Phase and Element Contents of the cBN Based Composites as Estimated by XPS

X-ray photoelectron spectroscopy (XPS) is used to estimate phase and element contents of the composites based on cubic boron nitride. A composite is a mixture of several compounds and the use of traditional X-ray diffraction for phase analysis in many cases can be difficult. By using XPS, we were able to evaluate the atomic concentration of elements and the content of different compounds of each element. SEM and XPS showed that samples are heterogeneous. The TiB₂ phase, expecting from thermodynamic calculations, was formed in both investigated samples of cBN/Ti₃SiC₂/TiC but in different amount. The Ti₃SiC₂ additive was found more chemically active then TiC.     

Applicability of new algorithms for determination of acids, bases, salts and their mixtures

Regression equations of the Padé type (PADE W, PADE 1 /W) and equations with Simms' constants involved (SIMMS 1/W) were applied for the determination of internal parameters (i.e. concentrations, equilibrium constants, activity coefficient of hydrogen ions) related to a titrand-titrant system with one- or two-component sample tested with the species having acid-base properties. The parameters were searched according to an iteration procedure (MINUITS computer program applied).     

Charge mediation by ruthenium poly(pyridine) complexes in 'second-generation' glucose biosensors based on carboxymethylated β-cyclodextrin polymer membranes

Four different poly(pyridine) complexes of ruthenium, viz. Ru(II)(trpy)(phen)(OH(2))](2+) (1), trans-[Ru(III)(2,2'bpy)(2)(OH(2))(OH)](2+) (2), [(2,2'bpy)(2)(OH)Ru(III)ORu(III)(OH)(2,2'bpy)(2)](4+) (3), and [Ru(II)(4,4'bpy)(NH(3))(5)](2+) (4) (2,2'bpy=2,2'-bipyridine, 4,4'bpy=4,4'-bipyridine, trpy=2,2',2"-terpyridine, phen=1,10-phenanthroline), were tested as non-physiological charge mediators of 'second-generation' glucose biosensors. The membranes for these biosensors were prepared by casting anionic carboxymethylated beta-cyclodextrin polymer films (beta-CDPA) directly onto the Pt or glassy carbon (GC) disk electrodes. Simultaneously, glucose oxidase (GOD) was immobilized in the films by covalent bonding and the Ru complexes were incorporated both by inclusion in the beta-CD molecular cavities and by ion exchange at the fixed carboxymethyl cation-exchange sites. The leakage of the mediator from the polymer has been minimized by adopting a suitable pre-treatment procedure. The biosensors catalytic activities increased in the order 1<2<3<4, as established by linear sweep voltammetry. In case of complexes 2-4, the enzymatic glucose oxidation was mediated by the Ru complexes at their redox potentials. However, this oxidation was mediated by oxygen in case of complex 1 where H(2)O(2) was detected as the reaction product. The effectiveness of the mediators used in the presence of oxygen has been estimated using Pt and GC supports. The redox potential of the mediator does not depend on the support used, while the oxidation of H(2)O(2) proceeds on GC at much higher positive potentials than on Pt. The sensitivity and the linear concentration range of the biosensor studied varied significantly. For complex 4, which forms stable inclusion complex with beta-CD, the biosensor sensitivity was the highest and equal to 7.2 micro A mM(-1) cm(-2), detectability was as low as 1 mM, but the linear concentration range was limited only to 4 mM. In contrast, for complexes 2 and 3 the sensitivity was 0.4 and 3.2 micro A mM(-1) cm(-2), while the linear concentration range extended up to at least 24 and 14 mM glucose, respectively. Even though some common interfering substances, such as ascorbate, paracetamol or urea, are oxidized at potentials close to those of the Ru complex redox couples, their electro-oxidation currents at physiological concentrations are insignificant compared to those due to the biocatalytic oxidation of glucose. The biosensor response to glucose is reversible as demonstrated by the inhibition of GOD activity by Cu(II). That is, the Cu(II) concentration required to inhibit by half the response to glucose of the biosensor containing complex 2 was 1.0 mM. This inhibitory effect was fully reversed by addition of citrate, a ligand forming sufficiently stable complex with Cu(II).     

