P-aminophenylacetic Acid Research Articles

Mucin 4 detection with a label-free electrochemical immunosensor

Mucin 4 (MUC4) is a useful biomarker for endometriosis and cancers of the pancreas, esophagus and breast. The very first electrochemical immunosensor for the detection of MUC4 is reported, using carbon-based screen-printed electrodes modified by reaction with the diazonium salt of p-aminophenylacetic acid. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize and optimize the electrografting process. The in situ surface modification through diazotation with phenylacetic groups enables the chemical binding of the specific antibody, followed by its affinity reaction with MUC4. The immunosensor was optimized with respect to several parameters and is very promising for clinical applications, having a limit of detection of 0.33μgmL−1 and a linear domain between 1 and 15μgmL−1 obtained by electrochemical impedance spectroscopy measurements.

Mucin 4 Immunosensor Based on p-aminophenylacetic Acid Grafting on Carbon Electrodes as Immobilization Platform

A simple impedimetric label-free immunosensor was developed for the specific and sensitive detection of mucin 4 (MUC 4) protein by using graphite based screen printed electrodes modified with an aryl diazonium salt or compound (p- aminophenylacetic acid) for the immobilization of antibody anti-MUC4 via amidic bond. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used in order to characterize and optimize the electrografting process. The parameters involved in each step of the immunosensor design were optimized. The performance of the immunoassay in terms of sensitivity, reproducibility and selectivity was studied.

Influence of Dicyclopentadiene Co-Polymers on the Hardening Processes and Properties of Portland Cement Composites

Dicyclopentadine (DCPD) polymers can be used for the manufacture of self healing materials due to their ability to form in the presence of a catalyst a highly cross-linked polycyclopendiene. The DCPD polymers selected for this work contain also another constituent sequence (maleic anhydride), therefore in this paper we assess also the possibility to use it for a potential self healing process. In this paper is presented the influence of two types of (DCPD) co-polymers based on maleic anhydride copolymers on the hardening processes and main properties of portland cement pastes and mortars, as a first step in the development of a self-healing cementitious composite. The properties (mechanical strengths and volume variations) of the cementitious composites with DCPD co-polymers are influenced by the chemical structure of the obtained compounds and curing medium (dry or humid air). The mortars with AM (maleic anhydride/dicyclopentadiene co-polymer) did not develop any mechanical strength due to an important swelling phenomenon determined by the hydrolysis of anhydride groups and sterical modifications in chain structures. The presence of APA (AM copolymer modified with p-amino phenyl acetic acid) decreases the compressive strengths but has a less important effect on the flexural strength. The APA polymer-cement interaction consists in a chelatization process involving the nitrogen atoms and hydrogen bonding of carboxyl groups providing, in this case, a good cohesion of the composite material. For both polymers a delay in cement hydration was noticed at early ages as well as the formation of organo-mineral phases.

Modeling the Solubility of Pharmaceuticals in Pure Solvents and Solvent Mixtures for Drug Process Design

The knowledge of the solubility of pharmaceuticals in pure solvents and solvent mixtures is crucial for designing the crystallization process of drug substances. The first step in finding optimal crystallization conditions is usually a solvent screening. Since experiments are very time consuming, a model which allows for solubility predictions in pure solvents and solvent mixtures based only on a small amount of experimental data is required. In this work, we investigated the applicability of the thermodynamic model perturbed-chain statistical associating fluid theory (PC-SAFT) to correlate and to predict the solubility of exemplary five typical drug substances and intermediates (paracetamol, ibuprofen, sulfadiazine, p-hydroxyphenylacetic acid, and p-aminophenylacetic acid) in pure solvents and solvent mixtures. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4205–4215, 2009

P-Aminophenylacetic acid-mediated synthesis of monodispersed titanium oxide hybrid microspheres in ethanol solution

Monodispersed TiO 2 hybrid microspheres were prepared via the hydrolysis of titanium isopropoxide (TTIP) in ethanol solution containing p-aminophenylacetic acid (APA). The effects of the APA:TTIP molar ratio, water content, reaction time and reaction temperature on the morphology of the resultant spheres were investigated. The products were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. It was demonstrated that the diameters of the resultant TiO 2 spheres could be tuned in the range of 380–800 nm by changing the APA:TTIP molar ratio (1:3 to 3:1) and water content (1–3 v/v%) in the reaction medium, and that increasing the APA:TTIP molar ratio led to larger TiO 2 hybrid spheres while increasing the water content decreased their size. The loading content of APA in the hybrid spheres could reach 20 wt.% as they were prepared with the APA:TTIP ratio of 3:1. The possible formation mechanism of the hybrid spheres was also investigated. It was found that APA slowed down the hydrolysis rate of the titanium precursor so that resulted in the formation of the TiO 2 spheres. In addition, the APA present in TiO 2 spheres acted as a reducing agent to in situ convert HAuCl 4 into metallic Au on the surface of the TiO 2 spheres. The catalytic activity of the resultant Au/APA–TiO 2 composite was examined using transfer hydrogenation of phenylacetone with 2-propanol, and it was indicated that the catalyst displayed high efficiency for this reaction.

