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001-es BibID:BIBFORM005984
Első szerző:Matkó János (biológus)
Cím:Correlation between activity and dynamics of the protein matrix of phosphorylase b / Janos Matko, Lajos Tron, Margit Balazs, Jozsef Hevessy, Bela Somogyi, Sandor Damjanovich
Dátum:1980
Megjegyzések:Quenching of the tryptophan fluorescence of phosphorylase b was studied by using iodide and acrylamide. Steady-state measurements indicated that all indole side chains were accessible to the nonionic quencher, although only 3 out of the total of 12 residues could be quenched by I-. From Stern--Volmer plots and the fluorescence lifetime data, it was concluded that the quenching was mainly of dynamic character. The value of the collisional quenching rate constant was found to be an order of magnitude less than that obtained in the case of fully exposed tryptophans. The relatively high activation energy, 30.9 kJ/mol, of the diffusion-controlled process and the value of the activation entropy suggest that the diffusion takes place in a fluctuating, structured medium. In spite of the application of sensitive fluorescent techniques, no gross conformational changes were found in the presence of acrylamide. However, the catalytic rate of the glycogen synthesis was decreased with the residual activity of the enzyme, proportional to the concentration of the probe. Binding of activator (AMP) and substrates (glucose 1-phosphate and glycogen) was found to be unaffected by acrylamide in concentrations applied (0--0.8 M). In a similar manner, activation enthalpy did not change in the presence of the quencher either. The complete reversibility of both activity inhibition and fluorescence quenching ruled out the irreversible denaturation of the enzyme or the covalent modification of any of the functional groups. We concluded that a model, suggesting the cross-correlation of activity and fluctuation, was consistent with the experimental findings.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Acrylamides
Animal
Diffusion
enzymology
Fluorescence
Glucose
Iodides
Kinetics
Ligands
metabolism
Muscles
pharmacology
Phosphorylase b
Phosphorylases
Protein Denaturation
Rabbits
Spectrometry,Fluorescence
Tryptophan
Megjelenés:Biochemistry. - 19 : 25 (1980), p. 5782-5786. -
További szerzők:Trón Lajos (1941-) (biofizikus) Balázs Margit (1952-) (sejtbiológus, molekuláris genetikus) Hevessy József Somogyi Béla (1945-2006) (biofizikus) Damjanovich Sándor (1936-2017) (biofizikus)
Internet cím:elektronikus változat
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2.

001-es BibID:BIBFORM005992
Első szerző:Somogyi Béla (biofizikus)
Cím:Forster-type energy transfer as a probe for changes in local fluctuations of the protein matrix / Bela Somogyi, Janos Matko, Sandor Papp, Jozsef Hevessy, G. Rickey Welch, Sandor Damjanovich
Dátum:1984
Megjegyzések:Much evidence, on both theoretical and experimental sides, indicates the importance of local fluctuations (in energy levels, conformational substates, etc.) of the macromolecular matrix in the biological activity of proteins. We describe here a novel application of the Forster-type energy-transfer process capable of monitoring changes both in local fluctuations and in conformational states of macromolecules. A new energy-transfer parameter, f, is defined as an average transfer efficiency, [E], normalized by the actual average quantum efficiency of the donor fluorescence, [phi D]. A simple oscillator model (for a one donor-one acceptor system) is presented to show the sensitivity of this parameter to changes in amplitudes of local fluctuations. The different modes of averaging (static, dynamic, and intermediate cases) occurring for a given value of the average transfer rate, [kt], and the experimental requirements as well as limitations of the method are also discussed. The experimental tests were performed on the ribonuclease T1-pyridoxamine 5'-phosphate conjugate (a one donor-one acceptor system) by studying the change of the f parameter with temperature, an environmental parameter expectedly perturbing local fluctuations of proteins. The parameter f increased with increasing temperature as expected on the basis of the oscillator model, suggesting that it really reflects changes of fluctuation amplitudes (significant changes in the orientation factor, k2, as well as in the spectral properties of the fluorophores can be excluded by anisotropy measurements and spectral investigations). Possibilities of the general applicability of the method are also discussed.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Energy Transfer
Fluorescence
Kinetics
Mathematics
metabolism
Phosphorylase b
Protein Conformation
Proteins
Ribonuclease T1
Spectrometry,Fluorescence
Thermodynamics
Megjelenés:Biochemistry. - 23 : 15 (1984), p. 3403-3411. -
További szerzők:Matkó János (1952-) (biológus) Papp Sándor Hevessy József Welch, Rickey G. Damjanovich Sándor (1936-2017) (biofizikus)
Internet cím:elektronikus változat
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3.

001-es BibID:BIBFORM043988
Első szerző:Szabó Gábor (biofizikus)
Cím:Light-induced permeabilization and merocyanine 540 staining of mouse spleen cells / Szabo Gábor, Rédai Imre, Bacso Zsolt, Hevessy Jozsef, Damjanovich Sándor
Dátum:1989
ISSN:0005-2736
Megjegyzések:Merocyanine 540 (M540) is a potential-sensitive, hydrophobic dye that preferentially incorporates into the 'fluid' domains of cellular membranes, distinguishing between hemopoietic cells according to their differentiation state. A bright staining with M540 is usually achieved by UV illumination of the cells during staining. We show by flow cytometric analysis that: (1) staining is greatly enhanced by UV illumination of mouse spleen cells before addition of the dye; (2) UV treatment causes an increased permeability toward propidium iodide and intracellular fluorescein as well; (3) the increment in M540 fluorescence precedes permeabilization to propidium iodide, while the latter precedes leakage of fluorescein. We also describe an overshoot and accelerated recovery of M540 fluorescence after photobleaching by a 514 nm laser beam. It is suggested that penetration of M540 to the more fluid inner membrane structures explains the fluorescence increment in both experiments.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Biochimica et Biophysica Acta (BBA). Biomembranes. - 979 : 3 (1989), p. 365-370. -
További szerzők:Rédai Imre (1961-) (sebész, aneszteziológus) Bacsó Zsolt (1963-) (biofizikus) Hevessy József Damjanovich Sándor (1936-2017) (biofizikus)
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