A cyclisation of humulene

Greenwood, J. M.; Solomon, M.; Sutherland, J. K.; Torre, A.

doi:10.1039/j39680003004

Cited by 25 publications

(31 citation statements)

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“…It was recognized by Gibson and Greenwood (1963) that photodissociation of CO from this inhibitor complex in the presence of 0 2 allows the 0 2 ligation and reduction reactions to be observed on a time scale approaching diffusion control rather than that of the mixing of the reactants. This elegant 'flow-flash" approach and related trapping techiques which were subsequently developed have allowed investigation of the 0 2 reactions in considerable detail and have provided significant information regarding the rates of internal electrontransfer processes and the possible structures of the transient intermediates that are generated in this reaction (Gibson & Greenwood, 1963;Greenwood & Gibson, 1967;Chance et al, 1975;Clore et al, 1980;Karlsson et al, 1981;Hill et al, 1986;Blackmore et al, 1991).…”

mentioning

confidence: 95%

“…step preceding the reduction of dioxygen to water (Babcock et al, 1984;Chance et al, 1975;Gibson & Greenwood, 1963;Greenwood & Gibson, 1967;Hill et al, 1986), the binding of ligands to CUB has only recently been demonstrated. Currently it appears that both CO and N O can bind to the cuprous center (Alben et al, 1981;Fiamingo et al, 1982;Stevens et al, 1979;Boelens et al, 1984).…”

mentioning

confidence: 97%

“…The coordination chemistry of the cytochrome @/CUB pair and the dynamics of the ligand binding reactions are key features of the physiological function of the enzyme and also of inhibitory phenomena manifested as CO and CN-toxicity. Due to the rapidity of the reaction of reduced cytochrome oxidase with dioxygen, this reaction is difficult to study by conventional rapid-mixing techniques (Gibson & Greenwood, 1963;Greenwood & Gibson, 1967;Hill et al, 1986;Wikstrom et al, 1981). Carbon monoxide, however, binds to ferrous cytochrome 0 3 and forms a thermodynamically (Kf = 3.3 X lo6 M-l) (Yoshikawa et al, 1977) and kinetically ( t l p = 30 s for dissociation ;Greenwood & Gibson, 1967) stable complex with the reduced enzyme.…”

mentioning

confidence: 98%

“…Due to the rapidity of the reaction of reduced cytochrome oxidase with dioxygen, this reaction is difficult to study by conventional rapid-mixing techniques (Gibson & Greenwood, 1963;Greenwood & Gibson, 1967;Hill et al, 1986;Wikstrom et al, 1981). Carbon monoxide, however, binds to ferrous cytochrome 0 3 and forms a thermodynamically (Kf = 3.3 X lo6 M-l) (Yoshikawa et al, 1977) and kinetically ( t l p = 30 s for dissociation ;Greenwood & Gibson, 1967) stable complex with the reduced enzyme. Since CO and 0 2 compete for the same binding site, the binding and reduction of 0 2 is blocked in the CO complex as long as CO remains bound to Fe,,2+.…”

mentioning

confidence: 98%

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Photodissociation and recombination of carbonmonoxy cytochrome oxidase: Dynamics from picoseconds to kiloseconds

