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Biomedical subjects

Jonathan A Ellman

Publications and source records attributed to Jonathan A Ellman.

At least 55 records · Page 3Linked to original sources
PubMed2003

The proapoptotic benzodiazepine Bz-423 affects the growth and survival of malignant B cells.

Bz-423 is a novel proapoptotic 1,4-benzodiazepine that induces cell death via a superoxide signal. Previous work has shown that Bz-423 ameliorates disease in animal models of systemic lupus erythematosus that also have features of lymphoproliferative disease. Here we describe the effects of Bz-423 against a group of malignant B-cell lines derived from Burkitt's lymphoma. These experiments demonstrate that Bz-423 has cytotoxic activity against all B-cell lines tested, regardless of EBV status or Bcl-2 and Bcl-x(L) expression levels. In addition to its cytotoxic properties, we found that Bz-423 is also a potent antiproliferative agent that induces a G(1)-phase arrest independent of p53. Mechanistically, both the cytotoxicity and growth arrest are mediated by increased reactive oxygen species levels and appear independent of binding to the peripheral benzodiazepine receptor. This work further defines the biological activities of Bz-423 that are consistent with those of other compounds in clinical development for antineoplastic therapies.

B-Lymphocytes↗
PubMed2003

Structure activity studies of a novel cytotoxic benzodiazepine.

Analogues of Bz-423, a pro-apoptotic 1,4-benzodiazepine with potent activity in animal models of systemic lupus erythematosus and rheumatoid arthritis, have been designed, synthesized, and evaluated in cell-culture assays. The results of these experiments have defined the structural elements of this new cytotoxic agent required for activity.

Animals↗
PubMed2003

Development and application of a new general method for the asymmetric synthesis of syn- and anti-1,3-amino alcohols.

A general method is described for asymmetric synthesis of both syn- and anti-1,3-amino alcohols. The first application of metalloenamines derived from N-sulfinyl imines is reported for the highly diastereoselective addition to aldehydes. The reduction of the product beta-hydroxy N-sulfinyl imines 2 with catecholborane and LiBHEt(3) provides syn- and anti-1,3-amino alcohols with very high diastereomeric ratios. This method was found to be effective for a variety of substrates incorporating either aromatic or various aliphatic substituents. The convergent and efficient asymmetric syntheses of the two natural products, (-)-8-epihalosaline and (-)-halosaline, were also accomplished.

Journal Article↗
PubMed2003

D-Ala-D-lac binding is not required for the high activity of vancomycin dimers against vancomycin resistant enterococci.

Covalent dimerization and oligomerization of vancomycin is an important and extensively used strategy to develop analogues active against vancomycin resistant enteroccoci (VRE). Here, we have carried out investigations to probe the role of peptide binding (Lys-d-Ala-d-Lac) in the high anti-VRE activities of covalently linked vancomycin dimers. Covalent dimers of damaged vancomycin (desleucyl) were prepared, and their anti-VRE activities and binding affinities toward various model peptides were measured. Despite the dramatic loss in affinity toward several model peptides in comparison to the corresponding intact vancomycin dimers, these damaged dimers maintained good activity against VRE. These results strongly suggest that the high anti-VRE activities of covalent vancomycin dimers are conferred from mechanisms other than Lys-d-Ala-d-Lac binding.

Alanine↗
PubMed2003

Microwave-assisted C-H bond activation: a rapid entry into functionalized heterocycles.

[reaction: see text] Microwave irradiation strongly accelerates the rhodium-catalyzed intramolecular coupling of a benzimidazole C-H bond to pendant alkenes. The cyclic products were formed in moderate to excellent yields with reaction times less than 20 min. Additionally, the use of microwave irradiation allowed the reactions to be performed without any solvent purification and with minimal precautions to exclude air.

Alkenes↗
PubMed2003

Identification of potent and broad-spectrum antibiotics from SAR studies of a synthetic vancomycin analogue.

