Wavefunction matching for solving quantum many-body problems.

Ab initio calculations have an essential role in our fundamental understanding of quantum many-body systems across many subfields, from strongly correlated fermions1-3 to quantum chemistry4-6 and from atomic and molecular systems7-9 to nuclear physics10-14. One of the primary challenges is to perform accurate calculations for systems where the interactions may be complicated and difficult for the chosen computational method to handle. Here we address the problem by introducing an approach called wavefunction matching. Wavefunction matching transforms the interaction between particles so that the wavefunctions up to some finite range match that of an easily computable interaction. This allows for calculations of systems that would otherwise be impossible owing to problems such as Monte Carlo sign cancellations. We apply the method to lattice Monte Carlo simulations15,16 of light nuclei, medium-mass nuclei, neutron matter and nuclear matter. We use high-fidelity chiral effective field theory interactions17,18 and find good agreement with empirical data. These results are accompanied by insights on the nuclear interactions that may help to resolve long-standing challenges in accurately reproducing nuclear binding energies, charge radii and nuclear-matter saturation in ab initio calculations19,20.

Maltose binding protein facilitates high-level expression and functional purification of the chemokines RANTES and SDF-1alpha from Escherichia coli.

The chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and SDF-1alpha (stromal cell-derived factor-1alpha) are important regulators of leukocyte trafficking and homing. Chemokines form insoluble inclusion bodies when expressed in Escherichia coli (E. coli), resulting in low yields of soluble protein. We have developed a novel chemokine expression system that generates a high amount of soluble protein and uses a simple purification scheme. We cloned different types of RANTES and SDF-1alpha fused to either maltose binding protein (MBP) or glutathione-S-transferase (GST) and expressed the fusion proteins in E. coli under various conditions. We found that the yield of soluble chemokine is influenced by the type of fusion partner. Fusion to MBP resulted in a higher yield of total and soluble chemokine compared to GST. Under optimized conditions, the yield of soluble MBP-RANTES and MBP-SDF-1alpha was 2.5- and 4.5-fold higher than that of the corresponding GST-fusion protein, respectively. Recombinant chemokine fusion proteins exhibited specific binding activity to chemokine receptors. These results demonstrate that the use of MBP-fusion proteins may provide an approach to generating high yields of soluble and functional chemokines, such as RANTES and SDF-1alpha.

Distraction histogenesis of an anastomosed artery.

This study examined the possibility of an adaptive reaction of anastomosed arteries under tension during a distraction lengthening procedure in the tibiae of rabbits. After an osteotomy at the mid tibia, the posterior tibial arteries were transected and anastomosed. Using a pair of small external fixators, the tibiae were distracted at a rate of 0.5mm/day (groups I-IV rabbits). Three weeks after 25% lengthening, the patency and histology of the arteries were examined. Angiography revealed that all of the anastomosed arteries were patent, and intimal hyperplasia was a constant finding. The mean thickness of the intima of the lengthened segment in group I was 60.4 microm, which is 5.0, 3.4 and 2.1 times higher that of the controls in groups IV (un-manipulated arteries, 12.2 microm), III (unlengthened but anastomosed arteries, 17.8 microm) and II (lengthened but untouched arteries, 28.7 microm), respectively. These results show that an anastomosed artery can maintain its patency at a certain level and speed of distraction lengthening. Therefore, it is possible that distraction lengthening and vascular anastomoses can be performed simultaneously provided there is careful monitoring of the circulation.