Bamboo (<Emphasis Type="Italic">Phyllostachys pubescens</Emphasis>) as a Natural Support for Neutral Protease Immobilization

Lignin polymers in bamboo (Phyllostachys pubescens) were decomposed into polyphenols at high temperatures and oxidized for the introduction of quinone groups from peroxidase extracted from bamboo shoots and catalysis of UV. According to the results of FT-IR spectra analysis, neutral proteases (NPs) can be immobilized on the oxidized lignin by covalent bonding formed by amine group and quinone group. The optimum condition for the immobilization of NPs on the bamboo bar was obtained at pH 7.0, 40 °C, and duration of 4 h; the amount of immobilized enzyme was up to 5 mg g^?1 bamboo bar. The optimal pH for both free NP (FNP) and INP was approximately 7.0, and the maximum activity of INP was determined at 60 °C, whereas FNP presented maximum activity at 50 °C. The K_m values of INP and FNP were determined as 0.773 and 0.843 mg ml^?1, respectively; INP showed a lower K_m value and V_max, than FNP, which demonstrated that INP presented higher affinity to substrate. Compared to FNP, INP showed broader thermal and storage stability under the same trial condition. With respect to cost, INP presented considerable recycling efficiency for up to six consecutive cycles.     

Radioiodination of 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine, 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine and their derivatives via isotopic and non-isotopic exchange reactions

A mild and simple technique for preparing of 4-benzyl-1-(3-[¹²⁵I]iodobenzylsulfonyl)piperidine, 4-(3-[¹²⁵I]iodobenzyl)-1-(benzylsulfonyl)piperazine and their derivatives, as sigma-1 receptor ligands, with relatively high radiochemical yields via nucleophilic substitution reaction by means of isotopic and non-isotopic exchange reactions is described. Some factors affecting the radiochemical yield were commonly studied in presence of acidic medium at elevated temperature. Unfortunately, the radiochemical yields were weak. Some attempts were carried out in presence of polar aprotic solvents to enhance the radiochemical yield. N,N-Dimethylformamide was proved highly efficient for preparing of radioiodinated 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine (4-B-[¹²⁵I]-IBSP, 70 ± 5.7 %) and 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine (4-[¹²⁵I]-IBBSPz, 72 ± 6.0 %) at moderate temperature (100–105 °C) within 8 h. The specific activities of 4-B-[¹²⁵I]-IBSP and 4-[¹²⁵I]-IBBSPz (6,534.2 and 5,927.4 MBq/mmol) were obtained respectively.     

Self-radiolysis of iodobenzene labelled with125I

The radiolysis of iodobenzene labelled with¹²⁵I has been investigated at liquid nitrogen and room temperatures, in the presence and absence of oxygen. After various storage times the samples were analyzed by gas chromatography, and benzene, vinyl iodide, biphenyl, and iodobiphenyl were detected. Biphenyl, benzene, and iodobiphenyl were found to be formed as a result of local radiolytic effect of Auger electrons of¹²⁵I, and vinyl iodide was probably produced due to the decay effect of¹²⁵I in labelled iodobenzene molecules. At the site of¹²⁵I decay the Auger electrons are radiolytically effective within a spherical volume with diameter of about 30 . Outside this sphere the energy absorbed by iodobenzene molecules is not high enough to produce any radiolytical damage.     

N-[11C]methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB): synthesis, quality control and biodistribution

N-[¹¹C]methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine ([¹¹C]MBDB) 3 was prepared by methylation of the demethyl precursor BDB with [¹¹C]CHI. The radiosynthesis was optimized with regard to temperature, reaction time and amount of precursor, best results (i.e., 84% radiochemical yield, based on [¹¹C]CH₃I activity) were obtained using 3 mg BDB at a reaction temperature of 130 °C in 8 minutes. With respect to a facilitated workup routine, productions were performed with 0.6 mg BDB at 110 °C for 10 minutes, yielding more than 50% of 3. The radiochemical purity of the final tracer solution was >98%, the specific activity was determined to be 300 GBq/mol (8000 Ci/mmol). Biodistribution, studies in rats showed two major metabolic pathways as indicated by an increasing liver uptake (9.1% ID/organ at 5 minutes to 21% ID/organ at 30 minutes) and a high urine activity (up to 16% ID/g). In brain tracer uptake was more than 1%, with a brain to blood ratio of almost 12 resulting from a very rapid blood clearance of 3.     

