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Sample records for chiral derivatizing reagents

  1. Indirect chiral separation of new recreational drugs by gas chromatography-mass spectrometry using trifluoroacetyl-L-prolyl chloride as chiral derivatization reagent.

    PubMed

    Weiß, Jennifer A; Mohr, Stefan; Schmid, Martin G

    2015-03-01

    New recreational drugs such as amphetamine-, cathinone, and benzofury derivatives gained high popularity on the drug market in recent years. They can be purchased via the Internet from different providers and online portals. Most of these compounds are chiral, which makes the development of chiral separation methods necessary. Besides this, it is useful to find out if the compounds were sold as racemic mixtures. Also, it is important to check whether the new psychoactive compounds contain further ingredients or impurities. The aim of this research was the continuation of the application of a method for indirect chiral separation of 24 new psychoactive compounds recently purchased via the Internet. After derivatization with the chiral derivatization reagent trifluoroacetyl-L-prolyl chloride, chromatographic separation of diastereomers was achieved using a 30 m HP5-MS capillary column. As carrier gas, helium was used with a constant flow of 1.0 ml/min. Three different column temperature programs were tested. Under optimum conditions 13 out of 24 compounds were successfully resolved into their enantiomers obtaining Rs values up to 7.0. The use of a single quadrupole mass spectrometer as the detector allowed the identification of the compounds in multicomponent samples.

  2. Application of cyanuric chloride-based six new chiral derivatizing reagents having amino acids and amino acid amides as chiral auxiliaries for enantioresolution of proteinogenic amino acids by reversed-phase high-performance liquid chromatography.

    PubMed

    Bhushan, Ravi; Dixit, Shuchi

    2012-04-01

    Six dichloro-s-triazine (DCT) reagents having L-Leu, D-Phg, L-Val, L-Met, L-Ala and L-Met-NH(2) as chiral auxiliaries in cyanuric chloride were introduced for enantioseparation of 13 proteinogenic amino acids. Four other DCTs and six monochloro-s-triazine (MCT) reagents having amino acid amides as chiral auxiliaries were also synthesized. These 16 chiral derivatizing reagents (CDRs) were used for synthesis of diastereomers of all the 13 analytes using microwave irradiation, which were resolved by reversed-phase high-performance liquid chromatography (RP-HPLC) using C18 column and gradient eluting mixture of aqueous TFA and acetonitrile with UV detection at 230 nm. It required only 60-90 s for derivatization using microwave irradiation. Better resolution and lower retention times were observed for the diastereomers prepared with CDRs having amino acids as chiral auxiliaries as compared to counterparts prepared with reagents having amino acid amides as chiral auxiliaries. As the best resolution of all the 13 analytes was observed for their diastereomers prepared using the DCT reagent having L-Leu as chiral auxiliary, this CDR was further employed for derivatization of Lys, Tyr, His and Arg followed by RP-HPLC analysis of resulting diastereomers. The results are discussed in light of acid and amide groups of chiral auxiliaries constituting CDRs, electronegativities of the atoms of achiral moieties constituting CDRs and hydrophobicities of side chains of amino acids constituting CDRs and analytes.

  3. Evaluation of a series of prolylamidepyridines as the chiral derivatization reagents for enantioseparation of carboxylic acids by LC-ESI-MS/MS and the application to human saliva.

    PubMed

    Kuwabara, Tomohiro; Takayama, Takahiro; Todoroki, Kenichiro; Inoue, Koichi; Min, Jun Zhe; Toyo'oka, Toshimasa

    2014-04-01

    Mass spectrometry has become a popular analytical tool because of its high sensitivity and specificity. The use of a chiral derivatization reagent for the mass spectrometry (MS) detection seems to be efficient for the enantiomeric separation of racemates. However, the number of chiral reagents for the liquid chromatography (LC)-MS/MS analysis is very limited. According to these observations, we are currently in the process of developing novel labeling reagents for chiral molecules in MS/MS analysis. The derivatization reagent that is effective for enhancing not only the electrospray ionization-MS/MS sensitivity but also the reversed-phase LC resolution of carboxylic acid enantiomers should have a highly proton-affinitive moiety and an asymmetric structure near the reactive functional group. Furthermore, the resulting derivative has to provide a characteristic product ion suitable for the selected reaction monitoring. Based upon these considerations, a series of prolylamidepyridines ((S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-2-yl)amide (PCP2), (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-3-yl)amide, and (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-4-yl)amide) was synthesized as ideal labeling reagents for the enantioseparation of chiral carboxylic acids and evaluated in terms of separation efficiency and detection sensitivity by ultra-performance LC (UPLC)-MS/MS. Among the synthesized reagents, PCP2 was the most efficient chiral derivatization reagent for the enantioseparation of carboxylic acid. The Rs values and the detection limits of the derivatives of non-steroidal anti-inflammatory drugs, which were selected as the representative carboxylic acids, were in the range of 2.52-6.07 and 49-260 amol, respectively. The sensitive detection of biological carboxylic acids (detection limits, 32-520 amol) was also carried out by the proposed method using PCP2 and UPLC-MS/MS. The PCP2 was applied to the determination of carboxylic acids in human saliva. Several

  4. Liquid chromatographic enantioseparation of (RS)-mexiletine and (RS)-fluoxetine using chiral derivatizing reagents synthesized with (S)-naproxen moiety.

    PubMed

    Batra, Sonika; Bhushan, Ravi

    2014-06-01

    Enantiomeric separation of racemic mexiletine and fluoxetine was achieved using three chiral derivatizing reagents (CDRs) based on (S)-naproxen. Diastereomers were synthesized by reaction of mexiletine or fluoxetine with the CDRs and were separated on a C18 column under reversed-phase conditions using a binary mixture of acetonitrile and triethylammonium phosphate/water, with UV detection at 230 and 226 nm. The results obtained for enantioseparation of the two drugs using the three CDRs were compiled and compared. The conditions for derivatization and chromatographic separation were optimized. The method was validated for linearity, repeatability, limit of detection and limit of quantification. PMID:24861749

  5. (S)-1-(4-Dimethylaminophenylcarbonyl)-3-aminopyrrolidine: a derivatization reagent for enantiomeric separation and sensitive detection of chiral carboxylic acids by LC/ESI-MS/MS.

    PubMed

    Ogawa, Shoujiro; Tadokoro, Hiroaki; Sato, Maho; Hanawa, Takehisa; Higashi, Tatsuya

    2013-12-01

    A novel derivatization reagent, (S)-1-(4-dimethylaminophenylcarbonyl)-3-aminopyrrolidine (1-DAPAP), was developed for increasing the detection sensitivity and enantiomeric separation of chiral carboxylic acids by liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). 1-DAPAP reacted with carboxylic acids at room temperature within 5min in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride. The epimerization (racemization) during the derivatization reaction was negligible. The resulting derivatives were highly responsive during the ESI-MS operating in the positive-ion mode and gave a characteristic product ion during the MS/MS, which enabled the sensitive detection using selected reaction monitoring; the detection responses of the 1-DAPAP-derivatives were increased by 10-1100-fold over the intact carboxylic acids and the limits of detection ranged from 0.97 and 5.2fmol on the column. The 1-DAPAP-derivatization was also effective for the enantiomeric separation of chiral carboxylic acids; the resolution values were 1.2-4.3 for the evaluated carboxylic acids. The derivatization procedure was successfully applied to biological sample analyses; the derivatization followed by LC/ESI-MS/MS enabled the separation and detection of trace amounts of ibuprofen and naproxen in human saliva with a simple pretreatment and small sample volume.

  6. Rapid Quantitative Chiral Amphetamines Liquid Chromatography-Tandem Mass Spectrometry Method in Plasma and Oral Fluid with a Cost-effective Chiral Derivatizing Reagent

    PubMed Central

    Newmeyer, Matthew N.; Concheiro, Marta; Huestis, Marilyn A.

    2014-01-01

    Methamphetamine is a widely abused psychostimulant containing a chiral center. Consumption of over-the-counter and prescription medications may yield positive amphetamines results, but chiral separation of l- and d- methamphetamine and its metabolite amphetamine can help determine whether the source was licit or illicit. We present the first LC-MS/MS method with precolumn derivatization for methamphetamine and amphetamine chiral resolution in plasma and oral fluid collected with the Oral-Eze® and Quantisal™ devices. To 0.5 mL plasma, 0.75 mL Oral-Eze, or 1 mL Quantisal specimen racemic d11-methamphetamine and amphetamine internal standards were added, followed by protein precipitation. Samples were centrifuged and supernatants loaded onto pre-conditioned Phenomenex® Strata™-XC Polymeric Strong Cation solid phase extraction columns. After washing, analytes were eluted with 5% ammonium hydroxide in methanol. The eluate was evaporated to dryness and reconstituted in water. Derivatization was performed with 1-fluoro-2,4-dinitrophenyl-5-l-alanineamide (Marfey's reagent) and heating at 45°C for 1 h. Derivatized enantiomer separations were performed under isocratic conditions (methanol:water, 60:40) with a Phenomenex® Kinetex® 2.6 μm C18 column. Analytes were identified and quantified by two MRM transitions and their ratio on a 3200 QTrap (AB Sciex) mass spectrometer in ESI negative mode. In all three matrices, the method was linear for all enantiomers from 1-500 μg/L, with imprecision and accuracy of ≤11.3% and 85.3-108%, respectively. Extraction efficiencies ranged from 67.4-117% and matrix effects from -17.0-468%, with variation always ≤19.1%. Authentic plasma and OF specimens were collected from an IRB-approved study that included controlled Vicks® VapoInhaler™ administration. The present method is sensitive, selective, economic and rapid (separations accomplished in <10 min), and improves methamphetamine result interpretation. PMID:25065924

  7. Rapid quantitative chiral amphetamines liquid chromatography-tandem mass spectrometry: method in plasma and oral fluid with a cost-effective chiral derivatizing reagent.

    PubMed

    Newmeyer, Matthew N; Concheiro, Marta; Huestis, Marilyn A

    2014-09-01

    Methamphetamine is a widely abused psychostimulant containing a chiral center. Consumption of over-the-counter and prescription medications may yield positive amphetamines results, but chiral separation of l- and d-methamphetamine and its metabolite amphetamine can help determine whether the source was licit or illicit. We present the first LC-MS/MS method with precolumn derivatization for methamphetamine and amphetamine chiral resolution in plasma and oral fluid collected with the Oral-Eze(®) and Quantisal™ devices. To 0.5mL plasma, 0.75mL Oral-Eze, or 1mL Quantisal specimen racemic d11-methamphetamine and amphetamine internal standards were added, followed by protein precipitation. Samples were centrifuged and supernatants loaded onto pre-conditioned Phenomenex(®) Strata™-XC Polymeric Strong Cation solid phase extraction columns. After washing, analytes were eluted with 5% ammonium hydroxide in methanol. The eluate was evaporated to dryness and reconstituted in water. Derivatization was performed with 1-fluoro-2,4-dinitrophenyl-5-l-alanineamide (Marfey's reagent) and heating at 45°C for 1h. Derivatized enantiomer separations were performed under isocratic conditions (methanol:water, 60:40) with a Phenomenex(®) Kinetex(®) 2.6μm C18 column. Analytes were identified and quantified by two MRM transitions and their ratio on a 3200 QTrap (AB Sciex) mass spectrometer in ESI negative mode. In all three matrices, the method was linear for all enantiomers from 1 to 500μg/L, with imprecision and accuracy of ≤11.3% and 85.3-108%, respectively. Extraction efficiencies ranged from 67.4 to 117% and matrix effects from -17.0 to 468%, with variation always ≤19.1%. Authentic plasma and OF specimens were collected from an IRB-approved study that included controlled Vicks(®) VapoInhaler™ administration. The present method is sensitive, selective, economic and rapid (separations accomplished in <10min), and improves methamphetamine result interpretation.

  8. Profiling of chiral and achiral carboxylic acid metabolomics: synthesis and evaluation of triazine-type chiral derivatization reagents for carboxylic acids by LC-ESI-MS/MS and the application to saliva of healthy volunteers and diabetic patients.

    PubMed

    Takayama, Takahiro; Kuwabara, Tomohiro; Maeda, Toshio; Noge, Ichiro; Kitagawa, Yutaka; Inoue, Koichi; Todoroki, Kenichiro; Min, Jun Zhe; Toyo'oka, Toshimasa

    2015-01-01

    Novel triazine-type chiral derivatization reagents, i.e., (S)-1-(4,6-dimethoxy-1,3,5-triazin-2-yl)pyrrolidin-3-amine (DMT-3(S)-Apy) and (S)-4,6-dimethoxy-N-(pyrrolidin-3-yl)-1,3,5-triazin-2-amine (DMT-1(S)-Apy), were developed for the highly sensitive and selective detection of chiral carboxylic acids by UPLC-MS/MS analysis. Among the synthesized reagents, DMT-3(S)-Apy was a more efficient chiral reagent for the enantiomeric separation of chiral carboxylic acids in terms of separation efficiency by reversed-phase chromatography and detection sensitivity by ESI-MS/MS. The DMT-3(S)-Apy was used for the determination of 13 carboxylic acids in human saliva of healthy volunteers and diabetic patients. Various biological carboxylic acids including chiral carboxylic acids, and mono- and di-carboxylic acids were clearly identified in the saliva of healthy persons and diabetic patients. The concentrations of carboxylic acids detected in the saliva of diabetic patients were relatively higher than those in the healthy persons. Furthermore, the concentration of D-lactic acid (LA) and the ratio of D/L-LA in the diabetic patients were significantly higher than those in the healthy persons. The low ratio of D/L-LA in healthy persons was also identified to be independent of age and sex. These results suggest that the determination of the D/L-LA ratio in saliva might be applicable for the diagnosis of diabetes. Based on these observations, DMT-3(S)-Apy seems to be a useful chiral derivatization reagent for the determination not only of chiral carboxylic acids but also achiral ones. In conclusion, the proposed method using DMT-3(S)-Apy is useful for the carboxylic acid metabolomics study of various specimens.

  9. Chiral separation of new cathinone- and amphetamine-related designer drugs by gas chromatography-mass spectrometry using trifluoroacetyl-l-prolyl chloride as chiral derivatization reagent.

    PubMed

    Mohr, Stefan; Weiß, Jennifer A; Spreitz, Josef; Schmid, Martin G

    2012-12-21

    Since cathinone derivatives gained high popularity on the recreational drugs market within the past 5 years the development of analytical methods for the achiral and chiral determination of this substance class is of great interest. Not at least because it is obvious that the pharmacological potency differs between both enantiomers. Cathinones are structurally closely related to amphetamines, which have similar stimulating effects and are somehow better investigated. The goal of this research was to perform indirect enantioseparation of novel psychoactive cathinone and amphetamine derivatives. Trifluoroacetyl-l-prolyl chloride was served as chiral derivatization agent (CDA). Chromatographic separation was performed using a commercially available HP5-MS capillary column with a length of 30 m. Helium was used as carrier gas with a constant flow of 1.0 ml/min. Under optimum conditions 14 amphetamine derivatives were successfully resolved into their enantiomers and detected with the single quadrupol detector. Racemic methcathinone derivatives analyzed with the same method showed different peak areas for each of the produced diastereomeric isomers, even if they are structurally closely related to the amphetamines. Derivatization experiments with the single isomers of methcathinone led to both diastereomers whereas the S(-) enantiomer seemed to racemize more likely. Based on comparative experiments with R-(-)-α-methoxy-α-(trifluoromethyl)phenylacetyl chloride (MTPA) as CDA, racemization due to the keto-enol-tautomerism of the cathinone derivatives seemed to be responsible for this phenomenon. Nevertheless, 18 cathinone derivatives were successfully enantioseparated and an approach of quantitative evaluation is demonstrated.

  10. Resolution and isolation of enantiomers of (±)-isoxsuprine using thin silica gel layers impregnated with L-glutamic acid, comparison of separation of its diastereomers prepared with chiral derivatizing reagents having L-amino acids as chiral auxiliaries.

    PubMed

    Bhushan, Ravi; Nagar, Hariom

    2015-03-01

    Thin silica gel layers impregnated with optically pure l-glutamic acid were used for direct resolution of enantiomers of (±)-isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l-alanine, l-valine and S-benzyl-l-cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed-phase high-performance liquid chromatography on a C18 column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin-layer chromatography (TLC) on reversed phase (RP) C18 plates. Diastereomers prepared with enantiomerically pure (+)-isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)-isoxsuprine. The elution order in the experimental study of RP-TLC and RP-HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1-0.09 µg/mL in TLC while it was in the range of 22-23 pg/mL in HPLC and 11-13 ng/mL in RP-TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification.

  11. Design and synthesis of a novel pre-column derivatization reagent with a 6-methoxy-4-quinolone moiety for fluorescence and tandem mass spectrometric detection and its application to chiral amino acid analysis.

    PubMed

    Oyama, Tsubasa; Negishi, Eiichi; Onigahara, Hirohisa; Kusano, Nao; Miyoshi, Yurika; Mita, Masashi; Nakazono, Manabu; Ohtsuki, Sumio; Ojida, Akio; Lindner, Wolfgang; Hamase, Kenji

    2015-12-10

    A new pre-column derivatization reagent with a 6-methoxy-4-quinolone (6-MOQ) moiety for amino acid analysis, 2,5-dioxopyrrolidin-1-yl(2-(6-methoxy-4-oxoquinolin-1(4H)-yl)ethyl) carbonate (6-MOQ-EtOCOOSu), was designed and synthesized. 6-MOQ is a thermo/photostable fluorophore with a high proton-affinity site and sensitive determination could be carried out by a fluorescence detector and also by an electrospray ionization mass spectrometer. Derivatization of amino acids with 6-MOQ-EtOCOOSu was completed within 1 min under mild basic conditions at room temperature. The 6-MOQ derivatives of all chiral proteinogenic amino acids were separated using the combination of three enantioselective columns, Chiralpak QN-AX, Chiralpak ZXIX(+), and KSAACSP-001S, with separation factors of higher than 1.07. The present reagent enables the sensitive determination of amino acid enantiomers, and the values of LLOD using a chiral-HPLC-MS/MS system were 0.05-50 fmol/injection. PMID:26166005

  12. Reversed-phase high-performance liquid chromatographic separation of diastereomers of (R,S)-mexiletine prepared by microwave irradiation with four new chiral derivatizing reagents based on trichloro-s-triazine having amino acids as chiral auxiliaries and 10 others having amino acid amides.

    PubMed

    Bhushan, Ravi; Dixit, Shuchi

    2010-12-01

    A new series of chiral derivatizing reagents (CDRs) consisting of four dichloro-s-triazine reagents was synthesized by nucleophilic substitution of one chlorine atom in trichloro-s-triazine with amino acids, namely L-Leu, D-Phg, L-Val and L-Ala as chiral auxiliaries. Two other sets of CDRs consisting of four dichloro-s-triazine (DCT) and six monochloro-s-triazine (MCT) reagents were also prepared by nucleophilic substitution of chlorine atom(s) with different amino acid amides as chiral auxiliaries in trichloro-s-triazine and its 6-methoxy derivative, respectively. These 14 CDRs were used for the synthesis of diastereomers of (R,S)-mexiletine under microwave irradiation (i.e. 60s and 90 s at 85% power (of 800 W) using DCT and MCT reagents, respectively), which were resolved by reversed-phase high-performance liquid chromatography using C18 column and gradient eluting mixtures of methanol with aqueous trifluoroacetic acid (TFA) with UV detection at 230 nm. The resolution (R(s)), difference between retention times of resolved diastereomers (Δt) and retention factors (k) obtained for the three sets of diastereomers were compared among themselves and among the three groups. Explanations have been offered for longer retention times and better resolution of diastereomers prepared with DCT reagents in comparison of their MCT counterparts and, for the influence of hydrophobicity of the side chain R of the amino acid in the CDRs on retention times and resolution. The newly synthesized CDRs were observed to be superior as compared to their amide counterparts in terms of providing better resolution and cost effectiveness. The method was validated for limit of detection, linearity, accuracy and precision. PMID:21035811

  13. Chiral hypervalent iodine reagents: synthesis and reactivity.

    PubMed

    Parra, Alejandro; Reboredo, Silvia

    2013-12-16

    Chiral hypervalent iodine chemistry has been steadily increasing in importance in recent years. This review catalogues enantioselective transformations triggered by chiral hypervalent iodine(III/V) reagents, in stoichiometric or catalytic quantities, highlighting the different reactivities in terms of yield and enantioselectivity. Moreover, the synthesis of the most remarkable and successful catalysts has been illustrated in detail.

  14. A new derivatization reagent for LC-MS/MS screening of potential genotoxic alkylation compounds.

    PubMed

    van Wijk, A M; Niederländer, H A G; Siebum, A H G; Vervaart, M A T; de Jong, G J

    2013-02-23

    A screening method for trace analysis of potentially genotoxic alkylating compounds has been developed using butyl 1-(pyridin-4-yl) piperidine 4-carboxylate (BPPC) as a new, selective pre-column derivatization reagent for their subsequent analysis by hydrophilic interaction liquid chromatography (HILIC) hyphenated with tandem mass spectrometry (LC-MS/MS). The new derivatization reagent is a modification of 4-dimethylaminopyridine (4-DMAP) previously used for the determination of potentially genotoxic compounds. By using the new reagent the screening potential was enhanced without compromising reactivity. Derivatization at a high pH value was carried out and the reaction time at 60°C was 24h to anticipate for alkyl chlorides showing to be less reactive. The new reagent was designed to obtain reagent related fragmentation of the whole reagent as well as a side group of the reagent. Collision energies for detection of alkylating components derivatized using the new reagent are shown to be significantly more universal than with 4-DMAP. Neutral loss scanning on the fragmentation related to the build in side group remedies shortcomings in the screening for alkyl halides observed when using 4-DMAP. The new approach allows for screening of alkyl halides and alkyl sulfonates at trace levels down to 1 mg kg(-1) and target analysis at about a factor of 10 lower without a significant effect of the active pharmaceutical ingredient (API) matrix. The synthesis of the reagent, investigation of reactivity, the specificity of the fragmentation of derivatives and screening conditions in MS/MS analysis are described. PMID:23245244

  15. N,N-Dicarboxymethyl hydrazine: an old but neglected reagent for chemoselective derivatization of carbonyl compounds.

    PubMed

    Zhen, Maomin; Peng, Yanqing

    2016-04-01

    N,N-Dicarboxymethyl hydrazine (DCMH) was found to be a chemoselective derivatization reagent of carbonyl compounds and its potential applications in organic synthesis was investigated for the first time. DCMH could be employed as a chemoselective protective reagent of aldehydes and gave the parent aldehydes in satisfactory yields. In proof-of-concept systems, DCMH could play the role of a scavenger to remove aldehydes in the presence of ketones. It was also used as a tagging reagent in the selective isolation of aldehyde from the complex mixture.

  16. Stable isotope coded derivatizing reagents as internal standards in metabolite profiling.

    PubMed

    Bruheim, Per; Kvitvang, Hans Fredrik Nyvold; Villas-Boas, Silas G

    2013-06-28

    Gas chromatography (GC) and liquid chromatography (LC) coupled to mass spectrometric (MS) detection have become the two main techniques for the analysis of metabolite pools (i.e. Metabolomics). These technologies are especially suited for Metabolite Profiling analysis of various metabolite groups due to high separation capabilities of the chromatographs and high sensitivity of the mass analysers. The trend in quantitative Metabolite Profiling is to add more metabolites and metabolite groups in a single method. This should not be done by compromising the analytical precision. Mass spectrometric detection comes with certain limitations, especially in the quantitative aspects as standards are needed for conversion of ion abundance to concentration and ionization efficiencies are directly dependent on eluent conditions. This calls for novel strategies to counteract all variables that can influence the quantitative precision. Usually, internal standards are used to correct any technical variation. For quantitation of single or just a few analytes this can be executed with spiking isotopically labeled standards. However, for more comprehensive analytical tasks, e.g. profiling tens or hundreds of analytes simultaneously, this strategy becomes expensive and in many cases isotopically labeled standards are not available. An alternative is to introduce a derivatizing step where the sample is derivatized with naturally labeled reagent, while a standard solution is separately derivatized with isotopically labeled reagent and spiked into the sample solution prior to analysis. This strategy, named isotope coded derivatization - ICD, is attractive in the emerging field of quantitative Metabolite Profiling where current protocols can easily comprise over hundred metabolites. This review provides an overview of isotopically labeled derivatizing reagents that have been developed for important metabolite groups with the aim to improve analytical performance and precision.

  17. A new chiral derivatizing agent for the HPLC separation of α-amino acids on a standard reverse-phase column.

    PubMed

    Kotthaus, A F; Altenbach, H-J

    2011-02-01

    A new chiral derivatizing agent for α-amino acids is described which leads to diastereomers that can be separated by reverse-phase HPLC with direct detection by a diode array detector. The main advantage of the presented procedure is the fact that an excess of the derivatizing reagent can be employed as the product exhibits an absorption maximum at 360 nm, while the reagent has its absorption maximum at 260 nm. Therefore, it is possible to suppress the reagent signal by a detection wavelength of 400 nm leading to an easy and general method for the enantioseparation of a mixture of DL-amino acids and the determination of the enantiomeric purity of α-amino acid as exemplified by 16 different α-amino acids.

  18. Study of highly selective and efficient thiol derivatization using selenium reagents by mass spectrometry.

    PubMed

    Xu, Kehua; Zhang, Yun; Tang, Bo; Laskin, Julia; Roach, Patrick J; Chen, Hao

    2010-08-15

    This paper reports a systemic mass spectrometry (MS) investigation of a novel strategy for labeling biological thiols, involving the cleavage of the Se-N bond by thiol to form a new Se-S bond. Our data show that the reaction is highly selective, rapid, reversible, and efficient. Among 20 amino acids, only cysteine is reactive toward Se-N containing reagents and the reaction occurs in seconds. With the addition of dithiothreitol, peptides derivatized by selenium reagents can be recovered. The high reaction selectivity and reversibility provide potential in both selective identification and isolation of thiols from mixtures. Also, with dependence on the selenium reagent used, derivatized peptide ions exhibit tunable dissociation behaviors (either facile cleavage or preservation of the formed Se-S bond upon collision-induced dissociation), a feature that is useful in proteomics studies. Equally importantly, the thiol derivatization yield is striking, as reflected by 100% conversion of protein beta-lactoglobulin A using ebselen within 30 s. In addition, preliminary applications such as rapid screening of thiol peptides from mixtures and identification of the number of protein free and bound thiols have been demonstrated. The unique selenium chemistry uncovered in this study would be valuable in the MS analysis of thiols and disulfide bonds of proteins/peptides.

  19. Amino acids as chiral auxiliaries in cyanuric chloride-based chiral derivatizing agents for enantioseparation by liquid chromatography.

    PubMed

    Batra, Sonika; Bhushan, Ravi

    2014-11-01

    This review summarizes and critically evaluates the recent research on application of amino acids and amino acid amides as chiral auxiliaries in cyanuric chloride (CC) based chiral derivatizing agents (CDRs), used in the indirect approach for enantiomeric resolution. Methods of synthesis of such CDRs, methods for synthesis of diastereomers of a variety of racemic compounds and parameters of liquid chromatographic separation, along with their prospects and their limitations in indirect enantioresolution, are discussed. Application of the said CDR(s) and the technical approach to be used that are discussed should be beneficial for control of enantiomeric purity in pharmaceutical industry, verification of enantiomeric ratio of commercial formulations and the development of methods for indirect resolution of a variety of chiral compounds. Derivatization methods are particularly required when a chromophore is to be introduced in low UV absorbing molecules, for their detection.

  20. Study of Highly Selective and Efficient Thiol Derivatization using Selenium Reagents by Mass Spectrometry

    SciTech Connect

    Xu, Kehua; Zhang, Yun W.; Tang, Bo; Laskin, Julia; Roach, Patrick J.; Chen, Hao

    2010-08-15

    Biological thiols are critical physiological components and their detection often involves derivatization. This paper reports a systemic mass spectrometry (MS) investigation of the cleavage of Se-N bond by thiol to form a new Se-S bond, the new selenium chemistry for thiol labeling. Our data shows that the reaction is highly selective, rapid, reversible and efficient. For instance, among twenty amino acids, only cysteine was found to be reactive with Se-N containing reagents and the reaction takes place in seconds. By adding dithiothreitol (DTT), the newly formed Se-S bond of peptides/proteins can be reduced back to free thiol. The high selectivity and excellent reversibility of the reaction provide potential of using this chemistry for selective identification of thiol compounds or enriching and purifying thiol peptides/proteins. In addition, the derivatized thiol peptides have interesting dissociation behavior, which is tunable using different selenium reagents. For example, by introducing an adjacent nucleophilic group into the selenium reagent in the case of using ebselen, the reaction product of ebselen with glutathione (GSH) is easy to lose the selenium tag upon collision-induced dissociation (CID), which is useful to "fish out" those peptides containing free cysteine residues by precursor ion scan. By contrast, the selenium tag of N-(phenylseleno) phthalimide reagent can be stable and survive in CID process, which would be of value in pinpointing thiol location using a top-down proteomic approach. Also, the high conversion yield of the reaction allows the counting of total number of thiol in proteins. We believe that ebselen or N-(phenylseleno) phthalimide as tagging thiol-protein reagents will have important applications in both qualitative and quantitative analysis of different thiol-proteins derived from living cells by MS method.

  1. Derivatization of phytochelatins from Silene vulgaris, induced upon exposure to arsenate and cadmium: comparison of derivatization with Ellman's reagent and monobromobimane.

    PubMed

    Sneller, F E; van Heerwaarden, L M; Koevoets, P L; Vooijs, R; Schat, H; Verkleij, J A

    2000-09-01

    Phytochelatins (PCs) are a family of thiol-rich peptides, with the general structure (gamma-Glu-Cys)(n)()-Gly, with n = 2-11, induced in plants upon exposure to excessive amounts of heavy metals and some metalloids, such as arsenic. Two types of PC analyses are currently used, i.e., acid extraction and separation on HPLC with either precolumn derivatization (pH 8.2) with monobromobimane (mBBr) or postcolumn derivatization (pH 7.8) with Ellman's reagent [5, 5'-dithiobis(2-nitrobenzoic acid), DTNB]. Although both methods were satisfactory for analysis of Cd-induced PCs, formation of (RS)(3)-As complexes during extraction of As-induced PCs rendered the DTNB method useless. This paper shows that precolumn derivatization with mBBr, during which the (RS)(3)-As complexes are disrupted, provides a qualitative and quantitative analysis of both Cd- and As-induced PCs. In addition, derivatization efficiencies of both methods for the oligomers with n = 2-4 (PC(2)(-)(4)) are compared. Derivatization efficiency decreased from 71.8% and 81.4% for mBBr and DTNB derivatization, respectively, for PC(2) to 27.4% and 50.2% for PC(4). This decrease is most likely due to steric hindrance. Correction of measured thiol concentration is therefore advised for better quantification of PC concentrations in plant material.

  2. Derivatization of phytochelatins from Silene vulgaris, induced upon exposure to arsenate and cadmium: comparison of derivatization with Ellman's reagent and monobromobimane.

    PubMed

    Sneller, F E; van Heerwaarden, L M; Koevoets, P L; Vooijs, R; Schat, H; Verkleij, J A

    2000-09-01

    Phytochelatins (PCs) are a family of thiol-rich peptides, with the general structure (gamma-Glu-Cys)(n)()-Gly, with n = 2-11, induced in plants upon exposure to excessive amounts of heavy metals and some metalloids, such as arsenic. Two types of PC analyses are currently used, i.e., acid extraction and separation on HPLC with either precolumn derivatization (pH 8.2) with monobromobimane (mBBr) or postcolumn derivatization (pH 7.8) with Ellman's reagent [5, 5'-dithiobis(2-nitrobenzoic acid), DTNB]. Although both methods were satisfactory for analysis of Cd-induced PCs, formation of (RS)(3)-As complexes during extraction of As-induced PCs rendered the DTNB method useless. This paper shows that precolumn derivatization with mBBr, during which the (RS)(3)-As complexes are disrupted, provides a qualitative and quantitative analysis of both Cd- and As-induced PCs. In addition, derivatization efficiencies of both methods for the oligomers with n = 2-4 (PC(2)(-)(4)) are compared. Derivatization efficiency decreased from 71.8% and 81.4% for mBBr and DTNB derivatization, respectively, for PC(2) to 27.4% and 50.2% for PC(4). This decrease is most likely due to steric hindrance. Correction of measured thiol concentration is therefore advised for better quantification of PC concentrations in plant material. PMID:10995306

  3. Enantiomeric derivatization on the Mars Organic Molecule Analyzer (MOMA) experiment aboard ExoMars 2018: how to unravel martian chirality

    NASA Astrophysics Data System (ADS)

    Freissinet, C.; Buch, A.; Szopa, C.; Morisson, M.; Grand, N.; Raulin, F.; Brinckerhoff, W.

    2015-10-01

    The origin of homochirality in life on Earth remains unknown. The answer to this question lies in the study of chirality elsewhere in the Solar System. The Sample Analysis at Mars (SAM) experiment aboard Curiosity established the presence of organic molecules indigenous to a clay-rich sample on Mars [1]. However, SAM does not have the ability to separate between the enantiomers of potential medium- or high- molecular weight organic molecules. One of the wet chemistry experiments to be used in the MOMA instrument of the Exomars mission is designed for the extraction and identification of refractory organic chemical components in solid samples using gas chromatography-mass spectrometry (GCMS), while keeping the chiral center of the molecules intact [2]. This derivatization technique, using dimethylformamide dimethylacetal (DMF-DMA) as a reagent, will allow MOMA to separate the enantiomers of molecules of interest for astrobiology, such as amino acids, sugars or carboxylic acids. We present here the results of laboratory experiments which display the feasability and limitations of the detection of an enantiomeric excess of complex organic molecules in various analog samples, depending on the mineralogy of the Mars analog solid sample.

  4. Synthesis of variants of Marfey's reagent having d-amino acids as chiral auxiliaries and liquid-chromatographic enantioseparation of (RS)-Mexiletine in spiked plasma: assessment and comparison with L-amino acid analogs.

    PubMed

    Bhushan, Ravi; Vashistha, Vinod Kumar

    2015-01-30

    Five d-amino acids have been used for the first time to synthesize chiral derivatizing reagents (as variants of Marfey's reagent) by nucleophilic displacement of one of the fluorine atoms in 1,5-difluoro-2,4-dinitrobenzene as against the literature reports on application of only l-amino acids or their amides as chiral auxiliaries in dinitrobenzene (DNB) moiety. Five other DNB based reagents were also prepared by nucleophilic substitution of fluorine atom with the set of the same amino acids in l-configuration, as chiral auxiliaries. These reagents were characterized and used for synthesis of diastereomers of (RS)-Mexiletine spiked in human plasma. Diastereomers were synthesized employing microwave irradiation and were separated on reversed-phase C18 column. Performance of the two types of chiral derivatizing reagents was compared. The reagents containing d-amino acids provided enhanced separation of diastereomers than those containing l-amino acids. The best resolution was obtained using mobile phase consisting of acetonitrile and 0.1% trifluoroacetic acid in gradient mode. The detection was carried out at 340nm. The method so developed was validated for linearity, accuracy and precision. The limit of quantitation was found to be approximately 25.2ngmL(-1) in human plasma. PMID:25576038

  5. Synthesis of variants of Marfey's reagent having d-amino acids as chiral auxiliaries and liquid-chromatographic enantioseparation of (RS)-Mexiletine in spiked plasma: assessment and comparison with L-amino acid analogs.

    PubMed

    Bhushan, Ravi; Vashistha, Vinod Kumar

    2015-01-30

    Five d-amino acids have been used for the first time to synthesize chiral derivatizing reagents (as variants of Marfey's reagent) by nucleophilic displacement of one of the fluorine atoms in 1,5-difluoro-2,4-dinitrobenzene as against the literature reports on application of only l-amino acids or their amides as chiral auxiliaries in dinitrobenzene (DNB) moiety. Five other DNB based reagents were also prepared by nucleophilic substitution of fluorine atom with the set of the same amino acids in l-configuration, as chiral auxiliaries. These reagents were characterized and used for synthesis of diastereomers of (RS)-Mexiletine spiked in human plasma. Diastereomers were synthesized employing microwave irradiation and were separated on reversed-phase C18 column. Performance of the two types of chiral derivatizing reagents was compared. The reagents containing d-amino acids provided enhanced separation of diastereomers than those containing l-amino acids. The best resolution was obtained using mobile phase consisting of acetonitrile and 0.1% trifluoroacetic acid in gradient mode. The detection was carried out at 340nm. The method so developed was validated for linearity, accuracy and precision. The limit of quantitation was found to be approximately 25.2ngmL(-1) in human plasma.

  6. A spectrophotometric assay for monoamine oxidase activity with 2, 4-dinitrophenylhydrazine as a derivatized reagent.

    PubMed

    Huang, Guili; Zhu, Fei; Chen, Yuhang; Chen, Shiqiang; Liu, Zhonghong; Li, Xin; Gan, Linlin; Zhang, Li; Yu, Yu

    2016-11-01

    A simple, rapid and reliable spectrophotometry was developed to determine monoamine oxidase (MAO). In this study, 2,4-dinitrophenylhydrazine (DNPH), a classic derivatizing reagent, was used to detect MAO-dependent aldehyde production; and traditional DNPH spectrophotometry was simplified. Benzylamine and serotonin oxidation were catalyzed by MAO-B and MAO-A, respectively, to aldehydes. These were derivatized with DNPH, and the corresponding quinones were further formed by adding NaOH. These DNPH derivatives with large conjugated structures were directly measured spectrophotometrically at 465 nm and 425 nm, without the need for precipitating, washing and suspending procedures. The addition of NaOH caused a red shift of the maximum absorption wavelength of these derivatives, which reduced the interference of free DNPH. MAO-B protein was as low as 47.5 μg in rat liver with correlation coefficients ranging within 0.995-0.999. This method is 2-3 times more sensitive than direct spectrophotometry. The detection of MAO inhibition through this method showed that IC50 values of rasagiline are 8.00 × 10(-9) M for MAO-B and 2.59 × 10(-7) M for MAO-A. These results are similar to the values obtained by direct spectrophotometry. Our study suggests that DNPH spectrophotometry is suitable to detect MAO activity, and has the potential for MAO inhibitor screening in the treatment of MAO-mediated diseases.

  7. Indirect enantioresolution of (R,S)-mexiletine by reversed-phase high-performance liquid chromatography via diastereomerization with [(S,S)-O,O'-di-p-toluoyl tartaric acid anhydride], (S)-naproxen and nine chiral reagents synthesized as variants of Marfey's reagent.

    PubMed

    Bhushan, R; Tanwar, Shivani; Dixit, Shuchi

    2011-03-01

    Eleven chiral derivatizing reagents (CDRs) were used for preparation of diastereomers of (R,S)-mexiletine containing a primary amino group in close proximity to the stereogenic center. One anhydride, namely [(S,S)-O,O'-di-p-toluoyl tartaric acid anhydride] was synthesized and (S)-naproxen was used as such as the chiral derivatizing reagent. The other nine CDRs were synthesized by substituting one of the fluorine atoms in 1,5-difluoro-2,4-dinitrobenzene with six amino acid amides and three amino acids. The diastereomers were separated by reversed-phase high-performance liquid chromatography. The method was validated for linearity, accuracy, limit of detection and limit of quantification. The limit of detection was found in the range of 10-30  pmol. PMID:20586109

  8. Measurement of Estradiol in Human Serum by LC-MS/MS Using a Novel Estrogen-Specific Derivatization Reagent.

    PubMed

    Keski-Rahkonen, Pekka; Desai, Reena; Jimenez, Mark; Harwood, D Tim; Handelsman, David J

    2015-07-21

    A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is described that employs a novel derivatization reagent for the measurement of serum estradiol (E2), with simultaneous analysis of underivatized testosterone (T) and dihydrotestosterone (DHT). The main advantage of the new derivatization reagent 1,2-dimethylimidazole-5-sulfonyl chloride is its analyte-specific fragmentation that enables monitoring of confirmatory mass transitions with high sensitivity. The reaction mixture can be analyzed without additional purification steps using a 9.5 min gradient run, and sensitive detection is achieved with a triple quadrupole mass spectrometer using atmospheric pressure photoionization. Method validation was performed with human serum samples, including a comparison with a standard LC-MS/MS method using 120 samples from a clinical study, and analysis of certified E2 serum reference materials BCR-576, BCR-577, and BCR-578. The lower limits of quantification for E2, T, and DHT were 0.5 pg/mL, 25 pg/mL, and 0.10 ng/mL, respectively, from a 200-μL sample. Validation results indicated good accuracy and agreement with established, conventional LC-MS/MS assays, demonstrating suitability for analysis of samples containing E2 in the low pg/mL range, such as serum from men, children, and postmenopausal women.

  9. Enantiomeric purity determination of (L)-amino acids with pre-column derivatization and chiral stationary phase: development and validation of the method.

    PubMed

    Cui, Yan; Jiang, Zhen; Sun, Jiayi; Yu, Jia; Li, Minghua; Li, Mingjie; Liu, Mingxia; Guo, Xingjie

    2014-09-01

    A simple, efficient and general HPLC method for the determination of enantiomeric purity of a series of (L)-amino acids was developed. In order to improve the detection sensitivity, pre-column derivatization was adopted and 7-chloro-4-nitrobenzoxadiazole (NBD-Cl) was selected as derivatization reagent. NBD-amino acid enantiomers were then enantioseparated on a Pirkle-type chiral stationary phase, Sumichiral OA-2500S (250 mm × 4.6 mm, 5 μm), using a mobile phase composed of acetonitrile-methanol (50:50, v/v) containing 5 mmol L(-1) citric acid at the flow rate of 0.5 mL min(-1). The detection wavelength was 470 nm. All the eleven pairs of tested amino acid enantiomers were well separated, and trace amounts of (D)-amino acids (0.5%) in the presence of a large excess of corresponding (L)-enantiomers could be quantified. The proposed method was validated in terms of selectivity, precision, linearity range, LOD, LOQ and accuracy, and then successfully applied to the determination of enantiomeric purity in bulk samples of (L)-amino acids.

  10. The use of cyclohexanone as a "derivatizing" reagent for the GC-MS detection of amphetamines and ephedrines in seizures and the urine.

    PubMed

    El-Haj, B M; Al-Amri, A M; Hassan, M H; Ali, H S; Bin Khadem, R K

    2003-07-29

    A GC-MS method has been developed for the detection of amphetamine, methamphetamine, and the ephedrines, in seizures and the urine, based on on-GC condensation (derivatization) with cyclohexanone. The method is simple: the dried seizure material or the urine extract was mixed with cyclohexanone and injected into the GC-MS. The method was found to be superior to the methods based on acyl and trimethylsilyl (TMS) derivatization. Unlike for the acyl and TMS derivatives, the molecular and fragment ions of the cyclohexanone condensation products (cyclohexanone derivatives) were of substantial abundance, a useful property in unambiguous compound characterization. Furthermore, the high stability of the "derivatizing" reagent, cyclohexanone, compared with acyl and TMS derivatizing reagents, is a useful property in method development. The present method has proved selective and, tentatively, sensitive enough in the following areas (where methods based on acyl and TMS derivatization, as tested in this laboratory, have failed): (a) detection of amphetamine as a metabolite of methamphetamine; (b) detection of norpseudoephedrine as a metabolite of pseudoephedrine; (c) detection of amphetamine as an impurity of methamphetamine; (d) detection of cathine (norephedrine) as a constituent of Khat leaves; and (e) differentiation of Khat use from phenylpropanolamine use.

  11. New Chiral Reagent for Installation of Pharmacophoric (S)- or (R)-2-(Alkoxyphosphono)-1-amino-2,2-difluoroethyl Groups.

    PubMed

    Xie, Chen; Zhang, Lijun; Mei, Haibo; Pajkert, Romana; Ponomarenko, Maksym; Pan, Yi; Röschenthaler, Gerd-Volker; Soloshonok, Vadim A; Han, Jianlin

    2016-05-17

    A new chiral reagent has been developed for generalized installation of pharmacophoric (S)- or (R)-2-(alkoxyphosphono)-1-amino-2,2-difluoroethyl group into organic compounds. The original synthetic application of this new reagent is exemplified by Friedel-Crafts reactions with indoles, which proceed efficiently with excellent diastereoselectivity to give enantiomerically pure products. PMID:26952046

  12. Enantioselective capillary electrophoresis-mass spectrometry of amino acids in cerebrospinal fluid using a chiral derivatizing agent and volatile surfactant.

    PubMed

    Prior, A; Moldovan, R C; Crommen, J; Servais, A C; Fillet, M; de Jong, G J; Somsen, G W

    2016-10-12

    The sensitivity of coupled enantioselective capillary electrophoresis-mass spectrometry (CE-MS) of amino acids (AAs) is often hampered by the chiral selectors in the background electrolyte (BGE). A new method is presented in which the use of a chiral selector is circumvented by employing (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC) as chiral AA derivatizing agent and ammonium perfluorooctanoate (APFO) as a volatile pseudostationary phase for separation of the formed diastereomers. Efficient AA derivatization with FLEC was completed within 10 min. Infusion experiments showed that the APFO concentration hardly affects the MS response of FLEC-AAs and presents significantly less ion suppression than equal concentrations of ammonium acetate. The effect of the pH and APFO concentration of the BGE and the capillary temperature were studied in order to achieve optimized enantioseparation. Optimization of CE-MS parameters, such as sheath-liquid composition and flow rate, ESI and MS settings was performed in order to prevent analyte fragmentation and achieve sensitive detection. Selective detection and quantification of 14 chiral proteinogenic AAs was achieved with chiral resolution between 1.2 and 8.6, and limits of detection ranging from 130 to 630 nM injected concentration. Aspartic acid and glutamic acid were detected, but not enantioseparated. The optimized method was applied to the analysis of chiral AAs in cerebrospinal fluid (CSF). Good linearity (R(2) > 0.99) and acceptable peak area and electrophoretic mobility repeatability (RSDs below 21% and 2.4%, respectively) were achieved for the chiral proteinogenic AAs, with sensitivity and chiral resolution mostly similar to obtained for standard solutions. Next to l-AAs, endogenous levels of d-serine and d-glutamine could be measured in CSF revealing enantiomeric ratios of 4.8%-8.0% and 0.34%-0.74%, respectively, and indicating the method's potential for the analysis of low concentrations of d-AAs in presence of

  13. Enantioselective capillary electrophoresis-mass spectrometry of amino acids in cerebrospinal fluid using a chiral derivatizing agent and volatile surfactant.

    PubMed

    Prior, A; Moldovan, R C; Crommen, J; Servais, A C; Fillet, M; de Jong, G J; Somsen, G W

    2016-10-12

    The sensitivity of coupled enantioselective capillary electrophoresis-mass spectrometry (CE-MS) of amino acids (AAs) is often hampered by the chiral selectors in the background electrolyte (BGE). A new method is presented in which the use of a chiral selector is circumvented by employing (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC) as chiral AA derivatizing agent and ammonium perfluorooctanoate (APFO) as a volatile pseudostationary phase for separation of the formed diastereomers. Efficient AA derivatization with FLEC was completed within 10 min. Infusion experiments showed that the APFO concentration hardly affects the MS response of FLEC-AAs and presents significantly less ion suppression than equal concentrations of ammonium acetate. The effect of the pH and APFO concentration of the BGE and the capillary temperature were studied in order to achieve optimized enantioseparation. Optimization of CE-MS parameters, such as sheath-liquid composition and flow rate, ESI and MS settings was performed in order to prevent analyte fragmentation and achieve sensitive detection. Selective detection and quantification of 14 chiral proteinogenic AAs was achieved with chiral resolution between 1.2 and 8.6, and limits of detection ranging from 130 to 630 nM injected concentration. Aspartic acid and glutamic acid were detected, but not enantioseparated. The optimized method was applied to the analysis of chiral AAs in cerebrospinal fluid (CSF). Good linearity (R(2) > 0.99) and acceptable peak area and electrophoretic mobility repeatability (RSDs below 21% and 2.4%, respectively) were achieved for the chiral proteinogenic AAs, with sensitivity and chiral resolution mostly similar to obtained for standard solutions. Next to l-AAs, endogenous levels of d-serine and d-glutamine could be measured in CSF revealing enantiomeric ratios of 4.8%-8.0% and 0.34%-0.74%, respectively, and indicating the method's potential for the analysis of low concentrations of d-AAs in presence of

  14. Synthesis of dinitrophenyl-L-Pro-N-hydroxysuccinimide ester and four new variants of Sanger's reagent having chiral amines and their application for enantioresolution of mexiletine using reversed-phase high-performance liquid chromatography.

    PubMed

    Bhushan, Ravi; Tanwar, Shivani

    2009-07-24

    Four chiral derivatizing reagents (CDRs) having enantiomerically pure amines and two CDRs namely, [N-succinimidyl-(S)-2-(6-methoxynaphth-2-yl)propionate], and [dinitrophenyl-L-Pro-N-hydroxysuccinimide ester, DNP-L-Pro-SU] were synthesized and were used to prepare diastereomers of (R,S)-mexiletine (MEX); these were separated by reversed-phase high-performance liquid chromatography (RP-HPLC). The method was validated for linearity, accuracy, limit of detection (LOD) and limit of quantification (LOQ). PMID:19552908

  15. Optimization of HPLC method for determination of cefixime using 2-thiophenecarboxaldehyde as derivatizing reagent: A new approach.

    PubMed

    Maheshwari, Madan Lal; Memon, Ayaz Ali; Memon, Shahabuddin; Memon, Fakhar-Un-Nisa; Mughal, Ubed Ur Rahman; Dayo, Abdullah; Memon, Naheed; Ghoto, Mohammed Ali; Khan Leghari, M

    2015-09-01

    The determination of cefixime 1 has clinical and analytical importance due to its broad spectrum antimicrobial activity and stability. Cefixime is a significant member of orally active third generation cephalosporin and has excellent activity against many pathogens. It is for first time that we have developed a new HPLC-DAD method for analysis of imine derivative 3 of cefixime by using reflux method at 100 °C for 50 min without any buffer solution. 2 Thiophenecarboxaldehyde (2TCA) 2 was used first time as a derivatizing reagent for cefixime drug. Furthermore, separation of three components, i.e. drug (cefixime), reagent (2TCA) and derivative was carried out using kromasil 100 C-18 (15 mm × 0.46 mm, 5 μm) column with isocratic elution of methanol: 0.1% aqueous formic acid (70:30 v/v) with flow rate of 1 ml min(-) (1) at retention time of 1.8, 2.4 and 3.3 min, respectively; while, total run time was 5 min. The developed method was repeatable with a relative standard deviation (RSD) of 0.81-1.88% for imine derivative. The limit of detection and quantification of imine derivative 3 were obtained within the range of 0.132-0.401 μg ml(-) (1) and compared with cefixime drug as 0.30-0.90 μg ml(-1), respectively. However, the formation of imine derivative 3 was confirmed by comparing peak height, retention time and spectral changes. The method is rapid, simple, very stable and accurate for the separation and determination of imine derivative 3 of cefixime 1.

  16. Optimization of HPLC method for determination of cefixime using 2-thiophenecarboxaldehyde as derivatizing reagent: A new approach.

    PubMed

    Maheshwari, Madan Lal; Memon, Ayaz Ali; Memon, Shahabuddin; Memon, Fakhar-Un-Nisa; Mughal, Ubed Ur Rahman; Dayo, Abdullah; Memon, Naheed; Ghoto, Mohammed Ali; Khan Leghari, M

    2015-09-01

    The determination of cefixime 1 has clinical and analytical importance due to its broad spectrum antimicrobial activity and stability. Cefixime is a significant member of orally active third generation cephalosporin and has excellent activity against many pathogens. It is for first time that we have developed a new HPLC-DAD method for analysis of imine derivative 3 of cefixime by using reflux method at 100 °C for 50 min without any buffer solution. 2 Thiophenecarboxaldehyde (2TCA) 2 was used first time as a derivatizing reagent for cefixime drug. Furthermore, separation of three components, i.e. drug (cefixime), reagent (2TCA) and derivative was carried out using kromasil 100 C-18 (15 mm × 0.46 mm, 5 μm) column with isocratic elution of methanol: 0.1% aqueous formic acid (70:30 v/v) with flow rate of 1 ml min(-) (1) at retention time of 1.8, 2.4 and 3.3 min, respectively; while, total run time was 5 min. The developed method was repeatable with a relative standard deviation (RSD) of 0.81-1.88% for imine derivative. The limit of detection and quantification of imine derivative 3 were obtained within the range of 0.132-0.401 μg ml(-) (1) and compared with cefixime drug as 0.30-0.90 μg ml(-1), respectively. However, the formation of imine derivative 3 was confirmed by comparing peak height, retention time and spectral changes. The method is rapid, simple, very stable and accurate for the separation and determination of imine derivative 3 of cefixime 1. PMID:27134548

  17. Synthesis of benzofurazan derivatization reagents for carboxylic acids in liquid chromatography/electrospray ionization-tandem mass spectrometry.

    PubMed

    Santa, Tomofumi; Al-Dirbashi, Osama Y; Ichibangase, Tomoko; Fukushima, Takeshi; Rashed, Mohamed S; Funatsu, Takashi; Imai, Kazuhiro

    2007-11-01

    The applicability of benzofurazan derivatization regents to carboxylic acids analysis in LC/ESI-MS/MS (high-performance liquid chromatography/electrospray ionization tandem mass spectrometry) was examined. The product ion spectra of DAABD-AE {4-[2-(N,N-dimethylamino)ethylaminosulfonyl]-7-(2-aminoethylamino)-2,1,3-benzoxadiazole}, DAABD-PZ {4-[2-(N,N-dimethylamino)ethylaminosulfonyl]-7-N-piperazino-2,1,3-benzoxadiazole}, DAABD-PiCZ {4-[4-carbazoylpiperidin-1-yl]-7-[2-(N,N-dimethylamino)ethylaminosulfonyl]-2,1,3-benzoxadiazole}, DAABD-ProCZ {4-[2-carbazoylpyrrolidin-1-yl]-7-[2-(N,N-dimethylamino) ethylaminosulfonyl]-2,1,3-benzoxadiazole} and DAABD-Apy {4-[2-(N,N-dimethylamino)ethylaminosulfonyl]-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole}, and their acetylated compounds were obtained. An intense fragment ion at m/z 151 corresponding to (dimethylamino)ethylaminosulfonyl moiety was observed in each spectra, suggesting that these reagents were suitable for ESI-MS/MS analysis. DAABD-AE, DAABD-APy and DAABD-PZ were applied to the analysis of octanoic acid and it was found that DAABD-AE and DAABD-APy gave high signal intensity suitable for LC/ESI-MS/MS.

  18. Enantiomeric differentiation of acyclic terpenes by 13C NMR spectroscopy using a chiral lanthanide shift reagent.

    PubMed

    Blanc, Marie-Cécile; Bradesi, Pascale; Casanova, Joseph

    2005-02-01

    The 13C NMR behaviour of ten acyclic terpene alcohols was examined in the presence of a chiral lanthanide shift reagent (CLSR). For each alcohol, we measured the lanthanide-induced shift (LIS) on the signals of the carbons and the splitting of some signals, which allowed the enantiomeric differentiation. As expected, the LIS decreased with the number of bonds between the binding function and the considered carbon. The enantiomeric splitting is observed for several signals in the spectrum of each compound. The influence of the hindrance of the binding function (primary, secondary or tertiary alcohol) and that of the stereochemistry of the double bonds is discussed.

  19. Highly sensitive derivatization reagents possessing positively charged structures for the determination of oligosaccharides in glycoproteins by high-performance liquid chromatography electrospray ionization tandem mass spectrometry.

    PubMed

    Min, Jun Zhe; Nagai, Keisuke; Shi, Qing; Zhou, Wenjun; Todoroki, Kenichiro; Inoue, Koichi; Lee, Yong-Ill; Toyo'oka, Toshimasa

    2016-09-23

    We have developed three kinds of novel derivatization reagents (4-CEBTPP, 4-CBBTPP, 5-COTPP) with triphenylphosphine (TPP) as a basic structure carrying a permanent positive charge for resolution of the oligosaccharides in glycoprotein using high-performance liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The synthesized reagents reacted with the sialylglycosylamine of the sialylglycopeptide after treatment by PNGase F. The final derivatives were analyzed by ESI-MS and sensitively detected in the selected reaction monitoring (SRM) mode. Furthermore, the limits of detection (S/N=3) on the SRM chromatograms were at the fmol level (30fmol). Therefore, we used the limit of detection of the reagent products detected by the SRM and evaluated the utility of each reagent. Among the reagents, the positively charged 4-CEBTPP derivative's peak area was the highest; 4-CEBTPP with a positively charged structure showed about a 20 times greater sensitivity for the glycosylamine of the SGP product compared to the conventional fluorescence reagent, Fmoc-Cl. In addition, various fragment ions based on the carbohydrate units also appeared in the MS/MS spectra. Among the fragment ions, m/z 627.37 (CE=40eV) corresponding to 4-CEBTPP-GlcNAc and m/z 120.09 (CE=100eV) corresponding to 4-CEBTPP are the most important ones for identifying the oligosaccharide. 4-CEBTPP-SGA was easily identified by the selected-ion chromatogram in the product ion scan (m/z 120.09) and in the precursor ion scan (m/z 627.37) by MS/MS detection. The derivatized analytes have a high ionization efficiency and they are detected with a high sensitivity in the electrospray ionization. The novel derivatization reagent with a multi-function provided a higher sensitivity for the oligosaccharide analysis, as well as a better specificity and feasibility. Furthermore, several oligosaccharides in fetuin and ribonuclease B were successfully identified by the proposed procedure. PMID

  20. HPLC determination of fumonisin mycotoxins in maize: a comparative study of naphthalene-2,3-dicarboxaldehyde and o-phthaldialdehyde derivatization reagents for fluorescence and diode array detection.

    PubMed

    Ndube, Ncediwe; van der Westhuizen, Liana; Green, Ivan R; Shephard, Gordon S

    2011-08-01

    Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contaminated maize and maize-based foods. Ingestion of fumonisins has considerable health implications for humans and animals. Since fumonisins lack a useful chromophore or fluorophore, their determination in maize is routinely achieved via HPLC with fluorescence detection (FLD) after precolumn derivatization. This study optimized naphthalene-2,3-dicarboxaldehyde (NDA) derivatization of fumonisins in naturally contaminated maize following strong anion exchange (SAX) solid phase extraction (SPE) clean-up and utilizing diode array detection (DAD) as a practical alternative simultaneously to FLD. The limit of detection (LOD) for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) with FLD was 0.11 ng, 0.50 ng and 0.27 ng, respectively, and with DAD it was 13.8 ng, 12.5 ng and 6.6 ng, respectively injected on column. The coefficient of variation (CV, n = 6) for FB(1), FB(2) and FB(3) in a naturally contaminated samples obtained with FLD was 2.6%, 1.8% and 5.3%, respectively, compared to 6.0%, 3.4% and 9.5%, respectively, obtained with DAD. Subsequently the optimized NDA derivatization was compared to the widely used o-phthaldialdehyde (OPA) derivatization agent as well as alternative sample clean-up with immunoaffinity column (IAC) by analyzing naturally contaminated maize samples (n = 15) ranging in total fumonisin (TFB = FB(1)+FB(2)+FB(3)) levels from 106 to 6000 μg/kg. After immunoaffinity column clean-up of extracted samples, the recoveries of spiked maize samples for NDA-FLD of FB(1), FB(2) and FB(3) were 62%, 94% and 64%, respectively. NDA proved to be an effective derivatization reagent of fumonisin in naturally contaminated maize samples following IAC clean-up, except for DAD at TFB levels below 1000 μg/kg. In contrast NDA derivatization following SAX clean-up produced results comparable to OPA only for levels below 1000 μg/kg. Aside from the

  1. Determination of efficacy of fingermark enhancement reagents; the use of propyl chloroformate for the derivatization of fingerprint amino acids extracted from paper.

    PubMed

    Mink, Tineke; Voorhaar, Annelies; Stoel, Reinoud; de Puit, Marcel

    2013-09-01

    The analysis of the constituents of fingerprints has been described numerous times, mainly with the purpose of determining the aging effect on fingerprints or showing the differences between donors or groups of donors. In this paper we describe the use of derivatized amino acids to determine the efficacy of the visualization reagents 1,8-diazafluoren-9-one (DFO) and ninhydrin. At present certain conditions are used for the application of these reagents, as determined by trial-and-error investigations, to the effect on fingerprints. The recovery of amino acids from a porous surface can be used as a measure for the efficacy of a visualization agent. In this paper we describe a method for the determination of the amount of amino acid left after reaction with well known fingerprint visualization reagents. This will allow a more scientific approach to method development for fingermark enhancement techniques. Furthermore, investigations on the influence of the concentration of fingermark amino acids, the order of application of and exposure time to reagents and the influence of age of the amino acids were carried out. These studies have resulted in a broader understanding of the mechanism involved in visualization of fingermarks using DFO and ninhydrin.

  2. Comparison of electrophilic amination reagents for N-amination of 2-oxazolidinones and application to synthesis of chiral hydrazones.

    PubMed

    Shen, Yuehai; Friestad, Gregory K

    2002-08-23

    Comparison of several hydroxylamine-based electrophilic ammonia equivalents in the N-amination of 2-oxazolidinones revealed that O-(p-nitrobenzoyl)hydroxylamine (NbzONH(2)) and sodium hydride in dioxane is a superior reagent combination for this purpose. Practical preparations of a variety of chiral N-acylhydrazones by this method gave yields ranging from 45 to 95%. Methods for exchange or removal of the aldehyde component have been developed, making this a general route to chiral N-acylhydrazones of interest for asymmetric synthesis applications. PMID:12182669

  3. Sensitive, accurate and rapid detection of trace aliphatic amines in environmental samples with ultrasonic-assisted derivatization microextraction using a new fluorescent reagent for high performance liquid chromatography.

