = 3), were analyzed according to ANSI/ADA specification no. 18. Specimens were stored at 23ºC and humidity and were then poured with gypsum immediately and after 1, 2, 3, 4, and 5 days. The data were analyzed by two-way analysis of variance (ANOVA) and Tukey's test at p < 0.05. All of the alginate impression materials tested exhibited detail reproduction and gypsum compatibility at all times. Hydro Print Premium and Hydrogum 5 showed recovery from deformation, as established by ANSI/ADA specification no. 18, after 5 days of storage. As the storage time increased, the compressive strength values also increased. Considering the properties of compounds' recovery from deformation, compressive strength, and detail reproduction and gypsum compatibility, irreversible hydrocolloids should be poured immediately.

  11. Evidence of irreversible CO2 intercalation in montmorillonite

    SciTech Connect

    Romanov, V

    2013-02-13

    Mitigation of the global climate change via sequestration of anthropogenic carbon dioxide (CO2) in geologic formations requires assessment of the reservoir storage capacity and cap rock seal integrity. The typical cap rock is shale or mudstone rich in clay minerals that may significantly affect the effectiveness of the CO2 trapping. Specific objectives of this study were to conduct experimental investigation into the processes associated with CO2 and H2O trapped in swelling clay, namely, Wyoming and Texas montmorillonite powder. Combined (same-sample) multi-technique data ? manometric sorption isotherm hysteresis, diffuse reflectance infrared spectroscopy ?trapped CO2? fingerprints, irreversible X-ray diffraction patterns for the clay interlayer in intermediate hydration state, and HF acid digestion resulting in formation of non-extractable F:CO2 adducts ? corroborate a hypothesis that carbon dioxide molecules can be irreversibly trapped via anomalous extreme confinement in the galleries associated with montmorillonite interlayer, which may result in formation of carbonates in the longer term. Validation on Arizona montmorillonite lumps substantiated the evidence that such processes may occur in natural clay deposits but possibly on a different scale and at a different rate.

  12. Irreversibility in physics stemming from unpredictable symbol-handling agents

    NASA Astrophysics Data System (ADS)

    Myers, John M.; Madjid, F. Hadi

    2016-05-01

    The basic equations of physics involve a time variable t and are invariant under the transformation t --> -t. This invariance at first sight appears to impose time reversibility as a principle of physics, in conflict with thermodynamics. But equations written on the blackboard are not the whole story in physics. In prior work we sharpened a distinction obscured in today's theoretical physics, the distinction between obtaining evidence from experiments on the laboratory bench and explaining that evidence in mathematical symbols on the blackboard. The sharp distinction rests on a proof within the mathematics of quantum theory that no amount of evidence, represented in quantum theory in terms of probabilities, can uniquely determine its explanation in terms of wave functions and linear operators. Building on the proof we show here a role in physics for unpredictable symbol-handling agents acting both at the blackboard and at the workbench, communicating back and forth by means of transmitted symbols. Because of their unpredictability, symbol-handling agents introduce a heretofore overlooked source of irreversibility into physics, even when the equations they write on the blackboard are invariant under t --> -t. Widening the scope of descriptions admissible to physics to include the agents and the symbols that link theory to experiments opens up a new source of time-irreversibility in physics.

  13. Carnot's cycle for small systems: Irreversibility and cost of operations

    NASA Astrophysics Data System (ADS)

    Sekimoto, Ken; Takagi, Fumiko; Hondou, Tsuyoshi

    2000-12-01

    In the thermodynamic limit, the existence of a maximal efficiency of energy conversion attainable by a Carnot cycle consisting of quasistatic isothermal and adiabatic processes precludes the existence of a perpetual machine of the second kind, whose cycles yield positive work in an isothermal environment. We employ the recently developed framework of the energetics of stochastic processes (called ``stochastic energetics'') to reanalyze the Carnot cycle in detail, taking account of fluctuations, without taking the thermodynamic limit. We find that in this nonmacroscopic situation both processes of connection to and disconnection from heat baths and adiabatic processes that cause distortion of the energy distribution are sources of inevitable irreversibility within the cycle. Also, the so-called null-recurrence property of the cumulative efficiency of energy conversion over many cycles and the irreversible property of isolated, purely mechanical processes under external ``macroscopic'' operations are discussed in relation to the impossibility of a perpetual machine, or Maxwell's demon. This analysis may serve as the basis for the design and analysis of mesoscopic energy converters in the near future.

  14. Inactivation of polyphenoloxidase by pulsed light.

    PubMed

    Manzocco, Lara; Panozzo, Agnese; Nicoli, Maria Cristina

    2013-08-01

    The effect of pulsed light on the inactivation of polyphenoloxidase (PPO) in model solutions was investigated focusing on the effect of enzyme concentration and total energy dose of the treatment. PPO inactivation increased with the dose of the treatment. Complete enzyme inactivation was achieved by pulsed light doses higher than 8.75 J cm(-2) . At low PPO concentrations (4 to 10 U), the enzyme resulted highly inactivated by pulsed light treatment. Further increase in enzyme units determined a progressive decrease in PPO inactivation. The latter was attributed to protein structural modifications including cleavage and unfolding/aggregation phenomena. PPO amounts higher than 10 U probably favoured enzyme conformations that were less prone to intermolecular rearrangements leading to inactivation. © 2013 Institute of Food Technologists®

  15. X;15 translocation in a retarded girl: X inactivation pattern and attempt to localise the hexosaminidase A and other loci.

    PubMed Central

    Bernstein, R; Dawson, B; Kohl, R; Jenkins, T

    1979-01-01

    Cytogenetic studies on a retarded girl showed a complex S;15 translocation, karyotype 45,X,-15,+t(X15). The translocation X chromosome was non-randomly partially inactivated, the inactivation being mainly confined to the X segment and in some cells only to the X long arm. Gene marker studies failed to show anomalous segregation of the hexosaminidase A gene or any other gene markers tested. Images PMID:290816

  16. Pressure Inactivation of Bacillus Endospores

    PubMed Central

    Margosch, Dirk; Gänzle, Michael G.; Ehrmann, Matthias A.; Vogel, Rudi F.

    2004-01-01

    The inactivation of bacterial endospores by hydrostatic pressure requires the combined application of heat and pressure. We have determined the resistance of spores of 14 food isolates and 5 laboratory strains of Bacillus subtilis, B. amyloliquefaciens, and B. licheniformis to treatments with pressure and temperature (200 to 800 MPa and 60 to 80°C) in mashed carrots. A large variation in the pressure resistance of spores was observed, and their reduction by treatments with 800 MPa and 70°C for 4 min ranged from more than 6 log units to no reduction. The sporulation conditions further influenced their pressure resistance. The loss of dipicolinic acid (DPA) from spores that varied in their pressure resistance was determined, and spore sublethal injury was assessed by determination of the detection times for individual spores. Treatment of spores with pressure and temperature resulted in DPA-free, phase-bright spores. These spores were sensitive to moderate heat and exhibited strongly increased detection times as judged by the time required for single spores to grow to visible turbidity of the growth medium. The role of DPA in heat and pressure resistance was further substantiated by the use of the DPA-deficient mutant strain B. subtilis CIP 76.26. Taken together, these results indicate that inactivation of spores by combined pressure and temperature processing is achieved by a two-stage mechanism that does not involve germination. At a pressure between 600 and 800 MPa and a temperature greater than 60°C, DPA is released predominantly by a physicochemical rather than a physiological process, and the DPA-free spores are inactivated by moderate heat independent of the pressure level. Relevant target organisms for pressure and temperature treatment of foods are proposed, namely, strains of B. amyloliquefaciens, which form highly pressure-resistant spores. PMID:15574932

  17. Photocatalytic bacterial inactivation by polyoxometalates.

    PubMed

    Bae, Eunyoung; Lee, Jae Won; Hwang, Byeong Hee; Yeo, Jiman; Yoon, Jeyong; Cha, Hyung Joon; Choi, Wonyong

    2008-05-01

    The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO2 photocatalyst. Aqueous suspensions of the microorganisms (10(7)-10(8)cfu ml(-1)) and POM (or TiO2) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO2-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H(3)PW(12)O(40), H(3)PMo(12)O(40), and H(4)SiW(12)O(40)) tested in this study, the inactivation of E. coli was fastest with H(4)SiW(12)O(40) while that of B. subtilis was the most efficient with H(3)PW(12)O(40). Although the biocidal action of TiO2 photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO2-PCI. While TiO2 caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO2-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology.

  18. Chromosomal rearrangement interferes with meiotic X chromosome inactivation.

    PubMed

    Homolka, David; Ivanek, Robert; Capkova, Jana; Jansa, Petr; Forejt, Jiri

    2007-10-01

    Heterozygosity for certain mouse and human chromosomal rearrangements is characterized by the incomplete meiotic synapsis of rearranged chromosomes, by their colocalization with the XY body in primary spermatocytes, and by male-limited sterility. Previously, we argued that such X-autosomal associations could interfere with meiotic sex chromosome inactivation. Recently, supporting evidence has reported modifications of histones in rearranged chromosomes by a process called the meiotic silencing of unsynapsed chromatin (MSUC). Here, we report on the transcriptional down-regulation of genes within the unsynapsed region of the rearranged mouse chromosome 17, and on the subsequent disturbance of X chromosome inactivation. The partial transcriptional suppression of genes in the unsynapsed chromatin was most prominent prior to the mid-pachytene stage of primary spermatocytes. Later, during the mid-late pachytene, the rearranged autosomes colocalized with the XY body, and the X chromosome failed to undergo proper transcriptional silencing. Our findings provide direct evidence on the MSUC acting at the mRNA level, and implicate that autosomal asynapsis in meiosis may cause male sterility by interfering with meiotic sex chromosome inactivation.

  19. Inactivation of poliovirus by formaldehyde

    PubMed Central

    Gard, Sven

    1957-01-01

    Since formaldehyde, either alone or in combination with other inactivating agents, is at present used in the production of all so-called “killed” poliovirus vaccines, a thorough knowledge of the kinetics of the reaction between the chemical agent and the virus, and of the mechanisms involved, is of great practical importance. In this paper the problem is discussed against the background of present knowledge of the structure of the virus and the chemical nature of the action of formaldehyde. PMID:13511143

  20. Phenol derivatives accelerate inactivation kinetics in one inactivation-deficient mutant human skeletal muscle Na(+) channel.

    PubMed

    Haeseler, G; Piepenbrink, A; Bufler, J; Dengler, R; Hecker, H; Aronson, J; Piepenbrock, S; Leuwer, M

    2001-03-23

    Altered inactivation kinetics in skeletal muscle Na(+) channels due to mutations in the encoding gene are causal for the alterations in muscle excitability in nondystrophic myotonia. Na(+) channel blockers like lidocaine and mexiletine, suggested for therapy of myotonia, do not reconstitute inactivation in channels with defective inactivation in vitro. We examined the effects of four methylated and/or halogenated phenol derivatives on one heterologously expressed inactivation-deficient Paramyotonia congenita-mutant (R1448H) muscle Na(+) channel in vitro. All these compounds accelerated delayed inactivation of R1448H-whole-cell currents during a depolarization and delayed accelerated recovery from inactivation. The potency of these effects paralleled the potency of the drugs to block the peak current amplitude. We conclude that the investigated phenol derivatives affect inactivation-deficient Na(+) channels more specifically than lidocaine and mexiletine. However, for all compounds, the effect on inactivation was accompanied by a substantial block of the peak current amplitude.

  1. Infectivity of RNA from Inactivated Poliovirus

    PubMed Central

    Nuanualsuwan, Suphachai; Cliver, Dean O.

    2003-01-01

    During inactivation of poliovirus type 1 (PV-1) by exposure to UV, hypochlorite, and heat (72°C), the infectivity of the virus was compared with that of its RNA. DEAE-dextran (1-mg/ml concentration in Dulbecco's modified Eagle medium buffered with 0.05 M Tris, pH 7.4) was used to facilitate transfecting PV-1 RNA into FRhK-4 host cells. After interaction of PV-1 RNA with cell monolayer at room temperature (21 to 22°C) for 20 min, the monolayers were washed with 5 ml of Hanks balanced salt solution. The remainder of the procedure was the same as that for the conventional plaque technique, which was also used for quantifying the PV-1 whole-particle infectivity. Plaque formation by extracted RNA was approximately 100,000-fold less efficient than that by whole virions. The slopes of best-fit regression lines of inactivation curves for virion infectivity and RNA infectivity were compared to determine the target of inactivation. For UV and hypochlorite inactivation the slopes of inactivation curves of virion infectivity and RNA infectivity were not statistically different. However, the difference of slopes of inactivation curves of virion infectivity and RNA infectivity was statistically significant for thermal inactivation. The results of these experiments indicate that viral RNA is a primary target of UV and hypochlorite inactivations but that the sole target of thermal inactivation is the viral capsid. PMID:12620852

  2. X-chromosome inactivation and escape

    PubMed Central

    DISTECHE, CHRISTINE M.; BERLETCH, JOEL B.

    2016-01-01

    X-chromosome inactivation, which was discovered by Mary Lyon in 1961 results in random silencing of one X chromosome in female mammals. This review is dedicated to Mary Lyon, who passed away last year. She predicted many of the features of X inactivation, for e.g., the existence of an X inactivation center, the role of L1 elements in spreading of silencing and the existence of genes that escape X inactivation. Starting from her published work here we summarize advances in the field. PMID:26690513

  3. Plasmonic Enhancement of Selective Photonic Virus Inactivation.

    PubMed

    Nazari, Mina; Xi, Min; Lerch, Sarah; Alizadeh, M H; Ettinger, Chelsea; Akiyama, Hisashi; Gillespie, Christopher; Gummuluru, Suryaram; Erramilli, Shyamsunder; Reinhard, Björn M

    2017-09-20

    Femtosecond (fs) pulsed laser irradiation techniques have attracted interest as a photonic approach for the selective inactivation of virus contaminations in biological samples. Conventional pulsed laser approaches require, however, relatively long irradiation times to achieve a significant inactivation of virus. In this study, we investigate the enhancement of the photonic inactivation of Murine Leukemia Virus (MLV) via 805 nm femtosecond pulses through gold nanorods whose localized surface plasmon resonance overlaps with the excitation laser. We report a plasmonically enhanced virus inactivation, with greater than 3.7-log reduction measured by virus infectivity assays. Reliable virus inactivation was obtained for 10 s laser exposure with incident laser powers ≥0.3 W. Importantly, the fs-pulse induced inactivation was selective to the virus and did not induce any measurable damage to co-incubated antibodies. The loss in viral infection was associated with reduced viral fusion, linking the loss in infectivity with a perturbation of the viral envelope. Based on the observations that physical contact between nanorods and virus particles was not required for viral inactivation and that reactive oxygen species (ROS) did not participate in the detected viral inactivation, a model of virus inactivation based on plasmon enhanced shockwave generation is proposed.

  4. Modeling of human factor Va inactivation by activated protein C

    PubMed Central

    2012-01-01

    Background Because understanding of the inventory, connectivity and dynamics of the components characterizing the process of coagulation is relatively mature, it has become an attractive target for physiochemical modeling. Such models can potentially improve the design of therapeutics. The prothrombinase complex (composed of the protease factor (F)Xa and its cofactor FVa) plays a central role in this network as the main producer of thrombin, which catalyses both the activation of platelets and the conversion of fibrinogen to fibrin, the main substances of a clot. A key negative feedback loop that prevents clot propagation beyond the site of injury is the thrombin-dependent generation of activated protein C (APC), an enzyme that inactivates FVa, thus neutralizing the prothrombinase complex. APC inactivation of FVa is complex, involving the production of partially active intermediates and “protection” of FVa from APC by both FXa and prothrombin. An empirically validated mathematical model of this process would be useful in advancing the predictive capacity of comprehensive models of coagulation. Results A model of human APC inactivation of prothrombinase was constructed in a stepwise fashion by analyzing time courses of FVa inactivation in empirical reaction systems with increasing number of interacting components and generating corresponding model constructs of each reaction system. Reaction mechanisms, rate constants and equilibrium constants informing these model constructs were initially derived from various research groups reporting on APC inactivation of FVa in isolation, or in the presence of FXa or prothrombin. Model predictions were assessed against empirical data measuring the appearance and disappearance of multiple FVa degradation intermediates as well as prothrombinase activity changes, with plasma proteins derived from multiple preparations. Our work integrates previously published findings and through the cooperative analysis of in vitro

  5. Charge Immobilization of Skeletal Muscle Na+ Channels: Role of Residues in the Inactivation Linker

    PubMed Central

    Groome, James R.; Dice, Margaret C.; Fujimoto, Esther; Ruben, Peter C.

    2007-01-01

    We investigated structural determinants of fast inactivation and deactivation in sodium channels by comparing ionic flux and charge movement in skeletal muscle channels, using mutations of DIII-DIV linker charges. Charge altering and substituting mutations at K-1317, K-1318 depolarized the g(V) curve but hyperpolarized the h∞ curve. Charge reversal and substitution at this locus reduced the apparent voltage sensitivity of open- and closed-state fast inactivation. These effects were not observed with charge reversal at E-1314, E-1315. Mutations swapping or neutralizing the negative cluster at 1314, 1315 and the positive cluster at 1317, 1318 indicated that local interactions dictate the coupling of activation to fast inactivation. Gating charge was immobilized before channel entry into fast inactivation in hNaV1.4 but to a lesser extent in mutations at K-1317, K-1318. These results suggest that charge is preferentially immobilized in channels inactivating from the open state. Recovery of gating charge proceeded with a single, fast phase in the double mutation K-1317R, K-1318R. This mutation also partially uncoupled recovery from deactivation. Our findings indicate that charged residues near the fast inactivation “particle” allosterically interact with voltage sensors to control aspects of gating in sodium channels. PMID:17513361

  6. Urease from Helicobacter pylori is inactivated by sulforaphane and other isothiocyanates

    PubMed Central

    Fahey, Jed W.; Stephenson, Katherine K.; Wade, Kristina L.; Talalay, Paul

    2013-01-01

    Infections by Helicobacter pylori are very common, causing gastroduodenal inflammation including peptic ulcers, and increasing the risk of gastric neoplasia. The isothiocyanate (ITC) sulforaphane [SF; 1-isothiocyanato-4-(methylsulfinyl)butane] derived from edible crucifers such as broccoli is potently bactericidal against Helicobacter, including antibiotic-resistant strains, suggesting a possible dietary therapy. Gastric H. pylori infections express high urease activity which generates ammonia, neutralizes gastric acidity, and promotes inflammation. The finding that SF inhibits (inactivates) urease (jack bean and Helicobacter) raised the issue of whether these properties might be functionally related. The rates of inactivation of urease activity depend on enzyme and SF concentrations and show first order kinetics. Treatment with SF results in time-dependent increases in the ultraviolet absorption of partially purified Helicobacter urease in the 280–340 nm region. This provides direct spectroscopic evidence for the formation of dithiocarbamates between the ITC group of SF and cysteine thiols of urease. The potencies of inactivation of Helicobacter urease by isothiocyanates structurally related to SF were surprisingly variable. Natural isothiocyanates closely related to SF, previously shown to be bactericidal (berteroin, hirsutin, phenethyl isothiocyanate, alyssin, and erucin), did not inactivate urease activity. Furthermore, SF is bactericidal against both urease positive and negative H. pylori strains. In contrast, some isothiocyanates such as benzoyl-ITC, are very potent urease inactivators, but are not bactericidal. The bactericidal effects of SF and other ITC against Helicobacter are therefore not obligatorily linked to urease inactivation, but may reduce the inflammatory component of Helicobacter infections. PMID:23583386

  7. Aminopyridines block an inactivating potassium current having slow recovery kinetics.

    PubMed Central

    Wagoner, P K; Oxford, G S

    1990-01-01

    The blocking action of aminopyridines on an inactivating K current (lKi) in GH3 pituitary cells was studied before and after altering the macroscopic decay of the current with N-bromoacetamide (NBA). The first depolarizing pulse delivered either seconds or minutes after beginning 4-aminopyridine (4AP) application, elicited a current with both a more rapid decay and a reduced peak amplitude. The rapid decay (or time-dependent block) was especially prominent in NBA-treated cells. With continued drug application, subsequent test pulses revealed a stable block of peak current, greater in NBA-treated than control cells. Recovery from block was enhanced by hyperpolarizing holding potentials and by the first depolarizing pulse delivered after prolonged recovery intervals. Unlike aminopyridine block of other K currents, there was no convincing evidence for voltage shifts in activation or inactivation, or for voltage and frequency-dependent unblock. Increasing the open probability of the channels did, however, facilitate the block. Although the behavior of currents in 4AP was suggestive of "open channel block," the block was not produced by 4-aminopyridine methiodide, a positively charged aminopyridine. Moreover, because partial block and recovery occurred without opening the channels we suggest that aminopyridines bind to, or near, this K channel, that this binding is enhanced by opening the channel, and that a conformational change is induced which mimics inactivation. Because recovery from block is enhanced by negative potentials, we suggest that aminopyridine molecules may become "trapped" by inactivation awaiting the slow process of reactivation to escape their binding sites. PMID:2275964

  8. Percutaneous irreversible electroporation of a renal tumor: Anesthetic management.

    PubMed

    de la Flor-Robledo, M; Solís-Muñoz, P; Sanjuán-Álvarez, M; Abadal-Villayandre, J M; Asensio-Merino, F

    2016-01-01

    Percutaneous irreversible electroporation (IRE) is a novel tumour ablation method. The application of short and high-voltage electrical pulses to the target lesion induces alterations in cell membrane permeability, finally causing tumour cell death. The extremely high-voltage that is needed in this technique requires the surveillance and management of an experienced anaesthesiologist, as it involves a significant risk of complications, such as cardiac arrhythmias or seizures. The case is presented of a 66 year-old patient diagnosed with a renal adenocarcinoma, and who received without intention-to-cure IRE under general anaesthesia. This case represents the first time this type of technique is used in Spain. Copyright © 2015 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Publicado por Elsevier España, S.L.U. All rights reserved.

  9. Sub-kBT micro-electromechanical irreversible logic gate.

    PubMed

    López-Suárez, M; Neri, I; Gammaitoni, L

    2016-06-28

    In modern computers, computation is performed by assembling together sets of logic gates. Popular gates like AND, OR and XOR, processing two logic inputs and yielding one logic output, are often addressed as irreversible logic gates, where the sole knowledge of the output logic value is not sufficient to infer the logic value of the two inputs. Such gates are usually believed to be bounded to dissipate a finite minimum amount of energy determined by the input-output information difference. Here we show that this is not necessarily the case, by presenting an experiment where a OR logic gate, realized with a micro-electromechanical cantilever, is operated with energy well below the expected limit, provided the operation is slow enough and frictional phenomena are properly addressed.

  10. Irreversible Adsorption Governs the Equilibration of Thin Polymer Films

    NASA Astrophysics Data System (ADS)

    Panagopoulou, Anna; Napolitano, Simone

    2017-09-01

    We demonstrate that the enhanced segmental motion commonly observed in spin cast thin polymer films is a nonequilibrium phenomenon. In the presence of nonrepulsive interfaces, prolonged annealing in the liquid state allows, in fact, recovering bulk segmental mobility. Our measurements prove that, while the fraction of unrelaxed chains increases upon nanoconfinement, the dynamics of equilibration is almost unaffected by the film thickness. We show that the rate of equilibration of nanoconfined chains does not depend on the structural relaxation process but on the feasibility to form an adsorbed layer. We propose that the equilibration of the thin polymer melts is driven by the slow relaxation of interfacial chains upon irreversible adsorption on the confining walls.

  11. Sub-kBT micro-electromechanical irreversible logic gate

    NASA Astrophysics Data System (ADS)

    López-Suárez, M.; Neri, I.; Gammaitoni, L.

    2016-06-01

    In modern computers, computation is performed by assembling together sets of logic gates. Popular gates like AND, OR and XOR, processing two logic inputs and yielding one logic output, are often addressed as irreversible logic gates, where the sole knowledge of the output logic value is not sufficient to infer the logic value of the two inputs. Such gates are usually believed to be bounded to dissipate a finite minimum amount of energy determined by the input-output information difference. Here we show that this is not necessarily the case, by presenting an experiment where a OR logic gate, realized with a micro-electromechanical cantilever, is operated with energy well below the expected limit, provided the operation is slow enough and frictional phenomena are properly addressed.

  12. Sub-kBT micro-electromechanical irreversible logic gate

    PubMed Central

    López-Suárez, M.; Neri, I.

    2016-01-01

    In modern computers, computation is performed by assembling together sets of logic gates. Popular gates like AND, OR and XOR, processing two logic inputs and yielding one logic output, are often addressed as irreversible logic gates, where the sole knowledge of the output logic value is not sufficient to infer the logic value of the two inputs. Such gates are usually believed to be bounded to dissipate a finite minimum amount of energy determined by the input–output information difference. Here we show that this is not necessarily the case, by presenting an experiment where a OR logic gate, realized with a micro-electromechanical cantilever, is operated with energy well below the expected limit, provided the operation is slow enough and frictional phenomena are properly addressed. PMID:27350333

  13. Non-thermal irreversible electroporation for deep intracranial disorders.

    PubMed

    Garcia, Paulo A; Neal, Robert E; Rossmeisl, John H; Davalos, Rafael V

    2010-01-01

    Non-thermal irreversible electroporation (N-TIRE) is a new minimally invasive technique to kill undesirable tissue. We build on our previous intracranial studies in order to evaluate the possibility of using N-TIRE for deep intracranial disorders. In this manuscript we describe a minimally invasive computed tomography (CT) guided N-TIRE procedure in white matter. In addition, we report the electric field threshold needed for white matter ablation (630 - 875 V/cm) using four sets of twenty 50 µs pulses at a voltage-to-distance ratio of 1000 V/cm. We also confirm the non-thermal aspect of the technique with real time temperature data measured at the electrode-tissue interface.

