P-nitrophenyl Ester Group Research Articles

Enzymatic photochemical sensing using luciferase-immobilized polymer nanoparticles covered with artificial cell membrane

We prepared phospholipid polymer nanoparticles immobilized with luciferase, and the nanoparticles were applied as photochemical sensing nanoparticles. An amphiphilic water-soluble polymer having a phosphorylcholine group was used as an emulsifier and a surface modifier to prepare the nanoparticles. The polymer was composed of three kinds of monomer units, that is, 2-methacryloyloxyethyl phosphorylcholine (MPC) as a hydrophilic and bioinert unit, n-butyl methacrylate as a hydrophobic unit and p-nitrophenyl ester having methacrylate as an enzyme-immobilizing unit. The p-nitrophenyl ester groups to immobilize the proteins were located on the surface of the nanoparticles. Luciferase was immobilized by the reaction between the p-nitrophenyl ester groups and the amino group. The enzymatic reaction on the nanoparticles was followed using a microdialysis system with an optical fiber having a 800 μm diameter in the probe. The nanoparticles conjugated with luciferase reacted with ATP, luciferin and oxygen. It is concluded that the nanoparticles are a promising tool for a photochemical sensing microdiagnostic system.

Water-soluble HPMA copolymer—prostaglandin E1 conjugates containing a cathepsin K sensitive spacer

A novel bone targeting, N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer based, prostaglandin E1 (PGE1) delivery system was designed, synthesized and characterized. PGE1 was bound to the polymer backbone via a spacer, composed of a cathepsin K sensitive tetrapeptide (Gly-Gly-Pro-Nle) and a self-eliminating 4-aminobenzyl alcohol structure. The HPMA copolymer conjugates were prepared by photo–initiated free radical copolymerization of HPMA, PGE1-containing macromonomer, and optionally a comonomer containing a reactive p-nitrophenyl ester group. The latter group was used as attachment points for the d-aspartic acid octapeptide targeting moieties. Incubation of the PGE1-containing macromonomer and HPMA copolymer-PGE1 conjugates with cathepsin K resulted in release of unmodified PGE1. The rate of release depended on the composition of the conjugate. The higher the PGE1 content in the conjugate, the slower the PGE1 release. This appeared to be the result of association of hydrophobic side-chains in aqueous media, which rendered the formation of the enzyme substrate complex more difficult. The data seems to indicate that HPMA copolymer-PGE1 conjugates have a potential in the treatment of osteoporosis and other bone diseases.

Conjugation of enzymes on polymer nanoparticles covered with phosphorylcholine groups.

We investigated the bioconjugation of enzymes on polymer nanoparticles covered with bioinert phosphorylcholine groups. A water-soluble amphiphilic phospholipid polymer (PMBN) was specially designed for preparation of nanoparticles and conjugation with enzymes on them. The PMBN was prepared by random copolymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC), n-butyl methacrylate, and p-nitrophenylester bearing methacrylate. The PMBN was used as an emulsifier and a surface modifier to prepare the poly(l-lactic acid) nanoparticles by a solvent evaporation technique in aqueous medium. The nanoparticles covered with phosphorylcholine groups were stably dispersed in an aqueous solution and a phosphate buffered saline. The diameter and surface zeta-potential of the nanoparticles were ca. 200 nm and -6 mV, respectively. The p-nitrophenyl ester groups, which are active ester units for the amino groups of the protein, were located at the surface of the nanoparticles. Both acetylcholine esterase and choline oxidase were co-immobilized (dual-mode conjugation) by the reaction between the p-nitrophenyl ester group and the amino group of these enzymes. The enzymatic reactions on the nanoparticles were followed using a microdialysis biosensor system with a microtype hydrogen peroxide electrode in the probe. The nanoparticles conjugated with these enzymes could detect the acetylcholine chloride as hydrogen peroxide, which is a product of the enzymatic reactions on the surface of the nanoparticles in the probe. Namely, continuous enzyme reactions could be occurring on the surface of the nanoparticles. It is concluded that the nanoparticles are a promising tool for a highly sensitive and microdiagnostic system.

Reactivity in Self-Assembled Monolayers: Effect of the Distance from the Reaction Center to the Monolayer−Solution Interface

Monolayers containing a reactive p-nitrophenyl ester group at different levels with respect to the monolayer interface have been self-assembled on a gold surface. Analysis of grazing angle IR spectra, surface plasmon resonance (SPR), and wettability measurements suggests disordered organization of the alkane chains in the monolayers. Kinetics of monolayer reactions with external reagents (alkylamines) have been studied and compared with those of the same process in bulk medium. Burying of a reaction center under the surface and other structural changes of monolayers were shown to have only a minor effect on the rates of reaction, implying that these monolayers could be easily penetrated by guest molecules. The higher reaction rates with monolayers than in bulk solution are possibly due to a weak binding of the external reagent to the monolayer prior to reaction.

Reactivity in Monolayers versus Bulk Media: Intra- and Intermolecular Aminolysis of Esters

Monolayers possessing reactive amino and p-nitrophenyl ester functional groups at the same or different levels with respect to the monolayer interface have been self-assembled on a gold surface. Intramolecular reactions in these monolayers are at least 1000 times slower than the same processes in the bulk medium. Control experiments with external reagents showed that the monolayer p-nitrophenyl ester group reacts readily with amines from solution, whereas nucleophilicity of the monolayer amino functionality is significantly suppressed. This unusually low reactivity of the amino group was tentatively assigned to its interaction with the gold surface.

