159 research outputs found
Clinical progress and pharmacology of small molecule bromodomain inhibitors
Bromodomains have emerged as an exciting target class for drug discovery over the past decade. Research has primarily focused on the bromodomain and extra terminal (BET) family of bromodomains, which has led to the development of multiple small molecule inhibitors and an increasing number of clinical assets. The excitement centred on the clinical potential of BET inhibition has stimulated intense interest in the broader family and the growing number of non-BET bromodomain chemical probes has facilitated phenotypic investigations, implicating these targets in a variety of disease pathways including cancer, inflammation, embryonic development and neurological disorders
Advancements in the development of non-BET bromodomain chemical probes
The bromodomain and extra terminal (BET) family of bromodomainâcontaining proteins (BCPs) have been the subject of extensive research over the past decade, resulting in a plethora of highâquality chemical probes for their tandem bromodomains. In turn, these chemical probes have helped reveal the profound biological role of the BET bromodomains and their role in disease, ultimately leading to a number of molecules in active clinical development. However, the BET subfamily represents just 8/61 of the known human bromodomains, and attention has now expanded to the biological role of the remaining 53 nonâBET bromodomains. Rapid growth of this research area has been accompanied by a greater understanding of the requirements for an effective bromodomain chemical probe and has led to a number of new nonâBET bromodomain chemical probes being developed. Advances since December 2015 are discussed, highlighting the strengths/caveats of each molecule, and the value they add toward validating the nonâBET bromodomains as tractable therapeutic targets
Alkene syn- and anti-oxyamination with malonoyl peroxides
Malonoyl peroxide [6] is an effective reagent for the syn- or anti-oxyamination of alkenes. Reaction of [6] and an alkene in the presence of O-tert-butyl-N-tosylcarbamate (R3 = CO2tBu) leads to the anti-oxyaminated product in up to 99% yield. Use of O-methyl-N-tosyl carbamate (R3 = CO2Me) as the nitrogen nucleophile followed by treatment of the product with trifluoroacetic acid leads to the syn-oxyaminated product in up to 77% yield. Mechanisms consistent with the observed selectivities are proposed
Small molecules and their roles in effective pre-clinical target validation
As demonstrated in multiple historical analyses, there are two main causes of clinical attrition; firstly drugs are not efficacious, and secondly they cause unacceptable toxicity, both of which can be the result of poor pre-clinical target validation. Target validation, one of the early stages of a drug discovery program, is the process of (in) validating a drug target to ensure it is significant to the intended disease, and unlikely to drive undesired toxicity. Target validation is vital in preventing late stage failures in the clinic and, if done effectively, can save pharmaceutical companies a great deal of time and money. As such, target validation is treated extremely seriously, as demonstrated by the formation of public - private partnerships, such as Open Targets, aimed to provide evidence of biological validity and the possible likelihood of pharmacological intervention. Central to the variety of molecular tools available for use in target validation are high quality small molecules called chemical probes
The Physical Properties of the Red Supergiant WOH G64: The Largest Star Known?