New polymeric structures designed for the removal of Cu(II) ions from aqueous solutions

New polymeric structures obtained by chemical transformations of maleic anhydride/dicyclopentadiene copolymer with triethylenetetraamine, p-aminobenzoic acid, and p-aminophenylacetic acid were used for the removal Cu(II) ions from aqueous solutions. The experimental values prove the importance of the chelator nature and of the macromolecular chain geometry for the retention efficiency. The retention efficiency (ηr), the retention capacity (Qe), and the distribution coefficient of the metal ion into the polymer matrix (Kd) are realized by evaluation of residual Cu(II) ions in the effluent waters, by atomic adsorption. Also are discussed the influence of pH, the thermal stability of the polymer, and their polymer–metal complex, as well as the particular aspects regarding the contact procedure and the batch time. Based on the polymers and polymer–metal complexes characterization a potential retention mechanism is proposed. All polymer supports as well theirs metal–complexes are characterized by ATD and FTIR measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1397–1405, 2007

4-Aminophenylacetic acid

This thesis deals with the controlled crystallization of small organic molecules and is focused on solubility and polymorphism. The solubility was determined for phenylacetic acid, p-hydroxyphenylacetic acid, p-aminophenylacetic acid, p-hydroxybenzoic acid and ibuprofen in both water and in a range of organic solvents. Data is discussed from the standpoint of molecular aspects of solute – solvent interactions and by estimated solid phase activity. It was shown that better understanding could be acquired by making a qualitative analysis of the molecular interactions in the solution and the crystal structure of the compounds in question. Solubility predictions that are carried out by the UNIFAC method are not sufficiently accurate to serve as a basis for a reliable design of a crystallization process or selection of a suitable solvent since they deviate more than 15% from experimental values. The reason for the discrepancies are related to uncertainties in the prediction of activity coefficients by UNIFAC, as well as, difficulties in the estimation of the activity of the solid state. p-Aminobenzoic acid (PABA) has been crystallized from thirteen different solvents either by slow cooling, after which the product is allowed to mature in suspension, or by rapid cooling followed by immediate isolation. Two different polymorphs have been crystallized. The system is found to be enantiotropic with the transition temperature of 25 °C, below which the β-form is the stable polymorph. The α-form was obtained from all solvents by both methods. The β-form is obtained only in carefully controlled conditions from water and ethyl acetate, well below the transition temperature. Often the α-form appears concomitantly. It is shown in this work that sonication significantly reduces the induction time for nucleation. The β-form crystallizes more reproducibly and at higher cooling rates when controlled sonication is used. In addition sonication is found to selectively favor the appearance of one of the polymorphs. Producing the pure β-form was possible even above the transition temperature where other crystallization techniques were only capable of producing the stable α-form. The α-form structure is based on centro symmetric dimers formed by association of carboxylic acid groups. It is suggested that the preference for nucleation of the α-polymorph is related to the formation of dimers in the supersaturated solution. Only at the condition where the formation of dimers is reduced sufficiently, (i.e. in the polar solvents or when sonication is applied) the nucleation of the β-form is favored.

Solubility of Phenylacetic Acid, p-Hydroxyphenylacetic Acid, p-Aminophenylacetic Acid, p-Hydroxybenzoic Acid, and Ibuprofen in Pure Solvents

The solubility of phenyl acetic acid, p-hydroxyphenylacetic acid, p-aminophenylacetic acid, p-hydroxybenzoic acid, and ibuprofen in water and in a range of organic solvents of relevance to industrial processing is reported. The solvents used are water, methanol, ethanol, 2-propanol, acetone, 4-methyl-2-pentanone, ethyl acetate, chloroform, and toluene. Solubility data are discussed from the standpoint of molecular aspects of solute−solvent interactions and by estimated solid-phase activity.

Synthesis and biological activity of N(alpha)-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinyl)methyl]-N-propargylamino]phenylacetyl]-L-glutamic acid.

