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1.
The oxidation of N-substituted aromatic amines by horseradish peroxidase   总被引:1,自引:0,他引:1  
The mechanism of N-dealkylation by peroxidases of the Ca2+ indicator quin2 and analogs was investigated and compared with the mechanism of N-dealkylation of some N-methyl-substituted aromatic amines. Nitrogen-centered cation radicals were detected by ESR spectroscopy for all the compounds studied. Further oxidation of the nitrogen-centered cation radicals, however, was dependent upon the structure of the radical formed. In the case of quin2 and analogs, a carbon-centered radical could be detected using the spin trap 5,5-dimethyl-1-pyrroline N-oxide. By using the spin trap 2-methyl-2-nitrosopropane (tert-nitrosobutane), it was determined that the carbon-centered radical was formed due to loss of a carboxylic acid group. This indicated that bond breakage most likely occurred through a rearrangement reaction. Furthermore, extensive oxygen consumption was detected, which was in agreement with the formation of carbon-centered radicals, as they avidly react with molecular oxygen. Thus, reaction of the carbon-centered radical with oxygen most likely led to the formation of a peroxyl radical. The peroxyl radical decomposed into superoxide that was spin trapped by 5,5-dimethyl-1-pyrroline N-oxide and an unstable iminium cation. The iminium cation would subsequently hydrolyze to the monomethyl amine and formaldehyde. In the case of N-methyl-substituted aromatic amines, carbon-centered radicals were not detected during the peroxidase-catalyzed oxidation of these compounds. Thus, rearrangement of the nitrogen-centered radical did not occur. Furthermore, little or no oxygen consumption was detected, whereas formaldehyde was formed in all cases. These results indicated that the N-methyl-substituted amines were oxidized by a mechanism different from the mechanism found for quin2 and analogs.  相似文献   

2.
The synthesis of several (3-noradamantyl)amines, [(3-noradamantyl)methyl]amines, (3,7-dimethyl-1-bisnoradamantyl)amines, and [(3,7-dimethyl-1-bisnoradamantyl)methyl]amines is reported. They were evaluated against a wide range of viruses and one of them inhibited the cytopathicity of influenza A virus at a concentration similar to that of amantadine. Several of the new polycyclic amines show an interesting activity as NMDA receptor antagonists. A rimantadine analogue displayed significant trypanocidal activity. Moreover, to further characterize the pharmacology of these compounds, their effects on dopamine uptake were also assessed.  相似文献   

3.
Biogenic amines, with a primary amino group, were reacted with glutaraldehyde to form insoluble precipitates. These precipitates had distinctive ultrastructural features upon further reaction with osmic acid. When tested in vitro, they had biological activity and showed evidence that part of this biological activity was due to the large polymer of glutaraldehyde and amine. Experiments with isotope-labelled amines in the production of these precipitates showed that the precipitated polymers were not completely stable and that free amine was liberated from them. Since they were not stable, , they could not be used for the morphological localization of the amines as had been intended, but they may have some use as depot drugs or in the immunization of animals against these amines.  相似文献   

4.
Reactions of alpha(2)-macroglobulin (alpha(2)M) with primary amines (ammonium chloride, methylammonium chloride and ethylammonium chloride) or proteolytic enzymes (trypsin, chymotrypsin and thrombin) resulted in changes of the absorption, fluorescence and circular-dichroism spectra and of the sedimentation coefficient of the inhibitor. All physico-chemical changes caused by the inactivation of alpha(2)M by the amines were identical with, or highly similar to, those induced by the formation of the enzyme-inhibitor complexes. This suggests that similar conformational changes of the inhibitor occur in the two types of reactions. The frictional ratio, calculated from the increase in sedimentation coefficient, decreased from 1.67 for untreated alpha(2)M to 1.57 for the amine- or proteinase-treated inhibitor. This change is due to a decrease in either asymmetry or hydration of the protein, resulting in a slightly smaller hydrodynamic volume. The circular-dichroism analyses indicated that the reaction of alpha(2)M with either amines or proteinases is accompanied by a loss of the small amount (about 5%) of alpha-helix of the untreated protein. The changes of u.v. absorption and fluorescence suggested that about one out of the eight to ten tryptophan residues of each alpha(2)M subunit is buried as a result of the conformational change. All spectroscopic and hydrodynamic changes that were observed are compatible with a spatial rearrangement of the subunits of alpha(2)M, as implicated by the ;trap' hypothesis for the mechanism of inhibition of proteinases. However, a conformational change involving a decrease in the hydrodynamic volume of each subunit cannot be excluded.  相似文献   