  14. Large-cell Monte Carlo renormalization of irreversible growth processes

    NASA Technical Reports Server (NTRS)

    Nakanishi, H.; Family, F.

    1985-01-01

    Monte Carlo sampling is applied to a recently formulated direct-cell renormalization method for irreversible, disorderly growth processes. Large-cell Monte Carlo renormalization is carried out for various nonequilibrium problems based on the formulation dealing with relative probabilities. Specifically, the method is demonstrated by application to the 'true' self-avoiding walk and the Eden model of growing animals for d = 2, 3, and 4 and to the invasion percolation problem for d = 2 and 3. The results are asymptotically in agreement with expectations; however, unexpected complications arise, suggesting the possibility of crossovers, and in any case, demonstrating the danger of using small cells alone, because of the very slow convergence as the cell size b is extrapolated to infinity. The difficulty of applying the present method to the diffusion-limited-aggregation model, is commented on.

  15. Citrate synthesis in intact rat-liver mitochondria is irreversible.

    PubMed

    Greksák, M; Lopes-Cardozo, M; van den Bergh, S G

    1982-02-01

    Rat-liver mitochondria were incubated with [1,5-14C]citrate in the presence of fluorocitrate to block its oxidation in the Krebs cycle. The reaction products were analysed enzymatically and by anion-exchange chromatography. Incorporation of 14C into acetyl-L-carnitine or ketone bodies via a backward action of citrate synthase was not observed. The optimal rate of citrate synthesis from pyruvate and malate in the presence of fluorocitrate was 15 nmol . mg-1 min-1. In the absence of fluorocitrate, but in the presence of malonate, citrate was oxidized to succinate at a rate of 4 nmol . mg-1 . min-1. We conclude that the synthesis of citrate by intact rat liver mitochondria is an irreversible process. The possible mechanism underlying this phenomenon and the consequence for metabolic regulation are discussed.

  16. Ac irreversibility line of bismuth-based high temperature superconductors

    SciTech Connect

    Mehdaoui, A.; Beille, J.; Berling, D.; Loegel, B.; Noudem, J.G.; Tournier, R.

    1997-09-01

    We discuss the magnetic properties of lead doped Bi-2223 bulk samples obtained through combined magnetic melt texturing and hot pressing (MMTHP). The ac complex susceptibility measurements are achieved over a broad ac field range (1 Oe{lt}h{sub ac}{lt}100 Oe) and show highly anisotropic properties. The intergranular coupling is improved in the direction perpendicular to the applied stress and magnetic field direction, and an intragranular loss peak is observed for the first time. A comparison is made with other bismuth-based compounds and it is shown that the MMTHP process shifts the ac irreversibility line (ac IL) toward higher fields. It is also shown that all the ac IL{close_quote}s for quasi 2D bismuth-based compounds show a nearly quadratic temperature dependence and deviate therefore strongly from the linear behavior observed in quasi 3D compounds and expected from a critical state model.{copyright} {ital 1997 Materials Research Society.}

  17. Exact solutions for mass-dependent irreversible aggregations.

    PubMed

    Son, Seung-Woo; Christensen, Claire; Bizhani, Golnoosh; Grassberger, Peter; Paczuski, Maya

    2011-10-01

    We consider the mass-dependent aggregation process (k+1)X→X, given a fixed number of unit mass particles in the initial state. One cluster is chosen proportional to its mass and is merged into one, either with k neighbors in one dimension, or--in the well-mixed case--with k other clusters picked randomly. We find the same combinatorial exact solutions for the probability to find any given configuration of particles on a ring or line, and in the well-mixed case. The mass distribution of a single cluster exhibits scaling laws and the finite-size scaling form is given. The relation to the classical sum kernel of irreversible aggregation is discussed.

  18. Rat liver regeneration following ablation with irreversible electroporation.

    PubMed

    Golberg, Alexander; Bruinsma, Bote G; Jaramillo, Maria; Yarmush, Martin L; Uygun, Basak E

    2016-01-01

    During the past decade, irreversible electroporation (IRE) ablation has emerged as a promising tool for the treatment of multiple diseases including hepatic cancer. However, the mechanisms behind the tissue regeneration following IRE ablation have not been investigated. Our results indicate that IRE treatment immediately kills the cells at the treatment site preserving the extracellular architecture, in effect causing in vivo decellularization. Over the course of 4 weeks, progenitor cell differentiation, through YAP and notch pathways, together with hepatocyte expansion led to almost complete regeneration of the ablated liver leading to the formation of hepatocyte like cells at the ablated zone. We did not observe significant scarring or tumor formation at the regenerated areas 6 months post IRE. Our study suggests a new model to study the regeneration of liver when the naïve extracellular matrix is decellularized in vivo with completely preserved extracellular architecture.

  19. Irreversible energy gain by linear and nonlinear oscillators

    NASA Astrophysics Data System (ADS)

    Bauer, D.; Mulser, P.

    2005-01-01

    A particle can gain appreciable irreversible energy ("absorption") from linear or nonlinear oscillations only by ballistic excitation ("collision") or, if excited by an adiabatic pulse of constant frequency, by undergoing resonance. For the linear oscillator it is shown that the transition from ballistic to adiabatic behavior out of resonance occurs for sin2-pulses 2 4 eigenperiod long. In the case of a linear oscillator with time-varying eigenfrequency it is shown that Cornu's double spiral represents an attractor, either for zero energy gain out of resonance or finite gain by transiting through resonance. One of the remarkable properties of nonlinear oscillators is that resonance depends on the level of excitation. It is this property which opens a new access to understanding the dominant heating process at high laser intensities, the so-called collisionless absorption phase in solids, extended cluster media, dusty plasmas, and sprays, well guaranteed by experiments and computer simulations but hitherto not well understood in physical terms.

  20. Rat liver regeneration following ablation with irreversible electroporation

    PubMed Central

    Bruinsma, Bote G.; Jaramillo, Maria; Yarmush, Martin L.

    2016-01-01

    During the past decade, irreversible electroporation (IRE) ablation has emerged as a promising tool for the treatment of multiple diseases including hepatic cancer. However, the mechanisms behind the tissue regeneration following IRE ablation have not been investigated. Our results indicate that IRE treatment immediately kills the cells at the treatment site preserving the extracellular architecture, in effect causing in vivo decellularization. Over the course of 4 weeks, progenitor cell differentiation, through YAP and notch pathways, together with hepatocyte expansion led to almost complete regeneration of the ablated liver leading to the formation of hepatocyte like cells at the ablated zone. We did not observe significant scarring or tumor formation at the regenerated areas 6 months post IRE. Our study suggests a new model to study the regeneration of liver when the naïve extracellular matrix is decellularized in vivo with completely preserved extracellular architecture. PMID:26819842

  1. Irreversible thermochromism in copper chloride Imidazolium Nanoparticle Networks.

    PubMed

    Kronstein, Martin; Kriechbaum, Konstantin; Akbarzadeh, Johanna; Peterlik, Herwig; Neouze, Marie-Alexandra

    2013-08-14

    In this work Imidazolium Nanoparticle Networks (INNs) with chloride counter-ions were used to complex copper dichloride. This complexation reaction leads to the formation of a green material. The properties of the copper INN material were compared to: first, copper imidazolium complexes, without the presence of silica nanoparticles, which are not thermochromic; second, chloride-containing INN material. The copper INN material showed irreversible thermochromic behaviour, with a clear colour change from green to yellow at 180 °C, which is due to a configuration change of the copper complex from planar to tetragonal. This structural change was studied using DSC and in situ SAXS measurements during heat treatment. The thermochromic material is stable under air up to 250 °C. This preliminary study opens the door of optical sensors for INN materials.

  2. Energy cascade and irreversibility in reversible shell models of turbulence

    NASA Astrophysics Data System (ADS)

    de Pietro, Massimo; Cencini, Massimo; Biferale, Luca; Boffetta, Guido

    2016-11-01

    Dissipation breaks the time reversibility of the Navier-Stokes equation. It has been conjectured that forced-dissipated Navier-Stokes equations are "equivalent" to a modified version of the equations in which the dissipative term is modified such as to preserve the time-inversion symmetry. This can be realized choosing a velocity dependent viscosity in such a way to preserve a global quantity, e.g. energy or enstrophy. Here we present results on shell models of turbulence where time reversibility is restored following the mechanism originally suggested. We show that when the time-dependent viscosity is chosen such as to conserve enstrophy, the resulting reversible dynamics exhibit an energy cascade, sharing the same features of the standard irreversible cascade. We acknowledge funding from ERC ADG NewTURB No. 339032.

  3. Advertising and Irreversible Opinion Spreading in Complex Social Networks

    NASA Astrophysics Data System (ADS)

    Candia, Julián

    Irreversible opinion spreading phenomena are studied on small-world and scale-free networks by means of the magnetic Eden model, a nonequilibrium kinetic model for the growth of binary mixtures in contact with a thermal bath. In this model, the opinion of an individual is affected by those of their acquaintances, but opinion changes (analogous to spin flips in an Ising-like model) are not allowed. We focus on the influence of advertising, which is represented by external magnetic fields. The interplay and competition between temperature and fields lead to order-disorder transitions, which are found to also depend on the link density and the topology of the complex network substrate. The effects of advertising campaigns with variable duration, as well as the best cost-effective strategies to achieve consensus within different scenarios, are also discussed.

  4. Large-cell Monte Carlo renormalization of irreversible growth processes

    NASA Technical Reports Server (NTRS)

    Nakanishi, H.; Family, F.

    1985-01-01

    Monte Carlo sampling is applied to a recently formulated direct-cell renormalization method for irreversible, disorderly growth processes. Large-cell Monte Carlo renormalization is carried out for various nonequilibrium problems based on the formulation dealing with relative probabilities. Specifically, the method is demonstrated by application to the 'true' self-avoiding walk and the Eden model of growing animals for d = 2, 3, and 4 and to the invasion percolation problem for d = 2 and 3. The results are asymptotically in agreement with expectations; however, unexpected complications arise, suggesting the possibility of crossovers, and in any case, demonstrating the danger of using small cells alone, because of the very slow convergence as the cell size b is extrapolated to infinity. The difficulty of applying the present method to the diffusion-limited-aggregation model, is commented on.

  5. [Irreversible coma following hypoglycemia in Sheehan syndrome with adrenocortical insufficiency].

    PubMed

    Sas, A M; Meynaar, I A; Laven, J S; Bakker, S L; Feelders, R A

    2003-08-23

    A 24-year-old woman of Somali origin delivered at term after an uncomplicated pregnancy. Post-partum haemorrhage resulted in hypovolaemic shock which was treated by hysterectomy. Five days later she became comatose due to unrecognised hypoglycaemia which caused severe irreversible brain damage and status epilepticus. Treatment in the intensive care unit with artificial respiration, prednisolone, desmopressin, inotropic support, barbiturates and an anaesthetic under EEG guidance was unsuccessful. The patient died 28 days post-partum. The hypoglycaemia was due to a combination of (a) inadequate glucose intake and (b) lack of counter-regulatory mechanisms due to a deficiency of steroids and growth hormone as a result of loss of pituitary function (Sheehan syndrome) together with adrenocortical insufficiency. The combination of Sheehan syndrome and primary adrenocortical insufficiency has not been described previously in the literature.

  6. The Social Cost of Stochastic and Irreversible Climate Change

    NASA Astrophysics Data System (ADS)

    Cai, Y.; Judd, K. L.; Lontzek, T.

    2013-12-01

    Many scientists are worried about climate change triggering abrupt and irreversible events leading to significant and long-lasting damages. For example, a rapid release of methane from permafrost may lead to amplified global warming, and global warming may increase the frequency and severity of heavy rainfall or typhoon, destroying large cities and killing numerous people. Some elements of the climate system which might exhibit such a triggering effect are called tipping elements. There is great uncertainty about the impact of anthropogenic carbon and tipping elements on future economic wellbeing. Any rational policy choice must consider the great uncertainty about the magnitude and timing of global warming's impact on economic productivity. While the likelihood of tipping points may be a function of contemporaneous temperature, their effects are long lasting and might be independent of future temperatures. It is assumed that some of these tipping points might occur even in this century, but also that their duration and post-tipping impact are uncertain. A faithful representation of the possibility of tipping points for the calculation of social cost of carbon would require a fully stochastic formulation of irreversibility, and accounting for the deep layer of uncertainties regarding the duration of the tipping process and also its economic impact. We use DSICE, a DSGE extension of the DICE2007 model of William Nordhaus, which incorporates beliefs about the uncertain economic impact of possible climate tipping events and uses empirically plausible parameterizations of Epstein-Zin preferences to represent attitudes towards risk. We find that the uncertainty associated with anthropogenic climate change imply carbon taxes much higher than implied by deterministic models. This analysis indicates that the absence of uncertainty in DICE2007 and similar IAM models may result in substantial understatement of the potential benefits of policies to reduce GHG emissions.

  7. Structural Basis for Reversible and Irreversible Inhibition of Human Cathepsin L by their Respective dipeptidyl glyoxal and diazomethylketone Inhibitors

    SciTech Connect

    R Shenoy; J Sivaraman

    2011-12-31

    Cathepsin L plays a key role in many pathophysiological conditions including rheumatoid arthritis, tumor invasion and metastasis, bone resorption and remodeling. Here we report the crystal structures of two analogous dipeptidyl inhibitor complexes which inhibit human cathepsin L in reversible and irreversible modes, respectively. To-date, there are no crystal structure reports of complexes of proteases with their glyoxal inhibitors or complexes of cathepsin L and their diazomethylketone inhibitors. These two inhibitors - inhibitor 1, an {alpha}-keto-{beta}-aldehyde and inhibitor 2, a diazomethylketone, have different groups in the S1 subsite. Inhibitor 1 [Z-Phe-Tyr (OBut)-COCHO], with a Ki of 0.6 nM, is the most potent, reversible, synthetic peptidyl inhibitor of cathepsin L reported to-date. The structure of the inhibitor 1 complex was refined up to 2.2 {angstrom} resolution. The structure of the complex of the inhibitor 2 [Z-Phe-Tyr (t-Bu)-diazomethylketone], an irreversible inhibitor that can inactivate cathepsin L at {micro}M concentrations, was refined up to 1.76 {angstrom} resolution. These two inhibitors have substrate-like interactions with the active site cysteine (Cys25). Inhibitor 1 forms a tetrahedral hemithioacetal adduct, whereas the inhibitor 2 forms a thioester with Cys25. The inhibitor 1 {beta}-aldehyde group is shown to make a hydrogen bond with catalytic His163, whereas the ketone carbonyl oxygen of the inhibitor 2 interacts with the oxyanion hole. tert-Butyl groups of both inhibitors are found to make several non-polar contacts with S' subsite residues of cathepsin L. These studies, combined with other complex structures of cathepsin L, reveal the structural basis for their potency and selectivity.

  8. Independent evolution of transcriptional inactivation on sex chromosomes in birds and mammals.

    PubMed

    Livernois, Alexandra M; Waters, Shafagh A; Deakin, Janine E; Marshall Graves, Jennifer A; Waters, Paul D

    2013-01-01

    X chromosome inactivation in eutherian mammals has been thought to be tightly controlled, as expected from a mechanism that compensates for the different dosage of X-borne genes in XX females and XY males. However, many X genes escape inactivation in humans, inactivation of the X in marsupials is partial, and the unrelated sex chromosomes of monotreme mammals have incomplete and gene-specific inactivation of X-linked genes. The bird ZW sex chromosome system represents a third independently evolved amniote sex chromosome system with dosage compensation, albeit partial and gene-specific, via an unknown mechanism (i.e. upregulation of the single Z in females, down regulation of one or both Zs in males, or a combination). We used RNA-fluorescent in situ hybridization (RNA-FISH) to demonstrate, on individual fibroblast cells, inactivation of 11 genes on the chicken Z and 28 genes on the X chromosomes of platypus. Each gene displayed a reproducible frequency of 1Z/1X-active and 2Z/2X-active cells in the homogametic sex. Our results indicate that the probability of inactivation is controlled on a gene-by-gene basis (or small domains) on the chicken Z and platypus X chromosomes. This regulatory mechanism must have been exapted independently to the non-homologous sex chromosomes in birds and mammals in response to an over-expressed Z or X in the homogametic sex, highlighting the universal importance that (at least partial) silencing plays in the evolution on amniote dosage compensation and, therefore, the differentiation of sex chromosomes.

  9. Cinnamic acid 4-hydroxylase mechanism-based inactivation by psoralen derivatives: cloning and characterization of a C4H from a psoralen producing plant-Ruta graveolens-exhibiting low sensitivity to psoralen inactivation.

    PubMed

    Gravot, Antoine; Larbat, Romain; Hehn, Alain; Lièvre, Karine; Gontier, Eric; Goergen, Jean Louis; Bourgaud, Frédéric

    2004-02-01

    Cinnamate 4-hydroxylase (C4H, EC 1.14.13.11) complete cDNA was cloned from the leaves of Ruta graveolens, a psoralen producing plant. The recombinant enzyme (classified CYP73A32) was expressed in Saccharomyces cerevisiae. Mechanism-based inactivation was investigated using various psoralen derivatives. Only psoralen and 8-methoxypsoralen were found to inactivate C4H. The inactivation was dependent on the presence of NADPH, time of pre-incubation, and inhibitor concentration. Inactivation stoichiometry was 0.9 (+/-0.2) for CYP73A1 and 1.1 (+/-0.2) for CYP73A32. SDS-PAGE analysis demonstrated that [3H]psoralen was irreversibly bound to the C4H apoprotein. K(i) and k(inact) for psoralen and 8-methoxypsoralen inactivation on the two C4H revealed a lower sensitivity for CYP73A32 compared to CYP73A1. Inactivation kinetics were also determined for CYP73A10, a C4H from another furocoumarin-producing plant, Petroselinum crispum. This enzyme was found to behave like CYP73A32, with a weak sensitivity to psoralen and 8-MOP inactivation. Cinnamic acid hydroxylation is a key step in the biosynthesis of phenylpropanoid compounds, psoralen derivatives included. Our results suggest a possible evolution of R. graveolens and P. crispum C4H that might tolerate substantial levels of psoralen derivatives in the cytoplasmic compartment without a depletive effect on C4H and the general phenylpropanoid metabolism.

  10. Inactivation and injury assessment of Escherichia coli during solar and photocatalytic disinfection in LDPE bags.

    PubMed

    Dunlop, P S M; Ciavola, M; Rizzo, L; Byrne, J A

    2011-11-01

    Solar disinfection (SODIS) of Escherichia coli suspensions in low-density polyethylene bag reactors was investigated as a low-cost disinfection method suitable for application in developing countries. The efficiency of a range of SODIS reactor configurations was examined (single skin (SS), double skin, black-backed single skin, silver-backed single skin (SBSS) and composite-backed single skin) using E. coli suspended in model and real surface water. Titanium dioxide was added to the reactors to improve the efficiency of the SODIS process. The effect of turbidity was also assessed. In addition to viable counts, E. coli injury was characterised through spread-plate analysis using selective and non-selective media. The optimal reactor configuration was determined to be the SBSS bag (t(50)=9.0min) demonstrating the importance of UVA photons, as opposed to infrared in the SODIS disinfection mechanism. Complete inactivation (6.5-log) was achieved in the presence of turbidity (50NTU) using the SBSS bag within 180min simulated solar exposure. The addition of titanium dioxide (0.025gL(-1)) significantly enhanced E. coli inactivation in the SS reactor, with 6-log inactivation observed within 90min simulated solar exposure. During the early stages of both SODIS and photocatalytic disinfection, injured E. coli were detected; however, irreversible injury was caused and re-growth was not observed. Experiments under solar conditions were undertaken with total inactivation (6.5-log) observed in the SS reactor within 240min, incomplete inactivation (4-log) was observed in SODIS bottles exposed to the same solar conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Performance of an irreversible quantum Carnot engine with spin 1/2

    NASA Astrophysics Data System (ADS)

    Wu, Feng; Chen, Lingen; Wu, Shuang; Sun, Fengrui; Wu, Chih

    2006-06-01

    The purpose of this paper is to investigate the effect of quantum properties of the working medium on the performance of an irreversible Carnot cycle with spin 1/2. The optimal relationship between the dimensionless power output P* versus the efficiency η for the irreversible quantum Carnot engine with heat leakage and other irreversible losses is derived. Especially, the performances of the engine at low temperature limit and at high temperature limit are discussed.

  12. Inactivation of enzymes and oxidative modification of proteins by stimulated neutrophils.

    PubMed

    Oliver, C N

    1987-02-15

    Differentiated, stimulated HL-60 cells and freshly isolated, stimulated neutrophils inactivate glutamine synthetase (L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2) either inside or outside of Escherichia coli. Stimulated neutrophils also inactivate at least four endogenous enzymes which are inactivated by mixed-function oxidation (MFO) systems in vitro (L. Fucci, C.N. Oliver, M.J. Coon, and E.R. Stadtman (1983) Proc. Natl. Acad. Sci. USA 80, 1521-1525). The inactivation of glutamine synthetase by stimulated neutrophils exhibits characteristics similar to those previously described using both enzymic and nonenzymic MFO systems (R.L. Levine, C.N. Oliver, R.M. Fulks, and E.R. Stadtman (1981) Proc. Natl. Acad. Sci. USA 78, 2120-2124). Although the reaction occurs in the absence of Fe(III), it is stimulated by added Fe (III). Inactivation required molecular oxygen and is partially inhibited by Mn(II), catalase, superoxide dismutase, and metal chelators, ethylenediaminetetraacetic acid and o-phenanthroline. Both the kinetics and the extent of glutamine synthetase inactivation differ when neutrophils are stimulated with phorbol esters compared with formylated peptides. Glutamine synthetase inactivation catalyzed by MFO systems is accompanied by the formation of protein carbonyl derivatives which form stable hydrazones when treated with 2,4-dinitrophenylhydrazine. Multiple carbonyl derivatives are formed in the soluble protein fraction of stimulated neutrophils and these derivatives collectively exhibit an absorbance spectrum similar to that of glutamine synthetase inactivated by liver microsomal cytochrome P-450 MFO system (K. Nakamura, C.N. Oliver, and E.R. Stadtman (1985) Arch. Biochem. Biophys. 240, 319-329).

  13. MPLEx: a method for simultaneous pathogen inactivation and extraction of samples for multi-omics profiling

    SciTech Connect

    Burnum-Johnson, Kristin E.; Kyle, Jennifer E.; Eisfeld, Amie J.; Casey, Cameron P.; Stratton, Kelly G.; Gonzalez, Juan F.; Habyarimana, Fabien; Negretti, Nicholas M.; Sims, Amy C.; Chauhan, Sadhana; Thackray, Larissa B.; Halfmann, Peter J.; Walters, Kevin B.; Kim, Young-Mo; Zink, Erika M.; Nicora, Carrie D.; Weitz, Karl K.; Webb-Robertson, Bobbie-Jo M.; Nakayasu, Ernesto S.; Ahmer, Brian; Konkel, Michael E.; Motin, Vladimir; Baric, Ralph S.; Diamond, Michael S.; Kawaoka, Yoshihiro; Waters, Katrina M.; Smith, Richard D.; Metz, Thomas O.

    2017-01-01

    The continued emergence and spread of infectious agents is of increasing concern due to increased population growth and the associated increased livestock production to meet food demands, increased urbanization and land-use changes, and greater travel. A systems biology approach to infectious disease research can significantly advance our understanding of host-pathogen relationships and facilitate the development of new therapies and vaccines. Molecular characterization of infectious samples outside of appropriate biosafety containment can only take place subsequent to pathogen inactivation. Herein, we describe a modified Folch extraction using chloroform/methanol that facilitates the molecular characterization of infectious samples by enabling simultaneous pathogen inactivation and extraction of proteins, metabolites, and lipids for subsequent mass spectrometry-based multi-omics measurements. This metabolite, protein and lipid extraction (MPLEx) method resulted in complete inactivation of bacterial and viral pathogens with exposed lipid membranes, including Yersinia pestis, Salmonella Typhimurium, and Campylobacter jejuni in pure culture, and Yersinia pestis, Campylobacter jejuni, West Nile, MERS-CoV, Ebola, and influenza H7N9 viruses in infection studies. Partial inactivation was observed for pathogens without exposed lipid membranes including 99.99% inactivation of community-associated methicillin-resistant Staphylococcus aureus, 99.6% and >99% inactivation of Clostridium difficile spores and vegetative cells, respectively, and 50% inactivation of adenovirus type 5. To demonstrate that MPLEx yields biomaterial of sufficient quality for subsequent multi-omics analyses, we highlight select proteomics, metabolomics and lipidomics data from human epithelial lung cells infected with wild-type and mutant forms of influenza H7N9. We believe that MPLEx will facilitate systems biology studies of infectious samples by enabling simultaneous pathogen inactivation and multi

  14. [Catalase inactivation during storage in solution and its stabilization by polysaccharides of microbial origin].