2-Deamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) is a potent inhibitor of thymidylate synthase. Its analogue, N(alpha)-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinyl)methyl]-N-propargylamino]phenylacetyl]-L-glutamic acid, containing p-aminophenylacetic acid residue substituting p-aminobenzoic acid residue, was synthesized. The new analogue exhibited a moderately potent thymidylate synthase inhibition, of linear mixed type vs. the cofactor, N(5,10)-methylenetetrahydrofolate. The Ki value of 0.34 microM, determined with a purified recombinant rat hepatoma enzyme, was about 30-fold higher than that reported for inhibition of thymidylate synthase from mouse leukemia L1210 cells by ICI 198583 (Hughes et al., 1990, J. Med. Chem. 33, 3060). Growth of mouse leukemia L5178Y cells was inhibited by the analogue (IC50 = 1.26 mM) 180-fold weaker than by ICI 198583 (IC50 = 6.9 microM).

Polymyxin permeabilization as a tool to investigate cytotoxicity of therapeutic aromatic alkylators in DNA repair-deficient Escherichia coli strains

Chlorambucil (CLB; N, N-bis(2-chloroethyl)- p-aminophenylbutyric acid) and its biologically active β-oxidation product phenylacetic acid mustard (PAM; N, N-bis(2-chloroethyl)- p-aminophenylacetic acid) are bifunctional aromatic alkylators. CLB is in wide clinical use as an anticancer drug and also as an immunosuppressant. The chemical structures indicate that CLB and PAM are mutagenic, teratogenic and carcinogenic, but the mode of action has remained obscure. We have investigated the biological effects of CLB and PAM with DNA repair-deficient Escherichia coli strains. In contrast to MNNG ( N-methyl- N′-nitro- N-nitrosoguanine), CLB and PAM were not toxic to E. coli, but permeabilization of the outer membrane of the cells through use of polymyxin B nonapeptide (PMBN) rendered them susceptible to these compounds. The importance of DNA repair, shown by reversal of damage and attenuation of the toxicity of CLB and PAM, was indicated by the susceptibility of cells lacking O 6-methylguanine–DNA methyltransferase I and II ( ada ogt). Similarly, the protective role of base excision repair (BER) was substantiated by demonstration of an even more increased susceptibility to CLB and PAM of cells lacking 3-methyladenine–DNA glycosylase I and II ( alkA1 tag-1). Cells deficient in mismatch repair ( mutS) appeared to be slightly more sensitive than normal cells to CLB and PAM, although no such sensitivity to MNNG was observed. This implicates the role of mismatches in CLB- and PAM-related cytotoxicity. It is generally believed that bifunctional alkylating agents, like CLB and PAM, exert their cytotoxic action via DNA cross-linking. Our results with O 6-methyltransferase– and 3-methyladenine–DNA glycosylase-deficient cells indicate that removal of the adducts prior to the formation of cross-links is an important mechanism maintaining cell viability. We conclude that PMBN permeabilization provides a valuable tool to investigate genetically engineered E. coli cells, whose outer membrane is not naturally permeable to mutagens or other interesting compounds.

Anaerobic degradation and transformation of p-toluidine by the sulfate-reducing bacterium Desulfobacula toluolica.

The ability of the strictly anaerobic sulfate-reducing bacterium Desulfobacula toluolica (strain Tol2) to cometabolically degrade p-toluidine (p-methylaniline) while using toluene as the primary source of carbon and energy has been studied. This organism has been shown to modify and degrade toluidine in dense cell suspensions when no other source of carbon and energy is added. The metabolism led to the formation of a variety of metabolites. From these metabolites a biphenyl-like compound as well as phenylacetic acid have been identified by means of HPLC/MS techniques. The probable conversion of p-toluidine to p-aminophenylacetic acid and phenylacetic acid as dead end products suggested that this organism initiates p-toluidine degradation by the carboxylation of the methyl group. If this could be validated in further experiments, it would be the first time that a toluidine was carboxylated at the methyl moiety by an anaerobic, sulfate-reducing bacterium.

