PTC209 HBr

PTC-209 HBr is the hydrobromide salt of PTC-209, a potent and selective BMI-1 inhibitor (IC50 = 0.5μM). It irreversibly impairs the colorectal tumor growth. [1]
BMI-1 is a component of polycomb repressive complex 1 (PRC1) and act as an epigenetic chromatin modifier for a variety of genes. [1]
PTC-209 inhibited both UTR-mediated reporter expression and endogenous BMI-1 expression in HCT116 (human colorectal cell) and HT1080 (human fibrosarcoma tumor cell) in a dose dependent manner. In addition, the inhibitory effect of PTC-209 was not from its cytotoxicity. PTC-209 also specifically reduced PRC1 activity. [1]
Viable colorectal cancer cell samples treated with PTC-209 ex vivo were injected back to the recipient mice in vivo, the mice exhibited reduced or no tumor growth comparing with the control groups. Thus PTC-209 irreversibly impaired colorectal cancer-initiating cells. Furthermore, in contrast with the control groups, tumor volume was significantly reduced in the colorectal tumor cell transplanted mice following PTC-209 administration. [1]
References:
[1] Kreso A, van Galen P, Pedley NM, Lima-Fernandes E, Frelin C, Davis T, Cao L,Baiazitov R, Du W, Sydorenko N, Moon YC, Gibson L, Wang Y, Leung C, Iscove NN,Arrowsmith CH, Szentgyorgyi E, Gallinger S, Dick JE, O'Brien CA. Self-renewal as a therapeutic target in human colorectal cancer. Nat Med. 2014 Jan;20(1):29-36.

Insights into acid dissociation of HCl and HBr with internal electric fields.[Pubmed:28252122]

Phys Chem Chem Phys. 2017 Mar 15;19(11):7461-7464.

The electric field experienced by an acid molecule in the acid-water cluster depends on its local environment comprising of surrounding water molecules. A critical field of about 193 and 163 MV cm(-1) is required for the dissociation of HCl and HBr, respectively, and is associated with the arrangement of water molecules around the acid. The critical field required for dissociation of isolated HCl and HBr is 510 and 462 MV cm(-1), respectively. Hence the solvation of the proton and the halide anion by water molecules substantially lowers the critical electric field by about 300 MV cm(-1), relative to vacuum.

Direct comparison of 3-centre and 4-centre HBr elimination pathways in methyl-substituted vinyl bromides.[Pubmed:27722312]

Phys Chem Chem Phys. 2016 Oct 12;18(40):28353-28364.

Elimination of HBr from UV-photoexcited vinyl bromides can occur through both 3-centre and 4-centre transition states (TSs). The competition between these pathways is examined using velocity map imaging of HBr (v = 0-2, J) photofragments. The three vinyl bromides chosen for study have methyl substituents that block either the 3-centre or the 4-centre TS, or leave both pathways open. The kinetic energy distributions extracted from velocity map images of HBr from 193 nm photolysis of the three vinyl bromide compounds are approximately described by a statistical model of energy disposal among the degrees of freedom of the photoproducts, and are attributed to dissociation on the lowest electronic state of the molecule after internal conversion. Dissociation via the 4-centre TS gives greater average kinetic energy release than for the 3-centre TS pathway. The resonance enhanced multi-photon ionization (REMPI) schemes used to detect HBr restrict measurements to J

Quantum dynamics study of energy requirement on reactivity for the HBr + OH reaction with a negative-energy barrier.[Pubmed:28071762]

Sci Rep. 2017 Jan 10;7:40314.

A time-dependent, quantum reaction dynamics approach in full dimensional, six degrees of freedom was carried out to study the energy requirement on reactivity for the HBr + OH reaction with an early, negative energy barrier. The calculation shows both the HBr and OH vibrational excitations enhance the reactivity. However, even this reaction has a negative energy barrier, the calculation shows not all forms of energy are equally effective in promoting the reactivity. On the basis of equal amount of total energy, the vibrational energies of both the HBr and OH are more effective in enhancing the reactivity than the translational energy, whereas the rotational excitations of both the HBr and OH hinder the reactivity. The rate constants were also calculated for the temperature range between 5 to 500 K. The quantal rate constants have a better slope agreement with the experimental data than quasi-classical trajectory results.

Reaction Kinetics of HBr with HO2: A New Channel for Isotope Scrambling Reactions.[Pubmed:27723341]

J Phys Chem A. 2016 Nov 3;120(43):8503-8511.

The gas phase reaction kinetics of HBr with the HO2 radical are investigated over the temperature range of T = 200-1500 K using a theoretical approach based on transition state theory. The parameters for the potential energy surface are computed using density functional theory with the M11 exchange functional. The rate coefficient for the HBr + HO2 --> Br + H2O2 abstraction channel is found to be somewhat larger than previous estimates at low temperatures due to quantum tunneling. The present study reveals the existence of a novel exchange pathway, HBr + H'O2 --> H'Br + HO2, which exhibits a much lower reaction barrier than does the abstraction route. The transition state for this process is a symmetrical planar five-membered-ring-shaped structure. At low temperatures, this concerted double hydrogen transfer reaction is several orders of magnitude faster than the abstraction channel. The exchange process may be observed using isotope scrambling reactions; such reactions may contribute to observed isotope abundances in the atmosphere. The rate coefficients for the isotopically labeled reactions are computed.