    PubMed

    Chen, Guang; Liu, Jianjun; Liu, Mengge; Li, Guoliang; Sun, Zhiwei; Zhang, Shijuan; Song, Cuihua; Wang, Hua; Suo, Yourui; You, Jinmao

    2014-07-25

    A new fluorescent reagent, 1-(1H-imidazol-1-yl)-2-(2-phenyl-1H-phenanthro[9,10-d]imidazol-1-yl)ethanone (IPPIE), is synthesized, and a simple pretreatment based on ultrasonic-assisted derivatization microextraction (UDME) with IPPIE is proposed for the selective derivatization of 12 aliphatic amines (C1: methylamine-C12: dodecylamine) in complex matrix samples (irrigation water, river water, waste water, cultivated soil, riverbank soil and riverbed soil). Under the optimal experimental conditions (solvent: ACN-HCl, catalyst: none, molar ratio: 4.3, time: 8 min and temperature: 80°C), micro amount of sample (40 μL; 5mg) can be pretreated in only 10 min, with no preconcentration, evaporation or other additional manual operations required. The interfering substances (aromatic amines, aliphatic alcohols and phenols) get the derivatization yields of <5%, causing insignificant matrix effects (<4%). IPPIE-analyte derivatives are separated by high performance liquid chromatography (HPLC) and quantified by fluorescence detection (FD). The very low instrumental detection limits (IDL: 0.66-4.02 ng/L) and method detection limits (MDL: 0.04-0.33 ng/g; 5.96-45.61 ng/L) are achieved. Analytes are further identified from adjacent peaks by on-line ion trap mass spectrometry (MS), thereby avoiding additional operations for impurities. With this UDME-HPLC-FD-MS method, the accuracy (-0.73-2.12%), precision (intra-day: 0.87-3.39%; inter-day: 0.16-4.12%), recovery (97.01-104.10%) and sensitivity were significantly improved. Successful applications in environmental samples demonstrate the superiority of this method in the sensitive, accurate and rapid determination of trace aliphatic amines in micro amount of complex samples. PMID:24925451

  4. Chiral NHC Ligands Bearing a Pyridine Moiety in Copper-Catalyzed 1,2-Addition of Dialkylzinc Reagents to β-Aryl-α,β-unsaturated N-Tosylaldimines.

    PubMed

    Soeta, Takahiro; Ishizaka, Tomohiro; Ukaji, Yutaka

    2016-04-01

    Asymmetric 1,2-addition of dialkylzinc reagents to α,β-unsaturated N-tosylaldimines was catalyzed by copper salt in the presence of chiral imidazolium salts having a pyridine ring, which were derived from amino acid, to afford the corresponding chiral allylic amines with up to 91% ee in reasonably high yields. The chiral N-heterocyclic carbene (NHC) ligand played an important role in controlling chemoselectivity. PMID:26967950

  5. Validation of an enantioselective analysis for (l)-pidolic acid by chiral gas chromatography with derivatization.

    PubMed

    Salisbury, John J; Li, Mingshu; Boyd, Aisha

    2016-02-20

    A sensitive and rapid analytical method has been validated for the enantiomeric purity determination of l-pidolic acid, a biological lactam and metabolite of glutamic acid commonly found in urine, skin, bones, brain and is available commercially as a food supplement. An efficient, two-step achiral derivatization was implemented which consisted of an alkylation step (using HCl-IPA) followed by an acylation step (using TFAA) of the carboxy and amide functional groups. This allowed detection with high sensitivity using gas chromatography with flame ionization detection. The described procedure employs a CP-Chiralsil-L Val column (25m×0.25mm) at a constant flow rate of 1.5mLmin(-1), a gradient temperature program from 80°C to 160°C and an injector and detector temperature of 250°C. The proposed method was validated according to ICH Q2 standards and included such parameters as specificity, system precision, analyst repeatability, intermediate precision, accuracy, linearity, LOD/LOQ and solution stability. PMID:26710173

  6. Use of Griess reagent containing vanadium(III) for post-column derivatization and simultaneous determination of nitrite and nitrate in baby food.

    PubMed

    Casanova, John A; Gross, Lois K; McMullen, Sarah E; Schenck, Frank J

    2006-01-01

    An ion chromatographic method with post-column derivatization and spectrophotometric detection is presented for the determination of nitrate and nitrite (NOx) in baby food. NOx residues found naturally or added as preservatives were extracted from baby foods and determined by using ion chromatography with post-column derivatization and spectrophotometric detection. Nitrate was reduced to nitrite online by post-column reduction using vanadium(lll) chloride and heat. Nitrite reacted with Griess reagent to produce a dye that was detected at 525 nm. The use of V(III) and heat to promote the reduction of nitrate to nitrite online is a novel feature of this detection system. The determination of incurred NOx residues in samples by using AOAC Method 993.03 yielded results comparable to those obtained by ion chromatography with spectrophotometric detection. The toxic and carcinogenic metal cadmium used in the AOAC Method to reduce the nitrate to nitrite was avoided. The proposed method provides simultaneous determination of nitrate and nitrite. Average recoveries of nitrate and nitrite residues ranged from 82 to 107% for fortification levels of 25-400 ppm.

  7. Determination of nitrofuran metabolites in shrimp by high performance liquid chromatography with fluorescence detection and liquid chromatography-tandem mass spectrometry using a new derivatization reagent.

    PubMed

    Du, Na-Na; Chen, Ming-Ming; Sheng, Liang-Quan; Chen, Shui-Sheng; Xu, Hua-Jie; Liu, Zhao-Di; Song, Chong-Fu; Qiao, Rui

    2014-01-31

    A high performance liquid chromatography with fluorescence detection (HPLC-FLD) method for the simultaneous determination of total nitrofuran metabolite residues (furazolidone, furaltadone, nitrofurantoin, and nitrofurazone) in shrimp was developed. The method involves the acid hydrolysis of protein-bound metabolites, followed by the derivatization of the freed metabolites with the new fluorescent derivatization reagent 2-hydroxy-1-naphthaldehyde (HN) and subsequent liquid-liquid extraction (LLE). Separation is achieved on a YMC-Pack Polymer C18 column under alkaline conditions, and the high fluorescence intensity of the derivatives at an emission wavelength Em=463nm (Ex=395nm) enables, for the first time, their simultaneous determination in shrimp at concentrations as low as 1μg/kg by HPLC-FLD. The method was validated using blank shrimp fortified with all four metabolites at 0.5, 1.0 and 2.0μg/kg. Recoveries were >87% with relative standard deviations of <8.1% for all four metabolites. Furthermore, the results obtained by HPLC-FLD were in very good agreement with those obtained by LC-MS/MS analysis.

  8. Towards the chiral metabolomics: Liquid chromatography-mass spectrometry based DL-amino acid analysis after labeling with a new chiral reagent, (S)-2,5-dioxopyrrolidin-1-yl-1-(4,6-dimethoxy-1,3,5-triazin-2-yl)pyrrolidine-2-carboxylate, and the application to saliva of healthy volunteers.

    PubMed

    Mochizuki, Toshiki; Takayama, Takahiro; Todoroki, Kenichiro; Inoue, Koichi; Min, Jun Zhe; Toyo'oka, Toshimasa

    2015-05-22

    A novel triazine-type chiral derivatization reagent, i.e., (S)-2,5-dioxopyrrolidin-1-yl-1-(4,6-dimethoxy-1,3,5-triazin-2-yl) pyrrolidine-2-carboxylate (DMT-(S)-Pro-OSu), was developed for the highly sensitive and selective detection of chiral amines and amino acids by UPLC-MS/MS analysis. The enantiomers of amino acids were easily labeled with the reagents at room temperature within 40 min in an alkaline medium containing triethylamine. The diastereomers derived from proteolytic amino acids, except serine, were well separated under isocratic elution conditions by reversed-phase chromatography using an ODS column (Rs=1.2-9.0). DL-Serine was separated by use of an ADME column which has relatively higher polar surface than the conventional ODS column. The characteristic product ions, i.e., m/z 195.3 and m/z 209.3, were detected from all the diastereomers by the collision-induced dissociation of the protonated molecule. A highly sensitive detection on the amol-fmol level was obtained from the selected reaction monitoring (SRM) chromatogram. The chiral amines (e.g., adrenaline and noradrenaline) labeled with DMT-(S)-Pro-OSu were also well separated and sensitively detected by the present procedure. The method using DMT-(S)-Pro-OSu was used for the determination of DL-amino acids in the human saliva from healthy volunteers. Various L-amino acids were identified in the saliva. Furthermore, D-alanine (D-Ala) and D-proline (D-Pro) were also detected in relatively high concentrations (>5%). The ratio was higher in male saliva than in female saliva. However, the difference in the ratio of D-Ala for one day was not very high and the effect of foods and beverage seemed to be negligible. Based on the results using L-Ala-d3, the D-Ala in saliva seemed to be produced due to the racemization with some enzymes such as racemase. The racemization reaction was reversible, i.e., D-Ala-d3 was also racemized to L-Ala-d3 in saliva. Thus, care should be taken during the analysis of DL

  9. Pre-Column Derivatization HPLC Procedure for the Quantitation of Aluminium Chlorohydrate in Antiperspirant Creams Using Quercetin as Chromogenic Reagent.

    PubMed

    Kalogria, Eleni; Varvaresou, Athanasia; Papageorgiou, Spyridon; Protopapa, Evaggelia; Tsaknis, Ioannis; Matikas, Alexios; Panderi, Irene

    2014-01-01

    This article describes the development and validation of a selective high-performance liquid chromatography method that allows, after liquid-liquid extraction and pre-column derivatization reaction with quercetin, the quantification of aluminium chlorohydrate in antiperspirant creams. Chromatographic separation was achieved on an XTerra MS C18 analytical column (150 × 3.0 mm i.d., particle size 5 μm) using a mobile phase of acetonitrile:water (15:85, v/v) containing 0.08 % trifluoroacetic acid at a flow rate of 0.30 mL min(-1). Ultraviolet spectrophotometric detection at 415 nm was used. The assay was linear over a concentration range of 3.7-30.6 μg mL(-1) for aluminium with a limit of quantitation of 3.74 μg mL(-1). Quality control samples (4.4, 17.1 and 30.6 μg mL(-1)) in five replicates from five different runs of analysis demonstrated intra-assay precision (% coefficient of variation <3.8 %), inter-assay precision (% coefficient of variation <5.4 %) and an overall accuracy (% recovery) between 96 and 101 %. The method was used to quantify aluminium in antiperspirant creams containing 11.0, 13.0 and 16.0 % (w/w) aluminium chlorohydrate, respectively. PMID:25278619

  10. Sample preconcentration with chemical derivatization in capillary electrophoresis. Capillary as preconcentrator, microreactor and chiral selector for high-throughput metabolite screening.

    PubMed

    Ptolemy, Adam S; Britz-McKibbin, Philip

    2006-02-17

    New strategies for integrating sample pretreatment with chemical analyses under a single format is required for rapid, sensitive and enantioselective analyses of low abundance metabolites in complex biological samples. Capillary electrophoresis (CE) offers a unique environment for controlling analyte/reagent band dispersion and electromigration properties using discontinuous electrolyte systems. Recent work in our laboratory towards developing a high-throughput CE platform for low abundance metabolites via on-line sample preconcentration with chemical derivatization (SPCD) is primarily examined in this review, as there have been surprisingly only a few strategies reported in the literature to date. In-capillary sample preconcentration serves to enhance concentration sensitivity via electrokinetic focusing of long sample injection volumes for lower detection limits, whereas chemical derivatization by zone passing is used to expand detectability and selectivity, notably for enantiomeric resolution of metabolites lacking intrinsic chromophores using nanolitre volumes of reagent. Together, on-line SPCD-CE can provide over a 100-fold improvement in concentration sensitivity, shorter total analysis times, reduced sample handling and improved reliability for a variety of amino acid and amino sugar metabolites, which is also amenable to automated high-throughput screening. This review will highlight basic method development and optimization parameters relevant to SPCD-CE, including applications to bacterial metabolite flux and biomarker analyses. Insight into the mechanism of analyte focusing and labeling by SPCD-CE is also discussed, as well as future directions for continued research.

  11. Sample preconcentration with chemical derivatization in capillary electrophoresis. Capillary as preconcentrator, microreactor and chiral selector for high-throughput metabolite screening.

    PubMed

    Ptolemy, Adam S; Britz-McKibbin, Philip

    2006-02-17

    New strategies for integrating sample pretreatment with chemical analyses under a single format is required for rapid, sensitive and enantioselective analyses of low abundance metabolites in complex biological samples. Capillary electrophoresis (CE) offers a unique environment for controlling analyte/reagent band dispersion and electromigration properties using discontinuous electrolyte systems. Recent work in our laboratory towards developing a high-throughput CE platform for low abundance metabolites via on-line sample preconcentration with chemical derivatization (SPCD) is primarily examined in this review, as there have been surprisingly only a few strategies reported in the literature to date. In-capillary sample preconcentration serves to enhance concentration sensitivity via electrokinetic focusing of long sample injection volumes for lower detection limits, whereas chemical derivatization by zone passing is used to expand detectability and selectivity, notably for enantiomeric resolution of metabolites lacking intrinsic chromophores using nanolitre volumes of reagent. Together, on-line SPCD-CE can provide over a 100-fold improvement in concentration sensitivity, shorter total analysis times, reduced sample handling and improved reliability for a variety of amino acid and amino sugar metabolites, which is also amenable to automated high-throughput screening. This review will highlight basic method development and optimization parameters relevant to SPCD-CE, including applications to bacterial metabolite flux and biomarker analyses. Insight into the mechanism of analyte focusing and labeling by SPCD-CE is also discussed, as well as future directions for continued research. PMID:16336972

  12. Chiral shift reagent for amino acids based on resonance-assisted hydrogen bonding.

    PubMed

    Chin, Jik; Kim, Dong Chan; Kim, Hae-Jo; Panosyan, Francis B; Kim, Kwan Mook

    2004-07-22

    [structure: see text] A chiral aldehyde that forms resonance-assisted hydrogen bonded imines with amino acids has been developed. This hydrogen bond not only increases the equilibrium constant for imine formation but also provides a highly downfield-shifted NMR singlet for evaluating enantiomeric excess and absolute stereochemistry of amino acids. PMID:15255698

  13. Using heteroaryl-lithium reagents as hydroxycarbonyl anion equivalents in conjugate addition reactions with (S,S)-(+)-pseudoephedrine as chiral auxiliary; enantioselective synthesis of 3-substituted pyrrolidines.

    PubMed

    Alonso, Beatriz; Ocejo, Marta; Carrillo, Luisa; Vicario, Jose L; Reyes, Efraim; Uria, Uxue

    2013-01-18

    We have developed an efficient protocol for carrying out the stereocontrolled formal conjugate addition of hydroxycarbonyl anion equivalents to α,β-unsaturated carboxylic acid derivatives using (S,S)-(+)-pseudoephedrine as chiral auxiliary, making use of the synthetic equivalence between the heteroaryl moieties and the carboxylate group. This protocol has been applied as key step in the enantioselective synthesis of 3-substituted pyrrolidines in which, after removing the chiral auxiliary, the heteroaryl moiety is converted into a carboxylate group followed by reduction and double nucleophilic displacement. Alternatively, the access to the same type of heterocyclic scaffold but with opposite absolute configuration has also been accomplished by making use of the regio- and diastereoselective conjugate addition of organolithium reagents to α,β,γ,δ-unsaturated amides derived from the same chiral auxiliary followed by chiral auxiliary removal, ozonolysis, and reductive amination/intramolecular nucleophilic displacement sequence.

  14. Dysprosium(III)-diethylenetriaminepentaacetate complexes of aminocyclodextrins as chiral NMR shift reagents.

    PubMed

    Wenzel, T J; Miles, R D; Zomlefer, K; Frederique, D E; Roan, M A; Troughton, J S; Pond, B V; Colby, A L

    2000-01-01

    A metal chelating ligand is bonded to alpha-, beta-, and gamma-cyclodextrin by the reaction of diethylenetraminepentaacetic dianhydride with the corresponding 6-mono- and 2-mono(amine)cyclodextrin. Adding Dy(III) to the cyclodextrin derivatives causes shifts in the (1)H-NMR spectra of substrates such as propranolol, tryptophan, aspartame, carbinoxamine, pheniramine, doxylamine, and 1-anilino-8-naphthalenesulfonate. The Dy(III)-induced shifts enhance the enantiomeric resolution in the NMR spectra of several substrates. Enhancements in enantiomeric resolution using cyclodextrin derivatives with the amine tether are compared to previously described compounds in which the chelating ligand is attached through an ethylenediamine tether. In general, the Dy(III) complex of the 6-beta-derivative with the amine tether is a more effective chiral resolving agent than the complex with the ethylenediamine tether. The opposite trend is observed with the 2-beta-derivatives. The presence of the chelating ligand in the 2-beta-derivative hinders certain substrates from entering the cavity. For cationic substrates, evidence suggests that a cooperative association involving inclusion in the cavity and association with the Dy(III) unit occurs. Enhancements in enantiomeric resolution in the spectrum of tryptophan are greater for the secondary alpha- and gamma-derivatives than the beta-derivative.

  15. New route to enantiopure MalphaNP acid, a powerful resolution and chiral 1H NMR anisotropy reagent.

    PubMed

    Naito, Junpei; Taji, Hiromi; Sekiguchi, Satoshi; Watanabe, Miwa; Kuwahara, Shunsuke; Watanabe, Masataka; Harada, Nobuyuki

    2007-05-15

    MalphaNP acid (+/-)-1, 2-methoxy-2-(1-naphthyl)propionic acid, was enantioresolved by the use of phenylalaninol (S)-(-)-4; a diastereomeric mixture of amides formed from acid (+/-)-1 and amine (S)-(-)-4 was easily separated by fractional recrystallization and/or HPLC on silica gel, yielding amides (R;S)-(-)-5a and (S;S)-(+)-5b. Their absolute configurations were determined by X-ray crystallography by reference to the S configuration of the phenylalaninol moiety. Amide (R;S)-(-)-5a was converted to oxazoline (R;S)-(+)-8a, from which enantiopure MalphaNP acid (R)-(-)-1 was recovered. In a similar way, enantiopure MalphaNP acid (S)-(+)-1 was obtained from amide (S;S)-(+)-5b. These reactions provide a new route for the large-scale preparation of enantiopure MalphaNP acid, a powerful chiral reagent for the enantioresolution of alcohols and simultaneous determination of their absolute configurations by (1)H NMR anisotropy. PMID:17354261

  16. Diagnostic Approach to Disease Using Non-invasive Samples Based on Derivatization and LC-ESI-MS/MS.

    PubMed

    Toyo'oka, Toshimasa

    2016-01-01

    The determination of biologically-active molecules is very important in order to understand biological functions. A novel approach for the highly sensitive and specific determination seems to be essential for this purpose. Based on this consideration, we synthesized various types of fluorogenic and fluorescent reagents for the derivatization of chiral and achiral molecules. The fluorescence analysis is excellent for the analysis of target molecules and generally provides good expected results. However, the trace analysis of the bioactive molecules in complex matrices, such as plasma and urine, is not always satisfactory even using high-performance fluorometry. In such a situation, mass spectrometry (MS) is another technique for the selective and sensitive determination of biological components. Therefore, various derivatization reagents for MS/MS detection were developed and used for the determination of amines and carboxyls including chiral molecules. These newly developed reagents were also adopted for the biomarker detection related to diseases using non-invasive samples (i.e., saliva, nail, hair). Although the determination of the targeted chiral molecules is relatively easy, it is very difficult to identify and/or determine the enantiomeric biomarker in real samples. To solve this difficulty, we proposed the strategy called "chiral metabolomics," which means the total analysis of the enantiomers of various chiral metabolites in complex matrices. This review paper focused on the development of various new derivatization reagents for amines and carboxyls by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and the detection of the biomarker candidates related to several diseases in non-invasive samples (i.e., hair, nail, saliva) using these reagents. PMID:27582321

  17. Reagent Precoated Targets for Rapid In-Tissue Derivatization of the Anti-Tuberculosis Drug Isoniazid Followed by MALDI Imaging Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Manier, M. Lisa; Reyzer, Michelle L.; Goh, Anne; Dartois, Veronique; Via, Laura E.; Barry, Clifton E.; Caprioli, Richard M.

    2011-08-01

    Isoniazid (INH) is an important component of front-line anti-tuberculosis therapy with good serum pharmacokinetics but unknown ability to penetrate tuberculous lesions. However, endogenous background interferences hinder our ability to directly analyze INH in tissues. Chemical derivatization has been successfully used to measure isoniazid directly from tissue samples using matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS). MALDI targets were pretreated with trans-cinnamaldehyde (CA) prior to mounting tissue slices. Isoniazid present in the tissues was efficiently derivatized and the INH-CA product measured by MS/MS. Precoating of MALDI targets allows the tissues to be directly thaw-mounted and derivatized, thus simplifying the preparation. A time-course series of tissues from tuberculosis infected/INH dosed animals were assayed and the MALDI MS/MS response correlates well with the amount of INH determined to be in the tissues by high-performance liquid chromatography (HPLC)-MS/MS.

  18. Acylation of Chiral Alcohols: A Simple Procedure for Chiral GC Analysis

    PubMed Central

    Oromí-Farrús, Mireia; Torres, Mercè; Canela, Ramon

    2012-01-01

    The use of iodine as a catalyst and either acetic or trifluoroacetic acid as a derivatizing reagent for determining the enantiomeric composition of acyclic and cyclic aliphatic chiral alcohols was investigated. Optimal conditions were selected according to the molar ratio of alcohol to acid, the reaction time, and the reaction temperature. Afterwards, chiral stability of chiral carbons was studied. Although no isomerization was observed when acetic acid was used, partial isomerization was detected with the trifluoroacetic acid. A series of chiral alcohols of a widely varying structural type were then derivatized with acetic acid using the optimal conditions. The resolution of the enantiomeric esters and the free chiral alcohols was measured using a capillary gas chromatograph equipped with a CP Chirasil-DEX CB column. The best resolutions were obtained with 2-pentyl acetates (α = 3.00) and 2-hexyl acetates (α = 1.95). This method provides a very simple and efficient experimental workup procedure for analyzing chiral alcohols by chiral-phase GC. PMID:22649749

  19. Derivatization in Capillary Electrophoresis.

    PubMed

    Marina, M Luisa; Castro-Puyana, María

    2016-01-01

    Capillary electrophoresis is a well-established separation technique in analytical research laboratories worldwide. Its interesting advantages make CE an efficient and potent alternative to other chromatographic techniques. However, it is also recognized that its main drawback is the relatively poor sensitivity when using optical detection. One way to overcome this limitation is to perform a derivatization reaction which is intended to provide the analyte more suitable analytical characteristics enabling a high sensitive detection. Based on the analytical step where the CE derivatization takes place, it can be classified as precapillary (before separation), in-capillary (during separation), or postcapillary (after separation). This chapter describes the application of four different derivatization protocols (in-capillary and precapillary modes) to carry out the achiral and chiral analysis of different compounds in food and biological samples with three different detection modes (UV, LIF, and MS). PMID:27645730

  20. Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs.

    PubMed

    Kostić, Nađa; Dotsikas, Yannis; Malenović, Anđelija; Medenica, Mirjana

    2013-11-15

    In the current study, three antiepileptic drugs with zwitterionic properties, namely vigabatrin, pregabalin and gabapentin, were chosen as model analytes to undergo derivatization by applying various n-alkyl chloroformate/n-alcohol combinations, followed by LC-ESI-MS/MS analysis. The employment of 16 combinations per drug using methyl, ethyl, propyl or butyl chloroformate coupled with methanol, ethanol, propanol or butanol, greatly affected a series of parameters of the derivatives, such as retention time on C8 column, signal expressed via areas, limit of detection values, as well as the yields of the main and side reactions. Practically, even slight modification of n-alkyl group of either chloroformate or alcohol resulted in significant changes in the chromatographic and mass spectrometric behavior of the novel derivative. It was clearly demonstrated that all the estimated parameters were highly correlated with the length of n-alkyl groups of the involved chloroformate and alcohol. The most significant influence was monitored in peak area values, indicating that the length of the n-alkyl chain plays an important role in electrospray ionization efficiency. For this parameter, increasing the n-alkyl chain from methyl to butyl led to increment up to 2089%, 508.7% and 1075% for area values of derivatized vigabatrin, pregabalin and gabapentin, respectively. These changes affected also the corresponding values of limits of detection, with the estimated improvements up to 1553%, 397.7% and 875.0% for the aforementioned derivatized drugs, respectively. Besides the obvious utilization of these conclusions in the development of bioanalytical methods for these analytes with the current protocol, this study offers valuable data which can be useful in more general approaches, giving insights into the effects of this derivatization reaction and its performances.

  1. Reagent Precoated Targets for Rapid In-Tissue Derivatization of the Anti-Tuberculosis Drug Isoniazid Followed by MALDI Imaging Mass Spectrometry

    PubMed Central

    Manier, M. Lisa; Reyzer, Michelle L.; Goh, Anne; Dartois, Veronique; Via, Laura E.; Barry, Clifton E.; Caprioli, Richard M.

    2012-01-01

    Isoniazid (INH) is an important component of front-line anti-tuberculosis therapy with good serum pharmacokinetics but unknown ability to penetrate tuberculous lesions. However, endogenous background interferences hinder our ability to directly analyze INH in tissues. Chemical derivatization has been successfully used to measure isoniazid directly from tissue samples using matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS). MALDI targets were pretreated with trans-cinnamaldehyde (CA) prior to mounting tissue slices. Isoniazid present in the tissues was efficiently derivatized and the INH-CA product measured by MS/MS. Precoating of MALDI targets allows the tissues to be directly thaw-mounted and derivatized, thus simplifying the preparation. A time-course series of tissues from tuberculosis infected/INH dosed animals were assayed and the MALDI MS/MS response correlates well with the amount of INH determined to be in the tissues by high-performance liquid chromatography (HPLC)-MS/MS. PMID:21953196

  2. Effect of solvents on the fumonisins analysis by high-performance liquid chromatography with AccQ.Fluor as the derivatizing reagent.

    PubMed

    Velázquez, C; Llovera, M; Plana, J; Canela, R

    2000-02-18

    The effect of several solvent systems on the chromatographic response of fumonisin B1 and B2 derived with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AccQ.Fluor) is described. Naturally contaminated corn samples were extracted and purified by a standard method. Then, samples were dissolved in different solvents, derived with AccQ.Fluor reagent and analysed using HPLC. Results were solvent dependent, methanol being the best one among all assayed solvents for both fumonisins studied and acetonitrile the poorest. o-Phthaldialdehyde (OPA) reagent was used as a reference method.

  3. Gas chromatographic analysis of guanidino compounds in sera and urine of uremic patients using glyoxal and ethyl chloroformate as derivatizing reagents.

    PubMed

    Majidano, Subhan Ali; Khuhawar, Muhammad Yar

    2013-01-01

    Gas chromatographic (GC) method has been developed for the determination of the guanidino compounds: guanidine (G), methylguanidine (MG), guanidinoacetic acid (GAA), guanidinopropionic acid (GPA), guanidinobutyric acid (GBA) and guanidinosuccinic acid (GSA) was carried out after precolumn derivatization with glyoxal and ethyl chloroformate from the column HP-5 (30 m × 0.32 mm i.d.) at 90°C for 3 min, followed by a heating rate 25°C/min up to 260°C with a nitrogen flow rate of 2 ml/min. Detection was by FID. The linear calibrations were obtained within 0.1-20.0 μmol/L, with limits of detection (LODs) within 0.014-0.024 μmol/L. The separation and derivatization was repeatable (n = 6) with relative standard deviations (RSD) within 0.8-1.9% in retention time and 0.5-1.8% in peak height/peak area. A number of additives and amino acids did not affect the determination. The method was applied for the determination of guanidino compounds from the serum and urine of 9 healthy volunteers and 8 uremic patients and the amounts found were in the range 0.08-0.48 and below the limit of detection (LOD) - 345 μmol/L and 1.82 - 13.88 and 0.77 - 432.0 μmol/L with RSDs within 4.2%, respectively. PMID:23400288

  4. Modification of Escherichia coli ribosomes with the fluorescent reagent N-[[(iodoacetyl)amino]ethyl]-5-naphthylamine-1-sulfonic acid. Identification of derivatized L31' and studies on its intraribosomal properties.

    PubMed

    Hanas, J S; Simpson, M V

    1985-12-01

    N-[[(Iodoacetyl)amino]ethyl]-5-naphthylamine-1-sulfonic acid (IAEDANS) is a fluorescent reagent which reacts covalently with the free thiol groups of proteins. When the reagent is reacted with the Escherichia coli ribosome under mild conditions, gel electrophoresis shows modification of predominantly two proteins, S18 and L31', which become labeled to an equal extent. When the native (i.e., untreated) ribosome is dissociated into 30S and 50S subunits, only the 30S ribosomal protein S18 reacts with IAEDANS despite the fact that L31' is still present on the large subunit. Upon heat activation of the subunits, a procedure which alters subunit conformation, S18 plus a number of higher molecular weight proteins is modified, but not L31'; the latter reacts with IAEDANS only in the 70S ribosome or when it is free. In contrast to the relatively stable association of L31' with native or with dissociated ribosomes, dissociation of N-[(acetylamino)ethyl]-5-naphthylaminesulfonic acid (AEDANS)-treated ribosomes weakens the AEDANS-L31'/ribosome interaction, resulting, upon gel filtration analysis, in ribosomes devoid of this derivatized protein.

  5. Ultrasensitive quantification of endogenous brassinosteroids in milligram fresh plant with a quaternary ammonium derivatization reagent by pipette-tip solid-phase extraction coupled with ultra-high-performance liquid chromatography tandem mass spectrometry.

    PubMed

    Deng, Ting; Wu, Dapeng; Duan, Chunfeng; Guan, Yafeng

    2016-07-22

    Determination of endogenous brassinosteroids (BRs) in limited sample amount is vital to elucidating their tissue- and even local tissue-specific signaling pathway and physiological effects on plant growth and development. In this work, an ultra-sensitive quantification method was established for endogenous BRs in milligram fresh plant by using pipette-tip solid-phase extraction coupled with ultra-performance liquid chromatography tandem mass spectrometry (PT-SPE-UPLC-MS/MS), in which a quaternary ammonium phenyl boronic acid, 4-borono-N,N,N-trimethylbenzenaminium iodide (BTBA) was first developed for chemical derivatization of BRs. Due to the cationic quaternary ammonium group of BTBA, the ionization efficiencies of the BRs chelates with BTBA (BTBA-BRs) were enhanced by 1190-448785 times, which is the highest response enhancement factor among all derivatization reagents reported for BRs. In addition, PT-SPE packed with C18 sorbent was first used for purifying BRs from plant extracts, so the required sample amount was minimized, and recoveries higher than 91% were achieved. Under the optimized conditions, the minimal detectable amounts (MDA) of five target BRs were in the range of 27-94 amol, and the correlation coefficients (R(2)) were >0.9985 over four orders of magnitude. The relative recoveries of 75.8-104.9% were obtained with the intra- and inter-day relative standard deviations (RSDs) less than 18.7% and 19.6%, respectively. Finally, three BRs were successfully quantified in only 5mg fresh rice plant samples, and 24-epiBL can even be detected in only 0.5mg FW rice leaf segments. It is the first time that the BRs content in sub-milligram fresh plant sample has been quantified.

  6. Ultrasensitive quantification of endogenous brassinosteroids in milligram fresh plant with a quaternary ammonium derivatization reagent by pipette-tip solid-phase extraction coupled with ultra-high-performance liquid chromatography tandem mass spectrometry.

    PubMed

    Deng, Ting; Wu, Dapeng; Duan, Chunfeng; Guan, Yafeng

    2016-07-22

    Determination of endogenous brassinosteroids (BRs) in limited sample amount is vital to elucidating their tissue- and even local tissue-specific signaling pathway and physiological effects on plant growth and development. In this work, an ultra-sensitive quantification method was established for endogenous BRs in milligram fresh plant by using pipette-tip solid-phase extraction coupled with ultra-performance liquid chromatography tandem mass spectrometry (PT-SPE-UPLC-MS/MS), in which a quaternary ammonium phenyl boronic acid, 4-borono-N,N,N-trimethylbenzenaminium iodide (BTBA) was first developed for chemical derivatization of BRs. Due to the cationic quaternary ammonium group of BTBA, the ionization efficiencies of the BRs chelates with BTBA (BTBA-BRs) were enhanced by 1190-448785 times, which is the highest response enhancement factor among all derivatization reagents reported for BRs. In addition, PT-SPE packed with C18 sorbent was first used for purifying BRs from plant extracts, so the required sample amount was minimized, and recoveries higher than 91% were achieved. Under the optimized conditions, the minimal detectable amounts (MDA) of five target BRs were in the range of 27-94 amol, and the correlation coefficients (R(2)) were >0.9985 over four orders of magnitude. The relative recoveries of 75.8-104.9% were obtained with the intra- and inter-day relative standard deviations (RSDs) less than 18.7% and 19.6%, respectively. Finally, three BRs were successfully quantified in only 5mg fresh rice plant samples, and 24-epiBL can even be detected in only 0.5mg FW rice leaf segments. It is the first time that the BRs content in sub-milligram fresh plant sample has been quantified. PMID:27338695

  7. An easy-to-use excimer fluorescence derivatization reagent, 2-chloro-4-methoxy-6-(4-(pyren-4-yl)butoxy)-1,3,5-triazine, for use in the highly sensitive and selective liquid chromatography analysis of histamine in Japanese soy sauces.

    PubMed

    Nakano, Tatsuki; Todoroki, Kenichiro; Ishii, Yasuhiro; Miyauchi, Chiemi; Palee, Arpaporn; Min, Jun Zhe; Inoue, Koichi; Suzuki, Kuniaki; Toyo'oka, Toshimasa

    2015-06-23

    In this study, a novel pre-column excimer fluorescence derivatization reagent, 2-chloro-4-methoxy-6-(4-(pyren-4-yl)butoxy)-1,3,5-triazine (CMPT), was developed for polyamines, specifically histamine. By CMPT derivatization, the polyamines, histamine and tyramine were converted to polypyrene derivatives, and emitted intra-molecular excimer fluorescence at 475nm. This could clearly be distinguished from the normal fluorescence emitted from reagent blanks at 375 nm. Unlike conventional excimer fluorescence derivatization reagents, CMPT is chemically stable and its reactivity sustained over at least 36 days even in solution state. We successfully applied this reagent to the sensitive and selective analysis of histamine in different kinds of Japanese commercial soy sauces. The detection and quantification limits of histamine were 15 and 50 μg L(-1), respectively, equating to 1.35 pmol and 4.5 pmol for a 6 μL injection. This sensitivity helped the direct analysis of soy sauce samples only treated by one-step liquid-liquid extraction without concentration. The histamine levels of commercial soy sauce samples (koikuchi, usukuchi and saishikomi) investigated were 1.24-768.5 mg L(-1).

  8. Tandem Mass Spectrometric Characterization of Thiol Peptides Modified by the Chemoselective Cationic Sulfhydryl Reagent (4-Iodobutyl)Triphenylphosphonium—. Effects of a Cationic Thiol Derivatization on Peptide Fragmentation

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Zhang, Jie; Arbogast, Brian; Maier, Claudia S.

    2011-10-01

    Fixed charge chemical modifications on peptides and proteins can impact fragmentation behaviors in tandem mass spectrometry (MS/MS). In this study, we employed a thiol-specific cationic alkylation reagent, (4-iodobutyl)triphenylphosphonium (IBTP), to selectively modify cysteine thiol groups in mitochondrial proteome samples. Tandem mass spectrometric characteristics of butyltriphenylphosphonium (BTP)-modified peptides were evaluated by comparison to their carbamidomethylated (CAM) analogues using a quadrupole time-of-flight (Q-TOF) instrument under low energy collision-induced dissociation (CID) conditions. Introduction of the fixed charge modification resulted in the observation of peptide and fragment (bn and yn) ions with higher charge states than those observed for CAM-modified analogues. The charged BTP moiety had a significant effect on the neighboring amide bond fragmentation products. A decrease in relative abundances of the product ions at the corresponding cleavage sites was observed compared with those from the CAM-modified derivatives. This effect was particularly noticeable when an Xxx-Pro bond was in the vicinity of a BTP group. We hypothesized that the presence of a phosphonium moiety will reduce the tendency for protonation of the proximal amide bonds in the peptide backbone. Indeed, calculations indicated that proton affinities of backbone amide bonds close to the modified cysteine residues were generally 20-50 kcal/mol lower for BTP-modified peptides than for the unmodified or CAM-modified analogues with the sequence motif -Ala-Cys-Alan-Ala2-, -Ala-Cys-Alan-Pro-Ala-, and -Ala-Pro-Alan-Cys-Ala-, n = 0-3.

  9. Study on determination of iron, cobalt, nickel, copper, zinc and manganese in drinking water by solid-phase extraction and RP-HPLC with 2-(2-quinolinylazo)-5-diethylaminophenol as precolumn derivatizing reagent.

    PubMed

    Hu, Qiufen; Yang, Guanyu; Yang, Jihong; Yin, Jiayuan

    2002-12-01

    A new method for the determination of iron, cobalt, nickel, copper, zinc and manganese in drinking water by the reversed-phase high-performance liquid chromatography (RP-HPLC) with 2-(2-quinolinylazo)-5-diethylaminophenol (QADEAP) as precolumn derivatizing reagent was studied in this paper. The iron, cobalt, nickel, copper, zinc, and manganese ions react with QADEAP to form color chelates in the presence of cetyl trimethylammonium bromide (CTMAB) and acetic acid-sodium acetic buffer solution medium of pH 4.0. These chelates were enriched by solid-phase extraction with a Waters Nova-Pak C18 cartridge and eluted the retained chelates from the cartridge with tetrahydrofuran (THF). The enrichment factor of 100 was achieved. Then the chelates were separated on a Waters Nova-Pak C18 column (3.9 x 150 mm, 5 microm) by gradient elution with methanol (containing 0.2% of acetic acid and 0.1% of CTMAB) and 0.05 mol L(-1) acetic acid-sodium acetic buffer solution (containing 0.1% of CTMAB) (pH 4.0) as mobile phase at a flow rate of 0.5 ml min(-1), and monitored with a photodiode array detector from 450 approximately 700 nm. The detection limits (S/N = 3) of iron, cobalt, nickel, copper, zinc and manganese are 0.8, 1.1, 0.9, 1.1, 1.5 and 2.0 ng L(-1), respectively, in the original sample. This method can be applied to determination at the microg L(-1) level of iron, cobalt, nickel, copper, zinc and manganese in drinking water with good results. PMID:12509050

  10. Enantioselective determination of selfotel in human urine by high-performance liquid chromatography on a chiral stationary phase after derivatization with 9-fluorenylmethyl chloroformate.

    PubMed

    Knoche, B; Milosavljev, S; Gropper, S; Brunner, L A; Powell, M L

    1997-08-01

    An analytical method for the enantioselective determination of selfotel in human urine has been developed and validated. The method is based on high-performance liquid chromatography and utilizes CGS 20005 (a selfotel analog) as the internal standard. Urine samples were derivatized in situ with o-phthalic dicarboxaldehyde-3-mercaptopropionic acid and 9-fluorenylmethyl chloroformate (FMOC). Chromatographic separations of the FMOC derivatives of selfotel enantiomers and the internal standard were achieved using a column switching system consisting of an Inertsil ODS-2 column (75x4.6 mm I.D., 5 microm) and a Chiralcel OD-R column (250x4.6 mm I.D., 10 microm). The composition of the mobile phase was acetonitrile-0.1 M phosphate buffer, pH 2.50 (35:65) for the Inertsil ODS-2 column and acetonitrile-0.1 M phosphate buffer, pH 2.00 (35:65) for the Chiralcel OD-R column. The analytes were monitored using fluorescence detection at an excitation wavelength of 262 nm and an emission wavelength of 314 nm. The limit of quantification (LOQ) for this method is 0.25 microg/ml for each selfotel enantiomer. The method was successfully utilized to determine preliminary selfotel stereospecific pharmacokinetics. PMID:9300872

  11. Targeted LC–MS derivatization for aldehydes and carboxylic acids with a new derivatization agent 4-APEBA

    PubMed Central

    Eggink, Mark; Wijtmans, Maikel; Kretschmer, Ansgar; Kool, Jeroen; Lingeman, Henk; de Esch, Iwan J. P.; Irth, Hubertus

    2010-01-01

    Based on the template of a recently introduced derivatization reagent for aldehydes, 4-(2-(trimethylammonio)ethoxy)benzeneaminium dibromide (4-APC), a new derivatization agent was designed with additional features for the analysis and screening of biomarkers of lipid peroxidation. The new derivatization reagent, 4-(2-((4-bromophenethyl)dimethylammonio)ethoxy)benzenaminium dibromide (4-APEBA) contains a bromophenethyl group to incorporate an isotopic signature to the derivatives and to add additional fragmentation identifiers, collectively enhancing the abilities for detection and screening of unknown aldehydes. Derivatization can be achieved under mild conditions (pH 5.7, 10 °C). By changing the secondary reagent (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide instead of sodium cyanoborohydride), 4-APEBA is also applicable to the selective derivatization of carboxylic acids. Synthesis of the new label, exploration of the derivatization conditions, characterization of the fragmentation of the aldehyde and carboxylic acid derivatives in MS/MS, and preliminary applications of the labeling strategy for the analysis of aldehydes in urine and plasma are described. Figure Structure and MS/MS fragmentation spectrum of 4-APEBA reagents derivatized with octanoic acid Electronic supplementary material The online version of this article (doi:10.1007/s00216-010-3575-1) contains supplementary material, which is available to authorized users. PMID:20238107

  12. Quantitative and isomeric determination of amphetamine and methamphetamine from urine using a nonprotic elution solvent and R(-)-alpha-methoxy-alpha-trifluoromethylphenylacetic acid chloride derivatization.

    PubMed

    Holler, Justin M; Vorce, Shawn P; Bosy, Thomas Z; Jacobs, Aaron

    2005-10-01

    Forensic Urine Drug Testing Laboratories often requires two confirmatory methods for a methamphetamine positive screen. First, methamphetamine is identified and quantitated using gas chromatography-mass spectrometry. If the total methamphetamine concentration is above the administrative cutoff level, the isomeric composition must be determined. This eliminates a possible contribution by over-the-counter cold medications that contain l-methamphetamine (Vick's inhalers). Products that contain only the l-isomer of methamphetamine must be distinguishable from prescription or illicitly manufactured methamphetamine, which consists mainly of the d-isomer. Optically impure derivatizing reagents will produce an impure mixture from a pure isomeric compound. Therefore, methods utilizing impure reagents can prove problematic when interpreting results. Use of an optically pure chiral derivatizing reagent, such as R(-)-alpha-methoxy-alpha-trifluoromethylphenylacetic acid chloride, allows for the creation and measurement of chromatographically separable isomeric compounds. The novel method described here utilizes a polymer-based solid-phase column adapted to a positive pressure manifold extraction system and a one-step derivatization process that occurs directly in the elution solvent. This methodology eliminates an elution solvent dry-down step that may adversely affect recovery of volatile amphetamine compounds. Although the method was designed for the quantitative analysis of the isomers of amphetamine and methamphetamine, it can be adapted for use with a wide range of phenethylamines including methylenedioxyamphetamine, N-methylenedioxymethamphetamine, and possibly N-methylenedioxyethylamphetamine. The linear range for quantitation was 25-10,000 ng/mL for d,l-methamphetamine and d,l-amphetamine, and correlation coefficients were 0.997 or better. The coefficient of variation for all four analytes did not exceed 2.8%. Concentrations analyzed ranged from 500 to 4000 ng/mL (n=40

  13. Development of a pair of differential H/D isotope-coded derivatization reagents d(0)/d(3)-4-(1-methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenlamine and its application for determination of aldehydes in selected aquatic products by liquid chromatography-tandem mass spectrometry.

    PubMed

    Sun, Zhiwei; Wang, Xiaoxiang; Cai, Yiping; Fu, Junqing; You, Jinmao

    2014-03-01

    A new pair of derivatization reagents, d0-4-(1-methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenlamine (d0-MPIA) and d3-4-(1-methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenlamine (d3-MPIA) have been designed and synthesized. It was successfully used to label aliphatic aldehydes and the aldehyde derivatives were analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The new isotope-coded reagents could easily label aldehydes under acidic conditions in the presence of NaCNBH3. The target derivatives exhibited intense [M+H](+) and regular product ions with electrospray ionization source in positive mode. The d0/d3-MPIA-aldehydes were monitored by the transitions of [M+H](+)→m/z 322 and [M+H](+)→m/z 165, and the obtained detection limits were in the range of 0.18-15.9 pg/mL at signal to noise ratio of 3. The global isotope internal standard technology was employed for quantification analysis with d3-MPIA-aldehyde as internal standard for corresponding d0-MPIA-aldehyde. Excellent linear responses for relative quantification were observed in the range of 1/10-10/1 with coefficients >0.998. The developed method has been applied to the quantification of aliphatic aldehydes in selected aquatic products with RSD<3.6% and recoveries >85.2%.

  14. Enantioselective nucleophilic difluoromethylation of aromatic aldehydes with Me3SiCF2SO2Ph and PhSO2CF2H reagents catalyzed by chiral quaternary ammonium salts

    PubMed Central

    Ni, Chuanfa; Wang, Fang

    2008-01-01

    Summary Background Although the nucleophilic difluoromethylation of aldehydes, ketones, and imines has been realized with PhSO2CF2H and related reagents, there are still no reports on the enantioselective nucleophilic reactions. Results With a chiral quaternary ammonium salt as the catalyst and KOH as the base, we describe the first enantioselective difluoromethylation of aromatic aldehydes with PhSO2CF2H or Me3SiCF2SO2Ph. The enantioselectivity is substrate-dependent and for 2-chlorinated benzaldehyde an ee up to 64% was obtained. Conclusion These results provide some insights into the enantioselective nucleophilic difluoromethylation chemistry, which will stimulate further progress in this field. PMID:18941491

  15. A Method for Simultaneous Determination of 25-Hydroxyvitamin D3 and Its 3-Sulfate in Newborn Plasma by LC/ESI-MS/MS after Derivatization with a Proton-Affinitive Cookson-Type Reagent.

    PubMed

    Higashi, Tatsuya; Yokota, Mai; Goto, Ayaka; Komatsu, Kenji; Sugiura, Takahiro; Ogawa, Shoujiro; Satoh, Mamoru; Nomura, Fumio

    2016-01-01

    A method for the simultaneous determination of 25-hydroxyvitamin D3 [25(OH)D3] and its 3-sulfate [25(OH)D3S] in newborn plasma, which is expected to be helpful in the assessment of the vitamin D status, using stable isotope-dilution liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been developed and validated. The plasma was pretreated based on the deproteinization and solid-phase extraction, then subjected to derivatization with 4-(4-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD). The derivatization enabled the accurate quantification of 25(OH)D3 without interference from 3-epi-25(OH)D3 and also facilitated the simultaneous determination of the two metabolites by LC/positive ESI-MS/MS. Quantification was based on the selected reaction monitoring with the characteristic fragmentation of the DAPTAD-derivatives during MS/MS. This method was reproducible (intra- and inter-assay relative standard deviations of 7.8% or lower for both metabolites) and accurate (analytical recovery, 95.4-105.6%). The limits of quantification were 1.0 ng/mL and 2.5 ng/mL for 25(OH)D3 and 25(OH)D3S, respectively, when using a 20-μL sample. The developed method was applied to the simultaneous determination of plasma 25(OH)D3 and 25(OH)D3S in newborns; it was recognized that the plasma concentration of 25(OH)D3S is significantly higher than that of 25(OH)D3, and preterm newborns have lower plasma 25(OH)D3S concentrations than full-term newborns. PMID:27656337

  16. A Method for Simultaneous Determination of 25-Hydroxyvitamin D3 and Its 3-Sulfate in Newborn Plasma by LC/ESI-MS/MS after Derivatization with a Proton-Affinitive Cookson-Type Reagent

    PubMed Central

    Higashi, Tatsuya; Yokota, Mai; Goto, Ayaka; Komatsu, Kenji; Sugiura, Takahiro; Ogawa, Shoujiro; Satoh, Mamoru; Nomura, Fumio

    2016-01-01

    A method for the simultaneous determination of 25-hydroxyvitamin D3 [25(OH)D3] and its 3-sulfate [25(OH)D3S] in newborn plasma, which is expected to be helpful in the assessment of the vitamin D status, using stable isotope-dilution liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been developed and validated. The plasma was pretreated based on the deproteinization and solid-phase extraction, then subjected to derivatization with 4-(4-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD). The derivatization enabled the accurate quantification of 25(OH)D3 without interference from 3-epi-25(OH)D3 and also facilitated the simultaneous determination of the two metabolites by LC/positive ESI-MS/MS. Quantification was based on the selected reaction monitoring with the characteristic fragmentation of the DAPTAD-derivatives during MS/MS. This method was reproducible (intra- and inter-assay relative standard deviations of 7.8% or lower for both metabolites) and accurate (analytical recovery, 95.4–105.6%). The limits of quantification were 1.0 ng/mL and 2.5 ng/mL for 25(OH)D3 and 25(OH)D3S, respectively, when using a 20-μL sample. The developed method was applied to the simultaneous determination of plasma 25(OH)D3 and 25(OH)D3S in newborns; it was recognized that the plasma concentration of 25(OH)D3S is significantly higher than that of 25(OH)D3, and preterm newborns have lower plasma 25(OH)D3S concentrations than full-term newborns. PMID:27656337

  17. A Method for Simultaneous Determination of 25-Hydroxyvitamin D3 and Its 3-Sulfate in Newborn Plasma by LC/ESI-MS/MS after Derivatization with a Proton-Affinitive Cookson-Type Reagent

    PubMed Central

    Higashi, Tatsuya; Yokota, Mai; Goto, Ayaka; Komatsu, Kenji; Sugiura, Takahiro; Ogawa, Shoujiro; Satoh, Mamoru; Nomura, Fumio

    2016-01-01

    A method for the simultaneous determination of 25-hydroxyvitamin D3 [25(OH)D3] and its 3-sulfate [25(OH)D3S] in newborn plasma, which is expected to be helpful in the assessment of the vitamin D status, using stable isotope-dilution liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been developed and validated. The plasma was pretreated based on the deproteinization and solid-phase extraction, then subjected to derivatization with 4-(4-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD). The derivatization enabled the accurate quantification of 25(OH)D3 without interference from 3-epi-25(OH)D3 and also facilitated the simultaneous determination of the two metabolites by LC/positive ESI-MS/MS. Quantification was based on the selected reaction monitoring with the characteristic fragmentation of the DAPTAD-derivatives during MS/MS. This method was reproducible (intra- and inter-assay relative standard deviations of 7.8% or lower for both metabolites) and accurate (analytical recovery, 95.4–105.6%). The limits of quantification were 1.0 ng/mL and 2.5 ng/mL for 25(OH)D3 and 25(OH)D3S, respectively, when using a 20-μL sample. The developed method was applied to the simultaneous determination of plasma 25(OH)D3 and 25(OH)D3S in newborns; it was recognized that the plasma concentration of 25(OH)D3S is significantly higher than that of 25(OH)D3, and preterm newborns have lower plasma 25(OH)D3S concentrations than full-term newborns.

  18. A Method for Simultaneous Determination of 25-Hydroxyvitamin D3 and Its 3-Sulfate in Newborn Plasma by LC/ESI-MS/MS after Derivatization with a Proton-Affinitive Cookson-Type Reagent.

    PubMed

    Higashi, Tatsuya; Yokota, Mai; Goto, Ayaka; Komatsu, Kenji; Sugiura, Takahiro; Ogawa, Shoujiro; Satoh, Mamoru; Nomura, Fumio

    2016-01-01

    A method for the simultaneous determination of 25-hydroxyvitamin D3 [25(OH)D3] and its 3-sulfate [25(OH)D3S] in newborn plasma, which is expected to be helpful in the assessment of the vitamin D status, using stable isotope-dilution liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been developed and validated. The plasma was pretreated based on the deproteinization and solid-phase extraction, then subjected to derivatization with 4-(4-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD). The derivatization enabled the accurate quantification of 25(OH)D3 without interference from 3-epi-25(OH)D3 and also facilitated the simultaneous determination of the two metabolites by LC/positive ESI-MS/MS. Quantification was based on the selected reaction monitoring with the characteristic fragmentation of the DAPTAD-derivatives during MS/MS. This method was reproducible (intra- and inter-assay relative standard deviations of 7.8% or lower for both metabolites) and accurate (analytical recovery, 95.4-105.6%). The limits of quantification were 1.0 ng/mL and 2.5 ng/mL for 25(OH)D3 and 25(OH)D3S, respectively, when using a 20-μL sample. The developed method was applied to the simultaneous determination of plasma 25(OH)D3 and 25(OH)D3S in newborns; it was recognized that the plasma concentration of 25(OH)D3S is significantly higher than that of 25(OH)D3, and preterm newborns have lower plasma 25(OH)D3S concentrations than full-term newborns.

  19. Simultaneous analysis of D-alanine, D-aspartic acid, and D-serine using chiral high-performance liquid chromatography-tandem mass spectrometry and its application to the rat plasma and tissues.

    PubMed

    Karakawa, Sachise; Shimbo, Kazutaka; Yamada, Naoyuki; Mizukoshi, Toshimi; Miyano, Hiroshi; Mita, Masashi; Lindner, Wolfgang; Hamase, Kenji

    2015-11-10

    A highly sensitive and selective chiral LC-MS/MS method for D-alanine, D-aspartic acid and D-serine has been developed using the precolumn derivatization reagents, 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AccQ-Tag) or p-N,N,N-trimethylammonioanilyl N'-hydroxysuccinimidyl carbamate iodide (TAHS). The thus N-tagged enantiomers of the derivatized amino acids were nicely separated within 20min using the cinchona alkaloid-based zwittterionic ion-exchange type enantioselective column, Chiralpak ZWIX(+). The selected reaction monitoring was applied for detecting the target d-amino acids in biological matrices. By using the present chiral LC-MS/MS method, the three d-amino acids and their l-forms could be simultaneously determined in the range of 0.1-500nmol/mL. Finally, the technique was successfully applied to rat plasma and tissue samples.

  20. Assessing solvent derivatization and carbon dioxide supercritical fluid simultaneous extraction/derivatization of cyprodinil.

    PubMed

    Aguilera, Ana; Valverde, Antonio; Valverde-Monterreal, Antonio; Garcia-Fuentes, Luis; Boulaid, Mourad

    2014-01-01

    Derivatization of cyprodinil with different reagents and solvents has been evaluated to improve the GC/MS characterization of this fungicide. After assessing some preliminary acylation and silylation reactions, derivatization with anhydrous heptafluorobutyric anhydride (HFBA) was selected as the best derivatization option for cyprodinil. The HFBA-cyprodinil derivative was clearly identified and characterized by GC/MS (ion-trap). The spectrum of the HFBA derivative of cyprodinil was characterized by the base peak, 252 m/z ion, and two other ions with relative abundances of 5% (224 m/z ion) and 4% (420 m/z molecular ion). Conversion rates in the range of 83-92% were obtained when 0.1-1 μg cyprodinil were derivatized in vial without solvent at 25ºC temperature for 120 min, with 5 μL HFBA and 5 μL pyridine. Simultaneous extraction-derivatization of cyprodinil in supercritical carbon dioxide was only achieved when no modifier was present, but conversion/recovery rates obtained in the replicate experiments carried out with 15 mL supercritical carbon dioxide at 50°C and 200 atm (n = 5), 300 atm (n = 7), and 400 atm (n = 5) were no reproducible (RSD > 50%) and ranged between 10% and 45% (related to the signal obtained for derivatization in vial).

  1. Simple and sensitive high-performance liquid chromatographic determination of methamphetamines in human urine as derivatives of 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride, a new fluorescence derivatization reagent.

    PubMed

    Al-Dirbashi, O; Qvarnstrom, J; Irgum, K; Nakashima, K

    1998-08-01

    A simple, rapid and highly sensitive high-performance liquid chromatographic method for the determination of methamphetamine and its metabolites in human urine was developed. Without tedious pretreatment procedures, aliquots of methamphetamine spiked or abusers' urine samples were simply acidified, dried under a stream of N2 gas, and then derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride in acetonitrile in the presence of traces of triethylamine. Five derivatives were isocratically separated within 33 min by an ODS column, and the effluent was monitored at 440 nm (lambda(ex), 330 nm). Using 1-phenylethylamine as an internal standard calibration curves were confirmed to be linear up to at least 2x10(-5) M in urine with correlation coefficients of 0.998-1.000, while the detection limits at S/N=3 were 0.6-5.2 fmol per 5-microl injection. The relative standard deviations (n=5) of inter- and intra-day variations were less than 8.9%. The correlation between the concentrations of methamphetamine and amphetamine in urine determined by the proposed method and another currently accepted one was satisfactory. The method was successfully applied to urine samples collected from methamphetamine addicts.

  2. Enantiomeric purity test of bevantolol by reversed-phase high performance liquid chromatography after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate.

    PubMed

    Kim, K H; Heo, S Y; Hong, S P; Lee, B C

    2000-12-01

    A reversed-phase high-performance liquid chromatographic method was developed to determine the optical purity of bevantolol enantiomers. (S)-(-)-Menthyl chloroformate((-)-MCF), (S)-(-)-alpha-methylbenzyl isocyanate((-)-MBIC) and 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate(GITC), which can react with the secondary amine group of bevantolol were investigated as chiral derivatization reagents. Among them indirect chiral HPLC method using GITC gave the best result. The derivatization proceeded quantitatively within 20 min at room temperature. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 20min using ODS column. Different ratios of (S)-(-)-bevantolol and (R)-(+)-bevantolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with GITC, on a ODS column. No racemization was found during the experiment. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequete linearity over the required range.

  3. A facile HPLC method for optical purity and quantitative measurements of phenylalanine from the hydrolyzed aspartame under different pH and temperature after its derivatization with a fluorescent reagent.

    PubMed

    Hsien, T-J; Chen, S

    2007-07-01

    In this paper, the artificial sweetener aspartame is deliberately hydrolyzed under different pH and temperature in the matrix, and time period for the hydrolysis. The HPLC analysis is then performed to quantitatively measure the amount and the optical purity of phenylalanine produced as a result of hydrolysis in the matrix after its functionalization with a fluorescent reagent. The results show that the amount of phenylalanine in the matrix is affected by the pH variation during the hydrolysis and found increased in low pH conditions. High temperature or long time periods for the decomposition also increases the amount, which indicates that beverages and foods containing aspartame as a sweetener may not be safe for phenylketonuria patients to consume if they are stored under these conditions. Conversely, the optical purity of phenylalanine, expressed as the percentage of D: -enantiomer, is not affected by pH variations. However, it decreases as the length of time elapsed is increased or surrounding temperature is elevated during the decomposition.

  4. Metabolomics relative quantitation with mass spectrometry using chemical derivatization and isotope labeling

    DOE PAGES

    O'Maille, Grace; Go, Eden P.; Hoang, Linh; Want, Elizabeth J.; Smith, Colin; O'Maille, Paul; NordstrÖm, Anders; Morita, Hirotoshi; Qin, Chuan; Uritboonthai, Wilasinee; et al

    2008-01-01

    Comprehensive detection and quantitation of metabolites from a biological source constitute the major challenges of current metabolomics research. Two chemical derivatization methodologies, butylation and amination, were applied to human serum for ionization enhancement of a broad spectrum of metabolite classes, including steroids and amino acids. LC-ESI-MS analysis of the derivatized serum samples provided a significant signal elevation across the total ion chromatogram to over a 100-fold increase in ionization efficiency. It was also demonstrated that derivatization combined with isotopically labeled reagents facilitated the relative quantitation of derivatized metabolites from individual as well as pooled samples.

  5. New osmium-based reagent for the dihydroxylation of alkenes.

    PubMed

    Donohoe, Timothy J; Harris, Robert M; Butterworth, Sam; Burrows, Jeremy N; Cowley, Andrew; Parker, Jeremy S

    2006-06-01

    The cis dihydroxylation of alkenes is most efficiently accomplished by reaction with osmium tetroxide. Recently, the expense and toxicity of osmium tetroxide have led to a number of attempts to harness alternative osmium-based reagents, including microencapsulation and solid support techniques. We describe here the development of a new nonvolatile, stable, and recoverable osmium-based reagent devised for the stoichiometric cis dihydroxylation of alkenes. Although attempts to make this new dihydroxylation work with catalytic amounts of this reagent were unsuccessful, we did develop a sensitive test for free osmium tetroxide leached from the reagent in situ: this test may well have uses in probing future applications of derivatized osmium reagents.

  6. In situ search for organics by gas chromatography analysis: new derivatization / thermochemolysis approach

    NASA Astrophysics Data System (ADS)

    Geffroy, Claude; Buch, Arnaud; David, Marc; Aissat, Lyes; El Mufleh, Amel; Papot, S.; Sternberg, Robert

    Many organic molecules are present in interstellar clouds and might be carried to the early Earth by comets and meteorites during the heavy bombardment phase in the first few hundred million years of the solar system. It has been suggested that extraterrestrial organic material may well represent an important part of the organic material available for the origin of life. Until samples, brought by future space missions, are available on Earth, in situ measurements are one of the way to get unaltered and non-contaminated samples for analysis. The analytical technique has to be robust, sensitive and non-specific due to the large scope of targets molecules. The only currently flight qualified technique of analysis of organic molecules in space is gas chromatography (Viking, Cassini-Huygens, SAM-MSL, COSAC-Rosetta). The main objective of this work is to present a new approach with multi step analysis using derivatisation and thermochemolysis reagents for a one pot in situ analysis of volatile and refractory organics in surface or sub-surface samples (Mars, comets).Indeed, no single technology enables to identify all organic compounds because naturally occurring molecules have different polarities, molecular weights, being extractible or recalcitrant, bonded trapped or adsorbed on minerals. Thus, we propose to wider the scope of chemical reagent already validated for in situ wet chemistry such as MTBSTFA (Rodier et al. 2001, 2002), DMF-DMA (Rodier et al. 2002), or TMAH (Rodier et al, 2005, Geffroy-Rodier et al; 2009) to analyze enantiomers of amino acids, carbohydrates and lipids in a one pot several steps sub system using a multi reagent and multi step approach. Thus using a new derivatizing agent, we successfully identified twenty one amino acids including twelve of the twenty proteinic amino acids without inhibiting following multi step thermochemolysis. *Geffroy-Rodier C, Grasset L, Sternberg R. Buch A. Amblès A. (2009) Thermochemolysis in search for organics in

  7. Post Column Derivatization Using Reaction Flow High Performance Liquid Chromatography Columns.

    PubMed

    Jones, Andrew; Pravadali-Cekic, Sercan; Hua, Stanley; Kocic, Danijela; Camenzuli, Michelle; Dennis, Gary; Shalliker, Andrew

    2016-04-26

    A protocol for the use of reaction flow high performance liquid chromatography columns for methods employing post column derivatization (PCD) is presented. A major difficulty in adapting PCD to modern HPLC systems and columns is the need for large volume reaction coils that enable reagent mixing and then the derivatization reaction to take place. This large post column dead volume leads to band broadening, which results in a loss of observed separation efficiency and indeed detection in sensitivity. In reaction flow post column derivatization (RF-PCD) the derivatization reagent(s) are pumped against the flow of mobile phase into either one or two of the outer ports of the reaction flow column where it is mixed with column effluent inside a frit housed within the column end fitting. This technique allows for more efficient mixing of the column effluent and derivatization reagent(s) meaning that the volume of the reaction loops can be minimized or even eliminated altogether. It has been found that RF-PCD methods perform better than conventional PCD methods in terms of observed separation efficiency and signal to noise ratio. A further advantage of RF-PCD techniques is the ability to monitor effluent coming from the central port in its underivatized state. RF-PCD has currently been trialed on a relatively small range of post column reactions, however, there is currently no reason to suggest that RF-PCD could not be adapted to any existing one or two component (as long as both reagents are added at the same time) post column derivatization reaction.