Magnetic silver(I) ion-imprinted polymeric nanoparticles on a carbon paste electrode for voltammetric determination of silver(I)

Magnetic silver ion imprinted polymer nanoparticles (mag-IIP-NPs) were prepared and used as a recognition element in electrochemical detection of silver(I). The procedure involves two steps: (a) the extraction of the Ag(I) by the mag-IIP-NPs, and (b) determination of the preconcentrated Ag(I) ions on the surface of the magneto carbon paste electrode (MCPE) using differential pulse voltammetry. The amount of sorbent, pH value of the sample solution, extraction time, supporting electrolyte, reduction potential and reduction time were optimized. Under optimal conditions and at a working voltage of +0.02 V (vs. Ag/AgCl), the method displays a linear response in the 0.05 to 150 μg?L^?1 Ag(I) concentration range. Other features include a low detection limit (15 ng?L^?1), a remarkable selectivity and good reproducibility (with an RSD of 4.7%). The results obtained with this analytical assay when analyzing different water samples were compared with the data obtained by GF-AAS, and the results agreed satisfactorily. In our perception, this approach also may be extended to electrochemical detection for other ions, and this makes it a widely applicable strategy for heavy metal ion analysis.

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Graphical abstract Schematic illustration of the procedure for the extraction and voltammetric detection of silver(I) ions.

     

Effect of experimental conditions on the in vitro stability of99mTc (Sn)-pyrophosphate

The in vitro stability of^99mTc (Sn)-PyP as a function of experimental conditions of the preparation of the kit and time elapsed after labeling has been tested. The preparation was protected by using nitrogen-purged reactant solutions and kit vials and by ascorbic acid. The samples under nitrogen are stable for 6 h when the content of^99mTc-pertechnetate raises to 5%. The best stability was achieved by addition of 5 g of ascorbic acid per ml of the kit (content of^99mTc-pertechnetate about 0.5%). To accelerate the decomposition, exogenous hydrogen peroxide was used. In this case it was found that the presence of 10 g of ascorbic acid inhibits the effect both of oxygen and peroxide (6 g H₂O₂/ml of the kit). Radiochemical purity of^99mTc (Sn)-PyP remains practically unchanged for 6 h (content of^99mTc-pertechnetate about 0.5%).     

XPS analysis (ESCA) of the surface composition of poly(styrene/2-hydroxyethyl methacrylate) microspheres produced by emulsifier-free emulsion polymerization

Polymer microspheres composed of various compositions of styrene and 2-hydroxyethyl methacrylate (HEMA) were produced by batch emulsifier-free emulsion polymerization. The HEMA content at the surface, [HEMA] _s , of the microspheres powdered by freeze-drying was determined by both quantitativeC ^1s /O ^1s analysis andC ^1s peak shape analysis of the x-ray photoelectron spectroscopic spectra. When the HEMA content in the microsphere, [HEMA] _p , was less than about 5 mole%, the [HEMA] _s values determined by the two different methods showed good agreement. At [HEMA]_p above 5 mole %, [HEMA]_s values determined by the first method were about 15 mole % greater than those determined by the second. They both showed a similar tendency with the [HEMA] _s being higher than the [HEMA] _p , e.g., when [HEMA] _p was 1 mole %, [HEMA] _s was 11 mole %. The intensity of the satellite peak due to the ^* transition of the benzene ring of the styrene component decreased with an increase in [HEMA] _p , to zero at 5 mole % of [HEMA] _p . These results indicate that the HEMA component is localized at the surface.Part CVIII of the series Studies on Suspension and Emulsion.     

Preparation of 125I-cytarabine and its radiochemical evaluation: Model of radio-therapeutic agent

This paper adresses the development of a new radiopharmaceutical for cancer imaging and therapy. The optimization of the labeling of thymidine analogous, cytarabine, with ¹²⁵I is described. High radiochemical yield and purity 98% was obtained by reacting 50 mg cytarabine with ¹²⁵I in the presence of iodogen as oxidizing agent and 0.5M phosphate buffer of pH 7 at 65 °C for 30 minutes. Preliminary in-vivo study was done in non-tumor bearing mice. The results revealed that this new tracer, ¹²⁵I-cytarabine, has a high affinity to be localized in tissues of high proliferation rate, e.g., bone marrow 10%, 60-minute post administration. Also, the labeled compound was cleared quickly from most of the body organs and concentrated in bladder 55%, 60-minute post administration. These findings suggest that ¹²⁵I-cytarabine, allows imaging and treatment of cancer. ¹²⁵I-cytarabine meets most of the requirements to be used as a successful diagnostic and therapeutic agent: it is a low molecular weight molecule that diffuses readily in tissues, it will not induce an antibody response, thereby leading itself to repeated injection or continuous infusion.     

