- Stable and Rapid Thiol Bioconjugation by Light-Triggered Thiomaleimide Ring Hydrolysis
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Maleimide-mediated thiol-specific derivatization of biomolecules is one of the most efficacious bioconjugation approaches currently available. Alarmingly, however, recent work demonstrates that the resulting thiomaleimide conjugates are susceptible to breakdown via thiol exchange reactions. Herein, we report a new class of maleimides, namely o-CH2NHiPr phenyl maleimides, that undergo unprecedentedly rapid ring hydrolysis after thiol conjugation to form stable thiol exchange-resistant conjugates. Furthermore, we overcome the problem of low shelf lives of maleimide reagents owing to their propensity to undergo ring hydrolysis prior to bioconjugation by developing a photocaged version of this scaffold that resists ring hydrolysis. UV irradiation of thiol bioconjugates formed with this photocaged maleimide unleashes rapid thiomaleimide ring hydrolysis to yield the desired stable conjugates within 1 h under gentle, ice-cold conditions.
- Kalia, Dimpy,Pawar, Sharad P.,Thopate, Jyoti S.
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p. 1885 - 1889
(2017/02/05)
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- Inhibitors of Cyclic AMP Phosphodiesterase. 2. Structural Variations of N-Cyclohexyl-N-methyl-4-quinazolin-7-yl)oxy>butyramide (RS-82856)
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A series of analogues of the cyclic AMP phosphodiesterase (PDE) inhibitor N-cyclohexyl-N-methyl-4-quinazolin-7-yl)oxy>butyramide (RS-82856, 1) was prepared by systematic variation of the side-chain substituent, length, position, connecting atom, and the parent heterocycle itself.The compounds were evaluated as inhibitors of cyclic AMP phosphodiesterase from both human platelets and rat or dog heart tissue and as inhibitors of ADP-induced platelet aggregation.Structure-activity correlations for the analogue series revealed significant limitations on the steric bulk of substituents on the 1,2,3,5-tetrahydroimidazoquinaazolin-2-one heterocycle and the position and length of the side-chain.As inhibitors of cyclic AMP phosphodiesterase (PDE), potency steadily increased with increasingly lipophilic side chains.In platelet aggregation inhibition studies, however, a maximum in activity was reached with 1, while more lipophilic compounds were significantly less active.Major changes in the heterocycle itself, represented by isomeric and other carbonyl variations, also decreased activity.The molecular features defined by this series of analogues of 1 correlate to a high degree with current understanding of thr chemical and topographical requirements of the active site of the FIII (type IV) form of cyclic AMP PDE.Selective inhibition of this enzyme has been proposed as the principal component of the positive inotropic action of a number of cardiotonic agents.
- Venuti, Michael C.,Jones, Gordon H.,Alvarez, Robert,Bruno, John J.
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p. 303 - 318
(2007/10/02)
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