Aliphatic Primary Amino Group Research Articles

QSAR and Chemical Read-Across Analysis of 370 Potential MGMT Inactivators to Identify the Structural Features Influencing Inactivation Potency.

O6-methylguanine-DNA methyltransferase (MGMT) constitutes an important cellular mechanism for repairing potentially cytotoxic DNA damage induced by guanine O6-alkylating agents and can render cells highly resistant to certain cancer chemotherapeutic drugs. A wide variety of potential MGMT inactivators have been designed and synthesized for the purpose of overcoming MGMT-mediated tumor resistance. We determined the inactivation potency of these compounds against human recombinant MGMT using [3H]-methylated-DNA-based MGMT inactivation assays and calculated the IC50 values. Using the results of 370 compounds, we performed quantitative structure-activity relationship (QSAR) modeling to identify the correlation between the chemical structure and MGMT-inactivating ability. Modeling was based on subdividing the sorted pIC50 values or on chemical structures or was random. A total of nine molecular descriptors were presented in the model equation, in which the mechanistic interpretation indicated that the status of nitrogen atoms, aliphatic primary amino groups, the presence of O-S at topological distance 3, the presence of Al-O-Ar/Ar-O-Ar/R..O..R/R-O-C=X, the ionization potential and hydrogen bond donors are the main factors responsible for inactivation ability. The final model was of high internal robustness, goodness of fit and prediction ability (R2pr = 0.7474, Q2Fn = 0.7375-0.7437, CCCpr = 0.8530). After the best splitting model was decided, we established the full model based on the entire set of compounds using the same descriptor combination. We also used a similarity-based read-across technique to further improve the external predictive ability of the model (R2pr = 0.7528, Q2Fn = 0.7387-0.7449, CCCpr = 0.8560). The prediction quality of 66 true external compounds was checked using the "Prediction Reliability Indicator" tool. In summary, we defined key structural features associated with MGMT inactivation, thus allowing for the design of MGMT inactivators that might improve clinical outcomes in cancer treatment.

Design and strategy for spectrofluorimetric determination of tranexamic acid in its authentic form and pharmaceutical preparations: application to spiked human plasma.

A creative, very sensitive and noncomplicated spectrofluorimetric technique was established and further validated to determine tranexamic acid in both its authentic form and its pharmaceutical preparation dosage forms. In the introduced technique, a reaction was found between the aliphatic primary amino group of tranexamic acid and ninhydrin/phenylacetaldehyde reagents in the presence of Torell and Steinhagen buffer pH 7.0, which led to the production of a highly fluorescent product; fluorescence intensity was measured at 475 nm after excitation at 391 nm. A calibration curve was drawn with a linear range of 0.3-2 μg/ml. Limit of detection and limit of quantification values were 0.051 and 0.155 μg/ml respectively. The introduced technique was validated based on the International Council for Harmonisation guidelines and agreed for determination of tranexamic acid in its pharmaceutical formulation. Finally, this simple method was also applied for determination of tranexamic acid in spiked human plasma.

Amine-to-Azide Conversion on Native RNA via Metal-Free Diazotransfer Opens New Avenues for RNA Manipulations.

A major challenge in the field of RNA chemistry is the identification of selective and quantitative conversion reactions on RNA that can be used for tagging and any other RNA tool development. Here, we introduce metal-free diazotransfer on native RNA containing an aliphatic primary amino group using the diazotizing reagent fluorosulfuryl azide (FSO2N3). The reaction provides the corresponding azide-modified RNA in nearly quantitatively yields without affecting the nucleobase amino groups. The obtained azido-RNA can then be further processed utilizing well-established bioortho-gonal reactions, such as azide-alkyne cycloadditions (Click) or Staudinger ligations. We exemplify the robustness of this approach for the synthesis of peptidyl-tRNA mimics and for the pull-down of 3-(3-amino-3-carboxypropyl)uridine (acp3U)- and lysidine (k2C)-containing tRNAs of an Escherichia coli tRNA pool isolated from cellular extracts. Our approach therefore adds a new dimension to the targeted chemical manipulation of diverse RNA species.

