Histidine Methyl Research Articles

Preparation and investigation of catalytic activity of a magnetic Cu-complex immobilized on the histidine modified starch biopolymer

In the present study, at first a magnetic starch oxide support that functionalized with histidine methyl ester was prepared. Then, histidine segments were alkylated with ethyl bromide to form imidazolium salts on this magnetic biopolymer hybrid. The successful synthesis of the prepared nanocomposite was proved by various analysis contain EDX, FE-SEM, FT-IR, VSM, ICP and XRD. The catalytic amount of this nanocomposite was accelerated coupling reaction of aryl boronic acids, NaN3 and phenylacetylene for the synthesis of different 1,4-diaryl-1,2,3-triazoles with high yields at proper reaction times under mild reaction conditions.

Electrochemical Detection of Cortisol by Silver Nanoparticle-Modified Molecularly Imprinted Polymer-Coated Pencil Graphite Electrodes.

The sensitive cortisol detection by an electrochemical sensor based on silver nanoparticle-doped molecularly imprinted polymer was successfully improved. This study describes the method development for cortisol detection in both aqueous solution and biological samples using molecularly imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-histidine methyl ester)-coated pencil graphite electrodes modified with silver nanoparticles (AgNPs) by differential pulse voltammetry (DPV). The cortisol-imprinted pencil graphite electrode (PGE) has a large surface area because of doped AgNPs with enhanced electroactivity. The prepared molecularly imprinted polymer was characterized by scanning electron microscopy. The DPV response of the synthesized electrode with outstanding electrical conductivity was clarified. Cortisol-imprinted polymer-coated PGEs (MIP), cortisol-imprinted polymer-coated PGEs with AgNPs (MIP@AgNPs), and nonimprinted polymer-coated PGEs with AgNPs (NIP@AgNPs) were evaluated for sensitive and selective detection of cortisol in aqueous solution. Five different cortisol concentrations (0.395, 0.791, 1.32, 2.64, and 3.96 nM) were applied to the MIP@AgNPs, and signal responses were detected by the DPV with a regression coefficient (R2) value of 0.9951. The modified electrode showed good electrocatalytic activity toward cortisol for the linear concentration range from 0.395 to 3.96 nM, and a low limit of detection was recorded as 0.214 nM. The results indicate that the MIP@AgNPs sensor has great potential for sensitive and selective cortisol determination in biological samples.

Molecularly Designed Ion-Imprinted Nanoparticles for Real-Time Sensing of Cu(II) Ions Using Quartz Crystal Microbalance.

A molecularly designed imprinting method was combined with a gravimetric nanosensor for the real-time detection Cu(II) ions in aqueous solutions without using expensive laboratory devices. Thus, 1:1 and 2:1 mol-ratio-dependent coordination modes between Cu(II), N-methacyloly-L histidine methyl ester (MAH) functional monomer complexes, and their four-fold and six-fold coordinations were calculated by means of density functional theory molecular modeling. Cu(II)-MIP1 and Cu(II)-MIP2 nanoparticles were synthesized in the size range of 80-100 nm and characterized by SEM, AFM and FTIR. Cu(II)-MIP nanoparticles were then conducted to a quartz crystal microbalance sensor for the real-time detection of Cu(II) ions in aqueous solutions. The effects of initial Cu(II) concentration, selectivity, and imprinting efficiency were investigated for the optimization of the nanosensor. Linearity of 99% was obtained in the Cu(II) ion linear concentration range of 0.15-1.57 µM with high sensitivity. The LOD was obtained as 40.7 nM for Cu(II)-MIP2 nanoparticles. The selectivity and the imprinting efficiency of the QCM nanosensor were obtained significantly in the presence of competitive ion samples (Co(II), Ni(II), Zn(II), and Fe(II)). The results are promising for sensing Cu(II) ions as environmental toxicants in water by combining molecularly designed ion-imprinted nanoparticles and a gravimetric sensor.

Ameliorative Effect of a Neoteric Regimen of Catechin plus Cetirizine on Ovalbumin-Induced Allergic Rhinitis in Rats.