  8. Tandem MS Analysis of Selenamide-Derivatized Peptide Ions

    PubMed Central

    Zhang, Yun; Zhang, Hao; Cui, Weidong; Chen, Hao

    2013-01-01

    Our previous study showed that selenamide reagents such as ebselen and N-(phenylseleno) phthalimide (NPSP) can be used for selective and rapid derivatization of protein/peptide thiols in high conversion yield. This paper reports the systematic investigation of MS/MS dissociation behaviors of selenamide-derivatized peptide ions upon collision induced dissociation (CID) and electron transfer dissociation (ETD). In the positive ion mode, derivatized peptide ions exhibit tag-dependent CID dissociation pathways. For instance, ebselen-derivatized peptide ions preferentially undergo Se–S bond cleavage upon CID to produce a characteristic fragment ion, the protonated ebselen (m/z 276), which allows selective identification of thiol peptides from protein digest as well as selective detection of thiol proteins from protein mixture using precursor ion scan (PIS). In contrast, NPSP-derivatized peptide ions retain their phenylselenenyl tags during CID, which is useful in sequencing peptides and locating cysteine residues. In the negative ion CID mode, both types of tags are preferentially lost via the Se–S cleavage, analogous to the S–S bond cleavage during CID of disulfide-containing peptide anions. In consideration of the convenience in preparing selenamide-derivatized peptides and the similarity of Se–S of the tag to the S–S bond, we also examined ETD of the derivatized peptide ions to probe the mechanism for electron-based ion dissociation. Interestingly, facile cleavage of Se–S bond occurs to the peptide ions carrying either protons or alkali metal ions, while backbone cleavage to form c/z ions is severely inhibited. These results are in agreement with the Utah-Washington mechanism proposed for depicting electron-based ion dissociation processes. PMID:21953264

  9. Determination of methamphetamine enantiomer composition in human hair by non-chiral liquid chromatography-tandem mass spectrometry method.

    PubMed

    Shu, Irene; Alexander, Amy; Jones, Mary; Jones, Joseph; Negrusz, Adam

    2016-08-15

    Chiral separation is crucial for investigating methamphetamine positive cases. While (S)-(+)-enantiomer of methamphetamine (S-MAMP) is a schedule II controlled substance, (R)-(-)-enantiomer (R-MAMP) is an active ingredient of a few over-the-counter drugs in the United States. Among biological specimen types, hair provides greater detection window than blood, urine or oral fluid, and are therefore regarded with particular interest. Herein we describe a novel non-chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to directly determine methamphetamine enantiomeric composition (percentage) in hair specimens. Hair samples were washed once with acetone, powdered, incubated overnight at 53°C in 0.1M hydrochloric acid (HCl), and subjected to a solid phase extraction (SPE). The extracts were derivatized using Marfey's reagent at 53°C for 60min. The final mixture was analyzed by LC-MS/MS. Chromatographic separation was achieved using a C18 Kinetex analytical column and 60% (v/v) aqueous methanol as mobile phase (isocratic). Triple quadrupole mass spectrometer was equipped with an electro-spray ionization (ESI) source operating in negative mode and the chromatograms were acquired using a multiple-reaction monitoring (MRM) approach. The results were expressed as ratio of R- to S-MAMP and then derived to composition percentages without requiring quantitating each enantiomer. The method was precise and accurate across 0-100% S-composition at a range of 80-18,000pg/mg. The performance of the new method was compared with an (S)-(-)-N-trifluoroacetylprolyl chloride (S-TPC) derivatization and gas chromatography-mass spectrometry (GC-MS) method on authentic methamphetamine-positive hair samples. Not only the new Marfey's reagent approach presented satisfactory correlation with the S-TPC approach, but it also exhibited significantly improved quality (e.g., S/N) of the chromatograms. In summary, our protocol employs cost effective and minimally hazardous Marfey

  10. Development and validation of an LC-MS/MS method after chiral derivatization for the simultaneous stereoselective determination of methylenedioxy-methamphetamine (MDMA) and its phase I and II metabolites in human blood plasma.

    PubMed

    Steuer, Andrea E; Schmidhauser, Corina; Liechti, Matthias E; Kraemer, Thomas

    2015-07-01

    3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is a racemic drug of abuse and its two enantiomers are known to differ in their dose-response curves. The S-enantiomer was shown to be eliminated at a higher rate than the R-enantiomer. The most likely explanation for this is a stereoselective metabolism also claimed in in vitro studies. Urinary excretion studies showed that the main metabolites in humans are 4-hydroxy 3-methoxymethamphetamine (HMMA) 4-sulfate, HMMA 4-glucuronide and 3,4-dihydroxymethamphetamine (DHMA) 3-sulfate. For stereoselective pharmacokinetic analysis of phase I and phase II metabolites in human blood plasma useful analytical methods are needed. Therefore the aim of the presented study was the development and validation of a stereoselective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of MDMA, 3,4-methylenedioxyamphetamine, DHMA, DHMA 3-sulfate, HMMA, HMMA 4-glucuronide, HMMA 4-sulfate, and 4-hydroxy 3-methoxyamphetamine in blood plasma for evaluation of the stereoselective pharmacokinetics in humans. Blood plasma samples were prepared by simple protein precipitation and afterwards all analytes were derivatized using N-(2,4-dinitro-5-fluorophenyl) L-valinamide resulting in the formation of diastereomers which were easily separable on standard reverse phase stationary phases. This simple and fast method was validated according to international guidelines including specificity, recovery, matrix effects, accuracy and precision, stabilities, and limits of quantification. The method proved to be selective, sensitive, accurate and precise for all tested analytes except for DHMA.

  11. Free amino acid quantification by LC-MS/MS using derivatization generated isotope-labelled standards.

    PubMed

    Johnson, David W

    2011-05-15

    The further development of derivatizing reagents for plasma amino acid quantification by tandem mass spectrometry is described. The succinimide ester of 4-methylpiperazineacetic acid (MPAS), the iTRAQ reagent, was systematically modified to improve tandem mass spectrometer (MS/MS) product ion intensity. 4-Methylpiperazinebutyryl succinimide (MPBS) and dimethylaminobutyryl succinimide (DMABS) afforded one to two orders of magnitude greater MS/MS product ion signal intensity than the MPAS derivative for simple amino acids. CD(3) analogues of the modified derivatizing reagents were evaluated for preparation of amino acid isotope-labelled quantifying standards. Acceptable accuracy and precision was obtained with d(3)-DMABS as the amino acid standards derivatizing reagent. The product ion spectra of the DMABS amino acid derivatives are diagnostic for structural isomers including valine/norvaline, alanine/sarcosine and leucine/isoleucine. Improved analytical sensitivity and specificity afforded by these derivatives may help to establish liquid chromatography tandem mass spectrometry (LC-MS/MS) with derivatization generated isotope-labelled standards a viable alternative to amino acids analysers.

  12. Determination of amphetamines in hair by integrating sample disruption, clean-up and solid phase derivatization.

    PubMed

    Argente-García, A; Moliner-Martínez, Y; Campíns-Falcó, P; Verdú-Andrés, J; Herráez-Hernández, R

    2016-05-20

    The utility of matrix solid phase dispersion (MSPD) for the direct analysis of amphetamines in hair samples has been evaluated, using liquid chromatography (LC) with fluorescence detection and precolumn derivatization. The proposed approach is based on the employment of MSPD for matrix disruption and clean-up, followed by the derivatization of the analytes onto the dispersant-sample blend. The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) has been used for derivatization. Different conditions for MSPD, analyte purification and solid phase derivatization have been tested, using amphetamine (AMP), methamphetamine (MET), ephedrine (EPE) and 3,4-methylenedioxymethamphetamine (MDMA) as model compounds. The results have been compared with those achieved by using ultrasound-assisted alkaline digestion and by MSPD combined with conventional solution derivatization. On the basis of the results obtained, a methodology is proposed for the analysis of amphetamines in hair which integrates sample disruption, clean-up and derivatization using a C18 phase. Improved sensitivity is achieved with respect to that obtained by the alkaline digestion or by the MSPD followed by solution derivatization methods. The method can be used for the quantification of the tested amphetamines within the 2.0-20.0ng/mg concentration interval, with limits of detection (LODs) of 0.25-0.75ng/mg. The methodology is very simple and rapid (the preparation of the sample takes less than 15min). PMID:27108048

  13. Determination of amphetamines in hair by integrating sample disruption, clean-up and solid phase derivatization.

    PubMed

    Argente-García, A; Moliner-Martínez, Y; Campíns-Falcó, P; Verdú-Andrés, J; Herráez-Hernández, R

    2016-05-20

    The utility of matrix solid phase dispersion (MSPD) for the direct analysis of amphetamines in hair samples has been evaluated, using liquid chromatography (LC) with fluorescence detection and precolumn derivatization. The proposed approach is based on the employment of MSPD for matrix disruption and clean-up, followed by the derivatization of the analytes onto the dispersant-sample blend. The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) has been used for derivatization. Different conditions for MSPD, analyte purification and solid phase derivatization have been tested, using amphetamine (AMP), methamphetamine (MET), ephedrine (EPE) and 3,4-methylenedioxymethamphetamine (MDMA) as model compounds. The results have been compared with those achieved by using ultrasound-assisted alkaline digestion and by MSPD combined with conventional solution derivatization. On the basis of the results obtained, a methodology is proposed for the analysis of amphetamines in hair which integrates sample disruption, clean-up and derivatization using a C18 phase. Improved sensitivity is achieved with respect to that obtained by the alkaline digestion or by the MSPD followed by solution derivatization methods. The method can be used for the quantification of the tested amphetamines within the 2.0-20.0ng/mg concentration interval, with limits of detection (LODs) of 0.25-0.75ng/mg. The methodology is very simple and rapid (the preparation of the sample takes less than 15min).

  14. Electron Transfer and Collision Induced Dissociation of Non-Derivatized and Derivatized Desmosine and Isodesmosine

    NASA Astrophysics Data System (ADS)

    Ongay, Sara; Hermans, Jos; Bruins, Andries P.; Nieuwendijk, Adrianus M. C. H.; Overkleeft, Hermen; Bischoff, Rainer

    2013-01-01

    Electron transfer dissociation (ETD) has attracted increasing interest due to its complementarity to collision-induced dissociation (CID). ETD allows the direct localization of labile post-translational modifications, which is of main interest in proteomics where differences and similarities between ETD and CID have been widely studied. However, due to the fact that ETD requires precursor ions to carry at least two charges, little is known about differences in ETD and CID of small molecules such as metabolites. In this work, ETD and CID of desmosine (DES) and isodesmosine (IDS), two isomers that due to the presence of a pyridinium group can carry two charges after protonation, are studied and compared. In addition, the influence of DES/IDS derivatization with propionic anhydride and polyethyleneglycol (PEG) reagents on ETD and CID was studied, since this is a common strategy to increase sensitivity and to facilitate the analysis by reversed-phase chromatography. Clear differences between ETD and CID of non-derivatized and derivatized-DES/IDS were observed. While CID is mainly attributable to charge-directed fragmentation, ETD is initiated by the generation of a hydrogen atom at the initial protonation site and its subsequent transfer to the pyridinium ring of DES/IDS. These differences are reflected in the generation of complex CID spectra dominated by the loss of small, noninformative molecules (NH3, CO, H2O), while ETD spectra are simpler and dominated by characteristic side-chain losses. This constitutes a potential advantage of ETD in comparison to CID when employed for the targeted analysis of DES/IDS in biological samples.

  15. Detecting refractory organic matter on Mars: how derivatization will help

    NASA Astrophysics Data System (ADS)

    Freissinet, C.; Kashyap, S.; Glavin, D. P.; Buch, A.; Brault, A.; Mahaffy, P. R.

    2012-12-01

    The search for organic molecules on Mars can provide important first clues of extinct or extant biota on the planet. Gas Chromatography Mass Spectrometry (GC-MS) is currently the most relevant space-compatible analytical tool for the detection of organics. Nevertheless, GC separation is intrinsically restricted to volatile molecules, and a lot of the molecules of exobiological interest are refractory or polar. To analyze these organics such as amino acids, nucleobases and carboxylic acids, an additional derivatization step is required to transform them into volatile derivatives that are amenable to GC analysis. As part of the Sample Analysis at Mars (SAM) experiment onboard Mars Science Laboratory (MSL) Curiosity rover which successfully landed on Mars on August 5, 2012, a single-step protocol of extraction and chemical derivatization with the silylating reagent N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide MTBSTFA has been developed to reach a wide range of astrobiology-relevant refractory organic molecules. Seven cups on SAM are devoted to MTBSTFA derivatization. However, this chemical reaction adds a protective silyl group in place of each labile hydrogen, which make the molecule non-identifiable in common mass spectra libraries. We thus created an extended library of mass spectra of derivatized compounds of interest, considering their potential occurrence in Mars soils. We then looked specifically at these compounds using the existing and the newly created library, in various Mars analog soils. To enable a more accurate interpretation of the in situ derivatization GC-MS results that will be obtained by SAM, the lab experiments are performed in the restrictive conditions of the SAM flight instrument. First experiments display promising results, the system permitting an extraction and detection of several proteinic amino and carboxylic acids from Martian representative matrices. Preliminary results show a lack of derivatized organic molecules in

  16. Handling Pyrophoric Reagents

    SciTech Connect

    Alnajjar, Mikhail S.; Haynie, Todd O.

    2009-08-14

    Pyrophoric reagents are extremely hazardous. Special handling techniques are required to prevent contact with air and the resulting fire. This document provides several methods for working with pyrophoric reagents outside of an inert atmosphere.

  17. Indirect chiral separation of tryptophan enantiomers by high performance liquid chromatography with indirect chemiluminiscence detection.

    PubMed

    Zhou, Jie; Chen, Shanshan; Sun, Fang; Luo, Pei; Du, Qiuzheng; Zhao, Suzhen

    2015-12-01

    In recent years, the study of chiral compounds in vivo has received much attention. In this study, a novel method based on high performance liquid chromatography (HPLC) coupled with chemiluminescence (CL) detection was developed for the separation of tryptophan (Trp) enantiomers. o-Phthalaldehyde and N-acetyl-l-cysteine were used as chiral derivatization reagents for Trp before it can be detected by HPLC-CL method. The separation was carried out on an ODS column using a mobile phase composed of methanol-0.01mol/L phosphate buffer (40/60, v/v). Under the optimum conditions, satisfactory results were obtained, including complete separation, good relative standard deviations and low detection limits. The applicability of the proposed method has been validated by determining Trp in biological samples. Linear responses (r>0.9990) were observed over the range of 2.5×10(-7) to 1.2×10(-5)g/mL of Trp enantiomers, with quantitation limit of 2.5×10(-7)g/mL. The assay method shows good specificity to Trp enantiomers, and thus it will have great potential application in clinical diagnosis. The mean extraction efficiency of Trp enantiomers in mice plasma samples were 98.48% and 97.40%, respectively. The mean relative standard deviation (RSD) of Trp enantiomers were <3%. PMID:26523665

  18. A simple protocol for NMR analysis of the enantiomeric purity of chiral hydroxylamines.

    PubMed

    Tickell, David A; Mahon, Mary F; Bull, Steven D; James, Tony D

    2013-02-15

    A practically simple three-component chiral derivatization protocol for determining the enantiopurity of chiral hydroxylamines by (1)H NMR spectroscopic analysis is described, involving their treatment with 2-formylphenylboronic acid and enantiopure BINOL to afford a mixture of diastereomeric nitrono-boronate esters whose ratio is an accurate reflection of the enantiopurity of the parent hydroxylamine.

  19. Application of the Novel 5-chloro-2,2,3,3,4,4,5,5-octafluoro-1-pentyl Chloroformate Derivatizing Agent for the Direct Determination of Highly Polar Water Disinfection Byproducts

    EPA Science Inventory

    A novel derivatizing agent, 5-chloro-2,2,3,3,4,4,5,5-octafluoropentyl chloroformate (ClOFPCF), was synthesized and tested as a reagent for direct water derivatization of highly polar and hydrophilic analytes. Its analytical performance satisfactorily compared to a perfluorinated ...

  20. A new agent for derivatizing carbonyl species used to investigate limonene ozonolysis

    NASA Astrophysics Data System (ADS)

    Wells, J. R.; Ham, Jason E.

    2014-12-01

    A new method for derivatizing carbonyl compounds is presented. The conversion of a series of dicarbonyls to oximes in aqueous solution and from gas-phase sampling was achieved using O-tert-butylhydroxylamine hydrochloride (TBOX). Some advantages of using this derivatization agent include: aqueous reactions, lower molecular weight oximes, and shortened oxime-formation reaction time. Additionally, the TBOX derivatization technique was used to investigate the carbonyl reaction products from limonene ozonolysis. With ozone (O3) as the limiting reagent, four carbonyl compounds were detected: 7-hydroxy-6-oxo-3-(prop-1-en-2-yl)heptanal; 3-Isopropenyl-6-oxoheptanal (IPOH), 3-acetyl-6-oxoheptanal (3A6O) and one carbonyl of unknown structure. Using cyclohexane as a hydroxyl (OHrad) radical scavenger, the relative yields (peak area) of the unknown carbonyl, IPOH, and 3A6O were reduced indicating the influence secondary OH radicals have on limonene ozonolysis products. The relative yield of the hydroxy-dicarbonyl based on the chromatogram was unchanged suggesting it is only made by the limonene + O3 reaction. The detection of 3A6O using TBOX highlights the advantages of a smaller molecular weight derivatization agent for the detection of multi-carbonyl compounds. The use of TBOX derivatization if combined with other derivatization agents may address a recurring need to simply and accurately detect multi-functional oxygenated species in air.

  1. Selenium Derivatization of Nucleic Acids for Crystallography

    SciTech Connect

    Jiang,J.; Sheng, J.; Carrasco, N.; Huang, Z.

    2007-01-01

    The high-resolution structure of the DNA (5'-GTGTACA-C-3') with the selenium derivatization at the 2'-position of T2 was determined via MAD and SAD phasing. The selenium-derivatized structure (1.28 {angstrom} resolution) with the 2'-Se modification in the minor groove is isomorphorous to the native structure (2.0 {angstrom}). To directly compare with the conventional bromine derivatization, we incorporated bromine into the 5-postion of T4, determined the bromine-derivatized DNA structure at 1.5 {angstrom} resolution, and found that the local backbone torsion angles and solvent hydration patterns were altered in the structure with the Br incorporation in the major groove. Furthermore, while the native and Br-derivatized DNAs needed over a week to form reasonable-size crystals, we observed that the Se-derivatized DNAs grew crystals overnight with high-diffraction quality, suggesting that the Se derivatization facilitated the crystal formation. In addition, the Se-derivatized DNA sequences crystallized under a broader range of buffer conditions, and generally had a faster crystal growth rate. Our experimental results indicate that the selenium derivatization of DNAs may facilitate the determination of nucleic acid X-ray crystal structures in phasing and high-quality crystal growth. In addition, our results suggest that the Se derivatization can be an alternative to the conventional Br derivatization.

  2. Enhancement of the capabilities of liquid chromatography-mass spectrometry with derivatization: general principles and applications.

    PubMed

    Xu, Fengguo; Zou, Li; Liu, Ying; Zhang, Zunjian; Ong, Choon Nam

    2011-01-01

    The integration of liquid chromatography-mass spectrometry (LC-MS) with derivatization is a relatively new and unique strategy that could add value and could enhance the capabilities of LC-MS-based technologies. The derivatization process could be carried out in various analytical steps, for example, sampling, storage, sample preparation, HPLC separation, and MS detection. This review presents an overview of derivatization-based LC-MS strategy over the past 10 years and covers both the general principles and applications in the fields of pharmaceutical and biomedical analysis, biomarker and metabolomic research, environmental analysis, and food-safety evaluation. The underlying mechanisms and theories for derivative reagent selection are summarized and highlighted to guide future studies.

  3. Fluorination, Defluorination, Derivatization and Solvation of Single-Wall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Margrave, John L.

    1999-10-01

    Direct fluorination has been used to create fluoronanotubes which have active sites for derivatizing carbon nanotubes. A new technique using hydrazine and its derivatives has been used for defluorination of fluoronanotubes. The products include N2 and HF. Fluorinated species can be derivatized with R-Li or Grignard Reagents to form inorganic fluorides and derivatized products e.g., methyl, butyl or hexyl-nanotubes, (NH2)x-nanotubes, etc. Mass-spectra IR and Raman spectra along with electron microprobe analyses have been utilized, along with AFM, SEM and TEM to characterize the products. ``Fluorotubes" can be solvated as individual tubes in various alcohol solvents via ultrasonication. These solutions persist long enough (over a week) to permit solution phase chemistry to be carried out on the fluorotubes. For example, the solvated fluorotubes can be precipitated out of solution with hydrazine to yield normal, unfluorinated SWNTs or they can be reacted with sodium methoxide to yield methoxylated SWNTs.

  4. Chiral squaring

    NASA Astrophysics Data System (ADS)

    Nagy, S.

    2016-07-01

    We construct the states and symmetries of N = 4 super-Yang-Mills by tensoring two N = 1 chiral multiplets and introducing two extra SUSY generators. This allows us to write the maximal N = 8 supergravity as four copies of the chiral multiplet. We extend this to higher dimensions and discuss applications to scattering amplitudes.

  5. Microfluidic lab-on-a-chip derivatization for gaseous carbonyl analysis.

    PubMed

    Pang, Xiaobing; Lewis, Alastair C; Ródenas-García, Milagros

    2013-06-28

    We present a microfluidic lab-on-a-chip derivatization technique for the analysis of gaseous carbonyl compounds using O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) as the derivatizing reagent. The novel microfluidic lab-on-a-chip derivatization technique has been developed to measure nmol per mole (ppbv) mixing ratios of gaseous carbonyl compounds, which are of particular importance to atmospheric chemistry. The technique utilised a planar glass microreactor comprising three inlets and one outlet, gas and fluid splitting and combining channels, mixing junctions, and a 2.0m long, 620μm internal diameter reaction microchannel. The microreactor integrated three functions, providing: (1) a gas and liquid mixer and reactor, (2) reagent heating, and (3) sample pre-concentration. The concentration of derivatization solution, the volumetric flow rates of the incoming gas sample and PFBHA solution, and the temperature of the microreactor were optimised to achieve a near real-time measurement. The enhanced phase contact area-to-volume ratio and the high heat transfer rate in the microreactor resulted in a fast and high efficiency derivatization reaction, generating an effluent stream which was ready for direct introduction to GC-MS. Good linearity was observed for eight carbonyl compounds over the measurement ranges of 1-500ppbv when they were derivatized under optimal reaction conditions. The method detection limits (MDLs) were below 0.10nmolmol(-1) for most carbonyls in this study, which is below or close to their typical concentrations in clean ambient air. The performance of the technique was assessed by applying the methodology to the quantification of glyoxal (GLY) and methylglyoxal (MGLY) formed during isoprene photo-oxidation in an outdoor photoreactor chamber (EUPHORE). Good agreements between GLY and MGLY measurements were obtained comparing this new technique with Fourier Transform InfraRed (FTIR), which provides support for the potential effectiveness of

  6. In-capillary derivatization and capillary electrophoresis separation of amino acid neurotransmitters from brain microdialysis samples.

    PubMed

    Denoroy, Luc; Parrot, Sandrine; Renaud, Louis; Renaud, Bernard; Zimmer, Luc

    2008-09-26

    A new in-capillary derivatization method with naphtalene-2,3-dicarboxyaldehyde (NDA)/CN(-) has been developed for capillary electrophoresis with laser-induced fluorescence detection of brain microdialysate amino acids. Samples are sandwiched between two plugs of reagent mixture at the capillary inlet and subsequently separated. Highest derivatization yields are obtained by using a reagent to sample plug length ratio equal to 4, performing a first electrophoretic mixing followed by a zero potential amplification step before applying the separation voltage and using a NaCN to NDA concentration ratio equal to 1. This new single-step methodology allows the analysis of amino acid neurotransmitters in rat brain microdialysis samples.

  7. Chemical synthesis of water-soluble, chiral conducting-polymer complexes

    DOEpatents

    Wang, Hsing-Lin; McCarthy, Patrick A.; Yang, Sze Cheng

    2003-01-01

    The template-guided synthesis of water-soluble, chiral conducting polymer complexes is described. Synthesis of water-soluble polyaniline complexes is achieved by carefully controlling the experimental parameters such as; acid concentration, ionic strength, monomer/template ratio, total reagent concentration, and order of reagent addition. Chiral (helical) polyaniline complexes can be synthesized by addition of a chiral inducing agent (chiral acid) prior to polymerization, and the polyaniline helix can be controlled by the addition of the (+) or (-) form of the chiral acid. Moreover the quantity of chiral acid and the salt content has a significant impact on the degree of chirality in the final polymer complexes. The polyaniline and the template have been found to be mixed at the molecular level which results in chiral complexes that are robust through repeated doping and dedoping cycles.

  8. p-Tolyl isocyanate derivatization for analysis of CWC-related polar degradation products by mass spectrometry.

    PubMed

    Karthikraj, R; Sridhar, L; Murty, M R V S; Raju, N P; Vairamani, M; Prabhakar, S

    2014-08-01

    Most of the precursors and/or degradation products related to the Chemical Weapons Convention (CWC) are polar. Identification of these molecules in environmental samples provides clues regarding the alleged usage and/or synthesis of the parent toxic chemicals. Such polar compounds need to be derivatized in order to analyze them by gas chromatography-mass spectrometry (GC-MS). In this study, we developed a new derivatizing reagent, para-tolyl isocyanate (PTI), for derivatization of polar CWC-related compounds. The PTI reagent selectively derivatizes the -OH and/or-SH functional groups with high efficiency, but does not react with carboxylic acid (-COOH) or phosphonic acid (-(O)P(OH)2) groups. The PTI derivatives of dialkyl aminoethanols, dialkyl aminoethanol-N-oxides, and 3-quinuclidinol were successfully eluted through GC, and their electron ionization (EI) mass spectra were distinct and provided the structure information by which the isomeric compounds can be easily distinguished. We also calculated the GC-retention index values that can be used for further confirmation of the target compounds. All the studied PTI derivatives can be analyzed by EI-MS with direct insertion probe and/or by direct electrospray ionization mass spectrometry (ESI-MS) together with the MS-MS data; both sets of data provide full structure information. The PTI reagent was found to be better in some respects than the conventional bistrimethylsilyl trifluoroacetamide (BSTFA), a trimethyl silylating reagent. The PTI reagent is commercially available, and the PTI derivatives are highly stable for months and are not sensitive to moisture. The applicability of the PTI derivatization for trace-level determination of the target CWC-related polar compounds in environmental matrices and in human plasma samples is also evaluated.

  9. [Applications of multi-micro-volume pressure-assisted derivatization reaction device for analysis of polar heterocyclic aromatic amines by gas chromatography-mass spectrometry].

    PubMed

    Wang, Yiru; Chen, Fangxiang; Shi, Yamei; Tan, Connieal; Chen, Xi

    2013-01-01

    A multi-micro-volume pressure-assisted derivatization reaction device has been designed and made for the silylation derivatization of polar heterocyclic aromatic amines by N-(tert-butyldimethylsilyl )-N-methyl-trifluoroacetamide (MTBSTFA) with 1% catalyst tert-butyldimethylchlorosilane (TBDMCS) at a high temperature. The tert-butyldimethylsilyl derivatives then could be automatically analyzed by gas chromatography-mass spectrometry. Using the pressure-assisted device, the silylation reaction may occur at a temperature higher than the boiling points of the reagents, and several micro-volume samples can be simultaneously pretreated in the same device to shorten the sample-preparation time and to improve the repeatability. The derivatization conditions including the headspace volume of the vial, the evaporative surface area of the reagent, derivatization temperature and time have been discussed for the use of the pressure-assisted device. The experimental results proved that the device is an effective way for the simultaneous derivatization of several micro-volume samples at a high temperature. Compared with a common device, the derivative amounts were obviously increased when using the pressure-assisted device at 90 degrees C. Quantitative derivatization can be achieved even at 150 degrees C while there was no common device could be applied at such a high temperature due to the heavy losses of reagents by evaporation. However, no obviously higher reaction speed has been observed in such a circumstance with a higher temperature and a higher pressure using the pressure-assisted device. PMID:23667982

  10. Chiral oxime ethers in asymmetric synthesis. O-(1-Phenylbutyl)benzyloxyacetaldoxime, a versatile reagent for the asymmetric synthesis of protected 1,2-aminoalcohols, alpha-amino acid derivatives, and 2-hydroxymethyl nitrogen heterocycles including iminosugars.

    PubMed

    Cooper, Tracey S; Larigo, Alexander S; Laurent, Pierre; Moody, Christopher J; Takle, Andrew K

    2005-04-01

    Addition of a range of organolithium and Grignard reagents to (E)-O-(1-phenylbutyl)benzyloxyacetaldoxime 1 in the presence of boron trifluoride diethyl etherate is highly diastereoselective. The resulting hydroxylamines undergo N-O bond cleavage upon treatment with zinc-acetic acid or molybdenum hexacarbonyl to give, after N-protection, protected 1,2-aminoalcohols 3 in high enantiomeric purity. Debenzylation of 3a and 3d gave N-Boc (R)-alaninol and (S)-phenylalaninol respectively. The hydroxylamines 2 also serve as alpha-amino acid precursors, 2i being converted into N-formyl-(R)-alaninyl-(S)-(4-bromo)phenylalanine ester 7, the N-terminal dipeptide of a natural depsipeptide. The versatility of the 1,2-aminoalcohol derivatives was further illustrated by their conversion into 5-, 6- and 7-membered 2-hydroxymethyl nitrogen heterocycles 15-19 in high enantiomeric excess by a ring-closing metathesis reaction. Further reaction of the dihydropyrrole 15 gave the iminosugar 1,4-dideoxy-1,4-imino-D-ribitol. PMID:15785815

  11. A Methodology for Simultaneous Fluorogenic Derivatization and Boronate Affinity Enrichment of 3-Nitrotyrosine Containing Peptides

    PubMed Central

    Dremina, Elena S.; Li, Xiaobao; Galeva, Nadezhda A.; Sharov, Victor S.; Stobaugh, John F.; Schöneich, Christian

    2011-01-01

    We synthesized and characterized a new tagging reagent, (3R,4S)-1-(4-(aminomethyl)phenylsulfonyl)pyrrolidine-3,4-diol (APPD), for the selective fluorogenic derivatization of 3-nitrotyrosine (3-NT) residues in peptides (after reduction to 3-aminotyrosine) and affinity enrichment. The synthetic 3-NT-containing peptide, FSAY(3-NO2)LER, was employed as a model for method validation. Further, this derivatization protocol was successfully tested for analysis of 3-NT-containing proteins exposed to peroxynitrite in the total protein lysate of cultured C2C12 cells. The quantitation of 3-NT content in samples was achieved through either fluorescence spectrometry or boronate affinity chromatography with detection by specific fluorescence (excitation and emission wavelengths of 360 and 510 nm, respectively); the respective limits of detection were 95 and 68 nM (19 and 13 pmol total amount) of 3-NT. Importantly, the derivatized peptides show a strong retention on a synthetic boronate affinity column, containing sulfonamide-phenylboronic acid, under mild chromatographic conditions, affording a route to separate the derivatized peptides from large amounts (milligrams) of non-derivatized peptides, and to enrich them for fluorescent detection and MS identification. Tandem MS analysis identified chemical structures of peptide 3-NT fluorescent derivatives and revealed that the fluorescent derivatives undergo efficient backbone fragmentations, permitting sequence-specific identification of protein nitration at low concentrations of 3-NT in complex protein mixtures. PMID:21855526

  12. Evaporative Derivatization of Phenols with 2-Sulfobenzoic Anhydride for Detection by MALDI-MS

    PubMed Central

    Yao, Yuanyuan; Wang, Poguang; Giese, Roger

    2014-01-01

    RATIONALE Phenols are an important class of analytes, for example as bioactive environmental contaminants. Towards a goal of improving their detection by MALDI-TOF-MS or MALDI-TOF/TOF-MS, we studied their derivatization with 2-sulfobenzoic anhydride (SBA). We chose SBA for this purpose since it is commercially available, inexpensive, and forms an anionic derivative. METHODS In selected conditions developed here for phenols, a reaction mixture of one or more of such compounds in acetonitrile containing SBA and 4-dimethylaminopyridine (DMAP) is evaporated to a solid, heated at 60°C for 1 h, redissolved in 50% acetonitrile containing matrix, spotted onto a MALDI target, and subjected to negative ion MALDI-TOF/TOF-MS. RESULTS While conventional (solution-phase) reaction of 4-phenylphenol (model analyte) with SBA and DMAP only gave a 47% yield of SBA-tagged 4-phenylphenol, evaporative derivatization as above gave a 96% yield, and 25 pmol (4.3 ng) of 4-phenylphenol could be detected in this way by MALDI-TOF/TOF-MS at S/N = 260, whereas even 1 nmol of the nonderivatized phenol was not detected in the absence of derivatization. A wide range of responses was observed when a mixture of 15 phenols was derivatized, with the higher responses coming from phenols with a pKa value above 9. Without derivatization, phenols with pKa values below 5 were the most readily detected. CONCLUSION Evaporative derivatization with SBA (a convenient reagent) can improve the detection of phenols with relatively high pKa values (above 9) by negative ion MALDI-TOF-MS, and accomplish this in the absence of post-derivatization reaction cleanup. PMID:24519828

  13. Nuclear Chirality

    SciTech Connect

    Starosta, Krzysztof

    2005-04-05

    Nuclear chirality is a novel manifestation of spontaneous symmetry breaking resulting from an orthogonal coupling of angular momentum vectors in triaxial nuclei. Three perpendicular angular momenta can form two systems of opposite handedness; the time reversal operator, which reverses orientation of each of the angular momentum components, relates these two systems. The status of current experimental searches for chiral doubling of states, as well as recent progress on the theoretical side is reviewed.

  14. Isotopic chirality

    SciTech Connect

    Floss, H.G.

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  15. Chemical Derivatization of Peptide Carboxyl Groups for Highly Efficient Electron Transfer Dissociation

    NASA Astrophysics Data System (ADS)

    Frey, Brian L.; Ladror, Daniel T.; Sondalle, Samuel B.; Krusemark, Casey J.; Jue, April L.; Coon, Joshua J.; Smith, Lloyd M.

    2013-11-01

    The carboxyl groups of tryptic peptides were derivatized with a tertiary or quaternary amine labeling reagent to generate more highly charged peptide ions that fragment efficiently by electron transfer dissociation (ETD). All peptide carboxyl groups—aspartic and glutamic acid side-chains as well as C-termini—were derivatized with an average reaction efficiency of 99 %. This nearly complete labeling avoids making complex peptide mixtures even more complex because of partially-labeled products, and it allows the use of static modifications during database searching. Alkyl tertiary amines were found to be the optimal labeling reagent among the four types tested. Charge states are substantially higher for derivatized peptides: a modified tryptic digest of bovine serum albumin (BSA) generates ~90% of its precursor ions with z > 2, compared with less than 40 % for the unmodified sample. The increased charge density of modified peptide ions yields highly efficient ETD fragmentation, leading to many additional peptide identifications and higher sequence coverage (e.g., 70 % for modified versus only 43 % for unmodified BSA). The utility of this labeling strategy was demonstrated on a tryptic digest of ribosomal proteins isolated from yeast cells. Peptide derivatization of this sample produced an increase in the number of identified proteins, a >50 % increase in the sequence coverage of these proteins, and a doubling of the number of peptide spectral matches. This carboxyl derivatization strategy greatly improves proteome coverage obtained from ETD-MS/MS of tryptic digests, and we anticipate that it will also enhance identification and localization of post-translational modifications.

  16. Chemical derivatization of peptide carboxyl groups for highly efficient electron transfer dissociation

    PubMed Central

    Frey, Brian L.; Ladror, Daniel T.; Sondalle, Samuel B.; Krusemark, Casey J.; Jue, April L.; Coon, Joshua J.; Smith, Lloyd M.

    2013-01-01

    The carboxyl groups of tryptic peptides were derivatized with a tertiary or quaternary amine labeling reagent to generate more highly charged peptide ions that fragment efficiently by electron transfer dissociation (ETD). All peptide carboxyl groups—aspartic and glutamic acid side-chains as well as C-termini—were derivatized with an average reaction efficiency of 99%. This nearly complete labeling avoids making complex peptide mixtures even more complex due to partially-labeled products, and it allows the use of static modifications during database searching. Alkyl tertiary amines were found to be the optimal labeling reagent among the four types tested. Charge states are substantially higher for derivatized peptides: a modified tryptic digest of bovine serum albumin (BSA) generates ∼90% of its precursor ions with z > 2, compared to less than 40% for the unmodified sample. The increased charge density of modified peptide ions yields highly efficient ETD fragmentation, leading to many additional peptide identifications and higher sequence coverage (e.g. 70% for modified versus only 43% for unmodified BSA). The utility of this labeling strategy was demonstrated on a tryptic digest of ribosomal proteins isolated from yeast cells. Peptide derivatization of this sample produced an increase in the number of identified proteins, a >50% increase in the sequence coverage of these proteins, and a doubling of the number of peptide spectral matches. This carboxyl derivatization strategy greatly improves proteome coverage obtained from ETD-MS/MS of tryptic digests, and we anticipate that it will also enhance identification and localization of post-translational modifications. PMID:23918461

  17. Prebiotic chirality

    NASA Astrophysics Data System (ADS)

    Mekki-Berrada, Ali

    Bringing closer phospholipids each other on a bilayer of liposome, causes their rotation around their fatty acids axis, generating a force which brings closer the two sheets of the bilayer. In this theoretical study I show that for getting the greater cohesion of the liposome, by these forces, the serine in the hydrophilic head must have a L chirality. In the case where the hydrophilic head is absent amino acids with L chirality could contribute to this cohesion by taking the place of L-serine. Some coenzymes having a configuration similar to ethanolamine may also contribute. This is the case of pyridoxamine, thiamine and tetrahydrofolic acid. The grouping of amino acids of L chirality and pyridoxamine on the wall could initialize the prebiotic metabolism of these L amino acids only. This would explain the origin of the homo-chirality of amino acids in living world. Furthermore I show that in the hydrophilic head, the esterification of glycerol-phosphate by two fatty acids go through the positioning of dihydroxyacetone-phosphate and L-glyceraldehyde-3-phosphate, but not of D-glyceraldehyde-3-phosphate, prior their hydrogenation to glycerol-3- phosphate. The accumulation of D-glyceraldehyde-3-phosphate in the cytoplasm displace the thermodynamic equilibria towards the synthesis of D-dATP from D-glyceraldehyde-3-phosphate, acetaldehyde and prebiotic adenine, a reaction which does not require a coenzyme in the biotic metabolism. D-dATP and thiamine, more prebiotic metabolism of L-amino acids on the wall, would initialize D-pentoses phosphate and D-nucleotides pathways from the reaction of D-glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate + prebiotic nucleic bases. The exhaustion of the prebiotic glyceraldehyde (racemic) and the nascent biotic metabolism dominated by D-glyceraldehyde-3-phosphate, would explain the origin of homo-chirality of sugars in living world. References: http://en.wikiversity.org/wiki/Prebiotic_chirality

  18. [Analyses of biogenic related compounds based on intramolecular excimer-forming fluorescence derivatization].

    PubMed

    Yoshida, Hideyuki

    2003-08-01

    A highly selective and sensitive method based on a novel concept is introduced for the assay of biological substances. This method is based on an intramolecular excimer-forming fluorescence derivatization with a pyrene reagent, followed by reverse-phase HPLC. Polyamines, polyphenols, and dicarboxylic acids, which have two or more reactive functional groups in a molecule, were converted to the corresponding polypyrene-labeled derivatives by reaction with the appropriate pyrene reagent. The derivatives exhibited intramolecular excimer fluorescence (440-520 nm), which can clearly be discriminated from the monomer (normal) fluorescence (360-420 nm) emitted by pyrene reagents and monopyrene-labeled derivatives of monofunctional compounds. With excimer fluorescence detection, highly selective and sensitive determination of polyamines, polyphenols, and dicarboxylic acids can be achieved. Furthermore, the methods were successfully applied to the determination of various biological and environmental substances in real samples, which require only a small amount of sample and simple pretreatment.

  19. Intelligent chiral sensing based on supramolecular and interfacial concepts.

    PubMed

    Ariga, Katsuhiko; Richards, Gary J; Ishihara, Shinsuke; Izawa, Hironori; Hill, Jonathan P

    2010-01-01

    Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized.

  20. Intelligent Chiral Sensing Based on Supramolecular and Interfacial Concepts

    PubMed Central

    Ariga, Katsuhiko; Richards, Gary J.; Ishihara, Shinsuke; Izawa, Hironori; Hill, Jonathan P.

    2010-01-01

    Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized. PMID:22163577

  1. Electrophilic, Activation-Free Fluorogenic Reagent for Labeling Bioactive Amines.

    PubMed

    Sintes, Miquel; De Moliner, Fabio; Caballero-Lima, David; Denning, David W; Read, Nick D; Kielland, Nicola; Vendrell, Marc; Lavilla, Rodolfo

    2016-06-15

    Herein we report the preparation of BODIPY mesoionic acid fluorides through a short sequence involving an isocyanide multicomponent reaction as the key synthetic step. These novel BODIPY acid fluorides are water-stable electrophilic reagents that can be used for the fluorescent derivatization of amine-containing biomolecules using mild and activation-free reaction conditions. As a proof of principle, we have labeled the antifungal natamycin and generated a novel fluorogenic probe for imaging a variety of human and plant fungal pathogens, with excellent selectivity over bacterial cells. PMID:27248580

  2. LC-MS determination of bioactive molecules based upon stable isotope-coded derivatization method.

    PubMed

    Toyo'oka, Toshimasa

    2012-10-01

    Liquid chromatography (LC) coupled with mass spectrometry (MS) has been widely used for the analyses of various molecules in many research fields. The electrospray ionization of MS has contributed to the advancement of the LC-MS and LC-MS/MS methods. However, the detection sensitivity is not always sufficient in biological samples, in spite of the highly sensitive ionization method. To increase the sensitivity, chemical derivatization, providing ionization enhancement and avoiding the matrix effect, is effective for various functional groups in the target molecules. However, the accuracy and precision by the determination is sometimes insufficient, especially in complex matrices. In such a case, stable isotope-labeled analogs are often used as the internal standards for the determination of the analytes. When the target compound in samples is limited, a high accuracy and precision is usually obtained by the isotope dilution method. However, the use of individual isotope standards is very difficult for the analyses of multiple molecules in complex matrices. Instead of the use of an isotope analog of the analytes, the differential isotope labeling method based upon chemical derivatization (stable isotope-coded derivatization) (ICD) by both reagents possessing different isotopes is realized. The ICD technique utilizing mass-different isotope tags is known to be an efficient means for metabolite profiling analyses. Thus, the present paper reviews the ICD method reported in the past 10 years. The species of the ICD reagents, their features and the applications to biological specimens are also described in this review.

  3. Diastereoselective Radical Hydroacylation of Alkylidenemalonates with Aliphatic Aldehydes Initiated by Photolysis of Hypervalent Iodine(III) Reagents.

    PubMed

    Selvakumar, Sermadurai; Sakamoto, Ryu; Maruoka, Keiji

    2016-05-01

    Diastereoselective radical hydroacylation of chiral alkylidenemalonates with aliphatic aldehydes is realized by the combination of a hypervalent iodine(III) reagent and UV-light irradiation. The reaction is initiated by the photolysis of hypervalent iodine(III) reagents under mild, metal-free conditions, and is the first example of diastereoselective addition of acyl radicals to olefins to afford chiral ketones in a highly stereoselective fashion. The obtained optically active ketones are useful chiral synthons, as exemplified by the short formal synthesis of (-)-methyleneolactocin.

  4. In situ Analysis of Organic Compounds on Mars using Chemical Derivatization and Gas Chromatography Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Buch, A.; Cabane, M.; Coll, P.; Navarro-Gonzalez, R.; Mahaffy, P. R.

    2005-01-01

    One of the core science objectives of NASA's 2009 Mars Science Laboratory (MSL) mission is to determine the past or present habitability of Mars. The search for key organic compounds relevant to terrestrial life will be an important part of that assessment. We have developed a protocol for the analysis of amino acids and carboxylic acids in Mars analogue materials using gas chromatography mass spectrometry (GCMS). As shown, a variety of carboxylic acids were readily identified in soil collected from the Atacama Desert in Chile at part-per-billion levels by GCMS after extraction and chemical derivatization using the reagent N,N-tert.-butyl (dimethylsilyl) trifluoroacetamide (MTBSTFA). Several derivatized amino acids including glycine and alanine were also detected by GCMS in the Atacama soil at lower concentrations (chromatogram not shown). Lacking derivatization capability, the Viking pyrolysis GCMS instruments could not have detected amino acids and carboxylic acids, since these non-volatile compounds require chemical transformation into volatile species that are stable in a GC column. We are currently optimizing the chemical extraction and derivatization technique for in situ GCMS analysis on Mars. Laboratory results of analyses of Atacama Desert samples and other Mars analogue materials using this protocol will be presented.

  5. A methodology for simultaneous fluorogenic derivatization and boronate affinity enrichment of 3-nitrotyrosine-containing peptides.

    PubMed

    Dremina, Elena S; Li, Xiaobao; Galeva, Nadezhda A; Sharov, Victor S; Stobaugh, John F; Schöneich, Christian

    2011-11-15

    We synthesized and characterized a new tagging reagent, (3R,4S)-1-(4-(aminomethyl)phenylsulfonyl)pyrrolidine-3,4-diol (APPD), for the selective fluorogenic derivatization of 3-nitrotyrosine (3-NT) residues in peptides (after reduction to 3-aminotyrosine) and affinity enrichment. The synthetic 3-NT-containing peptide, FSAY(3-NO(2))LER, was employed as a model for method validation. Furthermore, this derivatization protocol was successfully tested for analysis of 3-NT-containing proteins exposed to peroxynitrite in the total protein lysate of cultured C2C12 cells. The quantitation of 3-NT content in samples was achieved through either fluorescence spectrometry or boronate affinity chromatography with detection by specific fluorescence (excitation and emission wavelengths of 360 and 510 nm, respectively); the respective limits of detection were 95 and 68 nM (19 and 13 pmol total amount) of 3-NT. Importantly, the derivatized peptides show a strong retention on a synthetic boronate affinity column, containing sulfonamide-phenylboronic acid, under mild chromatographic conditions, affording a route to separate the derivatized peptides from large amounts (milligrams) of nonderivatized peptides and to enrich them for fluorescent detection and mass spectrometry (MS) identification. Tandem MS analysis identified chemical structures of peptide 3-NT fluorescent derivatives and revealed that the fluorescent derivatives undergo efficient backbone fragmentations, permitting sequence-specific identification of protein nitration at low concentrations of 3-NT in complex protein mixtures. PMID:21855526

  6. Technical Note: In-situ derivatization thermal desorption GC-TOFMS for direct analysis of particle-bound non-polar and polar organic species

    NASA Astrophysics Data System (ADS)

    Orasche, J.; Schnelle-Kreis, J.; Abbaszade, G.; Zimmermann, R.

    2011-09-01

    An in-situ derivatization thermal desorption method followed by gas chromatography and time-of-flight mass spectrometry (IDTD-GC-TOFMS) was developed for determination of polar organic compounds together with non-polar compounds in one measurement. Hydroxyl and carboxyl groups of compounds such as anhydrous sugars, alcohols and phenols, fatty acids and resin acids are targets of the derivatization procedure. Derivatization is based on silylation with N-Methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA) during the step of thermal desorption. The high temperature of 300 °C during desorption is utilized for the in-situ derivatization on the collection substrate (quartz fibre filters) accelerating the reaction rate. Thereby, the analysis time is as short as without derivatization. At first the filter surface is dampened with derivatization reagent before insertion of the sample into the thermal desorption unit. To ensure ongoing derivatization during thermal desorption the carrier gas is enriched with MSTFA until the desorption procedure is finished. The precisions of all studied analytes were below 17 % within a calibration range from 22 pg (abietic acid) up to 342 ng (levoglucosan). Limits of quantification (LOQ) for polycyclic aromatic hydrocarbons (PAH) were between 1 pg (fluoranthene) and 8 pg (indeno[1,2,3-cd]pyrene), for resin acids 37-102 pg and for studied phenols 4-144 pg. LOQ for levoglucosan was 17 pg.

  7. Technical Note: In-situ derivatization thermal desorption GC-TOFMS for direct analysis of particle-bound non-polar and polar organic species

    NASA Astrophysics Data System (ADS)

    Orasche, J.; Schnelle-Kreis, J.; Abbaszade, G.; Zimmermann, R.

    2011-05-01

    An in-situ derivatization thermal desorption method followed by gas chromatography and time-of-flight mass spectrometry (IDTD-GC-TOFMS) was developed for determination of polar organic compounds. Hydroxyl and carboxyl groups of compounds such as anhydrous sugars, alcohols and phenols, fatty acids and resin acids are targets of the derivatization procedure. Derivatization is based on silylation with N-Methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA) during the step of thermal desorption. The high temperature of 300 °C during desorption is utilized for the in-situ derivatization on the collection substrate (quartz fibre filters) accelerating the reaction rate. Thereby, the analysis time is as short as without derivatization. At first the filter surface is dampened with derivatization reagent before insertion of the sample into the thermal desorption unit. To ensure ongoing derivatization during thermal desorption the carrier gas is saturated with MSTFA until the desorption procedure is finished. The method introduced here was compared with direct thermal desorption gas chromatography time-of-flight-mass spectrometry (DTD-GC-TOFMS) and with solvent extraction (SE) procedures followed by gas chromatography and mass spectrometry. Comparisons were carried out with field samples originating from ambient aerosol collected on quartz fibre filters. Moreover, the methods have been applied on NIST Standard Reference Material Urban Dust (SRM 1649a).

  8. On-matrix derivatization extraction of chemical weapons convention relevant alcohols from soil.

    PubMed

    Chinthakindi, Sridhar; Purohit, Ajay; Singh, Varoon; Dubey, D K; Pardasani, Deepak

    2013-10-11

    Present study deals with the on-matrix derivatization-extraction of aminoalcohols and thiodiglycols, which are important precursors and/or degradation products of VX analogues and vesicants class of chemical warfare agents (CWAs). The method involved hexamethyldisilazane (HMDS) mediated in situ silylation of analytes on the soil. Subsequent extraction and gas chromatography-mass spectrometry analysis of derivatized analytes offered better recoveries in comparison to the procedure recommended by the Organization for the Prohibition of Chemical Weapons (OPCW). Various experimental conditions such as extraction solvent, reagent and catalyst amount, reaction time and temperature were optimized. Best recoveries of analytes ranging from 45% to 103% were obtained with DCM solvent containing 5%, v/v HMDS and 0.01%, w/v iodine as catalyst. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes ranged from 8 to 277 and 21 to 665ngmL(-1), respectively, in selected ion monitoring mode.

  9. Solid supported in situ derivatization extraction of acidic degradation products of nerve agents from aqueous samples.

    PubMed

    Chinthakindi, Sridhar; Purohit, Ajay; Singh, Varoon; Tak, Vijay; Dubey, D K; Pardasani, Deepak

    2014-09-12

    This study deals with the solid supported in situ derivatization extraction of acidic degradation products of nerve agents present in aqueous samples. Target analytes were alkyl alkylphosphonic acids and alkylphosphonic acids, which are important environmental signatures of nerve agents. The method involved tert-butyldimethylchlorosilane mediated in situ silylation of analytes on commercially available diatomaceous solid phase extraction cartridges. Various parameters such as derivatizing reagent, its concentration, reaction time, temperature and eluting solvent were optimized. Recoveries of the analytes were determined by GC-MS which ranged from 60% to 86%. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 78 and 213ngmL(-1) respectively, in selected ion monitoring mode. The successful applicability of method was also demonstrated on samples of biological origin such as plasma and to the samples received in 34th official proficiency test conducted by the Organization for Prohibition the of Chemical Weapons. PMID:25103280

  10. Chiral streamers

    SciTech Connect

    Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya

    2015-10-15

    The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.

  11. Determination of residual arsenic compounds in chicken muscle by ultra-performance liquid chromatography coupled with ultraviolet detection after pre-column derivatization with toluene-3,4-dithiol.

    PubMed

    Eom, Han Young; Yang, Dong-Hyug; Suh, Joon Hyuk; Kim, Unyong; Kim, Junghyun; Cho, Hyun-Deok; Han, Sang Beom

    2015-12-01

    A simple and sensitive derivatization method using toluene-3,4-dithiol as a derivatization reagent for the simultaneous analysis of seven arsenic compounds (roxarsone, nitarsone, p-arsanilic acid, o-arsanilic acid, phenylarsonic acid, phenylarsine oxide, and mono-methylarsonic acid) in chicken muscle was developed and validated by ultra-performance liquid chromatography coupled with ultraviolet detection (UPLC-UV). The structure of the derivatized arsenic compounds was confirmed by liquid chromatography-ion trap mass spectrometry or gas chromatography-mass spectrometry. Optimization of the derivatization reaction conditions was carried out by investigating the influence of reagent concentration, buffer or additive acids, temperature, and time. The optimized conditions were a derivatization reagent concentration of 20mg/mL with 0.05mol/L HCl as an additive acid at 60°C for 15min. In this study, baseline separation of arsenic compounds could be achieved within 13min, except for phenylarsonic acid and phenylarsine oxide whose derivatized products are equal. The developed method was successfully validated and applied to 12 chicken muscle samples from Korean districts and other countries.

  12. Enantioselective Oxidative Rearrangements with Chiral Hypervalent Iodine Reagents

    PubMed Central

    Brown, Michael; Kumar, Ravi; Rehbein, Julia

    2016-01-01

    Abstract A stereoselective hypervalent iodine‐promoted oxidative rearrangement of 1,1‐disubstituted alkenes has been developed. This practically simple protocol provides access to enantioenriched α‐arylated ketones without the use of transition metals from readily accessible alkenes. PMID:26800241

  13. Derivatization of haemoglobin with periodate-generated reticulation agents: evaluation of oxidative reactivity for potential blood substitutes.

    PubMed

    Deac, Florina; Iacob, Bianca; Fischer-Fodor, Eva; Damian, Grigore; Silaghi-Dumitrescu, Radu

    2011-01-01

    Periodate modification of the sugar moiety in sugars, including adenosine triphosphate (ATP), has previously been employed in order to prepare dialdehyde-type reagents, which were then utilized in crosslinking reactions on haemoglobin, yielding polymerized material with useful dioxygen-binding properties and hence proposed as possible artificial oxygen carriers ('blood substitutes'). Here, the periodate protocol is shown to be applicable to a wider range of oxygen-containing compounds, illustrated by starch and polyethylene glycol. Derivatization protocols are described for haemoglobin with such periodate-treated crosslinking agents, and the dioxygen-binding properties and redox reactivities are investigated for the derivatized haemoglobins, with emphasis on pro-oxidative properties. There is a general tendency of the derivatization to result in higher autooxidation rates. The peroxide reactivity of the met (ferric) form is also affected by derivatization, as witnessed, among others, by varying yields of ferryl [Fe (IV)-oxo] and free radical generated. In cell, culture tests (human umbilical vein epithelial cells, HUVEC), the derivatization protocols show no toxic effect. PMID:20961862

  14. Derivatization of haemoglobin with periodate-generated reticulation agents: evaluation of oxidative reactivity for potential blood substitutes.

    PubMed

    Deac, Florina; Iacob, Bianca; Fischer-Fodor, Eva; Damian, Grigore; Silaghi-Dumitrescu, Radu

    2011-01-01

    Periodate modification of the sugar moiety in sugars, including adenosine triphosphate (ATP), has previously been employed in order to prepare dialdehyde-type reagents, which were then utilized in crosslinking reactions on haemoglobin, yielding polymerized material with useful dioxygen-binding properties and hence proposed as possible artificial oxygen carriers ('blood substitutes'). Here, the periodate protocol is shown to be applicable to a wider range of oxygen-containing compounds, illustrated by starch and polyethylene glycol. Derivatization protocols are described for haemoglobin with such periodate-treated crosslinking agents, and the dioxygen-binding properties and redox reactivities are investigated for the derivatized haemoglobins, with emphasis on pro-oxidative properties. There is a general tendency of the derivatization to result in higher autooxidation rates. The peroxide reactivity of the met (ferric) form is also affected by derivatization, as witnessed, among others, by varying yields of ferryl [Fe (IV)-oxo] and free radical generated. In cell, culture tests (human umbilical vein epithelial cells, HUVEC), the derivatization protocols show no toxic effect.

  15. Tagging the Untaggable: A Difluoroalkyl-Sulfinate Ketone-Based Reagent for Direct C-H Functionalization of Bioactive Heteroarenes.

    PubMed

    Gnaim, Samer; Scomparin, Anna; Li, Xiuling; Baran, Phil S; Rader, Christoph; Satchi-Fainaro, Ronit; Shabat, Doron

    2016-09-21

    We have developed a new difluoroalkyl ketal sulfinate salt reagent suitable for direct derivatization of heteroarene C-H bonds. The reagent is capable of introducing a ketone functional group on heteroarene bioactive compounds via a one-pot reaction. Remarkably, in three examples the ketone analog and its parent drug had almost identical cytotoxicity. In a representative example, the ketone analog was bioconjugated with a delivery vehicle via an acid-labile semicarbazone linkage and with a photolabile protecting group to produce the corresponding prodrug. Controlled release of the drug-ketone analog was demonstrated in vitro for both systems. This study provides a general approach to obtain taggable ketone analogs directly from bioactive heteroarene compounds with limited options for conjugation. We anticipate that this sodium ketal-sulfinate reagent will be useful for derivatization of other heteroarene-based drugs to obtain ketone-taggable analogs with retained efficacy. PMID:27494153

  16. Monolithic silica columns functionalized with substituted polyproline-derived chiral selectors as chiral stationary phases for high-performance liquid chromatography.

    PubMed

    Sancho, Raquel; Novell, Arnau; Svec, Frantisek; Minguillón, Cristina

    2014-10-01

    In this study, two polyproline-derived chiral selectors are bonded to monolithic silica gel columns. In spite of high chiral selector coverage, the derivatization was found to have only a slight effect on the hydrodynamics of the mobile phase through the column. The enantioseparation ability of the resulting chiral monolithic columns was evaluated with a series of structurally diverse racemic test compounds. When compared to analogous bead-based chiral stationary phases, higher enantioseparation and broader application domain were observed for monolithic columns. Moreover, the increase in flow rate produces a minor reduction of resolution, which permits to shorten analysis time. Additionally, increased loadability defines chiral polyproline derived monoliths as adequate for preparative chromatography.

  17. Derivatization of vinyl aldehydes with anthrone prior to high-performance liquid chromatography with fluorometric detection

    SciTech Connect

    Miller, B.E.; Danielson, N.D.

    1988-04-01

    Precolumn high-performance liquid chromatography derivatization of several vinyl aldehydes, specifically acrolein, crotonaldehyde, and methacrolein, has been studied by use of the reagent anthrone. After selective condensation of these ..cap alpha..- or ..beta..-unsaturated aldehydes to form fluorescent benzanthrone derivatives, separation of these compounds was facile on a 10-cm C-18 column. Although ultraviolet detection was possible, fluorescent detection proved more versatile and sensitive. Four liquor samples were subsequently assayed for acrolein and crotonaldehyde. Linearity for these compounds in alcoholic solutions ranged from 0.02 to at least 14 ppm with detection limits reaching down to 0.005 ppm.

  18. Controllable layer-by-layer assembly of PVA and phenylboronic acid-derivatized chitosan.

    PubMed

    Zhang, Dan; Yu, Guanghua; Long, Zhu; Yang, Guihua; Wang, Bin

    2016-04-20

    Phenylboronic acid-derivatized chitosan (chitosan-PBA) were prepared by grafting small molecules bearing phenylboronic acid groups onto chitosan with N-hydroxysuccinimide (NHS) and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) as a coupling reagent pair. Self-assembly multilayer thin films of chitosan-PBA and poly(vinyl alcohol) were subsequently produced under pH control on supporting surfaces, either a silicon wafer or polystyrene latex particles. The driving force of the self-assembly was the ester formation of phenylboronic acid containing polymers with PVA, which can be "turned off" by simple pH control. PMID:26876848

  19. Inherently chiral calix[4]arenes via oxazoline directed ortholithiation: synthesis and probe of chiral space.

    PubMed

    Herbert, Simon A; van Laeren, Laura J; Castell, Dominic C; Arnott, Gareth E

    2014-01-01

    The diastereoselective oxazoline-directed lithiation of calix[4]arenes is reported with diastereoselective ratios of greater than 100:1 in some instances. Notably, it has been found that the opposite diastereomer can be accessed via this approach merely through the choice of an alkyllithium reagent. The inherently chiral oxazoline calix[4]arenes have also been preliminarily examined as ligands in the palladium-catalyzed Tsuji-Trost allylation reaction, returning results comparable to their planar chiral ferrocene counterparts pointing towards future application of these types of compounds.

  20. Increments to chiral recognition facilitating enantiomer separations of chiral acids, bases, and ampholytes using Cinchona-based zwitterion exchanger chiral stationary phases.

