EPJ E Topical Review: Gyrotactic phytoplankton in laminar and turbulent ﬂows: A dynamical systems approach
- Published on 20 March 2019
Biological and geophysical fluids host a sea of microorganisms many of which are motile. An often overlooked aspect of the life of such microorganisms is that the fluids where they are suspended are not still but flowing. In this brief review published in EPJ E, the authors aim to describe some of the interesting phenomena that can emerge due to the modification of the microorganisms' swimming direction by velocity gradients, which affect both the individual motion of microorganisms and their spatial distribution in dilute suspensions.
- Published on 06 February 2019
Moving around small objects using capillary forces is a phenomenon that has stimulated scientists trying to understand the fundamental mechanisms at play. It is also important for many industrial, technological and analytical processes, for example micro-fluidics, oil and gas displacement, mineral flotation, miniature robot and biomechanics. In this EPJ E topical review article Jianlin Liu and Shanpeng Li present a critical review of capillarity-driven migration in which many examples are presented and explained. The small objects in question are non-deformable objects, such as particles, rods, disks and metal sheets as well as soft objects, such as droplets and bubbles. The authors clarify some misunderstandings on the conventional views on these systems.
- Published on 15 January 2019
A new study presents new models describing how the adsorption of calcium, barium and strontium ions onto biological membranes may affect the functions of cells
Ions with two positive electrical charges, such as calcium ions, play a key role in biological cell membranes. The adsorption of ions in solution onto the membrane surface is so significant that it affects the structural and functional properties of the biological cells. Specifically, ions interact with surface molecules such as a double layer of lipids, or liposomes, formed from phosphatidylcholines (PC). In a new study published in EPJ E, Izabela Dobrzyńska from the University of Białystok, Poland, develops a mathematical model describing the electrical properties of biological membranes when ions such as calcium, barium and strontium adsorb onto them at different pH levels. Her works helps shed light on how ion adsorption reduces the effective surface concentration of add-on molecules with a specific function that can take part in biochemical reactions. These factors need to be taken into account when studying the diverse phenomena that occur at the lipid membrane in living cells, such as ion transport mechanisms.
EPJ E Highlight - Sac with spiral surface patterns facilitate substance delivery through biological membranes
- Published on 17 December 2018
Faceted microfilms made up of liquid crystals arranged in spiral patterns can help squeeze through membranes and deliver helpful molecules
Imagine a micron-sized ball of fluid enclosed in a thin film, similar to the film in soap bubbles, but made up of molecules resembling liquid crystal. These molecules can lower their overall energy by aligning their directions with their ever-changing neighbours—a state referred to as smectic phase. This means stacks of parallel stripe-like liquid-crystal layers form in the film. In a new study published in EPJ E, Francesco Serafin, affiliated with both Syracuse University, New York, and the Kavli Institute for Theoretical Physics (KITP) at UCSB, USA, together with his advisor Mark Bowick, also at the KITP, and Sid Nagel, from the University of Chicago, IL,USA, map out all the possible smectic patterns of such spherical films, or sac, at zero temperature. They determine the conditions under which it becomes easier for such sacs to pass through biological membranes and, potentially, deliver molecules attached to them at specific locations.
- Published on 21 November 2018
A new study outlines the key parameters affecting the production of gas from shale reservoirs, by simulating what is happening at the microscopic scale.
Extracting gas from new sources is vital in order to supplement dwindling conventional supplies. Shale reservoirs host gas trapped in the pores of mudstone, which consists of a mixture of silt mineral particles ranging from 4 to 60 microns in size, and clay elements smaller than 4 microns. Surprisingly, the oil and gas industry still lacks a firm understanding of how the pore space and geological factors affect gas storage and its ability to flow in the shale. In a study published in EPJ E, Natalia Kovalchuk and Constantinos Hadjistassou from the University of Nicosia, Cyprus, review the current state of knowledge regarding flow processes occurring at scales ranging from the nano- to the microscopic during shale gas extraction. This knowledge can help to improve gas recovery and lower shale gas production costs.
