Amino Nitrogen Atom Research Articles

Structure and stability of low molecular weight collagen peptide (prepared from white carp skin) -calcium complex

The low molecular weight (≤3 kDa) collagen peptide (CPLW) was prepared from white carp skin by intestinal simulation digested and ultrafiltration membranes. CPLW and calcium ions were combined to form a peptide-calcium complex (CPLW-Ca), and the structure and stability of the complex were characterized. The single factor optimization results indicated that the highest protein conversion rate and the maximum calcium binding ability were 60%, and 22.16 ± 0.55 mg/g, respectively. Structural analysis demonstrated that calcium ions bound to CPLW mainly via the formation of ionic bonds with carboxyl oxygen, hydroxyl oxygen and amino nitrogen atom of CPLW. The CD and particle size analyses showed that after CPLW was combined with calcium ions, the spatial structure was folded, which reduced the particle size with the formation of irregular nanoparticles. Stability analysis revealed that the calcium retention rate of the prepared CPLW-Ca remained substantially at 90% below 90 °C, and the calcium content of CPLW-Ca was significantly decreased under high acidic conditions. CPLW-Ca has the potential to be applied as an alternative for dietary calcium supplements.

Preparation process optimization, structural characterization and in vitro digestion stability analysis of Antarctic krill (Euphausia superba) peptides-zinc chelate

In the study, a novel kind of peptides-zinc (AKP-Zn) chelate was obtained using the Antarctic krill (Euphausia superba) peptides (AKP) as raw material, the reaction was carried out with the mass ratio of the AKP to ZnSO4·7H2O of 1:2 at pH 6.0 and 60 °C for 10 min. The structure and composition of the AKP, including particle size, Zeta potential, molecular weight distribution, amino acid composition, microstructure and surface elemental composition, changed significantly after chelating with zinc. The result of Fourier transform infrared spectroscopy indicated that zinc could be chelated by carboxyl oxygen and amino nitrogen atoms of the AKP. Furthermore, compared with zinc sulfate and zinc gluconate, the AKP-Zn chelate was more stable at various pH conditions and the simulated gastrointestinal digestion experiment. These findings would provide a scientific basis for developing new zinc supplements and the high-value utilization of Antarctic krill protein resource.

Oyster hydrolysate-zinc complex ameliorates carrageenan-induced rat prostatitis via an anti-inflammatory mechanism and reduced oxidative stress

Abstract Nonbacterial prostatitis has been reported to be associated with reduced zinc intake, but the role of zinc remains unclear. Here, oyster hydrolysate-zinc complex (OH-Zn) was prepared to attenuate rat prostatitis. We found using dynamic light scattering and energy-dispersive X-ray analysis that OH-Zn was a nanostructure complex (49.06 ± 0.26 nm) with a prominent signal of zinc. Fourier transform infrared spectroscopy illustrated that OH-Zn was formed via interactions among zinc ions, amino nitrogen atoms and carboxyl oxygen. OH-Zn treatment significantly reduced the prostatic index value, prostatic specific antigen, tumor necrosis factor-alpha, interleukin-1 beta, malonaldehyde, prostatic acid phosphatase, and acid phosphatase in prostatitis rats. OH-Zn increased the levels of superoxide dismutase, glutathione and serum zinc concentration in prostatitis rats relative to the control group. Moreover, histological analyses revealed OH-Zn prevented the carrageen-induced pathological morphology of the prostate. Therefore, OH-Zn might be a preferable paradigm to ameliorate prostatitis as a novel zinc supplement.

Characterization and antioxidant properties of Manchurian walnut meal hydrolysates after calcium chelation

A Manchurian walnut protein hydrolysates-calcium (MWPH-Ca) was prepared its characteristics and antioxidant activities after in vitro simulated gastrointestinal digestion were investigated. The optimal conditions for the chelation reaction were peptide to calcium ratio of 3:1, pH of 8, chelation time of 40 min, and chelation temperature of 45 °C, and the final chelation rate was 67.2%. The peptides were agglomerated after chelation, as the particle size increased. The FTIR results showed that the main sites of chelation are amino nitrogen atoms, carboxyl groups and the CO of the peptide bond which has a negative dipole. The MWPH-Ca generally maintained good solubility in the gastrointestinal environment, which could improve the calcium absorption. In addition, the MWPH-Ca still retained antioxidant activity and was stronger than that of the MWPH after simulated digestion.

