Interaction of phospholipids (Lysophosphatidylethanolamines) with water and sodium cation

We have performed detailed ab initio SCF calculations on the intermolecular interaction energies for one Na⁺ ion and one water molecule with two molecular fragments, one exemplifying a phospholipid (PL) head (PLHD) and the other, a phospholipid tail (PLTL). A 6-12-1 atom-atom pair potential for the interaction of a Na⁺ ion and water with a lysophosphatidyl-ethanolamine (LPEA) was derived from these results by a fitting procedure. This fitted potential was used to obtain isoenergy maps that provide energy profiles of the Na⁺ ion and the water around the phospholipids. The interaction of the Na⁺ ion with PL, as well as the interaction of water with the PL, can be visualized from these maps, which, as expected, show regions of hydrophilicity and hydrophobicity for the water and indicate a very strong binding site for the Na⁺ ion on the phosphate. It appears to be a stationary site that would limit the Na⁺ ion mobility. This binding site is located near the double-bonded oxygen atom of the phosphate group; its binding energy for Na⁺ is 67 kcal/mol. On the other hand the NH⁺ group of PLHD ahows strong electrostatic repulsion of Na⁺ while interacting with water with a binding energy of 13 kcal/mol. This potential energy well region for water is separated from another of similar depth near the phosphate by a barrier and both regions are expected to act as binding sites for water.     

Location of major antigenic sites of the beta subunit of human chorionic gonadotropin.

Purified beta subunit of human chorionic gonadotropin (hCG) was partially reduced with beta-mercaptoethanol, carboxymethylated, and digested with chymotrypsin. The peptides were isolated by high-voltage electrophoresis and paper chromatography. Five major disulfide-containing peptides were isolated, and their location in the parent molecule was established by amino acid composition and amino- and carboxy-terminal analyses. All of these peptides inhibited the binding of 125I-labeled hCG by anti-beta hCG serum. The inhibitory effect of these peptides was lost when their disulfide bonds were reduced and alkylated. Synthetic carboxy-terminal peptides were not inhibitory. Based on these data it is concluded that a major antigenic site of hCG resides in the region of residues 21-23 with a disulfide bond connecting cysteine-23 or -26 with the cysteines at positions 72 or 110.     

Data Deposition and Annotation at the Worldwide Protein Data Bank

The Protein Data Bank (PDB) is the repository for three-dimensional structures of biological macromolecules, determined by experimental methods. The data in the archive is free and easily available via the Internet from any of the worldwide centers managing this global archive. These data are used by scientists, researchers, bioinformatics specialists, educators, students, and general audiences to understand biological phenomenon at a molecular level. Analysis of this structural data also inspires and facilitates new discoveries in science. This chapter describes the tools and methods currently used for deposition, processing, and release of data in the PDB. References to future enhancements are also included. Shuchismita Dutta, Kyle Burkhardt, and Ganesh J. Swaminathan have contributed equally to this work.     

Protein Changes in Response to Salt Stress in Porteresia coarctata Tateoka

One-month-old plants of Porteresia coarctata were subjected to salt stress of 150 mM for 10 days. Changes induced in leaf proteins were studied by two-dimensional electrophoresis and quantitatively analyzed using image analysis. Thirty-five number of proteins were significantly affected by salt and seventeen were detected only in stressed plants.