|
|
Controlled modification of tips usable for selected measurement modes of atomic force microscopy
Lišková, Kateřina ; Szabová, Jana (referee) ; Smilek, Jiří (advisor)
This master's thesis deals with the modification of tips commonly used in atomic force microscopy and their following utilization for determining the mechanical properties of selected hydrogel systems at the local level. For targeted modification, a method of micro-particle fixation on a cantilever was chosen, which was successfully modified using melamine resin particles. Initially, the mechanical properties of a selected representative of physically cross-linked hydrogels (agarose polysaccharide) were measured, which were evaluated based on the Young's modulus of elasticity, adhesive force, and work. The obtained results were compared with values measured using two commercially available cantilevers differing in both shape and basic parameters such as spring constant and resonance frequency. Subsequently, the influence of the setpoint force applied to the sample by the cantilever was verified. The usability of modified cantilevers was also tested on a selected representative of ionically cross-linked hydrogels (sodium alginate cross-linked with multivalent ions). Within the experimental part of the master's thesis, it was verified that the use of cantilevers with a higher contact area leads to more reliable results in terms of reliability and reproducibility, considering that the final value of the Young's modulus includes not only the contribution of the polymer chain but also the pores. When determining mechanical values, it is important to specify not only the cantilever used and its properties but also all other experimental parameters, the change of which may affect the final values of the Young's modulus determined at the micro level by atomic force microscopy.
|
|
| |
|
| |
|
|
Membrane protein interactions studied on single molecular level by force spectroscopy, optical spectroscopy and methods of computational biochemistry
MATĚNOVÁ, Martina
I have set for a challenging study that combined experimental and theoretical approaches in an attempt to resolve a role of small aminoacids in intermolecular interactions. First, I have proposed a hypothesis that described the interaction among individual aminoacids forming D helices of D1 and D2 proteins based on molecular dynamic simulations of a simplified model representing the reaction centre of photosystem II. Stability of the putative interhelical hydrogen bond network connecting D1 and D2 proteins was investigated experimentally with dynamic force spectroscopy using atomic force microscope. The results of both methods are in a full agreement with each other and reveal the key role of D1-Gly208 aminoacid in stability and functionality of photosystem II by providing milieu for weak interactions among three contact points at the cross of D helices: D1-Gly208 (O) and D2-Cys211 (O?), D1-Ser209 (O?) and D2-Ile204 (O), D1-Ser212 (O?) and D2-Gly207 (O). Mutation of the D1-Gly208 led to the increase in probability of the binding among the aforementioned aminoacids, undesirably strengthening the overall interactions among the proteins compromising photosynthetic capacity (D1-Ser208) or disabling of autotrophic growth (D1-Val208).
|
|
|
Mechanisms involved in sodium uptake activation by the Tumor Necrosis Factor-derived TIP peptide
DULEBO, Alexander
The Tumor Necrosis Factor derived-TIP peptide is a small 17 amino acids cyclic peptide with lectin-like activity, that possesses several therapeutically relevant biological activities, among which is activation of alveolar liquid clearance in both healthy and injured lungs in vivo. Accumulation of fluid in the lungs? alveoli and interstitial spaces is a life-threatening condition called pulmonary edema. The mortality rate due permeability pulmonary edema, accompanied by a dysfunction of the alveolar/capillary barrier, is high because no effective treatment lacking side effects exists nowadays. It is known that the TIP peptide is able to activate vectorial Na+ transport ? which mediates lung liquid clearance. However, the mechanism of action of remains elusive. The aim of this thesis was to investigate the initial steps of interaction between the TIP peptide and airway epithelial cells. Numerous novel methods and single-molecule techniques were used to unravel: (i) how the TIP peptide interacts with the molecules on the apical side of the lung epithelial cells; (ii) whether the TIP peptide need to be internalized inside of the cells to trigger its effects; (iii) the nature of the interaction between the TIP peptide and its putative receptor(s); (iv) the putative receptor(s) for the TIP peptide on the apical surface of the lung epithelial cells.
|
|
|
Membrane protein interactions studied on single molecular level by force spectroscopy, optical spectroscopy and methods of computational biochemistry
MATĚNOVÁ, Martina
I have set for a challenging study that combined experimental and theoretical approaches in an attempt to resolve a role of small aminoacids in intermolecular interactions. First, I have proposed a hypothesis that described the interaction among individual aminoacids forming D helices of D1 and D2 proteins based on molecular dynamic simulations of a simplified model representing the reaction centre of photosystem II. Stability of the putative interhelical hydrogen bond network connecting D1 and D2 proteins was investigated experimentally with dynamic force spectroscopy using atomic force microscope. The results of both methods are in a full agreement with each other and reveal the key role of D1-Gly208 aminoacid in stability and functionality of photosystem II by providing milieu for weak interactions among three contact points at the cross of D helices: D1-Gly208 (O) and D2-Cys211 (O?), D1-Ser209 (O?) and D2-Ile204 (O), D1-Ser212 (O?) and D2-Gly207 (O). Mutation of the D1-Gly208 led to the increase in probability of the binding among the aforementioned aminoacids, undesirably strengthening the overall interactions among the proteins compromising photosynthetic capacity (D1-Ser208) or disabling of autotrophic growth (D1-Val208).
|
guest ::