5.
6.
A library of 132 racemic chiral amines (α-substituted methylbenzylamines, benzhydrylamines, 1,2,3,4-tetrahydronaphthylamines (THNs), indanylamines, allylic and homoallylic amines, propargyl amines) was screened against the most versatile monoamine oxidase (MAO-N) variants D5, D9 and D11. MAO-N D9 exhibited the highest activity for most substrates and was applied to the deracemisation of a comprehensive set of selected primary amines. In all cases, excellent enantioselectivity was achieved (e.e. >99%) with moderate to good yields (55–80%). Conditions for the deracemisation of primary amines using a MAO-N/borane system were further optimised using THN as a template addressing substrate load, nature of the enzyme preparation, buffer systems, borane sources, and organic co-solvents.  相似文献   

7.
Preparation and characterisation of chitosans with oligosaccharide branches   总被引:3,自引:0,他引:3  
The trimer 2-acetamido-2-deoxy-D-glucopyranosyl-beta-(1-->4)-2-acetamido-2-deoxy-D-glucopyranosyl-beta-(1-->4)-2,5-anhydro-D-mannofuranose (A-A-M) was reductively N-alkylated onto a fully de-N-acetylated chitosan (F(A)<0.001, DP(n)=25) to obtain branched chitosans with degree of substitution (DS) of 0.070, 0.23 and 0.40, as determined by 1H NMR spectroscopy. The apparent pK(a) values of the primary and secondary amines of the chitosans substituted with the trimer A-A-M were determined by monitoring the chemical shift of the H-2 of GlcN, and were determined as 6.5-6.9 for the primary (unsubstituted) amines and as 5.0-5.2 for the secondary (substituted) amines. The intrinsic pK(a) values (pK(int)) were found to be 7.3-7.4 for the substituted and 8.7 for the unsubstituted amines. The chitosan branched with A-A-M (DS 0.40) was found to be soluble in aqueous solution over the entire pH range. SEC-MALLS (size-exclusion chromatography with a multi-angle laser light scattering detector) further showed that addition of branches did not affect the molar hydrodynamic volume of the chitosan.  相似文献   

8.
Fluorescamine is a useful reagent for the fluorometric assay of primary amines. The extent of the reaction between fluorescamine and primary amines, as well as the fluorescence intensities of the resulting fluorophors depend on pH, solvent composition and reagent concentration. Optimum values for these variables further depend on the amine under study. The influence of these parameters on the fluorogenic reaction of representative amines, and on their fluorophoric derivatives has been investigated, and the results are reported here.  相似文献   

9.
Transglutaminase enzyme activity was demonstrated in murine splenic B lymphocytes. Preincubation of cell cultures with primary amines that are known substrates for transglutaminase inhibited the triggering of murine B lymphocytes to form clones of antibody-producing plasma cells. B cells could be rescued from this inhibition by incubating cultures with anti-immunoglobulin or multivalent antigens under nonstimulatory conditions. Rescue of B cells exhibited the same requirements as stimulation, which suggests that rescue is a dynamic process and not simply a receptor-ligand binding event. Primary amines appeared to inhibit an early, T cell-independent event in the B cell activation pathway, which was not sufficient to trigger B cells to form antibody-producing clones. Subsequent receptor-mediated events, required to further trigger B cells, were not inhibited by the presence of primary amines.  相似文献   

10.
13α-18-nor-16-Carboxamido steroids were synthesized via a palladium-catalyzed aminocarbonylation reaction of the corresponding iodoalkenes. The starting material was an unnatural 13α-16-keto steroid, obtained by a Wagner–Meerwein rearrangement of a 16α,17α-epoxide in the presence of [BMIM][BF4]. The 13α-16-keto steroid was converted to a mixture of 16-iodo-16-ene and 16-iodo-15-ene derivatives in two steps by Barton’s methodology. Aminocarbonylation of the steroidal alkenyl iodides was carried out using different primary and secondary amines as nucleophiles. The products, 16-carboxamido-16-ene and 16-carboxamido-15-ene derivatives, were obtained in good yields and were characterized by 1H and 13C NMR, IR and MS.The reduction of the above two unsaturated carboxamides resulted in the same product, 17α-methyl-16α-carboxamido-androstane.  相似文献   

11.
12.
A receptor assembly composed of iron(II) triflate and pyridine‐2,6‐dicarbaldehyde was used to determine the enantiomeric excess (ee) of alpha‐chiral primary amines using circular dichroism spectroscopy. The alpha chiral amines condense with the dialdehyde to form a diimine, which forms a 2:1 octahedral complex with iron(II). The ee values of unknown concentrations of alpha‐chiral amines were determined by constructing calibration curves for each amine and then measuring the ellipticity at 600 nm. This improves our previously reported assay for ee determination of chiral primary amines by further increasing the wavelength at which CD is measured and reducing the absolute error of the assay. Chirality 27:294–298, 2015. 2015 Wiley Periodicals, Inc.  相似文献   

