Psychomotor stimulant effects of α-pyrrolidinovalerophenone (αPVP) enantiomers correlate with drug binding kinetics at the dopamine transporter

α-Pyrrolidinovalerophenone (αPVP) is a psychostimulant and drug of abuse associated with severe intoxications in humans. αPVP exerts long-lasting psychostimulant effects, when compared to the classical dopamine transporter (DAT) inhibitor cocaine. Here, we compared the two enantiomeric forms of αPVP, the R- and the S-αPVP, with cocaine using a combination of in silico, in vitro and in vivo approaches. We found that αPVP enantiomers substantially differ from cocaine in their binding kinetics. The two enantiomers differ from each other in their association rates. However, they show similar slow dissociation rates leading to pseudo-irreversible binding kinetics at DAT. The pseudo-irreversible binding kinetics of αPVP is responsible for the observed non-competitive pharmacology and it correlates with persistent psychostimulant effects in mice. Thus, the slow binding kinetics of αPVP enantiomers profoundly differ from the fast kinetics of cocaine both in vitro and in vivo, suggesting drug-binding kinetics as a potential driver of psychostimulant effects in vivo.

Stoichiometry of irreversible ligand binding to a one-dimensional lattice

In this paper we investigate the problem of irreversible binding of a ligand that covers several identical binding sites on a macromolecule with a one-dimensional lattice. Due to steric constraints, irreversible binding or binding with slow kinetics results in partial saturation of the binding sites thus impacting the stoichiometry of the interaction. Here we present a recursive formula to calculate the exact fraction of the occupied binding sites for a ligand and macromolecule of arbitrary lengths. We also provide an analytical result for the exact fraction of the occupied sites in case of an infinitely long lattice. We conclude with a simplified empirical formula for the exact fraction of the occupied sites in case of an infinitely long lattice.

COVID - 19 infection: the perspectives on Angiotensin II role

Since who characterized COVID-19 as a pandemic, all scientists and clinicians studied the viral effects on the various organs and tissues of the infected patients. The virus irreversible binding to the ACE2 in the target cell in the lungs is the first step of the viral deleterious pathway to invade the target tissues. As the virus replicates and its number increase, the ACE2 in lung type II alveolar cells become inactive. ACE2 is also located in the arterial and venous endothelial cells and arterial smooth muscle cells in most organs. ACE2 is the enzyme catalyzing the conversion of angiotensin II to angiotensin (1–7). Nitric oxide Should be tested as a potential treatment.

Efficient targeted degradation via reversible and irreversible covalent PROTACs

<p>PROteolysis Targeting Chimeras (PROTACs) represent an exciting inhibitory modality with many advantages, including sub-stoichiometric degradation of targets. Their scope, though, is still limited to-date by the requirement for a sufficiently potent target binder. A solution that proved useful in tackling challenging targets is the use of electrophiles to allow irreversible binding to the target. However, such binding will negate the catalytic nature of PROTACs. Reversible covalent PROTACs potentially offer the best of both worlds. They possess the potency and selectivity associated with the formation of the covalent bond, while being able to dissociate and regenerate once the protein target is degraded. Using Bruton’s tyrosine kinase (BTK) as a clinically relevant model system, we show efficient covalent degradation by non-covalent, irreversible covalent and reversible covalent PROTACs, with <10 nM DC50’s and >85% degradation. Our data suggests that part of the degradation by our irreversible covalent PROTACs is driven by reversible binding prior to covalent bond formation, while the reversible covalent PROTACs drive degradation primarily by covalent engagement. The PROTACs showed enhanced inhibition of B cell activation compared to Ibrutinib, and exhibit potent degradation of BTK in patients-derived primary chronic lymphocytic leukemia cells. The most potent reversible covalent PROTAC, RC-3, exhibited enhanced selectivity towards BTK compared to non-covalent and irreversible covalent PROTACs. These compounds may pave the way for the design of covalent PROTACs for a wide variety of challenging targets.</p>

Efficient targeted degradation via reversible and irreversible covalent PROTACs

<p>PROteolysis Targeting Chimeras (PROTACs) represent an exciting inhibitory modality with many advantages, including sub-stoichiometric degradation of targets. Their scope, though, is still limited to-date by the requirement for a sufficiently potent target binder. A solution that proved useful in tackling challenging targets is the use of electrophiles to allow irreversible binding to the target. However, such binding will negate the catalytic nature of PROTACs. Reversible covalent PROTACs potentially offer the best of both worlds. They possess the potency and selectivity associated with the formation of the covalent bond, while being able to dissociate and regenerate once the protein target is degraded. Using Bruton’s tyrosine kinase (BTK) as a clinically relevant model system, we show efficient covalent degradation by non-covalent, irreversible covalent and reversible covalent PROTACs, with <10 nM DC50’s and >85% degradation. Our data suggests that part of the degradation by our irreversible covalent PROTACs is driven by reversible binding prior to covalent bond formation, while the reversible covalent PROTACs drive degradation primarily by covalent engagement. The PROTACs showed enhanced inhibition of B cell activation compared to Ibrutinib, and exhibit potent degradation of BTK in patients-derived primary chronic lymphocytic leukemia cells. The most potent reversible covalent PROTAC, RC-3, exhibited enhanced selectivity towards BTK compared to non-covalent and irreversible covalent PROTACs. These compounds may pave the way for the design of covalent PROTACs for a wide variety of challenging targets.</p>

