Isolation and purification of biopolymers by affinity chromatography. VI. Preparation and properties of an affinity adsorbent with a polysaccharide spacer for the purification of proteolytic enzymes

A new affinity sorbent has been synthesized — soybean trypsin inhibitor (STI)-amylopectin-hydrazidosuccinyl-Sepharose — and its properties have been studied in comparison with those of an analogous adsorbent without the spacer STI-Sepharose. The STI-amylopectin-hydrazidosuccinyl-Sepharose adsorbent has been used for the purification of trypsin from porcine pancreas and of callicrein from human blood plasma.     

Phospholipase A2 from the venom of the spider Eresus niger

A phospholipase A₂ with a molecular mass of 12–14 kDa has been isolated from the venom of the spiderEresus niger by three-stage column chromatography. Asparagine has been identified as the N-terminal amino acid.     

Kinetics and possible mechanism of hydrogen chloride oxidation over supported copper-containing salt catalysts: I. Kinetics of HCl oxidation in the deacon and methane oxychlorination reactions over a copper-potassium salt catalyst

The kinetics of HCl oxidation at 350–425°C over a (CuCl₂-KCl)/support catalyst in two complementary processes—Deacon and methane oxychlorination reactions—has been investigated using a gradientless technique. This has allowed the range of \(P_{Cl_2 }\) in the reaction mixture to be markedly extended. New kinetic features of HCl oxidation under conditions such that this process does and does not depend on P _HCl have been discovered. The kinetic equations obtained in this study fit experimental data in a wider range of conditions than the equations proposed earlier. The results of this study suggest the existence of two HCl oxidation pathways in the Deacon reaction.     

Isolation of nonprotamine proteins from the nuclei of the gonad cells of the Russian sturgeonAcipenser güldenstadti

Eight nonprotamine proteins have extracted from the nuclei of the cells of the gonads of the Russian sturgeon with 0.35 M sodium chloride solution followed by fractionation of carboxymethyl-Sephadex G-25 and desalting on Bio-Gel P-2, and their amino acid compositions have been determined.     

Lariat ethers in the chiral recognition of amino acid esters:electrospray ionization mass spectrometry investigation

The ability of the crown ethers (1–4), containing the ortho- or para- methoxyphenoxy-methyl substituents in their structure, to chiral recognition in reference to amino acid esters has been investigated by electrospray ionization mass spectrometry (ESI-MS). The method allows registering the diastereomeric complexes between the studied crowns as hosts and the protonated alanine, phenylglycine and phenylalanine methyl esters as guests in the gas phase. ESI-MS experiments using isotopically labeled guests provide robust and reproducible results, indicating a moderate degree of chiral discrimination in the series of the studied crown ethers. ESI-MS experiments using achiral amine as a reference yielded the results comparable with the previous method. It has been found that (S)-enantiomers of the crowns bind predominately (S)-enantiomers of the amino acid esters, and vice-versa. It has been shown that the chiral ortho-substituted crown (S)-1 demonstrates the more pronounced values for chiral discrimination as compared with the para-substituted crown (S)-2. This fact indicates the interrelationship between the chiral recognition and the lariat nature of crown 1. Increasing the size of the cavity and the presence of a flat aromatic moiety in crowns 3 and 4 strengthens their complexing ability, simultaneously weakening the enantioselectivity of the complexation.     

Primary structure of stellin B

Stellin B, a protamine fromAcipenser stellatus, has been subjected to thermolysin hydrolysis. Eight peptides have been isolated by chromatography on CM-Sephadex, and their structures have been determined by dansylation and by hydrolysis with carboxypeptidases A and B and with trypsin. From the results obtained, the complete amino acid sequence of stellin B has been established.     