Kinetics and mechanism of the copper(II) promoted hydrolysis of the methyl ester of ethylenediaminemonoacetate

Summary Base hydrolysis of methyl ethylenediaminemonoacetate has been studied at I=0.1 mol dm^–3 (NaClO₄) over the pH range 7.4–8.8 at 25 °C. The proton equilibria of the ligand can be represented by the equations, where E is the free unprotonated ester species. Values of pK₁ and pK₂ are 4.69 andca. 7.5 at 25° (I=0.1 mol dm^–3). For base hydrolysis of EH⁺, k_OH=1.1×10³ dm³ mol^–1 s^–1 at 25 °C. The species E is shown to undergo lactamisation to give 2-oxopiperazine (k_lact ca. 1×10^–3 s^–1) at 25 °C. Formation of the lactam is indicated both by u.v. measurements and by isolation and characterisation of the compound.Base hydrolysis of the ester ligand in the complex [CuE]²⁺ has been studied over a range of pH and temperature, k _OH ²⁵ =9.3×10⁴ dm³ mol^–1 s^–1 with H=107 kJ mol^–1 and S ₂₉₈ =209 JK^–1 mol^–1. Base hydrolysis of [CuE]²⁺ is estimated to be some 10⁵5 fold faster than that of the free ester ligand. The results suggest that base hydrolysis occursvia a chelate ester species in which the methoxycarbonyl group of the ligand is bonded to copper(II).     

Spectrophotometric determination of vanadium(IV) in the presence of vanadium(V) using Br-PADAP

In the present paper, a simple and sensitive method is proposed for vanadium(IV) determination in the presence of vanadium(V). This is based on the oxidation of vanadium(IV) present in the sample to vanadium(V) by addition of iron(III) cation, followed by a complexation reaction of iron(II) with the spectrophotometric reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). The iron(II) reacts with Br-PADAP immediately, forming a stable complex with a large molar absorptivity. The vanadium(IV) determination is possible, with a calibration sensitivity of 0.549 g ml^–1, for an analytical curve of 18.8 ng ml^–1 to 2.40 g ml^–1, molar absorptivity of 2.80 × 10⁴ 1 mole^–1 cm^–1 and a detection limit of 5.5 ng ml^–1. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for the vanadium(IV) determination in the presence of several amounts of vanadium(V). The results revealed that 200 g of vanadium(V) do not interfere with determination of 5.00 g of vanadium(IV). The precision and the accuracy obtained were satisfactory (R. S. D.<2%).     

Formation of uniform silver particles from bis (1,2-ethanediamine)silver(I) complex

Uniform spherical silver particles were produced by decomposing the bis(1,2-ethanediamine)silver(I) complex, by aging a solution of 1.0×10^–3 mole dm^–3 in silver (I) nitrate, 1.0 mole dm^–3 in 1,2-ethanediamine, and 2.5×10^–1 mole dm^–3 in nitric acid (basic solution) at 100°C for 42 min. The average modal diameter was estimated to be 0.52 m with a relative standard deviation of 0.10. A moderately oxygenrich layer, 40 Å thick, on the surface of the particles was detected by means of photoelectron surface microanalysis (XPS). The silver particles grew through a polynuclear-layer mechanism, as judged from the concentration change in soluble silver(I) species in the supernatant solution. The particles' point of zero charge (PZC) was estimated at pH 6.5 by potentiometric titration.     

Spectrophotometric determination of uranium (VI) with 5-hydroxy-flavone and 5-hydroxy-7-methoxy-flavone

Summary 5-Hydroxy-flavone and 5-hydroxy-7-methoxy-flavone have been used for the spectrophotometric determination of uranium. With uranium(VI) both the reagents form yellowish-orange complexes soluble in 50% v/v ethanol. The characteristics of the complexes have been studied spectrophotometrically. The molar composition of uranyl-5-hydroxy-flavone complex shows that it contains uranium and the reagent in the ratio of 11, while in case of uranyl-5-hydroxy-7-methoxy-flavone complex, it contains uranium and the reagent in the molar ratio of 12. The logK values, as determined by method based on Beer's law have been found to be 9.22 and 9.70 respectively, at 30°C.

