Anders Irbäck

TL;DR: The isolated Abeta16-22 peptide is mainly a random coil in the sense that both the alpha-helix and beta-strand contents are low, whereas the three- and six-chain systems form aggregated structures with a high beta-sheet content.

Abstract: We study the thermodynamic behavior of a simple off‐lattice model for protein folding. The model is two dimensional and has two different ‘‘amino acids.’’ Using numerical simulations of all chains containing eight or ten monomers, we examine the sequence dependence at a fixed temperature. It is shown that only a few of the chains exist in unique folded state at this temperature, and the energy level spectra of chains with different types of behavior are compared. Furthermore, we use this model as a testbed for two improved Monte Carlo algorithms. Both algorithms are based on letting some parameter of the model become a dynamical variable; one of the algorithms uses a fluctuating temperature and the other a fluctuating monomer sequence. We find that by these algorithms one gains large factors in efficiency in comparison with conventional methods.

TL;DR: The decay from the 23+ state at about 2-MeV excitation in the nuclei Ba140, Ce142, and Nd144, with 84 neutrons, was shown to be consistent with its identification as the lowest state of mixed symmetry in the U(5) limit of the neutron-proton version of the interacting-boson model as mentioned in this paper.

TL;DR: A flexible and efficient program package written in C++, PROFASI, for simulating protein folding and aggregation, which is able to fold several peptides with about 20 residues, and has been used to study aggregation and force‐induced unfolding.

TL;DR: The results convincingly show that the amino acid sequences in proteins differ from what is expected from random sequences in a statistically significant way, and can be interpreted as originating from anticorrelations in terms of an Ising spin model for the hydrophobicities.