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991.
Vitorino R Lobo MJ Duarte JA Ferrer-Correia AJ Domingues PM Amado FM 《Biomedical chromatography : BMC》2004,18(8):570-575
Salivary peptides are involved in a wide range of functions constituting the first line of defence of oral cavity and precursors of dental pellicle formation. The presence of mucins in saliva makes difficult the analysis of the proteic content. This is due mainly to aggregation phenomenon between mucins and other high molecular weight glycoproteins and salivary proteins. Considering the importance of salivary peptides in biological functions, we have evaluated the influence of four different extraction methodologies on the separation and identification of these proteins by HPLC-MS. Based on their molecular weight, we identified a total of 22 peptides when extraction was performed using a solution of guanidine (6 m), compared with 14 peptides identified when saliva is acidified with TFA, which is an often used procedure. Our results also show the presence of mucin bind peptides, which include statherin, PRP1, PRP3, Histatin 1 and Histatin 5. 相似文献
992.
M. C. T. P. Carvalho J. A. M. S. Duarte 《Zeitschrift für Physik B Condensed Matter》1988,70(2):203-208
Exact series for lattices of dimension between 2 and 6 are used to report on the asymptotic features of the scaling function for the average number of clusters in directed percolation, close to, and away from, the most recent estimated intervals forp
c
. Scanning of the noncritical regions yields exponent ranges compatible with the undirected percolation equivalents. Close top
c
the scaling function varies fairly linearly in terms of the variablez=(p–p
c
)s
and this result is rather stable particularly bearing in mind the modestly available precision forp
c
in higher dimensionalities. 相似文献
993.
994.
Ana M Martins Rita Branquinho Jinlan Cui Alberto R Dias M.Teresa Duarte José Fernandes Sandra S Rodrigues 《Journal of organometallic chemistry》2004,689(14):2368-2376
[M(CpBz)(CO)3CH3] (M=Mo, 2a, W, 2b; CpBz=C5(CH2Ph)5) have been prepared and reacted with PCl5 and PhI · Cl2. Depending on the metal and on the chlorinating reagent used [Mo(CpBz)(η2-COCH3)Cl3], 3, [W(CpBz)Cl4], 4, [Mo(CpBz)(CO)3Cl], 5 and [Mo(CpBz)Cl4], 6 have been obtained. The molecular structures of all compounds are reported and two conformations have been characterised for the benzyl substituents. In complexes 2a, 2b and 5 one phenyl ring bends towards the metals while in 3 and 4 the five phenyls point opposite to the metals. 相似文献
995.
The composition of the water-soluble organic matter from fine aerosols collected in a rural location during two different meteorological conditions (summer and autumn) was investigated by UV-vis, synchronous fluorescence (with Δλ = 20 nm), FT-IR and CPMAS-13C NMR spectroscopies. A seasonal variation in the concentration of total carbon, organic carbon and water-soluble organic carbon was confirmed, with higher values during the autumn and lower values during the summer season. The chemical characterisation of the water-soluble organic matter showed that both samples are dominated by a high content of aliphatic structures, carboxyl groups and aliphatic carbons single bonded to one oxygen or nitrogen atom. However, the autumn sample exhibits a higher aromatic content than the summer sample, plus signals due to carbons of phenol, ketones and methoxyl groups. These signals were attributed to lignin breakdown products which are likely to be released during wood combustion processes. The obtained results put into evidence the major contribution of biomass burning processes in domestic fireplaces during low temperature conditions into both the concentration and the bulk chemical properties of the WSOC from fine aerosols. 相似文献
996.
