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Characterization of labelling and de-labelling reagents for detection and recovery of tyrosine residue in peptide.

This paper characterized the labelling and de-labelling reagents for reversible labelling of tyrosine (Tyr)-containing peptide, which involves detection and recovery. The phenolic hydroxyl group (-OH) in Tyr structure reacted with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F), and 1-fluoro-2,4-dinitrobenzene (DNFB) under mild conditions at room temperature at pH 9.3. The labels in the resulting derivatives were removed with the treatment of nucleophiles, such as thiols (cysteine, N-acetyl-L-cysteine and dithiothreitol) and amines (dimethylamine, methylamine, diethylamine, ethylamine and pyrrolidine). The de-labelling reactions of NBD-labelled N-acetyl-L-tyrosine (N-AcTyr) with the nucleophiles produced N-AcTyr, accompanied by NBD-nucleophile. Although DBD-F and DNFB also successfully labeled the -OH group in N-AcTyr, the efficiency of Cbond;O bond cleavage and recovery of N-AcTyr by the nucleophiles was relatively low compared with NBD-label. Among the de-labelling reagents, N-acetyl-L-cysteine and dimethylamine were recommended for the elimination of NBD moiety, with respect to the reaction rate, the side reaction, and the yield of recovery. The proposed procedure, which includes the labelling with NBD-F and the removal of NBD moiety by the nucleophiles, was successfully applied to the reversible labelling of N-terminal amine-blocked peptides, i.e. N-AcTyr-Val-Gly, Z-Glu-Tyr, Z-Phe-Tyr, N-Formyl-Met-Leu-Tyr, and N-AcArg-Pro-Pro-Gly-Phe-Ser-Pro-Tyr-Arg.

Chromatography, High Pressure Liquid↗
PubMed1983

Significance of yeast peroxisomes in the metabolism of choline and ethanolamine.

The yeasts Candida utilis and Hansenula polymorpha were able to grow in media containing choline or ethanolamine as the sole nitrogen source. During growth in the presence of these substrates, large peroxisomes developed in the cells, and extracts of choline-grown C. utilis cells contained increased levels of amine oxidase and catalase. Incubation of whole cells with choline in the presence of the amine oxidase inhibitor aminoacetonitrile led to excretion of dimethylamine and methylamine. Cytochemical experiments in which spheroplasts prepared from choline-grown cells were incubated with CeCl3 and choline, trimethylamine, dimethylamine or methylamine revealed positively stained peroxisomes, whereas in the presence of 1 mM aminoacetonitrile staining was not observed. This indicated that choline was degraded via methylated amines and that peroxisomes played a role in its metabolism. A similar involvement of peroxisomes in choline degradation was observed in H. polymorpha. Cell-free extracts of ethanolamine-grown C. utilis and H. polymorpha also contained increased levels of amine oxidase and catalase. Ethanolamine was oxidized by cell-free extracts of both organisms after growth in the presence of ethanolamine or choline. Incubation of spheroplasts of ethanolamine- or choline-grown C. utilis with CeCl3 and ethanolamine resulted in positively stained peroxisomes. In this organism peroxisomes were therefore also involved in ethanolamine degradation.

Ascomycota↗
PubMed1985

Suicide inhibition as a likely cause of variable specific activity in trimethylamine dehydrogenase from bacterium W3A1.

Trimethylamine hydrogenase isolated from bacterium W3A1 grown on dimethylamine was of variable, but low specific activity and had modified spectral properties. Chemical analyses for Fe, S and P indicated that the [4Fe-4S] clusters of the modified enzyme are intact and that the covalently bound flavin is probably present, but in modified form. A peptide with absorbance maximum at 358 nm and fluorescence excitation and emission maxima in dimethylformamide at 358 nm and 495 nm, respectively, was isolated by gel chromatography and HPLC of tryptic peptides of acetamidylated, modified trimethylamine dehydrogenase. These spectral properties are similar to those of 4a- or 5a-substituted flavins and suggest that the enzyme had been modified by in vivo reaction with a suicide inhibitor. This inhibitor, or a compound giving rise to it, seems to be present in a commercial source of dimethylamine.