Synthesis and properties of nylon 6 modified with various aromatic polyamides

In this study, flexible nylon 6 was reinforced by the following rigid-chain aromatic polyamides: poly (m-phenylene isophthalamide) (PmIA), poly(4,4′-diphenylsulfone terephthalamide) (PSA), poly( p-diphenyloxide terephthalamide) (POA), and poly(p-diphenylmethane terephthalamide) (PMA). Various high-molecular-weight block copolyamides were synthesized by solution polymerization using p-aminophenylacetic acid (p-APA) as a coupling agent. Their thermal properties have shown that the block copolyamides exhibit higher Tg and Tm and better thermal stability than those of nylon 6, especially PmIA-modified nylon 6. The order of their thermal properties of aromatic modified nylon 6 copolyamides is PmIA > PMA > POA > PSA. Besides, the Tg and Tm of multiblock copolyamides are higher than those of triblock copolyamides. From the wide-angle X-ray diffraction pattern, it is found that the triblock copolyamides have two diffraction peaks (i.e., 2θ = 20.5 and 24°). However, the multiblock has only one at 2θ = 20°, indicating a different crystal structure for multiblock copolyamides. This can be further confirmed from scanning electron microscopy. It shows that the triblock copolyamides are a dispersed phase structure, although the multiblock copolyamides exhibit a homogeneous texture rather than an aggregated one. For the mechanical properties, it is found that the multiblock copolyamides have a more significant reinforcing effect than the triblock copolyamides. Also, the order of their physical properties of aromatic modified nylon 6 copolyamides, such as tensile strength, is PmIA > PMA > POA > PSA; but for the elongation, the order is PSA > POA > PMA > PmIA. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1031–1043, 1998

Modification of nylon-6 with semi-or wholly-aromatic polyamides

In this study, flexible Nylon-6 was reinforced by semi-or wholly-aromatic polyamides; poly(m-phenylene isophthalamide) (PmIA), poly(4,4′-diphenylmethane terephthalamide) (PMA), and poly(4,4′-diphenylsulfone terephthalamide) (PSA). Various high molecular weight block copolyamides were synthesized by solution polymerization using p-aminophenylacetic acid (p-APA) as a coupling agent. Their thermal properties have shown that the block copolyamides exhibit higher Tg and Tm, and better thermal stability than those of Nylon-6, especially PmIA modified Nylon-6. The order of their thermal properties of aromatic modified Nylon-6 copolyamides is PmIA > PMA > PSA. Moreover, the Tg and Tm of multiblock copolyamides are higher than those of triblock copolyamides. From the wide-angle X-ray diffraction pattern, it is found that the triblock copolyamides have two diffraction peaks, i.e., 2θ = 20.5° and 24°. However, the multiblock has only one peak at 2θ = 20°, indicating a different crystal structure for multiblock copolyamides. For the mechanical properties, it is found that the multiblock copolyamides have a more significant reinforcing effect than the triblock copolyamides. Also, the order of the physical properties of aromatic modified Nylon-6 copolyamides, such as tensile strength, is PmIA > PMA > PSA, but for the elongation PSA > PMA > PmIA.

Pyrroles, Imidazoles and Poly(vinamidines) from Bis(vinamidinium salts)

The reaction of bis(vinamidinium salts) (5a, 6) and amidinium-vinamidinium salts (7, 21) with primary amines was studied. Whereas the condensation of 6 and 7a with p-phenylenediamine and 4,4′ diaminostilbene gave rise to polymeric vinamidines (12, 18), 5a and 7b reacted with aromatic amines and diamines to give pyrrole and imidazole derivatives. The reaction of p-aminophenylacetic acid with DMF-POCl3 produced a new amidinium–vinamidinium salt (21) which could be converted into a donor-acceptor substituted diazaterphenyl derivative (22) displaying a strong solvatochromism. – The crystal structure analysis of the 2,2′-bis(vinamidinium salt) 5b revealed a 73° twist angle between the planes of the vinamidinium moieties.

Affinity purification and properties of polyphenoloxidase from Solanum tuberosum

Polyphenoloxidase from potato tuber was purified to homogeneity in a single step by affinity chromatography using p-aminophenyl acetic acid as a ligand coupled to Sepharose 4B by the divinylsulphone activation method. The purified enzyme was homogeneous on native and SDS-PAGE, indicating the absence of multiple forms of the enzyme. Spectroscopic studies of the purified enzyme indicated a peak at 275 nm and a broad shoulder in the region between 320 and 340 nm, which is a characteristic of a purified preparation. The M r was 60 × 10 s. The kinetics of the purified enzyme were studied.