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Zusammenfassung 5-Hydroxy-flavon (I) und 5-Hydroxy-7-methoxy-flavon (II) wurden als Reagentien zur spektrophotometrischen Bestimmung von Uran benutzt. Beide Substanzen geben mit U^VI einen gelborange gefärbten Komplex, der in 50%igem Äthanol löslich ist. Die Eigenschaften der Komplexe wurden untersucht. Das Verhältnis U:Reagens im Komplex beträgt 11 (I) bzw. 12 (II). Die logK-Werte wurden zu 9,22 (I) bzw. 9,70 (II) gefunden (30° C).

     

Assembly of cyano-bridged Cu(II)/Cu(II) and Cu(I)/Cu(II) compounds obtained by controlled ration of cyanide

One reaction system of Cu²⁺, dipn, and CN⁻ with two different molar ratio sets of 1:1:5, and 2:1:8 produced two compounds 1 [Cu^II(dipn)][Cu^II(CN)₄], and 2, respectively (dipn = dipropylenetriamine). Their structures were determined by X-ray crystallography. Compound 2 is built from Cu(I) and Cu(II) centers, which are bridged by cyanide groups and metal-metal bonds. The magnetic properties of 1 and 2 were investigated in 2-300 K. Compound 1 exhibits an antiferromagnetic exchange interaction between copper(II) ions mediated by cyano-bridges.     

Spectrophotometric determination of ruthenium(III) using diphenylcarbazone

Summary The purple violet ruthenium(III)-diphenylcarbazone complex which is formed at p _h 5–7, and has an absorption maximum at 530 nm with molar absorption coefficient 16.2·10⁴l.cm^–1.mole^–1 is suggested for the estimation of 20–125g ruthenium(III) spectrophotometrically in 30–60% ethanol. The complex is stable over p _h range 3.2–8.4. The limits of interference due to foreign ions have been studied.

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Zusammenfassung Der bei p _h 5 bis7 entstehende Ruthenium(III)-Diphenylcarbazon-Komplex hat ein Absorptionsmaximum bei 530 nm und einen Absorptionskoeffizienten von 16,2·10⁴ l.cm^–1.Mol^–1. Die spektrophotometrische Bestimmung von 20 bis 125g Ruthenium(III) in 30 bis 60%igem Äthanol mit Hilfe dieses zwischen p _h 3,2 und 8,4 beständigen Komplexes wurde vorgeschlagen. Die Störung durch Fremdionen wurde geprüft.

     

Phenylcopper(I) clusters in the gas phase obtained by laser desorption/ionization from bis(dibenzoylmethane)copper(II)

It has been demonstrated that phenylcopper(I)-containing clusters are generated in the gas phase from bis(dibenzoylmethane) copper(II) (Cu(dbm)₂) by laser desorption/ ionization (LDI) method. For example, the [Cu₅dbm₂(C₆H₅)₂]⁺ ion can be considered as consisting of two Cudbm molecules, two CuC₆H₅ molecules and a Cu⁺ cation. The [Cu₅(C₆H₅)₄]⁺ ion can be considered as phenylcopper(I) cluster (consisting of four phenylcopper molecules) ionized by additional Cu⁺ cation. Results from MS/MS (tandem mass spectrometry) experiments have confirmed the presence of phenylcopper molecules in the analyzed clusters. Ease of preparation of dibenzoylmethane-metal complexes and straightforward method to obtain LDI mass spectra offer a wide range of possibilities to study similar organometallic clusters in the gas phase.      

Adsorption of Cs(I), Sr(II) and Co(II) on Al2O3

The sorption of Cs(I), Sr(II) and Co(II) from aqueous solutions on alumina under various experimental conditions has been studied by batch techniques. Freundlich, Langmuir and Dubnin-Raduskevich equations have been used to interpret the sorption data. The values of various thermodynamic parameters have been determined. The sorption of Cs(I) and Sr(II) on alumina is exothermic in nature while that of Co(II) is an endothermic process. The H ^o values for Cs(I), Sr(II) and Co(II) were–23.29 KJ/mol at 298K,–35.3 KJ/mol at 293 K and 13.49 KJ/mol at 293 K, respectively. Negative values of G ^o show the spontaneity of the sorption processes; G ^o values of Cs(I) and Sr(II) becomes less negative at higher temperatures while the G ^o values of Co(II) become more negative with increasing temperature. At higher temperatures, less amounts of Cs(I) and Sr(II) and greater amounts of Co(II) are sorbed on alumina. The values of the mean free energies of sorption,E, for Sr(II) and Co(II) at various temperatures were within the range of 7–10 KJ/mol which show that these metals are sorbed on alumina predominantly by an ion-exchange process.     