Allergic rhinitis (AR) affects 20–50% of the global population. Available treatments are limited by their adverse effects. We investigated the anti-allergic effects of catechin alone and combined with cetirizine against ovalbumin-induced AR. Rats were sensitized with ovalbumin and received catechin (14 days) and then challenged with aerosolized ovalbumin (1%) to determine AR clinical scores. Histamine, histamine release, and histidine decarboxylase (HDC) activity were determined in blood, peritoneal mast cells, and stomachs, respectively. Vascular permeability and safety were assessed using Evans blue leakage and barbiturate-induced sleeping-time assays, respectively. Catechin and cetirizine binding with HDC was investigated by docking and binding energy analyses. The clinical scores of the combination regimen were superior to either drug alone. All treatments reduced vascular leakage, with no effect on barbiturate-induced sleeping time. Only the catechin-treated rats showed reduced histamine levels and HDC activity. Docking studies revealed that catechin has a 1.34-fold higher extra-precision docking score than L-histidine. The binding energy scores for catechin-HDC, L-histidine-HDC, and histamine-HDC were −50.86, −37.64, and −32.27 kcal/mol, respectively. The binding pattern of catechin was comparable to the standard HDC inhibitor, histidine methyl ester, but with higher binding free energy. Catechin binds the catalytic residue S354, unlike cetirizine. The anti-allergic effects of catechin can be explained by HDC inhibition and possible antihistaminic activity.

Preparation and Investigation of Antibacterial Activities of Ciprofloxacin Imprinted p(HEMAH) Cryogels

Staphylococcus aureus, Enterococcus faecalis and Escherichia coli are the common causes of wound infections. For the treatment of these infections, ciprofloxacin can be recommended as a broad-spectrum antibiotic that acts on both Gram-negative and Gram-positive microorganisms. Besides, antimicrobial agents could be integrated into polymeric materials. Cryogels, one of these polymeric materials, are spongy polymers showing high macroporosity. In addition to their attractive usage as affinity support materials and scaffolds, they also appear as drug carrier materials in recent years. Molecular imprinting method is a recognition technique prepared by forming a polymeric network around the template. Although this method has been used in purification and separation processes for more than thirty years, it has gained great interest as a new approach that provides an advantage in drug release studies in terms of high drug loading capacity and long-term release.
 In this study, ciprofloxacin (CIP) imprinted 2-Hydroxyethyl methacrylate (HEMA) based N-methacryloyl-(L)-histidine methyl ester (MAH) containing [CIP-p(HEMAH)] cryogels was prepared and characterized. CIP releasing experiments were performed, and then, antimicrobial activities of CIP p(HEMAH) cryogels were examined against S. aureus, E. faecalis and E. coli. It can be concluded that CIP-p(HEMAH) cryogels could be proposed as promising polymeric materials for wound healing applications.

Amino acid functionalized macroporous gelatin cryogels: Characterization and effects on cell proliferation

Gelatin and N-methacryloyl-(L)-histidine methyl ester [MAH] containing poly(2-hydroxyethyl methacrylate) [PHEMA] based cryogels were prepared to aid in enhancing cell proliferation. In order to evaluate effects of MAH comonomer and gelatin, cryogels were prepared containing different amounts of gelatin and MAH. Accordingly, four different groups of cryogels which were PHEMA, poly(2-hydroxyethyl methacrylate)-gelatin [PHEMA/GEL], poly(2-hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester) [PHEMAH] and poly(2-hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester)-gelatin [PHEMAH/GEL] were prepared and a total of eight cryogel groups were obtained depending on the varying gelatin ratios. Swelling tests, scanning electron microscope (SEM), microcomputed tomography (Micro-CT) and Fourier transform infrared spectroscopy- Attenuated Total Reflectance (FTIR-ATR) were performed for characterization studies. FTIR-ATR studies confirmed that gelatin and MAH were incorporated into the cryogel structures. Average pore size of cryogels was in the range of 18−198 μm confirmed by Micro-CT and SEM analysis. Then, cryogels were evaluated for cell proliferation abilities by MTT analysis for 24 h and 48 h for cell viability in L929 mouse fibroblast cells. Cell viability of PHEMAH/0.2GEL cryogels reached 209 %. Interaction and proliferation of fibroblast cells on cryogels demonstrated by SEM examination.

