Proteomic analysis of complex protein samples by MALDI-TOF mass spectrometry

MALDI-TOF Mass Spectrometry Applications for Food Fraud Detection

Chemical analysis of food products relating to the detection of the most common frauds is a complex task due to the complexity of the matrices and the unknown nature of most processes. Moreover, frauds are becoming more and more sophisticated, making the development of reliable, rapid, cost-effective new analytical methods for food control even more pressing. Over the years, MALDI-TOF MS has demonstrated the potential to meet this need, also due to a series of undeniable intrinsic advantages including ease of use, fast data collection, and capability to obtain valuable information even from complex samples subjected to simple pre-treatment procedures. These features have been conveniently exploited in the field of food frauds in several matrices, including milk and dairy products, oils, fish and seafood, meat, fruit, vegetables, and a few other categories. The present review provides a comprehensive overview of the existing MALDI-based applications for food quality assessment and detection of adulterations.

Protein carbonylation associated with nickel liberation in orthodontic gingival overgrowth

OBJECTIVE

To determine nickel levels and their impact on protein carbonylation in gum samples from patients with gingival overgrowth by orthodontic treatment.

DESIGN

A retrospective observational study with 33 patients divided into three groups. Group 1 patients with gingival overgrowth by orthodontic appliances; group 2 patients without gingival overgrowth but with a history of orthodontic treatment; group 3 patients without overgrowth and history of orthodontic appliances. Nickel level in gingiva samples was measured by atomic absorption while protein carbonylation was determined by Western Blot. Furthermore, three proteins were identified in carbonylated protein bands by mass spectrometry.

RESULTS

Statistically significant differences (p < 0,05) in tissue nickel levels among groups were established (nickel levels group 1: 1.33 ± 1.52; group 2: 0.33 ± 0.44; group 3: 0.20 ± 0.22 μg Ni/g tissue). Protein carbonylation was higher in patients with gingival enlargement (group 1) and history of appliance use (group 2) than controls (group 3). It was observed that band A of the Western blots presented the highest intensity (Rf 0.23) with an average intensity of 4.133.830 ± 1.958.569 for group 1; 4.420.146 ± 1.594.679 for group 2 and 2.110. 727 ± 1.640.721 for group 3. Also, the proteins Teneurin-4, Bromodomain adjacent to zinc finger domain protein 2B, Lysine-specific demethylase 5B, and Serum albumin, were identified from oxidized bands.

CONCLUSIONS

The gum of patients with gingival overgrowth by orthodontic appliances contains higher nickel residues and carbonylation of its proteins.