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101.
Juhlin KD Swift DD Lacey MP Correa PE Keough TW 《European journal of mass spectrometry (Chichester, England)》2005,11(2):161-167
Many laboratories identify proteins by searching tandem mass spectrometry data against genomic or protein sequence databases. These database searches typically use the measured peptide masses or the derived peptide sequence and, in this paper, we focus on the latter. We study the minimum peptide sequence data requirements for definitive protein identification from protein sequence databases. Accurate mass measurements are not needed for definitive protein identification, even when a limited amount of sequence data is available for searching. This information has implications for the mass spectrometry performance (and cost), data base search strategies and proteomics research. 相似文献
102.
A. A. Lacey C. Nikolopoulos M. Reading 《Journal of Thermal Analysis and Calorimetry》1997,50(1-2):279-333
Reading and co-workers introduced a new technique a few years ago called Modulated Differential Scanning Calorimetry or MDSC. Here the first part of a theoretical analysis for this technique is given. A simple mathematical model for modulated differential scanning calorimetry in the form of an ordinary differential equation is derived. The model is analysed to find the effect of a kinetic event in the form of a chemical reaction. Some possible sources of error are discussed. A more sophisticated version of the model allowing for spatial variation in a calorimeter is developed and it is seen how it can be reduced to the earlier model. Some preliminary work on a phase change is also presented.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday 相似文献
103.
Eric E. Kingston James S. Shannon Michael J. Lacey 《Journal of mass spectrometry : JMS》1987,22(1):30-35
The skeletal rearrangement for water loss is the dominant ion reaction in the chemical ionization mass spectrum of benzyl 2-phenylethyl ether. Isotopic distributions obtained for this reaction with specifically labelled derivatives have been interpreted in terms of competing five- and six-centred skeletal rearrangements. Chemical substitution of the alternative aromatic rings strongly influences the balance of the competition. 相似文献
104.
ZORA relativistic DFT calculations are presented which aim to reproduce geometric structures and EPR properties of [Ni(mnt)(2)](-) (H(2)mnt = maleonitrildithiol), two other paramagnetic low-spin Ni(III) complexes, and an asymmetric paramagnetic Co(II) complex. The study tests the accuracy of the computational method as a prior step to the modeling of the geometric and electronic structure of the active site of NiFe hydrogenases in its EPR-active oxidized states Ni-A and Ni-B. Systematic deviations from experiment are found for the calculated g-values; relative differences among them are, however, well reproduced. Because no significant improvements have been achieved by using larger basis sets or more sophisticated functionals, g-values may be calculated rather rapidly at the VWN level. This is most important for the modeling of the active site of NiFe hydrogenases because its complexity does not permit calculations at high levels of theory. For [Ni(mnt)(2)](-), excellent agreement between calculated and experimental results is obtained for the (14)N quadrupole coupling, whereas the calculated hyperfine couplings are not always in good agreement with experimental data. 相似文献
105.
Pharmaceuticals are continually introduced into the environment as a result of industrial and domestic use. In recent years they have emerged as environmental pollutants. An analytical method has been developed allowing for simultaneous detection and identification of 20 pharmaceutical compounds from various therapeutic classes using solid phase extraction (SPE) followed by liquid chromatography-electrospray ionisation mass spectrometry (LC-MS/MS). The limits of detection and limits of quantitation for the method were in the ng/L-microg/L range. The method was applied to influent and effluent samples from three wastewater treatment plants (WWTPs). Fifteen compounds were identified in the sample matrix with salicylic acid and ibuprofen being the most abundant at 9.17 and 3.20 microg/L respectively. 相似文献
106.
Capon RJ Ratnayake R Stewart M Lacey E Tennant S Gill JH 《Organic & biomolecular chemistry》2005,3(1):123-129
Biological and chemical profiling of an Australian strain of the fungus Aspergillus unilateralis(MST-F8675), isolated from a soil sample collected near Mount Isa, Queensland, revealed a complex array of metabolites displaying broad chemotherapeutic properties. Noteworthy among these metabolites were a unique series of highly modified dipeptides aspergillazines A-E, incorporating a selection of unprecedented and yet biosynthetically related heterocyclic systems. Co-occurring with the aspergillazines was the recently described marine-derived fungal metabolite trichodermamide A (cf. penicillazine), whereas re-fermentation of A. unilateralis in NaCl (1%) enriched media resulted in co-production of the only other known example of this structure class, the marine-derived fungal metabolite trichodermamide B. Further investigation of A. unilateralis returned the known terrestrial fungal metabolite viridicatumtoxin as the cytotoxic and antibacterial principle, together with E-2-decenedioic acid, ferulic acid, (7E,7'E)-5,5'-diferulic acid and (7E,7'E)-8,5'-diferulic acid. The aromatic diacids have previously been reported from the chemical and enzymatic (esterase) treatment of plant cell wall material, with their isolation from A. unilateralis being their first apparent reported occurrence as natural products. Structures for all metabolites were determined by detailed spectroscopic analysis and, where appropriate, comparison to literature data and/or authentic samples. 相似文献
107.
Analyses of masses and relative kinetic energies for metastable peaks may be achieved by the use in alternation of two types of linked scans of the electric sector voltage and magnetic field. The method is demonstrated by an appraisal of hydrogen exchange in molecular ions of 2-methyl-[2H3]-benzoic acid. 相似文献
108.
109.
The preparation of several 4'-alkylphenylethyl- and trans-4'-alkylcyclohexyl-ethyl-4,4'-disubstituted biphenyls and their 2-fiuoro derivatives is described and their transition temperatures are reported. The effect on the transition temperatures caused by the replacement of a cyclohexane ring by a benzene ring and the effect of fluoro-substitution on nematic, smectic A and smectic B thermal stabilities is discussed. In these systems, and in others, when the lateral fluoro-substituent points towards the longer terminal aliphatic unit (alkyl or alkylcyclo-hexylethyl) it causes a greater depression of smectic properties. 相似文献
110.
Alkyl (2-dimethylamino)ethyl methyl phosphates are prepared and isomerize smoothly to the corresponding alkyl choline phosphates. 相似文献