Mimicking of the histidine brace structural motif in molecular copper(I) compounds

AbstractL‐Nτ‐methylhistidine methyl ester, MeHisOMe, has been employed as a potential ligand to mimic the histidine brace‐type coordination of copper ions in enzymes such as the particulate methane monoxygenase or lytic polysaccharide monooxygenases. MeHisOMe was prepared by double‐methylation of histidine methyl ester. Subsequently, its complexation by diphosphine copper(I) precursors [Cu(P^P)(MeCN)2]BF4 was tested, which led to the complexes [Cu(P^P)(MeHisOMe)]BF4 (P^P=dpePhos: 1, P^P=XantPhos: 2, P^P=dppf: 3). 1–3 were fully characterized, also by single crystal X‐ray analysis, thus providing first structural data for copper complexes with a synthetic, authentic histidine brace. The complexes proved inert in contact with dioxygen. To improve the biomimetic character attempts were made to formally replace the diphosphine ligands by bis(pyrazolyl)methanes, Bpm. Correspondingly, [BpmCu(NCMe)x]BF4 precursors were synthesized, with different substituents at the 3‐positions of the pyrazolyl (i. e. Bpm=di(3‐(phenyl)‐1H‐pyrazol‐1‐yl)diphenylmethane, di(3‐(mesityl)‐1H‐pyrazol‐1‐yl)methane and di(3‐(tert‐butyl)‐1H‐pyrazol‐1‐yl)diphenylmethane). Addition of MeHisOMe to these complexes led to products that were so sensitive towards oxidation by the environment that they eluded isolation. One experiment provided blue crystals as a product of such a reaction. They belonged to a salt with a complex cation consisting of a Cu(μ‐OH)2Cu core ligated by two MeHisOMe ligands, which dimerises in the solid state to give [Cu4(OH)4(MeHisOMe)4]4+.

Molecularly imprinted nanofilms for endotoxin detection using an surface plasmon resonance sensor

In this study, a simple, fast, sensitive and selective surface plasmon resonance (SPR) sensor was prepared using molecular imprinting method for endotoxin detection. Endotoxin imprinted and non-imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester) based nanofilms were synthesized on the SPR chip surfaces using ultraviolet polymerization. Endotoxin imprinted and non-imprinted SPR sensors were characterized by using contact angle, atomic force microscopy and ellipsometry. After characterization studies, kinetic studies was carried out in the concentration range of 0.5–100 ng/mL. The limit of detection and quantification were obtained as 0.023 and 0.078 ng/mL, respectively. The response time for the equilibration, adsorption and regeneration was approximately 14 min. The selectivity studies with cholesterol and hemoglobin of endotoxin imprinted SPR sensor were examined. Validation studies were carried out via limulus amebocyte lysate (LAL) in order to demonstrate the applicability of the SPR sensor.

Optical Sensor-Based Molecular Imprinted Poly(Hydroxyethyl Methacrylate-N-Methacryloyl-(L)-Histidine Methyl ester) Thin Films for Determination of Tartrazine in Fruit Juice

In this study, a selective, rapid and sensitive surface plasmon resonance (SPR) sensor is prepared for real time detection of tartrazine in fruit juice. Tartrazine imprinted and non-imprinted poly(hydroxyethylmethacrylate-N-methacryloyl-(L)-histidine methyl ester) thin films are synthesized onto SPR chip surface using ultraviolet polymerization. The characterization studies of tartrazine imprinted and non-imprinted SPR sensors are performed with contact angle measurements, atomic force microscopy and ellipsometry. Then, kinetic studies for tartrazine are carried out in the concentration range of 0.5-100.0 μM. The response time for adsorption, desorption and regeneration cycles is approximately about 15 min for the optical sensor system. The limit of detection and quantification are obtained as 0.0076 μM and 0.0252 μM, respectively. The selectivity studies of the tartrazine imprinted and non-imprinted SPR sensors are determined in the presence of allura red and sunset yellow molecules. In order to demonstrate the applicability, validation studies of tartrazine imprinted SPR sensor are performed by liquid chromatography-tandem mass spectrometry (LC-MS).

Antibacterial effect against both Gram-positive and Gram-negative bacteria via lysozyme imprinted cryogel membranes

