Biomedical subjects

A Spaltenstein

Publications and source records attributed to A Spaltenstein.

10 recordsLinked to original sources

PubMed2000

Novel inhibitors of HIV protease: design, synthesis and biological evaluation of picomolar inhibitors containing cyclic P1/P2 scaffolds.

A novel series of HIV protease inhibitors containing cyclic P1/P2 scaffolds has been synthesized and evaluated for biological activity. The trans 3,5-dibenzyl-2-oxo pyrrolidinone ring system resulted in a 50 pM enzyme inhibitor against HIV protease in vitro when combined with an indanolamine derived P'-backbone. This compound also shows comparable activity to currently marketed drugs in the MT-4 cell-based antiviral assay.

Anti-HIV Agents↗

PubMed2000

Dietary fat alters HIV protease inhibitor-induced metabolic changes in mice.

Human immunodeficiency virus (HIV) protease inhibitors (PI) may alter lipid metabolism in patients with acquired immunodeficiency syndrome (AIDS). However, the influence of dietary fat on the metabolic effects of PI therapy remains unknown. AKR/J mice were fed high or low fat diets and treated with the PI indinavir (IDV), nelfinavir (NFV), saquinavir (SQV) or amprenavir (APV) by subcutaneous delivery for 2 wk. Serum concentrations of glucose, insulin, triglyceride, free fatty acid, glycerol, pancreatic lipase, bilirubin, alkaline phosphatase, blood urea nitrogen and PI, and interscapular and epididymal fat weights were determined. Some metabolic effects of PI were dependent on diet. IDV- and NFV-treated mice had greater serum glucose concentration and body weight; IDV-treated mice had lower serum insulin; NFV-treated mice had greater interscapular fat mass; and SQV treated mice had lower serum triglyceride concentration than control mice fed the low but not the high fat diet. In contrast, NFV- and IDV-treated mice had greater triglyceride concentration and blood urea nitrogen, and SQV treated mice had greater serum cholesterol than control mice fed the high but not the low fat diet. The serum concentration of SQV was lower in mice fed the high fat compared with the low fat diet. Other effects were not dependent on diet. IDV- and NFV-treated mice had greater fatty acids, and IDV-treated mice had greater pancreatic lipase, bilirubin and alkaline phosphatase than control mice fed either diet. APV treatment had little effect on these serum measurements. Thus, changes in dietary fat can influence some but not all of the effects of PI on metabolism. Furthermore, each PI produces different effects in vivo, indicating that various PI affect distinct metabolic pathways.

Adipose Tissue↗

PubMed1996

Hemodynamic characterization of a novel neuropeptide Y receptor antagonist.

Defining the roles of the vasoconstrictor peptide neuropeptide Y (NPY) in the cardiovascular system is difficult due to lack of availability of specific NPY receptor antagonists. We report the in vivo NPY receptor blocking actions of a novel nonapeptide dimer, 1229U91 {(IleGluProDprTyrArgLeuArgTyrNH(2)(2)}, and describe its hemodynamic effects. In anesthetized normotensive rats, 1229U91 produced significant and dose-dependent reductions in NPY-reduced hemodynamic responses. 1229U91 (3-30 nmol/kg intravenously, i.v.) attenuated the pressor response (34 +/- 6-84 +/- 1%) and the increases in renal vascular resistance (RVR, 56 +/- 9-94 +/- 2%) produced by NPY (1 nmol/kg i.v.). Intravenous norepinephrine (NE)-induced hemodynamic responses were not altered by 1229U91. 1229U91 also produced dose-dependent inhibition of NPYinduced vasoconstrictor responses in anesthetized dogs and spontaneously hypertensive rats (SHR). These data demonstrate that 1229U91 is a selective NPY receptor antagonist. 1229U91 had no effect on resting hemodynamic variables in these preparations. In conscious SHR, 1229U91 did not produce significant changes in blood pressure (BP) or heart rate (HR) over a wide dose-range (15-1,500 nmol/kg i.v.). Lack of effect of the NPY receptor antagonist in SHR suggests that NPY does not contribute to the maintenance of BP in this hypertension model.

Anesthesia↗

PubMed1996

Synthesis, structure and stability of novel dimeric peptide-disulfides.

Oxidation of nonapeptide dithiol (2) with K3Fe(CN)6 leads to either monomeric disulfide (4) or antiparallel and parallel dimeric disulfides (3a and 3b) depending upon reaction conditions. When exposed to small amounts of thiols or cyanide in aqueous solution, these three species interconvert to an equilibrium mixture of 2:1:8 (3a:3b:4).

