Exploratory study of possible resonances in the heavy meson - heavy baryon coupled-channel interactions

We use a unitary coupled-channel model to study the $\bar{D} \Lambda_c - \bar{D} \Sigma_c$ interactions. In our calculation, SU(3) flavor symmetry is applied to determine the coupling constants. Several resonant and bound states with different spin and parity are dynamically generated in the mass range of the recently observed pentaquarks. The approach is also extended to the hidden beauty sector to study the $B \Lambda_b - B \Sigma_b$ interactions. As the $b$-quark mass is heavier than the $c$-quark mass, there are more resonances observed for $B \Lambda_b - B \Sigma_b$ interactions and they are more tightly bound.Comment: 10 pages, 11 figures, updated to the published versio

Biosynthesis and NMR-studies of a double transmembrane domain from the Y4 receptor, a human GPCR

The human Y4 receptor, a class A G-protein coupled receptor (GPCR) primarily targeted by the pancreatic polypeptide (PP), is involved in a large number of physiologically important functions. This paper investigates a Y4 receptor fragment (N-TM1-TM2) comprising the N-terminal domain, the first two transmembrane (TM) helices and the first extracellular loop followed by a (His)6 tag, and addresses synthetic problems encountered when recombinantly producing such fragments from GPCRs in Escherichia coli. Rigorous purification and usage of the optimized detergent mixture 28mM dodecylphosphocholine (DPC)/118mM% 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LPPG) resulted in high quality TROSY spectra indicating protein conformational homogeneity. Almost complete assignment of the backbone, including all TM residue resonances was obtained. Data on internal backbone dynamics revealed a high secondary structure content for N-TM1-TM2. Secondary chemical shifts and sequential amide proton nuclear Overhauser effects defined the TM helices. Interestingly, the properties of the N-terminal domain of this large fragment are highly similar to those determined on the isolated N-terminal domain in the presence of DPC micelle