Cyanoacrylate Inhibitors of the Hill Reaction V. The Effect of Chirality on Inhibitor Binding

1987 ◽  
Vol 42 (6) ◽  
pp. 684-689 ◽  
Author(s):  
John L. Huppatz ◽  
John N. Phillips
Keyword(s):  
Phenyl Ring ◽  
Alkyl Substituent ◽  
Receptor Site ◽  
Optically Active ◽  
Hill Reaction ◽  
Inhibitor Binding ◽  
Level Of Activity ◽  
The Difference ◽  
The Hill

Optically active α-methylbenzylamino 2-cyanoacrylic esters were synthesized and assayed as inhibitors of the Hill reaction in isolated pea chloroplast fragments. The 5-isomers were more potent inhibitors than the S-isomers with discriminations of from ten to greater than 100-fold being observed. A β-alkyl substituent in the cyanoacrylate molecule affected both the level of activity and the difference in activity between the isomers. An α,α-dimethylbenzylamino derivative was also active at about the same level as the corresponding α-methylbenzylamino racemate. This result could be explained in terms of the orientation of the phenyl ring in the receptor site. Replacement of the α-methylbenzylamino group by other α-alkyl and α-phenyl substituents had little effect on activity. However, an α-benzyl group was beneficial.

Stereospecific Inhibitor Probes of the PS II Herbicide Binding Site

1987 ◽  
Vol 42 (6) ◽  
pp. 674-678 ◽  
Author(s):  
John L. Huppatz ◽  
John N. Phillips
Keyword(s):  
Phenyl Ring ◽  
Receptor Site ◽  
Spatial Arrangement ◽  
Hill Reaction ◽  
Hydrophobic Region ◽  
Inhibitor Molecule ◽  
Ps Ii ◽  
Hydrophobic Domain ◽  
The Difference ◽  
The Hill

The influence of steric factors on the activity of 2-cyanoacrylic esters as inhibitors of the Hill reaction was examined. The spatial arrangement of the different groups in the inhibitor molecule was found to be an important factor in determining potency. The positioning of the phenyl ring in aralkylamino derivatives and the steric properties of the β-substituent are particularly significant in the interaction of molecules with the) hydrophobic domain of the receptor site. The difference in activity observed with optically active α-methylbenzylamino derivatives confirmed the importance of the orientation of the phenyl ring and indicated an interaction with a specific hydrophobic region.

Cyanoacrylate Inhibitors of the Hill Reaction III. Stereochemical and Electronic Aspects of Inhibitor Binding

1984 ◽  
Vol 39 (6) ◽  
pp. 617-622 ◽  
Author(s):  
John L. Huppatz ◽  
John N. Phillips
Keyword(s):  
Alkyl Chain ◽  
Olefinic Proton ◽  
Alkyl Substituent ◽  
Hill Reaction ◽  
Amino Group ◽  
Inhibitor Binding ◽  
Pmr Spectra ◽  
The Hill ◽  
Electronic Character ◽  
Related Compounds

Ethoxyethyl 3-octylamino-2-cyanoacrylate and related compounds in which the amino group was replaced by N-CH3, S, O and CH2 were synthesized and their activity as inhibitors of the Hill reaction in isolated pea chloroplasts determined. All compounds showed moderate to high activity but there was no obvious correlation between activity and the electronic character of the ester carbonyl group. The stereochemistry of the various inhibitor molecules was deduced from the PMR spectra and the possible influence of stereochemistry on Hill inhibitory activity discussed. Replacement of the olefinic proton in the 2-cyanoacrylates with a β-alkyl substituent was examined and a specific relationship between the length of the alkyl chain and activity was observed.

