katsonis
49 flashcards · Other · by Giulia Mihaica
Artificial molecular mashines
class of molecules intended to produce mecha ical movements in response to certain stimuli mimiking macromolecular devices.
Nature’s molecular machines (made out of proteins)
Kinesin walkers - motor protein carries vesicle in a very specific direction to overcome diffusion Microtubuls - pulling forces for division of the cell Myosin V walking along actin filaments - contraction of muscles John Walker (rotor) - synthesise ATP - produces chemical potential, not forces
what are the catenanes?
type of molecule made up of two or more interlocked rings that cannot be separated without breaking their chemical bonds
how to make catenanes?
Cut ring in half performe a ring-closing reaction with a hope that some rings will form around others Use metal coordination (Cu ions) as a template to interlock the ring
what are the rotaxanes?
mechanically interlocked molecular architecture consisting of a dumbbell-shaped molecule which is threaded through a macrocycle (ring along molecular thread) first example of translational isomerism - control the ring position by protonation > musle based system (stretch or contract by adding or removing a proton)
application of rotoxanes
stroring info - chips in which one molecular state corresponds to one bit of information molecular switch - a ring shaped molecule threaded onto a liear molecule shifts between two binding sites depending on the acidity of the surrounding solution
What is a nanoscale molecular motor (feringa motor)?
molecule which has access to more complex movement - beyond translation with chirality and with double bonds
how does the molecular motor work
the double bond is rigid > shine light > electron goes from homo to lumo (from pi to pi*) > the electron is localized on the carbons > weak pi bond > free rotation > photoisomerization (go from trans to cis - unstable because of steric hindrance of Me groups) > helix inversion (180 rotation) > repeat photoisomerization and helix inv > 360 rotation. Light excites the molecule (crowded alkene). there is electronic transition from HOMO to LUMO (pi-pi* transition so the antobonding orbital is popul…
How to measure the motor
put molecule in solution > different spectra for each of the 4 steps
what is a nanocar?
combine four molecular motors on a scaffold. The direction of the rotation of each motor is determined by the asymmetric center - designed in such a way that the overall movement is translation. Overcrowded alkenes are difficult to make, so it is a very challenging molecule to make.
how to measure the nanocar?
The electrons from the tip of the STM leap onto the molecules that form the wheels, causing them to change configuration, rotate and move the car forward - There is one pulse between two images - the rotation is unidirectional because the helix inv goes only one way
how to Make molecules (nano objects) work together in space and time and preserve the properties?
Amplifying molecular motion (space) Synchronizing molecular machines Collective effects at the macroscopic level
how to amplify the nanoscale motion?
decouple form brownian storm encode cooperativity > macroscopic motion (work)
examples of amplification of nanoscale motion
bending - based on molecular switches (organise molecules from open form to closed form - top part photoswitches, bottom one not) move water droplet - light driven rotoxanes
what is active soft matter?
materials composed of many active agents that consume energy to move or exert forces, resulting in behaviors that are not in thermal equilibrium (eg bacteria)
what is chemo-mechanical transduction?
the process by which biological systems convert chemical energy into mechanical energy, allowing for the transport and release of specific biomolecules - myosin walking on actin filaments
Key elements for effective chemo-mechanical transduction
Originates at the molecular level (myosin motors) Anisotropy - orients the operation of the motors (Helical) structuration across length scales - mechanical properties
what is the best way to improve the directionality?
helical pathways - less sensitive to external perturbations (eg in bacteria, zooplankton, sperm cells, ciliates and flagellate protozoa etc)
Effect of handedness on the directionality of movemen
Nematic liquid crystal > Cholesteric liquid crystal > Disclination lines form a spiral (perpendicular anchoring) The solubilization rate of the molecules depends on their orientation at the droplet interface
liquid crystals
phase of matter which has the properties between the conventional liquid and solid phases.