    PubMed

    Shataeva, L K; Zaikina, N A; Samsonov, G V

    1976-01-01

    It has been experimentally shown that the rate of inactivation of pure catalase in solution does not obey the kinetics of the first order. The kinetics of denaturation taking into account partial stabilization of catalase due to the formation of intermolecular complexes of native molecules with denatured molecules has been derived. Using the equation, the rate of catalase inativation during storage in pure solutions has been calculated from the experimental data. Polysaccharides of microbial origin can also stabilize catalase. The kinetics of catalase inactivation in the system where the enzyme and polysaccharide forms a reversibly dissociating complex has been described.

  15. Inactivation of Penicillins by Thiol Broth

    PubMed Central

    Murray, Patrick R.; Niles, Ann C.

    1982-01-01

    Thiol broth with sodium polyanetholesulfonate inactivated penicillin G, carbenicillin, nafcillin, oxacillin, and gentamicin, but had no effect on cephalothin, cefoxitin, clindamycin, chloramphenicol, erythromycin, and tetracycline. Only Thiol broth was capable of this inactivation, which was not influenced by the presence of blood. PMID:7153352

  16. Photodynamic inactivation of mammalian viruses and bacteriophages.

    PubMed

    Costa, Liliana; Faustino, Maria Amparo F; Neves, Maria Graça P M S; Cunha, Angela; Almeida, Adelaide

    2012-07-01

    Photodynamic inactivation (PDI) has been used to inactivate microorganisms through the use of photosensitizers. The inactivation of mammalian viruses and bacteriophages by photosensitization has been applied with success since the first decades of the last century. Due to the fact that mammalian viruses are known to pose a threat to public health and that bacteriophages are frequently used as models of mammalian viruses, it is important to know and understand the mechanisms and photodynamic procedures involved in their photoinactivation. The aim of this review is to (i) summarize the main approaches developed until now for the photodynamic inactivation of bacteriophages and mammalian viruses and, (ii) discuss and compare the present state of the art of mammalian viruses PDI with phage photoinactivation, with special focus on the most relevant mechanisms, molecular targets and factors affecting the viral inactivation process.

  17. [Oxidative inactivation of angiotensin-converting enzyme].

    PubMed

    Sakharov, I Iu; Dukhanina, E A; Puchnina, E A; Danilov, S M; Muzykantov, V R

    1991-01-01

    Hydrogen peroxide inactivates the purified human angiotensin-converting enzyme (ACE) in vitro; the inactivating effect of H2O2 is eliminated by an addition of catalase. The lung and kidney ACE are equally sensitive to the effect of hydrogen peroxide. After addition of oxidants (H2O2 alone or H2O2 + ascorbate or H2O2 + Fe2+ mixtures) to the membranes or homogenates of the lung, the inactivation of membrane-bound ACE is far less pronounced despite the large-scale accumulation of lipid peroxidation products. The marked inactivation of ACE in the membrane fraction (up to 55% of original activity) was observed during ACE incubation with a glucose:glucose oxidase:Fe2+ mixture. Presumably the oxidative potential of H2O2 in tissues in consumed, predominantly, for the oxidation of other components of the membrane (e.g., lipids) rather than for ACE inactivation.

  18. Photodynamic Inactivation of Mammalian Viruses and Bacteriophages

    PubMed Central

    Costa, Liliana; Faustino, Maria Amparo F.; Neves, Maria Graça P. M. S.; Cunha, Ângela; Almeida, Adelaide

    2012-01-01

    Photodynamic inactivation (PDI) has been used to inactivate microorganisms through the use of photosensitizers. The inactivation of mammalian viruses and bacteriophages by photosensitization has been applied with success since the first decades of the last century. Due to the fact that mammalian viruses are known to pose a threat to public health and that bacteriophages are frequently used as models of mammalian viruses, it is important to know and understand the mechanisms and photodynamic procedures involved in their photoinactivation. The aim of this review is to (i) summarize the main approaches developed until now for the photodynamic inactivation of bacteriophages and mammalian viruses and, (ii) discuss and compare the present state of the art of mammalian viruses PDI with phage photoinactivation, with special focus on the most relevant mechanisms, molecular targets and factors affecting the viral inactivation process. PMID:22852040

  19. Histological and Finite Element Analysis of Cell Death due to Irreversible Electroporation

    PubMed Central

    Long, G.; Bakos, G.; Shires, P. K.; Gritter, L.; Crissman, J. W.; Harris, J. L.; Clymer, J. W.

    2014-01-01

    Irreversible electroporation (IRE) has been shown to be an effective method of killing cells locally. In contrast to radiofrequency ablation, the mechanism by which cells are thought to die via IRE is the creation of pores in cell membranes, without substantial increase in tissue temperature. To determine the degree to which cell death is non-thermal, we evaluated IRE in porcine hepatocytes in vivo. Using pulse widths of 10μs, bursts of 3 kV square-wave pulses were applied through a custom probe to the liver of an anesthetized pig. Affected tissue was evaluated histologically via stainings of hematoxylin & eosin (H&E), nitroblue tetrazolium (NBT) to monitor cell respiration and TUNEL to gauge apoptosis. Temperature was measured during the application of electroporation, and heat transfer was modeled via finite element analysis. Cell death was calculated via Arrhenius kinetics. Four distinct zones were observed within the ring return electrode; heat-fixed tissue, coagulation, necrotic, and viable. The Arrhenius damage integral estimated complete cell death only in the first zone, where the temperature exceeded 70°C, and partial or no cell death in the other zones, where maximum temperature was approximately 45°C. Except for a limited area near the electrode tip, cell death in IRE is predominantly due to a non-thermal mechanism. PMID:24000980

  20. Percutaneous Irreversible Electroporation Lung Ablation: Preliminary Results in a Porcine Model

    SciTech Connect

    Deodhar, Ajita; Monette, Sebastien; Single, Gordon W.; Hamilton, William C.; Thornton, Raymond H.; Sofocleous, Constantinos T.; Maybody, Majid; Solomon, Stephen B.

    2011-12-15

    Objective: Irreversible electroporation (IRE) uses direct electrical pulses to create permanent 'pores' in cell membranes to cause cell death. In contrast to conventional modalities, IRE has a nonthermal mechanism of action. Our objective was to study the histopathological and imaging features of IRE in normal swine lung. Materials and Methods: Eleven female swine were studied for hyperacute (8 h), acute (24 h), subacute (96 h), and chronic (3 week) effects of IRE ablation in lung. Paired unipolar IRE applicators were placed under computed tomography (CT) guidance. Some applicators were deliberately positioned near bronchovascular structures. IRE pulse delivery was synchronized with the cardiac rhythm only when ablation was performed within 2 cm of the heart. Contrast-enhanced CT scan was performed immediately before and after IRE and at 1 and 3 weeks after IRE ablation. Representative tissue was stained with hematoxylin and eosin for histopathology. Results: Twenty-five ablations were created: ten hyperacute, four acute, and three subacute ablations showed alveolar edema and necrosis with necrosis of bronchial, bronchiolar, and vascular epithelium. Bronchovascular architecture was maintained. Chronic ablations showed bronchiolitis obliterans and alveolar interstitial fibrosis. Immediate post-procedure CT images showed linear or patchy density along the applicator tract. At 1 week, there was consolidation that resolved partially or completely by 3 weeks. Pneumothorax requiring chest tube developed in two animals; no significant cardiac arrhythmias were noted. Conclusion: Our preliminary porcine study demonstrates the nonthermal and extracellular matrix sparing mechanism of action of IRE. IRE is a potential alternative to thermal ablative modalities.

  1. Irreversible and reversible reactive chromatography: analytical solutions and moment analysis for rectangular pulse injections.

    PubMed

    Bibi, Sameena; Qamar, Shamsul; Seidel-Morgenstern, Andreas

    2015-03-13

    This work is concerned with the analysis of models for linear reactive chromatography describing irreversible A→B and reversible A↔B reactions. In contrast to previously published results rectangular reactant pulses are injected into initially empty or pre-equilibrated columns assuming both Dirichlet and Danckwerts boundary conditions. The models consist of two partial differential equations, accounting for convection, longitudinal dispersion and first order chemical reactions. Due to the effect of involved mechanisms on solute transport, analytical and numerical solutions of the models could be helpful to understand, design and optimize chromatographic reactors. The Laplace transformation is applied to solve the model equations analytically for linear adsorption isotherms. Statistical temporal moments are derived from solutions in the Laplace domain. Analytical results are compared with numerical predictions generated using a high-resolution finite volume scheme for two sets of boundary conditions. Several case studies are carried out to analyze reactive liquid chromatographic processes for a wide range of mass transfer and reaction kinetics. Good agreements in the results validate the correctness of the analytical solutions and accuracy of the proposed numerical algorithm.

  2. Susceptibility of the early Earth to irreversible glaciation caused by carbon dioxide clouds.

    PubMed

    Caldeira, K; Kasting, J F

    1992-09-17

    Simple energy-balance climate models of the Budyko/Sellers type predict that a small (2-5%) decrease in solar output could result in runaway glaciation on the Earth. But solar fluxes 25-30% lower early in the Earth's history apparently did not lead to this result. One currently favoured explanation is that high partial pressures of carbon dioxide, caused by higher volcanic outgassing rates and/or slower rates of silicate weathering, created a large enough greenhouse effect to keep the planet warm. This does not resolve the problem of climate stability, however, because as we argue here, the oceans can freeze much more quickly than CO2 can accumulate in the atmosphere. Had such a transient global glaciation occurred in the distant past when solar luminosity was low, it might have been irreversible because of the formation of highly reflective CO2 clouds, similar to those encountered in climate simulations of early Mars. Our simulations of the early Earth, incorporating the possible formation of such clouds, suggest that the Earth might not be habitable today had it not been warm during the first part of its history.

  3. Irreversible denaturation mapping of a pyrimidine-rich domain of a complex satellite DNA

    SciTech Connect

    LaMarca, M.E.; Allison, D.P.; Skinner, D.M.

    1981-06-25

    The highly complex G + C-rich satellite DNA of the Bermuda land crab Gecarcinus lateralis has been studied by denaturation mapping. Following digestion of the satellite with EndoR.Eco RI, the major 2.07-kilo-base pair (kbp) basic repeating unit and a minor 4.14-kbp fragment were exposed to 254 nm light in the presence of silver ions, conditions which resulted in essentially irreversible denaturation of regions rich in adjacent pyrimidines by the formation of pyrimidine dimers. The positions and sizes of the denatured regions were determined in electron micrographs of partially denatured 2.07-kbp and 4.14-kbp fragments spread in the presence of formamide. The positions of the denaturation bubbles in the 4.14-kbp fragments support restriction enzyme mapping evidence that it is a dimer of the 2.07-kbp fragment arranged head to tail. Sequencing data show that the predominant sequence of a 0.29-kbp region centered aroung 0.64 kbp in the basic repeat unit is 49% A + T and that 42% of the bases are adjacent TTs and CTs capable of dimerization under the conditions used.

  4. Histological and finite element analysis of cell death due to irreversible electroporation.

    PubMed

    Long, G; Bakos, G; Shires, P K; Gritter, L; Crissman, J W; Harris, J L; Clymer, J W

    2014-12-01

    Irreversible electroporation (IRE) has been shown to be an effective method of killing cells locally. In contrast to radiofrequency ablation, the mechanism by which cells are thought to die via IRE is the creation of pores in cell membranes, without substantial increase in tissue temperature. To determine the degree to which cell death is non-thermal, we evaluated IRE in porcine hepatocytes in vivo. Using pulse widths of 10 µs, bursts of 3 kV square-wave pulses were applied through a custom probe to the liver of an anesthetized pig. Affected tissue was evaluated histologically via stainings of hematoxylin & eosin (H&E), nitroblue tetrazolium (NBT) to monitor cell respiration and TUNEL to gauge apoptosis. Temperature was measured during the application of electroporation, and heat transfer was modeled via finite element analysis. Cell death was calculated via Arrhenius kinetics. Four distinct zones were observed within the ring return electrode; heat-fixed tissue, coagulation, necrotic, and viable. The Arrhenius damage integral estimated complete cell death only in the first zone, where the temperature exceeded 70°C, and partial or no cell death in the other zones, where maximum temperature was approximately 45°C. Except for a limited area near the electrode tip, cell death in IRE is predominantly due to a non-thermal mechanism.

  5. Irreversible binding of an anticancer compound (BI-94) to plasma proteins

    PubMed Central

    Gautam, Nagsen; Thakare, Rhishikesh; Rana, Sandeep; Natarajan, Amarnath; Alnouti, Yazen

    2015-01-01

    1. We investigated the mechanisms responsible for the in vivo instability of a benzofurazan compound BI-94 (NSC228148) with potent anti-cancer activity. 2. BI-94 was stable in MeOH, water, and in various buffers at pHs 2.5–5, regardless of the buffer composition. In contrast, BI-94 was unstable in NaOH and at pHs 7–9, regardless of the buffer composition. BI-94 disappeared immediately after spiking into mice, rat, monkey, and human plasma. BI-94 stability in plasma can be only partially restored by acidifying it, which indicated other mechanisms in addition to pH for BI-94 instability in plasma. 3. BI-94 formed adducts with the trapping agents, glutathione (GSH) and N-acetylcysteine (NAC), in vivo and in vitro via nucleophilic aromatic substitution reaction. The kinetics of adduct formation showed that neutral or physiological pHs enhanced and accelerated GSH and NAC adduct formation with BI-94, whereas acidic pHs prevented it. Therefore, physiological pHs not only altered BI-94 chemical stability but also enhanced adduct formation with endogenous nucleophiles. In addition, adduct formation with human serum albumin-peptide 3 (HSA-T3) at the Cys34 position was demonstrated. 4. In conclusion, BI-94 was unstable at physiological conditions due to chemical instability and irreversible binding to plasma proteins. PMID:25869245

  6. Cholesterol oxidase from Bordetella species promotes irreversible cell apoptosis in lung adenocarcinoma by cholesterol oxidation

    PubMed Central

    Liu, J; Xian, G; Li, M; Zhang, Y; Yang, M; Yu, Y; Lv, H; Xuan, S; Lin, Y; Gao, L

    2014-01-01

    Cholesterol oxidase (COD), an enzyme catalyzing the oxidation of cholesterol, has been applied to track the distribution of membrane cholesterol. Little investigations about the effect of COD on tumor cells have been performed. In the present study, we provided evidence that COD from Bordetella species (COD-B), induced apoptosis of lung cancer cells in vitro and in vivo. COD-B treatment inhibited Akt and ERK1/2 phosphorylation in dose- and time-dependent manner, which was not reversed and was even aggravated by cholesterol addition. Further investigation indicated that COD-B treatment promoted the generation of reactive oxygen species (ROS) and that cholesterol addition further elevated ROS levels. Moreover, COD-B treatment resulted in JNK and p38 phosphorylation, downregulation of Bcl-2, upregulation of Bax, activated caspase-3 and cytochrome C release, which likely responded to freshly produced hydrogen peroxide that accompanied cholesterol oxidation. Catalase pretreatment could only partially prevent COD-B-induced events, suggesting that catalase inhibited H2O2-induced signal transduction but had little effect on signal pathways involved in cholesterol depletion. Our results demonstrated that COD-B led to irreversible cell apoptosis by decreasing cholesterol content and increasing ROS level. In addition, COD-B may be a promising candidate for a novel anti-tumor therapy. PMID:25118932

  7. Partial breast brachytherapy

    MedlinePlus

    ... brachytherapy; Accelerated partial breast irradiation - brachytherapy; Partial breast radiation therapy - brachytherapy; Permanent breast seed implant; PBSI; Low-dose radiotherapy - breast; High-dose radiotherapy - breast; Electronic balloon ...

  8. Synthesis and biochemical studies of 7 alpha-substituted androsta-1,4-diene-3,17-diones as enzyme-activated irreversible inhibitors of aromatase.

    PubMed

    Ebrahimian, S; Chen, H H; Brueggemeier, R W

    1993-09-01

    Several 7 alpha-thiosubstituted derivatives of androstenedione have demonstrated effective inhibition of aromatase, the cytochrome P450 enzyme complex responsible for the biosynthesis of estrogens. Introduction of an additional double bond in the A ring resulted in 7 alpha-(4'-amino)phenylthioandrosta-1,4-diene-3,17-dione (7 alpha-APTADD), a potent inhibitor that inactivated aromatase by an enzyme-catalyzed process. Additional 7 alpha-thiosubstituted androsta-1,4-diene-3,17-dione derivatives were designed to further examine enzyme-catalyzed inactivation. Two halogenated and one unsubstituted 7 alpha-phenylthioandrosta-1,4-diene-3,17-diones were synthesized via an acid-catalyzed conjugate Michael addition of substituted thiophenols with androsta-1,4,6-triene-3,17-dione. Two 7 alpha-naphthylthioandrosta-1,4-diene-3,17-diones were synthesized via either acid-catalyzed or based-catalyzed conjugate Michael addition of substituted thionaphthols with androsta-1,4,6-triene-3,17-dione. These agents were evaluated for aromatase inhibitory activity in the human placental microsomal preparation. Under initial velocity assay conditions of low product formation, the inhibitors demonstrated potent inhibition of aromatase, with apparent Ki's ranging from 12 to 27 nM. Furthermore, these compounds produced time-dependent, first-order inactivation of aromatase in the presence of NADPH, whereas no aromatase inactivation was observed in the absence of NADPH. This enzyme-activated irreversible inhibition, also referred to as mechanism-based inhibition, can be prevented by the substrate androstenedione. Thus, the apparent Ki values for these inhibitors are consistent with earlier studies on 7 alpha-substituted competitive inhibitors that indicate bulky substituents can be accommodated at the 7 alpha-position.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Resistance to PARP inhibitors by SLFN11 inactivation can be overcome by ATR inhibition

    PubMed Central

    Murai, Junko; Feng, Ying; Yu, Guoying K.; Ru, Yuanbin; Tang, Sai-Wen; Shen, Yuqiao; Pommier, Yves

    2016-01-01

    Poly(ADP-ribose) polymerase inhibitors (PARPIs) kill cancer cells by trapping PARP1 and PARP2. Talazoparib, the most potent PARPI inhibitor (PARPI), exhibits remarkable selectivity among the NCI-60 cancer cell lines beyond BRCA inactivation. Our genomic analyses reveal high correlation between response to talazoparib and Schlafen 11 (SLFN11) expression. Causality was established in four isogenic SLFN11-positive and -negative cell lines and extended to olaparib. Response to the talazoparib-temozolomide combination was also driven by SLFN11 and validated in 36 small cell lung cancer cell lines, and in xenograft models. Resistance in SLFN11-deficient cells was caused neither by impaired drug penetration nor by activation of homologous recombination. Rather, SLFN11 induced irreversible and lethal replication inhibition, which was independent of ATR-mediated S-phase checkpoint. The resistance to PARPIs by SLFN11 inactivation was overcome by ATR inhibition, mechanistically because SLFN11-deficient cells solely rely on ATR activation for their survival under PARPI treatment. Our study reveals that SLFN11 inactivation, which is common (~45%) in cancer cells, is a novel and dominant resistance determinant to PARPIs. PMID:27708213

  10. Resistance to PARP inhibitors by SLFN11 inactivation can be overcome by ATR inhibition.

    PubMed

    Murai, Junko; Feng, Ying; Yu, Guoying K; Ru, Yuanbin; Tang, Sai-Wen; Shen, Yuqiao; Pommier, Yves

    2016-11-22

    Poly(ADP-ribose) polymerase inhibitors (PARPIs) kill cancer cells by trapping PARP1 and PARP2. Talazoparib, the most potent PARPI inhibitor (PARPI), exhibits remarkable selectivity among the NCI-60 cancer cell lines beyond BRCA inactivation. Our genomic analyses reveal high correlation between response to talazoparib and Schlafen 11 (SLFN11) expression. Causality was established in four isogenic SLFN11-positive and -negative cell lines and extended to olaparib. Response to the talazoparib-temozolomide combination was also driven by SLFN11 and validated in 36 small cell lung cancer cell lines, and in xenograft models. Resistance in SLFN11-deficient cells was caused neither by impaired drug penetration nor by activation of homologous recombination. Rather, SLFN11 induced irreversible and lethal replication inhibition, which was independent of ATR-mediated S-phase checkpoint. The resistance to PARPIs by SLFN11 inactivation was overcome by ATR inhibition, mechanistically because SLFN11-deficient cells solely rely on ATR activation for their survival under PARPI treatment. Our study reveals that SLFN11 inactivation, which is common (~45%) in cancer cells, is a novel and dominant resistance determinant to PARPIs.

  11. Studies on the inactivation of medically important Candida species on agar surfaces using pulsed light.

    PubMed

    Farrell, Hugh; Garvey, Mary; Rowan, Neil

    2009-09-01

    Development of a pulsed-light (PL) approach to inanimate surface decontamination is timely, as the incidence of yeast-related infections in healthcare remains unacceptably high. Critical electrical and biological factors governing the efficacy of PL for the in vitro inactivation of medically important yeast were established in this study. Predetermined cell numbers of yeast were inoculated separately on agar plates and were flashed with < or =90 pulses of broad-spectrum light under varying operating conditions, and their inactivation was measured. Significant differences in inactivation among different yeasts occurred depending on the intensity of the applied lamp discharge energy and the amount of pulsing applied. Levels of yeast sensitivity also varied depending on the distance between the light source and the treatment surface used, and the population size, type and age of cultures treated. Yeast strains were shown to be significantly more resistant to PL irradiation compared with similarly treated bacterial control cultures. A clear relationship was observed between the concentration of eluted proteins from treated yeast and the severity of PL conditions, with scanning electron micrographs showing irreversible cellular damage. Therefore, the findings from this study will enable further development and optimization of PL as a method of decontaminating surfaces in healthcare setting.