Dimeric vancomycin analogues based on a lead compound identified from a library of synthetic analogues of vancomycin have up to 60-fold greater activity than vancomycin against vancomycin-resistant Enterococcus faecium (VRE, VanA phenotype). Simplified analogues have also been prepared and found to maintain activity against VRE and have broad-spectrum antibiotic activity.

Anti-Bacterial Agents↗
PubMed2003

Improved synthesis of tert-butanesulfinamide suitable for large-scale production.

[reaction: see text] An improved synthesis of tert-butanesulfinamide that overcomes the scalability problems of the previous syntheses is described. The key step is the catalytic asymmetric oxidation of the inexpensive di-tert-butyl disulfide starting material. The new homogeneous reaction conditions utilize an inexpensive chiral ligand prepared in a single step from commercially available cis-1-amino-indan-2-ol. The reaction is performed at a 2.3 M concentration in the practical solvent acetone and can readily be run on a kilogram scale.

Journal Article↗
PubMed2003

Catalytic properties and inhibition of proline-specific dipeptidyl peptidases II, IV and VII.

There is currently intense interest in the emerging group of proline-specific dipeptidases, and their roles in the regulation of biological processes. Dipeptidyl peptidase IV (DPP-IV) is involved in glucose metabolism by contributing to the regulation of glucagon family peptides and has emerged as a potential target for the treatment of metabolic diseases. Two other proline-specific dipeptidases, DPP-VII (also known as quiescent cell proline dipeptidase) and DPP-II, have unknown functions and have recently been suggested to be identical proteases based on a sequence comparison of human DPP-VII and rat DPP-II (78% identity) [Araki, Li, Yamamoto, Haneda, Nishi, Kikkawa and Ohkubo (2001) J. Biochem. 129, 279-288; Fukasawa, Fukasawa, Higaki, Shiina, Ohno, Ito, Otogoto and Ota (2001) Biochem. J. 353, 283-290]. To facilitate the identification of selective substrates and inhibitors for these enzymes, a complete biochemical profile of these enzymes was obtained. The pH profiles, substrate specificities as determined by positional scanning, Michaelis-Menten constants and inhibition profiles for DPP-VII and DPP-II were shown to be virtually identical, strongly supporting the hypothesis that they are the same protease. In addition, substrate specificities, catalytic constants and IC(50) values were shown to be markedly different from those of DPP-IV. Selective DPP-IV and DPP-VII substrates were identified and they can be used to design selective inhibitors and probe further into the biology of these enzymes.

Base Sequence↗
PubMed2003

Novel uncomplexed and complexed structures of plasmepsin II, an aspartic protease from Plasmodium falciparum.

Malaria remains a human disease of global significance and a major cause of high infant mortality in endemic nations. Parasites of the genus Plasmodium cause the disease by degrading human hemoglobin as a source of amino acids for their growth and maturation. Hemoglobin degradation is initiated by aspartic proteases, termed plasmepsins, with a cleavage at the alpha-chain between residues Phe33 and Leu34. Plasmepsin II is one of the four catalytically active plasmepsins that has been identified in the food vacuole of Plasmodium falciparum. Novel crystal structures of uncomplexed plasmepsin II as well as the complex with a potent inhibitor have been refined with data extending to resolution limits of 1.9A and 2.7A, and to R factors of 17% and 18%, respectively. The inhibitor, N-(3-[(2-benzo[1,3]dioxol-5-yl-ethyl)[3-(1-methyl-3-oxo-1,3-dihydro-isoindol-2-yl)-propionyl]-amino]-1-benzyl-2-(hydroxypropyl)-4-benzyloxy-3,5-dimethoxy-benzamide, belongs to a family of potent non-peptidic inhibitors that have large P1' groups. Such inhibitors could not be modeled into the binding cavity of the structure of plasmepsin II in complex with pepstatin A. Our structures reveal that the binding cavities of the new complex and uncomplexed plasmepsin II are considerably more open than that of the pepstatin A complex, allowing for larger heterocyclic groups in the P1', P2' and P2 positions. Both complexed and uncomplexed plasmepsin II crystallized in space group P2, with one monomer in the asymmetric unit. The structures show extensive interlocking of monomers around the crystallographic axis of symmetry, with areas in excess of 2300A(2) buried at the interface, and a loop of one monomer interacting with the binding cavity of the 2-fold related monomer. Electron density for this loop is only fully ordered in the complexed structure.

Amino Acid Sequence↗
PubMed2003

Novel sulfinyl imine ligands for asymmetric catalysis.

[structure: see text] A novel class of P,N-sulfinyl imine ligands has been prepared that incorporates chirality solely at sulfur. The Pd complex of ligand 14 catalyzes the allylic alkylation reaction with high enantioselectivity (94%), and the first crystal structure of a Pd-bound sulfinyl imine provides insight into binding mode and origins of stereoselectivity.

Journal Article↗
PubMed2003

The preparation and utility of bis(sulfinyl)imidoamidine ligands for the copper-catalyzed Diels-Alder reaction.

The design and preparation of a novel class of ligands based on the sulfinyl imine functionality is described. In particular, an efficient and modular synthesis of bis(sulfinyl)imidoamidine (siam) ligands is reported. The versatility of the synthetic sequence is demonstrated by the preparation of various analogues to explore the effect of substitution about the ligand framework on catalytic activity. The utility of the siam ligands in asymmetric catalysis is demonstrated in the Cu(II)-catalyzed Diels-Alder reaction where highly enantio- and diastereoselective reactions are reported for a range of N-acyloxazolidinone dienophile and diene substrate combinations. Of particular note is the efficiency of these asymmetric catalysts for reactions involving challenging and relatively unreactive acyclic diene substrates. Finally, structural data are provided for several ligands as well as metal-ligand complexes.

Journal Article↗
PubMed2003

Enantioselective oxidation of di-tert-butyl disulfide with a vanadium catalyst: progress toward mechanism elucidation.

The mechanism of the oxidation of di-tert-butyl disulfide (1) to the chiral thiosulfinate (2) by H(2)O(2) catalyzed by bis(acetylacetonato)oxovanadium and a chiral Schiff-base ligand (3) has been investigated. Techniques included (51)V NMR spectroscopy, solvent effects on reaction enantioselectivity, and the isolation and full characterization of a 2:1 ligand-to-vanadium catalyst precursor. A model for the dramatic solvent effect on the enantioselectivity of this reaction was developed, based on the identification of a competing nonselective oxidation pathway. From this model, strategies for limiting this competing pathway were developed.

Journal Article↗
PubMed2003

Crystal structures of reversible ketone-Based inhibitors of the cysteine protease cruzain.

The crystal structures of two hydroxymethyl ketone inhibitors complexed to the cysteine protease cruzain have been determined at 1.1 and 1.2 A resolution, respectively. These high resolution crystal structures provide the first structures of non-covalent inhibitors bound to cruzain. A series of compounds were prepared and tested based upon the structures providing further insight into the key binding interactions.

Animals↗
PubMed2003

Attenuation of autoimmune disease in Fas-deficient mice by treatment with a cytotoxic benzodiazepine.