Oliveira BG Duarte EM Araújo RC Ramos MN Carvalho AB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(3):491-494
Ab initio calculations are performed at the MP2/6-311++G(d,p) and DFT/B3LYP/6-311++G(d,p) theoretical levels to obtain geometries, H-bond energies and harmonic infrared vibrational properties for the Cs symmetry structures of heterocyclic hydrogen-bonded complexes, CnHmY-HX. The H-bond lengths in DFT/B3LYP calculation level are in better agreement with the experimental values than the MP2 results. The geometry optimization are interpreted in terms of hydrogen bond nonlinearity represented by theta; and phi angles, once the hydrogen bond is formed among n-electrons pairs of the heteroatom in heterocyclic and the hydrogen atom in HX. The hydrogen bond energy after of the zero-point vibrational energy (ZPE) and basis set superposition error (BSSE) corrections are overestimated at DFT/B3LYP, whereas the MP2 BSSE corrections are very large than corresponding DFT/B3LYP. For example, the BSSE corrections for the C2H4S-HNC complex are 7.60 and 0.09 kJ mol(-1) in MP2 and DFT/B3LYP calculations levels, respectively. The new vibrational modes in infrared harmonic spectrum arising from complexation show several interesting features, especially the intermolecular stretching mode. 相似文献
997.
J. Regis Botelho A. Duarte Gondim I. M Garcia dos Santos P. O. Dunstan A. G. Souza V. J. Fernandes Jr. A. S. Araújo 《Journal of Thermal Analysis and Calorimetry》2004,75(2):607-613
The standard molar enthalpy of formation of crystalline dialkyldithiocarbamate chelates, [Pd(S2CNR2)2], with R=CH3 and i-C3H7, was determined through reaction-solution calorimetry in 1,2-dichloroethane, at 298 K. Using the standard molar enthalpies
of formation of the gaseous chelates, the homolytic (526±18 and 666±10) and heterolytic (2693±18 and 2957±10 kJ mol-1) mean enthalpies of palladium-sulphur bond dissociation were calculated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
998.
Eduardo CortS Corts Ana MarÍA Mendoza Ambrosio 《Journal of heterocyclic chemistry》1996,33(4):1159-1162
The preparation of twelve novel substituted [1,2,4]oxadiazolo[4,5-a][1,5]benzodiazepines which have potentially useful pharmacological properties; by 1.3-dipolar cycloaddition of benzonitrile oxides, generated in situ from benzohydroxamoyl chloride and triethylamine, to 1,5-benzodiazepine derivatives, is described. The structure of all products was corroborated by ir, 1H-nmr, 13C-nmr and ms. 相似文献
999.
Javier Cataln Margarita Menndez Jos Laynez Rosa María Claramunt Marta Bruix Javier De Mendoza Jos Elguero 《Journal of heterocyclic chemistry》1985,22(4):997-1000
The pKa values of five aminopyrazoles [3(5)-amino, 1-methyl-3-amino, 1-methyl-5-amino, 4-amino and 1-methyl-4-amino] were determined. The aqueous basicities are discussed in terms of tautomerism (72% of 3-amino tautomer), protonation site (only 4-aminopyrazoles protonate on the amino group) and amino substituent effects. The results of theoretical calculations, carried out at the semiempirical INDO level, indicate that in the gas phase 3- and 5-aminopyrazoles protonate on the pyrazolic nitrogen atom, whereas 4-aminopyrazoles possess similar proton affinities for both nitrogen atoms (pyrazolic and amino). 相似文献
1000.
A. G. Bibiloni M. C. Caracoche A. R. Lopez García J. A. Martinez L. A. Mendoza Zelis R. C. Mercader A. F. Pasquevich 《Hyperfine Interactions》1977,5(1):381-389
The hyperfine interaction of140Ce in nickel has been investigated by the time-differential perturbed-angular-correlation technique (TDPAC). The probe was produced by isotope separator implantation of the fission product140Xe, the - decay chain of which finally populates excited states of140Ce.Different spin rotation spectra were observed before and after an 8 h annealing at 415°C. The analysis of the spectra led to the conclusion that the Ce ions were in the diamagnetic 4+ state. The dominant contributions to the hyperfine interaction are two different magnetic hyperfine fields: |H
hf
1|=385±7 kOe and |H
hf
2|=276±12 kOe.H
hf
1 disappears after annealing. The fraction of nuclei which observeH
hf
2 is increased by the annealing procedure from 16% to 75%. It is assumed thatH
hf
1 is the hyperfine field of CeNi in an unperturbed substitutional site andH
hf
2 is attributed to Ce ions which have trapped a single vacancy. 相似文献