Formation Of Amino Groups Research Articles

Rutile facet-dependent fibrinogen conformation: Why crystallographic orientation matters

Previous studies implied that single crystalline rutile surfaces have the ability to guide the functionality of adsorbed blood plasma proteins. However, a clear relation between the rutile crystallographic orientation and conformation of adsorbed proteins is still missing. Here, we examine the adsorption characteristics of human plasma fibrinogen (HPF) on atomically flat single rutile crystals with (110), (100), (101) and (001) facets. By direct visualization of individual protein molecules through atomic force microscopy (AFM) imaging, the distinct conformations of HPF were determined depending on rutile surface crystallographic orientation. In particular, dominant trinodular and globular conformation was found on (110) and (001) facets, respectively. The observed variations of HPF conformation were reasoned from the surface water contact angle and surface energy point of view. By analyzing AFM-based force measurements, statistically significant changes in surface energies of rutile surfaces covered with HPF were determined and linked to HPF conformation. Furthermore, the facet-dependent structural rearrangement of HPF was indirectly confirmed through deconvolution of high-resolution X-ray photoelectron spectroscopy (XPS) carbon and nitrogen spectra. The globular, and thus native-like HPF conformation observed on (001) facet, was reflected in the lowest level of amino group formation. We propose that the mechanism behind the crystallographic orientation-induced HPF conformation is driven by the facet-specific surface hydrophilicity and energy. From the biomedical material perspective, our results demonstrate that the conformation of HPF can be guided by controlling the crystallographic orientation of the underlying material surface. This might be beneficial to the field of titanium-based biomaterials design and development.

Synthesis, Characterization, and Synergistic Effects of Modified Biochar in Combination with α-Fe2O3 NPs on Biogas Production from Red Algae Pterocladia capillacea

This study is the first work that evaluated the effectiveness of unmodified (SD) and modified biochar with ammonium hydroxide (SD-NH2) derived from sawdust waste biomass as an additive for biogas production from red algae Pterocladia capillacea either individually or in combination with hematite α-Fe2O3 NPs. Brunauer, Emmett, and Teller, Fourier transform infrared, thermal gravimetric analysis, X-ray diffraction, transmission electron microscopy, Raman, and a particle size analyzer were used to characterize the generated biochars and the synthesized α-Fe2O3. Fourier transform infrared (FTIR) measurements confirmed the formation of amino groups on the modified biochar surface. The kinetic research demonstrated that both the modified Gompertz and logistic function models fit the experimental data satisfactorily except for 150 SD-NH2 alone or in combination with α-Fe2O3 at a concentration of 10 mg/L. The data suggested that adding unmodified biochar at doses of 50 and 100 mg significantly increased biogas yield compared to untreated algae. The maximum biogas generation (219 mL/g VS) was obtained when 100 mg of unmodified biochar was mixed with 10 mg of α-Fe2O3 in the inoculum.

Electrochemical detection of protein post-translational modifications: Phosphorylation and nitration of amyloid-beta (1–16)

Post-translational modifications (PTM) such as O-phosphorylation of tyrosine (Tyr) and serine (Ser) and 3-nitration of Tyr amino acid residues of proteinaceous molecules were successfully detected by electrochemistry with the amyloid-beta (1–16) peptide (Aβ16) as an example. The detection strategy was based on the effects of Tyr or Ser O-phosphorylation and Tyr 3-nitration on electrochemical activity of the peptide molecule. Square wave voltammograms of the oxidation and reduction of Aβ16 with the unmodified residues, O-phosphorylated Tyr-10 or Ser-8 (Aβ16-pTyr10 or Aβ16-pS8) and 3-nitrated Tyr-10 (Aβ16-nTyr10) were registered on carbon screen printed electrodes within the potential ranges of 0 to 1.7 V and −0.4 to −1.0 V (vs. Ag/AgCl), respectively. The Aβ16 Tyr-10 oxidation which proceeds via the hydroxyl group of benzene ring manifested as a peak at the potential maximum of about 0.6 V. O-phosphorylation of Aβ16 Tyr-10 dramatically reduced the peak at 0.6 V and produced a new oxidation wave at potentials of 1.1–1.7 V. The oxidation process registered at these elevated positive potentials has been attributed to oxidation of the phosphoryl group of benzene ring of Aβ16 Tyr-10. The role of benzene ring in the phosphoryl group oxidation was evaluated by comparing the electrochemical behavior of Aβ16-pTyr10 and Aβ16-pSer8 peptides. The addition of nitro group at the 3rd position of benzene ring of Tyr-10 caused a shift of the oxidation peak potential maximum from 0.6 to 0.75 V. Moreover, the reduction of nitro group of Aβ16-nTyr10 leading to the amino group formation was registered at −0.75 V. The results obtained for unmodified and modified Aβ16 peptides were confirmed by the data on electrochemical behavior of the corresponding free amino acids, viz. Tyr, nTyr, pTyr, and pSer. Each PTM studied was found to strongly influence the electrochemical properties of amino acids and peptides. Electrochemistry allowing to detect O-phosphorylation of Tyr and Ser and 3-nitration of Tyr residues of peptide molecules seems very promising for the study of these and, likely, many other PTM of interest in diverse in vitro systems.