The block copolymer of nylon-6 with semi-rigid poly(p-diphenylmethyl terephthalamide)

In this study, the flexible nylon-6 was reinforced by the semi-rigid aromatic polyamide poly(p-diphenylmethyl terephthalamide) through chemical copolymerization using p-aminophenylacetic acid as a coupling agent. From differential scanning calorimetry it was discovered that theTg andTm of multiblock copolyamides were higher than those of triblock copolyamides. From observation by scanning electron microscopy the multiblock copolyamides exhibited a homogeneous texture rather than an aggregated one. We found that in wide-angle X-ray diffraction patterns the triblock copolyamides had two diffraction peaks, i.e. 2θ=20 and 24‡. However, the multiblock had only one peak at 2θ=20‡ which evidently indicates that a new crystal structure of multiblock copolyamides was formed. As for the mechanical properties, the multiblock copolyamides were found to have more significant reinforcing effects than those of triblock copolyamides.

Modification of nylon‐6 with semirigid poly(p‐diphenylmethyl terephthalamide)

AbstractIn this research, flexible nylon‐6 was reinforced by semirigid aromatic polyamide poly(p‐diphenylmethyl terephthalamide) (PMA) through physical polyblending and chemical copolymerization using p‐aminophenylacetic acid (P‐APA) as a coupling agent. From the DSC measurement, it was shown that the Tg of the polyblends was increased with the increase of PMA content. It was discovered that the Tg and Tm of multiblock copolyamides would be higher than those of polyblends and triblock copolyamides. The multiblock copolyamides exhibited a homogeneous texture rather than an aggregated one. Scanning electron microscopy revealed that the polyblends were a dispersed‐phase structure. We found that from the wide‐angle X‐ray diffraction pattern the triblock copolyamides and polyblends had two diffraction peaks, i.e., 2θ = 20° and 24°. However, the multiblock had only one at 2θ = 20°, which evidently indicates that a new crystal structure of multiblock copolyamides was formed. As for the mechanical properties, the multiblock copolyamides were found to have more significant reinforcing effects than those of polyblends and triblock copolyamides. © 1993 John Wiley & Sons, Inc.

Modification of nylon‐6 with wholly rigid poly(m‐phenylene isophthalamide)

AbstractIn this study, the flexible nylon‐6 was reinforced by the wholly rigid aromatic polyamide poly(m‐phenylene isophthalamide) (PmIA) (Nomex) by physical polyblending and chemical copolymerization using p‐aminophenylacetic acid (P‐APA) as a coupling agent. From DSC measurements, it was shown that Tg of the polyblends increased with the increase of Nomex content. The Tg and Tm of multiblock copolyamides were found to be higher than those of polyblends and triblock copolyamides. Scanning electron microscopy revealed that the polyblends were a dispersed phase structure, although the multiblock copolyamides exhibited a homogeneous texture rather than an aggregated one. From the wide‐angle X‐ray diffraction pattern, it was found that the triblock copolyamides and polyblends had two diffraction peaks, i.e., 2 θ = 20.5 and 24°. However, the multiblock had only one at 2 θ = 20°, indicating a different crystal structure for multiblock copolyamides. For the mechanical properties, it was found that the multiblock copolyamides had a more significant reinforcing effect than those of polyblends and triblock copolyamides.

The biosynthesis of the pseudomonas antibiotic obafluorin from p-aminophenylalanine and glycine (glyoxylate)

DL-[2,3- 2H 3]- p-Aminophenylalanine is incorporated into obafluorin (1) with retention of C-3 deuterium and loss of deuterium from C-2. Labelled samples of p-nitrophenylacetic acid, p-aminophenylacetic acid and the N-acetylcysteamine thioester of the latter are not incorporated into obafluorin. Results of experiments with [2- 13C]-, [1- 13C]-, and [2- 2H 2]-glycine show that glyoxylic acid is specifically the source of C-1 and C-2 of the antibiotic. A mechanism is proposed for the biosynthesis of the unit (2) in obafluorin (1).

13C nuclear magnetic resonance study of acid–base tautomeric equilibria

Acid–base tautomerisation equilibria are reported for o-, m-, and p-aminobenzoic acids, p-aminophenylacetic acid, pyridine-3-carboxylic (nicotinic) acid, and pyridine-4-carboxylic (isonicotinic) acid. These equilibria are determined by modelling the displacements of 13C n.m.r. chemical shifts of each carbon due to protonation of basic sites. The models are based on the corresponding displacement due to protonation of as many as twelve related compounds. Each such model compound yields several independent estimates of the tautomeric partitioning ratio corresponding to the several carbon resonances. It is observed that the mean tautomeric partitioning ratio and its estimated uncertainty are independent of the nature or the location of ring substituents and are unaffected by heteroatom substitution in the aromatic ring. This observation has led to the development of generic models for 13C n.m.r. chemical shift protonation displacements based on collections of similar model compounds. The use of generic models summarises and simplifies the determination of tautomeric equilibria.