The development of novel biocompatible and cost effective cryogel membrane which shows enhanced antimicrobial properties in order to use for several approaches such as wound dressing, scaffold or food packaging was aimed in this study. A super macro porous lysozyme imprinted cryogel membranes showing antibacterial effect against both Gram-positive and Gram-negative bacteria were prepared by using molecular imprinting technique. N-methacryloyl-(L)-histidine methyl ester (MAH) was used as the pseudo specific ligand and complexed with Cu++ in order to provide metal ion coordination between MAH and template molecule (lysozyme). Comparing the antibacterial activity of different lysozyme concentrations, cryogel membranes were prepared in three different concentrations. To synthesize Poly (hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methylester) P(HEMA-MAH) cryogel membrane, free radical polymerization initiated by N, N, N′, N′-tetramethylene diamine (TEMED) and ammonium persulfate (APS) was carried out at −12 °C. The characterization of the lysozyme imprinted cryogel membrane was accomplished by using scanning electron microscopy (SEM), swelling degree measurements and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) spectroscopy. The cytotoxicity test of produced membrane was performed by using mouse fibroblast cell line L929. The antibacterial activity of P(HEMA-MAH) lysozyme molecular imprinted [P(HEMA-MAH) Lyz-MIP] cryogel membranes against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were determined by Kirby-Bauer membranes diffusion and viable cell counting methods. When the antibacterial effect of P(HEMA-MAH) Lyz-MIP cryogel membranes were evaluated, it was found that P(HEMA-MAH) Lyz-MIP cryogel membranes had stronger antibacterial effects against Gram-negative E. coli bacteria even in low lysozyme concentrations. In addition, 100% bacterial inhibition was detected for both of two bacteria at increasing lysozyme concentrations.

Cytochrome c adsorption in a continuous flow system by using Cu(II)-chelated magnetic affinity particles

Background and methodology: In the current study magnetic poly(ethylene glycoldimethacrylate-N-methacryloyl-(L)-histidine methyl ester) poly(Egdma–Mah)) was used as ametal chelated affinity particles. Cu2+ ions loaded directly to MAH ligand of magnetic particlesfor the adsorption of cytochrome c (Cyt c) in a continuous flow system.
 Results: The maximumCyt c adsorption capacity on the magnetic particles and Cu2+-chelated magnetic particles were42 mg/g and 197 mg/g in phosphate buffer (pH 8.0), respectively. Cu2+ loading increased theCyt c adsorption capacity, significantly. Cyt c adsorption capacity decreased with increasedtemperature and with increasing magnetic field. According to reusability studies Cyt c moleculescould be reversibly adsorbed and desorbed five times. The binding isotherm was determined byscatchard analysis followed by application of Hill equation to the data obtained, then bindingconstant and nH Hill coefficient were calculated.
 Bangladesh Journal of Medical Science Vol.20(1) 2021 p.159-163

Surface plasmon resonance based biomimetic sensor for urinary tract infections

Tailor-made Escherichia coli (E. coli) receptors were created with microcontact imprinted technique and binding events of E. coli were carried out by a surface plasmon resonance (SPR) sensor in aqueous solution and in urine mimic in real time and label-free. N-methacryloyl-(l)-histidine methyl ester (MAH) was selected as a functional monomer to design tailor-made E. coli receptors on the polymeric film and during the formation of the polymeric film on a chip surface, Ag nanoparticles (AgNPs) were entrapped into the polymer mixture in order to lower the detection limit of biomimetic SPR based sensor. The polymeric film was characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometer and contact angle measurements. Limit of detection (LOD) was found 0.57 CFU/mL and feasibility of the biomimetic sensor was investigated in urine mimic.

Design and preparation of imprinted surface plasmon resonance (SPR) nanosensor for detection of Zn(II) ions

A novel Zn(II) ions imprinted poly (2-hydroxyethyl Methacrylate-N-methacryloyl-(L)-histidine methyl ester) poly(HEMAH) surface plasmon resonance (SPR) nanosensor were designed for detection of Zn(II) ions in aqueous solution and artificial plasma providing a low cost, rapid and reliable results compared to other techniques such as atomic absorption spectroscopy, inductively coupled plasma-mass spectrometer, X-ray fluorescence with synchrotron radiation. Zn(II) ions imprinted nanofilm on the SPR chip surface was synthesized by bulk polymerization. Characterization of Zn(II) ions imprinted nanosensor was performed by contact angle measurement, atomic force microscopy (AFM), ellipsometry and Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR). Designed nanosensor was applied for selective detection of Zn(II) ions in aqueous solution within the range of 0.5–1.0 µg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were calculated as 0.19 and 0.64 ng/mL, respectively. Association kinetics analysis, Scatchard, Langmuir, Freundlich, Langmuir–Freundlich, Tempkin and Dubinin-Radushkevich isotherms were analyzed to the experimental data in order to identify the adsorption behavior. The selectivity of the SPR nanosensor was examined by using competitive metal ions such as Cd(II), Cu(II), Pb(II), and Fe(II). To evaluate the imprinting effect of Zn(II) ions imprinted (MIP) and non-imprinted (NIP) nanosensor was also prepared as the control. Repeatability of the response signal was tested by four times adsorption–desorption–regeneration cycle.

