Reversable deformation of artificial cell colony for muscle behavior mimicry triggered by actin polymerization

The mimicry of living tissues from artificial cells is beneficial to understanding the interaction mechanism among cells, as well as holding great potentials in the tissue engineering field. Self-powered artificial cells capable of reversible deformation are developed by encapsulating living mitochondria, actin proteins, and methylcellulose. Upon the addition of pyruvate molecules, the mitochondria produce ATP molecules as energy sources to trigger the polymerization of actin. ATP molecules were produced by mitochondria (2.76×1010/ml) with the concentrations of 35.8±3.2 µ M, 158.2±19.3 µ M and 200.7±20.1 µ M by adding pyruvate molecules with the concentration of 3 µ M; 12 µ M and 21 µ M, respectively. The reversible deformation of artificial cells is experienced with spindle shape resulting from the polymerization of actins to form filaments adjacent to the lipid bilayer, subsequently back to spherical shape resulting from the depolymerization of actin filaments upon laser irradiations. The linear colonies composed of these artificial cells exhibit collective contraction and relaxation behavior to mimic muscle tissues. At the stage of maximum contraction, the long axis of each GUV is in parallel to each other. All colonies are synchronized in the contraction phase. The deformation of each GUV in the colonies is influenced by its adjacent GUVs. The muscle-like artificial cell colonies paved the path to develop sustainably self-powered artificial tissues in the field of tissue engineering.

Moisture-induced deformations of wood and shape memory

Wood is known to swell substantially during moisture adsorption and shrink during desorption. These deformations may lead to wood damage in the form of cracking and disjoining of wooden components in e.g. floor or windows. Two swelling mechanisms may be distinguished: reversible swelling/shrinkage and moisture-induced shape memory effect. In the latter, wood is deformed in the wet state and afterward dried under maintained deformation, in order that wood retains its deformed shape even after the removal of the mechanical loading, called fixation. When wood is wetted again, it loses its fixation, partially regains its original shape, called recovery. These two mechanisms have their origin at the nanoscale and are modelled here using atomistic simulation and after upscaled to continuum level allowing finite element modelling. Hysteretic sorption and swelling are explained at nanoscale by the opening and closing of sorption sites in ad-and desorption, where in desorption water molecules preferentially remained bonded at sorption sites. The moisture-induced shape memory is explained by the moisture-induced activation of the interfaces between the reinforcing crystalline cellulose fibres and its matrix at nanoscale, referred to as a molecular switch. Our work aims to highlight that the understanding of sorption-induced reversible deformation and moisture-induced shape memory may play an important role in wood engineering and in building physics applications.

Erythrocyte Plasmalemma and Its Changes During the Cell Lifespan

The article reviews literature on the organization of the erythrocyte plasmalemma and its rearrangements at different periods of the cell lifespan. In the absence of a nucleus and organelles, the plasmalemma is the only structural element of erythrocytes involved in all processes of their vital activity. The plasmalemma supports the disk-like shape of the erythrocyte, provides its ability to reversible deformation, maintains intracellular homeostasis, participates in gas transport and energy metabolism, also transfers hormones, enzymes, antibodies, medicines and other substances on its surface. The polyfunctionality of the plasmalemma is provided by the peculiarities of its lipid, protein, and carbohydrate composition, as well as by the presence of a unique cytoskeleto n, morphologically associated with the erythrocyte membrane. The plasmalemma has the substantial modifications during the erythrocyte lifespan, namely, in maturation of reticulocytes, in the processes of functioning, aging, and cell death. Biochemical rearrangements of the plasmalemma serve as triggers for events such as membrane vesiculation, eryptosis, and elimination of senescent erythrocytes by macrophages. Age-related changes in the erythrocyte plasmalemma are adoptive in nature and aimed at maintaining cellular homeostasis and functional activity of these formed elements during a four-month stay in the bloodstream.

How Do Molecular Motions Affect Structures and Properties at Molecule and Aggregate Levels?

<p>Experimental and theoretical analysis demonstrated that the active intramolecular motions in the excited state of all molecules at single molecule level imparted them with more twisted structural conformations and weak emission. However, owing to the restriction of intramolecular motions in the nano/macro aggregate state, all the molecules assumed less twisted conformations with bright emission. Synergic strong and weak intermolecular interactions allowed their crystals to undergo reversible deformation, which effectively solved the problem of the brittles of organic crystals, meanwhile imparted them with excellent elastic performance. </p>

How Do Molecular Motions Affect Structures and Properties at Molecule and Aggregate Levels?

<p>Experimental and theoretical analysis demonstrated that the active intramolecular motions in the excited state of all molecules at single molecule level imparted them with more twisted structural conformations and weak emission. However, owing to the restriction of intramolecular motions in the nano/macro aggregate state, all the molecules assumed less twisted conformations with bright emission. Synergic strong and weak intermolecular interactions allowed their crystals to undergo reversible deformation, which effectively solved the problem of the brittles of organic crystals, meanwhile imparted them with excellent elastic performance. </p>