Gary I. Dmitrienko

N-Arylsulfonyl Hydrazones as Inhibitors of IMP-1 Metallo-β-Lactamase

ABSTRACT Members of a family of N-arylsulfonyl hydrazones have been identified as novel inhibitors of IMP-1, a metallo-β-lactamase of increasing prevalence. Structure-activity relationship studies have indicated a requirement for bulky aromatic substituents on each side of the sulfonyl hydrazone backbone for these compounds to serve as efficient inhibitors of IMP-1. Molecular modeling has provided insight into the structural basis for the anti-metallo-β-lactamase activity exhibited by this class of compounds.

Cyclobutanone analogues of beta-lactams revisited: insights into conformational requirements for inhibition of serine- and metallo-beta-lactamases.

The most important mode of bacterial resistance to beta-lactam antibiotics is the expression of beta-lactamases. New cyclobutanone analogues of penams and penems have been prepared and evaluated for inhibition of class A, B, C, and D beta-lactamases. Inhibitors which favor conformations in which the C4 carboxylate is equatorial were found to be more potent than those in which the carboxylate is axial, and molecular modeling studies with enzyme-inhibitor complexes indicate that an equatorial orientation of the carboxylate is required for binding to beta-lactamases. An X-ray structure of OXA-10 complexed with a cyclobutanone confirms that a serine hemiketal is formed in the active site and that the inhibitor adopts the exo envelope. An unsaturated penem analogue was also found to enhance the potency of meropenem against carbapenem-resistant MBL-producing strains of Chryseobacterium meningosepticum and Stenotrophomonas maltophilia. These cyclobutanones represent the first type of reversible inhibitors to show moderate (low micromolar) inhibition of both serine- and metallo-beta-lactamases and should be considered for further development into practical inhibitors.

Cyclobutanone mimics of penicillins: effects of substitution on conformation and hemiketal stability.

The tendency for carbocyclic analogues of penicillins to undergo hydrate and hemiketal formation is central to their ability to function as beta-lactamase inhibitors. 2-Thiabicyclo[3.2.0]heptan-6-one-4-carboxylates with alkoxy functionality at C3 have been prepared through two complementary diastereoselective substitution reactions following a highly stereoselective chlorination with sulfuryl chloride. We have found that carbocyclic analogues with 3beta substituents favor an endo envelope conformation in solution, the solid state, and the gas phase, whereas those with 3alpha substituents adopt an exo envelope. Evidence from X-ray crystal structures and ab initio calculations suggests that an anomeric effect contributes to the large conformational preference of the tetrahydrothiophene ring that favors the C3 substituent in an axial orientation. In addition, the envelope conformation of the bicycle, which is determined by the stereochemistry of the C3 substituent, has a dramatic effect on the ability of the cyclobutanone to undergo hemiketal formation in methanol-d4.

A biogenetically-inspired synthesis of a ring-D model of kinamycin F: insights into the conformation of ring D.

An efficient three-step construction of the highly oxygenated D-ring of the kinamycin antibiotics is reported for a simple model system. A comparison of the spectroscopic characteristics of the synthetic models with those of natural kinamycin F, which is suspected to be the bioactive form of the kinamycins, leads to the conclusion that the favored D-ring conformation of kinamycin F differs from that of the other partially or fully acylated variants.

Experimental Estimation of Average Fidelity of a Clifford Gate on a 7-qubit Quantum Processor

One of the major experimental achievements in the past decades is the ability to control quantum systems to high levels of precision. To quantify the level of control we need to characterize the dynamical evolution. Full characterization via quantum process tomography is impractical and often unnecessary. For most practical purposes, it is enough to estimate more general quantities such as the average fidelity. Here we use a unitary 2-design and twirling protocol for efficiently estimating the average fidelity of Clifford gates, to certify a 7-qubit entangling gate in a nuclear magnetic resonance quantum processor. Compared with more than 10^{8} experiments required by full process tomography, we conducted 1656 experiments to satisfy a statistical confidence level of 99%. The average fidelity of this Clifford gate in experiment is 55.1%, and rises to at least 87.5% if the signals decay due to decoherence is taken into account. The entire protocol of certifying Clifford gates is efficient and scalable, and can easily be extended to any general quantum information processor with minor modifications.

Assays for Β-Lactamase Activity and Inhibition

The ability, either innate or acquired, to produce beta-lactamases, enzymes capable of hydrolyzing the endocyclic peptide bond in beta-lactam antibiotics, would appear to be a primary contributor to the ever-increasing incidences of resistance to this class of antibiotics. To date, four distinct classes, A, B, C, and D, of beta-lactamases have been identified. Of these, enzymes in classes A, C, and D utilize a serine residue as a nucleophile in their catalytic mechanism while class B members are Zn2+-dependent for their function. Efforts have been and still continue to be made toward the development of potent inhibitors of these enzymes as a means to ensure the efficacy of beta-lactam antibiotics in clinical medicine. This chapter concerns procedures for the evaluation of the catalytic activity of beta-lactamases as a means to screen compounds for their inhibitory potency.

Inhibition of carboxypeptidase A by (S)-2-mercapto-3-phenylpropanoic acid

(S)-2-Mercapto-3-phenylpropanoic acid is an effective competitive inhibitor of carboxypeptidase A, comparable in potency to (S)-3-mercapto-2-benzylpropanoic acid.