Intercalation Of Amino Acids Research Articles

Facile preparation of high-efficiency peroxidase mimics: modulation of the catalytic microenvironment of LDH nanozymes through defect engineering induced by amino acid intercalation.

Nanozymes have gained much attention as a replacement for natural enzymes duo to their unique advantages. Two-dimensional layered double hydroxide (LDH) nanomaterials with high physicochemical plasticity are emerging as the main forces for the construction of nanozymes. Unfortunately, high-performance LDH nanozymes are still scarce. Recently, defects in nanomaterials have been verified to play a significant role in modulating the catalytic microenvironment, thereby improving catalytic performances of nanozymes. Therefore, the marriage between defect engineering and LDH nanozymes is expected to spark new possibilities. In this work, twenty kinds of natural amino acids were separately inserted into the interlayer of CoFe-LDH to obtain defect-rich CoFe-LDH nanozymes. The peroxidase (POD)-like activity and catalytic mechanism of the as-prepared LDH nanozymes were systematically studied. The results showed that the intercalation of amino acids can effectively enhance the POD-like activity of LDH nanozymes owing to the increasing oxygen/metal vacancies. And l-cysteine intercalated LDH exhibited the highest catalytic activity ascribed to its thiol group. As a proof of concept, LDH nanozymes with superb POD-like activity were used in biosensing and antibacterial applications. This work suggests that modulating the catalytic microenvironment through defect engineering is an effective way to obtain high-efficiency POD mimics.

Separation of amino acids by selective sorption through reconstructive intercalation in calcined MgAl-layered double hydroxide.

Mg-Al layered double hydroxide (MgAl-LDH) exhibits selectivity in the intercalation of amino acids (AAs). When the MgAl-LDH derived mixed metal oxide was treated with different mixtures of AAs, preferential sorption of one AA over the other(s) was observed as indicated by XRD analysis of the products and HPLC analysis of the interlayer AA contents in the products. The order of preference was aspartic acid, glutamic acid (acidic AAs) > glycine, alanine (neutral AAs) > hystidine, and arginine (basic AAs). Among the acidic AAs, aspartic acid was preferred over glutamic acid and among the basic AAs, histidine was preferred over arginine. LDH shows equal preference for glycine and alanine. The selectivity can be explained on the basis of the isoelectric pH (pI) of the AA. A similar selectivity order was obtained when the mixtures of AAs were treated with nitrate-intercalated LDH (direct anion exchange) although the net AA intercalated is much lower due to competition with carbonate derived from atmospheric CO2. The high selectivity observed in some cases (such as aspartic acid and glycine) would result in the quantitative separation of the individual AAs from their mixture.

Environmental impact of amino acids on the release of selenate immobilized in hydrotalcite: Integrated interpretation of experimental and density-functional theory study

The environmental impact of amino acids on the release of SeO42− immobilized into hydrotalcite (Mg2Al-LDH) which belongs to the layered double hydroxides (LDHs) family was investigated by experimental study and the observed layer structure of hydrotalcite was verified through density-functional theory (DFT) calculations. Glycine, l-cysteine, and l-aspartic acid, which have smaller molecular sizes, can release SeO42− largely due to intercalation, unstabilization of Mg2Al-LDH and simple dissolution, while l-tryptophan and l-phenylalanine caused limited SeO42− release due to their larger sizes and aromaticity. XRD patterns for the solid residues after intercalation of amino acids revealed that the layer distance of Mg2Al-LDH was partially expanded. The main peaks and shoulder features corresponding to d003 diffraction were well explained by DFT simulations using glycine as a model: the layer spacing of the main peak is responsible for the remaining SeO42− and singly stacked glycine molecule and the layer spacing of the shoulder peak was well explained by doubly stacked glycine molecules. Hydrogen bonds between amino acids and hydroxyl ions in the metallic layers of Mg2Al-LDH were responsible for the stable configuration of the intercalated Mg2Al-LDH. This study indicates potential limitations to the stability of low-level radioactive wastes of 79Se in repositories which are affected by smaller molecules of amino acids released through degradation of organic matters in the pedosphere.

