scholarly journals The reaction of nitrite with the haemocyanin of the Roman snail (Helix pomatia)

1990 ◽  
Vol 271 (3) ◽  
pp. 779-783 ◽  
Author(s):  
J P Tahon ◽  
G Maes ◽  
C Vinckier ◽  
R Witters ◽  
T Zeegers-Huyskens ◽  
...  
Keyword(s):  
Active Site ◽  
Reaction Rate ◽  
Helix Pomatia ◽  
Astacus Leptodactylus ◽  
Raman Spectrometry ◽  
Signal Characteristic ◽  
Bridging Ligand ◽  
Pka Value ◽  
Snail Helix Pomatia ◽  
Hasselbalch Equation

The reaction of nitrite at pH 5.0-7.0 with the deoxyhaemocyanin of a mollusc, the Roman snail (Helix pomatia), yielded nitrosylhaemocyanin (CuIA.NO+ CuIIB), in contrast with the formation of methaemocyanin with the deoxyhaemocyanin of the crustacean Astacus leptodactylus (mud crayfish). With Helix haemocyanin 1 NO was thereby liberated per active site, as shown by m.s., as against 2 NO with Astacus haemocyanin. Helix nitrosylhaemocyanin was characterized in c.d. by the negative extremum at 336 nm (CuIA.NO+) and by the mononuclear e.p.r. signal at g = 2 (CuIIB). Binuclear e.p.r. signals have been observed after the addition of nitrite to methaemocyanins. With Astacus methaemocyanin, no further reaction occurred, whereas with Helix methaemocyanin the mononuclear e.p.r. signal, characteristic for nitrosylhaemocyanin gradually appeared. This formation of Helix nitrosylhaemocyanin implicates the binding, most likely on CuIIA, of a second nitrite besides a bridging nitrite, so that a dismutation into NO and NO2 can occur there. A further dismutation of NO2 yields nitrite and nitrate. The formation of the latter was demonstrated by Raman spectrometry. The reaction rate of Helix methaemocyanin with nitrite decreased with increasing pH according to the Henderson-Hasselbalch equation with a pKa value of 6.77, attributed to a mu-aquo bridging ligand, which can be exchanged for nitrite, in equilibrium with a mu-hydroxo ligand which cannot. These data also favour the formulation of the final reaction product as nitrosylhaemocyanin instead of semi-methaemocyanin, with or without bound nitrite.

scholarly journals The reaction of nitrogen monoxide with the haemocyanins of the crayfish Astacus leptodactylus and the snail Helix pomatia

1989 ◽  
Vol 262 (1) ◽  
pp. 253-260
Author(s):  
J P Tahon ◽  
C Gielens ◽  
C Vinckier ◽  
R Witters ◽  
M De Ley ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Rate Increase ◽  
Formation Rate ◽  
Helix Pomatia ◽  
Nitrogen Monoxide ◽  
Astacus Leptodactylus ◽  
Fast Reaction ◽  
Bridging Ligand ◽  
Snail Helix Pomatia ◽  
Hasselbalch Equation

The rate of the reaction of Astacus leptodactylus methaemocyanin with NO follows the Henderson-Hasselbalch equation with a pKa of 5.85, suggesting that one imidazole ligand of Cu was exchanged for NO. The reaction is blocked by F- as a bridging ligand. The same imidazole residue might be responsible for the decomposition of nitrosylhaemocyanin, [Cu1NO+CuII], with an unlocated binding site for NO, into methaemocyanin and NO, as the rate increase with pH. NO could react preferentially with CuA of Helix pomatia methaemocyanin, CuA′IICuBII, as it possibly has only two histidine ligands instead of the three of CuA in Astacus haemocyanin. This difference might explain the higher formation rate and the much greater stability of Helix nitrosylhaemocyanin. The fast reaction is governed by a pKa of 6.80, probably of a bridging mu-aquo ligand. With F- or a mu-hydroxo bridging ligand a low reaction rate was still observed, in contrast with Astacus methaemocyanin. Helix nitrosylhaemocyanin was transformed by N3- into methaemocyanin with the liberation of N2 and N2O. This methaemocyanin could almost quantitatively be regenerated with H2O2. Helix nitrosylhaemocyanin was only partially regenerated by a direct treatment with H2O2 and almost quantitatively by HONH2 in a similar fairly fast reaction, followed by a much slower one.