WOH G64 is an unusual red supergiant (RSG) in the Large Magellanic Cloud
(LMC), with a number of properties that set it apart from the rest of the LMC
RSG population, including a thick circumstellar dust torus, an unusually late
spectral type, maser activity, and nebular emission lines. Its reported
physical properties are also extreme, including the largest radius for any star
known and an effective temperature that is much cooler than other RSGs in the
LMC, both of which are at variance with stellar evolutionary theory. We fit
moderate-resolution optical spectrophotometry of WOH G64 with the MARCS stellar
atmosphere models, determining an effective temperature of 3400 +/- 25 K. We
obtain a similar result from the star's broadband V - K colors. With this
effective temperature, and taking into account the flux contribution from the
aysmmetric circumstellar dust envelope, we calculate log(L/L_sun) = 5.45 +/-
0.05 for WOH G64, quite similar to the luminosity reported by Ohnaka and
collaborators based on their radiative transfer modeling of the star's dust
torus. We determine a radius of R/R_sun = 1540, bringing the size of WOH G64
and its position on the H-R diagram into agreement with the largest known
Galactic RSGs, although it is still extreme for the LMC. In addition, we use
the Ca II triplet absorption feature to determine a radial velocity of 294 +/-
2 km/s for the star; this is the same radial velocity as the rotating gas in
the LMC's disk, which confirms its membership in the LMC and precludes it from
being an unusual Galactic halo giant. Finally, we describe the star's unusual
nebula emission spectrum; the gas is nitrogen-rich and shock-heated, and
displays a radial velocity that is significantly more positive than the star
itself by 50 km/s.Comment: 25 pages, 5 figures; accepted for publication in The Astronomical
Journa
Alkene anti-dihydroxylation with malonoyl peroxides
Malonoyl peroxide 1, prepared in a single step from the commercially available diacid, is an effective reagent for the anti-dihydroxylation of alkenes. Reaction of 1 with an alkene in the presence of acetic acid at 40 °C followed by alkaline hydrolysis leads to the corresponding diol (35-92%) with up to 13:1 anti-selectivity. A mechanism consistent with experimental findings is proposed that accounts for the selectivity observed
The Physical Properties of Red Supergiants: Comparing Theory and Observations
Red supergiants (RSGs) are an evolved stage in the life of intermediate
massive stars (than than 25 solar masses). For many years, their location in
the H-R diagram was at variance with the evolutionary models. Using the MARCS
stellar atmospheres, we have determined new effective temperatures and
bolometric luminosities for RSGs in the Milky Way, LMC, and SMC, and our work
has resulted in much better agreement with the evolutionary models. We have
also found evidence of significant visual extinction due to circumstellar dust.
Although in the Milky Way the RSGs contribute only a small fraction (than than
1 percent) of the dust to the interstellar medium (ISM), in starburst galaxies
or galaxies at large look-back times, we expect that RSGs may be the main dust
source. We are in the process of extending this work now to RSGs of higher and
lower metallicities using the galaxies M31 and WLM.Comment: Invited review; to appear in Massive Stars as Cosmic Engines, IAU
Symp. 250, ed. F. Bresolin, P. A. Crowther, and J. Puls (Cambridge University
Press
Yellow Supergiants in the Small Magellanic Cloud (SMC): Putting Current Evolutionary Theory to the Test
The yellow supergiant content of nearby galaxies provides a critical test of
massive star evolutionary theory. While these stars are the brightest in a
galaxy, they are difficult to identify because a large number of foreground
Milky Way stars have similar colors and magnitudes. We previously conducted a
census of yellow supergiants within M31 and found that the evolutionary tracks
predict a yellow supergiant duration an order of magnitude longer than we
observed. Here we turn our attention to the SMC, where the metallicity is 10x
lower than that of M31, which is important as metallicity strongly affects
massive star evolution. The SMC's large radial velocity (~160 km/s) allows us
to separate members from foreground stars. Observations of ~500 candidates
yielded 176 near-certain SMC supergiants, 16 possible SMC supergiants, along
with 306 foreground stars and provide good relative numbers of yellow
supergiants down to 12Mo. Of the 176 near-certain SMC supergiants, the
kinematics predicted by the Besancon model of the Milky Way suggest a
foreground contamination of >4%. After placing the SMC supergiants on the H-R
diagram and comparing our results to the Geneva evolutionary tracks, we find
results similar to those of the M31 study: while the locations of the stars on
the H-R diagram match the locations of evolutionary tracks well, the models
over-predict the yellow supergiant lifetime by a factor of ten. Uncertainties
about the mass-loss rates on the main-sequence thus cannot be the primary
problem with the models.Comment: Accepted by the Ap
Red Supergiants in the Andromeda Galaxy (M31)
Red supergiants are a short-lived stage in the evolution of moderately
massive stars (10-25Mo), and as such their location in the H-R diagram provides
an exacting test of stellar evolutionary models. Since massive star evolution
is strongly affected by the amount of mass-loss a star suffers, and since the
mass-loss rates depend upon metallicity, it is highly desirable to study the
physical properties of these stars in galaxies of various metallicities. Here
we identify a sample of red supergiants in M31 (the most metal-rich of the
Local Group galaxies) and derive their physical properties by fitting MARCS
atmosphere models to moderate resolution optical spectroscopy, and from V-K
photometry.Comment: Accepted for publication in the Astrophysical Journa
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