ChemInform Abstract: Copper‐Catalyzed Domino Synthesis of 4‐Oxopyrimido[1,2‐a]indole Derivatives.

AbstractThe reaction sequence involves sequential Cu‐catalyzed intermolecular C‐arylation of N‐(2‐halophenyl)‐3‐oxoalkanamides (I), intramolecular addition of NH to nitrile function, followed by nucleophilic attack of the formed amino group to the carbonyl moiety.

Hydrogen-Bond-Assisted Controlled C–H Functionalization via Adaptive Recognition of a Purine Directing Group

We have developed the Rh-catalyzed selective C-H functionalization of 6-arylpurines, in which the purine moiety directs the C-H bond activation of the aryl pendant. While the first C-H amination proceeds via the N1-chelation assistance, the subsequent second C-H bond activation takes advantage of an intramolecular hydrogen-bonding interaction between the initially formed amino group and one nitrogen atom, either N1 or N7, of the purinyl part. Isolation of a rhodacycle intermediate and the substrate variation studies suggest that N1 is the main active site for the C-H functionalization of both the first and second amination in 6-arylpurines, while N7 plays an essential role in controlling the degree of functionalization serving as an intramolecular hydrogen-bonding site in the second amination process. This pseudo-Curtin-Hammett situation was supported by density functional calculations, which suggest that the intramolecular hydrogen-bonding capability helps second amination by reducing the steric repulsion between the first installed ArNH and the directing group.

ChemInform Abstract: Synthesis and Structure of Aryl(hetaryl)spiropyrrolidones.

AbstractHydrogenation of diastereomerically pure nitroethylpyrrolidinecarboxylates (I) is accompanied by intramolecular acylation of the formed amino group to furnish diastereomerically pure spiropyrrolidines (II).

Proteolysis of meat and bone meal to increase utilisation

Meat and bone meal (MBM), an important by-product of the meat industry, is the ground, rendered remainder of farm animals after removal of the hide and meat. Most protein in MBM is insoluble, which limits its usefulness. Defatted, milled porcine MBM was subjected to saturating amounts of trypsin, a selective protease, and subtilisin, a protease with broad selectivity. Samples were withdrawn over a 48-h time course of hydrolysis and filtered to remove insoluble material. The rate at which the MBM protein was converted to a soluble form was equivalent for both proteases. Over the time course, trypsin generated fewer free amino groups than did subtilisin, and at a specified time, the molecular weight (MW) of the soluble trypsin hydrolysate was higher than that of the subtilisin hydrolysate. Assay of amino group formation showed that the proteases were still active even after soluble protein generation had ceased. The hydrolysates are useful for a variety of food and non-food uses. The hydrolysates were tested for flocculation activity in an ongoing effort to find sources for renewable flocculant. Kaolin flocculant activity was observed with the soluble fraction obtained before hydrolysis of MBM and also observed with the relatively high MW hydrolysates from short treatment with trypsin and subtilisin. Low MW fractions obtained from by subtilisin treatment at 30–48 h also showed kaolin-settling ability, probably through a coagulation or charge neutralisation process.

