Dragana Stanic

Consequences of MnSOD interactions with nitric oxide : Nitric oxide dismutation and the generation of peroxynitrite and hydrogen peroxide

The present study demonstrates that manganese superoxide dismutase (MnSOD) (Escherichia coli), binds nitric oxide (√NO) and stimulates its decay under both anaerobic and aerobic conditions. The results indicate that previously observed MnSOD-catalyzed √NO disproportionation (dismutation) into nitrosonium (NO+) and nitroxyl (NO− ) species under anaerobic conditions is also operative in the presence of molecular oxygen. Upon sustained aerobic exposure to √NO, MnSOD-derived NO− species initiate the formation of peroxynitrite (ONOO− ) leading to enzyme tyrosine nitration, oxidation and (partial) inactivation. The results suggest that both ONOO− decomposition and ONOO− -dependent tyrosine residue nitration and oxidation are enhanced by metal centre-mediated catalysis. We show that the generation of ONOO− is accompanied by the formation of substantial amounts of H2O2. MnSOD is a critical mitochondrial antioxidant enzyme, which has been found to undergo tyrosine nitration and inactivation in various pathologies associated with the overproduction of √NO. The results of the present study can account for the molecular specificity of MnSOD nitration in vivo. The interaction of √NO with MnSOD may represent a novel mechanism by which MnSOD protects the cell from deleterious effects associated with overproduction of √NO.

Allergenicity and immunogenicity of the major mugwort pollen allergen Art v 1 chemically modified by acetylation

Background Treating allergies with modified allergens is an approach to make the treatment safer and more efficient. Art v 1 is the most prominent allergen of mugwort pollen and a significant cause of hayfever around Europe. The aim of this study was to reduce the allergenicity of Art v 1 by acetylation, and to investigate the capacity of the modified protein to generate blocking antibodies.

Digestibility of food allergens

Almost all known food allergens that sensitize via the gastrointestinal system belong to the prolamin and cupin protein superfamilies of allergens. These are mainly characterized by resistance to heat and digestion. Though appealing, the hypothesis that allergenicity is directly linked to stability to pepsin digestion remains controversial. Besides allergen structure, new data are emerging on the influence of various other factors on allergen survival and uptake by the gut immune system, some of them related to the properties of the food matrix, and others to the way we process food. Nevertheless, the accumulation of knowledge on all those various and complex interactions between food components and gut immune system will help us understand better food allergies and manufacture safer food.

Dietary lipid intake influences the level of cholesterol bound to haemoglobin in human erythrocytes

BackgroundBlood cholesterol levels are affected by diet and in particular by the type of fat intake. We originally showed that a significant but variable amount of cholesterol is firmly bound to haemoglobin (Hb) yielding the Hb-lipid adduct (Hb-Ch) in erythrocytes isolated from normo-lipidemic males.Aim of the studyTo establish whether dietary lipids affect the level of Hb-Ch in human erythrocytes.MethodsSeventy-four healthy free-living adults were separated according to their serum cholesterol levels into two groups: normo-cholesterolemic (LDL cholesterol <3.4 mmol/l and total cholesterol <5.2 mmol/l) (NC) and hyper-cholesterolemic (LDL cholesterol ≥3.4 mmol/l) (HC). Habitual dietary information was used to classify subjects in both study groups into sub-groups of low-fat (≤30% total energy as fat) and high-fat consumers (>30% total energy as fat). The NC low-fat consumers were placed on a high-lipid (high-fat and high-cholesterol) diet whereas the HC subjects with high-fat intake were assigned to a low-lipid (low-fat and low-cholesterol) diet. Both types of dietary intervention were allowed to continue for 6 weeks. The main variable under scrutiny was the Hb-Ch concentration.ResultsIn both study groups low-fat intake subjects had low levels of Hb-Ch (approx. 0.35 mmol/l RBC) compared with high-fat intake subjects (approx. 0.60 mmol/l RBC), and serum cholesterol was not correlated with Hb-Ch. The two dietary interventions produced substantial changes in the Hb-Ch level that paralleled variation in the serum cholesterol concentration. A high-lipid diet (35% fat, 15% saturated; 580 mg cholesterol) increased Hb-Ch (by approximately 47%, P < 0.001) in subjects with low Hb-Ch at onset, whereas a low-lipid diet (28% fat, 9% saturated; 280 mg cholesterol) decreased Hb-Ch (by approximately 40%, P < 0.001) in subjects with high Hb-Ch at onset.ConclusionHigh consumption of dietary lipids, including saturated fat and cholesterol, has an important influence on the level of Hb-Ch in human erythrocytes.

Application of Ion Exchanger in the Separation of Whey Proteins and Lactin from Milk Whey

Whey disposal represents a huge obstacle for dairy industry, being costly and problematic. On the other hand, it could be used as a starting material for isolation of some components that are valuable on the market. Whey processing is not an easy operation; it requires robust techniques of high volumetric throughput with minimal pretreatment of the starting material. For this purpose, ion exchangers can be used, due to their versatility, safety, and relative cheapness. Being a mixture of acidic and basic proteins, double-step ion exchange chromatography, involving both cation and anion exchangers, must be performed to obtain highly purified whey proteins. Development of new technologies, based on ion exchange, which can provide fast and efficient whey processing, provides maximal exploitation in environmentally safe way.