Structure Versus Activity of Substituted Pyridazinones as Related to Mechanism of Action

Weed Science ◽  
1976 ◽  
Vol 24 (6) ◽  
pp. 579-582 ◽  
Author(s):  
J. B. St. John ◽  
J. L. Hilton
Keyword(s):  
Fatty Acids ◽  
Phenyl Ring ◽  
Membrane Lipids ◽  
Carotenoid Biosynthesis ◽  
Polar Lipids ◽  
Maximum Effect ◽  
Hill Reaction ◽  
Methyl Substitution ◽  
Chloroplast Membrane ◽  
The Hill

In at least three metabolic processes in wheat (Triticum aestivumL. var. ‘Arthur’) shoots inhibitory activity can be related to the chemical structure of substituted pyridazinones. Inhibitory activities include: inhibition of the Hill reaction and photosynthetic CO2fixation; inhibition of carotenoid biosynthesis accompanied by photodestruction of chlorophyll; and interference with the formation of chloroplast membrane polar lipids. The parent compound, pyrazon [5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone], inhibits the Hill reaction and photosynthetic CO2fixation. Trifluoromethyl substitution of the phenyl ring of pyrazon, mono-methyl substitution of the amine, or substitutions at both positions result in inhibition of carotenoid biosynthesis. However, both substitutions are required for maximum effect. Substitutions onto the molecular structure of pyrazon are also related to alterations in the formation of membrane polar lipids. Dimethyl substitution of the amine of pyrazon is related to a decrease in linolenic acid accompanied by an increase in linoleic acid without a shift in the relative proportion of saturated to unsaturated fatty acids of the membrane lipids. The trifluoromethyl substitution of the phenyl ring and mono-methyl substitution of the amine are related to a shift toward a higher proportion of saturated fatty acids of chloroplast membrane lipids. Results obtained with diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and with dark-grown wheat tissue indicated that activity of the pyridazinones on the formation of membrane lipids was probably not related to inhibition of the Hill reaction.

Über eine p-Hydroxylierung in isolierten Chloroplasten

1963 ◽  
Vol 18 (2) ◽  
pp. 105-109 ◽  
Author(s):  
Achim Trebst ◽  
Herbert Eck
Keyword(s):  
Electron Transport ◽  
Transport System ◽  
Phenyl Ring ◽  
Functional Role ◽  
Electron Transport System ◽  
Hill Reaction ◽  
The Hill ◽  
Isolated Chloroplasts ◽  
Carbonyl Function

Salicylaldoxime at a concentration of 10-2-m. is an inhibitor of the Hill - reaction and therefore also of aerobic photophosphorylation in isolated chloroplasts. This might indicate a functional role for copper in the electron transport system of photosynthesis.At a concentration of 10-3-m. and lower, salicylaldoxime is not an inhibitor, but a cofactor of aerobic photophosphorylation. This is due to its hydroxylation to the p-hydroquinone, which is the actual cofactor. This p-hydroxylation, which is probably catalyzed by a peroxidase, takes place only with salicylaldehyde and its oxime, but not with other phenols, whether they have a carbonyl function attached to the phenyl ring or not. A number of o- and p-hydroquinones with a carbonyl function at the phenyl ring and two naphthohydroquinones, of which the corresponding quinone cannot be prepared by chemical means, are reversibly oxidized and reduced in photosynthetic phosphorylation in chloroplasts. A possible explanation is that these hydroquinones are oxidized only to the semiquinone level and rapidly reduced again.

scholarly journals Analog Electronic Circuits to Model Cooperativity in Hill Process

2020 ◽  
Vol 39 (4) ◽  
pp. 678-685
Author(s):  
Maria Waqas ◽  
Muhammad Khurram ◽  
S.M. Razaul Hasan
Keyword(s):  
Chemical Reactions ◽  
Electronic Circuit ◽  
Main Idea ◽  
Receptor Site ◽  
The Other ◽  
Hill Reaction ◽  
Cellular Processes ◽  
Receptor Sites ◽  
Model Dynamics ◽  
The Hill

In the field of computational biology, electronic modeling of bio-cellular processes is in vogue for about a couple of decades. Fast, efficient and scalable electronic mimetics of recurrently found bio-chemical reactions are expected to provide better electronic circuit simulators that can also be used as bio-sensors or implantable biodevices at cellular levels. This paper presents some possible electronic circuit equivalents to model dynamics of one such bio-chemical reaction commonly involved in many bio-cellular processes, specifically pathways in living cells, known as the Hill process. The distinguishing feature of this process is cooperativity which has been modeled in silicon substrate using a pair of transistors, one transistor driving current in the other the same way ligand binding to one receptor site controls the binding affinity of the other receptor sites. Two possible circuits have been proposed and compared to electronically model cooperativity of a Hill reaction. The main idea is to exploit the natural analogies found between structures and processes of a bio-cell and electronic transistor mechanics, to efficiently model fundamental bio-chemical reactions found recurring in bio-processes. These circuits can then be combined and rearranged quickly to form larger, more complex bio-networks, thus mitigating the intricacies involved in modeling of such systems.