DendriPeps: Expanding Dendrimer Functionality by Hybridizing Poly(amidoamine) (PAMAM) Scaffolds with Peptide Segments.

In this work, the first synthesis of poly(amidoamine) (PAMAM) dendrimers whose branches are hybridized with peptide segments (DendriPeps) is reported. The intercalation of amino acids within the branches of PAMAMs provides supplementary internal functionalities to the coronal groups. Four DendriPep prototypes are synthesized with lysine or glutamic acid as "guest" amino acids, displaying, respectively, a primary amine or a carboxyl group, on generation (G)2 and G3 PAMAMs as host scaffolds. The precise control over the number, type, and topological placement of functional groups expands the functional behavior of DendriPeps beyond current PAMAM dendrimers toward new frontiers or colloids, drug delivery vectors, and catalysis.

Tuning molecular sieving channels of layered double hydroxides membrane with direct intercalation of amino acids

A facile and feasible approach was developed to prepare layered double hydroxide (LDH) composite membranes by using amino acids as intercalation molecules.

Intercalation of Amino Acids into Eu3+‐Doped Layered Gadolinium Hydroxide and Quenching of Eu3+ Luminescence

AbstractThe NO3–‐type Eu3+‐doped layered gadolinium hydroxide (NO3–LGdH:Eu) was prepared by a developed homogeneous precipitation method through hexamethylenetetramine (HMT) hydrolysis with hydrothermal treatment. Two amino acid anions, phenylalanine (Phe) and tyrosine (Tyr), were intercalated into LGdH:Eu to form composites Phe–LGdH:Eu and Tyr–LGdH:Eu. Photoluminescence studies show that the incorporation of Phe and Tyr into the host layer can sharply quench the Eu3+ luminescence. This simple method is expected to be applied in biological systems for detecting amino acids.

Preparation and characterization of new organoclays using natural amino acids and Cloisite Na+

In this investigation, several simple positively charged natural amino acids were used for organo-modification of unmodified Cloisite Na+ montmorillonite. Different α-amino acid molecules such as: l-alanine, l-valine, l-leucine, l-isoleucine, l-phenylalanine as well as l-methionine and Cloisite Na+ were used for the preparation of the novel organoclays by an intercalation reaction in an aqueous solution. The intercalated materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, dispersibility measurement, scanning electron microscopy, field emission scanning electron microscopy and transmission electron microscopy. According to the XRD patterns of the samples, the intercalation of amino acids was successful as the increased basal spacing confirmed. TGA characterization and analysis showed that the amount of organic modifier in the organo-modified clays is in good agreement with the theoretically calculated stoichiometric content. The intercalated organic amino acid ions make these novel clays organophile, biocompatible and biodegradable.

Intercalation of amino acids into layered MnPS 3: Synthesis, characterization and magnetic properties

Three bioorganic–inorganic hybrid nanocomposites based on amino acids into layered MnPS 3 have been synthesized and characterized with powder X-ray diffraction (XRD), infrared spectroscopy (IR) and elemental analysis. The expanded MnPS 3 structure as well as the characteristic IR absorption supports the successful and full intercalation of amino acids as the guests into interlayered space of MnPS 3 host. The lattice spacing expansion from XRD patterns indicates that the inserted guest is arranged in the monolayer with carbon chain parallel to the layer of MnPS 3. The magnetic measurements indicate that all three nanocomposites show paramagnetism above 50 K and obey Curie–Weiss law; however, at T c of 40 K a ferrimagnetic transition is observed. The hysteresis of magnetization ( M) versus magnetic field ( H) at 1.85 K further confirms that these intercalation compounds are low-temperature ferrimagnets.