  12. DIDS modifies the conductance, gating, and inactivation mechanisms of the cardiac ryanodine receptor.

    PubMed Central

    Hill, Adam Parker; Sitsapesan, Rebecca

    2002-01-01

    The effects of the covalent modifier of amino groups, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) on the single-channel properties of purified sheep cardiac ryanodine receptors (RyR) incorporated into planar phospholipid bilayers were investigated. DIDS increased single-channel conductance and open probability (P(o)) and induced unique modifications to the voltage-dependence of gating. The effects of DIDS on conduction and gating were irreversible within the time scale of the experiments, and both effects were dependent on the permeant ion. DIDS induced a greater increase in conductance with Ca(2+) (20%) compared with K(+) (8%) as the permeant ion. After modification by DIDS, all channels could be rapidly inactivated in a voltage-dependent manner. The open probability of the DIDS-modified channel decreased with increasing positive or negative transmembrane potentials; however, inactivation was only observed at negative potentials. Our results demonstrate that inactivation of RyR channels is dependent on the ligand activating the channel, and this will have consequences for the control and termination of sarcoplasmic reticulum Ca(2+) release in cardiac cells. PMID:12023226

  13. Evaluation of irreversible JPEG compression for a clinical ultrasound practice.

    PubMed

    Persons, Kenneth R; Hangiandreou, Nicholas J; Charboneau, Nicholas T; Charboneau, J; James, E; Douglas, Bruce R; Salmon, Ann P; Knudsen, John M; Erickson, Bradley J

    2002-03-01

    A prior ultrasound study indicated that images with low to moderate levels of JPEG and wavelet compression were acceptable for diagnostic purposes. The purpose of this study is to validate this prior finding using the Joint Photographic Experts Group (JPEG) baseline compression algorithm, at a compression ratio of approximately 10:1, on a sufficiently large number of grayscale and color ultrasound images to attain a statistically significant result. The practical goal of this study is to determine if it is feasible for radiologists to use irreversibly compressed images as an integral part of the day to day ultrasound practice (ie, perform primary diagnosis with, and store irreversibly compressed images in the ultrasound PACS archive). In this study, 5 Radiologists were asked to review 300 grayscale and color static ultrasound images selected from 4 major anatomic groups. Each image was compressed and decompressed using the JPEG baseline compression algorithm at a fixed quality factor resulting in an average compression ratio of approximately 9:1. The images were presented in pairs (original and compressed) in a blinded fashion on a PACS workstation in the ultrasound reading areas, and radiologists were asked to pick which image they preferred in terms of diagnostic utility and their degree of certainty (on a scale from 1 to 4). Of the 1499 total readings, 50.17% (95% confidence intervals at 47.6%, and 52.7%) indicated a preference for the original image in the pair, and 49.83% (95% confidence intervals at 47.3%, and 52.0%) indicated a preference for the compressed image. These findings led the authors to conclude that static color and gray-scale ultrasound images compressed with JPEG at approximately 9:1 are statistically indistinguishable from the originals for primary diagnostic purposes. Based on the authors laboratory experience with compression and the results of this and other prior studies, JPEG compression is now being applied to all ultrasound images in

  14. Effect of formaldehyde inactivation on poliovirus.

    PubMed

    Wilton, Thomas; Dunn, Glynis; Eastwood, David; Minor, Philip D; Martin, Javier

    2014-10-01

    Inactivated polio vaccines, which have been used in many countries for more than 50 years, are produced by treating live poliovirus (PV) with formaldehyde. However, the molecular mechanisms underlying virus inactivation are not well understood. Infection by PV is initiated by virus binding to specific cell receptors, which results in viral particles undergoing sequential conformational changes that generate altered structural forms (135S and 80S particles) and leads to virus cell entry. We have analyzed the ability of inactivated PV to bind to the human poliovirus receptor (hPVR) using various techniques such as ultracentrifugation, fluorescence-activated cell sorting flow cytometry and real-time reverse transcription-PCR (RT-PCR). The results showed that although retaining the ability to bind to hPVR, inactivated PV bound less efficiently in comparison to live PV. We also found that inactivated PV showed resistance to structural conversion in vitro, as judged by measuring changes in antigenicity, the ability to bind to hPVR, and viral RNA release at high temperature. Furthermore, viral RNA from inactivated PV was shown to be modified, since cDNA yields obtained by RT-PCR amplification were severely reduced and no infectious virus was recovered after RNA transfection into susceptible cells. Importance: This study represents a novel insight into the molecular mechanisms responsible for poliovirus inactivation. We show that inactivation with formaldehyde has an effect on early steps of viral replication as it reduces the ability of PV to bind to hPVR, decreases the sensitivity of PV to convert to 135S particles, and abolishes the infectivity of its viral RNA. These changes are likely responsible for the loss of infectivity shown by PV following inactivation. Techniques used in this study represent new approaches for the characterization of inactivated PV products and could be useful in developing improved methods for the production and quality control testing of

  15. Effect of Formaldehyde Inactivation on Poliovirus

    PubMed Central

    Dunn, Glynis; Eastwood, David; Minor, Philip D.; Martin, Javier

    2014-01-01

    ABSTRACT Inactivated polio vaccines, which have been used in many countries for more than 50 years, are produced by treating live poliovirus (PV) with formaldehyde. However, the molecular mechanisms underlying virus inactivation are not well understood. Infection by PV is initiated by virus binding to specific cell receptors, which results in viral particles undergoing sequential conformational changes that generate altered structural forms (135S and 80S particles) and leads to virus cell entry. We have analyzed the ability of inactivated PV to bind to the human poliovirus receptor (hPVR) using various techniques such as ultracentrifugation, fluorescence-activated cell sorting flow cytometry and real-time reverse transcription-PCR (RT-PCR). The results showed that although retaining the ability to bind to hPVR, inactivated PV bound less efficiently in comparison to live PV. We also found that inactivated PV showed resistance to structural conversion in vitro, as judged by measuring changes in antigenicity, the ability to bind to hPVR, and viral RNA release at high temperature. Furthermore, viral RNA from inactivated PV was shown to be modified, since cDNA yields obtained by RT-PCR amplification were severely reduced and no infectious virus was recovered after RNA transfection into susceptible cells. IMPORTANCE This study represents a novel insight into the molecular mechanisms responsible for poliovirus inactivation. We show that inactivation with formaldehyde has an effect on early steps of viral replication as it reduces the ability of PV to bind to hPVR, decreases the sensitivity of PV to convert to 135S particles, and abolishes the infectivity of its viral RNA. These changes are likely responsible for the loss of infectivity shown by PV following inactivation. Techniques used in this study represent new approaches for the characterization of inactivated PV products and could be useful in developing improved methods for the production and quality control testing

  16. N- versus C-domain selectivity of catalytic inactivation of human angiotensin converting enzyme by lisinopril-coupled transition metal chelates.

    PubMed

    Hocharoen, Lalintip; Joyner, Jeff C; Cowan, J A

    2013-12-27

    The N- and C-terminal domains of human somatic angiotensin I converting enzyme (sACE-1) demonstrate distinct physiological functions, with resulting interest in the development of domain-selective inhibitors for specific therapeutic applications. Herein, the activity of lisinopril-coupled transition metal chelates was tested for both reversible binding and irreversible catalytic inactivation of each domain of sACE-1. C/N domain binding selectivity ratios ranged from 1 to 350, while rates of irreversible catalytic inactivation of the N- and C-domains were found to be significantly greater for the N-domain, suggesting a more optimal orientation of M-chelate-lisinopril complexes within the active site of the N-domain of sACE-1. Finally, the combined effect of binding selectivity and inactivation selectivity was assessed for each catalyst (double-filter selectivity factors), and several catalysts were found to cause domain-selective catalytic inactivation. The results of this study demonstrate the ability to optimize the target selectivity of catalytic metallopeptides through both binding and catalytic factors (double-filter effect).

  17. N- vs. C-Domain Selectivity of Catalytic Inactivation of Human Angiotensin Converting Enzyme by Lisinopril-Coupled Transition Metal Chelates

    PubMed Central

    Hocharoen, Lalintip; Joyner, Jeff C.; Cowan, J. A.

    2014-01-01

    The N- and C-terminal domains of human somatic Angiotensin I Converting Enzyme (sACE-1) demonstrate distinct physiological functions, with resulting interest in the development of domain-selective inhibitors for specific therapeutic applications. Herein, the activity of lisinopril-coupled transition metal chelates were tested for both reversible binding and irreversible catalytic inactivation of sACE-1. C/N domain binding selectivity ratios ranged from 1 to 350, while rates of irreversible catalytic inactivation of the N- and C-domains were found to be significantly greater for the N-domain, suggesting a more optimal orientation of the M-chelate-lisinopril complexes within the active site of the N-domain of sACE-1. Finally, the combined effect of binding selectivity and inactivation selectivity was assessed for each catalyst (double-filter selectivity factors), and several catalysts were found to cause domain-selective catalytic inactivation. The results of this study demonstrate the ability to optimize the target selectivity of catalytic metallopeptides through both binding and orientation factors (double-filter effect). PMID:24228790

  18. Large field-induced irreversibility in Ni-Mn based Heusler shape-memory alloys: A pulsed magnetic field study

    NASA Astrophysics Data System (ADS)

    Nayak, A. K.; Mejia, C. Salazar; D'Souza, S. W.; Chadov, S.; Skourski, Y.; Felser, C.; Nicklas, M.

    2014-12-01

    We present a pulsed magnetic field study on the magnetic and magnetostriction properties of Ni-Mn-Z (Z =In , Sn, and Sb) based Heusler shape-memory alloys. These materials generally display a field-induced magnetostructural transition that could lead to an irreversible phase transition, when measured near the martensitic transition temperature. Here, we show that independently of the transition temperature, the critical field for the phase transition sensitively depends on the main-group element in the sample. Irrespective of their compositions, all samples display a magnetization of around 2 μB/f .u . in the martensite phase and about 6 μB/f .u . in the cubic austenite phase. Our magnetic and magnetostriction measurements at low temperatures exhibit a partial or complete arrest of the high-field austenite phase below the reverse martensitic transition. This results in a large irreversibility with a hysteresis width as high as 24 T. We introduce a theoretical model to discuss the experimental results.

  19. Process boundaries of irreversible scCO2 -assisted phase separation in biphasic whole-cell biocatalysis.

    PubMed

    Brandenbusch, Christoph; Glonke, Sebastian; Collins, Jonathan; Hoffrogge, Raimund; Grunwald, Klaudia; Bühler, Bruno; Schmid, Andreas; Sadowski, Gabriele

    2015-11-01

    The formation of stable emulsions in biphasic biotransformations catalyzed by microbial cells turned out to be a major hurdle for industrial implementation. Recently, a cost-effective and efficient downstream processing approach, using supercritical carbon dioxide (scCO2 ) for both irreversible emulsion destabilization (enabling complete phase separation within minutes of emulsion treatment) and product purification via extraction has been proposed by Brandenbusch et al. (2010). One of the key factors for a further development and scale-up of the approach is the understanding of the mechanism underlying scCO2 -assisted phase separation. A systematic approach was applied within this work to investigate the various factors influencing phase separation during scCO2 treatment (that is pressure, exposure of the cells to CO2 , and changes of cell surface properties). It was shown that cell toxification and cell disrupture are not responsible for emulsion destabilization. Proteins from the aqueous phase partially adsorb to cells present at the aqueous-organic interface, causing hydrophobic cell surface characteristics, and thus contribute to emulsion stabilization. By investigating the change in cell-surface hydrophobicity of these cells during CO2 treatment, it was found that a combination of catastrophic phase inversion and desorption of proteins from the cell surface is responsible for irreversible scCO2 mediated phase separation. These findings are essential for the definition of process windows for scCO2 -assisted phase separation in biphasic whole-cell biocatalysis.

  20. In Situ TEM Study of Reversible and Irreversible Electroforming in Pt/Ti:NiO/Pt Heterostructures

    SciTech Connect

    D'Aquila, Kenneth; Liu, Yuzi; Iddir, Hakim; Petford-Long, Amanda K.

    2015-05-01

    Experimental verification of the microscopic origin of resistance switching in metal/oxide/metal heterostructures is needed for applications in non-volatile memory and neuromorphic computing. Numerous reports suggest that resistance switching in NiO is caused by local reduction of the oxide layer into nanoscale conducting filaments, but few reports have shown experimental evidence correlating electroforming with site-specific changes in composition. We have investigated the mechanisms of reversible and irreversible electroforming in 250–500 nm wide pillars patterned from a single Ta/Ti/Pt/Ti-doped NiO/Pt/Ta heterostructure and have shown that these can coexist within a single sample. We performed in situ transmission electron microscopy (TEM) electroform- ing and switching on each pillar to correlate the local electron transport behavior with microstructure and composition in each pillar. DFT calculations fitted to electron energy loss spectroscopy data showed that the Ti-doped NiO layer is partially reduced after reversible electroforming, with the formation of oxygen vacancies ordered into lines in the <110> direction. However, under the same probing conditions, adjacent pillars show irreversible electroforming caused by electromigration of metallic Ta to form a single bridge across the oxide layer. We propose that the different electroforming behaviors are related to microstructural variations across the sample and may lead to switching variability.

  1. Voltage sensor inactivation in potassium channels.

    PubMed

    Bähring, Robert; Barghaan, Jan; Westermeier, Regina; Wollberg, Jessica

    2012-01-01

    In voltage-gated potassium (Kv) channels membrane depolarization causes movement of a voltage sensor domain. This conformational change of the protein is transmitted to the pore domain and eventually leads to pore opening. However, the voltage sensor domain may interact with two distinct gates in the pore domain: the activation gate (A-gate), involving the cytoplasmic S6 bundle crossing, and the pore gate (P-gate), located externally in the selectivity filter. How the voltage sensor moves and how tightly it interacts with these two gates on its way to adopt a relaxed conformation when the membrane is depolarized may critically determine the mode of Kv channel inactivation. In certain Kv channels, voltage sensor movement leads to a tight interaction with the P-gate, which may cause conformational changes that render the selectivity filter non-conductive ("P/C-type inactivation"). Other Kv channels may preferably undergo inactivation from pre-open closed-states during voltage sensor movement, because the voltage sensor temporarily uncouples from the A-gate. For this behavior, known as "preferential" closed-state inactivation, we introduce the term "A/C-type inactivation". Mechanistically, P/C- and A/C-type inactivation represent two forms of "voltage sensor inactivation."

  2. Roles of reversible and irreversible aggregation in sugar processing.

    PubMed

    Uchimiya, Minori

    2017-04-13

    Colloids (1-1000-nm particles) in sugarcane/beet juice originate from non-sucrose impurities (polyphenolic colorants, residual soil, polysaccharides) of the plant materials; additional colloids form during the high temperature processing. Colloids are reactive toward aggregation, sorption, desorption, and redox/hydrolysis/thermal transformation reactions. Both Derjaguin-Landau-Verwey-Overbeek (DLVO; van der Waals and electrostatic forces) and non-DLVO (involving hydrophilic colloids) interactions control the stability of colloids in juice. Heteroaggregation causes a range of feedstock and end product problems, including turbidity, viscosity, color, gelling, crystallization, starch ghost, and heat transfer problems. Even after intensive clarification and refining, trace colloidal impurities on white (refined) sugar remain to cause a problem known as acid beverage floc. Acid beverage floc is an example of DLVO-type aggregation of oppositely charged particles at decreased pH. Examples of irreversible aggregates include starch ghost and recalcitrant organomineral composites formed at elevated temperature that resist heat transfer. Fundamental knowledge in aggregation kinetics is necessary to predict the occurrence of undesirable aggregates, as pH, ionic strength, temperature, and sucrose concentration change during the processing of sugarcane/beet juice.

  3. Irreversible Entropy Production in Two-Phase Mixing Layers

    NASA Technical Reports Server (NTRS)

    Okongo, Nora

    2003-01-01

    This report presents a study of dissipation (irreversible production of entropy) in three-dimensional, temporal mixing layers laden with evaporating liquid drops. The purpose of the study is to examine the effects of evaporating drops on the development of turbulent features in flows. Direct numerical simulations were performed to analyze transitional states of three mixing layers: one without drops, and two that included drops at different initial mass loadings. Without drops, the dissipation is essentially due to viscous effects. It was found that in the presence of drops, the largest contribution to dissipation was made by heating and evaporation of the drops, and that at large length scales, this contribution is positive (signifying that the drops reduce turbulence), while at small scales, this contribution is negative (the drops increase turbulence). The second largest contribution to dissipation was found to be associated with the chemical potential, which leads to an increase in turbulence at large scales and a decrease in turbulence at small scales. The next smaller contribution was found to be that of viscosity. The fact that viscosity effects are only third in order of magnitude in the dissipation is in sharp contrast to the situation for the mixing layer without the drops. The next smaller contribution - that of the drag and momentum of the vapor from the drops - was found to be negative at lower mass loading but to become positive at higher mass loading.

  4. Percolation of heteronuclear dimers irreversibly deposited on square lattices

    NASA Astrophysics Data System (ADS)

    Gimenez, M. C.; Ramirez-Pastor, A. J.

    2016-09-01

    The percolation problem of irreversibly deposited heteronuclear dimers on square lattices is studied. A dimer is composed of two segments, and it occupies two adjacent adsorption sites. Each segment can be either a conductive segment (segment type A ) or a nonconductive segment (segment type B ). Three types of dimers are considered: A A , B B , and A B . The connectivity analysis is carried out by accounting only for the conductive segments (segments type A ). The model offers a simplified representation of the problem of percolation of defective (nonideal) particles, where the presence of defects in the system is simulated by introducing a mixture of conductive and nonconductive segments. Different cases were investigated, according to the sequence of deposition of the particles, the types of dimers involved in the process, and the degree of alignment of the deposited objects. By means of numerical simulations and finite-size scaling analysis, the complete phase diagram separating a percolating from a nonpercolating region was determined for each case. Finally, the consistency of our results was examined by comparing with previous data in the literature for linear k -mers (particles occupying k adjacent sites) with defects.

  5. General performance characteristics of an irreversible ferromagnetic Stirling refrigeration cycle

    NASA Astrophysics Data System (ADS)

    Lin, G.; Tegus, O.; Zhang, L.; Brück, E.

    2004-02-01

    A new magnetic-refrigeration-cycle model using ferromagnetic materials as a cyclic working substance is set up, in which finite-rate heat transfer, heat leak and regeneration time are taken into account. On the basis of the thermodynamic properties of a ferromagnetic material, the general performance characteristics of the ferromagnetic Stirling refrigeration cycle are investigated and the effects of some key irreversibilities on the performance of the cycle are revealed. By using the optimal-control theory, the optimal relation between the coefficient of performance and the cooling rate is derived and some important performance bounds, e.g., the maximum cooling rate, the maximum coefficient of performance, are determined. Moreover, the optimal operating regions for cooling rate, coefficient of performance and the optimal operating temperatures of a cyclic working substance in the two heat-transfer processes are obtained. Furthermore, the influences of magnetization and magnetic field on the performance characteristics of the cycle are discussed. The results obtained here have general significance and can be deduced to the related ones of the Stirling refrigeration cycle using paramagnetic salt as a cyclic working substance.

  6. Irreversible chemical steps control intersubunit dynamics during translation.

    PubMed

    Marshall, R Andrew; Dorywalska, Magdalena; Puglisi, Joseph D

    2008-10-07

    The ribosome, a two-subunit macromolecular machine, deciphers the genetic code and catalyzes peptide bond formation. Dynamic rotational movement between ribosomal subunits is likely required for efficient and accurate protein synthesis, but direct observation of intersubunit dynamics has been obscured by the repetitive, multistep nature of translation. Here, we report a collection of single-molecule fluorescence resonance energy transfer assays that reveal a ribosomal intersubunit conformational cycle in real time during initiation and the first round of elongation. After subunit joining and delivery of correct aminoacyl-tRNA to the ribosome, peptide bond formation results in a rapid conformational change, consistent with the counterclockwise rotation of the 30S subunit with respect to the 50S subunit implied by prior structural and biochemical studies. Subsequent binding of elongation factor G and GTP hydrolysis results in a clockwise rotation of the 30S subunit relative to the 50S subunit, preparing the ribosome for the next round of tRNA selection and peptide bond formation. The ribosome thus harnesses the free energy of irreversible peptidyl transfer and GTP hydrolysis to surmount activation barriers to large-scale conformational changes during translation. Intersubunit rotation is likely a requirement for the concerted movement of tRNA and mRNA substrates during translocation.

  7. Membrane alterations in irreversibly sickled cells: hemoglobin--membrane interaction.

    PubMed

    Lessin, L S; Kurantsin-Mills, J; Wallas, C; Weems, H

    1978-01-01

    Irreversibly sickled cells (ISCs) are sickle erythrocytes which retain bipolar elongated shapes despite reoxygenation and owe their biophysical abnormalities to acquired membrane alterations. Freeze-etched membranes both of ISCs produced in vitro and ISCs isolated in vivo reveal microbodies fixed to the internal (PS) surface which obscure spectrin filaments. Intramembranous particles (IMPs) on the intramembrane (PF) surface aggregate over regions of subsurface microbodies. Electron microscopy of diaminobenzidine-treated of ISC ghosts show the microbodies to contain hemoglobin and/or hemoglobin derivatives. Scanning electron microscopy and freeze-etching demonstrate that membrane--hemoglobin S interaction in ISCs enhances the membrane loss by microspherulation. Membrane-bound hemoglobin is five times greater in in vivo ISCs than non-ISCs, and increases during ISC production, parallelling depletion of adenosine triphosphate. Polyacrylamide gel electrophoresis of ISC membranes shows the presence of high-molecular-weight heteropolymers in the pre--band 1 region, a decrease in band 4.1 and an increase in bands 7, 8, and globin. The role of cross-linked membrane protein polymers in the generation of ISCs is discussed and is synthesized in terms of a unified concept for the determinants of the genesis of ISCs.

  8. Intrinsic randomness and intrinsic irreversibility in classical dynamical systems

    PubMed Central

    Courbage, M.; Prigogine, I.

    1983-01-01

    We continue our previous work on dynamic “intrinsically random” systems for which we can derive dissipative Markov processes through a one-to-one change of representation. For these systems, the unitary group of evolution can be transformed in this way into two distinct Markov processes leading to equilibrium for either t→ + ∞ or t→ - ∞. To lift the degeneracy, we first formulate the second principle as a selection rule that is meaningful in intrinsically random systems. For these systems, this excludes a set of unrealizable states. As a result of this exclusion, permitted initial conditions correspond to a set of states that is not invariant through velocity inversion. In this way, the time-reversal symmetry of dynamics is broken and these systems acquire a new feature we may call “intrinsic irreversibility.” The set of admitted initial conditions can be characterized by an entropy displaying the amount of information necessary for their preparation. The initial conditions selected by the second law correspond to a finite amount of information, while the initial conditions that are rejected correspond to an infinite amount of information and are therefore “impossible.” We believe that our formulation permits a microscopic formulation of the second law of thermodynamics for well-defined classes of dynamical systems. PMID:16578774

  9. Scaling Law for Irreversible Entropy Production in Critical Systems

    PubMed Central

    Hoang, Danh-Tai; Prasanna Venkatesh, B.; Han, Seungju; Jo, Junghyo; Watanabe, Gentaro; Choi, Mahn-Soo

    2016-01-01

    We examine the Jarzynski equality for a quenching process across the critical point of second-order phase transitions, where absolute irreversibility and the effect of finite-sampling of the initial equilibrium distribution arise in a single setup with equal significance. We consider the Ising model as a prototypical example for spontaneous symmetry breaking and take into account the finite sampling issue by introducing a tolerance parameter. The initially ordered spins become disordered by quenching the ferromagnetic coupling constant. For a sudden quench, the deviation from the Jarzynski equality evaluated from the ideal ensemble average could, in principle, depend on the reduced coupling constant ε0 of the initial state and the system size L. We find that, instead of depending on ε0 and L separately, this deviation exhibits a scaling behavior through a universal combination of ε0 and L for a given tolerance parameter, inherited from the critical scaling laws of second-order phase transitions. A similar scaling law can be obtained for the finite-speed quench as well within the Kibble-Zurek mechanism. PMID:27277558

  10. Irreversibility and the breaking of resonance-antiresonance symmetry

    NASA Astrophysics Data System (ADS)

    Ordonez, Gonzalo; Hatano, Naomichi

    2017-10-01

    We consider open quantum systems modeled as discrete lattices. Using a simple model of a single-site coupled to two leads as an example, we show that the time evolution of these systems can be analyzed in terms of an explicitly time-reversal symmetric resolution of unity. This resolution of unity includes both resonant states, which decay in the future, and anti-resonant states, which decay in the past. We show that a time-reversal invariant state contains both resonant and anti-resonant components with equal weights. However, this symmetry is automatically broken as the system evolves in time, with the resonant component becoming much larger than the anti-resonant component for t > 0 (and vice versa for t < 0). We argue that irreversibility is a manifestation of this symmetry breaking. We also compare our present approach with the subdynamics approach developed by Prof. Prigogine and collaborators. Finally, we suggest an extension of our present approach from the level of wave functions to the level of density matrices.

  11. Irreversible Gelation in Wormlike Micellar Solutions via Microfluidics

    NASA Astrophysics Data System (ADS)

    Cardiel, Joshua; Zhao, Ya; Cheung, Perry; Shen, Amy

    2013-11-01

    Surfactant molecules can self-assemble into various morphologies under proper combinations of ionic strength, temperature, and flow conditions. At equilibrium, the wormlike micelles can transition from entangled to branched and multi-connected structures with increasing salt concentration. Under specific flow conditions, micellar structure transition can follow different trajectories. In this work we consider the flow of two semi-dilute wormlike micellar solutions through microposts, focusing on their microstructural and rheological evolution. Both solutions contain cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal). One is weakly viscoelastic and shear thickening while the other is strongly viscoelastic and shear thinning. When subject to strain rates ~103 s-1 and strain ~103, we observe irreversible gelation, with entangled, branched, and multi-connected micellar bundles, evidenced by electron microscopy. We also show that the rheological properties of the shear-thickening precursor are smaller than those of the gel, while the rheological properties of the shear-thinning precursor are several times larger than those of the ge. This rheological property variation is associated with their respective structural evolution.

  12. The nineteenth century conflict between mechanism and irreversibility

    NASA Astrophysics Data System (ADS)

    van Strien, Marij

    2013-08-01

    The reversibility problem (better known as the reversibility objection) is usually taken to be an internal problem in the kinetic theory of gases, namely the problem of how to account for the second law of thermodynamics within this theory. Historically, it is seen as an objection that was raised against Boltzmann's kinetic theory of gases, which led Boltzmann to a statistical approach to the kinetic theory, culminating in the development of statistical mechanics. In this paper, I show that in the late nineteenth century, the reversibility problem had a much broader significance-it was widely discussed and certainly not only as an objection to Boltzmann's kinetic theory of gases. In this period, there was a conflict between mechanism and irreversibility in physics which was tied up with central issues in philosophy of science such as materialism, empiricism and the need for mechanistic foundations of physical theories, as well as with concerns about the heat death of the universe. I discuss how this conflict was handled by the major physicists of the period, such as Maxwell, Kelvin, Duhem, Poincaré, Mach and Planck, as well as by a number of lesser-known authors.

  13. Percolation of heteronuclear dimers irreversibly deposited on square lattices.

    PubMed

    Gimenez, M C; Ramirez-Pastor, A J

    2016-09-01

    The percolation problem of irreversibly deposited heteronuclear dimers on square lattices is studied. A dimer is composed of two segments, and it occupies two adjacent adsorption sites. Each segment can be either a conductive segment (segment type A) or a nonconductive segment (segment type B). Three types of dimers are considered: AA, BB, and AB. The connectivity analysis is carried out by accounting only for the conductive segments (segments type A). The model offers a simplified representation of the problem of percolation of defective (nonideal) particles, where the presence of defects in the system is simulated by introducing a mixture of conductive and nonconductive segments. Different cases were investigated, according to the sequence of deposition of the particles, the types of dimers involved in the process, and the degree of alignment of the deposited objects. By means of numerical simulations and finite-size scaling analysis, the complete phase diagram separating a percolating from a nonpercolating region was determined for each case. Finally, the consistency of our results was examined by comparing with previous data in the literature for linear k-mers (particles occupying k adjacent sites) with defects.

