GADDLE Maps: General Algorithm for Discrete Object Deformations Based on Local Exchange Maps

Initiating Coarse-Grained MD Simulations for Membrane-Bound Proteins

Molecular dynamics (MD) simulations have become a widely used tool in the scientific community for understanding molecular scale phenomena that are challenging to address with wet-lab techniques. Coarse-grained simulations, in which multiple atoms are combined into single beads, allow for larger systems and longer time scales to be explored than atomistic techniques. Here, we describe the procedures and equipment required to set up coarse-grained simulations of membrane-bound proteins in a lipid bilayer that can mimic many membrane environments.

In Vitro-In Silico Modeling Approach to Rationally Designed Simple and Versatile Drug Delivery Systems

Rational design and development of a nanosystem usually relies on empirical approaches as well as a fair degree of serendipity. Understanding how nanosystems behave at the molecular level is of great importance for potential biomedical applications. In this work, we describe a nanosystem composed of two natural compounds, vitamin E and sphingomyelin, prepared by spontaneous emulsification (vitamin E-sphingomyelin nanosystems (VSNs)). Extensive characterization revealed suitable physicochemical properties, very high biocompatibility in vitro and in vivo, and colloidal stability during storage and in biological media, all relevant properties for clinical translation. We have additionally pursued a computational approach to gain an improved understanding of the assembling, structure, dynamics, and drug-loading capacity of VSNs, using both small molecules and biomolecules (resveratrol, curcumin, gemcitabine, and two peptides). The spontaneous formation of compartmentalized VSNs starting from completely disassembled molecules, observed here for the first time, was accurately assessed from the computational molecular dynamics trajectories. We describe here a synergistic in silico/in vitro approach showing the predictive power of computational simulations for VSNs' structural characterization and description of internal interaction mechanisms responsible for the association of bioactive molecules, representing a paradigm shift in the rational design of nanotechnologies as drug delivery systems for advanced personalized medicine.

Rings, Hexagons, Hetals, and Dipolar Moment Sink-Sources: The Fanciful Behavior of Water around Cyclodextrin Complexes

The basket-like geometry of cyclodextrins (CDs), with a cavity able to host hydrophobic groups, makes these molecules well suited for a large number of fundamental and industrial applications. Most of the established CD-based applications rely on trial and error studies, often ignoring key information at the atomic level that could be employed to design new products and to optimize their use. Computational simulations are well suited to fill this gap, especially in the case of CD systems due to their low number of degrees of freedom compared with typical macromolecular systems. Thus, the design and validation of solid and efficient methods to simulate and analyze CD-based systems is key to contribute to this field. The behavior of supramolecular complexes critically depends on the media where they are embedded, so the detailed characterization of the solvent is required to fully understand these systems. In the present work, we use the inclusion complex formed by two α-CDs and one sodium dodecyl sulfate molecule to test eight different parameterizations of the GROMOS and AMBER force fields, including several methods aimed to increase the conformational sampling in computational molecular dynamics simulation trajectories. The system proved to be extremely sensitive to the employed force field, as well as to the presence of a water/air interface. In agreement with previous experiments and in contrast to the results obtained with AMBER, the analysis of the simulations using GROMOS showed a quick adsorption of the complex to the interface as well as an extremely exotic behavior of the water molecules surrounding the structure both in the bulk aqueous solution and at the water surface. The chirality of the CD molecule seems to play an important role in this behavior. All together, these results are expected to be useful to better understand the behavior of CD-based supramolecular complexes such as adsorption or aggregation driving forces, as well as to introduce new methods able to speed up general MD simulations.

Computational Modeling of Realistic Cell Membranes

Cell membranes contain a large variety of lipid types and are crowded with proteins, endowing them with the plasticity needed to fulfill their key roles in cell functioning. The compositional complexity of cellular membranes gives rise to a heterogeneous lateral organization, which is still poorly understood. Computational models, in particular molecular dynamics simulations and related techniques, have provided important insight into the organizational principles of cell membranes over the past decades. Now, we are witnessing a transition from simulations of simpler membrane models to multicomponent systems, culminating in realistic models of an increasing variety of cell types and organelles. Here, we review the state of the art in the field of realistic membrane simulations and discuss the current limitations and challenges ahead.