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81.
82.
Rai DK Green BN Landin B Alvelius G Griffiths WJ 《Journal of mass spectrometry : JMS》2004,39(3):289-294
Within a mixture of proteins, minor polymorphic components are difficult to identify using a conventional proteomic approach. Their identification generally requires multi-dimensional separation steps, before or after proteolytic cleavage, followed by sequence analysis of the proteolytic products. In this study, we investigated the potential of tandem mass spectrometry for protein characterization by identifying the delta-beta hybrid human hemoglobin variant Lepore-Boston-Washington using electrospray ionization tandem mass spectrometry. Hemoglobin Lepore-Boston-Washington occurs mainly in heterozygotes, where it comprises approximately 10% of the total non-alpha-chains, the dominant non-alpha-chain being the normal beta (approximately 90%). Furthermore, Hemoglobin Lepore-Boston-Washington has an average molecular mass (15,865.23 Da) that is only 2 Da lower than that of the normal beta-chain (15,867.24 Da). Consequently, it cannot be resolved from the normal beta-chain by mass spectrometry. Here we show how Hemoglobin Lepore-Boston-Washington was identified directly from the diluted blood of a heterozygote by analyzing the product ions from the Lepore-Boston-Washington and normal beta-chain ions without prior separation of the individual chains. This study shows the potential of the tandem mass spectrometry for identifying a minor component in an unseparated mixture of proteins. 相似文献
83.
Chung P Ajitanand NN Alexander JM Anderson M Best D Brady FP Case T Caskey W Cebra D Chance JL Cole B Crowe K Das A Draper JE Gilkes ML Gushue S Heffner M Hirsch AS Hjort EL Huo L Justice M Kaplan M Keane D Kintner JC Klay J Krofcheck D Lacey RA Lauret J Lisa MA Liu H Liu YM McGrath R Milosevich Z Odyniec G Olson DL Panitkin SY Pinkenburg C Porile NT Rai G Ritter HG Romero JL Scharenberg R Schroeder L Srivastava B Stone NT Symons TJ Wienold T Witt R Whitfield J Wood L Zhang WN;E Collaboration 《Physical review letters》2001,86(12):2533-2536
Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy. 相似文献
84.
The possibilities of graphic STM image simulation of a clean Si(1 1 1) 7 × 7 surface at atomic level are indicated. The presented procedure takes into account various types of deformation on the surface near the Fermi level in order to classify them and explain their origin. It also gives a clear hint to insert relevant physical phenomena in a suggested analysis. This goal is achieved exploiting the results of DAS (dimmer adatom stacing fault) model by means of standard mathematical programmes. A clean Si(1 1 1) 7 × 7 surface is considered as the representative example, but similar evaluation is possible for another non-metal and metal surfaces. 相似文献
85.
Proton induced X-ray emission has been used to measureL-subshell and total ionization cross-sections of Au, Pb and Bi in the energy range of 200–350 keV. The ionization cross-sections have been extracted using the X-ray spectra and other quantities like fluorescence yields, transition probabilities, relative widths and Coster-Krönig fraction etc. involved in the process. The results have been compared with the cross-sections measured before and discussed in the light of known theories regarding the ion-atom collisions. 相似文献
86.
Gundibasappa K. Nagaraja Vijayavittala P. Vaidya Koodamara Sheshappa Rai Kittappa M. Mahadevan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2797-2806
A novel and efficient method for the synthesis of substituted thiazepines and diazepines has been developed. A simple one-pot reaction of chalcones 1a–f with 1-amino-2-mercapto-5-phenyl-1,3,4-triazole and o-phenylenediamine in the presence of a catalytic amount of sodium acetate under microwave irradiation gave 2-(3,8-diphenyl-7,8-dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazepin-6-yl)phenoles 2a–f and 2-(2-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-4-yl)phenoles 3a–f, respectively. The structure of all the synthesized compounds was elucidated on the basis of elemental analysis, IR, 1H and 13C NMR, and mass spectral data. 相似文献
87.
Why chaos is rarely observed in natural populations 总被引:2,自引:0,他引:2
An attempt has been made to understand why chaotic dynamics have received poor evidential support from field studies. Our study opens up the possibility that the cause of failure might not be poor quality of data, as pointed out by earlier authors, but an ecological reality. We have designed two model food chains to examine whether there is a biological basis for the crisis. This investigation is effected with the help of a new method which we introduce at an appropriate place in the text. The fact that chaos exists in a narrow range of parametric values in both the model systems suggests that the crisis indeed has a biological origin. 相似文献
88.
The solubility of NdPO4(c) was studied at 23±2 °C from both the over and undersaturation directions, with pH ranging from 0 to 9, P concentrations ranging from 0.0003 to 1.00M, and equilibration periods ranging from 6 to 57 days. Equilibrium was reached in <6 days. From the H+, Nd, and P concentrations in equilibrated solutions, the logarithm of the thermodynamic equilibrium constant for the reaction (NdPO4(c) Nd3++PO4
3-) was calculated to be -24.65±0.23 and the value of the Pitzer ion-interaction parameter (2)for Nd3+-H2PO4
- was determined to be -92.9. Predictions based on these thermodynamic quantities were in excellent agreement with the experimental data. 相似文献
89.
Pandey VK Singh VB Rai AK Asthana BP Rai SB Rai DK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(2):213-218
Raman spectra of 2 (3H) benzofuranone have been recorded in the region 400-3200 cm(-1) and the IR spectra have been recorded in the region 200-4000 cm(-1). Vibrational frequencies for the fundamental modes of this bicyclic heteroatomic molecule have also been calculated using Austin method 1 (AM1) semiempirical molecular orbital method. Vibrational assignments have been made for the fundamental modes and the observed combination and overtone bands are also assigned. A splitting in the carbonyl group (C=O stretching) frequency observed at 1640-1660 cm(-1) in both Raman and IR spectra, is explained as Fermi-resonance. Net atomic charges for each atom of this molecule along with its heat of formation were also calculated. It is evident from the calculations that the 2 (3H) benzofuranone is more stable than the 3 (2H) benzofuranone in contrast to earlier estimates. 相似文献
90.
Quantitative determination of isoquinoline alkaloids and chlorogenic acid in Berberis species using ultra high performance liquid chromatography with hybrid triple quadrupole linear ion trap mass spectrometry 下载免费PDF全文
Awantika Singh Vikas Bajpai Sunil Kumar Kamal Ram Arya Kulwant Rai Sharma Brijesh Kumar 《Journal of separation science》2015,38(12):2007-2013
Berberis species are well known and used extensively as medicinal plants in traditional medicine. They have many medicinal values attributable to the presence of alkaloids having different pharmacological activities. In this study, a method was developed and validated as per international conference on harmonization guidelines using ultra high performance liquid chromatography with hybrid triple quadrupole‐linear ion trap mass spectrometry operated in the multiple reaction monitoring mode for nine bioactive compounds, including protoberberine alkaloids, aporphine alkaloids and chlorogenic acid. This method was applied in different plant parts of eight Berberis species to determine variations in content of nine bioactive compounds. The separation was achieved on an ACQUITY UPLC CSH? C18 column using a gradient mobile phase at flow rate 0.3 mL/min. Calibration curves for all the nine analytes provided optimum linear detector response (with R2 ≥0.9989) over the concentration range of 0.5–1000 ng/mL. The precision and accuracy were within RSDs ≤2.4 and ≤2.3%, respectively. The results indicated significant variation in the total contents of the nine compounds in Berberis species. 相似文献