  14. Use of irreversible electroporation in unresectable pancreatic cancer

    PubMed Central

    2015-01-01

    Irreversible electroporation is a non-thermal injury ablative modality that has been in clinical use since 2008 in the treatment of locally advanced soft tissue tumors. It has been reported to be utilized intraoperatively, laparoscopically or percutaneously. The method of action of IRE relies on a high voltage (maximum 3,000 volts) small microsecond pulse lengths (70 to 90 microseconds) to induce cell membrane porosity which leads to slow/protracted cell death over time. One of the largest unmet needs in oncology that IRE has been utilized is in locally advanced (stage III) pancreatic cancer. Recent studies have demonstrated the safety and palliation with encouraging improvement in overall survival. Its inherent limitation still remains tissue heterogeneity and the unique settings based on tumor histology and prior induction therapy. There remains a high technical demand of the end-user and the more extensive knowledge transfer which makes the learning curve longer in order to achieve appropriate and safe utilization. PMID:26151062

  15. Irreversible electroporation of locally advanced pancreatic neck/body adenocarcinoma

    PubMed Central

    2015-01-01

    Objective Irreversible electroporation (IRE) of locally advanced pancreatic adenocarcinoma of the neck has been used to palliate appropriate stage 3 pancreatic cancers without evidence of metastasis and who have undergone appropriate induction therapy. Currently there has not been a standardized reported technique for pancreatic mid-body tumors for patient selection and intra-operative technique. Patients Subjects are patients with locally advanced pancreatic adenocarcinoma of the body/neck who have undergone appropriate induction chemotherapy for a reasonable duration. Main outcome measures Technique of open IRE of locally advanced pancreatic adenocarcinoma of the neck/body is described, with the emphasis on intra-operative ultrasound and intra-operative electroporation management. Results The technique of open IRE of the pancreatic neck/body with bracketing of the celiac axis and superior mesenteric artery with continuous intraoperative ultrasound imaging and consideration of intraoperative navigational system is described. Conclusions IRE of locally advanced pancreatic adenocarcinoma of the body/neck is feasible for appropriate patients with locally advanced unresectable pancreatic cancer. PMID:26029461

  16. Scaling Law for Irreversible Entropy Production in Critical Systems

    NASA Astrophysics Data System (ADS)

    Hoang, Danh-Tai; Prasanna Venkatesh, B.; Han, Seungju; Jo, Junghyo; Watanabe, Gentaro; Choi, Mahn-Soo

    2016-06-01

    We examine the Jarzynski equality for a quenching process across the critical point of second-order phase transitions, where absolute irreversibility and the effect of finite-sampling of the initial equilibrium distribution arise in a single setup with equal significance. We consider the Ising model as a prototypical example for spontaneous symmetry breaking and take into account the finite sampling issue by introducing a tolerance parameter. The initially ordered spins become disordered by quenching the ferromagnetic coupling constant. For a sudden quench, the deviation from the Jarzynski equality evaluated from the ideal ensemble average could, in principle, depend on the reduced coupling constant ε0 of the initial state and the system size L. We find that, instead of depending on ε0 and L separately, this deviation exhibits a scaling behavior through a universal combination of ε0 and L for a given tolerance parameter, inherited from the critical scaling laws of second-order phase transitions. A similar scaling law can be obtained for the finite-speed quench as well within the Kibble-Zurek mechanism.

  17. Irreversibility of birth-related changes in the pulmonary circulation.

    PubMed

    Levine, G L; Goetzman, B W; Milstein, J M; Bennett, S H

    1994-12-01

    We hypothesized that establishing conditions of hypoxia and fluid filling of the airways in lungs of newborns would reproduce the high levels of pulmonary vascular resistance (PVR) observed in the fetal state. We assessed the hemodynamics of the left pulmonary circulation of 1- to 3-day-old lambs during a variety of airway states while attempting to reestablish fetal conditions. Eleven animals were studied during both normoxemia and hypoxemia in a baseline airway state with a positive end-expiratory pressure (PEEP) of 4 cm H2O, and in experimental airway states, of atelectasis, and fluid filling to 15 and 30 mL/kg and with PEEP of 12 cm H2O. PVR increased while pulmonary blood flow decreased with all airway state changes as compared to baseline, suggesting a passive mechanism for these changes. With the addition of hypoxemia there was a further increase in PVR in all states accompanied by an increase in pulmonary blood flow, indicating that active vasoconstriction was responsible for the increase in PVR. The combined effects of hypoxemia and fluid filling, designed to approximate the fetal state, increased PVR to only 20-30% of fetal values. Thus, additional factors appear to be important in maintaining the high PVR of the fetal state. We speculate that ventilation of the lungs at birth irreversibly alters these factors.

  18. Fundamental economic irreversibilities influence policies for enhancing international forest phytosanitary security

    Treesearch

    Thomas P. Holmes; Will Allen; Robert G. Haight; E. Carina H. Keskitalo; Mariella Marzano; Maria Pettersson; Christopher P. Quine; E. R. Langer

    2017-01-01

    National and international efforts to manage forest biosecurity create tension between opposing sources of ecological and economic irreversibility. Phytosanitary policies designed to protect national borders from biological invasions incur sunk costs deriving from economic and political irreversibilities that incentivizes wait-and-see decision-making. However, the...

  19. "Adult" Conceptualization of Irreversibility: Implications for the Development of the Concept of Death.

    ERIC Educational Resources Information Center

    Brent, Sandor B.; Speece, Mark W.

    1993-01-01

    Studies of development of children's understanding of death compares children's understanding against presumed adult concept. Examined validity of adult concept of irreversibility by comparing actual adult data to presumed adult standard and to actual child data. Undergraduates (n=165) completed questionnaire on irreversibility of death. Subjects…

  20. A minimal dissipation type-based classification in irreversible thermodynamics and microeconomics

    NASA Astrophysics Data System (ADS)

    Tsirlin, A. M.; Kazakov, V.; Kolinko, N. A.

    2003-10-01

    We formulate the problem of finding classes of kinetic dependencies in irreversible thermodynamic and microeconomic systems for which minimal dissipation processes belong to the same type. We show that this problem is an inverse optimal control problem and solve it. The commonality of this problem in irreversible thermodynamics and microeconomics is emphasized.

  1. Optimization of a solar-driven irreversible Carnot heat engine at maximum power output

    SciTech Connect

    Goektun, S.

    1997-08-01

    By employing the energetic optimization technique, the optimum performance of an irreversible Carnot heat engine system driven by a corrugated sheet collector is investigated at maximum power output. The maximum overall efficiency of the system is expressed in terms of the operating parameter of the collector and the cycle-irreversibility parameter of the heat engine.

  2. The Impact of Uncertainty and Irreversibility on Investments in Online Learning

    ERIC Educational Resources Information Center

    Oslington, Paul

    2004-01-01

    Uncertainty and irreversibility are central to online learning projects, but have been neglected in the existing educational cost-benefit analysis literature. This paper builds some simple illustrative models of the impact of irreversibility and uncertainty, and shows how different types of cost and demand uncertainty can have substantial impacts…

  3. Inactivation of ribulosebisphosphate carboxylase/oxygenase from Rhodospirillum rubrum and spinach with the new affinity label 2-bromo-1,5-dihydroxy-3-pentanone 1,5-bisphosphate

    SciTech Connect

    Donnelly, M.I.; Hartman, F.C.

    1981-11-16

    In an attempt to identify the active-site base believed to initiate catalysis by ribulosebisphosphate carboxylase, we have synthesized 2-bromo-1, 5-dihydroxy-3-pentanone 1,5-bisphosphate, a reactive analogue of a postulated intermediate of carboxylation. Although highly unstable, this compound can be shown to inactivate the carboxylases from both Rhodospirillum rubrum and spinach rapidly and irreversibly. Inactivation follows pseudo first-order kinetics, shows rate saturation and is greatly reduced by saturating amounts of the competitive inhibitor, 2-carboxyribitol 1,5-bisphosphate. The incorporation of reagent, quantified by reducing the modified carboxylases with (/sup 3/H)NaBH/sub 4/, shows that inactivation results from the modification of approximately one residue per catalytic subunit of the Rhodospirillum rubrum enzyme and less than one residue per protomeric unit of the spinach enzyme.

  4. Inactivation of Mycobacterium avium with monochloramine.

    PubMed

    Luh, Jeanne; Tong, Ning; Raskin, Lutgarde; Mariñas, Benito J

    2008-11-01

    Batch experiments were performed to study the inactivation kinetics of Mycobacterium avium in the presence of monochloramine at 5-30 degrees C, pH 6-10, and 0.30-42.3 mg Cl2/ L. For each temperature and pH investigated, limiting high and low inactivation rates were observed for high and low disinfectant concentrations, respectively, within the range investigated. The rate of inactivation transitioned from high to low over a relatively narrow range of intermediate monochloramine concentrations. The observed temperature dependence of inactivation was consistent with an Arrhenius expression with activation energies of 58.0 and 71.7 kJ/mol for the high and low concentration ranges, respectively. The rate of inactivation increased with decreasing pH, consistent with trends reported for the reaction of monochloramine with protein thiols. Experiments performed at pH approximately 3.5 showed that dichloramine was a weaker disinfectant than monochloramine, and that its contribution to the overall inactivation of M. avium with combined chlorine was negligible at pH 6-10. A kinetic model incorporating disinfectant concentration, temperature, and pH effects was used to illustrate that monochloramine efficiency to inactivate M. avium in water could vary broadly from adequate (e.g., 99.9% inactivation efficiency in 32 min at 5 mg Cl2/L, pH 6, 30 degrees C) to impractical (e.g., 99.9% inactivation efficiency in 9 d at 1 mg Cl2/L, pH 9, 5 degrees C).

  5. 6-Azido-7-nitro-1,4-dihydroquinoxaline-2,3-dione (ANQX) Forms an Irreversible Bond To the Active Site of the GluR2 AMPA Receptor†

    PubMed Central

    Cruz, Leslie A.; Estébanez-Perpiñá, Eva; Pfaff, Sam; Borngraeber, Sabine; Bao, Ning; Blethrow, Justin; Fletterick, Robert J.; England, Pamela M.

    2010-01-01

    AMPA receptors mediate fast excitatory synaptic transmission and are essential for synaptic plasticity. ANQX, a photoreactive AMPA receptor antagonist, is an important biological probe used to irreversibly inactivate AMPA receptors. Here, using X-ray crystallography and mass spectroscopy, we report that ANQX forms two major products in the presence of the GluR2 AMPAR ligand-binding core (S1S2J). Upon photostimulation, ANQX reacts intramolecularly to form FQX or intermolecularly to form a covalent adduct with Glu705. PMID:18754610

  6. GnRH Neuron-Specific Ablation of Gαq/11 Results in Only Partial Inactivation of the Neuroendocrine-Reproductive Axis in Both Male and Female Mice: In Vivo Evidence for Kiss1r-Coupled Gαq/11-Independent GnRH Secretion

    PubMed Central

    Navarro, Víctor M.; Ahow, Maryse; Pampillo, Macarena; Nash, Connor; Fayazi, Mehri; Calder, Michele; Elbert, Adrienne; Urbanski, Henryk F.; Wettschureck, Nina; Offermanns, Stefan; Carroll, Rona S.; Bhattacharya, Moshmi; Tobet, Stuart A.; Kaiser, Ursula B.

    2015-01-01

    The gonadotropin-releasing hormone (GnRH) is the master regulator of fertility and kisspeptin (KP) is a potent trigger of GnRH secretion from GnRH neurons. KP signals via KISS1R, a Gαq/11-coupled receptor, and mice bearing a global deletion of Kiss1r (Kiss1r−/−) or a GnRH neuron-specific deletion of Kiss1r (Kiss1rd/d) display hypogonadotropic hypogonadism and infertility. KISS1R also signals via β-arrestin, and in mice lacking β-arrestin-1 or -2, KP-triggered GnRH secretion is significantly diminished. Based on these findings, we hypothesized that ablation of Gαq/11 in GnRH neurons would diminish but not completely block KP-triggered GnRH secretion and that Gαq/11-independent GnRH secretion would be sufficient to maintain fertility. To test this, Gnaq (encodes Gαq) was selectively inactivated in the GnRH neurons of global Gna11 (encodes Gα11)-null mice by crossing Gnrh-Cre and Gnaqfl/fl;Gna11−/− mice. Experimental Gnaqfl/fl;Gna11−/−;Gnrh-Cre (Gnaqd/d) and control Gnaqfl/fl;Gna11−/− (Gnaqfl/fl) littermate mice were generated and subjected to reproductive profiling. This process revealed that testicular development and spermatogenesis, preputial separation, and anogenital distance in males and day of vaginal opening and of first estrus in females were significantly less affected in Gnaqd/d mice than in previously characterized Kiss1r−/− or Kiss1rd/d mice. Additionally, Gnaqd/d males were subfertile, and although Gnaqd/d females did not ovulate spontaneously, they responded efficiently to a single dose of gonadotropins. Finally, KP stimulation triggered a significant increase in gonadotropins and testosterone levels in Gnaqd/d mice. We therefore conclude that the milder reproductive phenotypes and maintained responsiveness to KP and gonadotropins reflect Gαq/11-independent GnRH secretion and activation of the neuroendocrine-reproductive axis in Gnaqd/d mice. SIGNIFICANCE STATEMENT The gonadotropin-releasing hormone (GnRH) is the master

  7. GnRH Neuron-Specific Ablation of Gαq/11 Results in Only Partial Inactivation of the Neuroendocrine-Reproductive Axis in Both Male and Female Mice: In Vivo Evidence for Kiss1r-Coupled Gαq/11-Independent GnRH Secretion.

    PubMed

    Babwah, Andy V; Navarro, Víctor M; Ahow, Maryse; Pampillo, Macarena; Nash, Connor; Fayazi, Mehri; Calder, Michele; Elbert, Adrienne; Urbanski, Henryk F; Wettschureck, Nina; Offermanns, Stefan; Carroll, Rona S; Bhattacharya, Moshmi; Tobet, Stuart A; Kaiser, Ursula B

    2015-09-16

    The gonadotropin-releasing hormone (GnRH) is the master regulator of fertility and kisspeptin (KP) is a potent trigger of GnRH secretion from GnRH neurons. KP signals via KISS1R, a Gαq/11-coupled receptor, and mice bearing a global deletion of Kiss1r (Kiss1r(-/-)) or a GnRH neuron-specific deletion of Kiss1r (Kiss1r(d/d)) display hypogonadotropic hypogonadism and infertility. KISS1R also signals via β-arrestin, and in mice lacking β-arrestin-1 or -2, KP-triggered GnRH secretion is significantly diminished. Based on these findings, we hypothesized that ablation of Gαq/11 in GnRH neurons would diminish but not completely block KP-triggered GnRH secretion and that Gαq/11-independent GnRH secretion would be sufficient to maintain fertility. To test this, Gnaq (encodes Gαq) was selectively inactivated in the GnRH neurons of global Gna11 (encodes Gα11)-null mice by crossing Gnrh-Cre and Gnaq(fl/fl);Gna11(-/-) mice. Experimental Gnaq(fl/fl);Gna11(-/-);Gnrh-Cre (Gnaq(d/d)) and control Gnaq(fl/fl);Gna11(-/-) (Gnaq(fl/fl)) littermate mice were generated and subjected to reproductive profiling. This process revealed that testicular development and spermatogenesis, preputial separation, and anogenital distance in males and day of vaginal opening and of first estrus in females were significantly less affected in Gnaq(d/d) mice than in previously characterized Kiss1r(-/-) or Kiss1r(d/d) mice. Additionally, Gnaq(d/d) males were subfertile, and although Gnaq(d/d) females did not ovulate spontaneously, they responded efficiently to a single dose of gonadotropins. Finally, KP stimulation triggered a significant increase in gonadotropins and testosterone levels in Gnaq(d/d) mice. We therefore conclude that the milder reproductive phenotypes and maintained responsiveness to KP and gonadotropins reflect Gαq/11-independent GnRH secretion and activation of the neuroendocrine-reproductive axis in Gnaq(d/d) mice. The gonadotropin-releasing hormone (GnRH) is the master regulator of

  8. Clozapine and other competitive antagonists reactivate risperidone-inactivated h5-HT7 receptors: radioligand binding and functional evidence for GPCR homodimer protomer interactions

    PubMed Central

    Toohey, Nicole; Knight, Jessica A.; Klein, Michael T.; Smith, Carol

    2011-01-01

    Rationale The h5-HT7 receptor is subject to inactivation by risperidone and 9-OH-risperidone, apparently through a pseudo-irreversible complex formed between these drugs and the receptor. Although risperidone and 9-OH-risperidone (“inactivating antagonists”) completely inactivate the receptor, only 50% of the receptors form a pseudo-irreversible complex with these drugs. Objectives This study aims to more fully determine the mechanism(s) responsible for the novel effects of risperidone and 9-OH-risperidone and to determine if the inactivation can be reversed (reactivation). Methods The ability of non-inactivating drugs (competitive antagonists) to dissociate wash-resistant [3H]risperidone binding from h5-HT7 receptors was investigated. Also, the ability of non-inactivating drugs to reactivate inactivated h5-HT7 receptors was investigated, using cAMP accumulation as a functional endpoint. Results The competitive (non-inactivating) antagonists clozapine and mesulergine released the wash-resistant [3H]risperidone binding to the h5-HT7 receptor. The competitive antagonists clozapine, SB269970, mianserin, cyproheptadine, mesulergine, and ICI169369 reactivated the risperidone-inactivated h5-HT7 receptors in a concentration-dependent manner. The potencies for reactivation closely match the affinities of these drugs for the h5-HT7 receptor (r2=0.95), indicating that the reactivating antagonists are binding to and producing their effects through the orthosteric binding site of the h5-HT7 receptor. Bioluminescence resonance energy transfer analyses indicate that the h5-HT7 receptor forms homodimers. Conclusions The ability of the non-inactivating drugs to bind h5-HT7 orthosteric sites and reverse the wash-resistant effects of risperidone or 9-OH-risperidone, also bound to h5-HT7 orthosteric sites, is evidence for protomer–protomer interactions between h5-HT7 homodimers. This is the first demonstration of a non-mutated G-protein-coupled receptor homodimer engaging in

  9. Irreversible inhibitors of the 3C protease of Coxsackie virus through templated assembly of protein-binding fragments

    PubMed Central

    Becker, Daniel; Kaczmarska, Zuzanna; Arkona, Christoph; Schulz, Robert; Tauber, Carolin; Wolber, Gerhard; Hilgenfeld, Rolf; Coll, Miquel; Rademann, Jörg

    2016-01-01

    Small-molecule fragments binding to biomacromolecules can be starting points for the development of drugs, but are often difficult to detect due to low affinities. Here we present a strategy that identifies protein-binding fragments through their potential to induce the target-guided formation of covalently bound, irreversible enzyme inhibitors. A protein-binding nucleophile reacts reversibly with a bis-electrophilic warhead, thereby positioning the second electrophile in close proximity of the active site of a viral protease, resulting in the covalent de-activation of the enzyme. The concept is implemented for Coxsackie virus B3 3C protease, a pharmacological target against enteroviral infections. Using an aldehyde-epoxide as bis-electrophile, active fragment combinations are validated through measuring the protein inactivation rate and by detecting covalent protein modification in mass spectrometry. The structure of one enzyme–inhibitor complex is determined by X-ray crystallography. The presented warhead activation assay provides potent non-peptidic, broad-spectrum inhibitors of enteroviral proteases. PMID:27677239

  10. Irreversible inhibitors of the 3C protease of Coxsackie virus through templated assembly of protein-binding fragments.

    PubMed

    Becker, Daniel; Kaczmarska, Zuzanna; Arkona, Christoph; Schulz, Robert; Tauber, Carolin; Wolber, Gerhard; Hilgenfeld, Rolf; Coll, Miquel; Rademann, Jörg

    2016-09-28

    Small-molecule fragments binding to biomacromolecules can be starting points for the development of drugs, but are often difficult to detect due to low affinities. Here we present a strategy that identifies protein-binding fragments through their potential to induce the target-guided formation of covalently bound, irreversible enzyme inhibitors. A protein-binding nucleophile reacts reversibly with a bis-electrophilic warhead, thereby positioning the second electrophile in close proximity of the active site of a viral protease, resulting in the covalent de-activation of the enzyme. The concept is implemented for Coxsackie virus B3 3C protease, a pharmacological target against enteroviral infections. Using an aldehyde-epoxide as bis-electrophile, active fragment combinations are validated through measuring the protein inactivation rate and by detecting covalent protein modification in mass spectrometry. The structure of one enzyme-inhibitor complex is determined by X-ray crystallography. The presented warhead activation assay provides potent non-peptidic, broad-spectrum inhibitors of enteroviral proteases.

  11. Irreversible photolabeling of active site of neutral endopeptidase-24. 11 enkephalinase by azidothiorphan and (/sup 14/C)-azidothiorphan

    SciTech Connect

    Beaumont, A.; Hernandez, J.F.; Chaillet, P.; Crine, P.; Roques, B.P.

    1987-11-01

    Azidothiorphan and its (/sup 14/C)-labeled analogue have been developed as photoaffinity ligands for the active site of the neutral endopeptidase 24.11. In in vitro assays azidothiorphan inhibits the endopeptidase activity with a Ki of 0.75 nM. After ultraviolet irradiation the inhibitor binds irreversibly to the enzyme, and many factors suggest that the photolabeling occurs at the active site. The binding is accompanied by a loss of enzymatic activity, and the inclusion of the competitive inhibitor thiorphan protects the endopeptidase from this inactivation. In addition the binding of another competitive inhibitor (/sup 3/H)N-((R,S)-3-hydroxyaminocarbonyl-2-benzyl-1-oxopropyl)-glycine to the active site of endopeptidase-24.11 is inhibited after irradiation with azidothiorphan. Experiments with (/sup 14/C)-azidothiorphan have shown that very little nonspecific binding of inhibitor to enzyme occurs and the the labeled probe remains bound under denaturing conditions. Azidothiorphan has also been found to produce a long-lasting naloxone-reversible analgesia after intracerebroventricular administration. The results show that azidothiorphan should prove useful both for structural studies and for investigations on the synthesis and turnover of the neutral endopeptidase-24.11.

  12. Irreversible inhibitors of the 3C protease of Coxsackie virus through templated assembly of protein-binding fragments

    NASA Astrophysics Data System (ADS)

    Becker, Daniel; Kaczmarska, Zuzanna; Arkona, Christoph; Schulz, Robert; Tauber, Carolin; Wolber, Gerhard; Hilgenfeld, Rolf; Coll, Miquel; Rademann, Jörg

    2016-09-01

    Small-molecule fragments binding to biomacromolecules can be starting points for the development of drugs, but are often difficult to detect due to low affinities. Here we present a strategy that identifies protein-binding fragments through their potential to induce the target-guided formation of covalently bound, irreversible enzyme inhibitors. A protein-binding nucleophile reacts reversibly with a bis-electrophilic warhead, thereby positioning the second electrophile in close proximity of the active site of a viral protease, resulting in the covalent de-activation of the enzyme. The concept is implemented for Coxsackie virus B3 3C protease, a pharmacological target against enteroviral infections. Using an aldehyde-epoxide as bis-electrophile, active fragment combinations are validated through measuring the protein inactivation rate and by detecting covalent protein modification in mass spectrometry. The structure of one enzyme-inhibitor complex is determined by X-ray crystallography. The presented warhead activation assay provides potent non-peptidic, broad-spectrum inhibitors of enteroviral proteases.

  13. Macroscopic irreversibility and microscopic paradox: A Constructal law analysis of atoms as open systems

    PubMed Central

    Lucia, Umberto

    2016-01-01

    The relation between macroscopic irreversibility and microscopic reversibility is a present unsolved problem. Constructal law is introduced to develop analytically the Einstein’s, Schrödinger’s, and Gibbs’ considerations on the interaction between particles and thermal radiation (photons). The result leads to consider the atoms and molecules as open systems in continuous interaction with flows of photons from their surroundings. The consequent result is that, in any atomic transition, the energy related to the microscopic irreversibility is negligible, while when a great number of atoms (of the order of Avogadro’s number) is considered, this energy related to irreversibility becomes so large that its order of magnitude must be taken into account. Consequently, macroscopic irreversibility results related to microscopic irreversibility by flows of photons and amount of atoms involved in the processes. PMID:27762333

  14. Macroscopic irreversibility and microscopic paradox: A Constructal law analysis of atoms as open systems

    NASA Astrophysics Data System (ADS)

    Lucia, Umberto

    2016-10-01

    The relation between macroscopic irreversibility and microscopic reversibility is a present unsolved problem. Constructal law is introduced to develop analytically the Einstein’s, Schrödinger’s, and Gibbs’ considerations on the interaction between particles and thermal radiation (photons). The result leads to consider the atoms and molecules as open systems in continuous interaction with flows of photons from their surroundings. The consequent result is that, in any atomic transition, the energy related to the microscopic irreversibility is negligible, while when a great number of atoms (of the order of Avogadro’s number) is considered, this energy related to irreversibility becomes so large that its order of magnitude must be taken into account. Consequently, macroscopic irreversibility results related to microscopic irreversibility by flows of photons and amount of atoms involved in the processes.

