Ionic strength dependence of enzyme-substrate interactions: Monte Carlo and Poisson-Boltzmann results for superoxide dismutase

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

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Proton magnetic relaxation studies of the interaction of D-xylose and xylitol with D-xylose isomerase. Characterization of metal-enzyme-substrate interactions

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)40688-1 ◽

1975 ◽

Vol 250 (23) ◽

pp. 9021-9027

Author(s):

JM Young ◽

KJ Schray ◽

AS Mildvan

Keyword(s):

Magnetic Relaxation ◽

Xylose Isomerase ◽

Substrate Interactions ◽

Enzyme Substrate ◽

Proton Magnetic Relaxation ◽

Relaxation Studies ◽

Enzyme Substrate Interactions

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Roles of Individual Enzyme−Substrate Interactions by α-1,3-Galactosyltransferase in Catalysis and Specificity†,‡

Biochemistry ◽

10.1021/bi035430r ◽

2003 ◽

Vol 42 (46) ◽

pp. 13512-13521 ◽

Cited By ~ 52

Author(s):

Yingnan Zhang ◽

G. Jawahar Swaminathan ◽

Ashlesha Deshpande ◽

Ester Boix ◽

Ramanathan Natesh ◽

...

Keyword(s):

Substrate Interactions ◽

Enzyme Substrate ◽

Individual Enzyme ◽

Enzyme Substrate Interactions

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Meso tetrakis ortho-, meta-, and para-N-alkylpyridiniopor-phyrins: kinetics of copper(II) and zinc(II) incorporation and zinc porphyrin demetalation

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424603000197 ◽

2003 ◽

Vol 07 (03) ◽

pp. 139-146 ◽

Cited By ~ 6

Author(s):

Peter Hambright ◽

Ines Batinić-Haberle ◽

Ivan Spasojević

Keyword(s):

Aqueous Solution ◽

Ionic Strength ◽

Effective Charge ◽

Methyl Ethyl ◽

Ionic Strength Dependence ◽

Zinc Porphyrin ◽

Cationic Porphyrin ◽

Strength Dependence ◽

Acid Catalyzed ◽

Kinetics Of

The relative reactivities of the tetrakis( N -alkylpyridinium- X - yl )-porphyrins where X = 4 (alkyl = methyl, ethyl, n -propyl) , X = 3 (methyl) , and X = 2 (methyl, ethyl, n -propyl, n -butyl, n -hexyl, n -octyl) were studied in aqueous solution. From the ionic strength dependence of the metalation rate constants, the effective charge of a particular cationic porphyrin was usually larger when copper(II) rather than zinc(II) was the reactant. The kinetics of ZnOH + incorporation and the acid catalyzed removal of zinc from the porphyrins in 1.0 M HCl were also studied. In general, the more basic 4- (para-) and 3- (meta-) isomers were the most reactive, followed by the less basic 2- (ortho-) methyl to n -butyl derivatives, with the lipophilic ortho n -hexyl and n -octyl porphyrins the least reactive.

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