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131.
Detection and sequencing of phosphopeptides 总被引:4,自引:0,他引:4
Zhou W Merrick BA Khaledi MG Tomer KB 《Journal of the American Society for Mass Spectrometry》2000,11(4):273-282
Consecutive enzymatic reactions of analytes which are affinity bound to immobilized metal ion beads with subsequent direct analysis of the products by matrix-assisted laser desorption/ionization mass spectrometry have been used for detecting phosphorylation sites. The usefulness of this method was demonstrated by analyzing two commercially available phosphoproteins, beta-casein and alpha-casein, as well as one phosphopeptide from a kinase reaction mixture. Agarose loaded with either Fe3+ or Ga3+ was used to isolate phosphopeptides from the protein digest. Results from using either metal ion were complementary. Less overall suppression effect was achieved when Ga3+-loaded agarose was used to isolate phosphopeptides. The selectivity for monophosphorylated peptides, however, was better with Fe3+-loaded agarose. This technique is easy to use and has the ability to analyze extremely complicated phosphopeptide mixtures. Moreover, it eliminates the need for prior high-performance liquid chromatography separation or radiolabeling, thus greatly simplifying the sample preparation. 相似文献
132.
A new micelle-mediated extraction method for preconcentration of ultra-trace quantities of beryllium and aluminum as a prior step to their simultaneous spectrophotometric determination has been developed. Chrome Azurol S (CAS), cetyltrimethylammonium bromide (CTAB) and Triton X-114 were used as chelating agent, cationic surfactant for extraction and co-extraction agent, respectively. Mean centering (MC) of ratio spectra has been used for simultaneous analysis of beryllium and aluminum. The optimal extraction and reaction conditions were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 5-40 ng mL−1 of beryllium and 3-100 ng mL−1 of aluminum. The detection limit of the method is 0.98 and 0.52 ng mL−1 for beryllium and aluminum, respectively. The interference effect of some anions and cations was also tested. The method was applied to the simultaneous determination of beryllium in water samples. 相似文献
133.
134.
Morteza Akhond Mohammad Bagher Najafi Javad Tashkhourian 《Analytica chimica acta》2005,531(2):179-184
In this study, a new poly(vinyl chloride) (PVC) membrane sensor for La3+ ion based on 2,2′-dithiodipyridine as an ion carrier was prepared. This electrode revealed good selectivity for La3+ over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of La3+ sensor were investigated. The electrode exhibited a Nernstian slope of 20.0 ± 1.0 mV per decade of La3+ over a concentration range of 7.1 × 10−6 to 2.2 × 10−2 M of La3+ in the pH range 3.3-8.0. The response time was about 7 s and the detection limit was 3.1 × 10−6 M. The electrode can be used for at least 2 months without a considerable divergence in potential. The proposed electrode was used as an indicator electrode in potentiometric titration of oxalate and fluoride ions and was applied for determination of F− ion in mouthwash solution. 相似文献
135.
M. Montazerozohori S.A. Musavi A. Masoudi-asl H. Mohammadi R. Naghiha A. Assoud 《Arabian Journal of Chemistry》2019,12(7):1463-1473
Three new four coordinated zinc(II) complexes have been synthesized and characterized by IR, UV, elemental analysis, 1H and 13C NMR and X-ray single crystal analysis. The elemental analyses of the complexes are in agreement with the general formula of ZnLX2 wherein L = Schiff base ligand and X = Cl?, Br? and I?. Low molar conductivities in DMF indicated non-electrolyte character of all complexes. Spectroscopic studies well confirmed the coordination via azomethine nitrogens of the ligand to zinc ion. The single crystal X-ray analysis shows that ZnLBr2 crystallizes in the triclinic crystal system with space group . It contains two crystallographically independent molecules noted as A and B, with both Zn1A and Zn1B being almost in perfect tetrahedral environments (τ4 = 0.94 for Zn1A and τ4 = 0.93 for Zn1B). A detailed structural analysis shows that there are three non-classical hydrogen bondings of C–H…Br in the structure. Various C–H…π and C–H…Br interactions play an important role in stabilizing the molecular structure and then give rise to a 3D supramolecular structure of the ZnLBr2 complex. After characterization, the Schiff base and its complexes were screened in vitro for their antibacterial and antifungal activities by disk diffusion technique. Also the ability of the complexes for DNA cleavage was studied by agarose gel electrophoresis method. Finally, thermal behavior of the complexes has been studied by thermo-gravimetry and then some activation kinetics parameters of decomposition steps were evaluated based on TG/DTG plots. 相似文献
136.
137.
Gaussian free field in the background of correlated random clusters,formed by metallic nanoparticles
Jafar Cheraghalizadeh Morteza N. Najafi Hossein Mohammadzadeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(5):81
The effect of metallic nano-particles (MNPs) on the electrostatic potential of a disordered 2D dielectric media is considered. The disorder in the media is assumed to be white-noise Coulomb impurities with normal distribution. To realize the correlations between the MNPs we have used the Ising model with an artificial temperature T that controls the number of MNPs as well as their correlations. In the T → 0 limit, one retrieves the Gaussian free field (GFF), and in the finite temperature the problem is equivalent to a GFF in iso-potential islands. The problem is argued to be equivalent to a scale-invariant random surface with some critical exponents which vary with T and correspondingly are correlation-dependent. Two type of observables have been considered: local and global quantities. We have observed that the MNPs soften the random potential and reduce its statistical fluctuations. This softening is observed in the local as well as the geometrical quantities. The correlation function of the electrostatic and its total variance are observed to be logarithmic just like the GFF, i.e. the roughness exponent remains zero for all temperatures, whereas the proportionality constants scale with T ? T c . The fractal dimension of iso-potential lines (D f ), the exponent of the distribution function of the gyration radius (τ r ), and the loop lengths (τ l ), and also the exponent of the loop Green function x l change in terms of T ? T c in a power-law fashion, with some critical exponents reported in the text. Importantly we have observed that D f (T) ? D f (T c ) ~ 1/√ξ(T), in which ξ(T) is the spin correlation length in the Ising model. 相似文献
138.
139.
Elmira Ghabraie Morteza Bararjanian Saeed Balalaie Frank Rominger Hamid Reza Bijanzadeh 《Helvetica chimica acta》2011,94(8):1440-1447
The Michael‐type addition of a 4‐hydroxycoumarin (=4‐hydroxy‐2H‐1‐benzopyran‐2‐one) 1 to a β‐nitrostyrene (=(2‐nitroethenyl)benzene) 2 in the presence of AcONH4 leads to substituted (3E)‐3‐[amino(aryl)methylidene]chroman‐2,4‐diones (=(3E)‐3‐[amino(aryl)methylene]‐2H‐1‐benzopyran‐2,4(3H)‐diones) 4 (Table 1). High yields, short reaction time, and easy workup are advantages of this novel one‐pot three‐component reaction. 相似文献
140.
Mahmood Esna-Ashari Mansour Gholami Mohammad Ali Zolfigol Morteza Shiri Aghil Mahmoodi-Pour Mehdi Hesari 《Chromatographia》2008,67(11-12):1017-1020
In this study, trans-resveratrol levels were determined in 147 Iranian grape cultivars using a modified extraction and gradient HPLC procedure with photodiode array detection. It was found that 41 out of 147 cultivars contained significant levels of trans-resveratrol. The detected amounts ranged from 0.98 to 6.25 mg kg?1 fresh weight with a mean value of 3.59 (white grapes) and 3.08 mg kg?1 (red grapes), respectively. 相似文献