Intercalation of amino acids and oligopeptides into Zn–Al layered double hydroxide by coprecipitation reaction

The coprecipitation of amino acids and oligopeptides with the Zn–Al LDH was investigated using phenylalanine (Phe), phenylalanyl-phenylalanine (Phe-Phe), glycyl-phenylalanine (Gly–Phe), glycine (Gly), glycyl-glycine (Gly–Gly), glycyl-glycyl-glycine (Gly–Gly–Gly) and N-(N-γ-glutamyl-cysteinyl)-glycine (GSH) as guest species. The coprecipitation behavior of amino acids and oligopeptides was found to be influenced by the solution pH and the kind of their side chain groups, and reached the maximum at pH 8 or 9. The basal spacing, d003, of the Phe, Phe-Phe and GSH/LDH was 1.81, 2.41 and 1.64 nm, supporting that guests were arranged vertical to the LDH basal layer. Acceding to the basal spacing of the Gly, Gly–Gly and Gly–Gly–Gly/LDH (d003=0.84–0.88 nm), these guests were oriented horizontal to the LDH basal layer with the co-intercalated NO3−. Moreover, the amount of Phe-Phe, Gly–Gly and Gly–Gly–Gly intercalated was almost the same as that of Phe and Gly despite increasing the number peptide bond and the molecular size. GSH was intercalated into the LDH interlayer space as GSH oxidized form with bridged LDH layers by their carboxylate groups.

Influence of Molar Ratio of Zn/Al/Tyr on the Formation of Tyr/Zn‐Al‐LDH Nanohybrids

AbstractThe intercalation of amphoteric amino acid tyrosine (Tyr) into LDH by co‐precipitation method was systematically studied. The influence of initial molar ratios (R) of LDH to Tyr has also been examined. Powder X‐ray diffraction, Fourier transform infrared spectroscopy, specific surface areas and pore size distributions, and thermal analysis have been employed for the characterization of the nanocomposites. The nanohybrids were found to have an expanded layered structure except the samples prepared with low R values, indicating that the biomolecules were intercalated into the gallery as anions. The intercalation of amino acids resulted in the increase of the surface areas and pore volumes, and the value of surface areas and pore volumes increased with enhancement of biomolecules intercalated. TEM analysis revealed that with increasing biomolecules into the gallery, the nanohybrids were changed from hexagonal particles to spherical ones. Moreover, the configuration of Tyr anions was varied under different R values, changed from monolayer to bilayers with more biomolecules intercalating into the gallery.

Influence of pH on the Formation of Tyr/LDH Nanohybrids

In this article, the intercalation of amphoteric amino acid tyrosine (Tyr) into LDH by the co‐precipitation method is systematically examined. The influence of pH values has been examined. Powder X‐ray diffraction, Fourier transform infrared spectroscopy, specific surface areas and pore size distributions, and thermal analysis have been employed for the characterization of the nanocomposites. The nanohybrids were found to have expanded layered structure, indicating that the biomolecules were intercalated into the gallery as anions. The intercalation of amino acids resulted in the increase of surface areas and pore volumes, and these values increased with increasing of biomolecules intercalated. TEM analysis revealed that with the decrease of pH values, the nanohybrids changed from hexagonal particles to spherical ones. Moreover, the configuration of Tyr anions varied under different pH values, the configuration changing from monolayer to bilayers with more biomolecules in the gallery.

Intercalation behavior of amino acids into Zn–Al-layered double hydroxide by calcination–rehydration reaction

