8 research outputs found
Automated Generation of Explicit Port-Hamiltonian Models from Multi-Bond Graphs
Port-Hamiltonian system theory is a well-known framework for the control of complex physical systems. The majority of port-Hamiltonian control design methods base on an \emph{explicit} input-state-output port-Hamiltonian model for the system under consideration. However in the literature, little effort has been made towards a systematic, automatable derivation of such explicit models.
In this paper, we present a constructive, formally rigorous method for an explicit port-Hamiltonian formulation of multi-bond graphs. Two conditions, one necessary and one sufficient, for the existence of an explicit port-Hamiltonian formulation of a multi-bond graph are given. We summarise our approach in a fully automated algorithm of which we provide an exemplary implementation along with this publication. The theoretical and practical results are illustrated through an academic example
Explicit port-Hamiltonian formulation of bond graphs with dependent storages
Explicit port-Hamiltonian systems (PHSs) are the starting point for many
powerful controller and observer design methods. It is well-known that explicit PHSs can be
formulated on the basis of bond graphs. Indeed, the port-Hamiltonian formulation of bond
graphs without dependent storages has been well investigated. However, little effort has been
made towards bond graphs with dependent storages. This is a problem as dependent storages
frequently occur in models from many engineering fields. In this paper, we address the explicit
port-Hamiltonian formulation of bond graphs with dependent storages. Our idea is to express the
port-Hamiltonian dynamics and output as functions of only the system inputs and independent
storages. The main result is a rigorous and constructive method to formulate bond graphs
containing dependent storages as explicit PHSs. An acadamic example illustrates and verifies
our method
Morphing of Amphipathic Helices to Explore the Activity and Selectivity of Membranolytic Antimicrobial Peptides
Naturally occurring membranolytic antimicrobial peptides (AMPs) are rarely cell-type selective and highly potent at the same time. Template-based peptide design can be used to generate AMPs with improved properties de novo. Following this approach, 18 linear peptides were obtained by computationally morphing the natural AMP Aurein 2.2d2 GLFDIVKKVVGALG into the synthetic model AMP KLLKLLKKLLKLLK. Eleven of the 18 chimeric designs inhibited the growth of Staphylococcus aureus, and six peptides were tested and found to be active against one resistant pathogenic strain or more. One of the peptides was broadly active against bacterial and fungal pathogens without exhibiting toxicity to certain human cell lines. Solution nuclear magnetic resonance and molecular dynamics simulation suggested an oblique-oriented membrane insertion mechanism of this helical de novo peptide. Temperature-resolved circular dichroism spectroscopy pointed to conformational flexibility as an essential feature of cell-type selective AMPs.ISSN:0006-2960ISSN:1520-499
Morphing of Amphipathic Helices to Explore the Activity and Selectivity of Membranolytic Antimicrobial Peptides
Naturally occurring membranolytic antimicrobial peptides (AMPs) are rarely cell-type selective and highly potent at the same time. Template-based peptide design can be used to generate AMPs with improved properties de novo. Following this approach, 18 linear peptides were obtained by computationally morphing the natural AMP Aurein 2.2d2 GLFDIVKKVVGALG into the synthetic model AMP KLLKLLKKLLKLLK. Eleven of the 18 chimeric designs inhibited the growth of Staphylococcus aureus, and six peptides were tested and found to be active against one resistant pathogenic strain or more. One of the peptides was broadly active against bacterial and fungal pathogens without exhibiting toxicity to certain human cell lines. Solution nuclear magnetic resonance and molecular dynamics simulation suggested an oblique-oriented membrane insertion mechanism of this helical de novo peptide. Temperature-resolved circular dichroism spectroscopy pointed to conformational flexibility as an essential feature of cell-type selective AMPs.ISSN:0006-2960ISSN:1520-499
Peptide–Membrane Interaction between Targeting and Lysis
Certain cationic
peptides interact with biological membranes. These
often-complex interactions can result in peptide targeting to the
membrane, or in membrane permeation, rupture, and cell lysis. We investigated
the relationship between the structural features of membrane-active
peptides and these effects, to better understand these processes.
To this end, we employed a computational method for morphing a membranolytic
antimicrobial peptide into a nonmembranolytic mitochondrial targeting
peptide by “directed simulated evolution.” The results
obtained demonstrate that superficially subtle sequence modifications
can strongly affect the peptides’ membranolytic and membrane-targeting
abilities. Spectroscopic and computational analyses suggest that N-
and C-terminal structural flexibility plays a crucial role in determining
the mode of peptide–membrane interaction