Chromatography, High Pressure Liquid↗

PubMed1995

High-affinity neuropeptide Y receptor antagonists.

Neuropeptide Y (NPY) is one of the most abundant peptide transmitters in the mammalian brain. In the periphery it is costored and coreleased with norepinephrine from sympathetic nerve terminals. However, the physiological functions of this peptide remain unclear because of the absence of specific high-affinity receptor antagonists. Three potent NPY receptor antagonists were synthesized and tested for their biological activity in in vitro, ex vivo, and in vivo functional assays. We describe here the effects of these antagonists inhibiting specific radiolabeled NPY binding at Y1 and Y2 receptors and antagonizing the effects of NPY in human erythroleukemia cell intracellular calcium mobilization perfusion pressure in the isolated rat kidney, and mean arterial blood pressure in anesthetized rats.

Amino Acid Sequence↗

PubMed1995

Monitoring DNA dynamics using spin-labels with different independent mobilities.

The electron paramagnetic resonance (EPR) spectra of spin-labeled DNA duplexes, both bound to DEAE-Sephadex and free in solution, have been analyzed. The nitroxide spin-labels are covalently linked to a deoxyuridine residue using either a monoacetylene or diacetylene tether. This difference in tether length produces a dramatic difference in the independent mobility of the nitroxide relative to the DNA. In the case of the monoacetylene tether, the motion of the nitroxide has previously been shown to be tightly coupled to that of the DNA duplex. With the diacetylene tether, there is considerable independent motion of the probe. The diacetylene tether is intended to minimize the possibility of the nitroxide producing a perturbation of the dynamics of DNA. It is demonstrated here that, when coupled via the diacetylene tether, the nitroxide undergoes a rapid uniaxial rotation about the tether. A detailed analysis of the EPR spectrum of duplex DNA in solution, spin-labeled using the diacetylene tether, demonstrates that the motion of the nitroxide can be modeled in terms of this independent uniaxial rotation together with motion of the DNA which is consistent with the global tumbling of the duplex. As was previously found using the monoacetylene tether, there is no evidence of rapid, large-amplitude motions of the base pair in the EPR spectrum of a nitroxide coupled to duplex DNA via the diacetylene tether. This result confirms the small amplitudes of internal motion, local and collective, previously observed in duplex DNA with the monoacetylene-tethered nitroxide.

Acetylene↗

PubMed1994

Polyacrylamides bearing pendant alpha-sialoside groups strongly inhibit agglutination of erythrocytes by influenza A virus: multivalency and steric stabilization of particulate biological systems.

An alpha-sialoside linked to acrylamide by a short connector (5-acetamido-2-O-(N-acryloyl-8-amino-5-oxaoctyl)-2,6-anhydro-3,5-d ideoxy-D-galacto-alpha-nonulopyranosonoic acid, 1) was prepared. Compound 1 formed high molecular weight copolymers with acrylamide, derivatives of acrylamide, and/or vinylpyrrolidone upon photochemically-initiated free radical polymerization. Those copolymers for which the substituents on the acrylamido nitrogen were small inhibited the agglutination of chicken erythrocytes induced by influenza virus (X-31 (H3N2); a recombinant strain of A/Aichi/2/68 (H3N2) and A/Puerto Rico/8/34 grown in chicken eggs). The inhibitory power of the polymers depended strongly on the conditions of polymerization and the sialic acid content of the polymer. The strongest inhibitors were copolymers (poly(1-co-acrylamide)) formed from mixtures of monomer containing [1]/([1] + [acrylamide]) approximately 0.2-0.7; these copolymers inhibited hemagglutination 10(4)-10(5) times more strongly than did similar concentrations of alpha-methyl sialoside (calculated on the basis of the total concentration of individual sialic acid groups in the solution, whether attached to polymer or present as monomers). Samples polymerized in the presence of low concentrations of cross-linking reagents (bis(acrylamido)methane, BIS, and 2,2'-bis(acrylamido)ethyl disulfide, BAC) also showed increased inhibition (10-10(3)-fold relative to monomers), but their use was limited by their poor solubility. Sterically demanding substituents on any position of the acrylamide component (substituents attached to the vinyl group or N-alkyl groups that are larger than hydroxyethyl) reduced the inhibitory power of the polymer. A 1H NMR assay and a fluorescence depolarization assay showed that poly(1-co-acrylamide) bound to a solubilized trimeric form of the viral receptor for sialic acid (bromelain cleaved hemagglutinin, BHA), less tightly than 1, on a per sialic acid basis. A similar result was also obtained with a model system comprising lactic dehydrogenase (a tetramer) and polymeric derivatives of oxamic acid: that is, poly((28, 29, 30, or 31)-co-acrylamide) had a higher inhibition constant for tetrameric lactic dehydrogenase than did the corresponding monomers (28, 29, 30, or 31) on a per oxamate basis. Poly(1-co-acrylamide) is, in principle, capable of inhibiting the agglutination of erythrocytes by several mechanisms: (1) entropically enhanced binding of the polymer (acting as a polyvalent inhibitor) to the surface of the virus; (2) steric interference of the approach of the virus to the surface of the erythrocyte by a water-swollen layer of the polymer on the surface of the virus; (3) aggregation of the virus induced by the polymer.(ABSTRACT TRUNCATED AT 400 WORDS)