13.
A cyclohexylamine oxidase (CHAO) of bacterial origin was previously shown to be a potentially useful catalyst in the deracemization of racemic primary amines. To further explore the properties and application of this enzyme, five single-amino acid substitution mutants (L199A, M226A, Y321A, Y321F, and L353M) were created based on superimposition of the tertiary structure of CHAO and the monoamine oxidase (MAO) B homolog. The substrate specificity of the purified wild-type and five mutant enzymes were examined towards 38 structurally diverse amines. All the enzymes exhibited better activity for primary amines than secondary and tertiary amines and in general exhibited high stereoselectivity. Among the mutant enzymes, M226A displayed an enhanced activity (5–400 %) towards most substrates, and L353M showed 7–445 % higher activity towards primary aliphatic amines with cycloalkane or aromatic moieties. Kinetic parameters revealed that both Y321 mutants showed higher catalytic efficiency towards cyclooctanamine, whereas the wild-type CHAO (wt CHAO) was most efficient towards cyclohexylamine. The wt CHAO or variant L353M in combination with a borane–ammonia complex as reducing agent was applied to the deracemization of 1-aminotetraline to give the (R)-enantiomer, a precursor of an antidepressant drug Norsertraline, in good yield (73–76 %), demonstrating their application potential in chiral amine synthesis.  相似文献   

14.
A new fixation method has been developed for localizing biogenic amines in nervous tissue. The method is a modification of the chromaffin reaction in which all fixation steps are buffered with mixtures of sodium chromate and potassium dichromate. In this way the fixation and cytochemical reaction are carried out almost simultaneously. Using the rat vas deferens as a model tissue, it was found that the preservation of electron dense (chromaffin) cores in the vesicles of adrenergic nerve terminals depended on several factors: a short primary fixation using low concentrations of aldehydes, the presence of the chromate/dichromate buffer during all fixation steps and, finally, a long incubation period in a slightly acidic (pH 6.0) solution of this buffer before postfixation in osmium tetroxide. Using this method it was possible to identify not only small and large dense-cored vesicles as storage sites for amines but also a tubular reticulum (neuronal endoplasmic reticulum), the latter especially in nerve terminals of mesenteric arteries and iris. Biogenic amines were also visualized in sympathetic ganglion cells and in the central nervous system e.g., supraependymal nerve terminals, tissues that up to now proved the most difficult in terms of amine localization. In all the tissues examined the cytochemical reaction was highly selective and present in well preserved tissue, which is a significant advance over previously available techniques. It therefore offers new opportunities for further studies on the role of biogenic amines as neurotransmitters.  相似文献   

15.
A series of N,N-bis(glycityl)amines with promising anti-cancer activity were prepared via the reductive amination of pentoses and hexoses, and subsequently screened for their ability to selectively inhibit the growth of cancerous versus non-cancerous cells. For the first time, we show that this class of compounds possesses anti-proliferative activity, and, while the selective killing of brain cancer (LN18) cells versus matched (SVG-P12) cells was modest, several of the amines, including d-arabinitylamine 1a and d-fucitylamine 1g, exhibited low micromolar IC50 values for HL60 cells. Moreover, these two amines showed good selectivity towards HL60 cells when compared to non-cancerous HEK-293 cells. The compounds also showed low micromolar inhibition of the leukaemic cell line, THP-1. The modes of action of amines 1a and 1g were then determined using yeast chemical genetics, whereby it was established that both compounds affect similar but distinct sets of biochemical pathways. Notably purine nucleoside monophosphate biosynthesis was identified as an enriched mechanism. The rapid synthesis of the amines and their unique mode of action thus make them attractive targets for further development as anti-cancer drugs.  相似文献   

16.
A capillary electrophoresis (CE) and a high-performance liquid chromatography (HPLC) method to analyze biogenic amines in food were compared. An automated precolumn derivatization with o-phthaldialdehyde (OPA) allows for the determination of aliphatic amines and amino acids by HPLC. In contrast, for the measurement of histamine and tyramine by CE, no laborious sample pretreatment was necessary. The biogenic amines were separated by CE or HPLC in less than 9 or 20 min, respectively. The calibration curves were linear to at least 100 mg/kg (r=0.999) and 1,000 mg/kg for HPLC and CE, respectively, with detection limits for histamine of 0.5 mg/kg (fluorescence detector) or 1 mg/kg (diode array detector) with HPLC and 2 mg/kg with CE. The detection limits for tyramine were 1.5 mg/kg with HPLC and 6 mg/kg with CE and for further amines (e.g., putrescine, spermidine, cadaverine, agmatine) ranging from 1.0 to 8.5 mg/kg with HPLC. There was a good correlation between CE and HPLC (correlation coefficient for histamine: 0.994).  相似文献   

