scholarly journals Detection of Frozen–Thawed Duck Fatty Liver by MALDI-TOF Mass Spectrometry: A Chemometrics Study

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3508
Author(s):  
Laurent Aubry ◽  
Thierry Sayd ◽  
Claude Ferreira ◽  
Christophe Chambon ◽  
Annie Vénien ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Protein Profile ◽  
Reference Method ◽  
Principal Component ◽  
Ionization Time ◽  
Flight Mass Spectrometry ◽  
Short Period ◽  
Before And After ◽  
Fresh Frozen ◽  
Discriminant Power

The marketing of poultry livers is only authorized as fresh, frozen, or deep-frozen. The higher consumer demand for these products for a short period of time may lead to the marketing of frozen–thawed poultry livers: this constitutes fraud. The aim of this study was to design a method for distinguishing frozen–thawed livers from fresh livers. For this, the spectral fingerprint of liver proteins was acquired using Matrix-Assisted Laser Dissociation Ionization-Time-Of-Flight mass spectrometry. The spectra were analyzed using the chemometrics approach. First, principal component analysis studied the expected variability of commercial conditions before and after freezing–thawing. Then, the discriminant power of spectral fingerprint of liver proteins was assessed using supervised model generation. The combined approach of mass spectrometry and chemometrics successfully described the evolution of protein profile during storage time, before and after freezing-thawing, and successfully discriminated the fresh and frozen–thawed livers. These results are promising in terms of fraud detection, providing an opportunity for implementation of a reference method for agencies to fight fraud.

scholarly journals Exploring the Inhibition of CTX-M-9 by β-Lactamase Inhibitors and Carbapenems

2011 ◽  
Vol 55 (7) ◽  
pp. 3465-3475 ◽  
Author(s):  
Christopher R. Bethel ◽  
Magdalena Taracila ◽  
Teresa Shyr ◽  
Jodi M. Thomson ◽  
Anne M. Distler ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Active Site ◽  
Positive Charge ◽  
Evolutionary Strategy ◽  
Ionization Mass ◽  
Ionization Time ◽  
Esi Ms ◽  
Flight Mass Spectrometry ◽  
Before And After ◽  
Enzyme Intermediate

ABSTRACTCurrently, CTX-M β-lactamases are among the most prevalent and most heterogeneous extended-spectrum β-lactamases (ESBLs). In general, CTX-M enzymes are susceptible to inhibition by β-lactamase inhibitors. However, it is unknown if the pathway to inhibition by β-lactamase inhibitors for CTX-M ESBLs is similar to TEM and SHV β-lactamases and why bacteria possessing only CTX-M ESBLs are so susceptible to carbapenems. Here, we have performed a kinetic analysis and timed electrospray ionization mass spectrometry (ESI-MS) studies to reveal the intermediates of inhibition of CTX-M-9, an ESBL representative of this family of enzymes. CTX-M-9 β-lactamase was inactivated by sulbactam, tazobactam, clavulanate, meropenem, doripenem, ertapenem, and a 6-methylidene penem, penem 1.Kivalues ranged from 1.6 ± 0.3 μM (mean ± standard error) for tazobactam to 0.02 ± 0.01 μM for penem 1. Before and after tryptic digestion of the CTX-M-9 β-lactamase apo-enzyme and CTX-M-9 inactivation by inhibitors (meropenem, clavulanate, sulbactam, tazobactam, and penem 1), ESI-MS and matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) identified different adducts attached to the peptide containing the active site Ser70 (+52, 70, 88, and 156 ± 3 atomic mass units). This study shows that a multistep inhibition pathway results from modification or fragmentation with clavulanate, sulbactam, and tazobactam, while a single acyl enzyme intermediate is detected when meropenem and penem 1 inactivate CTX-M-9 β-lactamase. More generally, we propose that Arg276 in CTX-M-9 plays an essential role in the recognition of the C3carboxylate of inhibitors and that the localization of this positive charge to a “region of the active site” rather than a specific residue represents an important evolutionary strategy used by β-lactamases.

scholarly journals Evaluation of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry for Identification of Nontuberculous Mycobacteria from Clinical Isolates

2015 ◽  
Vol 53 (8) ◽  
pp. 2737-2740 ◽  
Author(s):  
Belén Rodríguez-Sánchez ◽  
María Jesús Ruiz-Serrano ◽  
Mercedes Marín ◽  
Paula López Roa ◽  
Marta Rodríguez-Créixems ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Reference Method ◽  
Laser Desorption ◽  
Laser Desorption Ionization ◽  
Ionization Time ◽  
Desorption Ionization ◽  
Maldi Tof ◽  
Flight Mass Spectrometry ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) for the identification of nontuberculous mycobacterial (NTM) isolates was evaluated in this study. Overall, 125 NTM isolates were analyzed by MALDI-TOF and GenoType CM/AS. Identification by 16S rRNA/hsp65sequencing was considered the gold standard. Agreements between MALDI-TOF and GenoType CM/AS with the reference method were, respectively, 94.4% and 84.0%. In 17 cases (13.6%), results provided by GenoType and MALDI-TOF were discordant; however, the reference method agreed with MALDI-TOF in 16/17 cases (94.1%;P= 0.002).

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