Tailoring the properties of thermoplastic starch by blending with cinnamyl alcohol and radiation processing: An insight into the competitive grafting and scission reactions

The present paper focuses on the effects of electron beam (EB) irradiation on thermoplastic materials based on destructurized starch including glycerol and water as plasticizers to assess the potentiality of cinnamyl alcohol as reactive additive capable of counterbalancing the degradation of the polysaccharide by inducing interchain covalent linkages. The tensile properties at break of test specimens of controlled composition submitted to EB irradiation at doses ranging from 50 to 200 kGy revealed the presence of competitive chain scission and bridging in samples containing cinnamyl alcohol at a relative concentration of 2.5% with regard to dry starch. The occurrence of crosslinking under particular conditions was evidenced by gel fraction measurements. The treatment under radiation was also applied to model blends including maltodextrin as a model for starch and the other ingredients to gain an insight into the radiation induced mechanisms at the molecular level. The presence of cinnamyl alcohol is found to limit degradation. Size exclusion chromatography and gel fraction allowed to monitor the effects and confirmed unambiguously the attachment of UV-absorbing chromophores onto the maltodextrin main chain. The combination of the obtained results demonstrates the possibility of altering in a favorable way the tensile properties of plasticized starch by applying high energy radiation to properly formulated blends including aromatic compounds like cinnamyl alcohol.     

Analysis of cytokinin nucleotides by capillary zone electrophoresis with diode array and mass spectrometric detection in a recombinant enzyme in vitro reaction

A capillary zone electrophoresis (CZE) method for separation of adenosine and N⁶-isopentenyladenosine (cytokinin) nucleotides was developed, optimized and validated. Aqueous solutions of several amino acids were evaluated as the background electrolyte constituents. Separation of six nucleotides in less than 20 min with high theoretical plate number (up to 400 000 for isopentenyladenosine triphosphate) was achieved using a 100 mM sarcosine/ammonia buffer at pH 10.0. The detection limits of the CZE-UV method are in the low micromolar range (0.69–1.27 μmol L⁻¹). Good repeatability of migration times (within 1.3%), peak areas (within 1.8%) and linearity (R² > 0.999) was achieved over the concentration range 5–1000 μmol L⁻¹. The method was used to assay the activity of the recombinant Arabidopsis thaliana isopentenyltransferase 1 (AtIPT1). Baseline separation of isopentenylated nucleotides by CE–ESI-MS using a volatile buffer (30 mM ammonium formate; pH 10.0) was accomplished. The identities of the reaction products – isopentenyladenosine di- and triphosphate were confirmed by HPLC-QqTOF-MS. Dephosphorylation of ATP was observed as a parallel reaction.     

Structural and morphological studies on Mn substituted ZnO nanometer‐sized crystals

Mn substituted ZnO nanocrystals synthesized by a co‐precipitation method. X‐ray diffraction (XRD) studies confirms the presence of wurtzite (hexagonal) crystal structure similar to un doped ZnO, suggesting that doped Mn ions go at the regular Zn sites. The lattice parameters a and c are increasing with increasing Mn content. The unit cell volume increases with increasing Mn concentration, indicating the homogeneous substitution of Mn²⁺ for the Zn²⁺. The lattice distortion parameter (ε_v) is evaluated from XRD data and found that it enhances as Mn content increases. Transmission electron microscopy photographs show that the size of the ZnO crystals is in the range of 20‐50 nm. The SAED pattern confirms the hexagonal and crystalline nature of the samples which are in agreement with X‐ray analysis. The chemical groups of the samples have been identified by FTIR studies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Oszillopolarographischer nachweis und bestimmung von jodat und perjodat

The oscillopolarographic behaviour of periodate and iodate has been investigated in acid, neutral and alkaline electrolytes. The detection and determination of periodate in iodate may be carried out using iodate as electrolyte and the detection and determination of iodate in periodate may be carried out using 5 M sodium hydroxide as electrolyte.     

Synthesis,characterization and antitumour activity of copper(II) 6-(4-chlorobenzylamino)purine complexes. X-ray structure of 6-(4-chloro-benzylamino)purinium perchlorate

Copper(II) complexes with 6-(4-chlorobenzylamino)purine (HL) have been prepared and characterized by elemental analysis, electronic, i.r., ES + mass and ¹³C-n.m.r. spectra, and by magnetic and conductivity data. Based on these physical methods, mainly the temperature dependence of magnetic susceptibility data, we conclude that the complexes are: [Cu₂(-Cl)₂(-HL)₂Cl₂] (1) and [CuCl₃(H⁺L)₂]Cl (2). They have been studied for their possible antitumour activity against human malignant melanoma G-361, human osteogenic sarcoma HOS, human chronic myelogenous leukaemia K-562 and human breast adenocarcinoma MCF7 cells in vitro. The IC₅₀ values were determined by calcein AM assay. The molecular structure of 6-(4-chlorobenzylamino)purinium perchlorate, i.e. a protonated form of the free HL ligand, has been determined by a single crystal X-ray analysis.     

On optimal control problems with general boundary conditions

It is shown that the necessary optimality conditions for optimal control problems with terminal constraints and with given initial state allow also to obtain in a straightforward way the necessary optimality conditions for problems involving parameters and general (mixed) boundary conditions. In a similar manner, the corresponding numerical algorithms can be adapted to handle this class of optimal control problems.This research was supported in part by the Commission on International Relations, National Academy of Sciences, under Exchange Visitor Program No. P-1-4174.The author is indebted to the anonymous reviewer bringing to his attention Ref. 9 and making him aware of the possible use of generalized inverse notation when formulating the optimality conditions.     

Microdetermination of aromatic nitro compounds with iron(II) in alkaline sorbitol media

In titrations with iron(II) sulphate in alkaline solutions of sorbitol, the iron(III) formed is bound in a strong complex and the formal redox potential of the Fe(III)/Fe(II) system is decreased to —1.10 V (SCE; 0.5 M sorbitol, 2 M KOH). This permits reducing titrations with a stable reagent, of systems which would otherwise require unstable strong reductants (e.g. Cr(II), Sn(II), V(II), etc.). Determinations of organic mono-, di- and tri-nitro compounds are described; these can be carried out directly on the microscale, with potentiometric, bipotentiometric or biamperometric end-point detection. Nitrate does not interfere; the method can also be employed for indirect determinations of various aromatic compounds after their conversion to nitro derivatives.