Bacteria↗
PubMed1989

In vitro metabolism of azasqualene derivatives and their effects on aminopyrine N-demethylase activity in rat liver microsomes.

The metabolism of squalene dimethylamine (I), a potent inhibitor of 2,3-oxidosqualene (SO) cyclase, and of sixteen other squalene derivatives was investigated in rat liver microsomes. N-oxidation was the only metabolic pathway observed, squalene dimethylamine N-oxide being the only metabolite isolated from incubation of I. The azasqualane and quaternary ammonium derivatives did not form N-oxides during their metabolism. The inhibition of aminopyrine N-demethylase activity was also studied and the IC50, for compound I, which shows weak competitive inhibition, was determined. At 1 mM concentration the other squalene derivatives showed a range of inhibition activity possibly due to their different lipophilicity.

Aminopyrine N-Demethylase↗
PubMed1982

Mutagenicity of pyrolysates from guanidine, ureide, secondary amines and polyamines found by the Salmonella/mammalian-microsome test.

Nitrogenous compounds such as guanidine, ureide, secondary amines and polyamines were pyrolysed at 300, 400, 500 and 600 degrees C for 3 min, and the mutagenic activities of the pyrolysates were assayed on Salmonella typhimurium TA98 and TA100 with or without metabolic activation by S9 mix. Among 21 pyrolysates tested, 14, from methylguanidine, agmatine, dihydrouracil, dimethylamine, diethylamine, trimethylamine, triethylamine, pyrrolidine, morpholine, sarcosine, piperazine, piperidine, spermine and spermidine, showed mutagenic activity. In the presence of S9 mix, the mutagenic activity began to appear from the pyrolysate at 400 degrees C, and the pyrolysate at 600 degrees C showed the highest mutagenic activity except that from methylguanidine. The mutagenic activity formed by pyrolysis was more active on TA98 than TA100. In the absence of S9 mix, only 3 pyrolysates - from dimethylamine, diethylamine and pyrrolidine - showed slight mutagenic activity toward TA100. The highest mutagenic activity was observed with the pyrolysate from spermine, followed by those from piperidine, spermidine, piperazine and triethylamine. Some nitrogenous compounds showed slight mutagenic activity after pyrolysis at 300 degrees C for 20 min, although none of the compounds tested showed any mutagenic activity after pyrolysis at 300 degrees C for 3 min.

Amines↗
PubMed1988

Formation of a mutagenic diazoquinone by interaction of phenol with nitrite.

Reaction of phenol with nitrite under mildly acidic conditions produced p-nitrosophenol, p-diazoquinone and o-diazoquinone. p-Diazoquinone showed mutagenicity in Salmonella typhimurium strains TA98 and TA100 without metabolic activation; the number of his+ revertant colonies in strain TA98 was 85 with a dose of 20 nmol (after deduction of the background (control) number of about 20). Higher doses of the compound were bactericidal. While the reaction of phenol with an equivalent amount of nitrite at pH 3 produced p-nitrosophenol in high yield, reaction with excess nitrite produced a high yield of p-diazoquinone. p-Nitrosophenol was converted to p-diazoquinone by reaction with nitrite. Formation of o-diazoquinone also increased with increasing amounts of nitrite. The formation of these compounds was not greatly affected by the presence of dimethylamine. Nitrosation of dimethylamine with nitrite was stimulated by phenol because of the formation of p-nitrosophenol and its stimulatory effect. Thus, the reaction of phenol with nitrite can produce mutagenic p-diazoquinone, and can also stimulate nitrosation of secondary amines by production of p-nitrosophenol.

Chromatography↗
PubMed2004

Neutrophil-mediated formation of carcinogenic N-nitroso compounds in an in vitro model for intestinal inflammation.

