Acetylene Production in the Radiolysis of Methane

Hummel, R. W.

doi:10.1021/j100880a501

Cited by 5 publications

(5 citation statements)

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“…This observation is similar to that reported for phosphate-containing compounds (26) and it indicates that protons are required for the binding of these complexes to RNase A.…”

Section: Nmr Binding Studiessupporting

confidence: 89%

Influence of vanadium(V) complexes on the catalytic activity of ribonuclease A. The role of vanadate complexes as transition state analogues to reactions at phosphate

Leon-Lai¹,

Gresser²,

Tracey³

1996

Can. J. Chem.

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Abstract:The interactions of vanadate and its complexes of uridine, 5,6-dihydrouridine, and methyl P-D-ribofuranoside with bovine pancreatic ribonuclease A (RNase A) (EC 3.1.27.5) were studied by 5 1~ NMR spectroscopy and enzyme kinetics. From kinetic studies, it was found that neither inorganic vanadate nor the methyl P-D-ribofuranoside-vanadate complex significantly inhibited the RNase A catalyzed hydrolysis of uridine 2',3'-cyclic monophosphate. The NMR binding studies were in full agreement with the kinetics studies and showed that neither inorganic vanadate nor the methyl P-D-ribofuranoside-vanadate complex was bound tightly by the enzyme. Approximate binding constants were (5.0 + 1.0) x M and (3.0 + 0.6) x M for the uridine-and 5.6-dihydrouridine-vanadate complexes, respectively. An induced-fit mechanism is suggested, in which the pyrimidine subsite of the active site of RNase A must be fully occupied for the enzyme to be able to tightly bind the transition state or transition state analog. Calculation of the binding energies of vanadate complexes in ribonuclease, phosphoglycerate mutase, and phosphoglucomutase revealed an excess of binding energy over the analogous phosphate derivative of about 25 kJ/mol for all enzymes, even though the binding constants themselves varied by about six orders of magnitude. This energy represents about 40% of that expected to be available for a trigonal-bipyramidal transition state and requires a reassessment of the role of vanadate as a transition state analogue for phosphate transfer.Key words: vanadate, ribonuclease, transition state, binding constants, phosphate analogues, kinetics.Resum6 : Faisant appel a la spectrscopie RMN du 5 1~ et de la cinCtique des enzymes, on a CtudiC les interactions entre le vanadate et ses complexes de I'uridine, de la 5,6-dihydrouridine et du P-D-ribofuranoside de mCthyle avec la ribunuclease A du pancrCas de boeuf (RNase A) (EC 3.1.27.5). Sur la base des Ctudes cinCtiques, on a trouvC que, vis-a-vis de I'hydrolyse du monophosphate 2',3'-cyclique de I'uridine de la RNase A, ni le vanadate inorganique ni le complexe du P-D-ribofuranoside de mCthyle-vanadate n'inhibent cette rCaction d'une f a~o n significative. Les Ctudes par RMN ont montrt qu'il ne se produit aucune fixation entre ces matCriaux et elles Ctaient en parfait accord avec les ttudes cinCtiques; elles montrent aussi que ni le vanadate inorganique ni le complexe du P-D-ribofuranoside de mCthyle-vanadate ne se complexent fortement avec I'enzyme. Les constantes apparentes de fixation ont respectivement de (5,O + 1.0) x M et (3,O + 0.6) x M pour les complexes de I'uridine et du 5,6-dihydrouridine avec le vanadate. On propose un mCcanisme induit d'ajustement dans lequel il est important que tout le sous site de la pyrimidine du site actif de la RNase A soit occupC pour que I'enzyme soit capable de bien fixer 1'Ctat de transition ou son analogue. Des calculs d'Cnergie de fixation des complexes du vanadate dans la ribonucltase, la phosphoglycCratemutase ou la phosphoglucomutase ont rCvC...

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“…This observation is similar to that reported for phosphate-containing compounds (26) and it indicates that protons are required for the binding of these complexes to RNase A.…”

Section: Nmr Binding Studiessupporting

confidence: 89%

Influence of vanadium(V) complexes on the catalytic activity of ribonuclease A. The role of vanadate complexes as transition state analogues to reactions at phosphate

Leon-Lai¹,

Gresser²,

Tracey³

1996

Can. J. Chem.

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“…eGl) executes a one-dimensional walk before undergoing geminate recombination. In this model, a geminate recombination controlled by I-D diffusion has the analytical solution: (72) which for Td = 1 /4X turns out to be identical with that given by H ~m m e l ~~ in describ-ing the lifetime of charged species in irradiated dielectric liquids. Nevertheless, this analytical solution is thought6' to describe a process in which the jump distance equals the recombination length and l/Td has the physical meaning of a jump rate.…”

Section: A Plonkamentioning

confidence: 74%

Chapter 3. Dispersive kinetics

Płonka¹

1992

Annu. Rep. Prog. Chem., Sect. C

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“…Ion pair yields of acetylene varying between 0.0 and 0.25 have been reported in various studies in which the dose rates were in the range 10 15 to 10 22 eV/g·s. There are indications that M(C 2H2 )/N + increases with an increase in dose rate [5] or decreases in absorbed dose [1]. Actually, consistently high values for M(C 2H 2 }/N+ have recently been reported in studies where a field emission source was employed [6-81 which delivered 3 to 60 ns electron pulses with average dose rates which were about five orders of magnitude higher than those in the linear accelerator studies [5].…”

Section: Introductionmentioning

confidence: 98%

“…The yield and mode of formation of acetylene in the radiolysis of CH4 at atmospheric pressures have been a matter of speculation for many years [1][2][3][4][5][6][7]t. Ion pair yields of acetylene varying between 0.0 and 0.25 have been reported in various studies in which the dose rates were in the range 10 15 to 10 22 eV/g·s.…”

Section: Introductionmentioning

confidence: 99%

“…There are indications that M(C 2H2 )/N + increases with an increase in dose rate [5] or decreases in absorbed dose [1]. Actually, consistently high values for M(C 2H 2 }/N+ have recently been reported in studies where a field emission source was employed [6-81 which delivered 3 to 60 ns electron pulses with average dose rates which were about five orders of magnitude higher than those in the linear accelerator studies [5]. In contrast with the lower dose rate studies the agreement between the three Febetron 2 studies r6-81 was excellent; ~ ~~~~essUi~~;!~t~~s~~~i~:t~hth~j~~:~I~r~e;:re~~~:i!~ilh~· end of this paper.…”

Section: Introductionmentioning

confidence: 99%

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