Extension of the Kendrick Mass Defect Analysis of Homopolymers to Low Resolution and High Mass Range Mass Spectra Using Fractional Base Units

Beyond the high resolution/low mass range data traditionally used, a Kendrick mass defect analysis (KMD) using the new concept of fractional base units has been successfully conducted on low resolution/low mass range and high resolution/high mass range data for the first time. Relying on a mathematical framework to rationalize the effect of the fractional base units, the electrospray ionization single stage and multistage mass spectra of a poly­(vinylpyrrolidone) recorded from a low resolution ion trap analyzer were turned into information-rich KMD plots using vinylpyrrolidone/112 and pyrrolidone/86 as base units. The distributions detected in the matrix assisted laser desorption ionization spiralTOF mass spectra of high molecular weight poly­(ethylene oxide) and poly­(caprolactone) were conveniently discriminated in KMD plots using (ethylene oxide)/45 and caprolactone/113 as base units with an unprecedented resolution at such a mass range. The high resolution KMD analysis using fractional base units opens new perspectives for the acquisition, visualization, and presentation of mass spectra of polymers with less restrictions in terms of required resolution and molecular weights

First Gut Instincts Are Always Right: The Resolution Required for a Mass Defect Analysis of Polymer Ions Can Be as Low as Oligomeric

Its recent adaptation to low-resolution mass spectra of polymers using fractional base units raises the question of the minimal resolution needed for a Kendrick mass defect (KMD) analysis. Intuiting an oligomeric resolution since the mass of a repeat unit is the sole value to be known, it is challenged by the relative failure of the KMD plots computed from an isotopically resolved matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrum to display clear alignments in the high mass range. Another procedure based on the remainders of Kendrick mass (RKMs) overcomes this pitfall with oligomers perfectly aligned in a new RKM plot. Despite a concomitant degradation of the resolving power and accuracy, with the example of MALDI-TOF/TOF mass spectra of a variety of homo- and copolymer ions, the RKM procedure still allows a rapid enumeration, assignment, and any further manipulation of all the product ion series in visual RKM plots. Successfully extended to the critical case of a MALDI mass spectrum recorded with a linear TOF analyzer allowing a bare oligomeric resolution, the RKM plot turns the distributions differing by their end-groups or adducted ion into clear horizontal lines. It eventually gives intuition its due by answering the original question: the minimal resolution required for a mass defect analysis can be as low as oligomeric with the appropriate formulas

Changes in hepatic IL-1β mRNA expression after hemorrhage.

<p>The IL-1β mRNA level in the Hemorrhage group was highest at 3 hours post-hemorrhage, and was higher than that of the Sham group at all timepoints. On the contrary, the IL-1β mRNA level in the FR+Hemorrhage group showed no change from baseline at any timepoint after hemorrhage. Similarly, the serum IL-1β level in the Hemorrhage group was significantly increased from baseline at 3 hours after hemorrhage and then decreased over time, but was significantly higher than in the Sham group at all the timepoints post-hemorrhage as shown in C. In contrast, the serum IL-1β level in the FR+Hemorrhage group showed no change from the baseline value throughout the experiment. Data are shown as mean±SE. n = 5/groups, * p<0.05 vs Sham, + p<0.05 between Hemorrhage and FR+Hemorrhage.</p

Time course of mean arterial blood pressure (MBP).

<p>Hemorrhage was induced for 20 minutes (shaded area). A: Sham group (Sham), B: Hemorrhage group (Hemorrhage), C: Sham with FR167653 treatment (FR), D: Hemorrhage with FR167653 treatment (FR+Hemorrhage). MBP decreased significantly just after hemorrhage and returned to baseline at 40 minutes, but decreased gradually in the latter phase in the Hemorrhage group (B). FR treatment did not have any effect on the primary MBP decrease, although it abolished the secondary MBP decrease after hemorrhage (D). Data are shown as mean±SE. n = 5/groups, * p<0.05 vs Sham, + p<0.05 between Hemorrhage and FR+Hemorrhage.</p

Time course of hepatic arterial blood flow (HBF).

<p>The abbreviations are the same as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030124#pone-0030124-g001" target="_blank">Fig. 1</a>. The change in HBF was similar to that in MBP. Data are shown as mean±SE. n = 5/groups, * p<0.05 vs Sham, + p<0.05 between Hemorrhage and FR+Hemorrhage.</p

Bacterial LPS concentration in the portal vein.

<p>There were no significant increases in the portal LPS concentration in any of the groups throughout the experimental period. Data are shown as mean±SE. n = 5/groups.</p

Light micrograph showing the liver at 5 hours post-hemorrhage.

<p>The interstitial space was edematous and the sinusoidal capillaries were dilated with diffuse congestion. Some neutrophils, which have the appearance of reddish brown precipitates, were present in the sinusoidal cavity and interstitial space in the Hemorrhage group (A). These histological changes were not observed in the FR+Hemorrhage group (B). Bar = 100 µm. Number of activated neutrophils in the liver (500 µm²) as shown in C. In the Hemorrhage group, activated neutrophils were significantly increased at 5 hours, but markedly reduced in the group treated with FR167653 (FR+Hemorrhage) at 5 hours post-hemorrhage. Data are shown as mean±SE. n = 5/groups, * p<0.05 vs Sham, + p<0.05 between Hemorrhage and FR+Hemorrhage.</p

Changes in hepatic p38 MAPK activation after hemorrhage.

<p>The activation of p38 MAPK was assessed by Western blotting analysis. p38 MAPK phosphorylation levels, shown on the vertical axis in B, were determined after normalization using the density ratio of the phosphorylated p38 MAPK band (p-p38 MAPK in A) divided by the p38 MAPK band (p38 MAPK in A). Activation of p38 MAPK was significantly higher at 1 hour and returned to the baseline level at 3 hours after hemorrhage. Activation of p38 MAPK activation in the FR+Hemorrhage group did not change significantly at any time after a hemorrhage. Data are shown as mean±SE. n = 5/groups, * p<0.05 vs Sham, + p<0.05 between Hemorrhage and FR+Hemorrhage.</p

Changes in serum AST and ALT levels.

<p>The levels of liver enzymes in the Hemorrhage group increased with time and were significantly higher than in the Sham group at 5 hours after hemorrhage. Administration of FR167653 (FR+Hemorrhage group) inhibited the increase AST and ALT (A and B respectively). Data are shown as mean±SE. n = 5/groups, * p<0.05 vs Sham, + p<0.05 between Hemorrhage and FR+Hemorrhage.</p

Additional file 2: Table SI-2. of Ribosomal subunit protein typing using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the identification and discrimination of Aspergillus species

Corrected amino acid sequences and relating information of RSPs. (DOCX 80 kb