    PubMed

    Wernisch, Stefanie; Pell, Reinhard; Lindner, Wolfgang

    2012-07-01

    The intramolecular distances of anion and cation exchanger sites of zwitterionic chiral stationary phases represent potential tuning sites for enantiomer selectivity. In this contribution, we investigate the influence of alkanesulfonic acid chain length and flexibility on enantiomer separations of chiral acids, bases, and amphoteric molecules for six Cinchona alkaloid-based chiral stationary phases in comparison with structurally related anion and cation exchangers. Employing polar-organic elution conditions, we observed an intramolecular counterion effect for acidic analytes which led to reduced retention times but did not impair enantiomer selectivities. Retention of amphoteric analytes is based on simultaneous double ion pairing of their charged functional groups with the acidic and basic sites of the zwitterionic selectors. A chiral center in the vicinity of the strong cation exchanger site is vital for chiral separations of bases. Sterically demanding side chains are beneficial for separations of free amino acids. Enantioseparations of free (un-derivatized) peptides were particularly successful in stationary phases with straight-chain alkanesulfonic acid sites, pointing to a beneficial influence of more flexible moieties. In addition, we observed pseudo-enantiomeric behavior of quinine and quinidine-derived chiral stationary phases facilitating reversal of elution orders for all analytes.

  1. Volatile chemical reagent detector

    DOEpatents

    Chen, Liaohai; McBranch, Duncan; Wang, Rong; Whitten, David

    2004-08-24

    A device for detecting volatile chemical reagents based on fluorescence quenching analysis that is capable of detecting neutral electron acceptor molecules. The device includes a fluorescent material, a contact region, a light source, and an optical detector. The fluorescent material includes at least one polymer-surfactant complex. The polymer-surfactant complex is formed by combining a fluorescent ionic conjugated polymer with an oppositely charged surfactant. The polymer-surfactant complex may be formed in a polar solvent and included in the fluorescent material as a solution. Alternatively, the complex may be included in the fluorescent material as a thin film. The use of a polymer-surfactant complex in the fluorescent material allows the device to detect both neutral and ionic acceptor molecules. The use of a polymer-surfactant complex film allows the device and the fluorescent material to be reusable after exposing the fluorescent material to a vacuum for limited time.

  2. Chiral mirrors

    NASA Astrophysics Data System (ADS)

    Plum, Eric; Zheludev, Nikolay I.

    2015-06-01

    Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.

  3. Chiral shielding

    SciTech Connect

    Babukhadia, L.; Berdnikov, Ya. A.; Ivanov, A. N.; Scadron, M. D.

    2000-08-01

    We demonstrate how a chiral soft pion theorem (SPT) shields the scalar meson ground-state isoscalar {sigma}(600-700) and isospinor {kappa}(800-900) from detection in a{sub 1}{yields}{pi}({pi}{pi}){sub swave}, {gamma}{gamma}{yields}2{pi}{sup 0}, {pi}{sup -}p{yields}{pi}{sup -}{pi}{sup +}n and K{sup -}p{yields}K{sup -}{pi}{sup +}n processes. While pseudoscalar meson PVV transitions are known to be determined by (only) quark loop diagrams, the above SPT also constrains scalar meson SVV transitions to be governed (only) by meson loop diagrams. We apply this latter SVV theorem to a{sub 0}{yields}{gamma}{gamma} and f{sub 0}{yields}{gamma}{gamma} decays. (c) 2000 The American Physical Society.

  4. Derivatization Strategy for the Comprehensive Characterization of Endogenous Fatty Aldehydes Using HPLC-Multiple Reaction Monitoring.

    PubMed

    Tie, Cai; Hu, Ting; Jia, Zhi-Xin; Zhang, Jin-Lan

    2016-08-01

    Fatty aldehydes are crucial substances that mediate a wide range of vital physiological functions, particularly lipid peroxidation. Fatty aldehydes such as acrolein and 4-hydroxynonenal (4-HNE) are considered potential biomarkers of myocardial ischemia and dementia, but analytical techniques for fatty aldehydes are lacking. In the present study, a comprehensive characterization strategy with high sensitivity and facility for fatty aldehydes based on derivatization and high-performance liquid chromatography-multiple reaction monitoring (HPLC-MRM) was developed. The fatty aldehydes of a biosample were derivatized using 2,4-bis(diethylamino)-6-hydrazino-1,3,5-triazine under mild and efficient reaction conditions at 37 °C for 15 min. The limit of detection (LOD) of the fatty aldehydes varied from 0.1 to 1 pg/mL, depending on the structures of these molecules. General MRM parameters were forged for the analysis of endogenous fatty aldehydes. "Heavy" derivatization reagents with 20 deuterium atoms were synthesized for both the discovery and comprehensive characterization of fatty aldehydes. More than 80 fatty aldehydes were detected in the biosamples. The new strategy was successfully implemented in global fatty aldehyde profiling of plasma and brain tissue of the bilateral common carotid artery (2VO) dementia rat model. Dozens of fatty aldehydes were significantly changed between the control and model groups. These findings further highlight the importance of endogenous fatty aldehydes. PMID:27397858

  5. Chiral Separation of Indapamide Enantiomers by Capillary Electrophoresis

    PubMed Central

    Tero-Vescan, Amelia; Hancu, Gabriel; Oroian, Mihaela; Cârje, Anca

    2014-01-01

    Purpose: Indapamide is probably the most frequently prescribed diuretic drug, generally being used for the treatment of hypertension. It contains a chiral center in its molecule; is marketed as a racemic mixture; but there are rather few studies regarding the pharmacokinetic and the pharmacological effect differences of the two enantiomers. Our aim was the development of a simple, rapid and precise analytical procedure for the chiral separation of indapamide enantiomers. Methods: In this study capillary zone electrophoresis was used for the enantiomeric separation of indapamide using a systematic screening approach involving different native and derivatized; neutral and charged cyclodextrines as chiral selectors. The effects of pH value and composition of the background electrolyte, capillary temperature, running voltage and injection parameters have been investigated. Results: After preliminary analysis a charged derivatized CD, sulfobuthyl ether- β-CD, proved to be the optimum chiral selector for the enantioseparation. Using a buffer solution containing 25 mM disodium hydrogenophosphate – 25 mM sodium didydrogenophosphate and 5 mM sulfobuthyl ether- β-CD as chiral selector at a pH - 7, a voltage of + 25 kV, temperature 15°C and UV detection at 242 nm, we succeeded in the separation of the two enantiomers in approximately 6 minutes, with a resolution of 4.30 and a separation factor of 1.08. Conclusion: Capillary zone electrophoresis using cyclodextrines as chiral selectors proved to be a suitable method for the enantioseparation of indapamide. Our method is rapid, specific, reliable, and cost-effective and can be proposed for laboratories performing indapamide routine analysis. PMID:24754011

  6. Understanding complex chiral plasmonics.

    PubMed

    Duan, Xiaoyang; Yue, Song; Liu, Na

    2015-11-01

    Chiral nanoplasmonics exhibits great potential for novel nanooptical devices due to the generation of a strong chiroptical response within nanoscale metallic structures. Recently, a number of different approaches have been utilized to create chiral nanoplasmonic structures. However, particularly for tailoring nanooptical chiral sensing devices, the understanding of the resulting chiroptical response when coupling chiral and achiral structures together is crucial and has not been completely understood to date. Here, we present a thorough and step-by-step experimental study to understand the intriguing chiral-achiral coupling scheme. We set up a hybrid plasmonic system, which bears resemblance to the 'host-guest' system in supramolecular chemistry to analyze and explain the complex chiral response both at the chiral and achiral plasmonic resonances. We also provide an elegant and simple analytical model, which can describe, predict, and comprehend the chiroptical spectra in detail. Our study will shed light on designing well-controlled chiral-achiral coupling platforms for reliable chiral sensing.

  7. Stable Oligomeric Clusters of Gold Nanoparticles: Preparation, Size Distribution, Derivatization, and Physical and Biological Properties

    PubMed Central

    2015-01-01

    Reducing dilute aqueous HAuCl4 with NaSCN under alkaline conditions produces 2–3 nm diameter yellow nanoparticles without the addition of extraneous capping agents. We here describe two very simple methods for producing highly stable oligomeric grape-like clusters (oligoclusters) of these small nanoparticles. The oligoclusters have well-controlled diameters ranging from ∼5 to ∼30 nm, depending mainly on the number of subunits in the cluster. Our first [“delay-time”] method controls the size of the oligoclusters by varying from seconds to hours the delay time between making the HAuCl4 alkaline and adding the reducing agent, NaSCN. Our second [“add-on”] method controls size by using yellow nanoparticles as seeds onto which varying amounts of gold derived from “hydroxylated gold”, Na+[Au(OH4–x)Clx]−, are added-on catalytically in the presence of NaSCN. Possible reaction mechanisms and a simple kinetic model fitting the data are discussed. The crude oligocluster preparations have narrow size distributions, and for most purposes do not require fractionation. The oligoclusters do not aggregate after ∼300-fold centrifugal-filter concentration, and at this high concentration are easily derivatized with a variety of thiol-containing reagents. This allows rare or expensive derivatizing reagents to be used economically. Unlike conventional glutathione-capped nanoparticles of comparable gold content, large oligoclusters derivatized with glutathione do not aggregate at high concentrations in phosphate-buffered saline (PBS) or in the circulation when injected into mice. Mice receiving them intravenously show no visible signs of distress. Their sizes can be made small enough to allow their excretion in the urine or large enough to prevent them from crossing capillary basement membranes. They are directly visible in electron micrographs without enhancement, and can model the biological fate of protein-like macromolecules with controlled sizes and charges

  8. Application of INEPT nitrogen-15 and silicon-29 nuclear magnetic resonance spectrometry to derivatized fulvic acids

    USGS Publications Warehouse

    Thorn, K.A.; Folan, D.W.; Arterburn, J.B.; Mikita, M.A.; MacCarthy, P.

    1989-01-01

    Use of the INEPT experiment has been examined in two derivatization studies of the Suwannee River fulvic acid. In the first study, the fulvic acid was derivatized with 15N enriched hydroxylamine. The quantitative 15N NMR spectrum, acquired with a 45° pulse angle, 2.0 second pulse delay and inverse gated decoupling, showed that oximes (390-340 ppm) were the major derivatives, followed by nitriles (270-240 ppm), hydroxamic acids (170-160 ppm), secondary amides (150-115 ppm), and lactams (115-90 ppm). The INEPT 15N NMR spectrum was acquired using refocussing delays and polarization transfer times optimized for signal enhancement of singly protonated nitrogens. INEPT greatly enhanced the amide and lactam resonances, and showed that resonances downfield of 180 ppm in the quantitative spectrum represented nonprotonated nitrogens. In the second study, the fulvic acid was first methylated with diazomethane and then silylated with hexamethyldisilazane. The 29Si NMR spectra exhibited two major peaks, from approximately 33 to 22 ppm, representing silyl esters of carboxylic acids, and from 22 to 13 ppm, representing silyl ethers of alcohols and phenols. The INEPT 29Si NMR spectrum was virtually identical to the quantitative 29Si spectrum, acquired with a 90° pulse angle, 5.0 second pulse delay, inverse gated decoupling, and relaxation reagent. INEPT therefore can be used for quantitative analysis of trimethylsilyl derivatives of the fulvic acid, saving spectrometer time and eliminating the need for relaxation reagents.

  9. Chemical derivatization for forensic drug analysis by GC- and LC-MS.

    PubMed

    Lin, D L; Wang, S M; Wu, C H; Chen, B G; Liu, R H

    2016-01-01

    Utilizing chemical derivatization (CD) to improve gas chromatographic (GC) and GC-mass spectrometric (MS) analysis of drugs has been abundantly studied and widely practiced, while in liquid chromatography (LC) and LC-MS, application of CD approaches is still at an early stage. Silylation, acylation, and alkylation are common CD reactions, long adopted by GC and GC-MS (including GC-MS/MS) methodologies, to improve analytes' stability and/or to optimize their extraction/separation and detection efficiencies. Highly polar and nonvolatile analytes are not amenable to GC-MS analysis without the CD step; however, CD can improve LC-MS analysis of highly polar analytes, especially those with low molecular weights. Many CD reagents developed for GC and GC-MS applications are also effective in LC-MS. Other CD reagents are developed for LC-MS to enhance analytes' performance under electrospray and atmospheric pressure ionization sources. Certain CD reagents are designed to facilitate analytes' fragmentation (upon collision-induced dissociation) in generating intense product ions for sensitive MS/MS detection. In this review, various CD reagents, reaction types, and application examples are presented and discussed, with emphases on GC-MS and LC-MS analysis of drugs of abuse.

  10. Advanced dress-up chiral columns: New removable chiral stationary phases for enantioseparation of chiral carboxylic acids.

    PubMed

    Todoroki, Kenichiro; Ishii, Yasuhiro; Ide, Takafumi; Min, Jun Zhe; Inoue, Koichi; Huang, Xin; Zhang, Wei; Hamashima, Yoshitaka; Toyo'oka, Toshimasa

    2015-07-01

    This paper describes the preparation of new dress-up columns featuring reproducibly removable and replaceable chiral stationary phases. After synthesizing perfluroalkylated quinine and quinidine derivatives as chiral stationary phase compounds (F-CSPs), we adsorbed them reversibly onto a fluorous LC column through pumping of their solutions. Using this dress-up chiral column and fluorophobic elution of aqueous ammonium formate/MeOH mixtures, we could enantioseparate four racemic N-acetyl amino acids, dichlorprop, and sixteen fluorescent 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC)-derivatized amino acids. Dressing and undressing of the coated F-CSPs could be controlled by varying the fluorophilicity and fluorophobicity of the eluent. The relative standard deviations of the retention times, the retention factors, the number of theoretical plates, the enantioseparation factors, and the resolutions of each of four preparations of such dress-up columns were all less than or equal to 5.26% (from 20 repeated analyses); the reproducibilities from four different preparations were all less than or equal to 10.6%. These columns also facilitated highly sensitive and selective analyses of AQC-amino acids when detected using LC-MS/MS.

  11. Chiral sensing by nonchiral tetrapyrroles.

    PubMed

    Labuta, Jan; Hill, Jonathan P; Ishihara, Shinsuke; Hanyková, Lenka; Ariga, Katsuhiko

    2015-03-17

    Enantiomeric excess (ee) is a measure of the purity of an enantiomer of a chiral compound with respect to the presence of the complementary enantiomer. It is an important aspect of chemistry, especially in the fields of pharmaceuticals and asymmetric catalysis. Existing methods for determination of enantiomeric excesses using nuclear magnetic resonance (NMR) spectroscopy mostly rely on special chiral reagents (auxiliaries) that form two or more diastereomeric complexes with a chiral compound. As a result of this, the NMR spectrum of each enantiomer is different, allowing the determination of enantiomeric excess. In this Account, we describe a molecular design process that has allowed us to prepare prochiral solvating agents for NMR determination of ee of a wide variety of analyte types. At the outset of this work, we initially encountered the phenomenon of NMR peak splitting in the oxoporphyrinogen (OxP) host component of a supramolecular host-guest complex, where the extent of the splitting is apparently proportional to the guests' ee. Upon closer examination of the mechanism of action, it was found that several complicating factors, including prototropic tautomerism, macrocyclic inversion (ring-flipping), and 1:2 host-guest stoichiometry, obstruct potential applications of OxP as a chiral solvating agent. By considering the molecular conformation of the OxP host, a saddle-shaped calix[4]pyrrole, we moved to study the tetraphenylporphyrin (TPP) dication since it has a similar form, and it was found that it could also be used to probe ee. However, although TPP does not suffer from disadvantageous tautomeric processes, it is still subject to macrocyclic inversion and has the additional serious disadvantage of operating for ee sensing only at depressed temperatures. The intrinsic disadvantages of the OxP and TPP systems were finally overcome by covalently modifying the OxP chromophore by regioselective N-alkylation at one face of the molecule. This procedure yields a

  12. Resolution of 1- and 2-naphthylmethoxyacetic acids, NMR reagents for absolute configuration determination, by use of L-phenylalaninol.

    PubMed

    Arita, Shoko; Yabuuchi, Tetsuya; Kusumi, Takenori

    2003-08-01

    Racemic 1- and 2-naphthylmethoxyacetic acids (1NMA and 2NMA), the chiral anisotropic reagents used for absolute configuration determination of chiral secondary alcohols and primary amines, were conveniently resolved to enantiomers (>99% ee) by condensation with L-phenylalaninol (2-amino-3-phenylpropanol), chromatographic separation of the diastereomers, and hydrolysis. This method enables large-scale preparation of enantiomeric 1NMA and 2NMA. PMID:12840826

  13. Gas-phase reaction products and yields of terpinolene with ozone and nitric oxide using a new derivatization agent

    NASA Astrophysics Data System (ADS)

    Ham, Jason E.; Jackson, Stephen R.; Harrison, Joel C.; Wells, J. R.

    2015-12-01

    The new derivatization agent, O-tert-butylhydroxylamine hydrochloride (TBOX) was used to investigate the carbonyl reaction products from terpinolene ozonolysis. With ozone (O3) as the limiting reagent, four carbonyl compounds were detected: methylglyoxal (MG), 4-methylcyclohex-3-en-1-one, (4MCH), 6-oxo-3-(propan-2-ylidene) heptanal (6OPH), and 3,6-dioxoheptanal (36DOH). The tricarbonyl 36DOH has not been previously observed. Using cyclohexane as a hydroxyl radical (OHrad) scavenger, the yields of 6OPH and 36DOH were reduced indicating the influence secondary OHrad radicals have on terpinolene ozonolysis products. However, the MG yield increased and the 4MCH yield was unchanged when OHrad radicals were scavenged suggesting they are only made by the terpinolene + O3 reaction. The detection of 36DOH using TBOX highlights the advantages of a smaller molecular weight derivatization agent for the detection of multi-carbonyl compounds. The product yields from terpinolene ozonolysis experiments conducted in the presence of 20 ppb nitric oxide (NO) remained unchanged except for MG which decreased. However, in experiments where O3 was kept constant at 50 ppb and NO was varied (20, 50, 100 ppb) MG, 6OPH, 36DOH decreased with increasing NO while 4MCH increased with increasing NO. The use of TBOX derivatization if combined with other derivatization agents may address a recurring need to simply and accurately detect multi-functional oxygenated species in air.

  14. Introduction to chiral symmetry

    SciTech Connect

    Koch, V.

    1996-01-08

    These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. Effective chiral models such as the linear and nonlinear sigma model will be discussed as well as the essential ideas of chiral perturbation theory. Some applications to the physics of ultrarelativistic heavy ion collisions will be presented.

  15. Novel one-step headspace dynamic in-syringe liquid phase derivatization-extraction technique for the determination of aqueous aliphatic amines by liquid chromatography with fluorescence detection.

    PubMed

    Muniraj, Sarangapani; Shih, Hou-Kung; Chen, Ying-Fang; Hsiech, Chunming; Ponnusamy, Vinoth Kumar; Jen, Jen-Fon

    2013-06-28

    A novel one-step headspace (HS) dynamic in-syringe (DIS) based liquid-phase derivatization-extraction (LPDE) technique has been developed for the selective determination of two short-chain aliphatic amines (SCAAs) in aqueous samples using high performance liquid chromatography (HPLC) with fluorescence detection (FLD). Methylamine (MA) and dimethylamine (DMA) were selected as model compounds of SCAAs. In this method, a micro-syringe pre-filled with derivatizing reagent solution (9-fluorenylmethyl chloroformate) in the barrel was applied to achieve the simultaneous derivatization and extraction of two methylamines evolved from alkalized aqueous samples through the automated reciprocated movements of syringe plunger. After the derivatization-extraction process, the derivatized phase was directly injected into HPLC-FLD for analysis. Parameters influencing the evolution of methylamines and the HS-DIS-LPDE efficiency, including sample pH and temperature, sampling time, as well as the composition of derivatization reagent, reaction temperature, and frequency of reciprocated plunger movements, were thoroughly examined and optimized. Under optimal conditions, detections were linear in the range of 25-500μgL(-1) for MA and DMA with correlation coefficients all above 0.995. The limits of detection (based on S/N=3) were 5 and 19ngmL(-1) for MA and DMA, respectively. The applicability of the developed method was demonstrated for the determination of MA and DMA in real water samples without any prior cleanup of the sample. The present method provides a simple, selective, automated, low cost and eco-friendly procedure to determine aliphatic amines in aqueous samples. PMID:23591526

  16. Reagent Cluster Anions for Multiple Gas-Phase Covalent Modifications of Peptide and Protein Cations

    NASA Astrophysics Data System (ADS)

    Prentice, Boone M.; Stutzman, John R.; McLuckey, Scott A.

    2013-07-01

    Multiple gas phase ion/ion covalent modifications of peptide and protein ions are demonstrated using cluster-type reagent anions of N-hydroxysulfosuccinimide acetate (sulfo-NHS acetate) and 2-formyl-benzenesulfonic acid (FBMSA). These reagents are used to selectively modify unprotonated primary amine functionalities of peptides and proteins. Multiple reactive reagent molecules can be present in a single cluster ion, which allows for multiple covalent modifications to be achieved in a single ion/ion encounter and at the `cost' of only a single analyte charge. Multiple derivatizations are demonstrated when the number of available reactive sites on the analyte cation exceeds the number of reagent molecules in the anionic cluster (e.g., data shown here for reactions between the polypeptide [K10 + 3H]3+ and the reagent cluster [5R5Na - Na]-). This type of gas-phase ion chemistry is also applicable to whole protein ions. Here, ubiquitin was successfully modified using an FBMSA cluster anion which, upon collisional activation, produced fragment ions with various numbers of modifications. Data for the pentamer cluster are included as illustrative of the results obtained for the clusters comprised of two to six reagent molecules.

  17. Fast derivatization of fatty acids in different meat samples for gas chromatography analysis.

    PubMed

    Figueiredo, Ingrid Lima; Claus, Thiago; Oliveira Santos Júnior, Oscar; Almeida, Vitor Cinque; Magon, Thiago; Visentainer, Jesuí Vergilio

    2016-07-22

    In order to analyze the composition of fatty acids employing gas chromatography as the separation method, a derivatization of lipids using esterification and transesterification reactions is needed. The methodologies currently available are time consuming and use large amounts of sample and reagents. Thus, this work proposes a new procedure to carry out the derivatization of fatty acids without the need for prior extraction of lipids. The use of small amounts of sample (100mg) allows the analysis to be performed in specific parts of animals, in most cases without having them slaughtered. Another benefit is the use of small amounts of reagents (only 2mL of NaOH/Methanol and H2SO4/Methanol). The use of an experimental design procedure (Design Expert software) allows the optimization of the alkaline and acid reaction times. The procedure was validated for five minutes in both steps. The method was validated for bovine fat, beef, chicken, pork, fish and shrimp meats. The results for the merit figures of accuracy (from 101.07% to 109.18%), precision (RSDintra-day (from 0.65 to 3.93%), RSDinter-day (from 1.57 to 5.22%)), linearity (R(2)=0.9864) and robustness confirmed that the new method is satisfactory within the linear range of 2-30% of lipids in the sample. Besides the benefits of minimizing the amount of samples and reagents, the procedure enables gas chromatography sample preparation in a very short time compared with traditional procedures. PMID:27320376

  18. A rapid gas chromatographic injection-port derivatization method for the tandem mass spectrometric determination of patulin and 5-hydroxymethylfurfural in fruit juices.

    PubMed

    Marsol-Vall, Alexis; Balcells, Mercè; Eras, Jordi; Canela-Garayoa, Ramon

    2016-07-01

    A novel method consisting of injection-port derivatization coupled to gas chromatography-tandem mass spectrometry is described. The method allows the rapid assessment of 5-hydroxymethylfurfural (HMF) and patulin content in apple and pear derivatives. The chromatographic separation of the compounds was achieved in a short chromatographic run (12.2min) suitable for routine controls of these compounds in the fruit juice industry. The optimal conditions for the injection-port derivatization were at 270°C, 0.5min purge-off, and a 1:2 sample:derivatization reagent ratio (v/v). These conditions represent an important saving in terms of derivatization reagent consumption and sample preparation time. Quality parameters were assessed for the target compounds, giving LOD of 0.7 and 1.6μg/kg and LOQ of 2 and 5μg/kg for patulin and HMF, respectively. These values are below the maximum patulin concentration in food products intended for infants and young children. Repeatability (%RSD n=5) was below 12% for both compounds. In addition, the method linearity ranged between 25 and 1000μg/kg and between 5 and 192μg/kg for HMF and patulin, respectively. Finally, the method was applied to study HMF and patulin content in various fruit juice samples. PMID:27240947

  19. An in situ derivatization - dispersive liquid-liquid microextraction combined with gas-chromatography - mass spectrometry for determining biogenic amines in home-made fermented alcoholic drinks.

    PubMed

    Płotka-Wasylka, Justyna; Simeonov, Vasil; Namieśnik, Jacek

    2016-07-01

    A novel dispersive liquid-liquid microextraction (DLLME) gas chromatography mass-spectrometry (GC-MS) method was developed for the determination of 13 biogenic amines in home-made wine samples. The method allows to simultaneous extraction and derivatization of the amines providing a simple and fast mode of extract enrichment. During the study, two different procedures were examined. Statistical analysis was performed to choose better procedure, as well as the conditions of derivatization reaction. At least, a mixture of methanol (dispersive solvent; 215μL), chloroform (extractive solvent; 400μL), and isobutyl choloroformate (derivatizing reagent; 90μL) was used as extractive/derivatizing reagent, added to 5mL of sample. The addition of mixture of pyridine and HCl was necessary to eliminate the by-products. The proposed method showed good linearity (correlation coefficients >0.9961), good recoveries (from 77 to 105%), and good intra-day precision (below 13%) and inter-day precision (below 10%). Moreover, detection limits were never over 4.1μg/L. The developed method was successfully applied to the analysis of 17 home-made wine samples not regulated by law. All of the biogenic amines analyzed were found in most of the wines.

  20. Determination of atranol and chloroatranol in perfumes using simultaneous derivatization and dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    López-Nogueroles, Marina; Chisvert, Alberto; Salvador, Amparo

    2014-05-15

    A new analytical method based on simultaneous derivatization and dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS), for the determination of the allergenic compounds atranol and chloroatranol in perfumes, is presented. Derivatization of the target analytes by means of acetylation with anhydride acetic in carbonate buffer was carried out. Thereby volatility and detectability were increased for improved GC-MS sensitivity. In addition, extractability by DLLME was also enhanced due to a less polar character of the solutes. A liquid-liquid extraction was performed before DLLME to clean up the sample and to obtain an aqueous sample solution, free of the low polar matrix from the essential oils, as donor phase. Different parameters, such as the nature and volume of both the extraction and disperser solvents, the ionic strength of the aqueous donor phase or the effect of the derivatization reagent volume, were optimized. Under the selected conditions (injection of a mixture of 750μL of acetone as disperser solvent, 100μL of chloroform as extraction solvent and 100μL of anhydride acetic as derivatization reagent) the figures of merit of the proposed method were evaluated. Limits of detection in the low ngmL(-1) range were obtained. Matrix effect was observed in real perfume samples and thus, standard addition calibration is recommended.

  1. Quantitative analysis of ripasudil hydrochloride hydrate and its impurities by reversed-phase high-performance liquid chromatography after precolumn derivatization: Identification of four impurities.

    PubMed

    Hui, Wenkai; Sun, Lili; Zhang, Hui; Zou, Liang; Zou, Qiaogen; Ouyang, Pingkai

    2016-09-01

    We report the development and validation of a stability-indicating reversed-phase high-performance liquid chromatography method with precolumn derivatization for the separation and identification of the impurities of ripasudil hydrochloride hydrate, a novel protein kinase inhibitor. 2,3,4,6-Tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate was chosen as the derivatizing reagent and triethylamine was added as catalyst. 200 μL sample solution (1 mg/mL), 600 μL derivatizing reagent (1 mg/mL), and 200 μL triethylamine solution (1%, v/v) were mixed and reacted at 40°C for 30 min. The separation was achieved on an Inertsil C18 ODS-3 (250 mm × 4.6 mm, 5 μm) column using mobile phases including 10 mmol monopotassium phosphate buffer (pH 3.0) and methanol in gradient mode. The column temperature was adjusted at 25°C and the flow rate at 1 mL/min. The detection was carried out at 220 nm. Different precolumn derivatization conditions as well as the high-performance liquid chromatography conditions were optimized. Ripasudil hydrochloride hydrate and its four impurities were detected and quantitated, among which two new compounds were characterized. The proposed method was validated and proven to be selective, accurate, and precise and suitable for the quantitative analysis of ripasudil hydrochloride hydrate. PMID:27390135

  2. Concerted derivatization and concentration method with dispersive liquid-liquid microextraction for liquid chromatographic analysis of 5-hydroxyindoles in human serum.

    PubMed

    Hayama, Tadashi; Yabuuchi, Yurika; Iwamatsu, Tomomi; Tamashima, Erina; Kawami, Yusuke; Itoyama, Miki; Yoshida, Hideyuki; Yamaguchi, Masatoshi; Nohta, Hitoshi

    2013-12-15

    We developed a concerted derivatization and concentration method based on dispersive liquid-liquid microextraction (DLLME) for the liquid chromatography (LC) determination of 5-hydroxyindoles (5-HIs; serotonin, 5-hydroxyindole-3-acetic acid, N-acetylserotonin, and 5-hydroxytryptohol). Concerted derivatization and concentration could be affected by adding a mixture of an ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate, extraction solvent), methanol (disperser), and water containing fluorescence derivatization reagents [benzylamine and potassium hexacyanoferrate(III)] into the sample. The resulting sedimented phase was injected into a reversed-phase LC column using a mixture of acetonitrile and 250 mM acetate buffer (pH 4.3) as the mobile phase for gradient elution, and the derivatives obtained were fluorometrically detected at excitation and emission wavelengths of 345 nm and 452 nm, respectively. The derivatization (reagent concentrations and pH) and extraction (extraction and disperser solvent type) conditions were optimized simultaneously. The limits of detection of the 5-HIs were in the range of 0.08-0.33 nM. The method was validated for 10 and 50 pmol/mL human serum levels, and the recovery of 5-HIs was between 66% and 98%, within a relative standard deviation of 9.5%. The proposed method is well suited for the highly sensitive analysis of trace amounts of 5-HIs in human serum samples. PMID:24209305

  3. Chiral separation of acidic compounds using an O-9-(tert-butylcarbamoyl)quinidine functionalized monolith in micro-liquid chromatography.

    PubMed

    Wang, Qiqin; Zhu, Peijie; Ruan, Meng; Wu, Huihui; Peng, Kun; Han, Hai; Somsen, Govert W; Crommen, Jacques; Jiang, Zhengjin

    2016-04-29

    An O-9-(tert-butylcarbamoyl) quinidine (t-BuCQD) functionalized polymeric monolithic capillary column was prepared by the in situ copolymerization method. The physicochemical properties of the optimized monolithic column were characterized by scanning electron microscopy and micro-LC. Satisfactory column permeability, efficiency, stability and reproducibility were obtained for this monolithic column. The chiral recognition ability of the resulting monolith was also evaluated using 47 N-derivatized amino acids, eight N-derivatized dipeptides, and two herbicides. Under the selected conditions, the enantiomers of all chiral analytes were baseline separated with exceptionally high selectivity and resolution using micro-LC. It is worth noting that this chiral stationary phase (CSP) containing quinidine with a tert-butyl carbamate residue as chiral selector exhibits much higher enantioselectivity and diastereoselectivity than the previously developed O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD) based CSP for N-derivatized amino acids and dipeptides. These results indicate that this novel quinidine-based polymeric monolith can be used as an effective tool for the enantioseparation of chiral acidic compounds.

  4. Chiral separation of acidic compounds using an O-9-(tert-butylcarbamoyl)quinidine functionalized monolith in micro-liquid chromatography.

    PubMed

    Wang, Qiqin; Zhu, Peijie; Ruan, Meng; Wu, Huihui; Peng, Kun; Han, Hai; Somsen, Govert W; Crommen, Jacques; Jiang, Zhengjin

    2016-04-29

    An O-9-(tert-butylcarbamoyl) quinidine (t-BuCQD) functionalized polymeric monolithic capillary column was prepared by the in situ copolymerization method. The physicochemical properties of the optimized monolithic column were characterized by scanning electron microscopy and micro-LC. Satisfactory column permeability, efficiency, stability and reproducibility were obtained for this monolithic column. The chiral recognition ability of the resulting monolith was also evaluated using 47 N-derivatized amino acids, eight N-derivatized dipeptides, and two herbicides. Under the selected conditions, the enantiomers of all chiral analytes were baseline separated with exceptionally high selectivity and resolution using micro-LC. It is worth noting that this chiral stationary phase (CSP) containing quinidine with a tert-butyl carbamate residue as chiral selector exhibits much higher enantioselectivity and diastereoselectivity than the previously developed O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD) based CSP for N-derivatized amino acids and dipeptides. These results indicate that this novel quinidine-based polymeric monolith can be used as an effective tool for the enantioseparation of chiral acidic compounds. PMID:27038701

  5. New approaches in sensitive chiral CE.

    PubMed

    Sánchez-Hernández, Laura; Guijarro-Diez, Miguel; Marina, María Luisa; Crego, Antonio L

    2014-01-01

    CE has shown to have a big potential for chiral separations, with advantages such as high efficiency, high resolution, and low sample and reagents consumption. Nevertheless, when UV detection is employed, CE has some drawbacks, especially the low sensitivity obtained due to the short optical path length. Notwithstanding, sensitivity improvements can be achieved when different approaches are employed, such as sample treatment strategies (off-line or on-line), in-capillary sample preconcentration techniques, and/or alternative detection systems to UV-Vis (such as fluorescence, conductimetry, electrochemiluminiscence, MS, etc.). This article reviews the most recent methodological and instrumental advances reported from June 2011 to May 2013 for enhancing the sensitivity in chiral analysis by CE. The sensitivity achieved for the enantioseparated analytes and the applications carried out using the developed methodologies are also summarized.

  6. Chiral symmetry and chiral-symmetry breaking

    SciTech Connect

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)

  7. Microwave-assisted on-spot derivatization for gas chromatography-mass spectrometry based determination of polar low molecular weight compounds in dried blood spots.

    PubMed

    Sadones, Nele; Van Bever, Elien; Archer, John R H; Wood, David M; Dargan, Paul I; Van Bortel, Luc; Lambert, Willy E; Stove, Christophe P

    2016-09-23

    Dried blood spot (DBS) sampling and analysis is increasingly being applied in bioanalysis. Although the use of DBS has many advantages, it is also associated with some challenges. E.g. given the limited amount of available material, highly sensitive detection techniques are often required to attain sufficient sensitivity. In gas chromatography coupled to mass spectrometry (GC-MS), derivatization can be helpful to achieve adequate sensitivity. Because this additional sample preparation step is considered as time-consuming, we introduce a new derivatization procedure, i.e. "microwave-assisted on-spot derivatization", to minimize sample preparation of DBS. In this approach the derivatization reagents are directly applied onto the DBS and derivatization takes place in a microwave instead of via conventional heating. In this manuscript we evaluated the applicability of this new concept of derivatization for the determination of two polar low molecular weight molecules, gamma-hydroxybutyric acid (GHB) and gabapentin, in DBS using a standard GC-MS configuration. The method was successfully validated for both compounds, with imprecision and bias values within acceptance criteria (<20% at LLOQ, <15% at 3 other QC levels). Calibration lines were linear over the 10-100μg/mL and 1-30μg/mL range for GHB and gabapentin, respectively. Stability studies revealed no significant decrease of gabapentin and GHB in DBS upon storage at room temperature for at least 84 days. Furthermore, DBS-specific parameters, including hematocrit and volume spotted, were evaluated. As demonstrated by the analysis of GHB and gabapentin positive samples, "microwave-assisted on-spot derivatization" proved to be reliable, fast and applicable in routine toxicology. Moreover, other polar low molecular weight compounds of interest in clinical and/or forensic toxicology, including vigabatrin, beta-hydroxybutyric acid, propylene glycol, diethylene glycol, 1,4-butanediol and 1,2-butanediol, can also be

  8. Microwave-assisted on-spot derivatization for gas chromatography-mass spectrometry based determination of polar low molecular weight compounds in dried blood spots.

    PubMed

    Sadones, Nele; Van Bever, Elien; Archer, John R H; Wood, David M; Dargan, Paul I; Van Bortel, Luc; Lambert, Willy E; Stove, Christophe P

    2016-09-23

    Dried blood spot (DBS) sampling and analysis is increasingly being applied in bioanalysis. Although the use of DBS has many advantages, it is also associated with some challenges. E.g. given the limited amount of available material, highly sensitive detection techniques are often required to attain sufficient sensitivity. In gas chromatography coupled to mass spectrometry (GC-MS), derivatization can be helpful to achieve adequate sensitivity. Because this additional sample preparation step is considered as time-consuming, we introduce a new derivatization procedure, i.e. "microwave-assisted on-spot derivatization", to minimize sample preparation of DBS. In this approach the derivatization reagents are directly applied onto the DBS and derivatization takes place in a microwave instead of via conventional heating. In this manuscript we evaluated the applicability of this new concept of derivatization for the determination of two polar low molecular weight molecules, gamma-hydroxybutyric acid (GHB) and gabapentin, in DBS using a standard GC-MS configuration. The method was successfully validated for both compounds, with imprecision and bias values within acceptance criteria (<20% at LLOQ, <15% at 3 other QC levels). Calibration lines were linear over the 10-100μg/mL and 1-30μg/mL range for GHB and gabapentin, respectively. Stability studies revealed no significant decrease of gabapentin and GHB in DBS upon storage at room temperature for at least 84 days. Furthermore, DBS-specific parameters, including hematocrit and volume spotted, were evaluated. As demonstrated by the analysis of GHB and gabapentin positive samples, "microwave-assisted on-spot derivatization" proved to be reliable, fast and applicable in routine toxicology. Moreover, other polar low molecular weight compounds of interest in clinical and/or forensic toxicology, including vigabatrin, beta-hydroxybutyric acid, propylene glycol, diethylene glycol, 1,4-butanediol and 1,2-butanediol, can also be

  9. A smog chamber comparison of a microfluidic derivatization measurement of gas-phase glyoxal and methylglyoxal with other analytical techniques

    NASA Astrophysics Data System (ADS)

    Pang, X.; Lewis, A. C.; Richard, A.; Baeza-Romero, M. T.; Adams, T. J.; Ball, S. M.; Daniels, M. J. S.; Goodall, I. C. A.; Monks, P. S.; Peppe, S.; Ródenas García, M.; Sánchez, P.; Muñoz, A.

    2013-06-01

    A microfluidic lab-on-a-chip derivatization technique has been developed to measure part per billion volume (ppbV) mixing ratios of gaseous glyoxal (GLY) and methylglyoxal (MGLY), and the method compared with other techniques in a smog chamber experiment. The method uses o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) as a derivatization reagent and a microfabricated planar glass micro-reactor comprising an inlet, gas and fluid splitting and combining channels, mixing junctions, and a heated capillary reaction microchannel. The enhanced phase contact area-to-volume ratio and the high heat transfer rate in the micro-reactor result in a fast and highly efficient derivatization reaction, generating an effluent stream ready for direct introduction to a gas chromatograph-mass spectrometer (GC-MS). A linear response for GLY was observed over a calibration range 0.7 to 400 ppbV, and for MGLY of 1.2 to 300 ppbV, when derivatized under optimal reaction conditions. The method detection limits (MDLs) were 80 pptV and 200 pptV for GLY and MGLY respectively, calculated as 3 times the standard deviation of the S/N of the blank sample chromatograms. These MDLs are below or close to typical concentrations in clean ambient air. The feasibility of the technique was assessed by applying the methodology under controlled conditions to quantify of α-dicarbonyls formed during the photo-oxidation of isoprene in a large scale outdoor atmospheric simulation chamber (EUPHORE). Good general agreement was seen between microfluidic measurements and Fourier Transform Infra Red (FTIR), Broad Band Cavity Enhanced Absorption Spectroscopy (BBCEAS) and a detailed photochemical chamber box modelling calculation for both GLY and MGLY. Less good agreement was found with Proton-Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) and Solid Phase Microextraction (SPME) derivatization methods for MGLY measurement.

  10. Stereoselective synthesis and reactions of secondary alkyllithium reagents functionalized at the 3-position.

    PubMed

    Moriya, Kohei; Didier, Dorian; Simon, Meike; Hammann, Jeffrey M; Berionni, Guillaume; Karaghiosoff, Konstantin; Zipse, Hendrik; Mayr, Herbert; Knochel, Paul

    2015-02-23

    Secondary alkyllithium reagents bearing an OTBS group (TBS=tert-butyldimethylsilyl) at the 3-position can be prepared stereoconvergently through an I/Li exchange from a diastereomeric mixture of the corresponding secondary alkyl iodides. These lithium reagents react with a range of electrophiles, including carbon electrophiles, with retention of configuration to yield various 1,3-difunctionalized derivatives with good diastereoselectivities. Kinetic studies show that the 3-siloxy group strongly accelerates the epimerization at the lithium-substituted carbon atom. This method offers a new way to construct chiral open-chain molecules with excellent stereoselectivity. PMID:25640227

  11. Metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates: construction of chiral nonracemic allylic isocyanates.

    PubMed

    Grange, Rebecca L; Evans, P Andrew

    2014-08-27

    We report the facile and efficient metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates. This process facilitates the room temperature construction of an array of chiral nonracemic allylic isocyanates, which are versatile intermediates for the construction of unsymmetrical ureas, carbamates, thiocarbamates and amides. Furthermore, the sulfilimine/isocyanate metathesis reaction with 4,4'-methylene diphenyl diisocyanate (4,4'-MDI) circumvents harsh reaction conditions and/or hazardous reagents employed with more classical methods for the preparation of this important functional group.

  12. Enantioselective iodolactonization catalyzed by chiral quaternary ammonium salts derived from cinchonidine.

    PubMed

    Wang, Mang; Gao, Lian Xun; Mai, Wen Peng; Xia, Ai Xiang; Wang, Fang; Zhang, Suo Bo

    2004-04-16

    Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent.

  13. Chiral rotational spectroscopy

    NASA Astrophysics Data System (ADS)

    Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.

    2016-09-01

    We introduce chiral rotational spectroscopy, a technique that enables the determination of the orientated optical activity pseudotensor components BX X, BY Y, and BZ Z of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample and provides an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral solely by virtue of their isotopic constitution and molecules with multiple chiral centers. A basic design for a chiral rotational spectrometer together with a model of its functionality is given. Our proposed technique offers the more familiar polarizability components αX X, αY Y, and αZ Z as by-products, which could see it find use even for achiral molecules.

  14. Chemical Amplification with Encapsulated Reagents

    NASA Technical Reports Server (NTRS)

    Chen, Jian; Koemer, Steffi; Craig, Stephen; Lin, Shirley; Rudkevich, Dmitry M.; Rebek, Julius, Jr.

    2002-01-01

    Autocatalysis and chemical amplification are characteristic properties of living systems, and they give rise to behaviors such as increased sensitivity, responsiveness, and self-replication. Here we report a synthetic system in which a unique form of compartmentalization leads to nonlinear, autocatalytic behavior. The compartment is a reversibly formed capsule in which a reagent is sequestered. Reaction products displace the reagent from the capsule into solution and the reaction rate is accelerated. The resulting self-regulation is sensitive to the highly selective molecular recognition properties of the capsule.

  15. Chiral atomically thin films

    NASA Astrophysics Data System (ADS)

    Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm–1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.

  16. Characterizing optical chirality

    SciTech Connect

    Bliokh, Konstantin Y.; Nori, Franco

    2011-02-15

    We examine the recently introduced measure of chirality of a monochromatic optical field [Y. Tang and A. E. Cohen, Phys. Rev. Lett. 104, 163901 (2010)] using the momentum (plane-wave) representation and helicity basis. Our analysis clarifies the physical meaning of the measure of chirality and unveils its close relation to the polarization helicity, spin angular momentum, energy density, and Poynting energy flow. We derive the operators of the optical chirality and of the corresponding chiral momentum, which acquire remarkably simple forms in the helicity representation.

  17. Chiral atomically thin films

    NASA Astrophysics Data System (ADS)

    Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm-1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.

  18. A method for the measurement of atmospheric HONO based on DNPH derivatization and HPLC analysis

    SciTech Connect

    Zhou, X.; Qiao, H.; Deng, G.; Civerolo, K.

    1999-10-15

    A simple measurement technique was developed for atmospheric HONO based on aqueous scrubbing using a coil sampler followed by 2,4-dinitrophenylhydrazine (DNPH) derivatization and high-performance liquid chromatographic (HPLC) analysis. Quantitative sampling efficiency was obtained using a 1 mM phosphate buffer, pH 7.0, as the scrubbing solution at a gas sampling flow rate of 2 L min{sup {minus}1} and a liquid flow rate of 0.24 mL min{sup {minus}1}. Derivation of the scrubbed nitrous acid by DNPH was fast and was completed within 5 min in a derivatization medium containing 300 {micro}M DNPH and 8 mM HCI at 45 C. The azide derivative was separated from DNPH reagent and carbonyl derivatives by reverse-phase HPLC and was detected with an UV detector at 309 nm. The detection limit is {le}5 pptv and may be lowered to 1 pptv with further DNPH purification. Interferences from NO, NO{sub 2} PAN, O{sub 3}, HNO{sub 3}, and HCHO were studied and found to be negligible. Ambient HONO concentration was measured simultaneously in downtown Albany, NY, by this method and by an ion chromatographic technique after sampling using a fritted bubbler. The results, from 70 pptv during the day to 1.7 ppbv in the early morning, were in very good agreement from the two techniques, within {+-} 20%.

  19. RESEARCH NOTE: INTERFERENCES DUE TO OZONE-SCAVENGING REAGENTS IN THE GC-ECD DETERMINATION OF ALDEHYDES AND KETONS AS THE O-(2,3,4,5,6-PENTAFLUOROBENZYL)OXIMES

    EPA Science Inventory

    Six potential ozone-scavenging reagents were tested for possible interference in the GC-ECD determination of aldehydes and ketones after derivatization with O-(2,3,4,5,6-pentafluorobenzyl)oxylamine (PFBOA). All six-nitrite, cynaide, methanoate (formate), indigo-55'-disulfonate d...

  20. Catalytic asymmetric addition of Grignard reagents to alkenyl-substituted aromatic N-heterocycles.

    PubMed

    Jumde, Ravindra P; Lanza, Francesco; Veenstra, Marieke J; Harutyunyan, Syuzanna R

    2016-04-22

    Catalytic asymmetric conjugate addition reactions represent a powerful strategy to access chiral molecules in contemporary organic synthesis. However, their applicability to conjugated alkenyl-N-heteroaromatic compounds, of particular interest in medicinal chemistry, has lagged behind applications to other substrates. We report a highly enantioselective and chemoselective catalytic transformation of a wide range of β-substituted conjugated alkenyl-N-heteroaromatics to their corresponding chiral alkylated products. This operationally simple methodology can introduce linear, branched, and cyclic alkyl chains, as well as a phenyl group, at the β-carbon position. The key to this success was enhancement of the reactivity of alkenyl-heteroaromatic substrates via Lewis acid activation, in combination with the use of readily available and highly reactive Grignard reagents and a copper catalyst coordinated by a chiral chelating diphosphine ligand. PMID:27102477

  1. Chiral geometry in multiple chiral doublet bands

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Chen, Qibo

    2016-02-01

    The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with . The energy spectra, electromagnetic transition probabilities B(M1) and B(E2), angular momenta, and K-distributions are studied. It is demonstrated that the chirality still remains not only in the yrast and yrare bands, but also in the two higher excited bands when γ deviates from 30°. The chiral geometry relies significantly on γ, and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands. Supported by Plan Project of Beijing College Students’ Scientific Research and Entrepreneurial Action, Major State 973 Program of China (2013CB834400), National Natural Science Foundation of China (11175002, 11335002, 11375015, 11461141002), National Fund for Fostering Talents of Basic Science (NFFTBS) (J1103206), Research Fund for Doctoral Program of Higher Education (20110001110087) and China Postdoctoral Science Foundation (2015M580007)

  2. Photorefractive effect in ferroelectric liquid crystal blends containing terthiophene photoconductive chiral dopants

    NASA Astrophysics Data System (ADS)

    Sasaki, Takeo; Yoshino, Masanori

    2016-04-01

    Ferroelectric liquid crystalline mixtures composed of a smectic liquid crystal, a photoconductive chiral dopant, and an electron trap reagent exhibit a large photorefractivity with a rapid response. It is expected that the photorefractive FLC blends can be utilized in dynamic amplification of moving optical signals. In the present study, the photorefractive properties of the ferroelectric liquid crystal blends containing different photoconductive chiral dopants were examined. The durability of the photoconductive chiral dopants during laser irradiation was investigated. Tthe effect of the conduction of photogenerated ionic species on the photorefractivity decay was clarified.

  3. On-Line Derivatization Gas Chromatography Ion Trap Mass Spectrometry for Determination of Endocrine Disruptors in Surface Water

    SciTech Connect

    Tzing, Shin-Hwa; Chang, Jia-Yaw; Ling, Yong-Chien

    2004-03-31

    A method has been developed for the determination of endocrine disruptors (EDs) (containing hydroxyl groups) in surface water from different sources. The surface water samples from different sites including school and local dormitory sewage effluents, lake water and river water were collected and analyzed. In this method, the pretreated sample is directly analyzed by GC-MS using on-line derivatization, where tetramethylammonium hydroxide (TMA-OH) was used as the derivatizing agent. Use of large-volume direct sample introduction (DSI) and co-injection of the sample and TMAOH avoids external contaminations as observed in conventional derivatization protocols. Additionally, the use of chemical ionization (CI) and CI-MS/MS could enable detection of EDs at lower concentrations and reduce the matrices' interference thereby enhancing detection sensitivity of EDs for quantification. In this work, the use of dichloromethane as CI reagent for EDs is reported for the first time and could detect EDs to concentrations as low as 0.5 pg/mL. The recovery ranged from 74 to 112 % and the relative standard derivations for replicate analyses ranged from 5 to 17 %. We hope that this method will be applicable for routine analysis of EDs with hydroxyl functional groups.

  4. [Determination of bisphenol A from toys and food contact materials by derivatization and gas chromatography-mass spectrometry].

    PubMed

    Gao, Yonggang; Zhang, Yanyan; Gao, Jianguo; Zhang, Huiling; Zheng, Lisha; Chen, Jing

    2012-10-01

    A method was developed for the determination of bisphenol A (BPA) in toys and food contact materials. The BPA was extracted with Soxhlet extraction method from the sample and reacted with acetic anhydride. The final product was determined by gas chromatography-mass spectrometry (GC-MS). To achieve the optimum derivatization performance, the derivatization time and dosage of derivatization reagent etc. were investigated. Under the optimized experimental conditions, the final product was stable and the peak shape was good. The linearity of the derivative was good in the range of 0.05 to 50 mg/L with the correlation coefficient (r2) above 0.999. The recoveries ranged from 80% to 93% at the spiked levels of 0.05, 1.00, 10.00 mg/kg with the relative standard deviations (RSDs) less than 3.7%. The limit of detection (S/N = 3) was 10 microg/kg. The method is accurate and has high recovery. The method is suitable for the inspection of bisphenol A in toys and food contact materials.

  5. Use of scavenger beads to remove excess labeling reagents from capillary zone electrophoresis samples.

    PubMed

    Mort, A J; Zhan, D; Rodriguez, V

    1998-09-01

    In many cases, samples for capillary zone electrophoresis (CZE) are derivatized with a chromophore or fluorophore to enhance their detectability. To ensure efficient labeling, a large excess of labeling agent is often used, which leads to the presence of a large peak for unreacted reagent. Here we report that excess reagent can be reacted with "scavenger beads" carrying an appropriate functional group to remove it from the sample solution. We present examples of removal of aminonaphthalene mono-, di-, and trisulfonic acid from mixtures in which they were used to label mono- or oligosaccharides by reductive amination. Aldehyde-containing scavenger beads were made by oxidizing Sephadex G-50 beads with sodium periodate. These were added to the labeling reaction mixtures after the reductive amination of the sugars was complete. Almost complete elimination of the peak from the labeling agent could be achieved.

  6. Asymmetric conjugate addition of Grignard reagents to 3-silyl unsaturated esters for the facile preparation of enantioenriched β-silylcarbonyl compounds and allylic silanes.

    PubMed

    Zhao, Kai; Loh, Teck-Peng

    2014-12-01

    A highly enantioselective conjugate addition of Grignard reagents to 3-silyl unsaturated esters to deliver synthetically useful chiral β-silylcarbonyl compounds was developed. The synthetic value of this methodology was further illustrated by the synthesis of enantioenriched β-hydroxyl esters and the facile access granted to various α-chiral allylic silanes. A plethora of diastereoselective transformations of β-silylenolates were also investigated and afforded manifold organosilanes that contained contiguous stereogenic centers with excellent enantioselectivity. PMID:25323817

  7. Zwitterionic chiral stationary phases based on cinchona and chiral sulfonic acids for the direct stereoselective separation of amino acids and other amphoteric compounds.

    PubMed

    Zhang, Tong; Holder, Emilie; Franco, Pilar; Lindner, Wolfgang

    2014-06-01

    An extensive series of free amino acids and analogs were directly resolved into enantiomers (and stereoisomers where appropriate) by HPLC on zwitterionic chiral stationary phases (Chiralpak ZWIX(+) and Chiralpak ZWIX(-)). The interaction and chiral recognition mechanisms were based on the synergistic double ion-paring process between the analyte and the chiral selectors. The chiral separation and elution order were found to be predictable for primary α-amino acids with apolar aliphatic side chains. A systematic investigation was undertaken to gain an insight into the influence of the structural features on the enantiorecognition. The presence of polar and/or aromatic groups in the analyte structure is believed to tune the double ion-paring equilibrium by the involvement of the secondary interaction forces such as hydrogen bonding, Van der Waals forces and π-π stacking in concert with steric parameters. The ZWIX chiral columns were able to separate enantiomers and stereoisomers of various amphoteric compounds with no need for precolumn derivatization. Column switching between ZWIX(+) and ZWIX(-) is believed to be an instrumental tool to reverse or control the enantiomers elution order, due to the complementarity of the applied chiral selectors.

  8. Trace analysis of acidic pharmaceutical residues in waters with isotope dilution gas chromatography-mass spectrometry via methylation derivatization.

    PubMed

    Hu, Ruikang; Yang, Zhaoguang; Zhang, Lifeng

    2011-09-30

    Acidic pharmaceutical residues are pollutants of emerging concern and are generally monitored by HPLC-MS/MS. However, due to the limited separation efficiency of HPLC column and lack of suitable mass transition for confirmation analysis, some interference may not be separated completely and differentiated from ibuprofen, which may cause the results with interference, especially in sample with complex matrix. The objective of this study is to develop a sensitive and reliable method for the determination of acidic pharmaceutical residues in water samples by GC-MS with better resolution by using methylation derivatization and isotope dilution techniques. TMSDM, a mild reagent, was used as the derivatization reagent coupling with the isotope dilution technique, for the first time, to improve the precision and accuracy of the analytical method to determine the pharmaceutical residues in water. The MDLs for the five acidic organic compounds: ibuprofen, gemfibrozil, naproxen, ketoprofen and diclofenac were from 0.7 to 1.1 ng/L, with recoveries ranging from 93 to 110%. Alternative to the HPLC-MS/MS method, the developed GC-MS protocols provides an additional option for the analysis of acidic pharmaceutical residues in water, with better separation efficiency in reducing interferences from complicated sample matrix, for determination of ibuprofen residues.

  9. Examination of the kinetic isotopic effect to the acetylation derivatization for the gas chromatographic-combustion-isotope ratio mass spectrometric doping control analysis of endogenous steroids.

    PubMed

    Angelis, Yiannis S; Kioussi, Maroula K; Kiousi, Polyxeni; Brenna, J Thomas; Georgakopoulos, Costas G

    2012-12-01

    In gas chromatographic-combustion-isotope ratio mass spectrometry (GC-C-IRMS) doping control analysis, endogenous androgenic anabolic steroids and their metabolites are commonly acetylated using acetic anhydride reagent, thus incorporating exogenous carbon that contributes to the measured isotope ratio. Comparison of the endogenous δ(13)C of free, mono-, and di-acetylated steroids requires application of corrections, typically through straightforward use of the mass balance equation. Variability in kinetic isotope effects (KIE) due to steroid structures could cause fractionation of endogenous steroid carbon, resulting in inaccurate results. To test for possible KIE influence on δ(13)C, acetic anhydride of graded isotope ratio within the natural abundance range was used under normal derivatization conditions to test for linearity. In all cases, plots of measured steroid acetate δ(13)C versus acetic anhydride δ(13)C were linear and slopes were not significantly different. Regression analysis of the Δδ(13)C of enriched acetic anhydrides versus Δδ(13)C of derivatized steroids shows that KIE are similar in all cases. We conclude that δ(13)C calculated from the mass balance equation is independent of the δ(13)C of the acetic anhydride reagent, and that net KIE under normal derivatization conditions do not bias the final reported steroid δ(13)C.

  10. Determination of atrazine and its major degradation products in soil pore water by solid-phase extraction, chemical derivatization, and gas chromatography/mass spectrometry

    USGS Publications Warehouse

    Carter, D.S.

    1996-01-01

    This report describes a method for the determination of atrazine, desethylatrazine, deisopropylatrazine, didealkylatrazine, and hydroxyatrazine from soil pore waters by use of solid-phase extractionfollowed by chemical derivatization and gas chromatography/mass spectrometry. The analytes are isolated from the pore-water matrix byextraction onto a graphitized carbon-black cartridge. The cartridge is dried under vacuum, and adsorbed analytes are removed by elution with ethyl acetate followed by dichloromethane/methanol (7:3, volume/volume). Water is removed from the ethyl acetate fraction on an anhydrous sodium sulfate column. The combined fractions are solvent exchanged into acetonitrile, evaporated by use of a nitrogen stream, and derivatized by use of N- methyl-N-(tert-butyldimethylsilyl)- trifluoroacetamide. The derivatized extracts are analyzed by capillary-column gaschromatography/electron-impact mass spectrometry in the scan mode. Estimated method detection limits range from 0.03 to 0.07 micrograms per liter. The mean recoveries of all analytes and surrogates determined at 0.74 to 0.82 micrograms per liter in reagent water in soil pore water were 94 percent and 98 percent, respectively. The mean recoveries of all analytes and surrogates determined at 7.4 to 8.2 micrograms per liter in reagent water and in soil pore water were 96 percent and 97 percent,respectively. Recoveries were 90 percent or higher, regardless of analyte concentration or matrix composition, for all compounds excepthydroxyatrazine, whose recoveries were slightly lower (77 percent) at the low concentration.

  11. Molecular model for chirality phenomena

    NASA Astrophysics Data System (ADS)

    Latinwo, Folarin; Stillinger, Frank H.; Debenedetti, Pablo G.

    2016-10-01

    Chirality is a hallmark feature for molecular recognition in biology and chemical physics. We present a three-dimensional continuum model for studying chirality phenomena in condensed phases using molecular simulations. Our model system is based upon a simple four-site molecule and incorporates non-trivial kinetic behavior, including the ability to switch chirality or racemize, as well as thermodynamics arising from an energetic preference for specific chiral interactions. In particular, we introduce a chiral renormalization parameter that can locally favor either homochiral or heterochiral configurations. Using this model, we explore a range of chirality-specific phenomena, including the kinetics of chiral inversion, the mechanism of spontaneous chiral symmetry breaking in the liquid, chirally driven liquid-liquid phase separation, and chiral crystal structures.

  12. Development and validation of an LC-ESI/MS/MS method with precolumn derivatization for the determination of betulin in rat plasma.

    PubMed

    Hu, Zhiwei; Guo, Na; Wang, Ziming; Liu, Yong; Wang, Yu; Ding, Weimin; Zhang, Dehui; Wang, Yang; Yan, Xiufeng

    2013-11-15

    Neutral pentacyclic triterpenes with only one or two hydroxyl groups, such as betulin, are not easily ionized by electrospray ionization (ESI). However, because betulin is reactive and neutral, derivatization may improve ionization efficiency. In the present study, the potency of different derivatization reagents was evaluated and p-toluenesulfonyl isocyanate (PTSI) was proven to be the optimal. The derivative generated by the reaction of betulin with PTSI was ionizable and fragmentable in the negative mode by liquid chromatography-electrospray ionization/tandem mass spectrometry (LC-ESI/MS/MS). Based on this chemical derivatization, an LC-ESI/MS/MS method was developed and validated for the quantification of betulin in rat plasma. The sample was extracted with ethyl acetate, derivatized with PTSI, separated on an ACQ UPLC BEH phenyl column, and analyzed in negative multiple reaction monitoring (MRM) mode. The calibration curve was linear over the betulin concentration range 2.5-200ng/mL. The lower limit of quantification was 2.5ng/mL. The inter- and intra-day accuracy and precision were within ±15%. Betulin recoveries were 86.7% or higher at three quality control levels (5, 50, and 160ng/mL). This validated method was subsequently applied to a pharmacokinetic study of betulin in rat plasma after oral administration.

  13. Simultaneous determination of individual isothiocyanates in plant samples by HPLC-DAD-MS following SPE and derivatization with N-acetyl-l-cysteine.

    PubMed

    Pilipczuk, Tadeusz; Kusznierewicz, Barbara; Chmiel, Tomasz; Przychodzeń, Witold; Bartoszek, Agnieszka

    2017-01-01

    The procedure for the isothiocyanates (ITCs) determination that involves derivatization with N-acetyl-l-cysteine (NAC) and separation by HPLC was developed. Prior to derivatization, plant ITCs were isolated and purified using solid-phase extraction (SPE). The optimum conditions of derivatization are: 500μL of isopropanolic eluate obtained by SPE combined with 500μL of derivatizing reagent (0.2M NAC and 0.2M NaHCO3 in water) and reaction time of 1h at 50°C. The formed dithiocarbamates are directly analyzed by HPLC coupled with diode array detector and mass spectrometer if required. The method was validated for nine common natural ITCs. Calibration curves were linear (R(2)⩾0.991) within a wide range of concentrations and limits of detection were below 4.9nmol/mL. The recoveries were in the range of 83.3-103.7%, with relative standard deviations <5.4%. The developed method has been successfully applied to determine ITCs in broccoli, white cabbage, garden cress, radish, horseradish and papaya. PMID:27507514

  14. A Derivatization and Validation Strategy for Determining the Spatial Localization of Endogenous Amine Metabolites in Tissues using MALDI Imaging Mass Spectrometry

    PubMed Central

    Manier, M. Lisa; Spraggins, Jeffrey M.; Reyzer, Michelle L.; Norris, Jeremy L.; Caprioli, Richard M.