Double crosslinked chitosan and gelatin submicronic capsules entrapping aminoacid derivatives with potential antitumoral activity

The aim of the article was the synthesis of novel l-phenylalanine derivatives with biological activity and their immobilization into polymeric particles. Thus, new formyl, acetyl and p-methoxy derivatives of l-phenylalanine with antitumor activity were synthesized by reaction with p-nitrobenzoyl chloride, followed by the reduction of nitro group and acylation of the new formed amino group. The chemical structures of the obtained aminoacid derivatives were determined by FT-IR, NMR, MS and elemental analyses. The compounds were encapsulated into chitosan- and gelatin-based submicronic capsules, prepared by double crosslinking (ionic and covalent) in a O/W/O double emulsion. The varying parameter polymer/ionic crosslinker molar ratio was seen to influence particle size, morphology, swelling degree, thermal properties, as well as their capacity to incorporate and release the new active principles. The in vivo acute toxicity and antitumoral effect of aminoacid derivatives in free form or encapsulated were evaluated on rats. Drug encapsulation into polymeric systems was proven to enhance antitumoral activity against implanted Guerin’s carcinoma.

Synthesis and structure of aryl(hetaryl)spiropyrrolidones

Hydrogenation of the diastereouniform 3-[1-aryl(hetaryl)-2-nitroethyl]-3-methoxycarb-onyl-4-phenyl(3-pyridyl)-2-pyrrolidones is accompanied by intramolecular acylation of the formed amino group to afford the diastereomerically pure 4,4′-aryl(hetaryl)-3,3′-spirobi-[2-pyrrolidones]. The structures of these diastereomers were characterized by IR, 1H and 13C NMR spectroscopy using heteronuclear correlation experiments, and X-ray diffraction study.

Surface modification of polyimide films by an ethylenediamine treatment for a flexible copper clad laminate

The surfaces of the polyimide films Kapton-E and Upilex-S are modified by ethylenediamine treatment to improve its adhesion to a subsequently deposited copper layer. The changes in the chemical composition, morphology, and adhesion properties of the modified polyimide surface are characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and the 90o peel test. An ethylenediamine polyimide treatment induces amino group formation from the broken imide group. The peel strength of Kapton-E and Upilex-S with a copper layer increases from 0.3 to 0.65 kgf/cm and 0.25 to 0.46 kgf/cm, respectively. The results show that ethylenediamine treatment is a good modification method to greatly increase the adhesion performance of polyimide films to a copper layer. Open image in new window

An Efficient Synthesis of 3‐Alkyl‐2‐alkyliminooxazolidin‐4‐one via a Domino Reaction

Abstract3‐Alkyl‐2‐alkyliminooxazolidin‐4‐ones were prepared from a copper‐catalyzed domino intermolecular nucleophilic addition of α‐hydroxy‐(or mecapto) carboxylic acid ester to carbodiimide and a followed nucleophilic substitution of the formed amino group to carboxylic acid ester. The reactions could be performed under convenient conditions and good yields were achieved in most cases.

Surface modification of polyacrylonitrile fiber for immobilization of antibodies and detection of analyte

Pendent nitrile groups of multifilamentous polyacrylonitrile (PAN) fibers were reduced to amino groups using lithium aluminum hydride for different time of reduction and amine content was estimated by performing acid–base titrations. Attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) and Differential Scanning Calorimetry (DSC) were used for the characterization of the generated amino groups and thermal properties of the reduced fibers, respectively. The surface morphology of the fibers after reduction and immobilization was characterized using Scanning Electron Microscope (SEM). The newly formed amino groups of the fibers were activated by using glutaraldehyde for the covalent linking of Goat anti-Rabbit IgG-HRP (GAR-HRP) antibody enzyme conjugate. Modified PAN fibers were evaluated as a matrix for sandwich ELISA by using Goat anti-Rabbit antibody (GAR-IgG), Rabbit anti-Goat (RAG-IgG) as analyte and enzyme conjugate GAR-HRP. The fibers reduced for 24 h were able to detect the analyte RAG-IgG at a concentration as low as 3.75 ng mL −1 with 12% skimmed milk as blocking reagent for the optimized concentration of primary antibody GAR-IgG 3 μg mL −1 and peroxidase conjugate GAR-HRP dilution of 8000 fold. The sensitivity, specificity and reproducibility of the developed immunoassay was further established with antibodies present in human blood using Rabbit anti-Human (RAH-IgG) antibody and the corresponding HRP enzyme conjugate. As low as 0.1 μL of human blood was sufficient to perform the assay with the modified fibers.