Amine-to-Azide Conversion on Native RNA via Metal-Free Diazotransfer Opens New Avenues for RNA Manipulations.

A major challenge in the field of RNA chemistry is the identification of selective and quantitative conversion reactions on RNA that can be used for tagging and any other RNA tool development. Here, we introduce metal‐free diazotransfer on native RNA containing an aliphatic primary amino group using the diazotizing reagent fluorosulfuryl azide (FSO2N3). The reaction provides the corresponding azide‐modified RNA in nearly quantitatively yields without affecting the nucleobase amino groups. The obtained azido‐RNA can then be further processed utilizing well‐established bioortho‐gonal reactions, such as azide‐alkyne cycloadditions (Click) or Staudinger ligations. We exemplify the robustness of this approach for the synthesis of peptidyl‐tRNA mimics and for the pull‐down of 3‐(3‐amino‐3‐carboxypropyl)uridine (acp3U)‐ and lysidine (k2C)‐containing tRNAs of an Escherichia coli tRNA pool isolated from cellular extracts. Our approach therefore adds a new dimension to the targeted chemical manipulation of diverse RNA species.

N-Heterocyclic-based adsorbents for antibody purification-effect of ligand structure

A new set of ligands based on substituted pyridine and other N-heterocyclic structures, possessing an aliphatic primary amino group tether and an exocyclic sulphur atom, has been prepared and immobilized onto epoxy-activated matrices such as Sepharose 6 Fast Flow®. The derived adsorbents have been evaluated for their utility to capture and purify humanized monoclonal antibodies. Favourable binding properties were assessed from screening assays to determine optimal conditions for the capture and elution of the monoclonal antibodies. Static and dynamic binding experiments were employed to derive the equilibrium dissociation constants KD 's and binding capacities Qmax 's. Typically, the KD values were in the range of 2-5 μM and the Qmax values between 20 and 75 mg mAb/ml resin, depending on the stereo-electronic properties of the substituent in the N-heterocyclic ring structure. The effect of ligand structure on the selectivity of these adsorbents was also investigated, and criteria for their use in the purification of monoclonal antibodies from cell culture supernatants established.

Introducing NH2 onto polymeric films via photo-induced C—H bond transformation with phenol derivatives as building blocks

A one-step process to introduce both the aromatic and aliphatic primary amino groups with high chemoselectivity was developed. Triplet state acetone abstracts the hydrogen atoms from both the C-H bond of the polymeric film substrate and the O-H bond of phenol which is the building block and the amino group carrier. As a result, two kinds of free radicals, confined carbon-centered chain radicals of the polymer substrate and mobile oxygen-centered phenoxy radicals, were generated. Then the C-O bonds were formed by the coupling reaction between these two kinds of free radicals. p-Tyramine and p-aminophenol were used as amino carriers. The successful introduction of amino groups onto LDPE, BOPP and PET film substrates was demonstrated by measurements of water contract angle (CA), ultraviolet spectra (UV), X-ray photoelectron spectroscopy (XPS) and fluorescent microscopy. The processing factors, such as the UV-light intensity and irradiation time, concentrations of p-tyramine and p-aminophenol, and the ratio of acetone/water were investigated. The optimized process parameters are as follows: UV light intensity 9500 μW/cm2; irradiation time 18 min for BOPP and LDPE, 22 min for PET; the ratio of acetone/water = 1; and concentration of p-tyramine and p-aminophenol 15% for BOPP and LDPE, 1% for PET. Based on the UV absorbance, the amino groups on the polymeric substrates were estimated to be in the range of 6.3 × 10-6–9.5 × 10-6 mmol/mm2.

