Strong Quantum Spin Correlations Observed in Atomic Spin Mixing

We have observed sub-Poissonian spin correlations generated by collisionally induced spin mixing in a spin-1 Bose-Einstein condensate. We measure a quantum noise reduction of -7 dB (-10 dB corrected for detection noise) below the standard quantum limit (SQL) for the corresponding coherent spin states. The spin fluctuations are detected as atom number differences in the spin states using fluorescent imaging that achieves a detection noise floor of 8 atoms per spin component for a probe time of 100 $\mu$s.Comment: 5 pages, 4 figure

Due Process as Separation of Powers

From its conceptual origin in Magna Charta, due process of law has required that government can deprive persons of rights only pursuant to a coordinated effort of separate institutions that make, execute, and adjudicate claims under the law. Originalist debates about whether the Fifth or Fourteenth Amendments were understood to entail modern “substantive due process” have obscured the way that many American lawyers and courts understood due process to limit the legislature from the Revolutionary era through the Civil War. They understood due process to prohibit legislatures from directly depriving persons of rights, especially vested property rights, because it was a court’s role to do so pursuant to established and general law. This principle was applied against insufficiently general and prospective legislative acts under a variety of state and federal constitutional provisions through the antebellum era. Contrary to the claims of some scholars, however, there was virtually no precedent before the Fourteenth Amendment for invalidating laws that restricted liberty or the use of property. Contemporary resorts to originalism to support modern substantive due process doctrines are therefore misplaced. Understanding due process as a particular instantiation of separation of powers does, however, shed new light on a number of key twentieth-century cases which have not been fully analyzed under the requirements of due process of law

A target repurposing approach identifies N-myristoyltransferase as a new candidate drug target in filarial nematodes

Myristoylation is a lipid modification involving the addition of a 14-carbon unsaturated fatty acid, myristic acid, to the N-terminal glycine of a subset of proteins, a modification that promotes their binding to cell membranes for varied biological functions. The process is catalyzed by myristoyl-CoA:protein N-myristoyltransferase (NMT), an enzyme which has been validated as a drug target in human cancers, and for infectious diseases caused by fungi, viruses and protozoan parasites. We purified Caenorhabditis elegans and Brugia malayi NMTs as active recombinant proteins and carried out kinetic analyses with their essential fatty acid donor, myristoyl-CoA and peptide substrates. Biochemical and structural analyses both revealed that the nematode enzymes are canonical NMTs, sharing a high degree of conservation with protozoan NMT enzymes. Inhibitory compounds that target NMT in protozoan species inhibited the nematode NMTs with IC50 values of 2.5-10 nM, and were active against B. malayi microfilariae and adult worms at 12.5 µM and 50 µM respectively, and C. elegans (25 µM) in culture. RNA interference and gene deletion in C. elegans further showed that NMT is essential for nematode viability. The effects observed are likely due to disruption of the function of several downstream target proteins. Potential substrates of NMT in B. malayi are predicted using bioinformatic analysis. Our genetic and chemical studies highlight the importance of myristoylation in the synthesis of functional proteins in nematodes and have shown for the first time that NMT is required for viability in parasitic nematodes. These results suggest that targeting NMT could be a valid approach for the development of chemotherapeutic agents against nematode diseases including filariasis

Photon induced coherence loss in atom interferometry

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1995.Includes bibliographical references (p. 173-177).by Michael S. Chapman.Ph.D

Squeezed Ground States in a Spin-1 Bose-Einstein Condensate

We generate spin squeezed ground states in an atomic spin-1 Bose-Einstein condensate tuned nearthe quantum critical point between the polar and ferromagnetic quantum phases of the interactingspin ensemble. In contrast to typical non-equilibrium methods for preparing atomic squeezed statesby quenching through a quantum phase transition, squeezed ground states are time-stationary andremain squeezed for the lifetime of the condensate. A squeezed ground state with a metrologicalimprovement up to 6-8 dB and a constant squeezing angle maintained over 2 s is demonstrated.Comment: 11 pages, 8 figure

Intrinsic Domain and Loop Dynamics Commensurate with Catalytic Turnover in an Induced-Fit Enzyme

SummaryArginine kinase catalyzes reversible phosphoryl transfer between ATP and arginine, buffering cellular ATP concentrations. Structures of substrate-free and -bound enzyme have highlighted a range of conformational changes thought to occur during the catalytic cycle. Here, NMR is used to characterize the intrinsic backbone dynamics over multiple timescales. Relaxation dispersion indicates rigid-body motion of the N-terminal domain and flexible dynamics in the I182–G209 loop, both at millisecond rates commensurate with kcat, implying that either might be rate limiting upon catalysis. Lipari-Szabo analysis indicates backbone flexibility on the nanosecond timescale in the V308–V322 loop, while the rest of the enzyme is more rigid in this timescale. Thus, intrinsic dynamics are most prominent in regions that have been independently implicated in conformational changes. Substrate-free enzyme may sample an ensemble of different conformations, of which a subset is selected upon substrate binding, with critical active site residues appropriately configured for binding and catalysis