Modes of Action of Pyridazinone Herbicides

Weed Science ◽  
1969 ◽  
Vol 17 (4) ◽  
pp. 541-547 ◽  
Author(s):  
J. L. Hilton ◽  
A. L. Scharen ◽  
J. B. St. John ◽  
D. E. Moreland ◽  
K. H. Norris
Keyword(s):  
Molecular Structure ◽  
Hordeum Vulgare ◽  
Phenyl Ring ◽  
Chloroplast Development ◽  
Biological Properties ◽  
Hill Reaction ◽  
Action Mechanism ◽  
Physiological Properties ◽  
Second Mode ◽  
The Hill

Four substituted pyridazinone compounds inhibited the Hill reaction and photosynthesis in barley (Hordeum vulgareL., var. Dayton C.I. 9517). These inhibitions appeared to account for the phytotoxicity of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon). The pyridazinone chemicals were weaker inhibitors than 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine). Two substitutions onto the molecular structure of pyrazon result in a new experimental herbicide, 4-chloro-5-(dimethylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone (hereinafter referred to as 6706), which retains the action mechanism of pyrazon but also has two additional biological properties. It is resistant to metabolic detoxication in plants, and it possesses a second mode of action involving interference with chloroplast development. The second action is like that expressed by 3-amino-s-triazole (amitrole) and by 3,4-dichlorobenzyl methylcarbamate (dichlormate). However, the new chemical is 100 to 1000 times more effective. The trifluoromethyl substitution on the phenyl ring and the dimethyl substitution on the amine are both required to give either of the two additional physiological properties. Analogs with only one of the two substitutions behave like pyrazon rather than like 6706.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

Metabolism of a Pyrrolidine Urea Herbicide in Corn and Weeds

Weed Science ◽  
1974 ◽  
Vol 22 (1) ◽  
pp. 10-14 ◽  
Author(s):  
R. E. Holm ◽  
D. E. Stallard
Keyword(s):  
Adventitious Roots ◽  
Parent Compound ◽  
Soil Surface ◽  
Abutilon Theophrasti ◽  
Water Soluble ◽  
Hill Reaction ◽  
Panicum Miliaceum ◽  
Proso Millet ◽  
Ipomoea Purpurea ◽  
The Hill

Five 2,5-dimethyl-1-pyrrolidinecarboxanilides were effective inhibitors of the Hill reaction. However, only thecisisomers were active; thetransisomers were totally inactive. Experiments were conducted using14C-5328 (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide). A correlation existed between resistance of various plants to 5328 and their ability to metabolize it to water soluble metabolites. Velvetleaf (Abutilon theophrastiMedic.) and proso millet (Panicum miliaceumL.) seedlings were very susceptible to 5328 and were unable to metabolize it. Tall morningglory [Ipomoea purpurea(L.) Roth] seedlings were highly tolerant to 5328 and converted it completely to its metabolites. Corn (Zea maysL. ‘DeKalb variety XL-45′) seedlings which were slightly susceptible to 5328 injury were able to metabolize up to 90% of the parent compound. Corn foliage uptake of14C-5328 applied to the soil surface occurred through the adventitious roots.

scholarly journals Studies on the Second Emerson Effect in the Hill Reaction in Algal Cells

1961 ◽  
Vol 1 (5) ◽  
pp. 377-388 ◽  
Author(s):  
Rajni Govindjee ◽  
Eugene Rabinowitch
Keyword(s):  
Hill Reaction ◽  
The Hill
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