scholarly journals The reaction of nitrite with the haemocyanin of Astacus leptodactylus

1988 ◽  
Vol 249 (3) ◽  
pp. 891-896 ◽  
Author(s):  
J P Tahon ◽  
D Van Hoof ◽  
C Vinckier ◽  
R Witters ◽  
M De Ley ◽  
...  
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Reaction Rate ◽  
Anaerobic Treatment ◽  
Astacus Leptodactylus ◽  
First Order ◽  
Bridging Ligand ◽  
A Value ◽  
Pseudo First Order

The reaction of nitrite at pH 5.7 with deoxyhaemocyanin of Astacus leptodactylus yielded methaemocyanin in two one-electron steps, as nitrite was reduced to NO. This methaemocyanin could be almost fully regenerated by an anaerobic treatment with HONH2, in contrast with the methaemocyanin prepared with H2O2. A destruction of active sites on treating oxyhaemocyanin with HONH2 explains the partial regeneration of methaemocyanin under air, as traces of H2O2 are formed in the autoxidation of HONH2. The reaction rate of nitrite with deoxyhaemocyanin is almost 15 times that with oxyhaemocyanin. The slope of -1.0 for the logarithm of the pseudo-first-order rate constants plotted against pH indicates that HNO2 is the reacting species. Methaemocyanin was e.p.r.-undetectable, but a binuclear signal was observed at g = 2 on binding nitrite to methaemocyanin. This signal disappeared with a pKa of 6.50, suggesting that a mu-aquo bridging ligand, which can be replaced by nitrite, is deprotonated to a mu-hydroxo bridging ligand, which resists substitution by nitrite. The intensity of this triplet e.p.r. signal allowed the determination of the association constant of nitrite to the active site of Astacus methaemocyanin and yielded a value of 237 M-1 at pH 5.7. The interpretation by some authors of nitrosylhaemocyanin as a nitrite derivative of semimethaemocyanin is contradicted by this rapid reaction of nitrite with copper(I) in deoxyhaemocyanin and in semi-methaemocyanin and by the low binding constant of nitrite to the active site of methaemocyanin.

scholarly journals The reaction of hydroxyurea with oxyhaemocyanin and methaemocyanin of the crayfish Astacus leptodactylus and the snail Helix pomatia

1988 ◽  
Vol 254 (2) ◽  
pp. 605-607 ◽  
Author(s):  
D Van Hoof ◽  
R Witters ◽  
R Lontie
Keyword(s):  
Steady State ◽  
Helix Pomatia ◽  
Astacus Leptodactylus ◽  
Snail Helix Pomatia

The reaction of hydroxyurea with the oxyhaemocyanins of Astacus leptodactylus and Helix pomatia yielded methaemocyanins which could be regenerated with hydroxylamine. Hydroxyurea did not react with Astacus methaemocyanin, but quantitatively regenerated Helix methaemocyanin under N2. The reaction of hydroxyurea with Helix haemocyanin at pH 5.7 under air thus led to a steady state, with an oxyhaemocyanin/methaemocyanin ratio of 2.05:1.

Locating Al in the DABCO catalyst before and after Al extraction

1990 ◽  
Vol 48 (4) ◽  
pp. 265-267
Author(s):  
Kathleen B. Reuter
Keyword(s):  
Active Site ◽  
Inverse Relationship ◽  
Transverse Direction ◽  
Reaction Rate ◽  
Acid Phosphate ◽  
Fracture Surfaces ◽  
Al Content ◽  
Before And After ◽  
Relationship Of

The reaction rate and efficiency of piperazine to 1,4-diazabicyclo-octane (DABCO) depends on the Si/Al ratio of the MFI topology catalysts. The Al was shown to be the active site, however, in the Si/Al range of 30-200 the reaction rate increases as the Si/Al ratio increases. The objective of this work was to determine the location and concentration of Al to explain this inverse relationship of Al content with reaction rate.Two silicalite catalysts in the form of 1/16 inch SiO2/Al2O3 bonded extrudates were examined: catalyst A with a Si/Al of 83; and catalyst B, the acid/phosphate Al extracted form of catalyst A, with a Si/Al of 175. Five extrudates from each catalyst were fractured in the transverse direction and particles were obtained from the fracture surfaces near the center of the extrudate diameter. Particles were also obtained from the outside surfaces of five extrudates.