Immunocytochemistry for Drugs Containing an Aliphatic Primary Amino Group in the Molecule, Anticancer Antibiotic Daunomycin as a Model

An immunocytochemistry (ICC) for the anticancer antibiotic daunomycin (DM) was developed using a combination of anti-DM serum produced against N-(gamma-maleimidobutyryloxy)succinimide (GMBS)-conjugated DM, and DM-uptake human melanoma BD cells. The antiserum was demonstrated to be specific for DM and the structurally related analogs adriamicin and epirubicin by an ICC model system of the enzyme immunoassay (EIA) using glutaraldehyde (GA)-conjugated DM as a solid phase antigen. No cross-reaction occurred with any of the other antibiotics tested such as bleomycin, pepleomycin, and mitomycin C. Successful DM ICC required a series of processes prior to the immunocytochemical reaction: the cells were first fixed with GA, then reduced with NaBH4, treated with hydrochloric acid, and finally digested with protease. The cell specimens were then subjected to immunoreaction with anti-DM serum followed by peroxidase-labeled goat anti-rabbit IgG/Fab', and in both immune reagents the detergent Triton X-100 was contained as well. The present ICC covering all these processes successfully stained for DM in the nucleus and in the perinuclear Golgi region of the cytoplasm of the BD cells, consistent with the results obtained by the DM autofluorescence method. This ICC was found to be three times as sensitive as the cytofluorometric method and applicable to the paraffin sections of the liver of rats 24 hr after an IV injection of DM. The principle used in the present study for developing DM ICC might be applied to other drugs containing the primary amino group(s) in the molecule. Thus, these ICCs for drugs are direct, precise and easy new methods that should have potential for pharmacology and toxicology studies of drugs, revealing the localization of a drug in cells and tissues.

Design of Metalloporphyrin−Carbohydrate Conjugates for a New Superoxide Dismutase Mimic with Cellular Recognition

Metalloporphyrin-carbohydrate conjugates have been synthesized as superoxide dismutase (SOD) mimics with cellular recognition. To synthesize the conjugates, aliphatic primary amino groups for conjugation were introduced, with the cationic pyridyl groups for the SOD activity of porphyrin preserved. The reductive amination between introduced amino groups and the reducing end of lactose was then carried out. The resulting conjugates consisting of manganese (Mn)-porphyrin surrounded by several lactose molecules possessed significant SOD activity and low cytotoxicity. Compared with metalloporphyrins having no lactose molecule, the recognition of the resulting conjugates by human hepatoma HepG2 cells increased. The cellular recognition was inhibited by competitors of beta-galactose. These results suggest that the Mn-porphyrin-lactose conjugates recognized the hepatic lectin on the cell surface.

Design of a poly(L‐histidine)‐carbohydrate conjugate for a new pH‐sensitive drug carrier

AbstractA poly(L‐histidine) (PLH)‐carbohydrate conjugate has been synthesized as a new macromolecule extracting pH‐dependent properties of PLH with imidazole groups. Because of poor water solubility at physiological pH, the application of PLH with a pKa around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the PLH modified with aliphatic primary amino groups suddenly precipitated out of the aqueous medium above pH 6.0 as a result of the deprotonation of the imidazole groups, the water solubility of PLH was improved at physiological pH by the conjugation of the aminated PLH with hydrophilic maltopentaose. The resulting PLH‐maltopentaose conjugates and metalloporphyrins formed the complexes which varied their assembling structure below pH 6.0. The PLH‐maltopentaose would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal pH. Copyright © 2004 John Wiley & Sons, Ltd.

Facile Chemical Modification of the Poly(l-histidine) for a New pH-Sensitive Polypeptide

Abstract We have synthesized the poly(l-histidine) (PLH) with aliphatic primary amino groups for conjugation as a new pH-sensitive polypeptide. The resulting aminated PLH suddenly precipitated out of the aqueous medium above pH 6.0 owing to the deprotonation of imidazole groups. The aminated PLH was successfully conjugated with maltopentaose by reductive amination. The resulting PLH-maltopentaose conjugate improved its water solubility at physiological pH.

ChemInform Abstract: A Novel Method for the Introduction of an Aliphatic Primary Amino Group at the 5′ Terminus of Synthetic Oligonucleotides.

AbstractThe phosphoramidite (III) is obtained from the compounds (I) and (II).