  15. Irreversible inhibitors of c-Src kinase that target a non-conserved cysteine

    PubMed Central

    Kwarcinski, Frank E.; Fox, Christel C.; Steffey, Michael E.; Soellner, Matthew B.

    2012-01-01

    We have developed the first irreversible inhibitors of wild-type c-Src kinase. We demonstrate that our irreversible inhibitors display improved potency and selectivity relative to their reversible counterparts. Our strategy involves modifying a promiscuous kinase inhibitor with an electrophile to generate covalent inhibitors of c-Src. We applied this methodology to two inhibitor scaffolds that exhibit increased cellular efficacy when rendered irreversible. In addition, we have demonstrated the utility of irreversible inhibitors in studying the conformation of an important loop in kinases that can control inhibitor selectivity and cause drug resistance. Together, we have developed a general and robust framework for generating selective irreversible inhibitors from reversible, promiscuous inhibitor scaffolds. PMID:22928736

  16. Generalized model and optimum performance of an irreversible quantum Brayton engine with spin systems.

    PubMed

    Wu, Feng; Chen, Lingen; Sun, Fengrui; Wu, Chih; Li, Qing

    2006-01-01

    The purpose of this paper is to establish a model of an irreversible quantum Brayton engine using many noninteracting spin systems as the working substance and consisting of two irreversible adiabatic and two isomagnetic field processes. The time evolution of the total magnetic moment M is determined by solving the generalized quantum master equation of an open system in the Heisenberg picture. The time of two irreversible adiabatic processes is considered based on finite-rate evolution. The relationship between the power output P and the efficiency eta for the irreversible quantum Brayton engine with spin systems is derived. The optimally operating region (or criteria) for the engine is determined. The influences of these important parameters on the performances (P and eta) of the engine are discussed. The results obtained herein will be useful for the further understanding and the selection of the optimal operating conditions for an irreversible quantum Brayton engine with spin systems.

  17. Effects of crystal quality and preferred orientation on the irreversible growth of compact TATB cylindrical explosives

    NASA Astrophysics Data System (ADS)

    Zhang, Haobin; Xu, Jingjiang; Liu, Yu; Huang, Hui; Sun, Jie

    2013-09-01

    Three kinds of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) cylinders compacted with TATB raw materials, recrystallized near-spherical and platy TATB crystals are compared to investigate the effects of crystal quality and preferred orientation on their irreversible growth. The results show that the higher the crystal quality, the lower the irreversible volume growth. The compacted cylinders of raw material TATB, with the poorest crystal quality, possess more irreversible growth than those with recrystallized high quality TATB crystals. Irreversible growth of TATB cylinders are also affected by crystal preferred orientation. With the same crystal quality, crystal preferred orientation leads to anisotropic irreversible dimension growth, but has no effect on the volume expansion of TATB cylinders. By changing the crystal quality and preferred orientation, the deformation problem of TATB-based PBX explosives may be restricted.

  18. Field-induced structural transition and irreversible domain detwinning in the antiferromagnet Fe1.1Te

    NASA Astrophysics Data System (ADS)

    Fabrèges, X.; Duc, F.; Roth, T.; Knafo, W.; Viennois, R.; Detlefs, C.

    2017-05-01

    Single-crystal x-ray diffraction in pulsed magnetic fields of up to 31 T was used to investigate the iron telluride antiferromagnet Fe1.1Te , which is a parent of the Fe-based chalcogenide superconductors. At temperatures below the Néel temperature TN≃60 K, high magnetic fields perpendicular to the c axis lead to an irreversible detwinning of the crystal at the field HR, where magnetocrystalline domains are selected by a moment reorientation process. Just below TN, the onset of a structural transition at the critical field HC>HR , which delimits the antiferromagnet phase, indicates a partial restoration of the high-temperature tetragonal symmetry. The lattice and magnetic answers to an in-plane magnetic field are discussed, emphasizing the strength of magnetoelastic coupling in Fe1.1Te .

  19. Stochastic foundations of undulatory transport phenomena: generalized Poisson-Kac processes—part II Irreversibility, norms and entropies

    NASA Astrophysics Data System (ADS)

    Giona, Massimiliano; Brasiello, Antonio; Crescitelli, Silvestro

    2017-08-01

    In this second part, we analyze the dissipation properties of generalized Poisson-Kac (GPK) processes, considering the decay of suitable L 2-norms and the definition of entropy functions. In both cases, consistent energy dissipation and entropy functions depend on the whole system of primitive statistical variables, the partial probability density functions \\{ p_α({x}, t) \\}α=1N , while the corresponding energy dissipation and entropy functions based on the overall probability density p({x}, t) do not satisfy monotonicity requirements as a function of time. These results provide new insights on the theory of Markov operators associated with irreversible stochastic dynamics. Examples from chaotic advection (standard map coupled to stochastic GPK processes) illustrate this phenomenon. Some complementary physical issues are also addressed: the ergodicity breaking in the presence of attractive potentials, and the use of GPK perturbations to mollify stochastic field equations.

  20. Population Dynamics of Viral Inactivation

    NASA Astrophysics Data System (ADS)

    Freeman, Krista; Li, Dong; Behrens, Manja; Streletzky, Kiril; Olsson, Ulf; Evilevitch, Alex

    We have investigated the population dynamics of viral inactivation in vitrousing time-resolved cryo electron microscopy combined with light and X-ray scattering techniques. Using bacteriophage λ as a model system for pressurized double-stranded DNA viruses, we found that virions incubated with their cell receptor eject their genome in a stochastic triggering process. The triggering of DNA ejection occurs in a non synchronized manner after the receptor addition, resulting in an exponential decay of the number of genome-filled viruses with time. We have explored the characteristic time constant of this triggering process at different temperatures, salt conditions, and packaged genome lengths. Furthermore, using the temperature dependence we determined an activation energy for DNA ejections. The dependences of the time constant and activation energy on internal DNA pressure, affected by salt conditions and encapsidated genome length, suggest that the triggering process is directly dependent on the conformational state of the encapsidated DNA. The results of this work provide insight into how the in vivo kinetics of the spread of viral infection are influenced by intra- and extra cellular environmental conditions. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1252522.

  1. Ribosome Inactivating Proteins from Rosaceae.

    PubMed

    Shang, Chenjing; Rougé, Pierre; Van Damme, Els J M

    2016-08-22

    Ribosome-inactivating proteins (RIPs) are widespread among higher plants of different taxonomic orders. In this study, we report on the RIP sequences found in the genome/transcriptome of several important Rosaceae species, including many economically important edible fruits such as apple, pear, peach, apricot, and strawberry. All RIP domains from Rosaceae share high sequence similarity with conserved residues in the catalytic site and the carbohydrate binding sites. The genomes of Malus domestica and Pyrus communis contain both type 1 and type 2 RIP sequences, whereas for Prunus mume, Prunus persica, Pyrus bretschneideri, and Pyrus communis a complex set of type 1 RIP sequences was retrieved. Heterologous expression and purification of the type 1 as well as the type 2 RIP from apple allowed to characterize the biological activity of the proteins. Both RIPs from Malus domestica can inhibit protein synthesis. Furthermore, molecular modelling suggests that RIPs from Rosaceae possess three-dimensional structures that are highly similar to the model proteins and can bind to RIP substrates. Screening of the recombinant type 2 RIP from apple on a glycan array revealed that this type 2 RIP interacts with terminal sialic acid residues. Our data suggest that the RIPs from Rosaceae are biologically active proteins.

  2. Identifying and Inactivating Bacterial Spores

    NASA Technical Reports Server (NTRS)

    Newcombe, David; Dekas, Anne; Venkateswaran, Kasthuri

    2009-01-01

    Problems associated with, and new strategies for, inactivating resistant organisms like Bacillus canaveralius (found at Kennedy Space Center during a survey of three NASA cleanrooms) have been defined. Identifying the particular component of the spore that allows its heightened resistance can guide the development of sterilization procedures that are targeted to the specific molecules responsible for resistance, while avoiding using unduly harsh methods that jeopardize equipment. The key element of spore resistance is a multilayered protein shell that encases the spore called the spore coat. The coat of the best-studied spore-forming microbe, B. subtilis, consists of at least 45 proteins, most of which are poorly characterized. Several protective roles for the coat are well characterized including resistance to desiccation, large toxic molecules, ortho-phthalaldehyde, and ultraviolet (UV) radiation. One important long-term specific goal is an improved sterilization procedure that will enable NASA to meet planetary protection requirements without a terminal heat sterilization step. This would support the implementation of planetary protection policies for life-detection missions. Typically, hospitals and government agencies use biological indicators to ensure the quality control of sterilization processes. The spores of B. canaveralius that are more resistant to osmotic stress would serve as a better biological indicator for potential survival than those in use currently.

  3. Elimination of rapid potassium channel inactivation by phosphorylation of the inactivation gate.

    PubMed

    Covarrubias, M; Wei, A; Salkoff, L; Vyas, T B

    1994-12-01

    The effect of protein kinase C (PKC) on rapid N-type inactivation of K+ channels has not been reported previously. We found that PKC specifically eliminates rapid inactivation of a cloned human A-type K+ channel (hKv3.4), converting this channel from a rapidly inactivating A type to a noninactivating delayed rectifier type. Biochemical analysis showed that the N-terminal domain of hKv3.4 is phosphorylated in vitro by PKC, and mutagenesis experiments revealed that two serines within the inactivation gate at the N-terminus are sites of direct PKC action. Moreover, mutating one of these serines to aspartic acid mimics the action of PKC. Serine phosphorylation may thus prevent rapid inactivation by shielding basic residues known to be critical to the function of the inactivation gate. The regulatory mechanism reported here may have substantial effects on signal coding in the nervous system.

  4. Efficacy of irreversible electroporation in human pancreatic adenocarcinoma: advanced murine model

    PubMed Central

    Philips, Prejesh; Li, Yan; Li, Suping; St Hill, Charles R; Martin, Robert CG

    2015-01-01

    Irreversible electroporation (IRE) is a promising cell membrane ablative modality for pancreatic cancer. There have been recent concerns regarding local recurrence and the potential use of IRE as a debulking (partial ablation) modality. We hypothesize that incomplete ablation leads to early recurrence and a more aggressive biology. We created the first ever heterotopic murine model by inoculating BALB/c nude mice in the hindlimb with a subcutaneous injection of Panc-1 cells, an immortalized human pancreatic adenocarcinoma cell line. Tumors were allowed to grow from 0.75 to 1.5 cm and then treated with the goal of complete ablation or partial ablation using standard IRE settings. Animals were recovered and survived for 2 days (n = 6), 7 (n = 6), 14 (n = 6), 21 (n = 6), 30 (n = 8), and 60 (n = 8) days. All 40 animals/tumors underwent successful IRE under general anesthesia with muscle paralysis. The mean tumor volume of the animals undergoing ablation was 1,447.6 mm3 ± 884). Histologically, in the 14-, 21-, 30-, and 60-day survival groups the entire tumor was nonviable, with a persistent tumor nodule completely replaced fibrosis. In the group treated with partial ablation, incomplete electroporation/recurrences (N = 10 animals) were seen, of which 66% had confluent tumors and this was a significant predictor of recurrence (P < 0.001). Recurrent tumors were also significantly larger (mean 4,578 mm3 ± SD 877 versus completed electroporated tumors 925.8 ± 277, P < 0.001). Recurrent tumors had a steeper growth curve (slope = 0.73) compared with primary tumors (0.60, P = 0.02). Recurrent tumors also had a significantly higher percentage of EpCAM expression, suggestive of stem cell activation. Tumors that recur after incomplete electroporation demonstrate a biologically aggressive tumor that could be more resistant to standard of care chemotherapy. Clinical correlation of this data is limited, but should be considered when IRE of pancreatic cancer is being

  5. Inactivation of nitric oxide by cytochrome c oxidase under steady-state oxygen conditions.

    PubMed

    Unitt, David C; Hollis, Veronica S; Palacios-Callender, Miriam; Frakich, Nanci; Moncada, Salvador

    2010-03-01

    We have developed a respiration chamber that allows intact cells to be studied under controlled oxygen (O(2)) conditions. The system measures the concentrations of O(2) and nitric oxide (NO) in the cell suspension, while the redox state of cytochrome c oxidase is continuously monitored optically. Using human embryonic kidney cells transfected with a tetracycline-inducible NO synthase we show that the inactivation of NO by cytochrome c oxidase is dependent on both O(2) concentration and electron turnover of the enzyme. At a high O(2) concentration (70 microM), and while the enzyme is in turnover, NO generated by the NO synthase upon addition of a given concentration of l-arginine is partially inactivated by cytochrome c oxidase and does not affect the redox state of the enzyme or consumption of O(2). At low O(2) (15 microM), when the cytochrome c oxidase is more reduced, inactivation of NO is decreased. In addition, the NO that is not inactivated inhibits the cytochrome c oxidase, further reducing the enzyme and lowering O(2) consumption. At both high and low O(2) concentrations the inactivation of NO is decreased when sodium azide is used to inhibit cytochrome c oxidase and decrease electron turnover.

  6. Photosensitizers mediated photodynamic inactivation against virus particles.

    PubMed

    Sobotta, Lukasz; Skupin-Mrugalska, Paulina; Mielcarek, Jadwiga; Goslinski, Tomasz; Balzarini, Jan

    2015-01-01

    Viruses cause many diseases in humans from the rather innocent common cold to more serious or chronic, life-threatening infections. The long-term side effects, sometimes low effectiveness of standard pharmacotherapy and the emergence of drug resistance require a search for new alternative or complementary antiviral therapeutic approaches. One new approach to inactivate microorganisms is photodynamic antimicrobial chemotherapy (PACT). PACT has evolved as a potential method to inactivate viruses. The great challenge for PACT is to develop a methodology enabling the effective inactivation of viruses while leaving the host cells as untouched as possible. This review aims to provide some main directions of antiviral PACT, taking into account different photosensitizers, which have been widely investigated as potential antiviral agents. In addition, several aspects concerning PACT as a tool to assure viral inactivation in human blood products will be addressed.

  7. Bacillus spore inactivation methods affect detection assays.

    PubMed

    Dang, J L; Heroux, K; Kearney, J; Arasteh, A; Gostomski, M; Emanuel, P A

    2001-08-01

    Detection of biological weapons is a primary concern in force protection, treaty verification, and safeguarding civilian populations against domestic terrorism. One great concern is the detection of Bacillus anthracis, the causative agent of anthrax. Assays for detection in the laboratory often employ inactivated preparations of spores or nonpathogenic simulants. This study uses several common biodetection platforms to detect B. anthracis spores that have been inactivated by two methods and compares those data to detection of spores that have not been inactivated. The data demonstrate that inactivation methods can affect the sensitivity of nucleic acid- and antibody-based assays for the detection of B. anthracis spores. These effects should be taken into consideration when comparing laboratory results to data collected and assayed during field deployment.

  8. Bacillus Spore Inactivation Methods Affect Detection Assays

    PubMed Central

    Dang, Jessica L.; Heroux, Karen; Kearney, John; Arasteh, Ameneh; Gostomski, Mark; Emanuel, Peter A.

    2001-01-01

    Detection of biological weapons is a primary concern in force protection, treaty verification, and safeguarding civilian populations against domestic terrorism. One great concern is the detection of Bacillus anthracis, the causative agent of anthrax. Assays for detection in the laboratory often employ inactivated preparations of spores or nonpathogenic simulants. This study uses several common biodetection platforms to detect B. anthracis spores that have been inactivated by two methods and compares those data to detection of spores that have not been inactivated. The data demonstrate that inactivation methods can affect the sensitivity of nucleic acid- and antibody-based assays for the detection of B. anthracis spores. These effects should be taken into consideration when comparing laboratory results to data collected and assayed during field deployment. PMID:11472945

  9. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Li, S.-M.

    2008-04-01

    Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA); however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ether formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ) were estimated for a fast initial uptake governed by the mass accommodation coefficient (α) and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7-1×10-4. These processes may potentially lead to a considerable amount of SOA from the various biogenic hydrocarbons under acidic conditions, which can be highly significant for freshly nucleated aerosols, particularly given the large array of atmospheric olefins.

  10. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Li, S.-M.

    2007-08-01

    Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA); however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ester formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ) were estimated for a fast initial uptake governed by the mass accommodation coefficient (α) and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7-1×10-4. These processes are estimated to potentially produce greater than 2.5 μg m-3 of SOA from the various biogenic hydrocarbons under atmospheric conditions, which can be highly significant given the large array of atmospheric olefins.

  11. Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions

    PubMed Central

    Dervaux, Julien; Mejean, Annick; Brunet, Philippe

    2015-01-01

    In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and signicantly degrade the quality of water resources. In order to determine the physico-chemical parameters involved in their formation and quantitatively predict their appearance, we successfully reproduced irreversible cyanobacterial blooms in vitro. By combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism, unrelated to the presence of internal gas vesicles, allowing the sudden collective upward migration in test tubes of several cyanobacterial strains (Microcystis aeruginosa PCC 7005, Microcystis aeruginosa PCC 7806 and Synechocystis sp. PCC 6803). The final state consists in a foamy layer of biomass at the air-liquid interface, in which micro-organisms remain alive for weeks, the medium lying below being almost completely depleted of cyanobacteria. These "laboratory blooms" start with the aggregation of cells at high ionic force in cyanobacterial strains that produce anionic extracellular polymeric substances (EPS). Under appropriate conditions of nutrients and light intensity, the high photosynthetic activity within cell clusters leads the dissolved oxygen (DO) to supersaturate and to nucleate into bubbles. Trapped within the EPS, these bubbles grow until their buoyancy pulls the biomass towards the free surface. By investigating a wide range of spatially homogeneous environmental conditions (illumination, salinity, cell and nutrient concentration) we identify species-dependent thresholds and timescales for bloom formation. We conclude on the relevance of such results for cyanobacterial bloom formation in the environment and we propose an ecient method for biomass harvesting in bioreactors. PMID:25799424

  12. Irreversible collective migration of cyanobacteria in eutrophic conditions.

    PubMed

    Dervaux, Julien; Mejean, Annick; Brunet, Philippe

    2015-01-01

    In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and significantly degrade the quality of water resources. In order to determine the physico-chemical parameters involved in their formation and quantitatively predict their appearance, we successfully reproduced irreversible cyanobacterial blooms in vitro. By combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism, unrelated to the presence of internal gas vesicles, allowing the sudden collective upward migration in test tubes of several cyanobacterial strains (Microcystis aeruginosa PCC 7005, Microcystis aeruginosa PCC 7806 and Synechocystis sp. PCC 6803). The final state consists in a foamy layer of biomass at the air-liquid interface, in which micro-organisms remain alive for weeks, the medium lying below being almost completely depleted of cyanobacteria. These "laboratory blooms" start with the aggregation of cells at high ionic force in cyanobacterial strains that produce anionic extracellular polymeric substances (EPS). Under appropriate conditions of nutrients and light intensity, the high photosynthetic activity within cell clusters leads the dissolved oxygen (DO) to supersaturate and to nucleate into bubbles. Trapped within the EPS, these bubbles grow until their buoyancy pulls the biomass towards the free surface. By investigating a wide range of spatially homogeneous environmental conditions (illumination, salinity, cell and nutrient concentration) we identify species-dependent thresholds and timescales for bloom formation. We conclude on the relevance of such results for cyanobacterial bloom formation in the environment and we propose an efficient method for biomass harvesting in bioreactors.

  13. Irreversible electroporation: Just another form of thermal therapy?

    PubMed Central

    van Gemert, Martin J C; Wagstaff, Peter G K; de Bruin, Daniel M; van Leeuwen, Ton G; van der Wal, Allard C; Heger, Michal; van der Geld, Cees W M

    2015-01-01

    Background Irreversible electroporation (IRE) is (virtually) always called non-thermal despite many reports showing that significant Joule heating occurs. Our first aim is to validate with mathematical simulations that IRE as currently practiced has a non-negligible thermal response. Our second aim is to present a method that allows simple temperature estimation to aid IRE treatment planning. Methods We derived an approximate analytical solution of the bio-heat equation for multiple 2-needle IRE pulses in an electrically conducting medium, with and without a blood vessel, and incorporated published observations that an electric pulse increases the medium's electric conductance. Results IRE simulation in prostate-resembling tissue shows thermal lesions with 67–92°C temperatures, which match the positions of the coagulative necrotic lesions seen in an experimental study. Simulation of IRE around a blood vessel when blood flow removes the heated blood between pulses confirms clinical observations that the perivascular tissue is thermally injured without affecting vascular patency. Conclusions The demonstration that significant Joule heating surrounds current multiple-pulsed IRE practice may contribute to future in-depth discussions on this thermal issue. This is an important subject because it has long been under-exposed in literature. Its awareness pleads for preventing IRE from calling “non-thermal” in future publications, in order to provide IRE-users with the most accurate information possible. The prospect of thermal treatment planning as outlined in this paper likely aids to the important further successful dissemination of IRE in interventional medicine. Prostate 75:332–335, 2015. © 2014 The Authors. The Prostate Published by Wiley Periodicals, Inc. PMID:25327875

  14. Pulsed Electric Field inactivation of microbial cells: the use of ceramic layers to increase the efficiency of treatment

    NASA Astrophysics Data System (ADS)

    Pizzichemi, M.

    2009-12-01

    The impact of Pulsed Electric Fields (PEF) on bacteria and plant or animal cells has been investigated since the early 1960s. High electric fields pulses (20-70 kV/cm, 1-10 μs) are reported to cause rupture of the cellular lipid membrane, through the mechanism of irreversible electroporation. Quantitative description of cell inactivation kinetics is based on the analysis of stability of lipid bilayers under electric fields and the thermal fluctuations associated with the production of pores. PEF has been successfully applied to inactivation of both Gram-positive and Gram-negative bacteria in many sorts of liquids, such as milk, fruit juices and liquid eggs. In all these media, the level of inactivation could reach the 5 Logs for an approximate range of pulses of 100-200, and an energy consumption of ˜ 10-100 kJ/kg. The advantages of PEF are the superior maintenance of functional and nutritional levels (if compared to traditional thermal treatment), continuous treatment and short processing times, while the current high costs of this technique make it more suitable for treatment of expensive media. We present a solution to the problem of volumes in PEF treatment through the use of high permittivity ceramics, while retaining the same inactivation efficiency and improving the duration of the electrodes.

  15. Inactivation of Viruses by Benzalkonium Chloride

    PubMed Central

    Armstrong, J. A.; Froelich, E. J.

    1964-01-01

    Benzalkonium chloride (as Roccal or Zephiran) was found to inactivate influenza, measles, canine distemper, rabies, fowl laryngotracheitis, vaccinia, Semliki Forest, feline pneumonitis, meningopneumonitis, and herpes simplex viruses after 10 min of exposure at 30 C or at room temperature. Poliovirus and encephalomyocarditis virus were not inactivated under the same conditions. It was concluded that all viruses tested were sensitive except members of the picorna group. The literature was reviewed. PMID:4288740

  16. Microbial Inactivation by Ultrasound Assisted Supercritical Fluids

    NASA Astrophysics Data System (ADS)

    Benedito, Jose; Ortuño, Carmen; Castillo-Zamudio, Rosa Isela; Mulet, Antonio

    A method combining supercritical carbon dioxide (SC-CO2) and high power ultrasound (HPU) has been developed and tested for microbial/enzyme inactivation purposes, at different process conditions for both liquid and solid matrices. In culture media, using only SC-CO2, the inactivation rate of E. coli and S. cerevisiae increased with pressure and temperature; and the total inactivation (7-8 log-cycles) was attained after 25 and 140 min of SC-CO2 (350 bar, 36 °C) treatment, respectively. Using SC-CO2+HPU, the time for the total inactivation of both microorganisms was reduced to only 1-2 min, at any condition selected. The SC-CO2+HPU inactivation of both microorganisms was slower in juices (avg. 4.9 min) than in culture media (avg. 1.5 min). In solid samples (chicken, turkey ham and dry-cured pork cured ham) treated with SC-CO2 and SC-CO2+HPU, the inactivation rate of E. coli increased with temperature. The application of HPU to the SC-CO2 treatments accelerated the inactivation rate of E. coli and that effect was more pronounced in treatments with isotonic solution surrounding the solid food samples. The application of HPU enhanced the SC-CO2 inactivation mechanisms of microorganisms, generating a vigorous agitation that facilitated the CO2 solubilization and the mass transfer process. The cavitation generated by HPU could damage the cell walls accelerating the extraction of vital constituents and the microbial death. Thus, using the combined technique, reasonable industrial processing times and mild process conditions could be used which could result into a cost reduction and lead to the minimization in the food nutritional and organoleptic changes.

  17. Pressure inactivation of microorganisms at moderate temperatures

    NASA Astrophysics Data System (ADS)

    Butz, P.; Ludwig, H.

    1986-05-01

    The inactivation of bacteria, bacterial spores, yeasts and molds by high hydrostatic pressure was investigated over a pressure range up to 3000 bar. Survival curves were measured as a function of temperature and pressure applied on the microorganisms. Conditions are looked for under which heat or radiation sensitive pharmaceutical preparations can be sterilized by high pressure treatment at moderate temperatures. All organisms tested can be inactivated in the range of 2000-2500 bar and between 40-60 degrees.

