Results found: 3

Number of results on page

Search results

Search:
in the keywords: 87.15.He

Sort By:

Limit search:

The Increase in Protein Contour Length Depends on Mechanical Unfolding Conditions

100%

Dąbrowska A., Lebed K., Lekka M., Kulik A., Forró L.

Acta Physica Polonica A

2008

vol. 113

issue 2

753-762

Many proteins in alive organisms have a domain structure providing them the possibility to reversible unfolding, which seems to play an essential role in those processes occurring in tissues which are controlled by mechanical cellular tension. In this work the atomic force microscopy was applied to investigate the mechanical properties of the single molecules of fibronectin, a protein participating in the important mechanical processes in extracellular matrix. The results showed that the conditions of mechanical stretching influence not only the force required to unfolding of a domain but also the increase in protein contour length induced by such unfolding event. Two mean values of the increase in length (called shortly the unfolding length) L_1 and L_2, were obtained and ascribed to unfolding of either the whole fibronectin domain of type III (L_2) or its fragment (L_1). Both unfolding lengths revealed similar dependence on the stretching conditions. This experimental observation of increase in unfolding length with increasing loading rate was successfully described with a combination of two theoretical models (Bell model and the worm-like-chain model), previously used separately in the analysis of protein unfolding. The general mechanical property of fibronectin domains was emphasized and proposed as a potential determinant of the cellular adhesion.

Mössbauer Studies of Cu(II) Ions Interaction with the Non-Heme Iron and Cytochrome b_{559} in a Chlamydomonas reinhardtii PSI Minus Mutant

75%

Burda K., Kruk J., Strzałka K., Stanek J., Schmid G., Kruse O.

Acta Physica Polonica A

2006

vol. 109

issue 3

237-247

Mössbauer spectroscopy was applied, for the first time, to study the interaction of copper ions with the non-heme iron and the heme iron of cytochrome b_{559} in photosystem II thylakoids isolated from a Chlamydomonas reinhardtii photosystem I minus mutant. We showed that copper ions oxidize the heme iron and change its low spin state into a high spin state. This is probably due to deprotonation of the histidine coordinating the heme. We also found that copper preserves the non-heme iron in a low spin ferrous state, enhancing the covalence of iron bonds as compared to the untreated sample. We suggest that a disruption of hydrogen bonds stabilizing the quinone-iron complex by Cu^{2+} is the mechanism responsible for a new arrangement of the binding site of the non-heme iron leading to its more "tense" structure. Such a diamagnetic state of the non-heme iron induced by copper results in a magnetic decoupling of iron from the primary quinone acceptor. These results indicate that Cu does not cause removal of the non-heme iron from its binding site. The observed Cu^{2+} action on the non-heme iron and cytochrome b_{559} is similar to that previously observed forα-tocopherol quinone.

^1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions

75%

Dobies M., Kuśmia S., Jurga S.

Acta Physica Polonica A

2005

vol. 108

issue 1

33-46

The ^1H NMR relaxometry in combination with water proton spin-spin relaxation time measurements and rheometry have been applied to study the ionic gelation of 1% w/w aqueous low methoxyl pectin solution induced by divalent Ca^{2+} cations from a calcium chloride solution. The model-free approach to the analysis of ^1H NMR relaxometry data has been used to separate the information on the static (β) and dynamic (〈τ_c〉) behaviour of the systems tested. The ^1H NMR results confirm that the average mobility of both water and the pectin molecules is largely dependent on the concentration of the cross-linking agent. The character of this dependency (β,〈τ_c〉 and T_2 vs. CaCl_2 concentration) is consistent with the two-stage gelation process of low methoxyl pectin, in which the formation of strongly linked dimer associations (in the range of 0-2.5 mM CaCl_2) is followed by the appearance of weak inter-dimer aggregations (for CaCl_2 ≥ 3.5 mM). The presence of the weak gel structure for the sample with 3.5 mM CaCl_2 has been confirmed by rheological measurements. Apart from that, the T_1 and T_2 relaxation times have been found to be highly sensitive to the syneresis phenomenon, which can be useful to monitor the low methoxyl pectin gel network stability.

Refine search results

3 Acta Physica Polonica A

1 2008

1 2006

1 2005

1 Burda K.

1 Dobies M.

1 Dąbrowska A.

1 Forró L.

1 Jurga S.

1 Kruk J.

1 Kruse O.

1 Kulik A.

1 Kuśmia S.

1 Lebed K.

1 Lekka M.

1 Schmid G.

1 Stanek J.

1 Strzałka K.

Search results

The Increase in Protein Contour Length Depends on Mechanical Unfolding Conditions

Mössbauer Studies of Cu(II) Ions Interaction with the Non-Heme Iron and Cytochrome b_{559} in a Chlamydomonas reinhardtii PSI Minus Mutant

^1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions