摘要:

AbstractWe found that picolinic acid is a very good matrix for matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometry of oligonucleotides, proteins and tRNA. Among the oligonucleotides, picolinic acid was shown to be effective for homo‐oligonucleotides, d(G)40and d(C)60, and for mixed‐base oligonucleotides up to 190 bases. In the case of the single‐stranded oligonucleotides, and of double‐stranded ones as well, only parent ions corresponding to single‐stranded DNA were observed. The efficiency for MALDI of oligonucleotides using the picolinic acid matrix was superior to that using 3‐hydroxypicolinic acid. MALDI of transfer RNA phenylalanine‐specific (tRNAphe), a 76‐base ribonucleic acid, was detected with a signal‐to‐noise ratio of>10. By comparison with 3‐hydroxypicolinic acid the results with picolinic acid are notably superi

ISSN:0951-4198    

DOI:10.1002/rcm.1290080902

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe study of large‐scale rearrangements of [b′]2+ions produced by electrospray ionization of Substance P (Tanget al., Anal. Chem.Vol. 65, p. 2824 (1993)) has been extended to 18 other peptides containing either a lysine or ornithine residue remote from the C‐terminus. Evidence for wholesale transfer of one or more residues, from the C‐terminus of the [b′]2+precursor to the ω‐amino group of the Lys (or Orn) residue, was observed for 12 of the 18 peptides studied. Unfortunately, no rigorous predictive rules, relating features of the peptide sequence to the propensity to undergo such rearrangements, could be discerned although a significant correlation with presence of a proline residue dose to the lysine or ornithine on the C‐terminal side was apparent. The resulting mass‐shifts can complicate derivation of peptide sequences from fragment‐ion spectra of [M+2H]2+peptide ions, for example, since the cyclized [b′]2+ions responsible for the rearrangements are readily formed as intermediate species in the frag

ISSN:0951-4198    

DOI:10.1002/rcm.1290080903

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractMatrix‐assisted laser desorption/ionization using a 3‐hydroxpicollinic acid matrix from an active Nafion substrate has been used for detection of restriction enzyme‐degested double‐stranded plasmid DNA using time‐of‐ flight mass spectrometry. DNA strands of up to 267 base pairs were detected with minimal sample purification, although only as species corresponding to single

ISSN:0951-4198    

DOI:10.1002/rcm.1290080904

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractElectrospray mass spectrometry has been applied to ionic inorganic systems such as heteropolyacids in methanol + water (1/1) or acetonitrile + water (1/1) solutions. Negative‐ion mass spectra were obtained on four different heteropolyacids. Heteropolymolybdates H3PMo12O40and H4PMo11VO40and heteropolytungstates H3PW12O40and H4SiW12O40gave ions with different charges. H3PMo12O40gave ions ofm/z1822, 912 and 608 which correspond respectively to [PMo12O 403−+ 2H+], [PMo12O 403−+ H+]2−and [PMo12O40]3−ions. Resolution of 1:2200 has demonstrated the charge of each ion acquired. Furthermore, the isotope distribution of the observed ions was in good agreement with theory. Thus, electrospray mass spectrometry has become a powerful soft ionization technique for the analysis of such ionic compounds, provided they are soluble and stable in the solven

ISSN:0951-4198    

DOI:10.1002/rcm.1290080905

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractPeptide analysis of cytochromecusing capillary electrophoresis/mass spectrometry was demonstrated to be a rapid, sensitive and useful technique for providing information concerning the location of variation. We analyzed tryptic digests of horse, bovine and dog cytochromec, and compared the peptide analysis results for information concerning amino acid sequences in proteins. The differences in amino acid sequence were confirmed by taking into consideration that all the other fragments are identical in each map. The use of an untreated capillary column with basic buffer condition (water+acetonitrile+(20 g/L) ammonium carbonate (70/20/10), pH 9.2) had a reproducibility of migration times to within about 2%.

ISSN:0951-4198    

DOI:10.1002/rcm.1290080906

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractWe describe the formation of pentavalent silicon anions, (CH3O)2Si(OEt) 3−and CH3OSiH(OEt) 3−, by a ligand exchange and a hydride reaction in the presence of argon buffer in the gas phase. A simple elimination is followed by double and triple cyclic elimination mechanisms, during the collision‐induced dissociation of CH3OSi

ISSN:0951-4198    

DOI:10.1002/rcm.1290080907

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mass spectra of hydroxymethyltetrathiafulvalenes and bis(hydroxymethyl)tetrathiafulvalenes have been studied by electron ionization, metastable analysis and accurate mass measurements. The elimination of water from molecular ions of bis(hydroxymethyl)tetrathiafulvalenes has been investigated with the aid of isotopic labelling and the structures of the ions thus formed have been established by collision‐induced dissociation studie

ISSN:0951-4198    

DOI:10.1002/rcm.1290080908

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

Abstract[Ru(bpy)3(X)2] and [Fe(bpy)3(X)2] complex salts (bpy=2,2′bipyridine; X = ClO 4−, PF 6−, Cl−) were investigated by means of Cs+fast‐ion bombardment and mass‐selected collision‐induced dissociation (CID). A number of dissociation channels which can be attributed to the loss of intact counterions, bpy neutral ligands and to the insertion of formal O 2−, fluoride or chloride from the counterions ClO 4−, PF 6−, Cl−are evident in both the fast‐ion bombardment and CID spectra. Formation of doubly charged intact cations is also observed for all the compounds investigated. The relative intensities of the major desorbed ions are monitored as a function of the Cs+kine

ISSN:0951-4198    

DOI:10.1002/rcm.1290080909

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractElectrospray ionization of solutions of Ultramark 1621, a commercially available mixture of fluorinated phosphazenes, in solution of 50:23:23:4 v/v of acetonitrile+water+methanol+acetic acid, produced a series of intense singly charged peaks in them/zrange of 900 toca. 2200 in both positive‐ and negative‐ionization modes. The chemical compositions and accurate masses of ions in both positive‐ and negative‐ion spectra have been reported. An accuracy of approximately 2 ppm has been achieved for the average molecular weight of bovine insulin using Ultramark 1621 peaks as reference st

ISSN:0951-4198    

DOI:10.1002/rcm.1290080910

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY

摘要:

AbstractThe introduction of 18‐crown‐6 into the liquid sheath during the electrospray ionization mass spectrometry (ESI‐MS) of peptides leads to the formation of crown ether/peptide complexes. The nominal mass spacing of the peaks from these complexes allows an unambiguous determination of the charge state of the ions and thus of their actual mass. The 264 Da mass shift is much larger than what is achieved by either Na+or Cu2+adduction, and is thus potentially more useful for the determination of charge states, especially for multiply charged high‐molecular‐weight species. The addition of an uncharged crown ether does not appear to interfere with the ESI process. Because the crown ether is added to the liquid sheath and not to the original solution, the method should be particularly amenable to chromatographic or electrophoretic techniques because it is essentially a post‐column noncovalent derivatization procedure. Finally, because the complex formation constants are relatively large, the peptide/crown ether complex yields high intensity ions, normally the base peak in the spectrum when analyzing pure peptide samples. Finally, as the crown ether is neutral and noncovalently complexed, a constant‐neutral‐loss scan of their collision‐induced dissociation spectra yields a simplified spectrum that is free

ISSN:0951-4198    

DOI:10.1002/rcm.1290080911

出版商:Heyden&Son Limited    

年代:1994

数据来源: WILEY