Intrinsic Photophysics of Light-harvesting Charge-tagged Chlorophyll a and b Pigments

Chlorophylls a and b (Chla/b) are responsible for light-harvesting by photosynthetic proteins in plants. They display broad absorption in the visible region with multiple bands, due to the asymmetry of the macrocycle and strong vibronic coupling. Their photophysics relies on the microenvironment, with regard to transition energies as well as quenching of triplet states. Here, we firmly establish the splitting of the Q and Soret bands into x- and y- polarized bands for the isolated molecules in vacuo, and resolve vibronic features. Storage-ring experiments reveal that dissociation of photoexcited charge-tagged complexes occurs over several milliseconds, but with two different time constants. A fast decay is ascribed to dissociation after internal conversion and a slow decay to the population of a triplet state that acts as a bottleneck. Support for the latter is provided by pump-probe experiments, where a second laser pulse probes the long-lived triplet state.     

DsJ (2317) meson production at RHIC

We study the production of D _sJ (2317) mesons in relativistic heavy ion collisions using the quark coalescence model. The predicted D _sJ (2317) abundance depends sensitively on the quark structure of the D _sJ (2317) meson. We have also evaluated the absorption cross sections of the D _sJ (2317) meson by π, ρ, kaon and K* in a phenomenological hadronic model. We find that the final yield of D _sJ (2317) mesons remains sensitive to its initial number produced from the quark-gluon plasma, providing thus the possibility of studying the quark structure of the D _sJ (2317) meson and its production mechanism in relativistic heavy ion collisions.     

Endomorphin analogues with balanced affinity for bothμ- andδ-opioid receptors

Analogues of endomorphin and tripeptidcs modified at positions 4 and 3,respectively,with various phenylalanine analogues were synthesized and their affinities for opioid receptors were evaluated.Most of the peptides exhibited potentμ-receptor affinity and selectivity,among them,compound 7(Dmt-Pro-Tmp-Tmp-NH_2) exhibited potent affinity for bothμ-andδ-receptors (K_iμ= 0.47 nmol/L,K_iδ= 1.63 nmol/L).     

Multistate Switches: Ruthenium Alkynyl–Dihydroazulene/Vinylheptafulvene Conjugates

Multimode molecular switches incorporating distinct and independently addressable functional components have potential applications as advanced switches and logic gates for molecular electronics and memory storage devices. Herein, we describe the synthesis and characterization of four switches based on the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermoswitch pair functionalized with the ruthenium‐based Cp*(dppe)Ru ([Ru*]) metal complex (dppe=1,2‐bis(diphenylphosphino)ethane; Cp*=pentamethylcyclopentadienyl). The [Ru*]–DHA conjugates can potentially exist in six different states accessible by alternation between DHA/VHF, Ru^II/Ru^III, and alkynyl/vinylidene, which can be individually stimulated by using light/heat, oxidation/reduction, and acid/base. Access to the full range of states was found to be strongly dependent on the electronic communication between the metal center and the organic photoswitch in these [Ru*]–DHA conjugates. Detailed electrochemical, spectroscopic (UV/Vis, IR, NMR), and X‐ray crystallographic studies indeed reveal significant electronic interactions between the two moieties. When in direct conjugation, the ruthenium metal center was found to quench the photochemical ring‐opening of DHA, which in one case could be restored by protonation or oxidation, allowing conversion to the VHF state.     

Directly estimating nonclassicality

We establish a method of directly measuring and estimating nonclassicality--operationally defined in terms of the distinguishability of a given state from one with a positive Wigner function. It allows us to certify nonclassicality, based on possibly much fewer measurement settings than necessary for obtaining complete tomographic knowledge, and is at the same time equipped with a full certificate. We find that even from measuring two conjugate variables alone, one may infer the nonclassicality of quantum mechanical modes. This method also provides a practical tool to eventually certify such features in mechanical degrees of freedom in opto-mechanics. The proof of the result is based on Bochner's theorem characterizing classical and quantum characteristic functions and on semidefinite programming. In this joint theoretical-experimental work we present data from experimental optical Fock state preparation.     

Plasmonic metamaterial wave retarders in reflection by orthogonally oriented detuned electrical dipoles

We demonstrate that a pair of perpendicular electrical dipolar scatterers resonating at different frequencies can be used as a metamaterial unit cell to construct a nanometer-thin retarder in reflection, designing nanocross and nanobrick plasmonic configurations to function as reflecting quarter-wave plates at ~1520 and 770 nm, respectively. The design is corroborated experimentally with a monolayer of gold nanobricks, transforming linearly polarized incident radiation into circularly polarized radiation at ~780 nm.     

Porous-core honeycomb bandgap THz fiber

In this Letter we propose a novel (to our knowledge) porous-core honeycomb bandgap design. The holes of the porous core are the same size as the holes in the surrounding cladding, thereby giving the proposed fiber important manufacturing benefits. The fiber is shown to have a 0.35-THz-wide fundamental bandgap centered at 1.05?THz. The calculated minimum loss of the fiber is 0.25?dB/cm.     

Microcrystallography, high-pressure cryocooling and BioSAXS at MacCHESS

The Macromolecular Diffraction Facility at the Cornell High Energy Synchrotron Source (MacCHESS) is a national research resource supported by the National Center for Research Resources of the US National Institutes of Health. MacCHESS is pursuing several research initiatives designed to benefit both CHESS users and the wider structural biology community. Three initiatives are presented in further detail: microcrystallography, which aims to improve the collection of diffraction data from crystals a few micrometers across, or small well diffracting regions of inhomogeneous crystals, so as to obtain high-resolution structures; pressure cryocooling, which can stabilize transient structures and reduce lattice damage during the cooling process; and BioSAXS (small-angle X-ray scattering on biological solutions), which can extract molecular shape and other structural information from macromolecules in solution.