56 research outputs found
Baryon Spin and Magnetic Moments in Relativistic Chiral Quark Models
Spin-flavor fractions of quarks in the proton and several hyperons are
obtained from their lowest order chiral fluctuations involving Goldstone
bosons. SU(3) flavor breaking, relativistic effects and the axial anomaly are
included. The validity of the Karl-Sehgal formulas for magnetic moments is
studied as well.Comment: 24 pages, 7 tables, no figure
Violations of Lorentz Covariance in Light Front Quark Models
Electromagnetic form factors of the nucleon from relativistic quark models
are analyzed: results from null-plane projection of the Feynman triangle
diagram are compared with a Bakamjian-Thomas model. The magnetic form factors
of the models differ by about 15% at spacelike momentum transfer 0.5 GeV^2,
while the charge form factors are much closer. Spurious contributions to
electromagnetic form factors due to violations of rotational symmetry are
eliminated from both models. One method changes magnetic form factors by about
10%, whereas the charge form factors stay nearly the same. Another one changes
the charge form factor of the Bakamjian-Thomas model by more than 50%.Comment: 19 pages, 9 figures, Late
Poor old pores-The challenge of making and maintaining nuclear pore complexes in aging
The nuclear pore complex (NPC) is the sole gateway to the nuclear interior, and its function is essential to all eukaryotic life. Controlling the functionality of NPCs is a tremendous challenge for cells. Firstly, NPCs are large structures, and their complex assembly does occasionally go awry. Secondly, once assembled, some components of the NPC persist for an extremely long time and, as a result, are susceptible to accumulate damage. Lastly, a significant proportion of the NPC is composed of intrinsically disordered proteins that are prone to aggregation. In this review, we summarize how the quality of NPCs is guarded in young cells and discuss the current knowledge on the fate of NPCs during normal aging in different tissues and organisms. We discuss the extent to which current data supports a hypothesis that NPCs are poorly maintained during aging of nondividing cells, while in dividing cells the main challenge is related to the assembly of new NPCs. Our survey of current knowledge points toward NPC quality control as an important node in aging of both dividing and nondividing cells. Here, the loss of protein homeostasis during aging is central and the NPC appears to both be impacted by, and to drive, this process
Independence of , Poincare Invariance and the Non-Conservation of Helicity
A relativistic constituent quark model is found to reproduce the recent data
regarding the ratio of proton form factors, . We show that
imposing Poincare invariance leads to substantial violation of the helicity
conservation rule, as well as an analytic result that the ratio
for intermediate values of .Comment: 13 pages, 7 figures, to be submitted to Phys. Rev. C typos corrected,
references added, 1 new figure to show very high Q^2 behavio
Identification of an Allosteric Small-Molecule Inhibitor Selective for the Inducible Form of Heat Shock Protein 70
Inducible Hsp70 (Hsp70i) is overexpressed in a wide spectrum of human tumors and its expression correlates with metastasis, poor outcomes, and resistance to chemotherapy in patients. Identification of small molecule inhibitors selective for Hsp70i could provide new therapeutic tools for cancer treatment. In this work, we used fluorescence-linked enzyme chemoproteomic strategy (FLECS) to identify HS-72, an allosteric inhibitor selective for Hsp70i. HS-72 displays the hallmarks of Hsp70 inhibition in cells, promoting substrate protein degradation and growth inhibition. Importantly, HS-72 is selective for Hsp70i over the closely related constitutively active Hsc70. Studies with purified protein show HS-72 acts as an allosteric inhibitor, reducing ATP affinity. In vivo HS-72 is well-tolerated, showing bioavailability and efficacy, inhibiting tumor growth and promoting survival in a HER2+ model of breast cancer. The HS-72 scaffold is amenable to resynthesis and iteration, suggesting an ideal starting point for a new generation of anticancer therapeutics targeting Hsp70i
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