OBJECTIVE: Elimination of autoreactive cells relies on Fas-dependent activation-induced cell death mechanisms, an important component of peripheral tolerance. Defects in Fas or its cognate ligand lead to inefficient activation-induced cell death and are specific causes of lymphoproliferative and autoimmune diseases. The present study was undertaken to investigate a novel 1,4-benzodiazepine (Bz-423) that induces apoptosis and limits autoimmune disease in NZB/NZW mice, to determine its activity against lupus-like disease associated with defective Fas expression. We investigated the Fas-dependence of its cytotoxic actions, its therapeutic potential in mice deficient in Fas, and its therapeutic mechanism of action. METHODS: Primary lymphocytes isolated from Fas-deficient MRL/MpJ-Fas(lpr) (MRL-lpr) mice were tested for sensitivity to Bz-423. Bz-423 was administered to MRL-lpr mice for short (1-week) or long (14-week) periods, and its effects on cell survival were determined along with measures of nephritis, arthritis, antibody titers, and Th subpopulations. BALB/c mice were similarly treated to determine if Bz-423 alters normal immune functions in vivo. RESULTS: Administration of Bz-423 to MRL-lpr mice significantly reduced autoimmune disease including glomerulonephritis and arthritis. Treatment was associated with decreases in CD4+ T cells and an alteration in the Th1/Th2 balance. At the therapeutic dosage, Bz-423 did not interfere with normal T and B cell responses in BALB/c mice, suggesting that this agent is not globally immunosuppressive. CONCLUSION: Bz-423 is a novel immunomodulatory agent that is active against disease even in the context of defective Fas signaling. It is a leading compound for further investigation into the development of selective therapies for lupus.

Adjuvants, Immunologic↗
PubMed2002

Peptide microarrays for the determination of protease substrate specificity.

A method is described for the preparation of substrate microarrays that allow for the rapid determination of protease substrate specificity. Peptidyl coumarin substrates, synthesized on solid support using standard techniques, are printed onto glass slides using DNA microarraying equipment. The linkage from the peptide to the slide is formed through a chemoselective reaction, resulting in an array of uniformly displayed fluorogenic substrates. The arrays can be treated with proteases to yield substrate specificity profiles. Standard instrumentation for visualization of microarrays can be used to obtain comparisons of the specificity constants for all of the prepared substrates. The utility of these arrays is demonstrated by the selective cleavage of preferred substrates with trypsin, thrombin, and granzyme B, and by assessing the extended substrate specificity of thrombin using a microarray of 361 different peptidyl coumarin substrates.

Amino Acids↗
PubMed2002

Synthesis and characterization of the first potent inhibitor of yapsin 1. Implications for the study of yapsin-like enzymes.

The potent peptidic inhibitor, Y1, of the basic residue-specific yeast aspartyl protease, yapsin 1, was synthesized and characterized. The inhibitor was based on the peptide sequence of a cholecystokinin(13-33) analog that yapsin 1 cleaved with an efficiency of 5.2 x 10(5) m(-1) s(-1) (Olsen, V., Guruprasad, K., Cawley, N. X., Chen, H. C., Blundell, T. L., and Loh, Y. P. (1998) Biochemistry 37, 2768-2777). The apparent K(i) of Y1 for the inhibition of yapsin 1 was determined to be 64.5 nm, and the mechanism is competitive. Y2 was also developed as an analog of Y1 for coupling to agarose beads. The resulting inhibitor-coupled agarose beads were successfully used to purify yapsin 1 to apparent homogeneity from conditioned medium of a yeast expression system. Utilization of this new reagent greatly facilitates the purification of yapsin 1 and should also enable the identification of new yapsin-like enzymes from mammalian and nonmammalian sources. In this regard, Y1 also efficiently inhibited Sap9p, a secreted aspartyl protease from the human pathogen, Candida albicans, which has specificity for basic residues similar to yapsin 1 and might provide the basis for the prevention or control of its virulence. A single-step purification of Sap9p from conditioned medium was also accomplished with the inhibitor column. N-terminal amino acid sequence analysis yielded two sequences indicating that Sap9p is composed of two subunits, designated here as alpha and beta, similar to yapsin 1.

Aspartic Acid Endopeptidases↗
PubMed2002

Intermolecular coupling of isomerizable alkenes to heterocycles via rhodium-catalyzed C-H bond activation.

This reports first intermolecular coupling of unactivated alkenes, including isomerizable alkenes, to a range of heterocycles using a Rh(I) catalyst. A variety of functional groups were incorporated, including esters, nitriles, and acetals. The intermolecular coupling became possible after it was discovered that weak acids dramatically increase the rate of both the inter- and intramolecular reactions.

Alkenes↗