    2014-01-01

    Imaging mass spectrometry (IMS) studies increasingly focus on endogenous small molecular weight metabolites and consequently bring special analytical challenges. Since analytical tissue blanks do not exist for endogenous metabolites, careful consideration must be given to confirm molecular identity. Here we present approaches for the improvement in detection of endogenous amine metabolites such as amino acids and neurotransmitters in tissues through chemical derivatization and matrix-assisted laser desorption/ionization (MALDI) IMS. Chemical derivatization with 4-hydroxy-3-methoxycinnamaldehyde (CA) was used to improve sensitivity and specificity. CA was applied to the tissue via MALDI sample targets precoated with a mixture of derivatization reagent and ferulic acid (FA) as a MALDI matrix. Spatial distributions of chemically derivatized endogenous metabolites in tissue were determined by high-mass resolution and MSn imaging mass spectrometry. We highlight an analytical strategy for metabolite validation whereby tissue extracts are analyzed by high-performance liquid chromatography (HPLC)-MS/MS to unambiguously identify metabolites and distinguish them from isobaric compounds. PMID:25044893

  15. The covariant chiral ring

    NASA Astrophysics Data System (ADS)

    Bourget, Antoine; Troost, Jan

    2016-03-01

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N = (4 , 4) supersymmetry in two dimensions. For seed target spaces K3 and T 4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  16. Synthesis of Chiral Cyclopentenones.

    PubMed

    Simeonov, Svilen P; Nunes, João P M; Guerra, Krassimira; Kurteva, Vanya B; Afonso, Carlos A M

    2016-05-25

    The cyclopentenone unit is a very powerful synthon for the synthesis of a variety of bioactive target molecules. This is due to the broad diversity of chemical modifications available for the enone structural motif. In particular, chiral cyclopentenones are important precursors in the asymmetric synthesis of target chiral molecules. This Review provides an overview of reported methods for enantioselective and asymmetric syntheses of cyclopentenones, including chemical and enzymatic resolution, asymmetric synthesis via Pauson-Khand reaction, Nazarov cyclization and organocatalyzed reactions, asymmetric functionalization of the existing cyclopentenone unit, and functionalization of chiral building blocks. PMID:27101336

  17. ESA Mission ROSETTA Will Probe for Chirality of Cometary Amino Acids

    NASA Astrophysics Data System (ADS)

    Thiemann, Wolfram H.-P.; Meierhenrich, Uwe

    2001-02-01

    New crucial theoretical investigations on the origin of biomolecular chirality are reviewed briefly. With the goal to investigate these theories our team is going to perform the `chirality-experiment' in the near future with cometary matter. In 2012 the robotical lander RoLand will detach from the orbiter of the ROSETTA spacecraft and set down on the surface of comet 46P/Wirtanen in order to separate and identify cometary organic compounds via GC-MS in situ. Chiral organics will be separated into their enantiomers by application of 3 capillary columns coated with different kinds of stationary phases. Non-volatile compounds like amino acids will be derivatized in especially developed gas phase alkylation steps avoiding reactions in the liquid phase. The results of these preliminary gas phase reactions are presented in this article.

  18. Catalysis of dynamical chiral symmetry breaking by chiral chemical potential

    NASA Astrophysics Data System (ADS)

    Braguta, V. V.; Kotov, A. Yu.

    2016-05-01

    In this paper, we study the properties of media with chiral imbalance parametrized by chiral chemical potential. It is shown that depending on the strength of interaction between constituents in the media the chiral chemical potential either creates or enhances dynamical chiral symmetry breaking. Thus, the chiral chemical potential plays the role of the catalyst of dynamical chiral symmetry breaking. Physically, this effect results from the appearance of the Fermi surface and additional fermion states on this surface, which take part in dynamical chiral symmetry breaking. An interesting conclusion which can be drawn is that at sufficiently small temperature chiral plasma is unstable with respect to condensation of Cooper pairs and dynamical chiral symmetry breaking even for vanishingly small interactions between constituents.

  19. Mass spectrometer having a derivatized sample presentation apparatus

    DOEpatents

    Nelson, Randall W.

    2000-07-25

    A mass spectrometer having a derivatized sample presentation apparatus is provided. The sample presentation apparatus has a complex bound to the surface of the sample presentation apparatus. This complex includes a molecule which may chemically modify a biomolecule.

  20. Spintronics: Chiral damping

    PubMed Central

    Kim, Kyoung-Whan; Lee, Hyun-Woo

    2016-01-01

    The analysis of the magnetic domain wall motion in a nanostructured magnetic system with strong spin-orbit coupling shows that the energy dissipation can be chiral when the inversion symmetry is broken. PMID:26906956

  1. Nonlinear chiral transport phenomena

    NASA Astrophysics Data System (ADS)

    Chen, Jiunn-Wei; Ishii, Takeaki; Pu, Shi; Yamamoto, Naoki

    2016-06-01

    We study the nonlinear responses of relativistic chiral matter to the external fields such as the electric field E , gradients of temperature and chemical potential, ∇T and ∇μ . Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to ∇μ ×E due to the interplay between the effects of the Berry curvature and collisions. We also derive an analog of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.

  2. The quest for chirality

    SciTech Connect

    Bonner, W.A.

    1996-07-01

    The indispensable role played by homochirality and chiral homogeneity in the self-replication of crucial biomolecules is stressed, with the conclusion that life could neither exist nor originate without these chiral molecular attributes. Hypotheses historically proposed for the origin of chiral molecules on Earth are reviewed, including biogenic theories as well as abiotic theories embracing both indeterminate and determinate mechanisms. Indeterminate mechanisms, including autocatalytic symmetry breaking, asymmetric adsorption on quartz and clay minerals, and asymmetric syntheses in chiral crystals, are discussed and evaluated in the context of the prebiotic environment. Abiotic determinate mechanisms based on electric, magnetic and gravitational fields, on circularly polarized light (CPL), and on parity violation effects are summarized, with the emphasis that only CPL has proved practicable experimentally, but that it would be implausible on the primitive Earth. Mechanisms for the amplification of small, indigenous enantiomeric excesses are discussed, with one involving the partial polymerization of amino acids and the partial hydrolysis of polypeptides suggested as potentially viable prebiotically. Aspects of the turbulent, chirality-destructive primeval environment are described, with the conclusion that all of the above mechanisms for the {ital terrestrial} prebiotic origin of chirality would be non-viable, and that an alternative extraterrestrial source for the accumulation of chiral molecules on primitive Earth must have been operative. A scenario for this is outlined, in which we postulate that asymmetric photolysis of the organic mantles on interstellar grains in molecular clouds by circularly polarized ultraviolet synchrotron radiation from the neutron star remnants of supernovae produces chiral molecules in the grain mantles. (Abstract Truncated)

  3. Analysis of cysteine-containing proteins using precolumn derivatization with N-(2-ferroceneethyl)maleimide and liquid chromatography/electrochemistry/mass spectrometry.

    PubMed

    Seiwert, Bettina; Karst, Uwe

    2007-08-01

    N-(2-ferroceneethyl)maleimide (FEM) is introduced as an electroactive derivatizing agent for thiol functionalities in proteins. Using appropriate reaction conditions, the derivatization is completed within five minutes and no unspecific labeling of free amino functions is observed. Liquid chromatography/electrochemistry/mass spectrometry was used to detect the reaction products. The reagent is a useful tool for determining the number of free thiol groups or the total number of free and disulfide-bound thiol groups in proteins. The electrochemical cell provides additional information, because the increase in mass spectrometric response upon electrochemical oxidation of the neutral ferrocene to the charged ferrocinium groups is monitored. The method was successfully applied to the analysis of native proteins and their tryptic digests.

  4. Liquid chromatography coupled to on-line post column derivatization for the determination of organic compounds: a review on instrumentation and chemistries.

    PubMed

    Zacharis, Constantinos K; Tzanavaras, Paraskevas D

    2013-10-10

    Analytical derivatization either in pre or post column modes is one of the most widely used sample pretreatment techniques coupled to liquid chromatography. In the present review article we selected to discuss the post column derivatization mode for the analysis of organic compounds. The first part of the review focuses to the instrumentation of post-column setups including not only fundamental components such as pumps and reactors but also less common parts such as static mixers and back-pressure regulators; the second part of the article discusses the most popular "chemistries" that are involved in post column applications, including reagent-less approaches and new sensing platforms such as the popular gold nanoparticles. Some representative recent applications are also presented as tables.

  5. Improved Chiral Separation of Methamphetamine Enantiomers Using CSP-LC-MS-MS.

    PubMed

    Ward, Lauren F; Enders, Jeffrey R; Bell, David S; Cramer, Hugh M; Wallace, Frank N; McIntire, Gregory L

    2016-05-01

    To determine the true enantiomeric composition of methamphetamine urine drug testing results, chiral separation of dextro (D) and levo (L) enantiomers is necessary. While enantiomeric separation of methamphetamine has traditionally been accomplished using gas chromatography-mass spectrometry (GC-MS), chiral separation of D- and L-methamphetamine by chiral stationary phase (CSP) liquid chromatography-mass spectrometry/mass spectrometry (LC-MS-MS) has proved more reliable. Chirally selective detection of methamphetamine by GC-MS is often performed using L-N-trifluoroacetyl-prolyl chloride (TPC). L-TPC, a chiral compound, is known to have impurities that can affect the chiral composition percentages of the methamphetamine sample, potentially leading to inaccurate patient results. The comparative analysis of the samples run by GC and LC methods showed preferential bias of the GC method for producing error rates, consistent with previous research, of 8-19%. The CSP-LC-MS-MS method produces percent deviation errors of <2%. Additionally, the GC method failed to produce results that were 100% D- or L-isomer even for enantiomerically pure standards. A higher rate of D- and L-methamphetamine isomer racemization is seen in samples when analyzed by GC-MS using L-TPC-derivatizing agent. This racemization is not seen when these samples are tested with CSP-LC-MS-MS. Thus, a more accurate method of enantiomeric analysis is provided by CSP-LC-MS-MS. PMID:26869715

  6. Renewable-reagent electrochemical sensor

    DOEpatents

    Wang, J.; Olsen, K.B.

    1999-08-24

    A new electrochemical probe(s) design allowing for continuous (renewable) reagent delivery is described. The probe comprises an integrated membrane sampling/electrochemical sensor that prevents interferences from surface-active materials and greatly extends the linear range. The probe(s) is useful for remote or laboratory-based monitoring in connection with microdialysis sampling and electrochemical measurements of metals and organic compounds that are not readily detected in the absence of reacting with the compound. Also disclosed is a method of using the probe(s). 19 figs.

  7. Renewable-reagent electrochemical sensor

    DOEpatents

    Wang, Joseph; Olsen, Khris B.

    1999-01-01

    A new electrochemical probe(s) design allowing for continuous (renewable) reagent delivery. The probe comprises an integrated membrane-sampling/electrochemical sensor that prevents interferences from surface-active materials and greatly extends the linear range. The probe(s) is useful for remote or laboratory-based monitoring in connection with microdialysis sampling and electrochemical measurements of metals and organic compounds that are not readily detected in the absence of reacting with the compound. Also disclosed is a method of using the probe(s).

  8. Microcalibrator system for chemical signature and reagent delivery.

    SciTech Connect

    Staton, Alan W.; Simonson, Robert Joseph; Adkins, Douglas Ray; Rawlinson, Kim Scott; Robinson, Alex Lockwood; Hance, Bradley G.; Manginell, Ronald Paul; Sanchez, Lawrence James; Ellison, Jennifer Anne; Sokolowski, Sara Suzette

    2005-03-01

    Networked systems of low-cost, small, integrable chemical sensors will enable monitoring of Nonproliferation and Materials Control targets and chemical weapons threats. Sandia-designed prototype chemical sensor systems are undergoing extended field testing supported by DOE and other government agencies. A required surety component will be verification of microanalytical system performance, which can be achieved by providing a programmable source of chemical signature(s) for autonomous calibration of analytical systems. In addition, such a controlled chemical source could be used to dispense microaliquots of derivatization reagents, extending the analysis capability of chemical sensors to a wider range of targets. We have developed a microfabricated system for controlled release of selected compounds (calibrants) into the analytical stream of microsensor systems. To minimize pumping and valve requirements of microfluidic systems, and to avoid degradation issues associated with storage of dilute solutions, we have utilized thermally labile organic salts as solid-phase reservoir materials. Reproducible deposition of tetrapropyl ammonium hydroxide onto arrays of microfabricated heating elements can provide a pair of calibration marker compounds (one fast and one slow-eluting compound) for GC analyses. The use of this microaliquot gas source array for hydrogen generation is currently under further development. The goal of the latter effort will be to provide a source of high-pressure, low viscosity GC carrier gas for Sandia's next-generation microfabricated gas-phase chemical analysis systems.

  9. New aniline-containing amino alcohols from trans-(R,R)-2-(2-nitrophenyl)-3-phenyloxirane as useful intermediates for the synthesis of chiral ligands, bases, and benzoxazine nucleus.

    PubMed

    Solladié-Cavallo, Arlette; Lupattelli, Paolo; Bonini, Carlo; Ostuni, Valeria; Blasio, Nadia Di

    2006-12-22

    New enantiopure aniline-containing amino alcohols are directly derived from trans-(R,R)-2-(2-nitrophenyl)-3-phenyloxirane, by alternative regioselective double reductions. Subsequent selective alkylation procedures and derivatizations provide a rapid and high-yielding access to different chiral ligands, bases, and benzoxazines, without loss of optical purity.

  10. Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases.

    PubMed

    Freissinet, C; Buch, A; Szopa, C; Sternberg, R

    2013-09-01

    The performances of several commercial chiral capillary columns have been evaluated with the aim of determining the one most suitable for enantiomeric separation in a gas chromatograph onboard a space probe. We compared the GC-MS response of three capillary columns coated with different chiral stationary phases (CSP) using volatile chiral organic molecules which are potential markers of a prebiotic organic chemistry. The three different chiral capillary columns are Chirasil-Val, with an amino acid derivative CSP, ChiralDex-β-PM, with a CSP composed of dissolved permethylated β-cyclodextrins in polysiloxane, and Chirasil-Dex, with a CSP made of modified cyclodextrins chemically bonded to the polysiloxane backbone. Both kinetics and thermodynamics studies have been carried out to evaluate the chiral recognition potential in these different types of columns. The thermodynamic parameters also allow a better understanding of the driving forces affecting the retention and separation of the enantiomers. The Chirasil-Dex-CSP displays the best characteristics for an optimal resolution of the chiral compounds, without preliminary derivatization. This CSP had been chosen to be the only chiral column in the Sample Analysis at Mars (SAM) experiment onboard the current Mars Science Laboratory (MSL) mission, and is also part of the Mars Organic Molecules Analyzer (MOMA) gas chromatograph onboard the next Martian mission ExoMars. The use of this column could also be extended to all space missions aimed at studying chirality in space. PMID:23921265

  11. Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases.

    PubMed

    Freissinet, C; Buch, A; Szopa, C; Sternberg, R

    2013-09-01

    The performances of several commercial chiral capillary columns have been evaluated with the aim of determining the one most suitable for enantiomeric separation in a gas chromatograph onboard a space probe. We compared the GC-MS response of three capillary columns coated with different chiral stationary phases (CSP) using volatile chiral organic molecules which are potential markers of a prebiotic organic chemistry. The three different chiral capillary columns are Chirasil-Val, with an amino acid derivative CSP, ChiralDex-β-PM, with a CSP composed of dissolved permethylated β-cyclodextrins in polysiloxane, and Chirasil-Dex, with a CSP made of modified cyclodextrins chemically bonded to the polysiloxane backbone. Both kinetics and thermodynamics studies have been carried out to evaluate the chiral recognition potential in these different types of columns. The thermodynamic parameters also allow a better understanding of the driving forces affecting the retention and separation of the enantiomers. The Chirasil-Dex-CSP displays the best characteristics for an optimal resolution of the chiral compounds, without preliminary derivatization. This CSP had been chosen to be the only chiral column in the Sample Analysis at Mars (SAM) experiment onboard the current Mars Science Laboratory (MSL) mission, and is also part of the Mars Organic Molecules Analyzer (MOMA) gas chromatograph onboard the next Martian mission ExoMars. The use of this column could also be extended to all space missions aimed at studying chirality in space.

  12. Sulfonium Ion Derivatization, Isobaric Stable Isotope Labeling and Data Dependent CID- and ETD-MS/MS for Enhanced Phosphopeptide Quantitation, Identification and Phosphorylation Site Characterization

    PubMed Central

    Lu, Yali; Zhou, Xiao; Stemmer, Paul M.; Reid, Gavin E.

    2014-01-01

    An amine specific peptide derivatization strategy involving the use of novel isobaric stable isotope encoded ‘fixed charge’ sulfonium ion reagents, coupled with an analysis strategy employing capillary HPLC, ESI-MS, and automated data dependent ion trap CID-MS/MS, -MS3, and/or ETD-MS/MS, has been developed for the improved quantitative analysis of protein phosphorylation, and for identification and characterization of their site(s) of modification. Derivatization of 50 synthetic phosphopeptides with S,S′-dimethylthiobutanoylhydroxysuccinimide ester iodide (DMBNHS), followed by analysis using capillary HPLC-ESI-MS, yielded an average 2.5-fold increase in ionization efficiencies and a significant increase in the presence and/or abundance of higher charge state precursor ions compared to the non-derivatized phosphopeptides. Notably, 44% of the phosphopeptides (22 of 50) in their underivatized states yielded precursor ions whose maximum charge states corresponded to +2, while only 8% (4 of 50) remained at this maximum charge state following DMBNHS derivatization. Quantitative analysis was achieved by measuring the abundances of the diagnostic product ions corresponding to the neutral losses of ‘light’ (S(CH3)2) and ‘heavy’ (S(CD3)2) dimethylsulfide exclusively formed upon CID-MS/MS of isobaric stable isotope labeled forms of the DMBNHS derivatized phosphopeptides. Under these conditions, the phosphate group stayed intact. Access for a greater number of peptides to provide enhanced phosphopeptide sequence identification and phosphorylation site characterization was achieved via automated data-dependent CID-MS3 or ETD-MS/MS analysis due to the formation of the higher charge state precursor ions. Importantly, improved sequence coverage was observed using ETD-MS/MS following introduction of the sulfonium ion fixed charge, but with no detrimental effects on ETD fragmentation efficiency. PMID:21952753

  13. Chiral anomalies and differential geometry

    SciTech Connect

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)

  14. Active Chiral Plasmonics.

    PubMed

    Yin, Xinghui; Schäferling, Martin; Michel, Ann-Katrin U; Tittl, Andreas; Wuttig, Matthias; Taubner, Thomas; Giessen, Harald

    2015-07-01

    Active control over the handedness of a chiral metamaterial has the potential to serve as key element for highly integrated polarization engineering approaches, polarization sensitive imaging devices, and stereo display technologies. However, this is hard to achieve as it seemingly involves the reconfiguration of the metamolecule from a left-handed into a right-handed enantiomer and vice versa. This type of mechanical actuation is intricate and usually neither monolithically realizable nor viable for high-speed applications. Here, enabled by the phase change material Ge3Sb2Te6 (GST-326), we demonstrate a tunable and switchable mid-infrared plasmonic chiral metamaterial in a proof-of-concept experiment. A large tunability range of the circular dichroism response from λ = 4.15 to 4.90 μm is achieved, and we experimentally demonstrate that the combination of a passive bias-type chiral layer with the active chiral metamaterial allows for switchable chirality, that is, the reversal of the circular dichroism sign, in a fully planar, layered design without the need for geometrical reconfiguration. Because phase change materials can be electrically and optically switched, our designs may open up a path for highly integrated mid-IR polarization engineering devices that can be modulated on ultrafast time scales.

  15. Nonmicrobial alternative to reagent quality control testing.

    PubMed Central

    Reynolds, S M

    1982-01-01

    The traditional approach to quality control in microbiology involves the routine testing of both media and reagents with live microbial cultures. This is expensive, time consuming, and subject to the variables associated with the use of live organisms. A system of reagent quality control based on the pure chemical form of the metabolic end products important to the identification of the Enterobacteriaceae was evaluated. The metabolite reagent control system is simple, reliable, and extremely cost effective, and it eliminates the need for live microbial cultures and media for reagent quality control. PMID:6759528

  16. Single-step enantioselective amino acid flux analysis by capillary electrophoresis using on-line sample preconcentration with chemical derivatization.

    PubMed

    Ptolemy, Adam S; Tran, Lara; Britz-McKibbin, Philip

    2006-07-15

    Capillary electrophoresis (CE) represents a versatile platform for integrating sample pretreatment with chemical analysis because of its ability to tune analyte electromigration and band dispersion properties in discontinuous electrolyte systems. In this article, a single-step method that combines on-line sample preconcentration with in-capillary chemical derivatization is developed for rapid, sensitive, and enantioselective analysis of micromolar levels of amino acids that lack intrinsic chromophores by CE with UV detection. Time-resolved electrophoretic studies revealed two distinct stages of amino acid band narrowing within the original long sample injection plug occurring both prior to and after in-capillary labeling via zone passing by ortho-phthalaldehyde/N-acetyl l-cysteine (OPA/NAC). This technique enabled direct analysis of d-amino acids in a 95% enantiomeric excess mixture with sub-micromolar detection limits and minimal sample handling, where the capillary functions as a preconcentrator, microreactor, and chiral selector. On-line sample preconcentration with chemical derivatization CE (SPCD-CE) was applied to study the enantioselective amino acid flux in Escherichia coli bacteria cultures, which demonstrated a unique l-Ala efflux into the extracellular medium. New strategies for high-throughput analyses of low-abundance metabolites are important for understanding fundamental physiological processes in bacteria required for screening the efficacy of new classes of antibiotics as well as altered metabolism in genetically modified mutant strains.

  17. Single-step enantioselective amino acid flux analysis by capillary electrophoresis using on-line sample preconcentration with chemical derivatization.

    PubMed

    Ptolemy, Adam S; Tran, Lara; Britz-McKibbin, Philip

    2006-07-15

    Capillary electrophoresis (CE) represents a versatile platform for integrating sample pretreatment with chemical analysis because of its ability to tune analyte electromigration and band dispersion properties in discontinuous electrolyte systems. In this article, a single-step method that combines on-line sample preconcentration with in-capillary chemical derivatization is developed for rapid, sensitive, and enantioselective analysis of micromolar levels of amino acids that lack intrinsic chromophores by CE with UV detection. Time-resolved electrophoretic studies revealed two distinct stages of amino acid band narrowing within the original long sample injection plug occurring both prior to and after in-capillary labeling via zone passing by ortho-phthalaldehyde/N-acetyl l-cysteine (OPA/NAC). This technique enabled direct analysis of d-amino acids in a 95% enantiomeric excess mixture with sub-micromolar detection limits and minimal sample handling, where the capillary functions as a preconcentrator, microreactor, and chiral selector. On-line sample preconcentration with chemical derivatization CE (SPCD-CE) was applied to study the enantioselective amino acid flux in Escherichia coli bacteria cultures, which demonstrated a unique l-Ala efflux into the extracellular medium. New strategies for high-throughput analyses of low-abundance metabolites are important for understanding fundamental physiological processes in bacteria required for screening the efficacy of new classes of antibiotics as well as altered metabolism in genetically modified mutant strains. PMID:16753129

  18. Chirality and Life

    NASA Astrophysics Data System (ADS)

    Barron, Laurence D.

    Chirality, meaning handedness, pervades much of modern science, from the physics of elementary particles to the chemistry of life. The amino acids and sugars from which the central molecules of life—proteins and nucleic acids—are constructed exhibit homochirality, which is expected to be a key biosignature in astrobiology. This article provides a brief review of molecular chirality and its significance for the detection of extant or extinct life on other worlds. Fundamental symmetry aspects are emphasized since these bring intrinsic physical properties of the universe to bear on the problem of the origin and role of homochirality in the living world.

  19. Chirality and Life

    NASA Astrophysics Data System (ADS)

    Barron, Laurence D.

    2008-03-01

    Chirality, meaning handedness, pervades much of modern science, from the physics of elementary particles to the chemistry of life. The amino acids and sugars from which the central molecules of life—proteins and nucleic acids—are constructed exhibit homochirality, which is expected to be a key biosignature in astrobiology. This article provides a brief review of molecular chirality and its significance for the detection of extant or extinct life on other worlds. Fundamental symmetry aspects are emphasized since these bring intrinsic physical properties of the universe to bear on the problem of the origin and role of homochirality in the living world.

  20. Asymmetric cyanation of imines via dipeptide-derived organophosphine dual-reagent catalysis

    PubMed Central

    Wang, Hong-Yu; Zheng, Chang-Wu; Chai, Zhuo; Zhang, Jia-Xing; Zhao, Gang

    2016-01-01

    Over the past few decades, enantioselective phosphine organocatalysis has evolved rapidly into a highly efficient catalytic strategy for a range of useful reactions. However, as restricted by the traditional catalytic modes, some important reactions, such as asymmetric Strecker-type reactions, have thus far been out of reach of this strategy. Reported herein is an application of enantioselective phosphine organocatalysis for asymmetric Strecker-type reactions, enabled by a dual-reagent catalyst system in which the key organophosphorus zwitterion intermediate, generated in situ by mixing a chiral dipeptide-derived multifunctional organophosphine with methyl acrylate, is used as a highly efficient chiral Lewis base catalyst. The high efficiency of this catalytic system is demonstrated in the asymmetric cyanation of isatin-derived ketimines and azomethine aldimines as well as in the kinetic resolution of racemic 3-substituted azomethines. Mechanistic studies provide experimental evidence for the intermediacy of the putative zwitterion and its role as a catalytically active Lewis base. PMID:27625043

  1. Asymmetric cyanation of imines via dipeptide-derived organophosphine dual-reagent catalysis.

    PubMed

    Wang, Hong-Yu; Zheng, Chang-Wu; Chai, Zhuo; Zhang, Jia-Xing; Zhao, Gang

    2016-01-01

    Over the past few decades, enantioselective phosphine organocatalysis has evolved rapidly into a highly efficient catalytic strategy for a range of useful reactions. However, as restricted by the traditional catalytic modes, some important reactions, such as asymmetric Strecker-type reactions, have thus far been out of reach of this strategy. Reported herein is an application of enantioselective phosphine organocatalysis for asymmetric Strecker-type reactions, enabled by a dual-reagent catalyst system in which the key organophosphorus zwitterion intermediate, generated in situ by mixing a chiral dipeptide-derived multifunctional organophosphine with methyl acrylate, is used as a highly efficient chiral Lewis base catalyst. The high efficiency of this catalytic system is demonstrated in the asymmetric cyanation of isatin-derived ketimines and azomethine aldimines as well as in the kinetic resolution of racemic 3-substituted azomethines. Mechanistic studies provide experimental evidence for the intermediacy of the putative zwitterion and its role as a catalytically active Lewis base. PMID:27625043

  2. Asymmetric cyanation of imines via dipeptide-derived organophosphine dual-reagent catalysis

    NASA Astrophysics Data System (ADS)

    Wang, Hong-Yu; Zheng, Chang-Wu; Chai, Zhuo; Zhang, Jia-Xing; Zhao, Gang

    2016-09-01

    Over the past few decades, enantioselective phosphine organocatalysis has evolved rapidly into a highly efficient catalytic strategy for a range of useful reactions. However, as restricted by the traditional catalytic modes, some important reactions, such as asymmetric Strecker-type reactions, have thus far been out of reach of this strategy. Reported herein is an application of enantioselective phosphine organocatalysis for asymmetric Strecker-type reactions, enabled by a dual-reagent catalyst system in which the key organophosphorus zwitterion intermediate, generated in situ by mixing a chiral dipeptide-derived multifunctional organophosphine with methyl acrylate, is used as a highly efficient chiral Lewis base catalyst. The high efficiency of this catalytic system is demonstrated in the asymmetric cyanation of isatin-derived ketimines and azomethine aldimines as well as in the kinetic resolution of racemic 3-substituted azomethines. Mechanistic studies provide experimental evidence for the intermediacy of the putative zwitterion and its role as a catalytically active Lewis base.

  3. On-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: a dual strategy for integrating sample pretreatment with chemical analysis.

    PubMed

    Ptolemy, Adam S; Le Bihan, Marianne; Britz-McKibbin, Philip

    2005-11-01

    Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho-phthalaldehyde/N-acetyl-L-cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector.

  4. On-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: a dual strategy for integrating sample pretreatment with chemical analysis.

    PubMed

    Ptolemy, Adam S; Le Bihan, Marianne; Britz-McKibbin, Philip

    2005-11-01

    Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho-phthalaldehyde/N-acetyl-L-cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector. PMID:16200529

  5. 21 CFR 866.4100 - Complement reagent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Complement reagent. 866.4100 Section 866.4100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents §...

  6. 21 CFR 866.4100 - Complement reagent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Complement reagent. 866.4100 Section 866.4100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents §...

  7. 21 CFR 866.4100 - Complement reagent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Complement reagent. 866.4100 Section 866.4100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents §...

  8. 21 CFR 866.4100 - Complement reagent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Complement reagent. 866.4100 Section 866.4100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents §...

  9. 21 CFR 866.4100 - Complement reagent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Complement reagent. 866.4100 Section 866.4100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents §...

  10. TREATMENT OF MTBE USING FENTON'S REAGENT

    EPA Science Inventory

    This paper addresses the removal of MTBE from water, using Fenton's Reagent. Although complete mineralization of MTBE by Fenton's Reagent was not achieved, greater than 99% destruction of MTBE was realized. This was accomplished at a Fe+2:H2O2 ratio of 1:1 and one hour of contact...

  11. Determination of theanine and gamma-aminobutyric acid in tea by high performance- liquid chromatography with precolumn derivatization.

    PubMed

    Tu, Yunfei; Yang, Xiufang; Zhang, Shikang; Zhu, Yuejin

    2012-02-01

    A method of precolumn derivatization-high performance liquid chromatography (HPLC) for the determination of theanine and gamma-aminobutyric acid (GABA) in tea was established. o-Phthalaldehyde (OPA) and N-acetyl-L-cysteine (NAC) were chosen as the derivatization reagents. The effects of teapolyphenol (Tp), proline (Pro) and Vitamin C (Vc) on derivatization yields were investigated. The results indicated that Vc not only stabilized the stock solution of OPA, but also enhanced the yield of GABA derivative. However, the yield of theanine derivative was less affected. The HPLC separation system was also optimized. The resolution of the derivatives was improved by adjusting the pH value and phosphate-citric buffer concentration of the mobile phase. The limits of detection (LODs) for GABA and theanine were 3.01 x 10(-5) mmol/L and 7.98 x 10(-5) mmol/L, and the limits of quantification (LOQs) were 9.99 x 10(-5) mmol/L and 2.658 x 10(-4) mmol/L, respectively. The linear ranges of GABA and theanine were 0.01 - 0.4 mmol/L with the correlation coefficient of 0.996 and 0.05 - 0.8 mmol/L with the correlation coefficient of 0.995, respectively. The main recoveries for GABA and theanine in green tea, Oolong tea, and black tea, ranged from 99.29% to 119.60% and from 62.88% to 141.06% respectively. The method with simple procedure and efficient separation was proved to be suitable for the determination of GABA and theanine in tea. PMID:22679834

  12. [Determination of 14 sulfonamide residues in shrimps by high performance liquid chromatography coupled with post-column derivatization].

    PubMed

    Huang, Dongmei; Huang, Xuanyun; Gu, Runrun; Hui, Yunhua; Tian, Liangliang; Feng, Bing; Zhang, Xuan; Yu, Huijuan

    2014-08-01

    A method for the determination of 14 sulfonamide residues in shrimps by high performance liquid chromatography coupled with post-column derivatization was established. The sulfonamide residues were extracted with ethyl acetate after adding sulfapyridine as internal standard. The extracts were vacuum-concentrated and reverse-extracted by 2 mol/L hydrochloric acid solution for clean-up, and then the hydrochloric acid solution was defatted with n-hex- ane. The solution after filtration was blended with a mixed solution of methanol, acetonitrile and 3. 5 mol/L sodium acetate solution (5:5:20, v/v/v). The sulfonamides were separated on a C18 column by RP-HPLC and on-line derivatized with a fluorescamine and detected with a fluorescence detector. The standard addition method was used for quantitative analysis. The parameters of post-column derivatization system, such as concentration of fluorescamine solution, velocity of reagent solution and reaction temperature, were optimized. The calibration curves of the method showed good linearity in the range of 5 - 200 μg/L. The limits of quantification (LOQ, S/N= 10) were 1.0-5.0 μg/kg for the 14 sulfonamides. The recoveries were 77.8%- 103. 6% in the spiked range of 1. 0-100.0 μg/kg in shrimps with the relative standard deviations of 2.9%-9.1% (n= 6). The results indicated that the method is sensitive, efficient and more accurate. It is suitable for the simultaneous determination of the 14 sulfonamide residues in shrimps.

  13. GC-based detection of aldononitrile acetate derivatized glucosamine and muramic acid for microbial residue determination in soil.

    PubMed

    Liang, Chao; Read, Harry W; Balser, Teri C

    2012-05-19

    Quantitative approaches to characterizing microorganisms are crucial for a broader understanding of the microbial status and function within ecosystems. Current strategies for microbial analysis include both traditional laboratory culture-dependent techniques and those based on direct extraction and determination of certain biomarkers. Few among the diversity of microbial species inhabiting soil can be cultured, so culture-dependent methods introduce significant biases, a limitation absent in biomarker analysis. The glucosamine, mannosamine, galactosamine and muramic acid have been well served as measures of both the living and dead microbial mass, of these the glucosamine (most abundant) and muramic acid (uniquely from bacterial cell) are most important constituents in the soil systems. However, the lack of knowledge on the analysis restricts the wide popularization among scientific peers. Among all existing analytical methods, derivatization to aldononitrile acetates followed by GC-based analysis has emerged as a good option with respect to optimally balancing precision, sensitivity, simplicity, good chromatographic separation, and stability upon sample storage. Here, we present a detailed protocol for a reliable and relatively simple analysis of glucosamine and muramic acid from soil after their conversion to aldononitrile acetates. The protocol mainly comprises four steps: acid digestion, sample purification, derivatization and GC determination. The step-by-step procedure is modified according to former publications. In addition, we present a strategy to structurally validate the molecular ion of the derivative and its ion fragments formed upon electron ionization. We applied GC-EI-MS-SIM, LC-ESI-TOF-MS and isotopically labeled reagents to determine the molecular weight of aldononitrile acetate derivatized glucosamine and muramic acid; we used the mass shift of isotope-labeled derivatives in the ion spectrum to investigate ion fragments of each derivatives. In

  14. Nucleic acid X-ray crystallography via direct selenium derivatization.

    PubMed

    Lin, Lina; Sheng, Jia; Huang, Zhen

    2011-09-01

    X-ray crystallography has proven to be an essential tool for structural studies of bio-macromolecules at the atomic level. There are two major bottle-neck problems in the macromolecular crystal structure determination: phasing and crystallization. Although the selenium derivatization is routinely used for solving novel protein structures through the MAD phasing technique, the phase problem is still a critical issue in nucleic acid crystallography. The background and current progress of using direct selenium-derivatization of nucleic acids (SeNA) to solve the phase problem and to facilitate nucleic acid crystallization for X-ray crystallography are summarized in this tutorial review. PMID:21666919

  15. Capillary gas chromatographic determination of putrescine and cadaverine in serum of cancer patients using trifluoroacetylacetone as derivatizing reagent.

    PubMed

    Khuhawar, M Y; Memon, A A; Jaipal, P D; Bhanger, M I

    1999-02-19

    Trifluoroacetylacetone (FAA) derivatives of 1,4-diaminobutane (putrescine) (Pu) and 1,5-diaminopentane (cadaverine) (CA) were prepared and characterized by elemental microanalysis, IR, and mass spectrometry. Diamine derivatives were eluted from capillary gas chromatographic (CGC) column BP1 (12 m x 0.22 mm I.D.) or BP5 (50 m x 0.22 mm) with layer thickness 0.25 microm, using nitrogen as a carrier gas and flame ionization detection (FID). A solvent extraction procedure was developed for the extraction of Pu and CA from aqueous solution with a linear calibration range 0-20 microg/0.2 ml of extract with a detection limit of 0.5-0.6 ng/injection. The method was applied for the determination of Pu and CA in the serum of five cancer patients before and after radiotherapy. The serum of two healthy persons was also analyzed for Pu and CA contents. Pu and CA concentrations were found within the range 1.16-3.96 microg/ml and 0.88-1.46 microg/ml in cancer patients as compared to 0.11-0.16 microg/ml and 0.06-0.075 microg/ml respectively in healthy persons with a coefficient of variation (CV) within 0.62-5.47%. Pu and CA concentrations decreased on radiotherapy in cancer patients, but were much higher than in healthy persons. PMID:10080628

  16. Critical ligand binding reagent preparation/selection: when specificity depends on reagents.

    PubMed

    Rup, Bonita; O'Hara, Denise

    2007-05-11

    Throughout the life cycle of biopharmaceutical products, bioanalytical support is provided using ligand binding assays to measure the drug product for pharmacokinetic, pharmacodynamic, and immunogenicity studies. The specificity and selectivity of these ligand binding assays are highly dependent on the ligand binding reagents. Thus the selection, characterization, and management processes for ligand binding reagents are crucial to successful assay development and application. This report describes process considerations for selection and characterization of ligand binding reagents that are integral parts of the different phases of assay development. Changes in expression, purification, modification, and storage of the ligand binding reagents may have a profound effect on the ligand binding assay performance. Thus long-term management of the critical ligand binding assay reagents is addressed including suggested characterization criteria that allow ligand binding reagents to be used in as consistent a manner as possible. Examples of challenges related to the selection, modification, and characterization of ligand binding reagents are included.

  17. Enantioseparation of α-amino acids by means of Cinchona alkaloids as selectors in chiral ligand-exchange chromatography.

    PubMed

    Keunchkarian, Sonia; Franca, Carlos A; Gagliardi, Leonardo G; Castells, Cecilia B

    2013-07-12

    A conventional nonchiral column was used for the enantioseparation of several racemic α-amino acids (native and derivatized) through the use of Cinchona alkaloids as chiral selectors along with Cu(II) ions in chiral ligand-exchange chromatography. The mobile phase composition (i.e., the organic modifier content and pH) was studied in order to modulate retention and enantioselectivity. Good enantioseparation of many amino acids was obtained using equimolar amounts of Cu(II) and either cinchonidine, quinine or quinidine as chiral selectors in the mobile phase. The molecular geometry of the diastereomeric complexes formed was modeled and energetic differences between both compounds were calculated by methods based on semi-empirical force-field. Good correlations were obtained between experimental enantioselectivity factors and calculated energetic differences.

  18. Determination of herbicides and its metabolite in soil and water samples by capillary electrophoresis-laser induced fluorescence detection using microwave-assisted derivatization.

    PubMed

    Cao, Liwei; Deng, Tao; Liang, Siliu; Tan, Xiaofang; Meng, Jianxin

    2014-01-01

    Methods were developed to determine glufosinate (GLUF), glyphosate (GLYP) and its metabolite, aminomethylphosphonic acid (AMPA) by capillary electrophoresis-laser induced fluorescence detection using 5-(4,6-dichlorotriazinylamino) fluorescein (DTAF) and fluorescein isothiocyanate (FITC) as the derivatizing reagents. To accelerate the labeling speed, a microwave-assisted derivatization method was adopted. The derivatizing reaction time was reduced to 180 and 150 s for DTAF and FITC, whose reaction time for conventional labeling was 50 min and 5 h, respectively. The optimum separation conditions for derivatives were as follows: a back ground electrolyte (BGE) of 30 mmol L(-1) sodium tetraborate containing 15 mmol L(-1) brij-35, hydrodynamic injection 15 s and a 10 kV separation voltage. Under these conditions, the LODs (S/N = 3) for DTAF derivatives were 0.32, 0.19 and 0.15 nmol L(-1) for GLUF, GLYP, and AMPA, respectively. The LODs (S/N = 3) for FITC derivatives were 2.60, 3.88 and 2.42 nmol L(-1) for GLUF, GLYP, and AMPA, respectively. The applicability of the developed method was demonstrated by the detection of the above herbicides and metabolite in water and soil samples.

  19. Headspace solid-phase microextraction with on-fiber derivatization for the determination of aldehydes in algae by gas chromatography-mass spectrometry.

    PubMed

    Ma, Jiping; Xiao, Ronghui; Li, Jinhua; Li, Jie; Shi, Benzhang; Liang, Yanjuan; Lu, Wenhui; Chen, Lingxin

    2011-06-01

    A simple, fast, sensitive and cost-effective method based on headspace solid-phase microextraction (HS-SPME) with on-fiber derivatization coupled with gas chromatography-mass spectrometry was developed for the determination of six typical aldehydes, 2E-hexenal, heptanal, 2E-heptenal, 2E,4E-heptadienal, 2E-decenal and 2E,4E-decadienal in laboratory algae cultures. As derivatization reagent, O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride, was loaded onto the poly(dimethylsiloxane)/divinylbenzene fiber for aldehydes on-fiber derivatization prior to HS-SPME. Various influence factors of extraction efficiency were systematically investigated. Under optimized extraction conditions, excellent method performances for all the six aldehydes were attained, such as satisfactory extraction recoveries ranging from 67.1 to 117%, with the precision (relative standard deviation) within 5.3-11.1%, and low detection limits in the range of 0.026-0.044 μg/L. The validated method was successfully applied for the analysis of the aldehydes in two diatoms (Skeletonema costatum and Chaetoceros muelleri), two pyrrophytas (Prorocentrum micans and Scrippsiella trochoidea) and Calanus sinicus eggs (feeding on the two diatoms above). PMID:21567947

  20. Development and validation of a simple and sensitive method for quantification of levodopa and carbidopa in rat and monkey plasma using derivatization and UPLC-MS/MS.

    PubMed

    Junnotula, Venkatraman; Licea-Perez, Hermes

    2013-05-01

    A simple, selective, and sensitive quantitative method has been developed for the simultaneous determination of levodopa and carbidopa in rat and monkey plasma by protein precipitation using acetonitrile containing the derivatizing reagent, flourescamine. Derivatized products of levodopa and carbidopa were separated on a BEH C18 column (2.1 mm × 50 mm; 1.7 μm particle size) using ultra high performance liquid chromatography (UHPLC) without any further purification. Tandem mass spectrometry (MS/MS) was used for detection. The method was validated over the concentration range of 5-5000 ng/mL and 3-3000 ng/mL for levodopa and carbidopa, respectively in rat and monkey plasma. Due to the poor stability of the investigated analytes in biological matrices, a mixture of sodium metabisulfite and hydrazine dihydrochloride was used as a stabilizer. This method was successfully utilized to support pharmacokinetic studies in both species. The results from assay validations and incurred samples re-analysis show that the method is selective, sensitive and robust. To our knowledge, this is the first UHPLC-MS/MS based method that utilizes derivatization with fluorescamine and provides adequate sensitivity for both levodopa and carbidopa with 50 μL of sample and a run time of 3.5 min.

  1. Determination of linear aliphatic aldehydes in heavy metal containing waters by high-performance liquid chromatography using 2,4-dinitrophenylhydrazine derivatization.

    PubMed

    Lin, Yi-Liang; Wang, Po-Yen; Hsieh, Ling-Ling; Ku, Kuan-Hsuan; Yeh, Yun-Tai; Wu, Chien-Hou

    2009-09-01

    A simple and sensitive method is described for the determination of picomolar amounts of C(1)-C(9) linear aliphatic aldehydes in waters containing heavy metal ions. In this method, aldehydes were first derivatized with 2,4-dinitrophenylhydrazine (DNPH) at optimized pH 1.8 for 30 min and analyzed by HPLC with UV detector at 365 nm. Factors affecting the derivatization reaction of aldehydes and DNPH were investigated. Cupric ion, an example of heavy metals, is a common oxidative reagent, which may oxidize DNPH and greatly interfere with the determination of aldehydes. EDTA was used to effectively mask the interferences by heavy metal ions. The method detection limits for direct injection of derivatized most aldehydes except formaldehyde were of the order of 7-28 nM. The detection limit can be further lowered by using off-line C(18) adsorption cartridge enrichment. The recoveries of C(1)-C(9) aldehydes were 93-115% with a relative standard deviation of 3.6-8.1% at the 0.1 microM level for aldehydes. The HPLC-DNPH method has been applied for determining aldehyde photoproducts from Cu(II)-amino acid complex systems. PMID:19643424

  2. Use of a macrocyclic antibiotic as the chiral selector for enantiomeric separations by TLC

    SciTech Connect

    Armstrong, D.W.; Zhou, Y. . Dept. of Chemistry)

    1994-01-01

    The macrocyclic antibiotic, vancomycin, was used as a chiral mobile phase additive for the thin layer chromatographic (TLC) resolution of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatized amino acids, racemic drugs and dansyl-amino acids. Excellent separations were achieved for most of these compounds in the reversed phase mode. Both the nature of the stationary phase and the composition of the mobile phase strongly influenced enantiomeric resolution. The best results were obtained using diphenyl stationary phases. Acetonitrile was the organic modifier that produced the most effective separations with the shortest development times. It is highly likely that macrocyclic antibiotics will play a major role in future enantiomeric separations.

  3. Shelf-stable electrophilic reagents for trifluoromethylthiolation.

    PubMed

    Shao, Xinxin; Xu, Chunfa; Lu, Long; Shen, Qilong

    2015-05-19

    Fluorine, which is the most electronegative element and has a small atomic radius, plays a key role in pharmaceutical, agrochemical, and materials sciences. One of the fluoroalkyl groups, the trifluoromethylthio group (CF3S-), has been well-recognized as an important structural motif in the design of lead compounds for new drug discovery because of its high lipophilicity (Hansch lipophilicity parameter π = 1.44) and strong electron-withdrawing properties, which could improve the drug molecule's cell-membrane permeability and enhance its chemical and metabolic stability. While classic methods for the preparation of trifluoromethylthiolated compounds typically involve halogen-fluorine exchange reactions of polyhalogenomethyl thioethers or trifluoromethylation of sulfur-containing compounds under harsh reaction conditions, an alternative but more attractive strategy is direct trifluoromethylthiolation of the substrate at a late stage by employing an electrophilic trifluoromethylthiolating reagent. Although several electrophilic trifluoromethylthiolating reagents have been reported previously, these reagents either require a strong Lewis acid/Brønsted acid as an activator or suffer from a toxic nature or limited substrate scope. To address these problems, in late 2011 we initiated a project with the aim to develop new, shelf-stable, and highly reactive electrophilic trifluoromethylthiolating reagents that could easily install the trifluoromethylthio group at the desired positions of the drug molecule at a late stage of drug development. Inspired by the broad reactivity of the hypervalent iodine reagent, we initially discovered a highly reactive trifluoromethylthiolating reagent, trifluoromethanesulfenate 1a. Structure-reactivity studies disclosed that the iodine atom of reagent 1a does not play an important role in this reagent's reactivity. Consequently, a simplified second-generation electrophilic reagent, trifluoromethanesulfenate 1b, was developed. In parallel

  4. Process for derivatizing carbon nanotubes with diazonium species

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

    2007-01-01

    The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications and sensor devices. The methods of derivatization include electrochemical induced reactions thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes ##STR00001##.

  5. Inactivation of rabies diagnostic reagents by gamma radiation

    SciTech Connect

    Gamble, W.C.; Chappell, W.A.; George, E.H.

    1980-11-01

    Treatment of CVS-11 rabies adsorbing suspensions and street rabies infected mouse brains with gamma radiation resulted in inactivated reagents that are safer to distribute and use. These irradiated reagents were as sensitive and reactive as the nonirradiated control reagents.

  6. 21 CFR 866.3740 - Streptococcus spp. serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3740 Streptococcus spp. serological reagents. (a) Identification. Streptococcus spp. serological reagents are devices... streptococci are associated with infections, such as sore throat, impetigo (an infection characterized by...

  7. 21 CFR 866.3740 - Streptococcus spp. serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3740 Streptococcus spp. serological reagents. (a) Identification. Streptococcus spp. serological reagents are devices... streptococci are associated with infections, such as sore throat, impetigo (an infection characterized by...

  8. Determination of cycloserine in human plasma by high-performance liquid chromatography with fluorescence detection, using derivatization with p-benzoquinone.

    PubMed

    David, V; Ionescu, M; Dumitrescu, V

    2001-09-15

    A new method for determining cycloserine in plasma samples is described. This method is based on the derivatization of cycloserine with p-benzoquinone, a reaction that takes place at the same time as the process of plasma deproteinization due to the presence of ethanol as solvent in the solution of the derivatization reagent. Four derivatives are obtained from this reaction. The main derivative is well correlated with the cycloserine concentration. The ratio between the volumes of the plasma sample and the reagent solution is 1:2 for a p-benzoquinone concentration of 1000 microg/mL. Elution from a C18 column was isocratic, using a mobile phase containing (v/v) 85% aqueous 0.1% formic acid solution, and 15% (v/v) of a mixture of methanol and acetonitrile (1:1), with a flow-rate of 1 mL/min, at 25 degrees C. Determinations by fluorescence detection were achieved with excitation at 381 nm and emission at 450 nm, with a detection limit of 10 ng/mL for an injection volume of 5 microL. This method was validated and applied to the determination of cycloserine in blood plasma samples of several healthy volunteers.

  9. Optical properties of chiral nanotubes

    NASA Astrophysics Data System (ADS)

    Cecilia, Noguez; Román-Velázquez Carlos, E.; Ariadna, Sánchez; Montes Lilia, Meza

    2004-03-01

    A recent theoretical model [1] is applied to study the optical properties chiral nanostructures like carbon nanotubes. We calculate the Circular Dichroism (CD) spectra for carbon nanotubes with different chirality. The calculated CD spectra show features that allow us to distinguish between nanotubes with different indexes of chirality. Other nanostructures, like chiral fullerenes are also investigated.These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral. This work has been partly financed by CONACyT grant No. 36651-E and by DGAPA-UNAM grants No. IN104201. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003)

  10. A feasible approach to evaluate the relative reactivity of NHS-ester activated group with primary amine-derivatized DNA analogue and non-derivatized impurity.

    PubMed

    Dou, Shuping; Virostko, John; Greiner, Dale L; Powers, Alvin C; Liu, Guozheng

    2015-01-01

    Synthetic DNA analogues with improved stability are widely used in life science. The 3'and/or 5' equivalent terminuses are often derivatized by attaching an active group for further modification, but a certain amount of non-derivatized impurity often remains. It is important to know to what extent the impurity would influence further modification. The reaction of an NHS ester with primary amine is one of the most widely used options to modify DNA analogues. In this short communication, a 3'-(NH2-biotin)-derivatized morpholino DNA analogue (MORF) was utilized as the model derivatized DNA analogue. Inclusion of a biotin concomitant with the primary amine at the 3'-terminus allows for the use of streptavidin to discriminate between the products from the derivatized MORF and non-derivatized MORF impurity. To detect the MORF reaction with NHS ester, S-acetyl NHS-MAG3 was conjugated to the DNA analogue for labeling with (99m)Tc, a widely used nuclide in the clinic. It was found that the non-derivatized MORF also reacted with the S-acetyl NHS-MAG3. Radiolabeling of the product yielded an equally high labeling efficiency. Nevertheless, streptavidin binding indicated that under the conditions of this investigation, the non-derivatized MORF was five times less reactive than the amine-derivatized MORF. PMID:25621701

  11. A FEASIBLE APPROACH TO EVALUATE THE RELATIVE REACTIVITY OF NHS-ESTER ACTIVATED GROUP WITH PRIMARY AMINE-DERIVATIZED DNA ANALOGUE AND NON-DERIVATIZED IMPURITY

    PubMed Central

    Dou, Shuping; Virostko, John; Greiner, Dale L.; Powers, Alvin C.; Liu, Guozheng

    2015-01-01

    Synthetic DNA analogues with improved stability are widely used in life science. The 3′ and/or 5′ equivalent terminuses are often derivatized by attaching an active group for further modification, but a certain amount of non-derivatized impurity often remains. It is important to know to what extent the impurity would influence further modification. The reaction of an NHS ester with primary amine is one of the most widely used options to modify DNA analogues. In this short communication, a 3′-(NH2-biotin)-derivatized morpholino DNA analogue (MORF) was utilized as the model derivatized DNA analogue. Inclusion of a biotin concomitant with the primary amine at the 3′-terminus allows for the use of streptavidin to discriminate between the products from the derivatized MORF and non-derivatized MORF impurity. To detect the MORF reaction with NHS ester, S-acetyl NHS-MAG3 was conjugated to the DNA analogue for labeling with 99mTc, a widely used nuclide in the clinic. It was found that the non-derivatized MORF also reacted with the S-acetyl NHS-MAG3. Radiolabeling of the product yielded an equally high labeling efficiency. Nevertheless, streptavidin binding indicated that under the conditions of this investigation, the non-derivatized MORF was five times less reactive than the amine-derivatized MORF. PMID:25621701

  12. ENANTIOMER-SPECIFIC EFFECTS OF CHIRAL POLLUTANTS

    EPA Science Inventory

    Enantiomers, the mirror image isomers of chiral pollutants, are known to be selective in their interaction with other chiral molecules, including enzymes and other biochemicals. Considerable research has shown, for example, that chiral pesticides are degraded selectively by micr...

  13. Comparison of five derivatizing agents for the determination of amphetamine-type stimulants in human urine by extractive acylation and gas chromatography-mass spectrometry.

    PubMed

    Dobos, Adrienn; Hidvégi, Elod; Somogyi, Gábor Pál

    2012-06-01

    Five acylation reagents have been compared for use as derivatizing agents for the analysis of amphetamine-type stimulants (ATS) in urine by gas chromatography-mass spectrometry (GC-MS). The evaluated reagents were heptafluorobutyric anhydride, pentafluoropropionic anhydride, trifluoroacetic anhydride, acetic anhydride (AA) and N-methyl-bis(trifluoroacetamide). The ATS included amphetamine, methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyethylamphetamine (MDEA). A mixture of the ATS was added to urine (1 mL) followed by KOH solution and saturated NaHCO(3) solution. The sample was then extracted with dichloromethane and the derivatizing agent and 2 µL were injected into the GC-MS instrument. The derivatizing agents were compared with reference to the signal-to-noise (S/N) ratios, peak area values, relative standard deviations (RSDs), linearities, limits of detection (LODs) and selectivities. The acetic anhydride proved to be the best according to the S/N ratio and peak area results for amphetamine, MA, MDMA and MDEA. The best RSD values of peak areas and of S/N ratios at 3 µg/mL were also given by AA in cases of MDA, MDMA and MDEA. At 20 µg/mL, the lowest RSD values of peak areas for MDA and the lowest RSD values of S/N ratios for MA, MDA, MDMA and MDEA were again given by AA. Additionally, the highest correlation coefficients for MA, MDA, MDMA and MDEA and the lowest LOD results for MA, MDMA and MDEA were produced by AA.

  14. Simultaneous determination of polycyclic aromatic hydrocarbon quinones by gas chromatography-tandem mass spectrometry, following a one-pot reductive trimethylsilyl derivatization.

    PubMed

    Toriba, Akira; Homma, Chiharu; Kita, Masahiro; Uozaki, Waka; Boongla, Yaowatat; Orakij, Walaiporn; Tang, Ning; Kameda, Takayuki; Hayakawa, Kazuichi

    2016-08-12

    We developed a sensitive and selective method to simultaneously analyze 37 polycyclic aromatic hydrocarbon quinones (PAHQs) with GC-MS/MS and applied the method to the analysis of standard atmospheric particulate matter samples. PAHQs were reduced with zinc granules and dithiothreitol (DTT) and the reductants were immediately converted to their silylated derivatives in a test tube. Two trimethylsilyl (TMS) groups were introduced into PAHQs through the one-pot reductive TMS derivatization. The PAHQs were derivatized with a mixed silylation reagent (BSA+TMCS+TMSI; (3:2:3)), which is one of the combinations of TMS-derivatization reagents with the highest reactivity. The derivatives produced different fragmentation between o-PAHQs and p-PAHQs. Therefore, isomers that have the same molecular weight are difficult to separate on a column were separated by the selected reaction monitoring (SRM) mode using the characteristic fragmentations, allowing separation and detection of all PAHQ derivatives in less than 30min. The instrumental detection limit (IDL) of each PAHQ was 1.2-29fg/injection and the method quantification limit (MQL) was 0.8-78μg/kg sample. For quantification, six deuterated PAHQs were used as internal standards to achieve high analytical precision. We applied the developed method to four standard atmospheric particulate matter samples. Results showed that out of 37 PAHQs, 33 compounds were identified and quantified. Moreover, from the 33 PAHQs, 14 were detected for the first time. Similar values were observed for the concentrations of PAHQs that have been quantified in previous reports. This method has the highest practicality in monitoring PAHQs in atmosphere, combustion exhaust gas, and toxicity evaluation. Thus, the method has the potential to become a standard analytical method for such applications. PMID:27401812

  15. 21 CFR 864.4010 - General purpose reagent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., fixative and adhesives, tissue processing reagents, isotonic solutions and pH buffers. Reagents used in...., Thermus aquaticus (TAQ) polymerase, substrates for enzyme immunoassay (EIA)). (b) Classification. Class...

  16. 21 CFR 864.4010 - General purpose reagent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ..., fixative and adhesives, tissue processing reagents, isotonic solutions and pH buffers. Reagents used in...., Thermus aquaticus (TAQ) polymerase, substrates for enzyme immunoassay (EIA)). (b) Classification. Class...

  17. 21 CFR 864.4010 - General purpose reagent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ..., fixative and adhesives, tissue processing reagents, isotonic solutions and pH buffers. Reagents used in...., Thermus aquaticus (TAQ) polymerase, substrates for enzyme immunoassay (EIA)). (b) Classification. Class...

  18. 21 CFR 864.4010 - General purpose reagent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., fixative and adhesives, tissue processing reagents, isotonic solutions and pH buffers. Reagents used in...., Thermus aquaticus (TAQ) polymerase, substrates for enzyme immunoassay (EIA)). (b) Classification. Class...

  19. Chiral Dynamics 2006

    NASA Astrophysics Data System (ADS)

    Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry

    2007-10-01

    pt. A. Plenary session. Opening remarks: experimental tests of chiral symmetry breaking / A. M. Bernstein. [Double pie symbols] scattering / H. Leutwyler. Chiral effective field theory in a [Triangle]-resonance region / V. Pascalutsa. Some recent developments in chiral perturbation theory / Ulf-G. Mei ner. Chiral extrapolation and nucleon structure from the lattice / R.D. Young. Recent results from HAPPEX / R. Michaels. Chiral symmetries and low energy searches for new physics / M.J. Ramsey-Musolf. Kaon physics: recent experimental progress / M. Moulson. Status of the Cabibbo angle / V. Cirigliano. Lattice QCD and nucleon spin structure / J.W. Negele. Spin sum rules and polarizabilities: results from Jefferson lab / J-P Chen. Compton scattering and nucleon polarisabilities / Judith A. McGovern. Virtual compton scattering at MIT-bates / R. Miskimen. Physics results from the BLAST detector at the BATES accelerator / R.P. Redwine. The [Pie sympbol]NN system, recent progress / C. Hanhart. Application of chiral nuclear forces to light nuclei / A. Nogga. New results on few-body experiments at low energy / Y. Nagai. Few-body lattice calculations / M.J. Savage. Research opportunities at the upgraded HI?S facility / H.R. Weller -- pt. B. Goldstone boson dynamics. Working group summary: Goldstone Boson dynamics / G. Colangelo and S. Giovannella. Recent results on radiative Kaon decays from NA48 and NA48/2 / S.G. López. Cusps in K-->3 [Pie symbol] decays / B. Kubis. Recent KTeV results on radiative Kaon decays / M.C. Ronquest. The [Double pie symbols] scattering amplitude / J.R. Peláez. Determination of the Regge parameters in the [Double pie symbols] scattering amplitude / I. Caprini. e+e- Hadronic cross section measurement at DA[symbol]NE with the KLOE detector / P. Beltrame. Measurement of the form factors of e+e- -->2([Pie symbol]+[Pie symbol]-), pp and the resonant parameters of the heavy charmonia at BES / H. Hu. Measurement of e+e- multihadronic cross section below 4

  20. Chiral symmetry and pentaquarks

    SciTech Connect

    Dmitri Diakonov

    2004-07-01

    Spontaneous chiral symmetry breaking, mesons and baryons are illustrated in the language of the Dirac theory. Various forces acting between quarks inside baryons are discussed. I explain why the naive quark models typically overestimate pentaquark masses by some 500 MeV and why in the fully relativistic approach to baryons pentaquarks turn out to be light. I discuss briefly why it can be easier to produce pentaquarks at low than at high energies.

  1. Chiral Biomarkers in Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2010-01-01

    The chirality of organic molecules with the asymmetric location of group radicals was discovered in 1848 by Louis Pasteur during his investigations of the rotation of the plane of polarization of light by crystals of sodium ammonium paratartrate. It is well established that the amino acids in proteins are exclusively Levorotary (L-aminos) and the sugars in DNA and RNA are Dextrorotary (D-sugars). This phenomenon of homochirality of biological polymers is a fundamental property of all life known on Earth. Furthermore, abiotic production mechanisms typically yield recemic mixtures (i.e. equal amounts of the two enantiomers). When amino acids were first detected in carbonaceous meteorites, it was concluded that they were racemates. This conclusion was taken as evidence that they were extraterrestrial and produced by abiologically. Subsequent studies by numerous researchers have revealed that many of the amino acids in carbonaceous meteorites exhibit a significant L-excess. The observed chirality is much greater than that produced by any currently known abiotic processes (e.g. Linearly polarized light from neutron stars; Circularly polarized ultraviolet light from faint stars; optically active quartz powders; inclusion polymerization in clay minerals; Vester-Ulbricht hypothesis of parity violations, etc.). This paper compares the measured chirality detected in the amino acids of carbonaceous meteorites with the effect of these diverse abiotic processes. IT is concluded that the levels observed are inconsistent with post-arrival biological contamination or with any of the currently known abiotic production mechanisms. However, they are consistent with ancient biological processes on the meteorite parent body. This paper will consider these chiral biomarkers in view of the detection of possible microfossils found in the Orgueil and Murchison carbonaceous meteorites. Energy dispersive x-ray spectroscopy (EDS) data obtained on these morphological biomarkers will be

  2. Organoiodine(V) reagents in organic synthesis.

    PubMed

    Zhdankin, Viktor V

    2011-03-01

    Organohypervalent iodine reagents have attracted significant recent interest as versatile and environmentally benign oxidants with numerous applications in organic synthesis. This Perspective summarizes synthetic applications of hypervalent iodine(V) reagents: 2-iodoxybenzoic acid (IBX), Dess-Martin periodinane (DMP), pseudocyclic iodylarenes, and their recyclable polymer-supported analogues. Recent advances in the development of new catalytic systems based on the generation of hypervalent iodine species in situ are also overviewed.

