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In this study we have described the p-p and cation-p interactions between the porphyrin ring and the protein part of porphyrin-containing proteins to better understand their stabilizing role. The number of pp interactions was higher than that of cation-p interactions in the same set of proteins studied. The pyrrole groups of one porphyrin can be involved in p-p interactions with p systems of another porphyrin in the protein. We have found 5.1% cation-p interactions between porphyrin Fe 2+ metal cations and p systems of surrounding amino acids as well as the pyrrole rings of other porphyrins. We observed that most of the p-p interactions have an energy in the range 20.5 to 22.0 kcal mol 21 , while the cation-p interactions showed an energy in the range 22 to 24 kcal mol 21. Further, an appreciable number of metal/cation-p interaction pairs have an energy in the range 26 to 213 kcal mol 21. The preferred parallel-stacked orientation is found to be more stable than a T-shaped structure for the full set of p-p interaction pairs. In the case of cation-p interactions, it was found that 44% of the cation-p interactions involved planar stacking, 37% of the interactions belonged to the oblique category, and the remaining 19% of the interactions were of the orthogonal type. The separation distance between the cation group and the aromatic ring decreases as the interplanar angle decreases. Furthermore, in the present study we have found that 10.4% of p residues and 3.9% of cationic residues were found to have one or more stabilization centers. Amino acids deployed in the environment of porphyrin rings are deposited in helices and coils. The results from this study might be used for structure-based porphyrin protein prediction and as scaffolds for future porphyrin-containing protein design.

Organic agricultural production enables the production of controlled, certified, safe, and high-quality food, and at the same time it provides high economic and ecological profit and preserves a healthy environment. Consumer interests in products of organic origin have been steadily growing for twenty years. The aim of this paper is to give an overview of the situation in the global organic food market, as well as to point out the most important motives for consumers to decide on the consumption of organically produced foods. All countries around the world record a trend of continual organic food and beverage market growth. In some countries this growth is expressed with doubledigit numbers. The United States is the largest organic food market, with a total of 35.8 trillion euros. Fruits, vegetables, bread, cereals, drinks, milk and meat have the biggest share in the organic food market in all countries of the world. Fresh fruits take the first position in international trade. Although the production and sale of organic food is concentrated in highly developed countries, less developed countries are becoming important producers and exporters of organic products.