Complexation of uranium(VI) by salicylate and substituted salicylates: A kinetic study

Summary Kinetic studies on the complexation of uranium(VI) by salicylate and various substituted salicylates have been carried out using the stopped-flow spectrophotometric technique at pH 7.0–8.5 (NH₄OH+NH₄NO₃ buffer). Results are in conformity with a mechanism involving binding of UO₂OH⁺ species through the carboxylate group of the salicylate to form an inner-sphere species in a fast equilibrium (equilibrium constant=K) followed by a slow rate-determining ring closure (rate constant=k) involving loss of a molecule of water between the OH group bound to uranium(VI) and the phenolic group of the salicylate. The value of the equilibrium constant (K) obtained from the kinetic data in the case of 5-sulphosalicylate (log K=3.21 at 25 °C, I=1 M) is compatible with the literature thermodynamic value (log K = 3.89 at 25 °C, I=0.015 M). Increase in pH retards the reaction due to the equilibrium, UO₂OH⁺ + OH^– UO₂(OH)₂, the UO₂(OH)₂ being unreactive. The average value of K (log K=8.58 at 25°C, I=1M) obtained kinetically from the results of investigation with different ligands is also in good agreement with the literature thermodynamic value (log K= 8.8 at 25°C, I=0.1M). Both K and k are sensitive to the nature of the substituent in the benzene ring, decreasing with increasing acidity of the -CO₂H group of the salicyclic acid; the substituent effect is well demonstrated by the plot of log kversus _L (where ), which is linear. H^# and S^# values corresponding to k have been evaluated in each case. S^# values are all negative in conformity with ring closure in the rate-determining step.     

Kinetics and mechanism of silver(I) catalyzed oxidation of tris(1,10-phenanthroline)iron(II) with peroxodiphosphate in acetate buffers

A kinetic study of the silver(I)-catalyzed oxidation of tris(1,10-phenanthroline)iron(II) with peroxodiphosphate was carried out by estimating tris-complex at 510 nm. The reaction is found to conform to the rate law (i). with K₂ and K₃ being the acid dissociation constants of H₃P₂O₈^? and H₂P₂O₈^2?, respectively. The silver(I) catalysis in the reaction has been explained on the basis of complex formation between pdp and silver(I).     

Temperature and ionic strength influence on U(VI/V) and U(IV/III) redox potentials in aqueous acidic and carbonate solutions

Redox potentials: E(UO ₂ ²⁺ /UO ₂ ⁺ )=60±4 mV/NHE, E(U⁴⁺/U³⁺)=–630±4mV/NHE measured at 25°C in acidic medium (HClO₄ 1M) using cyclic voltametry are in accordance with the published data. From 5°C to 55°C the variations of the potentials of these systems (measured against Ag/AgCl electrode) are linear. The entropies are then constant: [S(UO ₂ ²⁺ /UO ₂ ⁺ )–S(Ag/AgCl)]/F=0±0.3 mV/°C, [S(U⁴⁺/U³⁺)–S(Ag/AgCl)]/F=1.5±0.3 mV/°C. From 5°C to 55°C, in carbonate medium (Na₂CO₃=0.2M), the Specific Ionic Interaction Theory can model the experimental results up to I=2M (Na⁺, ClO ₄ ^– , CO ₃ ^2– ): E(UO₂(CO₃) ₃ ^4– /UO₂(CO₃) ₃ ^5– )=–778±5 mv/NHE (I=0, T=25°C, (25°C)=(UO₂(CO₃) ₃ ^4– , Na⁺)–(UO₂(CO₃) ₃ ^5– , Na⁺)=0.92 kg/mole, S(UO₂(CO₃) ₃ ^4– /UO₂(CO₃) ₃ ^5– =–1.8±0.5 mV/°C (I=0), =(Cl^–, Na⁺)=(1.14–0.007T) kg/mole. The U(VI/V) potential shift, between carbonate and acidic media, is used to calculate (at I=0,25°C):

2-(2-Thiazolylazo)-pcresol (TAC) as a reagent for the spectrophotometric determination of titanium (IV)

The reaction between titanium(IV) and 2-(2-thiazolylazo)-p-cresol-(TAC) in aqueous methanol media at apparent pH 4.0–5.6 results in a intensely coloured complex that is stable for at least 2 h. The combining ratio is 1 1 cation TAC. Beer's law is obeyed up to 5.0 g/ml titanium(IV) at 580 nm. The apparent molar absorptivity at 580 nm is 9.82.10³ l.mole^–1.cm^–1 and the detection limit obtained was 5 ng/ml titanium (IV). A spectrophotometric method for the simultaneous determination of titanium and iron with TAC is proposed.