EPJ E Highlight - Pore size alone does not matter when biological nanopores act as sugar chain biosensors
- Published on 07 November 2018
The effectiveness of nanopore biosensors capable of identifying sugar chains from biological molecules involved in key biological processes also depends on the nanopore's electrical charge and inner pore design
Protein nanopores are present in cell membranes and act as biological gateways. This means that they can also be used for the detection of specific bioactive molecular chains, like sugar chains, such as molecules from the glycosaminoglycan family. The latter are responsible for key interactions at the cellular level. They typically mediate interactions with cell surfaces or with proteins, resulting in the activiation of physiological and pathological effects in embryonic development, cell growth and differentiation, inflammatory response, tumour growth and microbial infection. The use of such nanopores as biosensors requires to fully understand the intricate mechanisms occurring as sugar chains pass through them. In a new study published in EPJ E, Aziz Fennouri from Paris-Saclay University in Evry, France, and colleagues outline the key criteria determining the effectiveness of two types of nanopores in the detection of sugar chains.
- Published on 16 October 2018
Physicists develop a model to explain how deforming a helix could generate additional locomotion for some microorganisms and mini-robots
Many microorganisms rely on helices to move. For example, some bacteria rotate a helical tail, called a flagellar filament, for thrust and deform these tails during rotation. In addition, some types of bacteria, named Spirochaetes, rely on the deformation of a helical body for their motion. To better understand such locomotion mechanisms, scientists have created mathematical models of mini-robots with helical structures, referred to as swimmers. In a recent study published in EPJ E, Lyndon Koens from the University of Cambridge, UK, and colleagues, identify the factors enhancing the agility of deforming helix swimmers.
EPJ E Highlight - How lactoferrin clamps down on free roaming iron ions to stop nefarious effects on cells
- Published on 20 September 2018
New study elucidates structure of the protein lactoferrin as it undergoes transition from an open to a closed structure to decrease the level of free iron ions in the body
What prevents our cells from being overexposed to iron ions roaming freely in the body is a protein called lactoferrin, known for its ability to bind tightly to such ions. These free ions are essential for a number of biological processes. If found in excessive quantities, however, they could cause damage to proteins and DNA in the body, sometimes even leading to cell death. This is because free iron ions lead to an increase of the concentration of reactive substances with oxidising power roaming freely in the body. This has driven scientists to develop a better understanding of how lactoferrin's structural change helps to clamp down on free iron ions. In a new study published in EPJ E, Lilia Anghel from the Institute of Chemistry in Chisinau, Republic of Moldova, and research collaborators study the changes in the structure of lactoferrin as it binds to iron ions, using combined experimental and molecular dynamics simulations.
- Published on 18 September 2018
New study demonstrates adsorption of chemotherapy drugs onto active carbon delivery capsule can be enhanced with aluminium atom inclusions
The efficacy of chemotherapy treatment depends on how effectively it reaches cancerous cells. Increasing targeted delivery could mean decreasing side effects. Scientists are enhancing methods of selectively transmitting active chemotherapy agents and reducing their toxicity by encapsulating chemo drugs into active carbon used as the targeted delivery device. In a new study published in EPJ E, Gabriel Román, from the National University of the South, in Bahia Blanca, Argentina, and colleagues have demonstrated that adding minute amounts of aluminium atoms onto activated carbon atoms helps increase the adsorption onto the delivery carbon capsule of a standard chemotherapy drug, called 5-Fluorouracil (5-FU). This drug is typically used for stomach, colorectal, neck and head cancer treatments. This model could lead to more effective and convenient cancer treatments with fewer side effects by encapsulating the chemo drug into the active carbon, so that it can be taken orally.
EPJE Colloquium – Theories that help us understand self-assembling soft matter with strong interacting groups
- Published on 12 September 2018
Amphiphilic molecules contain both hydrophilic and lipophilic moieties. When in solution they produce structures coming from cooperative interactions of many functional units acting in synergy. Most self-assembling soft matter systems involve strong specific interactions of functional units leading to qualitatively new structures of highly soluble micellar or fibrillar aggregates. In this EPJ E Colloquium, Nyrkova and Semenov focus on the systems with the incorporated into unimer molecules and discuss the effects of packing frustrations and unimer chirality as well as the origins of spontaneous morphological chirality in the case of achiral unimers. They describe several theoretical approaches (overcoming the limitations of weak interaction models) including the concepts of super-strong segregation, geometrical mismatch and orientational frustration. They also review some recently developed phenomenological theories of surfactant membranes and multiscale hierarchical approaches based on all-atomic modeling of packing structures of amphiphilic molecules with strongly interacting groups.