Mechanism and improvement of complex formation between LPS and polymyxin B that is immobilized on an ion exchanger

Polymyxin B was immobilized on the ion exchanger, Amberlite IRC-50. The modified support was used as an adsorbent for lipopolysaccharide ofE. coli from a phosphate buffer at pH = 7.0 and T = 20°C. The insertion of a spacer, 6-amino hexanoic acid, improved the adsorption capacity of the modified carrier significantly. Upon partial acetylation (25%) of primary amino groups of immobilized Polymyxin B, the adsorption capacity of the support was halved. From our results, it is concluded that the complex formation between lipopolysaccharide and immobilized Polymyxin B is based on both lipophilic, as well as electrostatic, interactions. Convenient procedures for the immobilization of the ligands and the characterization of the ion exchanger are described.     

Structure of britannin. Use of two-dimensional1H NMR spectroscopy

Two-dimensional¹H NMR spectroscopy (COSY, NOESY) in combination with the one-dimensional variant has been used to establish the conformation of the molecule of britannin — a sesquiterpene lactone of the ambrosane type. The comparative possibilities of one- and two-dimensional NMR spectroscopies in stereochemical investigations of sesquiterpene lactone with ambrosane skeletons are considered.     

Polysaccharides ofEremurus. X. Characteristics of the polysaccharides ofEremurus lactiflorus andE. luteus

Water-soluble polysaccharides have been isolated from two species ofEremurus — E. lactiflorus andE. luteus — with yields of 13.5% and 20.5%, respectively. They contained mainly glucose and mannose in ratios of 1:5 and 1:3.1. The polysaccharides ofE. lactiflorus were separated from a column of DEAE-cellulose. The yield of neutral fraction was 10.3%. Gel filtration of the polysaccharides on Sephadex G-200 showed their polydispersity. Homogeneous fractions were obtained by fractional precipitation with ethanol. They have been characterized with respect to monosaccharide composition, molecular weight, and IR spectra.     

Visual detection of arginine,histidine and lysine using quercetin-functionalized gold nanoparticles

We report on the use of quercetin-functionalized gold nanoparticles (QC-AuNPs) as a colorimetric probe for the amino acids arginine (Arg), histidine (His) and lysine (Lys). The method is based on the aggregation of the QC-AuNPs that is caused by these amino acids and leads to a visually detectable color change from red to blue. The absorption maxima shift from 525 nm to 702, 693, and 745 nm, respectively. Aggregations are confirmed by dynamic light scattering (DLS) and transmission electron microscopic techniques (TEM). The effects of the QC concentration, temperature and reaction time for the preparation of QC-Au NPs were tested. Other amino acids do not interfere. Under the optimal conditions, linear relationships exist between the absorption ratios at 702/525 nm (for Arg), 693/525 nm (for His), and 745/525 nm (for Lys) over the concentrations ranges from 2.5–1,250 μM (Arg) and 1–1,000 μM (His and Lys), respectively. The respective limits of detection are 0.04, 0.03, and 0.02 μM. The method provides a useful tool for the rapid visual and instrumental determination of the three amino acids. Figure

We report the use of quercetin as novel reagent for preparation and functionalization of gold nanoparticles to colorimetric sensing of three aminoacids (arginine, histidine and lysine). This is based on the aggregation of QC-AuNPs induced by three aminoacids.     

A label-free electrochemical biosensor for microRNA detection based on apoferritin-encapsulated Cu nanoparticles

MicroRNAs (miRNAs), a class of small endogenous nonprotein-coding RNAs, regulate a wide range of biological processes, and their abnormal expressions are related to the growth and development of plants. Thus, a simple, rapid, and highly sensitive assay for miRNA detection is of great significance. In this work, a label-free and ultrasensitive assay for miRNA detection using protein cage nanoparticles has been developed. Apoferritin-encapsulated Cu nanoparticles (Cu-apoferritin) could be immobilized on the electrode through special reaction between amino and carboxyl. Hybridization event between the probe DNA and the target miRNA-159a is confirmed by electrochemical oxidation signal after Cu released into the detection buffer by adjusting the pH. This assay is highly selective and sensitive with a low detection limit of 3.5 fM. Moreover, the developed method can even discriminate single-base mismatched strand between the complementary targets. The effect of abscisic acid on the expression level of miRNA-159a in Arabidopsis thaliana seeds was also investigated.     