Construction of Strandberg‐Type Polyoxometalate‐Based Inorganic‐Organic Hybrid Material with Water‐Assisted Proton Conductivity

AbstractPolyoxometalates (POMs) were widely applied in the field of proton conduction due to their rapid charge transfer capability and large proton capacity. The Strandberg‐type POM has small size and large charge density, can form functional organometallic compounds with metal ions. In this study, by using [P2Mo5O23]6− coordinate with the cobalt ion with cytosine as the structure‐directing agent, a compound of Co1.5(C4H6N3O)3[P2Mo5O23]⋅8.5H2O was synthesized, which showed one‐dimensional chain structure and exhibits proton conductivity of 3.62 × 10−4 S cm−1 at 98 °C and 97% RH. The amino group and nitrogen atoms in the cytosine can form hydrogen bond with the coordination water molecules. Meanwhile, the hydrogen bond network can also be formed between the water molecules, which is one of the main factors for proton conduction performance. The compound Co1.5(C4H6N3O)3[P2Mo5O23]⋅8.5H2O exhibited the corresponding activation energies and conduction mechanisms at different temperature intervals, by analyzing the temperature‐dependent PXRD spectrum under high‐humidity conditions, which showed the hydrogen bond network of the crystal during the temperature changes affects its proton conduction performance.

Synthesis and biological evaluation of \u03b1- and \u03b2-hydroxy substituted amino acid derivatives as potential mGAT1\u20134 inhibitors

In this study, we report the synthesis and biological evaluation of a variety of α- and β-hydroxy substituted amino acid derivatives as potential amino acid subunits in inhibitors of GABA uptake transporters (GATs). In order to ensure that the test compounds adopt a binding pose similar to that presumed for related larger GAT inhibitors, lipophilic residues were introduced either at the amino nitrogen atom or at the alcohol function. Several of the synthesized compounds were found to exhibit similar inhibitory activity at the GAT subtypes mGAT2, mGAT3, and mGAT4, respectively, as compared with the reference N-butylnipecotic acid. Hence, these compounds might serve as starting point for future developments of more complex GAT inhibitors.

Adsorption of U(VI) onto Amidoxime-functionalized Hydrothermal Carbon in the Presence of Ca-U(VI)-CO3 Complexes

The aim is collecting uranium from groundwater in which uranium mainly exists in negative species, the amidoxime-functionalized hydrothermal carbon (AO-HTC) was synthesized. From the results of N2 adsorption-desorption and SEM, AO-HTC is a small spherical surface; FT-IR and Elemental analysis showed that the amidoxime group was successfully grafted onto the surface of the material; Zeta-potential measurement showed that the amino nitrogen atom is protonated in the oxime group. The optimum pH value of AO-HTC for uranium adsorption is 6.0, and the adsorption equilibrium is reached within 80 min, which is in accordance with the pseudo-second order adsorption kinetic model. The adsorption of uranium by AO-HTC accords with the Langmuir isotherm adsorption model, and the single-layer saturated adsorption capacity is 254.13mg·g-1. The thermodynamic parameters calculated by the adsorption isotherm indicate that AO-HTC adsorption of uranium is a spontaneous endothermic chemical process and Carbonate ion, calcium ion and humic acid concentration have great influence on uranium adsorption. The experiments results show that AO-HTC has the potential to elimination of U(VI) from groundwater.

Polyethylenimine-modified chitosan materials for the recovery of La(III) from leachates of bauxite residue

The separation and recovery of rare earth elements (REEs) from leachates of bauxite residue has attracted increasing attention. Yet, the characteristics of bauxite residue leachates (low pH, low concentration of REEs, and co-existence of other trivalent ions) results in a longstanding challenge in the recovery of REEs. Here, we reported on the development of polyethylenimine (PEI) modified chitosan materials as efficient adsorbents for REE, La(III). The introduction of PEI brought abundant protonatable amino nitrogen atoms, which endows materials with excellent buffering capacity at extremely acidic pH. The PEI-chitosan materials can easily separate La(III) from Al(III), a major co-existing ion, with a separation factor of 3.1. The single-metal adsorption behavior showed fast and efficient adsorption capacity of 2.015 mmol/g for La(III). In binary systems, La(III) was preferentially adsorbed over Al(III) due to the higher degree of association with PEI. The FT-IR, XPS and EDS mapping results revealed that in the binding mechanism the N atoms form coordination bonds with La(III) by sharing an electron pair, resulting in eight-membered chelate rings. The PEI-chitosan materials also exhibited an excellent reusability with regeneration efficiency of 90% after 4 recycles. Overall, PEI-chitosan demonstrates that it is a viable and economical material for the separation and preconcentration of REEs from leachates of bauxite residue.

