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1
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NMR-based localization of ions involved in salting out of hen egg white lysozyme

100%
Poznański J.
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2006
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vol. 53
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issue 2
421-424
EN
NaCl-induced aggregation of hen egg white lysozyme (HEWL) was monitored by NMR spectroscopy. Small, but significant, changes induced by salt addition in TOCSY spectra were attributed to the effect of local reorganization of protein backbone upon ion binding. Salt-induced variations in HN and Hα chemical shifts were mapped on the HEWL 3D structure which allowed the construction of a scheme of the spatial localization of potential ion binding sites. It was found that in a 0.5 M NaCl solution six chloride anions and at least one sodium cation are bound to preferred sites on the HEWL surface.
2
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Poszukiwanie modelu wody opisującego hydratację biologicznych makromolekuł

100%
Poznański J.
Kosmos
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2006
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vol. 55
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issue 2-3
149-164
EN
The first model of liquid water at atomic resolution was proposed as early as in 1933. Since that time a vast amount of data concerning both microscopic and macroscopic parameters describing hydration phenomena has been collected. Majority of experimental and theoretical studies pointed out that the main driving force of the so called “hydrophobic interactions” is an entropic effect connected with the solute-induced reorganization of solvation shells. Water molecules surrounding apolar solutes were shown to organize in ice-like structures, the properties of which, in particular molecular packing, proton relaxation rates, distribution and strength of intermolecular H-bonds, differ significantly from those determined for the bulk water. Dozens of models were proposed to describe properties of aqueous solutions at different length-scales, but up to 1999 there was no uniform theory of water for the scales varying from nanometers up to millimeters/centimeters, Recently developed LCW model, by K. Lum, D. Chandler and J. D. Weeks, is the first one, which could be applied to a wide range of phenomena including atom hydration, macromolecule solvation, surface wetting, etc.
3
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CD investigations on conformation of H-X-(Pro)i_n-Y-OH peptides (X = Trp, Tyr; Y = Tyr, Met); models for intramolecular long range electron transfer

51%
Wierzchowski K. L., Majcher K., Poznański J.
Acta Biochimica Polonica
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1995
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vol. 42
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issue 2
259-268
4
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Circular dichroism analysis for multidomain proteins: studies of the irreversible unfolding of Hepatitis C virus helicase

51%
Gozdek A., Stankiewicz-Drogoń A., Poznański J., Boguszewska-Chachulska A. M.
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2008
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vol. 55
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issue 1
57-66
EN
The non-structural protein 3 (NS3) of Hepatitis C virus (HCV) is a bifunctional enzyme with RNA-dependent NTPase/RNA helicase and serine protease activities, and thus represents a promising target for anti-HCV therapy. These functions are performed by two distinct moieties; the N-terminal protease domain and the C-terminal helicase domain that further folds into three structural subdomains. To obtain lower molecular mass proteins suitable for nuclear magnetic resonance studies of helicase-inhibitor complexes, helicase domains 1, 2, and 1+2 devoid of a hydrophobic β-loop were overexpressed and purified. Circular dichroism studies were carried out to confirm the secondary structure content and to determine thermodynamic parameters describing the stability of the proteins. Both thermal and GuHCl-induced unfolding experiments confirmed the multidomain organization of the helicase. The unfolding transition observed for domain 1+2 was in agreement with the model of two well-resolved successive steps corresponding to the independent unfolding of domains 1 and 2, respectively. In the case of the full-length helicase, the presence of domain 3 remarkably changed the transition profile, leading to fast and irreversible transformation of partially unfolded protein.
5
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Halogen bonds involved in binding of halogenated ligands by protein kinases

45%
Poznański J., Winiewska M., Czapinska H., Poznańska A., Shugar D.
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2016
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vol. 63
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issue 2
203-214
EN
Analysis of 664 known structures of protein kinase complexes with halogenated ligands revealed 424 short contacts between a halogen atom and a potential protein X-bond acceptor, the topology and geometry of which were analyzed according to the type of a halogen atom (X = Cl, Br, I) and a putative protein X-bond acceptor. Among 236 identified halogen bonds, the most represented ones are directed to backbone carbonyls of the hinge region and may replace the pattern of ATP-like hydrogen bonds. Some halogen-π interactions with either aromatic residues or peptide bonds, that accompany the interaction with the hinge region, may possibly enhance ligand selectivity. Interestingly, many of these halogen-π interactions are bifurcated. Geometrical preferences identify iodine as the strongest X-bond donor, less so bromine, while virtually no such preferences were observed for chlorine; and a backbone carbonyl as the strongest X-bond acceptor. The presence of a halogen atom in a ligand additionally affects the properties of proximal hydrogen bonds, which according to geometrical parameters get strengthened, when a nitrogen of a halogenated ligand acts as the hydrogen bond donor.
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