  18. Azide protection of bacteroides superoxide dismutases from inactivation by hydrogen peroxide

    SciTech Connect

    Barkley, K.B.; Gregory, E.M.

    1986-05-01

    The anaerobes Bacteroides fragilis, B. distasonis and B. thetaiotaomicron produce an iron-containing superoxide dismutase (FeSOD). These FeSODs are reversibly inhibited by 1 mM azide (NaN/sub 3/) and are irreversibly inactivated upon incubation with hydrogen peroxide (H/sub 2/O/sub 2/). H/sub 2/O/sub 2/ inactivation of the enzyme likely depends on a Fenton type reaction with the production of hydroxyl radical (OH). Addition of NaN/sub 3/ to the enzyme solution decreased the rate of inactivation by H/sub 2/O/sub 2/. After 20 minutes incubation of purified B. distasonis FeSOD with 2.5 mM H/sub 2/O/sub 2/, 61% of the initial enzymatic activity remained when 1 mM NaN/sub 3/ was also present compared with 29% activity without NaN/sub 3/. Similar results were seen with FeSOD from B. fragilis and B. thetaiotaomicron. Metal analyses of the native, peroxidized, and NaN/sub 3/ protected samples are consistent with loss of Fe from the enzyme upon peroxidation, but retention of Fe and enzymatic activity in the NaN/sub 3/ protected sample. Protection of FeSOD activity from H/sub 2/O/sub 2/ inactivation was dependent on NaN/sub 3/ concentration. Anionic hydroxyl radical scavengers, such as urate and xanthine did not significantly protect the enzyme. The results are consistent with binding of azide to the active site either preventing entry of H/sub 2/O/sub 2/ or altering Fe redox potential, preventing OH production.

  19. Ozone-induced inactivation of antioxidant enzymes.

    PubMed

    Lee, Yong-Ki; Mok Kim, Sang; Han, Sanghwa

    2003-10-01

    Ozone is an air pollutant that damages a variety of biomolecules. We investigated ozone-induced inactivation of three major antioxidant enzymes. Cu/Zn superoxide dismutase was inactivated by ozone in a concentration-dependent manner. The concentration of ozone for 50% inactivation was approximately 45 microM when 10 microM Cu/Zn superoxide dismutase was incubated for 30 min in the presence of ozone. SDS-polyacrylamide gel electrophoresis (PAGE) showed that the enzyme was randomly fragmented. Both ascorbate and glutathione were very effective in protecting Cu/Zn superoxide dismutase from ozone-induced inactivation. The other two enzymes, catalase and glutathione peroxidase, were much more resistant to ozone than Cu/Zn superoxide dismutase. The ozone concentrations for 50% inactivation of 10 microM catalase and glutathione peroxidase were 500 and 240 microM, respectively. SDS-PAGE demonstrated that ozone caused formation of high molecular weight aggregates in catalase and dimerization in glutathione peroxidase. Glutathione protected catalase and glutathione peroxidase from ozone but the effective concentrations were much higher than that for Cu/Zn superoxide dismutase. Ascorbate was almost ineffective. The result suggests that, among the three antioxidant enzymes, Cu/Zn superoxide dismutase is a major target for ozone-induced inactivation and both glutathione and ascorbate are very effective in protecting the enzyme from ozone.

  20. Photodynamic-induced inactivation of Propionibacterium acnes

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Teschke, M.; Eick, Stephen G.; Pfister, W.; Meyer, Herbert; Halbhuber, Karl-Juergen

    1998-05-01

    We report on photodynamically induced inactivation of the skin bacterium Propionibacterium acnes (P. acnes) using endogenous as well as exogenous photosensitizers and red light sources. P. acnes is involved in the pathogenesis of the skin disease acne vulgaris. The skin bacterium is able to synthesize the metal-free fluorescent porphyrins protoporphyrin IX (PP) and coproporphyrin (CP) as shown by in situ spectrally-resolved detection of natural autofluorescence of human skin and bacteria colonies. These naturally occurring intracellular porphyrins act as efficient endogenous photosensitizers. Inactivation of P. acnes suspensions was achieved by irradiation with He-Ne laser light in the red spectral region (632.8 nm). We monitored the photodynamically-induced death of single bacteria using a fluorescent viability kit in combination with confocal laser scanning microscopy. In addition, the photo-induced inactivation was calculated by CFU (colony forming units) determination. We found 633 nm-induced inactivation (60 mW, 0.12 cm2 exposure area, 1 hour irradiation) of 72% in the case of non-incubated bacteria based on the destructive effect of singlet oxygen produced by red light excited endogenous porphyrins and subsequent energy transfer to molecular oxygen. In order to achieve a nearly complete inactivation within one exposure procedure, the exogenous photosensitizer Methylene Blue (Mb) was added. Far red exposure of Mb-labeled bacteria using a krypton ion laser at 647 nm and 676 nm resulted in 99% inactivation.

  1. Spore inactivation and DPA release in Alicyclobacillus acidoterrestris under different stress conditions.

    PubMed

    Bevilacqua, Antonio; Ciuffreda, Emanuela; Sinigaglia, Milena; Corbo, Maria Rosaria

    2015-04-01

    This paper reports on the inactivation of spores of 5 strains of Alicyclobacillus acidoterrestris under different stress conditions (acidic and alkaline pH, high temperature, addition of lysozyme, hydrogen peroxide and p-coumaric acid). The research was divided into two different steps; first, each stress was studied alone, thus pointing out a partial uncoupling between spore inactivation and DPA release, as H2O2 reduced spore level below the detection but it did not cause the release of DPA. A partial correlation was found only for acidic and alkaline pH. 2nd step was focused on the combination of pH, temperature and H2O2 through a factorial design; experiments were performed on both fresh and 4 month-old spores and pinpointed a different trend for DPA release as a function of spore age. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Ictal time-irreversible intracranial EEG signals as markers of the epileptogenic zone.

    PubMed

    Schindler, Kaspar; Rummel, Christian; Andrzejak, Ralph G; Goodfellow, Marc; Zubler, Frédéric; Abela, Eugenio; Wiest, Roland; Pollo, Claudio; Steimer, Andreas; Gast, Heidemarie

    2016-09-01

    To show that time-irreversible EEG signals recorded with intracranial electrodes during seizures can serve as markers of the epileptogenic zone. We use the recently developed method of mapping time series into directed horizontal graphs (dHVG). Each node of the dHVG represents a time point in the original intracranial EEG (iEEG) signal. Statistically significant differences between the distributions of the nodes' number of input and output connections are used to detect time-irreversible iEEG signals. In 31 of 32 seizure recordings we found time-irreversible iEEG signals. The maximally time-irreversible signals always occurred during seizures, with highest probability in the middle of the first seizure half. These signals spanned a large range of frequencies and amplitudes but were all characterized by saw-tooth like shaped components. Brain regions removed from patients who became post-surgically seizure-free generated significantly larger time-irreversibilities than regions removed from patients who still had seizures after surgery. Our results corroborate that ictal time-irreversible iEEG signals can indeed serve as markers of the epileptogenic zone and can be efficiently detected and quantified in a time-resolved manner by dHVG based methods. Ictal time-irreversible EEG signals can help to improve pre-surgical evaluation in patients suffering from pharmaco-resistant epilepsies. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  3. [Amphotericin B channel conductance inactivation].

    PubMed

    Ibragimova, V Kh; Alieva, I N; Aliev, D I

    2003-01-01

    Effects induced in bilayer lipid membranes by amphotericin B and its alkyl derivatives was analysed. Inactivation of the antibiotic-dependent multichannel membrane conductance was discovered. Kinetics of membrane conductivity was shown to depend on the antibiotic concentration in the membrane. At concentrations between 10(-8) and 10(-7) M, the resulting conductance appeared to the transient. We suggest that the phenomenon of biphasic kinetics of membrane conductance is the result of a consecutive transformation of polyene channels in the membrane: half-pores are assembled on either side of membrane-nonconducting 1; two half-pores combine to build up a conducting channels-conducting 2, and the conducting channels are disassemled to monomers and nonconducting self-associated forms inside the membrane-disassembled state (nonconducting 3). To explain the transient characteristics of the induced conductance, it is proposed that the antibiotic, present in the solution under self-associated form, binds the membrane and forms pores, then dissociates in the bilayer in a non-active monomeric form. The existence of definite monomers and nonconducting self-associated forms of amphotericin B molecules inside the membrane was estimated from the dependence of kinetic conductance of lipid membranes of amphotericin B and its alkyl derivatives, when the antibiotics are washed out from aqueous medium. Equilibrium between different antibiotic assemblies inside the membrane was demonstrated by the kinetics of conductance decrease following washing the antibiotic. Using circular dichroism measurements, we observed that amphotericin B alkyl derivatives were in self-associated form being susceptible to form pores across cholesterol-containing membranes. The phenomenon of biophasic kinetics was observed only in the cholesterol-containing membrane. The substitution of membrane cholesterol for ergosterol provides monotonic kinetics of membrane conductance at any antibiotic concentration.

  4. Physicochemical stability and inactivation of human and simian rotaviruses

    SciTech Connect

    Meng, Z.D.; Birch, C.; Heath, R.; Gust, I.

    1987-04-01

    The effects of various physical and chemical treatments on the stability of a human serotype 1 rotavirus and simian agent 11 (SA11) were compared by using a fluorescence focus assay. The infectivity of both strains was retained after storage at room temperature for 14 days, 4 degree C for 22 days, and -20 degree C for 32 days; lyophilization; and treatment at pH 3 to 11. Both viruses were inactivated at pH 12, as was the human virus at pH 2, although this pH resulted in only partial inactivation of SA11. The human virus also appeared to be more sensitive than SA11 to the action of ether and chloroform. The infectivity of both viruses was lost after UV irradiation for 15 min and after treatment with 8% formaldehyde for 5 min, 70% (vol/vol) ethanol for 30 min, and 2% lysol, 2% phenol, and 1% H/sub 2/O/sub 2/ for 1 h each.

  5. Virus inactivation studies using ion beams, electron and gamma irradiation

    NASA Astrophysics Data System (ADS)

    Smolko, Eduardo E.; Lombardo, Jorge H.

    2005-07-01

    Known methods of virus inactivation are based on the chemical action of some substances such as acetylethylenimine, betapropiolactone, glycidalaldehyde, formaldehyde, etc. In such a process, the viral suspension should be kept at room or higher temperatures for 24-48 h. Under these conditions, physical and chemical agents act to degrade the virus antigenic proteins. On the contrary with ionizing radiations at low temperatures, the treatment does not cause such degradation allowing the study of different viral functions. In this work, particle (α, d and ß) and γ irradiations were used for partial and total inactivation of Foot and Mouth Disease Virus (FMDV), Rauscher Leukemia Virus (RLV) and Herpes Simplex Virus (HSV). Obtention of the D37 dose from survival curves and the application of the target theory, permitted the determination of molecular weight of the nucleic acid genomes, EBR values and useful information for vaccine preparation. For RLV virus, a two target model of the RNA genome was deduced in accordance with biological information while from data from the literature and our own work on the structure of the scrapie prion, considering the molecular weight obtained by application of the theory, a new model for prion replication is presented, based on a trimer molecule.

  6. Quantifying irreversible movement in steep, fractured bedrock permafrost on Matterhorn (CH)

    NASA Astrophysics Data System (ADS)

    Weber, Samuel; Beutel, Jan; Faillettaz, Jérome; Hasler, Andreas; Krautblatter, Michael; Vieli, Andreas

    2017-02-01

    Understanding rock slope kinematics in steep, fractured bedrock permafrost is a challenging task. Recent laboratory studies have provided enhanced understanding of rock fatigue and fracturing in cold environments but were not successfully confirmed by field studies. This study presents a unique time series of fracture kinematics, rock temperatures and environmental conditions at 3500 m a. s. l. on the steep, strongly fractured Hörnligrat of the Matterhorn (Swiss Alps). Thanks to 8 years of continuous data, the longer-term evolution of fracture kinematics in permafrost can be analyzed with an unprecedented level of detail. Evidence for common trends in spatiotemporal pattern of fracture kinematics could be found: a partly reversible seasonal movement can be observed at all locations, with variable amplitudes. In the wider context of rock slope stability assessment, we propose separating reversible (elastic) components of fracture kinematics, caused by thermoelastic strains, from the irreversible (plastic) component due to other processes. A regression analysis between temperature and fracture displacement shows that all instrumented fractures exhibit reversible displacements that dominate fracture kinematics in winter. Furthermore, removing this reversible component from the observed displacement enables us to quantify the irreversible component. From this, a new metric - termed index of irreversibility - is proposed to quantify relative irreversibility of fracture kinematics. This new index can identify periods when fracture displacements are dominated by irreversible processes. For many sensors, irreversible enhanced fracture displacement is observed in summer and its initiation coincides with the onset of positive rock temperatures. This likely indicates thawing-related processes, such as meltwater percolation into fractures, as a forcing mechanism for irreversible displacements. For a few instrumented fractures, irreversible displacements were found at the

  7. Irreversible Electroporation Near the Heart: Ventricular Arrhythmias Can Be Prevented With ECG Synchronization

    PubMed Central

    Deodhar, Ajita; Dickfeld, Timm; Single, Gordon W.; Hamilton, William C.; Thornton, Raymond H.; Sofocleous, Constantinos T.; Maybody, Majid; Gónen, Mithat; Rubinsky, Boris; Solomon, Stephen B.

    2013-01-01

    OBJECTIVE Irreversible electroporation is a nonthermal ablative tool that uses direct electrical pulses to create irreversible membrane pores and cell death. The ablation zone is surrounded by a zone of reversibly increased permeability; either zone can cause cardiac arrhythmias. Our purpose was to establish a safety profile for the use of irreversible electroporation close to the heart. MATERIALS and METHODS The effect of unsynchronized and synchronized (with the R wave on ECG) irreversible electroporation in swine lung and myocardium was studied in 11 pigs. Twelve lead ECG recordings were analyzed by an electrophysiologist for the presence of arrhythmia. Ventricular arrhythmias were categorized as major events. Minor events included all other dysrhythmias or ECG changes. Cardiac and lung tissue was submitted for histopathologic analysis. Electrical field modeling was performed to predict the distance from the applicators over which cells show electroporation-induced increased permeability. RESULTS At less than or equal to 1.7 cm from the heart, fatal (major) events occurred with all unsynchronized irreversible electroporation. No major and three minor events were seen with synchronized irreversible electroporation. At more than 1.7 cm from the heart, two minor events occurred with only unsynchronized irreversible electroporation. Electrical field modeling correlates well with the clinical results, revealing increased cell membrane permeability up to 1.7 cm away from the applicators. Complete lung ablation without intervening live cells was seen. No myocardial injury was seen. CONCLUSION Unsynchronized irreversible electroporation close to the heart can cause fatal ventricular arrhythmias. Synchronizing irreversible electroporation pulse delivery with absolute refractory period avoids significant cardiac arrhythmias. PMID:21343484

  8. Vaccine-associated enhanced respiratory disease is influenced by hemagglutinin and neuraminidase in whole inactivated influenza virus vaccines

    USDA-ARS?s Scientific Manuscript database

    Multiple subtypes and many antigenic variants of influenza A virus (IAV) co-circulate in swine in the USA, complicating effective use of commercial vaccines to control disease and transmission. Whole inactivated virus (WIV) vaccines may provide partial protection against IAV with substantial antigen...

  9. A fingerprint encryption scheme based on irreversible function and secure authentication.

    PubMed

    Yang, Yijun; Yu, Jianping; Zhang, Peng; Wang, Shulan

    2015-01-01

    A fingerprint encryption scheme based on irreversible function has been designed in this paper. Since the fingerprint template includes almost the entire information of users' fingerprints, the personal authentication can be determined only by the fingerprint features. This paper proposes an irreversible transforming function (using the improved SHA1 algorithm) to transform the original minutiae which are extracted from the thinned fingerprint image. Then, Chinese remainder theorem is used to obtain the biokey from the integration of the transformed minutiae and the private key. The result shows that the scheme has better performance on security and efficiency comparing with other irreversible function schemes.

  10. A Fingerprint Encryption Scheme Based on Irreversible Function and Secure Authentication

    PubMed Central

    Yu, Jianping; Zhang, Peng; Wang, Shulan

    2015-01-01

    A fingerprint encryption scheme based on irreversible function has been designed in this paper. Since the fingerprint template includes almost the entire information of users' fingerprints, the personal authentication can be determined only by the fingerprint features. This paper proposes an irreversible transforming function (using the improved SHA1 algorithm) to transform the original minutiae which are extracted from the thinned fingerprint image. Then, Chinese remainder theorem is used to obtain the biokey from the integration of the transformed minutiae and the private key. The result shows that the scheme has better performance on security and efficiency comparing with other irreversible function schemes. PMID:25873989

  11. A Fragment-Based Method to Discover Irreversible Covalent Inhibitors of Cysteine Proteases

    PubMed Central

    2015-01-01

    A novel fragment-based drug discovery approach is reported which irreversibly tethers drug-like fragments to catalytic cysteines. We attached an electrophile to 100 fragments without significant alterations in the reactivity of the electrophile. A mass spectrometry assay discovered three nonpeptidic inhibitors of the cysteine protease papain. The identified compounds display the characteristics of irreversible inhibitors. The irreversible tethering system also displays specificity: the three identified papain inhibitors did not covalently react with UbcH7, USP08, or GST-tagged human rhinovirus 3C protease. PMID:24870364

  12. Effect of graphite surface structure on initial irreversible reaction in graphite anodes

    SciTech Connect

    Suzuki, Kimihito; Hamada, Takeshi; Sugiura, Tsutomu

    1999-03-01

    The initial irreversible reaction that occurs in graphite anodes during the first lithium intercalation in lithium rechargeable batteries was studied in view of graphite surface structure. Graphitized mesophase spheres and pitch-based carbon fibers, which show low irreversible capacity, were shown to have turbostatic surface regions and highly graphitized cores using Ar-ion laser Raman spectroscopy. Burning off these surface regions resulted in remarkable increases of initial irreversible capacity. Those results can be explained by a proposed model that a turbostatic structure of the graphite surface region resists drastic swelling of interlayer spaces arising from cointercalation of solvated ions and depresses the side reaction.

  13. Mesoscale modeling of irreversible volume growth in powders of anisotropic crystals

    SciTech Connect

    Gee, R; Maiti, A; Fried, L

    2006-05-05

    Careful thermometric analysis (TMA) on powders of micron-sized triamino-trinitrobenzene (TATB) crystallites are shown to display irreversible growth in volume when subjected to repeated cycles of heating and cooling. Such behavior is counter-intuitive to typical materials response to simulated annealing cycles in atomic-scale molecular dynamics. However, through coarse-grained simulations using a mesoscale Hamiltonian we quantitatively reproduce irreversible growth behavior in such powdered material. We demonstrate that irreversible growth happens only in the presence of intrinsic crystalline anisotropy, and is mediated by particles much smaller than the average crystallite size.

  14. Partial tooth gear bearings

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    2010-01-01

    A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.

  15. Partial (focal) seizure

    MedlinePlus

    ... Jacksonian seizure; Seizure - partial (focal); Temporal lobe seizure; Epilepsy - partial seizures ... Abou-Khalil BW, Gallagher MJ, Macdonald RL. Epilepsies. In: Daroff ... Practice . 7th ed. Philadelphia, PA: Elsevier; 2016:chap 101. ...

  16. A Single-institution Experience with Open Irreversible Electroporation for Locally Advanced Pancreatic Carcinoma

    PubMed Central

    Yan, Li; Chen, Yong-Liang; Su, Ming; Liu, Tian; Xu, Kai; Liang, Feng; Gu, Wan-Qing; Lu, Shi-Chun

    2016-01-01

    Background: Locally advanced pancreatic carcinoma (LAPC) is characterized by poor prognosis despite recommended concurrent chemoradiotherapy. Irreversible electroporation (IRE) has emerged as a potential option for the management of unresectable pancreatic cancer. This study was conducted to evaluate the safety and short-term efficacy of open IRE for the treatment of LAPC. Methods: Retrospective data of 25 consecutive patients receiving IRE for T3 lesions from July 2015 to June 2016 at a single center were analyzed. The perioperative and long-term IRE-related complications were reviewed to evaluate the safety of the procedure. The tumor reduction and biological response were analyzed through computed tomography/magnetic resonance imaging; the serum level of CA19-9 was measured as a secondary endpoint to evaluate the short-term efficacy of IRE. Results: All patients were successfully treated; the median tumor size was 4.2 cm and the median IRE time was 36 min. Four intraoperative procedure-related complications were observed (16%): two transient hypertensive episodes, one hypotension case, and one transient supraventricular tachycardia case. Nine postoperative complications were described, including three Grade A pancreatic fistulas, three delayed gastric emptying, one acute pancreatitis, one upper gastrointestinal hemorrhage, and one portal vein thrombosis. The overall rate of stable disease was 28%, 36% achieved partial response, and lower serum CA19-9 levels were recorded in all patients at discharge. Conclusions: IRE is feasible for the treatment of LAPC and is a reasonable intervention strategy owing to its combined attributes of safety and efficacy. PMID:27958223

  17. Irreversible adsorption/deposition kinetics: A generalized approach

    NASA Astrophysics Data System (ADS)

    Adamczyk, Z.; Senger, B.; Voegel, J.-C.; Schaaf, P.

    1999-02-01

    . This can be explained by the fact that for a high energy barrier the adsorbing particles could randomize over the deposition plane before crossing the barrier and adsorbing irreversibly.

  18. Succination of proteins by fumarate: mechanism of inactivation of glyceraldehyde-3-phosphate dehydrogenase in diabetes.

    PubMed

    Blatnik, Matthew; Thorpe, Suzanne R; Baynes, John W

    2008-04-01

    S-(2-succinyl)cysteine (2SC) is a chemical modification of proteins formed by a Michael addition reaction between the Krebs cycle intermediate, fumarate, and thiol groups in protein--a process known as succination of protein. Succination causes irreversible inactivation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in vitro. GAPDH was immunoprecipitated from muscle of diabetic rats, then analyzed by ultra-performance liquid chromatography-electrospray ionization-mass spectroscopy. Succination of GAPDH was increased in muscle of diabetic rats, and the extent of succination correlated strongly with the decrease in specific activity of the enzyme. We propose that 2SC is a biomarker of mitochondrial and oxidative stress in diabetes and that succination of GAPDH and other thiol proteins may provide the chemical link between glucotoxicity and the pathogenesis of diabetic complications.

  19. Succination of Proteins by Fumarate: Mechanism of Inactivation of Glyceraldehyde-3-Phosphate Dehydrogenase in Diabetes

    PubMed Central

    Blatnik, Matthew; Thorpe, Suzanne R.; Baynes, John W.

    2008-01-01

    S-(2-succinyl)cysteine (2SC) is a chemical modification of proteins formed by a Michael addition reaction between the Krebs cycle intermediate, fumarate, and thiol groups in protein—a process known as succination of protein. Succination causes irreversible inactivation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in vitro. GAPDH was immunoprecipitated from muscle of diabetic rats, then analyzed by ultra-performance liquid chromatography–electrospray ionization–mass spectroscopy. Succination of GAPDH was increased in muscle of diabetic rats, and the extent of succination correlated strongly with the decrease in specific activity of the enzyme. We propose that 2SC is a biomarker of mitochondrial and oxidative stress in diabetes and that succination of GAPDH and other thiol proteins may provide the chemical link between glucotoxicity and the pathogenesis of diabetic complications. PMID:18448829

  20. State-dependent inactivation of the Kv3 potassium channel.

    PubMed Central

    Marom, S; Levitan, I B

    1994-01-01

    Inactivation of Kv3 (Kv1.3) delayed rectifier potassium channels was studied in the Xenopus oocyte expression system. These channels inactivate slowly during a long depolarizing pulse. In addition, inactivation accumulates in response to a series of short depolarizing pulses (cumulative inactivation), although no significant inactivation occurs within each short pulse. The extent of cumulative inactivation does not depend on the voltage during the depolarizing pulse, but it does vary in a biphasic manner as a function of the interpulse duration. Furthermore, the rate of cumulative inactivation is influenced by changing the rate of deactivation. These data are consistent with a model in which Kv3 channel inactivation is a state-dependent and voltage-independent process. Macroscopic and single channel experiments indicate that inactivation can occur from a closed (silent) state before channel opening. That is, channels need not open to inactivate. The transition that leads to the inactivated state from the silent state is, in fact, severalfold faster then the observed inactivation of current during long depolarizing pulses. Long pulse-induced inactivation appears to be slow, because its rate is limited by the probability that channels are in the open state, rather than in the silent state from which they can inactivate. External potassium and external calcium ions alter the rates of cumulative and long pulse-induced inactivation, suggesting that antagonistic potassium and calcium binding steps are involved in the normal gating of the channel. PMID:7948675

  1. Inactivation of pathogenic bacteria in food matrices: high pressure processing, photodynamic inactivation and pressure-assisted photodynamic inactivation

    NASA Astrophysics Data System (ADS)

    Cunha, A.; Couceiro, J.; Bonifácio, D.; Martins, C.; Almeida, A.; Neves, M. G. P. M. S.; Faustino, M. A. F.; Saraiva, J. A.

