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101.
J W Crabb W R Harris C M Johnson T G Sotiroudis C C Kuhn L M Heilmeyer 《Electrophoresis》1990,11(2):133-140
A simple, rapid sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) method is presented for isolating the alpha, alpha' and beta subunits of rabbit muscle phosphorylase kinase. The SDS-PAGE procedure can yield milligram amounts of alpha and beta from a single preparative gel and also allows isolation of the alpha' isozyme free of alpha. Notably the method provides the purified subunits in a form amenable to structural analysis. Edman degradation of alpha and alpha' reveal identical NH2-terminal structures. Amino acid analysis of the electrophoretically purified alpha and beta subunits are in good agreement with their deduced primary structures. The amino acid sequence of 488 residues in alpha and 713 residues in beta were determined by gas phase Edman degradation. The data support the recently deduced primary structures of alpha (Zander et al., Proc. Natl. Acad. Sci. USA, 1988, 85, 9381-9385). 相似文献
102.
The first isocyanide ligated hexanuclear zirconium halide cluster is reported. The unoxidized [(Zr6Be)Cl12(CNXyl)6] (CNXyl = 2,6-dimethylphenyl isocyanide) was obtained from the solid state precursor K3Zr6Cl15Be by dissolution in CH3CN in the presence of CNXyl. The CNXyl ligands occupy all the axial positions on the cluster. The compound was recrystallized from CH2Cl2 and Et2O. [(Zr6Be)Cl12(CNXyl)6].2CH2Cl2 crystallizes in the space group
(#2) with a = 12.092(5) Å, b=12.728(5) Å, c = 14.102(8) Å, = 104.98(4)°, =107.11°, = 100.94°, V = 1919(2) Å3, Z = l, R = 11.3% and R
W
= 27.0%. For the bound isocyanide ligands, v
CN increases to 2140 cm–1. 相似文献
103.
Russell P. Newton Jalal A. Khan Dipankar Ghosh James I. Langridge A. Gareth Brenton Frank M. Harris Terence J. Walton 《Journal of mass spectrometry : JMS》1991,26(5):447-453
The determination of cytidine 3′,5′-cyclic monophosphate-specific phosphodiesterase activity by means of fast-atom bombardment (FAB) mass Spectrometry with mass-analysed ion kinetic energy (MIKE) spectrum scanning is described. Initial efforts to determine the activity of the enzyme by this method were unsuccessful owing to the obfuscation of sample-related peaks by peaks emanating from the incubation buffer and cation adducts; dilution of buffer and a desalting procedure overcame these difficulties. In the resulting positive-ion FAB mass spectra, characteristic peaks of the enzyme substrate and product could be readily identified and the protonated molecular ions selected for MIKE scanning. By spiking enzyme incubates with known amounts of substrate and product, and measuring peak heights in the MIKE spectra of both spiked and unspiked samples, the substrate/product ratio at the end of a series of phosphodiesterase incubations was determined. From the data obtained, the Km and Vmax of the phosphodiesterase were calculated as 6.08 mM and 11 μmol min?1 mg?1, respectively, showing good agreement with the analogous values of 8.06 mM and 5.8 μmol?1 min?1 mg?1 obtained by radioactive assay. 相似文献
104.
MacLean EJ Harris KD Kariuki BM Kitchin SJ Tykwinski RR Swainson IP Dunitz JD 《Journal of the American Chemical Society》2003,125(47):14449-14451
The transformation of ammonium cyanate into urea, first studied over 170 years ago by W?hler and Liebig, has an important place in the history of chemistry. To understand the nature of this solid state reaction, knowledge of the crystal structure of ammonium cyanate is a prerequisite. Employing neutron powder diffraction, we demonstrate conclusively that, in the structure of ammonium cyanate, the NH(4)(+) cation forms N-H...N hydrogen bonds to four cyanate N atoms at alternate corners of a distorted cube, rather than our previously proposed alternative arrangement with N-H...O hydrogen bonds to cyanate O atoms at the other four corners. 相似文献
105.
It is shown that in the limit of large detuning energy and in the absence of coordinate dependence of the transition moment, the resonance Raman amplitude for a 0 → n transition on a harmonic potential surface is proportional to (δ2? + δ2+)?1 × ?∞?∞ exp (?q2) · [?nΔV(q)/?q11] dq< where ΔV(q) is the difference between the arbitrary excited-state surface and the initial harmonic potential. The resonant and non-resonant detuning energies are given by δ? = E ? hv and δ+ = E + hv, where v is the incident laser frequency and E is the minimum separation between the potential surfaces. 相似文献
106.
107.
Through NMR spectroscopic monitoring of barbituric acid addition to carbodiimide, a general synthetic procedure for the preparation of 5-diaminomethylenebarbiturates (DABA) was developed. This procedure is very simple and applicable to the preparation of large quantities of DABA derivatives. Through an X-ray structural study of one of the DABA derivatives, it was established that these compounds have an ylide-type structure with strong charge separation within the molecule. 相似文献
108.
Proteins with molecular mass (M(r)) <20 kDa are often poorly separated in 2-D sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition, low-M(r) proteins may not be readily identified using peptide mass fingerprinting (PMF) owing to the small number of peptides generated in tryptic digestion. In this work, we used a 2-D liquid separation method based on chromatofocusing and non-porous silica reversed-phase high-performance liquid chromatography to purify proteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analysis and protein identification. Several proteins were identified using the PMF method where the result was supported using an accurate M(r) value obtained from electrospray ionization TOFMS. However, many proteins were not identified owing to an insufficient number of peptides observed in the MALDI-TOF experiments. The small number of peptides detected in MALDI-TOFMS can result from internal fragmentation, the few arginines in its sequence and incomplete tryptic digestion. MALDI-QTOFMS/MS can be used to identify many of these proteins. The accurate experimental M(r) and pI confirm identification and aid in identifying post-translational modifications such as truncations and acetylations. In some cases, high-quality MS/MS data obtained from the MALDI-QTOF spectrometer overcome preferential cleavages and result in protein identification. 相似文献
109.
Calculations of three-electron atomic systems in Hylleraas coordinates require integrals involving all the interparticle distances r(ij), which have usually been evaluated by introducing series expansions. For integrals with the smallest powers of r(ij) these expansions do not converge at a satisfactory rate, leading some investigators to introduce convergence-acceleration procedures. This paper recommends the alternative of evaluating these integrals in closed form and presents stable explicit formulas for so doing. Some of the formulas are more compact versions of those in the literature; others have not been previously reported. It is also shown that finite-difference methods can be used with advantage to obtain additional low-order integrals. Sample integral values have been provided for test purposes. 相似文献
110.