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41.
Bermel W Bertini I Felli IC Matzapetakis M Pierattelli R Theil EC Turano P 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,188(2):301-310
Attempts are made to efficiently decouple (13)C nuclei without significant loss of coherence during the application of the decoupling package. Such attempts are based on the S(3)E spin-state selection method. A newly developed double S(3)E (DS(3)E) is particularly efficient for C(alpha) detection for proteins as large as 480 kDa. 相似文献
42.
43.
This study aimed to carry out complete 1H and 13C NMR assignment of 13 protobassic acid saponins, including arganins A–C ( 1 – 3 ) and F ( 4 ), butyrosides B–D ( 5 – 7 ), tieghemelin ( 8 ), 3′-O-glucosyl-arganin C ( 9 ), Mi-saponins A–C ( 10 – 12 ), and mimusopsin ( 13 ), recorded in methanol-d4. This was accomplished by the analysis of high-resolution one-dimensional (1D) NMR (1H and 13C), two-dimensional (2D) NMR (1H–1H COSY, HSQC, and HMBC), and selectively excited 1D TOCSY spectra. Before this study, 1H and 13C NMR data of arganins A–C ( 1 – 3 ) and F ( 4 ) were partially assigned. Our effort leads to their complete assignment, especially the glycon residue, and revises some reported data. Some revisions of the 1H and 13C NMR data in the glycon part of butyroside C ( 6 ), tieghemelin ( 8 ), Mi-saponin A ( 10 ), and mimusopsin ( 13 ) were made. Those data of butyrosides B and D ( 5 & 7 ) and Mi-saponin B ( 11 ), which had not been recorded in methanol-d4, are provided. In addition, the 1H and 13C NMR data of Mi-saponin C ( 12 ) are reported for the first time. These data, being recorded in methanol-d4, should be more friendly for use as a reference for identifying the related triterpenoid saponins. 相似文献
44.
Compound annotation using MS/MS data is the major bottleneck in interpretation of mass spectrometry data during non-targeted screening and suspect screening exposomics studies. Apart from compound identification using available databases or mass spectral libraries, the true challenge comes when completely new compounds have to be identified. Along with recent advances in MS instrumentation that set grounds to a new revolutionary age in environmental exposomics, a multitude of cheminformatics annotation approaches has been developed. Herein, we review the basic principles of the cutting-edge cheminformatics MS-based approaches employed in eco-exposome annotation.We give a solid background discussing the eco-exposome concept in relation to the advances in MS instrumentation, and define the three crucial cheminformatics tasks used in the eco-exposome annotation: molecular formula assignment, compound prioritization and compound annotation. The basic principles of compound annotation are discussed, which are based on three approaches of utilizing structural information inherent to MS data. These involve direct, indirect and joint annotation approaches. We assess their performance through the ability to annotate eco-exposome constituents. We discuss future perspectives and give directions to new annotation strategies and performance evaluation protocols aiming to solve current issues hampering the incorporation of cheminformatics annotation approaches in regular eco-exposome annotation workflows. 相似文献
45.
脯氨酸类衍生物结构独特,鲜有报道利用核磁共振(nuclear magnetic resonance,NMR)技术对氨基酸的手性进行鉴别.利用多种NMR技术:1H NMR、1H-1H同核位移相关谱(1H-1H COSY)、1H-1H质子全相关谱(1H-1H TOCSY)、1H-1H核Overhauser效应谱(1H-1H NOESY)、13C NMR、无畸变的极化转移增强法(DEPT135°)、1H-13C检出1H的异核单量子相干(1H-13C HSQC)和1H-13C检出1H的异核多键相关(1H-13C HMBC),对脯氨酸类N-酰胺衍生物两种构象异构体的1H和13C NMR进行了全归属,确定了室温下在二甲基亚砜(DMSO)中L型和D型的顺反异构体以相同的比例同时存在. 相似文献
46.
《光谱学快报》2013,46(5):647-663
The normal coordinate analysis of the title complex, 1,2-bis(2-formylglycinebenzenesulfenyl) ethane Pd(II) dichloride has been carried out by using the Urey-Bradley force field. According to the molecular structure determined by x-ray crystallographic analysis, 182 internal coordinates were established and 112 theoretical vibration frequencies agree well with the observed values with the average difference of 2.53 cm?1 and the maximum deviation of 16.0 cm?1. 相似文献
47.
We study bicriteria problems of minimizing maximum tardiness and total due date assignment cost in various scheduling environments. We assume that each job can be assigned a different due date without any restriction, and that each due date assignment cost is a non-decreasing function of the quoted due date. We settle the complexity of most of the problems studied by either proving that they are NP-hard or finding a polynomial time solution for them. We also include approximation and non-approximability results for several parallel-machine problems. 相似文献
48.
Kristiansen PE Mitchell DJ Evans JN 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,157(2):253-266
A full investigation of the possible homonuclear double-quantum recoupling sequences, based on the RN family of sequences with N < or = 20, is given. Several new RN sequences, R16(6)(5), R18(8)(5), and R18(10)(5), were applied at high magic-angle spinning rates and compared with theory. The R18(10)(5) technique can be used to recouple dipolar couplings at spinning rates up to 39 kHz, and the application of the sequence in an INADEQUATE experiment is shown for a spinning rate of 30 kHz. 相似文献
49.
We analyse thegeneralised assignment problem under the assumption that all coefficients are drawn uniformly and independently from [0, 1]. We show that such problems can be solved exactly with high probability, in a well-defined sense. The results are closely related to earlier work of Lueker, Goldberg and Marchetti-Spaccamela and ourselves.Supported by NATO grant RG0088/89.Supported by NSF grant CCR-8900112 and NATO grant RG0088/89. 相似文献
50.
The generalized assignment problem can be viewed as the following problem of scheduling parallel machines with costs. Each job is to be processed by exactly one machine; processing jobj on machinei requires timep
ij
and incurs a cost ofc
ij
; each machinei is available forT
i
time units, and the objective is to minimize the total cost incurred. Our main result is as follows. There is a polynomial-time algorithm that, given a valueC, either proves that no feasible schedule of costC exists, or else finds a schedule of cost at mostC where each machinei is used for at most 2T
i
time units.We also extend this result to a variant of the problem where, instead of a fixed processing timep
ij
, there is a range of possible processing times for each machine—job pair, and the cost linearly increases as the processing time decreases. We show that these results imply a polynomial-time 2-approximation algorithm to minimize a weighted sum of the cost and the makespan, i.e., the maximum job completion time. We also consider the objective of minimizing the mean job completion time. We show that there is a polynomial-time algorithm that, given valuesM andT, either proves that no schedule of mean job completion timeM and makespanT exists, or else finds a schedule of mean job completion time at mostM and makespan at most 2T.
Research partially supported by an NSF PYI award CCR-89-96272 with matching support from UPS, and Sun Microsystems, and by the National Science Foundation, the Air Force Office of Scientific Research, and the Office of Naval Research, through NSF grant DMS-8920550.Research supported in part by a Packard Fellowship, a Sloan Fellowship, an NSF PYI award, and by the National Science Foundation, the Air Force Office of Scientific Research, and the Office of Naval Research, through NSF grant DMS-8920550. 相似文献