Stable and reproducible supramolecular motif in the crystal structure of sulfonamides of the benzothiazine series fused to an epoxybornane moiety

The crystal structures of four sulfonamides of the benzothiazine series, fused to an epoxidized norbornane moiety and containing various substituents in the para position of the aromatic ring, were determined. Despite the different volume and acceptor/donor properties of substituents (hydrogen, a methyl group, a cyano group, fluorine), these compounds form isostructural crystals. The main supramolecular motif of these crystals consists of heterochiral chains, which run along a glide plane and are formed via hydrogen bonds between the axial oxygen atom of the sulfonyl group and the amino-group nitrogen atom. The chains are cross-linked to form a crystal structure through C—H…O interactions between the hydrogen atom at the epoxide ring and the equatorial sulfonyl oxygen atom.

α-Actinin-1 promotes activity of the L-type Ca2+ channel Cav 1.2.

The L-type Ca2+ channel CaV 1.2 governs gene expression, cardiac contraction, and neuronal activity. Binding of α-actinin to the IQ motif of CaV 1.2 supports its surface localization and postsynaptic targeting in neurons. We report a bi-functional mechanism that restricts CaV 1.2 activity to its target sites. We solved separate NMR structures of the IQ motif (residues 1,646-1,664) bound to α-actinin-1 and to apo-calmodulin (apoCaM). The CaV 1.2 K1647A and Y1649A mutations, which impair α-actinin-1 but not apoCaM binding, but not the F1658A and K1662E mutations, which impair apoCaM but not α-actinin-1 binding, decreased single-channel open probability, gating charge movement, and its coupling to channel opening. Thus, α-actinin recruits CaV 1.2 to defined surface regions and simultaneously boosts its open probability so that CaV 1.2 is mostly active when appropriately localized.

Investigating the calcium binding characteristics of black bean protein hydrolysate.

The black bean protein has been widely utilized to prepare hydrolysates with different bioactive properties. Herein, we hydrolyzed the black bean protein to prepare hydrolysate with calcium binding activity and characterized its behavior. Our results showed that ficin was superior in obtaining hydrolysate with calcium binding capacity in comparison with trypsin, alcalase and bromelain. In particular, the optimal capacity of ficin hydrolysate reached 77.54 ± 1.61 μg mg-1, where the optimal hydrolysis conditions of ficin were a temperature of 70 °C, a pH value of 6.2, an enzyme concentration of 1.61% and a time of 3 h. This might be due to high proportions of aspartic acid and glutamic acid (35.59%). Further spectral analysis evidenced the formation of hydrolysate-calcium complexes, demonstrating that the interaction between hydrolysate and calcium ions primarily occur on carboxyl oxygen atoms and amino nitrogen atoms. These findings provide a possible utilization of black bean hydrolysate to serve as a calcium supplement nutraceutical to enhance the absorption and bioavailability.

Preparation of sheep bone collagen peptide-calcium chelate using enzymolysis-fermentation methodology and its structural characterization and stability analysis.

In this study, enzymatic hydrolysis and Lactobacillus fermentation were used in combination to prepare collagen peptide with high free calcium content, followed by the addition of anhydrous ethanol to obtain peptide–calcium chelate. The optimal conditions for the fermentation of enzymatic hydrolysate (glucose 3%, inoculum size 6%, 24.5 h, 37 °C and pH 6.5) were determined by response surface methodology (RSM), under which a free calcium content of 2212.58 mg/100 g was obtained. The calcium–chelating capacity was 42.57 ± 0.09%. The results of ultraviolet absorption spectrum, Fourier transform infrared (FT-IR) spectra, differential scanning calorimeter (DSC), X-ray diffraction and amino acid analysis indicated that calcium could be chelated through carboxyl oxygen and amino nitrogen atoms of collagen peptides, forming peptide–calcium chelate. The chelate is stable at 30–80 °C of temperatures and during in simulated gastrointestinal digestion, which could promote calcium absorption in human. The test intended to provide a basis for developing a novel calcium supplement and promoting utilization of sheep bone.

Fabrication of snapper fish scales protein hydrolysate-calcium complex and the promotion in calcium cellular uptake

Abstract It has become a hot topic to find natural food substances which can effectively promote calcium absorption in human body. Given this, protein hydrolysate with calcium-binding capacity was prepared from fish scales (FSPH) and its promotion in calcium cellular uptake was investigated in this study. The binding of calcium to the amino nitrogen atoms and the carbonyl oxygen atoms of FSPH led to the structural folding and aggregation. The calcium cellular uptake efficiency in Caco-2 cells population model was significantly increased in the form of FSPH-calcium complex. Furthermore, FSPH-Ca could effectively resist the inhibitory effect of dietary inhibitors on calcium cellular uptake. The mRNA expression of transient receptor potential vanilloid 6 (TRPV6) in Caco-2 cells was remarkably elevated with FSPH-Ca treatment. The results improved the understanding of the interaction mode of protein hydrolysate and calcium, and provided a basis for developing FSPH-Ca as functional foods to improve calcium absorption.

