Fast Amide Bond Cleavage Assisted by a Secondary Amino and a Carboxyl Group-A Model for yet Unknown Peptidases?

Unconstrained amides that undergo fast hydrolysis under mild conditions are valuable sources of information about how amide bonds may be activated in enzymatic transformations. We report a compound possessing an unconstrained amide bond surrounded by an amino and a carboxyl group, each mounted in close proximity on a bicyclic scaffold. Fast amide hydrolysis of this model compound was found to depend on the presence of both the amino and carboxyl functions, and to involve a proton transfer in the rate-limiting step. Possible mechanisms for the hydrolytic cleavage and their relevance to peptide bond cleavage catalyzed by natural enzymes are discussed. Experimental observations suggest that the most probable mechanisms of the model compound hydrolysis might include a twisted amide intermediate and a rate-determining proton transfer

Intrusion features of a high-speed striker of a porous tungsten-based alloy with a strengthening filler in a steel barrier

The complex problem of increasing the penetrating power of strikers based on highly porous tungsten composites is considered by improving their strengthening properties by alloying the hardening components under high-speed collision conditions. Using the method of liquid-phase sintering, we fabricated samples of strikers based on a porous WNiFeCo alloy (tungsten + nickel + iron + cobalt), alloyed with tungsten carbide with cobalt (WCCo8) and titanium-tungsten carbide (TiWC). Dynamic tests of the strikers from the developed alloys were carried out at the collision velocity with a steel barrier of the order of 2800 m/s. The penetration depth of the striker based on a porous WNiFeCo alloy doped with tungsten carbides is 30% higher than the penetration depth of a striker of a monolithic WNiFe-90 alloy (tungsten + nickel + iron with a tungsten content of 90%)

Fast Amide Bond Cleavage Assisted by a Secondary Amino and a Carboxyl Group—A Model for yet Unknown Peptidases?

Unconstrained amides that undergo fast hydrolysis under mild conditions are valuable sources of information about how amide bonds may be activated in enzymatic transformations. We report a compound possessing an unconstrained amide bond surrounded by an amino and a carboxyl group, each mounted in close proximity on a bicyclic scaffold. Fast amide hydrolysis of this model compound was found to depend on the presence of both the amino and carboxyl functions, and to involve a proton transfer in the rate-limiting step. Possible mechanisms for the hydrolytic cleavage and their relevance to peptide bond cleavage catalyzed by natural enzymes are discussed. Experimental observations suggest that the most probable mechanisms of the model compound hydrolysis might include a twisted amide intermediate and a rate-determining proton transfer

Determination of limit velocities of supercavitating motion of strikers from various materials in water

Experimental-theoretical investigations have been conducted into underwater supercavitating motion of cone strikers from various materials in a broad range of velocities. An estimate of the range of strikers' velocities has been performed for the implementation of their nondestructive entry into water and motion in it in a supercavitating regime. A possibility of an accurate hit by supercavitating strikers on underwater barriers in a supersonic range of motion velocities has been shown

Interaction of supercavitating strikers with underwater obstacles

The interaction of supercavitating strikers with obstacles placed in water was investigated in a wide range of intersection angles. Several options of the interaction of strikers with obstacles are considered, including through puncturing, destruction of the striker, and ricochet. Estimation was made of the magnitude of the decrease in the speed of strikers in the cases of through puncturing and ricochet

The Most Reactive Amide As a Transition-State Mimic For <i>cis</i>–<i>trans</i> Interconversion

1-Azatricyclo­[3.3.1.1^3,7]­decan-2-one (<b>3</b>), the parent compound of a rare class of 90°-twisted amides, has finally been synthesized, using an unprecedented transformation. These compounds are of special interest as transition-state mimics for the enzyme-catalyzed <i>cis</i>–<i>trans</i> rotamer interconversion of amides involved in peptide and protein folding and function. The stabilization of the amide group in its high energy, perpendicular conformation common to both systems is shown for the rigid tricyclic system to depend, as predicted by calculation, on its methyl group substitution pattern, making <b>3</b> by some way the most reactive known “amide”

The Most Reactive Amide As a Transition-State Mimic For <i>cis</i>–<i>trans</i> Interconversion

1-Azatricyclo­[3.3.1.1^3,7]­decan-2-one (<b>3</b>), the parent compound of a rare class of 90°-twisted amides, has finally been synthesized, using an unprecedented transformation. These compounds are of special interest as transition-state mimics for the enzyme-catalyzed <i>cis</i>–<i>trans</i> rotamer interconversion of amides involved in peptide and protein folding and function. The stabilization of the amide group in its high energy, perpendicular conformation common to both systems is shown for the rigid tricyclic system to depend, as predicted by calculation, on its methyl group substitution pattern, making <b>3</b> by some way the most reactive known “amide”