Real time monitoring and label free creatinine detection with artificial receptors

Molecular imprinting technique is used to design artificial creatinine receptor on the gold surface of surface plasmon resonance (SPR) chip using N-methacryloyl-(l)-histidine methyl ester (MAH), as a functional monomer. Surface characterization of SPR sensor chip is performed with atomic force microscope (AFM), ellipsometry and contact angle measurements. Creatinine imprinted SPR sensor is characterized with a linear range between 1 and 100 mM and limit of detection (LOD) and limit of quantification (LOQ) of creatinine are found 57 μM and 190 μM, respectively. N-hydroxysuccinimide (NHS) and creatine molecules are selected to examine the selectivity of creatinine imprinted SPR sensor. Reusability studies of SPR sensor is determined in urine mimic samples.

Evaluating the impacts of amino acids in the second and outer coordination spheres of Rh-bis(diphosphine) complexes for CO2 hydrogenation.

To explore the influence of a biologically inspired second and outer coordination sphere on Rh-bis(diphosphine) CO2 hydrogenation catalysts, a series of five complexes were prepared by varying the substituents on the pendant amine in the P(Et)2CH2NRCH2P(Et)2 ligands (PEtNRPEt), where R consists of methyl ester modified amino acids, including three neutral (glycine methyl ester (GlyOMe), leucine methyl ester (LeuOMe), and phenylalanine methyl ester (PheOMe)), one acidic (aspartic acid dimethyl ester (AspOMe)) and one basic (histidine methyl ester (MeHisOMe)) amino acid esters. The turnover frequencies (TOFs) for CO2 hydrogenation for each of these complexes were compared to those of the non-amino acid containing [Rh(depp)2]+ (depp) and [Rh(PEtNMePEt)2]+ (NMe) complexes. Each complex is catalytically active for CO2 hydrogenation to formate under mild conditions in THF. Catalytic activity spanned a factor of four, with the most active species being the NMe catalyst, while the slowest were the GlyOMe and the AspOMe complexes. When compared to a similar set of catalysts with phenyl-substituted phosphorous groups, a clear contribution of the outer coordination sphere is seen for this family of CO2 hydrogenation catalysts.

Molecularly imprinted polymer based quartz crystal microbalance sensor for the clinical detection of insulin

In this study, quartz crystal microbalance sensors based on molecular imprinting technology were fabricated for real-time detection of insulin in aqueous solution and artificial plasma. This study describes the preparation of insulin imprinted poly(hydroxyethyl methacrylate)-N-methacryloyl-(l)-histidine methyl ester based quartz crystal microbalance sensor for insulin determination. Poly(hydroxyethyl methacrylate)-N-methacryloyl-(l)-histidine methyl ester based film on chip surface was synthesized by ultra violet (UV) polymerization for the detection of insulin at low concentrations. At the first step, N-methacryloyl-(l)-histidine methyl ester complex was formed with insulin and then, the insulin imprinted film has been prepared. The characterization of the polymeric film has been conducted with ellipsometry, contact angle, Fourier transform infrared-attenuated total reflectance and atomic force microscopy measurements. Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherm models were applied for this system. The best fitted model to explain the interactions between molecular imprinted chip and insulin molecules was the Langmuir adsorption isotherm (R2: 0.999). The repeatability of insulin imprinted chip was investigated by using of equilibration-binding-regeneration cycles for four times. The detection limit was found as 0.00158 ng/mL. According to the results, the QCM sensor has showed low-detection limit, high selectivity and sensitivity for insulin assay.

Schiff Base Ligands Derived from l‐Histidine Methyl Ester: Characterization, Racemization, and Dimerization of Their Transition‐Metal Complexes