LC in biological systems
crab shell - helical organization - mechanically work like springs which absorb energy at impact > the material does not break scarab - irredescent shell (different color depending on the angle) in material that forms the bone - packing properties DNA is packed tightly in chromosomes
Lyotropic liquid crystals in biology
Lamellar liquid crystalline phase Lα = organization Lalpha of liquid bilayer that constitutes the membrane • Maintaining cellular integrity but allows selective transport
Physical properties of liquid crystals
Sensitivity to small changes in their composition and/or in their environment – like other representatives of soft matter, liquid crystals are governed by weak forces – the typical energies associated with the bonds between structures and with the distortions of those structures are comparable in size to thermal energies. small changes yield large transformations sensitive matter (also sensitivity to boundary conditions) • Long-range order – propensity for self-assembly (at increasing hierarchi…
what are the two types of LC depending on how they reach the liquid crystalline phase
lyotropic and thermotropic
what are Lyotropic liquid crystals (+solvent, polydispersity, interactions, additives etc
The phase is formed by amphiphilic molecules in a certain concentration range The molecules composing the liquid crystal do not necessarily display pronounced shape anisotropy, but, in solution, supramolecular aggregates do
what are Thermotropic (rod-like) liquid crystals
the phase is formed by shape anisotropic molecules in a certain temperature rang The molecules composing the liquid crystal display shape anisotropy
types of thermotropic lc
calamitic, discotic, bend core
what are the different liquid crystalline phases
nematic - one preferential direction cholesteric - helical motion, periodic twist smectic - Orientational order + center of mass columnar phase - Orientational order + center of mass
what does the orientational order parameter S indicate
how well a quantity follows the avg orientation S = 0 [random and isotropic sample] • S = 1 [perfectly aligned sample] • 0.3<S<0.8 [typical liquid crystal sample] • S decreases with increasing temperature S nematic < S smectic
what is a helix described by
axis handedness (turns left or right) pitch = double geometrical period of helix - the vector rotates 360
role of chiral liquid crystals in biological materials
Maximization of packing efficiency Morphogenesis Mechanical stability Optical information Radiation protection
Optical properties of chiral liquid crystals
Selectivity in polarization- 50% reflection selective reflection of wavelength - delta lambda corresponds to the pitch in the cholesteric LC > change the angle of incidence = change the light observed
how can beetles be superreflectors?
half wave plate - switch polarization of light - first layer reflects rh polarized light - half wave plate (unidirectional layer) - second layer reflects lh polarised light
what is the Iridescence of liquid crystals
ridescence is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstructures or thin fil
what does Liquid-Liquid Crystalline Phase Separation do
helps spider silk proteins organise before they solidify in the final fiber - proteins undergo liquid-liquid and liquid -LC transformation as they concentrate. Aligment necessary for strength is already develped before fiber is spun
anisotropy in dna
dna wrappes around histeon protein to form nucleozomes (building blocks that are anisotropic) - form chromosomes (a lot of info, but it remains fluid and can dissasamble)
biomimetic shape shifting materials
potential properties of soft robots
adaptive delf healing outperforming current materials Suppressing the need to assemble devices
what are Liquid crystal polymers
Key structural fragment is the mesogenic group quantitatively dominating in macromolecule and predetermining the LC phase formation. All other groups taken separately or together transform LC polymer into the functional or multifunctional LC polymer with desired properties mesogens (rod like molec) - connect by covalent bonds > elastomers
examples of combining L crystalinity with other properties
kevlar - tough although it is held by H bonds - multivalency (a lot of H bonds) virus connect to cell - multivalency spider silk - LC polymer - the proteins that form the silk form platelets that connect - inspired technical clothing
cross linked polymer networks
linear polymers become cross linked - they have very different mechanical properties depending on the density of the links we can have elastomers or rubber (eg. sulfide bonds that connect polymers > vulcanization > tires)
LC polymer networks
Increasing the number of cross-links drives a transition from viscoelasticity (polymer) to rubber elasticity (elastomer or gel ==> elastic response to deformations, instead of flow
Molecular switches in liquid crystal elastomer
In LC networks, the order parameter is strongly correlated to the mechanical strain molecular switch - used in photochromic glasses molecular motor - helix inversion = 360 unidirectional rotation
azobenzenes
phenyl-N=N-phenyl electrostatics makes E isomer more stable than Z isomer no free rotation around the double bond
example of helix based movement in plants
cooling of cucumber tendrils opening of chiral seed pods the drilling motion of awns
example of application based on helix based movements in plants
the tendrils inspired soft robots flytrap inspired soft robots - LC with azobenzenes - contraction and expansion in different layers > bending seedpod (fast movement) inspired soft robot - the energy is not released gradually - we need to store energy and release it fast - we accumulate strain and when it passes a treshhold it releases it fast (in seedpods The pod valves are enantiomers that twist in opposite directions. At the structural level, this involves fibers integrated into a deformable…
examples of bioinspired applications
velcro - inspired from the way burr (polymer organized with hook structures that can attach to clothing fibers) attaches to furr sharkskin inpired surfaces - Sharkskin has inspired the design of surfaces that resist the growth of bacteria and algae. This has applications in creating more hygienic surfaces for medical equipment. The platelets of the shark skin have a V shape which promotes laminar flow. The platelets also have surface corrugation which disfavours adhesion of bacteria lotus insip…
what is biomimetics
creating policies materials and processes that are adapted to life on earth with a clear intention of solving societal challenges
Why are nanoscience and nanotechnology so specifically relevant to biomimetic design ?
In biology, materials are structured from nanoscale upwards. An important question in nanoscience is how to bring nanoscale object together and maintain their properties. So considering that the hierarchal organization is important, nanoscience has a great impact in biomimetics (implants inspired from cholesteric organization of compact bones, glues inpired by gekko, surfaces impired by shark skin etc). Moreover, in out technology we use over 40 elements, while in biology around 6 are necessary…