Inhibition of microbial growth by interference with siderophore biosynthesis. Oxidation of primary amino groups in aerobactin synthesis byEscherichia coli

The first step of aerobactin biosynthesis, oxidation of an aliphatic primary amino group to an N-hydroxy-amino compound seems to be involved in the biosynthesis of most of the hydroxamatetype siderophores which are widely distributed among bacteria and fungi. Therefore, the first step of aerobactin biosynthesis, oxidation of lysine to N6-hydroxylysine was studied as a model reaction using a strain of Escherichia coli that contains the first gene aerA of aerobactin synthesis on a multi-copy plasmid and which is lacking the gene for the subsequent step in the pathway. In addition, culture conditions are described which lead to the secretion of N6-hydroxylysine into the medium in amounts that can easily be quantitatively determined by a simple, reliable chemical assay. This assay can be used for screening inhibitors of the oxidation of α-amino groups, which should interfere with the biosynthesis of siderophore hydroxamates and thus should create bacteriostatic conditions.

Inhibition of microbial growth by interference with siderophore biosynthesis. Oxidation of primary amino groups in aerobactin synthesis by Escherichia coli

The first step of aerobactin biosynthesis, oxidation of an aliphatic primary amino group to an N-hydroxy-amino compound seems to be involved in the biosynthesis of most of the hydroxamatetype siderophores which are widely distributed among bacteria and fungi. Therefore, the first step of aerobactin biosynthesis, oxidation of lysine to N6-hydroxylysine was studied as a model reaction using a strain of Escherichia coli that contains the first gene aerA of aerobactin synthesis on a multi-copy plasmid and which is lacking the gene for the subsequent step in the pathway. In addition, culture conditions are described which lead to the secretion of N6-hydroxylysine into the medium in amounts that can easily be quantitatively determined by a simple, reliable chemical assay. This assay can be used for screening inhibitors of the oxidation of α-amino groups, which should interfere with the biosynthesis of siderophore hydroxamates and thus should create bacteriostatic conditions.

A novel method for the introduction of an aliphatic primary amino group at the 5′ terminus of synthetic oligonucleotides

Reaction of the 5′ hydroxyl group of a support bound synthetic oligonucleotide with the new reagent N-trifluoroacetyl-2-aminoethyl-(2-cyanoethyl)-N,N-diisopropylaminophosphor-amidite yields, upon deprotection, an oligonucleotide having a 5′ primary amino terminus. The amino derivatized oligomer can then be specifically reacted with the N-hydroxysuccinimide ester of d -biotin to give a stable oligonucleotide-biotin adduct.

Purification of γ-aminobutyric acid (GABA) receptor from rat brain by affinity column chromatography using a new benzodiazepine, 1012-S, as an immobilized ligand

The purification of γ-aminobutyric acid (GABA) and benzodiazepine receptors from the rat brain was employed by the affinity column using a new benzodiazepine, 1012-S, as immobilized ligand. The 1012-S has a aliphatic primary amino group and exhibited an extremely high potency for displacing [ 3H]flunitrazepam binding to solubilized benzodiazepine receptor preparation (IC 50 = 6.0 × 10 −11M). This benzodiazepine affinity gel retained almost all of the solubilized GABA receptors from synaptic membranes applied to the column, and 25.6% of the receptor was eluted bio-specifically following the application of 1 mM 1012-S. The highest purification fold thus obtained was 4576 (specific activity: 0.99 nmol/mg protein). Furthermore, the successive application of 1–2 M NaSCN also resulted the elution of a highly enriched GABA receptor (specific activity: 0.41 nmol/mg protein; purification fold: 1889). SDS-polyacrylamide gel electrophoretic profiles of the bio-specifically eluted fraction with 1012-S showed the existence of two major bands having the molecular weights of approximately 48,500 and 54,500 in which the former band was selectively photoaffinity-labelled with [ 3H]flunitrazepam. On the other hand, it was found that the non-specifically eluted fraction with NaSCN contained 4 additional minor bands having molecular weights of 41,000 to 51,000. These results indicate that GABA receptor of the rat brain is coupled, at least in part, with benzodiazepine receptor and is readily purified by the use of highly specific benzodiazepine affinity gel, 1012-S-acetamide adipic hydrazide Sepharose 4B. The present results also suggest that the purified GABA/benzodiazepine receptor complex may contain two different kinds of subunits having the molecular weights of 48,000 and 54,500, in which the former subunit may possess benzodiazepine binding sites.