17.
Nonenzymatic protein glycation is caused by a Schiff's base reaction between the aldehyde groups of reducing sugars and the primary amines of proteins. These structures may undergo further Amadori rearrangement and free radical‐mediated oxidation to finally generate irreversible advanced glycation end products (AGEs). One of the factors known to modulate the glycation of proteins is glutathione, the most abundant nonprotein thiol tripeptide with the γ‐linkage, H‐Glu(Cys‐Gly‐OH)‐OH (GSH). Screening for products formed by GSH with D ‐glucose is an essential step in understanding the participation of GSH in glycation (the Maillard) reaction. Under the conditions used in these studies we observed N‐(1‐deoxy‐D ‐fructos‐1‐yl)‐pyroglutamic acid as the major glycation product formed in the mixtures of GSH and glucose in vitro. A RP HPLC/MS and tandem MS analyses of the GSH/glucose mixtures revealed that cleavage of the N‐terminal glutamic acid and the formation of pyroglutamic acid‐related Amadori product were accompanied by generation of Cys‐Gly‐derived Amadori and thiazolidine compounds. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.  相似文献   

18.
Activated eosinophils, and hypobromous acid (HOBr) generated by these cells, have been implicated in the tissue injury in asthma, allergic reactions, and some infections. Proteins are major targets for this oxidant, but limited information is available on the mechanisms of damage and intermediates formed. Reaction of HOBr with proteins is shown to result in the formation of bromamines and bromamides, from side-chain and backbone amines and amides, and 3-bromo- and 3,5-dibromo-Tyr, from Tyr residues; these materials account for ca. 70% of the oxidant consumed. Protein carbonyls, dityrosine, and 3,4-dihydroxyphenylalanine are also formed, though these are minor products (<5% of HOBr added). With BSA, extensive (selective and nonspecific) protein fragmentation and limited aggregation are also observed. The bromamines/bromamides are unstable and induce further oxidation and free radical formation as detected by EPR spin trapping. Evidence was obtained for the generation of nitrogen-centered radicals on side-chain and backbone amide groups of amino acids, peptides, and proteins. These radicals readily undergo rearrangement reactions to give carbon-centered radicals. With proteins, alpha-carbon (backbone) radicals are detected, which may play a role in protein fragmentation. A novel damage transfer pathway from Gln side-chain amide groups to backbone sites was also observed.  相似文献   

19.
The ability of Dictyostelium discoideum amoebae to synthesize and secrete cAMP in response to exogenous cAMP is called cAMP signaling. Concanavalin A is a potent, rapid, noncompetitive inhibitor of this response, with the rate of inhibition consistent with its rate of binding. The concanavalin A does not deplete cellular ATP, alter cAMP binding to its surface receptors, or affect basal adenylate cyclase activity, but blocks the cAMP-stimulated activation of adenylate cyclase. Therefore, concanavalin A appears to inhibit a step between the receptor and the adenylate cyclase which is necessary for the transduction of the cAMP signal. Wheat germ agglutinin, a polyclonal antibody against an 80-kDa glycoprotein, four monoclonal antibodies against the amoebal surface, and a chemical cross-linking agent which reacts with cell surface primary amines also inhibit signaling. To determine the importance of cross-linking in the inhibition, succinylated concanavalin A and the unlinked, reactive portion of the chemical cross-linker were tested and found to be relatively ineffective inhibitors. Thus it appears that ligands capable of cross-linking molecules on the external surface of D. discoideum amoebae inhibit cAMP signaling. It is proposed that these cross-linking agents prevent membrane or cytoskeletal rearrangement and that this rearrangement must occur before the adenylate cyclase is activated.  相似文献   

20.
S E Bodrug  J J Holden  P N Ray    R G Worton 《The EMBO journal》1991,10(12):3931-3939
To further an understanding of the mechanism of constitutional chromosomal rearrangement, the translocation breakpoints of two X-autosome translocations carried by females with Duchenne or Becker muscular dystrophy have been mapped, cloned and sequenced. Breakpoints were mapped to specific introns within the dystrophin gene and intron sequences spanning the two breakpoints were cloned and used as probes to identify DNA fragments containing the translocation junctions. The junction-containing fragments were cloned after amplification by inverse PCR or single-specific-primer PCR. Sequence through the junctions and the autosomal regions spanning the breakpoints identified the mechanism of rearrangement as non-homologous exchange with minor additions or deletions (0-8 nucleotides) at the breakpoints. Paternal origin of these X-autosome translocations, coupled with evidence for non-transmission of X-autosome translocations through male meiosis suggested that the translocations were the result of a post-meiotic rearrangement in spermiogenesis.  相似文献   

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