The transamidase subunit GAA1/GPAA1 is predicted to be the enzyme that catalyzes the attachment of the glycosylphosphatidyl (GPI) lipid anchor to the carbonyl intermediate of the substrate protein at the ω-site. Its ~300-amino acid residue lumenal domain is a M28 family metallo-peptide-synthetase with an α/β hydrolase fold, including a central 8-strand β-sheet and a single metal (most likely zinc) ion coordinated by 3 conserved polar residues. Phosphoethanolamine is used as an adaptor to make the non-peptide GPI lipid anchor look chemically similar to the N terminus of a peptide.
By the use of a dynamic Monte Carlo method, three‐generation dendrimers of type F1F2F2 with functionalities F1 = 3 to 6 and F2 = 2 to F1–1 are simulated and investigated as functions of spacer lengths, with a total chain length up to 200 000 segments. Highly diluted athermal and theta solutions are studied as well as properties of non‐reversal random walk dendrimers for comparison. For athermal conditions mean square dimensions obey the same scaling law regarding the total number of bonds as linear chains, irrespective of functionality and complexity. Likewise the theta parameter is the same for all systems investigated. Dimensions of theta systems are slightly expanded as compared to non‐reversal random walk data, the effect increasing with increasing F1 and F2 while shape data near to theta conditions fairly well coincide with those of non‐reversal random walks.
Pairs of linear chains – the end segment of one of each fixed at a surface – are analyzed for the relative probability of mutual contact formation between particularly specified segments i and j belonging to different chains within these pairs. Several positions are of general interest only, while other portray specific experimental conditions, e.g., the basic step in surface initiated Z‐RAFT polymerization (contact of the end of the free chain with the anchored segment of the fixed one). Contact probabilities are calculated for athermal cubic lattice chains by means of exact enumeration. Basic results are chain‐length dependences of shielding factors Kij in form of scaling laws and changes of size and shape properties of the involved molecules while approaching and penetration as functions of chain separation.
Modification of inorganic particles with organic polymer layers leads to well defined hybrid nanoparticles with tunable properties. Studies of such systems rely on the investigation of polymers near to or attached at a surface. In the present investigation, size, shape, and orientation are investigated as functions of the distance of the center of gravity of linear and starbranched polymers from the surface by use of Monte Carlo methods for neutral and attractive surfaces in good and moderate solvents. To quantify the strength of interaction, a parameter ''excluded distance'' is introduced. It vanishes if repulsive interaction due to the excluded volume effect and attractive ones compensate, which is roughly the case for surfacepolymer interactions similar to polymer-polymer interactions in theta solvents.
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