Chiral Recognition of Amino Acid Esters in Organic Solvents Using a Glucose-Based Receptor

Due to the chemical and biological relevance of amino acids, efficient methods for the recognition and separation of their enantiomers are highly sought after. Chiral receptors based on extended molecular scaffolds are typically employed for this purpose. These receptors are often effective only in specific environments and towards a narrow scope of amino acid guests. Recently we reported a simple, glucose-based macrocycle capable of enantioselective binding of a broad range of amino acid methyl esters in water. Herein we demonstrate that the same receptor can be used for chiral recognition of amino acid esters in organic solvents. We show that the binding affinity and selectivity of the receptor are highly dependent on the coordinating strength of the solvent. An in-depth analysis of the receptor’s conformation and its interactions with amino acid methyl esters allowed us to propose a binding mode of amino acids to the receptor in CDCl₃. The binding modes in CDCl₃ and D₂O were then compared, highlighting the main interactions responsible for binding affinity and selectivity in each solvent. We envision that the insight provided by this study will facilitate the development of further amino acid receptors based on monosaccharides with improved binding affinities and both enantio- as well as chemoselectivities.     

Order parameter and barrier height in LaSrMnO cluster glasses

Using the results of magnetization measurements of LaSrMnO cluster glasses, it is shown that the concentration of frozen magnetic moments exponentially decreases with the increase of temperature. We find that temperature dependence of the order parameter q, of the form q−q(T)∼T−5/2, is universal characteristic of the investigated cluster glasses and that the barrier height Δ closely follows the quadratic relation to the temperature, Δ≈BT².     

Changes in the electronic,optical, and magnetic properties of LaSrMnO films upon transition from the rhombohedral phase to the orthorhombic phase

The properties of LaSrMnO films are investigated in the temperature range of the transition from the rhombohedral phase to the orthorhombic phase (600–650° C). It is shown that, with a variation in the growth temperature T_s, the change in the film properties is governed by the interaction of Mn-O metallic (ferromagnetic) clusters in the dielectric (antiferromagnetic) matrix. At T_s≤600°C, the low density of e _g states and the dielectric gap (E _g =0.3–0.5 eV) are responsible for the following features: (i) the optical transparency in the range ?ω=0.5–2 eV, (ii) the difference between the FC and ZFC magnetizations M(T), (iii) the high resistance, and (iv) the appearance of the portions R(T) ≈ const in the dependence R(T) due to the transformation of clusters into a system of tunnel-coupled quantum dots. At T_s≥650°C, the local increase in the atomic and electronic densities leads to a decrease in the optical transmission and the resistance by three to nine orders of magnitude, the appearance of a maximum and a minimum in the dependences R(T) of the LaSrMnO films, and an increase in the magnetization M(10 K) by one order of magnitude. The inference is drawn that magnetic ordering of the system of tunnel-coupled clusters encourages an increase in the cluster size and in the content of the metallic (ferromagnetic) phase.     

Decoherence-driven cooling of a degenerate spinor Bose gas

We investigate the relationship between the coherence of a partially Bose-condensed spinor gas and its temperature. We observe cooling of the normal component driven by decoherence as well as the effect of temperature on decoherence rates.     

Search for lepton-flavor and lepton-number violation in the decay tau(-) -->l-(+)h+(-)h'(-)

A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons is performed using 221.4 fb(-1) of data collected at an e+e- center-of-mass energy of 10.58 GeV with the BABAR detector at the SLAC PEP-II storage ring. In all 14 decay modes considered, the observed data are compatible with background expectations, and upper limits are set in the range B(tau-->lhh')<(0.7 - 4.8) x 10(-7) at 90% confidence level.     

Measurements of branching fractions and Dalitz distributions for B0 --> D(*)+/-K0pi-/+ decays

We present measurements of the branching fractions for the three-body decays B0 --> D(*)-/+K0pi+/- and their resonant submodes B0 --> D(*)-/+K*+/-using a sample of approximately 88 x 10(6) BB pairs collected by the BABAR detector at the SLAC PEP-II asymmetric energy storage ring. We measure: B(B0 --> D-/+K0pi+/-) = (4.9 +/- 0.7stat +/- 0.5syst) x 10(-4), B(B0 --> D*-/+K0pi+/-) = (3.0 +/- 0.7stat +/- 0.3syst) x 10(-4), B(B0 --> D-/+K*+/-) = (4.6 +/- 0.6stat +/- 0.5syst) x 10(-4), B(B0 --> D*-/+K*+/-) = (3.2 +/- 0.6stat +/- 0.3syst) x 10(-4). From these measurements we determine the fractions of resonant events to be f(B0 --> D-/+K*+/-) = 0.63 +/- 0.08stat +/- 0.04syst and f(B0 --> D*-/+K*+/-) = 0.72 +/- 0.14stat +/-0.05syst.     

Search for decays of B0-->e+ e-, B0-->mu+ mu-, B0-->e +/- mu-/+

We present a search for the decays B0-->e+ e-, B0-->mu+ mu-, and B0-->e (+/-) mu (-/+) in data collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC B Factory. Using a data set of 111 fb(-1), we find no evidence for a signal in any of the three channels investigated and set the following branching fraction upper limits at the 90% confidence level: B(B0-->e+ e-) < 6.1 x 10(-8), B(B0-->mu+ mu-) < 8.3 x 10(-8), and B(B0-->e (+/-) mu (-/+) )<18 x 10(-8).