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81.
High-resolution electron energy loss spectroscopy has been used to study low-energy bulk excitation modes of planar-bound electrons (bulk plasmons) in nickel. We observed for the first time a bulk plasmon at about 1.2 eV, in agreement with dielectric theory. The behavior of its amplitude with the off-specular angle ensures the dipolar nature of such mode. On the other hand, the intensity of the plasmon peak is vanishing upon ion bombardment due to the sputtering-induced modification of dielectric function. 相似文献
82.
Oliviero G Amato J Borbone N D'Errico S Galeone A Mayol L Haider S Olubiyi O Hoorelbeke B Balzarini J Piccialli G 《Chemical communications (Cambridge, England)》2010,46(47):8971-8973
The biophysical and biological properties of unprecedented anti-HIV aptamers are presented. The most active aptamer (1L) shows a significant affinity to the HIV protein gp120. 相似文献
83.
Pescitelli G Berova N Xiao TL Rozhkov RV Larock RC Armstrong DW 《Organic & biomolecular chemistry》2003,1(1):186-190
A phenyl-substituted chiral dihydrofuroangelicin, 4-methyl-8-(2-E-phenylethenyl)-8,9-dihydro-2H-furo[2,3-h]- 1-benzopyran-2-one, synthesized in racemic form, has been resolved by HPLC chiral separation, and its absolute configuration determined by the non-empirical exciton chirality method. The solution conformation has been investigated through NMR and molecular modeling methods: two minima found by molecular mechanics and DFT methods are in keeping with observed 1H-1H 3J coupling constants and NOE effects. The experimental CD spectrum for the second eluted enantiomer shows a positive couplet between 230 and 350 nm (amplitude A = + 15.7); by application of the exciton chirality method, the absolute configuration of this enantiomer at C8 is determined as (S). The experimental spectrum is in very good agreement with the one evaluated by means of DeVoe coupled-oscillator calculations, using the DFT calculated geometries. 相似文献
84.
Summary Separation methods have been developed by means of reversed-phase ion-interaction HPLC chromatography, using octylamine ortho-phosphate as the interaction reagent. In particular the separation of some antioxidants of relevant interest (known also as radical scavengers) such as L(+)-ascorbic acid, uric acid, orotic acid and cysteine, as well as the separation of creatine and creatinine have been performed. The results have been applied to the analysis of different kinds of milk, namely a dairy farm milk, a commercial whole fresh milk and a UHT-sterilized one: creatinine, uric, L(+)-ascorbic and orotic acids were identified and quantified. 相似文献
85.
P. Bruno M. Caselli G. de Gennaro P. Ielpo T. Ladisa C. M. Placentino 《Chromatographia》2006,64(9-10):537-542
A flow injection analysis system with on-line enrichment was developed for simultaneous determination of trace levels of Cu2+, Ni2+, Zn2+, Co2+, Mn2+, Cd2+, Pb2+ and Fe3+, by high-performance ion chromatography (HPIC) with spectrophotometric detection. It is a highly sensitive and low cost alternative methodology. Ion Pac CS5A was used as the analytical column with eluent composition of sodium nitrate 160 mM and oxalic acid 36 mM. Quantification after post-column reaction with PAR allows detection limits between 0.5 and 5.0 ppb to be attained. The total analysis time is less than 30 min. The proposed procedure was compared with a large volume direct injection method using loop volumes up to 5 mL. Both procedures were applied to the analysis of heavy metals in the PM10 fraction of atmospheric particulate samples. Airborne pollutants such as nickel and cobalt can be quantified in 24 h samples of particulate matter at concentrations of a few ng m?3. 相似文献
86.
Purification of Phleum pratense pollen extract by immunoaffinity chromatography and high-performance ion-exchange chromatography 总被引:1,自引:0,他引:1
E Bolzacchini P Di Gennaro G Di Gregorio B Rindone P Falagiani G Mistrello I Sondergaard 《Journal of chromatography. A》1991,548(1-2):229-234
Basic allergens of Phleum pratense pollen extract have been purified by either sequence gel filtration-ion-exchange high-performance liquid chromatography (HPIEX) and size-exclusion HPLC or sequence gel filtration-immunoaffinity chromatography and HPIEX. The second procedure seems to be suitable for preparative purposes. 相似文献
87.
The Carlo Alberto Canal connects Bormida and Tanaro rivers in Piedmont (ITALY). It was created for irrigation purposes but since its waters are suspected to be polluted, a sampling campaign was performed by the ARPA of Alessandria. The physico-chemical parameters analysed along 3 years (1998-2000) were investigated by multivariate chemometric methods. PCA showed that the waters situation depends heavily on the sampling period. Also a Kohonen self-organising map confirmed the clustering observed, providing insights into the causes of the clusterisation. New samplings are now being performed and a larger set of environmental variables is determined on each sample. 相似文献
88.