In order to study neutrophil-mediated formation of carcinogenic N-nitroso compounds as a mechanism of inflammation-related colon carcinogenesis, we designed an in vitro model for intestinal inflammation, consisting of a coincubation system with human colon cells (Caco-2 cells) and activated human neutrophils (PMN), as important immunoreactive cells. We investigated whether nitrosamines and nitrosamides could be formed upon addition of dimethylamine, morpholine and methylurea to the coincubations as nitrosatable precursors, which are known to produce carcinogenic N-nitroso compounds. Incubations of pure nitric oxide with dimethylamine and morpholine showed that NO-mediated formation of nitrosodimethylamine and nitrosomorpholine is possible under the incubation conditions. During the coincubations of activated PMN and Caco-2 cells, 0.34 nmol nitrite/10(6) PMN was produced. Dose-dependent formation of NMOR was observed in this PMN/Caco-2 system; addition of 5mM morpholine resulted in a significantly increased NMOR formation of 4.2 nM. However, no detectable NDMA and methylnitrosourea were formed in this coincubation system. These results suggest that activated human neutrophils are able to synthesize carcinogenic N-nitrosamines, e.g. NMOR, which implies a risk of colon carcinogenesis during chronic inflammation. However, the observed relatively low level of nitrosation suggests that also other risk factors are contributing to the association between chronic inflammation and colon cancer risk.

Caco-2 Cells↗
PubMed2002

Comparison of the separation of large DNA fragments in the presence and absence of electroosmotic flow at high pH.

This paper describes the analysis of large DNA fragments at pH > 10.0 by capillary electrophoresis (CE) in the presence of electroosmotic flow (EOF) using hydroxyethylcellulose (HEC) solution. HEC solution in the anodic reservoir enters the capillaries filled with high-pH buffer by EOF after sample injection. With respect to resolution, sensitivity, and speed, separation conducted under discontinuous conditions (different pH values of HEC solutions and buffer filling the capillary) is appropriate. Using HEC solution at concentrations higher than its entanglement threshold ensures a good separation of large DNA fragments in the presence of EOF at high pH. In addition to pH and HEC, the electrolyte species, dimethylamine, methylamine, and piperidine, play different roles in determining the resolution. The separation of DNA fragments ranging in size from 5 to 40 kilo base pairs was completed in 6 min using 1.5% HEC prepared in 20 mM methylamine-borate, pH 12.0, and the capillary filled with 40 mM dimethylamine-borate, pH 10.0. In comparison, this method allows faster separations of large DNA fragments compared with that conducted in the absence of EOF using dilute HEC solutions.

Cellulose↗
PubMed2001

Polar nitrogen compounds and their behaviour in the drinking water treatment process.

Aliphatic and alicyclic amines as well as ethanolamines are extremely polar compounds, frequently found in the environment, and some of them have high toxicity. To address the contamination of selected German surface waters examined and the importance of bank filtration in Eastern Germany, investigations on the behaviour of polar organic nitrogen compounds during water treatment were carried out. Test conditions were designed appropriately for drinking water treatment conditions, and the tests were carried out using model water as well as bank filtrate. Test filter studies of microbial degradation of selected compounds demonstrated the following order of biodegradability: ethanolamine > dimethylamine > pyrrolidine > ethylenediamine. piperidine > diethylamine > morpholine > piperazine > cyclohexylamine. Flocculation tests using iron salts as well as aluminium salts as coagulants showed very low removal rates for the amines. The best results for the removal of the polar organic nitrogen compounds from the water were obtained using ozonation. Based on the reaction-rate constants, the order of degradation by ozone is: piperazine > morpholine > ethylenediamine > piperidine, cyclohexylamine > dimethylamine > ethanolamine > pyrrolidine > diethylamine. Disinfection by chlorine-containing agents under drinking water treatment conditions did not give effective elimination of the selected polar nitrogen compounds.

Amines↗
PubMed2003

A N-Nitrosodimethylamine (NDMA) precursor analysis for chlorination of water and wastewater.

N-nitrosodimethylamine (NDMA) is a potent carcinogen formed during chloramination of water and wastewater treatment plant effluents. A procedure is described for quantifying the concentration of the organic precursors of NDMA that could be formed during chlorination of wastewaters and natural waters. The method involves applying a high dose of monochloramine to a pH-buffered sample followed by a 10-day contact period, during which the monochloramine decays at a rate unrelated to the composition of the sample. Analyses of samples of municipal wastewater effluents and surface waters indicate that the method provides a robust and reproducible measurement of NDMA precursors over a wide range of conditions. A sensitive GC/CI/MS/MS analytical procedure for dimethylamine also is described and used to demonstrate that NDMA formation during chlorination of wastewater and natural waters cannot be explained by dimethylamine concentrations alone.