Reproduction of the Roman snail (Helix pomatia L.) from a local natural population in farm conditions and in a natural habitat

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Maciej Ligaszewski ◽  
Przemysław Pol
Keyword(s):  
Natural Population ◽  
Natural Habitat ◽  
Local Population ◽  
Helix Pomatia ◽  
Second Phase ◽  
Animal Reproduction ◽  
Snail Helix Pomatia ◽  
June July ◽  
A Site

AbstractThe aim of this study was to compare the quality of clutches and reproduction results of two groups of Roman snails (Helix pomatia) from the same local population, laying eggs simultaneously in semi-natural farm conditions and in a natural habitat. The study material were Roman snails aged 2 or more years which had entered the third phenological season of their life and thus the first season of sexual maturity. Observations were conducted at an earthen enclosure in a greenhouse belonging to the experimental farm for edible snails at the National Research Institute of Animal Reproduction in Balice near Kraków (Poland) as well as at a site where a local population naturally occurs in the uncultivated park surrounding the Radziwiłł Palace. In the June-July season, differences among such parameters as weight of clutch, number of eggs in clutch, mean egg weight, and hatchling percentage when compared to the total number of eggs in the clutch were compared. It was determined that clutches of eggs from the natural population laid in the greenhouse were of lesser weight (P<0.01), contained fewer eggs (P<0.05), and the mean weight of individual eggs was less (P<0.05) than in clutches laid simultaneously in a natural habitat. Both in the greenhouse and the natural habitat, in the first phase of laying eggs (June) the weight of the clutch and number of eggs its contained were greater than in the second phase (July). However, only for snails laying eggs in the greenhouse were these differences statistically significant (P<0.05) and highly significant (P<0.01), respectively. Statistically significant differences were not observed in hatchling percentage between eggs laid in the greenhouse and the natural habitat. The lower number of eggs laid in the farmed conditions of the greenhouse was successfully compensated for by the absence of mass destruction by rodents which occurred in the natural habitat.

scholarly journals Probing the ionization state of substrate α-d-glucopyranosyl phosphate bound to glycogen phosphorylase b

1995 ◽  
Vol 308 (3) ◽  
pp. 1017-1023 ◽  
Author(s):  
I P Street ◽  
S G Withers
Keyword(s):  
Active Site ◽  
Glycogen Phosphorylase ◽  
Ph Dependence ◽  
Substrate Inhibition ◽  
19F Nmr ◽  
Ionization State ◽  
Nmr Studies ◽  
Substrate Analogues ◽  
Glycogen Phosphorylase B ◽  
Pka Value

The ionization state of the substrate alpha-D-glucopyranosyl phosphate bound at the active site of glycogen phosphorylase has been probed by a number of techniques. Values of Ki determined for a series of substrate analogue inhibitors in which the phosphate moiety bears differing charges suggest that the enzyme will bind both the monoanionic and dianionic substrates with approximately equal affinity. These results are strongly supported by 31P- and 19F-NMR studies of the bound substrate analogues alpha-D-glucopyranosyl 1-methylenephosphonate and 2-deoxy-2-fluoro-alpha-D-glucopyranosyl phosphate, which also suggest that the substrate can be bound in either ionization state. The pH-dependences of the inhibition constants K1 for these two analogues, which have substantially different phosphate pK2 values (7.3 and 5.9 respectively), are found to be essentially identical with the pH-dependence of K(m) values for the substrate, inhibition decreasing according to an apparent pKa value of 7.2. This again indicates that there is no specificity for monoanion or dianion binding and also reveals that binding is associated with the uptake of a proton. As the bound substrate is not protonated, this proton must be taken up by the proton.

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