Reactions of hydroxymesitylboranes with metal alkyls: an approach to new sterically hindered (metaloxy)mesitylboranes

Reactions of mesitylboronic acid with alkyl derivatives of aluminum R(3)Al (R = Me, Et, Bu(i)), gallium (Me(3)Ga), and zinc (Et(2)Zn) were investigated. The treatment of mesitylboronic acid, MesB(OH)(2), with trimethylgallium afforded the discrete dimer [mu-(MesB(OH)O)GaMe(2)](2) (1), which is the simple example of a O-metalated boronic acid with no hydrogen bonding in the crystal lattice. In addition, the reaction of dimesitylborinic acid, Mes(2)BOH, with diethylzinc produced the low-valent zinc compound [(mu-Mes(2)BO)ZnEt](2) (2), which was also characterized by X-ray diffraction.     

Antiviral Effect of Nonfunctionalized Gold Nanoparticles against Herpes Simplex Virus Type-1 (HSV-1) and Possible Contribution of Near-Field Interaction Mechanism

The antiviral activity of nonfunctionalized gold nanoparticles (AuNPs) against herpes simplex virus type-1 (HSV-1) in vitro was revealed in this study. We found that AuNPs are capable of reducing the cytopathic effect (CPE) of HSV-1 in Vero cells in a dose- and time-dependent manner when used in pretreatment mode. The demonstrated antiviral activity was within the nontoxic concentration range of AuNPs. Interestingly, we noted that nanoparticles with smaller sizes reduced the CPE of HSV-1 more effectively than larger ones. The observed phenomenon can be tentatively explained by the near-field action of nanoparticles at the virus envelope. These results show that AuNPs can be considered as potential candidates for the treatment of HSV-1 infections.     

Influence of production progress on the heavy metal content in flax fibers

The aim of this work was to determine the content of selected heavy metals in flax materials depending on the stage of fiber manufacturing. Non-treated natural fiber composition was compared with that of fibers processed. Changes in the composition of yarn before and after the following scutching, hackling, washing, and bleaching were also investigated. Analysis of heavy metals was performed applying inductively coupled plasma mass spectrometry. Flax material was mineralized in closed Teflon vials with a mixture of concentrated nitric acid which were then placed in a microwave oven system. Analytical quality of the obtained results was checked by the determination of elements in the Certificate Reference Materials of IAEA-V-10. The acquired results proved that the content of metals in flax clearly varies depending on the treatment process applied (bleaching, washing, coloration). Significant differences were also connected with the dye used. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Regiospecific Hydrogenation of Bromochalcone by Unconventional Yeast Strains

This research aimed to select yeast strains capable of the biotransformation of selected 2′-hydroxybromochalcones. Small-scale biotransformations were carried out using four substrates obtained by chemical synthesis (2′-hydroxy-2″-bromochalcone, 2′-hydroxy-3″-bromochalcone, 2′-hydroxy-4″-bromochalcone and 2′-hydroxy-5′-bromochalcone) and eight strains of non-conventional yeasts. Screening allowed for the determination of the substrate specificity of selected microorganisms and the selection of biocatalysts that carried out the hydrogenation of tested compounds in the most effective way. It was found that the position of the bromine atom has a crucial influence on the degree of substrate conversion by the tested yeast strains. As a result of the biotransformation of the 2′-hydroxybromochalcones, the corresponding 2′-hydroxybromodihydrochalcones were obtained. The products obtained belong to the group of compounds with high potential as precursors of sweet substances.     