  3. Generalized simplicial chiral models

    NASA Astrophysics Data System (ADS)

    Alimohammadi, Masoud

    2000-02-01

    Using the auxiliary field representation of the simplicial chiral models on a ( d-1)-dimensional simplex, the simplicial chiral models are generalized through replacing the term Tr (AA †) in the Lagrangian of these models by an arbitrary class function of AA †; V(AA †) . This is the same method used in defining the generalized two-dimensional Yang-Mills theories (gYM 2) from ordinary YM 2. We call these models the "generalized simplicial chiral models". Using the results of the one-link integral over a U( N) matrix, the large- N saddle-point equations for eigenvalue density function ρ( z) in the weak ( β> βc) and strong ( β< βc) regions are computed. In d=2, where the model is in some sense related to the gYM 2 theory, the saddle-point equations are solved for ρ( z) in the two regions, and the explicit value of critical point βc is calculated for V(B)= Tr B n(B=AA †) . For V(B)= Tr B 2, Tr B 3, and Tr B4, the critical behaviour of the model at d=2 is studied, and by calculating the internal energy, it is shown that these models have a third order phase transition.

  4. A simultaneous derivatization of 3-monochloropropanediol and 1,3-dichloropropane with hexamethyldisilazane-trimethylsilyl trifluoromethanesulfonate at room temperature for efficient analysis of food sample analysis.

    PubMed

    Lee, Bai Qin; Wan Mohamed Radzi, Che Wan Jasimah Bt; Khor, Sook Mei

    2016-02-01

    This paper reports the application of hexamethyldisilazane-trimethylsilyl trifluoromethanesulfonate (HMDS-TMSOTf) for the simultaneous silylation of 3-monochloro-1,2-propanediol (3-MCPD) and 1,3-dicholoropropanol (1,3-DCP) in solid and liquid food samples. 3-MCPD and 1,3-DCP are chloropropanols that have been established as Group 2B carcinogens in clinical testing. They can be found in heat-processed food, especially when an extended high-temperature treatment is required. However, the current AOAC detection method is time-consuming and expensive. Thus, HMDS-TMSOTf was used in this study to provide a safer, and cost-effective alternative to the HFBI method. Three important steps are involved in the quantification of 3-MCPD and 1,3-DCP: extraction, derivatization and quantification. The optimization of the derivatization process, which involved focusing on the catalyst volume, derivatization temperature, and derivatization time was performed based on the findings obtained from both the Box-Behnken modeling and a real experimental set up. With the optimized conditions, the newly developed method was used for actual food sample quantification and the results were compared with those obtained via the standard AOAC method. The developed method required less samples and reagents but it could be used to achieve lower limits of quantification (0.0043mgL(-1) for 1,3-DCP and 0.0011mgL(-1) for 3-MCPD) and detection (0.0028mgL(-1) for 1,3-DCP and 0.0008mgL(-1) for 3-MCPD). All the detected concentrations are below the maximum tolerable limit of 0.02mgL(-1). The percentage of recovery obtained from food sample analysis was between 83% and 96%. The new procedure was validated with the AOAC method and showed a comparable performance. The HMDS-TMSOTf derivatization strategy is capable of simultaneously derivatizing 1,3-DCP and 3-MCPD at room temperature, and it also serves as a rapid, sensitive, and accurate analytical method for food samples analysis. PMID:26792449

  5. A simultaneous derivatization of 3-monochloropropanediol and 1,3-dichloropropane with hexamethyldisilazane-trimethylsilyl trifluoromethanesulfonate at room temperature for efficient analysis of food sample analysis.

    PubMed

    Lee, Bai Qin; Wan Mohamed Radzi, Che Wan Jasimah Bt; Khor, Sook Mei

    2016-02-01

    This paper reports the application of hexamethyldisilazane-trimethylsilyl trifluoromethanesulfonate (HMDS-TMSOTf) for the simultaneous silylation of 3-monochloro-1,2-propanediol (3-MCPD) and 1,3-dicholoropropanol (1,3-DCP) in solid and liquid food samples. 3-MCPD and 1,3-DCP are chloropropanols that have been established as Group 2B carcinogens in clinical testing. They can be found in heat-processed food, especially when an extended high-temperature treatment is required. However, the current AOAC detection method is time-consuming and expensive. Thus, HMDS-TMSOTf was used in this study to provide a safer, and cost-effective alternative to the HFBI method. Three important steps are involved in the quantification of 3-MCPD and 1,3-DCP: extraction, derivatization and quantification. The optimization of the derivatization process, which involved focusing on the catalyst volume, derivatization temperature, and derivatization time was performed based on the findings obtained from both the Box-Behnken modeling and a real experimental set up. With the optimized conditions, the newly developed method was used for actual food sample quantification and the results were compared with those obtained via the standard AOAC method. The developed method required less samples and reagents but it could be used to achieve lower limits of quantification (0.0043mgL(-1) for 1,3-DCP and 0.0011mgL(-1) for 3-MCPD) and detection (0.0028mgL(-1) for 1,3-DCP and 0.0008mgL(-1) for 3-MCPD). All the detected concentrations are below the maximum tolerable limit of 0.02mgL(-1). The percentage of recovery obtained from food sample analysis was between 83% and 96%. The new procedure was validated with the AOAC method and showed a comparable performance. The HMDS-TMSOTf derivatization strategy is capable of simultaneously derivatizing 1,3-DCP and 3-MCPD at room temperature, and it also serves as a rapid, sensitive, and accurate analytical method for food samples analysis.

  6. Implementation and evaluation of an analytical method for a novel derivatizing agent to measure 4,4'-methylene diphenyl diisocyanate atmospheres.

    PubMed

    Puscasu, Silvia; Aubin, Simon; Spence, Mark; Gagné, Sébastien

    2016-08-01

    Accurate measurement of 4,4'-methylene diphenyl diisocyanate (MDI) atmospheres is a challenge since the molecule is both chemically reactive and likely to be present in aerosol form when heated and sprayed because of its low vapor pressure. Meeting this challenge requires optimizing both the sampling device used and the derivatization agent employed to stabilize the isocyanate functional group. This study describes the use of a novel derivatization reagent for isocyanate sampling to address the challenge of MDI aerosol exposure sampling. Like most conventional derivatizing agents for isocyanates, 1,8-diaminonapthalene (DAN) reacts with isocyanate functional groups to form a urea. However, unlike other isocyanate derivatizing agents, the sample workup procedure with DAN includes a second step which yields a single analyte molecule, perimidone, for each isocyanate group. This feature gives DAN the unique ability to assess exposure to "total reactive isocyanate group" (TRIG). The analytical method implemented to quantitate the perimidone uses liquid chromatography coupled with tandem mass spectrometry. Positive mode ionization led to LOD and LOQ of 10 ng/mL and 34 ng/mL, respectively. The dynamic range was from 50-2000 ng/mL (with R(2) ≥ 0.990), which corresponds to TRIG concentrations in air from 0.07-3.04 µg/m(3), assuming 60 min of sampling at 10 L/min (based on use of the CIP-10M sampler). The intra-day and inter-day analytical precisions were <4% for all of the concentration levels tested, and the accuracy was within an appropriate range of 98 ± 2%. Minimal matrix effect was observed, and a total recovery of 109% was obtained. The approach seems to be promising for TRIG measurements and further work is planned to establish DAN method behavior in samplers used for workplace monitoring. PMID:26954368

  7. Determination of small halogenated carboxylic acid residues in drug substances by high performance liquid chromatography-diode array detection following derivatization with nitro-substituted phenylhydrazines.

    PubMed

    Hou, Desheng; Fan, Jingjing; Han, Lingfei; Ruan, Xiaoling; Feng, Feng; Liu, Wenyuan; Zheng, Feng

    2016-03-18

    A method for the determination of small halogenated carboxylic acid (HCA) residues in drug substances is urgently needed because of the potential of HCAs for genotoxicity and carcinogenicity in humans. We have now developed a simple method, involving derivatization followed by high performance liquid chromatography-diode array detection (HPLC-DAD), for the determination of six likely residual HCAs (monochloroacetic acid, monobromoacetic acid, dichloroacetic acid, 2-chloropropionic acid, 2-bromopropionic acid and 3-chloropropionic acid) in drug substances. Different nitro-substituted phenylhydrazines (NPHs) derivatization reagents were systematically compared and evaluated. 2-Nitrophenylhydrazine hydrochloride (2-NPH·HCl) was selected as the most suitable choice since its derivatives absorb strongly at 392 nm, a region of the spectrum where most drug substances and impurities absorb very weakly. During the derivatization process, the commonly used catalyst, pyridine, caused rapid dechlorination or chlorine substitution of α-halogenated derivatives. To avoid these unwanted side reactions, a reliable derivatization method that did not use pyridine was developed. Reaction with 2-NPH·HCl using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride as coupling agent in acetonitrile-water (70:30) at room temperature for 2h gave complete reaction and avoided degradation products. The derivatives were analyzed, without any pretreatment, using gradient HPLC with detection in the near visible region. Organic acids commonly found in drug substances and other impurities did not interfere with the analysis. Good linearity (r>0.999) and low limits of quantitation (0.05-0.12 μg mL(-1)) were obtained. The mean recoveries were in the range of 80-115% with RSD <5.81% except for 3-CPA in ibuprofen which was 78.5%. The intra- and inter-day precisions were expressed as RSD <1.98% and <4.39%, respectively. Finally, the proposed method was successfully used for the residue

  8. Determination of small halogenated carboxylic acid residues in drug substances by high performance liquid chromatography-diode array detection following derivatization with nitro-substituted phenylhydrazines.

    PubMed

    Hou, Desheng; Fan, Jingjing; Han, Lingfei; Ruan, Xiaoling; Feng, Feng; Liu, Wenyuan; Zheng, Feng

    2016-03-18

    A method for the determination of small halogenated carboxylic acid (HCA) residues in drug substances is urgently needed because of the potential of HCAs for genotoxicity and carcinogenicity in humans. We have now developed a simple method, involving derivatization followed by high performance liquid chromatography-diode array detection (HPLC-DAD), for the determination of six likely residual HCAs (monochloroacetic acid, monobromoacetic acid, dichloroacetic acid, 2-chloropropionic acid, 2-bromopropionic acid and 3-chloropropionic acid) in drug substances. Different nitro-substituted phenylhydrazines (NPHs) derivatization reagents were systematically compared and evaluated. 2-Nitrophenylhydrazine hydrochloride (2-NPH·HCl) was selected as the most suitable choice since its derivatives absorb strongly at 392 nm, a region of the spectrum where most drug substances and impurities absorb very weakly. During the derivatization process, the commonly used catalyst, pyridine, caused rapid dechlorination or chlorine substitution of α-halogenated derivatives. To avoid these unwanted side reactions, a reliable derivatization method that did not use pyridine was developed. Reaction with 2-NPH·HCl using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride as coupling agent in acetonitrile-water (70:30) at room temperature for 2h gave complete reaction and avoided degradation products. The derivatives were analyzed, without any pretreatment, using gradient HPLC with detection in the near visible region. Organic acids commonly found in drug substances and other impurities did not interfere with the analysis. Good linearity (r>0.999) and low limits of quantitation (0.05-0.12 μg mL(-1)) were obtained. The mean recoveries were in the range of 80-115% with RSD <5.81% except for 3-CPA in ibuprofen which was 78.5%. The intra- and inter-day precisions were expressed as RSD <1.98% and <4.39%, respectively. Finally, the proposed method was successfully used for the residue

  9. Chiral microemulsion electrokinetic chromatography with two chiral components: Improved separations via synergies between a chiral surfactant and a chiral cosurfactant.

    PubMed

    Kahle, Kimberly A; Foley, Joe P

    2006-02-01

    In this study, the combination of two chiral components in a microemulsion formulation for the separation of enantiomers via microemulsion EKC (MEEKC) was successfully accomplished. Previous publications of chiral microemulsions have utilized only one chiral entity; the surfactant, cosurfactant, or oil was chiral. This is the first study, to date, of the effects of using two chiral species in a single pseudostationary phase (PSP). The chiral surfactant dodecoxycarbonylvaline (DDCV) was used in conjunction with the chiral cosurfactant S-2-hexanol. Ethyl acetate was incorporated as the oil core of the microemulsion and the buffer was 50 mM phosphate at a pH of 7. Additionally, a microemulsion prepared with racemic 2-hexanol was used for comparison to a previous DDCV microemulsion and as a baseline for the newly formulated dual chiral microemulsion. The efficiencies, resolutions, and enantioselectivities for the S-2-hexanol, racemic 2-hexanol, and original 1-butanol DDCV microemulsions are compared. The hexanol-based PSPs provide improved efficiencies and resolutions. To evaluate the combination of each DDCV enantiomer (R and S) with S-2-hexanol, changes in Gibb's free energy were calculated. A synergistic effect was found when two chiral components were combined to form a microemulsion.

  10. [An automatic and sensitive method for the determination of endogenous brassinosteroids in plant tissues by an online trapping-in situ derivatization-ultra performance liquid chromatography-tandem mass spectrometry system].

    PubMed

    Ding, Jun; Jiang, Li; Feng, Yuqi

    2014-10-01

    Brassinosteroids (BRs) are a class of naturally occurring phytohormones with poly- hydroxy steroid structure, which regulate general plant growth and many physiological processes. The reported methods for BR analysis were complicated, and the detection sensitivity was relatively low. To realize the automatic analysis of trace BRs in limited plant tissues, an in-tube solid phase microextraction-ultra performance liquid chromatography-tandem mass spectrometry (SPME-UPLC-MS/MS) system was constructed based on two valves-two pumps. Using C18 PEEK column as the trapping column and 4-(dimethylamino) phenylboronic acid (4-DMAPBA) as the derivatization reagent, an on line trapping and in situ derivatization assay method of BRs was developed. BRs could be programmed to fulfill the procedures of injection, extraction, derivatization, LC separation and MS detection in the system. The detection limits of BRs were improved more than one order of magnitude by the online trapping and in situ derivatization techniques, thus endogenous BRs could be quantified in only 300 mg plant tissues.

  11. Chiral drag force

    NASA Astrophysics Data System (ADS)

    Rajagopal, Krishna; Sadofyev, Andrey V.

    2015-10-01

    We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and

  12. Isothermal Titration Calorimetry of Chiral Polymeric Nanoparticles.

    PubMed

    Werber, Liora; Preiss, Laura C; Landfester, Katharina; Muñoz-Espí, Rafael; Mastai, Yitzhak

    2015-09-01

    Chiral polymeric nanoparticles are of prime importance, mainly due to their enantioselective potential, for many applications such as catalysis and chiral separation in chromatography. In this article we report on the preparation of chiral polymeric nanoparticles by miniemulsion polymerization. In addition, we describe the use of isothermal titration calorimetry (ITC) to measure the chiral interactions and the energetics of the adsorption of enantiomers from aqueous solutions onto chiral polymeric nanoparticles. The characterization of chirality in nano-systems is a very challenging task; here, we demonstrate that ITC can be used to accurately determine the thermodynamic parameters associated with the chiral interactions of nanoparticles. The use of ITC to measure the energetics of chiral interactions and recognition at the surfaces of chiral nanoparticles can be applied to other nanoscale chiral systems and can provide further insight into the chiral discrimination processes of nanomaterials.

  13. Hydroxypyridyl Imines: Enhancing Chromatographic Separation and Stereochemical Analysis of Chiral Amines via Circular Dichroism.

    PubMed

    Joyce, Leo A; Regalado, Erik L; Welch, Christopher J

    2016-09-16

    Imine-bond formation between chiral amines and commercially available 3-hydroxypyridine-2-carboxaldehyde (HCA) was exploited for rapid determination of stereochemical composition. Chiral supercritical fluid chromatography (SFC) screening of the derivatized imine compounds led to the elucidation of multiple combinations of mobile and stationary phases that gave resolution of all members of a series of chiral amines. The first eluting enantiomer was generally the derivative of the (R)-amine enantiomer across the series that was studied, indicating that the imine formed from the (S)-amine has more favorable interaction with the chiral stationary phase of the column. These conditions were then applied to more challenging compounds, namely amino alcohols and diastereomers possessing more than one stereocenter. The approach was utilized to monitor stereoselective biocatalytic transamination and assign the absolute configuration of the enantiomeric products. Finally, hydrolysis of the imine bond of the derivative was shown to generate enantiopure amine starting materials without racemization. This further highlights the value of this approach for creating readily reversed derivatives that enhance chromatographic separation and aid in the determination of absolute configuration. PMID:27529785

  14. Hydroxypyridyl Imines: Enhancing Chromatographic Separation and Stereochemical Analysis of Chiral Amines via Circular Dichroism.

    PubMed

    Joyce, Leo A; Regalado, Erik L; Welch, Christopher J

    2016-09-16

    Imine-bond formation between chiral amines and commercially available 3-hydroxypyridine-2-carboxaldehyde (HCA) was exploited for rapid determination of stereochemical composition. Chiral supercritical fluid chromatography (SFC) screening of the derivatized imine compounds led to the elucidation of multiple combinations of mobile and stationary phases that gave resolution of all members of a series of chiral amines. The first eluting enantiomer was generally the derivative of the (R)-amine enantiomer across the series that was studied, indicating that the imine formed from the (S)-amine has more favorable interaction with the chiral stationary phase of the column. These conditions were then applied to more challenging compounds, namely amino alcohols and diastereomers possessing more than one stereocenter. The approach was utilized to monitor stereoselective biocatalytic transamination and assign the absolute configuration of the enantiomeric products. Finally, hydrolysis of the imine bond of the derivative was shown to generate enantiopure amine starting materials without racemization. This further highlights the value of this approach for creating readily reversed derivatives that enhance chromatographic separation and aid in the determination of absolute configuration.

  15. An overview of heavy-atom derivatization of protein crystals

    PubMed Central

    Pike, Ashley C. W.; Garman, Elspeth F.; Krojer, Tobias; von Delft, Frank; Carpenter, Elisabeth P.

    2016-01-01

    Heavy-atom derivatization is one of the oldest techniques for obtaining phase information for protein crystals and, although it is no longer the first choice, it remains a useful technique for obtaining phases for unknown structures and for low-resolution data sets. It is also valuable for confirming the chain trace in low-resolution electron-density maps. This overview provides a summary of the technique and is aimed at first-time users of the method. It includes guidelines on when to use it, which heavy atoms are most likely to work, how to prepare heavy-atom solutions, how to derivatize crystals and how to determine whether a crystal is in fact a derivative. PMID:26960118

  16. Separation of derivatized glucoside anomers using supercritical fluid chromatography.

    PubMed

    Montañés, Fernando; Rose, Paul; Tallon, Stephen; Shirazi, Rahau

    2015-10-30

    Preparative scale supercritical fluid chromatography was used to separate derivatized anomeric monosaccharides. Methyl 2,3,4,6-tetra-O-benzoyl-α-d-glucopyranoside and methyl 2,3,4,6-tetra-O-benzoyl-β-d-glucopyranoside were synthesized by benzoyl derivatization of the parent anomerically pure monosaccharides. The elution profiles of each anomer were studied, suggesting that separation was possible. Mixtures of the compounds were then prepared at different ratios and separation was achieved using carbon dioxide/ethanol mixtures as the mobile phase and GreenSep™ 5micron particle size silica as the stationary phase. Ethanol co-solvent in the mobile phase was required to give a successful separation of the anomers however over the range 6.5-10.4wt% ethanol concentration studied here there was little variation in the degree of separation. In fractionation trials, separation of mixtures into fractions with >98% purity was achieved, with recoveries greater than 96%. PMID:26411481

  17. Analysis of cell surface properties using derivatized agarose beads.

    PubMed

    Salbilla, B A; Vaghefi, H; Chhabra, P; Hall, G; Brown, D; Sadoughi, F; Francisco, E; Attas, L; Walker, S L; Nguyen, B N; Oppenheimer, S B

    1999-07-01

    An assay has been developed to analyse cell surface properties using agarose beads derivatized with amino acids, sugars, proteins, and other molecules. The assay is simple and rapid and is useful to identify new cell surface markers. Various species and strains of yeast, paramecium, and Euglena were tested for their ability to bind to over 100 types of derivatized beads. A variety of specificity studies were performed in order to understand the nature of cell-bead binding. Our results indicate that cell-bead binding is often specific enough to distinguish between configurational isomers and spacer sizes and can be blocked by addition of specific molecules to the incubation medium. In some cases, different species or strains differed only by their binding to a single bead type. This simple and rapid assay may help to uncover new cell surface receptors and may lead to the development of clinically useful compounds for therapeutic applications.

  18. Chiral Crystallization of Ethylenediamine Sulfate

    ERIC Educational Resources Information Center

    Koby, Lawrence; Ningappa, Jyothi B.; Dakesssian, Maria; Cuccia, Louis A.

    2005-01-01

    The optimal conditions for the crystallization of achiral ethylenediamine sulfate into large chiral crystals that are ideal for polarimetry studies and observation using Polaroid sheets are presented. This experiment is an ideal undergraduate experiment, which clearly demonstrates the chiral crystallization of an achiral molecule.

  19. CHIRAL PESTICIDES: OCCURRENCE AND SIGNIFICANCE

    EPA Science Inventory

    Like amino acids, certain pesticides exist in "left-handed" and "right-handed" (chiral) forms. Commercially available chiral pesticides are produced as racemic mixtures in which the ratio of the two forms (or enantiomers) is 1:1. Enantiomers have the same ...

  20. Phosphopeptide Enrichment by Covalent Chromatography after Derivatization of Protein Digests Immobilized on Reversed-Phase Supports

    PubMed Central

    Nika, Heinz; Nieves, Edward; Hawke, David H.; Angeletti, Ruth Hogue

    2013-01-01

    A rugged sample-preparation method for comprehensive affinity enrichment of phosphopeptides from protein digests has been developed. The method uses a series of chemical reactions to incorporate efficiently and specifically a thiol-functionalized affinity tag into the analyte by barium hydroxide catalyzed β-elimination with Michael addition using 2-aminoethanethiol as nucleophile and subsequent thiolation of the resulting amino group with sulfosuccinimidyl-2-(biotinamido) ethyl-1,3-dithiopropionate. Gentle oxidation of cysteine residues, followed by acetylation of α- and ε-amino groups before these reactions, ensured selectivity of reversible capture of the modified phosphopeptides by covalent chromatography on activated thiol sepharose. The use of C18 reversed-phase supports as a miniaturized reaction bed facilitated optimization of the individual modification steps for throughput and completeness of derivatization. Reagents were exchanged directly on the supports, eliminating sample transfer between the reaction steps and thus, allowing the immobilized analyte to be carried through the multistep reaction scheme with minimal sample loss. The use of this sample-preparation method for phosphopeptide enrichment was demonstrated with low-level amounts of in-gel-digested protein. As applied to tryptic digests of α-S1- and β-casein, the method enabled the enrichment and detection of the phosphorylated peptides contained in the mixture, including the tetraphosphorylated species of β-casein, which has escaped chemical procedures reported previously. The isolates proved highly suitable for mapping the sites of phosphorylation by collisionally induced dissociation. β-Elimination, with consecutive Michael addition, expanded the use of the solid-phase-based enrichment strategy to phosphothreonyl peptides and to phosphoseryl/phosphothreonyl peptides derived from proline-directed kinase substrates and to their O-sulfono- and O-linked β-N-acetylglucosamine (O

  1. 21 CFR 864.8540 - Red cell lysing reagent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Red cell lysing reagent. 864.8540 Section 864.8540...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8540 Red cell lysing reagent. (a) Identification. A red cell lysing reagent is a device used to lyse (destroy) red blood cells...

  2. 21 CFR 660.30 - Reagent Red Blood Cells.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 7 2011-04-01 2010-04-01 true Reagent Red Blood Cells. 660.30 Section 660.30 Food... ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Reagent Red Blood Cells § 660.30 Reagent Red Blood Cells. (a) Proper name and definition. The proper name of the product shall be Reagent...

  3. 21 CFR 864.8540 - Red cell lysing reagent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Red cell lysing reagent. 864.8540 Section 864.8540...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8540 Red cell lysing reagent. (a) Identification. A red cell lysing reagent is a device used to lyse (destroy) red blood cells...

  4. 21 CFR 864.8540 - Red cell lysing reagent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Red cell lysing reagent. 864.8540 Section 864.8540...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8540 Red cell lysing reagent. (a) Identification. A red cell lysing reagent is a device used to lyse (destroy) red blood cells...

  5. 21 CFR 864.8540 - Red cell lysing reagent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Red cell lysing reagent. 864.8540 Section 864.8540...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8540 Red cell lysing reagent. (a) Identification. A red cell lysing reagent is a device used to lyse (destroy) red blood cells...

  6. 21 CFR 864.8540 - Red cell lysing reagent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Red cell lysing reagent. 864.8540 Section 864.8540...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8540 Red cell lysing reagent. (a) Identification. A red cell lysing reagent is a device used to lyse (destroy) red blood cells...

  7. Novel and cost-effective 6-plex isobaric tagging reagent, DiART, is effective for identification and relative quantification of complex protein mixtures using PQD fragmentation.

    PubMed

    Ramsubramaniam, Nikhil; Tao, Feng; Li, Shuwei; Marten, Mark R

    2013-09-01

    Deuterium isobaric Amine Reactive Tag (DiART) reagents facilitate relative quantification during proteomic analysis in a functionally similar manner to commercially available isobaric tag for relative and absolute quantitation (iTRAQ) and tandem mass tag (TMT) reagents. In contrast to iTRAQ and TMT, DiART reagents incorporate deuterium isotopes which significantly reduce the number of required synthesis steps and hence have potential to significantly reduce reagent production cost. We examined the capability of DiART for performing quantitative proteomic experiments using a linear ion-trap mass spectrometer with Pulsed Q Dissociation (PQD) fragmentation. Using a synthetic peptide tagged with DiART reagent, we observed a precise mass shift of 144.79 Da on the triply charged precursor ion, which shows complete derivatization of the N-terminus and ε-amino group of lysine. A DiART tagged tryptic digest of bovine serum albumin showed a sequence coverage of 57.99% which was very comparable to that showed by iTRAQ, 54.77%. Furthermore, a ten protein mixture tagged with DiART reagents and mixed in 1:1:1:1:1:1 exhibited < 15% error, whereas a linear trend (slope of 1.085) was observed when tagged proteins were mixed in the ratio 2:1:2:4:10:14 and plotted against theoretical ratios. Finally, when complex cell-wall protein mixtures from the model fungus A. nidulans were tagged with DiART reagents and mixed in different ratios, they exhibited similar trends. We conclude that DiART reagents are capable of performing quantitative proteomic experiments using PQD on a linear ion trap mass spectrometer.

  8. Synthesis and conformational studies of calixarene analogue chiral [3.3.1]metacyclophanes

    NASA Astrophysics Data System (ADS)

    Islam, Md Monarul; Hirotsugu, Tomiyasu; Thuery, Pierre; Matsumoto, Taisuke; Tanaka, Junji; Elsegood, Mark R. J.; Redshaw, Carl; Yamato, Takehiko

    2015-10-01

    Trihydroxy[3.3.1]metacyclophane, which can be regarded as an unsymmetrical or incomplete "homocalix[3]arene", has been prepared from trimethoxy[3.3.1]metacyclophane by demethylation with trimethylsilyl iodide in MeCN. Di-O-methylation at the lower rim of trihydroxy[3.3.1]metacyclophane in the presence of K2CO3 in acetone afforded a novel, inherently chiral calixarene-analogue, namely a macrocyclic [3.3.1]metacyclophane, possessing C1 symmetry. The inherent chirality of the two conformers was characterized by 1H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent [(S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol], which caused a splitting of the OMe group and AB patterns corresponding to the methylene protons.

  9. Controlling Chirality of Entropic Crystals

    NASA Astrophysics Data System (ADS)

    Damasceno, Pablo F.; Karas, Andrew S.; Schultz, Benjamin A.; Engel, Michael; Glotzer, Sharon C.

    2015-10-01

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

  10. Controlling Chirality of Entropic Crystals.

    PubMed

    Damasceno, Pablo F; Karas, Andrew S; Schultz, Benjamin A; Engel, Michael; Glotzer, Sharon C

    2015-10-01

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. PMID:26550757

  11. Unnatural Isotopic Composition of Lithium Reagents

    USGS Publications Warehouse

    Qi, H.P.; Coplen, T.B.; Wang, Q. Zh; Wang, Y.-H.

    1997-01-01

    Isotopic analysis of 39 lithium reagents from several manufacturers indicates that seven were artificially depleted in 6Li significantly in excess of the variation found in terrestrial materials. The atomic weight of lithium in analyzed reagents ranged from 6.939 to 6.996, and ??7-Li, reported relative to L-SVEC lithium carbonate, ranged from -11 to +3013???. This investigation indicates that 6Li-depleted reagents are now found on chemists' shelves, and the labels of these 6Li-depleted reagents do not accurately reflect the atomic and (or) molecular weights of these reagents. In 1993, IUPAC issued the following statement: "Commercially available Li materials have atomic weights that range between 6.94 and 6.99; if a more accurate value is required, it must be determined for the specific material." This statement has been found to be incorrect In two of the 39 samples analyzed, the atomic weight of Li was in excess of 6.99.

  12. Modern affinity reagents: Recombinant antibodies and aptamers.

    PubMed

    Groff, Katherine; Brown, Jeffrey; Clippinger, Amy J

    2015-12-01

    Affinity reagents are essential tools in both basic and applied research; however, there is a growing concern about the reproducibility of animal-derived monoclonal antibodies. The need for higher quality affinity reagents has prompted the development of methods that provide scientific, economic, and time-saving advantages and do not require the use of animals. This review describes two types of affinity reagents, recombinant antibodies and aptamers, which are non-animal technologies that can replace the use of animal-derived monoclonal antibodies. Recombinant antibodies are protein-based reagents, while aptamers are nucleic-acid-based. In light of the scientific advantages of these technologies, this review also discusses ways to gain momentum in the use of modern affinity reagents, including an update to the 1999 National Academy of Sciences monoclonal antibody production report and federal incentives for recombinant antibody and aptamer efforts. In the long-term, these efforts have the potential to improve the overall quality and decrease the cost of scientific research.

  13. Chiral Shielding Revisited

    SciTech Connect

    Scadron, M. D.

    2008-08-31

    A model-independent chiral soft-pion theorem (SPT) shields the now observed scalar-meson ground-state isoscalar {sigma}(600) and isospinor {kappa}(800) resonances from detection in a{sub 1}{yields}{pi}({pi}{pi}){sub S-wave}, {gamma}{gamma}{yields}2{pi}{sup 0}, {pi}{sup -}P{yields}{pi}{sup -}{pi}{sup +}n, and K{sup -}P{yields}K{sup -}{pi}{sup +}n processes. Moreover, for pseudoscalar-to-vector-vector (PVV) decays, quark loops only are required.

  14. Chiral limit of QCD

    SciTech Connect

    Gupta, R.

    1994-12-31

    This talk contains an analysis of quenched chiral perturbation theory and its consequences. The chiral behavior of a number of quantities such as the pion mass m{sub pi}{sup 2}, the Bernard-Golterman ratios R and {sub X}, the masses of nucleons, and the kaon B-parameter are examined to see if the singular terms induced by the additional Goldstone boson, {eta}{prime}, are visible in present data. The overall conclusion (different from that presented at the lattice meeting) of this analysis is that even though there are some caveats attached to the indications of the extra terms induced by {eta}{prime} loops, the standard expressions break down when extrapolating the quenched data with m{sub q} < m{sub s}/2 to physical light quarks. I then show that due to the single and double poles in the quenched {eta}{prime}, the axial charge of the proton cannot be calculated using the Adler-Bell-Jackiw anomaly condition. I conclude with a review of the status of the calculation of light quark masses from lattice QCD.

  15. Two new spectrophotometric reagents for copper.

    PubMed

    Stookey, L

    1970-07-01

    Two ferroin-type compounds are proposed as spectrophotometric reagents for copper(I): 6-methyl-2-pyridylhydrazidine, which forms a yellow complex with lambda(max) 426 nm and molar absorptivity 700 l.mole(-1).mm(-1), and 3-(6-methyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine, which forms a red-orange complex with (lambda)max 492 nm and molar absorptivity of 955 l.mole(-1).mm(-1). These reagents are specific for copper and the complexes can be extracted into isopentanol for increased sensitivity.

  16. Use of alumosilicic reagent for water purification

    NASA Astrophysics Data System (ADS)

    Tikhonov, S. N.; Kurchatov, I. M.; Byrkin, V. A.; Feklistov, D. Y.; Laguntsov, N. I.

    2016-09-01

    Workability of the hybrid reagent based on aluminium salts and the use of active silicic acid for the purposes of water treatment was investigated in this paper. The research of the residual aluminium concentration in the water was conducted after the introduction of the reagent into the model solution. The optimum concentration ASFC and the pH value was determined at which the coagulation process is intensified. The approaches of the interaction of the dispersed particles, specified method for calculating the interaction potential of the dispersed particles in the circumstance were described.

  17. Chiral quantum dot based materials

    NASA Astrophysics Data System (ADS)

    Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii

    2014-05-01

    Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

  18. Chiral perturbation theory with nucleons

    SciTech Connect

    Meissner, U.G.

    1991-09-01

    I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, {pi}N scattering and the {sigma}-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon.

  19. Simultaneous derivatization and solid-based disperser liquid-liquid microextraction for extraction and preconcentration of some antidepressants and an antiarrhythmic agent in urine and plasma samples followed by GC-FID.

    PubMed

    Farajzadeh, Mir Ali; Khorram, Parisa; Ghorbanpour, Houshang

    2015-03-01

    The present work is based on a one-step method including derivatization and solid-based disperser liquid-liquid microextraction followed by gas chromatography-flame ionization detection (GC-FID) for the determination of four antidepressants (fluoxetine, fluvoxamine, tranylcypromine, and nortriptyline) and an antiarrhythmic agent (mexiletine) in human urine and plasma samples. In this method, a mixture of 1,1,2,2-tetrachloroethane (extraction solvent) and butylchloroformate (derivatizing reagent) is added on a sugar cube (solid disperser) and it is introduced into an aqueous sample containing the analytes and a catalyst, e.g. 3-methylpyridine (picoline). During dissolving the sugar cube by manual shaking, the extractant and derivatization agent are gradually released into the sample as very fine droplets. Then the resulted cloudy solution is centrifuged and the sedimented phase is analyzed by GC-FID. The influence of several variables on the efficiency of derivatization/microextraction procedure such as kind and volume of extraction solvent, type and amount of disperser, amount of derivatization agent, and catalyst volume are optimized. Under the optimum conditions the calibration curves are linear in the range of 8-100,000μgL(-1) (coefficient of determination ≥0.994). The relative standard deviations are obtained in the range of 3.0-6.0% for all compounds. Moreover, the detection limits and enrichment factors of the target analytes are obtained in the ranges 1-15μgL(-1) and 228-268, respectively, for both plasma and urine samples. The relative recoveries obtained for the spiked plasma and urine samples are between 70 and 91%. The results show that the proposed method is simple, reliable, low cost, and applicable to determine trace amounts of the studied drugs in biological samples. PMID:25618251

  20. Addition of organometallic reagents to chiral N-methoxylactams: enantioselective syntheses of pyrrolidines and piperidines.

    PubMed

    Jäkel, Mascha; Qu, Jianping; Schnitzer, Tobias; Helmchen, Günter

    2013-12-01

    Enantioselective iridium-catalyzed allylic substitutions were used to prepare N-allyl hydroxamic acid derivatives that were suitable for ring-closing metathesis, giving N-methoxylactams. Reactions of these derivatives with Grignard or organolithium compounds gave hemiaminals, which could be reduced diastereoselectively via acyliminium intermediates to give cis-piperidines or cis-pyrrolidines with substituents in the 2,6- or 2,5-positions, respectively. In addition, compounds with a quaternary carbon center could be synthesized by corresponding reactions with potassium cyanide/AcOH. The procedures were applied in the syntheses of alkaloids (-)-209D and (+)-prosophylline. PMID:24151151

  1. Chiral Shift Reagent Analysis of Enantioselectivity in Baker's Yeast Reductions of Ethylacetoacetate.

    ERIC Educational Resources Information Center

    Lipkowitz, K. B.; Mooney, J. L.

    1987-01-01

    Described is a laboratory exercise that uses nuclear magnetic resonance to monitor enantiomeric excess in asymmetric reductions. The laboratory exercise has been used successfully with undergraduate organic chemistry students. (RH)

  2. Luminescent determination of quinolones in milk samples by liquid chromatography/post-column derivatization with terbium oxide nanoparticles.

    PubMed

    Yánez-Jácome, G S; Aguilar-Caballos, M P; Gómez-Hens, A

    2015-07-31

    The usefulness of terbium oxide nanoparticles (Tb4O7NPs) as post-column derivatizing reagent for the liquid chromatographic determination of residues of quinolone antibiotics in milk samples has been studied. Seven quinolones of veterinary use have been chosen as model analytes to develop this method. The derivatization step is based on the formation of luminescent chelates of quinolones with Tb4O7NPs, which are monitored at λex=340nm and λem=545nm. Another relevant feature of the method is that the use of a 10-cm column and a ternary mixture of methanol, acetonitrile and acetic acid as mobile phase in gradient elution mode allow the chromatographic separation of the quinolones in about 13min, whereas previously described chromatographic methods require about 20min. The dynamic ranges of the calibration graphs and limits of detection are, respectively: 65-900ngmL(-1) and 35ngmL(-1) for marbofloxacin, 7.2-900ngmL(-1) and 2.5ngmL(-1) for ciprofloxacin, 6-900ngmL(-1) and 2ngmL(-1) for danofloxacin, 50-900ngmL(-1) and 20ngmL(-1) for enrofloxacin, 35-900ngmL(-1) and 12ngmL(-1) for sarafloxacin, 5-900ngmL(-1) and 2ngmL(-1) for oxolinic acid, and 7-900ngmL(-1) and 2.5ngmL(-1) for flumequine. The precision, established at two concentration levels of each analyte and expressed as the percentage of the relative standard deviation is in the range of 1.9-8.1% using standards, and of 3.4-10.7% in the presence of milk samples. The method has been satisfactorily applied to the analysis of skimmed, semi-skimmed and whole milk samples, with recoveries ranging from 89.0 to 106.5%.

  3. Simultaneous in-cell derivatization pressurized liquid extraction for the determination of multiclass preservatives in leave-on cosmetics.

    PubMed

    Sanchez-Prado, Lucia; Lamas, J Pablo; Lores, Marta; Garcia-Jares, Carmen; Llompart, Maria

    2010-11-15

    An effective one-step sample preparation methodology for the determination of multiclass preservatives in cosmetics has been developed, applying, for the first time to this kind of matrix, pressurized liquid extraction (PLE) and a very simple, cheap, and fast derivatization procedure: acetylation with acetic anhydride and pyridine. A multifactorial experimental design has been used to evaluate and optimize the main experimental parameters potentially affecting the extraction process. In the final conditions the sample was mixed with Florisil as the dispersing sorbent and extracted with ethyl acetate for 15 min at 120 °C. One of the main goals of this work was to demonstrate the possibility of carrying out direct cosmetic preservative acetylation by simply adding the derivatization reagents into the PLE cell. The extract was then analyzed by GC/MS without any further cleanup or concentration step. The accuracy, precision, linearity, and detection limits (LODs) were evaluated to assess the performance of the proposed method. Quantitative recoveries were obtained, and relative standard deviation values were lower than 10% in all cases. The obtained LODs ranged from 0.000004% to 0.0001% (w/w), values far below the established restrictions in the European Cosmetics Regulation, making this multicomponent analytical method suitable for routine control. Finally, several cosmetic products such as moisturizing and antiwrinkle creams and lotions, hand creams, sunscreen and after-sun creams, baby lotions, and hair care products were analyzed. All the samples contained several of the target cosmetic ingredients, in some cases at quite high concentrations, although the actual European Cosmetics Regulation was fulfilled in all cases.

  4. Derivatization of estrogens enhances specificity and sensitivity of analysis of human plasma and serum by liquid chromatography tandem mass spectrometry.

    PubMed

    Faqehi, Abdullah M M; Cobice, Diego F; Naredo, Gregorio; Mak, Tracy C S; Upreti, Rita; Gibb, Fraser W; Beckett, Geoffrey J; Walker, Brian R; Homer, Natalie Z M; Andrew, Ruth

    2016-05-01

    Estrogens circulate at concentrations less than 20pg/mL in men and postmenopausal women, presenting analytical challenges. Quantitation by immunoassay is unreliable at these low concentrations. Liquid chromatography tandem mass spectrometry (LC-MS/MS) offers greater specificity and sometimes greater sensitivity, but ionization of estrogens is inefficient. Introduction of charged moieties may enhance ionization, but many such derivatives of estrogens generate non-specific product ions originating from the "reagent" group. Therefore an approach generating derivatives with product ions specific to individual estrogens was sought. Estrogens were extracted from human plasma and serum using solid phase extraction and derivatized using 2-fluoro-1-methylpyridinium-p-toluenesulfonate (FMP-TS). Electrospray in positive mode with multiple reaction monitoring using a QTrap 5500 mass spectrometer was used to quantify "FMP" derivatives of estrogens, following LC separation. Transitions for the FMP derivatives of estrone (E1) and estradiol (E2) were compound specific (m/z 362→238 and m/z 364→128, respectively). The limits of detection and quantitation were 0.2pg on-column and the method was linear from 1-400pg/sample. Measures of intra- and inter-assay variability, precision and accuracy were acceptable (<20%). The derivatives were stable over 24h at 10°C (7-9% degradation). Using this approach, E1 and E2, respectively were detected in human plasma and serum: pre-menopausal female serum (0.5mL) 135-473, 193-722pmol/L; male plasma (1mL) 25-111, 60-180pmol/L and post-menopausal female plasma (2mL), 22-78, 29-50pmol/L. Thus FMP derivatization, in conjunction with LC-MS/MS, is suitable for quantitative analysis of estrogens in low abundance in plasma and serum, offering advantages in specificity over immunoassay and existing MS techniques.

  5. USE OF FENTON'S REAGENT AS A DISINFECTANT

    EPA Science Inventory

    Combined sewage samples obtained from a wastewater treatment facility were disinfected by the Fenton's Reagent of several different compositions. The pre-settled samples contained both suspended solids (SS) and dissolved organic carbon (DOC) at concentrations of 28 and 290 mg/L,...

  6. Chemistry Students' Erroneous Conceptions of Limiting Reagent.

    ERIC Educational Resources Information Center

    Mammen, K. J.

    1996-01-01

    Describes a study of 32 University of Transkei (South Africa) freshmen's conceptualization of "limiting reagent," a basic concept in chemistry, based on student responses to two written test questions and clinical interviews. Results indicated that a high percentage of students had misconceptions and could not apply the concept successfully. Makes…

  7. Tritioacetylating reagents and processes for preparation thereof

    DOEpatents

    Saljoughian, Manoucher; Morimoto, Hiromi; Williams, Philip G.; Than, Chit

    2000-01-01

    Novel acetylating and tritioacetylating reagents suitable for preparation of nonlabelled and radiolabelled organic compounds. N-acetoxynaphthalimide, N-tritioacetoxyphthalimide, N-tritioacetoxysuccinimide, N-tritioacetoxynaphthalimide and processes of their preparation. The invention also concerns synthesis of nonlabelled acetylated and tritioacetylated organic compounds from precursors containing a free --NH.sub.2, --SH or --OH group.

  8. DEGRADATION OF MTBE INTERMEDIATES USING FENTON'S REAGENT

    EPA Science Inventory

    In a previous study, the chemical oxidation of MTBE at low concentrations in water using the Fenton's reagent (FR) was investigated. At certain reaction conditions the process achieved 99.99% degradation of MTBE but it did not result in complete MTBE mineralization. In the pres...

  9. Remarks on preparation of indandione detection reagents

    NASA Technical Reports Server (NTRS)

    Stepan, J.; Kral, V.

    1985-01-01

    A modified Claisen condensation with sliced sodium at a higher temperature was recommended for the production of ungranulated charcoal. A new ninhydrin production method by oxidation of benzaldiketohydrinden using available reagents was tried and was unsuccessful. Triketohydrinden was obtained by boiling ninhydrin in acetic acid anhydrides.

  10. Tetramethyleneethane Equivalents: Recursive Reagents for Serialized Cycloadditions

    PubMed Central

    2015-01-01

    New reactions and reagents that allow for multiple bond-forming events per synthetic operation are required to achieve structural complexity and thus value with step-, time-, cost-, and waste-economy. Here we report a new class of reagents that function like tetramethyleneethane (TME), allowing for back-to-back [4 + 2] cycloadditions, thereby amplifying the complexity-increasing benefits of Diels–Alder and metal-catalyzed cycloadditions. The parent recursive reagent, 2,3-dimethylene-4-trimethylsilylbutan-1-ol (DMTB), is readily available from the metathesis of ethylene and THP-protected 4-trimethylsilylbutyn-1-ol. DMTB and related reagents engage diverse dienophiles in an initial Diels–Alder or metal-catalyzed [4 + 2] cycloaddition, triggering a subsequent vinylogous Peterson elimination that recursively generates a new diene for a second cycloaddition. Overall, this multicomponent catalytic cascade produces in one operation carbo- and heterobicyclic building blocks for the synthesis of a variety of natural products, therapeutic leads, imaging agents, and materials. Its application to the three step synthesis of a new solvatochromic fluorophore, N-ethyl(6-N,N-dimethylaminoanthracene-2,3-dicarboximide) (6-DMA), and the photophysical characterization of this fluorophore are described. PMID:25961416

  11. Chirality and numbering of substituted tropane alkaloids.

    PubMed

    Humam, Munir; Shoul, Tarik; Jeannerat, Damien; Muñoz, Orlando; Christen, Philippe

    2011-08-25

    The strict application of IUPAC rules for the numbering of tropane alkaloids is not always applied by authors and there is hence a lot of confusion in the literature. In most cases, the notation of 3, 6/7-disubstituted derivatives has been chosen arbitrarily, based on NMR and MS data, without taking into account the absolute configuration of these two carbons. This paper discusses the problem and the relevance of CD and NMR to determine molecular configurations. We report on the use of (1)H-NMR anisochrony (Δδ) induced by the Mosher's chiral auxiliary reagents (R)-(-)- and (S)-(+)-α-methoxy-α-trifluoromethyl-phenylacetyl chlorides (MTPA-Cl), to determine the absolute configuration of (3R,6R)-3α-hydroxy-6β-senecioyloxytropane, a disubstituted tropane alkaloid isolated from the aerial parts of Schizanthus grahamii (Solanaceae). These analytical tools should help future works in correctly assigning the configuration of additional 3, 6/7 disubstituted tropane derivatives.

  12. Chiral analysis by capillary electrophoresis using antibiotics as chiral selector.

    PubMed

    Desiderio, C; Fanali, S

    1998-05-20

    The separation of chiral compounds by capillary electrophoresis (CE) is a very interesting field of research in different areas such as pharmaceutical, environmental, agricultural analysis etc. The separation of two enantiomers can be achieved in CE using a chiral environment interacting with the two analytes on forming diastereoisomers with different stability constants and thus different mobilities. A wide number of chiral selectors have been employed in CE and among them glycopeptide antibiotics exhibited excellent enantioselective properties towards a wide number of racemic compounds. Vancomycin, ristocetin A, rifamycins, teicoplanin, kanamycin, streptomycin, fradiomycin, and two vancomycin analogues, added to the background electrolyte (BGE), are the antibiotics studied by CE running the separation in untreated and/or coated fused-silica capillary. Due to adsorption and absorption phenomena, some drawbacks can be expected when using bare fused-silica capillary, e.g., changes of electroosmotic flow (EOF), broaden peaks, reduced efficiency and low sensitivity. Coated capillary and counter current mode can be the solution to overcome the above mentioned problems. This review surveys the separation of enantiomers by CE when macrocyclic antibiotics are used as chiral selector. The enantioselectivity can be easily controlled modifying several parameters such as antibiotic type and concentration, pH, ionic strength and concentration of the background electrolyte, organic modifier etc. The paper also presents a list of the latest chiral separations achieved by CE where antibiotics were used as chiral selector.

  13. Asymmetric Iridium-Catalyzed C-C Coupling of Chiral Diols via Site-Selective Redox-Triggered Carbonyl Addition.

    PubMed

    Shin, Inji; Krische, Michael J

    2016-01-01

    Cyclometalated π-allyliridium C,O-benzoate complexes modified by axially chiral chelating phosphine ligands display a pronounced kinetic preference for primary alcohol dehydrogenation, enabling highly site-selective redox-triggered carbonyl additions of chiral primary-secondary 1,3-diols with exceptional levels of catalyst-directed diastereoselectivity. Unlike conventional methods for carbonyl allylation, the present redox-triggered alcohol C-H functionalizations bypass the use of protecting groups, premetalated reagents, and discrete alcohol-to-aldehyde redox reactions.

  14. Chirality in photonic systems

    NASA Astrophysics Data System (ADS)

    Solnyshkov, Dmitry; Malpuech, Guillaume

    2016-10-01

    The optical modes of photonic structures are the so-called TE and TM modes that bring intrinsic spin-orbit coupling and chirality to these systems. This, combined with the unique flexibility of design of the photonic potential, and the possibility to mix photon states with excitonic resonances, sensitive to magnetic field and interactions, allows us to achieve many phenomena, often analogous to other solid-state systems. In this contribution, we review in a qualitative and comprehensive way several of these realizations, namely the optical spin Hall effect, the creation of spin currents protected by a non-trivial geometry, the Berry curvature for photons, and the photonic/polaritonic topological insulator.

  15. Amino Acids and Chirality

    NASA Technical Reports Server (NTRS)

    Cook, Jamie E.

    2012-01-01

    Amino acids are among the most heavily studied organic compound class in carbonaceous chondrites. The abundance, distributions, enantiomeric compositions, and stable isotopic ratios of amino acids have been determined in carbonaceous chondrites fi'om a range of classes and petrographic types, with interesting correlations observed between these properties and the class and typc of the chondritcs. In particular, isomeric distributions appear to correlate with parent bodies (chondrite class). In addition, certain chiral amino acids are found in enantiomeric excess in some chondrites. The delivery of these enantiomeric excesses to the early Earth may have contributed to the origin of the homochirality that is central to life on Earth today. This talk will explore the amino acids in carbonaceous chondritcs and their relevance to the origin of life.

  16. SYNTHESIS OF HIGHLY FLUORINATED CHLOROFORMATES AND THEIR USE AS DERIVATIZING AGENTS FOR HYDROPHILIC COMPOUNDS AND DRINKING WATER DISINFECTION BY-PRODUCTS

    EPA Science Inventory

    A rapid, safe and efficient procedure was developed to synthesize perfluorinated chloroformates in the small scale generally required to perform analytical derivatizations. This new family of derivatizing agents allows straightforward derivatization of highly polar compounds, co...

  17. Chiral Bosonization of Superconformal Ghosts

    NASA Technical Reports Server (NTRS)

    Shi, Deheng; Shen, Yang; Liu, Jinling; Xiong, Yongjian

    1996-01-01

    We explain the difference of the Hilbert space of the superconformal ghosts (beta,gamma) system from that of its bosonized fields phi and chi. We calculate the chiral correlation functions of phi, chi fields by inserting appropriate projectors.

  18. Life's chirality from prebiotic environments

    NASA Astrophysics Data System (ADS)

    Gleiser, Marcelo; Walker, Sara Imari

    2012-10-01

    A key open question in the study of life is the origin of biomolecular homochirality: almost every life-form on Earth has exclusively levorotary amino acids and dextrorotary sugars. Will the same handedness be preferred if life is found elsewhere? We review some of the pertinent literature and discuss recent results suggesting that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events. In one scenario, autocatalytic prebiotic reactions undergo stochastic fluctuations due to environmental disturbances, in a mechanism reminiscent of evolutionary punctuated equilibrium: short-lived destructive events may lead to long-term enantiomeric excess. In another, chiral-selective polymerization reaction rates influenced by environmental effects lead to substantial chiral excess even in the absence of autocatalysis. Applying these arguments to other potentially life-bearing platforms has implications to the search for extraterrestrial life: we predict that a statistically representative sampling of extraterrestrial stereochemistry will be racemic (chirally neutral) on average.

  19. Interconversion of ephedrine and pseudoephedrine during chemical derivatization.

    PubMed

    Wong, Colton H F; Ho, Emmie N M; Kwok, W H; Leung, David K K; Leung, Gary N W; Tang, Francis P W; Wong, April S Y; Wong, Jenny K Y; Yu, Nola H; Wan, Terence S M

    2012-12-01

    Gas chromatography-mass spectrometry (GC-MS) analysis after heptafluorobutyric anhydride (HFBA) derivatization was one of the published methods used for the quantification of ephedrine (EP) and pseudoephedrine (PE) in urine. This method allows the clear separation of the derivatized diastereoisomers on a methyl-silicone-based column. Recently the authors came across a human urine sample with apparently high levels (µg/ml) of EP and PE upon initial screening. However, duplicate analyses of this sample using the HFBA-GC-MS method revealed an unusual discrepancy in the estimated levels of EP and PE, with the area response ratios of EP/PE at around 29% on one occasion and around 57% on another. The same sample was re-analyzed for EP and PE using other techniques, including GC-MS after trimethylsilylation and ultra-high-performance liquid chromatography-tandem mass spectrometry. Surprisingly, the concentration of EP in the sample was determined to be at least two orders of magnitude less than what was observed with the HFBA-GC-MS method. A thorough investigation was then conducted, and the results showed that both substances could interconvert during HFBA derivatization. Similar diastereoisomeric conversion was also observed using other fluorinated acylating agents (e.g. pentafluoropropionic anhydride and trifluoroacetic anhydride). The extent of interconversion was correlated with the degree of fluorination of the acylating agents, with HFBA giving the highest conversion. This conversion has never been reported before. A mechanism for the interconversion was proposed. These findings indicated that fluorinated acylating agents should not be used for the unequivocal identification or quantification of EP and PE as the results obtained can be erroneous.

  20. Rotation of the chiral bag

    NASA Astrophysics Data System (ADS)

    Kahana, David E.; Jackson, A. D.; Ripka, G.

    1986-11-01

    Cranking of the chiral bag model is carried out in order to generate the correct quantum numbers for SU(2) baryons. The moment of inertia of the system is found to be divided between the meson and quark sectors. A numerical evaluation of the contributions to the moment of inertia from valence quarks and from mesons is presented. Finally, a discussion is given of the nucleon-delta mass splitting predicted in the chiral bag model.

  1. Gluons in the chiral bag

    NASA Astrophysics Data System (ADS)

    Kahana, D. E.; Milana, J.

    1987-07-01

    A perturbative QCD calculation of gluon exchange corrections to the cranking moment of inertia of the chiral bag model is done using the full time-dependent cavity propagators. Cranking is used to construct the nucleon and delta states and a value of the effective strong coupling constant is extracted by fitting the empirical Δ N mass splitting. The MIT bag limit (large bag radius) of the chiral bag model is also examined.

  2. Optical properties of chiral nanostructures

    NASA Astrophysics Data System (ADS)

    Cecilia, Noguez; Román-Velázquez, Carlos E.; Garzón, Ignacio L.

    2004-03-01

    We present a computational model to study the optical properties chiral nanostructures[1] . In this work the nanostructures of interest are composed by N atoms, where each one is represented by a polarizable point dipole located at theposition of the atom. We assume that the dipole located is characterized by a polarizability. The nanostructure is excited by a circularly polarized incident wave, such that, each dipole is subject to a total electric field due to: (i) the incident radiation field, plus (ii) the radiation field resulting from all of the other induced dipoles. Once we solve the complex-linear equations, the dipole moment on each atom in the cluster can be determined and we can find the extinction cross section of the whole nanoparticle. Circular dichroism (CD) spectra of chiral bare and thiol-passivated gold nanoclusters have been calculated within the dipole approximation. The calculated CD spectra show features that allow us to distinguish between clusters with different indexes of chirality. The main factor responsible of the differences in the CD lineshapes is the distribution of interatomic distances that characterize the chiral cluster geometry. These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral metal nanoclusters. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003) This work has been partly supported by DGAPA-UNAM grants No. IN104201 and IN104402, and by CONACyT grant 36651-E.

  3. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

    PubMed Central

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-01-01

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application. PMID:27401541

  4. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

    NASA Astrophysics Data System (ADS)

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-07-01

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application.

  5. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation.

    PubMed

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-07-12

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application.

  6. Correlation between structures of chiral polymers and their efficiency for chiral resolution by crystallization.

    PubMed

    Menahem, Tali; Pravda, Martin; Mastai, Yitzhak

    2009-10-01

    In this work, we describe the correlation between chiral polymer structures, particularly alpha-helical and random coil conformations, and their efficiency as chiral resolving agents in crystallization processes. A set of chiral block copolymers based on polyethylene oxide with chiral glutamic acid oligopeptide segments (PEG(113)-b-(+)-(S)-Glu(20)) were synthesized and employed as additives in the crystallization of rac-threonine. CD spectroscopy demonstrates that structures of chiral polymers could be switched between a helical and a disordered random coil by pH. The effect of these polymers at different conformations on the crystallization kinetics, crystal morphology, and chiral resolution of rac-threonine is reported. Our study demonstrates that only chiral polymers with alpha-helical conformations of the chiral segment are effective as additives for chiral resolution throughout crystallization. Overall, our results provide useful guidelines for the selection and design of chiral polymer additives that will act efficiently for chiral resolution by crystallization. PMID:19455618

  7. Atropisomeric determination of chiral hydroxylated metabolites of polychlorinated biphenyls using HPLC-MS

    PubMed Central

    2013-01-01

    Background Polychlorinated biphenyls (PCBs) are a group of environmental persistent organic pollutants, which can be metabolized into a series of metabolites, including hydroxylated metabolites (OH-PCBs) in biota. Nineteen of 209 PCB congeners can form chiral stable isomers. However, atropisomeric determination of the hydroxylated metabolites of these chiral PCBs has never been reported by LC methods. In this work, a novel HPLC-MS method was developed to detect five chiral OH-PCBs (4OH-PCB91, 5OH-PCB91, 4OH-PCB95, 5OH-PCB95 and 5OH-PCB149) using HPLC-MS without a derivatization step. Results The influences of column-type, column temperature, flow rate and ratio of the mobile phase on the atropisomeric separation were investigated in detail. In the final method, calibration curves, based on peak areas against concentration, were linear in a range of 1–100 ng mL-1 of five chiral OH-PCBs with correlation coefficients ranging from 0.9996 to 0.9999 for all atropisomers of OH-PCBs. The relative standard deviations measured at the 10.0 ng mL-1 level for atropisomers of five chiral OH-PCBs were in the range of 0.60-7.55% (n = 5). Calculated detection limits (S/N = 3) of five chiral OH-PCBs were between 0.31 and 0.60 ng mL-1 for all OH-PCB atropisomers. Conclusion This HPLC-MS method was developed to detect chiral OH-PCBs and further successfully applied to measure OH-PCB atropisomer levels and enantiomeric fractions (EFs) in rat liver microsomal samples. The results from LC-MS method were highly consistent with those from GC-ECD method. It is the first time to report these OH-PCB atropisomers detected in microsomes by HPLC-MS. The proposed method might be applied also to detect chiral OH-PCBs in environmental samples and for metabolites of PCBs in vivo. PMID:24360245

  8. TADDOLs, Their Derivatives, and TADDOL Analogues: Versatile Chiral Auxiliaries.

    PubMed

    Seebach, Dieter; Beck, Albert K.; Heckel, Alexander

    2001-01-01

    TADDOLs, which contain two adjacent diarylhydroxymethyl groups in a trans relationship on a 1,3-dioxolane ring, can be prepared from acetals or ketals of tartrate esters by reaction of the latter with aromatic Grignard reagents. They are extraordinarily versatile chiral auxiliaries. Here, a historical review of the subject is followed by discussion of the preparation of TADDOLs and analogous systems, including TADDOLs with N-, P-, O-, and S-heteroatom ligands appropriate for metals. Crystal structure analysis reveals that the heteroatoms on the diarylmethyl groups are almost always in close proximity to each other, joined together by H-bonds, and predisposed to form chelate complexes in which the metallic centers reside in propeller-like chiral environments. Applications of TADDOL derivatives in enantioselective synthesis extend from utilization as stoichiometric chiral reagents or in Lewis acid mediated reactions, to roles in catalytic hydrogenation and stereoregular metathesis polymerization. Derivatives and complexes based on the following metals have so far been investigated: Li, B, Mg, Al, Si, Cu, Zn, Ce, Ti, Zr, Mo, Rh, Ir, Pd, Pt. The number of stereoselective reactions already accomplished with TADDOLs is correspondingly large. It is also easy to prepare TADDOL derivatives that are readily polymerizable and graftable, and to transform them into immobilized solid-phase catalysts. The result is catalysts, simply or dendritically immobilized in polystyrene or on silica gel and characterized by unexpected stability even after multiple use in titanium TADDOLate mediated reactions. TADDOLs show further unusual characteristics that make them useful for applications in material science and supramolecular chemistry: they are the most effective doping agents known for phase transformations of achiral (nematic) into chiral (cholesteric) liquid crystals. The TADDOL OH group that is not involved in intramolecular H-bonding shows a strong tendency to associate

  9. 21 CFR 606.65 - Supplies and reagents.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... other contaminants. (b) Each blood collecting container and its satellite container(s), if any, shall be... and reverse grouping cells Do. Hepatitis test reagents Each run. Syphilis serology reagents...

  10. 21 CFR 606.65 - Supplies and reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... other contaminants. (b) Each blood collecting container and its satellite container(s), if any, shall be... and reverse grouping cells Do. Hepatitis test reagents Each run. Syphilis serology reagents...

  11. 21 CFR 606.65 - Supplies and reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... other contaminants. (b) Each blood collecting container and its satellite container(s), if any, shall be... and reverse grouping cells Do. Hepatitis test reagents Each run. Syphilis serology reagents...

  12. CLAY AND CLAY-SUPPORTED REAGENTS IN ORGANIC SYNTHESES

    EPA Science Inventory

    CLAY AND CLAY-SUPPORTED REAGENTS HAVE BEEN USED EXTENSIVELY FOR SYNTHETIC ORGANIC TRANSFORMATIONS. THIS OVERVIEW DESCRIBES THE SALIENT STRUCTURAL PROPERTIES OF VARIOUS CLAY MATERIALS AND EXTENDS THE DISCUSSION TO PILLARED CLAYS AND REAGENTS SUPPORTED ON CLAY MATERIALS. A VARIET...