ChemInform Abstract: PHYSICAL AND CHEMICAL PROPERTIES OF AMINO ACIDS

Publisher Summary This chapter discusses physical and chemical properties of amino acids. Amino acids constitute a group of neutral products clearly distinguished from other natural compounds chemically, mainly because of their ampholytic properties, and biochemically, mainly because of their role as protein constituents. An amino acid is a carboxylic acid containing an aliphatic primary amino group in the α position to the carboxyl group and with a characteristic stereochemistry, for example, L-alanine. Proteins are biosynthesized from 20 amino acids in a system involving strict genetic control. Additional amino acids have been isolated from proteins after hydrolysis; however, these amino acids are produced in the proteins by transformations of the primary amino acids. A number of amino acids act as intermediates in the biosynthesis of various protein amino acids and are thus present in plants, although often in low concentrations. These include homoserine, homocysteine, cystathionine, ornithine, and citrulline. The properties of these amino acids are similar to those of the protein amino acids. The amino acids are ampholytes having both acid and basic properties.

Synthesis and structure of vinyl polymer-poly(α-amino acid) graft copolymers

N-(2-Carbobenzyloxyaminoethyl)acrylamide (CAEA) which is a vinyl compound carrying a protected aliphatic primary amino group in the side chain has been synthesized and its homopolymerization and copolymerization induced by radical initiators have been investigated. CAEA was found to possess good copolymerizability with vinyl monomers having large Q values such as styrene, 2-vinyl pyridine, acrylonitrile and methyl methacrylate. Vinyl polymers containing a small amount of aliphatic primary amino group in the side chain were produced by the treatment of vinyl polymers containing a small amount of CAEA unit with HBr/AcOH or H 2 Pd . Using the former polymers as initiators for the polymerization of N-carboxyanhydrides of ( RS)-Phe and ( S)-Glu(OBz), vinly polymer (trunk)-poly-(α-amino acid) (branch) graft copolymers were synthesized. These copolymers were investigated by transmission electron microscopy, and the development of domain structure due to microphase separation was observed.

Fluorescence labeling method for estimation of soluble polymers in the living material

The highly fluorescent derivatives of fluorescein, bearing the aliphatic primary amino groups, N-(2-aminoethylcarbonyl)-5(6)-aminofluorescein and 5-[ N′-(2-aminoethyl)thioureido]fluorescein, were prepared for labeling of soluble polymers. The absorption and emission properties of these labels and polymers labeled with them were compared with properties of fluorescein and fluorescein isothiocyanate (FITC)-bovine serum albumin conjugate. Effects of the chemical structure of the polymer on the relative fluorescence quantum yield of a covalently attached label were evaluated using ionogenic, olefinic, or phenolic groups in side chains. The fluorescence of labeled polymers was adequate for their tracing in all the cases studied. The most pronounced quenching of fluorescence in the presence of phenolic groups is comparable with the quenching of fluorescence of FITC observed in FITC-protein conjugates. The long-term stability of the polymer-fluorochrome bond was checked in solutions of pH 2.10, 7.46, and 11.84; a higher stability of simple amide over amide plus the thiourea bond was found. The quantitative method of measurement of the concentration of labeled polymers in the biological material in a range of about 10 ng was developed; factors affecting the reproducibility are discussed.

Spectrofluorometric determination of pharmaceuticals containing aromatic or aliphatic primary amino groups as their fluorescamine (Fluram) derivatives

Spectrofluorometric determination of pharmaceuticals containing aromatic or aliphatic primary amino groups as their fluorescamine (Fluram) derivatives

Sur un principe de colorimetrie en milieu non aqueux. Son application a l'analyse organique fonctionnelle

In non-aqueous medium it is possible to characterise the hydroxyl, the carbonyl and the aliphatic primary amino groups, by formation of a derivative (an ester, hydrazone or arylamine) containing nitro groups. Without either extraction or elimination of the excess of reagent, a characteristic coloration is developed in dimethylformamide by using an organic base. Determinations are possible on the hundredths of a milligram scale.