Does the efficiency of high energy collisions depend on a hard scale?

The multiplicity of charged hadrons in the current fragmentation region of both the c.m.s. and the Breit frame of deep inelastic scattering is calculated and compared with the HERA data. The results are in agreement with Yang's hypothesis that the efficiency of high energy processes increases at larger momentum transfer, although the effect is rather weak numerically at present values of . Received: 29 November 2000 / Revised version: 21 December 2000 / Published online: 15 March 2001     

Quark mass effects in deeply inelastic scattering

We argue that the difference between the structure functions corresponding to deep inelastic scattering with and without heavy quarks in the current fragmentation region scales at high Q² and fixed (low) x _Bj.     

Specific cell-permeable inhibitor of proteasome trypsin-like sites selectively sensitizes myeloma cells to bortezomib and carfilzomib

Proteasomes degrade the majority of proteins in mammalian cells, are involved in the regulation of multiple physiological functions, and are established targets of anticancer drugs. The proteasome has three types of active sites. Chymotrypsin-like sites are the most important for protein breakdown and have long been considered the only suitable targets for antineoplastic drugs; however, our recent work demonstrated that inhibitors of caspase-like sites sensitize malignant cells to inhibitors of the chymotrypsin-like sites. Here, we describe the development of specific cell-permeable inhibitors and an activity-based probe of the trypsin-like sites. These compounds selectively sensitize multiple myeloma cells to inhibitors of the chymotrypsin-like sites, including antimyeloma agents bortezomib and carfilzomib. Thus, trypsin-like sites are cotargets for anticancers drugs. Together with inhibitors of chymotrypsin- and caspase-like sites developed earlier, we provide the scientific community with a complete set of tools to separately modulate proteasome active sites in living cells.