Acrylic Resins↗

PubMed1993

Motions of short DNA duplexes: an analysis of DNA dynamics using an EPR-active probe.

The dynamics of a series of four DNA duplexes of length 12, 24, 48, and 96 base pairs have been studied using an electron paramagnetic resonance (EPR) active nitroxide spin-label covalently attached to a thymidine located near the center of each duplex. The linear EPR spectra were simulated by solving the stochastic Liouville equation for anisotropic rotational diffusion. The diffusion tensor for global rotation of the duplex was predicted from hydrodynamic theory for a right circular cylinder. All internal motions, assumed to be rapid, are modeled by reduced electron Zeeman and hyperfine tensor anisotropies. Best fit simulations to the data were then obtained by adjusting the total amplitude of all internal dynamics. The local, length-independent and the collective, length-dependent contributions to the internal dynamics were separated by determining the total amplitude of internal motion as a function of duplex length. The major axis of the spin tensors was determined to be tilted 20 degrees from the helix axis. As a result, the spin-label is most sensitive to flexural motions of the DNA duplex. It is found that the global tumbling of duplex is accurately modeled by hydrodynamic theory. The length-independent motion is characterized by a root-mean-squared amplitude of oscillation of 10 degrees in two dimensions at 20 degrees C and has a strong temperature dependence, indicating that the local structure of the DNA changes with temperature. The length dependence of the internal dynamics leads to an estimate of the dynamic flexural persistence length of 2500 +/- 340 A. There was no statistically significant difference between models assuming a harmonic or a square-well local bending potential.

Base Sequence↗

PubMed1989

Sequence- and structure-dependent DNA base dynamics: synthesis, structure, and dynamics of site and sequence specifically spin-labeled DNA.

A nitroxide spin-labeled analogue of thymidine (1a), in which the methyl group is replaced by an acetylene-tethered nitroxide, was evaluated as a probe for structural and dynamics studies of sequence specifically spin-labeled DNA. Residue 1a was incorporated into synthetic deoxyoligonucleotides by using automated phosphite triester methods. 1H NMR, CD, and thermal denaturation studies indicate that 1a (T*) does not significantly alter the structure of 5'-d(CGCGAATT*CGCG) from that of the native dodecamer. EPR studies on monomer, single-stranded, and duplexed DNA show that 1a readily distinguishes environments of different rigidity. Comparison of the general line-shape features of the observed EPR spectra of several small duplexes (12-mer, 24-mer) with simulated EPR spectra assuming isotropic motion suggests that probe 1a monitors global tumbling of small duplexes. Increasing the length of the DNA oligomers results in significant deviation from isotropic motion, with line-shape features similar to those of calculated spectra of objects with isotropic rotational correlation times of 20-100 ns. EPR spectra of a spin-labeled GT mismatch and a T bulge in long DNAs are distinct from those of spin-labeled Watson-Crick paired DNAs, further demonstrating the value of EPR as a tool in the evaluation of local dynamic and structural features in macromolecules.

Base Sequence↗

PubMed1987

Fluoro ketone containing peptides as inhibitors of human renin.

The pentapeptide BOC-Phe-Phe-difluorostatone-Leu-Phe-NH2 has been prepared and found to be a potent inhibitor of human renin. This compound contains a difluoromethylene ketone group that exists predominantly in the hydrated form in water. The difluorostatone-containing peptide is 7-fold and 22-fold more potent than the analogous statine- and statone-containing peptides, respectively. Structure/activity analysis of the most potent inhibitor was carried out by replacing some of the peptide bonds with trans-alkenes. In all cases, a dramatic loss in binding to renin was observed. A number of statine-containing inhibitors of renin have been reported and this work suggests that the replacement of statine with difluorostatone will yield more potent compounds.

Amino Acid Sequence↗