Structural—functional investigations based

Structural-Functional Investigations Based on Partial Proteolysis and Physical Measurements... 

Ras and its relatives are subjects of intensive investigations by biological, biochemical, biophysical, and medical studies. Within just one decade more than 17,000 articles (Medline, 1966-2000) deal with function and properties of this protein. Structural and functional data, based on Ras as a prototype, have provided insight into the basic principles of GTP-binding proteins, their activation, de-activation, and signal transmission. 

From a pharmacological point of view the first two strategies raise several distinct disadvantages. First, the exact structures of these fullerene-based systems in solution are usually unknown and, especially for polymeric materials inhomogeneous samples are frequently obtained. Furthermore, in many cases the amount of incorporated fullerene is not clearly determined. In addition, the presence of other molecules like the hosts or polymeric residues can cause unpredictable side effects and in no case the mode of action or activity can doubtlessly be associated with the fullerenes. However, for systematic investigations on structure-function relationships or extensive testings of toxicological or human availability properties, the use of structurally well-defined and characterized materials is mandatory. 

Proteins interact with each other in many different ways. These interactions may be structural, evolutionary, functional, sequence based, and metabolical. Life depends on such biomolecular interactions. Among all these interactions, structural ones are the simplest and easiest to investigate because they are the most definite. Therefore, the main goals of bioinformatics are to create and to maintain the databases of the biological information which may lead to better understanding of these interactions. 

In this paper we present a comprehensive first-principles study of the structural, electronic and optical properties of undoped and doped Si nanosystems. The aim is to investigate, in a systematic way, their structural, electronic and stability properties as a function of dimensionality and size, as well as pointing out the main changes induced by the nanostructure excitation. A comparison between the results obtained using different Density Functional Theory based methods will be presented. We will report results concerning two-dimensional, one-dimensional and zero-dimensional systems. In particular the absorption and emission spectra and the effects induced by the creation of an electron-hole pair are calculated and discussed in detail, including many-body effects. 

However, a new cause for the -type conductivity of ZnO has recently been proposed First-principles investigations based on density functional theory suggest that hydrogen in ZnO occurs exclusively in the positive charge state, i.e., it always acts as a donor." Recent muon spin rotation (pSR) and EPR studies confirmed the presence of hydrogen-related shallow donors. However, the molecular structure of these defects remains unknown. 

---