Tree-like molecules surface

Lipids form membranes inside and around the cell. Carbohydrates form complex tree-like molecules that become attached to the surface of proteins and cellular membranes. In both cases, the three-dimensional molecular structure is not unique, but the molecular assemblies are highly flexible. Thus, analyzing the molecular structure involves the inspection of a process in time. Molecular dynamics is the only available computer-based method for doing so. Compared with protein structures there are relatively few results on lipids and carbohydrates. The book does not detail this topic. 

The acetylcholinesterase enzyme has a fascinating tree-like structure (Fig. 11.45). The trunk of the tree is a collagen molecule which is anchored to the cell membrane. There are three branches (disulfide bridges) leading off from the trunk, each of which hold the acetylcholinesterase enzyme above the surface of the membrane. The enzyme itself is made up of four protein subunits, each of which has an active site. Therefore, each enzyme tree has twelve active sites. 

A dendrimer is a hyperbranched polymer molecule that has a well-defined molecular weight. It has a globular architecture with several dendrons (dendron a tree-like polymer molecule with a trunk) that are connected to a central core. Its distinctive features include a controlled size (15 nm in diameter), multivalency, and the surface charge of ionizable dendrimer terminal groups, which can vary in the generation number [4]. 

In catalysis of cyclohexane on platinized spirals of nichrome heated by electric current, the author and Kotelkov observed 327) considerable coke formation. A puzzling feature of this process is that with the accumulation of coke the reaction rate not only does not fall but at first even increases. This was explained by the author with the help of the dendrite hypothesis of coke formation coke grows in the form of dendrites the foundations of which lie on the interface between chromium (or chromia) and nickel (see above). Dendrites do not prevent the molecules of cyclohexane from getting to the surface of nickel, just like trees that do not prevent the rain from getting into the ground in the forest. The initial acceleration of the reaction with the accumulation of coke was explained by the corrosion of metal because of the formation of carbides as the first stage of coke formation and of the decomposition of these carbides. 

Condensation of water vapor occurs when the dew point is undershot onto cooler surfaces resulting in a subsequent diffusion process in the direction of the surface (that is dry deposition, similar to surface removal of other molecules than H2O, but these are ad- or absorbed onto the surface - only water can condense into liquid in the earth s climate system). When the temperature is above 0°C, liquid drops (not film) are formed on the surface - most likely on condensation or crystallization centers - and we call it dew. If r < 0 °C, water vapor is transferred into ice on the surface frost) in different sizes and forms, mostly depending on temperature and wind on trees, filigreed ice needles and structures are formed hoar frost). 

The name dendrimer comes from the ancient Greek words dendron , which means tree, and meros , which means part. Dendrimers are synthetic highly branched globular molecules.They consist of a central core molecule with three attachment points dendrons which bind to these attachment points look like tree arms and sometimes have surface modification (see Figure 11.5). They form highly symmetric, generally mono-disperse and pure nanocarriers which have well-defined architecture, size and shape. 

---