Vestar (United States)

This paper aims to point out the presence and distribution of honey plants along the canal network of the Banat region, and the relationship between their basic ecological (ecological group, ecological indices) and biological (life form, flowering time, pollination) characteristics. A total of 18 honey plants were observed, dominated by hemicryptophytes and phanerophytes (over 70%). Species Salix alba, Populus alba and invasive species Amorpha fruticosa were found along the largest number of canals. Correlation and PCA analyses determined that the flowering time of the honey plants depends on their ecological group, plant life form and habitat characteristics (pH, temperature, light, aeration, the nutrients content in the soil). Forest, wetland and woody plants have a shorter flowering time, compared with weed-ruderal species. Twelve species are invasive in Europe, while Acer negundo and Amorpha fruticosa are highly invasive species in Serbia. It has been ascertained that honey species which are not invasive in Serbia (but in the wider Europe region they are) are often recommended for planting, which can lead to their more intensive spread and increase the possibility of them becoming invasive in our country.

The mechanism of protein-mediated membrane fusion and lysis has been investigated by solution-state studies of the effects of peptides on liposomes. A peptide (SI) corresponding to a highly amphiphilic C-terminal segment from the envelope protein (gp41) of the human immunodeficiency virus (HIV) was synthesized and tested for its ability to cause lipid membranes to fuse together (fusion) or to break open (lysis). These effects were compared to those produced by the lytic and fusogenic peptide from bee venom, melittin. Other properties studied included the changes in visible absorbance and mean particle size, and the secondary structure of peptides as judged by CD spectroscopy. Taken together, the observations suggest that protein-mediated membrane fusion is dependent not only on hydrophobic and electrostatic forces but also on the spatial arrangement of the amino acid residues to form an amphiphilic structure that promotes the mixing of the lipids between membranes. A speculative molecular model is proposed for membrane fusion by alpha-helical peptides, and its relationship to the forces involved in protein-membrane interactions is discussed.

The crystal structure of the diphtheria toxin dimer at 2.5 A resolution reveals a Y-shaped molecule of three domains. The catalytic domain, called fragment A, is of the alpha + beta type. Fragment B actually consists of two domains. The transmembrane domain consists of nine alpha-helices, two pairs of which are unusually apolar and may participate in pH-triggered membrane insertion and translocation. The receptor-binding domain is a flattened beta-barrel with a jelly-roll-like topology. Three distinct functions of the toxin, each carried out by a separate structural domain, can be useful in designing chimaeric proteins, such as immunotoxins, in which the receptor-binding domain is substituted with antibodies to target other cell types.

Williams, Lawrence E.; Patel, K. R.; Tin, George W.; Proffitt, Richard T.; Baldeschwieler, John D. Author Information