The correlation between protein motions and function is a central problem in protein science. Several studies have demonstrated that ligand binding and protein dynamics are strongly correlated in intracellular lipid binding proteins (iLBPs), in which the high degree of flexibility, principally occurring at the level of helix-II, CD, and EF loops (the so-called portal area), is significantly reduced upon ligand binding. We have recently investigated by NMR the dynamic properties of a member of the iLBP family, chicken liver bile acid binding protein (cL-BABP), in its apo and holo form, as a complex with two bile salts molecules. Binding was found to be regulated by a dynamic process and a conformational rearrangement was associated with this event. We report here the results of molecular dynamics (MD) simulations performed on apo and holo cL-BABP with the aim of further characterizing the protein regions involved in motion propagation and of evaluating the main molecular interactions stabilizing bound ligands. Upon binding, the root mean square fluctuation values substantially decrease for CD and EF loops while increase for the helix-loop-helix region, thus indicating that the portal area is the region mostly affected by complex formation. These results nicely correlate with backbone dynamics data derived from NMR experiments. Essential dynamics analysis of the MD trajectories indicates that the major concerted motions involve the three contiguous structural elements of the portal area, which however are dynamically coupled in different ways whether in the presence or in the absence of the ligands. Motions of the EF loop and of the helical region are part of the essential space of both apo and holo-BABP and sample a much wider conformational space in the apo form. Together with NMR results, these data support the view that, in the apo protein, the flexible EF loop visits many conformational states including those typical of the holo state and that the ligand acts stabilizing one of these pre-existing conformations. The present results, in agreement with data reported for other iLBPs, sharpen our knowledge on the binding mechanism for this protein family.
Sulphiting agents are well-known food preservatives. The European legislation does not allow their addition in fresh meat preparations. Therefore this type of food products has often been verified. To high sulphite levels in food is a health safety risk, due to toxic effects that these compounds may exercise on humans. In this study the control activity as performed by an Italian accredited laboratory from 2013 to 2015, relating to determination of sulphites in meat products, is described. Six hundred and sixty-nine meat product samples were analysed. Both applied techniques, a screening method (malachite green test) and a confirmatory method (ion chromatography), were accredited. Forty-three samples resulted positive at screening test and nineteen of these samples showed high-sulphite concentrations, in the range 67.6-1437 mg kg. The non-negligible percentage of positives (6.4%) and the high concentrations verified confirmed that the control of sulphuring treatment of fresh meat preparations is an important task for organisations in charge of food inspections and control.
In shrimps the treatment with sulphiting agents is currently the best option for controlling Melanosis, which is a visual defect of the products that compromises marketability. However, sulphites may cause pseudo-allergic reactions in humans. In this study, 210 samples of shrimps were analysed in order to assess the residual levels of sulphiting agents. A quantifiable sulphites concentration was detected in 76 samples, and these concentrations were higher than the legal limits in eight samples. Considering the important pseudo-allergenic effects caused by these food additives, the non-negligible percentage of 3.8% and the high levels registered in non-compliant samples (up to 1174.1 mg kg(-1)), a strong contrast action based on permanent controls is necessary. Moreover, the levels measured in whole samples were up to four times higher than in the edible parts. These results suggest to consider the introduction of legal limits, related to sulphurous anhydride in the whole product.
Mozzarella is an unripened cheese widely consumed worldwide. Due to short shelf-life of these products, the addition of few food additives, such as citric acid and lactic acid is allowed by the actual Legislation. However, these two compounds are present in the aqueous phase of milk, making difficult a correct discrimination between products with added food additives from those declared as "with no added food additives". This work is collocated in this contest. It may be considered as a contribution for a correct food additives determination in mozzarella cheese. 14 samples (7 with citric acid declared on the label and 7 without declared food additives) were analysed, by using a reliable analytical method by ion chromatography with conductivity detection, for the quantification citric acid. The results were compared in order to verify a statistically significant difference between two data populations. The same samples were analysed, by using a validated ion chromatography with conductivity detection method, for the determination of lactic acid, and the results were evaluated in order to give a contribution to the determination of a maximum natural level of lactic acid in mozzarella cheese, in products without added food additives. Regarding citric acid, a cutoff value, equal to 0.65 g kg-1 was suggested as maximum admissible level in products without added food additives; while, as it concerns lactic acid, a maximum level corresponding to 4.0 g kg-1 was suggested.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.