The intercalation of amino acids for the Zn–Al-layered double hydroxide (LDH) has been investigated by the calcination–rehydration reaction at 298 K using mainly phenylalanine (Phe) as a guest amino acid. The Zn–Al oxide precursor prepared by the calcination of Zn–Al-carbonated LDH at 773 K for 2 h was used as the host material. The amount of Phe intercalated by the rehydration was remarkably influenced by the initial solution pH and reached ca. 2.7 times for anion exchange capacity (AEC) of the LDH at neutral and weak alkaline solutions, suggesting that Phe was intercalated as amphoteric ion form into the LDH interlayer. As Phe is intercalated for the LDH as monovalent anion in alkaline solution, the amount of Phe intercalated at pH 10.5 corresponded with AEC of the LDH. The solid products were found to have the expanded LDH structure, which confirmed that Phe was intercalated into the LDH interlayer as amphoteric ion or anion form. The basal spacing, d 003, of the Phe/LDH was 1.58 nm at pH 7.0 and 0.80 nm at pH 10.5; two kinds of expansion suggested for Phe in the interlayer space as vertical (pH 7.0) and horizontal (pH 10.5) orientations. The intercalation behavior of various amino acids for the LDH was also found to be greatly influenced by the feature of the amino acid side-chain, namely, its carbon-chain length, structure and physicochemical property. In particular, α-amino acids possessing a hydrophobic or negative-charged side-chain were preferentially intercalated for the LDH.

Intercalation of amino acids and peptides into Mg–Al layered double hydroxide by reconstruction method

The intercalation of amino acids and some peptides into Mg–Al layered double hydroxide known as hydrotalcite was examined. Although the intercalation by ion-exchange method was unsuccessful, all the amino acids except for Lys and Arg, and peptides examined could be intercalated into the layered double hydroxide by reconstruction method using Mg–Al oxide precursor. The uptake amounts of amino acids and peptides were 0.9–2.7 mmol per 1 g of LDH. Intercalation compounds were examined by using XRD and solid-state NMR. For Gly, Ala, Ser, Thr, Pro, Asn, Gln, Asp, Glu, and aspartame the intercalation accompanied the expansion of interlayer distance of the solid products, whereas the other amino acids and oligoglycine showed no expansion. The intercalation mechanism and release profile in K 2CO 3 aqueous solution were also investigated. And the cointercalation of amino acids and peptides into Mg–Al LDH and easy release of amino acids from the LDH layer were found.

Direct Intercalation of Amino Acids into Layered Double Hydroxides by Coprecipitation

First, the direct intercalation of amino acids into various layered double hydroxides (Mg–Al, Mn–Al, Ni–Al, Zn–Al, and Zn–Cr LDHs) by coprecipitation has been investigated using phenylalanine (Phe) as a guest amino acid. The degree of Phe coprecipitation was strongly influenced by the solution pH and kind of LDH system and reached a maximum in the pH 8–10 region. The solid products were found to have an expanded LDH structure, which supported the belief that Phe was intercalated into LDHs as an amphoteric ion or anion. Two kinds of configuration for Phe in the gallery, either vertical (Mn–Al, Zn–Al, and Zn–Cr LDHs) or horizontal (Mg–Al LDH) in orientation were observed. Only in the Ni–Al system was the solid product a mixture of Phe/Ni–Al LDH and Phe/Ni(OH)2 composite. Next, the thermal decomposition of the intercalated Phe was revealed to be accelerated by the catalytic action of metal ions in the host basal layer. The formation of Phe/Mg–Al, Mn–Al, and Zn–Al LDHs was also elucidated as being appreciably different by the kind of LDH system. Moreover, for various amino acids, the degree of coprecipitation was found to be strongly influenced by amino acid sidechains, i.e., length, structure, and physicochemical properties.

Intercalation of amino acids and polypeptides into 2H-TaS2

2H-TaS2 can be intercalated by organic amines and empirical rules have been formulated1–3 governing the properties that chemical species must possess in order to intercalate. One of these rules is that molecules in which the nitrogen is basic (pKa>4) usually form stable compounds provided the amine does not have bulky substituents. For certain amino acids, the values of pKa are significantly larger than this critical value (for example, glycine pK2=9.78)5 so that if the zwitterion is in a state where it can function as a base, it might be expected that the amino acid would intercalate 2H-TaS2. This prediction has been verified for a number of amino acids. The discovery of these intercalation reactions provides a new range of intercalated compounds for study and also opens up the possibility of in situ polymerisation.