Effects of Chemical Composition and the Addition of H2 in a N2 Atmospheric Pressure Dielectric Barrier Discharge on Polymer Surface Functionalization

We examined the effect of hydrogen content in various polymers in a N2/H2 discharge for surface amine functionalization. Three polymers (polyethylene (PE), polyvinylidene fluoride (PVDF), and poly(tetrafluoroethylene) (PTFE)) containing various amounts of hydrogen and fluorine were treated with an atmospheric pressure dielectric barrier discharge (DBD). While surface modification was observed on the PE and the PVDF in a pure N2 discharge, adding H2 in a N2 discharge was necessary to observe the fluorine etching on the surface of the PVDF and PTFE polymers. The presence of a slight amount of hydrogen in the gas mixture was also a prerequisite to the formation of amino groups on the surface of all three polymers (max NH2/C approximately 5%). Aging revealed that the modified polymer surfaces treated in a N2-H2 discharge were less prone to hydrophobic recovery than were surfaces treated in pure N2, due primarily to the presence of a higher density of polar groups on the surfaces. We demonstrated that H atoms in the discharge are necessary for the surface amine functionalization of polymers in a N2 atmospheric pressure DBD, regardless of polymer chemical composition. It is therefore possible to control the plasma functionalization process and to optimize the concentration and specificity of NH2 grafted onto polymer surfaces by varying the H2 concentration in a N2 atmospheric pressure DBD.

Characterization of Amino Groups for Cotton Fibers Coated with Chitosan

The adsorption of chitosan onto cellulose cotton fibers introduces antimicrobial properties, mainly created by the amount and location of amino groups. Therefore, it is important to be able to analyze both parameters, especially in a heterogeneous system, namely cotton fibers coated with chitosan. In this research, three different analytical techniques were applied to determine amino groups of cotton fibers coated with chitosan. The number of positively charged groups was determined indirectly by the spectrophotometric method using Acid Orange 7 dye, and the use of polyelectrolyte titration. In addition, the chemical surface composition regarding non-modified, as well as modified cotton fibers (coated with chitosan), was investigated using X-ray Photoelectron Spectroscopy (XPS). The results from a combination of these methods show that chitosan treatment introduces more than 14 mmol/kg of accessible amino groups onto the cotton fibers. The results were in good agreement with the results of XPS. The use of spectrophotometric and titration methods in combination with XPS appears to be a very useful tool for identifying the formation of amino groups in modified cotton fibers and their surfaces.

Effect of commercial adjunct lactobacilli on biochemical and sensory characteristics of Iranian white‐brined cheese

Iranian white‐brined cheese was made in open vats using commercial adjunct culture of Lactobacillus helveticus Lh.Bo2 in viable and freeze‐shocked (FS) forms. Biochemical and sensory characteristics of the trial cheese were studied during 2 months of ripening. Assessment of primary proteolysis by SDS‐PAGE and water soluble nitrogen for the trial cheese showed no or small differences throughout ripening. However, the experimental cheeses exhibited significantly greater rates of free amino group formation. Lipolysis as measured by total free fatty acid was consistently higher in cheese made with the FS adjunct culture. Expert panellists detected significant differences between the control and the experimental cheese.

Synthesis of Both Enantiomers of Diastereomeric 4‐Fluoro‐4,5‐Dihydroceramides

AbstractTwo diastereomeric enantiopure 4‐fluoro‐4,5‐dihydroceramides with the natural D‐erythro configuration at the 2‐ and 3‐carbon atoms have been synthesized in an enantioselective eleven‐step sequence. The key step of the synthesis was a diastereoselective asymmetric Sharpless dihydroxylation of ethyl trans‐4‐fluorooctadec‐2‐enoate (8) with AD‐mix‐β to afford the D‐erythro arrangement. The diastereomers of the other enantiomeric series were synthesized analogously with the use of AD‐mix‐α. In all cases, the nitrogen heteroatom was introduced into the 2‐position by regio‐ and stereoselective ring opening of cyclic sulfates 13 and 14 with azide. Staudinger reduction, acylation of the intermediary formed amino group, chromatographic separation of the diastereomers and chemoselective reduction of the ester functionality with sodium borohydride in the presence of methanol afforded both title compounds in an enantiopure form. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Application of Novel Base Amplifiers with 3-Nitropentan-2-yl Group to Photoreactive Materials