Reactions of methyl (S)‐2‐[(2‐hydroxybenzylidene)amino]‐3‐(1H‐imidazol‐4‐yl)propanoate (S‐H2LMe) and various transition‐metal(II) salts (MX2: M = Mn, Fe, Co, and Ni; X = ClO4, Cl, OAc, etc.) are examined. During the reactions with MnII and CoII salts, the MII ion is oxidized by air to form a cationic complex with two mono‐deprotonated ligands, [MIII(S‐HLMe)2]X [M, X = Mn, ClO4 (S‐1ClO4); Co, ClO4 (S‐3ClO4); and Co, Cl (S‐3Cl)], where (S‐HLMe)– is coordinated to a MIII center in a tridentate κ3O,N,N′ mode with a mer configuration. In contrast, the NiII ion is not oxidized; only one of the ligands is deprotonated to form a similar monocationic complex, [NiII(S‐HLMe)(S‐H2LMe)]PF6 (S‐6PF6), which forms a dimer structure by double hydrogen bonds between the coordinating phenoxide and phenol groups in the crystal. Interestingly, the above complexes show slow racemization of the ligand, as confirmed by circular dichroism spectroscopy. Racemic NiII complexes of [Ni(HLMe)(H2LMe)](PF6 or Cl) (rac‐6PF6 or rac‐6Cl) are isolated and their crystal structures are confirmed by X‐ray diffraction analysis. In the case where Co(OAc)2 is used as the metal(II) salt, a new ligand dimerization reaction takes place to afford a complex of [Co(H2LLMe)]Cl (7Cl, H4LLMe = methyl (E)‐3‐{[3‐(1H‐imidazol‐4‐yl)‐1‐methoxy‐1‐oxopropano‐2‐yl]amino}‐2‐[(1H‐imidazol‐4‐yl)methyl]‐2‐[(2‐hydroxybenzylidene)amino]‐3‐(2‐hydroxyphenyl)propanoate).

Controlled release of mitomycin C from PHEMAH–Cu(II) cryogel membranes

Molecular imprinting technique was used for the preparation of antibiotic and anti-neoplastic chemotherapy drug (mitomycin C) imprinted cryogel membranes (MMC-ICM). The membranes were synthezied by using metal ion coordination interactions with N-methacryloyl-(l)-histidine methyl ester (MAH) functional monomer and template molecules (i.e. MMC). The 2-hydroxyethyl methacrylate (HEMA) monomer and methylene bisacrylamide (MBAAm) crosslinker were used for the preparation of mitomycin C imprinted cryogel membranes by radical suspension polymerization technique. The imprinted cryogel membranes were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and swelling degree measurements. Cytotoxicity of MMC-ICMs was investigated using mouse fibroblast cell line L929. Time-dependent release of MMC was demonstrated within 150 h from cryogel membranes. Cryogels demonstrated very high MMC loading efficiency (70–80%) and sustained MMC release over hours.

Synthesis of hydroxyethyl-methacrylate-(L)-histidine methyl ester cryogels. Application on the separation of bovine immunoglobulin G

In this study cryogels based 2-hydroxyethyl methacrylate (HEMA) functionalized with N-methacryloyl-L-histidine methyl ester (MAH) were synthesized and used for the adsorption and separation of bovine IgG. Two series of cryogels functionalized with 5 and 10 mg of MAH as pseudobioaffinity ligand were prepared and characterized by swelling test, FTIR and SEM analysis. The adsorption efficiency of the bovine immunoglobulin into cryogels is discussed with respect to the following chromatographic parameters: pH, flow rate, initial IgG concentration, adsorption time and ionic strength. Our results show good adsorption of bovine immunoglobulin under mild separation conditions at pH 7.4. The maximum binding capacity was determined (32.4 mg/g of cryogel) and demonstrates the efficiency of the used cryogels. This efficacy is clearly seen upon increasing the maximum binding capacity from 23.2 mg (obtained with cryogels with 5 mg MAH) to 32.4 mg/g (for cryogel with 10 mg MAH ligand concentration). The purity of separated fractions was evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Together our observations highlights poly (HEMA-MAH) as an efficient adsorbent for bovine immunoglobulins G separation.

Base hydrolysis of α-amino acid esters catalysed by [Pd(N-ethylethylenediamine)(H2O)2]2+. Kinetic study and DFT calculations

Amino acid esters (L) react with [Pd(Eten)(H2O)2]2+ (Eten=N-ethyl ethylenediamine) giving mixed ligand complexes of the type [Pd(Eten)L]2+. Base hydrolysis of [Pd(Eten)L]2+ was studied by pH-stat technique from which rate constants for the base hydrolysis of the esters were obtained. The glycine methyl ester hydrolysed significantly, whereas the methionine methyl and histidine methyl esters hydrolysed much slower. The mode of coordination of the ester plays a role in the catalysis, and possible mechanisms for these reactions are considered. Activation parameters were determined for the hydrolysis of the glycine methyl ester. The effect of the dielectric constant of the medium on the hydrolysis process was also investigated. The B3LYP/LANL2DZ method was used for geometric optimization of the free ligand and the complex using the Gaussian 09 program. The calculations are compared with the kinetic data. In addition, the vibrational frequencies of the molecules were computed for the optimized geometries.