  13. The Grignard Reagent: Preparation, Structure, and Some Reactions.

    ERIC Educational Resources Information Center

    Orchin, Milton

    1989-01-01

    The Grignard reagent used in the laboratory synthesis of organic compounds is the product resulting from the reaction of an alkyl or aryl halide with elemental magnesium. Describes the structure, formation, and some reactions of the reagent. (YP)

  14. 40 CFR 160.83 - Reagents and solutions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... LABORATORY PRACTICE STANDARDS Testing Facilities Operation § 160.83 Reagents and solutions. All reagents and solutions in the laboratory areas shall be labeled to indicate identity, titer or concentration,...

  15. 21 CFR 866.3550 - Salmonella spp. serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3550 Salmonella... isolates derived from clinical specimens. Additionally, some of these reagents consist of antisera... clinical specimens or cultured isolates derived from clinical specimens. The identification aids in...

  16. 21 CFR 866.3550 - Salmonella spp. serological reagents.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3550 Salmonella... isolates derived from clinical specimens. Additionally, some of these reagents consist of antisera... clinical specimens or cultured isolates derived from clinical specimens. The identification aids in...

  17. 21 CFR 866.3550 - Salmonella spp. serological reagents.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3550 Salmonella... isolates derived from clinical specimens. Additionally, some of these reagents consist of antisera... clinical specimens or cultured isolates derived from clinical specimens. The identification aids in...

  18. 21 CFR 866.3550 - Salmonella spp. serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3550 Salmonella... isolates derived from clinical specimens. Additionally, some of these reagents consist of antisera... clinical specimens or cultured isolates derived from clinical specimens. The identification aids in...

  19. 21 CFR 866.3550 - Salmonella spp. serological reagents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3550 Salmonella... isolates derived from clinical specimens. Additionally, some of these reagents consist of antisera... clinical specimens or cultured isolates derived from clinical specimens. The identification aids in...

  20. Using design of experiments to optimize derivatization with methyl chloroformate for quantitative analysis of the aqueous phase from hydrothermal liquefaction of biomass.

    PubMed

    Madsen, René Bjerregaard; Jensen, Mads Mørk; Mørup, Anders Juul; Houlberg, Kasper; Christensen, Per Sigaard; Klemmer, Maika; Becker, Jacob; Iversen, Bo Brummerstedt; Glasius, Marianne

    2016-03-01

    Hydrothermal liquefaction is a promising technique for the production of bio-oil. The process produces an oil phase, a gas phase, a solid residue, and an aqueous phase. Gas chromatography coupled with mass spectrometry is used to analyze the complex aqueous phase. Especially small organic acids and nitrogen-containing compounds are of interest. The efficient derivatization reagent methyl chloroformate was used to make analysis of the complex aqueous phase from hydrothermal liquefaction of dried distillers grains with solubles possible. A circumscribed central composite design was used to optimize the responses of both derivatized and nonderivatized analytes, which included small organic acids, pyrazines, phenol, and cyclic ketones. Response surface methodology was used to visualize significant factors and identify optimized derivatization conditions (volumes of methyl chloroformate, NaOH solution, methanol, and pyridine). Twenty-nine analytes of small organic acids, pyrazines, phenol, and cyclic ketones were quantified. An additional three analytes were pseudoquantified with use of standards with similar mass spectra. Calibration curves with high correlation coefficients were obtained, in most cases R (2)  > 0.991. Method validation was evaluated with repeatability, and spike recoveries of all 29 analytes were obtained. The 32 analytes were quantified in samples from the commissioning of a continuous flow reactor and in samples from recirculation experiments involving the aqueous phase. The results indicated when the steady-state condition of the flow reactor was obtained and the effects of recirculation. The validated method will be especially useful for investigations of the effect of small organic acids on the hydrothermal liquefaction process. PMID:26804738

  1. Using design of experiments to optimize derivatization with methyl chloroformate for quantitative analysis of the aqueous phase from hydrothermal liquefaction of biomass.

    PubMed

    Madsen, René Bjerregaard; Jensen, Mads Mørk; Mørup, Anders Juul; Houlberg, Kasper; Christensen, Per Sigaard; Klemmer, Maika; Becker, Jacob; Iversen, Bo Brummerstedt; Glasius, Marianne

    2016-03-01

    Hydrothermal liquefaction is a promising technique for the production of bio-oil. The process produces an oil phase, a gas phase, a solid residue, and an aqueous phase. Gas chromatography coupled with mass spectrometry is used to analyze the complex aqueous phase. Especially small organic acids and nitrogen-containing compounds are of interest. The efficient derivatization reagent methyl chloroformate was used to make analysis of the complex aqueous phase from hydrothermal liquefaction of dried distillers grains with solubles possible. A circumscribed central composite design was used to optimize the responses of both derivatized and nonderivatized analytes, which included small organic acids, pyrazines, phenol, and cyclic ketones. Response surface methodology was used to visualize significant factors and identify optimized derivatization conditions (volumes of methyl chloroformate, NaOH solution, methanol, and pyridine). Twenty-nine analytes of small organic acids, pyrazines, phenol, and cyclic ketones were quantified. An additional three analytes were pseudoquantified with use of standards with similar mass spectra. Calibration curves with high correlation coefficients were obtained, in most cases R (2)  > 0.991. Method validation was evaluated with repeatability, and spike recoveries of all 29 analytes were obtained. The 32 analytes were quantified in samples from the commissioning of a continuous flow reactor and in samples from recirculation experiments involving the aqueous phase. The results indicated when the steady-state condition of the flow reactor was obtained and the effects of recirculation. The validated method will be especially useful for investigations of the effect of small organic acids on the hydrothermal liquefaction process.

  2. Application of Screening Experimental Designs to Assess Chromatographic Isotope Effect upon Isotope-Coded Derivatization for Quantitative Liquid Chromatography–Mass Spectrometry

    PubMed Central

    2015-01-01

    Isotope effect may cause partial chromatographic separation of labeled (heavy) and unlabeled (light) isotopologue pairs. Together with a simultaneous matrix effect, this could lead to unacceptable accuracy in quantitative liquid chromatography–mass spectrometry assays, especially when electrospray ionization is used. Four biologically relevant reactive aldehydes (acrolein, malondialdehyde, 4-hydroxy-2-nonenal, and 4-oxo-2-nonenal) were derivatized with light or heavy (d3-, 13C6-, 15N2-, or 15N4-labeled) 2,4-dinitrophenylhydrazine and used as model compounds to evaluate chromatographic isotope effects. For comprehensive assessment of retention time differences between light/heavy pairs under various gradient reversed-phase liquid chromatography conditions, major chromatographic parameters (stationary phase, mobile phase pH, temperature, organic solvent, and gradient slope) and different isotope labelings were addressed by multiple-factor screening using experimental designs that included both asymmetrical (Addelman) and Plackett–Burman schemes followed by statistical evaluations. Results confirmed that the most effective approach to avoid chromatographic isotope effect is the use of 15N or 13C labeling instead of deuterium labeling, while chromatographic parameters had no general influence. Comparison of the alternate isotope-coded derivatization assay (AIDA) using deuterium versus 15N labeling gave unacceptable differences (>15%) upon quantifying some of the model aldehydes from biological matrixes. On the basis of our results, we recommend the modification of the AIDA protocol by replacing d3-2,4-dinitrophenylhydrazine with 15N- or 13C-labeled derivatizing reagent to avoid possible unfavorable consequences of chromatographic isotope effects. PMID:24922593

  3. Application of screening experimental designs to assess chromatographic isotope effect upon isotope-coded derivatization for quantitative liquid chromatography-mass spectrometry.

    PubMed

    Szarka, Szabolcs; Prokai-Tatrai, Katalin; Prokai, Laszlo

    2014-07-15

    Isotope effect may cause partial chromatographic separation of labeled (heavy) and unlabeled (light) isotopologue pairs. Together with a simultaneous matrix effect, this could lead to unacceptable accuracy in quantitative liquid chromatography-mass spectrometry assays, especially when electrospray ionization is used. Four biologically relevant reactive aldehydes (acrolein, malondialdehyde, 4-hydroxy-2-nonenal, and 4-oxo-2-nonenal) were derivatized with light or heavy (d3-, (13)C6-, (15)N2-, or (15)N4-labeled) 2,4-dinitrophenylhydrazine and used as model compounds to evaluate chromatographic isotope effects. For comprehensive assessment of retention time differences between light/heavy pairs under various gradient reversed-phase liquid chromatography conditions, major chromatographic parameters (stationary phase, mobile phase pH, temperature, organic solvent, and gradient slope) and different isotope labelings were addressed by multiple-factor screening using experimental designs that included both asymmetrical (Addelman) and Plackett-Burman schemes followed by statistical evaluations. Results confirmed that the most effective approach to avoid chromatographic isotope effect is the use of (15)N or (13)C labeling instead of deuterium labeling, while chromatographic parameters had no general influence. Comparison of the alternate isotope-coded derivatization assay (AIDA) using deuterium versus (15)N labeling gave unacceptable differences (>15%) upon quantifying some of the model aldehydes from biological matrixes. On the basis of our results, we recommend the modification of the AIDA protocol by replacing d3-2,4-dinitrophenylhydrazine with (15)N- or (13)C-labeled derivatizing reagent to avoid possible unfavorable consequences of chromatographic isotope effects. PMID:24922593

  4. [Determination of 11 sulfonamide residues in aquaculture water and sediments by high performance liquid chromatography coupled with post-column derivatization].

    PubMed

    Liu, Jinghua; Sun, Zhenzhong; Huang, Xueling; Guo, Xia; Sun, Jianhua

    2015-04-01

    An analytical method was developed for the determination of 11 sulfonamide compounds in aquaculture water and sediments by high performance liquid chromatography (HPLC) coupled with post-column derivatization. The filtered water sample was purified and concentrated with HLB cartridge, while the sediment sample was extracted with a mixture of methanol and EDTA-McIlvaine buffer (1:1, v/v), and then purified and enriched through HLB solid-phase extraction. The sulfonamides were separated on a C18 column by HPLC and on-line derivatized with a fluorescamine and detected with a fluorescence detector. The parameters of post-column derivatization system were optimized, and the fluorescamine solution concentration, velocity of reagent solution and reaction temperature were 0.2 g/L, 0.15 mL/min and 50 °C, respectively. The calibration curves of the method showed good linearity in the range of 0.01-1.0 mg/L, with the correlation coefficients (r2) all above 0.99995. The recoveries were 79.3%-100.7% and 74.6%-95.3% with RSD values of 2.2%-11.0% and 2.6%-10.3% for the 11 sulfonamides in aquaculture water and sediments, respectively. The respective limits of detection (LODs, S/N = 3) were 0.9-5.5 ng/L and 0.3-1.3 µg/kg and the limits of quantification (LOQs, S/N = 10) were 3.0-18.1 ng/L and 1.0-4.4 µg/kg. The method can be applied to the determination of sulfonamides in the aquaculture environment, and it has a good practicability.

  5. Determination of acrolein in serum by high-performance liquid chromatography with fluorescence detection after pre-column fluorogenic derivatization using 1,2-diamino-4,5-dimethoxybenzene.

    PubMed

    Imazato, Takahiro; Kanematsu, Mariko; Kishikawa, Naoya; Ohyama, Kaname; Hino, Takako; Ueki, Yukitaka; Maehata, Eisuke; Kuroda, Naotaka

    2015-09-01

    Acrolein is a major unsaturated aldehyde that is generated during the lipid peroxidation process. The measurement of acrolein in biological samples should be useful to estimate the degree of lipid peroxidation and to evaluate the effect of hazardous properties of acrolein on human health. In this study, a highly sensitive and selective high-performance liquid chromatography with fluorescence detection method was developed for the determination of acrolein in human serum. The proposed method involves the pre-column fluorogenic derivatization of acrolein with 1,2-diamino-4,5-dimethoxybenzene (DDB) as a reagent. The fluorescent derivative of acrolein could be detected clearly without any interfering reagent blank peaks because DDB does not have intrinsic fluorescence itself, and the detection limit was 10 nM (signal-to-noise ratio = 3). The proposed method could selectively detect acrolein in human serum with a simple protein precipitation treatment. PMID:25620324

  6. Determination of acrolein in serum by high-performance liquid chromatography with fluorescence detection after pre-column fluorogenic derivatization using 1,2-diamino-4,5-dimethoxybenzene.

    PubMed

    Imazato, Takahiro; Kanematsu, Mariko; Kishikawa, Naoya; Ohyama, Kaname; Hino, Takako; Ueki, Yukitaka; Maehata, Eisuke; Kuroda, Naotaka

    2015-09-01

    Acrolein is a major unsaturated aldehyde that is generated during the lipid peroxidation process. The measurement of acrolein in biological samples should be useful to estimate the degree of lipid peroxidation and to evaluate the effect of hazardous properties of acrolein on human health. In this study, a highly sensitive and selective high-performance liquid chromatography with fluorescence detection method was developed for the determination of acrolein in human serum. The proposed method involves the pre-column fluorogenic derivatization of acrolein with 1,2-diamino-4,5-dimethoxybenzene (DDB) as a reagent. The fluorescent derivative of acrolein could be detected clearly without any interfering reagent blank peaks because DDB does not have intrinsic fluorescence itself, and the detection limit was 10 nM (signal-to-noise ratio = 3). The proposed method could selectively detect acrolein in human serum with a simple protein precipitation treatment.

  7. What's going on with these lithium reagents?

    PubMed

    Reich, Hans J

    2012-07-01

    This Perspective describes a series of research projects that led the author from an interest in lithium reagents as synthetically valuable building blocks to studies aimed at understanding the science behind the empirical art developed by synthetic chemists trying to impose their will on these reactive species. Understanding lithium reagent behavior is not an easy task; since many are mixtures of aggregates, various solvates are present, and frequently new mixed aggregates are formed during their reactions with electrophiles. All of these species are typically in fast exchange at temperatures above -78 °C. Described are multinuclear NMR experiments at very low temperatures aimed at defining solution structures and dynamics and some kinetic studies, both using classic techniques as well as the rapid inject NMR (RINMR) technique, which can in favorable cases operate on multispecies solutions without the masking effect of the Curtin-Hammett principle.

  8. Hydrazones as Singular Reagents in Asymmetric Organocatalysis.

    PubMed

    de Gracia Retamosa, María; Matador, Esteban; Monge, David; Lassaletta, José M; Fernández, Rosario

    2016-09-12

    This Minireview summarizes strategies and developments regarding the use of hydrazones as reagents in asymmetric organocatalysis, their distinct roles in nucleophile-electrophile, cycloaddition, and cyclization reactions. The key structural elements governing the reactivity of these reagents in a preferred pathway will be discussed, as well as their different interactions with organocatalysts, leading to diverse activation modes. Along these studies, the synthetic equivalence of N-monoalkyl, N,N-dialkyl, and N-acyl hydrazones with several synthons is also highlighted. Emphasis is also put on the mechanistic studies performed to understand the observed reactivities. Finally, the functional group transformations performed from the available products has also been analyzed, highlighting the synthetic value of these methodologies, which served to access numerous families of valuable multifunctional compounds and nitrogen-containing heterocycles.

  9. Hydrazones as Singular Reagents in Asymmetric Organocatalysis.

    PubMed

    de Gracia Retamosa, María; Matador, Esteban; Monge, David; Lassaletta, José M; Fernández, Rosario

    2016-09-12

    This Minireview summarizes strategies and developments regarding the use of hydrazones as reagents in asymmetric organocatalysis, their distinct roles in nucleophile-electrophile, cycloaddition, and cyclization reactions. The key structural elements governing the reactivity of these reagents in a preferred pathway will be discussed, as well as their different interactions with organocatalysts, leading to diverse activation modes. Along these studies, the synthetic equivalence of N-monoalkyl, N,N-dialkyl, and N-acyl hydrazones with several synthons is also highlighted. Emphasis is also put on the mechanistic studies performed to understand the observed reactivities. Finally, the functional group transformations performed from the available products has also been analyzed, highlighting the synthetic value of these methodologies, which served to access numerous families of valuable multifunctional compounds and nitrogen-containing heterocycles. PMID:27552942

  10. Hydrophobically derivatized hyperbranched polyglycerol as a human serum albumin substitute.

    PubMed

    Kainthan, Rajesh K; Janzen, Johan; Kizhakkedathu, Jayachandran N; Devine, Dana V; Brooks, Donald E

    2008-04-01

    There is a huge clinical demand for Human Serum Albumin (HSA), with a world market of approximately $1.5B/year. Concern over prion and viral transmission in the blood supply has led to a need for safer substitutes and offers the opportunity for development of materials with enhanced properties over the presently available plasma expanders. We report here the synthesis and testing of a new synthetic plasma expander that can replace not only the osmotic and volume expansion properties of HSA but, uniquely, its binding and transport properties. We have synthesized several hyperbranched polyglycerols derivatized with hydrophobic groups and short poly(ethylene glycol) (PEG) chains. The hydrophobic groups provide regions for binding fatty acids and other hydrophobic materials while PEG imparts the necessary protection from host defense systems and enhances circulation longevity. These polymers, being hyperbranched, have only a small effect on plasma viscosity. We have shown in vitro that our materials bind 2-3 moles palmitic acid per mole, do not activate the platelet, coagulation or complement systems and do not cause red cell aggregation. In mice these materials are non-toxic with circulation half-lives as high as 34h, controllable by manipulating the molecular weight and the degree of PEG derivatization. PMID:18194812

  11. [Analysis of thickening polysaccharides by the improved diethyldithioacetal derivatization method].

    PubMed

    Akiyama, Takumi; Yamazaki, Takeshi; Tanamoto, Kenichi

    2011-01-01

    The identification test for thickening polysaccharides containing neutral saccharides and uronic acids was investigated by GC analysis of constituent monosaccharides. The reported method, in which monosaccharides were converted to diethyldithioacetal derivatives with ethanethiol followed by trimethylsilylation, was improved in terms of operability and reproducibility of GC/MS analysis. The suitability of the improved diethyldithioacetal derivatization method was determined for seven thickening polysaccharides, i.e., carob bean gum, guar gum, karaya gum, gum arabic, gum ghatti, tragacanth gum and peach gum. The samples were acid-hydrolyzed to form monosaccharides. The hydrolysates were derivatized and analyzed with GC/FID. Each sugar derivative was detected as a single peak and was well separated from others on the chromatograms. The amounts of constituent monosaccharides in thickening polysaccharides were successfully estimated. Seven polysaccharides were distinguished from each other on the basis of constituent monosaccharides. Further examination of the time period of hydrolysis of polysaccharides using peach gum showed that the optimal times were not the same for all monosaccharides. A longer time was needed to hydrolyze glucuronic acid than neutral saccharides. The findings suggest that hydrolysis time may sometimes affect the analytical results on composition of constituent monosaccharides in polysaccharides.

  12. Monoclonal antibodies as blood grouping reagents.

    PubMed

    Voak, D

    1990-04-01

    The large volume requirements for high quality ABO and Rh(D) typing reagents can now be supplied by selected monoclonal antibodies. Superior anti-A and anti-B monoclonal reagents can be prepared, from blends of at least two antibodies, to optimize the intensity of agglutination for slide tests and the potency for the detection of the weaker sub-groups, including Ax and Bw, by tube techniques. New quality control steps have been described for some highly sensitive anti-A/anti-B antibodies to avoid the detection of traces of A on B cells or traces of B on A1 cells, which results from the non-specific activity of A and B transferases. Excellent anti-A,B reagents may also be made by blends of at least two antibodies to optimize both A and B reactions, but the need for their continued use is now debatable. The development of high titre IgM monoclonal anti-D reagents offers simple rapid saline Rh(D) typing of both patients and donors, but they cannot reliably detect weak D (Du) and some D variants, e.g. the epitopes on D category VI cells. However, this can be achieved by blending an IgM anti-D with IgG (polyclonal) anti-D which can detect these types after conversion of negative saline tests to an antiglobulin phase. In addition, high grade Du, D categories and variants can be reliably detected (for typing donors) by selected monoclonal IgM and IgG anti-Ds by use of suitably enhanced tests without the use of an antiglobulin test.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Determination of histamine in wines with an on-line pre-column flow derivatization system coupled to high performance liquid chromatography.

    PubMed

    García-Villar, Natividad; Saurina, Javier; Hernández-Cassou, Santiago

    2005-09-01

    A new rapid and sensitive high performance liquid chromatography (HPLC) method for determining histamine in red wine samples, based on continuous flow derivatization with 1,2-naphthoquinone-4-sulfonate (NQS), is proposed. In this system, samples are derivatized on-line in a three-channel flow manifold for reagent, buffer and sample. The reaction takes place in a PTFE coil heated at 80 degrees C and with a residence time of 2.9 min. The reaction mixture is injected directly into the chromatographic system, where the histamine derivative is separated from other aminated compounds present in the wine matrix in less than ten minutes. The HPLC procedure involves a C18 column, a binary gradient of 2% acetic acid-methanol as a mobile phase, and UV detection at 305 nm. Analytical parameters of the method are evaluated using red wine samples. The linear range is up to 66.7 mg L(-1) (r = 0.9999), the precision (RSD) is 3%, the detection limit is 0.22 mg L(-1), and the average histamine recovery is 101.5% +/- 6.7%. Commercial red wines from different Spanish regions are analyzed with the proposed method.

  14. Simple and sensitive determination of hydrazine in drinking water by ultra-high-performance liquid chromatography-tandem mass spectrometry after derivatization with naphthalene-2,3-dialdehyde.

    PubMed

    Oh, Jin-Aa; Shin, Ho-Sang

    2015-05-22

    An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to determine the level of hydrazine in drinking water. The method is based on the derivatization of hydrazine with naphthalene-2,3-dicarboxaldehyde (NDA) in water. The optimum conditions for UPLC-MS/MS detection were determined as follows: derivatization reagent dosage, 50mg/L of NDA; pH 2; and reaction time, 1min; room temperature. The formed derivative was injected into an LC system without extraction or purification procedures. Under the established conditions, the method was used to detect hydrazine in raw drinking water and chlorinated drinking water. The limits of detection and quantification for hydrazine in drinking water were 0.003μg/L and 0.01μg/L, respectively. The accuracy was in the range of 97-104%, and precision, expressed as relative standard deviation, was less than 9% in drinking water. Hydrazine was detected at a concentration of 0.13μg/L in one sample among 24 raw drinking water samples and in a range of 0.04-0.45μg/L in three samples among 24 chlorinated drinking water samples.

  15. Orthogonal array optimization of microwave-assisted derivatization for determination of trace amphetamine and methamphetamine using negative chemical ionization gas chromatography-mass spectrometry.

    PubMed

    Chung, Li-Wen; Lin, Keh-Liang; Yang, Thomas Ching-Cherng; Lee, Maw-Rong

    2009-05-01

    An orthogonal array design (OAD) was applied to optimize microwave-assisted derivatization (MAD) for analysis of trace amphetamine (AM) and methamphetamine (MA) by negative chemical ionization gas chromatography-mass spectrometry (NCI GC-MS). The 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) was used as a derivatization reagent. Experimental factors including solvent, microwave power, and irradiation time at four-levels were studied in 16 trials by OAD(16) (4(4)). The significance of these factors was investigated using analysis of variance (ANOVA) and percent contribution (PC). Solvent is statistically demonstrated a chief factor; microwave power and irradiation time are secondary factors. Under the optimum condition, calibration curve of AM is linear over a range from 0.01 to 100 ng mL(-1) with correlation coefficient 0.9988, and MA from 0.1 to 1000 ng mL(-1) with correlation coefficient 0.9951. The limit of detection (LOD) is 1.20 pg mL(-1) for AM and 13.04 pg mL(-1) for MA. An applicability of the method was tested by analyzing urine samples from amphetamine-type stimulants (ATS)-abusing suspects. Consequently, the OAD method not only optimizes the MAD condition for determination of trace AM and MA, but identifies the effects of factor solvent, microwave power and irradiation time on the MAD performance.

  16. Analysis of 26 amino acids in human plasma by HPLC using AQC as derivatizing agent and its application in metabolic laboratory.

    PubMed

    Sharma, Gaurav; Attri, Savita Verma; Behra, Bijaylaxmi; Bhisikar, Swapnil; Kumar, Praveen; Tageja, Minni; Sharda, Sheetal; Singhi, Pratibha; Singhi, Sunit

    2014-05-01

    The present study reports the simultaneous analysis of 26 physiological amino acids in plasma along with total cysteine and homocysteine by high-performance liquid chromatography (HPLC) employing 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) as precolumn derivatizing reagent. Separations were carried out using Lichrospher 100 RP-18e (5 μm) 250 × 4.0 mm column connected to 100 CN 4.0 × 4.0 mm guard column on a quaternary HPLC system and run time was 53 min. Linearity of the peak areas for different concentrations ranging from 2.5 to 100 pmol/μL of individual amino acids was determined. A good linearity (R (2) > 0.998) was achieved in the standard mixture for each amino acid. Recovery of amino acids incorporated at the time of derivatization ranged from 95 to 106 %. Using this method we have established the normative data of amino acids in plasma, the profile being comparable to the range reported in literature and identified cases of classical homocystinuria, cobalamin defect/deficiency, non-ketotic hyperglycinemia, hyperprolinemia, ketotic hyperglycinemia, urea cycle defect and maple syrup urine disease.

  17. Simultaneous derivatization and extraction of nitrophenols in soil and rain samples using modified hollow-fiber liquid-phase microextraction followed by gas chromatography-mass spectrometry.

    PubMed

    Sobhi, Hamid Reza; Esrafili, Ali; Farahani, Hadi; Gholami, Mitra; Baneshi, Mohammad Mehdi

    2013-11-01

    A simple and sensitive method based on a modified hollow-fiber liquid-phase microextraction followed by gas chromatography-mass spectrometry has been successfully developed for the extraction and simultaneous derivatization of some nitrophenols (NPs) in soil and rain samples. Microwave-assisted solvent extraction was used for the extraction of NPs from the soil, while the rain sample was directly applied to the previously mentioned method. Briefly, in this method, the analytes were extracted from aqueous samples into a thin layer of organic solvent (dodecane + 10% tri-n-octylphosphine oxide) sustained in the pores of a porous hollow fiber. Then, they were back-extracted using a small volume of organic acceptor solution (25 μl; 10 mg/L N-methyl-N-(trimethylsilyl)trifluoroacetamide, as derivatization reagent, in acetonitrile) that was located inside the lumen of the hollow fiber. Under the optimized extraction conditions, enrichment factors of 255 to 280 and limits of detection of 0.1 to 0.2 μg/L (S/N = 3) with dynamic linear ranges of 1-100 μg/L were obtained for the analytes. The accuracy of the approach was tested by the relative recovery experiments on spiked samples, with results ranging from 93 to 113%. The method was shown to be rapid, cost-effective, and potentially interesting for screening purposes.

  18. Analysis of sterols and fatty acids in natural and cultured Cordyceps by one-step derivatization followed with gas chromatography-mass spectrometry.

    PubMed

    Yang, F Q; Feng, K; Zhao, J; Li, S P

    2009-07-12

    Ten free fatty acids namely lauric acid, myristic acid, pentadecanoic acid, palmitoleic acid, palmitic acid, linoleic acid, oleic acid, stearic acid, docosanoic acid and lignoceric acid and four free sterols including ergosterol, cholesterol, campesterol and beta-sitosterol in natural (wild) Cordyceps sinensis, Cordyceps liangshanensis and Cordyceps gunnii, as well as cultured C. sinensis and Cordyceps militaris were first determined using pressurized liquid extraction (PLE), trimethylsilyl (TMS) derivatization and GC-MS analysis. The conditions such as the amount of reagent, temperature and time for TMS derivatization of analytes were optimized. Under the optimum conditions, all calibration curves showed good linearity within the tested ranges. The intra- and inter-day variations for 14 investigated compounds were less than 3.4% and 5.2%, respectively. The results showed that palmitic acid, linoleic acid, oleic acid, stearic acid and ergosterol are main components in natural and cultured Cordyceps which could be discriminated by hierarchical clustering analysis based on the contents of 14 investigated compounds or the 4 fatty acids, where the contents of palmitic acid and oleic acid in natural Cordyceps are significantly higher than those in the cultured ones.

  19. 21 CFR 864.8100 - Bothrops atrox reagent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Bothrops atrox reagent. 864.8100 Section 864.8100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8100 Bothrops atrox reagent....

  20. 21 CFR 864.8100 - Bothrops atrox reagent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Bothrops atrox reagent. 864.8100 Section 864.8100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8100 Bothrops atrox reagent....

  1. 21 CFR 864.8100 - Bothrops atrox reagent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Bothrops atrox reagent. 864.8100 Section 864.8100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8100 Bothrops atrox reagent....

  2. 21 CFR 864.8100 - Bothrops atrox reagent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Bothrops atrox reagent. 864.8100 Section 864.8100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8100 Bothrops atrox reagent....

  3. 21 CFR 864.8100 - Bothrops atrox reagent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Bothrops atrox reagent. 864.8100 Section 864.8100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8100 Bothrops atrox reagent....

  4. 21 CFR 660.20 - Blood Grouping Reagent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Blood Grouping Reagent. 660.20 Section 660.20 Food... ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Blood Grouping Reagent § 660.20 Blood Grouping Reagent. (a) Proper name and definition. The proper name of this product shall be Blood...

  5. 21 CFR 660.20 - Blood Grouping Reagent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 7 2011-04-01 2010-04-01 true Blood Grouping Reagent. 660.20 Section 660.20 Food... ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Blood Grouping Reagent § 660.20 Blood Grouping Reagent. (a) Proper name and definition. The proper name of this product shall be Blood...

  6. 21 CFR 660.20 - Blood Grouping Reagent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 7 2012-04-01 2012-04-01 false Blood Grouping Reagent. 660.20 Section 660.20 Food... ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Blood Grouping Reagent § 660.20 Blood Grouping Reagent. (a) Proper name and definition. The proper name of this product shall be Blood...

  7. 21 CFR 660.20 - Blood Grouping Reagent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 7 2013-04-01 2013-04-01 false Blood Grouping Reagent. 660.20 Section 660.20 Food... ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Blood Grouping Reagent § 660.20 Blood Grouping Reagent. (a) Proper name and definition. The proper name of this product shall be Blood...

  8. 21 CFR 660.20 - Blood Grouping Reagent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 7 2014-04-01 2014-04-01 false Blood Grouping Reagent. 660.20 Section 660.20 Food... ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Blood Grouping Reagent § 660.20 Blood Grouping Reagent. (a) Proper name and definition. The proper name of this product shall be Blood...

  9. 21 CFR 660.30 - Reagent Red Blood Cells.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 7 2012-04-01 2012-04-01 false Reagent Red Blood Cells. 660.30 Section 660.30...) BIOLOGICS ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Reagent Red Blood Cells § 660.30 Reagent Red Blood Cells. (a) Proper name and definition. The proper name of the product shall...

  10. 21 CFR 660.30 - Reagent Red Blood Cells.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 7 2014-04-01 2014-04-01 false Reagent Red Blood Cells. 660.30 Section 660.30...) BIOLOGICS ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Reagent Red Blood Cells § 660.30 Reagent Red Blood Cells. (a) Proper name and definition. The proper name of the product shall...

  11. 21 CFR 660.30 - Reagent Red Blood Cells.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Reagent Red Blood Cells. 660.30 Section 660.30...) BIOLOGICS ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Reagent Red Blood Cells § 660.30 Reagent Red Blood Cells. (a) Proper name and definition. The proper name of the product shall...

  12. 21 CFR 660.30 - Reagent Red Blood Cells.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 7 2013-04-01 2013-04-01 false Reagent Red Blood Cells. 660.30 Section 660.30...) BIOLOGICS ADDITIONAL STANDARDS FOR DIAGNOSTIC SUBSTANCES FOR LABORATORY TESTS Reagent Red Blood Cells § 660.30 Reagent Red Blood Cells. (a) Proper name and definition. The proper name of the product shall...

  13. 21 CFR 866.3700 - Staphylococcus aureus serological reagents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Staphylococcus aureus serological reagents. 866... Staphylococcus aureus serological reagents. (a) Identification. Staphylococcus aureus serological reagents are... epidemiological information on these diseases. Certain strains of Staphylococcus aureus produce an...

  14. 21 CFR 866.3700 - Staphylococcus aureus serological reagents.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Staphylococcus aureus serological reagents. 866... Staphylococcus aureus serological reagents. (a) Identification. Staphylococcus aureus serological reagents are... epidemiological information on these diseases. Certain strains of Staphylococcus aureus produce an...

  15. 21 CFR 866.3700 - Staphylococcus aureus serological reagents.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Staphylococcus aureus serological reagents. 866... Staphylococcus aureus serological reagents. (a) Identification. Staphylococcus aureus serological reagents are... epidemiological information on these diseases. Certain strains of Staphylococcus aureus produce an...

  16. 21 CFR 866.3700 - Staphylococcus aureus serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Staphylococcus aureus serological reagents. 866... Staphylococcus aureus serological reagents. (a) Identification. Staphylococcus aureus serological reagents are... epidemiological information on these diseases. Certain strains of Staphylococcus aureus produce an...

  17. 21 CFR 866.3700 - Staphylococcus aureus serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Staphylococcus aureus serological reagents. 866... Staphylococcus aureus serological reagents. (a) Identification. Staphylococcus aureus serological reagents are... epidemiological information on these diseases. Certain strains of Staphylococcus aureus produce an...

  18. 40 CFR 160.83 - Reagents and solutions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Reagents and solutions. 160.83 Section... LABORATORY PRACTICE STANDARDS Testing Facilities Operation § 160.83 Reagents and solutions. All reagents and solutions in the laboratory areas shall be labeled to indicate identity, titer or concentration,...

  19. Radical migration-addition of N-tert-butanesulfinyl imines with organozinc reagents.

    PubMed

    Huang, Wei; Ye, Jian-Liang; Zheng, Wei; Dong, Han-Qing; Wei, Bang-Guo

    2013-11-15

    A novel migration-addition sequence was discovered for the reaction of enantioenriched N-tert-butanesulfinyl iminoacetate 1a with functionalized benzylzinc bromide reagents, producing tert-leucine derivatives in excellent diastereoselectivity (dr 98:2). The absolute configurations of two new chiral centers were unambiguously assigned by chemical transformations and X-ray crystallography. In addition, the regio- and diastereoselectivities of this novel reaction were both explained through the key N-sulfinamine intermediate M6 generated by the tert-butyl radical attack on the imine. Computational analysis of this reaction process, which was performed at the B3LYP/6-311++G(3df,2p)//B3LYP/6-31G*-LANL2DZ level, also supported our proposed two-stage mechanism. PMID:24160561

  20. Ion chromatography with the indirect ultraviolet detection of alkali metal ions and ammonium using imidazolium ionic liquid as ultraviolet absorption reagent and eluent.

    PubMed

    Liu, Yong-Qiang; Yu, Hong

    2016-08-01

    Indirect ultraviolet detection was conducted in ultraviolet-absorption-agent-added mobile phase to complete the detection of the absence of ultraviolet absorption functional group in analytes. Compared with precolumn derivatization or postcolumn derivatization, this method can be widely used, has the advantages of simple operation and good linear relationship. Chromatographic separation of Li(+) , Na(+) , K(+) , and NH4 (+) was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid/organic solvent as the mobile phase, in which imidazolium ionic liquids acted as ultraviolet absorption reagent and eluting agent. The retention behaviors of four kinds of cations are discussed, and the mechanism of separation and detection are described. The main factors influencing the separation and detection were the background ultraviolet absorption reagent and the concentration of hydrogen ion in the ion chromatography-indirect ultraviolet detection. The successful separation and detection of Li(+) , Na(+) , K(+) , and NH4 (+) within 13 min was achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.02, 0.11, 0.30, and 0.06 mg/L, respectively. A new separation and analysis method of alkali metal ions and ammonium by ion chromatography with indirect ultraviolet detection method was developed, and the application range of ionic liquid was expanded. PMID:27377245

  1. Ion chromatography with the indirect ultraviolet detection of alkali metal ions and ammonium using imidazolium ionic liquid as ultraviolet absorption reagent and eluent.

    PubMed

    Liu, Yong-Qiang; Yu, Hong

    2016-08-01

    Indirect ultraviolet detection was conducted in ultraviolet-absorption-agent-added mobile phase to complete the detection of the absence of ultraviolet absorption functional group in analytes. Compared with precolumn derivatization or postcolumn derivatization, this method can be widely used, has the advantages of simple operation and good linear relationship. Chromatographic separation of Li(+) , Na(+) , K(+) , and NH4 (+) was performed on a carboxylic acid base cation exchange column using imidazolium ionic liquid/acid/organic solvent as the mobile phase, in which imidazolium ionic liquids acted as ultraviolet absorption reagent and eluting agent. The retention behaviors of four kinds of cations are discussed, and the mechanism of separation and detection are described. The main factors influencing the separation and detection were the background ultraviolet absorption reagent and the concentration of hydrogen ion in the ion chromatography-indirect ultraviolet detection. The successful separation and detection of Li(+) , Na(+) , K(+) , and NH4 (+) within 13 min was achieved using the selected chromatographic conditions, and the detection limits (S/N = 3) were 0.02, 0.11, 0.30, and 0.06 mg/L, respectively. A new separation and analysis method of alkali metal ions and ammonium by ion chromatography with indirect ultraviolet detection method was developed, and the application range of ionic liquid was expanded.

  2. Can a Non-Chiral Object Be Made of Two Identical Chiral Moieties?

    ERIC Educational Resources Information Center

    LeMarechal, Jean Francois

    2008-01-01

    Several pedagogical objects can be used to discuss chirality. Here, we use the cut of an apple to show that the association of identical chiral moieties can form a non-chiral object. Octahedral chirality is used to find situations equivalent to the cut of the apple. (Contains 5 figures.)

  3. Strange Disoriented Chiral Condensates

    NASA Astrophysics Data System (ADS)

    Abdel-Aziz, Mohamed; Gavin, Sean

    2002-10-01

    Enhancement of omega and anti-omega baryon production in Pb+Pb collisions at the CERN SPS can be explained by the formation of many small regions of disordered chiral condensate. This explanation implies that neutral and charged kaons as well as pions must exhibit novel isospin fluctuations. Fluctuations due to transient behavior of the Polyakov Loop condensate can produce similar phenomena. Kapusta and Gavin have computed the distribution of the fraction of neutral pions and kaons from such regions. We proposed robust statistical observables that can be used to extract the novel isospin fluctuations from background contributions in neutral/charged pion and K-short/K-charged correlation measurements at RHIC and LHC. The STAR experiment is currently examining K-short/K-charged correlations. Note that Pruneau, Voloshin and Gavin have proposed similar observables to study net-charge fluctuations. To obtain a baseline for comparison to RHIC and SPS experiments, Abdel-Aziz and Gavin compute these observables using numerical simulations using HIJING and URQMD event generators. We also obtain limits on the size and number of disordered regions by comparing to photon and charged-pion searches from WA98 and other SPS experiments. We will compare to the first results from STAR K-short/K-charged analysis.

  4. Asymmetric Conjugate Alkynylation of Cyclic α,β-Unsaturated Carbonyl Compounds with a Chiral Diene Rhodium Catalyst.

    PubMed

    Dou, Xiaowei; Huang, Yinhua; Hayashi, Tamio

    2016-01-18

    Asymmetric conjugate alkynylation of cyclic α,β-unsaturated carbonyl compounds (ketones, esters, and amides) was realized by use of diphenyl[(triisopropylsilyl)ethynyl]methanol as an alkynylating reagent in the presence of a rhodium catalyst coordinated with a new chiral diene ligand (Fc-bod; bod=bicyclo[2.2.2]octa-2,5-diene, Fc=ferrocenyl) to give high yields of the corresponding β-alkynyl-substituted carbonyl compounds with 95-98% ee. PMID:26636764

  5. Phase diagram of chirally imbalanced QCD matter

    SciTech Connect

    Chernodub, M. N.; Nedelin, A. S.

    2011-05-15

    We compute the QCD phase diagram in the plane of the chiral chemical potential and temperature using the linear sigma model coupled to quarks and to the Polyakov loop. The chiral chemical potential accounts for effects of imbalanced chirality due to QCD sphaleron transitions which may emerge in heavy-ion collisions. We found three effects caused by the chiral chemical potential: the imbalanced chirality (i) tightens the link between deconfinement and chiral phase transitions; (ii) lowers the common critical temperature; (iii) strengthens the order of the phase transition by converting the crossover into the strong first order phase transition passing via the second order end point. Since the fermionic determinant with the chiral chemical potential has no sign problem, the chirally imbalanced QCD matter can be studied in numerical lattice simulations.

  6. Chiral Chlordane Components in Environmental Matrices

    EPA Science Inventory

    Chlordane, a persistent, bioaccumulative and toxic organochlorine pesticide, has been studied for many years. Since the advent of chiral analysis for environmental samples, over 2,400 measurements have been made of various chiral chlordane components. Chlordane enantiomer fractio...

  7. Automated pre-column derivatization of thiolic fruit-antibrowning agents by sequential injection coupled to high-performance liquid chromatography using a monolithic stationary phase and an in-loop stopped-flow approach.

    PubMed

    Karakosta, Theano D; Tzanavaras, Paraskevas D; Themelis, Demetrius G

    2011-08-01

    The present study reports the very first application of ethyl propiolate (EP) as an advantageous pre-column derivatization reagent for the determination of thiols by liquid chromatography (LC). Cysteine (CYS), glutathione (GSH) and N-acetylcysteine (NAC) were derivatized online under stopped-flow conditions in a sequential injection (SI) system coupled to HPLC. The formed derivatives were separated isocratically with a monolithic stationary phase (100×4.6 mm id) and UV detected at 285 nm. Critical parameters that affected the online pre-column derivatization reaction (e.g. the reaction time and the amount concentration of EP) and the separation (e.g. pH and the composition of the mobile phase) were investigated. The developed analytical scheme offers a total analysis time of less than 10 min, limits of detection in the range of 0.24-0.35 μmol/L and satisfactory linearity up to 200 μmol/L for all analytes. The proposed method was applied to the analysis of the selected thiols--that are often employed as antibrowning agents--in fresh fruit samples.

  8. Monitoring the contents of six steroidal and phenolic endocrine disrupting chemicals in chicken, fish and aquaculture pond water samples using pre-column derivatization and dispersive liquid-liquid microextraction with the aid of experimental design methodology.

    PubMed

    Wu, Hongliang; Li, Guoliang; Liu, Shucheng; Hu, Na; Geng, Dandan; Chen, Guang; Sun, Zhiwei; Zhao, Xianen; Xia, Lian; You, Jinmao

    2016-02-01

    This research established a sensitive and efficient pre-column derivatization HPLC method based on dispersive liquid-liquid microextraction (DLLME) for the simultaneous determination of six steroidal and phenolic endocrine disrupting chemicals (EDCs). In this study, EDCs were firstly labeled by the derivatization reagent 2-(11H-benzo[a]carbazol-11-yl) ethyl carbonochloridate (BCEC-Cl) and then extracted by DLLME. The response surface methodology was employed to investigate the key parameters of pre-column derivatization and DLLME. Under the optimal conditions, a good linear relationship between the peak area and the concentration of analytes was observed with correlation coefficients of >0.9991. Limits of detection for all EDCs derivatives were achieved within the range of 0.02-0.07 μg L(-1). The proposed method has the advantages of simple operation, low consumption of organic solvent, saving time, low output limit and good selectivity. When applied to several food and water samples analysis, it demonstrated good applicability for the determination of EDCs.

  9. Synthesis and conformational studies of chiral macrocyclic [1.1.1]metacyclophanes containing benzofuran rings.

    PubMed

    Islam, Md Monarul; Tomiyasu, Hirotsugu; Matsumoto, Taisuke; Tanaka, Junji; Rahman, Shofiur; Georghiou, Paris E; Redshaw, Carl; Yamato, Takehiko

    2015-09-14

    Macrocyclic [1.1.1]metacyclophanes (MCPs) containing benzene and benzofuran rings linked by methylene bridges and which can be viewed as calixarene analogues, have been synthesized by demethylation of [3.3.1]MCP-diones with trimethylsilyl iodide (TMSI) in MeCN. The [3.3.1]MCP-diones are synthesized by using (p-tolylsulfonyl)methyl isocyanide (TosMIC) as the cyclization reagent in N,N-dimethylformamide (DMF) with an excess of sodium hydride. (1)H NMR spectroscopy revealed that the remaining hydroxyl group on the phenyl ring is involved in intramolecular hydrogen bonding with the oxygen of one of the benzofuran rings. O-Methylation at the lower rim of monohydroxy[1.1.1]MCP in the presence of K2CO3 in acetone afforded a novel and inherently chiral calixarene analogue, namely the macrocyclic [1.1.1]MCP, possessing C1 symmetry. The inherent chirality of the two conformers was characterized by (1)H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent, which caused a splitting of the corresponding methylene protons to AB patterns. Single crystal X-ray analysis revealed the adoptation of a hemisphere-shaped cone isomer. DFT calculations were carried out to investigate the energy-minimized structures and the hydrogen bonds of the synthesized MCPs. PMID:26220058

  10. Tactoids of chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Palacio-Betancur, Viviana; Villada-Gil, Stiven; Zhou, Ye; Armas-Pérez, Julio C.; de Pablo, Juan José; Hernández-Ortiz, Juan Pablo

    The phase diagram of chiral liquid crystals confined in ellipsoids is obtained, by following a theoretically informed Monte Carlo relaxation of the tensor alignment field Q. The free energy of the system is described by a functional in the framework of the Landau-de Gennes formalism. This study also includes the effect of anchoring strength, curvature, and chirality of the system. In the low chirality region of the phase diagram we found the twist bipolar (BS) phase and some cholesteric phases such as the radial spherical structure (RSS), twist cylinder (TC) and double twist cylinder (DTC) whose axis of rotation is not necessarily aligned with the major axis of the geometry. For high chirality scenarios, the disclination lines are twisted or bent near the surface preventing the formation of symmetric networks of defects, although an hexagonal pattern is formed on the surface which might serve as open sites for collocation of colloids. By analyzing the free energies of isochoric systems, prolate geometries tend to be more favorable for high chirality and low anchoring conditions. Universidad Nacional de Colombia Ph.D. grant and COLCIENCIAS under the Contract No. 110-165-843-748. CONACYT for Postdoctoral Fellowships Nos. 186166 and 203840.

  11. Controlling Chirality of Entropic Crystals

    NASA Astrophysics Data System (ADS)

    Damasceno, Pablo; Karas, Andrew; Schultz, Benjamin; Engel, Michael; Glotzer, Sharon

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. Work supported by the National Science Foundation, Division of Materials Research Award No. DMR 1120923, U.S. Army Research Office under Grant Award No. W911NF-10-1-0518, and also by the DOD/ASD (R&E) under Award No. N00244-09-1-0062.

  12. Chiral Thirring–Wess model

    SciTech Connect

    Rahaman, Anisur

    2015-10-15

    The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.

  13. Chirality: a relational geometric-physical property.

    PubMed

    Gerlach, Hans

    2013-11-01

    The definition of the term chirality by Lord Kelvin in 1893 and 1904 is analyzed by taking crystallography at that time into account. This shows clearly that chirality is a relational geometric-physical property, i.e., two relations between isometric objects are possible: homochiral or heterochiral. In scientific articles the relational term chirality is often mistaken for the two valued measure for the individual (absolute) sense of chirality, an arbitrary attributive term.

  14. Flow-injection MS/MS for gas-phase chiral recognition and enantiomeric quantitation of a novel boron-containing antibiotic (GSK2251052A) by the mass spectrometric kinetic method.

    PubMed

    Wu, Lianming; Vogt, Frederick G; Liu, David Q

    2013-05-21

    The present work demonstrates, for the first time, the application of the mass spectrometric kinetic method for quantitative chiral purity determination by automatic flow-injection MS/MS. The particular compound analyzed is GSK2251052A, a novel boron-containing systemic antibiotic for the treatment of multidrug-resistant Gram-negative bacterial infections. Chiral recognition and quantitation of GSK2251052A was achieved based on the competitive dissociation kinetics of the Cu(II)-bound trimeric complex [Cu(II)(A)(ref*)2-H](+) (A = GSK2251052A or its R-enantiomer, ref* = L-tryptophan) that gives rise to Cu(II)-bound dimeric complexes. The sensitive nature of the methodology and the linear relationship between the logarithm of the fragment ion abundance ratio and the optical purity, characteristic of the kinetic method, allow chiral purity determination of pharmaceutical compounds during enantioselective synthesis. By using flow-injection MS/MS, enantiomeric quantitation of GSK2251052A by the kinetic method proved to be fast (2 min for analysis of each sample) and to have accuracy comparable to chiral LC-MS/MS and LC-UV methods as well as the method using chiral derivatization followed by LC-MS/MS analysis. This flow-injection MS/MS method represents an alternative approach to commonly used chromatographic techniques as a means of chiral purity determination and is particularly useful for rapid screening of chiral drugs during pharmaceutical development. PMID:23650921

  15. Chiral lattice fermions with correct vacuum polarization and chiral anomaly

    SciTech Connect

    Pryor, C. )

    1991-04-15

    An action for chiral lattice fermions is proposed, which avoids the Nielsen-Ninomiya theorem by virtue of its nonlocality and nonbilinearity. The action is constructed by eliminating the extra fermion modes with a gauge-violating Majorana-type Wilson mass, which is then rendered invariant by an integration over gauge transformations. The free propagator is calculated, and the one-loop vacuum polarization is shown to be identical to that for Wilson fermions, even at nonzero lattice spacing. Also the chiral anomaly is shown to be the same as for Wilson fermions in the continuum limit.

  16. Field induced spin chirality and chirality switching in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Tartakovskaya, Elena V.

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman-Kittel-Kasuya-Yosida and the Dsyaloshinsky-Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness.

  17. Iron-Catalyzed Enantioselective Cross-Coupling Reactions of α-Chloroesters with Aryl Grignard Reagents.

    PubMed

    Jin, Masayoshi; Adak, Laksmikanta; Nakamura, Masaharu

    2015-06-10

    The first iron-catalyzed enantioselective cross-coupling reaction between an organometallic compound and an organic electrophile is reported. Synthetically versatile racemic α-chloro- and α-bromoalkanoates were coupled with aryl Grignard reagents in the presence of catalytic amounts of an iron salt and a chiral bisphosphine ligand, giving the products in high yields with acceptable and synthetically useful enantioselectivities (er up to 91:9). The produced α-arylalkanoates were readily converted to the corresponding α-arylalkanoic acids with high optical enrichment (er up to >99:1) via simple deprotections/recrystallizations. The results of radical probe experiments are consistent with a mechanism that involves the formation of an alkyl radical intermediate, which undergoes subsequent enantioconvergent arylation in an intermolecular manner. The developed asymmetric coupling offers not only facile and practical access to various chiral α-arylalkanoic acid derivatives, which are of significant pharmaceutical importance, but also a basis of controlling enantioselectivity in an iron-catalyzed organometallic transformation. PMID:25955413

  18. Sulfo-NHS-SS-biotin derivatization: a versatile tool for MALDI mass analysis of PTMs in lysine-rich proteins.

    PubMed

    Markoutsa, Stavroula; Bahr, Ute; Papasotiriou, Dimitrios G; Häfner, Ann-Kathrin; Karas, Michael; Sorg, Bernd L

    2014-03-01

    The discovery of PTMs in proteins by MS requires nearly complete sequence coverage of the detected proteolytic peptides. Unfortunately, mass spectrometric analysis of the desired sequence fragments is often impeded due to low ionization efficiency and/or signal suppression in complex samples. When several lysine residues are in close proximity tryptic peptides may be too short for mass analysis. Moreover, modified peptides often appear in low stoichiometry and need to be enriched before analysis. We present here how the use of sulfo-NHS-SS-biotin derivatization of lysine side chain can help to detect PTMs in lysine-rich proteins. This label leads to a mass shift which can be adjusted by reduction of the SS bridge and alkylation with different reagents. Low intensity peptides can be enriched by use of streptavidin beads. Using this method, the functionally relevant protein kinase A phosphorylation site in 5-lipoxygenase was detected for the first time by MS. Additionally, methylation and acetylation could be unambiguously determined in histones. PMID:24449390

  19. Sulfo-NHS-SS-biotin derivatization: a versatile tool for MALDI mass analysis of PTMs in lysine-rich proteins.

    PubMed

    Markoutsa, Stavroula; Bahr, Ute; Papasotiriou, Dimitrios G; Häfner, Ann-Kathrin; Karas, Michael; Sorg, Bernd L

    2014-03-01

    The discovery of PTMs in proteins by MS requires nearly complete sequence coverage of the detected proteolytic peptides. Unfortunately, mass spectrometric analysis of the desired sequence fragments is often impeded due to low ionization efficiency and/or signal suppression in complex samples. When several lysine residues are in close proximity tryptic peptides may be too short for mass analysis. Moreover, modified peptides often appear in low stoichiometry and need to be enriched before analysis. We present here how the use of sulfo-NHS-SS-biotin derivatization of lysine side chain can help to detect PTMs in lysine-rich proteins. This label leads to a mass shift which can be adjusted by reduction of the SS bridge and alkylation with different reagents. Low intensity peptides can be enriched by use of streptavidin beads. Using this method, the functionally relevant protein kinase A phosphorylation site in 5-lipoxygenase was detected for the first time by MS. Additionally, methylation and acetylation could be unambiguously determined in histones.

  20. C-Terminal Protein Characterization by Mass Spectrometry using Combined Micro Scale Liquid and Solid-Phase Derivatization

    PubMed Central

    Nika, Heinz; Nieves, Edward; Hawke, David H.; Angeletti, Ruth Hogue

    2013-01-01

    A sample preparation method for protein C-terminal peptide isolation has been developed. In this strategy, protein carboxylate glycinamidation was preceded by carboxyamidomethylation and optional α- and ϵ-amine acetylation in a one-pot reaction, followed by tryptic digestion of the modified protein. The digest was adsorbed on ZipTipC18 pipette tips for sequential peptide α- and ϵ-amine acetylation and 1-ethyl-(3-dimethylaminopropyl) carbodiimide-mediated carboxylate condensation with ethylenediamine. Amino group-functionalized peptides were scavenged on N-hydroxysuccinimide-activated agarose, leaving the C-terminal peptide in the flow-through fraction. The use of reversed-phase supports as a venue for peptide derivatization enabled facile optimization of the individual reaction steps for throughput and completeness of reaction. Reagents were exchanged directly on the support, eliminating sample transfer between the reaction steps. By this sequence of solid-phase reactions, the C-terminal peptide could be uniquely recognized in mass spectra of unfractionated digests of moderate complexity. The use of the sample preparation method was demonstrated with low-level amounts of a model protein. The C-terminal peptides were selectively retrieved from the affinity support and proved highly suitable for structural characterization by collisionally induced dissociation. The sample preparation method provides for robustness and simplicity of operation using standard equipment readily available in most biological laboratories and is expected to be readily expanded to gel-separated proteins. PMID:23543807

  1. Determination of ammonium ion by fluorometry or spectrophotometry after on-line derivatization with o-phthalaldehyde

    NASA Technical Reports Server (NTRS)

    Goyal, S. S.; Rains, D. W.; Huffaker, R. C.

    1988-01-01

    A fast, sensitive, simple, and highly reproducible method for routine assay of ammonium ion (NH4+) was developed by using HPLC equipment. The method is based on the reaction of NH4+ with o-phthalaldehyde (OPA) in the presence of 2-mercaptoethanol. After an on-line derivatization, the resulting NH4(+)-OPA product was quantified by using fluorometric or spectrophotometric detection. For fluorometric detection, the excitation and emission wavelengths were 410 and 470 nm, respectively. The spectrophotometric detection was made by measuring absorbance at 410 nm. Results on the effects of OPA-reagent composition and pH, reaction temperature, sample matrix, and linearity of the assay are presented. Even though it took about 2 min from the time of sample injection to the appearance of sample peak, sample injections could be overlapped at an interval of about 1 min. Thus, the actual time needed for analysis was about 1 min per assay. The method can be used in a fully automated mode by using an autosampler injector.

  2. Chiral cardiovascular drugs: an overview.

    PubMed

    Ranade, Vasant V; Somberg, John C

    2005-01-01

    Stereochemistry in drug molecules is rapidly becoming an important aspect in drug research, design, and development. Recently, individual stereoisomers of drug molecules with asymmetric centers such as fexofenadine, cetirizine, verapamil, fluoxetine, levalbutarol, and amphetamine, for example, have been separated and developed as individual drugs. These stereoisomers have different therapeutic activity, and each isomer has contributed differently with respect to its formulation's pharmacologic activity, side effects, and toxicity. The present overview discusses chirality among a select group of cardiovascular drugs, their stereochemical synthesis/preparation, isolation techniques using chiral chromatography, methods for confirmation of their enantiomeric purity, pharmacodynamics, and pharmacokinetics. Chirality has been visualized as an important factor in cardiovascular research. It is also becoming evident in other areas of therapeutics.

  3. Chirality and gravitational parity violation.

    PubMed

    Bargueño, Pedro

    2015-06-01

    In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented. PMID:25919812

  4. Chirality and gravitational parity violation.

    PubMed

    Bargueño, Pedro

    2015-06-01

    In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented.

  5. Dual ultrasonic-assisted dispersive liquid-liquid microextraction coupled with microwave-assisted derivatization for simultaneous determination of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol by ultra high performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhao, Xian-En; Lv, Tao; Zhu, Shuyun; Qu, Fei; Chen, Guang; He, Yongrui; Wei, Na; Li, Guoliang; Xia, Lian; Sun, Zhiwei; Zhang, Shijuan; You, Jinmao; Liu, Shu; Liu, Zhiqiang; Sun, Jing; Liu, Shuying

    2016-03-11

    This paper, for the first time, reported a speedy hyphenated technique of low toxic dual ultrasonic-assisted dispersive liquid-liquid microextraction (dual-UADLLME) coupled with microwave-assisted derivatization (MAD) for the simultaneous determination of 20(S)-protopanaxadiol (PPD) and 20(S)-protopanaxatriol (PPT). The developed method was based on ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection using multiple-reaction monitoring (MRM) mode. A mass spectrometry sensitizing reagent, 4'-carboxy-substituted rosamine (CSR) with high reaction activity and ionization efficiency was synthesized and firstly used as derivatization reagent. Parameters of dual-UADLLME, MAD and UHPLC-MS/MS conditions were all optimized in detail. Low toxic brominated solvents were used as extractant instead of traditional chlorinated solvents. Satisfactory linearity, recovery, repeatability, accuracy and precision, absence of matrix effect and extremely low limits of detection (LODs, 0.010 and 0.015ng/mL for PPD and PPT, respectively) were achieved. The main advantages were rapid, sensitive and environmentally friendly, and exhibited high selectivity, accuracy and good matrix effect results. The proposed method was successfully applied to pharmacokinetics of PPD and PPT in rat plasma. PMID:26877173

  6. Dual ultrasonic-assisted dispersive liquid-liquid microextraction coupled with microwave-assisted derivatization for simultaneous determination of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol by ultra high performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhao, Xian-En; Lv, Tao; Zhu, Shuyun; Qu, Fei; Chen, Guang; He, Yongrui; Wei, Na; Li, Guoliang; Xia, Lian; Sun, Zhiwei; Zhang, Shijuan; You, Jinmao; Liu, Shu; Liu, Zhiqiang; Sun, Jing; Liu, Shuying

    2016-03-11

    This paper, for the first time, reported a speedy hyphenated technique of low toxic dual ultrasonic-assisted dispersive liquid-liquid microextraction (dual-UADLLME) coupled with microwave-assisted derivatization (MAD) for the simultaneous determination of 20(S)-protopanaxadiol (PPD) and 20(S)-protopanaxatriol (PPT). The developed method was based on ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection using multiple-reaction monitoring (MRM) mode. A mass spectrometry sensitizing reagent, 4'-carboxy-substituted rosamine (CSR) with high reaction activity and ionization efficiency was synthesized and firstly used as derivatization reagent. Parameters of dual-UADLLME, MAD and UHPLC-MS/MS conditions were all optimized in detail. Low toxic brominated solvents were used as extractant instead of traditional chlorinated solvents. Satisfactory linearity, recovery, repeatability, accuracy and precision, absence of matrix effect and extremely low limits of detection (LODs, 0.010 and 0.015ng/mL for PPD and PPT, respectively) were achieved. The main advantages were rapid, sensitive and environmentally friendly, and exhibited high selectivity, accuracy and good matrix effect results. The proposed method was successfully applied to pharmacokinetics of PPD and PPT in rat plasma.

  7. Determination of D-serine in human serum by LC-MS/MS using a triazole-bonded column after pre-column derivatization with (S)-4-(3-isothiocyanatopyrrolidin-1-yl)-7- (N, N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole.

    PubMed

    Sakamoto, Tatsuya; Kuwabara, Ryousuke; Takahashi, Shuhei; Onozato, Mayu; Ichiba, Hideaki; Iizuka, Hideaki; Fukushima, Takeshi

    2016-01-01

    An LC-MS/MS-based method for determining D-serine (Ser), an endogenous co-agonist of the N-methyl-D-aspartate receptor, in human serum, was developed and validated using a triazole-bonded silica-packed column after pre-column fluorescence derivatization with a chiral labeling reagent, (S)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole. Enantiomeric separation of the D- and L-Ser derivatives occurred in the triazole-bonded column (R s: 1.85) with CH3CN/100 mM HCO2NH4 in H2O (95.5:4.5) as the mobile phase with isocratic elution. The ln(capacity factor of D-Ser) in the van't Hoff plot gradually decreased with the inverse of temperature, suggesting enhanced hydrophilic interactions with the triazole-bonded stationary phase with increasing column temperature, owing to decrease in the partition coefficient to the mobile phase. Multiple reaction monitoring (m/z 457.10 > 409.00) by triple quadrupole mass spectrometry was used for quantifying D-Ser in human serum. The presence of D-Ser in the serum was confirmed by treatment with commercial D-amino acid oxidase. A linear calibration curve was constructed in the D-Ser concentration range of 0.5-5.0 μM (r (2) = 0.999, n = 3) using D-homoserine as the internal standard. The precision and recovery values were adequate for quantification. The detection limit for D-Ser was 1.1 fmol/injection (signal-to-noise ratio = 3), owing to the high CH3CN content in the mobile phase. The proposed LC-MS/MS method showed few fluctuations in the retention times of D- and L-Ser, and R s was stable until the 40th injection of serum without column washing, and thus can be useful for D-Ser determination in human serum in clinical research.