Einarsdóttir

Rb²,

Dd³

et al. 1993

Biochemistry

131

156

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The kinetics of the flash-induced photodissociation and rebinding of carbon monoxide in cytochrome aa3-CO have been studied by time-resolved infrared (TRIR) and transient ultraviolet-visible (UV-vis) spectroscopy at room temperature and by Fourier transform infrared (FTIR) spectroscopy at low temperature. The binding of photodissociated CO to CuB+ at room temperature is conclusively established by the TRIR absorption at 2061 cm-1 due to the C-O stretching mode of the CuB(+)-CO complex. These measurements yield a first-order rate constant of (4.7 +/- 0.6) x 10(5) s-1 (t1/2 = 1.5 +/- 0.2 microseconds) for the dissociation of CO from the CuB(+)-CO complex into solution. The rate of rebinding of flash-photodissociated CO to cytochrome a(3)2+ exhibits saturation kinetics at [CO] > 1 mM due to a preequilibrium between CO in solution and the CuB(+)-CO complex (K1 = 87 M-1), followed by transfer of CO to cytochrome a(3)2+ (k2 = 1030 s-1). The CO transfer from CuB to Fe alpha 3 was followed by CO-FTIR between 158 and 179 K and by UV-vis at room temperature. The activation parameters over the temperature range 140-300 K are delta H++ = 10.0 kcal mol-1 and delta S++ = -12.0 cal mol-1 K-1. The value of delta H++ is temperature independent over this range; i.e., delta Cp++ = 0 for CO transfer. Rapid events following photodissociation and preceding rebinding of CO to cytochrome a(3)2+ were observed. An increase in the alpha-band of cytochrome a3 near 615 nm (t1/2 ca. 6 ps) follows the initial femtosecond time-scale events accompanying photodissociation. Subsequently, a decrease is observed in the alpha-band absorbance (t1/2 approximately 1 microsecond) to a value typical of unliganded cytochrome a3. This latter absorbance change appears to occur simultaneously with the loss of CO by CuB+. We ascribe these observations to structural changes at the cytochrome a3 induced by the formation and dissociation of the CuB(+)-CO complex. We suggest that the picosecond binding of photodissociated CO to CuB triggers the release of a ligand L from CuB. We infer that L then binds to cytochrome a3 on the distal side and that this process is directly responsible for the observed alpha-band absorbance changes. We have previously suggested that the transfer of L produces a transient five-coordinate high-spin cytochrome a3 species where the proximal histidine has been replaced by L. When CO binds to the enzyme from solution, these processes are reversed.(ABSTRACT TRUNCATED AT 400 WORDS)

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mentioning

confidence: 95%

mentioning

confidence: 97%

mentioning

confidence: 98%

mentioning

confidence: 98%

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Photodissociation and recombination of carbonmonoxy cytochrome oxidase: Dynamics from picoseconds to kiloseconds

Einarsdóttir

Rb²,

Dd³

et al. 1993

Biochemistry

131

156

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“…With N-bromosuccinimide in aqueous acetone, the attack of bromonium ion triggers a double cyclization to tricyclic bromohydrin (104) (147). The formation of the trans-fused cyclobutane ring by electrophilic cyclization onto the 2,3-double bond is similar to the second ring closure in the caryophyllene biogenesis.…”

Section: R (52-0pp)mentioning

confidence: 97%

Biogenetic-Type Rearrangements of Terpenes

Coates

1976

Fortschritte Der Chemie Organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products

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Most‐probable distribution at enzyme depolymerization of polysaccharides

Mazur

1984

Biopolymers

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SynopsisSeveral research groups have studied depolymerizing processes by enzyme cleavage using product distribution. Although only the shortest chain products can be measured experimentally, interpretation of much evidence requires an assumption of the nature of high polymer distribution. The present work analyzes the high polymer distribution of products on the basis of mathematical models suggested for the two most widespread a-amylase action-mechanisms. The most-probable distribution was found to be distorted by hydrolysis only for the shortest chain products. The size of the distorted region is directly dependent on the characteristics of a specific enzyme. We studied the distribution of products for substrates of varying composition to show that it approaches the most-probable distribution at depolymerization.

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A cyclisation of humulene

Cited by 25 publications

References 0 publications

Photodissociation and recombination of carbonmonoxy cytochrome oxidase: Dynamics from picoseconds to kiloseconds

Photodissociation and recombination of carbonmonoxy cytochrome oxidase: Dynamics from picoseconds to kiloseconds

Biogenetic-Type Rearrangements of Terpenes

Most‐probable distribution at enzyme depolymerization of polysaccharides

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