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Scientists say they have determined how red blood cells (RBCs) move, showing that RBCs can be moved by external forces and actively “wriggle” on their own.
Linking physical principles and biological reality, the team found that fast molecules in the vicinity of RBCs make the cell membranes wriggle, but the cells themselves also become active when they have enough reaction time.
The group recounted these findings in Nature Physics.
Previously, scientists had only shown that RBCs’ constant wriggling was caused by external forces. But biological considerations suggested that internal forces might also be responsible for the RBCs’ membranes changing shape.
“So we started with the following question, ‘As blood cells are living cells, why shouldn’t internal forces inside the cell also have an impact on the membrane?’” said study author Timo Betz, PhD, of Münster University in Münster, Germany.
“For biologists, this is all clear, but these forces were just never a part of any physical equation.”
Dr Betz and his colleagues wanted to find out more about the mechanics of blood cells and gain a detailed understanding of the forces that move and shape cells.
The team said it is important to learn about RBCs’ properties and their internal forces because they are unusually soft and elastic and must change their shape to pass through blood vessels. It is precisely because RBCs are normally so soft that, in previous studies, physicists measured large thermal fluctuations at the outer membrane of the cells.
These natural movements of molecules are defined by the ambient temperature. In other words, the cell membrane moves because molecules in the vicinity jog it. Under the microscope, this makes the RBCs appear to be wriggling.
Although this explains why RBCs move, it does not address the question of possible internal forces being a contributing factor.
So Dr Betz and his colleagues used optical tweezers to take a close look at the fluctuations of RBCs. The team stretched RBCs in a petri dish and analyzed the behavior of the cells.
The result was that, if the RBCs had enough reaction time, they became active themselves and were able to counteract the force of the optical tweezers. If they did not have this time, they were at the mercy of their environment, and only temperature-related forces were measured.
“By comparing both sets of measurements, we can exactly define how fast the cells become active themselves and what force they generate in order to change shape,” Dr Betz explained.
He and his colleagues have a theory as to which forces inside RBCs cause the cell membrane to change shape.
“Transport proteins could generate such forces in the membrane by moving ions from one side of the membrane to the other,” said study author Gerhard Gompper, PhD, of the Jülich Institute of Complex Systems in Jülich, Germany.
“Now, it’s up to the biologists, because we physicists only have a rough idea about which proteins might be the drivers for this movement,” Dr Betz added. “On the other hand, we can predict exactly how fast and how strong they are.” 
Scientists say they have determined how red blood cells (RBCs) move, showing that RBCs can be moved by external forces and actively “wriggle” on their own.
Linking physical principles and biological reality, the team found that fast molecules in the vicinity of RBCs make the cell membranes wriggle, but the cells themselves also become active when they have enough reaction time.
The group recounted these findings in Nature Physics.
Previously, scientists had only shown that RBCs’ constant wriggling was caused by external forces. But biological considerations suggested that internal forces might also be responsible for the RBCs’ membranes changing shape.
“So we started with the following question, ‘As blood cells are living cells, why shouldn’t internal forces inside the cell also have an impact on the membrane?’” said study author Timo Betz, PhD, of Münster University in Münster, Germany.
“For biologists, this is all clear, but these forces were just never a part of any physical equation.”
Dr Betz and his colleagues wanted to find out more about the mechanics of blood cells and gain a detailed understanding of the forces that move and shape cells.
The team said it is important to learn about RBCs’ properties and their internal forces because they are unusually soft and elastic and must change their shape to pass through blood vessels. It is precisely because RBCs are normally so soft that, in previous studies, physicists measured large thermal fluctuations at the outer membrane of the cells.
These natural movements of molecules are defined by the ambient temperature. In other words, the cell membrane moves because molecules in the vicinity jog it. Under the microscope, this makes the RBCs appear to be wriggling.
Although this explains why RBCs move, it does not address the question of possible internal forces being a contributing factor.
So Dr Betz and his colleagues used optical tweezers to take a close look at the fluctuations of RBCs. The team stretched RBCs in a petri dish and analyzed the behavior of the cells.
The result was that, if the RBCs had enough reaction time, they became active themselves and were able to counteract the force of the optical tweezers. If they did not have this time, they were at the mercy of their environment, and only temperature-related forces were measured.
“By comparing both sets of measurements, we can exactly define how fast the cells become active themselves and what force they generate in order to change shape,” Dr Betz explained.
He and his colleagues have a theory as to which forces inside RBCs cause the cell membrane to change shape.
“Transport proteins could generate such forces in the membrane by moving ions from one side of the membrane to the other,” said study author Gerhard Gompper, PhD, of the Jülich Institute of Complex Systems in Jülich, Germany.
“Now, it’s up to the biologists, because we physicists only have a rough idea about which proteins might be the drivers for this movement,” Dr Betz added. “On the other hand, we can predict exactly how fast and how strong they are.”
Scientists say they have determined how red blood cells (RBCs) move, showing that RBCs can be moved by external forces and actively “wriggle” on their own.
Linking physical principles and biological reality, the team found that fast molecules in the vicinity of RBCs make the cell membranes wriggle, but the cells themselves also become active when they have enough reaction time.
The group recounted these findings in Nature Physics.
Previously, scientists had only shown that RBCs’ constant wriggling was caused by external forces. But biological considerations suggested that internal forces might also be responsible for the RBCs’ membranes changing shape.
“So we started with the following question, ‘As blood cells are living cells, why shouldn’t internal forces inside the cell also have an impact on the membrane?’” said study author Timo Betz, PhD, of Münster University in Münster, Germany.
“For biologists, this is all clear, but these forces were just never a part of any physical equation.”
Dr Betz and his colleagues wanted to find out more about the mechanics of blood cells and gain a detailed understanding of the forces that move and shape cells.
The team said it is important to learn about RBCs’ properties and their internal forces because they are unusually soft and elastic and must change their shape to pass through blood vessels. It is precisely because RBCs are normally so soft that, in previous studies, physicists measured large thermal fluctuations at the outer membrane of the cells.
These natural movements of molecules are defined by the ambient temperature. In other words, the cell membrane moves because molecules in the vicinity jog it. Under the microscope, this makes the RBCs appear to be wriggling.
Although this explains why RBCs move, it does not address the question of possible internal forces being a contributing factor.
So Dr Betz and his colleagues used optical tweezers to take a close look at the fluctuations of RBCs. The team stretched RBCs in a petri dish and analyzed the behavior of the cells.
The result was that, if the RBCs had enough reaction time, they became active themselves and were able to counteract the force of the optical tweezers. If they did not have this time, they were at the mercy of their environment, and only temperature-related forces were measured.
“By comparing both sets of measurements, we can exactly define how fast the cells become active themselves and what force they generate in order to change shape,” Dr Betz explained.
He and his colleagues have a theory as to which forces inside RBCs cause the cell membrane to change shape.
“Transport proteins could generate such forces in the membrane by moving ions from one side of the membrane to the other,” said study author Gerhard Gompper, PhD, of the Jülich Institute of Complex Systems in Jülich, Germany.
“Now, it’s up to the biologists, because we physicists only have a rough idea about which proteins might be the drivers for this movement,” Dr Betz added. “On the other hand, we can predict exactly how fast and how strong they are.”