Carcinogens↗
PubMed1999

Apoptosis induction and inhibition of H-ras overexpression by novel trans-[PtCl2(isopropylamine)(amine')] complexes.

Hitherto, it has been generally accepted as a paradigm of the biochemical pharmacology of platinum antitumor drugs that a cis configuration of the leaving groups is necessary for antitumor activity of platinum compounds. However, it has been recently observed that certain trans-platinum complexes have both in vitro and in vivo antitumor activity. We previously reported the synthesis, characterization and cytotoxic activity against ras-transformed cells of several trans-[PtCl2LL'] complexes where L and L' are asymmetric aliphatic amines (L = dimethylamine and butylamine, L' = isopropylamine). The results reported in this paper show that the compounds trans-[PtCl2(isopropylamine)(dimethylamine)] and trans-[PtCl2(isopropylamine)(butylamine)] kill Pam 212-ras cisplatin resistant cells through apoptosis induction. Moreover, Western blot data show that both compounds inhibit overexpression of H-ras oncogene in Pam 212-ras cells. Altogether, these data indicate that, in contrast with cis-DDP, the apoptotic activity of these novel trans-Pt(II) compounds in ras-transformed cells is associated with their ability to abolish ras-overexpression.

Animals↗
PubMed2002

Volatile N-nitrosamine inhibition after intake Korean green tea and Maesil (Prunus mume SIEB. et ZACC.) extracts with an amine-rich diet in subjects ingesting nitrate.

The formation of carcinogenic nitrosamines under simulated gastric conditions was studied during the incubation of amine rich food and nitrate, and its possible inhibition by adding kumquat, sweet orange, strawberry, garlic, kale juices, Maesil (Prunus mume) and green tea extracts. The strawberry, kale juices, Maesil and green tea extracts were equally effective in reducing the formation of N-nitrosodimethylamine (NDMA). The fruits of P. mume SIEB. et ZACC. (Korean name, Maesil) have been used as a traditional drug and health food in Korea. During four weeks of test (designated EW1, EW2, EW3 and EW4; experiment week 1, 2, 3 and 4 diets) volunteers consumed a diet of low nitrate and amine (EW1) and consumed a fish meal rich in amines as nitrosatable precursors in combination with intake of nitrate-containing drinking water without (EW2) or with Maesil and green tea extracts (EW3 and EW4, respectively). The intake of nitrate-containing drinking water (340 mg nitrate/100 ml) resulted in a significant rise in mean salivary nitrate and nitrite concentrations and in mean urinary nitrate levels. Mean urinary nitrate was increased to 455.0+/-66.2, 334.6+/-67.8 and 333.4+/-50.7 mg/18 h after the nitrate intake of EW2, EW3 and EW4, respectively. Significant increases in urinary dimethylamine and trimethylamine levels were observed in consumption of diets (EW2, EW3, and EW4) rich in amine and nitrate. Maesil and green tea extract in EW3 and EW4 enhanced the increase of urinary dimethylamine and trimethylamine levels. Urinary excretion of N-nitrosodimethylamine in consumption of diet rich in nitrate and amine (EW2) increased to 6504.4+/-2638.7 ng/18 h from 257.0+/-112.0 ng/18 h of low nitrate and amine diet (EW1). Korean green tea and Maesil extracts in nitrate and amine rich diet reduced the excretion of N-nitrosodimethylamine to 249.7+/-90.6 and 752.7+/-595.3 ng/18 h, respectively, compared with 6504.4+/-2638.7 ng /18 h after ingestion of TD1 diet.

Adult↗
PubMed1980

Site of attachment of 11-cis-retinal in bovine rhodopsin.

