Subject(s)
Camphor 5-Monooxygenase/chemistry , Crystallization/methods , Electron Transport Complex III/chemistry , Proteins/chemistry , Electron Transport Complex III/chemical synthesis , Gels , Membrane Proteins/chemistry , Protein Binding , Protein Conformation , Proteins/chemical synthesis , SolubilityABSTRACT
Two candidate photoaffinity probes are designed from 4-substituted quinazolines known to be potent insecticides/acaricides and NADH:ubiquinone oxidoreductase inhibitors acting at or near the rotenone site. 4-(11-Azidoundecyl-2-amino)quinazoline, based on the undecylamino analog SAN 548A as a prototype, was synthesized in 18% overall yield from ethyl 10-undecenoate by oxidation of the terminal double bond, reductive amination, coupling to 4-chloroquinazoline, and functional group manipulation of the terminal ethyl ester to an alcohol, a mesylate and finally nucleophilic displacement with azide ions. 4-(4-(3-(Trifluoromethyl)-3H-diazirin-3-yl)phenethoxy)quinaz oline [the (trifluoromethyl)diazirinyl analog of fenazaquin insecticide/acaricide] was prepared from 4-bromophenethyl alcohol in 31% overall yield by first introducing the trifluoromethylketone moiety followed by its conversion to the (trifluoromethyl)-diazirine and finally coupling to 4-chloroquinazoline as above. Both candidate photoaffinity probes have the inhibitory potency of rotenone (IC50 of 3-4 nM in each case). The azidoundecylamino compound has inadequate photoreactivity whereas that of the (trifluoromethyl)diazirinyl analog is ideal at 350 nm. Radiosynthesis of the latter photoaffinity ligand included introduction of the diazirinyl moiety as the carbene precursor, oxidation of (trifluoromethyl)diazirinylphenethyl alcohol to the corresponding acid with Jones' reagent, and reduction of the phenacetyl chloride intermediate with sodium borotritide to incorporate tritium.
Subject(s)
Affinity Labels/analysis , Azides/chemistry , Azirines/chemistry , Electron Transport Complex III/antagonists & inhibitors , Electron Transport Complex III/analysis , Hydrocarbons, Fluorinated/analysis , Insecticides/chemistry , Photochemistry/methods , Quinazolines/chemistry , Electron Transport Complex III/chemical synthesisABSTRACT
A water-soluble, 62-residue, di-alpha-helical peptide has been synthesized which accommodates two bis-histidyl haem groups. The peptide assembles into a four-helix dimer with 2-fold symmetry and four parallel haems that closely resemble native haems in their spectral and electrochemical properties, including haem-haem redox interaction. This protein is an essential intermediate in the synthesis of molecular 'maquettes', a novel class of simplified versions of the metalloproteins involved in redox catalysis and in energy conversion in respiratory and photosynthetic electron transfer.
