scholarly journals Electrospray mass spectrometric evidence for the occurrence of two major variants in native pig pepsin A

1996 ◽  
Vol 313 (1) ◽  
pp. 241-244 ◽  
Author(s):  
Brian N. GREEN ◽  
Arwyn T. JONES ◽  
Norman B. ROBERTS
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Amino Acid Residue ◽  
Electrospray Mass Spectrometry ◽  
Mass Spectrometric ◽  
Native Enzyme ◽  
Negative Ion ◽  
Mass Spectrometric Evidence

Native pig pepsin was analysed by negative ion electrospray mass spectrometry in order to rationalize anomalies between the published sequences. Outstanding variations in otherwise identical sequences indicate that amino acid residue 242 is either Asp or Tyr, and in some determinations an additional Ile is inserted at position 230. Mass spectrometric evidence is consistent with the presence, in the native enzyme, of two variants in comparable abundance, with either Asp or Tyr at residue 242. There is no evidence for the additional Ile at position 230.

Confounding contaminants in mass spectrometric reaction monitoring

2018 ◽  
Author(s):  
Gilian T. Thomas ◽  
Landon MacGillivray ◽  
Natalie L. Dean ◽  
Rhonda L. Stoddard ◽  
Lars Yunker ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrometric ◽  
Negative Ion ◽  
Reaction Monitoring ◽  
Schlenk Flask ◽  
Dynamic Analyses ◽  
Rubber Septa ◽  
Negative Ion Mode ◽  
Mode A

<p>Reactions carried out in the presence of rubber septa run the risk of additives being leached out by the solvent. Normally, such species are present at low enough levels that they do not interfere with the reaction significantly. However, when studying reactions using sensitive methods such as mass spectrometry, the appearance of even trace amounts of material can confuse dynamic analyses of reactions. A wide variety of additives are present in rubber along with the polymer: antioxidants, dyes, detergent, and vulcanization agents, and these are all especially problematic in negative ion mode. A redesigned Schlenk flask for pressurized sample infusion (PSI) is presented as a means of practically eliminating the presence of contaminants during reaction analyses.</p>

Resolution of a protein sequence ambiguity by X-ray crystallographic and mass spectrometric methods

1992 ◽  
Vol 25 (2) ◽  
pp. 205-210 ◽  
Author(s):  
L. J. Keefe ◽  
E. E. Lattman ◽  
C. Wolkow ◽  
A. Woods ◽  
M. Chevrier ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Electron Density ◽  
Mass Spectrometric ◽  
Amino Acid Sequences ◽  
Data Matrix ◽  
Protein Crystal ◽  
Insertion Mutant ◽  
Laser Desorption Mass Spectrometry ◽  
X Ray

Ambiguities in amino acid sequences are a potential problem in X-ray crystallographic studies of proteins. Amino acid side chains often cannot be reliably identified from the electron density. Many protein crystal structures that are now being solved are simple variants of a known wild-type structure. Thus, cloning artifacts or other untoward events can readily lead to cases in which the proposed sequence is not correct. An example is presented showing that mass spectrometry provides an excellent tool for analyzing suspected errors. The X-ray crystal structure of an insertion mutant of Staphylococcal nuclease has been solved to 1.67 Å resolution and refined to a crystallographic R value of 0.170 [Keefe & Lattman (1992). In preparation]. A single residue has been inserted in the C-terminal α helix. The inserted amino acid was believed to be an alanine residue, but the final electron density maps strongly indicated that a glycine had been inserted instead. To confirm the observations from the X-ray data, matrix-assisted laser desorption mass spectrometry was employed to verify the glycine insertion. This mass spectrometric technique has sufficient mass accuracy to detect the methyl group that distinguishes glycine from alanine and can be extended to the more common situation in which crystallographic measurements suggest a problem with the sequence, but cannot pinpoint its location or nature.

Determination of Solution Ions by Electrospray Mass Spectrometry

1994 ◽  
Vol 48 (6) ◽  
pp. 655-661 ◽  
Author(s):  
George R. Agnes ◽  
Gary Horlick
Keyword(s):  
Mass Spectrometry ◽  
Metal Ion ◽  
Gas Flow ◽  
Electrospray Mass Spectrometry ◽  
Negative Ion ◽  
Molecular Forms ◽  
Mass Spectral ◽  
Oxo Anions ◽  
Electrospray Source

Spectral results are presented illustrating the capability of electrospray mass spectrometry (ES-MS) for the determination of the composition of solution samples. The solution components that can be determined include the elemental and molecular forms of anions and cations. Three modes of positive-ion ES-MS are described: the ion cluster mode, the metal-ion mode, and an intermediate mode. The modes are established by operating the electrospray source at specific voltages and curtain gas flow rate values, and each mode provides a unique mass spectral picture of the solution components with primary focus on cationic species (i.e., metal ions). Results are also presented for operation of the electrospray source in negative-ion mode. In this mode both elemental anions (i.e., halides) and molecular anions (i.e., oxo-anions) can be determined.

Sign in / Sign up

Export Citation Format

Share Document