Efficient targeted degradation via reversible and irreversible covalent PROTACs

<p>PROteolysis Targeting Chimeras (PROTACs) represent an exciting inhibitory modality with many advantages, including sub-stoichiometric degradation of targets. Their scope, though, is still limited to-date by the requirement for a sufficiently potent target binder. A solution that proved useful in tackling challenging targets is the use of electrophiles to allow irreversible binding to the target. However, such binding will negate the catalytic nature of PROTACs. Reversible covalent PROTACs offer the best of both worlds. They possess the potency and selectivity associated with the formation of the covalent bond, while being able to dissociate and regenerate once the protein target is degraded. Using Bruton’s tyrosine kinase (BTK) as a clinically relevant model system, we present a proof-of concept for the first in class cyanoacrylamide reversible covalent PROTACs. We show efficient degradation with reversible covalent PROTACs, as well as their non-covalent and irreversible counterparts. The latter are amongst the most efficient PROTACs reported for BTK. They display single digit nM DC50, full degradation within 2-4 hours, proteome wide selectivity and show ~10-fold better inhibition of B cell activation than Ibrutinib. These examples refute the notion that covalent binders are not suitable as the basis for PROTACs, and may pave the way for the design of covalent PROTACs for a wide variety of challenging targets.</p>

Allocolchicinoids bearing a Michael acceptor fragment for possible irreversible binding of tubulin

We describe an attempt to apply the concept of covalent binding towards the highly active allocolchicinoids selected on the basis of SAR analysis of previously synthesized molecules.

Controlled Electron-Beam Synthesis of Transparent Hydrogels for Drug Delivery Applications

In this study, we highlight hydrogels prepared by electron-beam polymerization. In general, the electron-beam-polymerized hydrogels showed improved mechanical and optical transmittances compared to the conventional UV-cured hydrogels. They were more elastic and had a higher crosslinking density. Additionally, they were transparent over a broader wavelength range. The dependence of the mechanical and optical properties of the hydrogels on the number of single differential and total irradiation doses was analyzed in detail. The hydrogels were prepared for usage as a drug delivery material with methylene blue as a drug model. In the first set of experiments, methylene blue was loaded reversibly after the hydrogel synthesis. Electron-beam-polymerized hydrogels incorporated twice as much methylene blue compared to the UV-polymerized gels. Furthermore, the release of the model drug was found to depend on the crosslinking degree of the hydrogels. In addition, electron-beam polymerization enabled the irreversible binding of the drug molecules if they were mixed with monomers before polymerization.

Unravelling the Links between Phage Adsorption and Successful Infection in Clostridium difficile

Bacteriophage (phage) therapy is a promising alternative to antibiotics for the treatment of bacterial pathogens, including Clostridium difficile. However, as for many species, in C. difficile the physical interactions between phages and bacterial cells have not been studied in detail. The initial interaction, known as phage adsorption, is initiated by the reversible attachment of phage tail fibers to bacterial cell surface receptors followed by an irreversible binding step. Therefore binding can dictate which strains are infected by the phage. In this study, we investigated the adsorption rates and irreversible binding of three C. difficile myoviruses: CDHM1, CDHM3 and CDHM6 to ten strains that represent ten prevalent C. difficile ribotypes, regardless of their ability to infect. CDHM1 and CDHM3 phage particles adsorbed by ~75% to some strains that they infected. The infection dynamics for CDHM6 are less clear and ~30% of the phage particles bound to all strains, irrespective of whether a successful infection was established. The data highlighted adsorption is phage-host specific. However, it was consistently observed that irreversible binding had to be above 80% for successful infection, which was also noted for another two C. difficile myoviruses. Furthermore, to understand if there is a relationship between infection, adsorption and phage tail fibers, the putative tail fiber protein sequences of CDHM1, CDHM3 and CDHM6 were compared. The putative tail fiber protein sequence of CDHM1 shares 45% homology at the amino acid level to CDHM3 and CDHM6, which are identical to each other. However, CDHM3 and CDHM6 display differences in adsorption, which highlights that there is no obvious relationship between putative tail fiber sequence and adsorption. The importance of adsorption and binding to successful infection is often overlooked, and this study provides useful insights into host-pathogen interactions within this phage-pathogen system.