Aldo Di Luccia

Mass spectrometric analysis of in vitro nuclear aggregates of polyamines

RATIONALE In the nuclei of eukaryotic cells, polyamines and phosphate ions self-assemble via ionic interactions and hydrogen bonding, generating three families of supramolecular compounds that have been named large (l-), medium (m-) and small (s-) nuclear aggregates of polyamines (NAPs). In a simulated nuclear environment, polyamines and phosphate ions generate the in vitro NAPs (ivNAPs) that share strict structural and functional analogies with their cellular cognates. Mass spectrometric data are expected to provide important structural details of NAPs/ivNAPs. METHODS We used both electrospray ionization (ESI) and nitrocellulose (NC) matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) to support a variety of analytical techniques previously addressed to structurally characterize NAPs/ivNAPs. RESULTS The dominant m/z values of s-ivNAP (m/z 735, 749, 761) are compatible with a defined set of cyclic or linear aggregates. On the basis of the experimental molecular mass (a cluster centred at m/z 2980), the m-ivNAP corresponds to the supramolecular assembly of four modules of s-ivNAPs. No informative mass spectra were obtained for the l-ivNAP. CONCLUSIONS MS data support the models of NAPs that have been inferred by using an array of analytical techniques. NC MALDI-MS contributed much more effectively than ESI-MS to the structural characterization of ivNAPs.

Protein Modifications in Cooked Pork Products

Abstract Heat treatment induces protein modifications in both cooked whole cuts of meat and in products such as emulsion sausages. Cooking results in shrinkage and water loss with the main proteins changing through conformational rearrangements, oxidation of amino acid residues, and polymeric aggregation (as supramolecular structures). The proteomes of whole-cut meats (e.g., Parma and “Praga” cooked hams) and comminuted pork (e.g., mortadella and wurstel) products have been compared to raw pork using traditional proteomics approaches employing two-dimensional gel electrophoresis (2-DE) coupled to image analysis and mass spectrometry (MS). These studies revealed that other than heat-induced breakdown of part of the myosin heavy chains, the 2-DE pattern of cooked ham was highly similar to that of raw pork. However, MS-based analysis showed protein modifications, including extensive oxidation of methionines. In contrast, likely due to emulsification, comminuted sausages were characterized by an abundant insoluble protein fraction. Interestingly, in comminuted sausages, tropomyosin and myosin light chains were exclusively found in the insoluble protein fraction, whereas actin was found in each supramolecular structure. Experimental evidence showed that the protein aggregation systems of cooked hams and emulsion sausages reflected the processing conditions and were definitely different, the former being characterized mainly by disulfide bridges and the latter by additional covalent interprotein links.

Fatty acid profile and coagulating ability of milk from Jersey and Friesian cows fed whole flaxseed

The experiment was carried out to evaluate the effects of a moderate level of flaxseed administration on milk coagulation properties and fatty acid profile of milk from two different breeds. The experiment was performed on 20 Italian Friesian cows and 20 Jersey cows divided into 2 groups of 10 animals each. The experimental diets were (1) a traditional diet (CON) administrated as unifeed and no supplemental fat and (2) a diet supplemented with 0·5 kg/d of whole flaxseed (FS). Cows were milked twice daily and milk yield was recorded. Milk samples were analysed at 1, 15, and 30 d of the experiment for composition, pH, and milk coagulation properties. To verify the effects of flaxseed administration on the coagulation properties of milk from Friesian and Jersey cows, an electrophoresis study on casein fractions was performed. Milk fatty acid profile can be improved by administrating a moderate level of flaxseed in the diet, however, milk fatty acid profile from Friesian and Jersey cows showed different contents of C18 : 1 trans-11, SFA and MUFA. The results demonstrated that milk coagulating ability can be increased by flaxseed administration in both breeds as a result of different aggregation of casein micelles.