Kristenson EM Angioi S Vreuls RJ Gennaro MC Brinkman UA 《Journal of chromatography. A》2004,1058(1-2):243-249
A number of chloroanilines were extracted from soil by means of miniaturised pressurised liquid extraction (PLE). The extraction procedure was optimised for both large-volume on-column (LV-OC) and programmed-temperature vaporisation (PTV) injections combined with GC-MS. Hexane was the only extraction solvent suited for LV-OC and hexane/acetone gave the best results when using a PTV. Overall, the hexane/acetone-plus-PTV procedure shows better results than the hexane-plus-LV-OC method in terms of analyte recovery (36-109% versus 5-87%), repeatability (8-13% versus 4-31%) and detection limits. Both approaches allow detection of the chloroanilines in complex soil samples down to the 5-50 ng/g range. However, the PTV-based procedure is superior as regards robustness: over one hundred samples can be analysed without any maintenance being required. 相似文献
89.
Esposito V Randazzo A Piccialli G Petraccone L Giancola C Mayol L 《Organic & biomolecular chemistry》2004,2(3):313-318
NMR, molecular dynamics and mechanics calculations, and CD spectroscopy were used to characterise three tetramolecular quadruplex complexes: [d(TG(Br)GGT)](4), [d(TGG(Br)GT)](4) and [d(TGGG(Br)T)](4), where G(Br) indicates an 8-bromoguanine residue. All three quadruplexes are characterised by a 4-fold symmetry with all strands parallel to each other and, differently to what has been observed for other parallel quadruplex structures, with a tetrad (formed by 8-Br-dGs) in a syn conformation. The whole of the data demonstrates that the replacement in turn of different dG residues with 8-Br-dG in the sequence 5[prime or minute]-TGGGT-3[prime or minute] affects the resulting structures in different ways, leading to different CD profiles and thermal stabilities. Particularly, [d(TG(Br)GGT)](4) and [d(TGG(Br)GT)](4) are more stable than the unmodified sequence, whereas [d(TGGG(Br)T)](4) is much less stable than the natural counterpart. The conformational features found in the three quadruplexes might, in principle, amplify the range of applicability of synthetic oligonucleotides as aptamers or catalysts, by providing novel structural motifs with different molecular recognition capabilities from those of native DNA sequences. 相似文献
90.
Gennaro LA Vadhanam M Gupta RC Vouros P 《Rapid communications in mass spectrometry : RCM》2004,18(14):1541-1547
Benzo[a]pyrene (BP) is a ubiquitous environmental polycyclic aromatic hydrocarbon (PAH) which, upon metabolic conversion to reactive benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), has been found to attach covalently to DNA. Given the low level of DNA adducts typically present in vivo or in vitro, an essential first step prior to capillary electrophoresis/mass spectrometry (CE/MS) (or liquid chromatography/mass spectrometry (LC/MS)) analysis of the DNA digests is the removal of the bulk non-adducted nucleotides, enzymes or salts, and isolation of enriched adducts. This report focuses on the development of novel sample handling methods aimed at facilitating the analysis of BPDE-DNA adducts by CE/MS. This approach involves a simple variation on the digestion procedure, in combination with the use of metal affinity ZipTips for the more efficient cleanup of BPDE-DNA adducts formed in vitro for subsequent CE/MS analysis. The previously described digestion procedure, consisting of micrococcal nuclease, spleen phosphodiesterase and nuclease P1, allows for selective dephosphorylation of normal nucleotides, while leaving adducted nucleotides intact. Metal affinity ZipTips, typically used for selective extraction of phosphopeptides, were used here for extraction of adducted nucleotides. The utility of metal affinity SPE was tested on mixtures of dG and dGp, wherein nucleotide extracts contained no detectable nucleosides by CE/UV analysis. An in vitro BPDE-DNA incubation was then digested using the above procedure. Metal affinity solid-phase extraction (SPE) was subsequently used for the selective isolation of phosphorylated components, i.e., adducted nucleotides, from the mixture of enzymes and non-adducted nucleosides. SPE extracts were enriched in nucleotide adducts and analyzed using sample stacking and CE/MS. This method has several advantages over previously described cleanup procedures for dGp-BPDE adducts: fast, simple, uses commercially available materials, no need for excessive dilution (small scale), the suitability for use with automation, and possible applicability to other bulky hydrophobic adducts. 相似文献