    2017-09-01

    Traditional food processing methods frequently depend on the application of high temperature. However, heat may cause undesirable changes in food properties and often has a negative impact on nutritional value and organoleptic characteristics. Therefore, reducing the microbial load without compromising the desirable properties of food products is still a technological challenge. High-pressure processing (HPP) can be classified as a cold pasteurization technique, since it is a non-thermal food preservation method that uses hydrostatic pressure to inactivate spoilage microorganisms. At the same time, it increases shelf life and retains the original features of food. Photodynamic inactivation (PDI) is also regarded as promising approach for the decontamination of food matrices. In this case, the inactivation of bacterial cells is achieved by the cytotoxic effects of reactive oxygens species (ROS) produced from the combined interaction of a photosensitizer molecule, light and oxygen. This short review examines some recent developments on the application of HPP and PDI with food-grade photosensitizers for the inactivation of listeriae, taken as a food pathogen model. The results of a proof-of-concept trial of the use of high-pressure as a coadjutant to increase the efficiency of photodynamic inactivation of bacterial endospores is also addressed.

  2. Inactivation of surfactant in rat lungs.

    PubMed

    Bruni, R; Fan, B R; David-Cu, R; Taeusch, H W; Walther, F J

    1996-02-01

    Although surfactant replacement therapy has dramatically improved the outcome of premature infants with respiratory distress syndrome, approximately 30% of treated infants show a transient or no response. Nonresponse to surfactant replacement therapy may be due to extreme lung immaturity and possibly surfactant inactivation. Surfactant inactivation involves aspecific biophysical events, such as interference with the formation or activity of an alveolar monolayer, and specific interactions with serum proteins, including antibodies, leaking into the alveolar space. As formulations containing surfactant proteins appear to better tolerate serum inactivation, we used an excised rat lung model to compare the susceptibility to serum inactivation of a mixture of synthetic phospholipids selected from surfactant lipid constituents, Exosurf (a protein-free synthetic surfactant), Survanta [containing surfactant proteins B and C (SP-B and -C)], and a porcine surfactant (containing SP-A, -B, and -C). For each of these preparations, we used pressure/volume determinations as an in situ measure of surfactant activity and retested the same preparations after mixing with human serum, a nonspecific surfactant inactivator. Human serum inactivated porcine surfactant to a lesser extent than Survanta, Exosurf, or synthetic phospholipids. Temperature exerted a significant effect on deflation stability, as shown by a greater lung compliance in untreated, normal lungs and a larger improvement in compliance after treating lavaged lungs with synthetic phospholipids at 37 degrees C than at 22 degrees C. We conclude that surfactant containing SP-A, -B, and -C is only moderately susceptible to inactivation with whole serum and may therefore exert a greater clinical response than protein-free surfactants or those containing only SP-B and -C.

  3. Irreversible deposition/adsorption processes on solid surfaces

    NASA Astrophysics Data System (ADS)

    Schaaf, P.; Voegel, J.-C.; Senger, B.

    In this article, we summarize the knowledge in the field of irreversible deposition processes of large molecules or colloidal particles on solid surfaces. An irreversible adsorption process is defined as a process in which, once adsorbed, a particle can neither diffuse along, nor desorb from the surface. We first introduce the basic tools used in these studies, one of the most important being the concept of available surface function. General results relative to these processes are then presented. We discuss, in particular, the connection between the reduced variance of the number density fluctuations of adsorbed particles and the available surface function. We then review the main models which were introduced in the literature to account for these phenomena. They can be divided in two classes: (i) the models which are based entirely on statistical and geometrical grounds. The best known and most widely studied of them is the Random Sequential Adsorption (RSA) model which is discussed in details. For the processes in which gravity plays an important role one uses the Ballistic Deposition (BD) model. We also present models which are aimed at accounting for the behavior lying between the ballistic deposition and the RSA. (ii) The second type of models corresponds to those which take explicitly the diffusion of the particles in the vicinity of the adsorption plane into account. The results relative to these models, called diffusional models, are discussed in details. Finally, the last part of the review is devoted to experimental results. We show, in particular, that the Langmuir model, which is the most widely used model in the literature to account for the protein adsorption kinetics, does not predict correctly the experimental observations. We present and discuss in a critical way experimental evidence which seems to indicate the validity of the RSA and ballistic models. Cet article présente une synthèse des connaissances dans le domaine des processus d

  4. Mechanism of multivalent nanoparticle encounter with HIV-1 for potency enhancement of peptide triazole virus inactivation.

    PubMed

    Rosemary Bastian, Arangassery; Nangarlia, Aakansha; Bailey, Lauren D; Holmes, Andrew; Kalyana Sundaram, R Venkat; Ang, Charles; Moreira, Diogo R M; Freedman, Kevin; Duffy, Caitlin; Contarino, Mark; Abrams, Cameron; Root, Michael; Chaiken, Irwin

    2015-01-02

    Entry of HIV-1 into host cells remains a compelling yet elusive target for developing agents to prevent infection. A peptide triazole (PT) class of entry inhibitor has previously been shown to bind to HIV-1 gp120, suppress interactions of the Env protein at host cell receptor binding sites, inhibit cell infection, and cause envelope spike protein breakdown, including gp120 shedding and, for some variants, virus membrane lysis. We found that gold nanoparticle-conjugated forms of peptide triazoles (AuNP-PT) exhibit substantially more potent antiviral effects against HIV-1 than corresponding peptide triazoles alone. Here, we sought to reveal the mechanism of potency enhancement underlying nanoparticle conjugate function. We found that altering the physical properties of the nanoparticle conjugate, by increasing the AuNP diameter and/or the density of PT conjugated on the AuNP surface, enhanced potency of infection inhibition to impressive picomolar levels. Further, compared with unconjugated PT, AuNP-PT was less susceptible to reduction of antiviral potency when the density of PT-competent Env spikes on the virus was reduced by incorporating a peptide-resistant mutant gp120. We conclude that potency enhancement of virolytic activity and corresponding irreversible HIV-1 inactivation of PTs upon AuNP conjugation derives from multivalent contact between the nanoconjugates and metastable Env spikes on the HIV-1 virus. The findings reveal that multispike engagement can exploit the metastability built into virus the envelope to irreversibly inactivate HIV-1 and provide a conceptual platform to design nanoparticle-based antiviral agents for HIV-1 specifically and putatively for metastable enveloped viruses generally.

  5. DL-canaline and 5-fluoromethylornithine. Comparison of two inactivators of ornithine aminotransferase.

    PubMed Central

    Bolkenius, F N; Knödgen, B; Seiler, N

    1990-01-01

    5-Fluoromethylornithine (5FMOrn) is an enzyme-activated irreversible inhibitor or ornithine aminotransferase (L-ornithine:2-oxo-acid 5-aminotransferase, OAT). For purified rat liver OAT, Ki(app.) was found to be 30 microM. and tau 1/2 = 4 min. Of the four stereomers of 5FMOrn only one reacts with OAT. The formation of a chromophore with an absorption maximum at 458 nm after inactivation of OAT by 5FMOrn suggests the formation of an enamine intermediate, which is slowly hydrolysed to release an unsaturated ketone. L-Canaline [(S)-2-amino-4-amino-oxybutyric acid] is a well-known irreversible inhibitor of OAT. Not only the natural L-enantiomer but also the D-enantiomer reacts by oxime formation with pyridoxal 5'-phosphate in the active site of the enzyme, although considerably more slowly. This demonstrates that the stereochemistry at C-2 of ornithine is not absolutely stringent. In vitro, canaline reacted faster than 5FMOrn with OAT. In vivo, however, only incomplete OAT inhibition was observed with canaline. Whereas intraperitoneal administration of 10 mg of 5FMOrn/kg body wt. to mice was sufficient to inactivate OAT in brain and liver by 90% for 24 h, 500 mg of DL-canaline/kg body wt. only produced a transient inhibition of 65-70%. The accumulation of ornithine in these tissues was considerably slower and the maximum concentrations lower than were achieved with 5FMOrn. It appears that DL-canaline, in contrast with 5FMOrn, is not useful as a tool in studies of biological consequences of OAT inhibition. PMID:2363680

  6. Kinetic analysis of virus adsorption and inactivation in batch experiments

    NASA Astrophysics Data System (ADS)

    Grant, Stanley B.; List, E. John; Lidstrom, Mary E.

    1993-07-01

    The mobility and ecology of viruses in natural environments is strongly influenced by the adsorption of virus particles to sand or soil surfaces. This binding process is frequently studied by conducting batch experiments in which fluid suspensions of virus particles are contacted with the adsorbent of interest. In this report, a simple first-order kinetic theory is presented which accounts for many of the complicated interactions that can occur when viruses contact an adsorbent in a batch system. Closed-form solutions and numerical simulations of the model indicate that four classes of virus-surface interactions can be identified, including quasi-equilibrium adsorption, quasi-equilibrium adsorption with surface sinks, quasi-equilibrium adsorption with reduced inactivation, and direct irreversible adsorption. Based on these results, a new experimental approach for studying virus-surface interactions is proposed and tested using a model system consisting of bacteriophage lambda and Ottawa sand. Fluid samples were collected from sand-containing and sand-free virus suspensions over the course of 5-6 days and analyzed for plaque forming units (PFU). These experiments were repeated using three different pH values and six different electrolyte compositions. Nondimensionalization of the PFU data from the sand-free suspension collapsed all of the data onto a single line, as predicted by the kinetic model. When plotted in a nondimensional format, data from the sandcontaining suspensions exhibited behavior which tould readily be interpreted within the context of the kinetic model. These results suggest that the proposed approach offers a powerful alternative to conventional methods for studying virus adsorption at the solid-liquid interface, and for predicting the potential mobility and fate of viruses in porous media.

  7. Functional inactivation of lymphocytes by methylene blue with visible light.

    PubMed

    Zhang, Bo; Cheng, Zhenzhen; Mo, Qin; Wang, Li; Wang, Xun; Wu, Xiaofei; Jia, Yao; Huang, Yuwen

    2015-10-01

    Transfusion of allogeneic white blood cells (WBCs) may cause adverse reactions in immunocompromised recipients, including transfusion-associated graft-versus-host disease (TA-GVHD), which is often fatal and incurable. In this study, the in vitro effect of methylene blue with visible light (MB + L) treatment on lymphocyte proliferation and cytokine production was measured to investigate whether MB + L can be used to prevent immune reactions that result from transfused lymphocytes. WBCs and 3 μM of MB were mixed and transferred into medical PVC bags, which were then exposed to visible light. Gamma irradiation was conducted as a parallel positive control. The cells without treatment were used as untreated group. All the groups were tested for the ability of cell proliferation and cytokine production upon stimulation. After incubation with mitogen phytohemagglutinin (PHA) or plate-bound anti-CD3 plus anti-CD28, the proliferation of MB + L/gamma-irradiation treated lymphocytes was significantly inhibited (P < 0.01) as compared to the untreated ones; the proliferation inhibitive rate of the MB + L group was even higher than that of gamma-irradiated cells (73.77% ± 28.75% vs. 44.72% ± 38.20%). MB + L treated cells incubated up to 7 days with PHA also showed no significant proliferation. The levels of TNF-α, IFN-γ, IL-6, IL-8, IL-10 and IL-1β present in the supernatant of MB + L treated lymphocytes upon stimulation were significantly lower than those of untreated lymphocytes. These results demonstrated that MB + L treatment functionally and irreversibly inactivated lymphocytes by inhibiting lymphocyte proliferation and the production of cytokines. MB + L treatment might be a promising method for the prevention of adverse immune responses caused by WBCs.

  8. Inactivation of microbial arginine deiminases by L-canavanine.

    PubMed

    Li, Ling; Li, Zhimin; Chen, Danqi; Lu, Xuefeng; Feng, Xiaohua; Wright, Elizabeth C; Solberg, Nathan O; Dunaway-Mariano, Debra; Mariano, Patrick S; Galkin, Andrey; Kulakova, Liudmila; Herzberg, Osnat; Green-Church, Kari B; Zhang, Liwen

    2008-02-13

    Arginine deiminase (ADI) catalyzes the hydrolytic conversion of L-arginine to ammonia and L-citrulline as part of the energy-producing L-arginine degradation pathway. The chemical mechanism for ADI catalysis involves initial formation and subsequent hydrolysis of a Cys-alkylthiouronium ion intermediate. The structure of the Pseudomonas aeruginosa ADI-(L-arginine) complex guided the design of arginine analogs that might react with the ADIs to form inactive covalent adducts during catalytic turnover. One such candidate is L-canavanine, in which an N-methylene of L-arginine is replaced by an N-O. This substance was shown to be a slow substrate-producing O-ureido-L-homoserine. An in depth kinetic and mass spectrometric analysis of P. aeruginosa ADI inhibition by L-canavanine showed that two competing pathways are followed that branch at the Cys-alkylthiouronium ion intermediate. One pathway leads to direct formation of O-ureido-L-homoserine via a reactive thiouronium intermediate. The other pathway leads to an inactive form of the enzyme, which was shown by chemical model and mass spectrometric studies to be a Cys-alkylisothiourea adduct. This adduct undergoes slow hydrolysis to form O-ureido-L-homoserine and regenerated enzyme. In contrast, kinetic and mass spectrometric investigations demonstrate that the Cys-alkylthiouronium ion intermediate formed in the reaction of L-canavanine with Bacillus cereus ADI partitions between the product forming pathway (O-ureido-L-homoserine and free enzyme) and an inactivation pathway that leads to a stable Cys-alkylthiocarbamate adduct. The ADIs from Escherichia coli, Burkholderia mallei, and Giardia intestinalis were examined in order to demonstrate the generality of the L-canavanine slow substrate inhibition and to distinguish the kinetic behavior that defines the irreversible inhibition observed with the B. cereus ADI from the time controlled inhibition observed with the P. aeruginosa, E. coli, B. mallei, and G. intestinalis ADIs.

  9. Irreversible entropy production in two-phase flows with evaporating drops

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Okong'o, N. A.

    2002-01-01

    A derivation of the irreversible entropy production, that is the dissipation, in two-phase flows is presented for the purpose of examining the effect of evaporative-drop modulation of flows having turbulent features.

  10. Ecological optimization of an irreversible quantum Carnot heat engine with spin-1/2 systems

    NASA Astrophysics Data System (ADS)

    Liu, Xiaowei; Chen, Lingen; Wu, Feng; Sun, Fengrui

    2010-02-01

    A model of a quantum heat engine with heat resistance, internal irreversibility and heat leakage and many non-interacting spin-1/2 systems is established in this paper. The quantum heat engine cycle is composed of two isothermal processes and two irreversible adiabatic processes and is referred to as a spin quantum Carnot heat engine. Based on the quantum master equation and the semi-group approach, equations of some important performance parameters, such as power output, efficiency, entropy generation rate and ecological function (a criterion representing the optimal compromise between exergy output rate and exergy loss rate), for the irreversible spin quantum Carnot heat engine are derived. The optimal ecological performance of the heat engine in the classical limit is analyzed with numerical examples. The effects of internal irreversibility and heat leakage on ecological performance are discussed in detail.

  11. The Effects of Internal and External Irreversibility of a Vapor Compression Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Wang, Fu-Jen; Chiou, Jeng-Shing

    The concept of finite-time thermodynamics is employed to investigate the optimal refrigeration rate for an irreversible refrigeration cycle. The heat transfer between the system (internal) fluid and cooling (external) fluid takes place at the actual heat exchanger, which has the finite-size heat transfer area and the realistic heat transfer effectiveness. The internal irreversibility results from the compression process and the expansion process are also considered. The optimal refrigeration rate is calculated and expressed in terms of the irreversibility parameter (Ir), coefficient of performance (COP), the time ratio(γ) of heat transfer processes and the effectiveness of heat exchanger. The derived COP which consider both the external and internal irreversibility can thus be considered as the benchmark value for a practical refrigeration cycle, and the parametric study can provide the basis for both determination of optimal operating conditions and design of a practical refrigeration cycle.

  12. Effect of design variables on irreversible magnet demagnetization in brushless dc motor

    NASA Astrophysics Data System (ADS)

    Kim, Tae Heoung; Lee, Ju

    2005-05-01

    The large demagnetizing currents in brushless dc (BLdc) motor are generated by the short-circuited stator windings and the fault of a drive circuit. So, irreversible magnet demagnetization occurs due to the external demagnetizing field by these currents. In this paper, we deal with the effect of design variables on irreversible magnet demagnetization in BLdc motor through the modeling approach using a two-dimensional finite-element method (2D FEM). The nonlinear analysis of a permanent magnet is added to 2D FEM to consider irreversible demagnetization. As a result, it is shown that magnet thickness, teeth surface width, and rotor back yoke thickness are the most important geometrical dimensions of BLdc motor in terms of irreversible magnet demagnetization.

  13. Reversible and irreversible structural transformations of nanocomponents of molecular layers by resonance photoexcitation or heating

    NASA Astrophysics Data System (ADS)

    Kaliteevskaya, Elena N.; Krutyakova, Valentina P.; Razumova, Tatyana K.; Starovoytov, Anton A.

    2010-09-01

    The reversible and irreversible structural transformations of monomolecular and associated nanocomponents of a polymethine dye layer by photoexcitation or heating are studied experimentally. The photo- and thermodestruction yields of the layers are investigated.

  14. The role of the irreversible electroporation in the hepato-pancreatico-biliary surgery.

    PubMed

    Sánchez-Velázquez, Patricia; Clavien, Pierre-Alain

    Irreversible electroporation is a novel technique growing in popularity over the last years among the ablative modalities. Its unique action mechanism produces irreversible nanopores in the membrane of the cell leading to apoptosis; therefore irreversible electroporation can be used to ablate substantial volumes of tissue without the undesirable thermal effects as the "heat sink effect". Moreover the extracellular matrix is left unperturbed, thus sparing the structural architecture of surrounding structures such as bile ducts and blood vessels. In the last years its use has been widespread in both liver and pancreatic ablation. Irreversible electroporation has shown its safety with however some caution, feasibility and favorable outcomes in clinical settings such as unresectable locally advanced disease in which the surgical and therapeutic options are very limited. Copyright © 2017 AEC. Publicado por Elsevier España, S.L.U. All rights reserved.

  15. Thermal inactivation of Salmonella in peanut butter.

    PubMed

    Ma, Li; Zhang, Guodong; Gerner-Smidt, Peter; Mantripragada, Vijaya; Ezeoke, Ifeoma; Doyle, Michael P

    2009-08-01

    The objective of this study was to determine the rates of thermal inactivation of three Salmonella Tennessee strains in peanut butter associated with an outbreak and to compare them to the rates of inactivation of Salmonella strains of other serotypes (Enteritidis, Typhimurium, and Heidelberg) (SSOS) and of clinical isolates of Salmonella Tennessee from sporadic cases (STSC). Commercial peanut butter was inoculated with Salmonella isolates and heated at 71, 77, 83, and 90 degrees C. The thermal inactivation curves were upwardly concave, indicating rapid death at the beginning (20 min) of heating followed by lower death rates thereafter. The first-order kinetics approach and nonlinear Weibull model were used to fit the inactivation curves and describe the rates of thermal inactivation of Salmonella in peanut butter. The calculated minimum times needed to obtain a 7-log reduction at 90 degrees C for the composited three outbreak-associated strains were significantly greater (P < 0.05) than those of SSOS and STSC. Approximately 120 min were needed to reduce the outbreak strains of Salmonella Tennessee by 7 log, whereas 86 and 55 min were needed for SSOS and STSC, respectively. These results indicate that the outbreak-associated Salmonella strains were more thermotolerant than the other Salmonella strains tested, and this greater thermal resistance was not serotype specific. Thermal treatments of peanut butter at 90 degrees C for less than 30 min are not sufficient to kill large populations (5 log CFU/g) of Salmonella in highly contaminated peanut butter.

  16. Inactivated infectious haematopoietic necrosis virus (IHNV) vaccines.

    PubMed

    Anderson, E; Clouthier, S; Shewmaker, W; Weighall, A; LaPatra, S

    2008-10-01

    The inactivation dynamics of infectious haematopoietic necrosis virus (IHNV) by b-propiolactone (BPL), binary ethylenimine (BEI), formaldehyde or heat and the antigenic and immunogenic properties of the inactivated vaccines were evaluated. Chemical treatment of IHNV with 2.7 mm BPL, 1.5 mm BEI or 50 mm formaldehyde abolished virus infectivity within 48 h whereas heat treatment at 50 or 100 degrees C rendered the virus innocuous within 30 min. The inactivated IHNV vaccines were recognized by rainbow trout, Oncorhynchus mykiss, IHNV-specific antibodies and were differentially recognized by antigenic site I or antigenic site II IHNV glycoprotein-specific neutralizing monoclonal antibodies. The BPL inactivated whole virus vaccine was highly efficacious in vaccinated rainbow trout challenged by waterborne exposure to IHNV 7, 28, 42 or 56 days (15 degrees C) after immunization. The formaldehyde inactivated whole virus vaccine was efficacious 7 or 11 days after vaccination of rainbow trout but performed inconsistently when tested at later time points. The other vaccines tested were not efficacious.

  17. Genes that escape from X inactivation.

    PubMed

    Berletch, Joel B; Yang, Fan; Xu, Jun; Carrel, Laura; Disteche, Christine M

    2011-08-01

    To achieve a balanced gene expression dosage between males (XY) and females (XX), mammals have evolved a compensatory mechanism to randomly inactivate one of the female X chromosomes. Despite this chromosome-wide silencing, a number of genes escape X inactivation: in women about 15% of X-linked genes are bi-allelically expressed and in mice, about 3%. Expression from the inactive X allele varies from a few percent of that from the active allele to near equal expression. While most genes have a stable inactivation pattern, a subset of genes exhibit tissue-specific differences in escape from X inactivation. Escape genes appear to be protected from the repressive chromatin modifications associated with X inactivation. Differences in the identity and distribution of escape genes between species and tissues suggest a role for these genes in the evolution of sex differences in specific phenotypes. The higher expression of escape genes in females than in males implies that they may have female-specific roles and may be responsible for some of the phenotypes observed in X aneuploidy.

  18. Inactivation of Escherichia coli by ultrasonic irradiation.

    PubMed

    Furuta, M; Yamaguchi, M; Tsukamoto, T; Yim, B; Stavarache, C E; Hasiba, K; Maeda, Y

    2004-04-01

    Ultrasonic inactivation of Escherichia coli XL1-Blue has been investigated by high-intensity ultrasonic waves from horn type sonicator (27.5 kHz) utilizing the "squeeze-film effect". The amplitude of the vibration face contacting the sample solution was used as an indication of the ultrasonic power intensity. The inactivation of the E. coli cells by ultrasonic irradiation shows pseudo first-order behavior. The inactivation rate constant gradually increased with increasing amplitude of the vibration face and showed rapid increase above 3 microm (p-p). In contrast, the H2O2 formation was not observed below 3 microm (p-p), indicating that the ultrasonic shock wave might be more important than indirect effect of OH radicals formed by ultrasonic cavitation in this system. The optimal thickness of the squeeze film was determined as 2 mm for the E. coli inactivation. More than 99% of E. coli cells was inactivated within 180-s sonication at the amplitude of 3 microm (p-p) and 2 mm of the thickness of the squeeze film.

  19. Kinetics of Hydrothermal Inactivation of Endotoxins ▿

    PubMed Central

    Li, Lixiong; Wilbur, Chris L.; Mintz, Kathryn L.

    2011-01-01

    A kinetic model was established for the inactivation of endotoxins in water at temperatures ranging from 210°C to 270°C and a pressure of 6.2 × 106 Pa. Data were generated using a bench scale continuous-flow reactor system to process feed water spiked with endotoxin standard (Escherichia coli O113:H10). Product water samples were collected and quantified by the Limulus amebocyte lysate assay. At 250°C, 5-log endotoxin inactivation was achieved in about 1 s of exposure, followed by a lower inactivation rate. This non-log-linear pattern is similar to reported trends in microbial survival curves. Predictions and parameters of several non-log-linear models are presented. In the fast-reaction zone (3- to 5-log reduction), the Arrhenius rate constant fits well at temperatures ranging from 120°C to 250°C on the basis of data from this work and the literature. Both biphasic and modified Weibull models are comparable to account for both the high and low rates of inactivation in terms of prediction accuracy and the number of parameters used. A unified representation of thermal resistance curves for a 3-log reduction and a 3 D value associated with endotoxin inactivation and microbial survival, respectively, is presented. PMID:21193667

  20. Nucleophilic Additions to Coordinated 1,10-Phenanthroline: Intramolecular, Intermolecular, Reversible, and Irreversible.

    PubMed

    Arévalo, Rebeca; Menéndez, M Isabel; López, Ramón; Merino, Isabel; Riera, Lucía; Pérez, Julio

    2016-12-12

    KN(SiMe3 )2 reacts with [Re(CO)3 (phen)(PMe3 )]OTf via reversible addition to the phen ligand and irreversible deprotonation of the PMe3 ligand followed by intramolecular attack to phen by the deprotonated phosphane, whereas MeLi irreversibly adds to phen. The addition of MeLi has been shown to be intermolecular, unlike previously known nucleophilic additions to pyridines. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.