Influence of backbone length and synthetic mutations on orientation of neurotensin fragments adsorbed onto a colloidal silver surface: SERS studies

Neurotensin (NT) is a naturally occurring neurotransmitter that mediates the metabotropic seven‐transmembrane G protein‐coupled receptors, namely NTR1s, richly expressed on tumor surface. Therefore, mutated active molecular fragments of NT that possess selective antagonist or weak agonist properties and the high affinity to NTR1 have attracted considerable interest for use in thrombus, inflammation, and imaging/treatment of tumors. In this work, SERS spectra of three N‐terminal fragments of human NT (NT^1‐6, NT^1‐8, and NT^1‐11) and six specifically mutated C‐terminal fragments of human NT, including NT^8‐13, [Dab⁹]NT^8‐13, [Lys⁸,Lys⁹]NT^8‐13, [Lys⁸‐(®)‐Lys⁹]NT^8‐13, [Lys⁹,Trp¹¹,Glu¹²]NT^8‐13, and NT^9‐13, adsorbed onto nanometer‐sized colloidal silver particles in an aqueous solution at pH level of the solution 2 are presented. A comparison was made between the structures of the native and mutated fragments to determine how changes in peptide length and mutations of the structure influenced the NT adsorption properties. Based on the interpretation of the obtained data, we showed that all of the investigated NT fragments, excluding [Lys⁹,Trp¹¹,Glu¹²]NT^8‐13, tended to adsorb on the silver surface mainly through the L‐tyrosine residue and the carboxylate group. The Tyr ring lied more‐or‐less flat on the silver surface. The hydrogen atom from the phenol group dissociated upon binding. On the other hand, [Lys⁹,Trp¹¹,Glu¹²]NT^8‐13 bound to this substrate through the close to vertical co‐pyrrole ring of the indole ring (Trp¹¹) and –COO^‐ . Comparison of the presented data with those obtained earlier for NT allows to suggest that in the case of naturally occurring neurotensin, both Tyr residues together with the carboxylate group play crucial role in the binding to the nanometer‐sized colloidal silver particles. This geometry of binding forces the NT molecule to lay flat on the surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of alpha-aminobenzylphosphonic acids with a stereogenic quaternary carbon atom via microscopically configurationally stable alpha-aminobenzyllithiums

The enantiomers of 1-phenylethylamine were phosphorylated with diethyl chlorophosphate/Et(3)N and then Boc-protected (Boc=tert-butoxycarbonyl) at the nitrogen atom. These phosphoramidates were metalated by using sBuLi/N,N,N',N'-tetramethylethylenediamine (TMEDA) to give alpha-aminobenzyllithiums that isomerised to alpha-aminophosphonates in yields of up to 80 % with retention of the configuration at the carbon atom. The intermediate tertiary organolithiums were found to be microscopically configurationally stable from -78 to 0 degrees C in Et(2)O. The protected alpha-aminophosphonates were deblocked by using boiling 6 M HCl or preferably Me(3)SiBr/(allyl)SiMe(3). When the Boc group was replaced by the diethoxyphosphinyl group, the alpha-aminobenzyllithium intermediate partially enantiomerised even at -78 degrees C and rearranged to yield an alpha-aminophosphonate with 50 % ee (ee=enantiomeric excess). Similarly, N-Boc-protected phosphoramidates derived from racemates and/or enantiomers of 1-(1-naphthyl)ethyl-, 1-indanyl- and 1,2,3,4-tetrahydro-1-naphthylamine or 1-azidoindan- and 1-azido-1,2,3,4-tetrahydronaphthalene were converted to aminophosphonates in good yields. Deblocking gave alpha-aminophosphonic acids of excellent enantiomeric excess (97-99 %), as determined by means of HPLC on a chiral ion-exchange stationary phase based on quinine carbamate. When racemic Boc-protected diethyl phosphoramidate derived from 1,2,3,4-tetrahydro-1-naphthylamine was metalated with LiTMP/TMEDA (TMP=2,2,6,6-tetramethylpiperidine), 1-hydroxyethylphosphonamidates resulted. The configuration of the main isomer was determined by means of a single-crystal X-ray structure analysis.