We find that the cell’s chemotaxis drift velocity v(d) is a constant in an exponential attractant concentration gradient [L]proportional to exp(Gx). v(d) depends linearly on the exponential gradient G before it saturates when G is larger than a critical
value G(C). We find that G(C) is determined by the intracellular adaptation rate k(R) with a simple scaling law: G(C) proportional to k(R)(1/2) . The linear dependence of v(d) on G = d(In[L])/dx directly demonstrates E. coli’s ability in sensing the derivative of the logarithmic attractant https://www.selleckchem.com/small-molecule-compound-libraries.html concentration. The existence of the limiting gradient G(C) and its scaling with k(R) are explained by the underlying intracellular adaptation dynamics and the flagellar motor response characteristics. For individual cells, we find that the overall average run length in an exponential gradient is longer than that in a homogeneous environment, which is caused by the constant kinase activity shift (decrease). The forward runs (up the gradient) are longer than the backward runs, as expected; and depending on the
exact gradient, the (shorter) backward runs can be comparable to runs Oligomycin A in a spatially homogeneous environment, consistent with previous experiments. In (spatial) ligand gradients that also vary in time, the chemotaxis motion is damped as the frequency omega of the time-varying Nec-1s concentration spatial gradient becomes faster than a critical value omega(c), which is controlled by the cell’s chemotaxis adaptation rate k(R). Finally, our model,
with no adjustable parameters, agrees quantitatively with the classical capillary assay experiments where the attractant concentration changes both in space and time. Our model can thus be used to study E. coli chemotaxis behavior in arbitrary spatiotemporally varying environments. Further experiments are suggested to test some of the model predictions.”
“P>The advent of novel immunosuppressive strategies in renal transplantation, with immunomodulatory properties, might facilitate long-term allograft survival. T-cell depletion, costimulation-blockade and mTor inhibition have been shown to favour anti-donor hyporesponsiveness. Recently, the combination of rATG, belatacept (Bela) and sirolimus (SRL) has been used in kidney transplantation, showing very low incidence of acute rejection and excellent 12-month graft and patient survival. Herein, we have analysed the 1-year evolution of memory/effector and regulatory T cells and assessed the donor-specific T-cell alloimmune response in a group of these patients and compared with others treated with a calcineurin-inhibitor(CNI)-based (rATG/tacrolimus/MMF), and two other Bela-based regimens (rATG/Bela/MMF and basiliximab/Bela/MMF/steroids).