Marco Lazzarino
The chemical description is linked with the study of some molecules that react at the end of a chain of reactions. Pointing in to forces will help us to develop new tech and a 'good carrier' Examples:
- Dna separetion in cellular mitosis
- Stem cell differentiation
- etc...
- Deseas involve biology mechaninc forces--> cancer, malaria, osteoporosys
Changement in mechanical properties of the cells are leading to many complec mechanism as cancer growth or diffusion in to the blood through cells' adhesion
Whic are the forces in our body?
- hearing
- touch
- control of vascula pressure
- proprioception --> position of the body All this elements are controlled from thousands of neurons
At nm scale energy and entropy have important roles, gravitational force is less than 10 pN
the force exerted by blood viscosity on blood cell is 300 pN
the entropy of a straighten line is very low, while the curled chain is much higher
The polymer acts like a spring and its spring constant goes $$ F = 3k_b T/ n b^2 = k R $$
it depends from the direction of exertion and can variate from breaking, unfolding and unzipping forces images from presentation Different mechanical force applied to same cells lead to cell death or proliferation. Another case is the focal adhesion mechanism, an experiment showed how the formation of actin in to cell is linked with direction and stiffness of the substrate. During mitosis the cell can exert even 1000 stronger forces on the substrate. A set of experiments explaining the effect of forces over cells.
Stem cells differentiate themselve depending of strenght of substrate, the soft substrate leads to neurons. Softness is defined trhough young modulus: Elasticity = P / elongation_rate = \frac {F L }{ \Delta L Area} the same parameters are used to the cell to, even if it s a visco elastic system, it wont' go back to same shape!
images from presentation. the neuron get confined from the graphene with different electrical properties, the graphene are 'suspended', 'not suspended', and neurons prefer to create wiring on more electrosensitive material.
There exist some mechano receptors which are protein of piezo family tranductors wich consists in ion channels letting ions flow when the cell membrane receive a pressure, a requirement of this is the membrane to be stiff, since the pressure can be applied far from the ion channel, and the pressure has to be transmitted to the ion channel.
On the other side a soft cytoskeleton is required since the pressure has to be unaffected from the rigidity of sub placed cytoskeleton.