d- and l-amino acids in Antarctic lakes: assessment of a very sensitive HPLC-MS method

Amino acids represent a fraction of organic matter in marine and freshwater ecosystems, and a source of carbon, nitrogen and energy. l-Amino acids are the most common enantiomers in nature because these chiral forms are used during the biosynthesis of proteins and peptide. To the contrary, the occurrence of d-amino acids is usually linked to the presence of bacteria. We investigated the distribution of l- and d-amino acids in the lacustrine environment of Terra Nova Bay, Antarctica, in order to define their natural composition in this area and to individuate a possible relationship with primary production. A simultaneous chromatographic separation of 40 l- and d-amino acids was performed using a chiral stationary phase based on teicoplainin aglycone (chirobiotic tag). The chromatographic separation was coupled to two different mass spectrometers—an LTQ-Orbitrap XL (Thermo Fisher Scientific) and an API 4000 (ABSciex)—in order to investigate their quantitative performance. High-performance liquid chromatography coupled with mass spectrometry methods were evaluated through the estimation of their linear ranges, repeatability, accuracy and detection and quantification limits. The high-resolution mass spectrometer LTQ-Orbitrap XL presented detection limits between 0.4 and 7 μg?l ^?1, while the triple quadrupole mass spectrometer API 4000 achieved the best detection limits reported in the literature for the quantification of amino acids (between 4 and 200 ng?l ^?1). The most sensitive method, HPLC-API 4000, was applied to lake water samples. Figure

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Investigation of the biosynthesis of acetyl-CoA and oxaloacetic acid from pyruvic acid and the quantitative evaluation of incorporated 13C-labeled l-alanine in Arthrobacter hyalinus

Studies on the contribution to acetyl-CoA and oxaloacetic acid from the pyruvic acid transformation from l-alanine in Arthrobacter hyalinus were conducted by means of feeding experiments with l-[1-¹³C]alanine and l-[3-¹³C]alanine, followed by an analysis of the labeling patterns of coproporphyrinogen III using ¹³C NMR spectroscopy. The results demonstrated that l-alanine was transformed via pyruvic acid to both acetyl-CoA and oxaloacetic acid. Additionally, the quantitative analysis indicated that pyruvic acid was transformed to acetyl-CoA and oxaloacetic acid in the ratio of 1:0.8.     

Analysis of citrate-capped gold and silver nanoparticles by thiol ligand exchange capillary electrophoresis

We report on the capillary electrophoretic behavior of citrate-capped gold and silver nanoparticles in aqueous medium when applying a ligand-exchange surface reaction with thiols. Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) of similar size (39?±?6 and 41?±?7 nm, respectively) and shape were synthesized, covered with a citrate shell, and characterized by microscopic and spectroscopic techniques. The analysis of these NPs by CE was accomplished by using a buffer solution (pH 9.7; 40 mM SDS, 10 mM CAPS; 0.1 % methanol) containing the anions of thioctic acid or thiomalic acid. These are capable of differently interacting with the surface of the AuNPs and AgNPs and thus introducing additional negative charges. This results in different migration times due to the formation of differently charged nanoparticles. Figure

Capillary electrophoretic behavior of citrate-capped gold and silver nanoparticles (NPs) in aqueous medium when applying a ligand-exchange surface reaction with thiols (thioctic and thiomalic acids), which introduces additional negative charges, has been studied     

Baicaline — A new aporphine alkaloid fromThalictrum baicalense

A new aporphine base — baicaline — has been isolated from the epigeal part ofThalictrum baicalense. Its structure has been established as 1,9,10-trimethoxy-2,3-methylenedioxynoraporphine. Magnoflorine and berberine have been isolated from the roots of the plant.     