A dipeptide containing the binding site for retinal in bovine rhodopsin has been isolated and its sequence determined. Rhodopsin containing [11-3H]retinal was prepared in chromatographically pure form, and the [3H]retinal was reductively linked to its binding site on opsin by using borane--dimethylamine. The [3H]retinylopsin in octyl glucoside was exhaustively digested with Pronase, and its peptides were separated on silica gel in chloroform/methanol/ammonia [Bownds, D. (1967) Nature (London) 216, 1178--1181] followed by silica gel thin-layer chromatography in two solvent systems. The major retinyl peptide was shown to be alanyl-N epsilon-retinyllysine by amino acid composition, 3H content, and amino acid sequence analysis. The retinyl binding site is located in the carboxyl-terminal region of rhodopsin: when rod cell disk membranes containing [3H]retinal rhodopsin were digested with thermolysin and then reacted with sodium borohydride or borane--dimethylamine, [3H]retinal was reduced onto the F2 (Mr congruent to 6000) fragment, which derives from rhodopsin's carboxyl-terminal region.

Animals↗
PubMed2004

Titanium hydrazido and imido complexes: synthesis, structure, reactivity, and relevance to alkyne hydroamination.

Treatment of Ti(NMe(2))(2)(dpma) (1) with aniline results in the protonation of the dimethylamido ligands, which are retained as dimethylamines, and generation of a titanium imido complex Ti(NPh)(NHMe(2))(2)(dpma) (2) in 94% yield. The monomeric imido 2 is converted to the reactive dimeric micro-imido [Ti(NPh)(dpma)](2) (3) on removal of the labile dimethylamine donors. The dimer 3 is converted to monomeric terminal imido complexes in the presence of added donors, e.g., 4,4'-di-tert-butyl-2,2'-bipyridine (Bu(t)-bpy) and DME. Compounds 1-3 exhibit the same rate constant for 1-phenylpropyne hydroamination by aniline and are all kinetically competent to be involved in the catalytic cycle. Attempts to use 1 as a catalyst for hydroaminations involving 1,1-dimethylhydrazine resulted in only a few turnovers under the best conditions. Consequently, the chemistry of 1 with hydrazines to generate hydrazido complexes was scrutinized for comparison with the imido species. Through these studies, titanium hydrazido complexes including Ti(eta(2)-NHNC(5)H(10))(2)(dpma) (5), Ti(eta(2)-NHNMe(2))(2)(dpma) (6), and [Ti(micro:eta(1),eta(2)-NNMe(2))(dpma)](2) (7) were characterized. In addition, a terminal hydrazido(2-) complex was available by addition of Bu(t)-bpy to 1 prior to 1,1-dimethylhydrazine addition, which provided Ti(eta(1)-NNMe(2))(Bu(t)-bpy)(dpma) (8). Compound 8 was structurally characterized and compared to Ti(NPh)(Bu(t)-bpy)(dpma) (4b), an imido derivative with the same ancillary ligand set. Compound 8 has a nucleophilic beta-nitrogen consistent with a hydrazido(2-) formulation, as determined by reaction with MeI to form the ammonium imido complex [Ti(NNMe(3))(Bu(t)-bpy)(dpma)]I (9). Analogous pyridinium imido complexes [Ti(N-1-pyridinium)(Bu(t)-bpy)(dpma)](+) (10) are available by addition of 1-aminopyridinium iodide to 1. From the investigations, some conclusions regarding the activity of titanium pyrrolyl complexes in hydroamination were drawn. The lack of conversion of the bis[micro-hydrazido(2-)] 7 to monomeric species in the presence of donor ligands is put forth as one explanation for the poor hydrazine hydroamination activity of 1. This problem was combated in the synthesis of Ti(NMe(2))(2)(dap)(2), which is an active catalyst for hydrazine hydroamination of alkynes.

Journal Article↗
PubMed2005

Mild oxidative one-carbon homologation of aldehyde to amide.

One-carbon homologation of aldehyde into amide is realized in one-pot by its reaction with potassium alpha-p-methoxyphenyl-alpha-isocyano acetic acid (1c) and hydrochloride salt of dimethylamine (3a) in toluene at room temperature followed by acidic workup. In this multicomponent reaction, 1c served as donor of the CONH2 function to aldehyde, while the dimethylamine acted as a shuttle molecule to initiate/terminate the sequence and to mediate the internal redox process of one of the three-component adducts. Ready accessibility, nominal cost of the reagents, and mild conditions are attractive features of the present method.