ABSTRACTIn order to enhance the photosensitivity of photoreactive materials utilizing base-catalyzed reactions, we developed base amplifiers that decompose autocatalytically to generate newborn amine molecules. Actually, we reported that the addition of base amplifiers to the photoreactive materials such as photoresists and UV-curing materials resulted in the marked improvement photosensitivity. However, conventional base amplifiers have aromatic rings such as fluorenyl groups and phenyl groups. Consequently, these base amplifiers have strong absorption of UV light which is a trigger of photolysis of a photobase generator. This leads to the hindrance of the photolysis. We report here novel base amplifiers with 3-nitropentan-2-yl group which has no aromatic rings.The base amplifiers decomposed autocatalytically to generate newborn amine molecules at an elevated temperature in solution and a polystyrene film in the presence of a catalytic amount of amines. Moreover, combining the base amplifiers with UV-curing materials consisting of a photobase generator and liquid epoxy resins resulted in the improvement of curing efficiency. To apply the base amplifier to photopatterning materials, we synthesized novel silicone resins with 3-nitropentan-2-yl groups as base-amplifying polymers. A film of the resin decomposed autocatalytically to generate amino groups in its side chains at an elevated temperature in the presence of a catalytic amount of amines. Furthermore, we demonstrated that the resins sensitized with a photobase generator provided negative- and positive-working photopolymers in the following ways. A thin film of the resin containing 10 wt% of a photobase generator became soluble in an acidic aqueous solution after 254 nm light irradiation of an exposure dose of 1 mJ/cm2 and subsequent baking at 50 oC for 20 min. This is because of formation of amino groups in its side chains. On the other hand, the film became insoluble in organic solvents after 254 nm light irradiation of an exposure dose of 1 mJ/cm2 and subsequent heat treatment at 50 oC for 40 min, this arises from that the photobase-catalyzed hydrolytic condensation of residual ethoxysilyl units of the resin proceeded to form crosslinked networks.

Microwave assisted rapid synthesis of 4-amino-3, 4-dihydroquinolin-2-ones from azetidin-2-ones

An efficient one-pot synthesis of 4-amino-3, 4-dihydroquinolin-2-ones from 3-(2-nitrophenyl)-1, 4-disubstituted azetidin-2-ones is described. Microwave assisted transfer hydrogenation of a nitro group followed by in situ β-lactam ring opening by the newly formed amino group is the key step in this synthesis.

Extended Langmuir approach to analyze the telomeric sequence using a biochromatographic concept

Immobilization of single-stranded DNA (ssDNA) on chromatographic support, i.e. copolymerized particles of styrene and glycidyl methacrylate via formation of amino groups with either N-methyl-1,3-propanediamine (stationary phase 1) or hexamethylenediamine (stationary phase 2) is a promise method to separate sequence specific DNA. However, the low ligand density of nonporous particles led to nonspecific interaction of the complementary oligonucleotide DNA in the sample with the stationary phase (1 or 2). In this paper, the binding process of telomere (tel; TTAGGG) to the complementary ssDNA immobilized (AATCCC) on the two chromatographic supports was studied for the first time using extended Langmuir equation. It appeared that the nonspecific adsorption of the tel due to electrostatic interaction between the polynucleotide sample (tel) and the residual amino groups on the particle surface via amination with hexamethylenediamine (stationary phase 2) was significant and could be reduced by using a high salt (NaCl) concentration in the bulk solvent. In contrast, the nonspecific adsorption of tel was neglected in the column using DNA-immobilized particles via amination with N-methyl-1,3-propanediamine (stationary phase 1). Thus, the affinity chromatography prepared via amination by N-methyl-1,3-propanediamine was more effective for analysis of sequence-specific DNA than the one prepared via amination by hexamethylenediamine. Moreover, for the two stationary phases, increasing NaCl concentration in the bulk solvent enhanced the hybridization between tel and the complementary immobilized oligonucleotide.

Identification of oxidized methionine residues in peptides containing two methionine residues by derivatization and matrix-assisted laser desorption/ionization mass spectrometry.

Oxidation of methionine residues in peptides and proteins occurs in vivo or may be an artifact resulting from purification steps. We present a three step method for the localization of methionine sulfoxides in peptides with two methionine residues. In the first step, the N-terminus as well as other reactive side chain functions are blocked by acetylation. The resulting protected peptides are cleaved by cyanogen bromide. The cleavage does not occur at methionine sulfoxide but only at reduced methionine residues forming new amino termini. The newly formed amino group is then derivatized with a bromine containing compound in the last step of the procedure. The resulting peptide can easily be identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry using both the characteristic isotope pattern of the halogen and the metastable loss of methanesulfenic acid from oxidized residues. This procedure allows the unequivocal localization of oxidized methionines even in complex peptide mixtures.