Toxicity Assessment of Biologically Degraded Product of Textile Dye Acid Red G

Azo dyes are of environmental concern due to their recalcitrant nature. Several azo dyes and their decolorized and degraded products exert toxic and mutagenic effects on the flora and fauna. The toxic properties of these azo dyes are due to nature and position of the substitution with respect to the aromatic rings and amino nitrogen atoms. Several studies have thus far been emphasized on biodegradation of azo dye pollutants, though role of their biodegraded product is rarely studied. Given a lack of this understanding, we have analyzed the effects of degraded products of a di-azo textile dye Acid Red G by newly isolated bacterial species, Pseudomonas aeruginosa PFK10 and Brevibacillus choshinensis PFK11. The genotoxicity and cytotoxicity of Acid Red G and their degraded products were tested on HeLa cell line and Human lymphocyte cell, respectively. The data of MTT assay has been shown that activity of degraded products of the Acid Red G were comparable to their parent dye. But chromosome aberration assay and sister chromatid exchange assay did not show any significant changes in chromosomes as compared to positive control mitomicine.

Synthesis, spectroscopic, thermal, and structural properties of cyanobridged metal complexes containing tetracyanonickelate(II) building blocks with 4-aminomethylpyridine

New cyano-bridged metal complexes with chemical formulas [Fe(NH3)2(ampy)Ni(CN)4]n, [Co(H2O)2(ampy)Ni(CN)4]n and [Ni(NH3)2(ampy)Ni(CN)4]n (ampy = 4-aminomethylpyridine, hereafter abbreviated as Fe–Ni–ampy, Co–Ni–ampy and Ni–Ni–ampy) were obtained in the form of powders and examined by vibrational (infrared and Raman) spectroscopy, thermal (TG, DTG and DTA), and elemental analysis techniques. The infrared and Raman spectra of the complexes were performed in the range of 4000–400 cm-1 and 4000–250 cm-1, respectively. General information about the structural features of synthesized complexes was obtained by considering the changes in the cyano group and characteristic peaks of ampy. The cleavage of the (CN) stretching bands in the infrared spectrum of the complexes shows that the terminal and bridge cyano groups are in the structure. Considering the variations in the vibrational frequencies of the cyano group and ampy ligand in the spectrum of the complexes, the Ni atom is in a square plane geometry with four cyano groups and two of these cyano groups are the bridge and the other two are terminal. In addition, the metal atoms [Fe(II), Co(II) or Ni(II)] are linked to the ring and amino nitrogen atoms of two symmetric ampy ligands, the two ammonia (two aqua ligands for Co–Ni–ampy) ligands and the two bridging cyano groups, and show a distorted octahedral geometry. The thermal degradation of the complexes was also studied between 30 and 950 ºC using TG, DTG, and DTA techniques.

Chelating behavior of 3-amino-4,6-dimethyl-1H-pyrazolo[3,4-b]pyridine ligand towards some metal ions, spectral and thermal measurements as well as molecular modeling and biological studies

Abstract The 3-amino-4,6-dimethyl-1H-pyrazolo [3,4-b]pyridine ligand and its Mn(II), Pd(II), Fe(III), Cr(III), Ru(III), Hf(IV), Zr(IV) and UO2(II) metal complexes were synthesized and characterized by means of elemental analysis, spectral studies and thermal investigation. Also, the theoretical studies that done by Spartan ‘14 V1.1.4 software supported the experimental studies. The infrared data suggest that the ligand coordinates to the metal ions as a neutral monodentate moiety through nitrogen atom of amino group. The complexes are formed with 1:2 and 1:3 (M:L) molar ratios. All complexes possesses octahedral geometry except the Pd(II) complex that presents a square planar geometry. Thermal analyses (TGA and DTG) of ligand and its metal complexes are performed in order to identify the external solvents molecules and thermal stability ranges of the complexes. The X-ray diffraction studies suggest orthorhombic structure of P type lattice for Pd(II) complex and monoclinic structure of P type lattice for Cr(III) and Zr(IV). Theoretical calculations are performed to corroborate the experimental results. Some theoretical parameters are reported in order to compare the reactivity of the compounds. The cytotoxic activity of the ligand and its Pd(II) and Ru(III) complexes is evaluated against breast MCF-7 cell line. Pd(II) complex presents a higher activity. The synthesized ligand and its Pd(II), Cr(III) and Zr(IV) metal complexes also are screened for antibacterial activity. The ligand and its tested complexes has weak activity towards a Gram-positive bacteria and no activity towards Gram-negative bacteria except Pd(II) complex.

