Standardization of 90Y solution by mean of a Cherenkov counting in comparison with a liquid scintillation counting technique

Journal of Radioanalytical and Nuclear Chemistry - This paper presents the standardization of 90Y solution using the Cherenkov method measuring in the TDCR counters. The counting efficiencies for...     

Symmetrization of the AMBER and CHARMM force fields

The AMBER and CHARMM force fields are analyzed from the viewpoint of the permutational symmetry of the potential for feasible exchanges of identical atoms and chemical groups in amino and nucleic acids. In each case, we propose schemes for symmetrizing the potentials, which greatly facilitate the bookkeeping associated with constructing kinetic transition networks via geometry optimization. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

1,2,4-triazines in organic synthesis. 8. Intramolecular diels-alder reaction of 5-acyl-1,2,4-triazineoxime ethers. New route of synthesis of alkylhetarylketones

Intramolecular diene cycloaddition of 5-acyl-1,2,4-triazineoxime ethers involving a dienophile substituent in the 3-position of the triazine ring is studied. New alkylhetarylketones are synthesized by hydrolysis of the condensed N- and O-containing heterocyclic products. The starting materials are prepared by oxidation of 5-acetyl- and 5-butyryl-3-methylthio-1,2,4-triazineoxime ethers with KMnO₄ to the sulfonyl derviatives with subsequent replacement of the CH₃SO₂ group by sodium 3-butyn-1-oxide, 4-pentyn-1-oxide and o-cyanophenoxide.For Communication 7, see [1].Institute of Chemistry, Agricultural and Teachers University, Siedlce, 08–110, Poland.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 381–389, March, 1999.     

Excited-State Proton Transfer in Hydroxynaphthaldehydes Covalently Bound to Proteins

The kinetics and equilibrium of excited-state proton transfer (ESPT) in 2-hydroxynaphthaldehyde-1 (HNA-2.1) bound to proteins (bovine serum albumin, cytochrome c, and lysozyme) by an alkylamino bond was studied by means of fluorimetric steady-state and time-resolved methods. The results were compared to analogous data for 1-hydroxy naphthaldehyde-4 (HNA-1.4) bound to proteins and for other 2-naphthol derivatives bound to proteins by a sulfonamide bond, Conclusions concerning the influence on ESPT of the mode of binding and of intramolecular hydrogen bonds occurring in the case of HNA-2. 1 were drawn. An intramolecular hydrogen bond enhances the rate of ESPT but the molecular environment in the protein leads to an opposite effect by increasing reorganization energy during proton transfer. The results obtained prove that the mode of binding and the kind of group linking fluorophores to proteins influence considerably the rate and mechanism of ESPT. In naphthol groups bound to proteins by an alkylamino bond, proton dissociation depends strongly on the molecular environment in the macromolecule. This is due to the short length of the alkylamino bridge and its small interaction with electronic orbitals of the aromatic system. Fluorophores bound to proteins by a sulfonamide bond show a higher rate of ESPT, which is due partly to the electron withdrawing effect of the linking arm. The efficiency of ESPT for naphthol groups bound to proteins by a sulfonamide bond is, in most cases, sufficient for acidification of the medium and influence of the proton gradient in biological membranes.     

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).     

High-resolution electronic spectra and luminescence properties of some benzonaphthyridines at 77 K. absorption and fluorescence spectra of 1,5-, 1,6- a

Absorption and fluorescence spectra of 1,5-, 1,6- and 4,6-benzo[h]naphthyridines (BN) were examined in Shpolskii matrices and in n-butanol at 77 K. Vibrational analysis of quasilinear spectra of 1,6- and 4,6-BN in n-hexane matrices was performed. Calcula- tions of the electronic structure of the isomers examined were done using a modified INDO CI method. The results of the experiments and calculations prove the π, π^* state to be the lowest excited singlet state of 1,6- and 4,6-BN molecules; in 1,5-BN molecule the S₁ (n, π^*) state is strongly perturbed by the nearby s₂(π π^*) state.     

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.     

Heterotelechelic poly(oxazolidine-acetals) and their functionalization

Telechelic poly(1,3-oxazolidine-acetal)s with -CH₂OH and -CHO groups were synthesized by polycondensation of the 2-amino-2-hydroxy-1,3-propanediol ( 1 ) (TRIS) with terephthaldehyde ( 2 ). The degree of polymerization (DP) was controlled by the ratio of 1 to 2 at the given reaction time. Characterization was achieved by ¹H and ¹³C NMR and IR spectroscopy. The distribution of oxazolidine-acetal units in the polymer chain has been performed using ESI-MS. The activities of telechelic poly(oxazolidine-acetal) were determined in reaction oxidation (4-chloroperbenzoic acid), reduction (CH₃MgCl) and nucleophilic substitution (acylation, alkylation).     

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.