Synthesis and Photoproperties of a Substituted Zinc(II) Phthalocyanine-N-(2-hydroxypropyl)methacrylamide Copolymer Conjugate

In cancer photodynamic therapy (PDT), improved efficiency of photosensitizer delivery to tumors may be obtained by binding them to targetable water soluble polymeric carriers. However, attachment of photosensitizers to Macromolecular carriers may alter their spectral and photosensitizing properties. In this study, a new monosubstituted phthalocyanine derivative, N-glycyl zinc(II) 4,9,16,23-tetraaminophthalocyanine (G-TAPC-Zn) was synthesized by the reaction of zinc(II) 4,9,16,23-tetraaminophthalocyanine (TAPC-Zn) with N-tert-butoxycarbonyl-glycine N'-hydroxybenzotriazole ester followed by deprotection of the tert-butoxycarbonyl (BOC) group. G-TAPC-Zn contains an aliphatic amino group suitable for attachment to water soluble polymeric carriers. By aminolysis of a polymeric precursor, an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer containing oligopeptide (GFLG) side-chains terminated in p-nitrophenyl ester groups, with G-TAPC-Zn a polymeric derivative of the latter (P-GFLGG-TAPC-Zn) was synthesized. Spectral data indicated that in aqueous solutions P-GFLGG-TAPC-Zn formed aggregates. The degree of aggregation decreased with increasing concentration of detergents or organic solvents in buffer solutions. Consequently, the release of the drug from carrier catalyzed by thiol proteinases, papain or cathepsin B, took place only in the presence of detergents or organic solvents, i.e., under conditions with a lower probability of aggregate formation. Binding of G-TAPC-Zn to HPMA copolymers decreased the quantum yield of singlet oxygen generation from 0.24 to 0.063 and significantly increased its resistance to photobleaching.

Reactive carbon black having active phenyl ester groups: Preparation and reaction with functional polymers having hydroxyl or amino groups

The introduction of active phenyl ester groups onto carbon black, such as p-nitrophenyl ester and pentachlorophenyl ester groups, was achieved by the reaction of carboxyl groups on the surface with the corresponding phenols by use of N,N′-dicyclohexylcarbodiimide as a coupling agent. The amounts of p-nitrophenyl ester and pentachlorophenyl ester groups introduced onto the surface were determined as being 0.26 mmol/g and 0.19 mmol/g, respectively. By the reaction of the carbon black thus obtained with commercially available polymers having hydroxyl or amino groups, the latter polymers were found to be grafted onto the surface via ester or amide bonds. For instance, by use of the reactive carbon black bearing p-nitrophenyl ester groups, the percentage of grafting of poly(propylene glycol) ( M n = 3.0 × 10 3 ), diol-type poly(dimethylsiloxane) (SDO; M n = 1.8 × 10 3 ), and diaminetype poly(dimethylsiloxane) ( M n = 3.0 × 10 3 ) was found to be as high as 25.0 %, 23.1 %, and 61.5%, respectively. The percentage of grafting increased with increase in the molecular weight of functional polymer, but the number of grafted polymer chains decreased. This is probably because the reactive groups become shielded by grafted polymer chains, and this effect increases with an increase in their molecular weight. The relationship between the number of grafted polymer chains (G n) and the molecular weight ( M n ) of SDO was found to be G n = 9.05 × 10 −2 M n −0.78 . The carbon black obtained from the reaction formed stable dispersions in good solvents for the grafted polymer.

The Intrachain Aminolysis of a Terminal p-Nitrophenyl Ester Group by a Terminal 4-Pyridyl Group Attached to Both Ends of a Poly(oxyethylene) Chain

Abstract The intrachain aminolysis by a terminal 4-pyridyl group of a p-nitrophenyl ester group at the other terminal of a poly(oxyethylene) chain was investigated. The rate constants of the intrachain reaction were determined as a function of the degree of polymerization, n, of the poly(oxyethylene) chain over the range of 5–33 at 15, 25, and 35 °C. The rate constant was at its maximum at n=7 and decreased with an increase in the chain length. A comparison of the data with those obtained with polysarcosine chain showed that the intrachain reaction proceeded more effectively in the latter chain. Some thermodynamic considerations were made as to the cyclization process of a poly(oxyethylene) chain.

Intrachain Reaction of a Pair of Reactive Groups Attached to Polymer Ends. I. Intramolecularly Catalyzed Hydrolysis of a Terminal p-Nitrophenyl Ester Group by a Terminal Pyridyl Group on Polysarcosine Chain

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntrachain Reaction of a Pair of Reactive Groups Attached to Polymer Ends. I. Intramolecularly Catalyzed Hydrolysis of a Terminal p-Nitrophenyl Ester Group by a Terminal Pyridyl Group on Polysarcosine ChainMasahiko Sisido, Takashi Mitamura, Yukio Imanishi, and Toshinobu HigashimuraCite this: Macromolecules 1976, 9, 2, 316–319Publication Date (Print):March 1, 1976Publication History Published online1 May 2002Published inissue 1 March 1976https://doi.org/10.1021/ma60050a027RIGHTS & PERMISSIONSArticle Views63Altmetric-Citations30LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (454 KB) Get e-Alerts Get e-Alerts