Substoichiometric determination of lanthanum by using EDTA and 8-hydroxyquinoline

The substoichiometric separation of lanthanum was studied on the system EDTA —lanthanum—8-hydroxyquinoline. The optimum conditions for the substoichiometric separation of lanthanum were calculated theoretically and these results were examined experimentally. By using the two chelating agents, EDTA and 8-hydroxyquinoline, lanthanum could be separated substoichiometrically with good accuracy and precision. This method was applied to the determination of lanthanum by activation analysis, and found to be available for the determination of trace amount of lanthanum.     

A new synthesis of bicyclic N,O- and N,S-enaminals by the anionic cyclization of alk-4-ynals with amino alcohols and amino thiols

A reaction of alk-4-ynals with aliphatic amino alcohols or 2-aminoethanethiol in the system DMSO—KOH gives bicyclic N,O- and N,S-enaminals: 6-methylidenehexahydro-2H-pyrrolo[2,1-b][1,3]oxazines, 5-methylidenehexahydropyrrolo[2,1-b]oxazoles, or 5-methyl-idenehexahydropyrrolo[2,1-b]thiazoles. The reaction proceeds through the formation of equilibrium mixtures of the corresponding imines and monocyclic aminals with subsequent 5-exodig-cyclization catalyzed by the superbasic system DMSO-KOH.     

Synthesis of uronoyldipeptide derivatives of N-acetylglucosamine and of N-acetylmuramoyldipeptide

Starting from benzyl 3,4-di-O-acetyl-6-O-trityl-N-acetyl-β-glucosamine and benzyl α-benzyl-4-O-acetyl-N-acetylmuramate, 2-acetamido-2-deoxy-D-glucopyranuronyl-L-alanyl-D-isoglutamine and O-(2-acetamido-2-deoxy-D-glucopyranuronyl-L-alanyl-D-isoglutamin-3-yl)-D-lactoyl-L-alanyl-D-isoglutamine — uronoyldipeptide analogs of N-acetylglucosamine and N-acetylmuramoyl dipeptides — have been synthesized.     

Solid-phase microextraction/gas chromatography–mass spectrometry method optimization for characterization of surface adsorption forces of nanoparticles

A complete characterization of the different physico-chemical properties of nanoparticles (NPs) is necessary for the evaluation of their impact on health and environment. Among these properties, the surface characterization of the nanomaterial is the least developed and in many cases limited to the measurement of surface composition and zetapotential. The biological surface adsorption index approach (BSAI) for characterization of surface adsorption properties of NPs has recently been introduced (Xia et al. Nat Nanotechnol 5:671–675, 2010; Xia et al. ACS Nano 5(11):9074–9081, 2011). The BSAI approach offers in principle the possibility to characterize the different interaction forces exerted between a NP's surface and an organic—and by extension biological—entity. The present work further develops the BSAI approach and optimizes a solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) method which, as an outcome, gives a better-defined quantification of the adsorption properties on NPs. We investigated the various aspects of the SPME/GC-MS method, including kinetics of adsorption of probe compounds on SPME fiber, kinetic of adsorption of probe compounds on NP's surface, and optimization of NP's concentration. The optimized conditions were then tested on 33 probe compounds and on Au NPs (15 nm) and SiO₂ NPs (50 nm). The procedure allowed the identification of three compounds adsorbed by silica NPs and nine compounds by Au NPs, with equilibrium times which varied between 30 min and 12 h. Adsorption coefficients of 4.66?±?0.23 and 4.44?±?0.26 were calculated for 1-methylnaphtalene and biphenyl, compared to literature values of 4.89 and 5.18, respectively. The results demonstrated that the detailed optimization of the SPME/GC-MS method under various conditions is a critical factor and a prerequisite to the application of the BSAI approach as a tool to characterize surface adsorption properties of NPs and therefore to draw any further conclusions on their potential impact on health. Graphical Abstract

The basic principle of SPME/GC-MS method for characterization of nanoparticles surface adsorption forces