Na+ interacting with gramicidin D. A nuclear magnetic resonance study.

23Na nuclei in a milk-white emulsion composed to nonionic surfactant and higher alcohol in saline were characterized by single values of T1 and T2 and a single Larmor frequency. In the presence of small amounts of gramicidin D (Dubos), the relaxations of 23Na were greatly accelerated, and the transverse relaxation was a sum of two decaying exponentials. But only a single T1 was observed; it was roughly equal to the slow T2. The slow T2 accounted for about 40% of the total resonance intensity. The relaxation rates increased linearly with the increase of the gramicidin concentration. The absorption signal consisted of a narrow and a broad line, both centered at the same frequency. The present results suggest that nuclear magnetic resonance spectroscopy is a useful tool for studying the nature of ion-permeable channels of biological membranes, even when the channel has no ionizable groups

ProTherm: Thermodynamic Database for Proteins and Mutants.

The first release of the Thermodynamic Database for Proteins and Mutants (ProTherm) contains more than 3300 data of several thermodynamic parameters for wild type and mutant proteins. Each entry includes numerical data for unfolding Gibbs free energy change, enthalpy change, heat capacity change, transition temperature, activity etc., which are important for understanding the mechanism of protein stability. ProTherm also includes structural information such as secondary structure and solvent accessibility of wild type residues, and experimental methods and other conditions. A WWW interface enables users to search data based on various conditions with different sorting options for outputs. Further, ProTherm is cross-linked with NCBI PUBMED literature database, Protein Mutant Database, Enzyme Code and Protein Data Bank structural database. Moreover, all the mutation sites associated with each PDB structure are automatically mapped and can be directly viewed through 3DinSight developed in our laboratory. The database is available at the URL, http://www.rtc.riken.go.jp/protherm.htm