Journal Article↗
PubMed1999

Major degradation pathway of thiuram in tap water processed by oxidation with sodium hypochlorite.

Thiuram (3 microM), a fungicide, was incubated in deionized water by adding 0-100 mg/L free chlorine at 30 degrees C for 30 min, and the solution was analyzed by HPLC and IC. The byproducts were identified by LC/MS, EI-MS, infrared, and (13)C NMR spectra and a reduction technique using 2-mercaptoethanol. On the basis of these results, it was found that the oxidation of thiuram with sodium hypochlorite initially produced an intermediate dimethylthiocarbamoyl dimethylcarbamoyl disulfide, which was finally degraded to bis(dimethylcarbamoyl) disulfide, its trisulfide, and dimethylamine. Subsequently, it was suggested that monitoring of bis(dimethylcarbamoyl) disulfide, its trisulfide, and dimethylamine should be included for the management and control of thiuram in tap water processed by oxidation with sodium hypochlorite.

Chromatography, Liquid↗
PubMed2001

O-Phosphonatomethylcholine, its analogues, alkyl esters, and their biological activity.

O-Phosphonatomethylcholine, an isopolar phosphocholine analogue with a phosphonomethyl ether group replacing a phosphomonoester residue, was prepared by reaction of diisopropyl 2-chloroethoxymethylphosphonate with dimethylamine followed by quaternization of the thus-obtained diisopropyl 2-dimethylaminoethoxymethylphosphonate with iodomethane; the ester groups in the quaternary intermediate were cleaved with bromotrimethylsilane. Replacement of dimethylamine in the reaction sequence by morpholine and/or pyrrolidine gave the N-methylmorpholinium or N-methylpyrrolidinium analogues of O-phosphonatomethylcholine. Reaction of O-phosphonomethylcholine monotetrabutylammonium salt with 1-bromoalkanes in acetonitrile afforded a series of the corresponding monoalkyl (C10-C16) esters. None of these compounds except for the hexadecyl ester exhibited any appreciable cytostatic activity against DU-145, H460, HT-29, or MES-SA cell lines in vitro (evaluated by 3H-Thd incorporation assay). The hexadecyl ester exhibited modest in vitro cytotoxic activity comparable to that of the anticancer drug miltefosine (hexadecyl O-phosphocholine). In vivo evaluation of hexadecyl O-phosphonomethylcholine [transplanted SD lymphoma in inbred SD/cub rats, 10 mg kg(-1) day(-1) intratumoral injection for 10 days] resulted in a 40% decrease in lymphoma mass.

Animals↗
PubMed2001

Determination of aliphatic amines in water by liquid chromatography using solid-phase extraction cartridges for preconcentration and derivatization.

Bond Elut C18 solid-phase extraction cartridges were used for preconcentration and pre-column derivatization with 3,5-dinitrobenzoyl chloride (DNB) of aliphatic amines in water. Conditions for analyte preconcentration and derivatization (including the volume of sample, concentration of reagent, time of reaction and pH) were investigated, using ethylamine, isopropylamine and dimethylamine as model compounds. On the basis of these studies, a rapid and sensitive method for the determination of aliphatic amines in water is presented. The analytes are retained and purified on the cartridges and then derivatized and desorbed by drawing in succession the DNB solution and acetonitrile. The collected extracts are subsequently chromatographed in a Hypersil ODS C18 column using acetonitrile-water for elution. The DNB derivatives are monitored at 230 nm. The method provides satisfactory reproducibility and linearity within the 0.050-1.0 mg l(-1) concentration interval, the limits of detection being 2-5 microg l(-1). Analyte recoveries were in the 70-102% range, whereas the conversion yields compared with those observed for the solution derivatization were in the 79-107% range. The total analysis time (sample treatment plus chromatography) was about 15 min. The method was applied to the determination of ethylamine, isopropylamine and dimethylamine in tap and river waters.

Amines↗