  8. Revisiting ether-derivatized imidazolium-based ionic liquids.

    PubMed

    Fei, Zhaofu; Ang, Wee Han; Zhao, Dongbin; Scopelliti, Rosario; Zvereva, Elena E; Katsyuba, Sergey A; Dyson, Paul J

    2007-08-30

    A series of ether-derivatized imidazolium halides have been prepared and characterized. Contrary to literature reports, they are all crystalline solids and have melting points well above room temperature (50-100 degrees C). Single crystals of the imidazolium salts, obtained in situ by slow cooling from their molten state to room temperature, were analyzed by X-ray crystallography, revealing various anion-cation interactions in the solid state. Exchange of the halides with [Tf(2)N]- yielded room temperature ionic liquids with viscosities that are comparable to related 1-alkyl-3-methylimidazolium ionic liquids. Density functional theory combined with IR spectroscopy has been used to analyze the role of functionalization of the imidazolium side chain on the formation of the molecular and supramolecular structure of the compounds and its possible impact on their physical properties. PMID:17676796

  9. Accurate determination of aldehydes in amine catalysts or amines by 2,4-dinitrophenylhydrazine derivatization.

    PubMed

    Barman, Bhajendra N

    2014-01-31

    Carbonyl compounds, specifically aldehydes, present in amine catalysts or amines are determined by reversed-phase liquid chromatography using ultraviolet detection of their corresponding 2,4-dinitrophenylhydrazones. The primary focus has been to establish optimum conditions for determining aldehydes accurately because these add exposure concerns when the amine catalysts are used to manufacture polyurethane products. Concentrations of aldehydes determined by this method are found to vary with the pH of the aqueous amine solution and the derivatization time, the latter being problematic when the derivatization reaction proceeds slowly and not to completion in neutral and basic media. Accurate determination of aldehydes in amines through derivatization can be carried out at an effective solution pH of about 2 and with derivatization time of 20min. Hydrochloric acid has been used for neutralization of an amine. For complete derivatization, it is essential to protonate all nitrogen atoms in the amine. An approach for the determination of an adequate amount of acid needed for complete derivatization has been described. Several 0.2M buffer solutions varying in pH from 4 to 8 have also been used to make amine solutions for carrying out derivatization of aldehydes. These solutions have effective pHs of 10 or higher and provide much lower aldehyde concentrations compared to their true values. Mechanisms for the formation of 2,4-dinitrophenylhydrazones in both acidic and basic media are discussed. PMID:24411140

  10. Collisions in Chiral Kinetic Theory.

    PubMed

    Chen, Jing-Yuan; Son, Dam T; Stephanov, Mikhail A

    2015-07-10

    Using a covariant formalism, we construct a chiral kinetic theory Lorentz invariant to order O(ℏ), which includes collisions. We find a new contribution to the particle number current due to the side jumps required by the conservation of angular momentum during collisions. We also find a conserved symmetric stress-energy tensor as well as the H function obeying Boltzmann's H theorem. We demonstrate their use by finding a general equilibrium solution and the values of the anomalous transport coefficients characterizing the chiral vortical effect.

  11. Chiral symmetry on the lattice

    SciTech Connect

    Creutz, M.

    1994-11-01

    The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model.

  12. Investigation of thiol derivatized gold nanoparticle sensors for gas analysis

    NASA Astrophysics Data System (ADS)

    Stephens, Jared S.

    Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

  13. Asymmetric Catalysis with Ethylene. Synthesis of Functionalized Chiral Enolates

    PubMed Central

    Biswas, Souvagya; Page, Jordan P.; Dewese, Kendra R.; RajanBabu, T. V.

    2016-01-01

    Trialkylsilyl enol ethers are versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the silyl enol ether moiety itself. Here we report a general procedure for highly catalytic (substrate:catalyst ratio up to 1000:1) and enantioselective (92% to 98% major enantiomer) synthesis of such compounds bearing a vinyl group at a chiral carbon at the β-position. The reactions, run under ambient conditions, use trialkylsiloxy-1,3-dienes and ethylene (1 atmosphere) as precursors, and readily available (bis-phosphine)-cobalt(II) complexes as catalysts. The silyl enolates can be readily converted into novel enantiopure vinyl triflates, a class of highly versatile cross-coupling reagents, enabling the syntheses of other enantiomerically pure, stereo-defined trisubstituted alkene intermediates not easily accessible by current methods. Examples of Kumada, Stille and Suzuki coupling reactions are illustrated. PMID:26529467

  14. [Management of POCT Devices and Reagents].

    PubMed

    Yamada, Osamu

    2015-02-01

    In order to ensure the accuracy of POCT devices and reagents, it is necessary to appropriately manage and store them. There are various points to be considered for these items, such as management before and environments when using them; it is more complex than when using conventional analysis apparatuses in clinical laboratories. In addition, staff using such devices should be provided with opportunities to obtain sufficient knowledge and skills. These approaches are indispensable to ensure POCT accuracy and provide reliable data, and, in this respect, support for staff with expertise in clinical examination is crucial. PMID:26529973

  15. [Determination of L-dopa and dopamine in rat brain microdialysate by ultra high performance liquid chromatography-tandem mass spectrometry using stable isotope-coded derivatization coupled with dispersive liquid-liquid microextraction].

    PubMed

    Qi, Weimei; Zhao, Xian-en; Qi, Yong; Sun, Zhiwei; Chen, Guang; You, Jinmao; Suo, Yourui

    2015-09-01

    The sensitive detection method of levodopa (L-DOPA) and dopamine (DA) in rat brain microdialysate of Parkinson's disease (PD) is an essential tool for the clinical study and attenuated synergistic drug screening for L-DOPA from traditional Chinese medicines. Using d0/d3-10-methyl-acridone-2-sulfonyl chloride (d0/d3-MASC) as stable isotope derivatization reagent, a novel ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for L-DOPA and DA by stable isotope- coded derivatization coupled with ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME). d3-MASC (light) and d3-MASC (heavy) were used as derivatization reagents for microdialysate samples and standards, respectively. Mixtures of the two solutions were prepared by UA-DLLME for UHPLC-MS/MS analysis with multiple reaction monitoring (MRM) mode. With d3-MASC heavy derivatives as internal standards for corresponding light derivatives from samples, the stable isotope internal standard quantification for L-DOPA and DA was carried out. The stable derivatives were obtained in aqueous acetonitrile (pH 10.8 sodium carbonate-sodium bicarbonate buffer) at 37 °C for 3.0 min, and then were separated within 2.0 min using gradient elution. Linear range was 0.20-1500.0 nmol/L (R > 0.994). LODs were 0.005 and 0.009 nmol/L for DA and L-DOPA (S/N = 3), respectively. This method was validated, and it showed obvious advantages in comparing with the reported methods in terms of sensitivity, analysis speed and anti-matrix interference. This method has been successfully applied to the study of effect of Shouwu Fang on L-DOPA and DA concentration fluctuations in PD rat brain microdialysate. PMID:26753287

  16. [Determination of L-dopa and dopamine in rat brain microdialysate by ultra high performance liquid chromatography-tandem mass spectrometry using stable isotope-coded derivatization coupled with dispersive liquid-liquid microextraction].

    PubMed

    Qi, Weimei; Zhao, Xian-en; Qi, Yong; Sun, Zhiwei; Chen, Guang; You, Jinmao; Suo, Yourui

    2015-09-01

    The sensitive detection method of levodopa (L-DOPA) and dopamine (DA) in rat brain microdialysate of Parkinson's disease (PD) is an essential tool for the clinical study and attenuated synergistic drug screening for L-DOPA from traditional Chinese medicines. Using d0/d3-10-methyl-acridone-2-sulfonyl chloride (d0/d3-MASC) as stable isotope derivatization reagent, a novel ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for L-DOPA and DA by stable isotope- coded derivatization coupled with ultrasonic-assisted dispersive liquid-liquid microextraction (UA-DLLME). d3-MASC (light) and d3-MASC (heavy) were used as derivatization reagents for microdialysate samples and standards, respectively. Mixtures of the two solutions were prepared by UA-DLLME for UHPLC-MS/MS analysis with multiple reaction monitoring (MRM) mode. With d3-MASC heavy derivatives as internal standards for corresponding light derivatives from samples, the stable isotope internal standard quantification for L-DOPA and DA was carried out. The stable derivatives were obtained in aqueous acetonitrile (pH 10.8 sodium carbonate-sodium bicarbonate buffer) at 37 °C for 3.0 min, and then were separated within 2.0 min using gradient elution. Linear range was 0.20-1500.0 nmol/L (R > 0.994). LODs were 0.005 and 0.009 nmol/L for DA and L-DOPA (S/N = 3), respectively. This method was validated, and it showed obvious advantages in comparing with the reported methods in terms of sensitivity, analysis speed and anti-matrix interference. This method has been successfully applied to the study of effect of Shouwu Fang on L-DOPA and DA concentration fluctuations in PD rat brain microdialysate.

  17. Quantification of endogenous brassinosteroids in plant by on-line two-dimensional microscale solid phase extraction-on column derivatization coupled with high performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Wu, Qian; Wu, Dapeng; Shen, Zheng; Duan, Chunfeng; Guan, Yafeng

    2013-07-01

    An on-line two-dimensional microscale solid phase extraction (2DμSPE)-on column derivatization (OCD)-high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method was developed for quantification of brassinosteroids (BRs) in plant tissues. Five BRs with widest distribution in plant species and high bioactivity (24-epibrassinolide, 24-epicastasterone, 6-deoxo-24-epicastasterone, teasterone and typhastero) were selected as target analytes. 2DμSPE column packed sequentially with phenyl boronic acid silica sorbent (the first dimension) and C18 silica sorbent (the second dimension) was used to selectively extract and enrich BRs by 110-146 times. OCD was carried out on the second dimension of 2DμSPE column with m-aminophenylboronic acid (m-APBA) as a derivatization reagent, enhancing the sensitivity of MS/MS to BRs by 13-8437 times. It was also found that pre-trap of derivatization reagent on the C18 section of 2DμSPE column could increase reaction efficiency by 3-10 times. The whole process time of the on-line system was less than 30min. The detection limits of the method for five BRs were between 1.4 and 6.6pg with RSDs less than 10%. Endogeneous BRs in tomato leaves were analyzed by using this method. Owing to the high selectivity of this on-line 2DμSPE system, BRs in plant extracts could be quantified using matrix-free standard calibration method with relative recoveries in the range of 80-124%.

  18. Chiral xenobiotics bioaccumulations and environmental health prospectives.

    PubMed

    Hussain, Iqbal; ALOthman, Zeid A; Alwarthan, Abdulrahman A; Sanagi, Mohd Marsin; Ali, Imran

    2015-08-01

    The chiral xenobiotics are very dangerous for all of us due to the different enantioselective toxicities of the enantiomers. Besides, these have different enantioselective bioaccumulations and behaviors in our body and other organisms. It is of urgent need to understand the enantioselective bioaccumulations, toxicities, and the health hazards of the chiral xenobiotics. The present article describes the classification, sources of contamination, distribution, enantioselective bioaccumulation, and the toxicities of the chiral xenobiotics. Besides, the efforts are also made to discuss the prevention and remedial measures of the havoc of the chiral xenobiotics. The challenges of the chiral xenobiotics have also been highlighted. Finally, future prospectives are also discussed.

  19. Selective determination of estrogenic compounds in water by microextraction by packed sorbents and a molecularly imprinted polymer coupled with large volume injection-in-port-derivatization gas chromatography-mass spectrometry.

    PubMed

    Prieto, A; Vallejo, A; Zuloaga, O; Paschke, A; Sellergen, B; Schillinger, E; Schrader, S; Möder, M

    2011-10-01

    A fully automated protocol consisting of microextraction by packed sorbents (MEPS) coupled with large volume injection-in-port-derivatization-gas chromatography-mass spectrometry (LVI-derivatization-GC-MS) was developed to determine endocrine disrupting compounds (EDCs) such as alkylphenols, bisphenol A, and natural and synthetic hormons in river and waste water samples. During method optimization, the extraction parameters as ion strength of the water sample, the MEPS extraction regime, the volume of organic solvent used for the elution/injection step, the type of elution solvents and the selectivity of the sorbents were studied. For optimum in-port-derivatization, 10 μL of the derivatization reagent N,O-bis(trimethylsilyl)triufloroacetamide with 1% of trimethylchlorosilane (BSTFA+1% TMCS) was used. 17β-Estradiol-molecularly imprinted polymer (MIP) and silica gel (modified with C-18) sorbents were examined for the enrichment of the target analytes from water samples and the obtained results revealed the high selectivity of the MIP material for extraction of substances with estrogen-like structures. Recovery values for most of the analytes ranged from 75 to 109% for the C18 sorbent and from 81 to 103% for the MIP material except for equilin (on C18 with only 57-66% recovery). Precision (n=4) of the entire analysis protocol ranged between 4% and 22% with both sorbents. Limits of detection (LODs) were at the low ngL(-1) level (0.02-87, C18 and 1.3-22, MIP) for the target analytes.

  20. International Standard Reagents for HPV Detection

    PubMed Central

    Pagliusi, Sonia R.; Garland, Suzanne M.

    2007-01-01

    Humam papillomavirus is the commonest genital viral infection in healthy sexually active subjects, and the presence of chronic or persistent HPV types in genital cells may constitute a prognostic marker of underlying, or predict future HPV-associated diseases. A variety of novel tests for detecting the presence of oncogenic HPV types in biological specimens have been reported. These are based on the various stages of infection and viral life cycle. HPV infects squamous epithelium with expression of various gene products intimately linked to epithelial cell differentiation. Hence, there are basically three classes of detectable markers directly derived from HPVs: molecular markers based on detection of nucleic acid sequences, serological markers based on detection of antibodies against viral proteins, and cellular markers based on detection of proteins expressed intracellularly, upon either infection or carcinogenesis. The nature of various assays and the development of international standard reagents for qualitative and quantitative assessment of assay performance are outlined. There is an increasing demand to develop standard tools to assess the quality of HPV detection systems, for regulatory and clinical management purposes. International standard reagents for HPV will help defining the analytical sensitivity and specificity of various detection methods, and will allow assuring that laboratory services used to evaluate disease burden, HPV vaccines, and cancer prevention strategies are accurate and comparable worldwide. The advancement of prophylactic vaccine candidates against HPV infections and related diseases stresses the increasing importance of HPV assays in monitoring the impact of HPV vaccination on disease burden. PMID:17627063

  1. Organometallic palladium reagents for cysteine bioconjugation.

    PubMed

    Vinogradova, Ekaterina V; Zhang, Chi; Spokoyny, Alexander M; Pentelute, Bradley L; Buchwald, Stephen L

    2015-10-29

    Reactions based on transition metals have found wide use in organic synthesis, in particular for the functionalization of small molecules. However, there are very few reports of using transition-metal-based reactions to modify complex biomolecules, which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature and mild pH) and the existence of multiple reactive functional groups found in biomolecules. Here we report that palladium(II) complexes can be used for efficient and highly selective cysteine conjugation (bioconjugation) reactions that are rapid and robust under a range of bio-compatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. The broad utility of the bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody-drug conjugates. These palladium complexes show potential as benchtop reagents for diverse bioconjugation applications.

  2. Coumarins give misleading absorbance with Ellman's reagent suggestive of thiol conjugates.

    PubMed

    Berlich, Maik; Menge, Sieglinde; Bruns, Ina; Schmidt, Juergen; Schneider, Bernd; Krauss, Gerd-Joachim

    2002-03-01

    In the course of a screening for phytochelatins in cadmium-exposed bryophytes in the terrestrial mosses Polytrichum formosum and Atrichum undulatum we detected compounds with absorption properties and retention times similar to phytochelatins when applying the commonly used standard method RP-HPLC and post-column derivatization with thiol-specific DTNB (Ellman) reagent. Moreover, as with phytochelatins known in other plants, the concentrations of these compounds increased slightly after Cd stress. The concentration of the precursor glutathione (gamma-ECG), however, increased in the presence of Cd. In order to verify the identity of these putative phytochelatins we performed LC-ESI-MS analyses as well as 1H NMR on extracts from P. formosum and A. undulatum. Spectroscopic investigations indicated that the detected compounds were neither phytochelatins nor other thiol compounds. From the results of HPLC-1H NMR and mass spectrometry we concluded that at least one of these substances was a coumarin, probably a 5,8-dihydroxy-7-methoxycoumarin-5-beta-glucopyranoside, which has already been described for A. undulatum and P. formosum. The results of our investigations prove that under the basic pH conditions essential for the Ellman test for thiol compounds, coumarins show comparable UV/VIS absorption properties. Therefore, a positive post-column Ellman reaction cannot unambiguously prove the presence of thiol-containing compounds in plants. PMID:11996355

  3. Simplified quantitative glycomics using the stable isotope label Girard's reagent p by electrospray ionization mass spectrometry.

    PubMed

    Wang, Chengjian; Wu, Zhiyu; Yuan, Jiangbei; Wang, Bo; Zhang, Ping; Zhang, Ying; Wang, Zhongfu; Huang, Linjuan

    2014-02-01

    Fast, sensitive, and simple methods for quantitative analysis of disparities in glycan expression between different biological samples are essential for studies of protein glycosylation patterns (glycomics) and the search for disease glycan biomarkers. Relative quantitation of glycans based on stable isotope labeling combined with mass spectrometric detection represents an emerging and promising technique. However, this technique is undermined by the complexity of mass spectra of isotope-labeled glycans caused by the presence of multiple metal ion adduct signals, which result in a decrease of detection sensitivity and an increase of difficulties in data interpretation. Herein we report a simplified quantitative glycomics strategy, which features nonreductive isotopic labeling of reducing glycans with either nondeuterated (d0-) or deuterated (d5-) Girard's reagent P (GP) without salts introduced and simplified mass spectrometric profiles of d0- and d5-GP derivatives of neutral glycans as molecular ions without complex metal ion adducts, allowing rapid and sensitive quantitative comparison between different glycan samples. We have obtained optimized GP-labeling conditions and good quantitation linearity, reproducibility, and accuracy of data by the method. Its excellent applicability was validated by comparatively quantitative analysis of the neutral N-glycans released from bovine and porcine immunoglobulin G as well as of those from mouse and rat sera. Additionally, we have revealed the potential of this strategy for the high-sensitivity analysis of sialylated glycans as GP derivatives, which involves neutralization of the carboxyl group of sialic acid by chemical derivatization.

  4. Chirality effect in disordered graphene ribbon junctions

    NASA Astrophysics Data System (ADS)

    Long, Wen

    2012-05-01

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.

  5. Micropatterning of cells reveals chiral morphogenesis

    PubMed Central

    2013-01-01

    Invariant left-right (LR) patterning or chirality is critical for embryonic development. The loss or reversal of LR asymmetry is often associated with malformations and disease. Although several theories have been proposed, the exact mechanism of the initiation of the LR symmetry has not yet been fully elucidated. Recently, chirality has been detected within single cells as well as multicellular structures using several in vitro approaches. These studies demonstrated the universality of cell chirality, its dependence on cell phenotype, and the role of physical boundaries. In this review, we discuss the theories for developmental LR asymmetry, compare various in vitro cell chirality model systems, and highlight possible roles of cell chirality in stem cell differentiation. We emphasize that the in vitro cell chirality systems have great promise for helping unveil the nature of chiral morphogenesis in development. PMID:23672821

  6. U. S. VETERINARY IMMUNE REAGENTS NETWORK: PROGRESS WITH POULTRY IMMUNE REAGENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This poster will present a progress report on the CSREES-funded NRI grant to support a broad community approach to systematically address the immunological reagent gap for the US veterinary immunology research community including for the following groups: ruminants (concentrating on cattle but inclu...

  7. Calixarene based chiral solvating agents for α-hydroxy carboxylic acids

    NASA Astrophysics Data System (ADS)

    Bozkurt, Selahattin

    2013-09-01

    Novel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reaction of p-tert-butylcalix[4]arene diamine derivative with N-Phthaloyl-L-phenylalanine or (2S)-2-((benzyloxy)carbonyl)amino)-3-hydroxypropanoic acid or (2S,3R)-2-((benzyloxy)carbonyl)amino-3-hydroxybutanoic acid in 63-81% yield. The structures of these receptors were characterized by FTIR, 1H, 13C and 2D COSY NMR spectroscopy. The enantioselective recognition of these receptors towards the enantiomers of racemic carboxylic acids was studied by 1H NMR spectroscopy. The molar ratios of the chiral compounds with each of the enantiomers of guests were determined by using Job plots. The Job plots indicate that the hosts form 1:2 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. NMR studies demonstrated that the receptors function as highly effective chiral shift reagents for determining the enantiomeric purity of a series of carboxylic acids.

  8. Construction and probing of multisite chiral catalysts: dendrimer fixation of c2-symmetrical diphosphinerhodium complexes.

    PubMed

    Engel, Gerald D; Gade, Lutz H

    2002-09-16

    A series of chiral phosphine-functionalized poly(propyleneimine) (PPI) dendrimers was synthesized by the reaction of carboxyl-linked C(2)-chiral pyrphos ligand (pyrphos=3,4-bis(diphenylphosphino)pyrrolidine) with zeroth-fourth generation PPI using ethyl-N,N-dimethylaminopropylcarbodiimide (EDC)/1-hydroxybenzotriazol as a coupling reagent. The dendrimers obtained were characterized by NMR spectroscopy and elemental analysis as well as FAB and MALDI-TOF mass spectrometry, which established their molecular masses of up to 20 700 amu. Metalation of the multi-site phosphines with [Rh(COD)(2)]BF(4) cleanly yielded the cationic rhododendrimers containing up to 32 metal centers (for the fourth generation species), representing the largest chiral phosphine dendrimer catalyst studied to date. The complete metalation of the chiral phosphine sites was demonstrated by (31)P NMR spectroscopy and the observation of the coordination-shifted AB part of the ABX spin system (delta(A)=33.9, delta(B)=32.9; (1)J(Rh,P)=150, 153 Hz; (2)J(P,P)=28 Hz). The relationship between the size/generation of the dendrimer and its catalytic properties was established in the asymmetric hydrogenation of Z-methyl-alpha-acetamidocinammate and dimethyl itaconate. A decrease in both activity and selectivity of the dendrimer catalysts was observed on going to the higher generations. PMID:12298024

  9. Basics of Resonance Chiral Theory

    SciTech Connect

    Portoles, J.

    2010-12-28

    We review the main components that have to be considered, within Resonance Chiral Theory, in the study of processes whose dynamics is dominated by hadron resonances. We show its application in the study of the {tau}{yields}{pi}{pi}{pi}{nu}{sub {tau}} decay.

  10. Chiral asymmetry in spiral galaxies?

    PubMed

    Kondepudi, D K; Durand, D J

    2001-07-01

    Spiral galaxies are chiral entities when coupled with the direction of their recession velocity. As viewed from the Earth, the S-shaped and Z-shaped spiral galaxies are two chiral forms. What is the nature of chiral symmetry in spiral galaxies? In the Carnegie Atlas of Galaxies that lists photographs of a total of 1,168 galaxies, we found 540 galaxies, classified as normal or barred spirals, that are clearly identifiable as S- or Z- type. The recession velocities for 538 of these galaxies could be obtained from this atlas and other sources. A statistical analysis of this sample reveals no overall asymmetry but there is a significant asymmetry in certain subclasses: dominance of S-type galaxies in the Sb class of normal spiral galaxies and a dominance of Z-type in the SBb class of barred spiral galaxies. Both S- and Z-type galaxies seem to have similar velocity distribution, indicating no spatial segregation of the two chiral forms.

  11. Baryon and chiral symmetry breaking

    SciTech Connect

    Gorsky, A.; Krikun, A.

    2014-07-23

    We briefly review the generalized Skyrmion model for the baryon recently suggested by us. It takes into account the tower of vector and axial mesons as well as the chiral symmetry breaking. The generalized Skyrmion model provides the qualitative explanation of the Ioffe’s formula for the baryon mass.

  12. Combined derivatization and high-performance liquid chromatography with fluorescence and ultraviolet detection for simultaneous analysis of octreotide and gabexate mesylate metabolite in human pancreatic juice samples.

    PubMed

    Carlucci, Giuseppe; Selvaggi, Federico; Sulpizio, Sara; Bassi, Claudio; Carlucci, Maura; Cotellese, Roberto; Ferrone, Vincenzo; Innocenti, Paolo; Locatelli, Marcello

    2015-06-01

    A simple and sensitive method based on the combination of derivatization and high-performance liquid chromatography with ultraviolet and fluorimetric detection was developed for the simultaneous determination of octreotide and gabexate mesylate metabolite in human pancreatic juice samples. Parameters of the derivatization procedure affecting extraction efficiency were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.1-15 µg/mL for octreotide and 0.20-15 µg/mL for gabexate mesylate metabolite. Derivatized products of octreotide and gabexate mesylate metabolite were separated on a Luna C18 column (4.6 × 250 mm; 5 µm particle size) using a gradient with a run time of 36 min, without further purification. The limits of detection were 0.025 and 0.05, respectively, for octreotide and gabexate mesylate metabolite. This paper reports the validation of a quantitative high performance liquid chromatography-photodiode array-fluorescence (HPLC-PDA-FL) method for the simultaneous analysis of octreotide and gabexate mesylate metabolite in pancreatic juice by protein precipitation using zinc sulfate-methanol-acetonitrile containing the derivatizing reagent, 4-fluoro-7-nitro-[2,1,3]-benzoxadiazole (NBD-F). Derivatized products of octreotide and gabexate mesylate metabolite were separated on a Luna C18 column (4.6 × 250 mm; 5 µm particle size) using a gradient with a run time of 36 min, without further purification. The method was validated over the concentration ranges 0.1-15 and 0.2-15 µg/mL for octreotide and gabexate mesylate metabolite, respectively, in human pancreatic juice. Biphalin and methyl-p-hydroxybenzoate were used as the internal standards. This method was successfully utilized to support clinical studies in humans. The results from assay validations show that the method is selective, sensitive and robust. The limit

  13. Nuclear chiral dynamics and thermodynamics

    NASA Astrophysics Data System (ADS)

    Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram

    2013-11-01

    This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.

  14. Synthesis of chiral cyclohexanes and carbasugars by 6-exo-dig radical cyclisation reactions

    PubMed Central

    Maudru, Elise; Wightman, Richard H; Morgan, Keith M

    2008-01-01

    Summary Treatment of 5-(tert-butyldimethylsilyl)-2,3-O-isopropylidene-D-ribose with lithium acetylides gave mixtures of syn- and anti-alkynols 2a– 2c which were separated following protection as methoxymethyl ethers. These were converted to the corresponding iodides which underwent 6-exo-dig radical cyclisation to afford chiral cyclohexanes and carbasugars. Oxidation of the primary alcohols 6a– b gave the corresponding aldehydes which on treatment with Grignard reagents afforded a mixture of alcohols. The corresponding iodides underwent similar 6-exo-dig cyclisation to give fully functionalised cyclohexanes. PMID:19104673

  15. A new polyethyleneglycol-derivatized hemoglobin derivative with decreased oxygen affinity and limited toxicity.

    PubMed

    Zolog, Oana; Mot, Augustin; Deac, Florina; Roman, Alina; Fischer-Fodor, Eva; Silaghi-Dumitrescu, Radu

    2011-01-01

    A new protocol is described for derivatization of hemoglobin with polyethyleneglycol (PEG) via reaction of the unmodified native hemoglobin with an activated amine-reacting polyethylene glycol derivative which, unlike protocols previously described, leads to formation of a peptide bond between hemoglobin and PEG. Dioxygen binding and peroxide reactivities of the derivatized hemoglobin are examined, and found to be within reasonable limits, with the particular observation that, unlike with a few other derivatization protocols, the dioxygen affinity is slightly lower than that of native Hb. In cell culture tests (human umbilical vein epithelial cells, HUVEC), the derivatization protocol induces no toxic effect. These results show promise towards applicability for production of hemoglobin-based blood substitutes. PMID:21161348

  16. Derivatization of steroids in biological samples for GC-MS and LC-MS analyses.

    PubMed

    Marcos, Josep; Pozo, Oscar J

    2015-10-01

    The determination of steroids in biological samples is essential in different areas of knowledge. MS combined with either GC or LC is considered the best analytical technique for specific and sensitive determinations. However, due to the physicochemical properties of some steroids, and the low concentrations found in biological samples, the formation of a derivative prior to their analysis is required. In GC-MS determinations, derivatization is needed for generating volatile and thermally stable compounds. The improvement in terms of stability and chromatographic retention are the main reasons for selecting the derivatization agent. On the other hand, derivatization is not compulsory in LC-MS analyses and the derivatization is typically used for improving the ionization and therefore the overall sensitivity achieved.

  17. A new polyethyleneglycol-derivatized hemoglobin derivative with decreased oxygen affinity and limited toxicity.

    PubMed

    Zolog, Oana; Mot, Augustin; Deac, Florina; Roman, Alina; Fischer-Fodor, Eva; Silaghi-Dumitrescu, Radu

    2011-01-01

    A new protocol is described for derivatization of hemoglobin with polyethyleneglycol (PEG) via reaction of the unmodified native hemoglobin with an activated amine-reacting polyethylene glycol derivative which, unlike protocols previously described, leads to formation of a peptide bond between hemoglobin and PEG. Dioxygen binding and peroxide reactivities of the derivatized hemoglobin are examined, and found to be within reasonable limits, with the particular observation that, unlike with a few other derivatization protocols, the dioxygen affinity is slightly lower than that of native Hb. In cell culture tests (human umbilical vein epithelial cells, HUVEC), the derivatization protocol induces no toxic effect. These results show promise towards applicability for production of hemoglobin-based blood substitutes.

  18. 15N and13C NMR investigation of hydroxylamine-derivatized humic substances

    USGS Publications Warehouse

    Thorn, K.A.; Arterburn, J.B.; Mikita, M.A.

    1992-01-01

    Five fulvic and humic acid samples of diverse origins were derivatized with 15N-labeled hydroxylamine and analyzed by liquid-phase 15N NMR spectrometry. The 15N NMR spectra indicated that hydroxylamine reacted similarly with all samples and could discriminate among carbonyl functional groups. Oximes were the major derivatives; resonances attributable to hydroxamic acids, the reaction products of hydroxylamine with esters, and resonances attributable to the tautomeric equilibrium position between the nitrosophenol and monoxime derivatives of quinones, the first direct spectroscopic evidence for quinones, also were evident. The 15N NMR spectra also suggested the presence of nitriles, oxazoles, oxazolines, isocyanides, amides, and lactams, which may all be explained in terms of Beckmann reactions of the initial oxime derivatives. INEPT and ACOUSTIC 15N NMR spectra provided complementary information on the derivatized samples. 13C NMR spectra of derivatized samples indicated that the ketone/quinone functionality is incompletely derivatized with hydroxylamine. ?? 1991 American Chemical Society.

  19. The Reagent-sorption Technology of Water Treatment

    NASA Astrophysics Data System (ADS)

    Kurchatov, I. M.; Laguntsov, N. I.; Neschimenko, Y. P.; Feklistov, D. Y.

    The main purpose of this work is to intensify and to improve the efficiency of water treatment processes as well as to combine optimally modern techniques and technological devices in water treatment processes. Offered comprehensive hybrid water treatment developing technology of different origin is based on the combination of the treatment by reagent and membrane electro dialysis. In offered technology, of water treatment as a reagent is proposed to use alumino-silicic reagent, which simultaneously is coagulant, flocculant and adsorbent.

  20. Effect of carbohydrates attached to polystyrene on hepatocyte morphology on sugar-derivatized polystyrene matrices.

    PubMed

    Kim, Sang-Heon; Hoshiba, Takashi; Akaike, Toshihiro

    2003-12-15

    Sugar-carrying polymers have been utilized as artificial matrices for cell adhesion in tissue engineering. We have developed sugar-derivatized polystyrenes (PV-sugars) as artificial matrices, which control hepatocyte adhesion and hepatic function. Hepatocytes adhere to PV-sugar matrices in a receptor-mediated manner. In this study, we designed a new galactose-derivatized PV-sugar, poly-(6-O-p-vinylbenzyl-alpha-D-galactose) (PV6Gal) and evaluated the role of carbohydrate attached to polystyrene (PS) backbone in the morphological difference of hepatocyte cultured on PV-sugar matrices. Hepatocytes spread on monosaccharide-derivatized PV-sugars but not on disaccharide-derivatized PV-sugars. The actin filament remained aggregated in the central area of the cell body on disaccharide-derivatized PV-sugars. Hepatocyte cell bodies fully were spread on collagen, and the actin filament was almost completely reorganized. Hepatocyte spreading on monosaccharide-derivatized PV-sugars, however, was caused by protrusive cell-matrix contact like lamellipodia and the actin filament was not completely reorganized. This indicated that hepatocyte spreading on PV-sugar matrices was restricted compared with ECM-mediated cell spreading. In addition, typical spheroid formation of hepatocytes was promoted on disaccharide-derivatized PV-sugars compared with monosaccharide-derivatized PV-sugars. Although hepatocytes adhered with different affinities to PV-sugar matrices, hepatocyte morphology was not affected by the adhesion affinity. We suggest that the type of carbohydrate attached to the PS backbone governs the morphology of hepatocyte cultured on PV-sugar matrices.

  1. Preparation of soluble and insoluble polymer supported IBX reagents.

    PubMed

    Reed, Neal N; Delgado, Mercedes; Hereford, Kristina; Clapham, Bruce; Janda, Kim D

    2002-08-01

    A series of soluble and insoluble polymer supported versions of the versatile oxidizing reagent IBX has been prepared. Each of the reagents were evaluated for their efficiency in the conversion of benzyl alcohol to benzaldehyde. Results from this study were that the soluble, non-crosslinked polystyrene supported IBX reagent gave the best rate of conversion to benzaldehyde, while the macroporous polymer supported IBX resin provided a superior rate of conversion to benzaldehyde when compared with a gel type resin. The macroporous IBX reagent was also shown to convert a series of alcohols to the corresponding aldehydes and ketones.

  2. 21 CFR 866.3740 - Streptococcus spp. serological reagents.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3740 Streptococcus... derived from clinical specimens. The identification aids in the diagnosis of diseases caused by...

  3. 21 CFR 866.3930 - Vibrio cholerae serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3930 Vibrio... from cultured isolates derived from clinical specimens. The identification aids in the diagnosis...

  4. 21 CFR 866.3740 - Streptococcus spp. serological reagents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3740 Streptococcus... derived from clinical specimens. The identification aids in the diagnosis of diseases caused by...

  5. 21 CFR 866.3740 - Streptococcus spp. serological reagents.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3740 Streptococcus... derived from clinical specimens. The identification aids in the diagnosis of diseases caused by...

  6. 21 CFR 866.3930 - Vibrio cholerae serological reagents.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3930 Vibrio... from cultured isolates derived from clinical specimens. The identification aids in the diagnosis...

  7. 21 CFR 866.3930 - Vibrio cholerae serological reagents.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3930 Vibrio... from cultured isolates derived from clinical specimens. The identification aids in the diagnosis...

  8. 21 CFR 866.3930 - Vibrio cholerae serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3930 Vibrio... from cultured isolates derived from clinical specimens. The identification aids in the diagnosis...

  9. 21 CFR 866.3930 - Vibrio cholerae serological reagents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3930 Vibrio... from cultured isolates derived from clinical specimens. The identification aids in the diagnosis...

  10. Exploiting personalized information for reagent selection in drug design.

    PubMed

    Boström, Jonas; Falk, Niklas; Tyrchan, Christian

    2011-03-01

    Drug discovery is currently being industrialized. This fact is confusing, given that it is happening in times when the rest of the world has entered the subsequent information age. Here, we introduce a concept and an infrastructure for the now popular and well-known recommender systems in the context of exploiting one of the cornerstones of drug design: chemical reagent selection. The goal is to create and transfer information openly to facilitate intuition and serendipity in drug design. The system is tailored to highlight reagents from our corporate reagent database; reagents that a chemist might not have considered based purely on their own experience.

  11. REVIEW ARTICLE: Chiral metamaterials: simulations and experiments

    NASA Astrophysics Data System (ADS)

    Wang, Bingnan; Zhou, Jiangfeng; Koschny, Thomas; Kafesaki, Maria; Soukoulis, Costas M.

    2009-11-01

    Electromagnetic metamaterials are composed of periodically arranged artificial structures. They show peculiar properties, such as negative refraction and super-lensing, which are not seen in natural materials. The conventional metamaterials require both negative epsilon and negative μ to achieve negative refraction. Chiral metamaterial is a new class of metamaterials offering a simpler route to negative refraction. In this paper, we briefly review the history of metamaterials and the developments on chiral metamaterials. We study the wave propagation properties in chiral metamaterials and show that negative refraction can be realized in chiral metamaterials with a strong chirality, with neither epsilon nor μ negative required. We have developed a retrieval procedure, adopting a uniaxial bi-isotropic model to calculate the effective parameters such as n ± , κ, epsilon and μ of the chiral metamaterials. Our work on the design, numerical calculations and experimental measurements of chiral metamaterials is introduced. Strong chiral behaviors such as optical activity and circular dichroism are observed and negative refraction is obtained for circularly polarized waves in these chiral metamaterials. We show that 3D isotropic chiral metamaterials can eventually be realized.

  12. Advances in synthetic peptides reagent discovery

    NASA Astrophysics Data System (ADS)

    Adams, Bryn L.; Sarkes, Deborah A.; Finch, Amethist S.; Stratis-Cullum, Dimitra N.

    2013-05-01

    Bacterial display technology offers a number of advantages over competing display technologies (e.g, phage) for the rapid discovery and development of peptides with interaction targeted to materials ranging from biological hazards through inorganic metals. We have previously shown that discovery of synthetic peptide reagents utilizing bacterial display technology is relatively simple and rapid to make laboratory automation possible. This included extensive study of the protective antigen system of Bacillus anthracis, including development of discovery, characterization, and computational biology capabilities for in-silico optimization. Although the benefits towards CBD goals are evident, the impact is far-reaching due to our ability to understand and harness peptide interactions that are ultimately extendable to the hybrid biomaterials of the future. In this paper, we describe advances in peptide discovery including, new target systems (e.g. non-biological materials), advanced library development and clone analysis including integrated reporting.

  13. Influence of the derivatization procedure on the results of the gaschromatographic fatty acid analysis of human milk and infant formulae.

    PubMed

    Kohn, G; van der Ploeg, P; Möbius, M; Sawatzki, G

    1996-09-01

    Many different analytical procedures for fatty acid analysis of infant formulae and human milk are described. The objective was to study possible pitfalls in the use of different acid-catalyzed procedures compared to a base-catalyzed procedure based on sodium-methoxide in methanol. The influence of the different methods on the relative fatty acid composition (wt% of total fatty acids) and the total fatty acid recovery rate (expressed as % of total lipids) was studied in two experimental LCP-containing formulae and a human milk sample. MeOH/HCl-procedures were found to result in an incomplete transesterification of triglycerides, if an additional nonpolar solvent like toluene or hexane is not added and a water-free preparation is not guaranteed. In infant formulae the low transesterification of triglycerides (up to only 37%) could result in an 100%-overestimation of the relative amount of LCP, if these fatty acids primarily derive from phospholipids. This is the case in infant formulae containing egg lipids as raw materials. In formula containing fish oils and in human milk the efficacy of esterification results in incorrect absolute amounts of fatty acids, but has no remarkable effect on the relative fatty acid distribution. This is due to the fact that in these samples LCP are primarily bound to triglycerides. Furthermore, in formulae based on butterfat the derivatization procedure should be designed in such a way that losses of short-chain fatty acids due to evaporation steps can be avoided. The procedure based on sodium methoxide was found to result in a satisfactory (about 90%) conversion of formula lipids and a reliable content of all individual fatty acids. Due to a possibly high amount of free fatty acids in human milk, which are not methylated by sodium-methoxide, caution is expressed about the use of this reagent for fatty acid analysis of mothers milk. It is concluded that accurate fatty acid analysis of infant formulae and human milk requires a careful

  14. An evaluation of microwave-assisted derivatization procedures using hyphenated mass spectrometric techniques.

    PubMed

    Damm, Markus; Rechberger, Gerald; Kollroser, Manfred; Kappe, C Oliver

    2009-07-31

    The potential of microwave-assisted derivatization techniques in systematic toxicological analysis using gas chromatography coupled with mass spectrometry (GC-MS) was evaluated. Special emphasis was placed on the use of dedicated microwave reactors incorporating online temperature and pressure control. The use of such equipment allowed a detailed analysis of several microwave-assisted derivatization protocols comparing the efficiency of microwave and conventional heating methods utilizing a combination of GC-MS and liquid chromatography coupled with mass detection (LC-MS and LC-MS/MS) techniques. These studies revealed that for standard derivatization protocols such as acetylation (exemplified for codeine and morphine), pentafluoropropionylation (for 6-monoacetylmorphine) and trimethylsilylation (for Delta9-tetrahydrocannabinol) a reaction time of 5 min at 100 degrees C in a microwave reactor was sufficient to allow for an effective derivatization. Control experiments using standard operating procedures (30 min at 60 degrees C conventional heating) indicated that the faster derivatization under microwave irradiation is a consequence of the higher reaction temperatures that can rapidly be attained in a sealed vessel and the more efficient heat transfer to the reaction mixture applying direct in core microwave dielectric heating. The results suggest that microwave derivatization procedures can significantly reduce the overall analysis time and increase sample throughput for GC-MS-based analytical methods.

  15. Molecular chirality and chiral capsule-type dimer formation of cyclic triamides via hydrogen-bonding interactions.

    PubMed

    Fujimoto, Noriko; Matsumura, Mio; Azumaya, Isao; Nishiyama, Shizuka; Masu, Hyuma; Kagechika, Hiroyuki; Tanatani, Aya

    2012-05-18

    Chiral properties of bowl-shaped cyclic triamides bearing functional groups with hydrogen-bonding ability were examined. Chiral induction of cyclic triamide 3a was observed by addition of chiral amine in solution, and chiral separation was achieved by simple crystallization to afford chiral capsule-type dimer structure of 4a.

  16. Derivatized gold clusters and antibody-gold cluster conjugates

    DOEpatents

    Hainfeld, J.F.; Furuya, F.R.

    1994-11-01

    Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be as small as 5.0 nm. Methods and reagents are disclosed in which antibodies, Fab' or F(ab')[sub 2] fragments are covalently bound to a stable cluster of gold atoms. The gold clusters may contain 6, 8, 9, 11, 13, 55 or 67 gold atoms in their inner core. The clusters may also contain radioactive gold. The antibody-cluster conjugates are useful in electron microscopy applications as well as in clinical applications that include imaging, diagnosis and therapy. 7 figs.

  17. Derivatized gold clusters and antibody-gold cluster conjugates

    DOEpatents

    Hainfeld, James F.; Furuya, Frederic R.

    1994-11-01

    Antibody- or antibody fragment-gold cluster conjugates are shown wherein the conjugate size can be as small as 5.0 nm. Methods and reagents are disclosed in which antibodies, Fab' or F(ab').sub.2 fragments thereof are covalently bound to a stable cluster of gold atoms. The gold clusters may contain 6, 8, 9, 11, 13, 55 or 67 gold atoms in their inner core. The clusters may also contain radioactive gold. The antibody-cluster conjugates are useful in electron microscopy applications as well as in clinical applications that include imaging, diagnosis and therapy.

  18. Chiral logarithms in quenched QCD

    SciTech Connect

    Y. Chen; S. J. Dong; T. Draper; I. Horvath; F. X. Lee; K. F. Liu; N. Mathur; and J. B. Zhang

    2004-08-01

    The quenched chiral logarithms are examined on a 163x28 lattice with Iwasaki gauge action and overlap fermions. The pion decay constant fpi is used to set the lattice spacing, a = 0.200(3) fm. With pion mass as low as {approx}180 MeV, we see the quenched chiral logarithms clearly in mpi2/m and fP, the pseudoscalar decay constant. The authors analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory (chiPT) to apply. With the constrained curve-fitting method, they are able to extract the quenched chiral logarithmic parameter delta together with other low-energy parameters. Only for mpi<=300 MeV do we obtain a consistent and stable fit with a constant delta which they determine to be 0.24(3)(4) (at the chiral scale Lambdachi = 0.8 GeV). By comparing to the 123x28 lattice, they estimate the finite volume effect to be about 2.7% for the smallest pion mass. They also fitted the pion mass to the form for the re-summed cactus diagrams and found that its applicable region is extended farther than the range for the one-loop formula, perhaps up to mpi {approx}500-600 MeV. The scale independent delta is determined to be 0.20(3) in this case. The authors study the quenched non-analytic terms in the nucleon mass and find that the coefficient C1/2 in the nucleon mass is consistent with the prediction of one-loop chiPT. They also obtain the low energy constant L5 from fpi. They conclude from this study that it is imperative to cover only the range of data with the pion mass less than {approx}300 MeV in order to examine the chiral behavior of the hadron masses and decay constants in quenched QCD and match them with quenched one-loop chiPT.

  19. Mechanism of chirality conversion by periodic change of temperature: Role of chiral clusters

    NASA Astrophysics Data System (ADS)

    Katsuno, Hiroyasu; Uwaha, Makio

    2016-01-01

    By grinding crystals in a solution, the chirality of crystal structure (and the molecular chirality for the case of chiral molecules as well) can be converted, and the cause of the phenomenon is attributed to crystal growth with chiral clusters. We show that the recently found chirality conversion with a periodic change of temperature can also be explained by crystal growth with chiral clusters. With the use of a generalized Becker-Döring model, which includes enantio-selective incorporation of small chiral clusters to large solid clusters, the change of cluster distribution and the mass flow between clusters are studied. The chiral clusters act as a reservoir to pump out the minority species to the majority, and the exponential amplification of the enantiomeric excess found in the experiment is reproduced in the numerical calculation.

  20. Alkylation of pyridines at their 4-positions with styrenes plus yttrium reagent or benzyl Grignard reagents.

    PubMed

    Mizumori, Tomoya; Hata, Takeshi; Urabe, Hirokazu

    2015-01-01

    A new regioselective alkylation of pyridines at their 4-position was achieved with styrenes in the presence of yttrium trichloride, BuLi, and diisobutylaluminium hydride (DIBAL-H) in THF. Alternatively, similar products were more simply prepared from pyridines and benzyl Grignard reagents. These reactions are not only a useful preparation of 4-substituted pyridines but are also complementary to other relevant reactions usually giving 2-substituted pyridines.

  1. Alkylation of pyridines at their 4-positions with styrenes plus yttrium reagent or benzyl Grignard reagents.

    PubMed

    Mizumori, Tomoya; Hata, Takeshi; Urabe, Hirokazu

    2015-01-01

    A new regioselective alkylation of pyridines at their 4-position was achieved with styrenes in the presence of yttrium trichloride, BuLi, and diisobutylaluminium hydride (DIBAL-H) in THF. Alternatively, similar products were more simply prepared from pyridines and benzyl Grignard reagents. These reactions are not only a useful preparation of 4-substituted pyridines but are also complementary to other relevant reactions usually giving 2-substituted pyridines. PMID:25352343

  2. Stable Pentaquarks from Strange Chiral Multiplets

    SciTech Connect

    Silas Beane

    2004-12-01

    The assumption of strong diquark correlations in the QCD spectrum suggests flavor multiplets of hadrons that are degenerate in the chiral limit. Generally it would be unnatural for there to be degeneracy in the hadron spectrum that is not protected by a QCD symmetry. Here we show--for pentaquarks constructed from diquarks--that these degeneracies can be naturally protected by the full chiral symmetry of QCD. The resulting chiral multiplet structure recovers the ideally-mixed pentaquark mass spectrum of the diquark model, and interestingly, requires that the axial couplings of the pentaquarks to states outside the degenerate multiplets vanish in the chiral limit. This result suggests that if these hadrons exist, they are stable in the chiral limit and therefore have widths that scale as the fourth power of the kaon mass over the chiral symmetry breaking scale. Natural-size widths are of order a few MeV.

  3. Asymmetric synthesis using chiral-encoded metal.

    PubMed

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-08-26

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

  4. Asymmetric synthesis using chiral-encoded metal.

    PubMed

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-01-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity. PMID:27562028

  5. Anomalous Maxwell equations for inhomogeneous chiral plasma

    NASA Astrophysics Data System (ADS)

    Gorbar, E. V.; Shovkovy, I. A.; Vilchinskii, S.; Rudenok, I.; Boyarsky, A.; Ruchayskiy, O.

    2016-05-01

    Using the chiral kinetic theory we derive the electric and chiral current densities in inhomogeneous relativistic plasma. We also derive equations for the electric and chiral chemical potentials that close the Maxwell equations in such a plasma. The analysis is done in the regimes with and without a drift of the plasma as a whole. In addition to the currents present in the homogeneous plasma (Hall current, chiral magnetic, chiral separation, and chiral electric separation effects, as well as Ohm's current) we derive several new terms associated with inhomogeneities of the plasma. Apart from various diffusionlike terms, we find also new dissipationless terms that are independent of relaxation time. Their origin can be traced to the Berry curvature modifications of the kinetic theory.

  6. Asymmetric synthesis using chiral-encoded metal

    PubMed Central

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-01-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity. PMID:27562028

  7. Asymmetric synthesis using chiral-encoded metal

    NASA Astrophysics Data System (ADS)

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-08-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

  8. Enantioselective recognition at mesoporous chiral metal surfaces

    PubMed Central

    Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A.; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2014-01-01

    Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes. PMID:24548992

  9. On chirality of slime mould.

    PubMed

    Dimonte, Alice; Adamatzky, Andrew; Erokhin, Victor; Levin, Michael

    2016-02-01

    Left-right patterning and lateralised behaviour is an ubiquitous aspect of plants and animals. The mechanisms linking cellular chirality to the large-scale asymmetry of multicellular structures are incompletely understood, and it has been suggested that the chirality of living cells is hardwired in their cytoskeleton. We examined the question of biased asymmetry in a unique organism: the slime mould Physarum polycephalum, which is unicellular yet possesses macroscopic, complex structure and behaviour. In laboratory experiment using a T-shape, we found that Physarum turns right in more than 74% of trials. The results are in agreement with previously published studies on asymmetric movement of muscle cells, neutrophils, liver cells and growing neural filaments, and for the first time reveal the presence of consistently-biased laterality in the fungi kingdom. Exact mechanisms of the slime mould's direction preference remain unknown.

  10. On chirality of slime mould.

    PubMed

    Dimonte, Alice; Adamatzky, Andrew; Erokhin, Victor; Levin, Michael

    2016-02-01

    Left-right patterning and lateralised behaviour is an ubiquitous aspect of plants and animals. The mechanisms linking cellular chirality to the large-scale asymmetry of multicellular structures are incompletely understood, and it has been suggested that the chirality of living cells is hardwired in their cytoskeleton. We examined the question of biased asymmetry in a unique organism: the slime mould Physarum polycephalum, which is unicellular yet possesses macroscopic, complex structure and behaviour. In laboratory experiment using a T-shape, we found that Physarum turns right in more than 74% of trials. The results are in agreement with previously published studies on asymmetric movement of muscle cells, neutrophils, liver cells and growing neural filaments, and for the first time reveal the presence of consistently-biased laterality in the fungi kingdom. Exact mechanisms of the slime mould's direction preference remain unknown. PMID:26747637

  11. On lattice chiral gauge theories

    NASA Technical Reports Server (NTRS)

    Maiani, L.; Rossi, G. C.; Testa, M.

    1991-01-01

    The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations.

  12. Optically controllable THz chiral metamaterials.

    PubMed

    Kenanakis, G; Zhao, R; Katsarakis, N; Kafesaki, M; Soukoulis, C M; Economou, E N

    2014-05-19

    Switchable and tunable chiral metamaterial response is numerically demonstrated here in different uniaxial chiral metamaterial structures operating in the THz regime. The structures are based on the bi-layer conductor design and the tunable/switchable response is achieved by replacing parts of the metallic components of the structures by photoconducting Si, which can be transformed from an insulating to an almost conducting state through photoexcitation, achievable under external optical pumping. All the structures proposed and discussed here exhibit frequency regions with giant tunable circular dichroism, as well as regions with giant tunable optical activity, showing unique potential in the achievement of active THz polarization components, like tunable polarizers and polarization filters. PMID:24921336

  13. Bootstrapping N=2 chiral correlators

    NASA Astrophysics Data System (ADS)

    Lemos, Madalena; Liendo, Pedro

    2016-01-01

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  14. Chiral anomaly, bosonization, and fractional charge

    SciTech Connect

    Mignaco, J.A.; Monteiro, M.A.R.

    1985-06-15

    We present a method to evaluate the Jacobian of chiral rotations, regulating determinants through the proper-time method and using Seeley's asymptotic expansion. With this method we compute easily the chiral anomaly for ..nu.. = 4,6 dimensions, discuss bosonization of some massless two-dimensional models, and handle the problem of charge fractionization. In addition, we comment on the general validity of Fujikawa's approach to regulate the Jacobian of chiral rotations with non-Hermitian operators.

  15. Thin-wire scatterers in chiral media.

    PubMed

    Jaggard, D L; Liu, J C; Grot, A; Pelet, P

    1991-06-01

    The effect of the handedness of chiral materials on the differential scattering cross section of embedded conducting wires is examined. The bow-tie-shaped induced current distributions and the resulting forbidden zone of radiation are explained through fundamental physical principles. We find that thin-wire scatterers can be divided into subchiral, chiral, and superchiral classes according to the degree of chirality of the host material and the electromagnetic length of the wire.

  16. Chirality operators for Heisenberg spin systems

    SciTech Connect

    Subrahmanyam, V. )

    1994-09-01

    The ground state of closed Heisenberg spin chains with an odd number of sites has a chiral degeneracy, in addition to a twofold Kramers degeneracy. A nonzero chirality implies that the spins are not coplanar, and is a measure of handedness. The chirality operator, which can be treated as a spin-1/2 operator, is explicitly constructed in terms of the spin operators, and is given as commutator of permutation operators.

  17. Flat-space chiral gravity.

    PubMed

    Bagchi, Arjun; Detournay, Stéphane; Grumiller, Daniel

    2012-10-12

    We provide the first evidence for a holographic correspondence between a gravitational theory in flat space and a specific unitary field theory in one dimension lower. The gravitational theory is a flat-space limit of topologically massive gravity in three dimensions at a Chern-Simons level of k=1. The field theory is a chiral two-dimensional conformal field theory with a central charge of c=24. PMID:23102291

  18. Anomalies and Discrete Chiral Symmetries

    SciTech Connect

    Creutz, M.

    2009-09-07

    The quantum anomaly that breaks the U(1) axial symmetry of massless multi-flavored QCD leaves behind a discrete flavor-singlet chiral invariance. With massive quarks, this residual symmetry has a close connection with the strong CP-violating parameter theta. One result is that if the lightest quarks are degenerate, then a first order transition will occur when theta passes through pi. The resulting framework helps clarify when the rooting prescription for extrapolating in the number of flavors is valid.

  19. Staggered chiral random matrix theory

    SciTech Connect

    Osborn, James C.

    2011-02-01

    We present a random matrix theory for the staggered lattice QCD Dirac operator. The staggered random matrix theory is equivalent to the zero-momentum limit of the staggered chiral Lagrangian and includes all taste breaking terms at their leading order. This is an extension of previous work which only included some of the taste breaking terms. We will also present some results for the taste breaking contributions to the partition function and the Dirac eigenvalues.

  20. Chiral symmetry and nucleon structure

    SciTech Connect

    Holstein, B.R. . Dept. of Physics and Astromony Washington Univ., Seattle, WA . Inst. for Nuclear Theory)

    1992-01-01

    Recently it has been realized that significant tests of the validity of QCD are available in low energy experiments (E < 500 MeV) by exploiting the property of (broken) chiral symmetry. This technique has been highly developed in The Goldstone boson sector by the work of Gasser and Leutwyler. Application to the nucleon system is much more difficult and is now being carefully developed.

  1. Chiral plasmons without magnetic field

    PubMed Central

    Song, Justin C. W.; Rudner, Mark S.

    2016-01-01

    Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons—chiral Berry plasmons (CBPs)—for a wide range of 2D metallic systems including gapped Dirac materials. As we show, in these materials the interplay between Berry curvature and electron–electron interactions yields chiral plasmonic modes at zero magnetic field. The CBP modes are confined to system boundaries, even in the absence of topological edge states, with chirality manifested in split energy dispersions for oppositely directed plasmon waves. We unveil a rich CBP phenomenology and propose setups for realizing them, including in anomalous Hall metals and optically pumped 2D Dirac materials. Realization of CBPs will offer a powerful paradigm for magnetic field-free, subwavelength optical nonreciprocity, in the mid-IR to terahertz range, with tunable splittings as large as tens of THz, as well as sensitive all-optical diagnostics of topological bands. PMID:27071090

  2. Objects of Maximum Electromagnetic Chirality

    NASA Astrophysics Data System (ADS)

    Fernandez-Corbaton, Ivan; Fruhnert, Martin; Rockstuhl, Carsten

    2016-07-01

    We introduce a definition of the electromagnetic chirality of an object and show that it has an upper bound. Reciprocal objects attain the upper bound if and only if they are transparent for all the fields of one polarization handedness (helicity). Additionally, electromagnetic duality symmetry, i.e., helicity preservation upon interaction, turns out to be a necessary condition for reciprocal objects to attain the upper bound. We use these results to provide requirements for the design of such extremal objects. The requirements can be formulated as constraints on the polarizability tensors for dipolar objects or on the material constitutive relations for continuous media. We also outline two applications for objects of maximum electromagnetic chirality: a twofold resonantly enhanced and background-free circular dichroism measurement setup, and angle-independent helicity filtering glasses. Finally, we use the theoretically obtained requirements to guide the design of a specific structure, which we then analyze numerically and discuss its performance with respect to maximal electromagnetic chirality.

  3. Chiral plasmons without magnetic field.

    PubMed

    Song, Justin C W; Rudner, Mark S

    2016-04-26

    Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons-chiral Berry plasmons (CBPs)-for a wide range of 2D metallic systems including gapped Dirac materials. As we show, in these materials the interplay between Berry curvature and electron-electron interactions yields chiral plasmonic modes at zero magnetic field. The CBP modes are confined to system boundaries, even in the absence of topological edge states, with chirality manifested in split energy dispersions for oppositely directed plasmon waves. We unveil a rich CBP phenomenology and propose setups for realizing them, including in anomalous Hall metals and optically pumped 2D Dirac materials. Realization of CBPs will offer a powerful paradigm for magnetic field-free, subwavelength optical nonreciprocity, in the mid-IR to terahertz range, with tunable splittings as large as tens of THz, as well as sensitive all-optical diagnostics of topological bands. PMID:27071090

  4. Chiral methyl-branched pheromones.

    PubMed

    Ando, Tetsu; Yamakawa, Rei

    2015-07-01

    Insect pheromones are some of the most interesting natural products because they are utilized for interspecific communication between various insects, such as beetles, moths, ants, and cockroaches. A large number of compounds of many kinds have been identified as pheromone components, reflecting the diversity of insect species. While this review deals only with chiral methyl-branched pheromones, the chemical structures of more than one hundred non-terpene compounds have been determined by applying excellent analytical techniques. Furthermore, their stereoselective syntheses have been achieved by employing trustworthy chiral sources and ingenious enantioselective reactions. The information has been reviewed here not only to make them available for new research but also to understand the characteristic chemical structures of the chiral pheromones. Since biosynthetic studies are still limited, it might be meaningful to examine whether the structures, particularly the positions and configurations of the branched methyl groups, are correlated with the taxonomy of the pheromone producers and also with the function of the pheromones in communication systems. PMID:25849023

  5. 21 CFR 864.8950 - Russell viper venom reagent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Russell viper venom reagent. 864.8950 Section 864.8950 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8950 Russell viper...

  6. 21 CFR 864.8950 - Russell viper venom reagent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Russell viper venom reagent. 864.8950 Section 864.8950 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8950 Russell viper...

  7. 21 CFR 864.8950 - Russell viper venom reagent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Russell viper venom reagent. 864.8950 Section 864.8950 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8950 Russell viper...

  8. 21 CFR 864.8950 - Russell viper venom reagent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Russell viper venom reagent. 864.8950 Section 864.8950 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8950 Russell viper...

  9. 21 CFR 864.8950 - Russell viper venom reagent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Russell viper venom reagent. 864.8950 Section 864.8950 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Reagents § 864.8950 Russell viper...

  10. IN-PLACE REGENERATION OF GAC USING FENTON'S REAGENTS

    EPA Science Inventory

    This paper evaluates the feasibility of using Fenton’s reagents for in-place recovery of spent granular activated carbon (GAC). Fenton’s reagents are cycled through spent GAC to degrade sorbed chlorinated hydrocarbons with little loss of carbon capacity. Seven chlorinated compou...

  11. 21 CFR 866.3630 - Serratia spp. serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Serratia spp. serological reagents. 866.3630 Section 866.3630 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3630 Serratia...

  12. 21 CFR 866.3660 - Shigella spp. serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Shigella spp. serological reagents. 866.3660 Section 866.3660 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3660 Shigella...

  13. 21 CFR 866.3660 - Shigella spp. serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Shigella spp. serological reagents. 866.3660 Section 866.3660 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3660 Shigella...

  14. 21 CFR 866.3680 - Sporothrix schenckii serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Sporothrix schenckii serological reagents. 866.3680 Section 866.3680 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents §...

  15. 21 CFR 866.3850 - Trichinella spiralis serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Trichinella spiralis serological reagents. 866.3850 Section 866.3850 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents §...

  16. 21 CFR 866.3680 - Sporothrix schenckii serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Sporothrix schenckii serological reagents. 866.3680 Section 866.3680 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents §...

  17. 21 CFR 866.3630 - Serratia spp. serological reagents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Serratia spp. serological reagents. 866.3630 Section 866.3630 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3630 Serratia...

  18. 21 CFR 866.3850 - Trichinella spiralis serological reagents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Trichinella spiralis serological reagents. 866.3850 Section 866.3850 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents §...

  19. 21 CFR 866.3630 - Serratia spp. serological reagents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Serratia spp. serological reagents. 866.3630 Section 866.3630 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents § 866.3630 Serratia...

  20. 21 CFR 866.3520 - Rubeola (measles) virus serological reagents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Rubeola (measles) virus serological reagents. 866.3520 Section 866.3520 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Serological Reagents §...