Nitrostyrene Derivatives of Adenosine 5′-Glutarates Modified with an Alkyl Spacer and their inhibitory activity on epidermal growth factor receptor protein tyrosine kinase

β-Nitrostyrene derivatives of adenosine 5′-glutarates are potent and selective bisubstrate-type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′-esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC₅₀ = 0.7–12 μM ), most of the modified compounds inhibited the EGF-R PTK only marginally or were inactive (IC₅₀ ≥ 100 μM ). The only exceptions were the free acids 19 and 20 with IC₅₀ values of ca. 5 μM . It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers.     

Aqueous flat-cells perpendicular to the electric field for use in electron paramagnetic resonance spectroscopy, II: design

This paper builds on the work of Mett and Hyde [J. Magn. Reson. 165 (2003) 137]. Various aqueous flat-cell geometries in the perpendicular orientation have been studied using Ansoft High Frequency Structure Simulator (version 9.0, Pittsburgh, PA) and Computer Simulation Technology Microwave Studio (version 5.0, Wellesley Hills, MA). The analytic theory of Mett and Hyde has been refined to predict optimum dimensions of multiple sample cell structures including the effect of the sample holder dielectric properties and the interaction of the cells with each other on EPR signal strength. From these calculations and simulations we propose a practical multiple cell sample structure for use in commercial rectangular TE102 cavities that yields 2.0-2.3 times higher sensitivity relative to a single flat-cell in the nodal orientation. We also describe a modified TE102 resonator design with square rather than cylindrical sample-access stacks that is predicted to give a factor of 2.2-2.7 enhancement in EPR signal strength of a single flat-cell in the nodal orientation. These signal enhancements are predicted with sample holders fabricated from polytetrafluoroethylene. Additional improvement in EPR signal of up to 75% can be achieved by using sample holder materials with lower dielectric constants.     

Identification of archaeal proteins that affect the exosome function in vitro

Background  

The archaeal exosome is formed by a hexameric RNase PH ring and three RNA binding subunits and has been shown to bind and degrade RNA in vitro. Despite extensive studies on the eukaryotic exosome and on the proteins interacting with this complex, little information is yet available on the identification and function of archaeal exosome regulatory factors.     

Modulation of humoral immune response to oral BCG vaccination by Mycobacterium bovis BCG Moreau Rio de Janeiro (RDJ) in healthy adults

We hypothesize that the energy strategy of a cell is a key factor for determining how, or if, the immune system interacts with that cell. Cells have a limited number of metabolic states, in part, depending on the type of fuels the cell consumes. Cellular fuels include glucose (carbohydrates), lipids (fats), and proteins. We propose that the cell's ability to switch to, and efficiently use, fat for fuel confers immune privilege. Additionally, because uncoupling proteins are involved in the fat burning process and reportedly in protection from free radicals, we hypothesize that uncoupling proteins play an important role in immune privilege. Thus, changes in metabolism (caused by oxidative stresses, fuel availability, age, hormones, radiation, or drugs) will dictate and initiate changes in immune recognition and in the nature of the immune response. This has profound implications for controlling the symptoms of autoimmune diseases, for preventing graft rejection, and for targeting tumor cells for destruction.     

Nitrostyrene Derivatives of Adenosine 5′-Glutarates as Selective Inhibitors of the Epidermal Growth Factor Receptor Protein Tyrosine Kinase

The syntheses and biological activities of some nitrostyrene derivatives of adenosine 5′-glutarates, a novel class of selective, bi-substrate-type inhibitors of the EGF receptor protein tyrosine kinase with IC₅₀ values around 1 μM . Only marginal inhibition of the tyrosine kinases v-able and c-src and of the serine/threonine kinase PKC was observed. Compounds 8, 9, 11 , and 12 – lacking the adenosine moiety – were ten times less active than the most potent derivatives, whereas 17 – lacking the nitrostyryl part – showed no inhibitory activity at all. Most of the compounds showed potent antiproliferative activity against an EGF-dependent mouse keratinocyte cell line.     

Synthesis of Modified Tripeptides and Tetrapeptides as potential bisubstrate inhibitors of the epidermal growth factor receptor protein tyrosine kinase

The synthesis of a series of bisubstrate inhibitors of the epidermal growth factor receptor protein kinase (EGF-R PTK) consisting of small pep tides linked covalently to adenosine via appropriate triphosphate substitutes is described. Boc-Glu(O^tBu)-Tyr-Leu-OBzl ( 5 ) and Ac-Glu(O^tBu)-Tyr-Leu-Arg(Pmc)-NH₂ ( 8 ; Pmc = 2,2,5,7,8-pentamethylchroman-6-sulfonyl) were prepared by standard peptide chemistry, (Scheme 1), then modified at the OH group of tyrosine either with adipic anhydride or with 4-(chlorosulfonyl)benzoic acid, 4-(chlorosulfonyl)-2-hydroxybenzoic acid, or benzene-1,4-disulfonyldichloride (Scheme 2), and finally coupled with the 5′-OH group of 2′,3′-O-isopropylideneadenosine (Scheme 3). In addition, N⁶-[(benzyloxy)carbonyl]-2′,3′-O-isopropylidene-adenosine 5′-(hydrogenhexanedioate) ( 26 ), an ATP substitute, was coupled with the morpholide of 5 (Scheme 4). Removal of the protecting groups gave the bisubstrate analogs 23, 24 , and 28. The compounds synthesized were tested as inhibitors of the EGF-R PTK. The most active bisubstrate-type inhibitor was 24 , composed of the tripeptide sequence H-Glu-Tyr-Leu-OBzl, the 2-hydroxy-4-sulfonylbenzoyl moiety, and adenosine; it showed an IC₅₀ value of 33 μM.     

Uniform radio frequency fields in loop-gap resonators for EPR spectroscopy

At high frequencies, e.g., Q- and W-bands, it is advantageous to make the axial length of loop-gap resonators (LGRs) at least as long as a free-space wavelength. The opposite scaling of capacitance and inductance with LGR length suggests that the length of an LGR can be increased without limit, with the axial radio frequency (rf) field profiles and resonance frequency independent of length. This scaling is accurate for resonator dimensions much less than one free-space wavelength. When the resonator length approaches one-tenth of a free-space wavelength, the rf field uniformity degrades. From one-tenth to one free-space wavelength, computer simulations and experimental measurements show that the axial magnetic field energy density profile is peaked in the center of the LGR, gradually decreases from 25 to 50% at a distance one radius from the end, and rapidly there-after. The nonuniformity is of two types. One type, in the vicinity of one radius of the end, is caused by the flaring of the field as it curves from the central loop to the end region, into the larger return loop(s). The other type, in the central part of the resonator, is caused by impedance mismatch at the ends of the LGR. The LGR may be viewed as a strongly reentrant (ridge) waveguide nearly open at both ends and supporting a standing wave. A transmission line model relates the central nonuniformity to the fringing capacitance and inductance at the ends of the resonator. This nonuniformity can be eliminated in several ways including modifying the ends of the LGR by adding a small metal bridge or a dielectric ring. These uniformity trimming elements increase the fringing capacitance and/or decrease the fringing inductance. With trimmed ends, LGRs can be made many free-space wavelengths long. The maximum resonator length is determined by the proximity in frequency of the fundamental LGR mode to the next highest frequency mode as well as the quality factor. Results of this theory are compared and conformed with finite-element simulations. This theory connects the uniform LGR with the uniform field cavity resonators previously introduced by this laboratory.