Ezra Shirin
Israel Institute for Biological Research
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Featured researches published by Ezra Shirin.
Biochemical Pharmacology | 1989
Jacob Grunwald; Yoffi Segall; Ezra Shirin; Daniel Waysbort; Nitza Steinberg; Israel Silman; Yacov Ashani
Homologous pairs of non-aged and aged pyrene-containing phosphoryl conjugates of chymotrypsin were prepared in order to characterize by NMR and optical spectroscopy putative differences in the conformation of non-aged and aged organophosphoryl conjugates of serine hydrolases. Pyrenebutyl-O-P(O)(OC2H5)F and pyrenebutyl-O-P(O)(OC2H5)Cl were used to obtain the non-aged form pyrenebutyl-O-P(O)(OC2H5)-Cht, whereas pyrenebutyl-O-P(O)Cl2, pyrenebutyl-O-P(O)(p-nitrophenoxy)Cl, and pyrenebutyl-O-P(O)(p-nitrophenoxy)2 were used to produce the aged conjugate pyrenebutyl-O-P(O)(O )-Cht. These ligands bind covalently to the active site of serine hydrolases. The absorption spectra of both the non-aged and aged conjugates fitted approximately a 1:1 stoichiometry of bound organophosphate and enzyme in the non-aged and aged conjugates. Pyrenebutyl-O-P(O)(OC2H5)-Cht could be reactivated by pyridine-3-aldoxime methiodide, whereas no reactivation was observed for the similarly treated pyrenebutyl-O-P(O)(O-)-Cht. The 31P-NMR and reactivation data taken together strongly support the hypothesis that the aged form of the OP-Cht conjugate contains a P--O- bond. These results provide a partial interpretation for the known resistance of the aged conjugates of serine hydrolases to reactivation.
Phosphorus Sulfur and Silicon and The Related Elements | 1980
Yoffi Segall; Ezra Shirin; Itshak Granoth
Abstract Derivatives of the novel dibenzo[b,f]phosphepin system are prepared from 10,11-dihydro-5-phenyl-5H-bibenzo[b,f]phosphepin 5-oxide (2). New members in the 10,11-dihydro-5H-dibenzo[b,f]phosphepin series, including phosphorus analogues (7, 10) of the andidepressant drug imipramine (30), are also reported. Products of nucleophilic substitution at tetrahedral phosphorus in 2 appear to be determined by the relative apicophilicity of the nucleophile. Conformational analysis based on 1H NMR data suggests folded (“butterfly”) conformation for the tricyclic compounds. The twisted boat conformation of the central ring in the 10,11-dihydro compounds bears a pseudo-equatorial P[dbnd]O oxygen or a P[dbnd]S sulfur, in solution. Symmetric AA‘BB’ spin systems are found in 4,5 and 7, and their solution conformations appear to be similar to those of analogous 10,11-dihydrodibenzo[b,f]azepine derivatives. The interaction of some compounds with NMR shift reagents and their mass spectral fragmentations are discussed.
Journal of The Chemical Society, Chemical Communications | 1981
Itshak Granoth; Rivka Alkabets; Ezra Shirin
Deprotonation of the alcohol (2) gives the phosphorane oxide anion (3) which equilibrates with its exceptionally reactive tautomeric phosphine oxide alkoxide (4).
Archive | 1993
Abraham Fisher; Yoffi Segall; Ezra Shirin; Yishai Karton; Haim Meshulam
Archive | 1991
Abraham Fisher; Yoffi Segall; Ezra Shirin; Yishai Karton; Haim Meshulam
Archive | 1987
Moshe A. Frommer; Yoffi Segall; Ezra Shirin
ChemInform | 1980
Itshak Granoth; Yoffi Segall; Daniel Waysbort; Ezra Shirin; Haim Leader
Archive | 1991
Abraham Fisher; Yoffi Segall; Ezra Shirin; Yishai Karton; Haim Meshulam
Archive | 1991
Abraham Fisher; Yoffi Segall; Ezra Shirin; Yishai Karton; Haim Meshulam
Archive | 1991
Abraham Fisher; Yoffi Segall; Ezra Shirin; Yishai Karton; Haim Meshulam