Remediation and Mechanisms of Cadmium Biosorption by a Cadmium-Binding Protein from Lentinula edodes.

Cadmium bioremediation with metal-binding proteins is primarily conducted using metallothioneins (MTs). However, in the present study, we investigated a non-MT cadmium-binding protein from Lentinula edodes (LECBP) as a remediation tool for cadmium biosorption in Escherichia coli. The results indicated that the expression of LECBP significantly enhanced the cadmium biosorption capacity of transgenic E. coli. The secondary structure and conformation of LECBP were changed after binding with cadmium as evidenced by circular dichroism and fluorescence spectroscopy. The results of Fourier transform infrared spectroscopy indicated that carboxyl oxygen and amino nitrogen atoms were involved in the interaction between LECBP and cadmium. The results further demonstrated that glutamic acid and histidine residues are the potential binding sites. Our results have thus provided new insights into cadmium bioremediation in an aquatic environment.

A Series of 2,5-Bis(5-aryl-2-thienyl)pyrazines with a Linear-Shaped (D-π)2-A System: Synthesis and Study of the Optical Properties Including Fluorosolvatochromism and Proton-Base-Sensing

Abstract A series of 2,5-bis(5-aryl-2-thienyl)pyrazines with distinct optical properties tuned by the intramolecular charge transfer (ICT) degree based on the donor strength of the aryl groups have been synthesized. It was found that 2,5-bis[5-(4-N,N-dibutylaminophenyl)-2-thienyl]pyrazine exhibits a fluorosolvatochromism that originates from its ICT excited state and proton sensibility with the result that the two-step protonation of the amino nitrogen atoms and pyrazinyl nitrogen atom leads to stepwise solution and emission color changes. Additionally, it should be noted that 2,5-bis[5-(4-hydroxyphenyl)-2-thienyl]pyrazine exhibits a base sensitivity through the obvious emission color change based on the combined process consisting of the deprotonation process of the phenolic hydrogen atoms and the subsequent ICT process. Consequently, by incorporating the N,N-dibutylaminophenyl group (acts as a strong electron donor and proton acceptor) or the phenolic group (acts as a proton donor) into the pyrazine (acts as an electron acceptor and proton acceptor)-cored (D-π)2-A structure, we have constructed an environmentally responsive optical probe.

Dipicolylamino-methoxy-1,2,4,5-tetrazine ligand and its metal complexes: Structural and photophysical studies

The ligand 6-methoxy-N,N-bis(pyridin-2-ylmethyl)-1,2,4,5-tetrazin-3-amine (L) has been prepared by nucleophilic substitution from 3-chloro-6-dipicolylamino-1,2,4,5-tetrazine (1). The ligand L, together with two neutral zinc(II) and cadmium(II) metal complexes, respectively formulated as [ZnLCl2] (2) and [CdLCl2]2 (3), have been crystallized and analyzed by single crystal X-ray diffraction analysis. The two metal complexes are isostructural and crystallize in the monoclinic system, space group P21/c. The structure analysis indicates that the amino nitrogen atom is involved in semi-coordination with the metal centers, thus leading to distorted coordination geometries. Photophysical studies of the ligand and its corresponding metal complexes 2 and 3 show a switch-on of the luminescence upon chelation with the diamagnetic Zn(II) and Cd(II) metal ions.

Hydrogen bonding and protonation effects in amino acids' anthraquinone derivatives - Spectroscopic and electrochemical studies.

Six novel amino acid chromophores were synthesized and their spectroscopic, acid-base, and electrochemical properties are discussed in this work. In studied compounds, selected amino acid residues (l-Aspartic acid, l-Glutamic acid, l-Glutamine, l-Histidine, l-Lysine, l-Arginine) are attached to the 1-(piperazine) 9,10-anthraquinone skeleton via the amide bond between the carboxyl group of amino acid and nitrogen atom of the piperazine ring. All derivatives have been characterized using a variety of spectroscopic techniques (mass spectrometry, 1HNMR, UV-Vis, IR spectroscopy), acid-base (electrochemical and UV-Vis) titrations, and cyclic voltammetry methods. Basing on observed experimental effects, supported by quantum chemical simulations, the structure-properties links were established. They are indicative of the specific interactions within and/or in-between amino acid side groups, which are prone to form both, intra- and intermolecular hydrogen bonds as well as electrostatic interactions with the anthraquinone system.