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991.
Nagihan Saglam Ahmet Colak Kerim Serbest Serdar Karab?cek Saadettin Güner 《Monatshefte für Chemie / Chemical Monthly》2004,15(4):1023-1031
Nucleolytic activities of novel mononuclear Cu(II), homo- and heterodinuclear Cu(II)–Ni(II) complexes with two diester-type ligands were investigated on pCYTEXP by neutral agarose gel electrophoresis. The analyses of the cleavage products obtained electrophoretically indicate that the examined complexes induce very similar conformational changes on supercoiled DNA by converting supercoiled form to nicked form. At concentrations greater than 100M, the complexes possessed effective nucleolytic activities for 10min of incubation time. However, their nucleolytic activities did not increase significantly with longer periods of incubation. The pH-nucleolytic activity profiles of the complexes differed significantly. Metal complex induced DNA cleavage was also tested for inhibition by various radical scavengers. It could be proposed from the data that diffusible intermediate oxidants are not involved in these reactions or they are not necessary for DNA cleavage since none of antioxidants inhibited DNA cleaving activities of the complexes. 相似文献
992.
A variety of biomolecules and their variants, which have previously been problematic to separate, have been analysed using a novel anion-exchange resin based on a non-porous polystyrene polymeric support with a hydrophilic coating and grafted tentacular quaternary ammonium functional groups. The hydrophilic coating results in minimal interaction between the support and the biomolecule, while the highly flexible tentacular-like anion-exchange groups increase the ionic interaction potential and act as an umbrella to hold the proteins away from the surface. Because of the removal of silanophilic interactions, minimisation of hydrophobic interactions, and the highly flexible nature of the tentacle-like ion exchangers, ionic interactions can therefore dominate the separation. As such this phase is highly suited to the separation of highly charged biomolecules and their variants. This polymeric strong anion-exchange (SAX) support was packed into a fused-silica capillary column and, using a salt concentration gradient, various recombinant proteins were analysed by -HPLC resulting in baseline resolution.Awarded a poster prize on the occasion of the Euranalysis XIII conference, Salamanca, Spain, 5–10 September 2004 相似文献
993.
In this paper the formation mechanism of iron macro-spheres in
a plasma medium is dealt with, including the conditions under which such
spheres are formed. The geometry of the spheres referred to above
depends on the main technological parameters involved in the production
of pores. Conditions under which pores occur within macro-spheres are
also established. The radii of these pores are sensitive to the velocity
distribution within the plasma jet section 相似文献
994.
This paper restudies the method of direct chelatometric titration of V(IV) with N-benzoyl-N-phenylhydroxylamine (BPHA) as indicator. The indicator functions entirely differently from indicators hitherto used in chelatometry. The solution contains two independent systems – the indicator and the titrand-titrant system – without any color changing species. The BPHA-V(V) chelate once formed as the result of aerial oxidation constitutes the indicator system and does not react with EDTA. Its color therefore remains unchanged throughout titration. It is not a metallochromic indicator. Its function is that of color-screening. The color of the titrant system deepens during titration, but does not change. The end-point is indicated by one color completely covering up the other. Hence, this method is of purely empirical nature.Received July 5, 2002; accepted February 11, 2003
Published online July 16, 2003 相似文献
995.
The fluorescence quenching reactions of barbaloin with bovine serum albumin (BSA) in pH 7.20 Tris-HCl buffer solution were studied. The quenching mechanism of BSA by barbaloin was interpreted using the Stern-Volmer (S-V) mechanism. The binding constant K values were 2.78 x 10(5) (293 K), 1.87 x 10(5) (310 K), 1.25 x 10(5) (318 K), and the number of binding sites (n) were 1.18, 1.14, and 1.09, respectively. In addition, the thermodynamic functions enthalpy (deltaH degrees ) and entropy (deltaS degrees ) for the reaction were also calculated according to Vant's Hoff equation were -23.7 kJ/mol and 23.6 J/mol, respectively. Plausible explanations of the quenching mechanism are discussed on the basis of a hydrophobic interaction between barbaloin and BSA. 相似文献
996.
Victor A.?ZammitEmail author Nigel T.?Price Vicky N.?Jackson Byun-Sung?Park 《Monatshefte für Chemie / Chemical Monthly》2005,136(8):1299-1309
Summary. Carnitine acyltransferases catalyse equilibria between acyl-CoA esters and the respective acylcarnitines. Therefore, they act not only as pathway enzymes, but also as modulators of acyl-CoA concentrations within individual sub-cellular compartments. Because acyl-CoA esters are potent biologically active metabolites, carnitine acyltransferase activities are potentially able to affect a diverse range of physiological processes, ranging from insulin secretion, to appetite control, and insulin sensitivity of tissues. The distinctive subcellular distributions of the different types of carnitine acyltransferases also enables them to participate in the transfer of acyl moieties across intracellular membranes, and of particular acylcarnitine esters across the plasma membrane and into the plasma. Pharmacological strategies that make use of these properties to improve cell function are discussed. 相似文献
997.
Bernd?Lackner Yulita?Popova Christoph?Etzlstorfer Andrija A.?Smelcerovic Christian W.?Klampfl Heinz?FalkEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(5):777-793
Summary. The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1). 相似文献
998.
Dr. Colin Thomson 《Theoretical chemistry accounts》1968,11(2):165-166
The zero-field splitting parametersD andE have been calculated for naphthalene using T.B.M. and I. R. M. wave functions, and accurate values of all significant two, three and four centre dipolar interaction integrals. Agreement with experiment is improved in the case ofE, but is less satisfactory forD. 相似文献
999.
The degradation behaviour of methylmercury (MeHg) under microwave irradiation is investigated, as is the (different) degradation
behaviour of ethylmercury (EtHg) under similar irradiation. A simple and highly sensitive SPME-GC-pyrolysis-AFS system was
used to analyse the aqueous MeHg and EtHg standard solutions after derivatization with sodium tetraphenylborate (NaBPh4). Samples were irradiated in a microwave digester at microwave powers ranging from 20 to 160 W for durations of 2 to 10 min.
The different tolerances towards microwave treatment of the two organomercury species were evident. Practically no degradation
was experienced for MeHg for up to 8 minutes of irradiation at 120 W or for up to 4 minutes at 160 W. Significant analyte
loss was observed for EtHg after 2 minutes at 40 W of microwave power.
Awarded a Poster Prize on the occasion of the European Winter Conference on Plasma Spectrochemistry, February 2005, Budapest,
Hungary 相似文献
1000.
Renata?Solarska Bruce?D.?Alexander Jan?AugustynskiEmail author 《Journal of Solid State Electrochemistry》2004,8(10):748-756
The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tungstic hexaethoxide precursors with the addition of an organic stabiliser via a sol-gel method is reported. These films have been structurally characterised and both the film morphology and crystalline composition of the films were found to be significantly dependent on the temperature at which the films were annealed and upon the choice of precursor. Films annealed at lower temperatures consisted of amorphous and hexagonal tungsten trioxide, whereas films annealed above 500 °C comprised solely of monoclinic WO3. The electrochromic activity of the films was found to be equally dependent on method of preparation, and both the composition and the structure of the WO3 films were shown to clearly influence the colouration efficiency of the films.Dedicated to Zbigniew Galus on the occasion of his 70th birthday. 相似文献